fix: scrollback duplicate when message streamed artificially mid-turn

[saucam]

Summary

• #artificiallyStreamText called #persistAndBuffer twice for the same message: once at start (empty placeholder) and once at end (full content).
• scrollback.push has no deduplication — both entries were stored in the buffer.
• On scrollback.replay (e.g. Telegram mini app opening, or any client reattaching), both entries were delivered and replaceScrollback stored them both in the bySession array, rendering the message twice in the UI.

Fix: The scrollback buffer holds msg by reference, so its content is already updated when the streaming loop finishes. Replace the second #persistAndBuffer call with #scrollback.updateMessage (recounts bytes in place, no second push) + a single transcript append.

Root cause

artificiallyStreamText:
  #persistAndBuffer(msg)   // push empty msg → scrollback entry 1
  ... stream deltas ...
  msg.content = fullContent
  #persistAndBuffer(msg)   // push full msg → scrollback entry 2 (SAME messageId!)

On scrollback.replay, client receives [empty_msg, full_msg] with same messageId → replaceScrollback stores both → message renders twice.

Test plan

• Send a message mid-turn to trigger #artificiallyStreamText
• Detach and reattach (or open the Telegram mini app fresh) — message should appear exactly once
• Normal streaming turns unaffected

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Prevented duplicate scrollback entries when an assistant message finishes streaming.
  • Final messages now update the existing chat entry in place and are saved consistently, reducing repeated or duplicated content in the conversation history.
  • Improved reliability of final message handling with clearer error logging during persistence.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 0e575d62-9c57-4ad6-a7f6-2e2bca50f057

📥 Commits

Reviewing files that changed from the base of the PR and between 8505395 and c91ca10.

📒 Files selected for processing (1)

• src/daemon/session.ts

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📝 Walkthrough

Walkthrough

In #artificiallyStreamText, the final persistence step no longer calls #persistAndBuffer(msg). Instead, it updates the existing scrollback entry in-place, appends the finalized message directly to the transcript store with error logging, and notifies the chunker.

Changes

Fix duplicate scrollback entry in artificiallyStreamText

Layer / File(s)	Summary
In-place scrollback update replaces persistAndBuffer src/daemon/session.ts	Removes the #persistAndBuffer(msg) call that created a duplicate scrollback entry for the same messageId; replaces it with an in-place scrollback update, a direct transcript append with explicit error logging, and a chunker notification for the finalized assistant message.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the duplicate scrollback fix for artificially streamed mid-turn messages.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/scrollback-duplicate-artificial-stream

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[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.07%. Comparing base (8505395) to head (c91ca10).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/daemon/session.ts	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #50      +/-   ##
==========================================
- Coverage   81.07%   81.07%   -0.01%     
==========================================
  Files          55       55              
  Lines        7593     7597       +4     
==========================================
+ Hits         6156     6159       +3     
- Misses       1437     1438       +1     

Flag	Coverage Δ
daemon	81.07% <80.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/daemon/session.ts	70.21% <80.00%> (+0.01%)	⬆️

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