feat(sdk-runner): expand KNOWN_SDKS to all tier 1 SDKs

[pcarleton]

Expands KNOWN_SDKS so every Tier 1 SDK (TypeScript, Python, C#, Go — per the SDK tiering table) can be driven by conformance sdk <name> --mode client|server with no CLI overrides:

• go-sdk: the entry pointed at examples/server/conformance, which no longer exists on main — fixtures moved to conformance/everything-{client,server}. Also adds the client fixture (go-sdk now has one) and wires conformance/baseline.yml as the expected-failures baseline. The server command pins -stateless=false to match go-sdk's own scripts/server-conformance.sh; a SEP-2575 run overrides --server-cmd (documented in the entry comment and README example).
• python-sdk (new entry): main, which targets 2026-07-28. Same uv-workspace layout as the existing python-sdk-v1 entry; defaults to the dated-spec baseline (expected-failures.yml), with expected-failures.2026-07-28.yml available via --expected-failures for --spec-version 2026-07-28 runs.
• csharp-sdk (new entry): drives tests/ModelContextProtocol.ConformanceClient / ConformanceServer via the .NET 10 SDK. Two quirks handled in the entry: the client takes the scenario as argv[0] rather than reading MCP_CONFORMANCE_SCENARIO, so the command bridges the env var into argv; and the repo uses UseArtifactsOutput, so binaries land under artifacts/bin/. The server exposes the SEP-2575 stateless lifecycle at /stateless (override --server-url for 2026-07-28 runs).

Also refreshes the README's one-off-override example, which referenced a mcp_go_client_oauth build tag that no longer exists in go-sdk.

Verified by running the full matrix (client+server × all five entries) locally at --suite all --spec-version 2026-07-28; go-sdk and python-sdk main come back fully green (go's baseline now has two stale entries to remove upstream), and the csharp entries produce clean per-scenario results (311/321 client, 90/110 server checks).

[pkg-pr-new]

Open in StackBlitz

npx https://pkg.pr.new/@modelcontextprotocol/conformance@417

commit: 02cbfae

[pcarleton]

Ran every entry end-to-end from this branch's build to show the config works per SDK: npm run build, then node dist/index.js sdk <name> --mode client|server --suite all --spec-version 2026-07-28 (plus the documented per-SDK overrides for the SEP-2575 legs). Output below is trimmed from real runs on 2026-07-27 against the alpha.10 scenario set.

Toolchain prereqs on the runner box: .NET 10 SDK (csharp-sdk global.json), go ≥ 1.25 (an older local go auto-fetches the toolchain via GOTOOLCHAIN), uv, node ≥ 20.

go-sdk — client 411/411, server 115/115 (exit 1 only from now-stale baseline entries)

$ node dist/index.js sdk go-sdk@main --mode client --suite all --spec-version 2026-07-28 --timeout 60000
[sdk] Cloning https://github.com/modelcontextprotocol/go-sdk.git -> .sdk-under-test/go-sdk/main
[sdk] HEAD is e761950
[sdk] Building: go build -o ./.conformance-server ./conformance/everything-server && go build -o ./.conformance-client ./conformance/everything-client
[sdk] conformance client --command ./.conformance-client --suite all --timeout 60000 --spec-version 2026-07-28 --expected-failures .../go-sdk/main/conformance/baseline.yml
...
✓ auth/iss-normalized: 15 passed, 0 failed
✓ sep-2322-client-request-state: 5 passed, 0 failed
✓ http-custom-headers: 18 passed, 0 failed
✓ json-schema-ref-no-deref: 1 passed, 0 failed

Total: 411 passed, 0 failed, 0 warnings

Stale baseline entries (now passing - remove from baseline):
  ✓ json-schema-ref-no-deref

$ node dist/index.js sdk go-sdk@main --mode server --suite all --spec-version 2026-07-28 \
    --server-cmd './.conformance-server -http=localhost:3000'   # SEP-2575 override from the entry comment
[sdk] Starting server: ./.conformance-server -http=localhost:3000
[sdk] Server ready at http://localhost:3000
...
✓ input-required-result-validate-input: 2 passed, 0 failed

Total: 115 passed, 0 failed

Stale baseline entries (now passing - remove from baseline):
  ✓ server-stateless

Both "stale" flags are the baseline machinery working as intended: go-sdk's conformance/baseline.yml predicted these entries would start passing once the suite picked up modelcontextprotocol/modelcontextprotocol#3002, which alpha.10 did — the cleanup belongs upstream in go-sdk.

