fix(unstable-v2): allow null auth capabilities

agent-client-protocol-schema/src/v2/agent.rs

@@ -57,13 +57,13 @@ use super::{
 pub struct InitializeRequest {
     /// The latest protocol version supported by the client.
     pub protocol_version: ProtocolVersion,
+    /// Information about the implementation sending this initialize request.
+    pub info: Implementation,
     /// Capabilities supported by the client.
     #[serde_as(deserialize_as = "DefaultOnError")]
     #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub capabilities: ClientCapabilities,
-    /// Information about the implementation sending this initialize request.
-    pub info: Implementation,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
     /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
     /// these keys.
@@ -124,6 +124,8 @@ pub struct InitializeResponse {
     ///
     /// The client should disconnect, if it doesn't support this version.
     pub protocol_version: ProtocolVersion,
+    /// Information about the implementation sending this initialize response.
+    pub info: Implementation,
     /// Capabilities supported by the agent.
     #[serde_as(deserialize_as = "DefaultOnError")]
     #[schemars(extend("x-deserialize-default-on-error" = true))]
@@ -134,8 +136,6 @@ pub struct InitializeResponse {
     #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     #[serde(default)]
     pub auth_methods: Vec<AuthMethod>,
-    /// Information about the implementation sending this initialize response.
-    pub info: Implementation,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
     /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
     /// these keys.
@@ -1231,10 +1231,8 @@ impl NewSessionResponse {
 #[serde(rename_all = "camelCase")]
 #[non_exhaustive]
 pub struct LoadSessionRequest {
-    /// List of MCP servers to connect to for this session.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
-    pub mcp_servers: Vec<McpServer>,
+    /// The ID of the session to load.
+    pub session_id: SessionId,
     /// The working directory for this session.
     pub cwd: PathBuf,
     /// Additional workspace roots to activate for this session. Each path must be absolute.
@@ -1247,8 +1245,10 @@ pub struct LoadSessionRequest {
     #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     #[serde(default, skip_serializing_if = "Vec::is_empty")]
     pub additional_directories: Vec<PathBuf>,
-    /// The ID of the session to load.
-    pub session_id: SessionId,
+    /// List of MCP servers to connect to for this session.
+    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
+    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
+    pub mcp_servers: Vec<McpServer>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
     /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
     /// these keys.
@@ -3902,7 +3902,7 @@ pub struct AgentCapabilities {
     #[serde_as(deserialize_as = "DefaultOnError")]
     #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
-    pub auth: AgentAuthCapabilities,
+    pub auth: Option<AgentAuthCapabilities>,
     /// **UNSTABLE**
     ///
     /// This capability is not part of the spec yet, and may be removed or changed at any point.
@@ -3968,8 +3968,8 @@ impl AgentCapabilities {
 
     /// Authentication-related capabilities supported by the agent.
     #[must_use]
-    pub fn auth(mut self, auth: AgentAuthCapabilities) -> Self {
-        self.auth = auth;
+    pub fn auth(mut self, auth: impl IntoOption<AgentAuthCapabilities>) -> Self {
+        self.auth = auth.into_option();
         self
     }
 
@@ -4804,10 +4804,10 @@ pub struct McpCapabilities {
     /// This capability is not part of the spec yet, and may be removed or changed at any point.
     ///
     /// Agent supports [`McpServer::Acp`].
-    #[cfg(feature = "unstable_mcp_over_acp")]
     ///
     /// Optional. Omitted or `null` both mean the agent does not advertise support.
     /// Supplying `{}` means the agent supports ACP MCP server transports.
+    #[cfg(feature = "unstable_mcp_over_acp")]
     #[serde_as(deserialize_as = "DefaultOnError")]
     #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
@@ -5001,6 +5001,52 @@ impl McpAcpCapabilities {
     }
 }
 
