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Export Protocol and mergeCapabilities from client/server package roots (#2501)

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Felix Weinberger 2026-07-17 14:37:31 +01:00 • committed by GitHub
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21
docs/migration/upgrade-to-v2.md
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@ -108,9 +108,8 @@ In addition the codemod:
`completable(schema, cb).optional()` (see
[Standard Schema objects](#standard-schema-objects-raw-shapes-deprecated)); shapes it
cannot invert get an `@mcp-codemod-error` marker.
- Drops `Protocol` / `mergeCapabilities` from `shared/protocol.js` imports, re-exports,
mocks, and dynamic imports — no v2 package exports them — leaving a marker with the
replacement at each site.
- Rewrites `Protocol` / `mergeCapabilities` imports from `shared/protocol.js` to the
client or server package root, like the module's other symbols.
## What the codemod does NOT handle
@ -1444,13 +1443,15 @@ now typed as JSON-compatible objects (nested JSON values) rather than arbitrary
objects. A payload typed `Record<string, unknown>` no longer assigns (`TS2322`) — give
the source a JSON-compatible type or cast at the boundary.
The `Protocol` base class itself is no longer exported (it is internal engine). If you
were reaching into protocol internals — rare, mostly debugging tools —
`client.fallbackRequestHandler` / `server.fallbackRequestHandler` receives every
inbound request that no registered handler matches, before capability gating. Delete
the v1 `shared/protocol.js` import: `Protocol` has no v2 import path. The codemod
drops `Protocol` (and `mergeCapabilities`) from the rewritten import and leaves an
`@mcp-codemod-error` marker at the site explaining the replacement.
The `Protocol` base class and `mergeCapabilities` moved: import them from the
`@modelcontextprotocol/client` or `@modelcontextprotocol/server` package root instead
of `shared/protocol.js`. Most code should not use `Protocol` directly — `Client` and
`Server` are the supported surfaces, and for observing unmatched inbound requests
prefer `client.fallbackRequestHandler` / `server.fallbackRequestHandler`. The codemod
rewrites `Protocol` and `mergeCapabilities` imports to the package root, like the
module's other symbols. One caveat: the client and server packages each bundle their
own compiled copy of the class, so the two roots' `Protocol` exports are distinct
classes — import it from one package consistently within a process.
#### JSON Schema 2020-12 posture (SEP-1613, SEP-2106)