diff --git a/CHANGELOG.md b/CHANGELOG.md
index b80595611..d6d3555fe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@
 - Models/Auth: add MiniMax Anthropic-compatible API onboarding (minimax-api). (#590) — thanks @mneves75
 - Models: centralize model override validation + hooks Gmail warnings in doctor. (#602) — thanks @steipete
 - Agents: avoid base-to-string error stringification in model fallback. (#604) — thanks @steipete
+- Agents: treat billing/insufficient-credits errors as failover-worthy so model fallbacks kick in. (#486) — thanks @steipete
 - Commands: harden slash command registry and list text-only commands in `/commands`.
 - Models/Auth: show per-agent auth candidates in `/model status`, and add `clawdbot models auth order {get,set,clear}` (per-agent auth rotation overrides). — thanks @steipete
 - Debugging: add raw model stream logging flags and document gateway watch mode.
diff --git a/src/agents/model-fallback.test.ts b/src/agents/model-fallback.test.ts
index 7bb3dda3c..211efcbc0 100644
--- a/src/agents/model-fallback.test.ts
+++ b/src/agents/model-fallback.test.ts
@@ -56,6 +56,30 @@ describe("runWithModelFallback", () => {
     expect(run.mock.calls[1]?.[1]).toBe("claude-haiku-3-5");
   });
 
+  it("falls back on billing errors", async () => {
+    const cfg = makeCfg();
+    const run = vi
+      .fn()
+      .mockRejectedValueOnce(
+        new Error(
+          "LLM request rejected: Your credit balance is too low to access the Anthropic API. Please go to Plans & Billing to upgrade or purchase credits.",
+        ),
+      )
+      .mockResolvedValueOnce("ok");
+
+    const result = await runWithModelFallback({
+      cfg,
+      provider: "openai",
+      model: "gpt-4.1-mini",
+      run,
+    });
+
+    expect(result.result).toBe("ok");
+    expect(run).toHaveBeenCalledTimes(2);
+    expect(run.mock.calls[1]?.[0]).toBe("anthropic");
+    expect(run.mock.calls[1]?.[1]).toBe("claude-haiku-3-5");
+  });
+
   it("appends the configured primary as a last fallback", async () => {
     const cfg = makeCfg({
       agents: {
diff --git a/src/agents/model-fallback.ts b/src/agents/model-fallback.ts
index b7724d74f..ac667411b 100644
--- a/src/agents/model-fallback.ts
+++ b/src/agents/model-fallback.ts
@@ -9,6 +9,7 @@ import {
 } from "./model-selection.js";
 import {
   isAuthErrorMessage,
+  isBillingErrorMessage,
   isRateLimitErrorMessage,
 } from "./pi-embedded-helpers.js";
 
@@ -82,7 +83,7 @@ function isTimeoutErrorMessage(raw: string): boolean {
 
 function shouldFallbackForError(err: unknown): boolean {
   const statusCode = getStatusCode(err);
-  if (statusCode && [401, 403, 429].includes(statusCode)) return true;
+  if (statusCode && [401, 402, 403, 429].includes(statusCode)) return true;
   const code = getErrorCode(err).toUpperCase();
   if (
     ["ETIMEDOUT", "ESOCKETTIMEDOUT", "ECONNRESET", "ECONNABORTED"].includes(
@@ -96,6 +97,7 @@ function shouldFallbackForError(err: unknown): boolean {
   return (
     isAuthErrorMessage(message) ||
     isRateLimitErrorMessage(message) ||
+    isBillingErrorMessage(message) ||
     isTimeoutErrorMessage(message)
   );
 }
diff --git a/src/agents/pi-embedded-helpers.test.ts b/src/agents/pi-embedded-helpers.test.ts
index 6908e2176..af70d0b72 100644
--- a/src/agents/pi-embedded-helpers.test.ts
+++ b/src/agents/pi-embedded-helpers.test.ts
@@ -4,6 +4,7 @@ import { describe, expect, it } from "vitest";
 import {
   buildBootstrapContextFiles,
   formatAssistantErrorText,
+  isBillingErrorMessage,
   isContextOverflowError,
   isMessagingToolDuplicate,
   normalizeTextForComparison,
@@ -215,6 +216,28 @@ describe("isContextOverflowError", () => {
   });
 });
 
