[WRONG BRANCH] fix(codex): preserve concurrent obsolete shim replacement

src/codex/shim.ts

@@ -644,6 +644,7 @@ let codexShimProbeHookForTests: (() => void) | null = null;
 let codexShimProbeShellForTests: string | null = null;
 let codexShimGuardedWriteHookForTests: (() => void) | null = null;
 let codexShimFreshWriteHookForTests: (() => void) | null = null;
+let codexShimObsoleteWriteHookForTests: (() => void) | null = null;
 let codexShimProbeObservationMs = CODEX_SHIM_INSTALL_PROBE_TIMEOUT_MS;
 
 /** Narrow deterministic seam for transaction rollback tests. */
@@ -671,6 +672,11 @@ export function setCodexShimFreshWriteHookForTests(hook: (() => void) | null): v
   codexShimFreshWriteHookForTests = hook;
 }
 
+/** @internal Test-only hook for races immediately after an obsolete shim write. */
+export function setCodexShimObsoleteWriteHookForTests(hook: (() => void) | null): void {
+  codexShimObsoleteWriteHookForTests = hook;
+}
+
 function readProbeMetadata(path: string, maxBytes: number): string | null {
   try {
     if (!existsSync(path)) return "";
@@ -1596,9 +1602,8 @@ function rollbackObsoleteUnixShimRefresh(journal: readonly ObsoleteUnixShimJourn
       const wrapper = stableShimPathProbe(entry.file.wrapperPath);
       const ownsWrapper = entry.wrapperWriteStarted
         && wrapper !== null
-        && (entry.writtenWrapperFingerprint
-          ? sameFingerprint(wrapper.fingerprint, entry.writtenWrapperFingerprint)
-          : wrapper.prefix.includes(UNIX_SHIM_REVISION_MARKER));
+        && entry.writtenWrapperFingerprint !== undefined
+        && sameFingerprint(wrapper.fingerprint, entry.writtenWrapperFingerprint);
       if (ownsWrapper) unlinkSync(entry.file.wrapperPath);
     });
     attempt(() => {
@@ -1654,6 +1659,7 @@ function refreshObsoleteUnixShims(files: readonly ShimFileState[]): ObsoleteUnix
       }
       entry.wrapperWriteStarted = true;
       const writtenInode = writeShim(file.wrapperPath, file.realPath ?? file.backupPath);
+      codexShimObsoleteWriteHookForTests?.();
       const writtenWrapper = stableShimPathProbe(file.wrapperPath);
       if (!writtenWrapper || !isCurrentUnixShimProbe(writtenWrapper)) {
         throw new Error("Codex autostart shim upgrade could not fingerprint the regenerated wrapper");

tests/codex-shim.test.ts

@@ -3,7 +3,7 @@ import { spawnSync } from "node:child_process";
 import { chmodSync, copyFileSync, existsSync, lstatSync, mkdirSync, mkdtempSync, readFileSync, readdirSync, renameSync, rmSync, statSync, symlinkSync, utimesSync, writeFileSync } from "node:fs";
 import { delimiter, dirname, join } from "node:path";
 import { tmpdir } from "node:os";
-import { autoRestoreCodexShim, buildUnixCodexShim, buildWindowsCodexShim, buildWindowsPowerShellCodexShim, diagnoseCodexShim, findCodexOnPath, installCodexShim, isWindowsInteropDir, lastCodexDiscoveryError, setCodexShimFreshWriteHookForTests, setCodexShimGuardedWriteHookForTests, setCodexShimProbeHookForTests, setCodexShimProbeObservationMsForTests, setCodexShimProbeShellForTests, uninstallCodexShim } from "../src/codex/shim";
+import { autoRestoreCodexShim, buildUnixCodexShim, buildWindowsCodexShim, buildWindowsPowerShellCodexShim, diagnoseCodexShim, findCodexOnPath, installCodexShim, isWindowsInteropDir, lastCodexDiscoveryError, setCodexShimFreshWriteHookForTests, setCodexShimGuardedWriteHookForTests, setCodexShimObsoleteWriteHookForTests, setCodexShimProbeHookForTests, setCodexShimProbeObservationMsForTests, setCodexShimProbeShellForTests, uninstallCodexShim } from "../src/codex/shim";
 
 const SHIM_MARKER = "opencodex codex autostart shim";
 const UNIX_SHIM_REVISION_MARKER = "opencodex unix codex shim revision 2";
@@ -1285,6 +1285,34 @@ printf '%s\\n' child-codex
     });
   });
 
+  test("obsolete Unix shim rollback preserves a concurrent current shim", () => {
+    if (process.platform === "win32") return;
+    withInstalledShim(({ binDir, wrappers, backups, statePath }) => {
+      const current = readFileSync(wrappers[0], "utf8");
+      const obsolete = obsoleteUnixShim(current);
+      const replacement = join(binDir, ".concurrent-current-shim");
+      const oldBackup = readFileSync(backups[0]);
+      const oldState = readFileSync(statePath);
+      writeFileSync(wrappers[0], obsolete, "utf8");
+      writeFileSync(replacement, current, "utf8");
+      chmodSync(replacement, 0o755);
+      setCodexShimObsoleteWriteHookForTests(() => renameSync(replacement, wrappers[0]));
+
+      let result!: ReturnType<typeof autoRestoreCodexShim>;
+      try {
+        result = autoRestoreCodexShim({ enabled: () => true, stabilitySleep: skipStabilityWait });
+      } finally {
+        setCodexShimObsoleteWriteHookForTests(null);
+      }
+
+      expect(result.status).toBe("deferred");
+      expect(readFileSync(wrappers[0], "utf8")).toBe(current);
+      expect(readFileSync(backups[0])).toEqual(oldBackup);
+      expect(readFileSync(statePath)).toEqual(oldState);
+      expect(readdirSync(binDir).some(name => name.includes(".upgrade-"))).toBe(false);
+    });
+  });
+
   test("stable shim replacement restores through the shared install transaction", () => {
     withInstalledShim(({ wrappers, backups }) => {
       const replacements = wrappers.map((wrapper, index) => successfulLauncher(`replacement-${index}`));