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MCP 2026-07-28 Final Spec: Stateless Protocol Drops Sessions and Handshake

Abhishek GautamJuly 28, 202612 min read

MCP 2026-07-28 Final Spec: Stateless Protocol Drops Sessions and Handshake

Quick summary

The largest MCP revision since launch goes live July 28, 2026. The initialize handshake and Mcp-Session-Id are gone — every request is self-contained, routable behind a round-robin load balancer, and hardened for enterprise OAuth.

What Changed in MCP 2026-07-28

MCP 2026-07-28 is not a patch release. Six Specification Enhancement Proposals (SEPs) work together to remove protocol-level state, completing the transport roadmap the MCP blog outlined in December 2025.

Area	2025-11-25 behavior	2026-07-28 behavior
Connection setup	Mandatory `initialize` handshake before any tool call	No handshake; version and capabilities in `_meta` on every request
Session routing	`Mcp-Session-Id` pins client to one server instance	No protocol session; any instance can serve any request
Server discovery	Capabilities exchanged once at init	Optional `server/discover` RPC when clients need upfront metadata
Server-to-client prompts	SSE stream held open during elicitation	Multi Round-Trip Requests (MRTR) via `InputRequiredResult` payloads
Tool schemas	Constrained JSON Schema subset	Full JSON Schema 2020-12 for `inputSchema` and `outputSchema`
Long-running work	Experimental Tasks in core spec	Tasks graduates to an official extension with a new lifecycle
Interactive UI	Not standardized	MCP Apps extension — server-rendered HTML in sandboxed iframes

The practical ops win: a remote MCP server that previously needed sticky sessions, a Redis session store, and body inspection at the API gateway can route on Mcp-Method and Mcp-Name headers and cache tools/list responses for as long as the server's ttlMs permits.

How a Tool Call Works Without Sessions

Under 2025-11-25 Streamable HTTP, a client first sent POST /mcp with an initialize method and protocolVersion: 2025-11-25. The server responded with an Mcp-Session-Id header that every subsequent request had to carry, pinning traffic to the instance that issued it.

Under 2026-07-28, the same tools/call is a single self-contained POST /mcp with headers MCP-Protocol-Version: 2026-07-28, Mcp-Method: tools/call, and Mcp-Name: search, plus a JSON body carrying tools/call params and client info in _meta. Any server instance can handle it — no session header required.

SEP-2575 removes the initialization handshake. Protocol version, client info, and client capabilities travel in _meta per request instead of being negotiated once. SEP-2567 removes Mcp-Session-Id and protocol-level sessions entirely.

SEP-2243 requires Mcp-Method and Mcp-Name headers on Streamable HTTP so load balancers and rate limiters can route without parsing JSON bodies. Servers must reject requests where headers and body disagree.

Stateless Protocol, Stateful Applications

Removing protocol sessions does not mean your MCP server cannot hold state. The spec explicitly recommends the pattern HTTP APIs have used for decades: mint an explicit handle from a tool (basket_id, browser_id, workflow_id) and have the model pass it back as a normal tool argument on later calls.

That pattern is often more capable than hidden session state. The model can compose handles across tools, reason about them, and pass them between agent steps — something opaque transport metadata never allowed cleanly.

If you built session affinity layers, custom auth shims, or homegrown trace propagation to compensate for 2025-era MCP limitations, those become technical debt with a countdown once clients adopt 2026-07-28.

Multi Round-Trip Requests and Elicitation

Stateless MCP still needs server-to-client interaction mid-call — for example, asking a user to confirm a destructive action. Two SEPs rebuild that flow without a persistent SSE connection.

SEP-2260 now requires that server-initiated requests only fire while the server is actively processing a client request. A user is never prompted out of nowhere; every elicitation traces to something the user or their agent started.

SEP-2322 (Multi Round-Trip Requests) delivers prompts via an InputRequiredResult instead of holding an SSE stream open. The server returns structured input requests plus a requestState blob; the client gathers answers and re-issues the original call with inputResponses. Any server instance can pick up the retry because everything needed is in the payload.

