diff --git a/packages/ai/src/providers/google-gemini-cli.ts b/packages/ai/src/providers/google-gemini-cli.ts
index 54ac33aa..02b11367 100644
--- a/packages/ai/src/providers/google-gemini-cli.ts
+++ b/packages/ai/src/providers/google-gemini-cli.ts
@@ -511,12 +511,10 @@ export const streamGoogleGeminiCli: StreamFunction<"google-gemini-cli"> = (
 										});
 									} else {
 										currentBlock.text += part.text;
-										if (part.thoughtSignature) {
-											currentBlock.textSignature = retainThoughtSignature(
-												currentBlock.textSignature,
-												part.thoughtSignature,
-											);
-										}
+										currentBlock.textSignature = retainThoughtSignature(
+											currentBlock.textSignature,
+											part.thoughtSignature,
+										);
 										stream.push({
 											type: "text_delta",
 											contentIndex: blockIndex(),
diff --git a/packages/ai/src/providers/google-shared.ts b/packages/ai/src/providers/google-shared.ts
index 5e680acd..60d8b058 100644
--- a/packages/ai/src/providers/google-shared.ts
+++ b/packages/ai/src/providers/google-shared.ts
@@ -85,7 +85,10 @@ export function convertMessages<T extends GoogleApiType>(model: Model<T>, contex
 				if (block.type === "text") {
 					// Skip empty text blocks - they can cause issues with some models (e.g. Claude via Antigravity)
 					if (!block.text || block.text.trim() === "") continue;
-					parts.push({ text: sanitizeSurrogates(block.text) });
+					parts.push({
+						text: sanitizeSurrogates(block.text),
+						...(block.textSignature && { thoughtSignature: block.textSignature }),
+					});
 				} else if (block.type === "thinking") {
 					// Skip empty thinking blocks
 					if (!block.thinking || block.thinking.trim() === "") continue;
diff --git a/packages/ai/src/providers/google-vertex.ts b/packages/ai/src/providers/google-vertex.ts
index b91c96eb..384e4ca3 100644
--- a/packages/ai/src/providers/google-vertex.ts
+++ b/packages/ai/src/providers/google-vertex.ts
@@ -142,12 +142,10 @@ export const streamGoogleVertex: StreamFunction<"google-vertex"> = (
 								});
 							} else {
 								currentBlock.text += part.text;
-								if (part.thoughtSignature) {
-									currentBlock.textSignature = retainThoughtSignature(
-										currentBlock.textSignature,
-										part.thoughtSignature,
-									);
-								}
+								currentBlock.textSignature = retainThoughtSignature(
+									currentBlock.textSignature,
+									part.thoughtSignature,
+								);
 								stream.push({
 									type: "text_delta",
 									contentIndex: blockIndex(),
diff --git a/packages/ai/src/providers/google.ts b/packages/ai/src/providers/google.ts
index eb7733df..128dde7c 100644
--- a/packages/ai/src/providers/google.ts
+++ b/packages/ai/src/providers/google.ts
@@ -129,12 +129,10 @@ export const streamGoogle: StreamFunction<"google-generative-ai"> = (
 								});
 							} else {
 								currentBlock.text += part.text;
-								if (part.thoughtSignature) {
-									currentBlock.textSignature = retainThoughtSignature(
-										currentBlock.textSignature,
-										part.thoughtSignature,
-									);
-								}
+								currentBlock.textSignature = retainThoughtSignature(
+									currentBlock.textSignature,
+									part.thoughtSignature,
+								);
 								stream.push({
 									type: "text_delta",
 									contentIndex: blockIndex(),