Default fallbacks and validation

Callers will send bad data. They will ask for "sentmient" with a typo. They will ask for the same task twice. They will send an empty list by accident. A good API does not return a 400 for every fat-fingered request. It validates gently, drops unknown values, and falls back to a sensible default.

agent/graph.py

python

def _validate_tasks(tasks: list[str]) -> list[str]:
    seen = []
    for t in tasks:
        t = t.lower().strip()
        if t in VALID_TASKS and t not in seen:
            seen.append(t)
    if not seen:
        seen = ["sentiment", "summary"]
    return seen

Three things happen here. Normalise to lowercase. Drop anything not in VALID_TASKS. De-duplicate while preserving order. Fall back to a safe pair if nothing valid remains. Silent, forgiving, predictable.

Matching exercise: Match each input to what _validate_tasks returns

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Checkpoint: Selective dispatch checkpoint

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