agentclientprotocol · PsiACE · Oct 25, 2025 · Oct 25, 2025 · Oct 25, 2025 · Oct 25, 2025
diff --git a/examples/agent.py b/examples/agent.py
@@ -24,69 +24,60 @@
     update_agent_message,
     PROTOCOL_VERSION,
 )
-from acp.schema import AgentCapabilities, McpCapabilities, PromptCapabilities
+from acp.schema import AgentCapabilities, AgentMessageChunk, Implementation
 
 
 class ExampleAgent(Agent):
     def __init__(self, conn: AgentSideConnection) -> None:
         self._conn = conn
         self._next_session_id = 0
+        self._sessions: set[str] = set()
 
-    async def _send_chunk(self, session_id: str, content: Any) -> None:
-        await self._conn.sessionUpdate(
-            session_notification(
-                session_id,
-                update_agent_message(content),
-            )
-        )
+    async def _send_agent_message(self, session_id: str, content: Any) -> None:
+        update = content if isinstance(content, AgentMessageChunk) else update_agent_message(content)
+        await self._conn.sessionUpdate(session_notification(session_id, update))
 
     async def initialize(self, params: InitializeRequest) -> InitializeResponse:  # noqa: ARG002
         logging.info("Received initialize request")
-        mcp_caps: McpCapabilities = McpCapabilities(http=False, sse=False)
-        prompt_caps: PromptCapabilities = PromptCapabilities(audio=False, embeddedContext=False, image=False)
-        agent_caps: AgentCapabilities = AgentCapabilities(
-            loadSession=False,
-            mcpCapabilities=mcp_caps,
-            promptCapabilities=prompt_caps,
-        )
         return InitializeResponse(
             protocolVersion=PROTOCOL_VERSION,
-            agentCapabilities=agent_caps,
+            agentCapabilities=AgentCapabilities(),
+            agentInfo=Implementation(name="example-agent", title="Example Agent", version="0.1.0"),
         )
 
     async def authenticate(self, params: AuthenticateRequest) -> AuthenticateResponse | None:  # noqa: ARG002
-        logging.info("Received authenticate request")
+        logging.info("Received authenticate request %s", params.methodId)
         return AuthenticateResponse()
 
     async def newSession(self, params: NewSessionRequest) -> NewSessionResponse:  # noqa: ARG002
         logging.info("Received new session request")
         session_id = str(self._next_session_id)
         self._next_session_id += 1
-        return NewSessionResponse(sessionId=session_id)
+        self._sessions.add(session_id)
+        return NewSessionResponse(sessionId=session_id, modes=None)
 
     async def loadSession(self, params: LoadSessionRequest) -> LoadSessionResponse | None:  # noqa: ARG002
-        logging.info("Received load session request")
+        logging.info("Received load session request %s", params.sessionId)
+        self._sessions.add(params.sessionId)
         return LoadSessionResponse()
 
     async def setSessionMode(self, params: SetSessionModeRequest) -> SetSessionModeResponse | None:  # noqa: ARG002
-        logging.info("Received set session mode request")
+        logging.info("Received set session mode request %s -> %s", params.sessionId, params.modeId)
         return SetSessionModeResponse()
 
     async def prompt(self, params: PromptRequest) -> PromptResponse:
-        logging.info("Received prompt request")
+        logging.info("Received prompt request for session %s", params.sessionId)
+        if params.sessionId not in self._sessions:
+            self._sessions.add(params.sessionId)
 
-        # Notify the client what it just sent and then echo each content block back.
-        await self._send_chunk(
-            params.sessionId,
-            text_block("Client sent:"),
-        )
+        await self._send_agent_message(params.sessionId, text_block("Client sent:"))
         for block in params.prompt:
-            await self._send_chunk(params.sessionId, block)
+            await self._send_agent_message(params.sessionId, block)
 
         return PromptResponse(stopReason="end_turn")
 
     async def cancel(self, params: CancelNotification) -> None:  # noqa: ARG002
-        logging.info("Received cancel notification")
+        logging.info("Received cancel notification for session %s", params.sessionId)
 
     async def extMethod(self, method: str, params: dict) -> dict:  # noqa: ARG002
         logging.info("Received extension method call: %s", method)

diff --git a/examples/client.py b/examples/client.py
@@ -17,6 +17,16 @@
     text_block,
     PROTOCOL_VERSION,
 )
+from acp.schema import (
+    AgentMessageChunk,
+    AudioContentBlock,
+    ClientCapabilities,
+    EmbeddedResourceContentBlock,
+    ImageContentBlock,
+    Implementation,
+    ResourceContentBlock,
+    TextContentBlock,
+)
 
 
 class ExampleClient(Client):
@@ -46,20 +56,24 @@ async def killTerminal(self, params):  # type: ignore[override]
 
     async def sessionUpdate(self, params: SessionNotification) -> None:
         update = params.update
-        if isinstance(update, dict):
-            kind = update.get("sessionUpdate")
-            content = update.get("content")
-        else:
-            kind = getattr(update, "sessionUpdate", None)
-            content = getattr(update, "content", None)
-
-        if kind != "agent_message_chunk" or content is None:
+        if not isinstance(update, AgentMessageChunk):
             return
 