python-sdk (new entry, main) — client 371/371, server 114/114, exit 0 both

$ node dist/index.js sdk python-sdk@main --mode client --suite all --spec-version 2026-07-28 --timeout 60000 \
    --expected-failures .../.github/actions/conformance/expected-failures.2026-07-28.yml
[sdk] Cloning https://github.com/modelcontextprotocol/python-sdk.git -> .sdk-under-test/python-sdk/main
[sdk] HEAD is dcd9c1ee
[sdk] Building: uv sync --frozen --all-extras --all-packages
[sdk] conformance client --command uv run --frozen python .github/actions/conformance/client.py ...
...
✓ auth/authorization-server-migration: 27 passed, 0 failed
✓ sep-2322-client-request-state: 5 passed, 0 failed
✓ http-custom-headers: 18 passed, 0 failed
✓ json-schema-ref-no-deref: 1 passed, 0 failed

Total: 371 passed, 0 failed, 0 warnings

$ node dist/index.js sdk python-sdk@main --mode server --suite all --spec-version 2026-07-28 \
    --expected-failures .../.github/actions/conformance/expected-failures.2026-07-28.yml
[sdk] Starting server: uv run --frozen mcp-everything-server --port 3000
[sdk] Server ready at http://localhost:3000/mcp
...
✓ input-required-result-tampered-state: 1 passed, 0 failed
✓ input-required-result-validate-input: 2 passed, 0 failed

Total: 114 passed, 0 failed

csharp-sdk (new entry) — client 311/321, server 90/110; failures are SDK-side findings, not entry misconfiguration

$ node dist/index.js sdk csharp-sdk@main --mode client --suite all --spec-version 2026-07-28 --timeout 60000
[sdk] Cloning https://github.com/modelcontextprotocol/csharp-sdk.git -> .sdk-under-test/csharp-sdk/main
[sdk] HEAD is 950ac7c
[sdk] Building: dotnet build tests/ModelContextProtocol.ConformanceClient -c Release -f net10.0 && dotnet build tests/ModelContextProtocol.ConformanceServer -c Release -f net10.0
[sdk] conformance client --command bash -c 'exec dotnet artifacts/bin/ModelContextProtocol.ConformanceClient/Release/net10.0/ModelContextProtocol.ConformanceClient.dll "$MCP_CONFORMANCE_SCENARIO" "$1"' conformance-client ...
...
✓ auth/token-endpoint-auth-none: 16 passed, 0 failed
✗ auth/authorization-server-migration: 13 passed, 1 failed
✓ auth/metadata-issuer-mismatch: 3 passed, 0 failed
✗ sep-2322-client-request-state: 0 passed, 5 failed
✓ http-custom-headers: 18 passed, 0 failed
✗ json-schema-ref-no-deref: 0 passed, 1 failed

Total: 311 passed, 10 failed, 0 warnings

$ node dist/index.js sdk csharp-sdk@main --mode server --suite all --spec-version 2026-07-28 \
    --server-url http://localhost:3000/stateless   # 2026-07-28 override from the entry comment
[sdk] Starting server: dotnet artifacts/bin/ModelContextProtocol.ConformanceServer/Release/net10.0/ModelContextProtocol.ConformanceServer.dll --urls http://localhost:3000
[sdk] Server ready at http://localhost:3000/stateless
...
✓ caching: 7 passed, 0 failed
✓ http-header-validation: 13 passed, 0 failed
✓ input-required-result-multi-round: 3 passed, 0 failed

Total: 90 passed, 20 failed

The 30 failing checks are genuine csharp-sdk conformance gaps, and the same scenarios pass through the identical plumbing on the other SDKs. The dominant cause is that csharp-sdk still implements the pre-modelcontextprotocol/modelcontextprotocol#3002 discover shape (DiscoverResult requires body serverInfo, so ConnectAsync throws on the alpha.10 mock — that alone accounts for tools_call, the five sep-2322-* checks, and json-schema-ref-no-deref on the client side); the rest are scope step-up / AS-migration on the client and SEP-2575 _meta strictness, JSON Schema 2020-12 keyword preservation, and DNS-rebinding host validation on the server.

typescript-sdk / typescript-sdk-v1 (entries unchanged) — re-validated as a control, incl. the @<ref> path

$ node dist/index.js sdk typescript-sdk@main --mode client --suite all --spec-version 2026-07-28 --timeout 60000
...
Total: 375 passed, 0 failed, 0 warnings
Baseline check passed: all failures are expected.

$ node dist/index.js sdk typescript-sdk@main --mode server --suite all --spec-version 2026-07-28
...
Total: 114 passed, 0 failed
Stale baseline entries (now passing - remove from baseline):
  ✓ server-stateless        # same #3002 story as go-sdk; cleanup belongs in typescript-sdk

The alias + ref-override path also works (this is the v1 line's 2026-07-28 integration branch, at its declared 2025-11-25 target):

$ node dist/index.js sdk typescript-sdk-v1@v1.x-2026-07-28 --mode client --suite all --timeout 60000
[sdk] conformance client --command npx tsx test/conformance/src/everythingClient.ts ... --spec-version 2025-11-25 --expected-failures .../test/conformance/conformance-baseline.yml
...
Total: 246 passed, 0 failed, 0 warnings

Full logs and per-check checks.json results are on the runner box if anyone wants the unabridged versions.