[NickolasBenakis]

Adds hookgres/mcp-events: the server side of webhook delivery for MCP Events (SEP-3415, draft). Stacked on #60.

• handle() answers events/list, events/subscribe and events/unsubscribe. Poll and push answer Unsupported.
• Subscribe checks that a principal is set, the URL is https, the secret is a valid whsec_ and the event name is known. The subscription id is derived from (principal, url, name, arguments).
• The endpoint is verified with a signed verification challenge, cached per (principal, url) and rate-limited per host, or with an allowlist (verify).
• Refresh: TTL grant and clamp, secret rotation that dual-signs for 5 minutes, deliveryStatus.
• emit(name, data, { client }) queues one message per matching subscription, inside the caller's transaction if one is passed. Delivery is Hookgres: Standard Webhooks signatures, X-MCP-Subscription-Id, 5 attempts over about 8 minutes, 410/413 final, no redirects, private addresses blocked at delivery time.
• Guide: docs/guides/mcp-events.md, including what isn't covered yet (cursor replay, gap/terminated envelopes, inputSchema validation).

Verification

• pnpm typecheck, pnpm lint, pnpm test: 364 tests pass, 17 of them in test/mcp-events.test.ts.
• The concurrent-subscribe test fails 3 of 3 runs without the advisory lock (3 endpoints) and passes with it.
• Passes all 36 sender checks in the conformance PR, including delivery after a SIGKILL and restart.

Decision Log

• Each subscription is a Hookgres endpoint in its own schema (hookgres_mcp_events), with the subscription id as tenantId, so webhook-id is unique per subscription.
• Endpoint auto-disable is off (disableEndpointAfterMs: null): disabling fails queued deliveries, while the SEP's suspension pauses them. TTL expiry does the cleanup.
• The hookgres passthrough excludes fetch, because a custom fetch would turn off delivery-time address checks.
• Review fixes: an advisory lock per subscription key, a bounded challenge read, a per-host verification limit, a 4 KB cap on arguments, and deleteExpired() going through deleteEndpoint.

Follow-ups

• Cursor watermarks for durable upstreams, gap and terminated envelopes.
• inputSchema validation of arguments.

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Project	Deployment	Actions	Updated
hookgres	Ready	Preview	Nov 13, 2026 9:30pm UTC