From cfe646dffe72f81e8fd0653be343424c60db1c35 Mon Sep 17 00:00:00 2001
From: Rahul Kundani <rahul.kundani@osttra.com>
Date: Wed, 9 Sep 2026 07:09:55 +0000
Subject: [PATCH 1/2] fix(agent): prevent session context poisoning on
 interrupted turns

---
 packages/core/src/core/geminiChat.test.ts | 45 +++++++++++++++++++++++
 packages/core/src/core/geminiChat.ts      | 24 +++++++++++-
 2 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/packages/core/src/core/geminiChat.test.ts b/packages/core/src/core/geminiChat.test.ts
index ff79deb976e..a59484ca589 100644
--- a/packages/core/src/core/geminiChat.test.ts
+++ b/packages/core/src/core/geminiChat.test.ts
@@ -27,6 +27,7 @@ import {
   THINKING_ONLY_NUDGE_MESSAGE,
   NO_RESPONSE_TEXT_NUDGE_MESSAGE,
   applyRetryNudge,
+  INTERRUPTED_RESPONSE_PLACEHOLDER,
 } from './geminiChat.js';
 import {
   type CompletedToolCall,
@@ -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, '', [], []);
diff --git a/packages/core/src/core/geminiChat.ts b/packages/core/src/core/geminiChat.ts
index 1fe4a305275..f98cd3ce6ae 100644
--- a/packages/core/src/core/geminiChat.ts
+++ b/packages/core/src/core/geminiChat.ts
@@ -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;
+          });
+          turn = {
+            ...turn,
+            content: {
+              ...turn.content,
+              parts: newParts,
+            },
+          };
+        }
+        modelOutput.push(turn);
+        if (isValid && !isValidContent(turn.content)) {
           isValid = false;
         }
         i++;

From 69b3a429fe1cc0ba85bf9fa92084941aaa418da2 Mon Sep 17 00:00:00 2001
From: Rahul Kundani <rahul.kundani@osttra.com>
Date: Wed, 9 Sep 2026 07:24:55 +0000
Subject: [PATCH 2/2] fix(agent): apply optional chaining on part.text in
 curated history

---
 packages/core/src/core/geminiChat.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/core/src/core/geminiChat.ts b/packages/core/src/core/geminiChat.ts
index f98cd3ce6ae..71b532f6fc9 100644
--- a/packages/core/src/core/geminiChat.ts
+++ b/packages/core/src/core/geminiChat.ts
@@ -230,11 +230,11 @@ function extractCuratedHistory(
         let turn = comprehensiveHistory[i];
         if (
           turn.content.parts?.some(
-            (part) => part.text === INTERRUPTED_RESPONSE_PLACEHOLDER,
+            (part) => part?.text === INTERRUPTED_RESPONSE_PLACEHOLDER,
           )
         ) {
           const newParts = turn.content.parts.map((part) => {
-            if (part.text === INTERRUPTED_RESPONSE_PLACEHOLDER) {
+            if (part?.text === INTERRUPTED_RESPONSE_PLACEHOLDER) {
               return { ...part, text: 'Continuing.' };
             }
             return part;