+describe("isBillingErrorMessage", () => {
+  it("matches credit / payment failures", () => {
+    const samples = [
+      "Your credit balance is too low to access the Anthropic API.",
+      "insufficient credits",
+      "Payment Required",
+      "HTTP 402 Payment Required",
+      "plans & billing",
+      "billing: please upgrade your plan",
+    ];
+    for (const sample of samples) {
+      expect(isBillingErrorMessage(sample)).toBe(true);
+    }
+  });
+
+  it("ignores unrelated errors", () => {
+    expect(isBillingErrorMessage("rate limit exceeded")).toBe(false);
+    expect(isBillingErrorMessage("invalid api key")).toBe(false);
+    expect(isBillingErrorMessage("context length exceeded")).toBe(false);
+  });
+});
+
 describe("formatAssistantErrorText", () => {
   const makeAssistantError = (errorMessage: string): AssistantMessage =>
     ({
diff --git a/src/agents/pi-embedded-helpers.ts b/src/agents/pi-embedded-helpers.ts
index 81d129b4a..58e6c2816 100644
--- a/src/agents/pi-embedded-helpers.ts
+++ b/src/agents/pi-embedded-helpers.ts
@@ -261,6 +261,30 @@ export function isRateLimitErrorMessage(raw: string): boolean {
   );
 }
 
+export function isBillingErrorMessage(raw: string): boolean {
+  const value = raw.toLowerCase();
+  if (!value) return false;
+  return (
+    /\b402\b/.test(value) ||
+    value.includes("payment required") ||
+    value.includes("insufficient credits") ||
+    value.includes("credit balance") ||
+    value.includes("plans & billing") ||
+    (value.includes("billing") &&
+      (value.includes("upgrade") ||
+        value.includes("credits") ||
+        value.includes("payment") ||
+        value.includes("plan")))
+  );
+}
+
+export function isBillingAssistantError(
+  msg: AssistantMessage | undefined,
+): boolean {
+  if (!msg || msg.stopReason !== "error") return false;
+  return isBillingErrorMessage(msg.errorMessage ?? "");
+}
+
 export function isAuthErrorMessage(raw: string): boolean {
   const value = raw.toLowerCase();
   if (!value) return false;
diff --git a/src/agents/pi-embedded-runner.ts b/src/agents/pi-embedded-runner.ts
index 03c7bb36c..1e5d80b67 100644
--- a/src/agents/pi-embedded-runner.ts
+++ b/src/agents/pi-embedded-runner.ts
@@ -60,6 +60,8 @@ import {
   formatAssistantErrorText,
   isAuthAssistantError,
   isAuthErrorMessage,
+  isBillingAssistantError,
+  isBillingErrorMessage,
   isContextOverflowError,
   isGoogleModelApi,
   isRateLimitAssistantError,
@@ -1421,7 +1423,8 @@ export async function runEmbeddedPiAgent(params: {
             }
             if (
               (isAuthErrorMessage(errorText) ||
-                isRateLimitErrorMessage(errorText)) &&
+                isRateLimitErrorMessage(errorText) ||
+                isBillingErrorMessage(errorText)) &&
               (await advanceAuthProfile())
             ) {
               continue;
@@ -1464,10 +1467,12 @@ export async function runEmbeddedPiAgent(params: {
             0;
           const authFailure = isAuthAssistantError(lastAssistant);
           const rateLimitFailure = isRateLimitAssistantError(lastAssistant);
+          const billingFailure = isBillingAssistantError(lastAssistant);
 
           // Treat timeout as potential rate limit (Antigravity hangs on rate limit)
           const shouldRotate =
-            (!aborted && (authFailure || rateLimitFailure)) || timedOut;
+            (!aborted && (authFailure || rateLimitFailure || billingFailure)) ||
+            timedOut;
 
           if (shouldRotate) {
             // Mark current profile for cooldown before rotating
@@ -1496,7 +1501,9 @@ export async function runEmbeddedPiAgent(params: {
                   ? "LLM request timed out."
                   : rateLimitFailure
                     ? "LLM request rate limited."
-                    : "LLM request unauthorized.");
+                    : billingFailure
+                      ? "LLM request payment required."
+                      : "LLM request unauthorized.");
               throw new Error(message);
             }
           }