Greptile Summary

This PR fixes a bug where incoming Mattermost messages that already belong to a thread (i.e., carry a non-empty root_id / threadRootId) would always be replied to inside that thread, ignoring the replyToMode: "off" configuration. The fix is a single targeted guard added to resolveMattermostEffectiveReplyToId in monitor.ts, and is accompanied by two new regression tests.

Changes:

• monitor.ts line 178: the early return threadRootId path is now short-circuited when replyToMode === "off", letting the function fall through to its existing bottom path which correctly returns undefined for that mode.
• All existing code paths for replyToMode: "first" and replyToMode: "all" are completely unchanged.
• Two new unit tests in monitor.test.ts verify both the low-level resolveMattermostEffectiveReplyToId and the higher-level resolveMattermostThreadSessionContext behave correctly for the fixed case.

No issues found. The logic is minimal, correct, and the test coverage matches the bugfix.

Confidence Score: 5/5

• Safe to merge — one-line targeted fix with direct regression coverage and no side-effects on existing modes.
• The change is minimal (a single boolean guard on an existing condition), leaves the "first" and "all" paths entirely untouched, and is validated by two new tests that precisely cover the previously broken scenario. No other callers of this function are affected.
• No files require special attention.

_{Reviews (1): Last reviewed commit: "fix(mattermost): honor replyToMode off f..." | Re-trigger Greptile}

Landed via temp rebase onto main.

• Gate: pnpm check && pnpm build && pnpm test
• Land commit: da2d347
• Merge commit: aaba1ae

Thanks @RichardCao!