Good — artifacts/ and test/ are gitignored (as expected, both are untracked deliverable/scratch areas), and collision.json is untracked at root, exactly as required. No git actions needed since nothing should be committed.

Summary

Found a genuine RIPEMD-160 collision truncated to the first 48 bits via a birthday attack (~10.9M evaluations, 27.7s), independently verified with both Python hashlib and Node crypto:

• collision.json written at repo root with the exact required schema, untracked.
• artifacts/report.md documents method, results, independent cross-verification, and explicitly separates facts from inferences/caveats (e.g., noting λ=24 in the task name refers to the birthday-cost exponent, while the truncation itself is 48 bits as the rules specify).