test(smoke): drive real omp turns through a scripted model

omp-port/scripted-model.mjs

@@ -0,0 +1,51 @@
+// A deterministic OpenAI-completions provider on loopback, so a smoke can drive real omp turns
+// without a model. Every request body lands in `requests`. The last user message decides the reply:
+//   a line `tool:<name> <json-args>`   one tool call with those arguments
+//   a tool result as the last message  the text `scripted-model: tool result received`
+//   anything else                      the text `scripted-model: no script for this prompt`
+
+export const text = (content) =>
+  typeof content === "string"
+    ? content
+    : (content ?? []).map((part) => (part.type === "text" ? part.text : "")).join("\n");
+
+function decide(messages) {
+  if (messages.at(-1)?.role === "tool") return { text: "scripted-model: tool result received" };
+  const user = messages.findLast((m) => m.role === "user");
+  const call = /^tool:(\w+) (\{.*\})\s*$/m.exec(text(user?.content));
+  if (call) return { tool: call[1], args: call[2] };
+  return { text: "scripted-model: no script for this prompt" };
+}
+
+const chunk = (delta, finish, extra = {}) =>
+  `data: ${JSON.stringify({
+    id: "scripted",
+    object: "chat.completion.chunk",
+    created: 0,
+    model: "scripted",
+    choices: [{ index: 0, delta, finish_reason: finish }],
+    ...extra,
+  })}\n\n`;
+
+function reply(plan) {
+  const call = plan.tool && { id: "call_scripted", type: "function", function: { name: plan.tool, arguments: plan.args } };
+  const delta = call ? { role: "assistant", tool_calls: [{ index: 0, ...call }] } : { role: "assistant", content: plan.text };
+  const usage = { prompt_tokens: 1, completion_tokens: 1, total_tokens: 2 };
+  const body = chunk(delta, null) + chunk({}, call ? "tool_calls" : "stop", { usage }) + "data: [DONE]\n\n";
+  return new Response(body, { headers: { "content-type": "text/event-stream" } });
+}
+
+export function scriptedModel() {
+  const requests = [];
+  const server = Bun.serve({
+    hostname: "127.0.0.1",
+    port: 0,
+    async fetch(request) {
+      if (!new URL(request.url).pathname.endsWith("/chat/completions")) return new Response("not found", { status: 404 });
+      const body = await request.json();
+      requests.push(body);
+      return reply(decide(body.messages));
+    },
+  });
+  return { baseUrl: `http://127.0.0.1:${server.port}/v1`, requests, stop: () => server.stop(true) };
+}