-        if isinstance(content, dict):
-            text = content.get("text", "<content>")
+        content = update.content
+        text: str
+        if isinstance(content, TextContentBlock):
+            text = content.text
+        elif isinstance(content, ImageContentBlock):
+            text = "<image>"
+        elif isinstance(content, AudioContentBlock):
+            text = "<audio>"
+        elif isinstance(content, ResourceContentBlock):
+            text = content.uri or "<resource>"
+        elif isinstance(content, EmbeddedResourceContentBlock):
+            text = "<resource>"
         else:
-            text = getattr(content, "text", "<content>")
+            text = "<content>"
+
         print(f"| Agent: {text}")
 
     async def extMethod(self, method: str, params: dict) -> dict:  # noqa: ARG002
@@ -130,7 +144,13 @@ async def main(argv: list[str]) -> int:
     client_impl = ExampleClient()
     conn = ClientSideConnection(lambda _agent: client_impl, proc.stdin, proc.stdout)
 
-    await conn.initialize(InitializeRequest(protocolVersion=PROTOCOL_VERSION, clientCapabilities=None))
+    await conn.initialize(
+        InitializeRequest(
+            protocolVersion=PROTOCOL_VERSION,
+            clientCapabilities=ClientCapabilities(),
+            clientInfo=Implementation(name="example-client", title="Example Client", version="0.1.0"),
+        )
+    )
     session = await conn.newSession(NewSessionRequest(mcpServers=[], cwd=os.getcwd()))
 
     await interactive_loop(conn, session.sessionId)

diff --git a/pyproject.toml b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "agent-client-protocol"
-version = "0.5.0"
+version = "0.6.2"
 description = "A Python implement of Agent Client Protocol (ACP, by Zed Industries)"
 authors = [{ name = "Chojan Shang", email = "psiace@apache.org" }]
 readme = "README.md"

diff --git a/schema/VERSION b/schema/VERSION
@@ -1 +1 @@
-refs/tags/v0.5.0
+refs/tags/v0.6.2
diff --git a/schema/schema.json b/schema/schema.json
@@ -1071,6 +1071,31 @@
       ],
       "type": "object"
     },
+    "Implementation": {
+      "description": "Describes the name and version of an MCP implementation, with an optional\ntitle for UI representation.",
+      "properties": {
+        "name": {
+          "description": "Intended for programmatic or logical use, but can be used as a display\nname fallback if title isn\u2019t present.",
+          "type": "string"
+        },
+        "title": {
+          "description": "Intended for UI and end-user contexts \u2014 optimized to be human-readable\nand easily understood.\n\nIf not provided, the name should be used for display.",
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "version": {
+          "description": "Version of the implementation. Can be displayed to the user or used\nfor debugging or metrics purposes.",
+          "type": "string"
+        }
+      },
+      "required": [
+        "name",
+        "version"
+      ],
+      "type": "object"
+    },
     "InitializeRequest": {
       "description": "Request parameters for the initialize method.\n\nSent by the client to establish connection and negotiate capabilities.\n\nSee protocol docs: [Initialization](https://agentclientprotocol.com/protocol/initialization)",
       "properties": {
@@ -1088,6 +1113,17 @@
           },
           "description": "Capabilities supported by the client."
         },
+        "clientInfo": {
+          "anyOf": [
+            {
+              "$ref": "#/$defs/Implementation"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "description": "Information about the Client name and version sent to the Agent.\n\nNote: in future versions of the protocol, this will be required."
+        },
         "protocolVersion": {
           "$ref": "#/$defs/ProtocolVersion",
           "description": "The latest protocol version supported by the client."
@@ -1122,6 +1158,17 @@
           },
           "description": "Capabilities supported by the agent."
         },
+        "agentInfo": {
+          "anyOf": [
+            {
+              "$ref": "#/$defs/Implementation"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "description": "Information about the Agent name and version sent to the Client.\n\nNote: in future versions of the protocol, this will be required."
+        },
         "authMethods": {
           "default": [],
           "description": "Authentication methods supported by the agent.",
@@ -2304,7 +2351,7 @@
     "SetSessionModeResponse": {
       "description": "Response to `session/set_mode` method.",
       "properties": {
-        "meta": true
+        "_meta": true
       },
       "type": "object",
       "x-method": "session/set_mode",

