SW-208 — Apply bounded backpressure when forwarding long-running child output #390

Summary

The supervisor forwards every child output chunk directly to TerminalOutput and ignores the destination stream's write/backpressure result. A noisy child can outpace a redirected or slow output stream and accumulate an unbounded writable queue. Define a bounded forwarding policy that pauses/resumes child streams or otherwise limits queued output.

Workstream

• Workstream: WS-PERFORMANCE
• Primary scope: src/dev/orchestrator.ts; src/output/terminal.ts; tests/dev-orchestrator-startup-and-buffering.test.ts
• Protected surface: Yes — maintainer review required
• Priority: P1
• Difficulty: high
• Proposed points: 200

Acceptance Criteria

• The output adapter exposes a testable backpressure signal.
• Child streams pause when the destination cannot accept more data and resume on drain.
• Buffering has an explicit upper bound and deterministic overflow behavior.
• stdout and stderr remain ordered independently.
• Redaction and line buffering remain applied before output is written.

Dependencies

None unless noted above.

Out of Scope

• Unrelated architecture or public command-contract changes.
• New runtime dependencies without maintainer approval.
• Mainnet deployment or remote template execution.

Definition of Done

• Acceptance criteria have deterministic regression coverage.
• Security and compatibility boundaries remain intact.
• Supported-platform CI passes.

Labels

• Stellar Wave (do not apply until activation is explicitly authorized)
• type: performance
• area: performance
• priority: P1
• difficulty: high
• points: 200
• workstream: performance

Sequencing and scope note

Sequencing: implement after SW-207 (#389) so stream error and shutdown semantics are stable before adding backpressure.