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perf(core): fix OOM crash in long-running sessions #21207

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jacob314 wants to merge 1 commit into from
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perf(core): fix OOM crash in long-running sessions #21207

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10 changes: 7 additions & 3 deletions packages/core/src/core/geminiChat.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -691,9 +691,13 @@ export class GeminiChat {
const history = curated
? extractCuratedHistory(this.history)
: this.history;
// Deep copy the history to avoid mutating the history outside of the
// chat session.
return structuredClone(history);
// Return a shallow copy of the array to prevent callers from mutating
// the internal history array (push/pop/splice). Content objects are
// shared references — callers MUST NOT mutate them in place.
// This replaces a prior structuredClone() which deep-copied the entire
// conversation on every call, causing O(n) memory pressure per turn
// that compounded into OOM crashes in long-running sessions.
return [...history];
Comment on lines +694 to +700
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@gemini-code-assist gemini-code-assist bot Mar 5, 2026

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high

The move to a shallow copy is a great performance optimization that resolves the OOM issue. However, relying solely on a comment to prevent callers from mutating the shared Content objects is fragile and could lead to hard-to-debug state corruption down the line.

To enforce this contract at compile time without any runtime performance penalty, you can leverage TypeScript's Readonly types. This provides a much stronger guarantee against accidental mutations.

I recommend updating the function signature to return a ReadonlyArray<Content>:

getHistory(curated: boolean = false): ReadonlyArray<Content> {

This change will prevent methods like .push() or direct index assignments on the returned array, making the implementation significantly safer.

getHistory(curated: boolean = false): ReadonlyArray<Content> {

}

/**
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13 changes: 9 additions & 4 deletions packages/core/src/core/turn.ts
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Expand Up @@ -241,6 +241,7 @@ export class Turn {
readonly pendingToolCalls: ToolCallRequestInfo[] = [];
private debugResponses: GenerateContentResponse[] = [];
private pendingCitations = new Set<string>();
private cachedResponseText: string | undefined = undefined;
finishReason: FinishReason | undefined = undefined;

constructor(
Expand Down Expand Up @@ -432,11 +433,15 @@ export class Turn {
/**
* Get the concatenated response text from all responses in this turn.
* This extracts and joins all text content from the model's responses.
* The result is cached since this is called multiple times per turn.
*/
getResponseText(): string {
return this.debugResponses
.map((response) => getResponseText(response))
.filter((text): text is string => text !== null)
.join(' ');
if (this.cachedResponseText === undefined) {
this.cachedResponseText = this.debugResponses
.map((response) => getResponseText(response))
.filter((text): text is string => text !== null)
.join(' ');
}
return this.cachedResponseText;
}
}
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