Reviewed and merged GitHub PRPublic

Now let me read the full file to understand the context:

Let me read more of the file to understand the flow, particularly around renderInitialMessages and the initialization:

Let me check if there are any linked issues and verify the documentation files:

Now let me verify the complete fix by looking at the exact code changes:

Now let me check if the README or docs need modification:

PR: https://github.com/badlogic/pi-mono/pull/765

Changelog:

• Missing entry. A changelog entry is required before merge. I will add it under ### Fixed in [Unreleased] if you decide to merge. Proposed entry:
  - Fixed extension messages rendering twice on startup when `pi.sendMessage({ display: true })` is called during `session_start` ([#765](https://github.com/badlogic/pi-mono/pull/765) by [@dannote](https://github.com/dannote))

Good:

• Simple, minimal fix that addresses the root cause correctly
• Clear PR description with problem, cause, and solution sections
• The flag-based approach is appropriate: renderInitialMessages() is responsible for the first render, subsequent rebuildChatFromMessages() calls handle updates afterward
• Code comment explains the reasoning for the guard condition
• Real-world validation: contributor discovered this while using their own rules extension (linked in PR comment)

Bad:

• Missing pkg:coding-agent label on the PR
• No automated test coverage for this initialization edge case (difficult to test without integration tests that spin up extensions)

Ugly:

• None

Questions or Assumptions:

• The fix assumes renderInitialMessages() is always called after init() completes and before any user interaction. Looking at run(), this is correct: await this.init() → this.renderInitialMessages() in sequence.

Change summary:

• Adds hasRenderedInitialMessages = false flag to InteractiveMode class (line 148)
• Sets flag to true at start of renderInitialMessages() (line 2010)
• Adds flag check in sendMessage handler to skip rebuildChatFromMessages() when initial render hasn't occurred yet (line 622)
• The fix ensures messages sent during session_start are rendered once by renderInitialMessages(), not twice

Tests:

• No automated tests added. This is an initialization timing edge case that would require integration testing with a mock extension to verify. Manual testing can be done using the contributor's linked rules extension.

Documentation:

• No changes needed to README.md or docs/extensions.md. This is a bug fix restoring expected behavior, not a change to the API contract. Extensions calling pi.sendMessage({ display: true }) during session_start should display messages once, which is what the fix achieves.

Done. Merged to main and commented on the PR.