diff --git a/LICENSE b/LICENSE
index 9b2da73fd..be1b6d45f 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2013-2021, Unison Computing, public benefit corp and contributors
+Copyright (c) 2013-2022, Unison Computing, public benefit corp and contributors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/chez-libs/readme.md b/chez-libs/readme.md
new file mode 100644
index 000000000..2e242c814
--- /dev/null
+++ b/chez-libs/readme.md
@@ -0,0 +1,49 @@
+This directory contains libraries necessary for building and running
+unison programs via Chez Scheme. At the moment, they need to be
+manually installed in the expected location. The default location is
+the `unisonlanguage` directory in the XDG data directory.
+Specifically, the `unison` subdirectory should be (recursively) copied
+to:
+
+    $XDG_DATA_DIRECTORY/unisonlanguage/scheme-libs
+
+On unix systems, the XDG directory is ~/.local/share by default, ~
+being the home directory. On Windows, this is instead the %APPDATA%
+directory. See:
+
+    https://hackage.haskell.org/package/directory/docs/System-Directory.html#t:XdgDirectory
+
+for more information.
+
+UCM can also be told to look in another directory by setting the
+`SchemeLibs.Static` item in the unison config file. If this path is
+denoted by `$CUSTOM`, then the compiler commands will look in:
+
+    $CUSTOM/scheme-libs/
+
+for the `unison/` directory containing the library files.
+
+The compiler commands also expect Chez Scheme to be installed
+separately, and for `scheme` to be callable on the user's path. For
+information on how to install, see:
+
+    https://github.com/cisco/ChezScheme/blob/main/BUILDING
+
+For more information on Chez Scheme in general, see:
+
+    https://cisco.github.io/ChezScheme/csug9.5/csug.html
+
+There are two ways to run code via scheme. The first is to use
+`run.native`, which compiles and immediately runs a given unison
+definition. The second is `compile.native`, which produces a Chez
+scheme `.boot` file with a specified name. The boot file can then be
+used with the scheme binary to run the precompiled program, like so:
+
+    scheme -b ./my-program.boot
+
+It is also possible to install the boot file in a particular
+directory, and make a renamed copy of the scheme binary, which will
+automatically execute the boot file with the corresponding name on
+start up. For more information on how to accomplish that, see:
+
+    https://cisco.github.io/ChezScheme/csug9.5/use.html#./use:h8
diff --git a/chez-libs/unison/boot.ss b/chez-libs/unison/boot.ss
new file mode 100644
index 000000000..96ab92f76
--- /dev/null
+++ b/chez-libs/unison/boot.ss
@@ -0,0 +1,130 @@
+; This library implements various syntactic constructs and functions
+; that are used in the compilation of unison (intermediate) source to
+; scheme. The intent is to provide for writing scheme definitions that
+; more directly match the source, so that the compiler doesn't need to
+; emit all the code necessary to fix up the difference itself.
+;
+; Probably the best example of this is the define-unison macro, which
+; looks similar to scheme's define, but the function being defined is
+; allowed to be under/over applied similar to a unison function. It
+; has an 'arity' at which computation happens, but the function
+; automatically handles being applied to fewer or more arguments than
+; that arity appropriately.
+(library (unison boot)
+  (export
+    name
+    define-unison
+    func-wrap
+    handle
+    request
+    unison-force)
+
+  (import (chezscheme)
+          (unison cont))
+
+  ; Helper function. Turns a list of syntax objects into a list-syntax object.
+  (meta define (list->syntax l) #`(#,@l))
+
+  ; Concatenates 
+  (meta define fun-sym
+    (case-lambda
+      [(pfx sfx) (string->symbol (string-append pfx "-" sfx))]
+      [(pfx ifx sfx)
+       (string->symbol (string-append pfx "-" ifx "-" sfx))]))
+
+  ; Computes a symbol for automatically generated partial application
+  ; cases, based on number of arguments applied. The partial
+  ; application of `f` is (locally) named `f-partial-N`
+  (meta define (partial-symbol name m)
+    (fun-sym (symbol->string name) "partial" (number->string m)))
+
+  ; As above, but takes a syntactic object representing the arguments
+  ; rather than their count.
+  (meta define (partial-name name us)
+    (datum->syntax name (syntax->datum name)))
+
+  (define-syntax with-name
+    (syntax-rules ()
+      [(with-name name e) (let ([name e]) name)]))
+
+  ; Builds partial application cases for unison functions. It seems
+  ; most efficient to have a case for each posible under-application.
+  (meta define (build-partials name formals)
+    (let rec ([us formals] [acc '()])
+      (syntax-case us ()
+        [() (list->syntax (cons #`[() #,name] acc))]
+        [(a ... z)
+         (rec #'(a ...)
+              (cons
+                #`[(a ... z)
+                   (with-name
+                     #,(partial-name name us)
+                     (lambda r (apply #,name a ... z r)))]
+                acc))])))
+
+  ; Given an overall function name, a fast path name, and a list of arguments,
+  ; builds the case-lambda body of a unison function that enables applying to
+  ; arbitrary numbers of arguments.
+  (meta define (func-cases name fast args)
+    (syntax-case args ()
+      [() #`(case-lambda
+              [() (#,fast)]
+              [r (apply (#,fast) r)])]
+      [(a ... z)
+       #`(case-lambda
+           #,@(build-partials name #'(a ...))
+           [(a ... z) (#,fast a ... z)]
+           [(a ... z . r) (apply (#,fast a ... z) r)])]))
+
+  (meta define (func-wrap name args body)
+    #`(let ([fast-path (lambda (#,@args) #,@body)])
+        #,(func-cases name #'fast-path args)))
+
+  ; function definition with slow/fast path. Slow path allows for
+  ; under/overapplication. Fast path is exact application.
+  ;
+  ; The intent is for the scheme compiler to be able to recognize and
+  ; optimize static, fast path calls itself, while still supporting
+  ; unison-like automatic partial application and such.
+  (define-syntax (define-unison x)
+    (syntax-case x ()
+      [(define-unison (name a ...) e ...)
+       #`(define name
+           #,(func-wrap #'name #'(a ...) #'(e ...)))]))
+
+  ; call-by-name bindings
+  (define-syntax name
+    (syntax-rules ()
+      ((name ([v (f . args)] ...) body)
+       (let ([v (lambda r (apply f (append (list . args) r)))]
+             ...)
+         body))))
+
+  ; wrapper that more closely matches `handle` constructs
+  (define-syntax handle
+    (syntax-rules ()
+      [(handle [r ...] h e ...)
+       (prompt p (fluid-let ([r (cons p h)] ...) e ...))]))
+
+  ; wrapper that more closely matches ability requests
+  (define-syntax request
+    (syntax-rules ()
+      [(request r t . args)
+       ((cdr r) (list (quote r) t . args))]))
+
+  (define-record-type
+    data
+    (fields type-ref payload))
+
+  (define-syntax data-case
+    (syntax-rules ()
+      [(data-case scrut c ...)
+       (record-case (data-payload scrut) c ...)]))
+
+  ; forces something that is expected to be a thunk, defined with
+  ; e.g. `name` above. In some cases, we might have a normal value,
+  ; so just do nothing in that case.
+  (define (unison-force x)
+    (if (procedure? x) (x) x))
+
+  )
diff --git a/chez-libs/unison/bytevector.ss b/chez-libs/unison/bytevector.ss
new file mode 100644
index 000000000..be58f9540
--- /dev/null
+++ b/chez-libs/unison/bytevector.ss
@@ -0,0 +1,35 @@
+; This library implements missing bytevector functionality for unison
+; builtins. The main missing bits are better support for immutable
+; bytevectors. Chez does provide a way to make an immutable
+; bytevector, but it copies its input, so implementing things that way
+; would make many unncessary copies. This library instead implements
+; functions on immutable bytevectors by directly freezing the newly
+; created mutable vector. It also provides the freezing function,
+; which is itself a unison builtin.
+(library (unison bytevector)
+  (export
+    freeze-bv!
+    ibytevector-drop
+    ibytevector-take
+    u8-list->ibytevector)
+
+  (import (chezscheme))
+
+  (define (freeze-bv! bs)
+    (($primitive $bytevector-set-immutable!) bs)
+    bs)
+
+  (define (ibytevector-drop n bs)
+    (let* ([l (bytevector-length bs)]
+           [k (max 0 (- l n))]
+           [br (make-bytevector k)])
+      (bytevector-copy! bs n br 0 k)
+      (freeze-bv! br)))
+
+  (define (ibytevector-take n bs)
+    (let* ([sz (min n (bytevector-length bs))]
+           [br (make-bytevector sz)])
+      (bytevector-copy! bs 0 br 0 sz)
+      (freeze-bv! br)))
+
+  (define (u8-list->ibytevector l) (freeze-bv! (u8-list->bytevector l))))
diff --git a/chez-libs/unison/cont.ss b/chez-libs/unison/cont.ss
new file mode 100644
index 000000000..7656c21f4
--- /dev/null
+++ b/chez-libs/unison/cont.ss
@@ -0,0 +1,47 @@
+; This library is intended to contain the implementation of
+; delimited continuations used in the semantics of abilities.
+;
+; Currently, it is a somewhat naive implementation based on call/cc.
+; This has known issues that seem to still be in force even though a
+; tweak has been applied that should fix certain space leaks. So, in
+; the future it will likely need to be rewritten using some
+; implementation specific machinery (possibly making use of
+; continuation attachments as in the Racket implementation).
+;
+; Also, although the API includes prompts, they are currently ignored
+; in `control` and `prompt` always uses the same prompt (0). This
+; means that nesting handlers will not work in general, since requests
+; will not be able to jump over an inner handler of unrelated
+; abilities. It should be sufficient for testing simple examples in
+; the mean time, though.
+(library (unison cont)
+  (export prompt control)
+
+  (import (chezscheme))
+
+  (define mk (lambda (x) (raise "fell off end")))
+
+  (define (prompt-impl h)
+    ((call/cc
+       (lambda (k)
+         (let ([ok mk])
+           (set! mk (lambda (x) (set! mk ok) (k x)))
+           ; (h 0) <-- prompt = 0
+           (mk (let ([v (h 0)]) (lambda () v))))))))
+
+  (define-syntax prompt
+    (syntax-rules ()
+      [(prompt p e ...)
+       (prompt-impl (lambda (p) e ...))]))
+
+  (define (control-impl h)
+    (call/cc
+      (lambda (k)
+        (let* ([g (lambda () (prompt p (h k)))])
+          (mk g)))))
+
+  (define-syntax control
+    (syntax-rules ()
+      [(control p k e ...)
+       (control-impl (lambda (k) e ...))])))
+
diff --git a/chez-libs/unison/core.ss b/chez-libs/unison/core.ss
new file mode 100644
index 000000000..474b37cc6
--- /dev/null
+++ b/chez-libs/unison/core.ss
@@ -0,0 +1,43 @@
+(library (unison core)
+  (export
+    identity
+
+    describe-value
+    decode-value)
+
+  (import (chezscheme))
+
+  (define (identity x) x)
+  
+  ; Recovers the original function name from the partial
+  ; application name.
+  (define (extract-name i)
+    (string->symbol ((i 'code) 'name)))
+
+  (define (describe-value x)
+    (let explain ([i (inspect/object x)])
+      (case (i 'type)
+        [(simple) (i 'value)]
+        [(variable) (explain (i 'ref))]
+        [(procedure)
+         (let explain-args ([j (- (i 'length) 1)] [args '()])
+           (if (< j 0)
+             (cons (extract-name i) args)
+             (explain-args
+               (- j 1)
+               (cons (explain (i 'ref j)) args))))])))
+
+  ; partial, data, cont, lit
+  (define (decode-value x)
+    (let reify ([i (inspect/object x)])
+      (case (i 'type)
+        [(simple) (list 3 (i 'value))]
+        [(variable) (reify (i 'ref))]
+        [(procedure)
+         (let reify-args ([j (- (i 'length) 1)] [args '()])
+           (if (< j 0)
+             (cons* 0 (extract-name i) args)
+             (reify-args
+               (- j 1)
+               (cons (reify (i 'ref j)) args))))])))
+  )
diff --git a/chez-libs/unison/primops.ss b/chez-libs/unison/primops.ss
new file mode 100644
index 000000000..9b7965ff3
--- /dev/null
+++ b/chez-libs/unison/primops.ss
@@ -0,0 +1,205 @@
+; This library implements pimitive operations that are used in
+; builtins. There are two different sorts of primitive operations, but
+; the difference is essentially irrelevant except for naming schemes.
+;
+; POps are part of a large enumeration of 'instructions' directly
+; implemented in the Haskell runtime. These are referred to using the
+; naming scheme `unison-POp-INST` where `INST` is the name of the
+; instruction, which is (at the time of this writing) 4 letters.
+;
+; FOps are 'foreign' functons, which are allowed to be declared more
+; flexibly in the Haskell runtime. Each such declaration associates a
+; builtin to a Haskell function. For these, the naming shceme is
+; `unison-FOp-NAME` where `NAME` is the name of the unison builtin
+; associated to the declaration.
+;
+; Both POps and FOps are always called with exactly the right number
+; of arguments, so they may be implemented as ordinary scheme
+; definitions with a fixed number of arguments. By implementing the
+; POp/FOp, you are expecting the associated unison function(s) to be
+; implemented by code generation from the wrappers in
+; Unison.Runtime.Builtin, so the POp/FOp implementation must
+; take/return arguments that match what is expected in those wrappers.
+
+(library (unison primops)
+  (export
+    ; unison-FOp-Bytes.decodeNat16be
+    ; unison-FOp-Bytes.decodeNat32be
+    ; unison-FOp-Bytes.decodeNat64be
+    unison-FOp-Char.toText
+    ; unison-FOp-Code.dependencies
+    ; unison-FOp-Code.serialize
+    unison-FOp-IO.closeFile.impl.v3
+    unison-FOp-IO.openFile.impl.v3
+    unison-FOp-IO.putBytes.impl.v3
+    ; unison-FOp-Text.fromUtf8.impl.v3
+    unison-FOp-Text.repeat
+    unison-FOp-Text.toUtf8
+    ; unison-FOp-Value.serialize
+    unison-FOp-IO.stdHandle
+
+    unison-FOp-ImmutableByteArray.copyTo!
+    unison-FOp-ImmutableByteArray.read8
+
+    unison-FOp-MutableByteArray.freeze!
+    unison-FOp-MutableByteArray.write8
+
+    unison-FOp-Scope.bytearray
+
+    unison-POp-ADDN
+    unison-POp-ANDN
+    unison-POp-BLDS
+    unison-POp-CATS
+    unison-POp-CATT
+    unison-POp-CMPU
+    unison-POp-COMN
+    unison-POp-CONS
+    unison-POp-DECI
+    unison-POp-DIVN
+    unison-POp-DRPB
+    unison-POp-DRPS
+    unison-POp-EQLN
+    unison-POp-EQLT
+    unison-POp-EQLU
+    unison-POp-EROR
+    unison-POp-FTOT
+    unison-POp-IDXB
+    unison-POp-IDXS
+    unison-POp-IORN
+    unison-POp-ITOT
+    unison-POp-LEQN
+    ; unison-POp-LKUP
+    unison-POp-MULN
+    unison-POp-NTOT
+    unison-POp-PAKT
+    unison-POp-SHLI
+    unison-POp-SHLN
+    unison-POp-SHRI
+    unison-POp-SHRN
+    unison-POp-SIZS
+    unison-POp-SIZT
+    unison-POp-SNOC
+    unison-POp-SUBN
+    unison-POp-TAKS
+    unison-POp-TAKT
+    unison-POp-TRCE
+    unison-POp-UPKT
+    unison-POp-VALU
+    unison-POp-VWLS
+
+    )
+
+  (import (chezscheme)
+          (unison core)
+          (unison string)
+          (unison bytevector))
+
+  ; Core implemented primops, upon which primops-in-unison can be built.
+  (define (unison-POp-ADDN m n) (fx+ m n))
+  (define (unison-POp-ANDN m n) (fxlogand m n))
+  (define unison-POp-BLDS list)
+  (define (unison-POp-CATS l r) (append l r))
+  (define (unison-POp-CATT l r) (istring-append l r))
+  (define (unison-POp-CMPU l r) (equal? l r))
+  (define (unison-POp-COMN n) (fxlognot n))
+  (define (unison-POp-CONS x xs) (cons x xs))
+  (define (unison-POp-DECI n) (+ n 1))
+  (define (unison-POp-DIVN m n) (fxdiv m n))
+  (define (unison-POp-DRPB n bs) (ibytevector-drop n bs))
+  (define (unison-POp-DRPS n l)
+    (let ([m (max 0 (min n (length l)))]) (list-tail l m)))
+  (define (unison-POp-DRPT n t) (istring-drop n t))
+  (define (unison-POp-EQLN m n) (if (fx= m n) 1 0))
+  (define (unison-POp-EQLT s t) (if (string=? s t) 1 0))
+  (define (unison-POp-EQLU x y) (equal? x y))
+  (define (unison-POp-EROR fnm x) (raise fnm))
+  (define (unison-POp-FTOT f) (number->istring f))
+  (define (unison-POp-IDXB n bs) (bytevector-u8-ref bs n))
+  (define (unison-POp-IDXS n l) (list-ref l n))
+  (define (unison-POp-IORN m n) (fxlogior m n))
+  (define (unison-POp-ITOT i) (signed-number->istring i))
+  (define (unison-POp-LEQN m n) (if (fx< m n) 1 0))
+  (define (unison-POp-MULN m n) (* m n))
+  (define (unison-POp-NTOT m) (number->istring m))
+  (define (unison-POp-PAKB l) (u8-list->ibytevector l))
+  (define (unison-POp-PAKT l) (list->istring l))
+  (define (unison-POp-SHLI i k) (fxarithmetic-shift-left i k))
+  (define (unison-POp-SHLN n k) (fxarithmetic-shift-left n k))
+  (define (unison-POp-SHRI i k) (fxarithmetic-shift-right i k))
+  (define (unison-POp-SHRN n k) (fxarithmetic-shift-right n k))
+  (define (unison-POp-SIZS l) (length l))
+  (define (unison-POp-SIZT t) (string-length t))
+  (define (unison-POp-SNOC xs x) (append xs (list x)))
+  (define (unison-POp-SUBN m n) (fx- m n))
+  (define (unison-POp-TAKS n s) (list-head s n))
+  (define (unison-POp-TAKT n t) (istring-take n t))
+  (define (unison-POp-TRCE x) (display (describe-value x)))
+  (define (unison-POp-UPKT t) (string->list t))
+  (define (unison-POp-VWLS l)
+    (if (null? l)
+      (list 0)
+      (list 1 (car l) (cdr l))))
+  (define (unison-POp-VALU c) (decode-value c))
+
+  (define (unison-FOp-IO.putBytes.impl.v3 p bs)
+    (begin
+      (put-bytevector p bs)
+      (flush-output-port p)
+      (list 1 #f)))
+
+  (define (unison-FOp-Char.toText c) (istring c))
+
+  (define stdin (standard-input-port))
+  (define stdout (standard-output-port))
+  (define stderr (standard-error-port))
+
+  (define (unison-FOp-IO.stdHandle n)
+    (case n
+      [(0) stdin]
+      [(1) stdout]
+      [(2) stderr]))
+
+  (define (unison-FOp-Text.toUtf8 s)
+    (string->bytevector s utf-8-transcoder))
+
+  (define (unison-FOp-IO.closeFile.impl.v3 h)
+    (close-input-port h))
+
+  (define (unison-FOp-IO.openFile.impl.v3 fn mode)
+    (case mode
+      [(0) (open-file-input-port fn)]
+      [(1) (open-file-output-port fn)]
+      [(2) (open-file-output-port fn 'no-truncate)]
+      [else (open-file-input/output-port fn)]))
+
+  (define (unison-FOp-Text.repeat n t) (istring-repeat n t))
+
+  (define (catch-array thunk)
+    (with-exception-handler
+      (lambda (e) (list 0 '() "array index out of boudns" e))
+      thunk))
+
+  (define (unison-FOp-ImmutableByteArray.copyTo! dst doff src soff n)
+    (catch-array
+      (lambda ()
+        (bytevector-copy! src soff dst doff n)
+        (list 1))))
+
+  (define (unison-FOp-ImmutableByteArray.read8 arr i)
+    (catch-array
+      (lambda ()
+        (list 1 (bytevector-u8-ref arr i)))))
+
+  (define (unison-FOp-MutableByteArray.freeze! arr)
+    (freeze-bv! arr))
+
+  (define (unison-FOp-MutableByteArray.write8 arr i b)
+    (catch-array
+      (lambda ()
+        (bytevector-u8-set! arr i b)
+        (list 1))))
+
+  (define (unison-FOp-Scope.bytearray n) (make-bytevector n))
+
+  )
+
diff --git a/chez-libs/unison/string.ss b/chez-libs/unison/string.ss
new file mode 100644
index 000000000..7df0502ad
--- /dev/null
+++ b/chez-libs/unison/string.ss
@@ -0,0 +1,60 @@
+; This library wraps some chez functionality to provide immutable
+; strings. There is a wrapper for making immutable strings in chez,
+; but it copies its input, so relying on that would involve every
+; string operation building a fresh mutable string, then making an
+; immutable copy. This library instead directly freezes the newly
+; created mutable strings.
+(library (unison string)
+  (export
+    istring
+    istring-append
+    istring-drop
+    istring-take
+    istring-repeat
+    list->istring
+    make-istring
+    number->istring
+    signed-number->istring
+    utf8-bytevector->istring
+    utf-8-transcoder)
+
+  (import (chezscheme))
+
+  (define (freeze-s! s)
+    (($primitive $string-set-immutable!) s)
+    s)
+
+  (define istring (lambda l (freeze-s! (apply string l))))
+
+  (define (make-istring n c) (freeze-s! (make-string n c)))
+
+  (define (istring-repeat n s)
+    (let* ([k (string-length s)]
+           [t (make-string (* k n))])
+      (let loop ([i 0])
+        (if (< i n)
+          (begin
+            (string-copy! s 0 t (* i k) k)
+            (loop (+ i 1)))
+          (freeze-s! t)))))
+
+  (define istring-append (lambda l (freeze-s! (apply string-append l))))
+
+  (define (istring-drop n s) (freeze-s! (substring s n (- (string-length s) n))))
+
+  (define (number->istring n) (freeze-s! (number->string n)))
+
+  (define (signed-number->istring n)
+    (freeze-s!
+      (if (>= n 0)
+        (string-append "+" (number->string n))
+        (number->string n))))
+
+  (define (list->istring l) (freeze-s! (list->string l)))
+
+  (define (istring-take n s) (freeze-s! (substring s 0 n)))
+
+  (define utf-8-transcoder (make-transcoder (utf-8-codec)))
+
+  (define (utf8-bytevector->istring bs)
+    (freeze-s! (bytevector->string bs utf-8-transcoder))))
diff --git a/parser-typechecker/package.yaml b/parser-typechecker/package.yaml
index 8c2949c36..50a2ebf34 100644
--- a/parser-typechecker/package.yaml
+++ b/parser-typechecker/package.yaml
@@ -41,6 +41,7 @@ dependencies:
   - errors
   - exceptions
   - extra
+  - filelock
   - filepath
   - fingertree
   - fsnotify
@@ -73,7 +74,6 @@ dependencies:
   - openapi3
   - optparse-applicative >= 0.16.1.0
   - pem
-  - prelude-extras
   - pretty-simple
   - primitive
   - process
@@ -91,7 +91,6 @@ dependencies:
   - servant-server
   - shellmet
   - stm
-  - strings
   - tagged
   - temporary
   - terminal-size
diff --git a/parser-typechecker/src/Unison/Codebase.hs b/parser-typechecker/src/Unison/Codebase.hs
index 481e9dbb4..36d9171d0 100644
--- a/parser-typechecker/src/Unison/Codebase.hs
+++ b/parser-typechecker/src/Unison/Codebase.hs
@@ -42,7 +42,7 @@ module Unison.Codebase
     SqliteCodebase.Operations.before,
     getShallowBranchAtPath,
     getShallowCausalAtPath,
-    getShallowCausalForHash,
+    Operations.expectCausalBranchByCausalHash,
     getShallowCausalFromRoot,
     getShallowRootBranch,
     getShallowRootCausal,
@@ -174,49 +174,53 @@ runTransaction Codebase {withConnection} action =
   withConnection \conn -> Sqlite.runTransaction conn action
 
 getShallowCausalFromRoot ::
-  MonadIO m =>
-  Codebase m v a ->
   -- Optional root branch, if Nothing use the codebase's root branch.
   Maybe V2.CausalHash ->
   Path.Path ->
-  m (V2Branch.CausalBranch m)
-getShallowCausalFromRoot codebase mayRootHash p = do
+  Sqlite.Transaction (V2Branch.CausalBranch Sqlite.Transaction)
+getShallowCausalFromRoot mayRootHash p = do
   rootCausal <- case mayRootHash of
-    Nothing -> getShallowRootCausal codebase
-    Just ch -> getShallowCausalForHash codebase ch
-  getShallowCausalAtPath codebase p (Just rootCausal)
+    Nothing -> getShallowRootCausal
+    Just ch -> Operations.expectCausalBranchByCausalHash ch
+  getShallowCausalAtPath p (Just rootCausal)
 
 -- | Get the shallow representation of the root branches without loading the children or
 -- history.
-getShallowRootBranch :: MonadIO m => Codebase m v a -> m (V2.Branch m)
-getShallowRootBranch codebase = do
-  getShallowRootCausal codebase >>= V2Causal.value
+getShallowRootBranch :: Sqlite.Transaction (V2.Branch Sqlite.Transaction)
+getShallowRootBranch = do
+  getShallowRootCausal >>= V2Causal.value
 
 -- | Get the shallow representation of the root branches without loading the children or
 -- history.
-getShallowRootCausal :: MonadIO m => Codebase m v a -> m (V2.CausalBranch m)
-getShallowRootCausal codebase = do
-  hash <- runTransaction codebase Operations.expectRootCausalHash
-  getShallowCausalForHash codebase hash
+getShallowRootCausal :: Sqlite.Transaction (V2.CausalBranch Sqlite.Transaction)
+getShallowRootCausal = do
+  hash <- Operations.expectRootCausalHash
+  Operations.expectCausalBranchByCausalHash hash
 
 -- | Recursively descend into causals following the given path,
 -- Use the root causal if none is provided.
-getShallowCausalAtPath :: MonadIO m => Codebase m v a -> Path -> Maybe (V2Branch.CausalBranch m) -> m (V2Branch.CausalBranch m)
-getShallowCausalAtPath codebase path mayCausal = do
-  causal <- whenNothing mayCausal (getShallowRootCausal codebase)
+getShallowCausalAtPath ::
+  Path ->
+  Maybe (V2Branch.CausalBranch Sqlite.Transaction) ->
+  Sqlite.Transaction (V2Branch.CausalBranch Sqlite.Transaction)
+getShallowCausalAtPath path mayCausal = do
+  causal <- whenNothing mayCausal getShallowRootCausal
   case path of
     Path.Empty -> pure causal
     (ns Path.:< p) -> do
       b <- V2Causal.value causal
       case (V2Branch.childAt (Cv.namesegment1to2 ns) b) of
         Nothing -> pure (Cv.causalbranch1to2 Branch.empty)
-        Just childCausal -> getShallowCausalAtPath codebase p (Just childCausal)
+        Just childCausal -> getShallowCausalAtPath p (Just childCausal)
 
 -- | Recursively descend into causals following the given path,
 -- Use the root causal if none is provided.
-getShallowBranchAtPath :: MonadIO m => Codebase m v a -> Path -> Maybe (V2Branch.Branch m) -> m (V2Branch.Branch m)
-getShallowBranchAtPath codebase path mayBranch = do
-  branch <- whenNothing mayBranch (getShallowRootCausal codebase >>= V2Causal.value)
+getShallowBranchAtPath ::
+  Path ->
+  Maybe (V2Branch.Branch Sqlite.Transaction) ->
+  Sqlite.Transaction (V2Branch.Branch Sqlite.Transaction)
+getShallowBranchAtPath path mayBranch = do
+  branch <- whenNothing mayBranch (getShallowRootCausal >>= V2Causal.value)
   case path of
     Path.Empty -> pure branch
     (ns Path.:< p) -> do
@@ -224,7 +228,7 @@ getShallowBranchAtPath codebase path mayBranch = do
         Nothing -> pure V2Branch.empty
         Just childCausal -> do
           childBranch <- V2Causal.value childCausal
-          getShallowBranchAtPath codebase p (Just childBranch)
+          getShallowBranchAtPath p (Just childBranch)
 
