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fix: allow returning a non-streaming reponse from onChatMessage() #761

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fix: allow returning a non-streaming reponse from onChatMessage() #761

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2bf694e
fix: insert `text-start` and `text-end` events when replying with a r…
iTrooz Dec 27, 2025
1e8d4f7
changeset
iTrooz Dec 30, 2025
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5 changes: 5 additions & 0 deletions .changeset/odd-signs-travel.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@cloudflare/ai-chat": patch
---

Allow returning a non-streaming reponse from onChatMessage()
40 changes: 36 additions & 4 deletions packages/ai-chat/src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1458,11 +1458,46 @@ export class AIChatAgent<
}
}

// Determine response format based on content-type
const contentType = response.headers.get("content-type") || "";
const isSSE = contentType.includes("text/event-stream"); // AI SDK v5 SSE format

// if not AI SDK SSE format, we need to inject text-start and text-end events ourselves
if (!isSSE) {
const body = JSON.stringify({
type: "text-start",
id
});
this._storeStreamChunk(streamId, body);
this._broadcastChatMessage({
body: body,
done: false,
id,
type: MessageType.CF_AGENT_USE_CHAT_RESPONSE,
...(continuation && { continuation: true })
});
}

let streamCompleted = false;
try {
while (true) {
const { done, value } = await reader.read();
if (done) {
if (!isSSE) {
const body = JSON.stringify({
type: "text-end",
id
});
this._storeStreamChunk(streamId, body);
this._broadcastChatMessage({
body: body,
done: false,
id,
type: MessageType.CF_AGENT_USE_CHAT_RESPONSE,
...(continuation && { continuation: true })
});
}

// Mark the stream as completed
this._completeStream(streamId);
streamCompleted = true;
Expand All @@ -1479,10 +1514,6 @@ export class AIChatAgent<

const chunk = decoder.decode(value);

// Determine response format based on content-type
const contentType = response.headers.get("content-type") || "";
const isSSE = contentType.includes("text/event-stream");

// After streaming is complete, persist the complete assistant's response
if (isSSE) {
// Parse AI SDK v5 SSE format and extract text deltas
Expand Down Expand Up @@ -1895,6 +1926,7 @@ export class AIChatAgent<
// Synthesize a text-delta event so clients can stream-render
const chunkBody = JSON.stringify({
type: "text-delta",
id,
delta: chunk
});
// Store chunk for replay on reconnection
Expand Down
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