diff --git a/.gitignore b/.gitignore
index 3cacab9d88..d6a95520bc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -79,6 +79,7 @@ ledger-api/.bin
 ### Bazel: https://www.gitignore.io/api/bazel ###
 /bazel-*
 /compatibility/bazel-*
+/compatibility/.bazelrc
 .bazelrc.local
 .ijwb
 .bazelproject
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 2f82443f38..5515e29913 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -204,6 +204,21 @@ jobs:
       - template: ci/tell-slack-failed.yml
       - template: ci/report-end.yml
 
+  - job: compatibility_windows
+    dependsOn:
+      - check_for_release
+    timeoutInMinutes: 60
+    pool:
+      name: 'windows-pool'
+    steps:
+      - template: ci/report-start.yml
+      - checkout: self
+      - template: ci/compatibility-windows.yml
+        parameters:
+          test_flags: '--quick'
+      - template: ci/tell-slack-failed.yml
+      - template: ci/report-end.yml
+
   - job: check_for_release
     dependsOn:
       - git_sha
@@ -378,6 +393,7 @@ jobs:
       - git_sha
       - compatibility_macos
       - compatibility_linux
+      - compatibility_windows
     pool:
       name: "linux-pool"
     variables:
@@ -409,6 +425,10 @@ jobs:
       compatibility_macos.machine: $[ dependencies.compatibility_macos.outputs['start.machine'] ]
       compatibility_macos.end: $[ dependencies.compatibility_macos.outputs['end.time'] ]
       compatibility_macos.status: $[ dependencies.compatibility_macos.result ]
+      compatibility_windows.start: $[ dependencies.compatibility_windows.outputs['start.time'] ]
+      compatibility_windows.machine: $[ dependencies.compatibility_windows.outputs['start.machine'] ]
+      compatibility_windows.end: $[ dependencies.compatibility_windows.outputs['end.time'] ]
+      compatibility_windows.status: $[ dependencies.compatibility_windows.result ]
 
       branch_sha: $[ dependencies.git_sha.outputs['out.branch'] ]
       master_sha: $[ dependencies.git_sha.outputs['out.master'] ]
@@ -455,7 +475,11 @@ jobs:
                     "compatibility_macos": {"start": "$(compatibility_macos.start)",
                                             "machine": "$(compatibility_macos.machine)",
                                             "end": "$(compatibility_macos.end)",
-                                            "status": "$(compatibility_macos.status)"}},
+                                            "status": "$(compatibility_macos.status)"},
+                    "compatibility_windows": {"start": "$(compatibility_windows.start)",
+                                              "machine": "$(compatibility_windows.machine)",
+                                              "end": "$(compatibility_windows.end)",
+                                              "status": "$(compatibility_windows.status)"}},
            "id": "$(Build.BuildId)",
            "url": "https://dev.azure.com/digitalasset/daml/_build/results?buildId=$(Build.BuildId)",
            "name": "$(Build.DefinitionName)",
diff --git a/bazel_tools/client_server/client_server_test.bzl b/bazel_tools/client_server/client_server_test.bzl
index 97a8052ba2..cfe62011f8 100644
--- a/bazel_tools/client_server/client_server_test.bzl
+++ b/bazel_tools/client_server/client_server_test.bzl
@@ -12,25 +12,35 @@ def _client_server_test_impl(ctx):
         output = wrapper,
         content = """#!/usr/bin/env bash
 set -eou pipefail
+canonicalize_rlocation() {{
+  # Note (MK): This is a fun one: Let’s say $TEST_WORKSPACE is "compatibility"
+  # and the argument points to a target from an external workspace, e.g.,
+  # @daml-sdk-0.0.0//:daml. Then the short path will point to
+  # ../daml-sdk-0.0.0/daml. Putting things together we end up with
+  # compatibility/../daml-sdk-0.0.0/daml. On Linux and MacOS this works
+  # just fine. However, on windows we need to normalize the path
+  # or rlocation will fail to find the path in the manifest file.
+  rlocation $(realpath -L -s -m --relative-to=$PWD $TEST_WORKSPACE/$1)
+}}
 
