fix(github): add targetFormat to GPT-5.6 Sol/Terra/Luna models (#8951)

GitHub Copilot GPT-5.6 Sol/Terra/Luna models were missing
targetFormat: 'openai-responses' in the GitHub provider registry,
causing them to be routed to /chat/completions instead of /responses.

changelog.d/fixes/8951-fix.plan.md

@@ -0,0 +1 @@
+- fix(github): add targetFormat to GPT-5.6 Sol/Terra/Luna models (#8951)

open-sse/config/providers/registry/github/index.ts

@@ -122,9 +122,9 @@ export const githubProvider: RegistryEntry = {
       contextLength: 1000000,
       maxOutputTokens: 64000,
     },
-    { id: "gpt-5.6-sol", name: "GPT-5.6 Sol", maxOutputTokens: 128000 },
-    { id: "gpt-5.6-terra", name: "GPT-5.6 Terra", maxOutputTokens: 128000 },
-    { id: "gpt-5.6-luna", name: "GPT-5.6 Luna", maxOutputTokens: 128000 },
+    { id: "gpt-5.6-sol", name: "GPT-5.6 Sol", targetFormat: "openai-responses", maxOutputTokens: 128000 },
+    { id: "gpt-5.6-terra", name: "GPT-5.6 Terra", targetFormat: "openai-responses", maxOutputTokens: 128000 },
+    { id: "gpt-5.6-luna", name: "GPT-5.6 Luna", targetFormat: "openai-responses", maxOutputTokens: 128000 },
     { id: "gpt-5.5", name: "GPT-5.5", ...GPT_5_5_CODEX_CAPABILITIES, maxOutputTokens: 128000 },
     {
       id: "gpt-5.4",

tests/unit/8951-github-gpt56-responses.test.ts

@@ -0,0 +1,19 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { GithubExecutor } from "../../open-sse/executors/github.ts";
+
+test("#8951 GitHub GPT-5.6 models must use the Responses endpoint", () => {
+  const executor = new GithubExecutor();
+  const urls = Object.fromEntries(
+    ["gpt-5.6-sol", "gpt-5.6-terra", "gpt-5.6-luna"].map((model) => [
+      model,
+      executor.buildUrl(model, false),
+    ])
+  );
+  assert.deepEqual(urls, {
+    "gpt-5.6-sol": "https://api.githubcopilot.com/responses",
+    "gpt-5.6-terra": "https://api.githubcopilot.com/responses",
+    "gpt-5.6-luna": "https://api.githubcopilot.com/responses",
+  });
+});

tests/unit/provider-registry-github-copilot-targetformat.test.ts

@@ -67,6 +67,9 @@ for (const id of [
   "gpt-5.4-mini",
   "gpt-5.4",
   "gpt-5.5",
+  "gpt-5.6-sol",
+  "gpt-5.6-terra",
+  "gpt-5.6-luna",
   "mai-code-1-flash",
   "gpt-5-mini",
   "oswe-vscode-prime",