agent's papermill parameters file had a typo, run failed over to defaults, wrong results

TL;DR

A typo in the papermill parameters file (wrong key name, wrong YAML structure) does not always error; if the notebook reads parameters defensively, the run silently uses defaults and produces wrong results that look right. Validate before executing: load the parameters file, check its keys against the notebook's parameters cell, and fail fast on any mismatch. Silent wrong results are worse than a crash.

agent's papermill parameters file had a typo, run failed over to defaults, wrong results

Use this when

• A papermill run produces default-looking results despite custom parameters.
• The parameters file was hand-edited or agent-generated.
• No error was raised; the results are just wrong.

Not for this skill when

• Papermill errors on the parameters. That is loud and debuggable.
• Defaults are correct but results are wrong. That is a logic bug.

Steps

1. Compare the parameters file keys against the notebook's parameters cell defaults. Verify: you find the typo or structural mismatch.
2. Fix the file. Verify: keys match exactly.
3. Add pre-run validation to the agent: parse the YAML, assert the key set matches, assert types. Verify: a typo'd file fails validation.
4. Make the notebook fail on unexpected parameters instead of defaulting silently. Verify: a bad key raises, not defaults.
5. Re-run with the fixed file. Verify: injected values appear in the output and results reflect them.

Variant phrasings

papermill typo parameters defaults

Short form. Validate keys before running.

papermill silent wrong parameters

The danger phrasing. Silent wrong beats loud wrong for harm.

parameters file key mismatch papermill

The cause phrasing. Assert the key set.

Compatibility: papermill 2.x, YAML parameters. The validation is agent-side.

Why it happens

Papermill injects what you give it without judging: a misspelled key becomes an unused variable, and the notebook's defaults fill the gap silently. The run completes successfully with plausible-looking wrong numbers, which is the most dangerous failure mode in automation. Validation moves the failure from 'wrong results discovered weeks later' to 'clear error before anything runs'.

Edge cases / pitfalls

• Extra keys should warn, missing keys should fail. Tune the strictness deliberately.
• The notebook's defensive defaults are the enabler. Consider making required parameters fail when absent.
• Agent-generated YAML needs the same validation as human YAML. Generators typo too.
• Log the effective parameters with every run. The audit trail is what makes wrong results diagnosable.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstaaEmHqBjAm19cT2EGUjRw