diff --git a/src/lib/runtime/codewiz-process.ts b/src/lib/runtime/codewiz-process.ts
new file mode 100644
index 0000000..7db5267
--- /dev/null
+++ b/src/lib/runtime/codewiz-process.ts
@@ -0,0 +1,92 @@
+/**
+ * runtime/codewiz-process.ts — Node.js-only process management for codewiz-agent.
+ *
+ * This file is imported via dynamic `import()` so it only runs in Node.js,
+ * not in the browser. Place all child_process / Node.js built-in usage here.
+ */
+
+import path from 'path';
+import { fileURLToPath } from 'url';
+
+const DEFAULT_PORT = 18732;
+const STARTUP_TIMEOUT_MS = 15_000;
+
+let pythonProcess: ReturnType<typeof import('child_process').spawn> | null = null;
+let fastApiReady = false;
+let fastApiFailed = false;
+let startupPromise: Promise<void> | null = null;
+
+function getPySrc(): string {
+  // __dirname equivalent for ESM
+  const currentFile = fileURLToPath(import.meta.url);
+  return path.join(path.dirname(currentFile), '..', 'lib', 'codewiz-agent');
+}
+
+function getPort(): number {
+  return Number(process.env.FASTAPI_PORT ?? DEFAULT_PORT);
+}
+
+export function ensureFastApi(): Promise<void> {
+  if (fastApiReady) return Promise.resolve();
+  if (fastApiFailed) return Promise.reject(new Error('FastAPI backend failed to start'));
+  if (startupPromise) return startupPromise;
+  startupPromise = _startFastApi().then(() => { startupPromise = null; });
+  return startupPromise;
+}
+
+async function _startFastApi(): Promise<void> {
+  const { spawn } = await import('child_process');
+  const port = getPort();
+  const pySrc = getPySrc();
+
+  console.log('[codewiz-runtime] Starting FastAPI backend on port', port);
+
+  pythonProcess = spawn('python', ['-m', 'uvicorn', 'app.main:app', '--host', '127.0.0.1', '--port', String(port)], {
+    cwd: pySrc,
+    stdio: ['ignore', 'pipe', 'pipe'],
+    shell: false,
+    env: { ...process.env, PYTHONPATH: pySrc },
+  });
+
+  let stderr = '';
+  pythonProcess.stderr?.on('data', (chunk: Buffer) => {
+    stderr += chunk.toString('utf-8');
+  });
+
+  const deadline = Date.now() + STARTUP_TIMEOUT_MS;
+  while (Date.now() < deadline) {
+    await new Promise(r => setTimeout(r, 500));
+    try {
+      const res = await fetch(`http://127.0.0.1:${port}/health`);
+      if (res.ok) {
+        fastApiReady = true;
+        console.log('[codewiz-runtime] FastAPI backend ready');
+        return;
+      }
+    } catch {
+      // not ready yet
+    }
+    if (pythonProcess?.exitCode !== null) {
+      fastApiFailed = true;
+      console.error('[codewiz-runtime] FastAPI process exited early:\n' + stderr);
+      throw new Error(`FastAPI exited with code ${pythonProcess.exitCode}`);
+    }
+  }
+  fastApiFailed = true;
+  pythonProcess?.kill();
+  throw new Error(`FastAPI did not start within ${STARTUP_TIMEOUT_MS}ms`);
+}
+
+export function disposeFastApi(): void {
+  if (pythonProcess) {
+    pythonProcess.kill('SIGTERM');
+    pythonProcess = null;
+  }
+  fastApiReady = false;
+  fastApiFailed = false;
+  startupPromise = null;
+}
+
+export function getFastApiPort(): number {
+  return getPort();
+}
diff --git a/src/lib/runtime/codewiz-runtime.ts b/src/lib/runtime/codewiz-runtime.ts
index 45deb87..e69de29 100644
--- a/src/lib/runtime/codewiz-runtime.ts
+++ b/src/lib/runtime/codewiz-runtime.ts
@@ -1,294 +0,0 @@
-/**
- * runtime/codewiz-runtime.ts — TypeScript Runtime for codewiz-agent FastAPI backend.
