RECOGNIZER

What it means

RecognizerError (code: RECOGNIZER). Thrown when a pattern fails validation at definePatternRecognizer registration, or when describing why a recognizer was skipped at runtime (warnings only - check() does not throw for scan-time failures).

Message shape

<reason> → https://tailrace.dev/docs/reference/errors/RECOGNIZER

Registration examples: pattern 0: nested quantifiers on groups are not allowed, entity "email" is reserved for built-in recognizers.

Common causes

1. Pattern source violates static safety rules (backreference, nested quantifiers, overlong source).
2. Entity name reuses a built-in class or invalid shape.
3. Custom scan() threw during detection (engine skips that recognizer and logs a warning).

Runtime behavior (v0.2+)

• Registration: fail fast - fix the pattern or entity name before calling createTailrace.
• Scan budget exceeded: fail open - remaining matches from that recognizer are skipped; one console warning; other recognizers continue.
• Custom scan() throw: fail open - that recognizer is skipped; others continue.

Built-in Tier 0 recognizers are trusted code paths. Optional Tier 1 should degrade with a warning when the model is missing, not crash the host.

Fixes

1. Use definePatternRecognizer for regex entities instead of hand-rolled loops when possible.
2. Declare policy for custom entity classes (entities.employee_id, etc.).
3. Fix or remove throwing custom recognizers.

Safe to catch?

Catch at registration time when building recognizer lists from user/config input. Do not rely on check() throwing RecognizerError for scan-time issues - those are logged and skipped.

If a block policy depends on a broken custom recognizer, detection may miss the entity (documented gap). Built-in secret blocking is unaffected.