ci: add windows-latest to test matrix

.github/workflows/ci.yml

@@ -44,7 +44,12 @@ jobs:
           PY
 
   pytest:
-    runs-on: ubuntu-latest
+    name: pytest (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
     permissions:
       contents: read
     steps:
@@ -63,6 +68,7 @@ jobs:
       - name: Install dev dependencies (Flask + pytest)
         run: pip install -r requirements-dev.txt
 
+      # Full suite gate (pyproject addopts include --cov + 60% fail-under).
       - name: Run tests
         run: pytest --tb=short -q
 
@@ -93,8 +99,12 @@ jobs:
         run: mypy tests --config-file mypy-tests.ini --follow-imports skip
 
   integration-tests:
-    name: API integration tests + coverage
-    runs-on: ubuntu-latest
+    name: API integration tests + coverage (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
     permissions:
       contents: read
       actions: write
@@ -114,18 +124,23 @@ jobs:
       - name: Install dev dependencies
         run: pip install -r requirements-dev.txt
 
-      # Subset run: skip fail-under (full suite enforces 60% in pytest job).
+      # Intentional overlap with pytest job: re-runs API/search subset with --cov
+      # and uploads coverage.xml per OS (pytest job is the full-suite gate).
       - name: Run integration tests with coverage
         run: pytest tests/test_api_integration.py tests/test_search.py -v --cov=api --cov=utils --cov-report=xml --cov-fail-under=0
 
       - uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
         with:
-          name: coverage-report
+          name: coverage-report-${{ matrix.os }}
           path: coverage.xml
 
   js-tests:
-    name: Frontend unit tests (vitest)
-    runs-on: ubuntu-latest
+    name: Frontend unit tests (vitest) (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
     permissions:
       contents: read
     steps:

CONTRIBUTING.md

@@ -9,6 +9,8 @@ Thanks for considering a patch. This repo is a small Flask app plus a hash-route
 - **Python 3.12** (matches CI)
 - **Node 20+** (only if you change `static/js/` or run frontend unit tests)
 