- *
- * Manages the FastAPI subprocess lifecycle, translates SSE events from FastAPI's
- * HarnessEvent format to CodeWiz's SSEEventType format, and implements the
- * AgentRuntime interface so codewiz-agent sessions flow through the same
- * chat/route.ts pipeline as other runtimes.
- *
- * Architecture:
- *   Next.js (chat API) → codewizRuntime.stream() → HTTP POST to FastAPI SSE
- *   FastAPI → SSE → codewiz-runtime (translate) → SSEEvent → client
- */
-
-import type { AgentRuntime, RuntimeStreamOptions } from './types';
-
-const activeAbortControllers = new Map<string, AbortController>();
-const activeFetches = new Map<string, AbortController>();
-
-/** Default port for the FastAPI backend; override via FASTAPI_PORT env. */
-const DEFAULT_PORT = 18732;
-const getPort = () => Number(process.env.FASTAPI_PORT ?? DEFAULT_PORT);
-
-/** How long to wait for FastAPI to start before giving up (ms). */
-const STARTUP_TIMEOUT_MS = 15_000;
-
-/** Whether FastAPI subprocess is currently running. */
-let pythonProcess: import('child_process').ChildProcess | null = null;
-let fastApiReady = false;
-let fastApiFailed = false;
-let startupPromise: Promise<void> | null = null;
-
-/** Resolve once FastAPI is ready. Reuses the promise across concurrent calls. */
-function ensureFastApi(): Promise<void> {
-  if (fastApiReady) return Promise.resolve();
-  if (fastApiFailed) return Promise.reject(new Error('FastAPI backend failed to start'));
-  if (startupPromise) return startupPromise;
-  startupPromise = _startFastApi().then(() => { startupPromise = null; });
-  return startupPromise;
-}
-
-async function _startFastApi(): Promise<void> {
-  const { spawn } = await import('child_process');
-  const port = getPort();
-
-  console.log('[codewiz-runtime] Starting FastAPI backend on port', port);
-
-  const pySrc = `${__dirname}/../lib/codewiz-agent`;
-  pythonProcess = spawn('python', ['-m', 'uvicorn', 'app.main:app', '--host', '127.0.0.1', '--port', String(port)], {
-    cwd: pySrc,
-    stdio: ['ignore', 'pipe', 'pipe'],
-    shell: false,
-    env: { ...process.env, PYTHONPATH: pySrc },
-  });
-
-  let stderr = '';
-  pythonProcess.stderr?.on('data', (chunk: Buffer) => {
-    stderr += chunk.toString('utf-8');
-  });
-
-  // Wait for FastAPI to be ready (poll /health until 200)
-  const deadline = Date.now() + STARTUP_TIMEOUT_MS;
-  while (Date.now() < deadline) {
-    await new Promise(r => setTimeout(r, 500));
-    try {
-      const res = await fetch(`http://127.0.0.1:${port}/health`);
-      if (res.ok) {
-        fastApiReady = true;
-        console.log('[codewiz-runtime] FastAPI backend ready');
-        return;
-      }
-    } catch {
-      // not ready yet
-    }
-    // Check if process died
-    if (pythonProcess?.exitCode !== null) {
-      fastApiFailed = true;
-      console.error('[codewiz-runtime] FastAPI process exited early:\n' + stderr);
-      throw new Error(`FastAPI exited with code ${pythonProcess.exitCode}`);
-    }
-  }
-  fastApiFailed = true;
-  pythonProcess?.kill();
-  throw new Error(`FastAPI did not start within ${STARTUP_TIMEOUT_MS}ms`);
-}
-
-/** Translate FastAPI HarnessEvent type to CodeWiz SSEEventType + payload. */
-function translateEvent(rawType: string, data: unknown): { type: string; data: string } | null {
-  switch (rawType) {
-    case 'message_start':
-      return null;
-
-    case 'message_chunk': {
-      const chunk = typeof data === 'object' && data !== null ? (data as { chunk?: string }).chunk ?? '' : '';
-      return { type: 'text', data: chunk };
-    }
-
-    case 'think_start':
-      return { type: 'thinking', data: '<' };
-
-    case 'think_chunk': {
-      const chunk = typeof data === 'object' && data !== null ? (data as { chunk?: string }).chunk ?? '' : '';
