diff --git a/.codex/environments/environment.toml b/.codex/environments/environment.toml
index 39c40eb07fa4..b3c5910fbcf4 100644
--- a/.codex/environments/environment.toml
+++ b/.codex/environments/environment.toml
@@ -2,9 +2,6 @@
 version = 1
 name = "codex"
 
-[setup]
-script = "python ./.codex/environments/setup.py"
-
 [[actions]]
 name = "Run"
 icon = "run"
diff --git a/.codex/environments/setup.py b/.codex/environments/setup.py
deleted file mode 100644
index a9d78c9405cf..000000000000
--- a/.codex/environments/setup.py
+++ /dev/null
@@ -1,65 +0,0 @@
-#!/usr/bin/env python3
-
-"""Set up ignored files that should be shared with Codex worktrees."""
-
-import shutil
-import subprocess
-from functools import cache
-from pathlib import Path
-
-
-@cache
-def worktree_paths() -> tuple[Path, Path]:
-    script_dir = Path(__file__).resolve().parent
-    worktree_root = git_path(script_dir / "../..", "--show-toplevel")
-    common_git_dir = git_path(worktree_root, "--git-common-dir")
-    return worktree_root, common_git_dir.parent
-
-
-def git_path(working_directory: Path, argument: str) -> Path:
-    output = subprocess.check_output(
-        [
-            "git",
-            "-C",
-            str(working_directory),
-            "rev-parse",
-            "--path-format=absolute",
-            argument,
-        ],
-        text=True,
-    )
-    return Path(output.strip())
-
-
-def copy_from_main_worktree_to_worktree(repo_relative_path: str) -> None:
-    relative_path = Path(repo_relative_path)
-    if relative_path.is_absolute() or ".." in relative_path.parts:
-        raise ValueError(f"path must be repository-relative: {repo_relative_path}")
-
-    worktree_root, main_worktree = worktree_paths()
-    source_path = main_worktree / relative_path
-    destination_path = worktree_root / relative_path
-
-    print(f"  source: {source_path}")
-    print(f"  destination: {destination_path}")
-
-    if source_path == destination_path:
-        print("  result: running in the main worktree; nothing to copy")
-    elif destination_path.exists():
-        print("  result: destination already exists; nothing to copy")
-    elif not source_path.is_file():
-        print("  result: source does not exist; nothing to copy")
-    else:
-        destination_path.parent.mkdir(parents=True, exist_ok=True)
-        shutil.copy2(source_path, destination_path)
-        print(f"  result: copied {repo_relative_path}")
-
-
-def main() -> None:
-    print("Codex environment setup:")
-    # See codex-rs/docs/bazel.md for the repository's Bazel workflow.
-    copy_from_main_worktree_to_worktree("user.bazelrc")
-
-
-if __name__ == "__main__":
-    main()
diff --git a/.worktreeinclude b/.worktreeinclude
new file mode 100644
index 000000000000..74824b01f957
--- /dev/null
+++ b/.worktreeinclude
@@ -0,0 +1 @@
+user.bazelrc