feat: add python-sdk as a built-in SDK runner target

[waprin]

Adds python-sdk to KNOWN_SDKS so conformance sdk python-sdk can clone, build, and run it like typescript-sdk and go-sdk. python-sdk already ships conformance fixtures; this is just the runner wiring.

• build: uv sync --frozen --all-extras --all-packages — one sync over the uv workspace covers both the mcp (client) and mcp-everything-server (server) packages.
• client/server: reuse the SDK's own fixtures (.github/actions/conformance/client.py and the everything-server console script). --port 3000 matches the url and the convention used by the other entries.

Validated: --mode server --scenario server-initialize (2/2) and --mode client --scenario initialize (1/1).

🤖 Generated with Claude Code

[pkg-pr-new]

Open in StackBlitz

npx https://pkg.pr.new/@modelcontextprotocol/conformance@329

commit: 44561d5

[pcarleton]

Thanks @waprin!

Can you check the full output? (from discord, seems like there are some failures).

python on the v1 branch should pass 100% at 2025-11-25 (that's what was submitted for tiering). That might mean a few things:

• i added a "v1" typescript sdk runner, which should pass there
• if you do run on the v1 branch, and it still fails, let's investigate the failures because it may be a harness regression due to some of the transport refactors

[waprin]

@pcarleton ok Im targeting Python v1 now. Following issues:

• json-schema-2020-12 (server) — json-schema-2020-12-tool-found FAILURE: no
  json_schema_2020_12_tool advertised.
• server-sse-polling (server) — server-sse-priming-event + server-sse-retry-field
  WARNINGs: no SSE priming event / retry field.
• auth/scope-step-up (client) — sep-2350-scope-union-on-reauth WARNING: drops
  previously-granted scope on re-auth.

• For json-schema tool and server-sse-polling found, looks likes its its cause the python sdk's own confrmance suite runs active instead of all . The server doesnt implement it.

So, should we be running active or all?

• for auth/scope-step-up seems the SEP-2350 check is newer than what the python-sdk pins , but it's missing on SDK side. Should we try to add it there or is it out of scope?

[pcarleton]

awesome, ty!

I'll approve this to merge in, however we should change it to run just active for servers (if you want to do that in this one, i'm happy to re-review). That's the suite we run for tiering, and so is the most reasonable default here to avoid confusion.

Here's where we set that in tiering:
https://github.com/modelcontextprotocol/conformance/blob/main/src/tier-check/checks/test-conformance-results.ts#L214

You're right about step-up... we should probably add a spec version branch in the step-up behavior so we don't fail on the "non accumulating" behavior from 2025-11-25 (we added "set-wise union" as a requirement in 2026-07-28).

[waprin]

@pcarleton ok I changed it to suite active please re-review . I will look into spec-version branch thing.

[pcarleton]

thanks @waprin !