diff --git a/src/plugin.ts b/src/plugin.ts
index 4e5d50ab..f65bc6ef 100644
--- a/src/plugin.ts
+++ b/src/plugin.ts
@@ -1608,6 +1608,46 @@ export const createAntigravityPlugin = (providerId: string) => async (
                   }
                 }
 
+                // Handle 403 VALIDATION_REQUIRED - account needs Google verification
+                // This prevents "Body already used" errors from SDK trying to parse the response twice
+                if (response.status === 403) {
+                  const cloned403 = response.clone();
+                  const body403 = await extractRetryInfoFromBody(cloned403);
+                  
+                  if (body403.reason === "VALIDATION_REQUIRED") {
+                    const cooldownMs = 10 * 60 * 1000; // 10 minutes - give user time to verify
+                    accountManager.markAccountCoolingDown(account, cooldownMs, "validation-required");
+                    accountManager.markRateLimited(account, cooldownMs, family, headerStyle, model);
+                    
+                    const accountLabel = account.email || `Account ${account.index + 1}`;
+                    await showToast(
+                      `${accountLabel} requires Google verification. Visit accounts.google.com to verify, then retry. Switching accounts...`,
+                      "warning"
+                    );
+                    pushDebug(`validation-required: account=${account.index} cooldown=${cooldownMs}ms`);
+                    
+                    // Record failure for health tracking
+                    getHealthTracker().recordFailure(account.index);
+                    
+                    // Force switch to another account
+                    lastFailure = {
+                      response,
+                      streaming: prepared.streaming,
+                      debugContext,
+                      requestedModel: prepared.requestedModel,
+                      projectId: prepared.projectId,
+                      endpoint: prepared.endpoint,
+                      effectiveModel: prepared.effectiveModel,
+                      sessionId: prepared.sessionId,
+                      toolDebugMissing: prepared.toolDebugMissing,
+                      toolDebugSummary: prepared.toolDebugSummary,
+                      toolDebugPayload: prepared.toolDebugPayload,
+                    };
+                    shouldSwitchAccount = true;
+                    break;
+                  }
+                }
+
                 // Success - reset rate limit backoff state for this quota
                 const quotaKey = headerStyleToQuotaKey(headerStyle, family);
                 resetRateLimitState(account.index, quotaKey);
diff --git a/src/plugin/storage.ts b/src/plugin/storage.ts
index c91ef2bc..48c7ccf3 100644
--- a/src/plugin/storage.ts
+++ b/src/plugin/storage.ts
@@ -173,7 +173,14 @@ export interface AccountStorage {
   activeIndex: number;
 }
 
-export type CooldownReason = "auth-failure" | "network-error" | "project-error";
+/**
+ * Reasons why an account may be cooling down.
+ * - "auth-failure": Authentication/token refresh failed
+ * - "network-error": Network connectivity issues
+ * - "project-error": Project ID resolution failed
+ * - "validation-required": Google requires account verification (403 PERMISSION_DENIED with VALIDATION_REQUIRED)
+ */
+export type CooldownReason = "auth-failure" | "network-error" | "project-error" | "validation-required";
 
 export interface AccountMetadataV3 {
   email?: string;
@@ -189,6 +196,8 @@ export interface AccountMetadataV3 {
   cooldownReason?: CooldownReason;
   /** Per-account device fingerprint for rate limit mitigation */
   fingerprint?: import("./fingerprint").Fingerprint;
+  /** History of previous fingerprints for this account */
+  fingerprintHistory?: import("./fingerprint").FingerprintVersion[];
 }
 
 export interface AccountStorageV3 {