 -- | Get a branch from the codebase.
 getBranchForHash :: Monad m => Codebase m v a -> Branch.CausalHash -> m (Maybe (Branch m))
@@ -246,17 +250,15 @@ getBranchForHash codebase h =
 
 -- | Get the metadata attached to the term at a given path and name relative to the given branch.
 termMetadata ::
-  MonadIO m =>
-  Codebase m v a ->
   -- | The branch to search inside. Use the current root if 'Nothing'.
-  Maybe (V2Branch.Branch m) ->
+  Maybe (V2Branch.Branch Sqlite.Transaction) ->
   Split ->
   -- | There may be multiple terms at the given name. You can specify a Referent to
   -- disambiguate if desired.
   Maybe V2.Referent ->
-  m [Map V2Branch.MetadataValue V2Branch.MetadataType]
-termMetadata codebase mayBranch (path, nameSeg) ref = do
-  b <- getShallowBranchAtPath codebase path mayBranch
+  Sqlite.Transaction [Map V2Branch.MetadataValue V2Branch.MetadataType]
+termMetadata mayBranch (path, nameSeg) ref = do
+  b <- getShallowBranchAtPath path mayBranch
   V2Branch.termMetadata b (coerce @NameSegment.NameSegment nameSeg) ref
 
 -- | Get the lowest common ancestor of two branches, i.e. the most recent branch that is an ancestor of both branches.
@@ -266,7 +268,7 @@ lca code b1@(Branch.headHash -> h1) b2@(Branch.headHash -> h2) = do
     runTransaction code do
       eb1 <- SqliteCodebase.Operations.branchExists h1
       eb2 <- SqliteCodebase.Operations.branchExists h2
-      if eb1 && eb2 
+      if eb1 && eb2
         then do
           SqliteCodebase.Operations.sqlLca h1 h2 >>= \case
             Just h -> pure (getBranchForHash code h)
@@ -329,7 +331,7 @@ getTypeOfConstructor codebase (ConstructorReference r0 cid) =
 --     MaybeT (getWatch codebase RegularWatch ref)
 --       <|> MaybeT (getWatch codebase TestWatch ref))
 -- @
-lookupWatchCache :: (Monad m) => Codebase m v a -> Reference.Id -> m (Maybe (Term v a))
+lookupWatchCache :: Codebase m v a -> Reference.Id -> Sqlite.Transaction (Maybe (Term v a))
 lookupWatchCache codebase h = do
   m1 <- getWatch codebase WK.RegularWatch h
   maybe (getWatch codebase WK.TestWatch h) (pure . Just) m1
diff --git a/parser-typechecker/src/Unison/Codebase/Init.hs b/parser-typechecker/src/Unison/Codebase/Init.hs
index 81983fe11..f2de5de2a 100644
--- a/parser-typechecker/src/Unison/Codebase/Init.hs
+++ b/parser-typechecker/src/Unison/Codebase/Init.hs
@@ -6,6 +6,7 @@ module Unison.Codebase.Init
     DebugName,
     InitError (..),
     CodebaseInitOptions (..),
+    CodebaseLockOption (..),
     InitResult (..),
     SpecifiedCodebase (..),
     MigrationStrategy (..),
@@ -42,6 +43,10 @@ data SpecifiedCodebase
   = CreateWhenMissing CodebasePath
   | DontCreateWhenMissing CodebasePath
 
+data CodebaseLockOption
+  = DoLock
+  | DontLock
+
 data MigrationStrategy
   = -- | Perform a migration immediately if one is required.
     MigrateAutomatically
@@ -60,9 +65,9 @@ type DebugName = String
 
 data Init m v a = Init
   { -- | open an existing codebase
-    withOpenCodebase :: forall r. DebugName -> CodebasePath -> MigrationStrategy -> (Codebase m v a -> m r) -> m (Either OpenCodebaseError r),
+    withOpenCodebase :: forall r. DebugName -> CodebasePath -> CodebaseLockOption -> MigrationStrategy -> (Codebase m v a -> m r) -> m (Either OpenCodebaseError r),
     -- | create a new codebase
-    withCreatedCodebase :: forall r. DebugName -> CodebasePath -> (Codebase m v a -> m r) -> m (Either CreateCodebaseError r),
+    withCreatedCodebase :: forall r. DebugName -> CodebasePath -> CodebaseLockOption -> (Codebase m v a -> m r) -> m (Either CreateCodebaseError r),
     -- | given a codebase root, and given that the codebase root may have other junk in it,
     -- give the path to the "actual" files; e.g. what a forked transcript should clone.
     codebasePath :: CodebasePath -> CodebasePath
@@ -85,10 +90,11 @@ createCodebaseWithResult ::
   Init m v a ->
   DebugName ->
   CodebasePath ->
+  CodebaseLockOption ->
   (Codebase m v a -> m r) ->
   m (Either (CodebasePath, InitError) r)
-createCodebaseWithResult cbInit debugName dir action =
-  createCodebase cbInit debugName dir action <&> mapLeft \case
+createCodebaseWithResult cbInit debugName dir lockOption action =
+  createCodebase cbInit debugName dir lockOption action <&> mapLeft \case
     errorMessage -> (dir, (CouldntCreateCodebase errorMessage))
 
 withOpenOrCreateCodebase ::
@@ -96,12 +102,13 @@ withOpenOrCreateCodebase ::
   Init m v a ->
   DebugName ->
   CodebaseInitOptions ->
+  CodebaseLockOption ->
   MigrationStrategy ->
   ((InitResult, CodebasePath, Codebase m v a) -> m r) ->
   m (Either (CodebasePath, InitError) r)
-withOpenOrCreateCodebase cbInit debugName initOptions migrationStrategy action = do
+withOpenOrCreateCodebase cbInit debugName initOptions lockOption migrationStrategy action = do
   let resolvedPath = initOptionsToDir initOptions
-  result <- withOpenCodebase cbInit debugName resolvedPath migrationStrategy \codebase -> do
+  result <- withOpenCodebase cbInit debugName resolvedPath lockOption migrationStrategy \codebase -> do
     action (OpenedCodebase, resolvedPath, codebase)
   case result of
     Right r -> pure $ Right r
@@ -114,7 +121,7 @@ withOpenOrCreateCodebase cbInit debugName initOptions migrationStrategy action =
               (do pure (Left (homeDir, FoundV1Codebase)))
               ( do
                   -- Create V2 codebase if neither a V1 or V2 exists
-                  createCodebaseWithResult cbInit debugName homeDir (\codebase -> action (CreatedCodebase, homeDir, codebase))
+                  createCodebaseWithResult cbInit debugName homeDir lockOption (\codebase -> action (CreatedCodebase, homeDir, codebase))
               )
           Specified specified ->
             ifM
@@ -124,14 +131,15 @@ withOpenOrCreateCodebase cbInit debugName initOptions migrationStrategy action =
                 DontCreateWhenMissing dir ->
                   pure (Left (dir, (InitErrorOpen OpenCodebaseDoesntExist)))
                 CreateWhenMissing dir ->
-                  createCodebaseWithResult cbInit debugName dir (\codebase -> action (CreatedCodebase, dir, codebase))
+                  createCodebaseWithResult cbInit debugName dir lockOption (\codebase -> action (CreatedCodebase, dir, codebase))
       OpenCodebaseUnknownSchemaVersion {} -> pure (Left (resolvedPath, InitErrorOpen err))
       OpenCodebaseRequiresMigration {} -> pure (Left (resolvedPath, InitErrorOpen err))
+      OpenCodebaseFileLockFailed {} -> pure (Left (resolvedPath, InitErrorOpen err))
 
-createCodebase :: MonadIO m => Init m v a -> DebugName -> CodebasePath -> (Codebase m v a -> m r) -> m (Either Pretty r)
-createCodebase cbInit debugName path action = do
+createCodebase :: MonadIO m => Init m v a -> DebugName -> CodebasePath -> CodebaseLockOption -> (Codebase m v a -> m r) -> m (Either Pretty r)
+createCodebase cbInit debugName path lockOption action = do
   prettyDir <- P.string <$> canonicalizePath path
-  withCreatedCodebase cbInit debugName path action <&> mapLeft \case
+  withCreatedCodebase cbInit debugName path lockOption action <&> mapLeft \case
     CreateCodebaseAlreadyExists ->
       P.wrap $
         "It looks like there's already a codebase in: "
@@ -141,30 +149,31 @@ createCodebase cbInit debugName path action = do
 
 -- previously: initCodebaseOrExit :: CodebasePath -> m (m (), Codebase m v a)
 -- previously: FileCodebase.initCodebase :: CodebasePath -> m (m (), Codebase m v a)
-withNewUcmCodebaseOrExit :: MonadIO m => Init m Symbol Ann -> DebugName -> CodebasePath -> (Codebase m Symbol Ann -> m r) -> m r
-withNewUcmCodebaseOrExit cbInit debugName path action = do
+withNewUcmCodebaseOrExit :: MonadIO m => Init m Symbol Ann -> DebugName -> CodebasePath -> CodebaseLockOption -> (Codebase m Symbol Ann -> m r) -> m r
+withNewUcmCodebaseOrExit cbInit debugName path lockOption action = do
   prettyDir <- P.string <$> canonicalizePath path
   let codebaseSetup codebase = do
         liftIO $ PT.putPrettyLn' . P.wrap $ "Initializing a new codebase in: " <> prettyDir
         Codebase.runTransaction codebase (Codebase.installUcmDependencies codebase)
-  createCodebase cbInit debugName path (\cb -> codebaseSetup cb *> action cb)
+  createCodebase cbInit debugName path lockOption (\cb -> codebaseSetup cb *> action cb)
     >>= \case
       Left error -> liftIO $ PT.putPrettyLn' error >> exitFailure
       Right result -> pure result
 
 -- | try to init a codebase where none exists and then exit regardless (i.e. `ucm --codebase dir init`)
-initCodebaseAndExit :: MonadIO m => Init m Symbol Ann -> DebugName -> Maybe CodebasePath -> m ()
-initCodebaseAndExit i debugName mdir = do
+initCodebaseAndExit :: MonadIO m => Init m Symbol Ann -> DebugName -> Maybe CodebasePath -> CodebaseLockOption -> m ()
+initCodebaseAndExit i debugName mdir lockOption = do
   codebaseDir <- Codebase.getCodebaseDir mdir
-  withNewUcmCodebaseOrExit i debugName codebaseDir (const $ pure ())
+  withNewUcmCodebaseOrExit i debugName codebaseDir lockOption (const $ pure ())
 
 withTemporaryUcmCodebase ::
   MonadUnliftIO m =>
   Init m Symbol Ann ->
   DebugName ->
+  CodebaseLockOption ->
   ((CodebasePath, Codebase m Symbol Ann) -> m r) ->
   m r
-withTemporaryUcmCodebase cbInit debugName action = do
+withTemporaryUcmCodebase cbInit debugName lockOption action = do
   UnliftIO.withSystemTempDirectory debugName $ \tempDir -> do
-    withNewUcmCodebaseOrExit cbInit debugName tempDir $ \codebase -> do
+    withNewUcmCodebaseOrExit cbInit debugName tempDir lockOption $ \codebase -> do
       action (tempDir, codebase)
diff --git a/parser-typechecker/src/Unison/Codebase/Init/OpenCodebaseError.hs b/parser-typechecker/src/Unison/Codebase/Init/OpenCodebaseError.hs
index 573261f81..ea9d0a2f5 100644
--- a/parser-typechecker/src/Unison/Codebase/Init/OpenCodebaseError.hs
+++ b/parser-typechecker/src/Unison/Codebase/Init/OpenCodebaseError.hs
@@ -15,6 +15,7 @@ data OpenCodebaseError
     OpenCodebaseDoesntExist
   | -- | The codebase exists, but its schema version is unknown to this application.
     OpenCodebaseUnknownSchemaVersion SchemaVersion
+  | OpenCodebaseFileLockFailed
   | -- | The codebase exists, but requires a migration before it can be used.
     OpenCodebaseRequiresMigration
       -- current version
diff --git a/parser-typechecker/src/Unison/Codebase/RootBranchCache.hs b/parser-typechecker/src/Unison/Codebase/RootBranchCache.hs
new file mode 100644
index 000000000..6fed979dc
--- /dev/null
+++ b/parser-typechecker/src/Unison/Codebase/RootBranchCache.hs
@@ -0,0 +1,110 @@
+module Unison.Codebase.RootBranchCache
+  ( RootBranchCache,
+    newEmptyRootBranchCache,
+    newEmptyRootBranchCacheIO,
+    fetchRootBranch,
+    withLock,
+  )
+where
+
+import Control.Concurrent.STM (newTVarIO)
+import Control.Monad (join)
+import Control.Monad.IO.Class
+import Data.Coerce (coerce)
+import Unison.Codebase.Branch.Type (Branch)
+import qualified Unison.Sqlite as Sqlite
+import UnliftIO (MonadUnliftIO, mask, onException)
+import UnliftIO.STM
+  ( STM,
+    TVar,
+    atomically,
+    newTVar,
+    readTVar,
+    retrySTM,
+    writeTVar,
+  )
+
+data RootBranchCacheVal
+  = Empty
+  | -- | Another thread is updating the cache. If this value is observed
+    -- then the reader should wait until the value is Empty or Full. The
+    -- api exposed from this module guarantees that a thread cannot exit
+    -- and leave the cache in this state.
+    ConcurrentModification
+  | Full (Branch Sqlite.Transaction)
+
+-- This is isomorphic to @TMVar (Maybe (Branch Sqlite.Transaction))@
+newtype RootBranchCache = RootBranchCache (TVar RootBranchCacheVal)
+
+newEmptyRootBranchCacheIO :: MonadIO m => m RootBranchCache
+newEmptyRootBranchCacheIO = liftIO (coerce $ newTVarIO Empty)
+
+newEmptyRootBranchCache :: STM RootBranchCache
+newEmptyRootBranchCache = coerce (newTVar Empty)
+
+readRbc :: RootBranchCache -> STM RootBranchCacheVal
+readRbc (RootBranchCache v) = readTVar v
+
+writeRbc :: RootBranchCache -> RootBranchCacheVal -> STM ()
+writeRbc (RootBranchCache v) x = writeTVar v x
+
+-- | Read the root branch cache, wait if the cache is currently being
+-- updated
+readRootBranchCache :: RootBranchCache -> STM (Maybe (Branch Sqlite.Transaction))
+readRootBranchCache v =
+  readRbc v >>= \case
+    Empty -> pure Nothing
+    ConcurrentModification -> retrySTM
+    Full x -> pure (Just x)
+
+fetchRootBranch :: forall m. MonadUnliftIO m => RootBranchCache -> m (Branch Sqlite.Transaction) -> m (Branch Sqlite.Transaction)
+fetchRootBranch rbc getFromDb = mask \restore -> do
+  join (atomically (fetch restore))
+  where
+    fetch :: (forall x. m x -> m x) -> STM (m (Branch Sqlite.Transaction))
+    fetch restore = do
+      readRbc rbc >>= \case
+        Empty -> do
+          writeRbc rbc ConcurrentModification
+          pure do
+            rootBranch <- restore getFromDb `onException` atomically (writeRbc rbc Empty)
+            atomically (writeRbc rbc (Full rootBranch))
+            pure rootBranch
+        ConcurrentModification -> retrySTM
+        Full x -> pure (pure x)
+
+-- | Take a cache lock so that no other thread can read or write to
+-- the cache, perform an action with the cached value, then restore
+-- the cache to Empty or Full
+withLock ::
+  forall m r.
+  MonadUnliftIO m =>
+  RootBranchCache ->
+  -- | Perform an action with the cached value
+  ( -- restore masking state
+    (forall x. m x -> m x) ->
+    -- value retrieved from cache
+    Maybe (Branch Sqlite.Transaction) ->
+    m r
+  ) ->
+  -- | compute value to restore to the cache
+  (r -> Maybe (Branch Sqlite.Transaction)) ->
+  m r
+withLock v f g = mask \restore -> do
+  mbranch <- atomically (takeLock v)
+  r <- f restore mbranch `onException` releaseLock mbranch
+  releaseLock (g r)
+  pure r
+  where
+    releaseLock :: Maybe (Branch Sqlite.Transaction) -> m ()
+    releaseLock mbranch =
+      let !val = case mbranch of
+            Nothing -> Empty
+            Just x -> Full x
+       in atomically (writeRbc v val)
+
+takeLock :: RootBranchCache -> STM (Maybe (Branch Sqlite.Transaction))
+takeLock v = do
+  res <- readRootBranchCache v
+  writeRbc v ConcurrentModification
+  pure res
diff --git a/parser-typechecker/src/Unison/Codebase/SqliteCodebase.hs b/parser-typechecker/src/Unison/Codebase/SqliteCodebase.hs
index 8a74577df..5bbb38c07 100644
--- a/parser-typechecker/src/Unison/Codebase/SqliteCodebase.hs
+++ b/parser-typechecker/src/Unison/Codebase/SqliteCodebase.hs
@@ -9,6 +9,7 @@
 module Unison.Codebase.SqliteCodebase
   ( Unison.Codebase.SqliteCodebase.init,
     MigrationStrategy (..),
+    CodebaseLockOption (..),
   )
 where
 
@@ -23,9 +24,9 @@ import qualified Data.Set as Set
 import qualified Data.Text as Text
 import Data.Time (getCurrentTime)
 import qualified System.Console.ANSI as ANSI
+import System.FileLock (SharedExclusive (Exclusive), withTryFileLock)
 import qualified System.FilePath as FilePath
 import qualified System.FilePath.Posix as FilePath.Posix
-import qualified U.Codebase.Branch as V2Branch
 import U.Codebase.HashTags (BranchHash, CausalHash (CausalHash))
 import qualified U.Codebase.Reflog as Reflog
 import qualified U.Codebase.Sqlite.Operations as Ops
@@ -48,12 +49,13 @@ import Unison.Codebase.Editor.RemoteRepo
     writeToReadGit,
   )
 import qualified Unison.Codebase.GitError as GitError
-import Unison.Codebase.Init (MigrationStrategy (..))
+import Unison.Codebase.Init (CodebaseLockOption (..), MigrationStrategy (..))
 import qualified Unison.Codebase.Init as Codebase
 import qualified Unison.Codebase.Init.CreateCodebaseError as Codebase1
 import Unison.Codebase.Init.OpenCodebaseError (OpenCodebaseError (..))
 import qualified Unison.Codebase.Init.OpenCodebaseError as Codebase1
 import Unison.Codebase.Path (Path)
+import Unison.Codebase.RootBranchCache
 import Unison.Codebase.SqliteCodebase.Branch.Cache (newBranchCache)
 import qualified Unison.Codebase.SqliteCodebase.Branch.Dependencies as BD
 import qualified Unison.Codebase.SqliteCodebase.Conversions as Cv
@@ -106,13 +108,14 @@ withOpenOrCreateCodebase ::
   Codebase.DebugName ->
   CodebasePath ->
   LocalOrRemote ->
+  CodebaseLockOption ->
   MigrationStrategy ->
   ((CodebaseStatus, Codebase m Symbol Ann) -> m r) ->
   m (Either Codebase1.OpenCodebaseError r)
-withOpenOrCreateCodebase debugName codebasePath localOrRemote migrationStrategy action = do
-  createCodebaseOrError debugName codebasePath (action' CreatedCodebase) >>= \case
+withOpenOrCreateCodebase debugName codebasePath localOrRemote lockOption migrationStrategy action = do
+  createCodebaseOrError debugName codebasePath lockOption (action' CreatedCodebase) >>= \case
     Left (Codebase1.CreateCodebaseAlreadyExists) -> do
-      sqliteCodebase debugName codebasePath localOrRemote migrationStrategy (action' ExistingCodebase)
+      sqliteCodebase debugName codebasePath localOrRemote lockOption migrationStrategy (action' ExistingCodebase)
     Right r -> pure (Right r)
   where
     action' openOrCreate codebase = action (openOrCreate, codebase)
@@ -122,9 +125,10 @@ createCodebaseOrError ::
   (MonadUnliftIO m) =>
   Codebase.DebugName ->
   CodebasePath ->
+  CodebaseLockOption ->
   (Codebase m Symbol Ann -> m r) ->
   m (Either Codebase1.CreateCodebaseError r)
-createCodebaseOrError debugName path action = do
+createCodebaseOrError debugName path lockOption action = do
   ifM
     (doesFileExist $ makeCodebasePath path)
     (pure $ Left Codebase1.CreateCodebaseAlreadyExists)
@@ -136,7 +140,7 @@ createCodebaseOrError debugName path action = do
           Q.createSchema
           void . Ops.saveRootBranch v2HashHandle $ Cv.causalbranch1to2 Branch.empty
 
-      sqliteCodebase debugName path Local DontMigrate action >>= \case
+      sqliteCodebase debugName path Local lockOption DontMigrate action >>= \case
         Left schemaVersion -> error ("Failed to open codebase with schema version: " ++ show schemaVersion ++ ", which is unexpected because I just created this codebase.")
         Right result -> pure (Right result)
 
@@ -147,13 +151,14 @@ withCodebaseOrError ::
   (MonadUnliftIO m) =>
   Codebase.DebugName ->
   CodebasePath ->
+  CodebaseLockOption ->
   MigrationStrategy ->
   (Codebase m Symbol Ann -> m r) ->
   m (Either Codebase1.OpenCodebaseError r)
-withCodebaseOrError debugName dir migrationStrategy action = do
+withCodebaseOrError debugName dir lockOption migrationStrategy action = do
   doesFileExist (makeCodebasePath dir) >>= \case
     False -> pure (Left Codebase1.OpenCodebaseDoesntExist)
-    True -> sqliteCodebase debugName dir Local migrationStrategy action
+    True -> sqliteCodebase debugName dir Local lockOption migrationStrategy action
 
 initSchemaIfNotExist :: MonadIO m => FilePath -> m ()
 initSchemaIfNotExist path = liftIO do
@@ -187,11 +192,12 @@ sqliteCodebase ::
   CodebasePath ->
   -- | When local, back up the existing codebase before migrating, in case there's a catastrophic bug in the migration.
   LocalOrRemote ->
+  CodebaseLockOption ->
   MigrationStrategy ->
   (Codebase m Symbol Ann -> m r) ->
   m (Either Codebase1.OpenCodebaseError r)
-sqliteCodebase debugName root localOrRemote migrationStrategy action = do
-  rootBranchCache <- newTVarIO Nothing
+sqliteCodebase debugName root localOrRemote lockOption migrationStrategy action = handleLockOption do
+  rootBranchCache <- newEmptyRootBranchCacheIO
   branchCache <- newBranchCache
   getDeclType <- CodebaseOps.makeCachedTransaction 2048 CodebaseOps.getDeclType
   -- The v1 codebase interface has operations to read and write individual definitions
@@ -264,25 +270,36 @@ sqliteCodebase debugName root localOrRemote migrationStrategy action = do
             putTypeDeclarationComponent =
               CodebaseOps.putTypeDeclarationComponent termBuffer declBuffer
 
-            getShallowCausalForHash :: MonadIO m => V2Branch.CausalHash -> m (V2Branch.CausalBranch m)
-            getShallowCausalForHash bh =
-              V2Branch.hoistCausalBranch runTransaction <$> runTransaction (Ops.expectCausalBranchByCausalHash bh)
+            getRootBranch :: m (Branch m)
+            getRootBranch =
+              Branch.transform runTransaction
+                <$> fetchRootBranch
+                  rootBranchCache
+                  (runTransaction (CodebaseOps.uncachedLoadRootBranch branchCache getDeclType))
 
-            getRootBranch :: TVar (Maybe (Sqlite.DataVersion, Branch Sqlite.Transaction)) -> m (Branch m)
-            getRootBranch rootBranchCache =
-              Branch.transform runTransaction <$> runTransaction (CodebaseOps.getRootBranch branchCache getDeclType rootBranchCache)
-
-            putRootBranch :: TVar (Maybe (Sqlite.DataVersion, Branch Sqlite.Transaction)) -> Text -> Branch m -> m ()
-            putRootBranch rootBranchCache reason branch1 = do
+            putRootBranch :: Text -> Branch m -> m ()
+            putRootBranch reason branch1 = do
               now <- liftIO getCurrentTime
               withRunInIO \runInIO -> do
-                runInIO do
-                  runTransaction do
-                    let emptyCausalHash = Cv.causalHash1to2 $ Branch.headHash Branch.empty
-                    fromRootCausalHash <- fromMaybe emptyCausalHash <$> Ops.loadRootCausalHash
-                    let toRootCausalHash = Cv.causalHash1to2 $ Branch.headHash branch1
-                    CodebaseOps.putRootBranch rootBranchCache (Branch.transform (Sqlite.unsafeIO . runInIO) branch1)
-                    Ops.appendReflog (Reflog.Entry {time = now, fromRootCausalHash, toRootCausalHash, reason})
+                -- this is naughty, the type says Transaction but it
+                -- won't run automatically with whatever Transaction
+                -- it is composed into unless the enclosing
+                -- Transaction is applied to the same db connection.
+                let branch1Trans = Branch.transform (Sqlite.unsafeIO . runInIO) branch1
+                    putRootBranchTrans :: Sqlite.Transaction () = do
+                      let emptyCausalHash = Cv.causalHash1to2 (Branch.headHash Branch.empty)
+                      fromRootCausalHash <- fromMaybe emptyCausalHash <$> Ops.loadRootCausalHash
+                      let toRootCausalHash = Cv.causalHash1to2 (Branch.headHash branch1)
+                      CodebaseOps.putRootBranch branch1Trans
+                      Ops.appendReflog (Reflog.Entry {time = now, fromRootCausalHash, toRootCausalHash, reason})
+
+                -- We need to update the database and the cached
+                -- value. We want to keep these in sync, so we take
+                -- the cache lock while updating sqlite.
+                withLock
+                  rootBranchCache
+                  (\restore _ -> restore $ runInIO $ runTransaction putRootBranchTrans)
+                  (\_ -> Just branch1Trans)
 
             -- if this blows up on cromulent hashes, then switch from `hashToHashId`
             -- to one that returns Maybe.
@@ -314,9 +331,9 @@ sqliteCodebase debugName root localOrRemote migrationStrategy action = do
                     Sqlite.runWriteTransaction destConn \runDest -> do
                       syncInternal (syncProgress progressStateRef) runSrc runDest b
 
-            getWatch :: UF.WatchKind -> Reference.Id -> m (Maybe (Term Symbol Ann))
-            getWatch k r =
-              runTransaction (CodebaseOps.getWatch getDeclType k r)
+            getWatch :: UF.WatchKind -> Reference.Id -> Sqlite.Transaction (Maybe (Term Symbol Ann))
+            getWatch =
+              CodebaseOps.getWatch getDeclType
 
             termsOfTypeImpl :: Reference -> m (Set Referent.Id)
             termsOfTypeImpl r =
@@ -348,9 +365,8 @@ sqliteCodebase debugName root localOrRemote migrationStrategy action = do
                   putTypeDeclaration,
                   putTypeDeclarationComponent,
                   getTermComponentWithTypes,
-                  getRootBranch = getRootBranch rootBranchCache,
-                  putRootBranch = putRootBranch rootBranchCache,
-                  getShallowCausalForHash,
+                  getRootBranch,
+                  putRootBranch,
                   getBranchForHashImpl = getBranchForHash,
                   putBranch,
                   syncFromDirectory,
@@ -375,6 +391,13 @@ sqliteCodebase debugName root localOrRemote migrationStrategy action = do
     runTransaction action =
       withConn \conn -> Sqlite.runTransaction conn action
 