+/// Notification to cancel ongoing operations for a session.
+///
+/// See protocol docs: [Cancellation](https://agentclientprotocol.com/protocol/prompt-lifecycle#cancellation)
+#[serde_as]
+#[skip_serializing_none]
+#[derive(Debug, Clone, Serialize, Deserialize, JsonSchema, PartialEq, Eq)]
+#[schemars(extend("x-side" = "agent", "x-method" = SESSION_CANCEL_METHOD_NAME))]
+#[serde(rename_all = "camelCase")]
+#[non_exhaustive]
+pub struct CancelSessionNotification {
+    /// The ID of the session to cancel operations for.
+    pub session_id: SessionId,
+    /// The _meta property is reserved by ACP to allow clients and agents to attach additional
+    /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
+    /// these keys.
+    ///
+    /// See protocol docs: [Extensibility](https://agentclientprotocol.com/protocol/extensibility)
+    #[serde_as(deserialize_as = "DefaultOnError")]
+    #[schemars(extend("x-deserialize-default-on-error" = true))]
+    #[serde(default)]
+    #[serde(rename = "_meta")]
+    pub meta: Option<Meta>,
+}
+
+impl CancelSessionNotification {
+    /// Builds [`CancelSessionNotification`] with the required notification fields set; optional fields start unset or empty.
+    #[must_use]
+    pub fn new(session_id: impl Into<SessionId>) -> Self {
+        Self {
+            session_id: session_id.into(),
+            meta: None,
+        }
+    }
+
+    /// The _meta property is reserved by ACP to allow clients and agents to attach additional
+    /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
+    /// these keys.
+    ///
+    /// See protocol docs: [Extensibility](https://agentclientprotocol.com/protocol/extensibility)
+    #[must_use]
+    pub fn meta(mut self, meta: impl IntoOption<Meta>) -> Self {
+        self.meta = meta.into_option();
+        self
+    }
+}
+
 // Method schema
 
 /// Names of all methods that agents handle.
@@ -5458,7 +5504,7 @@ pub enum ClientNotification {
     ///   cancellation succeeds
     ///
     /// See protocol docs: [Cancellation](https://agentclientprotocol.com/protocol/prompt-lifecycle#cancellation)
-    CancelNotification(CancelNotification),
+    CancelSessionNotification(CancelSessionNotification),
     #[cfg(feature = "unstable_nes")]
     /// **UNSTABLE**
     ///
@@ -5515,7 +5561,7 @@ impl ClientNotification {
     #[must_use]
     pub fn method(&self) -> &str {
         match self {
-            Self::CancelNotification(_) => AGENT_METHOD_NAMES.session_cancel,
+            Self::CancelSessionNotification(_) => AGENT_METHOD_NAMES.session_cancel,
             #[cfg(feature = "unstable_nes")]
             Self::DidOpenDocumentNotification(_) => AGENT_METHOD_NAMES.document_did_open,
             #[cfg(feature = "unstable_nes")]
@@ -5537,52 +5583,6 @@ impl ClientNotification {
     }
 }
 
-/// Notification to cancel ongoing operations for a session.
-///
-/// See protocol docs: [Cancellation](https://agentclientprotocol.com/protocol/prompt-lifecycle#cancellation)
-#[serde_as]
-#[skip_serializing_none]
-#[derive(Debug, Clone, Serialize, Deserialize, JsonSchema, PartialEq, Eq)]
-#[schemars(extend("x-side" = "agent", "x-method" = SESSION_CANCEL_METHOD_NAME))]
-#[serde(rename_all = "camelCase")]
-#[non_exhaustive]
-pub struct CancelNotification {
-    /// The ID of the session to cancel operations for.
-    pub session_id: SessionId,
-    /// The _meta property is reserved by ACP to allow clients and agents to attach additional
-    /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
-    /// these keys.
-    ///
-    /// See protocol docs: [Extensibility](https://agentclientprotocol.com/protocol/extensibility)
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
-    #[serde(default)]
-    #[serde(rename = "_meta")]
-    pub meta: Option<Meta>,
-}
-
-impl CancelNotification {
-    /// Builds [`CancelNotification`] with the required notification fields set; optional fields start unset or empty.
-    #[must_use]
-    pub fn new(session_id: impl Into<SessionId>) -> Self {
-        Self {
-            session_id: session_id.into(),
-            meta: None,
-        }
-    }
-
-    /// The _meta property is reserved by ACP to allow clients and agents to attach additional
-    /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
-    /// these keys.
-    ///
-    /// See protocol docs: [Extensibility](https://agentclientprotocol.com/protocol/extensibility)
-    #[must_use]
-    pub fn meta(mut self, meta: impl IntoOption<Meta>) -> Self {
-        self.meta = meta.into_option();
-        self
-    }
-}
-
 #[cfg(test)]
 mod test_serialization {
     use super::*;
@@ -5633,7 +5633,7 @@ mod test_serialization {
         .unwrap();
 
