Five fixes from the May 2 2026 maintainer review:
1. messages and tool_calls now use copy.deepcopy() — prior plain assignment
shared list refs between source and duplicate, so appending a turn to one
mutated the other.
2. copied_session.save() called explicitly — pre-fix, the duplicate was
in-memory only until the user sent a turn. Refreshing mid-flow lost it.
3. pinned and archived reset to False — duplicating an archived conversation
should produce a visible (un-archived) copy.
4. Missing-session error is now status=404 (was default 400).
5. Removed redundant `import uuid` / `import time` inside the handler — both
are already at the top of routes.py.
Test updates:
- Two existing static-grep tests widened to accept the new
`copy.deepcopy(session.messages)` form alongside the original
`messages=session.messages`.
- Five new static-grep regression tests pin each of the five fixes so
reverting any single one trips a test.
All 3775 tests pass.
Co-authored-by: Alexey Dsov <AlexeyDsov@users.noreply.github.com>
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