app/engine/model.ts

 // BYO model: a configured Ollama server by default, or any of zz

 // work's own --provider backends (groq/gemini/cloudflare) via

 // createChatSummaryBackend below. No backend here ever shells out to

 // the `claude` CLI -- that's what caused the quota incident this

 // replaces.

 import type { ChatBackend } from "../agent/chatBackend.js";

 import { resolveBackend, type Provider } from "../cli/lib/resolveChatBackend.js";

 export interface ModelBackend {

  name: string;

  summarize(prompt: string): Promise<string | null>; // null = unreachable; caller falls back to mechanical text

 }

 /** Adapts any ChatBackend (zz work's own groq/gemini/cloudflare/ollama backends, cli/lib/resolveChatBackend.ts) to this module's simpler summarize-only interface -- the ingestion pipeline (ladder-build.ts) only ever needs one-shot text generation, never tool-calling. Unlike the plain Ollama path below, a resolution failure here (e.g. a missing API key) throws rather than falling back to the null backend -- the same fail-fast-at-launch convention --provider already uses elsewhere, since a remote provider the caller explicitly asked for should error loudly, not silently degrade to mechanical text. */

 export function createChatSummaryBackend(chat: ChatBackend): ModelBackend {

  return {

  name: chat.name,

  async summarize(prompt: string): Promise<string | null> {

  const reply = await chat.chat([{ role: "user", content: prompt }], []);

  return reply.content?.trim() || null;

  },

  };

 }

 export function createNullBackend(): ModelBackend {

  return { name: "null", summarize: async () => null };

 }

 export function createOllamaBackend(baseUrl: string, model: string): ModelBackend {

  return {

  name: `ollama:${model}`,

  async summarize(prompt: string): Promise<string | null> {

  try {

  const res = await fetch(`${baseUrl}/api/generate`, {

  method: "POST",

  headers: { "content-type": "application/json" },

  body: JSON.stringify({ model, prompt, stream: false }),

  });

  if (!res.ok) return null;

  const data = (await res.json()) as { response?: string };

  return data.response?.trim() || null;

  } catch {

  return null;

  }

  },

  };

 }

 /**

  * Ollama if ZZ_OLLAMA_MODEL is set (or the default) and reachable;

  * otherwise the null backend -- unchanged, still the zero-config

  * default for ladder-build's own ingestion summaries. A non-ollama

  * `provider` (zz ladder build --provider groq, etc.) skips the

  * reachability dance entirely and resolves through the same

  * --provider machinery zz work uses, via createChatSummaryBackend.

  */

 export async function resolveModelBackend(provider?: Provider, model?: string): Promise<ModelBackend> {

  if (provider && provider !== "ollama") return createChatSummaryBackend(resolveBackend(provider, model));

  const baseUrl = process.env.ZZ_OLLAMA_HOST ?? "http://localhost:11434";

  const resolvedModel = model ?? process.env.ZZ_OLLAMA_MODEL ?? "qwen2.5:14b-instruct";

  const backend = createOllamaBackend(baseUrl, resolvedModel);

  try {

  const res = await fetch(`${baseUrl}/api/tags`, { signal: AbortSignal.timeout(2000) });

  if (res.ok) return backend;

  } catch {

  // fall through to null backend

  }

  console.error(`(ollama at ${baseUrl} not reachable; falling back to mechanical text)`);

  return createNullBackend();

 }