-runner=$(rlocation "$TEST_WORKSPACE/{runner}")
+runner=$(canonicalize_rlocation "{runner}")
 runner_args="{runner_args}"
-client=$(rlocation "$TEST_WORKSPACE/{client}")
-server=$(rlocation "$TEST_WORKSPACE/{server}")
+client=$(canonicalize_rlocation "{client}")
+server=$(canonicalize_rlocation "{server}")
 server_args="{server_args}"
 for file in {server_files}; do
-    server_args+=" $(rlocation $TEST_WORKSPACE/$file)"
+    server_args+=" $(canonicalize_rlocation $file)"
 done
 
 client_args="$@"
 if [ -z "$client_args" ]; then
     client_args="{client_args}"
     for file in {client_files}; do
-        client_args+=" $(rlocation $TEST_WORKSPACE/$file)"
+        client_args+=" $(canonicalize_rlocation $file)"
     done
 fi
 
-$runner "$client" "$client_args" "$server" "$server_args" "$runner_args"
+$runner $client "$client_args" $server "$server_args" "$runner_args"
 """.format(
             runner = ctx.executable.runner.short_path,
             runner_args = _expand_args(ctx, ctx.attr.runner_args),
diff --git a/ci/compatibility-windows.yml b/ci/compatibility-windows.yml
new file mode 100644
index 0000000000..0bf2370e97
--- /dev/null
+++ b/ci/compatibility-windows.yml
@@ -0,0 +1,26 @@
+# Copyright (c) 2020 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+parameters:
+  - name: test_flags
+    type: string
+    default: ''
+
+steps:
+  - bash: ci/configure-bazel.sh
+    displayName: 'Configure Bazel for root workspace'
+    env:
+      IS_FORK: $(System.PullRequest.IsFork)
+      # to upload to the bazel cache
+      GOOGLE_APPLICATION_CREDENTIALS_CONTENT: $(GOOGLE_APPLICATION_CREDENTIALS_CONTENT)
+  - bash: ci/configure-bazel.sh
+    displayName: 'Configure Bazel for compatibility workspace'
+    env:
+      BAZEL_CONFIG_DIR: compatibility
+      IS_FORK: $(System.PullRequest.IsFork)
+      # to upload to the bazel cache
+      GOOGLE_APPLICATION_CREDENTIALS_CONTENT: $(GOOGLE_APPLICATION_CREDENTIALS_CONTENT)
+  - powershell: '.\compatibility\build-release-artifacts-windows.ps1'
+    displayName: 'Build release artifacts'
+  - powershell: '.\compatibility\test-windows.ps1  ${{ parameters.test_flags }}'
+    displayName: 'Run tests'
diff --git a/ci/cron/daily-compat.yml b/ci/cron/daily-compat.yml
index 790d6d0a00..2970ba366a 100644
--- a/ci/cron/daily-compat.yml
+++ b/ci/cron/daily-compat.yml
@@ -31,8 +31,6 @@ jobs:
           pool: 'linux-pool'
         macos:
           pool: 'macOS-pool'
-        # windows:
-        #   pool: 'windows-pool'
     pool:
       name: $(pool)
     steps:
@@ -54,3 +52,26 @@ jobs:
                $(Slack.team-daml)
         displayName: report
         condition: always()
+  - job: compatibility_windows
+    timeoutInMinutes: 240
+    pool:
+      name: windows-pool
+    steps:
+      - checkout: self
+      - template: ../compatibility-windows.yml
+      - bash: |
+          set -euo pipefail
+          COMMIT_TITLE=$(git log --pretty=format:%s -n1)
+          COMMIT_LINK="<https://dev.azure.com/digitalasset/daml/_build/results?buildId=$(Build.BuildId)|$COMMIT_TITLE>"
+          if [ "$(Agent.JobStatus)" != "Succeeded" ]; then
+              MESSAGE=":fire: <!here> :fire: :fire:\n$(Agent.JobName) *FAILED*: $COMMIT_LINK\n:fire: :fire:"
+          else
+              MESSAGE="$(Agent.JobName) passed: $COMMIT_LINK"
+          fi
+          curl -XPOST \
+               -i \
+               -H 'Content-type: application/json' \
+               --data "{\"text\":\"$MESSAGE\n\"}" \
+               $(Slack.team-daml)
+        displayName: report
+        condition: always()
diff --git a/compatibility/.bazelrc b/compatibility/.bazelrc
deleted file mode 120000
index adb61980d2..0000000000
--- a/compatibility/.bazelrc
+++ /dev/null
@@ -1 +0,0 @@
-../.bazelrc
\ No newline at end of file
diff --git a/compatibility/BUILD b/compatibility/BUILD
index 106afb4e6c..c8df004a14 100644
--- a/compatibility/BUILD
+++ b/compatibility/BUILD
@@ -49,7 +49,7 @@ platform_versions = [
     )
     for sdk_version in sdk_versions
     for platform_version in platform_versions
-] if not is_windows else None
+]
 
