Correction vs error (catalogue)

This document summarizes how Plasm surfaces failures to operators vs to the LLM.

Roles

Concept	Audience	Content
ERROR	Logs, REPL, StepError::error	thiserror / parser line; optional span_offset for tooling. Omitted from eval correction_context JSON.
CORRECTION	correction_context, retries	Single correction string: everything the model should act on (may contain multiple paragraphs).

JSON (eval / BAML)

• correction — the only LLM-facing instruction block (merged from any former “hint” lines).
• span_offset — optional byte offset.
• Raw ERROR strings are not included in this JSON.

Legacy eval JSON may still have message and/or hints / correction_hints; those are merged into correction when deserializing.

Merge policy (parse + recovery)

When deterministic recovery returns multiple candidate lines, they are appended into correction after the expression (one block, no separate hint array).

Type check: chain without Get

TypeError::ChainTargetMissingGet is raised when a chain step would auto-fetch an entity that has no Get capability; correction text tells the model to fetch another way or extend the schema.