OAuth 2.1 Enhancements and RubyLLM integration

1.0.1 (2026-03-22)

New Features

OAuth 2.1 Enhancements

• Supported Scopes Discovery: New supported_scopes method on OAuthProvider and scope: :all shorthand to request all server-advertised scopes (#109)
• Extra Client Metadata in DCR: Dynamic client registration now supports optional OIDC metadata fields (client_name, client_uri, logo_uri, tos_uri, policy_uri, contacts) (#110)
• PKCE Serialization: PKCE#to_h and PKCE.from_h methods for persisting and restoring PKCE state (#100)

RubyLLM Integration Example

• New examples/ruby_llm_mcp.rb: Demonstrates bridging MCP tools to RubyLLM using a minimal Class.new(RubyLLM::Tool) wrapper, with OpenAI as the LLM provider and Playwright MCP for browser automation. RubyLLM handles the tool call loop automatically.

MCP 2025-11-25 specification full support

1.0.0 (2026-02-15)

MCP 2025-11-25 Protocol Support

Full implementation of the MCP 2025-11-25 specification, upgrading from 2025-06-18.

New Protocol Features

• Audio Content: Support for audio content type in tool results and messages (#82)
• Resource Annotations: Added lastModified field to resource annotations (#83)
• Enhanced Tool Annotations: Hint-style annotation API (readOnlyHint, destructiveHint, idempotentHint, openWorldHint) alongside legacy annotations (#84)
• Enhanced Elicitation: Improved server-initiated user interaction support for MCP 2025-11-25 (#85)
• Enhanced Sampling: Added modelPreferences support for server-requested LLM completions (#86)
• Completion Context: Completion requests now support context parameter for MCP 2025-11-25 (#87)
• Structured Task Management: Server-driven task tracking with tasks/list, tasks/get, progress notifications, and cancellation (#88)
• ResourceLink Content Type: New content type for linking to MCP resources from tool results (#89)
• Tool Title: Optional human-readable title field for tools, separate from the programmatic name (by @conr) (#72)

Protocol Compliance

• Mcp-Protocol-Version Header: All HTTP transports now send the negotiated protocol version header on post-initialization requests, as required by the MCP spec
• Protocol version captured from server initialize response and used in all subsequent requests

Bug Fixes

• Parameter Validation: validate_params! now skips required parameters that have a default value in the schema, fixing compatibility with Playwright MCP and other Zod-based servers
• Anthropic Tool Schema Cleaning: to_anthropic_tool now strips $schema keys from tool schemas, preventing 400 errors from the Anthropic Messages API
• Streamable HTTP Example: Updated to use environment variables for server URL and Bearer token authentication instead of hardcoded credentials
• Anthropic Example: Fixed model name to use current claude-sonnet-4-5-20250929
• Fixed JSON parsing edge cases

Universal Connect

New Features

Simplified API - MCPClient.connect(url)

• New single entry point that auto-detects transport based on URL patterns (#62)
  • MCPClient.connect('http://localhost:8000/sse') → SSE transport
  • MCPClient.connect('http://localhost:8931/mcp') → Streamable HTTP transport
  • MCPClient.connect('npx -y @modelcontextprotocol/server-filesystem /home') → stdio transport
  • Supports options: headers, read_timeout, sampling_handler, etc.
  • Multiple servers: MCPClient.connect(['http://server1/mcp', 'http://server2/sse'])

MCP 2025-06-18 Protocol Compliance (#62)

• Roots Support: Define filesystem scope boundaries

  • client.set_roots([{ uri: 'file:///path', name: 'Root' }])
  • Sends notifications/roots/list_changed to servers
  • Handles roots/list requests from servers

• Sampling Support: Server-initiated LLM completions

  • sampling_handler: parameter for MCPClient.connect() and Client.new
  • Handles sampling/createMessage requests from servers
  • Supports variable arity handlers (1-4 args)

• Completion Support: Autocomplete suggestions

  • client.complete(ref:, argument:) method
  • Works with prompts (ref/prompt) and resources (ref/resource)
  • Returns completion values with pagination info

• Logging Support: Server log messages

  • client.set_log_level(level) method
  • Handles notifications/message from servers
  • Maps MCP levels to Ruby Logger levels

Faraday Connection Customization (by @conr) (#58)

• Added ability to customize Faraday HTTP connections
• Pass custom middleware, adapters, or configuration blocks

