feat: add OAuth authentication support for remote MCP servers

src/mcp/mod.rs

@@ -1,3 +1,4 @@
+pub(crate) mod oauth;
 mod sse_transport;
 
 use crate::config::AppConfig;
@@ -73,6 +74,8 @@ pub(crate) struct McpServer {
     pub url: Option<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub headers: Option<IndexMap<String, String>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub oauth_client_id: Option<String>,
 }
 
 impl McpServer {
@@ -107,10 +110,10 @@ impl McpServer {
                     "MCP server '{name}' is missing a \"command\" field (required for stdio transport)"
                 ));
             }
-            if self.url.is_some() || self.headers.is_some() {
+            if self.url.is_some() || self.headers.is_some() || self.oauth_client_id.is_some() {
                 return Err(anyhow!(
                     "MCP server '{name}' has type \"stdio\" but also specifies remote fields \
-                     (url/headers). Remove the remote fields or change the type to \"http\" or \"sse\"."
+                     (url/headers/oauth_client_id). Remove the remote fields or change the type to \"http\" or \"sse\"."
                 ));
             }
         }
@@ -237,7 +240,7 @@ impl McpRegistry {
 
         debug!("Starting selected MCP servers: {:?}", ids_to_start);
 
-        let results: Vec<(String, Arc<_>, ServerCatalog)> = stream::iter(
+        let results: Vec<Option<(String, Arc<ConnectedServer>, ServerCatalog)>> = stream::iter(
             ids_to_start
                 .into_iter()
                 .map(|id| async { self.start_server(id).await }),
@@ -246,7 +249,7 @@ impl McpRegistry {
         .try_collect()
         .await?;
 
-        for (id, server, catalog) in results {
+        for (id, server, catalog) in results.into_iter().flatten() {
             self.servers.insert(id.clone(), server);
             self.catalogs.insert(id, catalog);
         }
@@ -257,14 +260,30 @@ impl McpRegistry {
     async fn start_server(
         &self,
         id: String,
-    ) -> Result<(String, Arc<ConnectedServer>, ServerCatalog)> {
+    ) -> Result<Option<(String, Arc<ConnectedServer>, ServerCatalog)>> {
         let spec = self
             .config
             .as_ref()
             .and_then(|c| c.mcp_servers.get(&id))
             .with_context(|| format!("MCP server not found in config: {id}"))?;
 
-        let service = spawn_mcp_server(spec, self.log_path.as_deref()).await?;
+        let bearer_token = if spec.is_remote() {
+            oauth::load_valid_mcp_token(&id)
+        } else {
+            None
+        };
+
+        let service = match spawn_mcp_server(spec, self.log_path.as_deref(), bearer_token).await {
+            Ok(s) => s,
+            Err(e) if is_auth_required_error(&e) => {
+                warn!(
+                    "MCP server '{id}' requires OAuth authentication. \
+                     Run `.mcp auth {id}` in the REPL to authenticate, then restart Coyote."
+                );
+                return Ok(None);
+            }
+            Err(e) => return Err(e),
+        };
 
         let tools = service.list_tools(None).await?;
         debug!("Available tools for MCP server {id}: {tools:?}");
@@ -289,7 +308,7 @@ impl McpRegistry {
 
         info!("Started MCP server: {id}");
 
-        Ok((id.to_string(), service, catalog))
+        Ok(Some((id.to_string(), service, catalog)))
     }
 
     fn resolve_server_ids(&self, enabled_mcp_servers: Option<Vec<String>>) -> Vec<String> {
@@ -337,15 +356,18 @@ impl McpRegistry {
 pub(crate) async fn spawn_mcp_server(
     spec: &McpServer,
     log_path: Option<&Path>,
+    bearer_token: Option<String>,
 ) -> Result<Arc<ConnectedServer>> {
     match spec.transport_type {
         McpTransportType::Http => {
             let url = spec.url.as_deref().expect("validated: http spec has url");
-            spawn_http_mcp_server(url, spec.headers.as_ref()).await
+            let headers = merge_bearer_token(spec.headers.as_ref(), bearer_token);
+            spawn_http_mcp_server(url, headers.as_ref()).await
         }
         McpTransportType::Sse => {
             let url = spec.url.as_deref().expect("validated: sse spec has url");
-            spawn_sse_mcp_server(url, spec.headers.as_ref()).await
+            let headers = merge_bearer_token(spec.headers.as_ref(), bearer_token);
+            spawn_sse_mcp_server(url, headers.as_ref()).await
         }
         McpTransportType::Stdio => {
             let command = spec
@@ -357,6 +379,30 @@ pub(crate) async fn spawn_mcp_server(
     }
 }
 