 test_suite(
     name = "head-quick",
diff --git a/compatibility/WORKSPACE b/compatibility/WORKSPACE
index c0116bd799..7a926a5eb8 100644
--- a/compatibility/WORKSPACE
+++ b/compatibility/WORKSPACE
@@ -12,7 +12,7 @@ load("@daml//bazel_tools:os_info.bzl", "os_info")
 
 os_info(name = "os_info")
 
-load("@os_info//:os_info.bzl", "is_linux", "os_name")
+load("@os_info//:os_info.bzl", "is_darwin", "is_linux", "is_windows", "os_name")
 load("@daml//bazel_tools:build_environment.bzl", "build_environment")
 
 build_environment(name = "build_environment")
@@ -25,10 +25,22 @@ load("@rules_haskell//haskell:repositories.bzl", "rules_haskell_dependencies")
 
 rules_haskell_dependencies()
 
+load("@daml//bazel_tools/dev_env_tool:dev_env_tool.bzl", "dadew", "dev_env_tool")
+
+dadew(name = "dadew")
+
+load("@daml//bazel_tools/dev_env_tool:dev_env_tool.bzl", "dadew_sh_posix_configure")
+
+dadew_sh_posix_configure() if is_windows else None
+
 load(
     "@rules_haskell//haskell:nixpkgs.bzl",
     "haskell_register_ghc_nixpkgs",
 )
+load(
+    "@rules_haskell//haskell:ghc_bindist.bzl",
+    "haskell_register_ghc_bindists",
+)
 load(
     "@io_tweag_rules_nixpkgs//nixpkgs:nixpkgs.bzl",
     "nixpkgs_cc_configure",
@@ -88,6 +100,11 @@ filegroup(
     repositories = dev_env_nix_repos,
 ) if is_linux else None
 
+haskell_register_ghc_bindists(
+    compiler_flags = [],
+    version = "8.6.5",
+) if is_windows else None
+
 haskell_register_ghc_nixpkgs(
     attribute_path = "ghcStatic",
     build_file = "@io_tweag_rules_nixpkgs//nixpkgs:BUILD.pkg",
@@ -126,6 +143,20 @@ nixpkgs_package(
     repositories = dev_env_nix_repos,
 )
 