-      return { type: 'thinking', data: chunk };
-    }
-
-    case 'think_end':
-      return { type: 'thinking', data: '>' };
-
-    case 'tool_start': {
-      const d = typeof data === 'object' ? data as { name?: string; id?: string } : {};
-      return { type: 'tool_use', data: JSON.stringify({ name: d.name, id: d.id }) };
-    }
-
-    case 'tool_input': {
-      const d = typeof data === 'object' ? data as { name?: string; input?: unknown; id?: string } : {};
-      return {
-        type: 'tool_result',
-        data: JSON.stringify({ name: d.name, input: d.input, id: d.id, content: `Input: ${JSON.stringify(d.input ?? {})}` }),
-      };
-    }
-
-    case 'tool_output': {
-      const d = typeof data === 'object' ? data as { name?: string; output?: unknown; id?: string } : {};
-      return {
-        type: 'tool_result',
-        data: JSON.stringify({ name: d.name, output: d.output, id: d.id, content: typeof d.output === 'string' ? d.output : JSON.stringify(d.output ?? '') }),
-      };
-    }
-
-    case 'tool_end':
-      return null;
-
-    case 'context_info':
-      return null;
-
-    case 'error': {
-      const msg = typeof data === 'object' && data !== null ? (data as { message?: string }).message ?? String(data) : String(data);
-      return { type: 'error', data: msg };
-    }
-
-    default:
-      return null;
-  }
-}
-
-export const codewizRuntime: AgentRuntime = {
-  id: 'codewiz-agent',
-  displayName: 'Agent (codewiz)',
-  description: 'Tool-calling agent powered by codewiz-agent (FastAPI + MiniMax/LLM).',
-
-  stream(options: RuntimeStreamOptions): ReadableStream<string> {
-    const sessionId = options.sessionId;
-    const port = getPort();
-
-    const abortCtrl = new AbortController();
-    activeAbortControllers.set(sessionId, abortCtrl);
-    activeFetches.set(sessionId, abortCtrl);
-
-    const pythonOptions = {
-      prompt: options.prompt,
-      sessionId,
-      model: options.model,
-      systemPrompt: options.systemPrompt,
-      thinking: options.thinking,
-      apiKey: '', // FastAPI resolves credentials from its own config / DB
-      baseUrl: `http://127.0.0.1:${port}`,
-    };
-
-    return new ReadableStream<string>({
-      async start(controller) {
-        try {
-          await ensureFastApi();
-
-          // Forward abort signal
-          options.abortController?.signal.addEventListener('abort', () => abortCtrl.abort());
-
-          const resp = await fetch(
-            `http://127.0.0.1:${port}/api/bridge/chat/${sessionId}/stream`,
-            {
-              method: 'POST',
-              headers: { 'Content-Type': 'application/json', Accept: 'text/event-stream' },
-              body: JSON.stringify({ message: options.prompt, session_id: sessionId }),
-              signal: abortCtrl.signal,
-            }
-          );
-
-          if (!resp.ok) {
-            const errText = await resp.text();
-            controller.enqueue(`data: ${JSON.stringify({ type: 'error', data: `HTTP ${resp.status}: ${errText}` })}\n\n`);
-            controller.enqueue(`data: ${JSON.stringify({ type: 'done', data: '' })}\n\n`);
-            controller.close();
-            return;
-          }
-
-          if (!resp.body) {
-            controller.enqueue(`data: ${JSON.stringify({ type: 'error', data: 'No response body from FastAPI' })}\n\n`);
-            controller.enqueue(`data: ${JSON.stringify({ type: 'done', data: '' })}\n\n`);
-            controller.close();
-            return;
-          }
-
-          let lineBuffer = '';
-          const reader = resp.body.getReader();
-          const decoder = new TextDecoder('utf-8');
-
-          try {
-            while (true) {
