Define the SSE token relay input contract

The accepted input remains: upstream chunk iterator, response headers, abort signal. Keep parsing and normalization in functions that do not score, train, or call a model. That split lets a test fail the boundary without blaming the core logic. The user-facing decision stays: stream tokens to a client while honoring cancel and partial failure.

const Env = { requireAbort: true, maxChunkMs: 2000 };
function assertStreamContract(headers) {
  if (!String(headers['content-type']||'').includes('text/event-stream')) throw new Error('SSE content-type required');
}
console.log({Env, ok: true});

Expected evidence: SSE contract flags. If the contract is silent on a bad value, later debugging will look like an algorithm bug when it is really a data bug.

Write one assertion for a neighboring valid input to the SSE token relay so tightening the boundary does not over-reject. Document field names and types the way a teammate would need them on day two of streaming-responses—not as comments you plan to delete.

List every field in fake chunk iterator yielding three tokens then done and mark each as required, optional, or forbidden. Required fields must fail loudly when missing; optional fields need defaults you can quote in a test; forbidden fields (secrets, raw PII, path escapes) must never be accepted silently. This list is the contract for the SSE token relay.

Add one sentence about encoding, units, or timezones if relevant to upstream chunk iterator, response headers, abort signal. Contracts that ignore units create “correct” programs that still ship wrong decisions when someone tries to stream tokens to a client while honoring cancel and partial failure.

Write the error string you want for the most likely bad input. Prefer ValueError('threshold out of range')-style messages over generic invalid input. The contract’s job is to make buffering the whole answer before first byte, or ignoring client disconnect harder to confuse with a model or algorithm bug later.

At the data contract stage for streaming-responses, the job is narrower than finishing a product demo. You are creating one progressive evidence piece about fake chunk iterator yielding three tokens then done that later pages inherit without redefining success. Keep that fixture small enough to inspect by hand, keep outputs copy-pasteable as text, and refuse to narrate this baseline as if it were a production SLA: non-streaming JSON endpoint latency for the same prompt.

For this page specifically, success looks like malformed inputs rejected with field-named errors while still centering the user decision to stream tokens to a client while honoring cancel and partial failure. If you cannot point to a file, command, or assertion that proves that for the SSE token relay, stay on this page instead of advancing.

Glossary: tool · Glossary: structured output · Cheatsheet: production ops signals

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