Forward OAuth client metadata URL

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: SamMorrowDrums

rust/src/types.rs

@@ -1860,6 +1860,12 @@ pub struct SessionConfig {
     /// applied automatically at session creation/resume time. `None` means no
     /// explicit value is set and the runtime default takes effect.
     pub mcp_oauth_token_storage: Option<String>,
+    /// URL identifying this host's OAuth client metadata document.
+    ///
+    /// Authorization servers that support client ID metadata documents can use
+    /// this URL as the MCP OAuth client ID. Older runtimes ignore this optional
+    /// field.
+    pub auth_client_id_metadata_url: Option<String>,
     /// Enables runtime discovery of supported configuration. Explicitly supplied
     /// configuration takes precedence over discovered values.
     pub enable_config_discovery: Option<bool>,
@@ -2235,6 +2241,7 @@ impl Default for SessionConfig {
             excluded_builtin_agents: None,
             mcp_servers: None,
             mcp_oauth_token_storage: None,
+            auth_client_id_metadata_url: None,
             enable_config_discovery: None,
             skip_embedding_retrieval: None,
             organization_custom_instructions: None,
@@ -2388,6 +2395,7 @@ impl SessionConfig {
             tool_filter_precedence: "excluded",
             mcp_servers: self.mcp_servers,
             mcp_oauth_token_storage: self.mcp_oauth_token_storage,
+            auth_client_id_metadata_url: self.auth_client_id_metadata_url,
             embedding_cache_storage: self.embedding_cache_storage,
             env_value_mode: "direct",
             enable_config_discovery: self.enable_config_discovery,
@@ -2715,6 +2723,12 @@ impl SessionConfig {
         self
     }
 
+    /// Set the URL identifying this host's OAuth client metadata document.
+    pub fn with_auth_client_id_metadata_url(mut self, url: impl Into<String>) -> Self {
+        self.auth_client_id_metadata_url = Some(url.into());
+        self
+    }
+
     /// Set embedding cache storage mode.
     pub fn with_embedding_cache_storage(
         mut self,
@@ -3101,6 +3115,9 @@ pub struct ResumeSessionConfig {
     /// Controls how MCP OAuth tokens are stored for this session.
     /// See [`SessionConfig::mcp_oauth_token_storage`] for details.
     pub mcp_oauth_token_storage: Option<String>,
+    /// Re-supply the host OAuth client metadata document URL on resume.
+    /// See [`SessionConfig::auth_client_id_metadata_url`] for details.
+    pub auth_client_id_metadata_url: Option<String>,
     /// Enables runtime discovery of supported configuration. Explicitly supplied
     /// configuration takes precedence over discovered values.
     pub enable_config_discovery: Option<bool>,
@@ -3457,6 +3474,7 @@ impl ResumeSessionConfig {
             tool_filter_precedence: "excluded",
             mcp_servers: self.mcp_servers,
             mcp_oauth_token_storage: self.mcp_oauth_token_storage,
+            auth_client_id_metadata_url: self.auth_client_id_metadata_url,
             embedding_cache_storage: self.embedding_cache_storage,
             env_value_mode: "direct",
             enable_config_discovery: self.enable_config_discovery,
@@ -3556,6 +3574,7 @@ impl ResumeSessionConfig {
             excluded_builtin_agents: None,
             mcp_servers: None,
             mcp_oauth_token_storage: None,
+            auth_client_id_metadata_url: None,
             enable_config_discovery: None,
             skip_embedding_retrieval: None,
             organization_custom_instructions: None,
@@ -3855,6 +3874,12 @@ impl ResumeSessionConfig {
         self
     }
 
+    /// Set the host OAuth client metadata document URL on resume.
+    pub fn with_auth_client_id_metadata_url(mut self, url: impl Into<String>) -> Self {
+        self.auth_client_id_metadata_url = Some(url.into());
+        self
+    }
+
     /// Set embedding cache storage mode on resume.
     pub fn with_embedding_cache_storage(
         mut self,
@@ -6375,6 +6400,25 @@ mod tests {
         assert!(empty_json.get("largeOutput").is_none());
     }
 
+    #[test]
+    fn auth_client_id_metadata_url_reaches_create_and_resume_wire_payloads() {
+        let url = "https://example.com/oauth/client-metadata.json";
+
+        let (create_wire, _) = SessionConfig::default()
+            .with_auth_client_id_metadata_url(url)
+            .into_wire(None)
+            .expect("default create has no duplicate handlers");
+        let create_json = serde_json::to_value(&create_wire).unwrap();
+        assert_eq!(create_json["authClientIdMetadataUrl"], url);
+
+        let (resume_wire, _) = ResumeSessionConfig::new(SessionId::from("sess-1"))
+            .with_auth_client_id_metadata_url(url)
+            .into_wire()
+            .expect("default resume has no duplicate handlers");
+        let resume_json = serde_json::to_value(&resume_wire).unwrap();
+        assert_eq!(resume_json["authClientIdMetadataUrl"], url);
+    }
+
     #[test]
     fn session_config_builder_composes() {
         use indexmap::IndexMap;

rust/src/wire.rs

@@ -90,6 +90,8 @@ pub(crate) struct SessionCreateWire {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub mcp_oauth_token_storage: Option<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
+    pub auth_client_id_metadata_url: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub embedding_cache_storage: Option<String>,
     pub env_value_mode: &'static str,
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -230,6 +232,8 @@ pub(crate) struct SessionResumeWire {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub mcp_oauth_token_storage: Option<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
+    pub auth_client_id_metadata_url: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub embedding_cache_storage: Option<String>,
     pub env_value_mode: &'static str,
     #[serde(skip_serializing_if = "Option::is_none")]