fix(broker): handle write_pty frames in PTY worker

[willwashburn]

Summary

Fixes #920.

AgentRelayClient.sendInput() / POST /api/input/{name} returned success for PTY workers but the bytes never reached the child process. The HTTP route forwards a write_pty frame via workers.send_to_worker(..., "write_pty", ...) (crates/broker/src/runtime/api.rs:893), but crates/broker/src/pty_worker.rs only handled resize_pty and snapshot_pty — write_pty fell through to the catch-all and emitted worker_error: unsupported message type 'write_pty'. Interactive clients (e.g. Pear's terminal tabs attaching to a spawned Claude/Codex PTY) could not type into the terminal.

Change

Add a write_pty arm to the PTY worker's stdin frame handler in crates/broker/src/pty_worker.rs that:

• Pulls the data string from the payload (matching runtime/api.rs's json!({ "data": data }) shape).
• Calls pty.write_all(data.as_bytes()) to push the keystrokes through the existing write queue.
• Emits a worker_error frame only on malformed payloads (invalid_payload) or PTY write failures (pty_write_failed, retryable).

The HTTP route is already correct — this just teaches the worker to honor the frame the route is already sending.

Test plan

• cargo build -p agent-relay-broker succeeds.
• cargo test -p agent-relay-broker --lib pty — all 57 PTY tests pass.
• Manual repro from the issue body: spawn a PTY agent, call client.sendInput(name, 'printf READY\n\r'), confirm the snapshot now contains READY and no worker_error event is emitted.

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Generated by Claude Code

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: dba3246d-e5cc-4582-870e-daeab1c38b4f

📥 Commits

Reviewing files that changed from the base of the PR and between def39b0 and 398a78f.

📒 Files selected for processing (1)

• crates/broker/src/pty_worker.rs

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📝 Walkthrough

Walkthrough

The PTY worker now accepts write_pty inbound messages from the broker's HTTP /api/input/{name} endpoint. When received, the handler extracts UTF-8 data from the payload, writes it directly to the child PTY process, and returns appropriate error frames for missing data fields or write failures.

Changes

PTY Write Input Support

Layer / File(s)	Summary
write_pty message handler crates/broker/src/pty_worker.rs	The run_pty_worker function now handles write_pty messages: parses the UTF-8 data field from the payload, writes it to the PTY, and emits non-retryable worker_error frames for missing data or retryable errors on write failures.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Suggested reviewers

• khaliqgant

Poem

🐰 A write_pty handler, oh what a treat,
Now input flows where agents and humans meet!
No more "unsupported" errors to lament,
The PTY worker speaks the protocol's intent.
hop hop

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix(broker): handle write_pty frames in PTY worker' clearly and concisely summarizes the main change—adding write_pty frame handling to the PTY worker.
Description check	✅ Passed	The description comprehensively explains the problem, solution, and testing approach. It references the linked issue, details why write_pty was falling through unhandled, and documents the implementation and test coverage.
Linked Issues check	✅ Passed	The changes fully address issue #920 by implementing the write_pty frame handler that extracts the data payload, writes to the PTY, and emits appropriate error frames, resolving the broken interactive API client scenario.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to the stated objective: adding write_pty frame handling in the PTY worker with no unrelated modifications.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/fix-issue-920-fGMJ4

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.