[Bug] Windows Settings → Compute still "mesh-llm feature not enabled" on 0.5.25 (#2836 closed in error; #3223 never merged) #7893

Describe the bug

On stock Windows, Settings → Compute still fails with:

mesh-llm feature not enabled

#2836 described this exactly and was closed as completed. That close is wrong for official Windows builds:

• The enablement PR (#3223) was closed unmerged (2026-09-10).
• GitHub auto-linked a fork PR (stevepresley/buzz#1), which does not ship in Block releases.
• ArneBroedel cannot reopen [Bug] Windows Settings → Compute: "mesh-llm feature not enabled" (mesh omitted from Windows builds) #2836 (ReopenIssue permission denied). Evidence is also on #2836 (comment).

Linux got --features mesh-llm (#3788 / #4524). Windows did not.

This is not #7731. That issue is the next wall for custom --features mesh-llm Windows builds (v0.75.1 LoadLibraryExW mixed-separator path). Stock release-windows never reaches that code: it still compiles mesh_llm_stubs.

To Reproduce

1. Install official Buzz Desktop Windows (tested: 0.5.25 x64 NSIS / updater).
2. Open Settings → Compute.
3. See mesh-llm feature not enabled.

Expected

Windows release and canary ship --features mesh-llm (and whatever Windows native-runtime bundling is required), matching macOS arm and Linux. A Windows GPU host can share compute with other members on the same relay.

Failing that, Compute should be hidden/disabled on stub builds rather than rendering the stub error. #2836 should not stay closed as completed.

Supporting Material

Installed C:\Users\arneb\AppData\Local\Buzz\buzz-desktop.exe:

• ProductVersion 0.5.25 (file date 2026-09-24, 96 529 920 bytes)
• Contains: mesh-llm feature not enabled, mesh_llm_stubs, Buzz shared compute is not available in this build
• Does not contain: mesh-llm-sdk, mesh_llm_host
• No %LOCALAPPDATA%\mesh-llm cache (stub never downloads a runtime)

CI on current main (checked 2026-09-25):

• .github/workflows/windows-canary.yml: No mesh-llm: release-windows doesn't build it.
• .github/workflows/release.yml release-windows: pnpm tauri build ... --bundles nsis without --features mesh-llm
• macOS arm and Linux jobs do pass --features mesh-llm

Environment

• OS: Windows 11
• Version: Buzz Desktop 0.5.25 (Windows x64 release/updater)
• GPU: NVIDIA GeForce RTX 4080 SUPER 16 376 MiB (Ada, sm_89), driver 610.47, CUDA UMD 13.3

Additional context

A follow-up Windows enablement PR should not treat “flag on” as “Share works”:

• #7731 — v0.75.1 Windows native-runtime load (OS error 126); main pin notes v0.76.x as the fix.
• MeshLLM Windows Vulkan MinGW ABI (Mesh-LLM#1160 / #1201).
• CUDA 12 Windows runtime needs cudart64_12 / cublas64_12 / cublasLt64_12 even on Ada (sm_89) when the driver is CUDA 13.x.

Please also link this from #2836 / #2388.