# MCP Migration > Diagnose and carry out the migration of an MCP server to the 2026-07-28 specification — the revision that made the transport stateless, formalized OAuth 2.1, and deprecated the logging, sampling, and roots capabilities. Use this skill whenever someone mentions migrating, upgrading, or checking an MCP server against the 2026-07-28 spec; asks whether their MCP server still works, is "ready", or will break; mentions the stateless transport model, Mcp-Session-Id, or OAuth 2.1 for MCP; or is debugging an MCP server that stopped working after a spec or SDK bump. Also use it when someone asks you to review or audit MCP server code for compatibility, even if they don't name the spec date. - Skill: `alpayc/mcp-migration` (Agent Skill, multi-file: 3 files) - Install (CLI): `npx skillmds@latest add alpayc/mcp-migration` - Raw SKILL.md: https://api.skillmd.com/api/skills/alpayc/mcp-migration/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - Author: AlpayC (https://skillmd.com/u/alpayc) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/alpayc/mcp-migration --- # MCP 2026-07-28 migration The 2026-07-28 revision is a refactor, not a version bump. Six things this checker looks for break existing servers: 1. **The transport is stateless.** The `initialize`/`notifications/initialized` handshake and the `Mcp-Session-Id` header are gone from *this* revision. Every request carries its own protocol version and client capabilities in `_meta`. **This does not mean deleting the handshake.** A server "wishing to support both legacy clients … and modern clients **MAY** implement both behaviors" and picks its semantics from how each request opens — so the goal is to *add* the modern path, and retire the legacy one on the schedule your own clients dictate. Removing it for compliance breaks every v1 client for no gain. 2. **OAuth 2.1 is formalized** for remote servers: a protected MCP server acts as an OAuth 2.1 resource server and **MUST** implement RFC 9728 protected-resource metadata. 3. **`logging`, `sampling`, and `roots` are deprecated** — still functional, with a twelve-month minimum window, but new implementations should not adopt them. 4. **The TypeScript SDK moved to v2 under new package names.** `@modelcontextprotocol/sdk` is the v1 line and stops at 1.30.0. v2 ships as `@modelcontextprotocol/server` + `@modelcontextprotocol/client` (plus `/core` and an `/express`, `/fastify` or `/hono` adapter). 5. **The Python SDK moved to v2 under the same package name.** The official PyPI package remains `mcp`, while `mcp.server.fastmcp.FastMCP` becomes `mcp.server.MCPServer`. A `<2` constraint or the old import is a v1 signal. The revision changed more than the checker covers: `server/discover` is now mandatory, all results carry a required `resultType`, the GET stream and `resources/subscribe` are replaced by `subscriptions/listen`, `ping` and `logging/setLevel` are gone, SSE resumability is removed, and `Mcp-Method` / `Mcp-Name` headers are required. **A clean checker run is not a migration.** Read the [changelog](https://modelcontextprotocol.io/specification/2026-07-28/changelog) before declaring a server done. **Do not tell anyone to upgrade `@modelcontextprotocol/sdk` to `^2`.** That package has never published a 2.x — the migration is to the new package names above. There *is* an official codemod, and it is a separate package: ```bash npx @modelcontextprotocol/codemod@latest v1-to-v2 . ``` **That codemod is TypeScript-only.** Do not reach for it, or for a package rename, when the project is Go — which is the next thing on this list. 6. **The Go SDK moved by a minor, on the same module path.** `github.com/modelcontextprotocol/go-sdk` speaks 2026-07-28 from **v1.7.0**; v1.6.1 is the last release on 2025-11-25. There is no `go-sdk/v2` — the module proxy 404s it — so never advise an import-path change or a 2.x. `github.com/mark3labs/mcp-go` crossed at its own **v1.0.0**. And for the official SDK the upgrade is only half of it: the streamable HTTP transport serves the revision **only** with `StreamableHTTPOptions.Stateless = true`. Left unset, clients negotiate down to 2025-11-25. A stdio server needs no such flag. C# moved differently again — a 2.x major of the `ModelContextProtocol` packages. Check the actual package before advising a version. Work in this order: diagnose, triage, remediate, re-verify. The diagnosis step is scripted so it gives the same answer every time — resist the urge to skip it and eyeball the code, because the rule ids it emits are what the remediation guidance keys off. ## Step 1 — Diagnose Run the bundled checker. It needs nothing but Node — no install step. ```bash # Scan a repository (the richest signal; this is the one to start with) node scripts/mcpcheck.mjs --source /path/to/the/server # Probe a running endpoint node scripts/mcpcheck.mjs https://example.com/mcp # Probe a local dev server (disables the SSRF guard) node scripts/mcpcheck.mjs --local http://localhost:3000/mcp # Machine-readable, if you want to process the findings node scripts/mcpcheck.mjs --source . --json ``` Run **both** the source scan and a live probe when a server is actually running. They see different things and neither is a superset of the other: | | Source scan | Live probe | |---|---|---| | Sees | code, `package.json`, Python manifests, `Cargo.toml`, `go.mod`, `file:line` | both protocol eras, headers, advertised capabilities, OAuth posture | | Finds | MCP001–005, **MCP007/MCP009/MCP010/MCP011** (SDK lines) | MCP001–006, **MCP008**, MCP101/102 | | Needs | a checkout | a reachable endpoint | Exit codes: `0` no critical findings · `1` at least one critical · `2` inconclusive (unreachable, blocked, or nothing to scan). ## Step 2 — Triage before you touch anything The source scan is **regex-based**. It greps for the patterns that correlate with each hazard, which means it reports signals, not proof. Two consequences worth internalising before you start editing: - **False positives are normal.