Split a workflow into tasks

One agent turn is rarely one job. This takes a support workflow billed as a single line item and splits it into four tasks. Time: about an hour of code changes, then a week of traffic to read.

List the model calls on one path

Pick your highest-volume path and write down every call it makes. Most teams find more than they expected, because retries, guardrails and formatting passes are easy to forget.For a support reply: classify the intent, fetch the account, draft the reply, check the tone.

Name each one

One name per job. A name that survives a prompt rewrite.

Call	Task
Classify the intent	`support_intent`
Fetch and summarise the account	`support_lookup`
Draft the reply	`support_draft`
Check the tone	`support_tone_check`

Resist the urge to encode the tenant or the model. Tenants go in user.

Label them

intent = client.chat.completions.create(
    model="auto", messages=intent_messages,
    extra_body={"task": "support_intent"},
)

draft = client.chat.completions.create(
    model="auto", messages=draft_messages,
    extra_body={"task": "support_draft"},
)

Keep model as it was if you want zero behaviour change; the labels work either way. Only auto lets a task get cheaper later.

Wait, then read the split

Give it enough traffic to be representative, usually a week. We report spend per task.The result is almost always lopsided. A guardrail call that nobody thought about turns out to be a third of the bill, because it runs on every turn while the expensive-looking reasoning call runs on one turn in twenty.

What good looks like

One task dominates the bill

Ideal. Take it to Write an eval contract and route it down.

Spend is spread evenly across tasks

Usually a sign the split is too fine. Merge tasks that share an input shape and a definition of correct.

One task has huge cost variance per call

Still too broad. Something inside it branches into genuinely different jobs. Split again.

Next: write an eval contract

Nothing can be routed until correct is defined.

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Split a workflow into tasks

What good looks like

Next: write an eval contract

​What good looks like

Next: write an eval contract

What good looks like