[minatoaquaMK2]

Long pane run and agent start commands sent while zsh is initializing can exceed Darwin's canonical input limit. The PTY write can report success while losing bytes, including Enter.

On macOS, preflight the complete encoded command before accepting it into the existing input queue. Oversized canonical lines return the existing API input error without queuing any prefix or reserving an agent name. The guard accounts for Enter, UTF-8 bytes, and termios delimiter/translation rules, while allowing multiple short lines and long raw-mode input. Its weak reference to the actor's existing master descriptor avoids duplicating or prolonging the PTY lifetime.

This PR retains the existing queue-admission response semantics and agent-start rollback. agent.prompt, input scheduling, launch deadlines, and Windows input behavior remain as on the base revision. The completion/admission redesign, global permits, and extra launch state have been removed from this PR.

The guard samples terminal mode at admission. It checks only this submission; it cannot inspect an earlier incomplete line or guarantee that terminal mode will not change while accepted input is queued.

Validation on macOS arm64:

• Real PTY/API regressions cover whole-command rejection, Enter/UTF-8 boundaries, a short first line followed by an oversized line, no agent-name/session reservation on rejection, and immediate same-name retry.
• Rejection and successful queue admission return while the actor is deliberately held; long input remains intact after changing to raw mode before retrying.
• Tests cover effective termios delimiters, descriptor lifetime, and the existing handoff/shutdown write gates.
• Native just ci passes: 3,796 Rust tests plus maintenance, architecture, and integration-asset checks. just docs-contract-test passes.
• Native Windows and Linux validation is provided by the PR CI; no Windows SDK was installed locally.

refs #4950

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📒 Files selected for processing (12)

• docs/next/website/src/content/docs/ja/socket-api.mdx
• docs/next/website/src/content/docs/socket-api.mdx
• docs/next/website/src/content/docs/zh-cn/socket-api.mdx
• src/app/agents.rs
• src/app/api/panes.rs
• src/pane.rs
• src/platform/macos.rs
• src/platform/macos/input.rs
• src/platform/macos/input_tests.rs
• src/platform/mod.rs
• src/pty/actor/unix.rs
• src/terminal/runtime.rs

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📝 Walkthrough

Walkthrough

Input submissions now pass through a validation method before pane input is sent or a managed agent launch begins. On macOS, the PTY guard checks encoded input against the current canonical-mode limit, including Enter. Tests cover rejection and retry behavior, terminal input cases, and actor write gates. Socket API documentation describes the behavior in three languages.

Suggested reviewers: jjliebig

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Priority: ➖ Normal

Merge Risk | ⚪ Minimal · up to c422c

Merge Risk: ⚪ Minimal · up to c422c

This change rejects oversized macOS canonical-mode commands before they are queued, and other platforms behave as before. I found no concrete merge-blocking risk in the supplied context.

Security Architecture Review

Security architecture risk: 🟡 Moderate · up to 6cba6

A stalled terminal can retain shared input capacity indefinitely and eventually prevent input submissions to otherwise healthy panes. Launch identity checks and pre-write validation provide useful safeguards, and no new privilege escalation was established.

Retained concerns

• Medium · reliability · inferred: One stalled terminal can exhaust input admission across unrelated panes. Each accepted pane.send_input retains a shared permit while awaiting PTY completion, without a deadline or caller-abandonment cleanup. If its live PTY stops consuming input, 64 outstanding submissions can prevent agent.start, agent.prompt, and pane.send_input on healthy terminals from being admitted until the stalled writes complete or the actor closes. The base acknowledged pane input after queue admission and did not couple it to this shared completion capacity. This is an introduced failure-containment concern, not a verified privilege-boundary vulnerability.

Security review details

Security Blast Radius

• inferred — The retained availability concern spans the three shared-capacity input APIs and all panes managed by one application instance. Triggering it through the reviewed API requires existing local socket access and a terminal that remains live without consuming queued input. No newly expanded cross-user, credential, or service authority was established.

Security Findings and Attack Paths

• inferred — An existing socket caller can enqueue repeated pane input against a backpressured terminal. Each accepted request retains a global permit, even after its response receiver disappears. Exhausting the pool denies subsequent submissions to healthy panes. This is a source-supported availability path, not an executed exploit or a verified authorization bypass.

Trust Boundaries and Controls

• observed — The existing local socket configuration requests owner-only permissions. Agent-start validation retains name, supported-kind, control-character, duplicate-name, target, runtime, shell-encoding, and timeout checks before submission. The full comparison does not modify socket or IPC boundary code.

