diff --git a/config/quality/file-size-baseline.json b/config/quality/file-size-baseline.json
index 57e30418c8..fef8ea6cfe 100644
--- a/config/quality/file-size-baseline.json
+++ b/config/quality/file-size-baseline.json
@@ -1,4 +1,5 @@
 {
+  "_rebaseline_2026_09_14_13547_noauth_model_lockout": "PR #13547 own growth: src/sse/services/auth.ts 3542->3556 (+14). The synthetic noauth connection short-circuited before the per-connection status pass, so a recorded model-only lockout was never enforced and the locked model was retried on every request. Irreducible at the early-return site. Covered by tests/unit/noauth-model-lockout.test.ts (carried from #13527).",
   "_rebaseline_2026_09_14_13404_healthcheck_backup_prune": "PR #13404 own growth: src/lib/db/core.ts 1745->1767 (+22). createManagedDbBackup (the health-check-repair snapshot path) never ran retention, so every restart of a healthy DB added a full-size copy to db_backups/; it now prunes with the same env-driven limits as backup.ts, importing backupRetention directly to avoid the backup.ts cycle. Covered by tests/unit/db-backup-healthcheck-prune-13308.test.ts.",
   "_rebaseline_2026_09_14_13349_virtualfactory_custom_models_guard": "PR #13349 own growth: open-sse/services/autoCombo/virtualFactory.ts 1219->1230 (+11). The customModels key_value blob is operator-writable raw JSON, so a null or non-object row null-derefed every read and no auto/* pool could materialize; the builder now filters rows the same way catalog.ts already does. Irreducible at the read site. Covered by tests/unit/combo-auto-pool-visible-only.test.ts.",
   "_rebaseline_2026_09_11_12732_catalog_timeout_pin": "+1 in tests/unit/models-catalog-route.test.ts (1652->1653) for a single line: process.env.CATALOG_BUILD_TIMEOUT_MS. #12627 bounds a cold catalog build at 8s; beforeEach resets the catalog cache so every case in this file pays a cold build, and a tsx runner needs 10-13s under load — the file returned catalog_build_timeout instead of rows and oscillated between 1 and 10 failures per run, reddening the whole PR queue (base-red #12732). The bound itself stays covered by tests/unit/12627-catalog-inflight-timeout.test.ts. The file is already at its frozen ceiling, so the pin cannot be absorbed; structural shrink tracked in #3501.",
@@ -477,7 +478,7 @@
     "src/shared/constants/providers/apikey/gateways.ts": 1502,
     "src/shared/services/cliRuntime.ts": 1296,
     "src/sse/handlers/chat.ts": 2462,
-    "src/sse/services/auth.ts": 3542,
+    "src/sse/services/auth.ts": 3556,
     "tests/unit/account-fallback-service.test.ts": 2453,
     "tests/unit/provider-validation-specialty.test.ts": 4656,
     "open-sse/services/autoCombo/virtualFactory.ts": 1230,
diff --git a/src/sse/services/auth.ts b/src/sse/services/auth.ts
index 65729efc73..a9be1beefa 100644
--- a/src/sse/services/auth.ts
+++ b/src/sse/services/auth.ts
@@ -1225,6 +1225,20 @@ export async function getProviderCredentials(
       // respected (the no-auth provider will be rejected if it has no real connections
       // matching the allowlist, or a real connection row will be selected if present).
       if (!allowedConnections || allowedConnections.length === 0) {
+        // #13483: check model-only lockout before handing back the synthetic
+        // connection. Without this, a locked model (e.g. 400 model_capacity)
+        // is retried on every request because the noauth path short-circuits
+        // before the per-connection status pass that classifies modelLocked.
