perf: reuse OpenAI client and add undici keep-alive Agent with connection warmup

Extract OpenAI client creation logic into src/common/openai-client.ts:
- Custom undici Agent with 60s keepAlive timeout (default is 4s)
- Module-level client instance cache (reuse across calls)
- Fire-and-forget connection warmup on first creation (3s timeout)
- getMachineId() helper

The App.tsx now simply imports and re-exports createOpenAIClient from
the new common module, keeping UI concerns separate from HTTP/client
lifecycle management.

Author: Lellansin

package-lock.json

@@ -48,6 +48,7 @@
     "ink-gradient": "^4.0.0",
     "openai": "^6.35.0",
     "react": "^19.2.5",
+    "undici": "^7.25.0",
     "zod": "^4.4.3"
   },
   "devDependencies": {

package.json

@@ -0,0 +1,117 @@
+import * as fs from "fs";
+import * as os from "os";
+import * as path from "path";
+import OpenAI from "openai";
+import { Agent, fetch as undiciFetch } from "undici";
+import { resolveCurrentSettings } from "../ui/App";
+
+// Custom undici Agent with a 60-second keepAlive timeout.  The default
+// global fetch (undici) only keeps connections alive for 4 seconds, which
+// is too short for a CLI where the user may spend 10–30 seconds reading
+// output between prompts.  By passing a dedicated Agent to undiciFetch we
+// keep connections reusable for a full minute after the last request.
+const keepAliveAgent = new Agent({ keepAliveTimeout: 60_000 });
+
+// Module-level cache for the OpenAI client instance.  The client itself is
+// a stateless fetch wrapper, so it is safe to share across calls as long as
+// the apiKey + baseURL stay the same.  Model, thinking-mode and other
+// settings are always read fresh from the project / user config files.
+let cachedOpenAI: OpenAI | null = null;
+let cachedOpenAIKey = "";
+
+export function createOpenAIClient(projectRoot: string = process.cwd()): {
+  client: OpenAI | null;
+  model: string;
+  baseURL: string;
+  thinkingEnabled: boolean;
+  reasoningEffort: "high" | "max";
+  debugLogEnabled: boolean;
+  notify?: string;
+  webSearchTool?: string;
+  env: Record<string, string>;
+  machineId?: string;
+} {
+  const settings = resolveCurrentSettings(projectRoot);
+  if (!settings.apiKey) {
+    return {
+      client: null,
+      model: settings.model,
+      baseURL: settings.baseURL,
+      thinkingEnabled: settings.thinkingEnabled,
+      reasoningEffort: settings.reasoningEffort,
+      debugLogEnabled: settings.debugLogEnabled,
+      notify: settings.notify,
+      webSearchTool: settings.webSearchTool,
+      env: settings.env,
+      machineId: getMachineId(),
+    };
+  }
+
+  const cacheKey = `${settings.apiKey}::${settings.baseURL}`;
+  if (cachedOpenAI && cachedOpenAIKey === cacheKey) {
+    return {
+      client: cachedOpenAI,
+      model: settings.model,
+      baseURL: settings.baseURL,
+      thinkingEnabled: settings.thinkingEnabled,
+      reasoningEffort: settings.reasoningEffort,
+      debugLogEnabled: settings.debugLogEnabled,
+      notify: settings.notify,
+      webSearchTool: settings.webSearchTool,
+      env: settings.env,
+      machineId: getMachineId(),
+    };
+  }
+
+  cachedOpenAI = new OpenAI({
+    apiKey: settings.apiKey,
+    baseURL: settings.baseURL || undefined,
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    fetch: (url: any, init: any) => undiciFetch(url, { ...init, dispatcher: keepAliveAgent }),
+  });
+  cachedOpenAIKey = cacheKey;
+
+  // Fire-and-forget warmup: pre-establish TCP+TLS connection to the API
+  // server while the user is composing their first prompt.  Bounded by a
+  // short timeout so a slow / unreachable API never blocks process exit.
+  void (async () => {
+    const ac = new AbortController();
+    const timer = setTimeout(() => ac.abort(), 3000);
+    try {
+      await cachedOpenAI.models.list({ signal: ac.signal }).catch(() => {});
+    } finally {
+      clearTimeout(timer);
+    }
+  })();
+
+  return {
+    client: cachedOpenAI,
+    model: settings.model,
+    baseURL: settings.baseURL,
+    thinkingEnabled: settings.thinkingEnabled,
+    reasoningEffort: settings.reasoningEffort,
+    debugLogEnabled: settings.debugLogEnabled,
+    notify: settings.notify,
+    webSearchTool: settings.webSearchTool,
+    env: settings.env,
+    machineId: getMachineId(),
+  };
+}
+
+function getMachineId(): string | undefined {
+  try {
+    const idPath = path.join(os.homedir(), ".deepcode", "machine-id");
+    if (fs.existsSync(idPath)) {
+      const raw = fs.readFileSync(idPath, "utf8").trim();
+      if (raw) {
+        return raw;
+      }
+    }
+    const generated = `${os.hostname()}-${Math.random().toString(36).slice(2)}-${Date.now()}`;
+    fs.mkdirSync(path.dirname(idPath), { recursive: true });
+    fs.writeFileSync(idPath, generated, "utf8");
+    return generated;
+  } catch {
+    return undefined;
+  }
+}

