## Motivation and Context
The Ruby SDK uses a 1-Server-to-many-sessions model where session-specific state
(`@client`, `@logging_message_notification`) is stored on the shared `Server` instance.
This causes the last client to connect to overwrite state for all sessions,
and requires `session_id` to be threaded through method signatures for session-scoped notifications.
The Python SDK avoids this by creating a `ServerSession` per connection that wraps a shared `Server`.
Each session holds its own state and naturally scopes notifications through its own stream.
### Changes
- Added `MCP::ServerSession` class holding per-session state: client info,
logging configuration, and a `transport` reference for session-scoped
notification delivery.
- `StreamableHTTPTransport#handle_initialization` creates a `ServerSession`
per `initialize` request and stores it in the session hash.
- `handle_regular_request` routes requests through the session's
`ServerSession` instead of the shared `Server` directly.
- `Server#handle` and `Server#handle_json` accept an optional `session:`
keyword (`ServerSession` instance).
- `Server#init` stores client info on the session when available.
- `Server#configure_logging_level` stores logging config on the session.
- `ServerContext` and `Progress` accept a `notification_target:` which
can be either a `ServerSession` (session-scoped) or a `Server` (broadcast).
No `session_id:` parameter needed.
- `ServerContext#notify_progress` and `#notify_log_message` delegate to
the `notification_target` without `session_id` threading.
- `StdioTransport` creates a single `ServerSession` on `open`,
making the session model transparent across both transports.
### Design Decision
This follows the Python SDK's "shared `Server` + per-connection `Session`" pattern.
The `Server` holds configuration (tools, prompts, resources, handlers).
Each `ServerSession` holds per-connection state (client info, logging level, stream writer).
Notifications from `ServerSession` go only to that session's stream.
## How Has This Been Tested?
All existing tests pass. All conformance tests pass. Added tests verifying:
- Session-scoped log notification is sent only to the originating session.
- Session-scoped progress notification is sent only to the originating session.
- Each session stores its own client info independently.
- Each session stores its own logging level independently.
- `StdioTransport#open` creates a `ServerSession` and stores client info on it.
## Breaking Change
None for end users.
The public API (`Server.new`, `define_tool`,`server_context.report_progress`,
`server_context.notify_log_message`, etc.) is unchanged. The following internal API
changes affect only SDK internals:
- `ServerContext.new` now requires `notification_target:` instead of just`progress:`.
- `Progress.new` now takes `notification_target:` instead of `server:`.
- `Server#handle` and `Server#handle_json` accept an optional `session:` keyword.
Due to overly aggressive detection by RuboCop Minitest, the distinction between `[]` and `{}` was uniformly replaced with `assert_empty`,
making it impossible to differentiate between them.
As a result of https://github.com/rubocop/rubocop-minitest/issues/344, where the `Minitest/AssertEmptyLiteral` cop was disabled,
the return value has been expressed using explicit literal forms.
Follow-up to #27.
This PR fixes the following build error:
```console
$ bundle exec rake
/Users/koic/.rbenv/versions/3.5-dev/lib/ruby/3.5.0+1/bundled_gems.rb:59:in 'Kernel.require': cannot load such file -- mcp/transports/stdio (LoadError)
Did you mean? mcp/transports/stdio_transport_test
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/3.5.0+1/bundled_gems.rb:59:in 'block (2 levels) in Kernel#replace_require'
from /Users/koic/src/github.com/modelcontextprotocol/ruby-sdk/test/mcp/transports/stdio_transport_test.rb:4:in '<top (required)>'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/3.5.0+1/bundled_gems.rb:59:in 'Kernel.require'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/3.5.0+1/bundled_gems.rb:59:in 'block (2 levels) in Kernel#replace_require'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/gems/3.5.0+1/gems/rake-13.3.0/lib/rake/rake_test_loader.rb:21:in 'block in <main>'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/gems/3.5.0+1/gems/rake-13.3.0/lib/rake/rake_test_loader.rb:6:in 'Array#select'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/gems/3.5.0+1/gems/rake-13.3.0/lib/rake/rake_test_loader.rb:6:in '<main>'
rake aborted!
Command failed with status (1)
/Users/koic/.rbenv/versions/3.5-dev/bin/bundle:25:in 'Kernel#load'
/Users/koic/.rbenv/versions/3.5-dev/bin/bundle:25:in '<main>'
Tasks: TOP => default => test
(See full trace by running task with --trace)
```
https://github.com/modelcontextprotocol/ruby-sdk/actions/runs/15428236624/job/43420346011
The following is stated in #27.
> Breaking Changes
> `MCP::Transports::StdioTransport` is now `MCP::Server::Transports::StdioTransport`
What is shown here is the new name `MCP::Server::Transports::StdioTransport`, not `MCP::Server::Transports::Stdio`.
Therefore, the file path has been updated from `lib/mcp/server/transports/stdio.rb` to `lib/mcp/server/transports/stdio_transport.rb` to
match the module name. If `MCP::Server::Transports::Stdio` is preferred instead, please let me know and I will open a separate PR.
2025-06-04 11:48:25 +09:00
Renamed from test/mcp/server/transports/stdio_test.rb (Previous history)
