ADR-079: A PR shows how it was built, generated from the run records

Status: Accepted (2026-11-03, spec 133)

Context

A build PR says what was built and verified, not how the agent loop got there: user decisions, hand-backs and fix rounds, accepted deviations, sequential fallback, budget and wall time were scattered across commits, verification.md and the orchestrator’s prose (#338). The run already records most of it locally (ADR-032 run records, spec 089 agent events, ADR-043 budget ledger). Contributors are asked how a PR was produced (#326); the platform’s own PRs should show it in a form a reviewer can check.

Decision

1. cplat writes it, not the orchestrator. cplat platform runs report --pr <run-id> renders a “How this was built” block from the run’s records and files; cplat pr open appends it to the body when the checkout has a current run. The model never writes or edits the block.
2. Only what was recorded. Facts come from the run record, the runs it resumes, the budget ledger and the spec’s verification.md; anything missing reads not recorded. No prompts, no message flow, no diffs.
3. Local records. The block is built on the machine that ran the build, from the active record or the local buffer, so it works without a run store.
4. Redacted and bounded. Every value goes through the run records’ redaction; lists are capped.
5. Never blocks a PR. A failure to build the block leaves the body unchanged and adds one note: line.
6. New facts are recorded, not inferred. What the block needs and no record holds (the sequential fallback; later user-approved test changes, #324) gets its own recording call or section.

Consequences

• Reviewers see decisions, hand-backs and accepted deviations in one collapsed block in every repo built by the platform.
• Adding a fact to the block means recording it first; the block’s contract is in spec 133’s design.md.
• Rerunning cplat pr open replaces the block (marker comments), so it stays current.