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Remove Server#notify_progress broadcast API

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## Motivation and Context

`Server#notify_progress` broadcasts progress notifications to all connected clients.
Progress notifications are tied to a specific request's `progressToken` and have no
meaningful broadcast use case. Neither the Python SDK nor the TypeScript SDK provides
a server-level progress broadcast capability.

The MCP specification requires that progress notifications only reference tokens
provided in an active request:

> Progress notifications MUST only reference tokens that:
> - Were provided in an active request
> - Are associated with an in-progress operation

Ref: https://modelcontextprotocol.io/specification/2025-11-25/basic/utilities/progress

Broadcasting progress to all clients does not comply with this requirement,
since clients that did not originate the request have no matching `progressToken`.

The introduction of `ServerSession` for per-connection state (#275) made
this removal possible: `Progress` and `ServerContext` now use `notification_target:`
(a `ServerSession`) to route notifications to the originating session only.

### Changes

- Removed `Server#notify_progress` entirely. The method is no longer needed as
  `notification_target` in `call_tool_with_args` now passes `session` directly
  (nil when no session is available, in which case `Progress#report` and
  `ServerContext#notify_log_message` are no-ops).
- Removed `ServerContext#notify_progress` as well. Progress notifications should
  only be sent via `server_context.report_progress`, which enforces the correct
  `progressToken` from the originating request.
- Added nil guards to `Progress#report` and `ServerContext#notify_log_message`
  for when no session is available.
- Rewrote progress tests to use `ServerSession#handle` instead of
  `Server#handle`, reflecting that progress notifications are always session-scoped.
- Removed 4 tests that called `server.notify_progress` directly as a public broadcast API.
- Removed `notify_progress` from the README.md notification methods list.
- Removed the "Server-Side: Direct `notify_progress` Usage" section from the README.md.

Progress notifications should be sent via `server_context.report_progress` inside tool handlers,
which automatically scopes them to the originating client session.

## Breaking Changes

Progress notifications are scoped to a specific request via `progressToken` per the MCP specification,
so the broadcast behavior of `Server#notify_progress` was a spec violation.
This is treated as a bug fix and is made without a deprecation period.
This aligns the Ruby SDK with the Python and TypeScript SDKs, neither of which provides
a server-level progress broadcast API.

`Server#notify_progress` and `ServerContext#notify_progress` are no longer available.
Users should use `server_context.report_progress` inside tool handlers instead, which
provides session-scoped delivery with the correct `progressToken`.

This feature was only recently introduced in mcp 0.9.0:
https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v0.9.0

So an early release should help limit its impact on adoption.
This commit is contained in:
Koichi ITO 2026-03-28 01:43:12 +09:00
commit b89f6e315d
7 changed files with 39 additions and 109 deletions
Download patch file Download diff file Expand all files Collapse all files

15
README.md
View file

@ -113,7 +113,6 @@ The server provides the following notification methods:
- `notify_tools_list_changed` - Send a notification when the tools list changes
- `notify_prompts_list_changed` - Send a notification when the prompts list changes
- `notify_resources_list_changed` - Send a notification when the resources list changes
- `notify_progress` - Send a progress notification for long-running operations
- `notify_log_message` - Send a structured logging notification message
#### Session Scoping
@ -178,24 +177,10 @@ The `server_context.report_progress` method accepts:
- `total:` (optional) — total expected value, so clients can display a percentage
- `message:` (optional) — human-readable status message
#### Server-Side: Direct `notify_progress` Usage
You can also call `notify_progress` directly on the server instance:
```ruby
server.notify_progress(
progress_token: "token-123",
progress: 50,
total: 100, # optional
message: "halfway" # optional
)
```
**Key Features:**
- Tools report progress via `server_context.report_progress`
- `report_progress` is a no-op when no `progressToken` was provided by the client
- `notify_progress` is a no-op when no transport is configured
- Supports both numeric and string progress tokens
### Logging

1
lib/mcp/progress.rb
View file

@ -9,6 +9,7 @@ module MCP
def report(progress, total: nil, message: nil)
return unless @progress_token
return unless @notification_target
@notification_target.notify_progress(
progress_token: @progress_token,

