Build & Embed operations hang silently on Windows 11 with uvx

[pvnsai73]

Bug Report — code-review-graph · Windows 11
Build and embed hang silently on a 6-file JS project. No error. No timeout.

---

Environment

OS: Windows 11 Enterprise 10.0.26200 · x86_64-pc-windows-msvc
uvx: 0.10.12 (2026-03-19)
Python: cpython-3.14.3 — uvx-managed, no system Python
code-review-graph: 1.8.4 [embeddings]
sentence-transformers / PyTorch / transformers: 3.4.1 / 2.10.0 / 4.57.6
Claude Code plugin: 1.8.3 (marketplace)
Required: UV_NATIVE_TLS=1 — without this, MCP server won't start

---

Reproduce

1. Windows 11, no system Python. Install uv/uvx, set UV_NATIVE_TLS=1.
2. uv tool install "code-review-graph[embeddings]"
3. Install marketplace plugin, configure .mcp.json.
4. Trigger build_or_update_graph_tool on a small JS project (6 files, ~240 nodes). → Hangs.
5. Trigger embed_graph_tool. → Also hangs.

---

What Happened

Build reported 310 nodes / 3,560 edges mid-run. Persisted DB shows 242 nodes / 1,808 edges. Post-processing deduplication is the likely culprit.

embed_graph_tool stalled during model inference. No error, no progress.

Workaround: Close Claude Code → restart → run "uvx code-review-graph status" from terminal. Build resumed. Embeddings were slow but finished.

---

Two Other Gotchas

Wrong install method breaks embed: "uvx pip install sentence-transformers" puts it in a different isolated env. embed_graph_tool then reports "not installed." Always use the [embeddings] extra — never install separately.

Corporate TLS: Add { "UV_NATIVE_TLS": "1" } under "env" in ~/.claude/settings.json.

---

Expected vs Actual

build — expected: seconds / actual: silent hang
embed — expected: under 1 min for ~240 nodes / actual: silent hang

---

Fixes Needed

1. Progress indicator + timeout on both build and embed.
2. README: document [embeddings] extra as the only correct install path on Windows/uvx.
3. README: document UV_NATIVE_TLS=1 for corporate environments.
4. Investigate the 310→242 node / 3,560→1,808 edge drop — that reconciliation step is probably the hang.

[pvnsai73]

● code-review-graph - list_graph_stats_tool (MCP)
⎿  {
"status": "ok",
"summary": "Graph statistics for new_hub:\n Files: 6\n Total nodes: 242\n Total edges: 1808\n Languages:
javascript\n Last updated: 2026-03-21T00:15:57\n\nNodes by kind:\n File: 6\n Function: 236\n\nEdges by
kind:\n CALLS: 1572\n CONTAINS: 236\n\nEmbeddings: 236 nodes embedded",
"total_nodes": 242,
"total_edges": 1808,
"nodes_by_kind": {
"File": 6,
"Function": 236
},
"edges_by_kind": {
"CALLS": 1572,
"CONTAINS": 236
},
"languages": [
"javascript"
],
"files_count": 6,
"last_updated": "2026-03-21T00:15:57",
"embeddings_count": 236
}

⎿  1 PostToolUse hook ran

                                                                                  02:13 AM claude-sonnet-4-6

● Graph exists from earlier today. Doing a full rebuild now.

● code-review-graph - build_or_update_graph_tool (MCP)(full_rebuild: true)
⎿  Error: MCP server "code-review-graph" tool "build_or_update_graph_tool" timed out after 100000s

                                                                                        08:22 PM <synthetic>

⎿  Please run /login · API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"OAuth token
has expired. Please obtain a new token or refresh your existing
token."},"request_id":"req_011CZJJrKVTJ9s9iYVKafgAw"}

✻ Cogitated for 1d 18h 9m

[JF10R]

Temporary workaround: Ask Claude Code to invoke the commands through a bash command instead of directly.

[tirth8205]

v2.0 adds progress logging during builds. The node/edge count discrepancy you saw was likely deduplication (expected behavior). For the embedding hang: try updating to v2.0 which has better error handling. The UV_NATIVE_TLS tip has been noted for docs.

[tirth8205]

Related to #136. v2.0+ added progress logging, but the core Windows hang may persist. We're investigating the threading/event-loop interaction on Windows. As a workaround, try running the build without embedding (code-review-graph build) and embedding separately.

[tirth8205]

This is the Windows async event loop hang — same root cause as #136. On Windows with ProactorEventLoop, synchronous MCP tool handlers block the entire event loop during build and embed operations.

PR #49 proposed wrapping all tool handlers with loop.run_in_executor() to fix this but was closed without merging.

The corporate TLS workaround (UV_NATIVE_TLS=1) is a valid configuration tip for Windows corporate environments. The wrong install method note (use [embeddings] extra, not separate pip install) is also important.

This remains an open bug primarily affecting Windows users.

[tirth8205]

Hi @pvnsai73 — I think we've identified the fix for this. PR #222 (branch fix/post-v2.2.3-cleanup) includes two changes that together should close this issue:

1. Root cause fix — main() now sets WindowsSelectorEventLoopPolicy before mcp.run() on sys.platform == "win32". The default ProactorEventLoop on Windows Python 3.8+ deadlocks with ProcessPoolExecutor (which full_build uses for parallel parsing) over a stdio MCP transport — which matches the exact "build/embed hangs silently" symptom you reported.

2. Dependency upgrade — fastmcp bumped from 1.0 → 2.14.6 (also closes Security: 4 critical CVEs in transitive dependency fastmcp (<2.14.0) #139, ImportError: FakeConnection renamed to FakeRedisConnection in fakeredis #195). fastmcp 2.x has substantially better Windows/asyncio handling beyond just our policy fix.

Since I can't verify Windows behavior from macOS, would you be willing to test the branch before we cut v2.2.4? Installing from the branch:

pip install --upgrade "git+https://github.com/tirth8205/code-review-graph.git@fix/post-v2.2.3-cleanup"

# or with uvx:
uvx --from "git+https://github.com/tirth8205/code-review-graph.git@fix/post-v2.2.3-cleanup" code-review-graph build

Then run your original repro — code-review-graph build (or embed) from uvx + Claude Code — and let us know whether it completes or still hangs. If you still see a hang, please paste:

• python -c "import sys, platform; print(sys.version, platform.platform())"
• Any console output before the hang
• Whether the hang happens on build, embed, or both

Thanks for the detailed report originally; I want to make sure this is actually fixed before we release.