fix: resolve BashTool hanging on background commands #1254
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BashTool hung indefinitely on background commands (`sleep 5 &`, `node server.js &`) due to file descriptor inheritance. `await process.exited` blocked because background processes inherited stdout/stderr pipes from the parent bash shell. 1. `Bun.spawn()` creates bash with `stdout: "pipe", stderr: "pipe"` 2. Bash executes `command &` and exits 3. Background process inherits pipe descriptors 4. `process.exited` waits for all descriptors to close 5. Background process keeps descriptors open → infinite hang Added background command detection with selective I/O redirection: ```typescript const isBackground = isBackgroundCommand(params.command) stdout: isBackground ? "ignore" : "pipe", stderr: isBackground ? "ignore" : "pipe", ``` Background detection handles: - Simple: `sleep 5 &` - Complex: `(cmd1; cmd2) &`, `nohup cmd &`, `cmd & disown` - Edge cases: quoted strings, escaped ampersands - Mixed commands treated as foreground to preserve output - Background commands return quickly (vs infinite hang) - 35 comprehensive tests covering unit, integration, and edge cases - Full backward compatibility maintained - No performance impact on foreground commands
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BashTool hung indefinitely on background commands (
sleep 5 &,node server.js &) due to file descriptor inheritance.await process.exitedblocked because background processes inherited stdout/stderr pipes from the parent bash shell.Bun.spawn()creates bash withstdout: "pipe", stderr: "pipe"command &and exitsprocess.exitedwaits for all descriptors to closeAdded background command detection with selective I/O redirection:
Background detection handles:
sleep 5 &(cmd1; cmd2) &,nohup cmd &,cmd & disownNow:
isBackgroundCommandfunction is 83 lines long and tries to handle a lot of cases. This might be a bit much for an issue that doesn't seem to occur for a lot of developers (haven't seen an open issue about this). At the same time, this PR might be a segway to fixing other issues with BashTool I/O as well such as #652 (App becomes unresponsive when executing commands requiring sudo password).