What problem does it solve? Fixing defects that involve external service calls is hard to verify because real vendor APIs cannot be safely exercised in tests. This Skill investigates a reported defect, implements the fix, and tests the changed application against a Veris twin that simulates the external services, producing receipt-based evidence that the fix works. ## Core Features & Use Cases - Defect Investigation: Reads the issue (via gh issue view) or prompt, inspects affected code, and reproduces failures through the application or twin fault injection. - Twin-Backed Verification: Runs the repository's existing integration tests against the sandbox twin, asserting responses and confirming traffic via receipts and traces. - Evidence and Handoff: Summarizes changes with cited evidence, updates .veris/NOTES.md findings, and follows the repository's PR conventions. - Use Case: Given an issue like "create_invoice duplicates the invoice when the response is lost", reproduce the retry behavior against the twin, fix the idempotency handling, and verify the affected caller passes with current-run twin evidence. ## Quick Start Ask the assistant to fix a defect by providing an issue link or prompt, for example: run the fix command for https://github.com/org/repo/issues/42 and verify the changed behavior against the Veris twin.