Extensions: MCP Apps and Tasks

SEP-2133 formalizes how extensions work: reverse-DNS IDs, capability negotiation via an extensions map, separate ext-* repositories, and an Extensions Track in the SEP process.

Two official extensions ship with this release:

MCP Apps (SEP-1865): Servers can ship interactive HTML UIs that hosts render in sandboxed iframes. Tools declare UI templates ahead of time so hosts can prefetch, cache, and security-review before execution. UI actions route through the same JSON-RPC audit path as direct tool calls.

Tasks extension: Tasks were experimental in 2025-11-25. Production feedback pushed them into an extension with a stateless-friendly lifecycle: a server can answer tools/call with a task handle; clients drive progress via tasks/get, tasks/update, and tasks/cancel. tasks/list is removed because it cannot be scoped safely without sessions. Anyone who shipped against the experimental Tasks API must migrate.

Authorization Hardening for Enterprise

Six SEPs align MCP authorization with how OAuth 2.0 and OpenID Connect are deployed in production:

SEP	Change
SEP-2468	Clients must validate `iss` on authorization responses (RFC 9207 mix-up mitigation)
SEP-837	Clients declare OpenID Connect `application_type` during Dynamic Client Registration
SEP-2352	Registered credentials bind to the authorization server `issuer`; re-register on resource migration
SEP-2207	Documented refresh-token request patterns for OIDC-style authorization servers
SEP-2350	Clarified scope accumulation during step-up
SEP-2351	Clarified `.well-known` discovery suffix behavior

Separately, the Enterprise-Managed Authorization (EMA) extension reached stable status on the MCP blog — enabling centralized OAuth for MCP servers so end users access connected tools through a single enterprise login. Anthropic, Microsoft, and Okta are among early adopters.

For teams shipping agents in EU markets, stateless MCP plus auditable OAuth flows align with Article 50 transparency obligations taking effect August 2, 2026.

Deprecated Core Features and Schema Upgrades

SEP-2577 introduces a formal feature lifecycle (Active → Deprecated → Removed, minimum twelve months between deprecation and earliest removal). Three core features are deprecated in this release:

Deprecated	Replacement
Roots	Tool parameters, resource URIs, or server configuration
Sampling	Direct integration with LLM provider APIs
Logging	`stderr` on stdio; OpenTelemetry for structured observability

These are annotation-only deprecations — methods still work in 2026-07-28 and for twelve months after.

SEP-2106 lifts tool inputSchema and outputSchema to full JSON Schema 2020-12, enabling oneOf, anyOf, allOf, conditionals, and $ref/$defs. Implementations must not auto-dereference external $ref URIs and should bound validation depth and time.

SEP-2164 changes missing-resource errors from MCP-custom -32002 to JSON-RPC standard -32602 Invalid Params. Update client error matchers accordingly.

SEP-2549 adds ttlMs and cacheScope on list and resource-read results (HTTP Cache-Control modeled). SEP-414 documents W3C Trace Context keys (traceparent, tracestate, baggage) in _meta for OpenTelemetry correlation across gateways and SDKs.

Our Analysis: What Platform Teams Should Do This Week

1. Inventory sessionful deployments. Any MCP server using sticky sessions, shared Redis for Mcp-Session-Id, or gateway rules that parse JSON bodies for routing is on the migration path. The TypeScript SDK v2 documents createMcpHandler with legacy: 'stateless' for dual-era serving and isLegacyRequest() routing for gradual cutover.

2. Treat OAuth as infrastructure, not an MCP afterthought. The 2025 production blocker was auth — which agent can read Slack for user A but not user B. 2026-07-28 puts agent identity in the standard IAM stack. Security teams can audit and revoke MCP clients like any other OAuth application.

3. Plan explicit-handle tool design. Teams that relied on hidden session state for multi-step workflows should refactor tools to return visible IDs the model threads forward. This pairs well with programmatic tool calling and agent orchestration patterns.

4. Do not conflate MCP adoption stats with spec maturity. The March MCP guide covered ecosystem scale (97M+ monthly SDK downloads per Anthropic's December 2025 ecosystem update). Today's spec change is about how you deploy at scale — not whether to adopt MCP at all.

5. Watch Tasks and MCP Apps separately. Extensions version independently. You can adopt stateless transport in August and defer MCP Apps until your host client supports the extension.

