feat: opt-in Copilot Responses API for GPT-5+

Author: christso

packages/opencode/src/provider/provider.ts

@@ -29,6 +29,14 @@ import { createOpenaiCompatible as createGitHubCopilotOpenAICompatible } from ".
 export namespace Provider {
   const log = Log.create({ service: "provider" })
 
+  function isGpt5OrLater(modelID: string): boolean {
+    const match = /^gpt-(\d+)/.exec(modelID)
+    if (!match) {
+      return false
+    }
+    return Number(match[1]) >= 5
+  }
+
   const BUNDLED_PROVIDERS: Record<string, (options: any) => SDK> = {
     "@ai-sdk/amazon-bedrock": createAmazonBedrock,
     "@ai-sdk/anthropic": createAnthropic,
@@ -91,25 +99,39 @@ export namespace Provider {
         options: {},
       }
     },
-    "github-copilot": async () => {
+    "github-copilot": async (input) => {
       return {
         autoload: false,
         async getModel(sdk: any, modelID: string, _options?: Record<string, any>) {
+          // GitHub Copilot can optionally route supported models through the Responses API.
+          // This enables settings like reasoningEffort/reasoningSummary for GPT-5+ models.
+          const useResponsesApi = Boolean(input.options?.useResponsesApi)
+
           if (modelID.includes("codex")) {
             return sdk.responses(modelID)
           }
+
+          if (useResponsesApi && isGpt5OrLater(modelID)) {
+            return sdk.responses(modelID)
+          }
           return sdk.chat(modelID)
         },
         options: {},
       }
     },
-    "github-copilot-enterprise": async () => {
+    "github-copilot-enterprise": async (input) => {
       return {
         autoload: false,
         async getModel(sdk: any, modelID: string, _options?: Record<string, any>) {
+          const useResponsesApi = Boolean(input.options?.useResponsesApi)
+
           if (modelID.includes("codex")) {
             return sdk.responses(modelID)
           }
+
+          if (useResponsesApi && isGpt5OrLater(modelID)) {
+            return sdk.responses(modelID)
+          }
           return sdk.chat(modelID)
         },
         options: {},