+CI runs **`pytest`**, **integration tests**, and **Vitest** on **ubuntu-latest** and **windows-latest** (Python 3.12, Node 20). Type-check (`mypy`) and production install smoke run on Ubuntu only.
+
 ### Bootstrap (Windows PowerShell)
 
 ```powershell
@@ -105,7 +107,7 @@ npm run test:coverage   # optional
 - PR checklist:
   - [ ] `pytest -q` green locally
   - [ ] `npm test` green if JS changed
-  - [ ] CI jobs green (`pytest`, `integration-tests`, `js-tests`, `prod-install-smoke`)
+  - [ ] CI jobs green (`pytest`, `integration-tests`, `js-tests` on Ubuntu + Windows; `mypy`, `prod-install-smoke` on Ubuntu)
   - [ ] PR description includes a **Test plan** section
   - [ ] API changes update [`docs/api-reference.md`](docs/api-reference.md) if behavior or errors change
 

tests/test_export_state_store.py

@@ -3,9 +3,38 @@
 from __future__ import annotations
 
 import json
+import subprocess
+import sys
+import time
 from pathlib import Path
 
-from utils.export_state_store import load_export_state_from_disk
+import pytest
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+
+
+def _wait_for_file(path: Path, timeout: float = 5.0) -> None:
+    deadline = time.monotonic() + timeout
+    while time.monotonic() < deadline:
+        if path.is_file():
+            return
+        time.sleep(0.01)
+    raise AssertionError(f"timed out waiting for {path}")
+
+
+def _assert_file_stays_absent(path: Path, timeout: float = 0.5) -> None:
+    """While parent holds the lock, child must not write *path* (still blocked)."""
+    deadline = time.monotonic() + timeout
+    while time.monotonic() < deadline:
+        if path.is_file():
+            raise AssertionError(f"{path} appeared while parent still holds the lock")
+        time.sleep(0.01)
+
+from utils.export_state_store import (
+    atomic_write_export_state,
+    export_state_lock,
+    load_export_state_from_disk,
+)
 
 
 def test_load_rejects_non_object_json(tmp_path: Path):
@@ -81,3 +110,70 @@ def locking(fd, mode, nbytes):
     with mod.export_state_lock(str(state_file)):
         assert (FakeMsvcrt.LK_LOCK, 1) in calls
     assert calls[-1] == (FakeMsvcrt.LK_UNLCK, 1)
+
+
+@pytest.mark.skipif(sys.platform != "win32", reason="requires Windows msvcrt")
+def test_export_state_lock_real_msvcrt_roundtrip(tmp_path: Path) -> None:
+    """Exercise real ``msvcrt.locking`` on a Windows runner (not FakeMsvcrt)."""
+    state_file = tmp_path / "export_state.json"
+    state_file.write_text("{}", encoding="utf-8")
+    payload = {
+        "sessions": {"sess-msvcrt-roundtrip": 1740000123.5},
+        "lastExportTime": "2026-06-04T18:30:00Z",
+        "exportedCount": 42,
+    }
+
+    with export_state_lock(str(state_file)):
+        atomic_write_export_state(payload, str(state_file))
+
+    loaded = load_export_state_from_disk(str(state_file))
+    assert loaded.get("exportedCount") == 42
+    assert loaded.get("sessions") == {"sess-msvcrt-roundtrip": 1740000123.5}
+    assert loaded.get("lastExportTime") == "2026-06-04T18:30:00Z"
+
+
+@pytest.mark.skipif(sys.platform != "win32", reason="requires Windows msvcrt")
+def test_export_state_lock_blocks_second_process(tmp_path: Path) -> None:
+    """While the parent holds ``msvcrt`` lock, a child process cannot acquire it."""
+    state_file = tmp_path / "export_state.json"
+    state_file.write_text("{}", encoding="utf-8")
+    attempting_marker = tmp_path / "child_attempting.lock"
+    acquired_marker = tmp_path / "child_acquired.lock"
+    child = (
+        "import sys\n"
+        "from pathlib import Path\n"
+        f"sys.path.insert(0, {str(REPO_ROOT)!r})\n"
+        "from utils.export_state_store import export_state_lock\n"
+        "path, attempting, acquired = sys.argv[1], sys.argv[2], sys.argv[3]\n"
+        "Path(attempting).write_text('ok', encoding='utf-8')\n"
+        "with export_state_lock(path):\n"
+        "    Path(acquired).write_text('ok', encoding='utf-8')\n"
+    )
+    proc: subprocess.Popen[bytes] | None = None
+    try:
+        with export_state_lock(str(state_file)):
+            proc = subprocess.Popen(
+                [
+                    sys.executable,
+                    "-c",
+                    child,
+                    str(state_file),
+                    str(attempting_marker),
+                    str(acquired_marker),
+                ],
+                cwd=str(REPO_ROOT),
+            )
+            _wait_for_file(attempting_marker)
+            _assert_file_stays_absent(acquired_marker)
+        assert proc is not None
+        try:
+            assert proc.wait(timeout=10) == 0
+        except subprocess.TimeoutExpired:
+            proc.kill()
+            proc.wait()
+            raise
+        assert acquired_marker.read_text(encoding="utf-8") == "ok"
+    finally:
+        if proc is not None and proc.poll() is None:
+            proc.kill()
+            proc.wait()

tests/test_session_path.py

@@ -0,0 +1,40 @@
+"""Tests for utils/session_path platform-specific home resolution."""
+
+from __future__ import annotations
+
+import os
+import sys
+from pathlib import Path
+
+import pytest
+
+from utils import session_path
+
+
+def test_get_claude_projects_dir_uses_userprofile_on_windows(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    """Linux/Windows CI smoke: patch ``session_path.platform.system`` (needs ``import platform`` in module).
+
+    If ``session_path`` ever switches to ``from platform import system``, this patch
+    no-ops but may still pass on Linux via ``expanduser("~")``. Real Windows behavior
+    is covered by ``test_get_claude_projects_dir_on_windows_runner`` (win32-only).
+    """
+    profile = tmp_path / "Users" / "testuser"
+    monkeypatch.setattr(session_path.platform, "system", lambda: "Windows")
+    monkeypatch.setenv("USERPROFILE", str(profile))
+
+    got = session_path.get_claude_projects_dir()
+    assert got == os.path.join(str(profile), ".claude", "projects")
+
+
+@pytest.mark.skipif(sys.platform != "win32", reason="native Windows runner")
+def test_get_claude_projects_dir_on_windows_runner(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    profile = tmp_path / "profile"
+    monkeypatch.setenv("USERPROFILE", str(profile))
+
+    got = session_path.get_claude_projects_dir()
+    expected = os.path.join(str(profile), ".claude", "projects")
+    assert got == expected