diff --git a/config/platform-infra/sub2api-codex-pool.yaml b/config/platform-infra/sub2api-codex-pool.yaml
index 69b58446..229a1964 100644
--- a/config/platform-infra/sub2api-codex-pool.yaml
+++ b/config/platform-infra/sub2api-codex-pool.yaml
@@ -31,9 +31,9 @@ pool:
         durationMinutes: 30
         description: Gateway upstream failures, including recovered upstream error wrappers, should cool down longer.
       - statusCode: 503
-        keywords: [capacity, overloaded, temporarily unavailable, temporary, upstream, recovered upstream error]
+        keywords: [capacity, overloaded, temporarily unavailable, temporary, upstream, recovered upstream error, model_not_found, no available channel for model]
         durationMinutes: 30
-        description: Service unavailable responses should cool down longer than one-off transient failures.
+        description: Service unavailable and upstream model-routing failures should cool down longer than one-off transient failures.
       - statusCode: 529
         keywords: [capacity, overloaded, temporarily unavailable, temporary, recovered upstream error]
         durationMinutes: 30
diff --git a/scripts/platform-infra-sub2api-codex-routing-contract-test.ts b/scripts/platform-infra-sub2api-codex-routing-contract-test.ts
index fd0faaaa..34bbc691 100644
--- a/scripts/platform-infra-sub2api-codex-routing-contract-test.ts
+++ b/scripts/platform-infra-sub2api-codex-routing-contract-test.ts
@@ -50,12 +50,17 @@ if (parsed.pool?.defaultTempUnschedulable?.enabled === true) {
   assertCondition(gateway502Keywords.has("recovered upstream error"), "502 temporary-unschedulable rule must catch recovered upstream error wrappers", gateway502Rule);
   const accountState403Rule = rules.find((rule) => rule.statusCode === 403);
   const quota429Rule = rules.find((rule) => rule.statusCode === 429);
+  const serviceUnavailable503Rule = rules.find((rule) => rule.statusCode === 503);
   const accountState403Keywords = new Set((accountState403Rule?.keywords ?? []).map((keyword) => keyword.toLowerCase()));
   const quota429Keywords = new Set((quota429Rule?.keywords ?? []).map((keyword) => keyword.toLowerCase()));
+  const serviceUnavailable503Keywords = new Set((serviceUnavailable503Rule?.keywords ?? []).map((keyword) => keyword.toLowerCase()));
   for (const keyword of ["weekly limit", "less than 10% of your weekly limit left", "run /status for a breakdown"]) {
     assertCondition(accountState403Keywords.has(keyword), "403 temporary-unschedulable rule must catch Codex weekly-limit account-state prompts", { keyword, accountState403Rule });
     assertCondition(quota429Keywords.has(keyword), "429 temporary-unschedulable rule must catch Codex weekly-limit quota prompts", { keyword, quota429Rule });
   }
+  for (const keyword of ["model_not_found", "no available channel for model"]) {
+    assertCondition(serviceUnavailable503Keywords.has(keyword), "503 temporary-unschedulable rule must catch upstream model-routing failures", { keyword, serviceUnavailable503Rule });
+  }
 }
 assertCondition(typeof parsed.localCodex?.responsesSmokeModel === "string" && parsed.localCodex.responsesSmokeModel.length > 0, "localCodex.responsesSmokeModel must be declared for Responses smoke validation", parsed.localCodex);
 
@@ -69,6 +74,7 @@ console.log(JSON.stringify({
     "temporary unschedulable rules are structurally valid when enabled",
     "generic recovered upstream error wrappers are caught by cooldown rules",
     "Codex weekly-limit prompts are caught by account-state and quota cooldown rules",
+    "upstream model-routing failures are caught by the 503 cooldown rule",
     "Responses smoke model is YAML-declared",
   ],
 }));
diff --git a/scripts/platform-infra-sub2api-codex-temp-unsched-contract-test.ts b/scripts/platform-infra-sub2api-codex-temp-unsched-contract-test.ts
index a937d755..a1e2da29 100644
--- a/scripts/platform-infra-sub2api-codex-temp-unsched-contract-test.ts
+++ b/scripts/platform-infra-sub2api-codex-temp-unsched-contract-test.ts
@@ -29,10 +29,14 @@ assertCondition(!("pool_mode" in credentials), "pool_mode must not be enabled be
 assertCondition(!("api_key" in credentials) && !("base_url" in credentials), "temporary-unschedulable rendering must not include secrets or endpoints", credentials);
 const accountState403Rule = rules.find((rule) => rule.error_code === 403);
 const quota429Rule = rules.find((rule) => rule.error_code === 429);
+const serviceUnavailable503Rule = rules.find((rule) => rule.error_code === 503);
 for (const keyword of ["weekly limit", "less than 10% of your weekly limit left", "run /status for a breakdown"]) {
   assertCondition(accountState403Rule?.keywords?.includes(keyword), "403 rendered rule must preserve Codex weekly-limit account-state keyword", { keyword, accountState403Rule });
   assertCondition(quota429Rule?.keywords?.includes(keyword), "429 rendered rule must preserve Codex weekly-limit quota keyword", { keyword, quota429Rule });
 }
+for (const keyword of ["model_not_found", "no available channel for model"]) {
+  assertCondition(serviceUnavailable503Rule?.keywords?.includes(keyword), "503 rendered rule must catch upstream model-routing failures", { keyword, serviceUnavailable503Rule });
+}
 
 const disabled = renderSub2ApiTempUnschedulableCredentials({ enabled: false, rules: policy.rules }) as {
   temp_unschedulable_enabled?: boolean;
@@ -48,6 +52,7 @@ console.log(JSON.stringify({
     "temporary unschedulable policy renders to Sub2API credential field names",
     "temporary unschedulable rendering follows the input policy without hard-coded policy gates",
     "Codex weekly-limit prompt keywords render into 403 and 429 cooldown rules",
+    "upstream model-routing failures render into the 503 cooldown rule",
     "disabled policies clear runtime rules",
   ],
 }));
diff --git a/scripts/src/platform-infra-sub2api-codex.ts b/scripts/src/platform-infra-sub2api-codex.ts
index 1f1d0a8a..1d91cb0e 100644
--- a/scripts/src/platform-infra-sub2api-codex.ts
+++ b/scripts/src/platform-infra-sub2api-codex.ts
@@ -684,9 +684,9 @@ export function defaultCodexTempUnschedulablePolicy(): CodexTempUnschedulablePol
       },
       {
         statusCode: 503,
-        keywords: ["capacity", "overloaded", "temporarily unavailable", "temporary", "upstream", "recovered upstream error"],
+        keywords: ["capacity", "overloaded", "temporarily unavailable", "temporary", "upstream", "recovered upstream error", "model_not_found", "no available channel for model"],
         durationMinutes: 30,
-        description: "Service unavailable responses should cool down longer than one-off transient failures.",
+        description: "Service unavailable and upstream model-routing failures should cool down longer than one-off transient failures.",
       },
       {
         statusCode: 529,