What problem does it solve? Single-model reviews can miss flaws because the same model that wrote a plan or diff also judges it. Spar sends the artifact to a different vendor's model as a read-only reviewer, producing an independent, evidence-grounded verdict before approval or publication. ## Core Features & Use Cases - Cross-vendor review bridges: Claude Code reviews via spar-codex, OpenCode via spar-claude, with explicit reviewer-ID resumption and provenance reporting. - Evidence-backed artifacts: The review-brief script records HEAD, source/index fingerprints, gate commands and results, and scans artifacts for sensitive content before disclosure. - Structured adversarial loop: A reviewer charter demands grounded objections classified by impact, ending in VERDICT: CONVERGED or VERDICT: OPEN with blocking counts. - Use Case: Before presenting an implementation plan for approval, generate a review brief with gate evidence, run the cross-vendor bridge, address or rebut each objection, and present one ruling packet per open item to the human arbitrator. ## Quick Start Ask the agent to run a spar review of the current plan or staged diff using the review-brief script and the appropriate cross-vendor bridge, then report the reviewer's verdict and provenance.