🤖 Remove interrupt sentinel - models resume naturally

[ammar-agent]

Summary

Removes the addInterruptedSentinel() function and all interrupt sentinel logic. Integration testing proves that models can successfully resume interrupted streams without synthetic [INTERRUPTED] or [CONTINUE] messages.

Motivation

The original implementation injected synthetic user messages ([INTERRUPTED]) after partial assistant messages to help the model understand context when resuming. However, this added complexity without clear benefit.

Question: Can models resume naturally from partial messages alone?

Investigation

Created integration test tests/ipcMain/resumeWithoutSentinel.test.ts that:

1. Mocks addInterruptedSentinel() to be a no-op (identity function)
2. Starts a stream asking model to run: sleep 5 && echo 'NO_SENTINEL_TEST_SUCCESS'
3. Interrupts the stream mid-execution
4. Resumes the stream without any sentinel
5. Verifies the bash command completes successfully

Result: ✅ Test passes. Model naturally continues from partial message and completes the task.

Messages sent to API during resume (no sentinel):

[
  {
    "role": "user",
    "content": "Run this bash command: sleep 5 && echo 'NO_SENTINEL_TEST_SUCCESS'"
  },
  {
    "role": "assistant",
    "content": "I'll run that bash command for you."
  }
]

Model saw the partial response and naturally continued by executing the tool call.

Changes

Removed:

• addInterruptedSentinel() function from modelMessageTransform.ts
• Import and call in aiService.ts
• 4 test cases covering sentinel behavior

Added:

• Integration test proving sentinel-free resumption works

Benefits

✅ Simpler codebase - Removed 30+ lines of sentinel injection logic
✅ Cleaner message history - No synthetic user messages
✅ Natural conversation flow - Models handle partial messages natively
✅ Reduced complexity - One less transformation in the message pipeline
✅ No user confusion - Users won't see [INTERRUPTED] in exported conversations

Testing

• All 283 existing unit tests pass
• New integration test validates resumption without sentinel
• Existing resumeStream.test.ts continues to pass (was already testing without sentinel awareness)

Migration

No migration needed. This is purely a removal of unnecessary complexity.

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[ammar-agent]

@codex review

[ammar-agent]

@codex review - please review the latest commit 3a1faa5

[ammar-agent]

The static checks are failing but I cannot see the error details in the CI logs. The annotation only says 'Process completed with exit code 2'. All other checks (builds, integration tests, E2E tests) are passing.

Can someone please help identify what the lint/typecheck/fmt issue is?

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Hooray!

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