Documentation

• Updated YARD documentation

MCP 2025-06-18 Support with Elicitation

0.9.0 (2025-11-05)

MCP Protocol Update

• Updated to MCP 2025-06-18: Latest protocol specification
  • Protocol version constant updated from 2025-03-26 to 2025-06-18
  • All documentation and code comments updated to reference 2025-06-18
  • Maintains full backward compatibility with previous versions

New Features

Streamable HTTP Gzip Support

• Added gzip compression support for streamable HTTP transport (by @purposemc) (#46)

Browser-based OAuth flow

• Added support for browser-based OAuth authentication flow (#50)

Elicitation (Server-initiated User Interactions)

• Full Elicitation Support: Servers can now request structured user input during tool execution
  • Implemented across all transports: stdio, SSE, and Streamable HTTP
  • Bidirectional JSON-RPC communication for interactive workflows
  • Support for all three response actions: accept, decline, cancel
  • Callback-based API with elicitation_handler parameter
  • Automatic decline when no handler registered
  • Thread-safe response delivery for HTTP-based transports
  • Proper handling of elicitation/create requests
  • Responses sent as JSON-RPC requests (method: elicitation/response)
  • Content field only included when present (not empty hash for decline/cancel)

Elicitation Examples

• stdio Transport Example (examples/elicitation/)

  • elicitation_server.py - Python MCP server with elicitation tools
  • test_elicitation.rb - Interactive Ruby client with user input
  • Tools: create_document, send_notification

• Streamable HTTP Transport Example (examples/elicitation/)

  • elicitation_streamable_server.py - Python server supporting both SSE and Streamable HTTP
  • test_elicitation_streamable.rb - Full-featured client with multi-step workflows
  • Tools: create_document, delete_files, deploy_application

• SSE Transport Example (examples/elicitation/)

  • test_elicitation_sse_simple.rb - Minimal SSE example with auto-response
  • Uses traditional SSE transport (GET /sse for stream, POST /sse for RPC)

Implementation Details

Core Changes

• lib/mcp_client/version.rb - Updated PROTOCOL_VERSION to '2025-06-18'
• lib/mcp_client/client.rb - Added elicitation handler registration and propagation
• lib/mcp_client/server_streamable_http.rb - Added elicitation support for Streamable HTTP
  • on_elicitation_request - Register callback
  • handle_elicitation_create - Process elicitation requests
  • send_elicitation_response - Send responses via HTTP POST
  • post_jsonrpc_response - Thread-safe response delivery
• lib/mcp_client/server_sse.rb - Added elicitation support for SSE
  • Queue-based response delivery
  • Proper handling of JSON-RPC requests vs responses
• lib/mcp_client/server_stdio.rb - Added elicitation support for stdio
  • Bidirectional JSON-RPC over stdin/stdout
• lib/mcp_client/json_rpc_common.rb - Enhanced message type detection
• lib/mcp_client/server_http.rb - Base class updates

Bug Fixes

• Fixed elicitation ID extraction to correctly use JSON-RPC request ID
• Fixed elicitation response format to only include content when present
• Fixed response delivery mechanism for HTTP-based transports

Documentation

• Consolidated feature list under "MCP 2025-06-18 (Latest)"

Dependencies

• Updated faraday from 2.13.4 to 2.14.0
• Updated faraday-follow_redirects from 0.3.0 to 0.4.0
• Various dev dependency updates

Developer Experience

• Enhanced CI configuration and workflows

Full MCP Resources Specification Compliance

0.8.1 (2025-09-17)

Breaking Changes

• Resources API: Updated resources implementation to fully comply with MCP specification
  • list_resources now returns { 'resources' => [...], 'nextCursor' => ... } hash format on both client and server levels
  • read_resource now returns array of ResourceContent objects instead of hash with 'contents' key

New Features

• Full MCP Resources Specification Compliance:
  • Added ResourceContent class for structured content handling with text? and binary? methods
  • Added ResourceTemplate class for URI templates following RFC 6570
  • Implemented cursor-based pagination for list_resources and list_resource_templates
  • Added subscribe_resource and unsubscribe_resource methods for real-time updates
  • Added support for resource annotations (audience, priority, lastModified)
  • Binary content properly handled with base64 encoding/decoding
  • All transport types (stdio, SSE, HTTP, streamable_http) now have consistent resource support

