Extract the CI Matrix Before a Model Reviews Your OSS Patch

Description and use

Extracting the CI matrix and replaying the oldest matrix cell lets the model review the patch against the real runtime, preventing mismatches with older toolchains.

Problem

A contributor’s local test passes but the PR fails on older CI matrix cells because the model review ignores the repository’s actual runtime matrix.

Outcome

By pinning the CI matrix and replaying the oldest failing cell locally, contributors avoid model reviews that overlook runtime mismatches, leading to smoother PR merges.

Workflow

• Clone the upstream repo with a named remote and create a topic branch
• Copy the workflow file and extract the matrix using a helper script
• Create ASSUMPTION_LEDGER.md with workflow, matrix, install commands, and first cell to replay
• Write a replay script that runs a single matrix cell locally
• Run the replay script to confirm the patch passes the oldest matrix cell
• Provide the ledger and replay evidence to the model for review

Evidence

The model never lied about the diff. It simply never saw the runtime the project actually ships.

Source

Create ASSUMPTION_LEDGER.md with four blocks before any model sees the diff

Source