Enterprise Migration Checklist

Week 1 — Discovery

[ ] List every production MCP server and whether it uses Mcp-Session-Id or sticky routing
[ ] Identify clients still sending initialize on every connection
[ ] Map OAuth flows: does your authorization server emit iss on responses?

Week 2 — SDK and gateway

[ ] Upgrade to SDK versions supporting 2026-07-28 (check official TypeScript/Python tier-1 releases)
[ ] Configure load balancers to route on Mcp-Method / Mcp-Name headers
[ ] Enable W3C Trace Context propagation to your OpenTelemetry backend

Week 3 — Application logic

[ ] Refactor multi-step tools to explicit-handle pattern
[ ] Migrate experimental Tasks integrations to the Tasks extension lifecycle
[ ] Update client error handling: -32002 → -32602 for missing resources

Week 4 — Security and compliance

[ ] Validate Dynamic Client Registration application_type for CLI and desktop clients
[ ] Evaluate Enterprise-Managed Authorization if users hit repeated consent prompts
[ ] Document agent audit trails for EU Article 50 chatbot disclosure requirements

Key Takeaways

MCP 2026-07-28 publishes July 28, 2026 — RC locked May 21; largest protocol revision since launch with breaking changes from 2025-11-25.
Stateless core: no initialize handshake (SEP-2575), no Mcp-Session-Id (SEP-2567); round-robin load balancing without sticky sessions.
New headers: MCP-Protocol-Version, Mcp-Method, Mcp-Name; client capabilities in _meta on every request.
Extensions: MCP Apps (sandboxed server UI) and Tasks (new stateless lifecycle); Roots, Sampling, Logging deprecated.
OAuth hardened: iss validation, application_type on DCR, issuer-bound credentials; EMA extension stable for enterprise SSO.
For developers: Audit sessionful MCP servers this week — migrate to explicit-handle tools and header-based routing before Q4 client upgrades.
What to watch: Tier 1 SDK releases through September 2026; host clients (Cursor, VS Code, Claude Desktop) announcing 2026-07-28 default support.

Sources

FAQ

Frequently Asked Questions

What is the MCP 2026-07-28 specification?

MCP 2026-07-28 is the July 28, 2026 revision of the Model Context Protocol — the largest update since launch. It makes MCP stateless at the protocol layer by removing the initialize handshake and Mcp-Session-Id sessions, adds MCP Apps and a redesigned Tasks extension, hardens OAuth authorization, and adopts JSON Schema 2020-12 for tool definitions. It is a breaking change from the 2025-11-25 revision.

Does MCP 2026-07-28 remove all session state?

No. MCP removes protocol-level sessions, not application state. Servers that need state across tool calls should mint explicit handles (such as a basket_id or workflow_id) from a tool and have the model pass them back as ordinary arguments on later calls — the same pattern HTTP APIs use. SEP-2567 documents this explicit-handle pattern.

When do I need to migrate my MCP server to 2026-07-28?

The final spec publishes July 28, 2026. Deprecated features from 2025-11-25 continue working for at least twelve months under the new lifecycle policy. Migrate soon if you rely on sticky sessions, shared session stores, the experimental Tasks API, or client error code -32002 for missing resources. Tier 1 official SDKs are expected to ship 2026-07-28 support within the ten-week validation window that began when the RC locked on May 21, 2026.

How does MCP 2026-07-28 improve enterprise deployment?

Stateless requests can route through ordinary round-robin load balancers using Mcp-Method and Mcp-Name headers without sticky sessions. OAuth is hardened with iss validation, application_type on Dynamic Client Registration, and issuer-bound credentials. The Enterprise-Managed Authorization extension is stable for centralized SSO. OpenTelemetry trace context is standardized in _meta for audit trails.

What MCP features are deprecated in 2026-07-28?

Roots, Sampling, and Logging core features are deprecated under SEP-2577 with at least a twelve-month window before removal. Roots should be replaced by tool parameters or resource URIs. Sampling should be replaced by direct LLM API integration. Logging should use stderr on stdio transports or OpenTelemetry elsewhere. The methods still work in this release.

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