chore: enter beta prerelease mode (#2402)

docs/migration/index.md

@@ -19,7 +19,7 @@ v2 packages (`@modelcontextprotocol/client`, `@modelcontextprotocol/server`, …
 Start by running the codemod:
 
 ```bash
-npx @modelcontextprotocol/codemod@alpha v1-to-v2 .
+npx @modelcontextprotocol/codemod@beta v1-to-v2 .
 ```
 
 Run it at the package root (`.`) — real projects import the SDK from `test/`,

docs/migration/support-2026-07-28.md

@@ -614,9 +614,10 @@ Task methods are excluded from the typed method maps: `RequestMethod` / `Request
 `ctx.mcpReq.send()`, `setRequestHandler()`, `setNotificationHandler()` reject task
 methods at compile time. `ResultTypeMap['tools/call']` is plain `CallToolResult` (no
 `| CreateTaskResult`); same for `sampling/createMessage` and `elicitation/create`.
-(The published `2.0.0-alpha.3` typings predate this exclusion — there the typed maps
-still carry the `tasks/*` entries and the `CreateTaskResult` unions; narrow with the
-`isCallToolResult` guard until the next published alpha.) Where
+(Typings published before `2.0.0-alpha.4` predate this exclusion: there the typed
+maps still carry the `tasks/*` entries and the `CreateTaskResult` unions; narrow with
+the `isCallToolResult` guard if you are pinned to one of those alphas. `2.0.0-alpha.4`
+and later include the exclusion.) Where
 task interop is genuinely required, use the explicit-schema custom-method form
 (`request({ method: 'tasks/get', params }, GetTaskResultSchema)`). Inbound `tasks/*`
 requests → `-32601`.

docs/migration/upgrade-to-v2.md

@@ -19,7 +19,7 @@ If you are already on v2 and want to adopt the **2026-07-28 protocol revision**,
    only; CommonJS callers must use dynamic `import()`.
 2. **Run the codemod.**
     ```bash
-    npx @modelcontextprotocol/codemod@alpha v1-to-v2 .
+    npx @modelcontextprotocol/codemod@beta v1-to-v2 .
     ```
     Run it at the **package root** (`.`), not `./src` — it also rewrites `package.json`,
     and real projects import the SDK from `test/`, `scripts/`, and fixtures too.
@@ -233,15 +233,14 @@ for the literal instead; and the emitted quote style differs from v1, so a
 quote-anchored pattern misses silently — match either quote. v2 also ships ESM only:
 `/dist/cjs/` ↔ `/dist/esm/` flavor-pair path swaps have no equivalent.
 
-#### Registry availability during the alpha
+#### Registry availability during the beta
 
-All v2 packages are published on the public npm registry. Two notes for the alpha
+All v2 packages are published on the public npm registry. Two notes for the beta
 window:
 
-- The packages do not share one version number — at the time of writing
-  `@modelcontextprotocol/core` rides a lower prerelease than its siblings. The
-  codemod writes ranges that match what is published, so prefer its manifest output
-  over hand-pinning every package to the same tag.
+- As of `2.0.0-beta.1` all v2 packages share one version number (earlier alphas
+  did not). The codemod writes ranges that match what is published, so prefer its
+  manifest output over hand-pinning every package.
 - Environments that resolve through a corporate or private registry mirror may not
   have synced the newer scoped packages yet (the symptom is "not found" for a package
   that exists on npmjs.org). Point the install at the public registry
@@ -1000,8 +999,9 @@ the third argument — `new SdkHttpError(SdkErrorCode.ClientHttpNotImplemented,
 (carries `data.requiredCapabilities`) are new typed `ProtocolError` subclasses.
 `resources/read` for an unknown URI now answers `-32602` on every protocol revision
 (v1.x already emitted `-32602`; an interim `-32002` from earlier v2 alphas is mapped at
-the encode seam — published `2.0.0-alpha.3` predates the mapping and still emits
-`-32002` on the wire, so accept both until the next published alpha). The encode-seam mapping applies to **your own throws too**: a handler
+the encode seam — `2.0.0-alpha.3` and earlier predate the mapping and still emit
+`-32002` on the wire, so accept both if peers may run those alphas; `2.0.0-alpha.4`
+and later emit `-32602`). The encode-seam mapping applies to **your own throws too**: a handler
 that deliberately throws `ProtocolError(ProtocolErrorCode.ResourceNotFound, …)` reaches
 peers as `-32602` — a server can no longer emit `-32002` on the wire.
 `ProtocolErrorCode.ResourceNotFound` (`-32002`) stays importable as
@@ -1373,12 +1373,12 @@ The role-aggregate unions (`ClientRequest`, `ServerResult`, `ServerRequest`,
 (`RequestMethod`, `RequestTypeMap`, `ResultTypeMap`, `NotificationTypeMap`) no longer
 include task vocabulary; the deprecated `Task*` types remain importable on their own.
 (One published-alpha qualification, like the `-32002` note in [Errors](#errors): the
-`2.0.0-alpha.3` typings predate this — the typed maps there still carry the `tasks/*`
-entries, and `ResultTypeMap['tools/call']` still unions `CreateTaskResult`, so a
-`client.request({ method: 'tools/call', … })` result does not assign to
-`Promise<CallToolResult>`. Narrow with the `isCallToolResult` guard until the next
-published alpha — the guard is the recommended discrimination tool anyway, per the next
-paragraph.)
+`2.0.0-alpha.3` and earlier typings predate this — the typed maps there still carry the
+`tasks/*` entries, and `ResultTypeMap['tools/call']` still unions `CreateTaskResult`, so
+a `client.request({ method: 'tools/call', … })` result does not assign to
+`Promise<CallToolResult>`. If pinned to those alphas, narrow with the
+`isCallToolResult` guard — the recommended discrimination tool anyway, per the next
+paragraph; `2.0.0-alpha.4` and later are unaffected.)
 
 **Discriminating result shapes: use guards, not the `in` operator.** The v2
 zod-inferred result types are passthrough objects — every union member carries an index