What file formats does Euphony support?

Euphony supports Harmony JSON (.json) and JSONL (.jsonl) files, including Codex CLI session rollout files.

Can I use Euphony without a server or internet connection?

Yes, Euphony can run in frontend-only mode, serving static files from a local build or via the hosted version at https://openai.github.io/euphony.

How do I embed Euphony into my own web app?

Build the Euphony library (pnpm install && pnpm run build:library) and import the resulting JavaScript. Then use the custom element with a src or data attribute.

Does Euphony support React or other frameworks?

Yes, since it's built on Web Components, it works with any framework including React, Svelte, and Vue. For React, you can use the custom element directly with appropriate type declarations.

Is Euphony free and open-source?

Yes, Euphony is released under the Apache 2.0 license and its source code is available on GitHub.

Euphony

Render AI chat data and Codex logs into browsable views

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What is Euphony

Euphony is an open-source web application from OpenAI that transforms raw Harmony chat conversations and Codex CLI session logs into interactive, filterable timelines in the browser. It supports JSON and JSONL formats, providing a visual interface for debugging agent workflows and inspecting structured chat data used in training, evaluation, and agent pipelines.

Key Features

Interactive timeline view with filters for role, channel, and token-level details

Supports multiple input methods: file upload, drag-and-drop, or embedding via Web Components

Token inspector for identifying tokenizer mismatches and message boundaries

Embeddable custom elements (euphony-conversation) with CSS variable theming

Frontend-only mode for static deployment without a backend

Use Cases

AI engineers debugging multi-turn agent conversations recorded in Harmony format
Developers inspecting Codex CLI session logs to understand agent tool calls and responses
Teams building on gpt-oss models needing to review training data quality and structure
Researchers analyzing conversation rollouts from RLHF or evaluation pipelines
Educators demonstrating chat-based AI workflows in a browser without external dependencies

Why do startups need this tool?

Startups building AI agent workflows or fine-tuning models on gpt-oss need to debug complex multi-turn interactions quickly. Euphony provides a free, open-source interface that transforms raw JSONL logs into comprehensible timelines, reducing debugging time and improving team collaboration. Its embeddable Web Components allow startups to integrate inspection tools directly into their internal dashboards without building custom UIs.