diff --git a/src/agents/model-fallback.test.ts b/src/agents/model-fallback.test.ts
index b9786f4b8..17a8835c7 100644
--- a/src/agents/model-fallback.test.ts
+++ b/src/agents/model-fallback.test.ts
@@ -144,6 +144,26 @@ describe("runWithModelFallback", () => {
     expect(run.mock.calls[1]?.[1]).toBe("claude-haiku-3-5");
   });
 
+  it("falls back on lowercase credential errors", async () => {
+    const cfg = makeCfg();
+    const run = vi
+      .fn()
+      .mockRejectedValueOnce(new Error("no api key found for profile openai"))
+      .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/pi-embedded-helpers.test.ts b/src/agents/pi-embedded-helpers.test.ts
index 4d9872ebf..55c85eb7d 100644
--- a/src/agents/pi-embedded-helpers.test.ts
+++ b/src/agents/pi-embedded-helpers.test.ts
@@ -5,6 +5,7 @@ import {
   buildBootstrapContextFiles,
   classifyFailoverReason,
   formatAssistantErrorText,
+  isAuthErrorMessage,
   isBillingErrorMessage,
   isCloudCodeAssistFormatError,
   isCompactionFailureError,
@@ -122,6 +123,23 @@ describe("isBillingErrorMessage", () => {
   });
 });
 
+describe("isAuthErrorMessage", () => {
+  it("matches credential validation errors", () => {
+    const samples = [
+      'No credentials found for profile "anthropic:claude-cli".',
+      "No API key found for profile openai.",
+    ];
+    for (const sample of samples) {
+      expect(isAuthErrorMessage(sample)).toBe(true);
+    }
+  });
+
+  it("ignores unrelated errors", () => {
+    expect(isAuthErrorMessage("rate limit exceeded")).toBe(false);
+    expect(isAuthErrorMessage("billing issue detected")).toBe(false);
+  });
+});
+
 describe("isFailoverErrorMessage", () => {
   it("matches auth/rate/billing/timeout", () => {
     const samples = [
@@ -140,6 +158,8 @@ describe("isFailoverErrorMessage", () => {
 describe("classifyFailoverReason", () => {
   it("returns a stable reason", () => {
     expect(classifyFailoverReason("invalid api key")).toBe("auth");
+    expect(classifyFailoverReason("no credentials found")).toBe("auth");
+    expect(classifyFailoverReason("no api key found")).toBe("auth");
     expect(classifyFailoverReason("429 too many requests")).toBe("rate_limit");
     expect(classifyFailoverReason("resource has been exhausted")).toBe(
       "rate_limit",