         assert!(capabilities.session.is_none());
-        assert_eq!(capabilities.auth, AgentAuthCapabilities::default());
+        assert_eq!(capabilities.auth, None);
     }
 
     #[test]
@@ -6923,7 +6923,6 @@ mod test_serialization {
         assert_eq!(
             serde_json::to_value(&caps).unwrap(),
             json!({
-                "auth": {},
                 "session": {
                     "prompt": {
                         "image": {}

agent-client-protocol-schema/src/v2/conversion.rs

@@ -4767,7 +4767,7 @@ impl IntoV1 for super::AgentCapabilities {
             prompt_capabilities,
             mcp_capabilities,
             session_capabilities,
-            auth: auth.into_v1()?,
+            auth: auth.map(IntoV1::into_v1).transpose()?.unwrap_or_default(),
             #[cfg(feature = "unstable_llm_providers")]
             providers: into_v1_default_on_error(providers),
             #[cfg(feature = "unstable_nes")]
@@ -4806,7 +4806,7 @@ impl IntoV2 for crate::v1::AgentCapabilities {
 
         Ok(super::AgentCapabilities {
             session: Some(session),
-            auth: auth.into_v2()?,
+            auth: Some(auth.into_v2()?),
             #[cfg(feature = "unstable_llm_providers")]
             providers: into_v2_default_on_error(providers),
             #[cfg(feature = "unstable_nes")]
@@ -5458,7 +5458,7 @@ impl IntoV1 for super::ClientNotification {
 
     fn into_v1(self) -> Result<Self::Output> {
         Ok(match self {
-            Self::CancelNotification(value) => {
+            Self::CancelSessionNotification(value) => {
                 crate::v1::ClientNotification::CancelNotification(value.into_v1()?)
             }
             #[cfg(feature = "unstable_nes")]
@@ -5506,7 +5506,7 @@ impl IntoV2 for crate::v1::ClientNotification {
     fn into_v2(self) -> Result<Self::Output> {
         Ok(match self {
             Self::CancelNotification(value) => {
-                super::ClientNotification::CancelNotification(value.into_v2()?)
+                super::ClientNotification::CancelSessionNotification(value.into_v2()?)
             }
             #[cfg(feature = "unstable_nes")]
             Self::DidOpenDocumentNotification(value) => {
@@ -5547,7 +5547,7 @@ impl IntoV2 for crate::v1::ClientNotification {
     }
 }
 
-impl IntoV1 for super::CancelNotification {
+impl IntoV1 for super::CancelSessionNotification {
     type Output = crate::v1::CancelNotification;
 
     fn into_v1(self) -> Result<Self::Output> {
@@ -5560,11 +5560,11 @@ impl IntoV1 for super::CancelNotification {
 }
 
 impl IntoV2 for crate::v1::CancelNotification {
-    type Output = super::CancelNotification;
+    type Output = super::CancelSessionNotification;
 
     fn into_v2(self) -> Result<Self::Output> {
         let Self { session_id, meta } = self;
-        Ok(super::CancelNotification {
+        Ok(super::CancelSessionNotification {
             session_id: session_id.into_v2()?,
             meta: meta.into_v2()?,
         })

docs/protocol/v2/draft/schema.mdx

@@ -363,7 +363,7 @@ See protocol docs: [Extensibility](https://agentclientprotocol.com/protocol/v2/d
 <ResponseField name="capabilities" type={<a href="#agentcapabilities">AgentCapabilities</a>} >
   Capabilities supported by the agent.
 