src/common/openai-client.ts

@@ -4,7 +4,7 @@ import chalk from "chalk";
 import * as fs from "fs";
 import * as os from "os";
 import * as path from "path";
-import OpenAI from "openai";
+import { createOpenAIClient } from "../common/openai-client";
 import {
   type LlmStreamProgress,
   type MessageMeta,
@@ -166,6 +166,13 @@ export function App({ projectRoot, initialPrompt, onRestart }: AppProps): React.
     void refreshSkills();
   }, [refreshSessionsList, refreshSkills]);
 
+  // Eagerly create the OpenAI client on mount so the TCP+TLS connection
+  // warmup (fire-and-forget inside createOpenAIClient) starts before the
+  // user sends their first prompt.
+  useEffect(() => {
+    createOpenAIClient(projectRoot);
+  }, [projectRoot]);
+
   useLayoutEffect(() => {
     const settings = resolveCurrentSettings(projectRoot);
     void sessionManager.initMcpServers(settings.mcpServers);
@@ -838,69 +845,7 @@ export function resolveCurrentSettings(projectRoot: string = process.cwd()): Res
   );
 }
 
-export function createOpenAIClient(projectRoot: string = process.cwd()): {
-  client: OpenAI | null;
-  model: string;
-  baseURL: string;
-  thinkingEnabled: boolean;
-  reasoningEffort: "high" | "max";
-  debugLogEnabled: boolean;
-  notify?: string;
-  webSearchTool?: string;
-  env: Record<string, string>;
-  machineId?: string;
-} {
-  const settings = resolveCurrentSettings(projectRoot);
-  if (!settings.apiKey) {
-    return {
-      client: null,
-      model: settings.model,
-      baseURL: settings.baseURL,
-      thinkingEnabled: settings.thinkingEnabled,
-      reasoningEffort: settings.reasoningEffort,
-      debugLogEnabled: settings.debugLogEnabled,
-      notify: settings.notify,
-      webSearchTool: settings.webSearchTool,
-      env: settings.env,
-      machineId: getMachineId(),
-    };
-  }
-
-  const client = new OpenAI({
-    apiKey: settings.apiKey,
-    baseURL: settings.baseURL || undefined,
-  });
-  return {
-    client,
-    model: settings.model,
-    baseURL: settings.baseURL,
-    thinkingEnabled: settings.thinkingEnabled,
-    reasoningEffort: settings.reasoningEffort,
-    debugLogEnabled: settings.debugLogEnabled,
-    notify: settings.notify,
-    webSearchTool: settings.webSearchTool,
-    env: settings.env,
-    machineId: getMachineId(),
-  };
-}
-
-function getMachineId(): string | undefined {
-  try {
-    const idPath = path.join(os.homedir(), ".deepcode", "machine-id");
-    if (fs.existsSync(idPath)) {
-      const raw = fs.readFileSync(idPath, "utf8").trim();
-      if (raw) {
-        return raw;
-      }
-    }
-    const generated = `${os.hostname()}-${Math.random().toString(36).slice(2)}-${Date.now()}`;
-    fs.mkdirSync(path.dirname(idPath), { recursive: true });
-    fs.writeFileSync(idPath, generated, "utf8");
-    return generated;
-  } catch {
-    return undefined;
-  }
-}
+export { createOpenAIClient } from "../common/openai-client";
 
 function getUserSettingsPath(): string {
   return path.join(os.homedir(), ".deepcode", "settings.json");

src/ui/App.tsx

@@ -11,9 +11,9 @@ export {
   writeProjectSettings,
   writeModelConfigSelection,
   resolveCurrentSettings,
-  createOpenAIClient,
   buildPromptDraftFromSessionMessage,
 } from "./App";
+export { createOpenAIClient } from "../common/openai-client";
 export { default as AppContainer } from "./AppContainer";
 export { AskUserQuestionPrompt } from "./AskUserQuestionPrompt";
 export { MessageView } from "./components";