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fix(agent): prevent session context poisoning on interrupted turns #29265

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fix(agent): prevent session context poisoning on interrupted turns #29265

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cfe646d
fix(agent): prevent session context poisoning on interrupted turns
rahuldevlab Sep 9, 2026
69b3a42
fix(agent): apply optional chaining on part.text in curated history
rahuldevlab Sep 9, 2026
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45 changes: 45 additions & 0 deletions packages/core/src/core/geminiChat.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ import {
THINKING_ONLY_NUDGE_MESSAGE,
NO_RESPONSE_TEXT_NUDGE_MESSAGE,
applyRetryNudge,
INTERRUPTED_RESPONSE_PLACEHOLDER,
} from './geminiChat.js';
import {
type CompletedToolCall,
Expand Down Expand Up @@ -3834,6 +3835,50 @@ describe('GeminiChat', () => {
});
});

describe('interruption handling in getHistoryTurns', () => {
it('should replace INTERRUPTED_RESPONSE_PLACEHOLDER with a benign continuing message in curated history to prevent poisoning while preventing turn fusion', () => {
vi.mocked(mockConfig.isContextManagementEnabled).mockReturnValue(false);
vi.mocked(mockConfig.getModel).mockReturnValue('gemini-2.5-pro');

chat.setHistory([
{ role: 'user', parts: [{ text: 'search for files' }] },
{
role: 'model',
parts: [{ functionCall: { name: 'glob', args: {} } }],
},
{
role: 'user',
parts: [{ functionResponse: { name: 'glob', response: { files: [] } } }],
},
{
role: 'model',
parts: [{ text: INTERRUPTED_RESPONSE_PLACEHOLDER }],
},
{ role: 'user', parts: [{ text: 'continue search' }] },
]);

const turns = chat.getHistoryTurns(true);

// The interrupted response turn should be mapped to "Continuing.".
// The turns should NOT be coalesced, and their roles must alternate perfectly.
expect(turns).toHaveLength(5);
expect(turns[0].content.role).toBe('user');
expect(turns[0].content.parts![0].text).toBe('search for files');

expect(turns[1].content.role).toBe('model');
expect(turns[1].content.parts![0].functionCall?.name).toBe('glob');

expect(turns[2].content.role).toBe('user');
expect(turns[2].content.parts![0].functionResponse?.name).toBe('glob');

expect(turns[3].content.role).toBe('model');
expect(turns[3].content.parts![0].text).toBe('Continuing.');

expect(turns[4].content.role).toBe('user');
expect(turns[4].content.parts![0].text).toBe('continue search');
});
});

describe('ensureActiveLoopHasThoughtSignatures', () => {
it('should add thoughtSignature to the first functionCall in each model turn of the active loop', () => {
const chat = new GeminiChat(mockConfig, '', [], []);
Expand Down
24 changes: 22 additions & 2 deletions packages/core/src/core/geminiChat.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -227,8 +227,28 @@ function extractCuratedHistory(
const modelOutput: HistoryTurn[] = [];
let isValid = true;
while (i < length && comprehensiveHistory[i].content.role === 'model') {
modelOutput.push(comprehensiveHistory[i]);
if (isValid && !isValidContent(comprehensiveHistory[i].content)) {
let turn = comprehensiveHistory[i];
if (
turn.content.parts?.some(
(part) => part?.text === INTERRUPTED_RESPONSE_PLACEHOLDER,
)
) {
const newParts = turn.content.parts.map((part) => {
if (part?.text === INTERRUPTED_RESPONSE_PLACEHOLDER) {
return { ...part, text: 'Continuing.' };
}
return part;
});
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turn = {
...turn,
content: {
...turn.content,
parts: newParts,
},
};
}
modelOutput.push(turn);
if (isValid && !isValidContent(turn.content)) {
isValid = false;
}
i++;
Expand Down