[thavelin]

Refs #117 and #130.

The existing posted-content check only sees valid descriptors in today's contract. Extract its field lookup into serverOwnedIn and exercise it with synthetic descriptors: reject id, recorded, and both together; accept empty content, ordinary fields, and similar names such as topic_id and recorded_at.

This retains #130's write-route scope, JSON-name lookup, diagnostics and nonempty-coverage guard. The same helper drives the manifest check and the six fixture cases. No schema or generated files change, and the descriptor builder uses existing protobuf dependencies.

Validation: both focused tests, both-module make test, contract go vet, formatting and diff checks pass. Removing either protected field makes the intended fixture cases fail; the original source was restored byte-for-byte and the focused suite passed again. Full make check, TypeScript, regeneration and downstream Chain checks were not run locally.

[Copilot]

🟢 Approval recommended

No active review issues were identified for the posted-content guard test improvements.

No open issues 🎉

What changed in this PR

This PR strengthens the contract tests by proving that the posted-content guard detects server-owned fields in synthetic message descriptors, rather than checking only the current valid schema.

Changes:

• Extracts serverOwnedIn and reuses it in the existing manifest check, preserving JSON-name lookup, write-route scope, diagnostics, and the nonempty-coverage guard.
• Adds six fixture cases covering protected fields individually and together, empty content, ordinary fields, and similar names. No schema or generated files change.

File	Description
go/​contract/​signing_test.go	Extracts the field-check helper and adds synthetic-descriptor tests for accepted and rejected content.

_{Review effort: Balanced}