v0.11.0

Added

• Support sampling/createMessage per MCP specification (#282)
• Support completion/complete per MCP specification (#289)

Fixed

• Support POST response SSE streams for server-to-client messages (#294)
• Return protocol errors for invalid arguments and server errors (#285)
• Fix client methods silently swallowing JSON-RPC error responses (#281)
• Close streams outside mutex in session cleanup (#291)

v0.10.0

Added

• Session expiry controls for StreamableHTTPTransport via session_idle_timeout: option (#268)

Changed

• ServerSession for per-connection state (#275)

Removed

• Remove Server#notify_progress broadcast API (#276)
• Remove undocumented handler override methods (#270)

Fixed

• Reject POST requests without session ID in stateful mode (#274)

v0.9.2

Fixed

• Use accessor method in server_context_with_meta instead of ivar (#273)
• Reject duplicate SSE connections with 409 to prevent stream hijacking

v0.9.1

Added

• Allow Client#call_tool to accept a tool name (#266)

Fixed

• Return 404 for invalid session ID in handle_delete (#261)

v0.9.0

Added

• MCP::Client::Stdio transport (#262)
• Progress notifications per MCP specification (#254)
• Automatic _meta parameter extraction support (#172)
• CORS and Accept wildcard support for browser-based MCP clients (#253)

Changed

• Use autoload to defer loading of unused subsystems (#255)
• Reduce release package size (#239)

Fixed

• Return 404 for invalid session ID in handle_regular_request (#257)
• Use mutex-protected session_exists? in handle_regular_request (#258)

v0.8.0

Added

• Content::EmbeddedResource class for embedded resource content type (#244)
• Content::Audio class for audio content type (#243)
• $ref support in Tool::Schema for protocol version 2025-11-25 (#242)
• MCP conformance test suite (#248)

Fixed

• Handle Errno::ECONNRESET in SSE stream operations (#249)
• Fix default handler return values to comply with MCP spec (#247)
• Fix Prompt#validate_arguments! crash when arguments are nil (#246)
• Return 202 Accepted for SSE responses per MCP spec (#245)
• Fix Content::Image#to_h to return mimeType (camelCase) per MCP spec (#241)

v0.7.1

Fixed

• Fix Resource::Contents#to_h to use correct property names per MCP spec (#235)
• Return JSON-RPC protocol errors for unknown tool calls (#231)
• Fix logging/setLevel to return empty hash per MCP specification (#230)

v0.7.0

Added

• logging support (#103)
• Protocol version negotiation to server initialization (#223)
• Tool arguments to instrumentation data (#218)
• Client info to instrumentation callback (#221)
• resource_templates to MCP::Client (#225)

Changed

• Extract MCP::Annotations into a dedicated file (#224)

Fixed

• Resource::Embedded not setting @resource in initialize (#220)

v0.6.0

Changed

• Update licensing to Apache 2.0 for new contributions (#213)

Fixed

• Omit icons from responses when empty or nil to reduce context window usage (#212)

v0.5.0

Added

• Protocol specification version "2025-11-25" support (#184)
• icons parameter support (#205)
• websiteUrl parameter in serverInfo (#188)
• description parameter in serverInfo (#201)
• additionalProperties support for schema validation (#198)
• "Draft" protocol version to supported versions (#179)
• stateless mode for high availability (#101)
• Exception messages for tool call errors (#194)
• Elicitation skeleton (#178)
• prompts/list and prompts/get support to client (#163)
• Accept header validation for HTTP client transport (#207)
• Ruby 2.7 - Ruby 3.1 support (#206)

Changed

• Make tool names stricter (#204)

Fixed

• Symlink path comparison in schema validation (#193)
• Duplicate tool names across namespaces now raise an error (#199)
• Tool error handling to follow MCP spec (#165)
• XSS vulnerability in json_rpc_handler (#175)