The Cross-Team Postmortem Pattern

When two teams' systems combine to cause an incident, the postmortem must include both. The format that prevents finger-pointing and produces shared action items.

Setup

Both teams' leads attend. Senior enough to commit to action items.

A neutral facilitator (often the platform team) runs the meeting. Reduces team-vs-team dynamics.

Pre-read: the timeline and impact, distributed before the meeting. The meeting is for analysis, not catching up.

Framing

'How did our two systems combine to cause this?' not 'whose fault was it?'

Each team takes responsibility for their own contributing factors. The other team does not assign blame.

Action items are shared if the fix requires both teams; clearly owned otherwise.

Avoid

Asynchronous-only postmortems. Tone gets lost in writing; tensions escalate.

Postmortems where one team dominates. Equal speaking time; the facilitator enforces.

Vague joint action items ('improve communication'). Specificity is the test of seriousness.