Windows: BUN_CHILD_FLAGS --config=NUL panics Bun 1.3.10 — terminal-agent crash window every few seconds #3085

Summary

On Windows, every terminal-agent spawn crashes Bun in ~3ms with:

panic(main thread): start index 1 is larger than end index 0
oh no: Bun has crashed. This indicates a bug in Bun, not your code.

The trigger is BUN_CHILD_FLAGS in browse/src/terminal-agent-control.ts:146, which passes --config=NUL on win32 (added in v1.91.19.0, #3025). Bun 1.3.10 on Windows panics while parsing that flag, before the script runs.

The crash opens a visible console window. The supervisor and watchdog then respawn the agent (1s/2s/4s/8s backoff, then every 30–60s), so the user gets a Bun crash window every few seconds for as long as a headed browse connect daemon is alive. This applies to any daemon on the machine, including one started by another session in a different repo.

Repro (no gstack needed)

echo 'console.log("ok")' > probe.ts
bun run --no-env-file --config=NUL probe.ts   # panic(main thread): start index 1 is larger than end index 0
bun run --no-env-file probe.ts                 # ok

Environment

• gstack v1.91.59.0
• Bun 1.3.10 (30e609e0), Windows 11 x64 (win11_dt)
• Daemon on the Node lane (server-node.mjs)

Suggested fix

• Don't pass --config=NUL on Windows. Either omit --config on win32, or point it at an empty temp bunfig.toml. It only matters if NUL really behaves as an empty file, and on this Bun it crashes instead. /cso on Windows: GIT_CONFIG_GLOBAL=NUL rejected by Git for Windows 2.56 (static-snapshot always fails) #3082 is the same NUL-as-empty-file assumption failing for Git.
• Or gate on a Bun version that accepts it, and fail loudly with a message instead of a crash window.

Related

• Windows: terminal-agent watchdog respawn-loops every 60s — console flash + unbounded bun.exe leak; circuit-breaker can never trip #2295: watchdog respawn loop / guard. A spawn that always crashes turns into a repeating visible window.
• Windows: bun-polyfill.cjs spawn/spawnSync drop windowsHide, and the terminal-agent watchdog duplicates live agents (node-path gaps #1952/#2019 won't cover) #2151: windowsHide dropped by bun-polyfill.cjs. This is why the crash surfaces as a console window at all.
• Windows: terminal-agent from browse connect dies with the CLI console (missing detached) and runs with its owner watchdog disabled (missing ownerPid) #2637, Sidebar Terminal pane fails on Windows: Bun PTY (terminal: spawn option) not supported #1221: other Windows terminal-agent failures.