[Bug]: Imported Claude/Codex threads are silently truncated to the last 200 messages #27580

Summary

Threads imported from existing Claude Code (and Codex) sessions only contain the last 200 messages of each session. Everything earlier is dropped during import, with no indication in the thread that history is missing. Scrolling back stops at a short recent window.

Environment

• T3 Code 0.1.5 (beta, desktop), macOS 26.7.2
• Claude Code 2.1.314

Steps to reproduce

1. Have a long Claude Code session in a project (several hundred user/assistant messages).
2. Import it through the welcome wizard.
3. Open the imported thread and scroll to the top.

Expected: the full conversation, or at least a visible note that older messages were not imported.
Actual: only the most recent ~200 messages exist. No marker or warning.

Evidence

In my import, 12 of 92 imported threads have exactly 200 messages (orchestration_v2_projection_messages, grouped by thread), including one whose source transcript is >100 MB.

Likely cause

In the session importer's transcript reader, retainMessage pushes each message and then does:

if (messages.length > MAX_IMPORTED_MESSAGES) messages.shift();

with MAX_IMPORTED_MESSAGES = 200, so the oldest messages are silently discarded.

Suggestions

• Import full history, or page older messages in lazily from the source transcript.
• If a cap stays, add a visible "N earlier messages not imported" marker at the top of the thread, and mention it in the import summary.