[bokelley]

Fixes #1771, found by the cross-SDK interop matrix (adcontextprotocol/adcp#8679). This is an early, standalone PR into next, because any seller built from the guide hits it.

Problem

A seller on the managed path (ReliableReportingService(subscriptions=SubscriptionOptions(...))) advertised a get_adcp_capabilities that the Python SDK's own client rejects against the 3.3.0-beta.3 schemas. Serving it over MCP also needed wiring the guide never mentions.

Fix

• adcp.principal.
  • optimistic_concurrency: true is now always advertised; the principal runtime enforces expected_configuration_version.
  • reporting_destinations is listed only when the seller's block carries the facts the schema then requires: max_reporting_destinations, reporting_destination_offerings and suspension_interval_seconds. This matches TS, which adds the section only with prepareReportingDestination.
• adcp.supported_versions is advertised on the managed path when the seller doesn't state it (the SDK's served releases, without RCs). Without it, a buyer negotiates down from major_versions and gets "get_principal is unavailable in AdCP 3.1".
• Plain MCP callers. On the managed path, a reporting task with an authenticated caller but no resolved account (a plain ToolContext from serve()) reads the account the request names.
  • This replaces the "Reporting service configuration failed" error.
  • The subscription grant check still refuses an account the caller holds no grant on, and ledger reads stay scoped to the caller's own consumer_id.
  • Outside the managed path, caller resolution is unchanged.
• Seller guide. A new Capabilities and serving subsection lists what the host still supplies:
  • adcp.idempotency, a fact only the seller knows;
  • the destination facts, to accept reporting_destinations;
  • context_factory=auth_context_factory.

Tests (the #1771 repros)

• test_issue_1771_managed_capabilities_pass_the_sdk_response_validation: the managed capabilities, with the seller's idempotency, validate against protocol/get-adcp-capabilities-response.json with zero errors, and include 3.3-beta.3 in supported_versions.
• test_issue_1771_status_is_served_to_a_plain_mcp_caller: get_reporting_status serves subscription_coverage to a plain ToolContext(caller_identity=...).
• The managed capability test is updated for the conditional reporting_destinations.

The managed, service and reliable-reporting suites are green. ruff and mypy are clean.

The reference seller in #1776 (PR 6) carries the same principal fix; this PR lands it on next without waiting for the stack. It also cherry-picks the row-lease test fix from #1767, so the Postgres job is green.

🤖 Generated with Claude Code

[aao-secretariat]

Ladon verdict: Approve

Approve — clean, well-scoped fix for #1771.

Checked: the security-sensitive _managed_caller fallback reads account_id from the request body but is properly guarded — consumer_id comes from the authenticated context, the grant check runs, and ledger reads stay consumer_id-scoped, so multi-tenant isolation holds; unauthenticated callers re-raise fail-closed. advertise_principal's conditional reporting_destinations and the supported_versions injection are correct and tested against the response schema. No public-API/semver, generated-code, forward-compat, or import-layering surface touched. No credentials routed through ctx_metadata. CI gates remain armed.

No blocking findings. No high-risk paths, no gated paths, no author team gate. Falls through to row 9.