+    handleLockOption ma = case lockOption of
+      DontLock -> ma
+      DoLock -> withRunInIO \runInIO ->
+        withTryFileLock (lockfilePath root) Exclusive (\_flock -> runInIO ma) <&> \case
+          Nothing -> Left OpenCodebaseFileLockFailed
+          Just x -> x
+
 syncInternal ::
   forall m.
   MonadUnliftIO m =>
@@ -567,7 +590,7 @@ viewRemoteBranch' ReadGitRemoteNamespace {repo, sch, path} gitBranchBehavior act
           then throwIO (C.GitSqliteCodebaseError (GitError.NoDatabaseFile repo remotePath))
           else throwIO exception
 
-      result <- sqliteCodebase "viewRemoteBranch.gitCache" remotePath Remote MigrateAfterPrompt \codebase -> do
+      result <- sqliteCodebase "viewRemoteBranch.gitCache" remotePath Remote DoLock MigrateAfterPrompt \codebase -> do
         -- try to load the requested branch from it
         branch <- time "Git fetch (sch)" $ case sch of
           -- no sub-branch was specified, so use the root.
@@ -617,7 +640,7 @@ pushGitBranch srcConn repo (PushGitBranchOpts behavior _syncMode) action = Unlif
   -- set up the cache dir
   throwEitherMWith C.GitProtocolError . withRepo readRepo Git.CreateBranchIfMissing $ \pushStaging -> do
     newBranchOrErr <- throwEitherMWith (C.GitSqliteCodebaseError . C.gitErrorFromOpenCodebaseError (Git.gitDirToPath pushStaging) readRepo)
-      . withOpenOrCreateCodebase "push.dest" (Git.gitDirToPath pushStaging) Remote MigrateAfterPrompt
+      . withOpenOrCreateCodebase "push.dest" (Git.gitDirToPath pushStaging) Remote DoLock MigrateAfterPrompt
       $ \(codebaseStatus, destCodebase) -> do
         currentRootBranch <-
           Codebase1.runTransaction destCodebase CodebaseOps.getRootBranchExists >>= \case
@@ -696,9 +719,10 @@ pushGitBranch srcConn repo (PushGitBranchOpts behavior _syncMode) action = Unlif
         -- so we have to convert our expected path to test.
         posixCodebasePath =
           FilePath.Posix.joinPath (FilePath.splitDirectories codebasePath)
+        posixLockfilePath = FilePath.replaceExtension posixCodebasePath "lockfile"
         statusLines = Text.unpack <$> Text.lines status
         t = dropWhile Char.isSpace
-        okLine (t -> '?' : '?' : (t -> p)) | p == posixCodebasePath = True
+        okLine (t -> '?' : '?' : (t -> p)) | p == posixCodebasePath || p == posixLockfilePath = True
         okLine (t -> 'M' : (t -> p)) | p == posixCodebasePath = True
         okLine line = isWalDelete line || isShmDelete line
         isWalDelete (t -> 'D' : (t -> p)) | p == posixCodebasePath ++ "-wal" = True
diff --git a/parser-typechecker/src/Unison/Codebase/SqliteCodebase/GitError.hs b/parser-typechecker/src/Unison/Codebase/SqliteCodebase/GitError.hs
index 92b170407..f60581214 100644
--- a/parser-typechecker/src/Unison/Codebase/SqliteCodebase/GitError.hs
+++ b/parser-typechecker/src/Unison/Codebase/SqliteCodebase/GitError.hs
@@ -6,6 +6,7 @@ import Unison.CodebasePath (CodebasePath)
 
 data GitSqliteCodebaseError
   = GitCouldntParseRootBranchHash ReadGitRepo String
+  | CodebaseFileLockFailed
   | NoDatabaseFile ReadGitRepo CodebasePath
   | UnrecognizedSchemaVersion ReadGitRepo CodebasePath SchemaVersion
   | CodebaseRequiresMigration SchemaVersion SchemaVersion
diff --git a/parser-typechecker/src/Unison/Codebase/SqliteCodebase/Operations.hs b/parser-typechecker/src/Unison/Codebase/SqliteCodebase/Operations.hs
index 4bb1ffd9f..c49d90bb8 100644
--- a/parser-typechecker/src/Unison/Codebase/SqliteCodebase/Operations.hs
+++ b/parser-typechecker/src/Unison/Codebase/SqliteCodebase/Operations.hs
@@ -8,14 +8,13 @@
 module Unison.Codebase.SqliteCodebase.Operations where
 
 import Control.Lens (ifor)
-import Data.Bifunctor (second)
-import Data.Maybe (fromJust)
 import Data.Bitraversable (bitraverse)
 import Data.Either.Extra ()
 import qualified Data.List as List
 import qualified Data.List.NonEmpty as NEList
 import Data.List.NonEmpty.Extra (NonEmpty ((:|)), maximum1)
 import qualified Data.Map as Map
+import Data.Maybe (fromJust)
 import qualified Data.Set as Set
 import qualified Data.Text as Text
 import qualified U.Codebase.Branch as V2Branch
@@ -377,36 +376,6 @@ tryFlushDeclBuffer termBuffer declBuffer =
           h
    in loop
 
-getRootBranch ::
-  -- | A 'getDeclType'-like lookup, possibly backed by a cache.
-  BranchCache Sqlite.Transaction ->
-  (C.Reference.Reference -> Transaction CT.ConstructorType) ->
-  TVar (Maybe (Sqlite.DataVersion, Branch Transaction)) ->
-  Transaction (Branch Transaction)
-getRootBranch branchCache doGetDeclType rootBranchCache =
-  Sqlite.unsafeIO (readTVarIO rootBranchCache) >>= \case
-    Nothing -> forceReload
-    Just (v, b) -> do
-      -- check to see if root namespace hash has been externally modified
-      -- and reload it if necessary
-      v' <- Sqlite.getDataVersion
-      if v == v'
-        then pure b
-        else do
-          newRootHash <- Ops.expectRootCausalHash
-          if Branch.headHash b == Cv.causalHash2to1 newRootHash
-            then pure b
-            else do
-              traceM $ "database was externally modified (" ++ show v ++ " -> " ++ show v' ++ ")"
-              forceReload
-  where
-    forceReload :: Transaction (Branch Transaction)
-    forceReload = do
-      branch1 <- uncachedLoadRootBranch branchCache doGetDeclType
-      ver <- Sqlite.getDataVersion
-      Sqlite.unsafeIO (atomically (writeTVar rootBranchCache (Just (ver, branch1))))
-      pure branch1
-
 uncachedLoadRootBranch ::
   BranchCache Sqlite.Transaction ->
   (C.Reference.Reference -> Sqlite.Transaction CT.ConstructorType) ->
@@ -420,12 +389,11 @@ getRootBranchExists :: Transaction Bool
 getRootBranchExists =
   isJust <$> Ops.loadRootCausalHash
 
-putRootBranch :: TVar (Maybe (Sqlite.DataVersion, Branch Transaction)) -> Branch Transaction -> Transaction ()
-putRootBranch rootBranchCache branch1 = do
+putRootBranch :: Branch Transaction -> Transaction ()
+putRootBranch branch1 = do
   -- todo: check to see if root namespace hash has been externally modified
   -- and do something (merge?) it if necessary. But for now, we just overwrite it.
   void (Ops.saveRootBranch v2HashHandle (Cv.causalbranch1to2 branch1))
-  Sqlite.unsafeIO (atomically $ modifyTVar' rootBranchCache (fmap . second $ const branch1))
 
 -- if this blows up on cromulent hashes, then switch from `hashToHashId`
 -- to one that returns Maybe.
diff --git a/parser-typechecker/src/Unison/Codebase/SqliteCodebase/Paths.hs b/parser-typechecker/src/Unison/Codebase/SqliteCodebase/Paths.hs
index 3ae689d48..d0e6871ef 100644
--- a/parser-typechecker/src/Unison/Codebase/SqliteCodebase/Paths.hs
+++ b/parser-typechecker/src/Unison/Codebase/SqliteCodebase/Paths.hs
@@ -3,6 +3,7 @@ module Unison.Codebase.SqliteCodebase.Paths
     makeCodebasePath,
     makeCodebaseDirPath,
     backupCodebasePath,
+    lockfilePath,
   )
 where
 
@@ -18,6 +19,9 @@ codebasePath = ".unison" </> "v2" </> "unison.sqlite3"
 makeCodebasePath :: CodebasePath -> FilePath
 makeCodebasePath root = makeCodebaseDirPath root </> "unison.sqlite3"
 
+lockfilePath :: CodebasePath -> FilePath
+lockfilePath root = makeCodebaseDirPath root </> "unison.lockfile"
+
 -- | Makes a path to the location where sqlite files are stored within a codebase path.
 makeCodebaseDirPath :: CodebasePath -> FilePath
 makeCodebaseDirPath root = root </> ".unison" </> "v2"
diff --git a/parser-typechecker/src/Unison/Codebase/Type.hs b/parser-typechecker/src/Unison/Codebase/Type.hs
index d37644afb..c9844f037 100644
--- a/parser-typechecker/src/Unison/Codebase/Type.hs
+++ b/parser-typechecker/src/Unison/Codebase/Type.hs
@@ -13,7 +13,6 @@ module Unison.Codebase.Type
   )
 where
 
-import qualified U.Codebase.Branch as V2
 import U.Codebase.HashTags (BranchHash)
 import qualified U.Codebase.Reference as V2
 import Unison.Codebase.Branch (Branch)
@@ -82,7 +81,6 @@ data Codebase m v a = Codebase
       Text -> -- Reason for the change, will be recorded in the reflog
       Branch m ->
       m (),
-    getShallowCausalForHash :: V2.CausalHash -> m (V2.CausalBranch m),
     getBranchForHashImpl :: Branch.CausalHash -> m (Maybe (Branch m)),
     -- | Put a branch into the codebase, which includes its children, its patches, and the branch itself, if they don't
     -- already exist.
@@ -97,7 +95,7 @@ data Codebase m v a = Codebase
     -- | Push the given branch to the given repo, and optionally set it as the root branch.
     pushGitBranch :: forall e. WriteGitRepo -> PushGitBranchOpts -> (Branch m -> m (Either e (Branch m))) -> m (Either GitError (Either e (Branch m))),
     -- | @getWatch k r@ returns watch result @t@ that was previously put by @putWatch k r t@.
-    getWatch :: WK.WatchKind -> Reference.Id -> m (Maybe (Term v a)),
+    getWatch :: WK.WatchKind -> Reference.Id -> Sqlite.Transaction (Maybe (Term v a)),
     -- | Get the set of user-defined terms-or-constructors that have the given type.
     termsOfTypeImpl :: Reference -> m (Set Referent.Id),
     -- | Get the set of user-defined terms-or-constructors mention the given type anywhere in their signature.
@@ -159,3 +157,4 @@ gitErrorFromOpenCodebaseError path repo = \case
     UnrecognizedSchemaVersion repo path (fromIntegral v)
   OpenCodebaseRequiresMigration fromSv toSv ->
     CodebaseRequiresMigration fromSv toSv
+  OpenCodebaseFileLockFailed -> CodebaseFileLockFailed
diff --git a/parser-typechecker/src/Unison/PrettyPrintEnv/Names.hs b/parser-typechecker/src/Unison/PrettyPrintEnv/Names.hs
index 90f600eee..e213ecfad 100644
--- a/parser-typechecker/src/Unison/PrettyPrintEnv/Names.hs
+++ b/parser-typechecker/src/Unison/PrettyPrintEnv/Names.hs
@@ -32,13 +32,13 @@ fromNames len names = PrettyPrintEnv terms' types'
 --
 -- 1. Prefer Relative Names to Absolute Names
 -- 2. Prefer names that aren't hash qualified to those that are
--- 3. Prefer names which have fewer segments in their suffixified form (if applicable)
--- 4. Prefer names which have fewer segments in their fully-qualified form
+-- 3. Prefer names which have fewer segments in their fully-qualified form
+-- 4. Prefer names which have fewer segments in their suffixified form (if applicable)
 prioritize :: [(HQ'.HashQualified Name, HQ'.HashQualified Name)] -> [(HQ'.HashQualified Name, HQ'.HashQualified Name)]
 prioritize =
   sortOn \case
-    (fqn, HQ'.NameOnly name) -> (Name.isAbsolute name, Nothing, Name.countSegments name, Name.countSegments (HQ'.toName fqn))
-    (fqn, HQ'.HashQualified name hash) -> (Name.isAbsolute name, Just hash, Name.countSegments name, Name.countSegments (HQ'.toName fqn))
+    (fqn, HQ'.NameOnly name) -> (Name.isAbsolute name, Nothing, Name.countSegments (HQ'.toName fqn), Name.countSegments name)
+    (fqn, HQ'.HashQualified name hash) -> (Name.isAbsolute name, Just hash, Name.countSegments (HQ'.toName fqn), Name.countSegments name)
 
 fromSuffixNames :: Int -> NamesWithHistory -> PrettyPrintEnv
 fromSuffixNames len names = PrettyPrintEnv terms' types'
diff --git a/parser-typechecker/src/Unison/Runtime/ANF.hs b/parser-typechecker/src/Unison/Runtime/ANF.hs
index 828782865..d0c0357f8 100644
--- a/parser-typechecker/src/Unison/Runtime/ANF.hs
+++ b/parser-typechecker/src/Unison/Runtime/ANF.hs
@@ -79,6 +79,7 @@ import Data.Bits (shiftL, shiftR, (.&.), (.|.))
 import Data.Functor.Compose (Compose (..))
 import Data.List hiding (and, or)
 import qualified Data.Map as Map
+import qualified Data.Primitive as PA
 import qualified Data.Set as Set
 import qualified Data.Text as Data.Text
 import GHC.Stack (CallStack, callStack)
@@ -226,12 +227,13 @@ newtype Prefix v x = Pfx (Map v [v]) deriving (Show)
 
 instance Functor (Prefix v) where
   fmap _ (Pfx m) = Pfx m
+
 instance Ord v => Applicative (Prefix v) where
   pure _ = Pfx Map.empty
   Pfx ml <*> Pfx mr = Pfx $ Map.unionWith common ml mr
 
 common :: Eq v => [v] -> [v] -> [v]
-common (u:us) (v:vs)
+common (u : us) (v : vs)
   | u == v = u : common us vs
 common _ _ = []
 
@@ -264,13 +266,13 @@ dropPrefix v n = ABT.visitPure rw
       | v == u = Just (apps' (var (ABT.annotation f) u) (drop n as))
     rw _ = Nothing
 
-dropPrefixes
-  :: Ord v => Semigroup a => Map v Int -> Term v a -> Term v a
+dropPrefixes ::
+  Ord v => Semigroup a => Map v Int -> Term v a -> Term v a
 dropPrefixes m = ABT.visitPure rw
   where
     rw (Apps' f@(Var' u) as)
       | Just n <- Map.lookup u m =
-        Just (apps' (var (ABT.annotation f) u) (drop n as))
+          Just (apps' (var (ABT.annotation f) u) (drop n as))
     rw _ = Nothing
 
 -- Performs opposite transformations to those in enclose. Named after
@@ -279,27 +281,28 @@ beta :: Var v => Monoid a => (Term v a -> Term v a) -> Term v a -> Maybe (Term v
 beta rec (LetRecNamedTop' top (fmap (fmap rec) -> vbs) (rec -> bd)) =
   Just $ letRec' top lvbs lbd
   where
-  -- Avoid completely reducing a lambda expression, because recursive
-  -- lets must be guarded.
-  args (v, LamsNamed' vs Ann'{}) = (v, vs)
-  args (v, LamsNamed' vs _) = (v, init vs)
-  args (v, _) = (v, [])
+    -- Avoid completely reducing a lambda expression, because recursive
+    -- lets must be guarded.
+    args (v, LamsNamed' vs Ann' {}) = (v, vs)
+    args (v, LamsNamed' vs _) = (v, init vs)
+    args (v, _) = (v, [])
 
-  Pfx m0 = traverse_ (prefix . snd) vbs *> prefix bd
+    Pfx m0 = traverse_ (prefix . snd) vbs *> prefix bd
 
-  f ls rs = case common ls rs of
-    [] -> Nothing
-    vs -> Just vs
+    f ls rs = case common ls rs of
+      [] -> Nothing
+      vs -> Just vs
 
-  m = Map.map length $ Map.differenceWith f (Map.fromList $ map args vbs) m0
-  lvbs = vbs <&> \(v, b0) -> (,) v $ case b0 of
-    LamsNamed' vs b | Just n <- Map.lookup v m ->
-      lam' (ABT.annotation b0) (drop n vs) (dropPrefixes m b)
-    -- shouldn't happen
-    b -> dropPrefixes m b
-
-  lbd = dropPrefixes m bd
+    m = Map.map length $ Map.differenceWith f (Map.fromList $ map args vbs) m0
+    lvbs =
+      vbs <&> \(v, b0) -> (,) v $ case b0 of
+        LamsNamed' vs b
+          | Just n <- Map.lookup v m ->
+              lam' (ABT.annotation b0) (drop n vs) (dropPrefixes m b)
+        -- shouldn't happen
+        b -> dropPrefixes m b
 
+    lbd = dropPrefixes m bd
 beta rec (Let1NamedTop' top v l@(LamsNamed' vs bd) (rec -> e))
   | n > 0 = Just $ let1' top [(v, lamb)] (dropPrefix v n e)
   | otherwise = Nothing
@@ -310,17 +313,18 @@ beta rec (Let1NamedTop' top v l@(LamsNamed' vs bd) (rec -> e))
     -- Enclosing doesn't create let-bound lambdas, so we
     -- should never reduce a lambda to a non-lambda, as that
     -- could affect evaluation order.
-    m | Ann' _ _ <- bd = length vs
+    m
+      | Ann' _ _ <- bd = length vs
       | otherwise = length vs - 1
     n = min m . length $ appPfx (prefix e) v vs
-
 beta rec (Apps' l@(LamsNamed' vs body) as)
-  | n <- matchVars 0 vs as
-  , n > 0 = Just $ apps' (lam' al (drop n vs) (rec body)) (drop n as)
+  | n <- matchVars 0 vs as,
+    n > 0 =
+      Just $ apps' (lam' al (drop n vs) (rec body)) (drop n as)
   | otherwise = Nothing
   where
     al = ABT.annotation l
-    matchVars !n (u:us) (Var' v : as) | u == v = matchVars (1+n) us as
+    matchVars !n (u : us) (Var' v : as) | u == v = matchVars (1 + n) us as
     matchVars n _ _ = n
 beta _ _ = Nothing
 
@@ -1261,6 +1265,7 @@ data BLit
   | Bytes Bytes
   | Quote Value
   | Code (SuperGroup Symbol)
+  | BArr PA.ByteArray
   deriving (Show)
 
 groupVars :: ANFM v (Set v)
diff --git a/parser-typechecker/src/Unison/Runtime/ANF/Serialize.hs b/parser-typechecker/src/Unison/Runtime/ANF/Serialize.hs
index 9a9392db4..201335dcb 100644
--- a/parser-typechecker/src/Unison/Runtime/ANF/Serialize.hs
+++ b/parser-typechecker/src/Unison/Runtime/ANF/Serialize.hs
@@ -70,7 +70,15 @@ data LtTag
   | LMT
   | LYT
 
-data BLTag = TextT | ListT | TmLinkT | TyLinkT | BytesT | QuoteT | CodeT
+data BLTag
+  = TextT
+  | ListT
+  | TmLinkT
+  | TyLinkT
+  | BytesT
+  | QuoteT
+  | CodeT
+  | BArrT
 
 data VaTag = PartialT | DataT | ContT | BLitT
 
@@ -170,6 +178,7 @@ instance Tag BLTag where
     BytesT -> 4
     QuoteT -> 5
     CodeT -> 6
+    BArrT -> 7
 
   word2tag = \case
     0 -> pure TextT
@@ -179,6 +188,7 @@ instance Tag BLTag where
     4 -> pure BytesT
     5 -> pure QuoteT
     6 -> pure CodeT
+    7 -> pure BArrT
     t -> unknownTag "BLTag" t
 
 instance Tag VaTag where
@@ -579,6 +589,7 @@ putBLit (TyLink r) = putTag TyLinkT *> putReference r
 putBLit (Bytes b) = putTag BytesT *> putBytes b
 putBLit (Quote v) = putTag QuoteT *> putValue v
 putBLit (Code g) = putTag CodeT *> putGroup mempty g
+putBLit (BArr a) = putTag BArrT *> putByteArray a
 
 getBLit :: MonadGet m => Version -> m BLit
 getBLit v =
@@ -590,6 +601,7 @@ getBLit v =
     BytesT -> Bytes <$> getBytes
     QuoteT -> Quote <$> getValue v
     CodeT -> Code <$> getGroup
+    BArrT -> BArr <$> getByteArray
 
 putRefs :: MonadPut m => [Reference] -> m ()
 putRefs rs = putFoldable putReference rs
@@ -775,7 +787,8 @@ deserializeValue bs = runGetS (getVersion >>= getValue) bs
   where
     getVersion =
       getWord32be >>= \case
-        n | n < 1 -> fail $ "deserializeValue: unknown version: " ++ show n
+        n
+          | n < 1 -> fail $ "deserializeValue: unknown version: " ++ show n
           | n < 3 -> fail $ "deserializeValue: unsupported version: " ++ show n
           | n == 3 -> pure n
           | otherwise -> fail $ "deserializeValue: unknown version: " ++ show n
diff --git a/parser-typechecker/src/Unison/Runtime/Machine.hs b/parser-typechecker/src/Unison/Runtime/Machine.hs
index 0aec1c143..53e7709e0 100644
--- a/parser-typechecker/src/Unison/Runtime/Machine.hs
+++ b/parser-typechecker/src/Unison/Runtime/Machine.hs
@@ -375,7 +375,7 @@ exec !_ !denv !_activeThreads !ustk !bstk !k _ (BPrim2 CMPU i j) = do
   ustk <- bump ustk
   poke ustk . fromEnum $ universalCompare compare x y
   pure (denv, ustk, bstk, k)
-exec !_   !_    !_activeThreads !_    !bstk !k r (BPrim2 THRO i j) = do
+exec !_ !_ !_activeThreads !_ !bstk !k r (BPrim2 THRO i j) = do
   name <- peekOffBi @Util.Text.Text bstk i
   x <- peekOff bstk j
   throwIO (BU (traceK r k) (Util.Text.toText name) x)
@@ -1938,6 +1938,8 @@ reflectValue rty = goV
           pure (ANF.Quote v)
       | Just g <- maybeUnwrapForeign Rf.codeRef f =
           pure (ANF.Code g)
+      | Just a <- maybeUnwrapForeign Rf.ibytearrayRef f =
+          pure (ANF.BArr a)
       | otherwise = die $ err $ "foreign value: " <> (show f)
 
 reifyValue :: CCache -> ANF.Value -> IO (Either [Reference] Closure)
@@ -2010,6 +2012,7 @@ reifyValue0 (rty, rtm) = goV
     goL (ANF.Bytes b) = pure . Foreign $ Wrap Rf.bytesRef b
     goL (ANF.Quote v) = pure . Foreign $ Wrap Rf.valueRef v
     goL (ANF.Code g) = pure . Foreign $ Wrap Rf.codeRef g
+    goL (ANF.BArr a) = pure . Foreign $ Wrap Rf.ibytearrayRef a
 
 -- Universal comparison functions
 
diff --git a/parser-typechecker/src/Unison/Runtime/Serialize.hs b/parser-typechecker/src/Unison/Runtime/Serialize.hs
index 735f2a418..6382eae29 100644
--- a/parser-typechecker/src/Unison/Runtime/Serialize.hs
+++ b/parser-typechecker/src/Unison/Runtime/Serialize.hs
@@ -15,10 +15,12 @@ import Data.Bytes.VarInt
 import Data.Foldable (traverse_)
 import Data.Int (Int64)
 import Data.Map.Strict as Map (Map, fromList, toList)
+import qualified Data.Primitive as PA
 import Data.Text (Text)
 import Data.Text.Encoding (decodeUtf8, encodeUtf8)
 import qualified Data.Vector.Primitive as BA
 import Data.Word (Word64, Word8)
+import GHC.Exts as IL (IsList (..))
 import qualified U.Util.Hash as Hash
 import Unison.ConstructorReference (ConstructorReference, GConstructorReference (..))
 import qualified Unison.ConstructorType as CT
@@ -156,6 +158,12 @@ getBytes = Bytes.fromChunks <$> getList getBlock
 putBytes :: MonadPut m => Bytes.Bytes -> m ()
 putBytes = putFoldable putBlock . Bytes.chunks
 