-    - Default: `{"auth":{}}`
+    - Default: `{}`
 
 </ResponseField>
 <ResponseField name="info" type={<a href="#implementation">Implementation</a>} required>
@@ -894,7 +894,7 @@ Upon receiving this notification, the Agent SHOULD:
 
 See protocol docs: [Cancellation](https://agentclientprotocol.com/protocol/v2/draft/prompt-lifecycle#cancellation)
 
-#### <span class="font-mono">CancelNotification</span>
+#### <span class="font-mono">CancelSessionNotification</span>
 
 Notification to cancel ongoing operations for a session.
 
@@ -2130,11 +2130,8 @@ these keys.
 See protocol docs: [Extensibility](https://agentclientprotocol.com/protocol/v2/draft/extensibility)
 
 </ResponseField>
-<ResponseField name="auth" type={<a href="#agentauthcapabilities">AgentAuthCapabilities</a>} >
+<ResponseField name="auth" type={<><span><a href="#agentauthcapabilities">AgentAuthCapabilities</a></span><span> | null</span></>} >
   Authentication-related capabilities supported by the agent.
-
-    - Default: `{}`
-
 </ResponseField>
 <ResponseField name="nes" type={<><span><a href="#nescapabilities">NesCapabilities</a></span><span> | null</span></>} >
   **UNSTABLE**

docs/protocol/v2/schema.mdx

@@ -189,7 +189,7 @@ See protocol docs: [Extensibility](https://agentclientprotocol.com/protocol/v2/e
 <ResponseField name="capabilities" type={<a href="#agentcapabilities">AgentCapabilities</a>} >
   Capabilities supported by the agent.
 
-    - Default: `{"auth":{}}`
+    - Default: `{}`
 
 </ResponseField>
 <ResponseField name="info" type={<a href="#implementation">Implementation</a>} required>
@@ -221,7 +221,7 @@ Upon receiving this notification, the Agent SHOULD:
 
 See protocol docs: [Cancellation](https://agentclientprotocol.com/protocol/v2/prompt-lifecycle#cancellation)
 
-#### <span class="font-mono">CancelNotification</span>
+#### <span class="font-mono">CancelSessionNotification</span>
 
 Notification to cancel ongoing operations for a session.
 
@@ -904,11 +904,8 @@ these keys.
 See protocol docs: [Extensibility](https://agentclientprotocol.com/protocol/v2/extensibility)
 
 </ResponseField>
-<ResponseField name="auth" type={<a href="#agentauthcapabilities">AgentAuthCapabilities</a>} >
+<ResponseField name="auth" type={<><span><a href="#agentauthcapabilities">AgentAuthCapabilities</a></span><span> | null</span></>} >
   Authentication-related capabilities supported by the agent.
-
-    - Default: `{}`
-
 </ResponseField>
 <ResponseField name="session" type={<><span><a href="#sessioncapabilities">SessionCapabilities</a></span><span> | null</span></>} >
   Session capabilities supported by the agent.

schema-generator/src/main.rs

@@ -1885,7 +1885,11 @@ starting with '$/' it is free to ignore the notification."
                     self.agent.get("SetSessionConfigOptionRequest").unwrap()
                 }
                 "session/prompt" => self.agent.get("PromptRequest").unwrap(),
-                "session/cancel" => self.agent.get("CancelNotification").unwrap(),
+                "session/cancel" => self
+                    .agent
+                    .get("CancelSessionNotification")
+                    .or_else(|| self.agent.get("CancelNotification"))
+                    .unwrap(),
                 "session/close" => self.agent.get("CloseSessionRequest").unwrap(),
                 "logout" => self.agent.get("LogoutRequest").unwrap(),
                 "auth/logout" => self.agent.get("LogoutAuthRequest").unwrap(),