fix(provider): select prompt cache keys by SDK (#38424)

packages/opencode/test/provider/transform.test.ts

@@ -88,6 +88,32 @@ describe("ProviderTransform.options - setCacheKey", () => {
     expect(result.promptCacheKey).toBe(sessionID)
   })
 
+  test("should set promptCacheKey for the OpenAI SDK regardless of provider ID", () => {
+    const result = ProviderTransform.options({
+      model: {
+        ...mockModel,
+        providerID: "custom-openai",
+        api: { id: "gpt-5", url: "https://example.com", npm: "@ai-sdk/openai" },
+      },
+      sessionID,
+      providerOptions: {},
+    })
+    expect(result.promptCacheKey).toBe(sessionID)
+  })
+
+  test("should not set promptCacheKey for the OpenAI-compatible SDK by provider name", () => {
+    const result = ProviderTransform.options({
+      model: {
+        ...mockModel,
+        providerID: "openai",
+        api: { id: "gpt-5", url: "https://example.com", npm: "@ai-sdk/openai-compatible" },
+      },
+      sessionID,
+      providerOptions: {},
+    })
+    expect(result.promptCacheKey).toBeUndefined()
+  })
+
   test("should not set promptCacheKey for openai when explicitly disabled", () => {
     const openaiModel = {
       ...mockModel,
@@ -209,6 +235,70 @@ describe("ProviderTransform.options - setCacheKey", () => {
       providerOptions: {},
     })
     expect(result.store).toBe(false)
+    expect(result.promptCacheKey).toBe(sessionID)
+  })
+
+  test("should disable the Azure cache key without disabling store=false", () => {
+    const result = ProviderTransform.options({
+      model: {
+        ...mockModel,
+        providerID: "azure",
+        api: { id: "gpt-5", url: "https://azure.com", npm: "@ai-sdk/azure" },
+      },
+      sessionID,
+      providerOptions: { setCacheKey: false },
+    })
+    expect(result.store).toBe(false)
+    expect(result.promptCacheKey).toBeUndefined()
+  })
+
+  test("should keep the Azure cache key for gpt-5.5 early return", () => {
+    const result = ProviderTransform.options({
+      model: {
+        ...mockModel,
+        providerID: "azure",
+        api: { id: "gpt-5.5", url: "https://azure.com", npm: "@ai-sdk/azure" },
+      },
+      sessionID,
+      providerOptions: {},
+    })
+    expect(result.store).toBe(false)
+    expect(result.reasoningSummary).toBe("auto")
+    expect(result.promptCacheKey).toBe(sessionID)
+  })
+
+  for (const npm of ["@ai-sdk/deepinfra", "@ai-sdk/cerebras"]) {
+    test(`should set the snake-case cache key for ${npm}`, () => {
+      const result = ProviderTransform.options({
+        model: { ...mockModel, providerID: "custom", api: { ...mockModel.api, npm } },
+        sessionID,
+        providerOptions: {},
+      })
+      expect(result.prompt_cache_key).toBe(sessionID)
+      expect(result.promptCacheKey).toBeUndefined()
+    })
+  }
+
+  test("should set promptCacheKey for the Mistral SDK", () => {
+    const result = ProviderTransform.options({
+      model: { ...mockModel, providerID: "custom", api: { ...mockModel.api, npm: "@ai-sdk/mistral" } },
+      sessionID,
+      providerOptions: {},
+    })
+    expect(result.promptCacheKey).toBe(sessionID)
+  })
+
+  test("should not send an undocumented OpenRouter prompt_cache_key", () => {
+    const result = ProviderTransform.options({
+      model: {
+        ...mockModel,
+        providerID: "openrouter",
+        api: { ...mockModel.api, npm: "@openrouter/ai-sdk-provider" },
+      },
+      sessionID,
+      providerOptions: {},
+    })
+    expect(result.prompt_cache_key).toBeUndefined()
   })
 })
 
@@ -722,6 +812,17 @@ describe("ProviderTransform.providerOptions", () => {
     })
   })
 
+  test("uses canonical sdk key for custom xAI models", () => {
+    const model = createModel({
+      providerID: "my-xai",
+      api: { id: "grok-4", url: "https://api.x.ai", npm: "@ai-sdk/xai" },
+    })
+
+    expect(ProviderTransform.providerOptions(model, { promptCacheKey: "session" })).toEqual({
+      xai: { promptCacheKey: "session" },
+    })
+  })
+
   test("forces reasoning for explicit effort even when model is not marked reasoning-capable", () => {
     const model = createModel({
       capabilities: {
@@ -3011,6 +3112,20 @@ describe("ProviderTransform.message - cache control on gateway", () => {
     })
   })
 
+  test("does not add explicit breakpoints when Anthropic automatic caching is enabled", () => {
+    const model = createModel({
+      providerID: "anthropic",
+      api: { id: "claude-sonnet-4", url: "https://api.anthropic.com", npm: "@ai-sdk/anthropic" },
+    })
+    const msgs = [
+      { role: "system", content: "You are a helpful assistant" },
+      { role: "user", content: "Hello" },
+    ] as any[]
+
+    const result = ProviderTransform.message(msgs, model, { cacheControl: { type: "ephemeral" } }) as any[]
+    expect(result.every((message) => message.providerOptions === undefined)).toBe(true)
+  })
+
   test("google-vertex-anthropic applies cache control", () => {
     const model = createModel({
       providerID: "google-vertex-anthropic",