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The ACP Dart SDK provides comprehensive support for the Agent Client Protocol, tracking both stable and unstable protocol surfaces explicitly.

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Stable Features

All ACP stable protocol features are fully supported and production-ready.

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Agent Methods

Methods that clients can call on agents:
MethodStatusDescription
initialize✅ SupportedEstablishes connection and negotiates protocol capabilities
authenticate✅ SupportedAuthenticates the client using specified authentication method
session/new✅ SupportedCreates a new conversation session
session/load✅ SupportedLoads an existing session to resume conversation
session/prompt✅ SupportedProcesses a user prompt within a session
session/cancel✅ SupportedCancels ongoing operations for a session
session/set_mode✅ SupportedSets the operational mode for a session
session/set_config_option✅ SupportedSets the current value for a session configuration option

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Client Methods

Methods that agents can call on clients:
MethodStatusDescription
fs/read_text_file✅ SupportedReads content from a text file
fs/write_text_file✅ SupportedWrites content to a text file
session/request_permission✅ SupportedRequests user permission for tool call operations
session/update✅ SupportedSends session update notifications to the client

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Terminal Methods

Methods for terminal management:
MethodStatusDescription
terminal/create✅ SupportedCreates a new terminal and executes a command
terminal/output✅ SupportedGets the current output and exit status
terminal/wait_for_exit✅ SupportedWaits for terminal command to exit
terminal/kill✅ SupportedKills a terminal command
terminal/release✅ SupportedReleases terminal and frees resources

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Protocol Notifications

NotificationStatusDescription
$/cancel_request✅ SupportedProtocol-level cancellation of specific JSON-RPC requests

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Session Updates

All stable session update variants are supported:

Content Updates

  • user_message_chunk
  • agent_message_chunk
  • agent_thought_chunk

Tool Updates

  • tool_call
  • tool_call_update

Planning Updates

  • plan
  • available_commands_update

State Updates

  • current_mode_update
  • config_option_update

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Unstable Features

Unstable features are not part of the official ACP specification yet and may be removed or changed at any point.

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Unstable Agent Methods

MethodStatusDescription
session/list✅ SupportedLists existing sessions from the agent
session/fork✅ SupportedForks an existing session to create a new independent session
session/resume✅ SupportedResumes an existing session without replaying messages
session/set_model✅ SupportedSelects the model for a given session

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Unstable Session Updates

Additional update variants implemented for parity tracking:
  • session_info_update - Updates to session metadata (title, timestamp)
  • usage_update - Token usage and cost information

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Known Limitations

The following filesystem operations are not currently supported:
  • File deletion operations
  • File move/rename operations
  • Directory creation (mkdir)
  • Directory listing operations
Only fs/read_text_file and fs/write_text_file from the ACP stable surface are implemented.
The SDK supports extension methods and notifications (method names prefixed with _).Method names are passed through exactly as provided without rewriting.See the Extensions page for implementation details.

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Protocol Version

The SDK implements ACP Protocol Version 0.1.0.

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Method Coverage Summary

// From lib/src/schema.dart:
const agentMethods = {
  'authenticate': 'authenticate',
  'initialize': 'initialize',
  'modelSelect': 'session/set_model',
  'sessionFork': 'session/fork',
  'sessionList': 'session/list',
  'sessionSetConfigOption': 'session/set_config_option',
  'sessionCancel': 'session/cancel',
  'sessionLoad': 'session/load',
  'sessionNew': 'session/new',
  'sessionPrompt': 'session/prompt',
  'sessionResume': 'session/resume',
  'sessionSetMode': 'session/set_mode',
};

const clientMethods = {
  'fsReadTextFile': 'fs/read_text_file',
  'fsWriteTextFile': 'fs/write_text_file',
  'sessionRequestPermission': 'session/request_permission',
  'sessionUpdate': 'session/update',
  'terminalCreate': 'terminal/create',
  'terminalKill': 'terminal/kill',
  'terminalOutput': 'terminal/output',
  'terminalRelease': 'terminal/release',
  'terminalWaitForExit': 'terminal/wait_for_exit',
};

const protocolMethods = {
  'cancelRequest': r'$/cancel_request'
};

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Verification Process

Before each release, the SDK undergoes a comprehensive parity verification process documented in parity_verification_checklist.md.

Next: Explore Stable Features

Learn how to use stable protocol features in your implementation

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