+        const modelLockout = requestedModel
+          ? getModelLockoutInfo(resolvedId, SYNTHETIC_NOAUTH_CONNECTION_ID, requestedModel)
+          : null;
+        if (modelLockout && modelLockout.remainingMs > 0) {
+          log.debug(
+            "AUTH",
+            `${resolvedId} | noauth model-only lockout for ${requestedModel} — ${modelLockout.remainingMs}ms remaining, returning null`
+          );
+          return null;
+        }
         return await maybeSyntheticNoAuthFallback(resolvedId, excludedForNoAuth);
       }
     }
diff --git a/tests/unit/noauth-model-lockout.test.ts b/tests/unit/noauth-model-lockout.test.ts
new file mode 100644
index 0000000000..33399adc32
--- /dev/null
+++ b/tests/unit/noauth-model-lockout.test.ts
@@ -0,0 +1,85 @@
+/**
+ * Tests for #13483: model-only lockout must be enforced for no-auth providers.
+ *
+ * Before the fix, no-auth providers (opencode, duckduckgo-web, etc.) returned
+ * synthetic "noauth" credentials early in getProviderCredentials, bypassing the
+ * model lockout check. A model_capacity lockout was recorded but never enforced
+ * — every request retried the same locked model, paying a wasted upstream
+ * round-trip (~2s) before failing over.
+ */
+import { test, after } from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import path from "node:path";
+import os from "node:os";
+
+const TEST_DATA_DIR = fs.mkdtempSync(path.join(os.tmpdir(), "omr-noauth-lockout-"));
+process.env.DATA_DIR = TEST_DATA_DIR;
+process.env.API_KEY_SECRET = "test-noauth-lockout-secret";
+
+const core = await import("../../src/lib/db/core.ts");
+const auth = await import("../../src/sse/services/auth.ts");
+const { recordModelLockoutFailure, clearAllModelLockouts } =
+  await import("../../open-sse/services/accountFallback.ts");
+
+after(() => {
+  clearAllModelLockouts();
+  core.resetDbInstance();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+});
+
+test("#13483: noauth provider returns null when model is lockout-blocked", async () => {
+  const provider = "opencode";
+  const model = "deepseek-v4-flash-free";
+
+  // Record a model lockout for the synthetic "noauth" connection
+  recordModelLockoutFailure(provider, "noauth", model, "model_capacity", 400, 1800_000);
+
+  // getProviderCredentials should return null because the model is locked
+  const result = await auth.getProviderCredentials(provider, null, null, model);
+  assert.equal(result, null, "noauth provider should return null when model is lockout-blocked");
+});
+
+test("#13483: noauth provider still works when model is NOT lockout-blocked", async () => {
+  clearAllModelLockouts();
+  const provider = "opencode";
+  const model = "some-other-model";
+
+  // No lockout recorded — should return synthetic credentials
+  const result = await auth.getProviderCredentials(provider, null, null, model);
+  assert.ok(result !== null, "noauth provider should return credentials when model is not locked");
+});
+
+test("#13483: noauth lockout does not block a different model", async () => {
+  clearAllModelLockouts();
+  const provider = "opencode";
+  const lockedModel = "deepseek-v4-flash-free";
+  const otherModel = "kimi-latest";
+
+  // Lock only one model
+  recordModelLockoutFailure(provider, "noauth", lockedModel, "model_capacity", 400, 1800_000);
+
+  // The locked model should be blocked
+  const result1 = await auth.getProviderCredentials(provider, null, null, lockedModel);
+  assert.equal(result1, null, "locked model should return null");
+
+  // A different model should NOT be blocked
+  const result2 = await auth.getProviderCredentials(provider, null, null, otherModel);
+  assert.ok(result2 !== null, "different model should still get credentials");
+});
+
+test("#13483: noauth lockout does not affect non-noauth providers", async () => {
+  clearAllModelLockouts();
+  const model = "gpt-4";
+
+  // Record lockout for a noauth provider
+  recordModelLockoutFailure("opencode", "noauth", model, "model_capacity", 400, 1800_000);
+
+  // openai is NOT a noauth provider — it should not be affected by this check
+  // (openai has its own connection-based lockout path; this test just verifies
+  // the noauth early-return path doesn't leak lockouts to other providers)
+  // We can't easily test openai here without DB connections, but we verify
+  // the opencode noauth path specifically.
+  const result = await auth.getProviderCredentials("opencode", null, null, model);
+  assert.equal(result, null, "opencode noauth should respect its own lockout");
+});