Resilience and Maintainability Implications

• observed — Generation matching prevents delayed failure from cancelling a replacement launch. Normal PTY completion consumes the active submission before notifying its waiter, and shutdown fails outstanding receipts. These controls protect identity and cleanup but do not impose a lifetime bound on live, stalled pane submissions.

Hardening Proposals

• proposed — Consider per-terminal admission isolation and bounded cleanup for submissions that have not begun writing, so one stalled pane cannot monopolize the global pool. Preserve non-cancellation after writing begins to avoid leaving partial commands.

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 84 functions across 19 files. (3 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check		The description clearly explains the macOS canonical-input validation change, its behavior, scope, tests, and preserved semantics.
Title check		The title clearly and concisely identifies the main change: rejecting oversized canonical input on macOS.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Full details: Docstring Coverage

Explanation

Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 84 functions across 19 files. (3 skipped: 3 unsupported.)

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Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no outstanding finding or new actionable issue was identified.

Summary

The PR adds a macOS admission-time check for oversized canonical input in pane.send_input and agent.start, while retaining queue-admission responses and the existing input scheduling model.

• It validates the encoded submission before queuing bytes or reserving an agent name.
• It uses a weak reference to the actor’s PTY master and leaves other platforms’ admission policy unchanged.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  API["pane.send_input / agent.start"] --> Encode["Encode complete input"]
  Encode --> Guard{"macOS canonical preflight"}
  Guard -->|Oversized| Error["Return input error"]
  Guard -->|Accepted| Queue["Existing PTY input queue"]
  Queue --> Actor["PTY actor writes to terminal"]

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Actionable comments posted: 1

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Inline comments:
Review comments at @src/app/api/input.rs:
- Around line 94-151: Update handle_agent_start_input_finished and the
managed-launch reconciliation path so a matching launch remains valid while its
PTY write is in flight, even after its deadline; reconcile successful completion
before allowing expiration. Preserve cancellation and cleanup when the write
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📒 Files selected for processing (20)

• docs/next/website/src/content/docs/ja/socket-api.mdx
• docs/next/website/src/content/docs/socket-api.mdx
• docs/next/website/src/content/docs/zh-cn/socket-api.mdx
• src/app/actions.rs
• src/app/agents.rs
• src/app/api.rs
• src/app/api/agents.rs
• src/app/api/input.rs
• src/app/api/input/tests.rs
• src/app/api/panes.rs
• src/app/mod.rs
• src/events.rs
• src/pane.rs
• src/platform/macos.rs
• src/platform/macos/input_tests.rs
• src/platform/mod.rs
• src/pty/actor.rs
• src/pty/actor/unix.rs
• src/server/headless.rs
• src/terminal/state.rs

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[minatoaquaMK2]

Updated to 6cba6c6 with the review fixes and regression tests. Native macOS just ci (3,805 Rust tests), docs checks, and the isolated zsh startup/retry reproduction pass. Each earlier finding has an inline response. Please review the latest commit.

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[ogulcancelik]

the macos guard and the error look right, thanks. the new admission/completion machinery worries me though: it applies on every platform, one stalled pane can hold the global permits and block pane run / agent start / agent prompt for healthy panes, and queued launches can't expire behind a stuck write. could you split this into the small macos canonical-limit guard (keeping today's send path elsewhere), and take the completion/admission redesign separately with per-terminal admission and queued deadlines?

[minatoaquaMK2]

Thanks for the careful review and for pointing out the failure-isolation problem. I expanded the macOS fix into a cross-platform completion/admission change without adequately isolating stalled terminals.

I've removed that redesign from this PR: no shared permits, extra launch state, or changes to input scheduling, launch deadlines, Windows input, or the existing agent.prompt path. The remaining guard checks the complete encoded pane.send_input / agent.start command on macOS before queue admission, and rejects before reserving an agent name. Successful requests retain the original queue-admission semantics.

The docs now state the admission-time boundary, including previously buffered input and later terminal-mode changes. Real PTY/API tests cover rejection without a partial command or name reservation, same-name retry, admission while the actor is held, raw-mode long input, and descriptor lifetime. Native just ci (3,796 Rust tests) and docs checks pass. The regression also fails as expected when the API preflight calls are removed.

Any future completion/admission redesign will need separate scope and review, with per-terminal isolation and deadlines that work while queued.

[minatoaquaMK2]

Please review the updated head c422cd671d45dd8084b7cbfa97728410fbe43fc2. The PR has been narrowed to the macOS admission-time guard as requested; the completion/admission redesign has been removed.

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