diff --git a/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.test.ts b/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.test.ts
index 130b34f53b3..0d066a4e4be 100644
--- a/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.test.ts
+++ b/packages/paperclip-runner/src/drivers/opencode/opencode-server-driver.test.ts
@@ -1,5 +1,6 @@
 import {
   chmod,
+  copyFile,
   lstat,
   mkdir,
   mkdtemp,
@@ -11,7 +12,7 @@ import {
 } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join, resolve } from "node:path";
-import { afterAll, afterEach, describe, expect, it } from "vitest";
+import { afterAll, afterEach, beforeAll, describe, expect, it } from "vitest";
 
 import {
   NATIVE_RUNTIME_ASSET_SCHEMA,
@@ -29,7 +30,15 @@ import {
 } from "./opencode-server-driver.js";
 
 const roots: string[] = [];
-const fixture = resolve("test/fixtures/fake-opencode-server.mjs");
+let fixtureRoot: string | undefined;
+let fixture: string;
+
+beforeAll(async () => {
+  fixtureRoot = await mkdtemp(join(tmpdir(), "paperclip-opencode-fixture-"));
+  fixture = join(fixtureRoot, "fake-opencode-server.mjs");
+  // Other suites execute this fixture concurrently. Never chmod their source.
+  await copyFile(resolve("test/fixtures/fake-opencode-server.mjs"), fixture);
+});
 
 function runtimeContext(
   skillRoot: string,
@@ -98,7 +107,7 @@ afterEach(async () => {
 });
 
 afterAll(async () => {
-  await chmod(fixture, 0o644);
+  if (fixtureRoot) await rm(fixtureRoot, { recursive: true, force: true });
 });
 
 describe("OpenCodeServerDriver", () => {
diff --git a/packages/paperclip-runner/src/drivers/opencode/prepared-context-transport.test.ts b/packages/paperclip-runner/src/drivers/opencode/prepared-context-transport.test.ts
index dd6f34e8677..6c592fbd6ec 100644
--- a/packages/paperclip-runner/src/drivers/opencode/prepared-context-transport.test.ts
+++ b/packages/paperclip-runner/src/drivers/opencode/prepared-context-transport.test.ts
@@ -1,4 +1,4 @@
-import { chmod, mkdtemp, rm } from "node:fs/promises";
+import { chmod, copyFile, mkdtemp, rm } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join, resolve } from "node:path";
 import { afterEach, describe, expect, it } from "vitest";
@@ -7,7 +7,6 @@ import {
   OpenCodeServerDriver,
 } from "./opencode-server-driver.js";
 
-const fixture = resolve("test/fixtures/fake-opencode-server.mjs");
 const roots: string[] = [];
 
 afterEach(async () => {
@@ -18,12 +17,16 @@ afterEach(async () => {
 
 describe("prepared OpenCode context transport", () => {
   it("sends prepared initial prompts without the proxy task envelope", async () => {
-    await chmod(fixture, 0o755);
     const root = await mkdtemp(join(tmpdir(), "paperclip-opencode-prepared-"));
+    roots.push(root);
+    // Executable modes belong to the test's copy, not the shared checkout.
+    const fixture = join(root, "fake-opencode-server.mjs");
+    await copyFile(resolve("test/fixtures/fake-opencode-server.mjs"), fixture);
+    await chmod(fixture, 0o755);
     const workspace = await mkdtemp(
       join(tmpdir(), "paperclip-opencode-prepared-workspace-"),
     );
-    roots.push(root, workspace);
+    roots.push(workspace);
     const submitted: Record<string, unknown>[] = [];
     const driver = new OpenCodeServerDriver({
       model: "openrouter/deepseek/deepseek-v4-flash-0731",