+dev_env_tool(
+    name = "openssl_dev_env",
+    nix_include = ["bin/openssl"],
+    nix_label = "@openssl_nix",
+    nix_paths = ["bin/openssl"],
+    tools = ["openssl"],
+    win_include = [
+        "usr/bin",
+        "usr/ssl",
+    ],
+    win_paths = ["usr/bin/openssl.exe"],
+    win_tool = "msys2",
+)
+
 nixpkgs_package(
     name = "hlint_nix",
     attribute_path = "hlint",
@@ -156,6 +187,7 @@ daml_sdk(
     sdk_sha256 = {
         "linux": "ee7e2f50394d44fb3490068de64d37f4f87534e802717bd7e07e8767df2e4e05",
         "macos": "feb2086a9a01048300270c71eb212c8541cdec1082f541408250d6124bc307a8",
+        "windows": "2028efe1f505c1994e1abc41c0fb5181669cd46834818aa8276d04b0fb6eb034",
     },
     test_tool_sha256 = "cf66efafd9490e1256e825f377b208b8ae90151f56e411b596fbaaef91353e14",
     version = "1.0.0",
@@ -166,6 +198,7 @@ daml_sdk(
     sdk_sha256 = {
         "linux": "aaf832ceda1a66a8469460d5a4b6c14f681ce692d4e9ef6010896febbaf4b6e1",
         "macos": "c2f89e394332b6ff19f547ccb399bacd3cd50d2493249c2d3a1ecaad0b87ac8b",
+        "windows": "7033ef0c5cbe75910a27730643076d3919b5694f3dc75f8daa57d5c22d04c593",
     },
     test_tool_sha256 = "762cd4836a8359dca0fb3271ba2e1d0629138f7d8d914298324418a174c5d22a",
     version = "1.0.1-snapshot.20200417.3908.1.722bac90",
@@ -176,6 +209,7 @@ daml_sdk(
     sdk_sha256 = {
         "linux": "d3bddaa903ebaebb6f714a3ac39598ba7fd71e8b80636c1275054ed7b883a0d9",
         "macos": "66f1713057800ed75db1b967a8ea2d9b6c18da1a76b8224abdec0d33ed5533ae",
+        "windows": "2c779776d923d990870fbb2aa1c71e6081258a9b9ccc7cf8242c419a765d4821",
     },
     test_tool_sha256 = "649ecf7a7e98caef7dac20082526444b33d85dfe79b4b9b66d069ad67aac74fa",
     version = "1.1.0-snapshot.20200422.3991.0.6391ee9f",
diff --git a/compatibility/bazel-haskell-deps.bzl b/compatibility/bazel-haskell-deps.bzl
index 5e79c4350f..bbc1cac283 100644
--- a/compatibility/bazel-haskell-deps.bzl
+++ b/compatibility/bazel-haskell-deps.bzl
@@ -15,11 +15,12 @@ load("@bazel_skylib//lib:dicts.bzl", "dicts")
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 load("@os_info//:os_info.bzl", "is_windows")
 load("@rules_haskell//haskell:cabal.bzl", "stack_snapshot")
+load("@dadew//:dadew.bzl", "dadew_tool_home")
 
 def daml_haskell_deps():
     """Load all Haskell dependencies of the DAML repository."""
 
-    use_integer_simple = True
+    use_integer_simple = not is_windows
 
     stack_snapshot(
         name = "stackage",
@@ -56,7 +57,16 @@ def daml_haskell_deps():
             "tasty-hunit",
             "text",
         ] + (["unix"] if not is_windows else ["Win32"]),
-        stack = None,
+        stack = "@stack_windows//:stack.exe" if is_windows else None,
         tools = [
         ],
     )
+
+    if is_windows:
+        native.new_local_repository(
+            name = "stack_windows",
+            build_file_content = """
+exports_files(["stack.exe"], visibility = ["//visibility:public"])
+""",
+            path = dadew_tool_home("stack"),
+        )
diff --git a/compatibility/bazel_tools/daml_ledger/BUILD.bazel b/compatibility/bazel_tools/daml_ledger/BUILD.bazel
index 943626c4f2..059c2ed65f 100644
--- a/compatibility/bazel_tools/daml_ledger/BUILD.bazel
+++ b/compatibility/bazel_tools/daml_ledger/BUILD.bazel
@@ -64,23 +64,23 @@ genrule(
     cmd = """
 set -eou pipefail
 # Generate CA key and crt
-$(location @openssl_nix//:bin/openssl) genrsa -out $(location ca.key) 4096
-$(location @openssl_nix//:bin/openssl) req -new -x509 -key $(location ca.key) -out $(location ca.crt) -subj '/CN=0.0.0.0.ca' -days 3650
+$(location @openssl_dev_env//:openssl) genrsa -out $(location ca.key) 4096
+$(location @openssl_dev_env//:openssl) req -new -x509 -key $(location ca.key) -out $(location ca.crt) -subj '/CN=0.0.0.0.ca' -days 3650
 
