diff --git a/src/agents/context.test.ts b/src/agents/context.test.ts
new file mode 100644
index 00000000000..41111b4bb41
--- /dev/null
+++ b/src/agents/context.test.ts
@@ -0,0 +1,41 @@
+import { describe, expect, it } from "vitest";
+import { applyConfiguredContextWindows } from "./context.js";
+
+describe("applyConfiguredContextWindows", () => {
+  it("overrides discovered cache values with explicit models.providers contextWindow", () => {
+    const cache = new Map<string, number>([["anthropic/claude-opus-4-6", 1_000_000]]);
+    applyConfiguredContextWindows({
+      cache,
+      modelsConfig: {
+        providers: {
+          openrouter: {
+            models: [{ id: "anthropic/claude-opus-4-6", contextWindow: 200_000 }],
+          },
+        },
+      },
+    });
+
+    expect(cache.get("anthropic/claude-opus-4-6")).toBe(200_000);
+  });
+
+  it("adds config-only model context windows and ignores invalid entries", () => {
+    const cache = new Map<string, number>();
+    applyConfiguredContextWindows({
+      cache,
+      modelsConfig: {
+        providers: {
+          openrouter: {
+            models: [
+              { id: "custom/model", contextWindow: 150_000 },
+              { id: "bad/model", contextWindow: 0 },
+              { id: "", contextWindow: 300_000 },
+            ],
+          },
+        },
+      },
+    });
+
+    expect(cache.get("custom/model")).toBe(150_000);
+    expect(cache.has("bad/model")).toBe(false);
+  });
+});
diff --git a/src/agents/context.ts b/src/agents/context.ts
index b3683e235f2..c919dbf9095 100644
--- a/src/agents/context.ts
+++ b/src/agents/context.ts
@@ -6,13 +6,52 @@ import { resolveOpenClawAgentDir } from "./agent-paths.js";
 import { ensureOpenClawModelsJson } from "./models-config.js";
 
 type ModelEntry = { id: string; contextWindow?: number };
+type ConfigModelEntry = { id?: string; contextWindow?: number };
+type ProviderConfigEntry = { models?: ConfigModelEntry[] };
+type ModelsConfig = { providers?: Record<string, ProviderConfigEntry | undefined> };
+
+export function applyConfiguredContextWindows(params: {
+  cache: Map<string, number>;
+  modelsConfig: ModelsConfig | undefined;
+}) {
+  const providers = params.modelsConfig?.providers;
+  if (!providers || typeof providers !== "object") {
+    return;
+  }
+  for (const provider of Object.values(providers)) {
+    if (!Array.isArray(provider?.models)) {
+      continue;
+    }
+    for (const model of provider.models) {
+      const modelId = typeof model?.id === "string" ? model.id : undefined;
+      const contextWindow =
+        typeof model?.contextWindow === "number" ? model.contextWindow : undefined;
+      if (!modelId || !contextWindow || contextWindow <= 0) {
+        continue;
+      }
+      params.cache.set(modelId, contextWindow);
+    }
+  }
+}
 
 const MODEL_CACHE = new Map<string, number>();
 const loadPromise = (async () => {
+  let cfg: ReturnType<typeof loadConfig> | undefined;
+  try {
+    cfg = loadConfig();
+  } catch {
+    // If config can't be loaded, leave cache empty.
+    return;
+  }
+
+  try {
+    await ensureOpenClawModelsJson(cfg);
+  } catch {
+    // Continue with best-effort discovery/overrides.
+  }
+
   try {
     const { discoverAuthStorage, discoverModels } = await import("./pi-model-discovery.js");
-    const cfg = loadConfig();
-    await ensureOpenClawModelsJson(cfg);
     const agentDir = resolveOpenClawAgentDir();
     const authStorage = discoverAuthStorage(agentDir);
     const modelRegistry = discoverModels(authStorage, agentDir);
@@ -26,9 +65,16 @@ const loadPromise = (async () => {
       }
     }
   } catch {
-    // If pi-ai isn't available, leave cache empty; lookup will fall back.
+    // If model discovery fails, continue with config overrides only.
   }
-})();
+
+  applyConfiguredContextWindows({
+    cache: MODEL_CACHE,
+    modelsConfig: cfg.models as ModelsConfig | undefined,
+  });
+})().catch(() => {
+  // Keep lookup best-effort.
+});
 
 export function lookupContextTokens(modelId?: string): number | undefined {
   if (!modelId) {