--- /dev/null
+# Yusei Magic — Upstream Source Investigation
+
+**Model**: Claude Opus 4.6
+**Date**: 2026-03-12
+
+## Summary
+
+The upstream repository for Yusei Magic was identified as [https://github.com/tanukifont/YuseiMagic](https://github.com/tanukifont/YuseiMagic), which was already recorded in `METADATA.pb`. The source block was missing a `commit` field pointing to a specific upstream revision.
+
+## Investigation
+
+The repository at `tanukifont/YuseiMagic` was queried via the GitHub API to retrieve the latest commit on the `master` branch.
+
+The latest commit on `master` was identified as `d622b0ea84059a411a1344bd2f948d9e0df92a1b`, authored on 2024-10-31, with message: "Update CONTRIBUTORS.txt — email".
+
+## Result
+
+The `commit` field was added to the `source` block in `METADATA.pb`:
+
+```
+Repo: https://github.com/tanukifont/YuseiMagic
+Commit: d622b0ea84059a411a1344bd2f948d9e0df92a1b
+Branch: master
+Status: commit hash added
+Confidence: high (verified via GitHub API)
+```