Resolve previous artifacts from commit declarations

docs/internal/stage-prepare.md

@@ -49,8 +49,10 @@ Materialize canonical current-session inputs before processing stages.
   - records previous inputs in `manifest.inputs`.
 
 Required previous-session inputs fail when unavailable; optional missing inputs
-are typed skipped results. Committed sources use their exact source-to-destination
-mapping, while the isolated legacy reader rejects ambiguous fallback matches.
+are typed skipped results. Each requirement resolves only from its unique
+`published_output` declaration in the pointer-selected remote commit. Prepare
+strips that selected run's immutable `published/` prefix to derive the local
+cache path, then validates the committed checksum, size, and generation.
 
 ## Invariants