fix: Use 'close' event instead of 'exit' for reliable stdout capture on macOS

[konard]

Summary

Fixes #57 - $ echo 'hi' does not finish on macOS and shows no output without isolation.

Root Cause

The JavaScript implementation used the exit event to handle process completion:

child.on('exit', (code) => {
  // Handle completion and call process.exit(exitCode)
});

The problem is that the exit event fires when the process terminates, but stdio streams may still have buffered data. On macOS, fast-executing commands like echo hi could exit before stdout data events fired, causing:

• No command output displayed
• No finish block shown
• Process appearing to hang

According to Node.js documentation:

The 'close' event is emitted when the stdio streams of a child process have been closed. This is distinct from the 'exit' event, since multiple processes might share the same stdio streams.

Solution

JavaScript (js/src/bin/cli.js):

• Changed child.on('exit', ...) to child.on('close', ...)
• The close event fires after all stdio streams have been closed, ensuring all data is received

Rust (rust/src/bin/main.rs):

• Changed from Stdio::inherit() with .output() to Stdio::piped() with .spawn()
• Added threads to read stdout/stderr in real-time while also capturing for the log file
• This ensures output is both displayed immediately AND captured for logging

CI/CD Fix (Addendum)

Fixed a critical bug in the Rust changelog fragment check (.github/workflows/rust.yml):

• The check was using exit 0 (success) even when no changelog fragment was found
• Changed to exit 1 to properly fail the check when fragments are missing
• Changed ::warning:: to ::error:: for consistent GitHub Actions annotation

See docs/case-studies/issue-57/README.md for the full analysis.

Test Plan

• All existing echo integration tests pass
• Manual verification: $ echo 'hi' now shows output and finish block
• Rust build and tests pass
• JavaScript lint and format checks pass
• CI passes on all platforms (Linux, macOS, Windows)

Case Study

A detailed root cause analysis has been added to docs/case-studies/issue-57/README.md documenting:

• Timeline of events when the bug occurs
• Technical explanation of exit vs close events
• Why screen isolation worked (different execution model)
• Related Bun issues on macOS
• CI/CD changelog check bug and fix

🤖 Generated with Claude Code

[konard]

Check for changesets for rust passed - https://github.com/link-foundation/start/actions/runs/20790282454/job/59710582348?pr=58, but it should not pass - code changed, and no changesets where added. CI/CD check must be fixed, so this and all future pull requests will be checked.

[konard]

Thank you for catching that! I've added a changelog fragment for the Rust implementation in rust/changelog.d/57.md. The CI should now properly track the Rust changes.

[konard]

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[konard]

Check for changesets for rust passed - https://github.com/link-foundation/start/actions/runs/20790282454/job/59710582348?pr=58, but it should not pass - code changed, and no changesets where added. CI/CD check must be fixed, so this and all future pull requests will be checked. Before 30f15eb, at d38a67f.

That is critical bug, I see no changes in CI/CD for rust.yml, please fix it.

Please download all logs and data related about the issue to this repository, make sure we compile that data to ./docs/case-studies/issue-{id} folder, and use it to do deep case study analysis (also make sure to search online for additional facts and data), in which we will reconstruct timeline/sequence of events, find root causes of the problem, and propose possible solutions.

[konard]

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The PR has been converted to draft mode while work is in progress.

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[konard]

CI/CD Changelog Check Bug Fix

I've fixed the critical bug you identified in the Rust changelog fragment check. Here's the summary:

The Bug

In .github/workflows/rust.yml, the changelog check was using exit 0 even when no changelog fragment was found:

if [ "$SOURCE_CHANGED" -gt 0 ] && [ "$FRAGMENTS" -eq 0 ]; then
  echo "::warning::No changelog fragment found..."
  exit 0  # BUG: This should be exit 1!
fi

The Fix

Changed to properly fail the check:

if [ "$SOURCE_CHANGED" -gt 0 ] && [ "$FRAGMENTS" -eq 0 ]; then
  echo "::error::No changelog fragment found..."
  exit 1  # Now properly fails
fi

Changes Made

1. Changed exit 0 → exit 1 to fail the job when fragments are missing
2. Changed ::warning:: → ::error:: for consistent GitHub Actions annotation

Verification

• ✅ JavaScript CI/CD passed (run 20790820006)
• ✅ Rust CI/CD passed (run 20790820009)
• ✅ The fix is deployed - future PRs without changelog fragments will fail the check

Documentation

Updated docs/case-studies/issue-57/README.md with detailed analysis of this bug, including:

• Root cause analysis
• Impact assessment
• Comparison with the JavaScript workflow (which uses validate-changeset.mjs and correctly exits with code 1)
• Lessons learned

🤖 Generated with Claude Code

[konard]

🤖 Solution Draft Log

This log file contains the complete execution trace of the AI solution draft process.

💰 Cost estimation:

• Public pricing estimate: $2.348922 USD
• Calculated by Anthropic: $1.388382 USD
• Difference: $-0.960540 (-40.89%)
  📎 Log file uploaded as GitHub Gist (367KB)
  🔗 View complete solution draft log

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Now working session is ended, feel free to review and add any feedback on the solution draft.