windows focused gate: test_openai_api_server aborts 0xC0000409 in the explicit-cpu/embeddings cases once the build compiles again

[lu-zero]

Observed

PR #2399 unblocked the Windows compile (the C4456/C2220 build break of #2372). The windows-msvc-cpu and windows-msvc-vulkan focused gates then ran for the first time since the build broke, and test_openai_api_server.exe aborts at runtime — no compiler diagnostics, 76/79 cases run, then:

FAILING CASE 56/79 rc=-1073740791 : api_server: an explicit-cpu device-selected engine serves /v1/completions
FAILING CASE 57/79 rc=-1073740791 : api_server: embeddings dispatch — OpenAI shape over the engine path
FAILING CASE 59/79 rc=-1073740791 : api_server: embeddings socket smoke; generate routes 404 on the embedding server

rc=-1073740791 is 0xC0000409 (STATUS_STACK_BUFFER_OVERRUN) — the MSVC fast-fail surface for abort()/fail-fast. Job 99460762370 (windows-msvc-cpu), head 9215260148 (#2399), failing step "Build and execute the native Windows CPU focused gate"; the shared windows-msvc-vulkan red shows the same class.

Attribution

Not caused by #2399: the crashing binary carries neither of that PR's changes' behavior — one is a call-site argument in test_glm_moe_dsa_schedule.cpp (a different binary), the other a declaration rename in glm5_next_weights.cpp with no behavior change. The defect was unreachable on main while the compile was broken, and main's own windows jobs have been skipped/cancelled across recent heads, so this runtime break has never had a passing build to run in until now — the same first-execution exposure as #2372's build facets.

The failing cases cluster on the explicit-cpu device selection and the embeddings dispatch/socket paths of the api server.

Owed

Owner: the api_server row (OPENAI-API-SERVER surface) for the abort, with the windows-gate owner CC'd for the focused-gate harness. The 0xC0000409 needs a Windows reproduction with a debugger or fail-fast hook; this host has no MSVC, so the repair rides CI evidence like the build fix did. Until repaired, both windows-msvc-* jobs stay red independently of #2372/#2399.

Found while reading CI for #2399; filed rather than fixed because the abort is outside that row's spec scope (compile breaks) and this host cannot run the failing binary.

FOLLOWING_AGENTS_PROTOCOL

Following-Agents-Protocol: true
AI-Assisted: true
Assisted-by: AGENT:zai-glm-5.3-flash [maki]