perf(acp): parallelize extension loading in ACP server (#8098)

Signed-off-by: Douwe Osinga <douwe@squareup.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Douwe Osinga <douwe@squareup.com>

crates/goose-acp/src/server.rs

@@ -479,21 +479,30 @@ impl GooseAcpAgent {
         let skip_developer = acp_developer.is_some();
         let sid_str = session_id.map(|s| s.0.to_string());
 
-        for ext in extensions {
+        if skip_developer {
-            if skip_developer && ext.name() == "developer" {
+            extensions.retain(|ext| ext.name() != "developer");
-                continue;
-            }
-            let name = ext.name().to_string();
-            match agent
-                .extension_manager
-                .add_extension(ext, None, None, sid_str.as_deref())
-                .await
-            {
-                Ok(_) => info!(extension = %name, "extension loaded"),
-                Err(e) => warn!(extension = %name, error = %e, "extension load failed"),
-            }
         }
 
+        let ext_manager = &agent.extension_manager;
+        let extension_futures = extensions
+            .into_iter()
+            .map(|ext| {
+                let ext_manager = Arc::clone(ext_manager);
+                let sid = sid_str.clone();
+                async move {
+                    let name = ext.name().to_string();
+                    match ext_manager
+                        .add_extension(ext, None, None, sid.as_deref())
+                        .await
+                    {
+                        Ok(_) => info!(extension = %name, "extension loaded"),
+                        Err(e) => warn!(extension = %name, error = %e, "extension load failed"),
+                    }
+                }
+            })
+            .collect::<Vec<_>>();
+        futures::future::join_all(extension_futures).await;
+
         if let Some((client, config)) = acp_developer {
             let info = client.get_info().cloned();
             agent
@@ -932,10 +941,11 @@ impl GooseAcpAgent {
     }
 
     async fn add_mcp_extensions(
-        agent: &Agent,
+        agent: &Arc<Agent>,
         mcp_servers: Vec<McpServer>,
         session_id: &str,
     ) -> Result<(), sacp::Error> {
+        let mut configs = Vec::with_capacity(mcp_servers.len());
         for mcp_server in mcp_servers {
             let config = match mcp_server_to_extension_config(mcp_server) {
                 Ok(c) => c,
@@ -943,10 +953,24 @@ impl GooseAcpAgent {
                     return Err(sacp::Error::invalid_params().data(msg));
                 }
             };
-            let name = config.name().to_string();
+            configs.push(config);
-            if let Err(e) = agent.add_extension(config, session_id).await {
+        }
-                return Err(sacp::Error::internal_error()
+
-                    .data(format!("Failed to add MCP server '{}': {}", name, e)));
+        if configs.is_empty() {
+            return Ok(());
+        }
+
+        let results = agent
+            .add_extensions_bulk(configs, session_id)
+            .await
+            .map_err(|e| sacp::Error::internal_error().data(e.to_string()))?;
+        for result in &results {
+            if !result.success {
+                let error_msg = result.error.as_deref().unwrap_or("unknown error");
+                return Err(sacp::Error::internal_error().data(format!(
+                    "Failed to add MCP server '{}': {}",
+                    result.name, error_msg
+                )));
             }
         }
         Ok(())

crates/goose/src/agents/agent.rs

@@ -761,6 +761,71 @@ impl Agent {
         Ok(())
     }
 
+    /// Load multiple extensions in parallel, persisting state once at the end.
+    ///
+    /// Unlike `add_extension`, this avoids per-extension persistence and acquires
+    /// the container lock once upfront to prevent serialisation of the parallel futures.
+    pub async fn add_extensions_bulk(
+        self: &Arc<Self>,
+        extensions: Vec<ExtensionConfig>,
+        session_id: &str,
+    ) -> anyhow::Result<Vec<ExtensionLoadResult>> {
+        let working_dir = match self
+            .config
+            .session_manager
+            .get_session(session_id, false)
+            .await
+        {
+            Ok(session) => Some(session.working_dir),
+            Err(e) => {
+                warn!("Failed to get session for bulk load: {}", e);
+                None
+            }
+        };
+        let container = self.container.lock().await.clone();
+
+        let extension_futures = extensions
+            .into_iter()
+            .map(|config| {
+                let ext_manager = Arc::clone(&self.extension_manager);
+                let working_dir = working_dir.clone();
+                let container = container.clone();
+                let sid = session_id.to_string();
+
+                async move {
+                    let name = config.name().to_string();
+                    match ext_manager
+                        .add_extension(config, working_dir, container.as_ref(), Some(&sid))
+                        .await
+                    {
+                        Ok(_) => ExtensionLoadResult {
+                            name,
+                            success: true,
+                            error: None,
+                        },
+                        Err(e) => {
+                            let error_msg = e.to_string();
+                            warn!("Failed to load extension {}: {}", name, error_msg);
+                            ExtensionLoadResult {
+                                name,
+                                success: false,
+                                error: Some(error_msg),
+                            }
+                        }
+                    }
+                }
+            })
+            .collect::<Vec<_>>();
+
+        let results = futures::future::join_all(extension_futures).await;
+
+        if results.iter().any(|r| r.success) {
+            self.persist_extension_state(session_id).await?;
+        }
+
+        Ok(results)
+    }
+
     async fn add_extension_inner(
         &self,
         extension: ExtensionConfig,