+fn merge_bearer_token(
+    headers: Option<&IndexMap<String, String>>,
+    bearer_token: Option<String>,
+) -> Option<IndexMap<String, String>> {
+    match (headers, bearer_token) {
+        (None, None) => None,
+        (Some(h), None) => Some(h.clone()),
+        (None, Some(token)) => {
+            let mut m = IndexMap::new();
+            m.insert("Authorization".to_string(), format!("Bearer {token}"));
+            Some(m)
+        }
+        (Some(h), Some(token)) => {
+            let mut m = h.clone();
+            m.insert("Authorization".to_string(), format!("Bearer {token}"));
+            Some(m)
+        }
+    }
+}
+
+fn is_auth_required_error(e: &anyhow::Error) -> bool {
+    e.to_string().contains("Auth required")
+}
+
 async fn spawn_http_mcp_server(
     url: &str,
     headers: Option<&IndexMap<String, String>>,
@@ -465,6 +511,7 @@ mod tests {
             cwd: None,
             url: None,
             headers: None,
+            oauth_client_id: None,
         }
     }
 
@@ -477,6 +524,7 @@ mod tests {
             cwd: None,
             url: Some(url.to_string()),
             headers: None,
+            oauth_client_id: None,
         }
     }
 
@@ -489,6 +537,7 @@ mod tests {
             cwd: None,
             url: Some(url.to_string()),
             headers: None,
+            oauth_client_id: None,
         }
     }
 
@@ -506,6 +555,7 @@ mod tests {
     #[test]
     fn validate_stdio_with_command_succeeds() {
         let spec = stdio_server("npx");
+
         assert!(spec.validate("test").is_ok());
     }
 
@@ -519,8 +569,11 @@ mod tests {
             cwd: None,
             url: None,
             headers: None,
+            oauth_client_id: None,
         };
+
         let err = spec.validate("test").unwrap_err();
+
         assert!(err.to_string().contains("missing a \"command\" field"));
     }
 
@@ -534,8 +587,11 @@ mod tests {
             cwd: None,
             url: Some("http://localhost".into()),
             headers: None,
+            oauth_client_id: None,
         };
+
         let err = spec.validate("test").unwrap_err();
+
         assert!(err.to_string().contains("remote fields"));
     }
 
@@ -551,14 +607,18 @@ mod tests {
             cwd: None,
             url: None,
             headers: Some(headers),
+            oauth_client_id: None,
         };
+
         let err = spec.validate("test").unwrap_err();
+
         assert!(err.to_string().contains("remote fields"));
     }
 
     #[test]
     fn validate_http_with_url_succeeds() {
         let spec = http_server("http://localhost:8080");
+
         assert!(spec.validate("test").is_ok());
     }
 
@@ -572,8 +632,11 @@ mod tests {
             cwd: None,
             url: None,
             headers: None,
+            oauth_client_id: None,
         };
+
         let err = spec.validate("test").unwrap_err();
+
         assert!(err.to_string().contains("missing a \"url\" field"));
     }
 
@@ -587,8 +650,11 @@ mod tests {
             cwd: None,
             url: Some("http://localhost".into()),
             headers: None,
+            oauth_client_id: None,
         };
+
         let err = spec.validate("test").unwrap_err();
+
         assert!(err.to_string().contains("stdio fields"));
     }
 
@@ -602,8 +668,11 @@ mod tests {
             cwd: None,
             url: Some("http://localhost".into()),
             headers: None,
+            oauth_client_id: None,
         };
+
         let err = spec.validate("test").unwrap_err();
+
         assert!(err.to_string().contains("stdio fields"));
     }
 
