fix(server): rewind on chats imported from the Claude desktop app - #5

Summary

Chats imported from the Claude desktop app had no rewind button, because the import heal recorded no rewind points for them. Two causes, both fixed:

 AgentSessionScanner.readThread
   for each transcript record
+    if its uuid was already seen: skip   # desktop app re-writes blocks of history
     keep record

 placedTurns(placed, transcript)
-  if first stored message != transcript's first prompt: return []   # long chats cut to their last 200
+  turns start at the first stored prompt; earlier stored replies get none
+  first turn remembers nativeResumeAt = transcript turn just before its prompt

A rewind to that first turn must not throw away the hidden earlier history:

 CheckpointRollbackService -> target thread_start
+  nativeResumeAt = threadStartResumeAt(providerTurns)
 ClaudeAdapterV2 rollback(thread_start)
-  start a fresh, empty Claude session
+  if nativeResumeAt: resume the same session at it
+  else: start a fresh session (unchanged for real first prompts)

nativeResumeAt is an optional field on the stored provider turn (JSON payload, no migration). Other providers ignore it; only Claude chats are imported.

Chats already imported heal on their own: ImportedRewindHeal runs every minute and skips only chats that already have rewind points.

Evidence

• Before: on a copy of the owner's real data (Mac, build b1ba5788), 275 of 884 imported prompts had no rewind point. Examples: 60491f83 0/85, d733ff9e 2/75, e43fd16c 1/67. The server log repeated "matches 2–3 transcript lines" / first-prompt skips every minute.
  After: same copy, preview build 81ed912b, one heal pass: 60491f83 85/85, d733ff9e 75/75, e43fd16c 67/67, 7cdea96a 37/37. 14 prompts left across 2 chats, being looked at separately.
• New tests, each red first, then green:
  • scanner keeps the first copy of a repeated uuid
  • heal of a transcript the desktop app wrote parts of twice
  • heal of a chat whose first stored message is a reply
  • Claude adapter resolves where a thread-start rewind resumes
  • replay: rewinding the first prompt of a mid-transcript import resumes at the prior reply
• Targeted run on the VPS: Test Files 6 passed (6) · Tests 269 passed (269). apps/server typecheck: exit 0.

Merge Danger

Door: two-way

Reverting the code is enough. Rewind points the heal already recorded stay in the database; they are ordinary imported runs and older builds read them fine.

Blast Radius: imported-chats

Only chats imported from Claude desktop or Claude CLI, and only their rewind. Native T3 chats and Codex/OpenCode/Pi never set the new field.

⚠️ The last commit, temp: build Mac preview…, only exists to build a Mac test archive for this branch. Drop it before merging.

🤖 Generated with Claude Code