[js_repl] paths for node module resolution can be specified for js_repl (#11944 )

# External (non-OpenAI) Pull Request Requirements

In `js_repl` mode, module resolution currently starts from
`js_repl_kernel.js`, which is written to a per-kernel temp dir. This
effectively means that bare imports will not resolve.

This PR adds a new config option, `js_repl_node_module_dirs`, which is a
list of dirs that are used (in order) to resolve a bare import. If none
of those work, the current working directory of the thread is used.

For example:
```toml
js_repl_node_module_dirs = [
    "/path/to/node_modules/",
    "/other/path/to/node_modules/",
]
```

2026-02-17 23:29:49 -08:00

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JavaScript REPL (`js_repl`)

js_repl runs JavaScript in a persistent Node-backed kernel with top-level await.

Feature gate

js_repl is disabled by default and only appears when:

[features]
js_repl = true

js_repl_tools_only can be enabled to force direct model tool calls through js_repl:

[features]
js_repl = true
js_repl_tools_only = true

When enabled, direct model tool calls are restricted to js_repl and js_repl_reset; other tools remain available via await codex.tool(...) inside js_repl.

Node runtime

js_repl requires a Node version that meets or exceeds codex-rs/node-version.txt.

Runtime resolution order:

CODEX_JS_REPL_NODE_PATH environment variable
js_repl_node_path in config/profile
node discovered on PATH

You can configure an explicit runtime path:

js_repl_node_path = "/absolute/path/to/node"

Module resolution

js_repl resolves bare specifiers (for example await import("pkg")) using an ordered search path. Path-style specifiers (./, ../, absolute paths, file: URLs) are rejected.

Module resolution proceeds in the following order:

CODEX_JS_REPL_NODE_MODULE_DIRS (PATH-delimited list)
js_repl_node_module_dirs in config/profile (array of absolute paths)
Thread working directory (cwd, always included as the last fallback)

For CODEX_JS_REPL_NODE_MODULE_DIRS and js_repl_node_module_dirs, module resolution is attempted in the order provided with earlier entries taking precedence.

Usage

js_repl is a freeform tool: send raw JavaScript source text.
Optional first-line pragma:
- // codex-js-repl: timeout_ms=15000
Top-level bindings persist across calls.
Top-level static import declarations (for example import x from "pkg") are currently unsupported; use dynamic imports with await import("pkg").
Use js_repl_reset to clear the kernel state.

Helper APIs inside the kernel

js_repl exposes these globals:

codex.state: mutable object persisted for the current kernel session.
codex.tmpDir: per-session scratch directory path.
codex.tool(name, args?): executes a normal Codex tool call from inside js_repl (including shell tools like shell / shell_command when available).
To share generated images with the model, write a file under codex.tmpDir, call await codex.tool("view_image", { path: "/absolute/path" }), then delete the file.

Avoid writing directly to process.stdout / process.stderr / process.stdin; the kernel uses a JSON-line transport over stdio.

Vendored parser asset (`meriyah.umd.min.js`)

The kernel embeds a vendored Meriyah bundle at:

codex-rs/core/src/tools/js_repl/meriyah.umd.min.js

Current source is meriyah@7.0.0 from npm (dist/meriyah.umd.min.js). Licensing is tracked in:

third_party/meriyah/LICENSE
NOTICE

How this file was sourced

From a clean temp directory:

tmp="$(mktemp -d)"
cd "$tmp"
npm pack meriyah@7.0.0
tar -xzf meriyah-7.0.0.tgz
cp package/dist/meriyah.umd.min.js /path/to/repo/codex-rs/core/src/tools/js_repl/meriyah.umd.min.js
cp package/LICENSE.md /path/to/repo/third_party/meriyah/LICENSE

How to update to a newer version

Replace 7.0.0 in the commands above with the target version.
Copy the new dist/meriyah.umd.min.js into codex-rs/core/src/tools/js_repl/meriyah.umd.min.js.
Copy the package license into third_party/meriyah/LICENSE.
Update the version string in the header comment at the top of meriyah.umd.min.js.
Update NOTICE if the upstream copyright notice changed.
Run the relevant js_repl tests.

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JavaScript REPL (js_repl)