diff --git a/src/core/task/Task.ts b/src/core/task/Task.ts
index 5602e8031e..b897337176 100644
--- a/src/core/task/Task.ts
+++ b/src/core/task/Task.ts
@@ -3501,7 +3501,29 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 
 						// Only show error and count toward mistake limit after 2 consecutive failures
 						if (this.consecutiveNoToolUseCount >= 2) {
-							await this.say("error", "MODEL_NO_TOOLS_USED")
+							// Create diagnostic information for the details popup
+							const diagnosticInfo = [
+								"Diagnostic Information:",
+								"",
+								`Tool Protocol: ${this._taskToolProtocol ?? "unknown"}`,
+								`Consecutive No-Tool-Use Count: ${this.consecutiveNoToolUseCount}`,
+								`Assistant Message Length: ${assistantMessage.length} characters`,
+								"",
+								"Assistant Message Content Blocks:",
+								this.assistantMessageContent.length > 0
+									? this.assistantMessageContent
+											.map(
+												(block, i) =>
+													`  ${i + 1}. Type: ${block.type}${block.type === "text" ? `, Length: ${(block as any).content?.length ?? 0} chars` : ""}`,
+											)
+											.join("\n")
+									: "  (none)",
+								"",
+								"Raw Assistant Message:",
+								assistantMessage || "(empty)",
+							].join("\n")
+
+							await this.say("error", `MODEL_NO_TOOLS_USED\n${diagnosticInfo}`)
 							// Only count toward mistake limit after second consecutive failure
 							this.consecutiveMistakeCount++
 						}
diff --git a/webview-ui/src/components/chat/ChatRow.tsx b/webview-ui/src/components/chat/ChatRow.tsx
index e36ef2811b..ac63df6b6b 100644
--- a/webview-ui/src/components/chat/ChatRow.tsx
+++ b/webview-ui/src/components/chat/ChatRow.tsx
@@ -1310,27 +1310,47 @@ export const ChatRowContent = ({
 					)
 				case "error":
 					// Check if this is a model response error based on marker strings from backend
-					const isNoToolsUsedError = message.text === "MODEL_NO_TOOLS_USED"
-					const isNoAssistantMessagesError = message.text === "MODEL_NO_ASSISTANT_MESSAGES"
+					// The format is "MARKER\nDiagnostic Info" where diagnostic info is optional
+					const messageText = message.text || ""
+					const isNoToolsUsedError = messageText.startsWith("MODEL_NO_TOOLS_USED")
+					const isNoAssistantMessagesError = messageText.startsWith("MODEL_NO_ASSISTANT_MESSAGES")
 
 					if (isNoToolsUsedError) {
+						// Extract diagnostic info if present (after the marker and newline)
+						const parts = messageText.split("\n")
+						const diagnosticInfo = parts.length > 1 ? parts.slice(1).join("\n") : undefined
+
+						// Combine i18n detailed explanation with diagnostic info
+						const fullDetails = diagnosticInfo
+							? `${t("chat:modelResponseErrors.noToolsUsedDetails")}\n\n${diagnosticInfo}`
+							: t("chat:modelResponseErrors.noToolsUsedDetails")
+
 						return (
 							<ErrorRow
 								type="error"
 								title={t("chat:modelResponseIncomplete")}
 								message={t("chat:modelResponseErrors.noToolsUsed")}
-								errorDetails={t("chat:modelResponseErrors.noToolsUsedDetails")}
+								errorDetails={fullDetails}
 							/>
 						)
 					}
 
 					if (isNoAssistantMessagesError) {
+						// Extract diagnostic info if present (after the marker and newline)
+						const parts = messageText.split("\n")
+						const diagnosticInfo = parts.length > 1 ? parts.slice(1).join("\n") : undefined
+
+						// Combine i18n detailed explanation with diagnostic info
+						const fullDetails = diagnosticInfo
+							? `${t("chat:modelResponseErrors.noAssistantMessagesDetails")}\n\n${diagnosticInfo}`
+							: t("chat:modelResponseErrors.noAssistantMessagesDetails")
+
 						return (
 							<ErrorRow
 								type="error"
 								title={t("chat:modelResponseIncomplete")}
 								message={t("chat:modelResponseErrors.noAssistantMessages")}
-								errorDetails={t("chat:modelResponseErrors.noAssistantMessagesDetails")}
+								errorDetails={fullDetails}
 							/>
 						)
 					}