** A file that merely mentions `initialize` in a comment, or a variable coincidentally named `sessionId`, will be flagged. The checker's own source flags itself for all five code rules, because the rules file contains the very strings it searches for. - **A clean scan is not a guarantee.** Session state can be spelled in ways the patterns don't catch — a `Map` keyed by something the code calls `clientKey`, for instance. So read each finding at its `file:line`, decide whether it is real, and say so explicitly before changing anything. A short triage table is a good artefact to produce here: rule, location, real or false positive, and why. Findings are graded: 100 minus 30 per critical and 15 per warning. `info` findings (`MCP1xx`) cost **nothing** — they record compatibility choices the spec permits, such as a dual-era server still answering `initialize`, so that a report can distinguish "still accepts legacy" from "only accepts legacy". Treat the letter grade as a headline for humans, not as the thing to optimize. Fixing the criticals matters far more than the score moving from D to B. ## Step 3 — Remediate Read `references/remediation.md` for the per-rule guidance. It is organised by rule id, so go straight to the sections your findings named rather than reading it end to end. Sequence matters. Do it in this order, because later steps depend on earlier ones: 1. **The SDK finding first** — MCP007 for TypeScript, MCP009 for Python, MCP010 for Rust, MCP011 for Go. Doing this before the code changes means you refactor against the API you are going to keep, instead of refactoring twice. For MCP007, move to the v2 packages and run the TypeScript codemod. For MCP009, move `mcp` to 2.x and follow the official Python migration guide (`FastMCP` → `MCPServer` is the first import change). For MCP010, upgrade to `rmcp` 3.x or `rust-mcp-sdk` 2.x (both speak spec 2026-07-28). For `tower-mcp`, enable the `protocol-2026-07-28` feature. For MCP011, `go get github.com/modelcontextprotocol/go-sdk@v1.7.0` — the module path is unchanged, so nothing imports differently — and if you serve streamable HTTP, set `StreamableHTTPOptions.Stateless: true`, because the upgrade alone leaves clients negotiating down to 2025-11-25. The remaining errors point at the architectural work. 2. **MCP002 (session state)** — the deepest change, and the one most likely to surface hidden design assumptions. 3. **MCP001 (legacy-only)** — add the modern request path and `server/discover`; largely mechanical once state is gone. Keep the legacy handshake serving alongside it unless you have decided, as a product call, to drop v1 clients. 4. **MCP003/004/005 (deprecated capabilities)** — removals, each one localised. These are `warning`, not `critical`, and the deprecation window is at least twelve months. If the migration is already large, deferring them is a defensible call — say so rather than silently skipping them. 4. **MCP006 (OAuth posture)** — deployment-facing; independent of the rest. After each step, re-run the scan. Watching one rule at a time go quiet is a much better signal than a single run at the end where you can't tell which change fixed what. ## Step 4 — Verify Re-run both the source scan and, if a server is running, the live probe. Then check the things the scanner structurally cannot see: - Does the server still behave correctly when two consecutive requests land on **different instances**? This is the real test of statelessness, and no static scan can answer it. Run two instances behind anything that round-robins, or restart the process between requests. - Do the tests still pass, and do they still cover the paths you changed? - If you removed `sampling`, has the model-calling responsibility actually moved to the client, or has it just been deleted? ## Reporting back Close with a short summary in this shape — it is what someone reviewing the migration needs, and nothing more: ``` ## Migration summary - Before: — findings ( critical) - After: — findings ( critical) ## Changed - : ## Dismissed as false positives - at : ## Still open - ``` The "dismissed" section is the one people skip and later regret. If you decided a finding was noise, the reasoning needs to survive past the end of the session. ## A note on the spec itself The findings link to the canonical spec at `https://modelcontextprotocol.io/specification/2026-07-28`. When a fix involves an exact API signature or a precise header name, check it there rather than trusting a remembered detail — this skill describes the shape of each change, not a frozen copy of the specification.