24
lib/mcp/server.rb
View file

@ -116,7 +116,7 @@ module MCP
# @param request [Hash] A parsed JSON-RPC request.
# @param session [ServerSession, nil] Per-connection session. Passed by
# `ServerSession#handle` for session-scoped notification delivery.
# When `nil`, notifications broadcast to all sessions.
# When `nil`, progress and logging notifications from tool handlers are silently skipped.
# @return [Hash, nil] The JSON-RPC response, or `nil` for notifications.
def handle(request, session: nil)
JsonRpcHandler.handle(request) do |method|
@ -129,7 +129,7 @@ module MCP
# @param request [String] A JSON-RPC request as a JSON string.
# @param session [ServerSession, nil] Per-connection session. Passed by
# `ServerSession#handle_json` for session-scoped notification delivery.
# When `nil`, notifications broadcast to all sessions.
# When `nil`, progress and logging notifications from tool handlers are silently skipped.
# @return [String, nil] The JSON-RPC response as JSON, or `nil` for notifications.
def handle_json(request, session: nil)
JsonRpcHandler.handle_json(request) do |method|
@ -186,21 +186,6 @@ module MCP
report_exception(e, { notification: "resources_list_changed" })
end
def notify_progress(progress_token:, progress:, total: nil, message: nil)
return unless @transport
params = {
"progressToken" => progress_token,
"progress" => progress,
"total" => total,
"message" => message,
}.compact
@transport.send_notification(Methods::NOTIFICATIONS_PROGRESS, params)
rescue => e
report_exception(e, notification: "progress")
end
def notify_log_message(data:, level:, logger: nil)
return unless @transport
return unless logging_message_notification&.should_notify?(level)
@ -524,9 +509,8 @@ module MCP
args = arguments&.transform_keys(&:to_sym) || {}
if accepts_server_context?(tool.method(:call))
notification_target = session || self
progress = Progress.new(notification_target: notification_target, progress_token: progress_token)
server_context = ServerContext.new(context, progress: progress, notification_target: notification_target)
progress = Progress.new(notification_target: session, progress_token: progress_token)
server_context = ServerContext.new(context, progress: progress, notification_target: session)
tool.call(**args, server_context: server_context).to_h
else
tool.call(**args).to_h

12
lib/mcp/server_context.rb
View file

@ -18,22 +18,14 @@ module MCP
@progress.report(progress, total: total, message: message)
end
# Sends a progress notification scoped to the originating session.
#
# @param progress_token [String, Integer] The token identifying the operation.
# @param progress [Numeric] Current progress value.
# @param total [Numeric, nil] Total expected value.
# @param message [String, nil] Human-readable status message.
def notify_progress(progress_token:, progress:, total: nil, message: nil)
@notification_target.notify_progress(progress_token: progress_token, progress: progress, total: total, message: message)
end
# Sends a log message notification scoped to the originating session.
#
# @param data [Object] The log data to send.
# @param level [String] Log level (e.g., `"debug"`, `"info"`, `"error"`).
# @param logger [String, nil] Logger name.
def notify_log_message(data:, level:, logger: nil)
return unless @notification_target
@notification_target.notify_log_message(data: data, level: level, logger: logger)
end

14
test/mcp/progress_test.rb
View file

@ -27,17 +27,25 @@ module MCP
@server = Server.new(name: "test_server")
@transport = MockTransport.new(@server)
@server.transport = @transport
@session = ServerSession.new(server: @server, transport: @transport)
end
test "#report is a no-op when progress_token is nil" do
progress = Progress.new(notification_target: @server, progress_token: nil)
progress = Progress.new(notification_target: @session, progress_token: nil)
progress.report(50, total: 100, message: "halfway")
assert_equal 0, @transport.notifications.size
end
test "#report is a no-op when notification_target is nil" do
progress = Progress.new(notification_target: nil, progress_token: "token-1")
progress.report(50, total: 100, message: "halfway")
assert_equal 0, @transport.notifications.size
end
test "#report sends notification when progress_token is present" do
progress = Progress.new(notification_target: @server, progress_token: "token-1")
progress = Progress.new(notification_target: @session, progress_token: "token-1")
progress.report(50, total: 100, message: "halfway")
assert_equal 1, @transport.notifications.size
@ -50,7 +58,7 @@ module MCP
end
test "#report omits total and message when not provided" do
progress = Progress.new(notification_target: @server, progress_token: "token-1")
progress = Progress.new(notification_target: @session, progress_token: "token-1")
progress.report(50)
assert_equal 1, @transport.notifications.size

7
test/mcp/server_context_test.rb
View file

@ -61,6 +61,13 @@ module MCP
server_context.report_progress(50, total: 100)
end
test "ServerContext#notify_log_message is a no-op when notification_target is nil" do
progress = Progress.new(notification_target: nil, progress_token: nil)
server_context = ServerContext.new(nil, progress: progress, notification_target: nil)
assert_nothing_raised { server_context.notify_log_message(data: "test", level: "info") }
end
# Tool without server_context parameter
class SimpleToolWithoutContext < Tool
tool_name "simple_without_context"

