feat(llm): OpenAI-compatible chatJSON helper with injectable fetch

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/test/llm.test.ts

@@ -0,0 +1,51 @@
+import { describe, expect, test } from "bun:test";
+import { mkdtempSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { openDb } from "../src/db";
+import { settings } from "../src/db/schema";
+import { encrypt, loadOrCreateKey } from "../src/lib/crypto";
+import { chatJSON } from "../src/lib/llm";
+
+function deps(fetchImpl: typeof fetch) {
+  const dir = mkdtempSync(join(tmpdir(), "helios-"));
+  const db = openDb(dir);
+  const key = loadOrCreateKey(dir);
+  return { db, key, fetchImpl };
+}
+
+describe("chatJSON", () => {
+  test("posts OpenAI-compatible request with bearer key and parses JSON content", async () => {
+    let captured: { url: string; init: RequestInit } | null = null;
+    const mock = (async (url: any, init: any) => {
+      captured = { url: String(url), init };
+      return new Response(JSON.stringify({ choices: [{ message: { content: '{"ok":1}' } }] }), { status: 200 });
+    }) as typeof fetch;
+    const d = deps(mock);
+    await d.db.insert(settings).values({ key: "llm_key", value: encrypt(d.key, "sk-test-1234") });
+
+    const out = await chatJSON(d, { system: "sys", user: "usr" });
+    expect(out).toEqual({ ok: 1 });
+    expect(captured!.url).toBe("https://openrouter.ai/api/v1/chat/completions");
+    const body = JSON.parse(String(captured!.init.body));
+    expect(body.response_format).toEqual({ type: "json_object" });
+    expect(body.messages).toEqual([{ role: "system", content: "sys" }, { role: "user", content: "usr" }]);
+    expect((captured!.init.headers as Record<string, string>).authorization).toBe("Bearer sk-test-1234");
+  });
+
+  test("no key → no auth header (Ollama)", async () => {
+    let headers: Record<string, string> = {};
+    const mock = (async (_: any, init: any) => {
+      headers = init.headers;
+      return new Response(JSON.stringify({ choices: [{ message: { content: "```json\n{\"a\":2}\n```" } }] }), { status: 200 });
+    }) as typeof fetch;
+    const out = await chatJSON(deps(mock), { system: "s", user: "u" });
+    expect(out).toEqual({ a: 2 }); // fenced JSON stripped
+    expect(headers.authorization).toBeUndefined();
+  });
+
+  test("non-2xx throws llm_error", async () => {
+    const mock = (async () => new Response("nope", { status: 401 })) as unknown as typeof fetch;
+    expect(chatJSON(deps(mock), { system: "s", user: "u" })).rejects.toThrow(/llm_error/);
+  });
+});