diff --git a/.github/workflows/esy-ci.yml b/.github/workflows/esy-ci.yml
index 2783730b4..124f31998 100644
--- a/.github/workflows/esy-ci.yml
+++ b/.github/workflows/esy-ci.yml
@@ -36,6 +36,13 @@ jobs:
         with:
           node-version: 20
 
+      - name: Set up MinGW (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          choco upgrade mingw -y --no-progress
+          echo "C:\ProgramData\mingw64\mingw64\bin" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
+
       - name: Install esy
         run: npm install -g esy@0.9.0-beta.1
 
@@ -44,7 +51,7 @@ jobs:
         uses: actions/cache/restore@v4
         with:
           path: ~/.esy/source
-          key: esy-source-${{ matrix.os }}-${{ matrix.ocaml-compiler }}-${{ hashFiles('esy.lock.json') }}
+          key: v0.0.2-esy-source-${{ matrix.os }}-${{ matrix.ocaml-compiler }}-${{ hashFiles('esy.lock.json') }}
 
       - name: Print esy cache
         id: print_esy_cache
@@ -57,8 +64,8 @@ jobs:
           path: |
             ${{ steps.print_esy_cache.outputs.ESY_CACHE }}
             _export
-          key: esy-build-${{ matrix.os }}-${{ matrix.ocaml-compiler }}-${{ hashFiles('esy.lock.json') }}
-          restore-keys: esy-build-${{ matrix.os }}-
+          key: v0.0.2-esy-build-${{ matrix.os }}-${{ matrix.ocaml-compiler }}-${{ hashFiles('esy.lock.json') }}
+          restore-keys: v0.0.2-esy-build-${{ matrix.os }}-
 
       - name: Install dependencies
         run: esy install
@@ -94,7 +101,7 @@ jobs:
         if: steps.global-cache.outputs.cache-hit != 'true'
         with:
           path: ~/.esy/source
-          key: esy-source-${{ matrix.os }}-${{ matrix.ocaml-compiler }}-${{ hashFiles('esy.lock.json') }}
+          key: v0.0.2-esy-source-${{ matrix.os }}-${{ matrix.ocaml-compiler }}-${{ hashFiles('esy.lock.json') }}
 
       - name: Save dependencies cache
         if: steps.deps-cache.outputs.cache-hit != 'true'
@@ -103,7 +110,7 @@ jobs:
           path: |
             ${{ steps.print_esy_cache.outputs.ESY_CACHE }}
             _export
-          key: esy-build-${{ matrix.os }}-${{ matrix.ocaml-compiler }}-${{ hashFiles('esy.lock.json') }}
+          key: v0.0.2-esy-build-${{ matrix.os }}-${{ matrix.ocaml-compiler }}-${{ hashFiles('esy.lock.json') }}
 
       # Cleanup build cache in case dependencies have changed
       - name: Cleanup
diff --git a/.github/workflows/opam-ci.yml b/.github/workflows/opam-ci.yml
index e4e8a1e25..f0ebe912d 100644
--- a/.github/workflows/opam-ci.yml
+++ b/.github/workflows/opam-ci.yml
@@ -32,6 +32,7 @@ jobs:
             # OCaml >= 4.13
             # https://github.com/ocaml/setup-ocaml/issues/822#issuecomment-2215525942
           - {ocaml-compiler: '4.14.x', os: windows-latest}
+          - {ocaml-compiler: 'ocaml-base-compiler.5.4.0', os: windows-latest}
 
     runs-on: ${{ matrix.setup.os }}
 
@@ -51,7 +52,7 @@ jobs:
         uses: actions/cache/restore@v4
         with:
           path: ~/.opam
-          key: opam-${{ matrix.setup.os }}-${{ matrix.setup.ocaml-compiler }}-${{ hashFiles('*.opam') }}
+          key: v0.0.1-opam-${{ matrix.setup.os }}-${{ matrix.setup.ocaml-compiler }}-${{ hashFiles('*.opam') }}
 
       - name: Load opam cache when Windows
         if: runner.os == 'Windows'
@@ -59,7 +60,7 @@ jobs:
         uses: actions/cache/restore@v4
         with:
           path: _opam
-          key: opam-${{ matrix.setup.os }}-${{ matrix.setup.ocaml-compiler }}-${{ hashFiles('**.opam') }}
+          key: v0.0.1-opam-${{ matrix.setup.os }}-${{ matrix.setup.ocaml-compiler }}-${{ hashFiles('**.opam') }}
 
       - name: Install dependencies
         run: opam install . --deps-only
@@ -87,12 +88,12 @@ jobs:
         if: steps.opam-cache.outputs.cache-hit != 'true' && runner.os != 'Windows'
         with:
           path: ~/.opam
-          key: opam-${{ matrix.setup.os }}-${{ matrix.setup.ocaml-compiler }}-${{ hashFiles('**.opam') }}
+          key: v0.0.1-opam-${{ matrix.setup.os }}-${{ matrix.setup.ocaml-compiler }}-${{ hashFiles('**.opam') }}
 
       - name: Save cache when Windows
         uses: actions/cache/save@v4
         if: steps.opam-cache-windows.outputs.cache-hit != 'true' && runner.os == 'Windows'
         with:
           path: _opam
-          key: opam-${{ matrix.setup.os }}-${{ matrix.setup.ocaml-compiler }}-${{ hashFiles('**.opam') }}
+          key: v0.0.1-opam-${{ matrix.setup.os }}-${{ matrix.setup.ocaml-compiler }}-${{ hashFiles('**.opam') }}
 
diff --git a/test/dune b/test/dune
index 7c1e528e0..418b8bf80 100644
--- a/test/dune
+++ b/test/dune
@@ -12,7 +12,12 @@
   ./lib/outcometreePrinter.exe
   ./lib/fdLeak.exe))
 
+; rtopIntegration is disabled on Windows due to a segfault in lambda-term's
+; Windows C stubs when stdout is not a real console handle (ConPTY issue).
+; See: https://github.com/ocaml-community/lambda-term/pull/125
+; Re-enable on Windows once lambda-term ships the fix.
 (cram
  (applies_to rtopIntegration)
  (package rtop)
+ (enabled_if (= %{os_type} Unix))
  (deps %{bin:ocamlc} %{bin:rtop}))
diff --git a/test/rtopIntegration.t b/test/rtopIntegration.t
index 66f9be4a3..1cac5f452 100644
--- a/test/rtopIntegration.t
+++ b/test/rtopIntegration.t
@@ -11,8 +11,8 @@ always error.
 Given the above, we're gonna test that utop integration works by piping code
 into it and asserting the existence of some output.
 
-  $ echo "let f = a => a;" | rtop | grep -o "let f: 'a => 'a = <fun>;"
+  $ echo "let f = a => a;" | rtop 2>&1 | grep -o "let f: 'a => 'a = <fun>;"
   let f: 'a => 'a = <fun>;
 
-  $ echo "let f = (a) => 1 + \"hi\";" | rtop | grep -o "has type"
+  $ echo "let f = (a) => 1 + \"hi\";" | rtop 2>&1 | grep -o "has type"
   has type