Write a foreign runtime

The determinism layer is the standard. Its artifacts are published as JSON Schemas, and a runtime in any language that executes plan.json and the bindings and writes conformant results is a Yam runtime. The reference is runtimes/java, on Playwright for Java, which passes the suite without the TypeScript compiler anywhere in the loop.

What you consume

@svatah/yam-schema ships the schemas under json/ and the conformance fixture under conformance/. A runtime is held to three of them:

Schema	What it is
ir.schema.json	the step intermediate representation you execute
results.schema.json	one line per step in results.jsonl
summary.schema.json	summary.json at the end of a run

The rest, plan, bindings, config, data, audit, checkpoints and the surface messages, are in the schema reference. Each schema's $id is under https://yam.svatah.com/schema/1.0.0/.

What you implement

1. Read plan.json, yam.config.yaml, data.yaml and bindings/.
2. For each story in the run block's expansion, for each step: resolve the target through the bindings (candidates in order, exactly one match), perform the action or evaluate the predicate on your platform driver, and write a full StepResult line: status, the candidate that matched, startedAt, endedAt, durationMs, and the failure class when it failed.
3. Apply the policies: stop, continue, compensate:<story>, and mark the run aborted when a compensation ran.
4. Write summary.json.

Refuse, with a clear diagnostic, a plan that needs something you did not implement: a custom step, an API request, a capability.

Prove it

node scripts/runtime-conformance.mjs --runtime java --report reports/runtime-java.md

The harness compiles the fixture project, checks the plan's hash, runs your runtime against the sample application, validates the artifacts you wrote against the schemas, and only then compares every step's status and matched candidate with the committed evals/conformance/runtime/results.jsonl. It refuses to call a runtime conformant whose artifacts do not validate, whatever the comparison says. --strip <field> shows that gate failing on purpose.

Add a --runtime <name> branch to the harness for your runtime, or run the same three steps yourself; the fixture and the expected results are what the package publishes.