diff --git a/src/agents/model-fallback.test.ts b/src/agents/model-fallback.test.ts
index ebb508481fd..464ea9e697b 100644
--- a/src/agents/model-fallback.test.ts
+++ b/src/agents/model-fallback.test.ts
@@ -21,6 +21,8 @@ import type { EmbeddedAgentRunResult } from "./embedded-agent-runner/types.js";
 import { FailoverError } from "./failover-error.js";
 import { resetFallbackSkipCacheForTest } from "./fallback-skip-cache.js";
 import { MissingAgentHarnessError } from "./harness/errors.js";
+import { clearAgentHarnesses, registerAgentHarness } from "./harness/registry.js";
+import type { AgentHarness } from "./harness/types.js";
 import { LiveSessionModelSwitchError } from "./live-model-switch-error.js";
 import {
   FallbackSummaryError,
@@ -191,6 +193,7 @@ afterAll(() => {
 
 function resetModelFallbackTestState(): void {
   resetFallbackSkipCacheForTest();
+  clearAgentHarnesses();
   authRuntimeMock.clear();
   authRuntimeMock.runtime.ensureAuthProfileStore.mockClear();
   authRuntimeMock.runtime.loadAuthProfileStoreForRuntime.mockClear();
@@ -971,6 +974,68 @@ describe("runWithModelFallback", () => {
     expect(run).not.toHaveBeenCalled();
   });
 
+  it("lets external plugin harnesses bypass stale provider auth cooldowns", async () => {
+    const cfg = makeCfg({
+      agents: {
+        defaults: {
+          model: {
+            primary: "anthropic/claude-sonnet-4-6",
+            fallbacks: ["openai/gpt-5.5"],
+          },
+          models: {
+            "anthropic/*": { agentRuntime: { id: "claude-tmux" } },
+          },
+        },
+      },
+    });
+    registerAgentHarness(
+      {
+        id: "claude-tmux",
+        label: "Claude tmux",
+        supports: ({ provider }) =>
+          provider === "anthropic" ? { supported: true } : { supported: false },
+        runAttempt: vi.fn<AgentHarness["runAttempt"]>(async () => {
+          throw new Error("fallback test should not invoke the harness runtime");
+        }),
+      },
+      { ownerPluginId: "claude-tmux-test" },
+    );
+    const tempDir = await makeAuthTempDir();
+    setAuthRuntimeStore(tempDir, {
+      version: AUTH_STORE_VERSION,
+      profiles: {
+        "anthropic:default": { type: "api_key", provider: "anthropic", key: "test-key" },
+        "openai:default": { type: "api_key", provider: "openai", key: "test-key" },
+      },
+      usageStats: {
+        "anthropic:default": {
+          disabledUntil: Date.now() + 60_000,
+          disabledReason: "billing",
+          failureCounts: { rate_limit: 4 },
+        },
+      },
+    });
+    const run = vi.fn().mockImplementation(async (provider: string) => {
+      if (provider === "anthropic") {
+        return "external cli ok";
+      }
+      throw new Error(`unexpected provider: ${provider}`);
+    });
+
+    const result = await runWithModelFallback({
+      cfg,
+      provider: "anthropic",
+      model: "claude-sonnet-4-6",
+      agentDir: tempDir,
+      run,
+    });
+
+    expect(result.result).toBe("external cli ok");
+    expect(run).toHaveBeenCalledTimes(1);
+    expect(run.mock.calls[0]).toEqual(["anthropic", "claude-sonnet-4-6"]);
+    expect(result.attempts).toStrictEqual([]);
+  });
+
   it("lets configured CLI runtimes reach the run callback", async () => {
     const cfg = makeCfg({
       agents: {
@@ -1781,9 +1846,9 @@ describe("runWithModelFallback", () => {
       { provider: "openai", model: "gpt-4.1-mini" },
       { provider: "tui-pty-mock", model: "gpt-5.5" },
     ]);
-    expect(providerModelNormalizationMock.normalizeProviderModelIdWithRuntime).not.toHaveBeenCalledWith(
-      expect.objectContaining({ provider: "tui-pty-mock" }),
-    );
+    expect(
+      providerModelNormalizationMock.normalizeProviderModelIdWithRuntime,
+    ).not.toHaveBeenCalledWith(expect.objectContaining({ provider: "tui-pty-mock" }));
   });
 
