# Postmortem

- **Event:** [Built with Opus 4.7: a Claude Code hackathon](https://cerebralvalley.ai/e/built-with-4-7-hackathon)
- **When:** Apr 21 at 12:00 PM – Apr 27 at 2:00 AM (EDT)
- **Where:** Online
- **Team:** [Rahil Singhi](https://cerebralvalley.ai/u/Rahilsinghi)
- **GitHub:** https://github.com/rahilsinghi/postmortem
- **Demo video:** https://youtu.be/9nbIVa_jnsU
- **Gallery:** https://cerebralvalley.ai/e/built-with-4-7-hackathon/hackathon/gallery
- **Page:** https://cerebralvalley.ai/e/built-with-4-7-hackathon/hackathon/gallery/56

Postmortem is a decision-archaeology agent for any GitHub repo. Point it at a codebase and it reads every PR review, every rejected alternative, every architectural debate — and builds a queryable decision ledger. Ask why the code is the way it is and get a cited answer back in seconds, with every claim traceable to the exact reviewer quote that decided it.

Five interaction modes ship:

1. Ask — natural-language query over the ledger; answers stream with live adaptive-thinking tokens and a self-check pass that verifies every inline citation before the answer is trusted.
2. Impact Ripple — BFS across the decision graph to trace what breaks when an assumption moves.
3. Open Decision — the full rationale + rejected alternatives for any single PR, cited.
4. Ghost Interview — pick a maintainer; Opus speaks in their register using only their own verbatim quotes, with every paraphrase openly disclosed.
5. Conflict Finder — scans the whole ledger for pairs of decisions that quietly contradict each other, ranked by severity.

Shipped with six hero ledgers (hono, zustand, next.js, shadcn-ui, supabase, and the Postmortem repo itself) totaling 155 decisions, 1,876 citations, and 410 rejected alternatives — a queryable public-domain artifact. Also ships as a Claude Code MCP server so all five modes are one claude mcp add postmortem away.
Live: postmortem-mauve.vercel.app · Video: youtu.be/9nbIVa_jnsU · 100% citation-grounded.

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Markdown version of https://cerebralvalley.ai/e/built-with-4-7-hackathon/hackathon/gallery/56. Site index for agents: https://cerebralvalley.ai/llms.txt · full text: https://cerebralvalley.ai/llms-full.txt