OptionalmodelOverride: PromptModelConfigProtected Optional ReadonlymodelProtected ReadonlyoutputProtected ReadonlysnapshotCommitted cold-start snapshot (hub name, template, model).
Hub identifier — derived from the committed snapshot.
ProtectedbuildBuild the ChatOpenAI instance. Default uses override → resolved hub/snapshot model. Tests override this to inject a fake.
ProtectedbuildPure: map typed input to the hub template's variables. Unit-testable without an LLM.
Optionalctx: RunnerContextResolve + format the prompt text without invoking the model. Useful for inspection, tests, and tooling that only needs the rendered string.
ProtectedtraceOptional non-PII trace inputs for the child span.
Structured shape the model must return. Stays in code (the hub resolves text + model).