   it("keeps configured fallbacks before configured primary for duplicate provider model ids", () => {
diff --git a/src/agents/model-fallback.ts b/src/agents/model-fallback.ts
index 384a9786620..5622f30c651 100644
--- a/src/agents/model-fallback.ts
+++ b/src/agents/model-fallback.ts
@@ -439,18 +439,18 @@ function isCliAgentRuntime(runtime: string | undefined, cfg: OpenClawConfig | un
   return isCliRuntimeAlias(normalized) || isCliProvider(normalized, cfg);
 }
 
-async function assertModelFallbackCandidateHarnessAvailable(
+async function resolveModelFallbackCandidateHarnessAuthPrecheck(
   params: ModelFallbackRuntimeContext & ModelCandidate,
-): Promise<void> {
+): Promise<{ skipsProviderAuthCooldown: boolean }> {
   if (!params.cfg) {
-    return;
+    return { skipsProviderAuthCooldown: false };
   }
   const agentHarnessRuntimeOverride = params.resolveAgentHarnessRuntimeOverride?.(
     params.provider,
     params.model,
   );
   if (isCliProvider(params.provider, params.cfg)) {
-    return;
+    return { skipsProviderAuthCooldown: false };
   }
   const agentRuntimeOverride = normalizeOptionalAgentRuntimeId(agentHarnessRuntimeOverride);
   const harnessPolicy = resolveAgentHarnessPolicy({
@@ -469,28 +469,25 @@ async function assertModelFallbackCandidateHarnessAvailable(
       ? "model"
       : harnessPolicy.runtimeSource;
   if (isCliAgentRuntime(agentRuntime, params.cfg)) {
-    return;
+    return { skipsProviderAuthCooldown: false };
   }
-  if (
-    agentRuntime === "auto" ||
-    agentRuntime === "openclaw" ||
-    (agentRuntime === "codex" && agentRuntimeSource === "implicit")
-  ) {
-    return;
+  if (agentRuntime === "openclaw") {
+    return { skipsProviderAuthCooldown: false };
+  }
+  if (agentRuntime === "auto" || (agentRuntime === "codex" && agentRuntimeSource === "implicit")) {
+    return { skipsProviderAuthCooldown: false };
   }
   await params.prepareAgentHarnessRuntime?.({
     provider: params.provider,
     model: params.model,
     agentHarnessRuntimeOverride,
   });
-  if (
-    agentRuntime !== "auto" &&
-    agentRuntime !== "openclaw" &&
-    !(agentRuntime === "codex" && agentRuntimeSource === "implicit") &&
-    !getRegisteredAgentHarness(agentRuntime)
-  ) {
+  if (!getRegisteredAgentHarness(agentRuntime)) {
     throw new MissingAgentHarnessError(agentRuntime);
   }
+  // Explicit non-Codex plugin harnesses own transport/auth; stale OpenClaw
+  // provider cooldowns must not block the harness before it starts.
+  return { skipsProviderAuthCooldown: agentRuntime !== "codex" };
 }
 
 function resolveCandidateAttemptError(
@@ -1275,7 +1272,7 @@ export async function runWithModelFallback<T>(
 
   for (let i = 0; i < candidates.length; i += 1) {
     const candidate = candidates[i];
-    await assertModelFallbackCandidateHarnessAvailable({
+    const candidateHarnessAuth = await resolveModelFallbackCandidateHarnessAuthPrecheck({
       cfg: params.cfg,
       agentId: params.agentId,
       sessionKey: params.sessionKey,
@@ -1342,7 +1339,7 @@ export async function runWithModelFallback<T>(
     let runOptions: ModelFallbackRunOptions | undefined;
     let attemptedDuringCooldown = false;
     let transientProbeProviderForAttempt: string | null = null;
-    if (authRuntime && authStore) {
+    if (authRuntime && authStore && !candidateHarnessAuth.skipsProviderAuthCooldown) {
       const profileIds = authRuntime.resolveAuthProfileOrder({
         cfg: params.cfg,
         store: authStore,