@mfui/anthropic

@mfui/anthropic adapts Anthropic Messages SSE streams into MFUI semantic SSE streams.

Use this package when the upstream stream emits Anthropic events such as content_block_delta, message_start, and message_delta.

createMFUIResponse()

Creates an MFUI semantic SSE Response from an upstream Anthropic stream.

Import

import { createMFUIResponse } from '@mfui/anthropic';

Signature

function createMFUIResponse(
  source: AnthropicStreamSource,
  mfui: MFUIManifest,
  options?: AnthropicMFUIResponseOptions,
): Response

Parameters

Name	Type	Required	Default	Description
source	AnthropicStreamSource	Yes	n/a	Provider Response, response body stream, or null.
mfui	MFUIManifest	Yes	n/a	Components available to this request.
options	AnthropicMFUIResponseOptions	No	{}	Response, parser, writer, and lifecycle options.

Returns

Type	Description
Response	text/event-stream response that emits MFUI semantic SSE events.

Example

import { createMFUIPrompt } from '@mfui/server';
import { createMFUIResponse } from '@mfui/anthropic';

const upstream = await fetch('https://api.anthropic.com/v1/messages', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    model: 'claude-sonnet-4-5',
    system: [
      'You are a helpful assistant.',
      createMFUIPrompt(mfui),
    ].join('\n\n'),
    messages,
    stream: true,
  }),
});

return createMFUIResponse(upstream, mfui);

Notes

When provider processing fails, the returned MFUI stream emits an error event and then closes. onError is called when provided.

AnthropicStreamSource

Source accepted by createMFUIResponse(), readStream(), and pipeMFUIStream().

Shape

type AnthropicStreamSource =
  | Response
  | ReadableStream<Uint8Array>
  | null

AnthropicMFUIResponseOptions

Options for createMFUIResponse().

Property	Type	Required	Default	Description
close	boolean	No	true	Whether to close the MFUI parser and writer when the provider stream finishes.
parser	MFUIBlockParserOptions	No	{}	Options passed to createMFUIBlockParser().
writer	MFUIStreamWriterOptions	No	{}	Options passed to createMFUIStreamWriter().
responseInit	ResponseInit	No	{}	Init object passed to the returned Response.
onMessage	MFUIMessageHandler	No	n/a	Called with the final projected message after the MFUI response finishes.
onError	MFUIErrorHandler	No	n/a	Called when provider stream processing or MFUI block parsing fails.

readStream()

Reads Anthropic SSE events and yields normalized JSON events.

Import

import { readStream } from '@mfui/anthropic';

Signature

function readStream(
  source: AnthropicStreamSource,
): AsyncIterable<AnthropicStreamEvent>

Parameters

Name	Type	Required	Default	Description
source	AnthropicStreamSource	Yes	n/a	Provider SSE source.

Returns

Type	Description
AsyncIterable<AnthropicStreamEvent>	Parsed provider events. The type field is taken from the SSE event name when present, otherwise from data.type.

AnthropicStreamEvent

Provider event shape consumed by writeMFUIStream().

Property	Type	Required	Default	Description
type	string	No	n/a	Provider event type. MFUI reads message_start, content_block_delta, and message_delta.
message	Record<string, unknown>	No	n/a	Message object. message.usage.input_tokens maps to inputTokens.
delta	Record<string, unknown>	No	n/a	Content block delta. Text is read when delta.type is text_delta and delta.text is a string.
usage	Record<string, unknown>	No	n/a	Message delta usage. usage.output_tokens maps to outputTokens.
[key]	unknown	No	n/a	Additional provider fields are ignored by MFUI.

writeMFUIStream()

Writes parsed Anthropic events into an MFUI block parser.

Import

import { writeMFUIStream } from '@mfui/anthropic';

Signature

function writeMFUIStream(
  stream: AsyncIterable<AnthropicStreamEvent>,
  parser: MFUIBlockParser,
  options?: AnthropicMFUIStreamOptions,
): Promise<void>

Parameters

Name	Type	Required	Default	Description
stream	AsyncIterable<AnthropicStreamEvent>	Yes	n/a	Parsed provider events.
parser	MFUIBlockParser	Yes	n/a	MFUI block parser receiving provider text deltas.
options	AnthropicMFUIStreamOptions	No	{}	Stream writing options.

Returns

Type	Description
Promise<void>	Resolves after the provider stream is fully consumed and the parser is flushed or closed.

AnthropicMFUIStreamOptions

Options for writeMFUIStream() and pipeMFUIStream().

Property	Type	Required	Default	Description
close	boolean	No	true	Whether to call parser.close() when the provider stream ends. When false, parser.flush() is called instead.

pipeMFUIStream()

Reads a provider SSE source and writes it into an MFUI block parser.

Import

import { pipeMFUIStream } from '@mfui/anthropic';

Signature

function pipeMFUIStream(
  source: AnthropicStreamSource,
  parser: MFUIBlockParser,
  options?: AnthropicMFUIStreamOptions,
): Promise<void>

Parameters

Name	Type	Required	Default	Description
source	AnthropicStreamSource	Yes	n/a	Provider SSE source.
parser	MFUIBlockParser	Yes	n/a	MFUI block parser receiving provider text deltas.
options	AnthropicMFUIStreamOptions	No	{}	Stream writing options.

Returns

Type	Description
Promise<void>	Resolves after the provider stream is consumed.