fix(runtime): normalize Bun override path

Author: luvs01

src/lib/bun-runtime.ts

@@ -11,7 +11,7 @@
  * back to `process.execPath` (which is itself Bun when run via `bun src/cli/index.ts`).
  */
 import { createRequire } from "node:module";
-import { dirname, join } from "node:path";
+import { dirname, join, resolve } from "node:path";
 import { isRealBunBinary } from "./bun-binary-validator.mjs";
 
 export { isRealBunBinary };
@@ -48,7 +48,8 @@ export function bundledBunPath(): string | null {
 export function overrideBunPath(): string | null {
   const value = process.env[BUN_OVERRIDE_ENV]?.trim();
   if (!value) return null;
-  return isRealBunBinary(value) ? value : null;
+  const resolved = resolve(value);
+  return isRealBunBinary(resolved) ? resolved : null;
 }
 
 export function durableBunRuntime(): DurableBunRuntime {

tests/bun-runtime.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect, afterAll } from "bun:test";
-import { mkdtempSync, writeFileSync, rmSync } from "node:fs";
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { isRealBunBinary, bundledBunPath, durableBunPath, durableBunRuntime, overrideBunPath } from "../src/lib/bun-runtime";
@@ -60,6 +60,31 @@ describe("bundledBunPath / durableBunPath", () => {
     else process.env.OPENCODEX_BUN_PATH = previousOverride;
   });
 
+  it("resolves a relative override against the launcher cwd", () => {
+    const launcherCwd = join(tmp, "launcher-cwd");
+    const real = join(launcherCwd, "relative-bun.exe");
+    const previousCwd = process.cwd();
+    const inheritedOverride = process.env.OPENCODEX_BUN_PATH;
+    mkdirSync(launcherCwd, { recursive: true });
+    writeFileSync(real, Buffer.alloc(1_000_000));
+
+    try {
+      process.chdir(launcherCwd);
+      process.env.OPENCODEX_BUN_PATH = "  relative-bun.exe  ";
+      expect(overrideBunPath()).toBe(real);
+      expect(durableBunRuntime()).toEqual({
+        path: real,
+        source: "override",
+        overrideEnv: "OPENCODEX_BUN_PATH",
+      });
+      expect(durableBunPath()).toBe(real);
+    } finally {
+      process.chdir(previousCwd);
+      if (inheritedOverride === undefined) delete process.env.OPENCODEX_BUN_PATH;
+      else process.env.OPENCODEX_BUN_PATH = inheritedOverride;
+    }
+  });
+
   it("resolves the installed bundled bun binary (dev has the bun dep)", () => {
     const p = bundledBunPath();
     // In this repo the `bun` dependency is installed, so the real binary resolves.