Expose a pure Rust EmbeddedHarness API in codex-wasm-harness so downstream browser apps can depend on the crate directly without going through the demo-specific wasm_bindgen wrapper. Introduce trait seams for Responses transport, tool execution, and event delivery, move shared response/event types into dedicated modules, and keep BrowserCodex as a thin compatibility adapter so the existing browser demo continues to build and run unchanged.
Upgrade the wasm harness from a one-shot sampler to a real Responses API loop that uses the Codex prompt, handles function_call / function_call_output turns, and exposes a browser exec_js callback. The example page now provisions a sandboxed iframe kernel, persists the API key in localStorage, surfaces browser errors inline, and has been verified in Chrome Testing with a live prompt that executes JavaScript and completes the turn.
Jeremy lewi