Page 3 of 8~112 min topic

Structured output lab

Build the first working ticket triage schema gate

Page 3 implements the shortest complete path for the ticket triage JSON endpoint with inspectable intermediate values.

~14 min this pageImplementation

1Learn the idea

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Implement the minimal working path

Build only what the claim requires: invalid model JSON is rejected; valid payloads pass a schema gate. Prefer boring, deterministic code over frameworks you cannot yet explain. Run the path twice; identical output on this fixture is a feature, not a lack of creativity.

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Run the working path

export async function run(input: unknown, deps: Dependencies) {
  const started = performance.now();
  const validated = deps.parseInput(input);
  const raw = await deps.execute(validated); // request provider-supported JSON Schema output when available, then parse locally with Zod
  const value = deps.parseOutput(raw);
  return { value, durationMs: Math.round(performance.now() - started) };
}

Expected evidence: “Charged twice” becomes billing/high with a short summary; extra keys are rejected.. Read each printed intermediate as part of the argument that the path works—not as decoration.

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Trace one input end to end

Narrate the journey from raw input to result for a single example from sample ticket + triage schema. If you cannot name an intermediate, the implementation is still too opaque for this lab. Only after this path is solid should you generalize data sources or UI.

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Lab notebook: intermediates worth printing

While implementing the ticket triage schema gate, print or log at least three intermediates that map to the claim (invalid model JSON is rejected; valid payloads pass a schema gate). Good intermediates are values a teammate could recompute with a calculator or diff. Bad intermediates are framework traces you cannot explain.

Re-run with sample ticket + triage schema twice. If the second run differs, either the path is nondeterministic (document the seed) or you have hidden global state—both are lab bugs until named.

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Worked judgment

Stop adding features once the path supports return validated category, priority, summary, and confidence for a support ticket. Extra UI, extra tools, or extra models belong in later chapters. The mastery bar for this page is simply: a deterministic end-to-end path with intermediates.

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Why this stage matters for the ticket triage schema gate

At the implementation stage for structured-output-lab, the job is narrower than finishing a product demo. You are creating one progressive evidence piece about sample ticket + triage schema 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: free-text model reply without schema validation.

For this page specifically, success looks like a deterministic path with printed intermediates while still centering the user decision to return validated category, priority, summary, and confidence for a support ticket. If you cannot point to a file, command, or assertion that proves that for the ticket triage schema gate, stay on this page instead of advancing.

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

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Before you start

Why this matters

Without running code, predict the final output for fixture sample ticket + triage schema. Name one intermediate value that would prove the prediction. Then answer: what could look successful while actually being wrong at this stage for the ticket triage schema gate?

In the wild

See how this idea shows up as a product and a company — then come back to the lesson. Skills transfer across vendors.

Check your understanding

Page assessment

Answer from memory. Completion is saved from this evidence, not from opening the next page.

1. Can you narrate every intermediate value?
2. Is the fixture deterministic and independently inspectable?
3. Did you avoid framework behavior you cannot explain yet?
4. Does the output still support the decision: return validated category, priority, summary, and confidence for a support ticket?

All responses are required.