Rosseta

Rosseta is a Visual Studio Code extension for editing Markdown prompts, agents, and skills in the language you understand while keeping a canonical version in another language on disk.

Open a Markdown file, select the Rosseta Stone icon, and work in the localized editor. When you save, Rosseta translates the complete Markdown blocks that changed and writes them back to the canonical file. Unchanged blocks are preserved.

Installation

Rosseta requires Visual Studio Code 1.95 or later.

1. Obtain the rosseta-<version>.vsix package for the version you want to install.
2. In Visual Studio Code, open the Command Palette.
3. Run Extensions: Install from VSIX... and select the package.
4. Reload Visual Studio Code when prompted.

Recommended first setup: Google Gemini

Google Gemini is the recommended provider for getting started because the Gemini API offers a free tier with enough capacity for initial use in many cases. Available models, rate limits, regional availability, and pricing can change, so review the current Gemini API pricing before relying on it for regular or high-volume work.

Create a Gemini API key

Google AI Studio is Google's console for creating and managing Gemini API keys.

1. Open the Google AI Studio API Keys page and sign in with your Google account.
2. If Google AI Studio has already created a project and API key for your account, select that key. Otherwise, choose Create API key.
3. Select an existing Google Cloud project or create/import one when prompted.
4. Copy the generated key and keep it private. You can review Google's current instructions in the Gemini API key documentation.
5. In Visual Studio Code, run Rosseta: Open control center from the Command Palette.
6. Select Google Gemini, paste the API key, and refresh the model list.
7. Select a translation model, set the source and editing languages, and save the configuration.

Treat the API key like a password: never add it to a repository, Markdown file, screenshot, or shared settings file. Rosseta stores provider keys in Visual Studio Code Secret Storage rather than in workspace settings. If you restrict the key in Google Cloud, allow the Generative Language API (Gemini API); Google AI Studio only displays unrestricted keys or keys restricted to that API.

Google currently states that content submitted through its free tier may be used to improve its products. Review the data-use column on the official pricing page and use a suitable paid plan or another provider when the documents require different handling.

Using Rosseta

1. Open a trusted workspace and select the canonical .md file you want to edit.
2. Select the Rosseta Stone icon in the editor title bar. It may appear inside the ... overflow menu when space is limited.
3. If the provider, required API key, or model is missing, Rosseta opens the control center so you can complete the configuration.
4. Once the configuration is valid, Rosseta translates the document and opens a localized virtual editor.
5. Edit the localized Markdown and save it normally.
6. Rosseta retranslates each complete block you changed and updates the canonical file on disk.

For example, changing one word in a paragraph causes the full paragraph to be translated again so that grammar and context remain coherent. Unchanged paragraphs are copied from the canonical document without another provider request.

The control center is global and is not associated with the last Markdown file you opened. It reports whether each provider has a stored credential without revealing the credential itself, and it lets you replace or remove an old key.

Providers and model fallback

Rosseta supports the native APIs of:

• Google Gemini
• OpenAI
• Anthropic
• GitHub Copilot, through the models made available by VS Code

OpenAI, Anthropic, and Gemini each have their own API key and model selection. The control center selects the primary model. To configure several models, run Rosseta: Select translation models from the Command Palette and select them in priority order. Rosseta tries the first model and moves to the next one if an attempt fails.

Provider requests use HTTPS and the official OpenAI, Anthropic, or Google Gemini endpoints. A workspace cannot redirect Rosseta to a custom endpoint.

Use GitHub Copilot instead of an API key

Rosseta can use the Language Model API built into VS Code to access models supplied by GitHub Copilot:

1. Install or enable GitHub Copilot in VS Code and sign in to a GitHub account with Copilot access.
2. Open Rosseta: Open control center and select GitHub Copilot.
3. Select Refresh models, choose one of the models currently available to your account, and save.
4. The first translation may show a VS Code consent prompt. Approve it to allow Rosseta to send the opened Markdown content to the selected model.

Rosseta never receives or stores a GitHub token. VS Code and GitHub Copilot manage authentication, consent, model availability, and request execution. Copilot use remains subject to the limits and billing rules of the account's Copilot plan; using an existing subscription does not make model requests unlimited.

Markdown preservation

Rosseta parses Markdown into blocks and compares the localized editor with the snapshot from which it was created. On save:

• changed paragraphs, headings, and other translatable nodes are translated as complete blocks;
• unchanged blocks retain their canonical content;
• frontmatter and fenced code blocks are synchronized literally rather than translated;
• inline code, template variables such as ${NAME} and {{ value }}, links, HTML/XML tags, and Markdown markers are protected with validated placeholders.

If a provider changes or removes protected structure, Rosseta cancels the save instead of risking corruption of the canonical file.

Security and privacy

• API keys are stored separately for each provider in Visual Studio Code Secret Storage.
• GitHub Copilot authentication is managed entirely by VS Code; Rosseta does not read or store GitHub credentials.
• Rosseta does not read provider credentials or make translation requests from an untrusted workspace.
• Only translatable Markdown blocks are sent to the selected provider; frontmatter and fenced code blocks are not sent for translation.
• Block-level translation results live only in memory for the current session. When rosseta.documentCache is enabled (off by default), finished localized documents — including frontmatter and fenced code — are additionally persisted as plain-text, unencrypted JSON under VS Code's local workspace storage (never synced), capped at roughly 40 documents or 5 MB. Disabling the setting stops future reads and writes; run Rosseta: Clear translation cache to delete existing data, which works even while the setting is disabled.
• Notifications and the Rosseta output channel redact known credentials, authorization headers, sensitive URLs, and unsafe provider payloads.
• Provider processing remains subject to that provider's terms, retention rules, and data-use policy.

Commands

The following commands are available from the Command Palette:

• Rosseta: Open control center
• Rosseta: Open localized editor
• Rosseta: Open canonical source
• Rosseta: Select translation provider
• Rosseta: Set provider API key
• Rosseta: Select translation models
• Rosseta: Clear translation cache

Troubleshooting

The Stone icon is not visible

Make sure the active editor is a file whose extension is exactly .md. When the editor title bar is crowded, open its ... menu. Also confirm that Rosseta is installed and enabled for the current workspace.

The control center opens instead of the localized editor

Rosseta needs a selected provider, a stored API key for OpenAI, Anthropic, or Gemini, and at least one selected model. GitHub Copilot does not require an API key in Rosseta, but it must be installed, signed in, available to the current account, and granted access when VS Code asks. Complete the highlighted configuration and save it. Rosseta also returns to the control center when a stored credential is rejected or the selected model is no longer available.

Model refresh or translation fails

Read the native notification first and use its suggested action, such as Replace API Key, Refresh Models, or Retry. For more information, select Show Details and inspect the Rosseta output channel. Common causes include an invalid or restricted key, exhausted quota, rate limits, network connectivity, unavailable models, and provider-side failures.

The canonical file changed outside Rosseta

Reopen the localized editor before continuing. Rosseta prevents a save when the source snapshot is stale so that external edits are not overwritten.

Credits

The editor action uses the Stone icon from Lucide, available under the ISC license.