The determinism kernel's only CI is check_determinism.py src — run against clean code. That proves the gate passes on clean code; it never proves the gate fails on a hazard. For a blocking gate, the catch-property being pinned only by a since-deleted dev fixture is exactly what silently rots.

The kernel is a vendored, package-free script (it must run standalone in any repo's CI), so the test loads it by file path and calls into it directly. Registering it in sys.modules before exec_module is what lets the script's @dataclass resolve its own module.

One workflow class touches all fifteen banned rules — including the resolutions a naive grep would miss: an aliased import (dt.now()) and a from-import (date.today()). The test asserts the exact rule set, so a regression that drops a category fails loudly.

Two companions: main([...]) == 1 pins the gate's actual contract (a non-zero exit blocks the merge), and a negatives test pins zero false positives on the sanctioned workflow.* replacements, a -> datetime.datetime annotation, and wall-clock inside an @activity.defn (legal there).

The differential test runs the same code through both layers. A workflow calls a helper one call out; the helper hides datetime.datetime.now(). The workflow file has no banned call lexically, and the helper file has no @workflow.defn — so the lexical, workflow-scoped kernel reports both files clean. The brain's call-graph follows the import and catches it.