Serialize typed artifacts at durable boundaries

docs/operations.md

@@ -91,6 +91,12 @@ digests match the current invocation. Changes to input bytes, the resolved
 pipeline, selected lanes, the runtime LLM profile override, or bound reference
 content invalidate reuse.
 
+Typed artifact checkpoints additionally record codec-owned bytes, artifact
+kind, schema ID and version, exact schema digest, and media type. A missing or
+mismatched codec identity, or bytes the current codec cannot decode, is reported
+as a checkpoint reuse miss. The affected operation executes normally and, when
+checkpoint writing is enabled, replaces the incompatible checkpoint.
+
 Current checkpoint manifests use workspace schema `notarius.workspace.v2`.
 Manifests written with `notarius.workspace.v1` are incompatible because their
 chunk provenance has an older shape. On the first explicit resume after an
@@ -126,7 +132,9 @@ the attempt `llm_calls` array. Prompt content is written inline in the prompt
 artifact. The response metadata and body use the paired files described above;
 the body is pretty-printed JSON when possible and raw text otherwise. Debug
 artifacts may contain source material, reference material, prompt inputs, model
-outputs, and other sensitive data. API keys are not written, and obvious
+outputs, and other sensitive data. Typed artifact envelopes include
+domain-neutral codec identity, redacted metadata and content, and digests of
+the stable codec bytes. API keys are not written, and obvious
 credential-shaped values and sensitive map keys are redacted, but debug
 directories should still be protected as sensitive local state.