[v2] Мonorepo, `sdk-client`, `sdk-server`, `sdk-core` package split #1279

KKonstantinov · 2025-12-10T08:03:04Z

Proof of Concept: v2 monorepo, package split

Motivation and Context

v1 of the sdk shipped both client and server in the same package, introducing extra dependencies to users who have a single concern (client or server only). Client and server packages are now split, depending on a shared core package.

Additionally, v1 exported all files as the public API of the SDK, limiting the SDK ability to iterate internally while keeping backwards compatibility. Barrel files are now introduced as the single entrypoint to the SDK and defining the public API of the SDK.

How Has This Been Tested?

Unit, integration tests

Breaking Changes

v2

Types of changes

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to change)
Documentation update

Checklist

I have read the MCP Documentation
My code follows the repository's style guidelines
New and existing tests pass locally
I have added appropriate error handling
I have added or updated documentation as needed

Additional context

pkg-pr-new · 2025-12-10T08:03:47Z

Open in StackBlitz

pnpm add https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/sdk-client@1279

pnpm add https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/sdk-server@1279

commit: b532047

felixweinberger

Is there a way we can break this PR up somehow so that this is more reviewable? E.g. with using git mv to preserve history and provenance of files? As it is it'll be quite hard to verify correctness of the split.

… into feature/v2-monorepo-setup

KKonstantinov · 2025-12-12T13:11:12Z

EDITs:

Provenance / history retained (except 3-4 files, will review them and bring it to them as well)
Dropped Node v18
Dropped CommonJS (ESM only)
Removed tsgo - that's running TS v7 - switched to tsc for our current typescript version
Bumped the ts version
Added eslint import rules to tidy up imports
cleaned-up package.json files - client-sdk and server-sdk ship with the minimum required dependencies (as opposed to v1, which shipped server deps if you were only interested in the client and vice versa
introduce catalogs for reusing dep versions
bundling tool change - tsdown as per @mattzcarey
... might be more, will add as quite tired after this one :)

TODOs still:

*.md - readme updates
test(18) check - no code change, repository config -> needs to be removed as required check from branch rulesets, and replaced with test(20)

… into feature/v2-monorepo-setup

…typescript-sdk into feature/v2-monorepo-setup

… into feature/v2-monorepo-setup

mattzcarey · 2025-12-17T13:43:13Z

I would push against removing tsgo from the check script. As we move to a monorepo it will be much much faster than tsc.

mattzcarey · 2025-12-17T13:49:52Z

packages/server/tsdown.config.ts

+export default defineConfig({
+    // 1. Entry Points
+    //    Directly matches package.json include/exclude globs
+    entry: ['src/**/*.ts', '!src/**/*.test.ts', '!src/__mocks__/**', '!src/examples/**'],


this should just be the root index.ts

mattzcarey · 2025-12-17T13:51:05Z

package.json

+        "node": ">=20",
+        "pnpm": ">=10.24.0"
    },
+    "packageManager": "[email protected]",


I dont hate this move. I like that we wont have to use turborepo or nx, at least initially. But it should be noted this will be a big dev ex change

Yes, we would need to update the README and the contribution guidelines

mattzcarey · 2025-12-17T13:51:49Z

vitest.workspace.js

@@ -0,0 +1,3 @@
+import { defineWorkspace } from 'vitest/config';
+
+export default defineWorkspace(['packages/**/vitest.config.js']);


I did not know this was a thing lol. why do we need this?

Basically different configs if we need to - https://v2.vitest.dev/guide/workspace

mattzcarey · 2025-12-17T13:54:57Z

packages/client/tsdown.config.ts

+export default defineConfig({
+    // 1. Entry Points
+    //    Directly matches package.json include/exclude globs
+    entry: ['src/**/*.ts', '!src/**/*.test.ts', '!src/__mocks__/**', '!src/examples/**'],


this should just be the index.ts also. Note there are other options: this config can also live in the package.json for each package or can be defined at root and imported here.

Tks, will update

mattzcarey · 2025-12-17T13:55:55Z

packages/core/src/index.ts

+export * from './validation/ajv-provider.js';
+export * from './validation/cfworker-provider.js';


these have to be exported in the package.json. otherwise they will both get included on import.

really we should use shims for this in the package.json and not have separate modules. similarly to this. mswjs/msw#2640

mattzcarey · 2025-12-17T13:57:53Z

packages/core/tsconfig.build.json

+        "rootDir": "./src"
+    },
+    "include": ["./"],
+    "exclude": ["dist", "node_modules", "test"]


we should not need seperate build tsconfigs. that is the beauty of tsdown.

Yes, this is leftover from before I added tsdown, will remove, tks

mattzcarey · 2025-12-17T13:58:34Z

packages/core/tsconfig.json

+            "@modelcontextprotocol/sdk-client": ["node_modules/@modelcontextprotocol/sdk-client/src/index.ts"],
+            "@modelcontextprotocol/sdk-server": ["node_modules/@modelcontextprotocol/sdk-server/src/index.ts"],


are these used? that would make for a weird dependency structure?