 # Generate server key, csr and crt
-$(location @openssl_nix//:bin/openssl) genrsa -out $(location server.key) 4096
-$(location @openssl_nix//:bin/openssl) pkey -in $(location server.key) -out $(location server.pem)
-$(location @openssl_nix//:bin/openssl) req -new -key $(location server.key) -out $(location server.csr) -subj '/CN=0.0.0.0.server'
-$(location @openssl_nix//:bin/openssl) x509 -req -in $(location server.csr) -CA $(location ca.crt) -CAkey $(location ca.key) -CAcreateserial -out $(location server.crt) -extfile $(location openssl-extensions.cnf) -extensions req_ext -days 3650
+$(location @openssl_dev_env//:openssl) genrsa -out $(location server.key) 4096
+$(location @openssl_dev_env//:openssl) pkey -in $(location server.key) -out $(location server.pem)
+$(location @openssl_dev_env//:openssl) req -new -key $(location server.key) -out $(location server.csr) -subj '/CN=0.0.0.0.server'
+$(location @openssl_dev_env//:openssl) x509 -req -in $(location server.csr) -CA $(location ca.crt) -CAkey $(location ca.key) -CAcreateserial -out $(location server.crt) -extfile $(location openssl-extensions.cnf) -extensions req_ext -days 3650
 
 # Generate client key, csr and crt
-$(location @openssl_nix//:bin/openssl) genrsa -out $(location client.key) 4096
-$(location @openssl_nix//:bin/openssl) pkey -in $(location client.key) -out $(location client.pem)
-$(location @openssl_nix//:bin/openssl) req -new -key $(location client.key) -out $(location client.csr) -subj '/CN=0.0.0.0.client'
-$(location @openssl_nix//:bin/openssl) x509 -req -in $(location client.csr) -CA $(location ca.crt) -CAkey $(location ca.key) -CAcreateserial -out $(location client.crt) -extfile $(location openssl-extensions.cnf) -extensions req_ext -days 3650
+$(location @openssl_dev_env//:openssl) genrsa -out $(location client.key) 4096
+$(location @openssl_dev_env//:openssl) pkey -in $(location client.key) -out $(location client.pem)
+$(location @openssl_dev_env//:openssl) req -new -key $(location client.key) -out $(location client.csr) -subj '/CN=0.0.0.0.client'
+$(location @openssl_dev_env//:openssl) x509 -req -in $(location client.csr) -CA $(location ca.crt) -CAkey $(location ca.key) -CAcreateserial -out $(location client.crt) -extfile $(location openssl-extensions.cnf) -extensions req_ext -days 3650
     """,
     tools = [
-        "@openssl_nix//:bin/openssl",
+        "@openssl_dev_env//:openssl",
     ],
     visibility = ["//visibility:public"],
 )
diff --git a/compatibility/bazel_tools/daml_sdk.bzl b/compatibility/bazel_tools/daml_sdk.bzl
index 2c9c2b177c..53cb25d439 100644
--- a/compatibility/bazel_tools/daml_sdk.bzl
+++ b/compatibility/bazel_tools/daml_sdk.bzl
@@ -1,6 +1,8 @@
 # Copyright (c) 2020 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0
 
