GPT-5.4 CUA Sample App

TypeScript sample app for browser-focused computer-use workflows with GPT-5.4. The repo includes:

• apps/demo-web: a Next.js operator console for starting runs and reviewing screenshots, events, and replay artifacts
• apps/runner: a Fastify runner that manages mutable workspaces, browser sessions, SSE, and replay bundles
• packages/*: shared scenario, runtime, and contract packages that make it easy to add new labs later

The legacy Python sample does not ship in this release branch. Keep that history on a separate v1 or legacy branch.

What This Repo Demonstrates

• how to integrate the Responses API from one canonical place: packages/runner-core/src/responses-loop.ts
• how to switch between code mode and native computer mode against the same browser lab
• how to define scenario manifests, launch isolated run workspaces, and verify outcomes
• how to build an operator-facing console that is understandable even when the runner is offline or a run fails

Prerequisites

• Node.js 22.20.0
• pnpm 10.26.0
• Playwright Chromium browser install

First Run

git clone <repo-url>
cd openai-cua-sample-app
corepack enable
pnpm install
cp .env.example .env

Edit .env and set at least this environment variable:

OPENAI_API_KEY=your_key_here

The runner reads the repo-root .env automatically when you start it through the provided scripts. The web app uses its built-in defaults; if you need to override NEXT_PUBLIC_* settings, add them in apps/demo-web/.env.local.

If pnpm install prints an Ignored build scripts warning for optional packages such as sharp or esbuild, you can ignore it for local development in this repo. A clean clone still installs, builds, and starts successfully without approving those scripts.

Install the Playwright browser:

On Linux, install Playwright OS dependencies as well:

pnpm playwright:install:with-deps

If Playwright later reports missing system libraries, rerun the with-deps command above and follow any OS package prompts it prints.

Start both apps together:

Open http://127.0.0.1:3000, choose a scenario, keep Headless selected, and start a run.

Local Development

Run the services separately if you want independent logs:

pnpm dev:runner
RUNNER_BASE_URL=http://127.0.0.1:4001 pnpm dev:web

Common checks:

pnpm lint
pnpm typecheck
pnpm test
pnpm build
pnpm check

Live smoke tests stay opt-in and secret-gated:

OPENAI_API_KEY=your_key_here pnpm test:live

Execution Modes

• native: exposes the Responses API computer tool directly. The model requests clicks, drags, typing, waits, and screenshots against the live browser session.
• code: exposes a persistent Playwright JavaScript REPL through exec_js. The model scripts the browser rather than emitting raw computer actions.

Both modes use the same scenario manifests and replay pipeline. native is the closest sample of the computer tool itself. code is the clearest sample of a browser REPL harness.

Official Scenarios

• kanban-reprioritize-sprint (kanban): teaches stateful drag-and-drop verification against a target board state derived from the operator prompt
• paint-draw-poster (paint): teaches cursor control, drawing, and verifying saved canvas state against the live canvas
• booking-complete-reservation (booking): teaches multi-step browsing and form completion with verification against a local confirmation record

More detail lives in docs/scenarios.md.

Repo Map

• apps/demo-web The operator console UI
• apps/runner The HTTP runner, SSE endpoints, and artifact serving layer
• packages/replay-schema Shared request, response, replay, and error contracts
• packages/scenario-kit Public scenario manifests and prompt defaults
• packages/browser-runtime Playwright session abstraction
• packages/runner-core Orchestration, Responses loop, scenario executors, and verification
• labs Static lab templates copied into run-scoped workspaces
• docs Architecture, scenarios, and contribution guidance

Environment Variables

Runner:

• OPENAI_API_KEY
• HOST (default 127.0.0.1)
• PORT (default 4001)
• CUA_DEFAULT_MODEL (default gpt-5.4)
• CUA_RESPONSES_MODE (auto, fallback, or live)

Web:

• RUNNER_BASE_URL (default http://127.0.0.1:4001)
• NEXT_PUBLIC_CUA_DEFAULT_MODEL (default gpt-5.4)
• NEXT_PUBLIC_CUA_DEFAULT_MAX_RESPONSE_TURNS (default 24)

See .env.example for a minimal local template.

Safety And Limitations

• Computer use remains high risk. Do not point this sample at authenticated, financial, medical, or otherwise high-stakes environments.
• This repo is intentionally browser-focused. Workspace patching and file-editing scenarios are out of scope for the OSS release branch.
• Pending computer-use safety acknowledgements are not implemented in this sample yet. Runs fail with the stable code unsupported_safety_acknowledgement when the API asks for one.
• The public scenarios are local labs designed for deterministic verification. They are not intended as proofs of general web autonomy.

Release Validation Checklist

• clean clone on a fresh machine
• setup succeeds from this README alone
• pnpm dev
• one successful headless run
• one successful headful run
• one intentional failure that shows the new runner guidance cleanly