+getByteArray :: MonadGet m => m PA.ByteArray
+getByteArray = PA.byteArrayFromList <$> getList getWord8
+
+putByteArray :: MonadPut m => PA.ByteArray -> m ()
+putByteArray a = putFoldable putWord8 (IL.toList a)
+
 getBlock :: MonadGet m => m Bytes.Chunk
 getBlock = getLength >>= fmap Bytes.byteStringToChunk . getByteString
 
diff --git a/parser-typechecker/src/Unison/Syntax/TermPrinter.hs b/parser-typechecker/src/Unison/Syntax/TermPrinter.hs
index 114180894..fa4839caf 100644
--- a/parser-typechecker/src/Unison/Syntax/TermPrinter.hs
+++ b/parser-typechecker/src/Unison/Syntax/TermPrinter.hs
@@ -193,6 +193,7 @@ pretty0
           fmt S.LinkKeyword "termLink "
             <> parenIfInfix name ic (styleHashQualified'' (fmt $ S.TermReference r) name)
         where
+
       TypeLink' r -> do
         n <- getPPE
         let name = elideFQN im $ PrettyPrintEnv.typeName n r
@@ -200,6 +201,7 @@ pretty0
           fmt S.LinkKeyword "typeLink "
             <> parenIfInfix name ic (styleHashQualified'' (fmt $ S.TypeReference r) name)
         where
+
       Ann' tm t -> do
         tm' <- pretty0 (ac 10 Normal im doc) tm
         tp' <- TypePrinter.pretty0 im 0 t
@@ -259,21 +261,17 @@ pretty0
           fmt S.DelayForceChar (l "!") <> px
       Delay' x
         | Lets' _ _ <- x -> do
-          px <- pretty0 (ac 0 Block im doc) x
-          pure . paren (p >= 3) $
-            fmt S.ControlKeyword "do" `PP.hang` px
+            px <- pretty0 (ac 0 Block im doc) x
+            pure . paren (p >= 3) $
+              fmt S.ControlKeyword "do" `PP.hang` px
         | otherwise -> do
-          px <- pretty0 (ac 10 Normal im doc) x
-          pure . paren (p >= 11 || isBlock x && p >= 3) $
-            fmt S.DelayForceChar (l "'")
-              <> ( case x of
-                     Lets' _ _ -> id
-                     -- Add indentation below if we're opening parens with '(
-                     -- This is in case the contents are a long function application
-                     -- in which case the arguments should be indented.
-                     _ -> PP.indentAfterNewline "  "
-                 )
-                px
+            px <- pretty0 (ac 10 Normal im doc) x
+            pure . paren (p >= 11 || isBlock x && p >= 3) $
+              fmt S.DelayForceChar (l "'")
+                -- Add indentation below since we're opening parens with '(
+                -- This is in case the contents are a long function application
+                -- in which case the arguments should be indented.
+                <> PP.indentAfterNewline "  " px
       List' xs ->
         PP.group <$> do
           xs' <- traverse (pretty0 (ac 0 Normal im doc)) xs
@@ -327,30 +325,30 @@ pretty0
       -- See `isDestructuringBind` definition.
       Match' scrutinee cs@[MatchCase pat guard (AbsN' vs body)]
         | p < 1 && isDestructuringBind scrutinee cs -> do
-          n <- getPPE
-          let letIntro = case bc of
-                Block -> id
-                Normal -> \x ->
-                  -- We don't call calcImports here, because we can't easily do the
-                  -- corequisite step in immediateChildBlockTerms (because it doesn't
-                  -- know bc.)  So we'll fail to take advantage of any opportunity
-                  -- this let block provides to add a use statement.  Not so bad.
-                  fmt S.ControlKeyword "let" `PP.hang` x
-          lhs <- do
-            let (lhs, _) = prettyPattern n (ac 0 Block im doc) 10 vs pat
-            guard' <- printGuard guard
-            pure $ PP.group lhs `PP.hang` guard'
-          let eq = fmt S.BindingEquals "="
-          rhs <- do
-            let (im', uses) = calcImports im scrutinee
-            uses <$> sequence [pretty0 (ac (-1) Block im' doc) scrutinee]
-          letIntro <$> do
-            prettyBody <- pretty0 (ac (-1) Block im doc) body
-            pure $
-              PP.lines
-                [ (lhs <> eq) `PP.hang` rhs,
-                  prettyBody
-                ]
+            n <- getPPE
+            let letIntro = case bc of
+                  Block -> id
+                  Normal -> \x ->
+                    -- We don't call calcImports here, because we can't easily do the
+                    -- corequisite step in immediateChildBlockTerms (because it doesn't
+                    -- know bc.)  So we'll fail to take advantage of any opportunity
+                    -- this let block provides to add a use statement.  Not so bad.
+                    fmt S.ControlKeyword "let" `PP.hang` x
+            lhs <- do
+              let (lhs, _) = prettyPattern n (ac 0 Block im doc) 10 vs pat
+              guard' <- printGuard guard
+              pure $ PP.group lhs `PP.hang` guard'
+            let eq = fmt S.BindingEquals "="
+            rhs <- do
+              let (im', uses) = calcImports im scrutinee
+              uses <$> sequence [pretty0 (ac (-1) Block im' doc) scrutinee]
+            letIntro <$> do
+              prettyBody <- pretty0 (ac (-1) Block im doc) body
+              pure $
+                PP.lines
+                  [ (lhs <> eq) `PP.hang` rhs,
+                    prettyBody
+                  ]
         where
           printGuard Nothing = pure mempty
           printGuard (Just g') = do
@@ -391,9 +389,9 @@ pretty0
             case (term, binaryOpsPred) of
               (DD.Doc, _)
                 | doc == MaybeDoc ->
-                  if isDocLiteral term
-                    then applyPPE3 prettyDoc im term
-                    else pretty0 (a {docContext = NoDoc}) term
+                    if isDocLiteral term
+                      then applyPPE3 prettyDoc im term
+                      else pretty0 (a {docContext = NoDoc}) term
               (TupleTerm' [x], _) -> do
                 let conRef = DD.pairCtorRef
                 name <- elideFQN im <$> applyPPE2 PrettyPrintEnv.termName conRef
@@ -465,12 +463,12 @@ pretty0
               _ -> case (term, nonForcePred) of
                 OverappliedBinaryAppPred' f a b r
                   | binaryOpsPred f ->
-                    -- Special case for overapplied binary op
-                    do
-                      prettyB <- pretty0 (ac 3 Normal im doc) b
-                      prettyR <- PP.spacedTraverse (pretty0 (ac 10 Normal im doc)) r
-                      prettyA <- binaryApps [(f, a)] prettyB
-                      pure $ paren True $ PP.hang prettyA prettyR
+                      -- Special case for overapplied binary op
+                      do
+                        prettyB <- pretty0 (ac 3 Normal im doc) b
+                        prettyR <- PP.spacedTraverse (pretty0 (ac 10 Normal im doc)) r
+                        prettyA <- binaryApps [(f, a)] prettyB
+                        pure $ paren True $ PP.hang prettyA prettyR
                 AppsPred' f args ->
                   paren (p >= 10) <$> do
                     f' <- pretty0 (ac 10 Normal im doc) f
@@ -611,8 +609,8 @@ prettyPattern n c@AmbientContext {imports = im} p vs patt = case patt of
   Pattern.Text _ t -> (fmt S.TextLiteral $ l $ show t, vs)
   TuplePattern pats
     | length pats /= 1 ->
-      let (pats_printed, tail_vs) = patterns (-1) vs pats
-       in (PP.parenthesizeCommas pats_printed, tail_vs)
+        let (pats_printed, tail_vs) = patterns (-1) vs pats
+         in (PP.parenthesizeCommas pats_printed, tail_vs)
   Pattern.Constructor _ ref [] ->
     (styleHashQualified'' (fmt $ S.TermReference conRef) name, vs)
     where
@@ -710,7 +708,10 @@ printCase ::
   DocLiteralContext ->
   [MatchCase' () (Term3 v PrintAnnotation)] ->
   m (Pretty SyntaxText)
-printCase im doc ms0 = PP.lines . alignGrid <$> grid
+printCase im doc ms0 =
+  PP.orElse
+    <$> (PP.lines . alignGrid True <$> grid)
+    <*> (PP.lines . alignGrid False <$> grid)
   where
     ms = groupCases ms0
     justify rows =
@@ -718,21 +719,34 @@ printCase im doc ms0 = PP.lines . alignGrid <$> grid
       where
         alignPatterns (p, _, _) = (p, Just "")
         gbs (_, gs, bs) = zip gs bs
-    alignGrid = fmap alignCase . justify
-    alignCase (p, gbs) =
-      if not (null (drop 1 gbs))
-        then PP.hang p guardBlock
-        else p <> guardBlock
+    nojustify = map f
       where
-        guardBlock =
-          PP.lines $
-            fmap (\(g, (a, b)) -> PP.hang (PP.group (g <> a)) b) justified
-        justified = PP.leftJustify $ fmap (\(g, b) -> (g, (arrow, b))) gbs
+        f (p, gs, bs) = (p, zip gs bs)
+    alignGrid alignArrows grid =
+      fmap alignCase $ if alignArrows then justify grid else nojustify grid
+      where
+        alignCase (p, gbs) =
+          if not (null (drop 1 gbs))
+            then PP.hang p guardBlock
+            else p <> guardBlock
+          where
+            guardBlock =
+              PP.lines $
+                fmap
+                  ( \(g, (a, b)) ->
+                      PP.hang
+                        ( PP.group
+                            (g <> (if alignArrows then "" else " ") <> a)
+                        )
+                        b
+                  )
+                  justified
+            justified = PP.leftJustify $ fmap (\(g, b) -> (g, (arrow, b))) gbs
     grid = traverse go ms
     patLhs env vs pats =
       case pats of
         [pat] -> PP.group (fst (prettyPattern env (ac 0 Block im doc) (-1) vs pat))
-        pats -> PP.group . PP.sep ("," <> PP.softbreak)
+        pats -> PP.group . PP.sep (PP.indentAfterNewline "  " $ "," <> PP.softbreak)
           . (`evalState` vs)
           . for pats
           $ \pat -> do
@@ -858,14 +872,14 @@ prettyBinding0 a@AmbientContext {imports = im, docContext = doc} v term =
       where
         defnLhs v vs
           | infix' = case vs of
-            x : y : _ ->
-              PP.sep
-                " "
-                [ fmt S.Var $ PP.text (Var.name x),
-                  styleHashQualified'' (fmt $ S.HashQualifier v) $ elideFQN im v,
-                  fmt S.Var $ PP.text (Var.name y)
-                ]
-            _ -> l "error"
+              x : y : _ ->
+                PP.sep
+                  " "
+                  [ fmt S.Var $ PP.text (Var.name x),
+                    styleHashQualified'' (fmt $ S.HashQualifier v) $ elideFQN im v,
+                    fmt S.Var $ PP.text (Var.name y)
+                  ]
+              _ -> l "error"
           | null vs = renderName v
           | otherwise = renderName v `PP.hang` args vs
         args = PP.spacedMap $ fmt S.Var . PP.text . Var.name
@@ -1466,7 +1480,7 @@ unLetBlock t = rec t
       Just (_isTop, bindings, body) -> case rec body of
         Just (innerBindings, innerBody)
           | dontIntersect bindings innerBindings ->
-            Just (bindings ++ innerBindings, innerBody)
+              Just (bindings ++ innerBindings, innerBody)
         _ -> Just (bindings, body)
     nonrec t = case unLet t of
       Nothing -> Nothing
@@ -1475,7 +1489,7 @@ unLetBlock t = rec t
          in case rec body of
               Just (innerBindings, innerBody)
                 | dontIntersect bindings innerBindings ->
-                  Just (bindings ++ innerBindings, innerBody)
+                    Just (bindings ++ innerBindings, innerBody)
               _ -> Just (bindings, body)
 
 pattern LamsNamedMatch' ::
@@ -1528,7 +1542,7 @@ unLamsMatch' t = case unLamsUntilDelay' t of
     | -- if `v1'` is referenced in any of the branches, we can't use lambda case
       -- syntax as we need to keep the `v1'` name that was introduced
       v1 == v1' && Set.notMember v1' (Set.unions $ freeVars <$> branches) ->
-      Just (reverse vs, [([p], guard, body) | MatchCase p guard body <- branches])
+        Just (reverse vs, [([p], guard, body) | MatchCase p guard body <- branches])
   -- x y z -> match (x,y,z) with (pat1, pat2, pat3) -> ...
   --   becomes
   -- cases pat1 pat2 pat3 -> ...`
@@ -1541,7 +1555,7 @@ unLamsMatch' t = case unLamsUntilDelay' t of
         all notFree (take len vs)
         && all isRightArity branches
         && len /= 0 -> -- all patterns need to match arity of scrutes
-      Just (reverse (drop len vs), branches')
+        Just (reverse (drop len vs), branches')
     where
       isRightArity (MatchCase (TuplePattern ps) _ _) = length ps == len
       isRightArity MatchCase {} = False
@@ -1793,7 +1807,7 @@ toDocExample' suffix ppe (Apps' (Ref' r) [Nat' n, l@(LamsNamed' vs tm)])
   | nameEndsWith ppe suffix r,
     ABT.freeVars l == mempty,
     ok tm =
-    Just (lam' (ABT.annotation l) (drop (fromIntegral n + 1) vs) tm)
+      Just (lam' (ABT.annotation l) (drop (fromIntegral n + 1) vs) tm)
   where
     ok (Apps' f _) = ABT.freeVars f == mempty
     ok tm = ABT.freeVars tm == mempty
@@ -1807,9 +1821,9 @@ toDocTransclude _ _ = Nothing
 toDocLink :: Ord v => PrettyPrintEnv -> Term3 v PrintAnnotation -> Maybe (Either Reference Referent)
 toDocLink ppe (App' (Ref' r) tm)
   | nameEndsWith ppe ".docLink" r = case tm of
-    (toDocEmbedTermLink ppe -> Just tm) -> Just (Right tm)
-    (toDocEmbedTypeLink ppe -> Just tm) -> Just (Left tm)
-    _ -> Nothing
+      (toDocEmbedTermLink ppe -> Just tm) -> Just (Right tm)
+      (toDocEmbedTypeLink ppe -> Just tm) -> Just (Left tm)
+      _ -> Nothing
 toDocLink _ _ = Nothing
 
 toDocNamedLink :: PrettyPrintEnv -> Term3 v PrintAnnotation -> Maybe (Term3 v PrintAnnotation, Term3 v PrintAnnotation)
@@ -1848,7 +1862,7 @@ toDocSourceAnnotations _ppe _tm = Just [] -- todo fetch annotations
 toDocSourceElement :: Ord v => PrettyPrintEnv -> Term3 v PrintAnnotation -> Maybe (Either Reference Referent, [Referent])
 toDocSourceElement ppe (Apps' (Ref' r) [tm, toDocSourceAnnotations ppe -> Just annotations])
   | nameEndsWith ppe ".docSourceElement" r =
-    (,annotations) <$> ok tm
+      (,annotations) <$> ok tm
   where
     ok tm =
       Right <$> toDocEmbedTermLink ppe tm
@@ -1863,9 +1877,9 @@ toDocSource' ::
   Maybe [(Either Reference Referent, [Referent])]
 toDocSource' suffix ppe (App' (Ref' r) (List' tms))
   | nameEndsWith ppe suffix r =
-    case [tm | Just tm <- toDocSourceElement ppe <$> toList tms] of
-      tms' | length tms' == length tms -> Just tms'
-      _ -> Nothing
+      case [tm | Just tm <- toDocSourceElement ppe <$> toList tms] of
+        tms' | length tms' == length tms -> Just tms'
+        _ -> Nothing
 toDocSource' _ _ _ = Nothing
 
 toDocSource,
@@ -1903,9 +1917,9 @@ toDocEmbedSignatureLink _ _ = Nothing
 toDocSignature :: Ord v => PrettyPrintEnv -> Term3 v PrintAnnotation -> Maybe [Referent]
 toDocSignature ppe (App' (Ref' r) (List' tms))
   | nameEndsWith ppe ".docSignature" r =
-    case [tm | Just tm <- toDocEmbedSignatureLink ppe <$> toList tms] of
-      tms' | length tms' == length tms -> Just tms'
-      _ -> Nothing
+      case [tm | Just tm <- toDocEmbedSignatureLink ppe <$> toList tms] of
+        tms' | length tms' == length tms -> Just tms'
+        _ -> Nothing
 toDocSignature _ _ = Nothing
 
 toDocBulletedList :: PrettyPrintEnv -> Term3 v PrintAnnotation -> Maybe [Term3 v PrintAnnotation]
diff --git a/parser-typechecker/tests/Unison/Test/CodebaseInit.hs b/parser-typechecker/tests/Unison/Test/CodebaseInit.hs
index dd4e76b68..6ac30e408 100644
--- a/parser-typechecker/tests/Unison/Test/CodebaseInit.hs
+++ b/parser-typechecker/tests/Unison/Test/CodebaseInit.hs
@@ -29,7 +29,7 @@ test =
             [ scope "a v2 codebase should be opened" do
                 tmp <- io (Temp.getCanonicalTemporaryDirectory >>= flip Temp.createTempDirectory "ucm-test")
                 cbInit <- io initMockWithCodebase
-                r <- io $ CI.withOpenOrCreateCodebase cbInit "ucm-test" (Home tmp) CI.DontMigrate \case
+                r <- io $ CI.withOpenOrCreateCodebase cbInit "ucm-test" (Home tmp) CI.DontLock CI.DontMigrate \case
                   (CI.OpenedCodebase, _, _) -> pure True
                   _ -> pure False
                 case r of
@@ -38,7 +38,7 @@ test =
               scope "a v2 codebase should be created when one does not exist" do
                 tmp <- io (Temp.getCanonicalTemporaryDirectory >>= flip Temp.createTempDirectory "ucm-test")
                 cbInit <- io initMockWithoutCodebase
-                r <- io $ CI.withOpenOrCreateCodebase cbInit "ucm-test" (Home tmp) CI.DontMigrate \case
+                r <- io $ CI.withOpenOrCreateCodebase cbInit "ucm-test" (Home tmp) CI.DontLock CI.DontMigrate \case
                   (CI.CreatedCodebase, _, _) -> pure True
                   _ -> pure False
                 case r of
@@ -51,7 +51,7 @@ test =
                 tmp <- io (Temp.getCanonicalTemporaryDirectory >>= flip Temp.createTempDirectory "ucm-test")
                 cbInit <- io initMockWithCodebase
                 res <- io $
-                  CI.withOpenOrCreateCodebase cbInit "ucm-test" (Specified (DontCreateWhenMissing tmp)) CI.DontMigrate $ \case
+                  CI.withOpenOrCreateCodebase cbInit "ucm-test" (Specified (DontCreateWhenMissing tmp)) CI.DontLock CI.DontMigrate $ \case
                     (CI.OpenedCodebase, _, _) -> pure True
                     _ -> pure False
                 case res of
@@ -61,7 +61,7 @@ test =
                 tmp <- io (Temp.getCanonicalTemporaryDirectory >>= flip Temp.createTempDirectory "ucm-test")
                 cbInit <- io initMockWithoutCodebase
                 res <- io $
-                  CI.withOpenOrCreateCodebase cbInit "ucm-test" (Specified (DontCreateWhenMissing tmp)) CI.DontMigrate $ \case
+                  CI.withOpenOrCreateCodebase cbInit "ucm-test" (Specified (DontCreateWhenMissing tmp)) CI.DontLock CI.DontMigrate $ \case
                     _ -> pure False
                 case res of
                   Left (_, CI.InitErrorOpen OpenCodebaseDoesntExist) -> expect True
@@ -72,7 +72,7 @@ test =
             [ scope "a v2 codebase should be created when one does not exist at the Specified dir" do
                 tmp <- io (Temp.getCanonicalTemporaryDirectory >>= flip Temp.createTempDirectory "ucm-test")
                 cbInit <- io initMockWithoutCodebase
-                res <- io $ CI.withOpenOrCreateCodebase cbInit "ucm-test" (Specified (CreateWhenMissing tmp)) CI.DontMigrate \case
+                res <- io $ CI.withOpenOrCreateCodebase cbInit "ucm-test" (Specified (CreateWhenMissing tmp)) CI.DontLock CI.DontMigrate \case
                   (CI.CreatedCodebase, _, _) -> pure True
                   _ -> pure False
                 case res of
@@ -81,7 +81,7 @@ test =
               scope "a v2 codebase should be opened when one exists" do
                 tmp <- io (Temp.getCanonicalTemporaryDirectory >>= flip Temp.createTempDirectory "ucm-test")
                 cbInit <- io initMockWithCodebase
-                res <- io $ CI.withOpenOrCreateCodebase cbInit "ucm-test" (Specified (CreateWhenMissing tmp)) CI.DontMigrate \case
+                res <- io $ CI.withOpenOrCreateCodebase cbInit "ucm-test" (Specified (CreateWhenMissing tmp)) CI.DontLock CI.DontMigrate \case
                   (CI.OpenedCodebase, _, _) -> pure True
                   _ -> pure False
                 case res of
@@ -98,9 +98,9 @@ initMockWithCodebase = do
   pure $
     Init
       { -- withOpenCodebase :: forall r. DebugName -> CodebasePath -> (Codebase m v a -> m r) -> m (Either Pretty r),
-        withOpenCodebase = \_ _ _ action -> Right <$> action codebase,
+        withOpenCodebase = \_ _ _ _ action -> Right <$> action codebase,
         -- withCreatedCodebase :: forall r. DebugName -> CodebasePath -> (Codebase m v a -> m r) -> m (Either CreateCodebaseError r),
-        withCreatedCodebase = \_ _ action -> Right <$> action codebase,
+        withCreatedCodebase = \_ _ _ action -> Right <$> action codebase,
         -- CodebasePath -> CodebasePath
         codebasePath = id
       }
@@ -110,9 +110,9 @@ initMockWithoutCodebase = do
   let codebase = error "did we /actually/ need a Codebase?"
   pure $
     Init
-      { withOpenCodebase = \_ _ _ _ -> pure (Left OpenCodebaseDoesntExist),
+      { withOpenCodebase = \_ _ _ _ _ -> pure (Left OpenCodebaseDoesntExist),
         -- withCreatedCodebase :: forall r. DebugName -> CodebasePath -> (Codebase m v a -> m r) -> m (Either CreateCodebaseError r),
-        withCreatedCodebase = \_ _ action -> Right <$> action codebase,
+        withCreatedCodebase = \_ _ _ action -> Right <$> action codebase,
         -- CodebasePath -> CodebasePath
         codebasePath = id
       }
diff --git a/parser-typechecker/unison-parser-typechecker.cabal b/parser-typechecker/unison-parser-typechecker.cabal
index 5652aaf4e..e373d76c2 100644
--- a/parser-typechecker/unison-parser-typechecker.cabal
+++ b/parser-typechecker/unison-parser-typechecker.cabal
@@ -59,6 +59,7 @@ library
       Unison.Codebase.Path
       Unison.Codebase.Path.Parse
       Unison.Codebase.PushBehavior
+      Unison.Codebase.RootBranchCache
       Unison.Codebase.Runtime
       Unison.Codebase.Serialization
       Unison.Codebase.ShortCausalHash
@@ -208,6 +209,7 @@ library
     , errors
     , exceptions
     , extra
+    , filelock
     , filepath
     , fingertree
     , free
@@ -240,7 +242,6 @@ library
     , openapi3
     , optparse-applicative >=0.16.1.0
     , pem
-    , prelude-extras
     , pretty-simple
     , primitive
     , process
@@ -258,7 +259,6 @@ library
     , servant-server
     , shellmet
     , stm
-    , strings
     , tagged
     , temporary
     , terminal-size
@@ -393,6 +393,7 @@ test-suite parser-typechecker-tests
     , errors
     , exceptions
     , extra
+    , filelock
     , filemanip
     , filepath
     , fingertree
@@ -426,7 +427,6 @@ test-suite parser-typechecker-tests
     , openapi3
     , optparse-applicative >=0.16.1.0
     , pem
-    , prelude-extras
     , pretty-simple
     , primitive
     , process
@@ -445,7 +445,6 @@ test-suite parser-typechecker-tests
     , shellmet
     , split
     , stm
-    , strings
     , tagged
     , temporary
     , terminal-size
diff --git a/stack.yaml b/stack.yaml
index 83716f37d..d72c82019 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -54,9 +54,7 @@ extra-deps:
 - github: judah/haskeline
   commit: d6c2643b0d5c19be7e440615c6f84d603d4bc648
 - guid-0.1.0@sha256:a7c975be473f6f142d5cc1b39bc807a99043d20b1bb0873fdfe7a3ce84d2faf1,1078
-- prelude-extras-0.4.0.3@sha256:1c10b0123ea13a6423d74a8fcbaeb2d5249b472588abde418a36b47b7c4f48c8,1163
 - sandi-0.5@sha256:b278d072ca717706ea38f9bd646e023f7f2576a778fb43565b434f93638849aa,3010
-- strings-1.1@sha256:0285dec4c8ab262359342b3e5ef1eb567074669461b9b38404f1cb870c881c5c,1617
 - fuzzyfind-3.0.0@sha256:d79a5d3ed194dd436c6b839bf187211d880cf773b2febaca456e5ccf93f5ac65,1814
 - monad-validate-1.2.0.0@sha256:9850f408431098b28806dd464b6825a88a0b56c84f380d7fe0454c1df9d6f881,3505
 - NanoID-3.1.0@sha256:9118ab00e8650b5a56a10c90295d357eb77a8057a598b7e56dfedc9c6d53c77d,1524
diff --git a/stack.yaml.lock b/stack.yaml.lock
index 22747c804..21913c23f 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -5,173 +5,159 @@
 
 packages:
 - completed:
-    sha256: d4fd87fb7bfc5d8e9fbc3e4ee7302c6b1500cdc00fdb9b659d0f4849b6ebe2d5
-    name: configurator
     size: 15989
     url: https://github.com/unisonweb/configurator/archive/e47e9e9fe1f576f8c835183b9def52d73c01327a.tar.gz
-    pantry-tree:
-      sha256: 90547cd983fd15ebdc803e057d3ef8735fe93a75e29a00f8a74eadc13ee0f6e9
-      size: 955
+    name: configurator
     version: 0.3.0.0
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 - completed:
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 snapshots:
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     size: 590100
     url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/18/28.yaml
+    sha256: 428ec8d5ce932190d3cbe266b9eb3c175cd81e984babf876b64019e2cbe4ea68
   original: lts-18.28
diff --git a/unison-cli/package.yaml b/unison-cli/package.yaml
index 4c13157b4..564646295 100644
--- a/unison-cli/package.yaml
+++ b/unison-cli/package.yaml
@@ -54,6 +54,7 @@ dependencies:
   - nonempty-containers
   - open-browser
   - pretty-simple
+  - process
   - random >= 1.2.0
   - regex-tdfa
   - semialign
@@ -117,7 +118,7 @@ executables:
         other-modules: Paths_unison_cli
     source-dirs: unison
     main: Main.hs
-    ghc-options: -threaded -rtsopts -with-rtsopts=-I0 -optP-Wno-nonportable-include-path
+    ghc-options: -threaded -rtsopts "-with-rtsopts=-I0 -N -qn4 -qg1 -T" -optP-Wno-nonportable-include-path
     dependencies:
       - code-page
       - optparse-applicative >= 0.16.1.0
@@ -132,7 +133,7 @@ executables:
         other-modules: Paths_unison_cli
     source-dirs: transcripts
     main: Transcripts.hs
-    ghc-options: -threaded -rtsopts -with-rtsopts=-N -v0
+    ghc-options: -threaded -rtsopts "-with-rtsopts=-I0 -N -qn4 -qg1" -v0
     dependencies:
       - code-page
       - easytest
diff --git a/unison-cli/src/Unison/Cli/MonadUtils.hs b/unison-cli/src/Unison/Cli/MonadUtils.hs
index 279a5e6c0..300e18ce1 100644
--- a/unison-cli/src/Unison/Cli/MonadUtils.hs
+++ b/unison-cli/src/Unison/Cli/MonadUtils.hs
@@ -251,11 +251,11 @@ assertNoBranchAtPath' path' = do
 branchExistsAtPath' :: Path' -> Cli Bool
 branchExistsAtPath' path' = do
   absPath <- resolvePath' path'
-  Cli.Env {codebase} <- ask
-  causal <- liftIO $ Codebase.getShallowCausalFromRoot codebase Nothing (Path.unabsolute absPath)
-  branch <- liftIO $ V2Causal.value causal
-  isEmpty <- Cli.runTransaction $ V2Branch.isEmpty branch
-  pure (not isEmpty)
+  Cli.runTransaction do
+    causal <- Codebase.getShallowCausalFromRoot Nothing (Path.unabsolute absPath)
+    branch <- V2Causal.value causal
+    isEmpty <- V2Branch.isEmpty branch
+    pure (not isEmpty)
 
 ------------------------------------------------------------------------------------------------------------------------
 -- Updating branches
diff --git a/unison-cli/src/Unison/Cli/TypeCheck.hs b/unison-cli/src/Unison/Cli/TypeCheck.hs
index e3931daea..382ad2e41 100644
--- a/unison-cli/src/Unison/Cli/TypeCheck.hs
+++ b/unison-cli/src/Unison/Cli/TypeCheck.hs
@@ -2,6 +2,7 @@ module Unison.Cli.TypeCheck
   ( typecheck,
     typecheckHelper,
     typecheckFile,
+    typecheckTerm,
   )
 where
 
@@ -19,11 +20,13 @@ import Unison.Parser.Ann (Ann (..))
 import Unison.Prelude
 import qualified Unison.Result as Result
 import qualified Unison.Sqlite as Sqlite
-import Unison.Symbol (Symbol)
+import Unison.Symbol (Symbol (Symbol))
 import qualified Unison.Syntax.Lexer as L
 import qualified Unison.Syntax.Parser as Parser
+import Unison.Term (Term)
 import Unison.Type (Type)
 import qualified Unison.UnisonFile as UF
+import qualified Unison.Var as Var
 
 typecheck ::
   [Type Symbol Ann] ->
@@ -70,6 +73,39 @@ typecheckHelper codebase generateUniqueName ambient names sourceName source = do
       (Text.unpack sourceName)
       (fst source)
 
