[bokelley]

Summary

Backport of #3322 to 15.9.x for the latest dist-tag. Fixes #3320.

Hosted compliance always runs comply() with an external schema root for the pinned release. The served-release rule from 15.9.2 (#3287) let that root win over the agent's echoed adcp_version, so a 3.0 target graded a conformant 3.2 get_adcp_capabilities response against 3.0. Every storyboard response_schema check on that task failed (52 steps across 43 storyboards in the 3.0.27 suite), and discovery raised spurious capabilities_response_schema_invalid notices (worked around in adcontextprotocol/adcp#8264).

For get_adcp_capabilities only, the storyboard response_schema check, discoverAgentProfile and TaskExecutor now validate against the echoed release when all of these hold:

• the echo is the pin's major;
• it is listed in the response's own adcp.supported_versions;
• it has a schema root: one supplied through servedReleaseSchemaRoots, an external root registered for it, or the SDK's bundled schemas.

This holds whether or not an external root is active for the pin. Otherwise validation stays strictly on the pin. Other tasks, storyboard selection, the run's adcp_version and grading are unchanged.

There is a new servedReleaseSchemaRoots option (version → schema root) on comply(), runStoryboard() and runStoryboardStep(), and a withServedReleaseSchemaRoots(roots, fn) helper exported from @adcp/sdk/testing. Hosted callers use them to supply their own roots for echoed releases. Those roots are activated only for this capabilities validation. See #3322 for the full design notes.

Differences from #3322

• TaskExecutor: 15.9.x has no identity-3.3 validation branch, so the extracted validateResponseSchemaAgainst calls validateIncomingResponse directly. That conflict is the only one. Everything else cherry-picked cleanly from both fix(testing): validate capabilities against the echoed release under an external pin root #3322 commits, which are squashed here.
• The changeset is patch, so this ships as the next 15.9.x patch (15.9.5).

Test plan

• test/lib/capabilities-echoed-release-hosted-validation.test.js (24 tests). Against unpatched 15.9.x, 17 fail; the 7 that pass are the pin-fallback guards. With the fix all pass, including the end-to-end comply() run in the hosted shape (version: '3.0.25' plus an external 3.0 schemaRoot).
• test/lib/capabilities-served-release-validation.test.js updated for the new supported_versions condition (17 tests, all pass).
• npm run typecheck, build:lib
• Full npm run test:node locally. Every suite passes except the Postgres-backed ones (ECONNREFUSED, no local database), which CI covers.

🤖 Generated with Claude Code

[aao-secretariat]

Ladon verdict: Approve

Approve — clean backport of #3322 to 15.9.x, fixing #3320.

The #3287 served-release rule let the pin's external schema root win over the agent's echoed adcp_version, causing hosted compliance to grade a 3.2 capabilities response against a 3.0 pin (52 failed steps + spurious notices). The fix drops external-root-wins for get_adcp_capabilities only, selecting the echoed release when same-major + in supported_versions + a schema root exists, scoped via withServedValidationVersion.

Checked:

• Cache safety: withServedValidationVersion (schema-loader.ts:744) merges the served root without clearStatesForBundle; safe because states/schemaRefValidators are keyed by stateCacheKey(bundleKey, root) — distinct root = distinct entry, no stale reuse.
• validateResponseSchemaAgainst (TaskExecutor.ts:153) is a verbatim extraction; only version source + scoping change.
• isExternalResponseSchemaAuthoritative widening (validations.ts:691) is additive; both call sites pass a full ValidationContext.
• Tests prove the correct root is selected over the bundled default and that served roots never leak across tasks; live-seller end-to-end comply() covered.
• Changeset present; patch justified for a maintenance-line backport that only selects validation version (no wire-shape change). Witness-not-translator preserved.

No blocking findings, no medium findings, no escalation triggers. gated_paths false, high_risk false, no team gate. Falls through to row 9.