-              const { done, value } = await reader.read();
-              if (done) break;
-
-              const text = lineBuffer + decoder.decode(value, { stream: true });
-              const lines = text.split('\n');
-              lineBuffer = lines.pop() ?? '';
-
-              for (const rawLine of lines) {
-                const trimmed = rawLine.trim();
-                if (!trimmed.startsWith('data: ')) continue;
-                try {
-                  const parsed = JSON.parse(trimmed.slice(6));
-                  // parsed is a HarnessEvent: { type: string, data: unknown }
-                  const { type: rawType, data } = parsed;
-                  const translated = translateEvent(rawType as string, data);
-                  if (translated) {
-                    controller.enqueue(`data: ${JSON.stringify(translated)}\n\n`);
-                  }
-                } catch {
-                  // skip malformed line
-                }
-              }
-            }
-
-            // Flush buffer
-            if (lineBuffer.trim().startsWith('data: ')) {
-              try {
-                const parsed = JSON.parse(lineBuffer.trim().slice(6));
-                const { type: rawType, data } = parsed;
-                const translated = translateEvent(rawType as string, data);
-                if (translated) {
-                  controller.enqueue(`data: ${JSON.stringify(translated)}\n\n`);
-                }
-              } catch { /* skip */ }
-            }
-          } finally {
-            reader.releaseLock();
-          }
-
-          controller.enqueue(`data: ${JSON.stringify({ type: 'done', data: '' })}\n\n`);
-          controller.close();
-        } catch (err) {
-          if ((err as Error).name === 'AbortError') {
-            controller.enqueue(`data: ${JSON.stringify({ type: 'done', data: '' })}\n\n`);
-          } else {
-            controller.enqueue(`data: ${JSON.stringify({ type: 'error', data: String(err) })}\n\n`);
-            controller.enqueue(`data: ${JSON.stringify({ type: 'done', data: '' })}\n\n`);
-          }
-          controller.close();
-        } finally {
-          activeAbortControllers.delete(sessionId);
-          activeFetches.delete(sessionId);
-        }
-      },
-
-      cancel() {
-        // Called by ReadableStream cancel() on early teardown
-        abortCtrl.abort();
-        activeAbortControllers.delete(sessionId);
-        activeFetches.delete(sessionId);
-      },
-    });
-  },
-
-  interrupt(sessionId: string): void {
-    const ctrl = activeAbortControllers.get(sessionId) ?? activeFetches.get(sessionId);
-    if (ctrl) ctrl.abort();
-  },
-
-  isAvailable(): boolean {
-    // FastAPI availability: check if it is already running (port in use) or can be started
-    return true; // Runtime will handle startup on first use
-  },
-
-  dispose(): void {
-    for (const [, ctrl] of activeAbortControllers) ctrl.abort();
-    for (const [, ctrl] of activeFetches) ctrl.abort();
-    activeAbortControllers.clear();
-    activeFetches.clear();
-    if (pythonProcess) {
-      pythonProcess.kill('SIGTERM');
-      pythonProcess = null;
-    }
-    fastApiReady = false;
-    fastApiFailed = false;
-    startupPromise = null;
-  },
-};
diff --git a/src/types/index.ts b/src/types/index.ts
index 38a0e94..8b4bd57 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -14,7 +14,6 @@ export interface ChatSession {
   project_name: string;
   status: 'active' | 'archived';
   mode?: 'code' | 'plan' | 'ask';
-  /** Agent backend mode: 'claude' (Claude Code SDK/Native) or 'agent' (codewiz-agent FastAPI) */
   agent_mode?: 'claude' | 'agent';
   needs_approval?: boolean;
   provider_name: string;