Root cause comment

Document why a High/Urgent bug happened and post it as a Linear comment, per the team rule that High/Urgent bugs get a written root cause. Draft-then-confirm: post only when explicitly approved.

1 — Gather context (sequential, before anything else)

Run /investigate $ARGUMENTS to pull the ticket, synced Slack thread, prior work, and the relevant code. Do not start code search or devsql until the ticket + thread are summarized.

If /investigate isn't run, at minimum: linear issue view <id> for the ticket and its synced Slack thread, then trace the offending behaviour to the write paths / commits that introduced and re-introduced it (git log -S, gh pr view).

2 — Find the real cause, not the symptom

Identify the earliest decision that made the bug possible and every later PR that re-introduced or only partially fixed it. The goal is the category of mistake (e.g. "deprecated pattern re-copied into new write paths", "no backfill when a dual-write was introduced"), not a single faulty line. Confirm against code/data — never assert a cause you haven't verified.

3 — Draft in the team format

Render in chat for review. Structure (keep what applies, drop what doesn't):