diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 747d7e2..80541e3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,10 +1,11 @@
 name: CI
 
 # Adapted from openai/codex-plugin-cc's pull-request-ci.yml.
-# Modified by JohnnyVicious (2026): drops the Codex CLI install step (this
-# fork wraps OpenCode, not Codex) and runs only on a single Node version
-# matching the package.json `engines.node` floor. (Apache License 2.0
-# §4(b) modification notice — see NOTICE.)
+# Modified by JohnnyVicious (2026): wraps OpenCode (not Codex), so installs
+# `opencode-ai` instead of `@openai/codex` for the integration tests, and
+# runs only on a single Node version matching the package.json
+# `engines.node` floor. (Apache License 2.0 §4(b) modification notice —
+# see NOTICE.)
 
 on:
   pull_request:
@@ -19,7 +20,7 @@ jobs:
   test:
     name: Test
     runs-on: ubuntu-latest
-    timeout-minutes: 5
+    timeout-minutes: 10
 
     steps:
       - name: Check out repository
@@ -34,6 +35,9 @@ jobs:
       - name: Install dependencies
         run: npm ci
 
+      - name: Install OpenCode CLI
+        run: npm install -g opencode-ai
+
       - name: Syntax-check companion scripts
         run: |
           node --check plugins/opencode/scripts/opencode-companion.mjs
diff --git a/plugins/opencode/scripts/lib/opencode-server.mjs b/plugins/opencode/scripts/lib/opencode-server.mjs
index f4192a8..14614bd 100644
--- a/plugins/opencode/scripts/lib/opencode-server.mjs
+++ b/plugins/opencode/scripts/lib/opencode-server.mjs
@@ -1,6 +1,15 @@
 // OpenCode HTTP API client.
 // Unlike codex-plugin-cc which uses JSON-RPC over stdin/stdout,
 // OpenCode exposes a REST API + SSE. This module wraps that API.
+//
+// Modified by JohnnyVicious (2026): `ensureServer` now spawns opencode
+// with `stdio: "ignore"` instead of piping stdout/stderr that nothing
+// reads. The piped streams were ref'd handles on the parent event loop,
+// which deadlocked any long-lived parent (e.g. `node:test`) once
+// opencode wrote enough log output to fill the pipe buffer. In normal
+// CLI usage the deadlock was masked because the companion script exited
+// before the buffer filled. (Apache License 2.0 §4(b) modification
+// notice — see NOTICE.)
 
 import { spawn } from "node:child_process";
 
@@ -42,9 +51,13 @@ export async function ensureServer(opts = {}) {
     return { url, alreadyRunning: true };
   }
 
