diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index 407c2687825d..e226a7ebc1ca 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -180,7 +180,7 @@ export namespace ProviderTransform {
         cacheControl: { type: "ephemeral" },
       },
       openrouter: {
-        cacheControl: { type: "ephemeral" },
+        cacheControl: { type: "ephemeral", ttl: "1h" },
       },
       bedrock: {
         cachePoint: { type: "default" },
diff --git a/packages/opencode/test/provider/transform.test.ts b/packages/opencode/test/provider/transform.test.ts
index 9dde1a7131e8..f8a16395ec14 100644
--- a/packages/opencode/test/provider/transform.test.ts
+++ b/packages/opencode/test/provider/transform.test.ts
@@ -101,6 +101,20 @@ describe("ProviderTransform.options - setCacheKey", () => {
     })
     expect(result.store).toBe(false)
   })
+
+  test("should set prompt_cache_key for openrouter provider", () => {
+    const model = {
+      ...mockModel,
+      providerID: "openrouter",
+      api: {
+        id: "anthropic/claude-sonnet-4-5",
+        url: "https://openrouter.ai/api/v1",
+        npm: "@openrouter/ai-sdk-provider",
+      },
+    }
+    const result = ProviderTransform.options({ model, sessionID, providerOptions: {} })
+    expect(result.prompt_cache_key).toBe(sessionID)
+  })
 })
 
 describe("ProviderTransform.options - gpt-5 textVerbosity", () => {
@@ -1608,6 +1622,7 @@ describe("ProviderTransform.message - cache control on gateway", () => {
       openrouter: {
         cacheControl: {
           type: "ephemeral",
+          ttl: "1h",
         },
       },
       bedrock: {