+typecheckTerm ::
+  Term Symbol Ann ->
+  Cli
+    ( Result.Result
+        (Seq (Result.Note Symbol Ann))
+        (Type Symbol Ann)
+    )
+typecheckTerm tm = do
+  Cli.Env {codebase} <- ask
+  let v = Symbol 0 (Var.Inference Var.Other)
+  liftIO $
+    fmap extract
+      <$> Codebase.runTransaction codebase (typecheckFile' codebase [] (UF.UnisonFileId mempty mempty [(v, tm)] mempty))
+  where
+    extract tuf
+      | [[(_, _, ty)]] <- UF.topLevelComponents' tuf = ty
+      | otherwise = error "internal error: typecheckTerm"
+
+typecheckFile' ::
+  Codebase m Symbol Ann ->
+  [Type Symbol Ann] ->
+  UF.UnisonFile Symbol Ann ->
+  Sqlite.Transaction
+    ( Result.Result
+        (Seq (Result.Note Symbol Ann))
+        (UF.TypecheckedUnisonFile Symbol Ann)
+    )
+typecheckFile' codebase ambient file = do
+  typeLookup <-
+    (<> Builtin.typeLookup)
+      <$> Codebase.typeLookupForDependencies codebase (UF.dependencies file)
+  pure $ synthesizeFile' ambient typeLookup file
+
 typecheckFile ::
   Codebase m Symbol Ann ->
   [Type Symbol Ann] ->
@@ -79,8 +115,5 @@ typecheckFile ::
         (Seq (Result.Note Symbol Ann))
         (Either Names (UF.TypecheckedUnisonFile Symbol Ann))
     )
-typecheckFile codebase ambient file = do
-  typeLookup <-
-    (<> Builtin.typeLookup)
-      <$> Codebase.typeLookupForDependencies codebase (UF.dependencies file)
-  pure . fmap Right $ synthesizeFile' ambient typeLookup file
+typecheckFile codebase ambient file =
+  fmap Right <$> typecheckFile' codebase ambient file
diff --git a/unison-cli/src/Unison/Codebase/Editor/HandleInput.hs b/unison-cli/src/Unison/Codebase/Editor/HandleInput.hs
index b99a1fcfa..6a6fd7825 100644
--- a/unison-cli/src/Unison/Codebase/Editor/HandleInput.hs
+++ b/unison-cli/src/Unison/Codebase/Editor/HandleInput.hs
@@ -7,6 +7,7 @@ where
 
 import Control.Concurrent.STM (atomically, modifyTVar', newTVarIO, readTVar, readTVarIO)
 import qualified Control.Error.Util as ErrorUtil
+import Control.Exception (catch)
 import Control.Lens
 import Control.Monad.Reader (ask)
 import Control.Monad.State (StateT)
@@ -27,7 +28,15 @@ import qualified Data.Text as Text
 import Data.Time (UTCTime)
 import Data.Tuple.Extra (uncurry3)
 import qualified System.Console.Regions as Console.Regions
+import System.Directory
+  ( XdgDirectory (..),
+    createDirectoryIfMissing,
+    doesFileExist,
+    getXdgDirectory,
+  )
 import System.Environment (withArgs)
+import System.FilePath ((</>))
+import System.Process (callCommand, readCreateProcess, shell)
 import qualified Text.Megaparsec as P
 import qualified U.Codebase.Branch.Diff as V2Branch
 import qualified U.Codebase.Causal as V2Causal
@@ -45,9 +54,9 @@ import qualified Unison.Builtin.Terms as Builtin
 import Unison.Cli.Monad (Cli)
 import qualified Unison.Cli.Monad as Cli
 import qualified Unison.Cli.MonadUtils as Cli
-import Unison.Cli.NamesUtils (basicParseNames, basicPrettyPrintNamesA, displayNames, findHistoricalHQs, getBasicPrettyPrintNames, makeHistoricalParsingNames, makePrintNamesFromLabeled', makeShadowedPrintNamesFromHQ)
+import Unison.Cli.NamesUtils (basicParseNames, displayNames, findHistoricalHQs, getBasicPrettyPrintNames, makeHistoricalParsingNames, makePrintNamesFromLabeled', makeShadowedPrintNamesFromHQ)
 import Unison.Cli.PrettyPrintUtils (currentPrettyPrintEnvDecl, prettyPrintEnvDecl)
-import Unison.Cli.TypeCheck (typecheck)
+import Unison.Cli.TypeCheck (typecheck, typecheckTerm)
 import Unison.Cli.UnisonConfigUtils (gitUrlKey, remoteMappingKey)
 import Unison.Codebase (Codebase, Preprocessing (..), PushGitBranchOpts (..))
 import qualified Unison.Codebase as Codebase
@@ -66,6 +75,11 @@ import Unison.Codebase.Editor.HandleInput.MetadataUtils (addDefaultMetadata, man
 import Unison.Codebase.Editor.HandleInput.MoveBranch (doMoveBranch)
 import qualified Unison.Codebase.Editor.HandleInput.NamespaceDependencies as NamespaceDependencies
 import Unison.Codebase.Editor.HandleInput.NamespaceDiffUtils (diffHelper)
+import Unison.Codebase.Editor.HandleInput.TermResolution
+  ( resolveCon,
+    resolveMainRef,
+    resolveTermRef,
+  )
 import Unison.Codebase.Editor.HandleInput.Update (doSlurpAdds, handleUpdate)
 import Unison.Codebase.Editor.Input
 import qualified Unison.Codebase.Editor.Input as Input
@@ -166,6 +180,7 @@ import Unison.Symbol (Symbol)
 import qualified Unison.Sync.Types as Share (Path (..), hashJWTHash)
 import qualified Unison.Syntax.Lexer as L
 import qualified Unison.Syntax.Parser as Parser
+import qualified Unison.Syntax.TermPrinter as TP
 import Unison.Term (Term)
 import qualified Unison.Term as Term
 import Unison.Type (Type)
@@ -373,7 +388,7 @@ loop e = do
               Cli.respond $ PrintMessage pretty
             ShowReflogI -> do
               let numEntriesToShow = 500
-              entries <- 
+              entries <-
                 Cli.runTransaction do
                   schLength <- Codebase.branchHashLength
                   Codebase.getReflog numEntriesToShow <&> fmap (first $ SCH.fromHash schLength)
@@ -1157,24 +1172,14 @@ loop e = do
               Cli.respond (RunResult ppe mainRes)
             MakeStandaloneI output main -> do
               Cli.Env {codebase, runtime} <- ask
-              let mainType = Runtime.mainType runtime
-              parseNames <-
-                flip NamesWithHistory.NamesWithHistory mempty <$> basicPrettyPrintNamesA
-              ppe <- suffixifiedPPE parseNames
-              let resolved = toList $ NamesWithHistory.lookupHQTerm main parseNames
-                  smain = HQ.toString main
-              filtered <-
-                Cli.runTransaction do
-                  catMaybes
-                    <$> traverse (\r -> fmap (r,) <$> loadTypeOfTerm codebase r) resolved
-              case filtered of
-                [(Referent.Ref ref, ty)]
-                  | Typechecker.fitsScheme ty mainType -> do
-                      let codeLookup = () <$ Codebase.toCodeLookup codebase
-                      whenJustM (liftIO (Runtime.compileTo runtime codeLookup ppe ref (output <> ".uc"))) \err ->
-                        Cli.returnEarly (EvaluationFailure err)
-                  | otherwise -> Cli.returnEarly (BadMainFunction smain ty ppe [mainType])
-                _ -> Cli.returnEarly (NoMainFunction smain ppe [mainType])
+              (ref, ppe) <- resolveMainRef main
+              let codeLookup = () <$ Codebase.toCodeLookup codebase
+              whenJustM (liftIO (Runtime.compileTo runtime codeLookup ppe ref (output <> ".uc"))) \err ->
+                Cli.returnEarly (EvaluationFailure err)
+            CompileSchemeI output main -> doCompileScheme output main
+            ExecuteSchemeI main -> doRunAsScheme main
+            GenSchemeLibsI -> doGenerateSchemeBoot True Nothing
+            FetchSchemeCompilerI -> doFetchCompiler
             IOTestI main -> do
               Cli.Env {codebase, runtime} <- ask
               -- todo - allow this to run tests from scratch file, using addRunMain
@@ -1261,46 +1266,9 @@ loop e = do
               patch <- Cli.getPatchAt (fromMaybe Cli.defaultPatchPath maybePath)
               ppe <- suffixifiedPPE =<< makePrintNamesFromLabeled' (Patch.labeledDependencies patch)
               Cli.respondNumbered $ ListEdits patch ppe
-            PullRemoteBranchI mayRepo path syncMode pullMode verbosity -> do
-              Cli.Env {codebase} <- ask
-              let preprocess = case pullMode of
-                    Input.PullWithHistory -> Unmodified
-                    Input.PullWithoutHistory -> Preprocessed $ pure . Branch.discardHistory
-              ns <- maybe (writePathToRead <$> resolveConfiguredUrl Pull path) pure mayRepo
-              remoteBranch <- case ns of
-                ReadRemoteNamespaceGit repo ->
-                  Cli.ioE (Codebase.importRemoteBranch codebase repo syncMode preprocess) \err ->
-                    Cli.returnEarly (Output.GitError err)
-                ReadRemoteNamespaceShare repo -> importRemoteShareBranch repo
-              description <- inputDescription input
-              let unchangedMsg = PullAlreadyUpToDate ns path
-              destAbs <- Cli.resolvePath' path
-              let printDiffPath = if Verbosity.isSilent verbosity then Nothing else Just path
-              case pullMode of
-                Input.PullWithHistory -> do
-                  destBranch <- Cli.getBranch0At destAbs
-                  if Branch.isEmpty0 destBranch
-                    then do
-                      void $ Cli.updateAtM description destAbs (const $ pure remoteBranch)
-                      Cli.respond $ MergeOverEmpty path
-                    else
-                      mergeBranchAndPropagateDefaultPatch
-                        Branch.RegularMerge
-                        description
-                        (Just unchangedMsg)
-                        remoteBranch
-                        printDiffPath
-                        destAbs
-                Input.PullWithoutHistory -> do
-                  didUpdate <-
-                    Cli.updateAtM
-                      description
-                      destAbs
-                      (\destBranch -> pure $ remoteBranch `Branch.consBranchSnapshot` destBranch)
-                  Cli.respond
-                    if didUpdate
-                      then PullSuccessful ns path
-                      else unchangedMsg
+            PullRemoteBranchI mRepo path sMode pMode verbosity ->
+              inputDescription input
+                >>= doPullRemoteBranch mRepo path sMode pMode verbosity
             PushRemoteBranchI pushRemoteBranchInput -> handlePushRemoteBranch pushRemoteBranchInput
             ListDependentsI hq -> handleDependents hq
             ListDependenciesI hq -> do
@@ -1413,14 +1381,13 @@ loop e = do
                 traceM $ show name ++ ",Type," ++ Text.unpack (Reference.toText r)
               for_ (Relation.toList . Branch.deepTerms $ rootBranch0) \(r, name) ->
                 traceM $ show name ++ ",Term," ++ Text.unpack (Referent.toText r)
-            DebugClearWatchI {} -> 
+            DebugClearWatchI {} ->
               Cli.runTransaction Codebase.clearWatches
             DebugDoctorI {} -> do
               r <- Cli.runTransaction IntegrityCheck.integrityCheckFullCodebase
               Cli.respond (IntegrityCheck r)
             DebugNameDiffI fromSCH toSCH -> do
-              Cli.Env {codebase} <- ask
-              (schLen, fromCHs, toCHs) <- 
+              (schLen, fromCHs, toCHs) <-
                 Cli.runTransaction do
                   schLen <- Codebase.branchHashLength
                   fromCHs <- Codebase.causalHashesByPrefix fromSCH
@@ -1432,12 +1399,13 @@ loop e = do
                 (_, []) -> Cli.returnEarly $ Output.NoBranchWithHash toSCH
                 (_, (_ : _ : _)) -> Cli.returnEarly $ Output.BranchHashAmbiguous toSCH (Set.map (SCH.fromHash schLen) toCHs)
                 ([fromCH], [toCH]) -> pure (fromCH, toCH)
-              output <- liftIO do
-                fromBranch <- (Codebase.getShallowCausalForHash codebase $ Cv.causalHash1to2 fromCH) >>= V2Causal.value
-                toBranch <- (Codebase.getShallowCausalForHash codebase $ Cv.causalHash1to2 toCH) >>= V2Causal.value
-                treeDiff <- V2Branch.diffBranches fromBranch toBranch
-                let nameChanges = V2Branch.nameChanges Nothing treeDiff
-                pure (DisplayDebugNameDiff nameChanges)
+              output <-
+                Cli.runTransaction do
+                  fromBranch <- (Codebase.expectCausalBranchByCausalHash $ Cv.causalHash1to2 fromCH) >>= V2Causal.value
+                  toBranch <- (Codebase.expectCausalBranchByCausalHash $ Cv.causalHash1to2 toCH) >>= V2Causal.value
+                  treeDiff <- V2Branch.diffBranches fromBranch toBranch
+                  let nameChanges = V2Branch.nameChanges Nothing treeDiff
+                  pure (DisplayDebugNameDiff nameChanges)
               Cli.respond output
             DeprecateTermI {} -> Cli.respond NotImplemented
             DeprecateTypeI {} -> Cli.respond NotImplemented
@@ -1564,6 +1532,10 @@ inputDescription input =
     MergeBuiltinsI -> pure "builtins.merge"
     MergeIOBuiltinsI -> pure "builtins.mergeio"
     MakeStandaloneI out nm -> pure ("compile " <> Text.pack out <> " " <> HQ.toText nm)
+    ExecuteSchemeI nm -> pure ("run.native " <> HQ.toText nm)
+    CompileSchemeI fi nm -> pure ("compile.native " <> HQ.toText nm <> " " <> Text.pack fi)
+    GenSchemeLibsI -> pure "compile.native.genlibs"
+    FetchSchemeCompilerI -> pure "compile.native.fetch"
     PullRemoteBranchI orepo dest0 _syncMode pullMode _ -> do
       dest <- p' dest0
       let command =
@@ -2068,7 +2040,7 @@ handleTest TestInput {includeLibNamespace, showFailures, showSuccesses} = do
     fmap Map.fromList do
       Set.toList testRefs & wither \case
         Reference.Builtin _ -> pure Nothing
-        r@(Reference.DerivedId rid) -> liftIO (fmap (r,) <$> Codebase.getWatch codebase WK.TestWatch rid)
+        r@(Reference.DerivedId rid) -> fmap (r,) <$> Cli.runTransaction (Codebase.getWatch codebase WK.TestWatch rid)
   let stats = Output.CachedTests (Set.size testRefs) (Map.size cachedTests)
   names <-
     makePrintNamesFromLabeled' $
@@ -2516,6 +2488,266 @@ mergeBranchAndPropagateDefaultPatch mode inputDescription unchangedMessage srcb
           Cli.respondNumbered (ShowDiffAfterMerge dest0 dest ppe diff)
         pure b
 
+basicPPE :: Cli PPE.PrettyPrintEnv
+basicPPE = do
+  parseNames <-
+    flip NamesWithHistory.NamesWithHistory mempty
+      <$> basicParseNames
+  suffixifiedPPE parseNames
+
+compilerPath :: Path.Path'
+compilerPath = Path.Path' {Path.unPath' = Left abs}
+  where
+    segs = NameSegment <$> ["unison", "internal"]
+    rootPath = Path.Path {Path.toSeq = Seq.fromList segs}
+    abs = Path.Absolute {Path.unabsolute = rootPath}
+
+doFetchCompiler :: Cli ()
+doFetchCompiler =
+  inputDescription pullInput
+    >>= doPullRemoteBranch
+      repo
+      compilerPath
+      SyncMode.Complete
+      Input.PullWithoutHistory
+      Verbosity.Silent
+  where
+    -- fetching info
+    ns =
+      ReadShareRemoteNamespace
+        { server = RemoteRepo.DefaultCodeserver,
+          repo = "dolio",
+          path =
+            Path.fromList $ NameSegment <$> ["public", "internal", "trunk"]
+        }
+    repo = Just $ ReadRemoteNamespaceShare ns
+
+    pullInput =
+      PullRemoteBranchI
+        repo
+        compilerPath
+        SyncMode.Complete
+        Input.PullWithoutHistory
+        Verbosity.Silent
+
+ensureCompilerExists :: Cli ()
+ensureCompilerExists =
+  Cli.branchExistsAtPath' compilerPath
+    >>= flip unless doFetchCompiler
+
+getCacheDir :: Cli String
+getCacheDir = liftIO $ getXdgDirectory XdgCache "unisonlanguage"
+
+getSchemeGenLibDir :: Cli String
+getSchemeGenLibDir =
+  Cli.getConfig "SchemeLibs.Generated" >>= \case
+    Just dir -> pure dir
+    Nothing -> (</> "scheme-libs") <$> getCacheDir
+
+getSchemeStaticLibDir :: Cli String
+getSchemeStaticLibDir =
+  Cli.getConfig "SchemeLibs.Static" >>= \case
+    Just dir -> pure dir
+    Nothing ->
+      liftIO $
+        getXdgDirectory XdgData ("unisonlanguage" </> "scheme-libs")
+
+doGenerateSchemeBoot :: Bool -> Maybe PPE.PrettyPrintEnv -> Cli ()
+doGenerateSchemeBoot force mppe = do
+  ppe <- maybe basicPPE pure mppe
+  dir <- getSchemeGenLibDir
+  let bootf = dir </> "unison" </> "boot-generated.ss"
+      binf = dir </> "unison" </> "builtin-generated.ss"
+      dirTm = Term.text a (Text.pack dir)
+  liftIO $ createDirectoryIfMissing True dir
+  saveBase <- Term.ref a <$> resolveTermRef sbName
+  gen ppe saveBase bootf dirTm bootName
+  gen ppe saveBase binf dirTm builtinName
+  where
+    a = External
+    hq nm
+      | Just hqn <- HQ.fromString nm = hqn
+      | otherwise = error $ "internal error: cannot hash qualify: " ++ nm
+
+    sbName = hq ".unison.internal.compiler.scheme.saveBaseFile"
+    bootName = hq ".unison.internal.compiler.scheme.bootSpec"
+    builtinName = hq ".unison.internal.compiler.scheme.builtinSpec"
+
+    gen ppe save file dir nm =
+      liftIO (doesFileExist file) >>= \b -> when (not b || force) do
+        spec <- Term.ref a <$> resolveTermRef nm
+        let make = Term.apps' save [dir, spec]
+        typecheckAndEval ppe make
+
+typecheckAndEval :: PPE.PrettyPrintEnv -> Term Symbol Ann -> Cli ()
+typecheckAndEval ppe tm = do
+  Cli.Env {runtime} <- ask
+  let mty = Runtime.mainType runtime
+  typecheckTerm (Term.delay a tm) >>= \case
+    -- Type checking succeeded
+    Result.Result _ (Just ty)
+      | Typechecker.fitsScheme ty mty ->
+          () <$ evalUnisonTerm False ppe False tm
+      | otherwise ->
+          Cli.returnEarly $ BadMainFunction rendered ty ppe [mty]
+    Result.Result notes Nothing -> do
+      currentPath <- Cli.getCurrentPath
+      let tes = [err | Result.TypeError err <- toList notes]
+      Cli.returnEarly (TypeErrors currentPath (Text.pack rendered) ppe tes)
+  where
+    a = External
+    rendered = P.toPlainUnbroken $ TP.pretty ppe tm
+
+ensureSchemeExists :: Cli ()
+ensureSchemeExists =
+  liftIO callScheme >>= \case
+    True -> pure ()
+    False -> Cli.returnEarly (PrintMessage msg)
+  where
+    msg =
+      P.lines
+        [ "I can't seem to call scheme. See",
+          "",
+          P.indentN
+            2
+            "https://github.com/cisco/ChezScheme/blob/main/BUILDING",
+          "",
+          "for how to install Chez Scheme."
+        ]
+
+    callScheme =
+      catch
+        (True <$ readCreateProcess (shell "scheme -q") "")
+        (\(_ :: IOException) -> pure False)
+
+runScheme :: String -> Cli ()
+runScheme file = do
+  ensureSchemeExists
+  gendir <- getSchemeGenLibDir
+  statdir <- getSchemeStaticLibDir
+  let includes = gendir ++ ":" ++ statdir
+      lib = "--libdirs " ++ includes
+      opt = "--optimize-level 3"
+      cmd = "scheme -q " ++ opt ++ " " ++ lib ++ " --script " ++ file
+  success <-
+    liftIO $
+      (True <$ callCommand cmd) `catch` \(_ :: IOException) ->
+        pure False
+  unless success $
+    Cli.returnEarly (PrintMessage "Scheme evaluation failed.")
+
+buildScheme :: String -> String -> Cli ()
+buildScheme main file = do
+  ensureSchemeExists
+  statDir <- getSchemeStaticLibDir
+  genDir <- getSchemeGenLibDir
+  let cmd = shell "scheme -q --optimize-level 3"
+  void . liftIO $ readCreateProcess cmd (build statDir genDir)
+  where
+    surround s = '"' : s ++ "\""
+    parens s = '(' : s ++ ")"
+    lns dir nms = surround . ln dir <$> nms
+    ln dir nm = dir </> "unison" </> (nm ++ ".ss")
+
+    static = ["core", "cont", "bytevector", "string", "primops", "boot"]
+    gen = ["boot-generated", "builtin-generated"]
+
+    bootf = surround $ main ++ ".boot"
+    base = "'(\"scheme\" \"petite\")"
+
+    build sd gd =
+      parens . List.intercalate " " $
+        ["make-boot-file", bootf, base]
+          ++ lns sd static
+          ++ lns gd gen
+          ++ [surround file]
+
+doRunAsScheme :: HQ.HashQualified Name -> Cli ()
+doRunAsScheme main = do
+  fullpath <- generateSchemeFile (HQ.toString main) main
+  runScheme fullpath
+
+doCompileScheme :: String -> HQ.HashQualified Name -> Cli ()
+doCompileScheme out main =
+  generateSchemeFile out main >>= buildScheme out
+
+generateSchemeFile :: String -> HQ.HashQualified Name -> Cli String
+generateSchemeFile out main = do
+  (comp, ppe) <- resolveMainRef main
+  ensureCompilerExists
+  doGenerateSchemeBoot False $ Just ppe
+  cacheDir <- getCacheDir
+  liftIO $ createDirectoryIfMissing True (cacheDir </> "scheme-tmp")
+  let scratch = out ++ ".scm"
+      fullpath = cacheDir </> "scheme-tmp" </> scratch
+      output = Text.pack fullpath
+  sscm <- Term.ref a <$> resolveTermRef saveNm
+  fprf <- resolveCon filePathNm
+  let toCmp = Term.termLink a (Referent.Ref comp)
+      outTm = Term.text a output
+      fpc = Term.constructor a fprf
+      fp = Term.app a fpc outTm
+      tm :: Term Symbol Ann
+      tm = Term.apps' sscm [toCmp, fp]
+  typecheckAndEval ppe tm
+  pure fullpath
+  where
+    a = External
+    hq nm
+      | Just hqn <- HQ.fromString nm = hqn
+      | otherwise = error $ "internal error: cannot hash qualify: " ++ nm
+
+    saveNm = hq ".unison.internal.compiler.saveScheme"
+    filePathNm = hq "FilePath.FilePath"
+
+doPullRemoteBranch ::
+  Maybe ReadRemoteNamespace ->
+  Path' ->
+  SyncMode.SyncMode ->
+  PullMode ->
+  Verbosity.Verbosity ->
+  Text ->
+  Cli ()
+doPullRemoteBranch mayRepo path syncMode pullMode verbosity description = do
+  Cli.Env {codebase} <- ask
+  let preprocess = case pullMode of
+        Input.PullWithHistory -> Unmodified
+        Input.PullWithoutHistory -> Preprocessed $ pure . Branch.discardHistory
+  ns <- maybe (writePathToRead <$> resolveConfiguredUrl Pull path) pure mayRepo
+  remoteBranch <- case ns of
+    ReadRemoteNamespaceGit repo ->
+      Cli.ioE (Codebase.importRemoteBranch codebase repo syncMode preprocess) \err ->
+        Cli.returnEarly (Output.GitError err)
+    ReadRemoteNamespaceShare repo -> importRemoteShareBranch repo
+  let unchangedMsg = PullAlreadyUpToDate ns path
+  destAbs <- Cli.resolvePath' path
+  let printDiffPath = if Verbosity.isSilent verbosity then Nothing else Just path
+  case pullMode of
+    Input.PullWithHistory -> do
+      destBranch <- Cli.getBranch0At destAbs
+      if Branch.isEmpty0 destBranch
+        then do
+          void $ Cli.updateAtM description destAbs (const $ pure remoteBranch)
+          Cli.respond $ MergeOverEmpty path
+        else
+          mergeBranchAndPropagateDefaultPatch
+            Branch.RegularMerge
+            description
+            (Just unchangedMsg)
+            remoteBranch
+            printDiffPath
+            destAbs
+    Input.PullWithoutHistory -> do
+      didUpdate <-
+        Cli.updateAtM
+          description
+          destAbs
+          (\destBranch -> pure $ remoteBranch `Branch.consBranchSnapshot` destBranch)
+      Cli.respond
+        if didUpdate
+          then PullSuccessful ns path
+          else unchangedMsg
+
 loadPropagateDiffDefaultPatch ::
   Text ->
   Maybe Path.Path' ->
@@ -2974,7 +3206,7 @@ evalUnisonFile sandbox ppe unisonFile args = do
 
   let watchCache :: Reference.Id -> IO (Maybe (Term Symbol ()))
       watchCache ref = do
-        maybeTerm <- Codebase.lookupWatchCache codebase ref
+        maybeTerm <- Codebase.runTransaction codebase (Codebase.lookupWatchCache codebase ref)
         pure (Term.amap (\(_ :: Ann) -> ()) <$> maybeTerm)
 
