diff --git a/test/safe-teardown.test.js b/test/safe-teardown.test.js
index 9b21f10..cb07d2e 100644
--- a/test/safe-teardown.test.js
+++ b/test/safe-teardown.test.js
@@ -1,10 +1,19 @@
 import assert from "node:assert/strict"
 import { Buffer } from "node:buffer"
 import http from "node:http"
-import test from "node:test"
+import test, { beforeEach } from "node:test"
 
 import { createProxyFetchHandler, sweepStaleProxySessions } from "../index.js"
 
+// Keep the suite hermetic: OPENCODE_LLM_PROXY_* variables from the developer's
+// shell or CI (e.g. a token, host or port) must not change outcomes. Tests that
+// need a specific value set it inside the test body, after this hook has run.
+beforeEach(() => {
+  for (const name of Object.keys(process.env)) {
+    if (name.startsWith("OPENCODE_LLM_PROXY_")) delete process.env[name]
+  }
+})
+
 const TOKENS = { input: 2, output: 1, reasoning: 0, cache: { read: 0, write: 0 } }
 
 function createMockClient({ promptMode = "hang", streamEvents = null } = {}) {