diff --git a/src/codex/catalog/provider-fetch.ts b/src/codex/catalog/provider-fetch.ts
index 5ffc357cb1..bc86c8c6e4 100644
--- a/src/codex/catalog/provider-fetch.ts
+++ b/src/codex/catalog/provider-fetch.ts
@@ -1195,9 +1195,15 @@ export function catalogHintsFromModelsApiItem(providerName: string, item: Provid
   const metadata = plainRecord(item.metadata);
   const capabilityRecord = plainRecord(metadata?.capabilities) ?? plainRecord(item.capabilities);
   const limits = plainRecord(metadata?.limits);
+  const capabilityLimits = plainRecord(plainRecord(item.capabilities)?.limits);
   const contextWindow =
     positiveSafeInteger(
       limits?.max_context_length,
+      // GitHub Copilot reports the live context window here instead of in the metadata or
+      // top-level fields used by other OpenAI-compatible catalogs (#3156). Keep the existing
+      // metadata field authoritative when both are present: adding this provider-specific
+      // fallback must not change previously recognized providers.
+      capabilityLimits?.max_context_window_tokens,
       metadata?.context_length,
       item.context_length,
       item.context_size,
diff --git a/tests/codex-catalog.test.ts b/tests/codex-catalog.test.ts
index 05223ca1e5..143dc8a986 100644
--- a/tests/codex-catalog.test.ts
+++ b/tests/codex-catalog.test.ts
@@ -5366,6 +5366,49 @@ describe("Codex catalog routed normalization", () => {
     expect(routed?.context_window).toBe(64_000);
   });
 
+  test("GitHub Copilot capabilities preserve the live context window (#3156)", async () => {
+    globalThis.fetch = (async () => new Response(JSON.stringify({
+      data: [{
+        id: "copilot-wide-model",
+        capabilities: {
+          limits: { max_context_window_tokens: 1_000_000 },
+        },
+      }, {
+        id: "copilot-existing-metadata",
+        metadata: { limits: { max_context_length: 256_000 } },
+        capabilities: {
+          limits: { max_context_window_tokens: 1_000_000 },
+        },
+      }, {
+        id: "copilot-invalid-window",
+        capabilities: {
+          limits: { max_context_window_tokens: -1 },
+        },
+      }],
+    }))) as typeof fetch;
+
+    const models = await gatherRoutedModels({
+      port: 10100,
+      defaultProvider: "github-copilot",
+      providers: {
+        "github-copilot": {
+          adapter: "openai-chat",
+          baseUrl: "https://api.githubcopilot.com",
+          apiKey: "sk-test",
+        },
+      },
+    });
+    const routed = buildCatalogEntries(nativeTemplate(), [], models)
+      .find(entry => entry.slug === "github-copilot/copilot-wide-model");
+
+    expect(models.find(model => model.id === "copilot-wide-model")?.contextWindow).toBe(1_000_000);
+    expect(routed?.context_window).toBe(1_000_000);
+    expect(routed?.max_context_window).toBe(1_000_000);
+    expect(routed?.auto_compact_token_limit).toBe(900_000);
+    expect(models.find(model => model.id === "copilot-existing-metadata")?.contextWindow).toBe(256_000);
+    expect(models.find(model => model.id === "copilot-invalid-window")?.contextWindow).toBeUndefined();
+  });
+
   test("liveModels false preserves configured catalog metadata without live fetch", async () => {
     let fetchCalls = 0;
     globalThis.fetch = (() => {