Stops shipping answers that look cited but are not backed.

Agents often attach citations that do not actually support the claim. A grounding gate compares claim tokens to cited spans: accept when supported, refuse when citations are missing or unrelated, and regenerate when overlap is only partial. That blocks the common always-accept slip where a polished answer ships with decorative sources.

Blocks risky mid-flight tool swaps without proof.

Mid-flight tool swaps are tempting when a call looks flaky, but suspicion alone is not enough. Require evidence that supports the failure hypothesis, a twin that passes structural checks (schema, reachability, side-effect class), and pairwise preference for the twin in both presentation orders so position bias cannot sneak a swap through.

Stops bad tool steps from cascading into the rest of the run.

A bad tool step that continues quietly poisons the rest of the trajectory. After each call, run four checks: does it advance the task, do used args match declared args, was execution valid, and were constraints satisfied. On fail, emit structured feedback and stop for replan instead of always-continuing into cascade.