Pre-release Opus review on v0.50.246 caught a SHOULD-FIX in PR #1338's
cancel_stream synthesis: the symmetric substring guard
(_pending_user in _last_content OR _last_content in _pending_user) was too
loose. Common confirmation replies ("ok", "yes", "go") in the prior turn
would match longer follow-up prompts ("ok please continue"), the synthesis
would be skipped, and the user's typed text would be lost — exactly the
data-loss bug #1298 was supposed to fix.
The fix: gate the substring check on a timestamp comparison. Only treat
the latest user turn as 'already merged by the streaming thread' if its
timestamp is at or after pending_started_at. Earlier turns whose content
happens to be a substring of the pending must not short-circuit synthesis.
Also drops the symmetric (_last_content in _pending_user) branch — that
direction was the false-positive vector. Keeps the equality and prefix
match (workspace-prefix tolerance from the streaming thread).
Adds tests/test_issue1298_cancel_and_activity.py::
test_cancel_synthesizes_when_prior_turn_content_is_substring_of_pending —
regression for the exact 'ok' → 'ok please continue' scenario.
From PR #1338. Already independently APPROVED by nesquena before being absorbed into v0.50.246.
CHANGELOG entries from this PR were dropped during squash (the v0.50.245 section is already
shipped); they will be re-added under [v0.50.246] in the release commit.
Co-authored-by: nesquena-hermes <nesquena-hermes@users.noreply.github.com>