@@ -617,14 +686,18 @@ mod tests {
             cwd: Some("/tmp".into()),
             url: Some("http://localhost".into()),
             headers: None,
+            oauth_client_id: None,
         };
+
         let err = spec.validate("test").unwrap_err();
+
         assert!(err.to_string().contains("stdio fields"));
     }
 
     #[test]
     fn validate_sse_with_url_succeeds() {
         let spec = sse_server("http://sse.example.com");
+
         assert!(spec.validate("test").is_ok());
     }
 
@@ -638,8 +711,11 @@ mod tests {
             cwd: None,
             url: None,
             headers: None,
+            oauth_client_id: None,
         };
+
         let err = spec.validate("test").unwrap_err();
+
         assert!(err.to_string().contains("missing a \"url\" field"));
     }
 
@@ -665,9 +741,13 @@ mod tests {
                 }
             }
         }"#;
+
         let config: McpServersConfig = serde_json::from_str(json).unwrap();
+
         assert!(config.mcp_servers.contains_key("my-server"));
+
         let spec = &config.mcp_servers["my-server"];
+
         assert_eq!(spec.transport_type, McpTransportType::Stdio);
         assert_eq!(spec.command.as_deref(), Some("npx"));
         assert_eq!(
@@ -688,7 +768,9 @@ mod tests {
             }
         }"#;
         let config: McpServersConfig = serde_json::from_str(json).unwrap();
+
         let spec = &config.mcp_servers["remote"];
+
         assert_eq!(spec.transport_type, McpTransportType::Http);
         assert_eq!(spec.url.as_deref(), Some("http://localhost:8080/mcp"));
         assert_eq!(
@@ -713,7 +795,9 @@ mod tests {
             }
         }"#;
         let config: McpServersConfig = serde_json::from_str(json).unwrap();
+
         let env = config.mcp_servers["s"].env.as_ref().unwrap();
+
         assert!(matches!(env["STR_VAR"], JsonField::Str(ref s) if s == "hello"));
         assert!(matches!(env["BOOL_VAR"], JsonField::Bool(true)));
         assert!(matches!(env["INT_VAR"], JsonField::Int(42)));
@@ -727,7 +811,9 @@ mod tests {
                 "remote-api": { "type": "http", "url": "http://api.example.com" }
             }
         }"#;
+
         let config: McpServersConfig = serde_json::from_str(json).unwrap();
+
         assert_eq!(config.mcp_servers.len(), 2);
         assert!(config.mcp_servers.contains_key("github"));
         assert!(config.mcp_servers.contains_key("remote-api"));
@@ -736,7 +822,9 @@ mod tests {
     #[test]
     fn deserialize_empty_servers_map() {
         let json = r#"{ "mcpServers": {} }"#;
+
         let config: McpServersConfig = serde_json::from_str(json).unwrap();
+
         assert!(config.mcp_servers.is_empty());
     }
 
@@ -751,77 +839,96 @@ mod tests {
                 }
             }
         }"#;
+
         let config: McpServersConfig = serde_json::from_str(json).unwrap();
+
         assert_eq!(config.mcp_servers["s"].cwd.as_deref(), Some("/tmp/work"));
     }
 
     #[test]
     fn resolve_all_returns_all_configured_servers() {
         let registry = make_registry_with_config(&["github", "slack", "jira"]);
+
         let mut ids = registry.resolve_server_ids(Some(vec!["all".to_string()]));
         ids.sort();
+
         assert_eq!(ids, vec!["github", "jira", "slack"]);
     }
 
     #[test]
     fn resolve_comma_separated_returns_matching_servers() {
         let registry = make_registry_with_config(&["github", "slack", "jira"]);
+
         let mut ids =
             registry.resolve_server_ids(Some(vec!["github".to_string(), "jira".to_string()]));
         ids.sort();
+
         assert_eq!(ids, vec!["github", "jira"]);
     }
 
