| Filename | Latest commit message | Latest commit date |
|---|---|---|
dc25610162
## Motivation and Context Clients that require MCP 2026-07-28, such as ChatGPT, reject connections because the SDK does not advertise that version: `Server#init` answers a 2026-07-28 request with 2025-11-25, the Streamable HTTP transport 400s an `MCP-Protocol-Version: 2026-07-28` header, and `server/discover` omits the version from `supportedVersions`. Making 2026-07-28 the latest entry in `SUPPORTED_STABLE_PROTOCOL_VERSIONS` fixes all three at once, since they all read that list. The version now serves both lifecycles of the SEP-2575 dual-era model: negotiable through the legacy `initialize` handshake, and simultaneously the version of the per-request modern lifecycle. Parts of the 2026-07-28 feature set remain unimplemented, such as the stateless modern lifecycle over the transports, and are being built separately. This change deliberately limits itself to the version bump, focusing first on eliminating the connection errors that 2026-07-28 clients hit. Known follow-up: the in-progress modern HTTP path routes requests to the sessionless modern lifecycle when the header version is absent from `SUPPORTED_STABLE_PROTOCOL_VERSIONS`, so that routing predicate needs rework on top of this change. Closes #474 ## How Has This Been Tested? New regression tests: `initialize` with `protocolVersion: "2026-07-28"` echoes it back (`server_test.rb`), a follow-up POST with `MCP-Protocol-Version: 2026-07-28` passes header validation (`streamable_http_transport_test.rb`), and `Configuration.new(protocol_version: "2026-07-28")` is accepted (`configuration_test.rb`). `bundle exec rake test` passes (1454 runs, 0 failures). The conformance server suite passes 30/30. The client `initialize` scenario is added to the expected-failures baseline: the conformance framework pins the client's requested version to 2025-11-25 and does not accept 2026-07-28 yet; the entry carries a TODO to remove it when the framework catches up. ## Breaking Changes Servers that do not pin `configuration.protocol_version` now answer version negotiation fallbacks and default client requests with 2026-07-28 instead of 2025-11-25. 2025-11-25 remains fully supported and negotiable; clients that request it are unaffected. |
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| .. | ||
| client.rb | ||
| client_runner.rb | ||
| expected_failures.yml | ||
| README.md | ||
| server.rb | ||
| server_runner.rb | ||
MCP Conformance Tests
Validates the Ruby SDK's conformance to the MCP specification using @modelcontextprotocol/conformance.
Prerequisites
- Node.js (for
npx) bundle installcompleted
Running the Tests
Run all scenarios
bundle exec rake conformance
Runs both server and client conformance tests in sequence. Server conformance starts the
conformance server and tests it. Client conformance spawns test servers for each scenario
and invokes conformance/client.rb against them. Scenarios listed in expected_failures.yml
are allowed to fail without affecting the exit code.
Environment variables
| Variable | Description | Default |
|---|---|---|
PORT |
Server port (server conformance only) | 9292 |
SCENARIO |
Run a single scenario by name | (all) |
SPEC_VERSION |
Filter scenarios by spec version | (all) |
VERBOSE |
Show raw JSON output when set | (off) |
# Run a single server scenario
bundle exec rake conformance SCENARIO=ping
# Use a different port with verbose output
bundle exec rake conformance PORT=3000 VERBOSE=1
# Start the server on a specific port
bundle exec rake conformance_server PORT=3000
Start the server and test separately
# Terminal 1: start the server
bundle exec rake conformance_server
# Terminal 2: run all scenarios
npx @modelcontextprotocol/conformance server --url http://localhost:9292/mcp
# Terminal 2: run a single scenario
npx @modelcontextprotocol/conformance server --url http://localhost:9292/mcp --scenario ping
Keeps the server alive between test runs, which avoids the startup overhead when iterating on a single scenario. Stop the server with Ctrl+C when done.
List available scenarios
bundle exec rake conformance_list
Prints all scenario names that can be passed to SCENARIO.
SDK Tier Report
The MCP SDK Tier system requires SDK maintainers to self-assess and report results to the SDK Working Group via modelcontextprotocol/modelcontextprotocol issues.
To generate a full tier assessment report, use the /mcp-sdk-tier-audit slash command from
the modelcontextprotocol/conformance
repository with the conformance server running:
# Terminal 1 (this repository): start the conformance server
bundle exec rake conformance_server
# Terminal 2 (conformance repository): run the tier audit skill as a slash command in Claude Code
/mcp-sdk-tier-audit /path/to/modelcontextprotocol/ruby-sdk http://localhost:9292/mcp
The skill evaluates conformance pass rate, issue label taxonomy, triage metrics, documentation coverage, and policy compliance, then produces a markdown report suitable for tier advancement submissions.
File Structure
conformance/
server.rb # Conformance server (Rack + Puma, default port 9292)
server_runner.rb # Starts the server, runs npx conformance server, exits with result code
client.rb # Conformance client (invoked by npx conformance client)
client_runner.rb # Runs npx conformance client, exits with result code
expected_failures.yml # Baseline of known-failing scenarios (server and client)
README.md # This file
Known Limitations
Known-failing scenarios are registered in conformance/expected_failures.yml. They are allowed to
fail without affecting the exit code and are tracked to catch regressions.
These are shown in the output of bundle exec rake conformance.