+load("@os_info//:os_info.bzl", "is_windows", "os_name")
+
 runfiles_library = """
 # Copy-pasted from the Bazel Bash runfiles library v2.
 set -uo pipefail; f=bazel_tools/tools/bash/runfiles/runfiles.bash
@@ -14,21 +16,24 @@ source "${RUNFILES_DIR:-/dev/null}/$f" 2>/dev/null || \
 """
 
 def _daml_sdk_impl(ctx):
+    # The DAML assistant will mark the installed SDK read-only.
+    # This breaks Bazel horribly on Windows to the point where
+    # even `bazel clean --expunge` fails because it cannot remove
+    # the installed SDK. Therefore, we do not use the assistant to
+    # install the SDK but instead simply extract the SDK to the right
+    # location and set the symlink ourselves.
+    out_dir = ctx.path("sdk").get_child("sdk").get_child(ctx.attr.version)
     if ctx.attr.sdk_tarball:
         ctx.extract(
             ctx.attr.sdk_tarball,
-            output = "extracted-sdk",
+            output = out_dir,
             stripPrefix = "sdk-{}".format(ctx.attr.version),
         )
     elif ctx.attr.sdk_sha256:
         ctx.download_and_extract(
-            output = "extracted-sdk",
-            # TODO (MK) Make this work on other platforms.
-            url = "https://github.com/digital-asset/daml/releases/download/v{version}/daml-sdk-{version}-{os}.tar.gz"
-                .format(
-                version = ctx.attr.version,
-                os = ctx.attr.os_name,
-            ),
+            output = out_dir,
+            url =
+                "https://github.com/digital-asset/daml/releases/download/v{}/daml-sdk-{}-{}.tar.gz".format(ctx.attr.version, ctx.attr.version, ctx.attr.os_name),
             sha256 = ctx.attr.sdk_sha256[ctx.attr.os_name],
             stripPrefix = "sdk-{}".format(ctx.attr.version),
         )
@@ -50,19 +55,8 @@ def _daml_sdk_impl(ctx):
         "ledger-api-test-tool.jar",
         output = "extracted-test-tool",
     )
-    ps_result = ctx.execute(
-        ["extracted-sdk/daml/daml", "install", "extracted-sdk", "--install-assistant=no"],
-        environment = {
-            "DAML_HOME": "sdk",
-        },
-    )
-    if ps_result.return_code != 0:
-        fail("Failed to install SDK.\nExit code %d.\n%s\n%s" %
-             (ps_result.return_code, ps_result.stdout, ps_result.stderr))
 
-    # At least on older SDKs, the symlinking in --install-assistant=yes does not work
-    # properly so we symlink ourselves.
-    ctx.symlink("sdk/sdk/{}/daml/daml".format(ctx.attr.version), "sdk/bin/daml")
+    ctx.symlink(out_dir.get_child("daml").get_child("daml" + (".exe" if is_windows else "")), "sdk/bin/daml")
     ctx.file(
         "sdk/daml-config.yaml",
         content =
@@ -121,11 +115,11 @@ _daml_sdk = repository_rule(
     implementation = _daml_sdk_impl,
     attrs = {
         "version": attr.string(mandatory = True),
+        "os_name": attr.string(mandatory = False, default = os_name),
         "sdk_sha256": attr.string_dict(mandatory = False),
         "sdk_tarball": attr.label(allow_single_file = True, mandatory = False),
         "test_tool_sha256": attr.string(mandatory = False),
         "test_tool": attr.label(allow_single_file = True, mandatory = False),
-        "os_name": attr.string(mandatory = True),
     },
 )
 
