Which code changes does a diff classifier read?

It reads the diff between a PR’s base and head commit and classifies which surfaces changed, not the line-by-line content itself. Tessary’s diff classifier names which parts of the agent a push touched; the CI gate’s own report request shows prompt and tool as example surface names it can carry.

Call the gate’s report endpoint without an explicit surfaces list and it resolves that list from the diff classification instead of making you say what changed by hand. That join is what lets the gate route to the graders and risk stats tied to what actually moved, rather than running everything against every PR regardless of what it edited. It re-derives that classification on every new push to the PR, so two pushes get two independent answers to what changed, not one carried forward from the last.