75
test/mcp/server_progress_test.rb
View file

@ -90,59 +90,7 @@ module MCP
@mock_transport = MockTransport.new(@server)
@server.transport = @mock_transport
end
test "#notify_progress sends correct notification through transport with all params" do
@server.notify_progress(progress_token: "token-1", progress: 50, total: 100, message: "halfway")
assert_equal 1, @mock_transport.notifications.size
notification = @mock_transport.notifications.first
assert_equal Methods::NOTIFICATIONS_PROGRESS, notification[:method]
assert_equal "token-1", notification[:params]["progressToken"]
assert_equal 50, notification[:params]["progress"]
assert_equal 100, notification[:params]["total"]
assert_equal "halfway", notification[:params]["message"]
end
test "#notify_progress omits total and message when nil" do
@server.notify_progress(progress_token: "token-1", progress: 50)
assert_equal 1, @mock_transport.notifications.size
notification = @mock_transport.notifications.first
assert_equal Methods::NOTIFICATIONS_PROGRESS, notification[:method]
assert_equal "token-1", notification[:params]["progressToken"]
assert_equal 50, notification[:params]["progress"]
refute notification[:params].key?("total")
refute notification[:params].key?("message")
end
test "#notify_progress does nothing without transport" do
server_without_transport = Server.new(name: "test_server")
assert_nothing_raised do
server_without_transport.notify_progress(progress_token: "token-1", progress: 50)
end
end
test "#notify_progress handles transport errors gracefully" do
error_transport = Class.new(MockTransport) do
def send_notification(method, params = nil)
raise StandardError, "Transport error"
end
end.new(@server)
@server.transport = error_transport
@server.configuration.exception_reporter.expects(:call).once.with do |exception, context|
assert_kind_of StandardError, exception
assert_equal "Transport error", exception.message
assert_equal({ notification: "progress" }, context)
true
end
assert_nothing_raised do
@server.notify_progress(progress_token: "token-1", progress: 50)
end
@session = ServerSession.new(server: @server, transport: @mock_transport)
end
test "tool with progress parameter receives Progress instance and sends notifications via _meta.progressToken" do
@ -157,7 +105,7 @@ module MCP
},
}
response = @server.handle(request)
response = @session.handle(request)
assert response[:result]
assert_equal "ToolWithProgress: Hello", response[:result][:content][0][:text]
@ -190,7 +138,7 @@ module MCP
},
}
response = @server.handle(request)
response = @session.handle(request)
assert response[:result]
assert_equal "SimpleToolWithoutProgress: Hello", response[:result][:content][0][:text]
@ -215,6 +163,7 @@ module MCP
server_context: { user: "test" },
)
server.transport = @mock_transport
session = ServerSession.new(server: server, transport: @mock_transport)
request = {
jsonrpc: "2.0",
@ -226,7 +175,7 @@ module MCP
},
}
server.handle(request)
session.handle(request)
assert_instance_of ServerContext, received_context
assert_nothing_raised { received_context.report_progress(50) }
@ -245,7 +194,7 @@ module MCP
},
}
response = @server.handle(request)
response = @session.handle(request)
assert response[:result]
assert_equal "ToolWithContextAndProgress: Hello context=test_user", response[:result][:content][0][:text]
@ -269,7 +218,7 @@ module MCP
},
}
response = @server.handle(request)
response = @session.handle(request)
assert response[:result]
assert_equal "ToolWithKwargs: progress=present", response[:result][:content][0][:text]
@ -290,6 +239,8 @@ module MCP
Tool::Response.new([{ type: "text", text: "block_tool done" }])
end
session = ServerSession.new(server: server, transport: @mock_transport)
request = {
jsonrpc: "2.0",
id: 1,
@ -301,7 +252,7 @@ module MCP
},
}
response = server.handle(request)
response = session.handle(request)
assert response[:result]
assert_equal "block_tool done", response[:result][:content][0][:text]
@ -325,6 +276,8 @@ module MCP
Tool::Response.new([{ type: "text", text: "done" }])
end
session = ServerSession.new(server: server, transport: @mock_transport)
request = {
jsonrpc: "2.0",
id: 1,
@ -336,7 +289,7 @@ module MCP
},
}
server.handle(request)
session.handle(request)
assert_equal 5, @mock_transport.notifications.size
@mock_transport.notifications.each_with_index do |n, i|
@ -358,7 +311,7 @@ module MCP
}
# Should not raise and should return nil (notification, no id).
result = @server.handle(request)
result = @session.handle(request)
assert_nil result
end
end