Custom adapters
Extend the document pipeline with your own formats.
A FormatAdapter declares a format identifier, extensions, MIME types, content detection, optional metadata extraction, and a synchronous parse(text, limits) function returning a DocumentPreview. Pass adapters to createController, processDocument, or a hook. Providing this list replaces the defaults; include the built-in markdownAdapter, jsonAdapter, csvAdapter, textAdapter, imageAdapter, pdfAdapter and docxAdapter as needed to retain those formats. acceptedFormats restricts the registered formats.
Adapters receive decoded source. Core owns validation, cancellation, immutable snapshots, and lazy preview caching. Custom parsers should honor the supplied preview limits. A parse exception falls back to a plain-text preview with a warning. Metadata extraction should be bounded and must not throw for damaged input. A dummy adapter test in packages/core/src/adapters/registry.test.ts demonstrates this contract without changing the input API.
Adapters and custom renderers are trusted code. The default renderer understands the Markdown preview node types; supply a custom renderer to DocumentViewer for other representations.
Text adapters may add inspect(text, limits) for metadata and warnings. Binary adapters use kind: 'binary', detectBytes, byte inspection and byte-based parsing. Core routes them without text decoding. Optional asynchronous extract(bytes, limits, signal) runs during processing and returns { raw, metadata?, warnings? }; the core generates a lazy plain text preview from extracted raw. See the dummy binary adapter test and format support.
Custom source formats and saved content
A registered text adapter's format ID can also be used by createContent, useSourceInput, useTexion, TexionInput, and saved messages. Pass the same adapters when editing and rendering. A custom format ID preserves source; it does not grant permission to render HTML.
<TexionInput
adapters={[queryAdapter]}
formats={['query']}
defaultContent={createContent('SELECT * FROM orders;', { format: 'query' })}
renderers={{ query: QueryPreview }}
onSubmit={save}
/>
<TexionViewer
content={saved.content}
options={{ adapters: [queryAdapter] }}
renderers={{ query: QueryPreview }}
/>queryAdapter is an application-defined FormatAdapter, and QueryPreview accepts PreviewRendererProps. The adapter parses and validates source into bounded preview nodes; the renderer presents it. DocumentViewer, TexionViewer, TexionInput, and TexionMessageViewer accept a renderers registry keyed by format ID. An explicit renderer on DocumentViewer overrides the registry. Without a custom renderer, valid adapter output uses the generic preview renderer. Unregistered formats report an error.
Adapters are fixed when the controller mounts. Remount when changing the registry. When using useSourceInput directly, pass both adapters and allowedFormats; automatic detection consults allowed text adapters after built-in detection. Custom format editing uses native source text; rich Markdown editing and built-in source highlighting remain specific to the built-in formats. Picker extensions and MIME types come from registered adapters.