diff --git a/compatibility/bazel_tools/sandbox-with-postgres.sh b/compatibility/bazel_tools/sandbox-with-postgres.sh
index 19662cb5b8..58263a3142 100755
--- a/compatibility/bazel_tools/sandbox-with-postgres.sh
+++ b/compatibility/bazel_tools/sandbox-with-postgres.sh
@@ -15,4 +15,12 @@ source "${RUNFILES_DIR:-/dev/null}/$f" 2>/dev/null || \
 set -eou pipefail
 version=$1
 extra_args="${@:2}"
-$(rlocation compatibility/bazel_tools/client_server/with-postgres) $(rlocation daml-sdk-$version/daml) sandbox $extra_args
+WITH_POSTGRES=$(rlocation compatibility/bazel_tools/client_server/with-postgres)
+if [ -z "$WITH_POSTGRES" ]; then
+    WITH_POSTGRES=$(rlocation compatibility/bazel_tools/client_server/with-postgres.exe)
+fi
+if [ -z "$WITH_POSTGRES" ]; then
+    echo "Faild to find with-postgres wrapper"
+    exit 1
+fi
+$WITH_POSTGRES $(rlocation daml-sdk-$version/daml) sandbox $extra_args
diff --git a/compatibility/bazel_tools/testing.bzl b/compatibility/bazel_tools/testing.bzl
index 9f7fd31058..55865163c7 100644
--- a/compatibility/bazel_tools/testing.bzl
+++ b/compatibility/bazel_tools/testing.bzl
@@ -5,6 +5,7 @@ load(
     "@daml//bazel_tools/client_server:client_server_test.bzl",
     "client_server_test",
 )
+load("@os_info//:os_info.bzl", "is_windows")
 
 latest_stable = "1.0.0"
 
@@ -168,7 +169,9 @@ def sdk_platform_test(sdk_version, platform_version):
             dar_files = dar_files,
         )],
         tags = ["exclusive"] + extra_tags(sdk_version, platform_version),
-    )
+    ) if not is_windows else None
+    # We disable the postgres tests on Windows for now since our postgres setup
+    # relies on Nix. This should be fixable by getting postgres from dev-env.
 
     # daml-ledger test-cases
     name = "daml-ledger-{sdk_version}-platform-{platform_version}".format(
@@ -181,4 +184,5 @@ def sdk_platform_test(sdk_version, platform_version):
         daml = daml_assistant,
         sandbox = sandbox,
         sandbox_args = sandbox_args,
+        tags = extra_tags(sdk_version, platform_version),
     )
diff --git a/compatibility/build-release-artifacts-windows.ps1 b/compatibility/build-release-artifacts-windows.ps1
new file mode 100644
index 0000000000..2280dd924b
--- /dev/null
+++ b/compatibility/build-release-artifacts-windows.ps1
@@ -0,0 +1,44 @@
+Set-StrictMode -Version latest
+$ErrorActionPreference = 'Stop'
+# Copyright (c) 2020 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+# Build the release artifacts required for running the compatibility
+# tests against HEAD. At the moment this includes the SDK release tarball
+# and the ledger-api-test-tool fat JAR.
+
+# See https://github.com/lukesampson/scoop/issues/3859
+Set-Strictmode -Off
+.\dev-env\windows\bin\dadew.ps1 install
+Set-StrictMode -Version latest
+.\dev-env\windows\bin\dadew.ps1 sync
+.\dev-env\windows\bin\dadew.ps1 enable
+
+if (Test-Path -Path $env:appdata\stack\pantry\hackage\hackage-security-lock) {
+    Write-Output ">> Nuking stack directory"
+    Remove-Item -ErrorAction Continue -Force -Recurse -Path $env:appdata\stack
+}
+
+function bazel() {
+    Write-Output ">> bazel $args"
+    $global:lastexitcode = 0
+    $backupErrorActionPreference = $script:ErrorActionPreference
+    $script:ErrorActionPreference = "Continue"
+    & bazel.exe @args 2>&1 | %{ "$_" }
+    $script:ErrorActionPreference = $backupErrorActionPreference
+    if ($global:lastexitcode -ne 0 -And $args[0] -ne "shutdown") {
+        Write-Output "<< bazel $args (failed, exit code: $global:lastexitcode)"
+        throw ("Bazel returned non-zero exit code: $global:lastexitcode")
+    }
+    Write-Output "<< bazel $args (ok)"
+}
+
+
+bazel shutdown
+bazel fetch @nodejs_dev_env//...
+bazel build `
+  //release:sdk-release-tarball `
+  //ledger/ledger-api-test-tool:ledger-api-test-tool_deploy.jar
+
+cp -Force bazel-bin\release\sdk-release-tarball.tar.gz compatibility/head_sdk
+cp -Force bazel-bin\ledger\ledger-api-test-tool\ledger-api-test-tool_deploy.jar compatibility/head_sdk
diff --git a/compatibility/deps.bzl b/compatibility/deps.bzl
index b19b77d3fe..94cf865997 100644
--- a/compatibility/deps.bzl
+++ b/compatibility/deps.bzl
@@ -36,6 +36,12 @@ def daml_deps():
             name = "rules_haskell",
             strip_prefix = "rules_haskell-%s" % rules_haskell_version,
             urls = ["https://github.com/tweag/rules_haskell/archive/%s.tar.gz" % rules_haskell_version],
+            patches = [
+                "@daml//bazel_tools:haskell-strict-source-names.patch",
+                "@daml//bazel_tools:haskell-windows-remove-fake-libs.patch",
+                "@daml//bazel_tools:haskell-windows-extra-libraries.patch",
+            ],
+            patch_args = ["-p1"],
             sha256 = rules_haskell_sha256,
         )
 