-  // Start the server
+  // Start the server.
+  // `stdio: "ignore"` is critical: piping stdout/stderr without draining
+  // them creates ref'd file descriptors on the parent that prevent any
+  // long-lived parent (notably `node:test`) from exiting cleanly once
+  // opencode writes enough output to fill the pipe buffer.
   const proc = spawn("opencode", ["serve", "--port", String(port)], {
-    stdio: ["ignore", "pipe", "pipe"],
+    stdio: "ignore",
     detached: true,
     cwd: opts.cwd,
   });
diff --git a/tests/opencode-server.test.mjs b/tests/opencode-server.test.mjs
new file mode 100644
index 0000000..ea1eccf
--- /dev/null
+++ b/tests/opencode-server.test.mjs
@@ -0,0 +1,133 @@
+// Integration tests for the OpenCode HTTP server wrapper.
+//
+// These tests start a real `opencode serve` process on a high test port
+// (so they don't collide with a user's default-port server) and exercise
+// the protocol surfaces our companion script depends on:
+//
+//   - server lifecycle (`isServerRunning`, `ensureServer`)
+//   - health endpoint
+//   - session create / get / list / delete
+//
+// They intentionally do NOT call `sendPrompt` because that requires a
+// configured AI provider and would burn paid API credits in CI.
+//
+// Locally, this suite is skipped if the `opencode` binary is not on PATH,
+// so developers without OpenCode installed can still run `npm test`.
+
+import { describe, it, before, after } from "node:test";
+import assert from "node:assert/strict";
+import {
+  isOpencodeInstalled,
+} from "../plugins/opencode/scripts/lib/process.mjs";
+import {
+  isServerRunning,
+  ensureServer,
+  createClient,
+} from "../plugins/opencode/scripts/lib/opencode-server.mjs";
+
+const TEST_HOST = "127.0.0.1";
+const TEST_PORT = Number(process.env.OPENCODE_TEST_PORT ?? 14096);
+
+const opencodeAvailable = await isOpencodeInstalled();
+const describeOrSkip = opencodeAvailable ? describe : describe.skip;
+
+describeOrSkip("opencode HTTP server (integration)", () => {
+  let serverInfo;
+  let client;
+
+  before(async () => {
+    // If something is already squatting our test port, fail fast with a
+    // useful message instead of silently sharing state with a foreign
+    // server.
+    if (await isServerRunning(TEST_HOST, TEST_PORT)) {
+      throw new Error(
+        `Test port ${TEST_PORT} is already in use. Set OPENCODE_TEST_PORT to a free port.`
+      );
+    }
+
+    serverInfo = await ensureServer({ host: TEST_HOST, port: TEST_PORT });
+    client = createClient(serverInfo.url);
+  });
+
+  after(async () => {
+    // Tear down the server we spawned. `ensureServer` only sets `pid`
+    // when it actually started a new process, so this is a no-op when
+    // the server was already running (which our `before` rejects, but
+    // be defensive).
+    if (!serverInfo?.pid || serverInfo.alreadyRunning) return;
+
+    // opencode is spawned with `detached: true`, which puts it in its
+    // own process group. SIGTERM the negative pid to take down the
+    // whole group (any children opencode forked included).
+    const pgid = -serverInfo.pid;
+    try {
+      process.kill(pgid, "SIGTERM");
+    } catch {
+      // group may already be gone — that's fine
+    }
+
+    // Wait briefly for graceful shutdown, then SIGKILL the group if
+    // anything is still alive. We poll instead of sleeping a fixed
+    // interval so a fast exit doesn't waste time.
+    const deadline = Date.now() + 3_000;
+    while (Date.now() < deadline) {
+      try {
+        process.kill(pgid, 0); // signal 0 = existence check
+      } catch {
+        return; // group is gone
+      }
+      await new Promise((r) => setTimeout(r, 100));
+    }
+
+    try {
+      process.kill(pgid, "SIGKILL");
+    } catch {
+      // already exited between checks
+    }
+  });
+
+  it("isServerRunning detects the spawned server", async () => {
+    assert.equal(await isServerRunning(TEST_HOST, TEST_PORT), true);
+  });
+
+  it("health() reports healthy with a version string", async () => {
+    const h = await client.health();
+    assert.equal(h.healthy, true);
+    assert.ok(typeof h.version === "string" && h.version.length > 0,
+      `expected version string, got ${JSON.stringify(h.version)}`);
+  });
+
+  it("createSession returns an id", async () => {
+    const session = await client.createSession({ title: "test session" });
+    assert.ok(typeof session.id === "string" && session.id.length > 0);
+    await client.deleteSession(session.id);
+  });
+
+  it("listSessions returns an array containing a freshly-created session", async () => {
+    const created = await client.createSession({ title: "list test" });
+    try {
+      const sessions = await client.listSessions();
+      assert.ok(Array.isArray(sessions));
+      assert.ok(
+        sessions.some((s) => s.id === created.id),
+        "freshly-created session was not present in listSessions output"
+      );
+    } finally {
+      await client.deleteSession(created.id);
+    }
+  });
+
+  it("createSession -> getSession -> deleteSession roundtrip", async () => {
+    const created = await client.createSession({ title: "roundtrip" });
+    const fetched = await client.getSession(created.id);
+    assert.equal(fetched.id, created.id);
+
+    await client.deleteSession(created.id);
+
+    // After deletion, getSession should reject with a non-2xx status.
+    await assert.rejects(
+      () => client.getSession(created.id),
+      /OpenCode API GET .* returned 4\d\d/
+    );
+  });
+});