From 6227ba73a73b3e78ce584624077d482fbf9b1533 Mon Sep 17 00:00:00 2001
From: Aishanee Shah <aishaneeshah@google.com>
Date: Fri, 6 Feb 2026 20:28:45 +0000
Subject: [PATCH] feat: implement late-binding tool updates in GeminiChat

---
 packages/core/src/core/client.ts     | 7 +++++++
 packages/core/src/core/geminiChat.ts | 5 +++++
 2 files changed, 12 insertions(+)

diff --git a/packages/core/src/core/client.ts b/packages/core/src/core/client.ts
index c793ed0bd7..fdfa1defce 100644
--- a/packages/core/src/core/client.ts
+++ b/packages/core/src/core/client.ts
@@ -256,7 +256,14 @@ export class GeminiClient {
     this.forceFullIdeContext = true;
   }
 
+  private lastUsedModelId?: string;
+
   async setTools(modelId?: string): Promise<void> {
+    if (modelId && modelId === this.lastUsedModelId) {
+      return;
+    }
+    this.lastUsedModelId = modelId;
+
     const toolRegistry = this.config.getToolRegistry();
     const toolDeclarations = toolRegistry.getFunctionDeclarations(modelId);
     const tools: Tool[] = [{ functionDeclarations: toolDeclarations }];
diff --git a/packages/core/src/core/geminiChat.ts b/packages/core/src/core/geminiChat.ts
index df98e3ebd7..de9dd6c6b0 100644
--- a/packages/core/src/core/geminiChat.ts
+++ b/packages/core/src/core/geminiChat.ts
@@ -240,6 +240,7 @@ export class GeminiChat {
   private sendPromise: Promise<void> = Promise.resolve();
   private readonly chatRecordingService: ChatRecordingService;
   private lastPromptTokenCount: number;
+  private lastUsedModel?: string;
 
   constructor(
     private readonly config: Config,
@@ -581,6 +582,10 @@ export class GeminiChat {
       }
 
       // Track final request parameters for AfterModel hooks
+      if (modelToUse !== this.lastUsedModel) {
+        await this.config.getGeminiClient().setTools(modelToUse);
+        this.lastUsedModel = modelToUse;
+      }
       lastModelToUse = modelToUse;
       lastConfig = config;
       lastContentsToUse = contentsToUse;