fix(copilot): honor advertised model endpoints (#34958)

packages/opencode/src/plugin/github-copilot/models.ts

@@ -72,6 +72,10 @@ type SelectableItem = Item & {
     }
   }
 }
+type CopilotEndpoint = "chat" | "responses" | "messages"
+type CopilotModel = Omit<Model, "api"> & {
+  api: Model["api"] & { endpoint?: CopilotEndpoint }
+}
 const decodeModels = Schema.decodeUnknownSync(schema)
 const decodeItem = Schema.decodeUnknownOption(item)
 
@@ -86,17 +90,25 @@ function build(key: string, remote: SelectableItem, url: string, prev?: Model):
     (remote.capabilities.limits.vision?.supported_media_types ?? []).some((item) => item.startsWith("image/"))
 
   const isMsgApi = remote.supported_endpoints?.includes("/v1/messages")
+  const endpoint: CopilotEndpoint | undefined = isMsgApi
+    ? "messages"
+    : remote.supported_endpoints?.includes("/responses")
+      ? "responses"
+      : remote.supported_endpoints?.includes("/chat/completions")
+        ? "chat"
+        : undefined
   const prices = remote.billing?.token_prices
   // Copilot prices are AIC per billing batch; OpenCode stores USD per million tokens.
   const usdPerMillion = prices ? 10_000 / prices.batch_size : 0
 
-  const model: Model = {
+  const model: CopilotModel = {
     id: key,
     providerID: "github-copilot",
     api: {
       id: remote.id,
       url: isMsgApi ? `${url}/v1` : url,
       npm: isMsgApi ? "@ai-sdk/anthropic" : "@ai-sdk/github-copilot",
+      ...(endpoint ? { endpoint } : {}),
     },
     // API response wins
     status: "active",

packages/opencode/src/provider/provider.ts

@@ -218,8 +218,12 @@ function custom(dep: CustomDep): Record<string, CustomLoader> {
     "github-copilot": () =>
       Effect.succeed({
         autoload: false,
-        async getModel(sdk: any, modelID: string, _options?: Record<string, any>) {
+        async getModel(sdk: any, modelID: string, _options?: Record<string, any>, model?: Model) {
           if (sdk.responses === undefined && sdk.chat === undefined) return sdk.languageModel(modelID)
+          if (model && "endpoint" in model.api) {
+            if (model.api.endpoint === "responses" && sdk.responses) return sdk.responses(modelID)
+            if (model.api.endpoint === "chat" && sdk.chat) return sdk.chat(modelID)
+          }
           const match = /^gpt-(\d+)/.exec(modelID)
           if (match && Number(match[1]) >= 5 && !modelID.startsWith("gpt-5-mini")) return sdk.responses(modelID)
           return sdk.chat(modelID)