What problem does it solve? When a periscope repository maintains ECC artifacts (repo-local skills and instincts) in multiple locations, the copies can silently drift out of sync after merges or harmonization edits. This sidecar documents the contract and provides an idempotent verification workflow so drift is detected instead of shipped. ## Core Features & Use Cases - Activation Guard: Runs a presence check first and prints SKIP when no periscope ECC bundle exists, so it never fails or blocks work when absent. - Mirror Verification: Confirms that .agents/skills/periscope/SKILL.md and .claude/skills/periscope/SKILL.md remain byte-identical via the verify-ecc-skill-mirror.sh script. - Path-Scoped PR Replay: Describes how to replay only the harmonized ECC paths onto an integration branch when a PR carries pre-merge commits, avoiding wholesale merges or rebases. - Use Case: After merging an ECC harmonization PR into periscope, run the mirror verifier with PERISCOPE_REPO set, then import the instincts file to confirm the Agents and Claude skill copies stayed in sync. ## Quick Start Ask the agent to run the periscope ECC mirror verification against your periscope checkout and report whether the Agents and Claude skill files are in sync.