Evidence record / hermes-agent
A dated record of one change, kept so the writing that cites it can be checked. Compiled from the sources listed below by the research run, not written for reading. The judgment lives in the issues that cite it, below.
2026-08-17-hermes-agent-mcp-servers-with-no-handshake-now-connect-the-2026-07-28-stateless
MCP servers with no handshake now connect: the 2026-07-28 stateless protocol.
A _negotiate_session() choke point on all four transport call sites (stdio, SSE, new HTTP, legacy HTTP) implements a per-server protocol key: auto (default) tries the legacy handshake first and falls back to server/discover when the server rejects it as modern-only (-32022/-32601, classified structurally then by substring, deliberately not by isinstance on SDK exception types); stateless probes discover-first; legacy disables the fallback. Handshake-first auto means zero extra round-trips and zero behaviour change for the existing fleet. Alongside it: SEP-2549 ttlMs/cacheScope from tools/list are now bound to the lazy-startup schema cache, so TTL'd entries expire and force a live re-probe while hint-less pre-2026 entries keep never-expires; SEP-837 declares application_type: native in OAuth client metadata; RFC 9207 iss validation and issuer-keyed credentials were verified already native in SDK 2.0 rather than reimplemented. SamplingHandler is marked upstream-deprecated on a 12-month window -- functional, but closed to new capability.
Channel: tagged-release. Ancestry: merge_commit_sha 382060f02277c6404d4f0f1ff4df1f5c974a26b8; compare/382060f0...v2026.8.16.2 -> status=ahead, ahead_by=57, behind_by=0 (ancestor of stable tag v2026.8.16.2).
Operator consequence: Nothing to do for existing servers -- auto mode is handshake-first by design. Do act on two things: if you run an MCP server that caches tool lists, you can now publish ttlMs and Hermes will honour it, and if you built anything on MCP sampling, start planning off it inside twelve months.
Receipt
Finding metadata
Run: 2026-08-17-weekly-digest-2026-08-10_2026-08-17-frontier-v0
Finding ID: 2026-08-17-hermes-agent-mcp-servers-with-no-handshake-now-connect-the-2026-07-28-stateless
Source links
Primary links, including exact changelog lines when available.
Versioned source: run artifact