[experimental - do not merge] Cut startup cost: lazy exports, pay-for-what-you-use imports, deferred model builds by maxisbey · Pull Request #3220 · modelcontextprotocol/python-sdk

Resolve the mcp package's exports lazily (PEP 562)

maxisbey

committed

622aed5

Resolve submodules of mcp.client, mcp.server, mcp.shared and mcp.os on attribute access

maxisbey

committed

2128b57

Stop mcp.client from importing the server stack

maxisbey

committed

1c1b7f8

Load httpx2 with the HTTP transports only

maxisbey

committed

1e00f42

Keep typing.get_type_hints(Client) resolvable at runtime

maxisbey

committed

5b25303

Make server-side imports pay-for-what-you-use

maxisbey

committed

fcaf297

Test HttpResource.read() instead of excluding it from coverage

maxisbey

committed

3ac881f

Load per-version wire packages lazily from the methods surface maps

maxisbey

committed

0237ed9

Keep PrimitiveSchemaDefinition reachable on mcp.server.elicitation

maxisbey

committed

2a7fb0c

Add an import-cost ratchet for the SDK's entry points

maxisbey

committed

ff6c36e

Keep the Client type-hints test green on Python 3.10

maxisbey

committed

2a13e6d

Use one lazy-attribute helper for the packages, invisible to type checkers

maxisbey

committed

1f3fbc7

Keep the public server signatures resolvable by typing.get_type_hints

maxisbey

committed

cdc78fc

Load the OAuth provider stack and cryptography with their first user, not the server

maxisbey

committed

9ef39b6

Keep the wire packages statically discoverable to bundlers

maxisbey

committed

695b1ab

Defer building the generated wire models and emit them in dependency order

maxisbey

committed

b8bc17d

Defer building the monolith protocol models and routing adapters

maxisbey

committed

08f4385

Defer building the SDK's own eager pydantic models and adapters

maxisbey

committed

45bb6c9

Document the import-cost contract and the deferred-work model

maxisbey

committed

1facb57

Cover the deferred-signature edge cases: instance access and defer_build turned off

maxisbey

committed

d515c85

Serialize the deferred first build of the SDK's pydantic models

maxisbey

committed

8c9f2a2

Add mcp.warm(): opt-in prewarming for the deferred validators

maxisbey

committed

33471c7

Document the deferred-work bills and correct the import-cost bullets

maxisbey

committed

7fae576

Construct DEFAULT_CLIENT_INFO without building the Implementation model

maxisbey

committed

53a46e6

Import the internal deferred_model decorator under a private name

maxisbey

committed

986d3b9

Fail generation if a non-class statement sits between generated classes

maxisbey

committed

e02caca

Cover the decorator's refusal paths and the runtime-only lazy-init branches

maxisbey

committed

fc4f4e6

Generate a deferred model's JSON schema under the rebuild lock too

maxisbey

committed

b592f09

Spell warm()'s every-version flag as all_versions and return a frozen dataclass

maxisbey

committed

6da7ba4

Document the prewarm recipe and the rebuild lock's terms

maxisbey

committed

008c74e

Resolve attribute chains through the four leaf sub-packages too

maxisbey

committed

cb7c68c

Pin the decorator's refusal messages and describe two wire-base tests

maxisbey

committed

2716d09

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[experimental - do not merge] Cut startup cost: lazy exports, pay-for-what-you-use imports, deferred model builds - #3220

[experimental - do not merge] Cut startup cost: lazy exports, pay-for-what-you-use imports, deferred model builds#3220
maxisbey wants to merge 32 commits into
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Commits on Jul 29, 2026

Resolve the mcp package's exports lazily (PEP 562)

Resolve submodules of mcp.client, mcp.server, mcp.shared and mcp.os on attribute access

Stop mcp.client from importing the server stack

Load httpx2 with the HTTP transports only

Keep typing.get_type_hints(Client) resolvable at runtime

Make server-side imports pay-for-what-you-use

Test HttpResource.read() instead of excluding it from coverage

Load per-version wire packages lazily from the methods surface maps

Keep PrimitiveSchemaDefinition reachable on mcp.server.elicitation

Add an import-cost ratchet for the SDK's entry points

Keep the Client type-hints test green on Python 3.10

Use one lazy-attribute helper for the packages, invisible to type checkers

Keep the public server signatures resolvable by typing.get_type_hints

Load the OAuth provider stack and cryptography with their first user, not the server

Keep the wire packages statically discoverable to bundlers

Defer building the generated wire models and emit them in dependency order

Defer building the monolith protocol models and routing adapters

Defer building the SDK's own eager pydantic models and adapters

Document the import-cost contract and the deferred-work model

Cover the deferred-signature edge cases: instance access and defer_build turned off

Serialize the deferred first build of the SDK's pydantic models

Add mcp.warm(): opt-in prewarming for the deferred validators

Document the deferred-work bills and correct the import-cost bullets

Construct DEFAULT_CLIENT_INFO without building the Implementation model

Import the internal deferred_model decorator under a private name

Fail generation if a non-class statement sits between generated classes

Cover the decorator's refusal paths and the runtime-only lazy-init branches

Generate a deferred model's JSON schema under the rebuild lock too

Spell warm()'s every-version flag as all_versions and return a frozen dataclass

Document the prewarm recipe and the rebuild lock's terms

Resolve attribute chains through the four leaf sub-packages too

Pin the decorator's refusal messages and describe two wire-base tests