[AI-30] Submit hosted-agent input as a bracketed paste

[alexeyzimarev]

Problem (AI-30)

Follow-up input to a hosted agent (SendInput → AgentOrchestrator.HandleSendInput) was written to the PTY as raw bytes followed by a fixed 50 ms-delayed carriage return. For a large multi-line paste the CR races the still-ingesting paste and is folded into it as a literal newline instead of a submit, so the message sits in the composer until a later, isolated keystroke finishes it.

• Codex never submits at all.
• Claude submits only ~50% of the time (the original AI-30 report, which predates Codex support).

This is also what caused a spec-review flow's round 2 to hang for 11 minutes: the ~17 KB re-submitted spec landed in the reviewer's composer but was never submitted until a manual keystroke flushed it. (Smaller rounds/messages settle within 50 ms, so their CR submits — which is why round 3 and typed messages worked.)

Fix

Deliver the message wrapped in bracketed-paste markers (ESC[200~ … ESC[201~) so the TUI treats it as one pasted block and the trailing CR is an unambiguous submit keypress. Both hosted CLIs enable bracketed-paste mode, so the markers are consumed as delimiters (not echoed). The text/Enter split is kept so the CR lands as a distinct PTY read. As a bonus, bracketed paste also stops message content from being interpreted as slash-commands.

Validation

Reproduced and fixed against the real CLIs (codex 0.142.5, claude 2.1.198) driving each in a PTY with the exact 17 KB paste that hung the flow round:

Pattern	Codex	Claude
raw bytes + 50 ms + CR (before)	✗ never submits	✗ ~50%
raw + wait-for-quiet + CR	✗ never submits	✓
bracketed paste + 50 ms + CR (this PR)	✓ (3/3 runs)	✓

• New unit test AgentOrchestratorBracketedPasteTests asserts the bracketed wire shape + separate Enter.
• Full CLI unit suite: 2069/2069 pass.

Notes

• Not the same as AI-1142 (fire-and-forget SendInput over a connection blip): this hang was reproduced locally with no connection involved. AI-1142's no-delivery-ack weakness is real but separate/lower priority.
• HandleStopAgent's /exit split is left unchanged (a 5-char command, unaffected by the paste race).

🤖 Generated with Claude Code

[linear-code]

AI-30

[qodo-code-review]

Qodo is busy working

Check back in a few minutes. Qodo's code review agents are on it.

[qodo-code-review]

PR Summary by Qodo

AI-30 Submit hosted-agent input as bracketed paste

🐞 Bug fix 🧪 Tests 🕐 20-40 Minutes

AI Description

• Wrap hosted-agent PTY input in bracketed-paste markers to prevent paste/Enter race.
• Keep Enter as a separate delayed write so submission is read unambiguously.
• Add a unit test asserting the exact write sequence (paste block, then carriage return).

Diagram

graph TD
  S["SendInput cmd"] --> O["AgentOrchestrator"] -->|"bracketed paste + Enter"| P["PTY process"] --> C["Codex/Claude TUI"]
  T["Unit test"] --> O

Loading

High-Level Assessment

The following are alternative approaches to this PR:

1. Wait-for-quiet before sending Enter

• ➕ Avoids emitting terminal escape sequences into the PTY stream
• ➕ Can improve reliability for some CLIs where timing is the only issue
• ➖ Still fails for Codex per reported validation; not purely a timing issue
• ➖ Adds complexity (idle detection/timeouts) and can regress latency for large inputs

2. Increase (or adaptive) fixed delay before Enter

• ➕ Minimal code change; no protocol/escape sequence dependence
• ➖ Brittle across machines and input sizes; still race-prone
• ➖ Does not address Codex behavior and can slow normal interactions

Recommendation: Keep the bracketed-paste approach: it leverages a standard terminal feature already enabled by both hosted CLIs, makes multi-line submissions deterministic, and prevents pasted content from being interpreted as interactive commands. The added unit test and explicit Enter split provide a stable contract for future changes.

Files changed (2) +97 / -2

Bug fix (1) +14 / -2

AgentOrchestrator.csSendInput uses bracketed paste markers and adds test hook +14/-2

SendInput uses bracketed paste markers and adds test hook

• Wraps hosted-agent input in bracketed-paste markers (ESC[200~…ESC[201~) before writing to the PTY, then sends a separate delayed carriage return to submit reliably. Exposes a test-only entry point for driving the private send-input handler in unit tests.

src/Capacitor.Cli.Daemon/Services/AgentOrchestrator.cs

Tests (1) +83 / -0

AgentOrchestratorBracketedPasteTests.csAdd unit test verifying bracketed-paste wire shape and Enter split +83/-0

Add unit test verifying bracketed-paste wire shape and Enter split

• Introduces a focused test that registers a fake agent with a recording PTY and asserts two ordered writes: a single bracketed-paste block containing the message, followed by a separate "\r" submit. Adds a minimal IPtyProcess double to capture both string and byte[] writes.

test/Capacitor.Cli.Tests.Unit/AgentOrchestratorBracketedPasteTests.cs