   Cli.with_ (withArgs args) do
@@ -3000,7 +3232,7 @@ evalUnisonTermE sandbox ppe useCache tm = do
 
   let watchCache :: Reference.Id -> IO (Maybe (Term Symbol ()))
       watchCache ref = do
-        maybeTerm <- Codebase.lookupWatchCache codebase ref
+        maybeTerm <- Codebase.runTransaction codebase (Codebase.lookupWatchCache codebase ref)
         pure (Term.amap (\(_ :: Ann) -> ()) <$> maybeTerm)
 
   let cache = if useCache then watchCache else Runtime.noCache
diff --git a/unison-cli/src/Unison/Codebase/Editor/HandleInput/TermResolution.hs b/unison-cli/src/Unison/Codebase/Editor/HandleInput/TermResolution.hs
new file mode 100644
index 000000000..7a3c2498a
--- /dev/null
+++ b/unison-cli/src/Unison/Codebase/Editor/HandleInput/TermResolution.hs
@@ -0,0 +1,123 @@
+module Unison.Codebase.Editor.HandleInput.TermResolution
+  ( lookupTermRefs,
+    lookupTermRefWithType,
+    resolveCon,
+    resolveTerm,
+    resolveTermRef,
+    resolveMainRef,
+  )
+where
+
+import Control.Monad.Reader (ask)
+import Control.Monad.Trans (liftIO)
+import Data.Maybe (catMaybes, fromJust)
+import Data.Set (fromList, toList)
+import Unison.Cli.Monad (Cli)
+import qualified Unison.Cli.Monad as Cli
+import Unison.Cli.NamesUtils (basicParseNames, basicPrettyPrintNamesA)
+import qualified Unison.Codebase as Codebase
+import Unison.Codebase.Editor.Output (Output (..))
+import Unison.Codebase.Path (hqSplitFromName')
+import qualified Unison.Codebase.Runtime as Runtime
+import Unison.ConstructorReference
+import qualified Unison.HashQualified as HQ
+import Unison.Name (Name)
+import Unison.Names (Names)
+import Unison.NamesWithHistory
+  ( NamesWithHistory (..),
+    lookupHQTerm,
+  )
+import Unison.Parser.Ann (Ann)
+import Unison.PrettyPrintEnv (PrettyPrintEnv)
+import Unison.PrettyPrintEnv.Names (fromSuffixNames)
+import Unison.Reference (Reference)
+import Unison.Referent (Referent, pattern Con, pattern Ref)
+import Unison.Symbol (Symbol)
+import Unison.Type (Type)
+import qualified Unison.Typechecker as Typechecker
+
+addHistory :: Names -> NamesWithHistory
+addHistory names = NamesWithHistory names mempty
+
+lookupTerm :: HQ.HashQualified Name -> Names -> [Referent]
+lookupTerm hq parseNames = toList (lookupHQTerm hq hnames)
+  where
+    hnames = addHistory parseNames
+
+lookupCon ::
+  HQ.HashQualified Name ->
+  Names ->
+  ([ConstructorReference], [Referent])
+lookupCon hq parseNames =
+  unzip . catMaybes . fmap extract $ lookupTerm hq parseNames
+  where
+    extract rt@(Con rf _) = Just (rf, rt)
+    extract _ = Nothing
+
+lookupTermRefs ::
+  HQ.HashQualified Name -> Names -> ([Reference], [Referent])
+lookupTermRefs hq parseNames =
+  unzip . catMaybes . fmap extract $ lookupTerm hq parseNames
+  where
+    extract rt@(Ref rf) = Just (rf, rt)
+    extract _ = Nothing
+
+lookupTermRefWithType ::
+  Codebase.Codebase IO Symbol Ann ->
+  HQ.HashQualified Name ->
+  Cli [(Reference, Type Symbol Ann)]
+lookupTermRefWithType codebase name = do
+  nms <- basicParseNames
+  liftIO
+    . Codebase.runTransaction codebase
+    . fmap catMaybes
+    . traverse annot
+    . fst
+    $ lookupTermRefs name nms
+  where
+    annot tm =
+      fmap ((,) tm) <$> Codebase.getTypeOfTerm codebase tm
+
+resolveTerm :: HQ.HashQualified Name -> Cli Referent
+resolveTerm name =
+  basicParseNames >>= \nms ->
+    case lookupTerm name nms of
+      [] -> Cli.returnEarly (TermNotFound $ fromJust parsed)
+        where
+          parsed = hqSplitFromName' =<< HQ.toName name
+      [rf] -> pure rf
+      rfs -> Cli.returnEarly (TermAmbiguous name (fromList rfs))
+
+resolveCon :: HQ.HashQualified Name -> Cli ConstructorReference
+resolveCon name =
+  basicParseNames >>= \nms ->
+    case lookupCon name nms of
+      ([], _) -> Cli.returnEarly (TermNotFound $ fromJust parsed)
+        where
+          parsed = hqSplitFromName' =<< HQ.toName name
+      ([co], _) -> pure co
+      (_, rfts) -> Cli.returnEarly (TermAmbiguous name (fromList rfts))
+
+resolveTermRef :: HQ.HashQualified Name -> Cli Reference
+resolveTermRef name =
+  basicParseNames >>= \nms ->
+    case lookupTermRefs name nms of
+      ([], _) -> Cli.returnEarly (TermNotFound $ fromJust parsed)
+        where
+          parsed = hqSplitFromName' =<< HQ.toName name
+      ([rf], _) -> pure rf
+      (_, rfts) -> Cli.returnEarly (TermAmbiguous name (fromList rfts))
+
+resolveMainRef :: HQ.HashQualified Name -> Cli (Reference, PrettyPrintEnv)
+resolveMainRef main = do
+  Cli.Env {codebase, runtime} <- ask
+  let mainType = Runtime.mainType runtime
+      smain = HQ.toString main
+  parseNames <- basicPrettyPrintNamesA
+  k <- Cli.runTransaction Codebase.hashLength
+  let ppe = fromSuffixNames k (addHistory parseNames)
+  lookupTermRefWithType codebase main >>= \case
+    [(rf, ty)]
+      | Typechecker.fitsScheme ty mainType -> pure (rf, ppe)
+      | otherwise -> Cli.returnEarly (BadMainFunction smain ty ppe [mainType])
+    _ -> Cli.returnEarly (NoMainFunction smain ppe [mainType])
diff --git a/unison-cli/src/Unison/Codebase/Editor/Input.hs b/unison-cli/src/Unison/Codebase/Editor/Input.hs
index c3ab90f55..fa02d011a 100644
--- a/unison-cli/src/Unison/Codebase/Editor/Input.hs
+++ b/unison-cli/src/Unison/Codebase/Editor/Input.hs
@@ -155,6 +155,14 @@ data Input
     IOTestI (HQ.HashQualified Name)
   | -- make a standalone binary file
     MakeStandaloneI String (HQ.HashQualified Name)
+  | -- execute an IO thunk using scheme
+    ExecuteSchemeI (HQ.HashQualified Name)
+  | -- compile to a scheme file
+    CompileSchemeI String (HQ.HashQualified Name)
+  | -- generate scheme libraries
+    GenSchemeLibsI
+  | -- fetch scheme compiler
+    FetchSchemeCompilerI
   | TestI TestInput
   | -- metadata
     -- `link metadata definitions` (adds metadata to all of `definitions`)
diff --git a/unison-cli/src/Unison/Codebase/Editor/Propagate.hs b/unison-cli/src/Unison/Codebase/Editor/Propagate.hs
index b0f608dac..9f6897540 100644
--- a/unison-cli/src/Unison/Codebase/Editor/Propagate.hs
+++ b/unison-cli/src/Unison/Codebase/Editor/Propagate.hs
@@ -36,13 +36,14 @@ import qualified Unison.DataDeclaration as Decl
 import Unison.FileParsers (synthesizeFile')
 import Unison.Hash (Hash)
 import qualified Unison.Hashing.V2.Convert as Hashing
+import Unison.Name (Name)
 import qualified Unison.Name as Name
 import Unison.NameSegment (NameSegment)
 import Unison.Names (Names)
 import qualified Unison.Names as Names
 import Unison.Parser.Ann (Ann (..))
 import Unison.Prelude
-import Unison.Reference (Reference (..))
+import Unison.Reference (Reference (..), TermReference, TypeReference)
 import qualified Unison.Reference as Reference
 import Unison.Referent (Referent)
 import qualified Unison.Referent as Referent
@@ -58,6 +59,7 @@ import Unison.UnisonFile (UnisonFile (..))
 import qualified Unison.UnisonFile as UF
 import Unison.Util.Monoid (foldMapM)
 import qualified Unison.Util.Relation as R
+import qualified Unison.Util.Set as Set
 import qualified Unison.Util.Star3 as Star3
 import Unison.Util.TransitiveClosure (transitiveClosure)
 import Unison.Var (Var)
@@ -240,14 +242,7 @@ propagate patch b = case validatePatch patch of
     -- TODO: this can be removed once patches have term replacement of type `Referent -> Referent`
     rootNames <- Branch.toNames <$> Cli.getRootBranch0
 
-    let entireBranch =
-          Set.union
-            (Branch.deepTypeReferences b)
-            ( Set.fromList
-                [r | Referent.Ref r <- Set.toList $ Branch.deepReferents b]
-            )
-
-        -- TODO: these are just used for tracing, could be deleted if we don't care
+    let -- TODO: these are just used for tracing, could be deleted if we don't care
         -- about printing meaningful names for definitions during propagation, or if
         -- we want to just remove the tracing.
         refName r =
@@ -270,7 +265,8 @@ propagate patch b = case validatePatch patch of
         computeDirty
           (Codebase.dependents Queries.ExcludeOwnComponent)
           patch
-          (Names.contains names0)
+          -- Dirty reference predicate: does the reference have a name in this branch that isn't in the "lib" namespace?
+          (Names.contains (Names.filter nameNotInLibNamespace (Branch.toNames b)))
 
       let initialTypeReplacements = Map.mapMaybe TypeEdit.toReference initialTypeEdits
       -- TODO: once patches can directly contain constructor replacements, this
@@ -278,7 +274,16 @@ propagate patch b = case validatePatch patch of
       -- in the patch which have a `Referent.Con` as their LHS.
       initialCtorMappings <- genInitialCtorMapping rootNames initialTypeReplacements
 
-      order <- sortDependentsGraph initialDirty entireBranch
+      order <-
+        let restrictToTypes :: Set TypeReference
+            restrictToTypes =
+              R.dom (R.filterRan nameNotInLibNamespace (Branch.deepTypes b))
+            restrictToTerms :: Set TermReference
+            restrictToTerms =
+              Set.mapMaybe Referent.toTermReference (R.dom (R.filterRan nameNotInLibNamespace (Branch.deepTerms b)))
+         in sortDependentsGraph
+              initialDirty
+              (Set.union restrictToTypes restrictToTerms)
 
       let getOrdered :: Set Reference -> Map Int Reference
           getOrdered rs =
@@ -478,7 +483,6 @@ propagate patch b = case validatePatch patch of
           (zip (view _1 . getReference <$> Graph.topSort graph) [0 ..])
     -- vertex i precedes j whenever i has an edge to j and not vice versa.
     -- vertex i precedes j when j is a dependent of i.
-    names0 = Branch.toNames b
     validatePatch ::
       Patch -> Maybe (Map Reference TermEdit, Map Reference TypeEdit)
     validatePatch p =
@@ -600,12 +604,20 @@ applyDeprecations patch =
 -- | Things in the patch are not marked as propagated changes, but every other
 -- definition that is created by the `Edits` which is passed in is marked as
 -- a propagated change.
-applyPropagate :: Applicative m => Patch -> Edits Symbol -> Branch0 m -> Branch0 m
-applyPropagate patch Edits {..} = do
+applyPropagate :: forall m. Applicative m => Patch -> Edits Symbol -> Branch0 m -> Branch0 m
+applyPropagate patch Edits {newTerms, termReplacements, typeReplacements, constructorReplacements} = do
   let termTypes = Map.map (Hashing.typeToReference . snd) newTerms
   -- recursively update names and delete deprecated definitions
-  Branch.stepEverywhere (updateLevel termReplacements typeReplacements termTypes)
+  stepEverywhereButLib (updateLevel termReplacements typeReplacements termTypes)
   where
+    -- Like Branch.stepEverywhere, but don't step the child named "lib"
+    stepEverywhereButLib :: (Branch0 m -> Branch0 m) -> (Branch0 m -> Branch0 m)
+    stepEverywhereButLib f branch =
+      let children =
+            Map.mapWithKey
+              (\name child -> if name == "lib" then child else Branch.step (Branch.stepEverywhere f) child)
+              (branch ^. Branch.children)
+       in f (Branch.branch0 (branch ^. Branch.terms) (branch ^. Branch.types) children (branch ^. Branch.edits))
     isPropagated r = Set.notMember r allPatchTargets
     allPatchTargets = Patch.allReferenceTargets patch
     propagatedMd :: forall r. r -> (r, Metadata.Type, Metadata.Value)
@@ -627,32 +639,28 @@ applyPropagate patch Edits {..} = do
         terms0 = Star3.replaceFacts replaceConstructor constructorReplacements _terms
         terms :: Branch.Star Referent NameSegment
         terms =
-          updateMetadatas Referent.Ref $
+          updateMetadatas $
             Star3.replaceFacts replaceTerm termEdits terms0
         types :: Branch.Star Reference NameSegment
         types =
-          updateMetadatas id $
+          updateMetadatas $
             Star3.replaceFacts replaceType typeEdits _types
 
         updateMetadatas ::
           Ord r =>
-          (Reference -> r) ->
           Star3.Star3 r NameSegment Metadata.Type (Metadata.Type, Metadata.Value) ->
           Star3.Star3 r NameSegment Metadata.Type (Metadata.Type, Metadata.Value)
-        updateMetadatas ref s = clearPropagated $ Star3.mapD3 go s
+        updateMetadatas s = Star3.mapD3 go s
           where
-            clearPropagated s = foldl' go s allPatchTargets
-              where
-                go s r = Metadata.delete (propagatedMd $ ref r) s
             go (tp, v) = case Map.lookup (Referent.Ref v) termEdits of
               Just (Referent.Ref r) -> (typeOf r tp, r)
               _ -> (tp, v)
             typeOf r t = fromMaybe t $ Map.lookup r termTypes
 
         replaceTerm :: Referent -> Referent -> Metadata.Star Referent NameSegment -> Metadata.Star Referent NameSegment
-        replaceTerm r r' s =
+        replaceTerm _r r' s =
           ( if isPropagatedReferent r'
-              then Metadata.insert (propagatedMd r') . Metadata.delete (propagatedMd r)
+              then Metadata.insert (propagatedMd r')
               else Metadata.delete (propagatedMd r')
           )
             $ s
@@ -682,11 +690,9 @@ applyPropagate patch Edits {..} = do
 
 -- | Compute the set of "dirty" references. They each:
 --
---   1. Depend directly on some reference that was edited in the given patch
---   2. Have a name in the current namespace (the given Names)
---   3. Are not themselves edited in the given patch.
---
--- Note: computeDirty a b c = R.dom <$> computeFrontier a b c
+-- 1. Depend directly on some reference that was edited in the given patch
+-- 2. Are not themselves edited in the given patch.
+-- 3. Pass the given predicate.
 computeDirty ::
   Monad m =>
   (Reference -> m (Set Reference)) -> -- eg Codebase.dependents codebase
@@ -703,3 +709,7 @@ computeDirty getDependents patch shouldUpdate =
 
     edited :: Set Reference
     edited = R.dom (Patch._termEdits patch) <> R.dom (Patch._typeEdits patch)
+
+nameNotInLibNamespace :: Name -> Bool
+nameNotInLibNamespace name =
+  not (Name.beginsWithSegment name "lib")
diff --git a/unison-cli/src/Unison/CommandLine/Completion.hs b/unison-cli/src/Unison/CommandLine/Completion.hs
index 42d6d0abf..72049767b 100644
--- a/unison-cli/src/Unison/CommandLine/Completion.hs
+++ b/unison-cli/src/Unison/CommandLine/Completion.hs
@@ -57,6 +57,7 @@ import qualified Unison.Server.Endpoints.NamespaceListing as Server
 import qualified Unison.Server.Types as Server
 import qualified Unison.Share.Codeserver as Codeserver
 import qualified Unison.Share.Types as Share
+import qualified Unison.Sqlite as Sqlite
 import qualified Unison.Util.Pretty as P
 import qualified UnliftIO
 import Prelude hiding (readFile, writeFile)
@@ -131,18 +132,15 @@ noCompletions _ _ _ _ = pure []
 -- .> view base.List.map#<Tab>
 -- base.List.map#0q926sgnn6
 completeWithinNamespace ::
-  forall m v a.
-  MonadIO m =>
   -- | The types of completions to return
   NESet CompletionType ->
   -- | The portion of this are that the user has already typed.
   String ->
-  Codebase m v a ->
   Path.Absolute ->
-  m [System.Console.Haskeline.Completion.Completion]
-completeWithinNamespace compTypes query codebase currentPath = do
-  shortHashLen <- Codebase.runTransaction codebase Codebase.hashLength
-  b <- Codebase.getShallowBranchAtPath codebase (Path.unabsolute absQueryPath) Nothing
+  Sqlite.Transaction [System.Console.Haskeline.Completion.Completion]
+completeWithinNamespace compTypes query currentPath = do
+  shortHashLen <- Codebase.hashLength
+  b <- Codebase.getShallowBranchAtPath (Path.unabsolute absQueryPath) Nothing
   currentBranchSuggestions <- do
     nib <- namesInBranch shortHashLen b
     nib
@@ -162,9 +160,9 @@ completeWithinNamespace compTypes query codebase currentPath = do
     (queryPathPrefix, querySuffix) = parseLaxPath'Query (Text.pack query)
     absQueryPath :: Path.Absolute
     absQueryPath = Path.resolve currentPath queryPathPrefix
-    getChildSuggestions :: Int -> V2Branch.Branch m -> m [Completion]
+    getChildSuggestions :: Int -> V2Branch.Branch Sqlite.Transaction -> Sqlite.Transaction [Completion]
     getChildSuggestions shortHashLen b = do
-      nonEmptyChildren <- Codebase.runTransaction codebase (V2Branch.nonEmptyChildren b)
+      nonEmptyChildren <- V2Branch.nonEmptyChildren b
       case querySuffix of
         "" -> pure []
         suffix -> do
@@ -180,9 +178,9 @@ completeWithinNamespace compTypes query codebase currentPath = do
                 & filter (\(_isFinished, match) -> List.isPrefixOf query match)
                 & fmap (\(isFinished, match) -> prettyCompletionWithQueryPrefix isFinished query match)
                 & pure
-    namesInBranch :: Int -> V2Branch.Branch m -> m [(Bool, Text)]
+    namesInBranch :: Int -> V2Branch.Branch Sqlite.Transaction -> Sqlite.Transaction [(Bool, Text)]
     namesInBranch hashLen b = do
-      nonEmptyChildren <- Codebase.runTransaction codebase (V2Branch.nonEmptyChildren b)
+      nonEmptyChildren <- V2Branch.nonEmptyChildren b
       let textifyHQ :: (V2Branch.NameSegment -> r -> HQ'.HashQualified V2Branch.NameSegment) -> Map V2Branch.NameSegment (Map r metadata) -> [(Bool, Text)]
           textifyHQ f xs =
             xs
@@ -208,9 +206,9 @@ completeWithinNamespace compTypes query codebase currentPath = do
         qualifyRefs :: V2Branch.NameSegment -> (Map r metadata) -> [HQ'.HashQualified V2Branch.NameSegment]
         qualifyRefs n refs
           | ((Text.isInfixOf "#" . NameSegment.toText) querySuffix) || length refs > 1 =
-            refs
-              & Map.keys
-              <&> qualify n
+              refs
+                & Map.keys
+                <&> qualify n
           | otherwise = [HQ'.NameOnly n]
 
     -- If we're not completing namespaces, then all namespace completions should automatically
@@ -265,52 +263,37 @@ parseLaxPath'Query txt =
 
 -- | Completes a namespace argument by prefix-matching against the query.
 prefixCompleteNamespace ::
-  forall m v a.
-  (MonadIO m) =>
   String ->
-  Codebase m v a ->
   Path.Absolute -> -- Current path
-  m [Line.Completion]
+  Sqlite.Transaction [Line.Completion]
 prefixCompleteNamespace = completeWithinNamespace (NESet.singleton NamespaceCompletion)
 
 -- | Completes a term or type argument by prefix-matching against the query.
 prefixCompleteTermOrType ::
-  forall m v a.
-  MonadIO m =>
   String ->
-  Codebase m v a ->
   Path.Absolute -> -- Current path
-  m [Line.Completion]
+  Sqlite.Transaction [Line.Completion]
 prefixCompleteTermOrType = completeWithinNamespace (NESet.fromList (TermCompletion NE.:| [TypeCompletion]))
 
 -- | Completes a term argument by prefix-matching against the query.
 prefixCompleteTerm ::
-  forall m v a.
-  MonadIO m =>
   String ->
-  Codebase m v a ->
   Path.Absolute -> -- Current path
-  m [Line.Completion]
+  Sqlite.Transaction [Line.Completion]
 prefixCompleteTerm = completeWithinNamespace (NESet.singleton TermCompletion)
 
 -- | Completes a term or type argument by prefix-matching against the query.
 prefixCompleteType ::
-  forall m v a.
-  MonadIO m =>
   String ->
-  Codebase m v a ->
   Path.Absolute -> -- Current path
-  m [Line.Completion]
+  Sqlite.Transaction [Line.Completion]
 prefixCompleteType = completeWithinNamespace (NESet.singleton TypeCompletion)
 
 -- | Completes a patch argument by prefix-matching against the query.
 prefixCompletePatch ::
-  forall m v a.
-  MonadIO m =>
   String ->
-  Codebase m v a ->
   Path.Absolute -> -- Current path
-  m [Line.Completion]
+  Sqlite.Transaction [Line.Completion]
 prefixCompletePatch = completeWithinNamespace (NESet.singleton PatchCompletion)
 
 -- | Renders a completion option with the prefix matching the query greyed out.
diff --git a/unison-cli/src/Unison/CommandLine/DisplayValues.hs b/unison-cli/src/Unison/CommandLine/DisplayValues.hs
index d821a8650..e1f817b39 100644
--- a/unison-cli/src/Unison/CommandLine/DisplayValues.hs
+++ b/unison-cli/src/Unison/CommandLine/DisplayValues.hs
@@ -193,11 +193,14 @@ displayPretty pped terms typeOf eval types tm = go tm
             go = pure . P.underline . P.syntaxToColor . NP.prettyHashQualified
          in case e of
               DD.EitherLeft' (Term.TypeLink' ref) -> go $ PPE.typeName ppe ref
-              DD.EitherRight' (DD.Doc2Term (Term.Ref' ref)) -> go $ PPE.termName ppe (Referent.Ref ref)
-              DD.EitherRight' (DD.Doc2Term (Term.Request' ref)) ->
-                go $ PPE.termName ppe (Referent.Con ref CT.Effect)
-              DD.EitherRight' (DD.Doc2Term (Term.Constructor' ref)) ->
-                go $ PPE.termName ppe (Referent.Con ref CT.Data)
+              -- Eta-reduce the term, as the compiler may have eta-expanded it.
+              DD.EitherRight' (DD.Doc2Term t) -> case Term.etaNormalForm t of
+                Term.Ref' ref -> go $ PPE.termName ppe (Referent.Ref ref)
+                Term.Request' ref ->
+                  go $ PPE.termName ppe (Referent.Con ref CT.Effect)
+                Term.Constructor' ref ->
+                  go $ PPE.termName ppe (Referent.Con ref CT.Data)
+                _ -> P.red <$> displayTerm pped terms typeOf eval types t
               _ -> P.red <$> displayTerm pped terms typeOf eval types e
       -- Signature [Doc2.Term]
       DD.Doc2SpecialFormSignature (Term.List' tms) ->
diff --git a/unison-cli/src/Unison/CommandLine/InputPatterns.hs b/unison-cli/src/Unison/CommandLine/InputPatterns.hs
index 324a009dd..ce3b87371 100644
--- a/unison-cli/src/Unison/CommandLine/InputPatterns.hs
+++ b/unison-cli/src/Unison/CommandLine/InputPatterns.hs
@@ -13,6 +13,7 @@ import qualified Data.Set as Set
 import qualified Data.Text as Text
 import System.Console.Haskeline.Completion (Completion (Completion))
 import qualified Text.Megaparsec as P
+import qualified Unison.Codebase as Codebase
 import qualified Unison.Codebase.Branch as Branch
 import qualified Unison.Codebase.Branch.Merge as Branch
 import Unison.Codebase.Editor.Input (Input)
@@ -332,8 +333,14 @@ view =
     I.Visible
     [(ZeroPlus, definitionQueryArg)]
     ( P.lines
-        [ "`view foo` prints definitions named `foo` within your current namespace.",
-          "`view` without arguments invokes a search to select definitions to view, which requires that `fzf` can be found within your PATH."
+        [ P.wrap $ makeExample view ["foo"] <> "shows definitions named `foo` within your current namespace.",
+          P.wrap $ makeExample view [] <> "without arguments invokes a search to select definitions to view, which requires that `fzf` can be found within your PATH.",
+          " ", -- hmm, this blankline seems to be ignored by pretty printer
+          P.wrap $
+            "Supports glob syntax, where ? acts a wildcard, so"
+              <> makeExample view ["List.?"]
+              <> "will show `List.map`, `List.filter`, etc, but "
+              <> "not `List.map.doc` (since ? only matches 1 name segment)."
         ]
     )
     ( fmap (Input.ShowDefinitionI Input.ConsoleLocation Input.ShowDefinitionLocal)
@@ -2116,6 +2123,96 @@ makeStandalone =
         _ -> Left $ showPatternHelp makeStandalone
     )
 
+runScheme :: InputPattern
+runScheme =
+  InputPattern
+    "run.native"
+    []
+    I.Visible
+    [(Required, exactDefinitionTermQueryArg)]
+    ( P.wrapColumn2
+        [ ( makeExample runScheme ["main"],
+            "Executes !main using native compilation via scheme."
+          )
+        ]
+    )
+    ( \case
+        [main] ->
+          Input.ExecuteSchemeI <$> parseHashQualifiedName main
+        _ -> Left $ showPatternHelp runScheme
+    )
+
+compileScheme :: InputPattern
+compileScheme =
+  InputPattern
+    "compile.native"
+    []
+    I.Visible
+    [(Required, exactDefinitionTermQueryArg), (Required, noCompletionsArg)]
+    ( P.wrapColumn2
+        [ ( makeExample compileScheme ["main", "file"],
+            "Creates stand alone executable via compilation to"
+              <> "scheme. The created executable will have the effect"
+              <> "of running `!main`."
+          )
+        ]
+    )
+    ( \case
+        [main, file] ->
+          Input.CompileSchemeI file <$> parseHashQualifiedName main
+        _ -> Left $ showPatternHelp compileScheme
+    )
+
+schemeLibgen :: InputPattern
+schemeLibgen =
+  InputPattern
+    "compile.native.genlibs"
+    []
+    I.Visible
+    []
+    ( P.wrapColumn2
+        [ ( makeExample schemeLibgen [],
+            "Generates libraries necessary for scheme compilation.\n\n\
+            \There is no need to run this before"
+              <> P.group (makeExample compileScheme [])
+              <> "as\
+                 \ the latter will check if the libraries are missing and\
+                 \ auto-generate them. However, this will generate the\
+                 \ libraries even if their files already exist, so if the\
+                 \ compiler has been upgraded, this can be used to ensure\
+                 \ the generated libraries are up to date."
+          )
+        ]
+    )
+    ( \case
+        [] -> pure Input.GenSchemeLibsI
+        _ -> Left $ showPatternHelp schemeLibgen
+    )
+
+fetchScheme :: InputPattern
+fetchScheme =
+  InputPattern
+    "compile.native.fetch"
+    []
+    I.Visible
+    []
+    ( P.wrapColumn2
+        [ ( makeExample fetchScheme [],
+            "Fetches the unison library for compiling to scheme.\n\n\
+            \This is done automatically when"
+              <> P.group (makeExample compileScheme [])
+              <> "is run\
+                 \ if the library is not already in the standard location\
+                 \ (unison.internal). However, this command will force\
+                 \ a pull even if the library already exists."
+          )
+        ]
+    )
+    ( \case
+        [] -> pure Input.FetchSchemeCompilerI
+        _ -> Left $ showPatternHelp fetchScheme
+    )
+
 createAuthor :: InputPattern
 createAuthor =
   InputPattern
@@ -2288,6 +2385,10 @@ validInputs =
       quit,
       updateBuiltins,
       makeStandalone,
+      runScheme,
+      compileScheme,
+      schemeLibgen,
+      fetchScheme,
       mergeBuiltins,
       mergeIOBuiltins,
       dependents,
@@ -2331,7 +2432,7 @@ exactDefinitionArg :: ArgumentType
 exactDefinitionArg =
   ArgumentType
     { typeName = "definition",
-      suggestions = \q cb _http p -> prefixCompleteTermOrType q cb p,
+      suggestions = \q cb _http p -> Codebase.runTransaction cb (prefixCompleteTermOrType q p),
       globTargets = Set.fromList [Globbing.Term, Globbing.Type]
     }
 
@@ -2339,7 +2440,7 @@ fuzzyDefinitionQueryArg :: ArgumentType
 fuzzyDefinitionQueryArg =
   ArgumentType
     { typeName = "fuzzy definition query",
-      suggestions = \q cb _http p -> prefixCompleteTermOrType q cb p,
+      suggestions = \q cb _http p -> Codebase.runTransaction cb (prefixCompleteTermOrType q p),
       globTargets = Set.fromList [Globbing.Term, Globbing.Type]
     }
 
@@ -2350,7 +2451,7 @@ exactDefinitionTypeQueryArg :: ArgumentType
 exactDefinitionTypeQueryArg =
   ArgumentType
     { typeName = "type definition query",
-      suggestions = \q cb _http p -> prefixCompleteType q cb p,
+      suggestions = \q cb _http p -> Codebase.runTransaction cb (prefixCompleteType q p),
       globTargets = Set.fromList [Globbing.Type]
     }
 
@@ -2358,7 +2459,7 @@ exactDefinitionTermQueryArg :: ArgumentType
 exactDefinitionTermQueryArg =
   ArgumentType
     { typeName = "term definition query",
-      suggestions = \q cb _http p -> prefixCompleteTerm q cb p,
+      suggestions = \q cb _http p -> Codebase.runTransaction cb (prefixCompleteTerm q p),
       globTargets = Set.fromList [Globbing.Term]
     }
 
@@ -2366,7 +2467,7 @@ patchArg :: ArgumentType
 patchArg =
   ArgumentType
     { typeName = "patch",
-      suggestions = \q cb _http p -> prefixCompletePatch q cb p,
+      suggestions = \q cb _http p -> Codebase.runTransaction cb (prefixCompletePatch q p),
       globTargets = Set.fromList []
     }
 
@@ -2374,7 +2475,7 @@ namespaceArg :: ArgumentType
 namespaceArg =
   ArgumentType
     { typeName = "namespace",
-      suggestions = \q cb _http p -> prefixCompleteNamespace q cb p,
+      suggestions = \q cb _http p -> Codebase.runTransaction cb (prefixCompleteNamespace q p),
       globTargets = Set.fromList [Globbing.Namespace]
     }
 
