CJK PDF Viewer

A read-only PDF file-viewer plugin for Codex in the ChatGPT desktop app. It packages the character maps, standard fonts, and rendering assets needed to display Japanese and other CJK text, and opens the original PDF in a plugin file panel.

This project is independent of OpenAI. It does not modify the desktop application or replace its files.

Why this exists

Some PDFs use named Adobe character maps such as Adobe-Japan1-UCS2. A PDF can contain its Japanese font and still need those maps for a viewer to interpret the text correctly. In the reproduced failure, a PDF.js loader without its external font/CMap resources omitted Japanese labels. Supplying the required resources restored both their rendering and text extraction.

This plugin bundles its PDF.js worker and support data rather than relying on a CDN or the host application's PDF-viewer configuration. The document is not converted into an image-only PDF; page rendering and the selectable text layer are generated from its original bytes.

See the root-cause investigation for the reproduced failure and the distinction between the native preview, SDK replay, and local image conversion.

Japanese PDF search and page navigation using a public synthetic fixture

Requirements

A ChatGPT desktop app / Codex version that supports OpenAI MCP file entrypoints.
macOS or Linux with /bin/sh.
Node.js 22 or later, installed on PATH, in a standard Homebrew location, or under NVM. The launcher also accepts an explicit CJK_PDF_NODE path.
A PDF opened through the desktop host, so it can provide a host-managed file resource to the plugin.

File entrypoints are desktop-only in the current OpenAI extension specification. Do not expect them to work on the web, iOS, Android, or in a headless CLI.

Version 0.1.1 fixes startup in GUI applications that do not inherit an interactive shell's Node/NVM PATH. The launcher does not source shell profiles or change global environment settings. Automatic Windows launching is not yet supported by this Unix launcher; the renderer and bundled server themselves remain portable.

Install from the GitHub marketplace

Add the marketplace with Codex CLI:

codex plugin marketplace add O-kAIru/codex-cjk-pdf-viewer

Install the plugin from that marketplace:

codex plugin add codex-cjk-pdf-viewer@cjk-pdf-viewer-marketplace

Then reopen the ChatGPT desktop app, or refresh its plugin connections if that control is available. Open a PDF and select this viewer if the host offers a choice of file handlers.

The release includes dist/server.mjs and dist/viewer.html. A plugin user needs Node.js, but does not need to run npm install, build the source, obtain an API key, or run a remote service. See installation and validation.

GitHub marketplace distribution is distinct from listing in OpenAI's public plugin directory. The latter has a separate submission and review process; local MCP submissions currently require approved-partner access.

Use

The plugin registers a .pdf file entrypoint. When the host opens a PDF in that entrypoint, it sends the viewer a filename and an opaque resource URI. The viewer reads the PDF through the host's resource API and displays it in the thread file panel. Page navigation, zoom, text selection, and text search operate on the loaded document.

The plugin is a viewer, not a PDF editor. Saving, rewriting, re-uploading, or changing the original PDF is outside its scope.

Privacy and access

The server exposes one viewer tool and one static HTML resource.
There are no general filesystem tools, upload endpoints, or network-fetch tools in this plugin.
The server reads only its packaged dist/viewer.html file. It does not accept a user-supplied filesystem path.
PDF bytes are obtained in the viewer from the host-authorized opaque resource URI. They are not uploaded to a developer-operated service.
The renderer's worker, CMaps, standard fonts, and WASM resources are bundled. Viewing does not require font or PDF requests to a CDN.
No API key, account connection, or environment variable is required.

These statements describe this plugin's behavior; the desktop host's own data handling and policies still apply.

Develop

npm ci
npm run build
npm test

The build produces a self-contained MCP server and HTML viewer in dist/. server.mjs is the source entry point. Run the built server with:

node dist/server.mjs

Standard output is reserved for MCP messages. The server reads viewer.html relative to its bundled location, so moving the installed plugin directory does not require editing a machine-specific path.

Commit the built dist/ assets when publishing a release so a clean plugin installation can run without npm or a development toolchain. Preserve third-party license notices included by the build. Do not commit private documents, credentials, application binaries, or extracted proprietary application code.

Validation boundaries

Local protocol and rendering tests do not by themselves establish that a plugin has been installed successfully in every desktop version. Before claiming a desktop release is verified, complete the manual file-entrypoint checks in installation and validation, including opening the PDF from the actual host and checking text selection and search.

References

License

The project's own code is MIT licensed. Bundled dependencies retain their own licenses and notices. See LICENSE.