From 476ec3facf60644a7cbe582d090dc01baaadb3cd Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Tue, 14 Jul 2026 13:28:04 +0100
Subject: [PATCH] refactor(anthropic): use SDK SSE parser

---
 packages/ai/src/providers/anthropic.ts | 152 +------------------------
 1 file changed, 3 insertions(+), 149 deletions(-)

diff --git a/packages/ai/src/providers/anthropic.ts b/packages/ai/src/providers/anthropic.ts
index b64de20f145b..50839278545c 100644
--- a/packages/ai/src/providers/anthropic.ts
+++ b/packages/ai/src/providers/anthropic.ts
@@ -1,5 +1,6 @@
 // Anthropic provider adapts Anthropic streams and tool calls for the runtime.
 import Anthropic from "@anthropic-ai/sdk";
+import { Stream } from "@anthropic-ai/sdk/core/streaming.js";
 import type {
   CacheControlEphemeral,
   ContentBlockParam,
@@ -303,18 +304,6 @@ function mergeHeaders(
   return merged;
 }
 
-interface ServerSentEvent {
-  event: string | null;
-  data: string;
-  raw: string[];
-}
-
-interface SseDecoderState {
-  event: string | null;
-  data: string[];
-  raw: string[];
-}
-
 const ANTHROPIC_MESSAGE_EVENTS: ReadonlySet<string> = new Set([
   "message_start",
   "message_delta",
@@ -324,139 +313,8 @@ const ANTHROPIC_MESSAGE_EVENTS: ReadonlySet<string> = new Set([
   "content_block_stop",
 ]);
 
-function flushSseEvent(state: SseDecoderState): ServerSentEvent | null {
-  if (!state.event && state.data.length === 0) {
-    return null;
-  }
-
-  const event: ServerSentEvent = {
-    event: state.event,
-    data: state.data.join("\n"),
-    raw: [...state.raw],
-  };
-  state.event = null;
-  state.data = [];
-  state.raw = [];
-  return event;
-}
-
-function decodeSseLine(line: string, state: SseDecoderState): ServerSentEvent | null {
-  if (line === "") {
-    return flushSseEvent(state);
-  }
-
-  state.raw.push(line);
-  if (line.startsWith(":")) {
-    return null;
-  }
-
-  const delimiterIndex = line.indexOf(":");
-  const fieldName = delimiterIndex === -1 ? line : line.slice(0, delimiterIndex);
-  let value = delimiterIndex === -1 ? "" : line.slice(delimiterIndex + 1);
-  if (value.startsWith(" ")) {
-    value = value.slice(1);
-  }
-
-  if (fieldName === "event") {
-    state.event = value;
-  } else if (fieldName === "data") {
-    state.data.push(value);
-  }
-
-  return null;
-}
-
-function nextLineBreakIndex(text: string): number {
-  const carriageReturnIndex = text.indexOf("\r");
-  const newlineIndex = text.indexOf("\n");
-  if (carriageReturnIndex === -1) {
-    return newlineIndex;
-  }
-  if (newlineIndex === -1) {
-    return carriageReturnIndex;
-  }
-  return Math.min(carriageReturnIndex, newlineIndex);
-}
-
-function consumeLine(text: string): { line: string; rest: string } | null {
-  const lineBreakIndex = nextLineBreakIndex(text);
-  if (lineBreakIndex === -1) {
-    return null;
-  }
-
-  let nextIndex = lineBreakIndex + 1;
-  if (text[lineBreakIndex] === "\r" && text[nextIndex] === "\n") {
-    nextIndex += 1;
-  }
-
-  return {
-    line: text.slice(0, lineBreakIndex),
-    rest: text.slice(nextIndex),
-  };
-}
-
-async function* iterateSseMessages(
-  body: ReadableStream<Uint8Array>,
-  signal?: AbortSignal,
-): AsyncGenerator<ServerSentEvent> {
-  const reader = body.getReader();
-  const decoder = new TextDecoder();
-  const state: SseDecoderState = { event: null, data: [], raw: [] };
-  let buffer = "";
-
-  try {
-    while (true) {
-      if (signal?.aborted) {
-        throw new Error("Request was aborted");
-      }
-
-      const { value, done } = await reader.read();
-      if (done) {
-        break;
-      }
-
-      buffer += decoder.decode(value, { stream: true });
-      let consumed = consumeLine(buffer);
-      while (consumed) {
-        buffer = consumed.rest;
-        const event = decodeSseLine(consumed.line, state);
-        if (event) {
-          yield event;
-        }
-        consumed = consumeLine(buffer);
-      }
-    }
-
-    buffer += decoder.decode();
-    let consumed = consumeLine(buffer);
-    while (consumed) {
-      buffer = consumed.rest;
-      const event = decodeSseLine(consumed.line, state);
-      if (event) {
-        yield event;
-      }
-      consumed = consumeLine(buffer);
-    }
-
-    if (buffer.length > 0) {
-      const event = decodeSseLine(buffer, state);
-      if (event) {
-        yield event;
-      }
-    }
-
-    const trailingEvent = flushSseEvent(state);
-    if (trailingEvent) {
-      yield trailingEvent;
-    }
-  } finally {
-    reader.releaseLock();
-  }
-}
-
 async function* iterateAnthropicEvents(
   response: Response,
-  signal?: AbortSignal,
   requireMessageStop = false,
 ): AsyncGenerator<RawMessageStreamEvent> {
   if (!response.body) {
@@ -466,7 +324,7 @@ async function* iterateAnthropicEvents(
   let sawMessageStart = false;
   let sawMessageEnd = false;
 
-  for await (const sse of iterateSseMessages(response.body, signal)) {
+  for await (const sse of Stream.rawEvents(response)) {
     if (sse.event === "error") {
       throw new Error(sse.data);
     }
@@ -612,11 +470,7 @@ export const streamAnthropic: StreamFunction<"anthropic-messages", AnthropicOpti
       const blocks = output.content as Block[];
       const blockIndexes = new Map<number, number>();
 
-      for await (const event of iterateAnthropicEvents(
-        response,
-        requestOptions?.signal,
-        refusalBuffer !== undefined,
-      )) {
+      for await (const event of iterateAnthropicEvents(response, refusalBuffer !== undefined)) {
         if (event.type === "message_start") {
           output.responseId = event.message.id;
           output.responseModel = event.message.model;