Its a leftover thing, tks, will clean up

mattzcarey · 2025-12-17T14:00:19Z

packages/examples/client/package.json

its weird that these examples live in packages. maybe put examples on the top level?

I think going forward, it'd be good to treat examples as real end-user scenarios, them being in a package and importing our real packages simulates that quite well - let's discuss

mattzcarey · 2025-12-17T14:01:29Z

packages/integration/package.json

also feels pretty weird that this is a package. imo these tests should live in either client or server depending on what they are testing.

you could have some test helpers but they would live in common.

Yes, this one felt weird to me as well and haven't spent a lot of time thinking about it.

Let's think how we want it and refactor in a separate PR.

proof of concept: v2 monorepo, package split

be2e264

KKonstantinov added 4 commits December 10, 2025 10:31

barrel exports, imports

cfa0615

add vitest config

8922ada

clean up

ebeacac

save commit

d372e75

KKonstantinov added the v2 Ideas, requests and plans for v2 of the SDK which will incorporate major changes and fixes label Dec 10, 2025

KKonstantinov self-assigned this Dec 10, 2025

eslint, vitest setup; successful shared/ tests pass

4db8d1b

felixweinberger reviewed Dec 10, 2025

View reviewed changes

KKonstantinov added 15 commits December 12, 2025 10:12

save commit; successful tests; successful checks

617f14e

Merge branch 'main' of github.com:modelcontextprotocol/typescript-sdk…

0446560

… into feature/v2-monorepo-setup

save commit

a089abc

save commit

647e5f0

lint fix

6c0818f

main.yml fix

ea354fc

main.yml fix

951a234

add packageManager in package.json

a7e60b9

typecheck fix, test main.yml fix

9d1e86c

check:all fix

236e934

import fixes

f20be12

test fix

c9fcc39

imports fix

f939900

imports fix

d9cd7fe

import sorting

f057363

KKonstantinov added this to the v2 milestone Dec 12, 2025

KKonstantinov linked an issue Dec 12, 2025 that may be closed by this pull request

SDK V2 #809

Open

23 tasks

KKonstantinov added 2 commits December 12, 2025 15:35

clean up

c3be975

pr-pkg-new update

c3353c9

KKonstantinov changed the title ~~[v2] Proof of Concept: monorepo, package split~~ [v2] Мonorepo, sdk-client, sdk-server, sdk-core package split Dec 14, 2025

KKonstantinov added 9 commits December 15, 2025 17:49

merge commit

2020e7f

ajv fix on nodenext

c21a566

Merge branch 'main' of github.com:modelcontextprotocol/typescript-sdk…

d957fc0

… into feature/v2-monorepo-setup

clean up package.json files

7e92ba4

add tsdown

7bd609c

update pnpm lock

15b27d0

eslint config

ea2fc03

merge commit

5662909

imports fix

b5390d4

KKonstantinov requested a review from mattzcarey December 15, 2025 18:26

KKonstantinov and others added 4 commits December 15, 2025 20:39

Merge branch 'main' into feature/v2-monorepo-setup

228097e

remove deprecated tseslint.config

76a86a5

Merge branch 'feature/v2-monorepo-setup' of github.com:KKonstantinov/…

2dee387

…typescript-sdk into feature/v2-monorepo-setup

Merge branch 'main' of github.com:modelcontextprotocol/typescript-sdk…

b532047

… into feature/v2-monorepo-setup

modelcontextprotocol deleted a comment from sonarqubecloud bot Dec 16, 2025

KKonstantinov linked an issue Dec 16, 2025 that may be closed by this pull request

Publish separate client and server packages #1256

Open

KKonstantinov mentioned this pull request Dec 16, 2025

Publish separate client and server packages #1256

Open

KKonstantinov linked an issue Dec 16, 2025 that may be closed by this pull request

ESM only (if feasible) #1258

Open

KKonstantinov mentioned this pull request Dec 16, 2025

ESM only (if feasible) #1258

Open

mattzcarey reviewed Dec 17, 2025

View reviewed changes

		@@ -0,0 +1,3 @@
		import { defineWorkspace } from 'vitest/config';

		export default defineWorkspace(['packages/**/vitest.config.js']);

		export * from './validation/ajv-provider.js';
		export * from './validation/cfworker-provider.js';

		"@modelcontextprotocol/sdk-client": ["node_modules/@modelcontextprotocol/sdk-client/src/index.ts"],
		"@modelcontextprotocol/sdk-server": ["node_modules/@modelcontextprotocol/sdk-server/src/index.ts"],

[v2] Мonorepo, sdk-client, sdk-server, sdk-core package split #1279

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[v2] Мonorepo, sdk-client, sdk-server, sdk-core package split #1279

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Motivation and Context

How Has This Been Tested?

Breaking Changes

Types of changes

Checklist

Additional context

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[v2] Мonorepo, `sdk-client`, `sdk-server`, `sdk-core` package split #1279

[v2] Мonorepo, `sdk-client`, `sdk-server`, `sdk-core` package split #1279

KKonstantinov commented Dec 10, 2025 •

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