diff --git a/.github/actions/setup-ci/action.yml b/.github/actions/setup-ci/action.yml
index 59f8850d27..8e95f29fa5 100644
--- a/.github/actions/setup-ci/action.yml
+++ b/.github/actions/setup-ci/action.yml
@@ -53,6 +53,7 @@ runs:
         echo "cargo-target-dir=$cargo_target_dir" >> "$GITHUB_OUTPUT"
 
         {
+          echo "CODEX_REPO_ROOT=$GITHUB_WORKSPACE"
           echo "BAZEL_OUTPUT_BASE=$bazel_output_base"
           echo "BAZEL_OUTPUT_USER_ROOT=$bazel_output_user_root"
           echo "BAZEL_REPOSITORY_CACHE=$bazel_repository_cache"
diff --git a/.github/workflows/rust-release.yml b/.github/workflows/rust-release.yml
index c154a8aed4..e07c23b3ba 100644
--- a/.github/workflows/rust-release.yml
+++ b/.github/workflows/rust-release.yml
@@ -15,6 +15,7 @@ on:
       - "rust-v*.*.*"
 
 env:
+  CODEX_REPO_ROOT: ${{ github.workspace }}
   CODEX_ZSH_RELEASE_TAG: codex-zsh-v0.1.0
   CODEX_ZSH_MANIFEST_SHA256: c534eab89dcea7e3d8a5e5b3f49c025c7c64cd4e4d9814ee24871de58a9359a1
 
diff --git a/justfile b/justfile
index d59e3b4e96..ec70adfc84 100644
--- a/justfile
+++ b/justfile
@@ -1,5 +1,6 @@
 set working-directory := "codex-rs"
 set positional-arguments
+export CODEX_REPO_ROOT := justfile_directory()
 export JUST_SHELL := justfile_directory() / "scripts/just-shell.py"
 set shell := ["python3", "-c", 'import os, runpy; runpy.run_path(os.environ["JUST_SHELL"], run_name="__main__")']
 set windows-shell := ["python", "-c", 'import os, runpy; runpy.run_path(os.environ["JUST_SHELL"], run_name="__main__")']
@@ -35,6 +36,11 @@ file-search *args:
 code-mode-host *args:
     cargo run --bin codex-code-mode-host -- {args}
 
+# Assemble a local Codex package.
+[no-cd]
+assemble-codex-package *args:
+    {{ python }} {{ justfile_directory() }}/scripts/build_codex_package.py {args}
+
 # Build the CLI and run the app-server test client
 app-server-test-client *args:
     cargo build -p codex-cli
diff --git a/scripts/codex_package/README.md b/scripts/codex_package/README.md
index 461b80e343..972659d4e6 100644
--- a/scripts/codex_package/README.md
+++ b/scripts/codex_package/README.md
@@ -4,6 +4,14 @@ This package contains the implementation behind `scripts/build_codex_package.py`
 The top-level script is the stable executable entry point; these modules keep the
 package-building logic split by responsibility.
 
+Run the builder through `just`:
+
+```bash
+just assemble-codex-package --help
+just assemble-codex-package --variant codex-app-server
+just assemble-codex-package --target x86_64-unknown-linux-gnu
+```
+
 The builder creates a canonical Codex package directory:
 
 ```text
diff --git a/scripts/codex_package/ripgrep.py b/scripts/codex_package/ripgrep.py
index 33a484022b..155c5d323e 100644
--- a/scripts/codex_package/ripgrep.py
+++ b/scripts/codex_package/ripgrep.py
@@ -3,12 +3,9 @@
 from pathlib import Path
 
 from .dotslash import fetch_dotslash_executable
-from .targets import REPO_ROOT
-from .targets import TargetSpec
-from .targets import resolve_input_path
+from .targets import TargetSpec, resolve_input_path
 
-
-RG_MANIFEST = REPO_ROOT / "scripts" / "codex_package" / "rg"
+RG_MANIFEST = Path(__file__).with_name("rg")
 
 
 def resolve_rg_bin(spec: TargetSpec, rg_bin: Path | None) -> Path:
diff --git a/scripts/codex_package/targets.py b/scripts/codex_package/targets.py
index 016202cf5f..e217e8d0fd 100644
--- a/scripts/codex_package/targets.py
+++ b/scripts/codex_package/targets.py
@@ -1,13 +1,18 @@
 """Supported package targets and default binary discovery."""
 
+import os
 import platform
 import stat
 from dataclasses import dataclass
 from pathlib import Path
 
-
-SCRIPT_DIR = Path(__file__).resolve().parents[1]
-REPO_ROOT = SCRIPT_DIR.parent
+_repo_root = os.environ.get("CODEX_REPO_ROOT")
+if _repo_root is None:
+    raise RuntimeError(
+        "CODEX_REPO_ROOT must point to the repository root; "
+        "run `just assemble-codex-package` to set it automatically"
+    )
+REPO_ROOT = Path(_repo_root)
 
 
 @dataclass(frozen=True)
diff --git a/scripts/codex_package/zsh.py b/scripts/codex_package/zsh.py
index 35c62a3854..e4ecc2de68 100644
--- a/scripts/codex_package/zsh.py
+++ b/scripts/codex_package/zsh.py
@@ -3,12 +3,9 @@
 from pathlib import Path
 
 from .dotslash import fetch_dotslash_executable
-from .targets import REPO_ROOT
-from .targets import TargetSpec
-from .targets import resolve_input_path
+from .targets import TargetSpec, resolve_input_path
 
-
-ZSH_MANIFEST = REPO_ROOT / "scripts" / "codex_package" / "codex-zsh"
+ZSH_MANIFEST = Path(__file__).with_name("codex-zsh")
 ZSH_RESOURCE_PATH = Path("zsh") / "bin" / "zsh"