@@ -2386,7 +2487,7 @@ newNameArg :: ArgumentType
 newNameArg =
   ArgumentType
     { typeName = "new-name",
-      suggestions = \q cb _http p -> prefixCompleteNamespace q cb p,
+      suggestions = \q cb _http p -> Codebase.runTransaction cb (prefixCompleteNamespace q p),
       globTargets = mempty
     }
 
diff --git a/unison-cli/src/Unison/CommandLine/OutputMessages.hs b/unison-cli/src/Unison/CommandLine/OutputMessages.hs
index 29b7a48eb..533f8c0da 100644
--- a/unison-cli/src/Unison/CommandLine/OutputMessages.hs
+++ b/unison-cli/src/Unison/CommandLine/OutputMessages.hs
@@ -665,8 +665,8 @@ notifyUser dir o = case o of
     CachedTests 0 _ -> pure . P.callout "😶" $ "No tests to run."
     CachedTests n n'
       | n == n' ->
-        pure $
-          P.lines [cache, "", displayTestResults True ppe oks fails]
+          pure $
+            P.lines [cache, "", displayTestResults True ppe oks fails]
     CachedTests _n m ->
       pure $
         if m == 0
@@ -675,6 +675,7 @@ notifyUser dir o = case o of
             P.indentN 2 $
               P.lines ["", cache, "", displayTestResults False ppe oks fails, "", "✅  "]
       where
+
     NewlyComputed -> do
       clearCurrentLine
       pure $
@@ -1131,6 +1132,9 @@ notifyUser dir o = case o of
           else pure mempty
   GitError e -> pure $ case e of
     GitSqliteCodebaseError e -> case e of
+      CodebaseFileLockFailed ->
+        P.wrap $
+          "It looks to me like another ucm process is using this codebase. Only one ucm process can use a codebase at a time."
       NoDatabaseFile repo localPath ->
         P.wrap $
           "I didn't find a codebase in the repository at"
@@ -2463,7 +2467,7 @@ showDiffNamespace ::
   (Pretty, NumberedArgs)
 showDiffNamespace _ _ _ _ diffOutput
   | OBD.isEmpty diffOutput =
-    ("The namespaces are identical.", mempty)
+      ("The namespaces are identical.", mempty)
 showDiffNamespace sn ppe oldPath newPath OBD.BranchDiffOutput {..} =
   (P.sepNonEmpty "\n\n" p, toList args)
   where
diff --git a/unison-cli/tests/Unison/Test/GitSync.hs b/unison-cli/tests/Unison/Test/GitSync.hs
index 7acbfbad2..93bb5f285 100644
--- a/unison-cli/tests/Unison/Test/GitSync.hs
+++ b/unison-cli/tests/Unison/Test/GitSync.hs
@@ -513,9 +513,10 @@ test =
                     |]
                 )
                 ( \cb -> do
-                    void . fmap (fromJust . sequence) $
-                      traverse (Codebase.getWatch cb TestWatch)
-                        =<< Codebase.runTransaction cb (Codebase.watches TestWatch)
+                    Codebase.runTransaction cb do
+                      void . fmap (fromJust . sequence) $
+                        traverse (Codebase.getWatch cb TestWatch)
+                          =<< Codebase.watches TestWatch
                 ),
               gistTest fmt,
               pushPullBranchesTests fmt,
diff --git a/unison-cli/tests/Unison/Test/Ucm.hs b/unison-cli/tests/Unison/Test/Ucm.hs
index 545fe9260..4a862e07f 100644
--- a/unison-cli/tests/Unison/Test/Ucm.hs
+++ b/unison-cli/tests/Unison/Test/Ucm.hs
@@ -53,7 +53,7 @@ initCodebase fmt = do
   tmp <-
     Temp.getCanonicalTemporaryDirectory
       >>= flip Temp.createTempDirectory "ucm-test"
-  result <- Codebase.Init.withCreatedCodebase cbInit "ucm-test" tmp (const $ pure ())
+  result <- Codebase.Init.withCreatedCodebase cbInit "ucm-test" tmp SC.DoLock (const $ pure ())
   case result of
     Left CreateCodebaseAlreadyExists -> fail $ P.toANSI 80 "Codebase already exists"
     Right _ -> pure $ Codebase tmp fmt
@@ -66,7 +66,7 @@ runTranscript (Codebase codebasePath fmt) transcript = do
   let err e = fail $ "Parse error: \n" <> show e
       cbInit = case fmt of CodebaseFormat2 -> SC.init
   TR.withTranscriptRunner "Unison.Test.Ucm.runTranscript Invalid Version String" configFile $ \runner -> do
-    result <- Codebase.Init.withOpenCodebase cbInit "transcript" codebasePath SC.DontMigrate \codebase -> do
+    result <- Codebase.Init.withOpenCodebase cbInit "transcript" codebasePath SC.DoLock SC.DontMigrate \codebase -> do
       Codebase.runTransaction codebase (Codebase.installUcmDependencies codebase)
       let transcriptSrc = Text.pack . stripMargin $ unTranscript transcript
       output <- either err Text.unpack <$> runner "transcript" transcriptSrc (codebasePath, codebase)
@@ -81,7 +81,7 @@ runTranscript (Codebase codebasePath fmt) transcript = do
 lowLevel :: Codebase -> (Codebase.Codebase IO Symbol Ann -> IO a) -> IO a
 lowLevel (Codebase root fmt) action = do
   let cbInit = case fmt of CodebaseFormat2 -> SC.init
-  result <- Codebase.Init.withOpenCodebase cbInit "lowLevel" root SC.DontMigrate action
+  result <- Codebase.Init.withOpenCodebase cbInit "lowLevel" root SC.DoLock SC.DontMigrate action
   case result of
     Left e -> PT.putPrettyLn (P.shown e) *> pure (error "This really should have loaded")
     Right a -> pure a
diff --git a/unison-cli/transcripts/Transcripts.hs b/unison-cli/transcripts/Transcripts.hs
index 7f4b2e338..52f8a2843 100644
--- a/unison-cli/transcripts/Transcripts.hs
+++ b/unison-cli/transcripts/Transcripts.hs
@@ -34,7 +34,7 @@ type TestBuilder = FilePath -> [String] -> String -> Test ()
 testBuilder ::
   Bool -> FilePath -> [String] -> String -> Test ()
 testBuilder expectFailure dir prelude transcript = scope transcript $ do
-  outputs <- io . withTemporaryUcmCodebase SC.init "transcript" $ \(codebasePath, codebase) -> do
+  outputs <- io . withTemporaryUcmCodebase SC.init "transcript" SC.DoLock $ \(codebasePath, codebase) -> do
     withTranscriptRunner "TODO: pass version here" Nothing $ \runTranscript -> do
       for files $ \filePath -> do
         transcriptSrc <- readUtf8 filePath
diff --git a/unison-cli/unison-cli.cabal b/unison-cli/unison-cli.cabal
index 401f275de..29616f879 100644
--- a/unison-cli/unison-cli.cabal
+++ b/unison-cli/unison-cli.cabal
@@ -43,6 +43,7 @@ library
       Unison.Codebase.Editor.HandleInput.MoveBranch
       Unison.Codebase.Editor.HandleInput.NamespaceDependencies
       Unison.Codebase.Editor.HandleInput.NamespaceDiffUtils
+      Unison.Codebase.Editor.HandleInput.TermResolution
       Unison.Codebase.Editor.HandleInput.Update
       Unison.Codebase.Editor.Input
       Unison.Codebase.Editor.Output
@@ -166,6 +167,7 @@ library
     , nonempty-containers
     , open-browser
     , pretty-simple
+    , process
     , random >=1.2.0
     , regex-tdfa
     , semialign
@@ -360,7 +362,7 @@ executable transcripts
       TupleSections
       TypeApplications
       ViewPatterns
-  ghc-options: -Wall -threaded -rtsopts -with-rtsopts=-N -v0
+  ghc-options: -Wall -threaded -rtsopts "-with-rtsopts=-I0 -N -qn4 -qg1" -v0
   build-depends:
       IntervalMap
     , ListLike
@@ -449,6 +451,7 @@ executable unison
   main-is: Main.hs
   other-modules:
       ArgParse
+      Stats
       System.Path
       Version
   hs-source-dirs:
@@ -483,7 +486,7 @@ executable unison
       TupleSections
       TypeApplications
       ViewPatterns
-  ghc-options: -Wall -threaded -rtsopts -with-rtsopts=-I0 -optP-Wno-nonportable-include-path
+  ghc-options: -Wall -threaded -rtsopts "-with-rtsopts=-I0 -N -qn4 -qg1 -T" -optP-Wno-nonportable-include-path
   build-depends:
       IntervalMap
     , ListLike
@@ -530,6 +533,7 @@ executable unison
     , open-browser
     , optparse-applicative >=0.16.1.0
     , pretty-simple
+    , process
     , random >=1.2.0
     , regex-tdfa
     , semialign
@@ -658,6 +662,7 @@ test-suite cli-tests
     , nonempty-containers
     , open-browser
     , pretty-simple
+    , process
     , random >=1.2.0
     , regex-tdfa
     , semialign
diff --git a/unison-cli/unison/ArgParse.hs b/unison-cli/unison/ArgParse.hs
index 8c3b85bf6..207e5b39b 100644
--- a/unison-cli/unison/ArgParse.hs
+++ b/unison-cli/unison/ArgParse.hs
@@ -53,6 +53,7 @@ import qualified Options.Applicative as OptParse
 import Options.Applicative.Builder.Internal (noGlobal {- https://github.com/pcapriotti/optparse-applicative/issues/461 -})
 import Options.Applicative.Help (bold, (<+>))
 import qualified Options.Applicative.Help.Pretty as P
+import Stats
 import System.Environment (lookupEnv)
 import Text.Read (readMaybe)
 import qualified Unison.Codebase.Path as Path
@@ -116,7 +117,7 @@ data Command
   | -- @deprecated in trunk after M2g. Remove the Init command completely after M2h has been released
     Init
   | Run RunSource [String]
-  | Transcript ShouldForkCodebase ShouldSaveCodebase (NonEmpty FilePath)
+  | Transcript ShouldForkCodebase ShouldSaveCodebase (Maybe RtsStatsPath) (NonEmpty FilePath)
   deriving (Show, Eq)
 
 -- | Options shared by sufficiently many subcommands.
@@ -381,6 +382,15 @@ runCompiledParser :: Parser Command
 runCompiledParser =
   Run . RunCompiled <$> fileArgument "path/to/file" <*> runArgumentParser
 
+rtsStatsOption :: Parser (Maybe RtsStatsPath)
+rtsStatsOption =
+  let meta =
+        metavar "FILE.json"
+          <> long "rts-stats"
+          <> help "Write json summary of rts stats to FILE"
+          <> noGlobal
+   in optional (option OptParse.str meta)
+
 saveCodebaseFlag :: Parser ShouldSaveCodebase
 saveCodebaseFlag = flag DontSaveCodebase SaveCodebase (long "save-codebase" <> help saveHelp)
   where
@@ -448,15 +458,17 @@ transcriptParser :: Parser Command
 transcriptParser = do
   -- ApplicativeDo
   shouldSaveCodebase <- saveCodebaseFlag
+  mrtsStatsFp <- rtsStatsOption
   files <- liftA2 (NE.:|) (fileArgument "FILE") (many (fileArgument "FILES..."))
-  pure (Transcript DontFork shouldSaveCodebase files)
+  pure (Transcript DontFork shouldSaveCodebase mrtsStatsFp files)
 
 transcriptForkParser :: Parser Command
 transcriptForkParser = do
   -- ApplicativeDo
   shouldSaveCodebase <- saveCodebaseFlag
+  mrtsStatsFp <- rtsStatsOption
   files <- liftA2 (NE.:|) (fileArgument "FILE") (many (fileArgument "FILES..."))
-  pure (Transcript UseFork shouldSaveCodebase files)
+  pure (Transcript UseFork shouldSaveCodebase mrtsStatsFp files)
 
 unisonHelp :: String -> String -> P.Doc
 unisonHelp (P.text -> executable) (P.text -> version) =
diff --git a/unison-cli/unison/Main.hs b/unison-cli/unison/Main.hs
index 3c5fdd52d..2bb07c19c 100644
--- a/unison-cli/unison/Main.hs
+++ b/unison-cli/unison/Main.hs
@@ -42,6 +42,7 @@ import qualified Language.Haskell.TH as TH
 import qualified Language.Haskell.TH.Syntax as TH
 import qualified Network.HTTP.Client as HTTP
 import qualified Network.HTTP.Client.TLS as HTTP
+import Stats (recordRtsStats)
 import System.Directory (canonicalizePath, getCurrentDirectory, removeDirectoryRecursive)
 import System.Environment (getProgName, lookupEnv, withArgs)
 import qualified System.Exit as Exit
@@ -240,8 +241,11 @@ main = withCP65001 . runInUnboundThread . Ki.scoped $ \scope -> do
                           "to produce a new compiled program \
                           \that matches your version of Unison."
                       ]
-        Transcript shouldFork shouldSaveCodebase transcriptFiles ->
-          runTranscripts renderUsageInfo shouldFork shouldSaveCodebase mCodePathOption transcriptFiles
+        Transcript shouldFork shouldSaveCodebase mrtsStatsFp transcriptFiles -> do
+          let action = runTranscripts renderUsageInfo shouldFork shouldSaveCodebase mCodePathOption transcriptFiles
+          case mrtsStatsFp of
+            Nothing -> action
+            Just fp -> recordRtsStats fp action
         Launch isHeadless codebaseServerOpts downloadBase mayStartingPath shouldWatchFiles -> do
           getCodebaseOrExit mCodePathOption SC.MigrateAfterPrompt \(initRes, _, theCodebase) -> do
             withRuntimes RTI.Persistent \(runtime, sbRuntime) -> do
@@ -347,7 +351,7 @@ prepareTranscriptDir shouldFork mCodePathOption = do
       Path.copyDir (CodebaseInit.codebasePath cbInit path) (CodebaseInit.codebasePath cbInit tmp)
     DontFork -> do
       PT.putPrettyLn . P.wrap $ "Transcript will be run on a new, empty codebase."
-      CodebaseInit.withNewUcmCodebaseOrExit cbInit "main.transcript" tmp (const $ pure ())
+      CodebaseInit.withNewUcmCodebaseOrExit cbInit "main.transcript" tmp SC.DoLock (const $ pure ())
   pure tmp
 
 runTranscripts' ::
@@ -527,7 +531,7 @@ defaultBaseLib =
 getCodebaseOrExit :: Maybe CodebasePathOption -> SC.MigrationStrategy -> ((InitResult, CodebasePath, Codebase IO Symbol Ann) -> IO r) -> IO r
 getCodebaseOrExit codebasePathOption migrationStrategy action = do
   initOptions <- argsToCodebaseInitOptions codebasePathOption
-  result <- CodebaseInit.withOpenOrCreateCodebase SC.init "main" initOptions migrationStrategy \case
+  result <- CodebaseInit.withOpenOrCreateCodebase SC.init "main" initOptions SC.DoLock migrationStrategy \case
     cbInit@(CreatedCodebase, dir, _) -> do
       pDir <- prettyDir dir
       PT.putPrettyLn' ""
@@ -546,6 +550,13 @@ getCodebaseOrExit codebasePathOption migrationStrategy action = do
             case err of
               InitErrorOpen err ->
                 case err of
+                  OpenCodebaseFileLockFailed ->
+                    pure
+                      ( P.lines
+                          [ "Failed to obtain a file lock on the codebase. ",
+                            "Perhaps you are running multiple ucm processes against the same codebase."
+                          ]
+                      )
                   OpenCodebaseDoesntExist ->
                     pure
                       ( P.lines
diff --git a/unison-cli/unison/Stats.hs b/unison-cli/unison/Stats.hs
new file mode 100644
index 000000000..cc96073b4
--- /dev/null
+++ b/unison-cli/unison/Stats.hs
@@ -0,0 +1,39 @@
+module Stats
+  ( RtsStatsPath (..),
+    recordRtsStats,
+  )
+where
+
+import Control.Exception (finally)
+import Data.Aeson (encode, object, (.=))
+import qualified Data.ByteString.Lazy as BL
+import Data.Function
+import Data.String (IsString)
+import GHC.Stats
+
+newtype RtsStatsPath
+  = RtsStatsPath FilePath
+  deriving stock (Show, Eq)
+  deriving newtype (IsString)
+
+recordRtsStats :: RtsStatsPath -> IO a -> IO a
+recordRtsStats (RtsStatsPath fp) action = do
+  r0 <- getRTSStats
+  action `finally` do
+    r1 <- getRTSStats
+    BL.writeFile fp (encode (produceStats r0 r1))
+  where
+    produceStats r0 r1 =
+      object
+        [ "gcs" .= on (-) gcs r1 r0,
+          "major_gcs" .= on (-) major_gcs r1 r0,
+          "allocated_bytes" .= on (-) allocated_bytes r1 r0,
+          "max_live_bytes" .= on (-) max_live_bytes r1 r0,
+          "copied_bytes" .= on (-) copied_bytes r1 r0,
+          "mutator_cpu_ns" .= on (-) mutator_cpu_ns r1 r0,
+          "mutator_elapsed_ns" .= on (-) mutator_elapsed_ns r1 r0,
+          "gc_cpu_ns" .= on (-) mutator_cpu_ns r1 r0,
+          "gc_elapsed_ns" .= on (-) mutator_elapsed_ns r1 r0,
+          "cpu_ns" .= on (-) cpu_ns r1 r0,
+          "elapsed_ns" .= on (-) cpu_ns r1 r0
+        ]
diff --git a/unison-core/package.yaml b/unison-core/package.yaml
index 205b65e2f..5a598f1cf 100644
--- a/unison-core/package.yaml
+++ b/unison-core/package.yaml
@@ -19,7 +19,6 @@ library:
     - fuzzyfind
     - generic-lens
     - lens
-    - prelude-extras
     - memory
     - mtl
     - rfc5051
diff --git a/unison-core/src/Unison/DataDeclaration.hs b/unison-core/src/Unison/DataDeclaration.hs
index ba581fbde..138a24ca1 100644
--- a/unison-core/src/Unison/DataDeclaration.hs
+++ b/unison-core/src/Unison/DataDeclaration.hs
@@ -43,7 +43,6 @@ import Control.Monad.State (evalState)
 import Data.Bifunctor (bimap, first, second)
 import qualified Data.Map as Map
 import qualified Data.Set as Set
-import Prelude.Extras (Show1)
 import qualified Unison.ABT as ABT
 import Unison.ConstructorReference (GConstructorReference (..))
 import qualified Unison.ConstructorType as CT
@@ -273,7 +272,7 @@ data F a
   | LetRec [a] a
   | Constructors [a]
   | Modified Modifier a
-  deriving (Functor, Foldable, Show, Show1)
+  deriving (Functor, Foldable, Show)
 
 updateDependencies :: Ord v => Map Reference Reference -> Decl v a -> Decl v a
 updateDependencies typeUpdates decl =
diff --git a/unison-core/src/Unison/Name.hs b/unison-core/src/Unison/Name.hs
index 788a4f7c3..0e908f085 100644
--- a/unison-core/src/Unison/Name.hs
+++ b/unison-core/src/Unison/Name.hs
@@ -21,6 +21,7 @@ module Unison.Name
     countSegments,
     isAbsolute,
     isPrefixOf,
+    beginsWithSegment,
     endsWithReverseSegments,
     endsWithSegments,
     stripReversedPrefix,
@@ -164,6 +165,19 @@ countSegments :: Name -> Int
 countSegments (Name _ ss) =
   length ss
 
+-- | @beginsWithSegment name segment@ returns whether @name@'s first name segment is @segment@.
+--
+-- >>> beginsWithSegment "abc.def" "abc"
+-- True
+--
+-- >>> beginsWithSegment "abc.def" "ab"
+-- False
+--
+-- /O(n)/, where /n/ is the number of name segments.
+beginsWithSegment :: Name -> NameSegment -> Bool
+beginsWithSegment name segment =
+  segment == List.NonEmpty.head (segments name)
+
 -- | @endsWithSegments x y@ returns whether @x@ ends with @y@.
 --
 -- >>> endsWithSegments "a.b.c" ["b", "c"]
@@ -559,7 +573,7 @@ commonPrefix :: Name -> Name -> [NameSegment]
 commonPrefix x@(Name p1 _) y@(Name p2 _)
   | p1 /= p2 = []
   | otherwise =
-    commonPrefix' (toList $ segments x) (toList $ segments y)
+      commonPrefix' (toList $ segments x) (toList $ segments y)
   where
     commonPrefix' (a : as) (b : bs)
       | a == b = a : commonPrefix' as bs
diff --git a/unison-core/src/Unison/Term.hs b/unison-core/src/Unison/Term.hs
index fc49f246a..a3f9bc3d9 100644
--- a/unison-core/src/Unison/Term.hs
+++ b/unison-core/src/Unison/Term.hs
@@ -21,7 +21,6 @@ import qualified Data.Sequence as Sequence
 import qualified Data.Set as Set
 import qualified Data.Set.NonEmpty as NES
 import qualified Data.Text as Text
-import Prelude.Extras (Eq1 (..), Show1 (..))
 import Text.Show
 import qualified Unison.ABT as ABT
 import qualified Unison.Blank as B
@@ -1354,10 +1353,6 @@ fromReferent a = \case
 
 -- mostly boring serialization code below ...
 
-instance (Eq a, ABT.Var v) => Eq1 (F v a p) where (==#) = (==)
-
-instance (Show v) => Show1 (F v a p) where showsPrec1 = showsPrec
-
 instance (ABT.Var vt, Eq at, Eq a) => Eq (F vt at p a) where
   Int x == Int y = x == y
   Nat x == Nat y = x == y
diff --git a/unison-core/src/Unison/Type.hs b/unison-core/src/Unison/Type.hs
index ad973b9d2..e394d4bf5 100644
--- a/unison-core/src/Unison/Type.hs
+++ b/unison-core/src/Unison/Type.hs
@@ -16,7 +16,6 @@ import Data.List.Extra (nubOrd)
 import qualified Data.Map as Map
 import Data.Monoid (Any (..))
 import qualified Data.Set as Set
-import Prelude.Extras (Eq1 (..), Ord1 (..), Show1 (..))
 import qualified Unison.ABT as ABT
 import qualified Unison.Kind as K
 import qualified Unison.Name as Name
@@ -43,12 +42,6 @@ data F a
   -- variables
   deriving (Foldable, Functor, Generic, Generic1, Eq, Ord, Traversable)
 
-instance Eq1 F where (==#) = (==)
-
-instance Ord1 F where compare1 = compare
-
-instance Show1 F where showsPrec1 = showsPrec
-
 _Ref :: Prism' (F a) Reference
 _Ref = _Ctor @"Ref"
 
diff --git a/unison-core/unison-core1.cabal b/unison-core/unison-core1.cabal
index 4fc9cf3a6..77104263c 100644
--- a/unison-core/unison-core1.cabal
+++ b/unison-core/unison-core1.cabal
@@ -94,7 +94,6 @@ library
     , memory
     , mtl
     , nonempty-containers
-    , prelude-extras
     , rfc5051
     , safe
     , text
diff --git a/unison-share-api/src/Unison/Server/Backend.hs b/unison-share-api/src/Unison/Server/Backend.hs
index 56ce44c41..5f7846584 100644
--- a/unison-share-api/src/Unison/Server/Backend.hs
+++ b/unison-share-api/src/Unison/Server/Backend.hs
@@ -338,12 +338,12 @@ lsAtPath ::
   MonadIO m =>
   Codebase m Symbol Ann ->
   -- The root to follow the path from.
-  Maybe (V2Branch.Branch m) ->
+  Maybe (V2Branch.Branch Sqlite.Transaction) ->
   -- Path from the root to the branch to 'ls'
   Path.Absolute ->
   m [ShallowListEntry Symbol Ann]
 lsAtPath codebase mayRootBranch absPath = do
-  b <- Codebase.getShallowBranchAtPath codebase (Path.unabsolute absPath) mayRootBranch
+  b <- Codebase.runTransaction codebase (Codebase.getShallowBranchAtPath (Path.unabsolute absPath) mayRootBranch)
   lsBranch codebase b
 
 findShallowReadmeInBranchAndRender ::
@@ -407,7 +407,7 @@ resultListType = Type.app mempty (Type.list mempty) (Type.ref mempty Decls.testR
 termListEntry ::
   MonadIO m =>
   Codebase m Symbol Ann ->
-  V2Branch.Branch m ->
+  V2Branch.Branch n ->
   ExactName NameSegment V2Referent.Referent ->
   m (TermEntry Symbol Ann)
 termListEntry codebase branch (ExactName nameSegment ref) = do
@@ -477,7 +477,7 @@ getTypeTag codebase r = do
 typeListEntry ::
   Var v =>
   Codebase m v Ann ->
-  V2Branch.Branch m ->
+  V2Branch.Branch n ->
   ExactName NameSegment Reference ->
   Sqlite.Transaction TypeEntry
 typeListEntry codebase b (ExactName nameSegment ref) = do
@@ -551,7 +551,7 @@ typeEntryToNamedType te@TypeEntry {typeEntryTag, typeEntryHash} =
 lsBranch ::
   MonadIO m =>
   Codebase m Symbol Ann ->
-  V2Branch.Branch m ->
+  V2Branch.Branch n ->
   m [ShallowListEntry Symbol Ann]
 lsBranch codebase b0 = do
   let flattenRefs :: Map V2Branch.NameSegment (Map ref v) -> [(ref, V2Branch.NameSegment)]
@@ -796,13 +796,15 @@ expandShortCausalHash hash = do
       throwError . AmbiguousBranchHash hash $ Set.map (SCH.fromHash len) hashSet
 
