Fail Fast¶

Detect and report invalid conditions close to their source.

Canonical interpretation¶

Do not continue with corrupted assumptions when a required contract is violated.

Purpose¶

Detect and report invalid conditions close to their source.

Apply when¶

Data or control crosses a trust, process, module, or API boundary.
Invalid state could threaten correctness, security, or recoverability.

This does not mean¶

Do not crash whole systems for recoverable external failures.
Do not expose sensitive diagnostics to untrusted users.

Trade-offs¶

Stricter contracts can reduce compatibility with inconsistent external producers.
Defensive checks can duplicate validation if trust boundaries are not explicit.

Conflicts with canonical entries¶

None recorded.

Broader policy tensions¶

fault-tolerance
tolerant-input

Reinforces canonical entries¶

design-by-contract
parse-dont-validate

Supports broader concerns¶

None recorded.

Core Skill ownership¶

Primary owner: contracts-and-errors

Positive example¶

Reject an invalid configuration during startup with a precise message.

Counterexample¶

Replace a missing required value with an arbitrary default and fail later.

Guidance for AI models¶

Apply this guidance only after considering the active project profile, constraints, and architecture authority.
State the concrete design consequence instead of citing the principle name as sufficient justification.

Editorial note¶

This page is generated from the canonical YAML entry. Edit principles/entries/fail-fast.yaml and regenerate the compendium instead of editing this file directly.