From ca57d9ca7726462257785777a5a827e3f8da58eb Mon Sep 17 00:00:00 2001
From: Aiden Cline <aidenpcline@gmail.com>
Date: Sat, 10 Oct 2026 18:09:31 -0500
Subject: [PATCH] fix(core): follow models.dev packages for Copilot fallback
 routing

---
 .../core/src/plugin/provider/github-copilot.ts     | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/packages/core/src/plugin/provider/github-copilot.ts b/packages/core/src/plugin/provider/github-copilot.ts
index 86fbe6fd3e85..19de498c5e81 100644
--- a/packages/core/src/plugin/provider/github-copilot.ts
+++ b/packages/core/src/plugin/provider/github-copilot.ts
@@ -226,10 +226,22 @@ export const GithubCopilotPlugin = define({
         })
         return
       }
+      // Without the live model list, the models.dev package says which Copilot API serves
+      // each model: Anthropic Messages stays native, OpenAI means Responses, and anything
+      // else goes through the bundled Copilot SDK's model ID fallback.
       for (const id of item.models.keys()) {
         evt.models.update(item.provider.id, id, (model) => {
+          if (model.package === "@opencode/ai/providers/anthropic") {
+            if (loaded.baseURL)
+              model.settings = Provider.mergeOverlay(model.settings, { baseURL: `${loaded.baseURL}/v1` })
+            return
+          }
+          const responses = model.package === "@opencode/ai/providers/openai"
           model.package = Provider.aisdk("@ai-sdk/github-copilot")
-          if (loaded.baseURL) model.settings = Provider.mergeOverlay(model.settings, { baseURL: loaded.baseURL })
+          model.settings = Provider.mergeOverlay(model.settings, {
+            ...(loaded.baseURL ? { baseURL: loaded.baseURL } : {}),
+            ...(responses ? { endpoint: "responses" } : {}),
+          })
         })
       }
     })