Improvements

• Code Quality: Refactored Client#read_resource to reduce cyclomatic complexity
  • Extracted helper methods: find_resource_on_server, find_resource_across_servers, execute_resource_read
• ServerHTTP: Added complete resource methods that were previously missing
• ServerHTTP: Added prompts support (list_prompts and get_prompt)
• Examples: Updated echo_server_client.rb to use new ResourceContent API
• Examples: Enhanced echo_server_streamable.py with full resource features

Prompts & Resources

0.8.0 (2025-09-16)

New Features

• MCP Prompts and Resources Support: Added full support for MCP prompts and resources (#31)
  • Implemented list_prompts and get_prompt methods for prompt management
  • Implemented list_resources and read_resource methods for resource access
  • Added support for both text and blob resource types

Bug Fixes

• Tool Caching: Fixed issue with caching tools that have the same name from different servers (#342ff55)
  • Tools are now properly disambiguated by server when cached
  • Improved tool resolution to prevent conflicts between servers

Dependencies

• Updated openai from 9e5d91e to 003ab1d (dev dependency) (#30)
• Updated rubocop from 1.77.0 to 1.80.2 (dev dependency) (#28)
• Updated gemini-ai from 4.2.0 to 4.3.0 (dev dependency) (#25)

Developer Experience

• Updated examples with improved error handling
• Enhanced CI workflow configuration

HTTP Streaming Improvements

0.7.3 (2025-09-01)

Bug Fixes

• Streaming JSON Parsing: Fixed streaming JSON parsing improvements for better handling of partial data chunks
• SSE Connection: Enhanced server-sent events connection reliability for real-time notifications (ty @dsablic )

Dependencies

• Updated faraday from 2.13.1 to 2.13.4
• Updated ruby-openai from 8.1.0 to 8.3.0 (dev dependency)
• Updated openai gem to latest version (dev dependency)
• Updated rdoc from 6.14.1 to 6.14.2 (dev dependency)

Developer Experience

• Improved CI configuration and permissions
• Enhanced examples with better cleanup and error handling

MCP Protocol Compatibility and Transport Improvements Release

Bug Fixes

• JSON-RPC Parameter Handling: Fixed SSE transport compatibility with Playwright MCP servers by reverting JSON-RPC parameter handling to not send null for empty parameters
• Logger Formatter Preservation: Fixed issue where custom logger formatters were being overridden in server implementations

Transport Improvements

• HTTP Redirect Support: Added automatic redirect following (up to 3 hops) for both SSE and HTTP transports via faraday-follow_redirects gem

Examples and Testing

• FastMCP Integration: Added complete FastMCP echo server example demonstrating Ruby-Python MCP interoperability
• Comprehensive Logger Tests: Added 29 new test cases covering logger functionality across all server types

Developer Experience

• Protocol Version Consistency: Updated all examples and configurations to use MCP protocol version 2025-03-26
• Enhanced Documentation: Improved example scripts with better error handling and user guidance

OAuth 2.1 implementation

0.7.1 (2025-06-20)

OAuth 2.1 Authentication Framework

• Added comprehensive OAuth 2.1 support with PKCE for secure authentication
• Implemented automatic authorization server discovery via .well-known endpoints
• Added dynamic client registration when supported by servers
• Implemented token refresh and automatic token management
• Added pluggable storage backends for tokens and client credentials
• Created MCPClient::OAuthClient utility class for easy OAuth-enabled server creation
• Added runtime configuration support via getter/setter methods in OAuthProvider
• Included complete OAuth examples and documentation

HTTP Transport Improvements

• Refactored HTTP transport layer using template method pattern for better code organization
• Added proper session management and validation

Documentation and Examples

• Added comprehensive OAuth documentation (OAUTH.md)
• Updated README with OAuth usage examples and 2025 protocol features
• Enhanced oauth_example.rb with practical implementation patterns

0.7.0

0.7.0 (2025-05-20)

What's New

• StreamableHTTP transport type handling - Enhanced HTTP transport layer with improved streaming capabilities
• Connection reliability improvements - Fixed reconnection attempt resets on successful connections
• Test coverage enhancements - Added verification for nested array removal operations
• Integration testing updates - Improved integration test specifications

Bug Fixes

• Fixed reset reconnect attempts on success to ensure proper connection management
• Improved stdio parameter handling for better server communication

Technical Improvements

• Extracted JSON RPC common functionality for better code organization
• Enhanced annotations and documentation
• Improved server reconnection reliability

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This release focuses on transport layer improvements and connection stability, making the MCP client more robust for production use.