diff --git a/package-lock.json b/package-lock.json
index c396338f9b..6ee13ac3f5 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -39240,6 +39240,7 @@
         "strip-ansi": "^7.1.2",
         "tree-kill": "^1.2.2",
         "typescript": "^5.9.3",
+        "undici": "^7.30.0",
         "uuid": "^9.0.1",
         "which": "^5.0.0",
         "ws": "^8.14.2",
@@ -39970,6 +39971,15 @@
         "url": "https://github.com/chalk/strip-ansi?sponsor=1"
       }
     },
+    "packages/server/node_modules/undici": {
+      "version": "7.30.0",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-7.30.0.tgz",
+      "integrity": "sha512-dkrQXeHSaoamnItlYbmzG0wFYrM0ZwDxCIg0A7aKjTyyhh9svRzCNFEzV+Vm05/yehjCzjDZ31KXfGEjYSztDQ==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=20.18.1"
+      }
+    },
     "packages/server/node_modules/vitest": {
       "version": "4.1.6",
       "resolved": "https://registry.npmjs.org/vitest/-/vitest-4.1.6.tgz",
diff --git a/packages/server/package.json b/packages/server/package.json
index 047c7b72a1..fad88186d6 100644
--- a/packages/server/package.json
+++ b/packages/server/package.json
@@ -141,6 +141,7 @@
     "strip-ansi": "^7.1.2",
     "tree-kill": "^1.2.2",
     "typescript": "^5.9.3",
+    "undici": "^7.30.0",
     "uuid": "^9.0.1",
     "which": "^5.0.0",
     "ws": "^8.14.2",
diff --git a/packages/server/src/server/agent/providers/opencode/v2/runtime.test.ts b/packages/server/src/server/agent/providers/opencode/v2/runtime.test.ts
new file mode 100644
index 0000000000..2cd7d20721
--- /dev/null
+++ b/packages/server/src/server/agent/providers/opencode/v2/runtime.test.ts
@@ -0,0 +1,62 @@
+import { mkdtemp, rm, writeFile } from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { Agent, getGlobalDispatcher, setGlobalDispatcher } from "undici";
+import { afterEach, beforeEach, expect, test, vi } from "vitest";
+
+import { createTestLogger } from "../../../../../test-utils/test-logger.js";
+import { V2Runtime } from "./runtime.js";
+
+// Answers every request at once except session.wait, which it holds for WAIT_MS before answering,
+// the way OpenCode holds the wait response until the session's agent loop is idle.
+const FAKE_HELPER = `
+import http from "node:http";
+const server = http.createServer((request, response) => {
+  if (request.url.endsWith("/wait")) {
+    setTimeout(() => { response.statusCode = 204; response.end(); }, Number(process.env.WAIT_MS));
+    return;
+  }
+  response.setHeader("content-type", "application/json");
+  response.end("{}");
+});
+server.listen(0, "127.0.0.1", () => {
+  console.log("server listening on http://127.0.0.1:" + server.address().port);
+});
+`;
+
+let root: string;
+const defaultDispatcher = getGlobalDispatcher();
+
+beforeEach(async () => {
+  root = await mkdtemp(path.join(os.tmpdir(), "paseo-opencode-v2-runtime-"));
+  vi.stubEnv("PASEO_HOME", path.join(root, "home"));
+});
+
+afterEach(async () => {
+  setGlobalDispatcher(defaultDispatcher);
+  vi.unstubAllEnvs();
+  await rm(root, { recursive: true, force: true });
+});
+
+test("session.wait outlasts the fetch header deadline until the helper reports the session idle", async () => {
+  // Stands in for undici's five-minute default, which ended every longer turn.
+  setGlobalDispatcher(new Agent({ headersTimeout: 200 }));
+  const helper = path.join(root, "fake-opencode.mjs");
+  await writeFile(helper, FAKE_HELPER);
+  const runtime = new V2Runtime({
+    logger: createTestLogger(),
+    settings: {
+      command: { mode: "replace", argv: [process.execPath, helper] },
+      env: { WAIT_MS: "2500" },
+    },
+    decorateEnv: async (env) => env,
+  });
+  try {
+    const connection = await runtime.acquire();
+    await expect(connection.client.session.wait({ sessionID: "ses_long" })).resolves.toBe(
+      undefined,
+    );
+  } finally {
+    await runtime.shutdown();
+  }
+});
diff --git a/packages/server/src/server/agent/providers/opencode/v2/runtime.ts b/packages/server/src/server/agent/providers/opencode/v2/runtime.ts
index cab5544582..a245e353c0 100644
--- a/packages/server/src/server/agent/providers/opencode/v2/runtime.ts
+++ b/packages/server/src/server/agent/providers/opencode/v2/runtime.ts
@@ -5,6 +5,7 @@ import type { V2Api } from "./api.js";
 import { randomBytes } from "node:crypto";
 import { mkdir } from "node:fs/promises";
 import type { Logger } from "pino";
+import { Agent } from "undici";
 import { spawnProcess } from "../../../../../utils/spawn.js";
 import { terminateWithTreeKill } from "../../../../../utils/tree-kill.js";
 import {
@@ -174,6 +175,9 @@ export class V2Runtime {
       }),
     });
     const processAbort = new AbortController();
+    // session.wait answers only once the session is idle, so a header deadline would fail any
+    // turn that outlasts it. Requests end when the helper exits or the caller aborts instead.
+    const dispatcher = new Agent({ headersTimeout: 0 });
     const exited = new Promise<Error>((resolve) =>
       process.once("exit", (code) => {
         const error = new Error(`OpenCode helper server exited (${code})`);
@@ -199,6 +203,7 @@ export class V2Runtime {
     const stop = () => {
       stopped ??= (async () => {
         await terminateWithTreeKill(process, { gracefulTimeoutMs: 5_000, forceTimeoutMs: 1_000 });
+        await dispatcher.destroy();
         const entry = await record;
         if (entry) await managedProcesses?.remove(entry.id);
       })();
@@ -243,7 +248,9 @@ export class V2Runtime {
           const signal = init?.signal
             ? AbortSignal.any([init.signal, processAbort.signal])
             : processAbort.signal;
-          const response = await fetch(request, { ...init, signal });
+          // Node's fetch accepts an undici dispatcher, which the DOM RequestInit type omits.
+          const requestInit: RequestInit & { dispatcher: Agent } = { ...init, signal, dispatcher };
+          const response = await fetch(request, requestInit);
           const html = response.headers.get("content-type")?.includes("text/html") ?? false;
           if (!response.ok || html) {
             const requestUrl = request instanceof Request ? request.url : String(request);