diff --git a/src/acp/meta.py b/src/acp/meta.py
@@ -1,5 +1,5 @@
 # Generated from schema/meta.json. Do not edit by hand.
-# Schema ref: refs/tags/v0.5.0
+# Schema ref: refs/tags/v0.6.2
 AGENT_METHODS = {'authenticate': 'authenticate', 'initialize': 'initialize', 'session_cancel': 'session/cancel', 'session_load': 'session/load', 'session_new': 'session/new', 'session_prompt': 'session/prompt', 'session_set_mode': 'session/set_mode', 'session_set_model': 'session/set_model'}
 CLIENT_METHODS = {'fs_read_text_file': 'fs/read_text_file', 'fs_write_text_file': 'fs/write_text_file', 'session_request_permission': 'session/request_permission', 'session_update': 'session/update', 'terminal_create': 'terminal/create', 'terminal_kill': 'terminal/kill', 'terminal_output': 'terminal/output', 'terminal_release': 'terminal/release', 'terminal_wait_for_exit': 'terminal/wait_for_exit'}
 PROTOCOL_VERSION = 1
diff --git a/src/acp/schema.py b/src/acp/schema.py
@@ -1,5 +1,5 @@
 # Generated from schema/schema.json. Do not edit by hand.
-# Schema ref: refs/tags/v0.5.0
+# Schema ref: refs/tags/v0.6.2
 
 from __future__ import annotations
 
@@ -151,6 +151,35 @@ class HttpHeader(BaseModel):
     value: Annotated[str, Field(description="The value to set for the HTTP header.")]
 
 
+class Implementation(BaseModel):
+    # Intended for programmatic or logical use, but can be used as a display
+    # name fallback if title isn’t present.
+    name: Annotated[
+        str,
+        Field(
+            description="Intended for programmatic or logical use, but can be used as a display\nname fallback if title isn’t present."
+        ),
+    ]
+    # Intended for UI and end-user contexts — optimized to be human-readable
+    # and easily understood.
+    #
+    # If not provided, the name should be used for display.
+    title: Annotated[
+        Optional[str],
+        Field(
+            description="Intended for UI and end-user contexts — optimized to be human-readable\nand easily understood.\n\nIf not provided, the name should be used for display."
+        ),
+    ] = None
+    # Version of the implementation. Can be displayed to the user or used
+    # for debugging or metrics purposes.
+    version: Annotated[
+        str,
+        Field(
+            description="Version of the implementation. Can be displayed to the user or used\nfor debugging or metrics purposes."
+        ),
+    ]
+
+
 class KillTerminalCommandResponse(BaseModel):
     # Extension point for implementations
     field_meta: Annotated[
@@ -349,7 +378,7 @@ class SetSessionModeRequest(BaseModel):
 
 
 class SetSessionModeResponse(BaseModel):
-    meta: Optional[Any] = None
+    field_meta: Annotated[Optional[Any], Field(alias="_meta")] = None
 
 
 class SetSessionModelRequest(BaseModel):
@@ -767,6 +796,15 @@ class InitializeRequest(BaseModel):
         Optional[ClientCapabilities],
         Field(description="Capabilities supported by the client."),
     ] = ClientCapabilities(fs=FileSystemCapability(readTextFile=False, writeTextFile=False), terminal=False)
+    # Information about the Client name and version sent to the Agent.
+    #
+    # Note: in future versions of the protocol, this will be required.
+    clientInfo: Annotated[
+        Optional[Implementation],
+        Field(
+            description="Information about the Client name and version sent to the Agent.\n\nNote: in future versions of the protocol, this will be required."
+        ),
+    ] = None
     # The latest protocol version supported by the client.
     protocolVersion: Annotated[
         int,
@@ -793,6 +831,15 @@ class InitializeResponse(BaseModel):
         mcpCapabilities=McpCapabilities(http=False, sse=False),
         promptCapabilities=PromptCapabilities(audio=False, embeddedContext=False, image=False),
     )
+    # Information about the Agent name and version sent to the Client.
+    #
+    # Note: in future versions of the protocol, this will be required.
+    agentInfo: Annotated[
+        Optional[Implementation],
+        Field(
+            description="Information about the Agent name and version sent to the Client.\n\nNote: in future versions of the protocol, this will be required."
+        ),
+    ] = None
     # Authentication methods supported by the agent.
     authMethods: Annotated[
         Optional[List[AuthMethod]],

diff --git a/uv.lock b/uv.lock