Follow-up to [#8294](https://github.com/block/buzz/pull/8294). Malformed
trailing thread tags could make a notification open the right thread
while Flutter indexed its reply elsewhere; uppercase references could
similarly miss lowercase event IDs.
Share one validated thread-reference parser between the mobile timeline,
Inbox, and feed helper. It ignores malformed markers, keeps the last
valid root/reply, and normalizes lookup IDs to lowercase. Native push
parsing now uses the same casing. Existing thread fixtures use valid
event IDs so they continue exercising real thread relationships.
Add RunnerTests coverage for the production native-to-Flutter argument
conversion, including buffered cold-start navigation and omitted
optional thread IDs, and run it in the native CI lane.
### Validation
- New parser and Inbox regressions cover malformed markers and uppercase
references. Widget regressions open and highlight the exact reply for
valid, uppercase, and trailing-malformed tags.
- After integrating [#8106](https://github.com/block/buzz/pull/8106),
Flutter analysis and the complete mobile suite pass: 3,337 tests, four
existing skips. Integration preserves per-event read predicates and
migrates incoming thread fixtures to valid IDs. An unchanged
keyboard-history test also failed with main's original parser; recording
reads before the scroll transition fixes its timing assumption while
retaining visibility assertions.
- Native package tests passed (127 tests), and both Runner bridge tests
passed on an iOS simulator with Xcode 26.5. Removing the production
`threadRootId` assignment made the bridge regression fail; restoring it
passed. Native code is unchanged by the main integration.
- [Current-head CI
passed](https://github.com/block/buzz/actions/runs/38659307247),
including Mobile and Mobile Swift. [Codex
review](https://github.com/block/buzz/pull/8332#issuecomment-6181458528)
and [security
review](https://github.com/block/buzz/pull/8332#issuecomment-6181449235)
found no issues on the integrated commit. [Owner
approval](https://github.com/block/buzz/pull/8332#pullrequestreview-5526812957)
covers the exact integrated commit.
- Standards and spec reviews found no blockers, including the merge
resolutions and test adjustments. Validation is scoped to mobile/native
per VISION_MOBILE; unrelated repository-wide checks were stopped, not
counted as passing.
The bridge test covers serialization and buffering, not end-to-end APNs
delivery or app launch. No new physical-device acceptance is claimed;
routine post-merge dogfood remains human-owned.
---------
Signed-off-by: Tom Brow <tomb@block.xyz>
## Summary
A failed mobile thread refresh could briefly remove replies and show “0
replies” even though Riverpod still retained the previous result. Read
the retained reply value directly and merge it with pending local
replies through errors and retries. When a reopened thread has no
retained result, show loading or failure instead of a false zero count.
Error status remains visible alongside retained replies.
No additional cache or retention is introduced. Current main
intentionally disposes thread queries on close; reopening still fetches
fresh data. The recorded symptom is reproduced by the failed-refresh
test, but the recording alone does not establish its network trigger.
### Related issue
Related to #4831 (thread refresh and disposal behavior), incorporated
into main through #6691. No duplicate for this rendering defect found.
### Testing
- Reproduced disappearing cached replies in widget tests before the fix;
the new retry/recovery, terminal-error, reopen/loading, initial-error,
and empty-result tests now pass.
- Provider coverage verifies cached and pending local replies survive a
failed refresh and confirmation still clears the local overlay.
- All five new widget regressions, the existing
hydration/scroll-position regression, all nine thread-provider tests,
Flutter analysis, and the final-head full mobile pre-push gate passed
(2,261 tests passed; four skipped).
- Phone-width and large-text rendering checked with synthetic messages.
[Before/after
screenshots](https://github.com/block/buzz/pull/7757#issuecomment-5743469556).
- All final-head GitHub checks passed, including mobile tests, Android
debug APK, iOS simulator app, and unsigned iOS release builds.
- Codex code review and security review are clean for `4e5f606ae`; the
earlier accessibility finding is fixed and resolved. Builderbot review
was requested but has not returned a result.
- Broad local `just ci` could not finish: unchanged ACP timing tests
failed, including `keepalive_resets_idle_past_deadline` on the
lower-concurrency retry. The separate ACP run passed all 941 tests.
Initial parallel mobile runs also hit timing flakes; the final-head full
mobile gate passed. No unrelated native code was changed.
---------
Signed-off-by: Tom Brow <tomb@block.xyz>
