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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/phpaisdk/anthropic/llms.txt

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Streaming uses Anthropic’s server-sent events (SSE) protocol to deliver the response incrementally as it is generated. The SDK yields TextDeltaPart, ReasoningDeltaPart, and ToolCallDeltaPart chunks as they arrive, so your application can begin rendering output without waiting for the full response to complete.

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Basic Streaming

Call .stream() instead of .run() to receive a stream handle. Iterate over $stream->chunks() to receive each text delta as a string, then call $stream->run() to obtain the fully-assembled TextModelResponse once the stream is exhausted. 
use AiSdk\Anthropic;
use AiSdk\Generate;

$stream = Generate::text('Tell me a story.')
    ->model(Anthropic::model('claude-sonnet-4'))
    ->stream();

foreach ($stream->chunks() as $chunk) {
    echo $chunk;
}

$result = $stream->run();
$stream->chunks() is a generator that yields plain text delta strings — the same content you would read from $result->text if you called .run() directly, but delivered piece by piece. After iterating all chunks, $stream->run() returns the complete TextModelResponse with final usage counts and finish reason.

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Stream Events

The Anthropic SSE protocol sends a sequence of typed events. The SDK’s stream parser handles the following event types internally:
1

message_start

Emitted once at the beginning of the stream. Contains the message ID and initial input token count. The SDK emits a ProviderMetadataPart carrying the Anthropic message ID.
2

content_block_start

Signals the start of a new content block. When the block type is tool_use, the parser emits a ToolCallStartPart with the tool call’s index, id, and name.
3

content_block_delta

Carries incremental content. The SDK maps the three delta subtypes as follows:
  • text_delta → yields a TextDeltaPart with the text fragment
  • thinking_delta → yields a ReasoningDeltaPart with the reasoning fragment
  • input_json_delta → yields a ToolCallDeltaPart with a partial JSON string
4

message_delta

Emitted once near the end of the stream. Contains the stop_reason and the final output token count. The SDK uses this to set the FinishReason on the assembled response.
5

error

Emitted when Anthropic reports a stream-level error. The SDK wraps the error message in a RuntimeException and yields an ErrorPart.
After all events have been consumed, the parser emits a final FinishPart carrying the resolved FinishReason and a Usage object with the complete input and output token counts.
The stream: true flag is set automatically when you call .stream(). Do not pass it manually via .providerOptions() — doing so would conflict with the SDK’s own stream handling.

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