     #[test]
     fn resolve_single_server_name() {
         let registry = make_registry_with_config(&["github", "slack"]);
+
         let ids = registry.resolve_server_ids(Some(vec!["slack".to_string()]));
+
         assert_eq!(ids, vec!["slack"]);
     }
 
     #[test]
     fn resolve_none_returns_empty() {
         let registry = make_registry_with_config(&["github"]);
+
         let ids = registry.resolve_server_ids(None);
+
         assert!(ids.is_empty());
     }
 
     #[test]
     fn resolve_no_config_returns_empty() {
         let registry = McpRegistry::default();
+
         let ids = registry.resolve_server_ids(Some(vec!["all".to_string()]));
+
         assert!(ids.is_empty());
     }
 
     #[test]
     fn resolve_nonexistent_server_filtered_out() {
         let registry = make_registry_with_config(&["github"]);
+
         let ids = registry
             .resolve_server_ids(Some(vec!["github".to_string(), "nonexistent".to_string()]));
+
         assert_eq!(ids, vec!["github"]);
     }
 
     #[test]
     fn resolve_all_nonexistent_returns_empty() {
         let registry = make_registry_with_config(&["github"]);
+
         let ids = registry.resolve_server_ids(Some(vec!["foo".to_string(), "bar".to_string()]));
+
         assert!(ids.is_empty());
     }
 
     #[test]
     fn resolve_trims_whitespace() {
         let registry = make_registry_with_config(&["github", "slack"]);
+
         let mut ids = registry.resolve_server_ids(Some(vec![
             "  github  ".to_string(),
             "  slack  ".to_string(),
         ]));
         ids.sort();
+
         assert_eq!(ids, vec!["github", "slack"]);
     }
 
     #[test]
     fn registry_default_is_empty() {
         let registry = McpRegistry::default();
+
         assert!(registry.is_empty());
         assert!(registry.list_started_servers().is_empty());
         assert!(registry.mcp_config().is_none());
@@ -831,6 +938,7 @@ mod tests {
     #[test]
     fn registry_with_config_reports_config() {
         let registry = make_registry_with_config(&["github"]);
+
         assert!(registry.mcp_config().is_some());
         assert!(
             registry
@@ -847,4 +955,53 @@ mod tests {
         assert_eq!(MCP_SEARCH_META_FUNCTION_NAME_PREFIX, "mcp_search");
         assert_eq!(MCP_DESCRIBE_META_FUNCTION_NAME_PREFIX, "mcp_describe");
     }
+
+    #[test]
+    fn merge_bearer_token_both_none_returns_none() {
+        assert!(merge_bearer_token(None, None).is_none());
+    }
+
+    #[test]
+    fn merge_bearer_token_headers_only_passes_through() {
+        let mut h = IndexMap::new();
+        h.insert("X-Key".to_string(), "val".to_string());
+
+        let result = merge_bearer_token(Some(&h), None).unwrap();
+
+        assert_eq!(result["X-Key"], "val");
+        assert!(!result.contains_key("Authorization"));
+    }
+
+    #[test]
+    fn merge_bearer_token_token_only_injects_bearer() {
+        let result = merge_bearer_token(None, Some("tok123".to_string())).unwrap();
+
+        assert_eq!(result["Authorization"], "Bearer tok123");
+    }
+
+    #[test]
+    fn merge_bearer_token_both_merges_and_overrides_authorization() {
+        let mut h = IndexMap::new();
+        h.insert("Authorization".to_string(), "old".to_string());
+        h.insert("X-Custom".to_string(), "keep".to_string());
+
+        let result = merge_bearer_token(Some(&h), Some("newtoken".to_string())).unwrap();
+
+        assert_eq!(result["Authorization"], "Bearer newtoken");
+        assert_eq!(result["X-Custom"], "keep");
+    }
+
+    #[test]
+    fn is_auth_required_error_matches_rmcp_message() {
+        let e = anyhow!("Auth required, when send initialize request");
+
+        assert!(is_auth_required_error(&e));
+    }
+
+    #[test]
+    fn is_auth_required_error_does_not_match_unrelated() {
+        let e = anyhow!("Connection refused");
+
+        assert!(!is_auth_required_error(&e));
+    }
 }