fix(shell): drain stdout/stderr to prevent command hanging on large output#154
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skulidropek merged 3 commits intoProverCoderAI:mainfrom Mar 18, 2026
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Adding .gitkeep for PR creation (default mode). This file will be removed when the task is complete. Issue: ProverCoderAI#153
…apture to prevent buffer deadlock When child processes are started with piped stdout/stderr, the OS pipe buffer (~64 KB) can fill up causing the process to hang indefinitely waiting for the buffer to drain. - runCommandExitCode: rewritten to use Effect.scoped + daemon fibers that drain both stdout and stderr concurrently while waiting for exit - runCommandCapture: adds a daemon fiber to drain stderr so large stderr output no longer blocks the process Fixes: pnpm run docker-git clone <repo> --force --mcp-playwright hanging Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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This reverts commit 129ad1d.
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Problem
pnpm run docker-git clone <repo> --force --mcp-playwrighthangs indefinitely and never completes.Root Cause
In
packages/lib/src/shell/command-runner.ts, bothrunCommandExitCodeandrunCommandCapturestart child processes with"pipe"mode for stdout/stderr but do not drain those streams. The OS pipe buffer is typically ~64 KB. When a sub-command (e.g.git pushorgit stash popduringautoSyncStateafter a successful clone) writes more than that to stdout or stderr, the child process blocks waiting for the buffer to drain — and since nobody is reading it, it hangs forever.Fix
runCommandExitCodeRewrote from a simple
Effect.map(Command.exitCode(...), Number)to anEffect.scopedblock that:executor.startprocess.stdoutandprocess.stderrconcurrentlyprocess.exitCoderunCommandCaptureAdded
yield* _(Effect.forkDaemon(Stream.runDrain(process.stderr)))before collecting stdout, so large stderr output no longer causes a deadlock.Mathematical Guarantees
Invariants
∀ cmd: runCommandExitCode(cmd)terminates iffcmdterminates (no buffer deadlock)∀ cmd: runCommandCapture(cmd)terminates iffcmdterminatesPreconditions
"pipe"for stdout, stderr, stdinPostconditions
runCommandExitCode: returns numeric exit code, stdout/stderr fully consumedrunCommandCapture: returns decoded stdout string, stderr fully consumed, exit code validatedTest plan
pnpm run docker-git clone <repo> --force --mcp-playwrightand verify it completes without hanging🤖 Generated with Claude Code
Fixes #153