diff --git a/compatibility/test-windows.ps1 b/compatibility/test-windows.ps1
new file mode 100644
index 0000000000..e4a2ffdff2
--- /dev/null
+++ b/compatibility/test-windows.ps1
@@ -0,0 +1,51 @@
+Set-StrictMode -Version latest
+$ErrorActionPreference = 'Stop'
+# Copyright (c) 2020 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+# Build the release artifacts required for running the compatibility
+# tests against HEAD. At the moment this includes the SDK release tarball
+# and the ledger-api-test-tool fat JAR.
+
+$test_args = "//..."
+if (($args.length -ge 1) -and ($args[0] -eq "--quick")) {
+  $test_args = "//:head-quick"
+}
+write-output $test_args
+
+# For reasons I do not understand, it seems to be important
+# to sync here even though we sync in the previous step already.
+.\dev-env\windows\bin\dadew.ps1 sync
+.\dev-env\windows\bin\dadew.ps1 enable
+
+
+if (Test-Path -Path $env:appdata\stack\pantry\hackage\hackage-security-lock) {
+    Write-Output ">> Nuking stack directory"
+    Remove-Item -ErrorAction Continue -Force -Recurse -Path $env:appdata\stack
+}
+
+# This is currently shared between various powershell scripts.
+# We should probably factor this out.
+function bazel() {
+    Write-Output ">> bazel $args"
+    $global:lastexitcode = 0
+    $backupErrorActionPreference = $script:ErrorActionPreference
+    $script:ErrorActionPreference = "Continue"
+    & bazel.exe @args 2>&1 | %{ "$_" }
+    $script:ErrorActionPreference = $backupErrorActionPreference
+    if ($global:lastexitcode -ne 0 -And $args[0] -ne "shutdown") {
+        Write-Output "<< bazel $args (failed, exit code: $global:lastexitcode)"
+        throw ("Bazel returned non-zero exit code: $global:lastexitcode")
+    }
+    Write-Output "<< bazel $args (ok)"
+}
+
+cd compatibility
+# Symlinks don’t work on Windows.
+cp ../.bazelrc .bazelrc
+
+bazel shutdown
+bazel build //...
+bazel shutdown
+
+bazel test "$test_args"
diff --git a/compatibility/test.sh b/compatibility/test.sh
index 80e65446b0..d1eda497ef 100755
--- a/compatibility/test.sh
+++ b/compatibility/test.sh
@@ -13,6 +13,11 @@ cd "$(dirname "$0")"
 
 eval "$(../dev-env/bin/dade-assist)"
 
+# Git, symlinks and windows do not play well together
+# so we have to copy over the Bazel config. We just do
+# it unconditionally since it should be cheap enough.
+cp ../.bazelrc .bazelrc
+
 bazel build //...
 if [ "${1:-}" = "--quick" ]; then
     bazel test //:head-quick