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[AI] Propagate Task cancellation when streaming #16123

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[AI] Propagate Task cancellation when streaming #16123

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[AI] Propagate `Task` cancellation when streaming
andrewheard Apr 26, 2026
0a77345
Merge branch 'main' into ah/ai-streaming-task-cancellation
andrewheard Jun 30, 2026
3fbc13f
Update GenerativeAIService.swift
andrewheard Jun 30, 2026
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5 changes: 4 additions & 1 deletion FirebaseAI/Sources/Chat.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -115,7 +115,7 @@ public final class Chat: Sendable {
let request = history + newContent
let stream = try model.generateContentStream(request, generationConfig: generationConfig)
return AsyncThrowingStream { continuation in
Task {
let task = Task {

@gemini-code-assist gemini-code-assist Bot Apr 27, 2026

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medium

The task should check for cancellation before modifying the chat history. If the stream is cancelled, appending newContent and the partial aggregatedContent to _history (lines 138-142) might lead to an inconsistent chat state. Consider adding a check like guard !Task.isCancelled else { return } before updating the history.

var aggregatedContent: [ModelContent] = []

do {
Expand All @@ -142,6 +142,9 @@ public final class Chat: Sendable {
self._history.append(aggregated)
continuation.finish()
}
continuation.onTermination = { _ in
task.cancel()
}
}
}

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5 changes: 4 additions & 1 deletion FirebaseAI/Sources/GenerativeAIService.swift
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Expand Up @@ -72,7 +72,7 @@ struct GenerativeAIService {
func loadRequestStream<T: GenerativeAIRequest>(request: T)
-> AsyncThrowingStream<T.Response, Error> where T: Sendable {
return AsyncThrowingStream { continuation in
Task {
let task = Task {
let urlRequest: URLRequest
do {
urlRequest = try await self.urlRequest(request: request)
Expand Down Expand Up @@ -160,6 +160,9 @@ struct GenerativeAIService {

continuation.finish(throwing: nil)
}
continuation.onTermination = { _ in
task.cancel()
}
}
}

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5 changes: 4 additions & 1 deletion FirebaseAI/Sources/GenerativeModel.swift
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Expand Up @@ -322,7 +322,7 @@ public final class GenerativeModel: Sendable {

return AsyncThrowingStream { continuation in
let responseStream = generativeAIService.loadRequestStream(request: generateContentRequest)
Task {
let task = Task {

@gemini-code-assist gemini-code-assist Bot Apr 27, 2026

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low

Consider checking for task cancellation before finishing the continuation. If the task is cancelled during the loop, the code currently proceeds to line 357 and might call continuation.finish(throwing:) with an emptyContent error if no responses were yielded yet. It would be cleaner to exit early if Task.isCancelled is true.

do {
var didYieldResponse = false
for try await response in responseStream {
Expand Down Expand Up @@ -368,6 +368,9 @@ public final class GenerativeModel: Sendable {
return
}
}
continuation.onTermination = { _ in
task.cancel()
}
}
}

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