Skill: Craft Oracle

"An adversary without an oracle is a critic."

The Standard

• An oracle is a command, not an opinion. It exits 0 or 1.
• The harness runs it. Never a judge. A model reporting its own gate result has voided the gate.
• Prefer the project's own script. composer test, pnpm test, make test. Re-specifying the raw invocation duplicates a definition that will drift.
• Judgment is not permanently judgment. A judgment that recurs identically becomes an oracle.

Choosing Them

Every stack has tests, types, and lint that exit 0 or 1. Start there.

# panel.yml
gates:
  - name: tests
    command: composer test
  - name: types
    command: vendor/bin/phpstan analyse
  - name: architecture
    command: vendor/bin/pest --testsuite=arch
  # polyglot repos scope by directory
  - { name: web-types, workdir: apps/web, command: pnpm tsc --noEmit }

Split by cost, not by category:

Cadence	What runs	Why
Every loop	tests, types, lint	Cheap, catches most
At approval	mutation, full acceptance	Expensive, run once

Promotion

The system gets cheaper here, or it does not get cheaper at all.

Round one, a judge argues that a module near IO must not be imported by a module far from it. Judgment: correct, expensive, and it will recur on every review forever.

Round five, it is a forbidden-import check. It costs an exit code.

The tell that something is ready to promote: you have written the same finding three times, in the same words.

Record candidates in the verdict's ### Promote section. Promotion is authored work like any other — a judge cannot write the check, and it should not arrive as a surprise commit.

A Green Gate Can Be Empty

Passing is not covering. Two ways a gate exits 0 while certifying nothing:

Failure	Tell
the inputs dodge the failure mode	the data was chosen by whoever wrote the code
the harness passes vacuously	zero cases executed, still exit 0

A charter demanding exact money, tested only on values binary floating point happens to represent exactly, has a gate certifying the author's choice of examples.

Audit a gate by breaking the code on purpose. If it stays green, it was never a gate.

The Coverage Rule

Panel is worth exactly what its oracles are worth. A task with four independent gates gets a real adversary. A task with none gets taste ping-pong wearing a protocol.

Before convening a panel, ask what would catch this mechanically. If the honest answer is nothing, either build an oracle first or do not convene.

The Anti-Patterns

Don't	Do	Why
Judge reports "tests pass"	Harness reads the exit code	Voids the gate entirely
Enumerate an open set in a lint	Narrow scope until it closes	Unbounded vocabularies produce false positives
One gate for everything	Name them separately	You cannot tell what failed
Re-specify a project script	composer test	Duplication drifts
Gate on a metric nobody agreed	Gate on a command everyone runs	A gate nobody trusts gets overridden

Real-World Examples

See examples.md.