# Code Review — Step 3: Implement the CI schema-stability check

Decision: **APPROVE**

## Summary

The Step 3 implementation now satisfies the planned schema-stability guard. The shared `internal/toolchecks` package generates schemas from the live registry, the snapshot freshness check detects missing/stale/drifted committed snapshots, and the additive-only check compares generated current schemas against an explicit non-empty baseline directory. Genuine new tool names are reported as additions while baseline tool removals, argument removals/renames, changed existing property schemas, and newly required arguments fail.

## Verification

I reviewed the full diff from `ea2717231a2e529dbedf691573c3876cd5fee6cf..HEAD` and ran:

```sh
go test ./internal/toolchecks ./internal/tools
go test ./...
golangci-lint run ./...
go run ./scripts/check_schema_stability.go -require-baseline -baseline-dir /tmp/does-not-exist-icuvisor-baseline
go run ./scripts/check_schema_stability.go -baseline-dir internal/tools/schema_snapshot -require-baseline
```

Results:

- unit/package tests passed;
- full repository tests passed;
- lint passed;
- a missing required baseline now exits non-zero with a clear error;
- using the current snapshot directory as the baseline passes both freshness and additive-only checks.

## Findings

No blocking findings.

## Notes

- The previous concerns about missing/empty baselines, `gosec` file permissions, and missing current paths in stability failures are addressed.
- Workflow wiring and helper unit tests are still listed under Step 5, so I did not treat their absence in this step as a defect.