 -- | Efficiently resolve a root hash and path to a shallow branch's causal.
-getShallowCausalAtPathFromRootHash :: MonadIO m => Codebase m v a -> Maybe Branch.CausalHash -> Path -> Backend m (V2Branch.CausalBranch m)
-getShallowCausalAtPathFromRootHash codebase mayRootHash path = do
+getShallowCausalAtPathFromRootHash ::
+  Maybe Branch.CausalHash ->
+  Path ->
+  Sqlite.Transaction (V2Branch.CausalBranch Sqlite.Transaction)
+getShallowCausalAtPathFromRootHash mayRootHash path = do
   shallowRoot <- case mayRootHash of
-    Nothing -> lift (Codebase.getShallowRootCausal codebase)
-    Just h -> do
-      lift $ Codebase.getShallowCausalForHash codebase (Cv.causalHash1to2 h)
-  lift $ Codebase.getShallowCausalAtPath codebase path (Just shallowRoot)
+    Nothing -> Codebase.getShallowRootCausal
+    Just h -> Codebase.expectCausalBranchByCausalHash (Cv.causalHash1to2 h)
+  Codebase.getShallowCausalAtPath path (Just shallowRoot)
 
 formatType' :: Var v => PPE.PrettyPrintEnv -> Width -> Type v a -> SyntaxText
 formatType' ppe w =
@@ -841,8 +843,11 @@ prettyDefinitionsForHQName ::
   HQ.HashQualified Name ->
   Backend IO DefinitionDisplayResults
 prettyDefinitionsForHQName path mayRoot renderWidth suffixifyBindings rt codebase query = do
-  shallowRoot <- resolveCausalHashV2 codebase (fmap Cv.causalHash1to2 mayRoot)
-  hqLength <- lift $ Codebase.runTransaction codebase Codebase.hashLength
+  (shallowRoot, hqLength) <-
+    (lift . Codebase.runTransaction codebase) do
+      shallowRoot <- resolveCausalHashV2 (fmap Cv.causalHash1to2 mayRoot)
+      hqLength <- Codebase.hashLength
+      pure (shallowRoot, hqLength)
   (localNamesOnly, unbiasedPPE) <- scopedNamesForBranchHash codebase (Just shallowRoot) path
   -- Bias towards both relative and absolute path to queries,
   -- This allows us to still bias towards definitions outside our perspective but within the
@@ -858,8 +863,10 @@ prettyDefinitionsForHQName path mayRoot renderWidth suffixifyBindings rt codebas
   let nameSearch :: NameSearch
       nameSearch = makeNameSearch hqLength (NamesWithHistory.fromCurrentNames localNamesOnly)
   DefinitionResults terms types misses <- lift (definitionsBySuffixes codebase nameSearch DontIncludeCycles [query])
-  causalAtPath <- lift $ Codebase.getShallowCausalAtPath codebase path (Just shallowRoot)
-  branchAtPath <- lift $ V2Causal.value causalAtPath
+  branchAtPath <- do
+    (lift . Codebase.runTransaction codebase) do
+      causalAtPath <- Codebase.getShallowCausalAtPath path (Just shallowRoot)
+      V2Causal.value causalAtPath
   let width = mayDefaultWidth renderWidth
       -- Return only references which refer to docs.
       filterForDocs :: [Referent] -> Sqlite.Transaction [TermReference]
@@ -982,7 +989,7 @@ renderDoc ppe width rt codebase r = do
     eval (Term.amap (const mempty) -> tm) = do
       let ppes = PPED.suffixifiedPPE ppe
       let codeLookup = Codebase.toCodeLookup codebase
-      let cache r = fmap Term.unannotate <$> Codebase.lookupWatchCache codebase r
+      let cache r = fmap Term.unannotate <$> Codebase.runTransaction codebase (Codebase.lookupWatchCache codebase r)
       r <- fmap hush . liftIO $ Rt.evaluateTerm' codeLookup cache ppes rt tm
       case r of
         Just tmr ->
@@ -1105,7 +1112,13 @@ bestNameForType ppe width =
 -- - 'local' includes ONLY the names within the provided path
 -- - 'ppe' is a ppe which searches for a name within the path first, but falls back to a global name search.
 --     The 'suffixified' component of this ppe will search for the shortest unambiguous suffix within the scope in which the name is found (local, falling back to global)
-scopedNamesForBranchHash :: forall m v a. MonadIO m => Codebase m v a -> Maybe (V2Branch.CausalBranch m) -> Path -> Backend m (Names, PPED.PrettyPrintEnvDecl)
+scopedNamesForBranchHash ::
+  forall m n v a.
+  MonadIO m =>
+  Codebase m v a ->
+  Maybe (V2Branch.CausalBranch n) ->
+  Path ->
+  Backend m (Names, PPED.PrettyPrintEnvDecl)
 scopedNamesForBranchHash codebase mbh path = do
   shouldUseNamesIndex <- asks useNamesIndex
   hashLen <- lift $ Codebase.runTransaction codebase Codebase.hashLength
@@ -1148,11 +1161,10 @@ resolveCausalHash h codebase = case h of
     mayBranch <- lift $ Codebase.getBranchForHash codebase bhash
     whenNothing mayBranch (throwError $ NoBranchForHash bhash)
 
-resolveCausalHashV2 ::
-  MonadIO m => Codebase m v a -> Maybe V2Branch.CausalHash -> Backend m (V2Branch.CausalBranch m)
-resolveCausalHashV2 codebase h = case h of
-  Nothing -> lift $ Codebase.getShallowRootCausal codebase
-  Just ch -> lift $ Codebase.getShallowCausalForHash codebase ch
+resolveCausalHashV2 :: Maybe V2Branch.CausalHash -> Sqlite.Transaction (V2Branch.CausalBranch Sqlite.Transaction)
+resolveCausalHashV2 h = case h of
+  Nothing -> Codebase.getShallowRootCausal
+  Just ch -> Codebase.expectCausalBranchByCausalHash ch
 
 resolveRootBranchHash ::
   MonadIO m => Maybe ShortCausalHash -> Codebase m v a -> Backend m (Branch m)
@@ -1164,12 +1176,12 @@ resolveRootBranchHash mayRoot codebase = case mayRoot of
     resolveCausalHash (Just h) codebase
 
 resolveRootBranchHashV2 ::
-  MonadIO m => Codebase m v a -> Maybe ShortCausalHash -> Backend m (V2Branch.CausalBranch m)
-resolveRootBranchHashV2 codebase mayRoot = case mayRoot of
-  Nothing -> lift (Codebase.getShallowRootCausal codebase)
+  Maybe ShortCausalHash -> Backend Sqlite.Transaction (V2Branch.CausalBranch Sqlite.Transaction)
+resolveRootBranchHashV2 mayRoot = case mayRoot of
+  Nothing -> lift Codebase.getShallowRootCausal
   Just sch -> do
-    h <- Cv.causalHash1to2 <$> hoistBackend (Codebase.runTransaction codebase) (expandShortCausalHash sch)
-    resolveCausalHashV2 codebase (Just h)
+    h <- Cv.causalHash1to2 <$> expandShortCausalHash sch
+    lift (resolveCausalHashV2 (Just h))
 
 -- | Determines whether we include full cycles in the results, (e.g. if I search for `isEven`, will I find `isOdd` too?)
 --
diff --git a/unison-share-api/src/Unison/Server/Doc.hs b/unison-share-api/src/Unison/Server/Doc.hs
index 87aa2f41e..ea0c9eb44 100644
--- a/unison-share-api/src/Unison/Server/Doc.hs
+++ b/unison-share-api/src/Unison/Server/Doc.hs
@@ -220,7 +220,10 @@ renderDoc pped terms typeOf eval types tm =
             ty r = (NP.styleHashQualified'' (NP.fmt (S.TypeReference r)) . PPE.typeName ppe) r
          in Link <$> case e of
               DD.EitherLeft' (Term.TypeLink' r) -> (pure . formatPretty . ty) r
-              DD.EitherRight' (DD.Doc2Term (Term.Referent' r)) -> (pure . formatPretty . tm) r
+              DD.EitherRight' (DD.Doc2Term t) ->
+                case Term.etaNormalForm t of
+                  Term.Referent' r -> (pure . formatPretty . tm) r
+                  x -> source x
               _ -> source e
       DD.Doc2SpecialFormSignature (Term.List' tms) ->
         let rs = [r | DD.Doc2Term (Term.Referent' r) <- toList tms]
diff --git a/unison-share-api/src/Unison/Server/Endpoints/DefinitionSummary.hs b/unison-share-api/src/Unison/Server/Endpoints/DefinitionSummary.hs
index 25d350f01..1aa7f60bc 100644
--- a/unison-share-api/src/Unison/Server/Endpoints/DefinitionSummary.hs
+++ b/unison-share-api/src/Unison/Server/Endpoints/DefinitionSummary.hs
@@ -90,8 +90,11 @@ serveTermSummary codebase referent mayName mayRoot relativeTo mayWidth = do
   let relativeToPath = fromMaybe Path.empty relativeTo
   let termReference = Referent.toReference referent
   let v2Referent = Cv.referent1to2 referent
-  root <- Backend.resolveRootBranchHashV2 codebase mayRoot
-  sig <- lift (Codebase.runTransaction codebase (Backend.loadReferentType codebase referent))
+  (root, sig) <-
+    Backend.hoistBackend (Codebase.runTransaction codebase) do
+      root <- Backend.resolveRootBranchHashV2 mayRoot
+      sig <- lift (Backend.loadReferentType codebase referent)
+      pure (root, sig)
   case sig of
     Nothing ->
       throwError (Backend.MissingSignatureForTerm termReference)
diff --git a/unison-share-api/src/Unison/Server/Endpoints/FuzzyFind.hs b/unison-share-api/src/Unison/Server/Endpoints/FuzzyFind.hs
index daa3afcd8..b6ef0fd3e 100644
--- a/unison-share-api/src/Unison/Server/Endpoints/FuzzyFind.hs
+++ b/unison-share-api/src/Unison/Server/Endpoints/FuzzyFind.hs
@@ -138,11 +138,15 @@ serveFuzzyFind ::
   Backend.Backend m [(FZF.Alignment, FoundResult)]
 serveFuzzyFind codebase mayRoot relativeTo limit typeWidth query = do
   let path = fromMaybe Path.empty relativeTo
-  rootHash <- traverse (Backend.hoistBackend (Codebase.runTransaction codebase) . Backend.expandShortCausalHash) mayRoot
-  rootCausal <- Backend.resolveCausalHashV2 codebase (Cv.causalHash1to2 <$> rootHash)
+  rootCausal <-
+    Backend.hoistBackend (Codebase.runTransaction codebase) do
+      rootHash <- traverse Backend.expandShortCausalHash mayRoot
+      lift (Backend.resolveCausalHashV2 (Cv.causalHash1to2 <$> rootHash))
   (localNamesOnly, ppe) <- Backend.scopedNamesForBranchHash codebase (Just rootCausal) path
-  relativeToCausal <- lift $ Codebase.getShallowCausalAtPath codebase path (Just rootCausal)
-  relativeToBranch <- lift $ V2Causal.value relativeToCausal
+  relativeToBranch <- do
+    (lift . Codebase.runTransaction codebase) do
+      relativeToCausal <- Codebase.getShallowCausalAtPath path (Just rootCausal)
+      V2Causal.value relativeToCausal
   let alignments ::
         ( [ ( FZF.Alignment,
               UnisonName,
diff --git a/unison-share-api/src/Unison/Server/Endpoints/NamespaceDetails.hs b/unison-share-api/src/Unison/Server/Endpoints/NamespaceDetails.hs
index bb1d4ac75..5d27be939 100644
--- a/unison-share-api/src/Unison/Server/Endpoints/NamespaceDetails.hs
+++ b/unison-share-api/src/Unison/Server/Endpoints/NamespaceDetails.hs
@@ -80,9 +80,12 @@ namespaceDetails ::
 namespaceDetails runtime codebase namespacePath maySCH mayWidth =
   let width = mayDefaultWidth mayWidth
    in do
-        rootCausal <- Backend.resolveRootBranchHashV2 codebase maySCH
-        namespaceCausal <- lift $ Codebase.getShallowCausalAtPath codebase namespacePath (Just rootCausal)
-        shallowBranch <- lift $ V2Causal.value namespaceCausal
+        (rootCausal, namespaceCausal, shallowBranch) <- 
+          Backend.hoistBackend (Codebase.runTransaction codebase) do
+            rootCausal <- Backend.resolveRootBranchHashV2 maySCH
+            namespaceCausal <- lift $ Codebase.getShallowCausalAtPath namespacePath (Just rootCausal)
+            shallowBranch <- lift $ V2Causal.value namespaceCausal
+            pure (rootCausal, namespaceCausal, shallowBranch)
         namespaceDetails <- do
           (_localNamesOnly, ppe) <- Backend.scopedNamesForBranchHash codebase (Just rootCausal) namespacePath
           readme <-
diff --git a/unison-share-api/src/Unison/Server/Endpoints/NamespaceListing.hs b/unison-share-api/src/Unison/Server/Endpoints/NamespaceListing.hs
index 4680407af..e5599aee3 100644
--- a/unison-share-api/src/Unison/Server/Endpoints/NamespaceListing.hs
+++ b/unison-share-api/src/Unison/Server/Endpoints/NamespaceListing.hs
@@ -171,7 +171,7 @@ serve ::
   Backend.Backend IO NamespaceListing
 serve codebase maySCH mayRelativeTo mayNamespaceName = do
   useIndex <- asks Backend.useNamesIndex
-  (mayRootHash, codebaseRootHash) <- 
+  (mayRootHash, codebaseRootHash) <-
     Backend.hoistBackend (Codebase.runTransaction codebase) do
       mayRootHash <- traverse Backend.expandShortCausalHash maySCH
       codebaseRootHash <- lift Operations.expectRootCausalHash
@@ -200,9 +200,9 @@ serve codebase maySCH mayRelativeTo mayNamespaceName = do
       serveFromIndex codebase mayRootHash path'
     (True, Just rh)
       | rh == causalHash2to1 codebaseRootHash ->
-        serveFromIndex codebase mayRootHash path'
+          serveFromIndex codebase mayRootHash path'
       | otherwise -> do
-        serveFromBranch codebase path' (Cv.causalHash1to2 rh)
+          serveFromBranch codebase path' (Cv.causalHash1to2 rh)
     (False, Just rh) -> do
       serveFromBranch codebase path' (Cv.causalHash1to2 rh)
     (False, Nothing) -> do
@@ -222,9 +222,12 @@ serveFromBranch codebase path' rootHash = do
   -- worth slowing down the request for this right now.
   let ppe = PPE.empty
   let listingFQN = Path.toText . Path.unabsolute . either id (Path.Absolute . Path.unrelative) $ Path.unPath' path'
-  causalAtPath <- liftIO $ Codebase.getShallowCausalFromRoot codebase (Just rootHash) (Path.unabsolute absPath)
+  (causalAtPath, branchAtPath) <-
+    (lift . Codebase.runTransaction codebase) do
+      causalAtPath <- Codebase.getShallowCausalFromRoot (Just rootHash) (Path.unabsolute absPath)
+      branchAtPath <- V2Causal.value causalAtPath
+      pure (causalAtPath, branchAtPath)
   let listingHash = v2CausalBranchToUnisonHash causalAtPath
-  branchAtPath <- liftIO $ V2Causal.value causalAtPath
   listingEntries <- liftIO $ Backend.lsBranch codebase branchAtPath
   makeNamespaceListing ppe listingFQN listingHash listingEntries
 
@@ -234,8 +237,11 @@ serveFromIndex ::
   Path.Path' ->
   Backend.Backend IO NamespaceListing
 serveFromIndex codebase mayRootHash path' = do
-  listingCausal <- Backend.getShallowCausalAtPathFromRootHash codebase mayRootHash (Path.fromPath' path')
-  listingBranch <- liftIO $ V2Causal.value listingCausal
+  (listingCausal, listingBranch) <-
+    (lift . Codebase.runTransaction codebase) do
+      listingCausal <- Backend.getShallowCausalAtPathFromRootHash mayRootHash (Path.fromPath' path')
+      listingBranch <- V2Causal.value listingCausal
+      pure (listingCausal, listingBranch)
   -- TODO: Currently the ppe is just used to render the types returned from the namespace
   -- listing, which are currently unused because we don't show types in the side-bar.
   -- If we ever show types on hover we need to build and use a proper PPE here, but it's not
diff --git a/unison-share-api/src/Unison/Server/Endpoints/Projects.hs b/unison-share-api/src/Unison/Server/Endpoints/Projects.hs
index 1f5e3a6f5..e3a8f3fc0 100644
--- a/unison-share-api/src/Unison/Server/Endpoints/Projects.hs
+++ b/unison-share-api/src/Unison/Server/Endpoints/Projects.hs
@@ -40,6 +40,7 @@ import Unison.Prelude
 import Unison.Server.Backend
 import qualified Unison.Server.Backend as Backend
 import Unison.Server.Types (APIGet, UnisonHash)
+import qualified Unison.Sqlite as Sqlite
 import Unison.Symbol (Symbol)
 import Unison.Util.Monoid (foldMapM)
 
@@ -133,13 +134,15 @@ serve codebase mayRoot mayOwner = projects
   where
     projects :: Backend m [ProjectListing]
     projects = do
-      shallowRootBranch <- case mayRoot of
-        Nothing -> lift (Codebase.getShallowRootBranch codebase)
-        Just sch -> do
-          h <- Backend.hoistBackend (Codebase.runTransaction codebase) (Backend.expandShortCausalHash sch)
-          -- TODO: can this ever be missing?
-          causal <- lift $ Codebase.getShallowCausalForHash codebase (Cv.causalHash1to2 h)
-          lift $ V2Causal.value causal
+      shallowRootBranch <-
+        Backend.hoistBackend (Codebase.runTransaction codebase) do
+          case mayRoot of
+            Nothing -> lift Codebase.getShallowRootBranch
+            Just sch -> do
+              h <- Backend.expandShortCausalHash sch
+              -- TODO: can this ever be missing?
+              causal <- lift $ Codebase.expectCausalBranchByCausalHash (Cv.causalHash1to2 h)
+              lift $ V2Causal.value causal
 
       ownerEntries <- lift $ Backend.lsBranch codebase shallowRootBranch
       -- If an owner is provided, we only want projects belonging to them
@@ -149,7 +152,7 @@ serve codebase mayRoot mayOwner = projects
               Nothing -> mapMaybe entryToOwner ownerEntries
       foldMapM (ownerToProjectListings shallowRootBranch) owners
 
-    ownerToProjectListings :: V2Branch.Branch m -> ProjectOwner -> Backend m [ProjectListing]
+    ownerToProjectListings :: V2Branch.Branch Sqlite.Transaction -> ProjectOwner -> Backend m [ProjectListing]
     ownerToProjectListings root owner = do
       let (ProjectOwner ownerName) = owner
       ownerPath' <- (parsePath . Text.unpack) ownerName
diff --git a/unison-src/transcripts-manual/scheme.md b/unison-src/transcripts-manual/scheme.md
new file mode 100644
index 000000000..8ae0d9805
--- /dev/null
+++ b/unison-src/transcripts-manual/scheme.md
@@ -0,0 +1,61 @@
+This transcript executes very slowly, because the compiler has an
+entire copy of base (and other stuff) within it.
+
+```ucm:hide
+.> builtins.mergeio
+.> pull.without-history unison.public.base.trunk base
+```
+
+```unison
+stdOut = stdHandle StdOut
+
+print txt =
+  match putBytes.impl stdOut (toUtf8 txt) with
+    Left f -> raise f
+    Right _ -> ()
+
+prints n f = print (join " " f n ++ "\n")
+
+join sep f =
+  use Text ++
+  loop acc = cases
+    0 -> acc
+    n -> loop (!f ++ (sep ++ acc)) (drop n 1)
+
+  cases
+    0 -> ""
+    n -> loop !f (drop n 1)
+
+addUp : Nat -> Nat -> Nat
+addUp acc = cases
+  0 -> acc
+  n -> addUp (1+acc) (drop n 1)
+
+repeat : Nat -> '{g} () -> '{g} ()
+repeat n act =
+  loop : Nat ->{g} ()
+  loop = cases
+    0 -> ()
+    k ->
+      !act
+      loop (drop k 1)
+
+  '(loop n)
+
+printAddUp : Nat ->{IO,Exception} ()
+printAddUp n =
+  ns = [addUp 0 n, addUp 0 n, addUp 0 n, addUp 0 n, addUp 0 n]
+  prints 8 '(toText (addUp 0 n))
+
+singleAddUp : '{IO,Exception} ()
+singleAddUp = do printAddUp 3000000
+
+multiAddUp : '{IO,Exception} ()
+multiAddUp = repeat 35 '(printAddUp 3000000)
+```
+
+```ucm
+.> add
+.> run singleAddUp
+.> run.native multiAddUp
+```
diff --git a/unison-src/transcripts-round-trip/main.md b/unison-src/transcripts-round-trip/main.md
index bf5034086..9870461a7 100644
--- a/unison-src/transcripts-round-trip/main.md
+++ b/unison-src/transcripts-round-trip/main.md
@@ -484,3 +484,26 @@ Regression test for https://github.com/unisonweb/unison/pull/3548
 ```ucm
 .> load scratch.u
 ```
+
+# Indent long pattern lists to avoid virtual semicolon
+
+Regression test for https://github.com/unisonweb/unison/issues/3627
+
+```unison:hide
+(+) a b = ##Nat.+ a b
+
+foo = cases
+  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+   bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+    -> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+```
+
+```ucm
+.> add
+.> edit foo
+.> undo
+```
+
+```ucm
+.> load scratch.u
+```
\ No newline at end of file
diff --git a/unison-src/transcripts-round-trip/main.output.md b/unison-src/transcripts-round-trip/main.output.md
index ff053e273..9f8099478 100644
--- a/unison-src/transcripts-round-trip/main.output.md
+++ b/unison-src/transcripts-round-trip/main.output.md
@@ -1469,3 +1469,63 @@ Regression test for https://github.com/unisonweb/unison/pull/3548
   I loaded scratch.u and didn't find anything.
 
 ```
+# Indent long pattern lists to avoid virtual semicolon
+
+Regression test for https://github.com/unisonweb/unison/issues/3627
+
+```unison
+(+) a b = ##Nat.+ a b
+
+foo = cases
+  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+   bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+    -> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+```
+
+```ucm
+.> add
+
+  ⍟ I've added these definitions:
+  
+    +   : Nat -> Nat -> Nat
+    foo : Nat -> Nat -> Nat
+
+.> edit foo
+
+  ☝️
+  
+  I added these definitions to the top of
+  /Users/runar/work/unison/scratch.u
+  
+    foo : Nat -> Nat -> Nat
+    foo = cases
+      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb ->
+        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+          + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+  
+  You can edit them there, then do `update` to replace the
+  definitions currently in this namespace.
+
+.> undo
+
+  Here are the changes I undid
+  
+  Added definitions:
+  
+    1. +   : Nat -> Nat -> Nat
+    2. foo : Nat -> Nat -> Nat
+
+```
+```ucm
+.> load scratch.u
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These new definitions are ok to `add`:
+    
+      foo : Nat -> Nat -> Nat
+
+```
diff --git a/unison-src/transcripts/fix3634.md b/unison-src/transcripts/fix3634.md
new file mode 100644
index 000000000..0cb5f88dd
--- /dev/null
+++ b/unison-src/transcripts/fix3634.md
@@ -0,0 +1,21 @@
+```ucm:hide
+.> builtins.mergeio
+```
+
+
+```unison
+structural type M a = N | J a
+
+d = {{
+
+{{ docExample 0 '(x -> J x) }}
+
+{J}
+
+}}
+```
+
+```ucm
+.> add
+.> display d
+```
\ No newline at end of file
diff --git a/unison-src/transcripts/fix3634.output.md b/unison-src/transcripts/fix3634.output.md
new file mode 100644
index 000000000..912c63353
--- /dev/null
+++ b/unison-src/transcripts/fix3634.output.md
@@ -0,0 +1,41 @@
+```unison
+structural type M a = N | J a
+
+d = {{
+
+{{ docExample 0 '(x -> J x) }}
+
+{J}
+
+}}
+```
+
+```ucm
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These new definitions are ok to `add`:
+    
+      structural type M a
+        (also named builtin.Optional)
+      d : Doc2
+
+```
+```ucm
+.> add
+
+  ⍟ I've added these definitions:
+  
+    structural type M a
+      (also named builtin.Optional)
+    d : Doc2
+
+.> display d
+
+  `x -> J x`
+  
+  J
+
+```
diff --git a/unison-src/transcripts/lambdacase.output.md b/unison-src/transcripts/lambdacase.output.md
index 12fa3b6c4..573138be6 100644
--- a/unison-src/transcripts/lambdacase.output.md
+++ b/unison-src/transcripts/lambdacase.output.md
@@ -105,8 +105,8 @@ Notice that Unison detects this as an alias of `merge`, and if we view `merge`
 
   merge : [a] -> [a] -> [a]
   merge = cases
-    [], ys           -> ys
-    xs, []           -> xs
+    [], ys -> ys
+    xs, [] -> xs
     h +: t, h2 +: t2 ->
       if h <= h2 then h +: merge t (h2 +: t2)
       else h2 +: merge (h +: t) t2
diff --git a/unison-src/transcripts/name-selection.md b/unison-src/transcripts/name-selection.md
index aeb9cf87c..fe3e76034 100644
--- a/unison-src/transcripts/name-selection.md
+++ b/unison-src/transcripts/name-selection.md
@@ -55,7 +55,7 @@ d = c + 10
 
 At this point, `a3` is conflicted for symbols `c` and `d`, so those are deprioritized. 
 The original `a2` namespace has an unconflicted definition for `c` and `d`, but since there are multiple 'c's in scope, 
-`long.name.but.shortest.suffixification` is chosen because its suffixified version has the fewest segments.
+`a2.c` is chosen because although the suffixified version has fewer segments, its fully-qualified name has the fewest segments.
 
 ```ucm
 .> view a b c d
@@ -88,7 +88,8 @@ other.value = 20
 
 ```ucm
 .biasing> add
--- nested.value should still be preferred even if the suffixification requires more segments than `a`
+-- nested.value should be preferred over the shorter name `a` due to biasing
+-- because `deeply.nested.value` is nearby to the term being viewed.
 .biasing> view deeply.nested.term
 ```
 
diff --git a/unison-src/transcripts/name-selection.output.md b/unison-src/transcripts/name-selection.output.md
index ffce4a7ad..f65b342f8 100644
--- a/unison-src/transcripts/name-selection.output.md
+++ b/unison-src/transcripts/name-selection.output.md
@@ -1373,7 +1373,7 @@ d = c + 10
 ```
 At this point, `a3` is conflicted for symbols `c` and `d`, so those are deprioritized. 
 The original `a2` namespace has an unconflicted definition for `c` and `d`, but since there are multiple 'c's in scope, 
-`long.name.but.shortest.suffixification` is chosen because its suffixified version has the fewest segments.
+`a2.c` is chosen because although the suffixified version has fewer segments, its fully-qualified name has the fewest segments.
 
 ```ucm
 .> view a b c d
@@ -1394,7 +1394,7 @@ The original `a2` namespace has an unconflicted definition for `c` and `d`, but
   a2.d : Nat
   a2.d =
     use Nat +
-    suffixification + 10
+    a2.c + 10
   
   a3.c#dcgdua2lj6 : Nat
   a3.c#dcgdua2lj6 = 2
@@ -1475,7 +1475,8 @@ other.value = 20
   
     other.value : Nat
 
--- nested.value should still be preferred even if the suffixification requires more segments than `a`
+-- nested.value should be preferred over the shorter name `a` due to biasing
+-- because `deeply.nested.value` is nearby to the term being viewed.
 .biasing> view deeply.nested.term
 
   deeply.nested.term : Nat
diff --git a/unison-src/transcripts/update-ignores-lib-namespace.md b/unison-src/transcripts/update-ignores-lib-namespace.md
new file mode 100644
index 000000000..04498e48a
--- /dev/null
+++ b/unison-src/transcripts/update-ignores-lib-namespace.md
@@ -0,0 +1,25 @@
+`update` / `patch` (anything that a patch) ignores the namespace named "lib" at the location it's applied. This follows
+the project organization convention that dependencies are put in "lib"; it's much easier to apply a patch to all of
+one's own code if the "lib" namespace is simply ignored.
+
+```ucm:hide
+.> builtins.merge
+```
+
+```unison
+foo = 100
+lib.foo = 100
+```
+
+```ucm
+.> add
+```
+
+```unison
+foo = 200
+```
+
+```ucm
+.> update
+.> names foo
+```
diff --git a/unison-src/transcripts/update-ignores-lib-namespace.output.md b/unison-src/transcripts/update-ignores-lib-namespace.output.md
new file mode 100644
index 000000000..cf5d1cce1
--- /dev/null
+++ b/unison-src/transcripts/update-ignores-lib-namespace.output.md
@@ -0,0 +1,66 @@
+`update` / `patch` (anything that a patch) ignores the namespace named "lib" at the location it's applied. This follows
+the project organization convention that dependencies are put in "lib"; it's much easier to apply a patch to all of
+one's own code if the "lib" namespace is simply ignored.
+
+```unison
+foo = 100
+lib.foo = 100
+```
+
+```ucm
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These new definitions are ok to `add`:
+    
+      foo     : Nat
+      lib.foo : Nat
+
+```
+```ucm
+.> add
+
+  ⍟ I've added these definitions:
+  
+    foo     : Nat
+    lib.foo : Nat
+
+```
+```unison
+foo = 200
+```
+
+```ucm
+
+  I found and typechecked these definitions in scratch.u. If you
+  do an `add` or `update`, here's how your codebase would
+  change:
+  
+    ⍟ These names already exist. You can `update` them to your
+      new definition:
+    
+      foo : Nat
+        (The old definition is also named lib.foo. I'll update
+        this name too.)
+
+```
+```ucm
+.> update
+
+  ⍟ I've updated these names to your new definition:
+  
+    foo : Nat
+      (The old definition was also named lib.foo. I updated this
+      name too.)
+
+.> names foo
+
+  Term
+  Hash:   #9ntnotdp87
+  Names:  foo
+  
+  Tip: Use `names.global` to see more results.
+
+```