diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..570428d
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,3 @@
+# CI-safe tests and scripts
+
+Do not assume local directories, files, tools, or generated artifacts exist in a clean CI environment. In particular, `/tmp/opencode` is an agent-environment convenience, not a CI guarantee. Tests should create temporary directories with `node:os` `tmpdir()` and `mkdtemp(join(tmpdir(), prefix))`, explicitly create required parent directories and fixtures, and clean up the files they create.
diff --git a/tests/install.test.ts b/tests/install.test.ts
index 3e5906a..91023cb 100644
--- a/tests/install.test.ts
+++ b/tests/install.test.ts
@@ -10,6 +10,7 @@ import {
     symlink,
     writeFile,
 } from "node:fs/promises";
+import { tmpdir } from "node:os";
 import { dirname, join } from "node:path";
 import { createHash } from "node:crypto";
 import { install } from "../scripts/install.js";
@@ -56,7 +57,7 @@ async function run(
     return { exitCode, stdout, stderr };
 }
 async function fixture() {
-    const directory = await mkdtemp("/tmp/opencode/plugin-install-");
+    const directory = await mkdtemp(join(tmpdir(), "plugin-install-"));
     directories.push(directory);
     const source = join(directory, "package with spaces");
     const config = join(directory, "config with spaces");
diff --git a/tests/package.test.ts b/tests/package.test.ts
index 474fcd1..9318d30 100644
--- a/tests/package.test.ts
+++ b/tests/package.test.ts
@@ -1,12 +1,13 @@
 import { expect, test } from "bun:test";
 import { mkdir, mkdtemp, rm } from "node:fs/promises";
+import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { Host } from "@opencode/plugin/host";
 import { build } from "../scripts/build.js";
 import { install } from "../scripts/install.js";
 
 test("packed package has independent native plugins and quota-only TUI discovery", async () => {
-    const directory = await mkdtemp("/tmp/opencode/plugin-package-");
+    const directory = await mkdtemp(join(tmpdir(), "plugin-package-"));
     try {
         await build();
         const archive = join(directory, "stanp-opencode.tgz");