Jixu

Jixu means continue in Chinese.

A small single-Agent Harness for TypeScript. Define one Agent, give it Tools and Skills, and continue its work in a durable Thread.

The core API stays small: createHarness, createThread, and thread.send. Underneath it, Jixu records execution, context decisions, and external work so the same Thread can recover, Replay, or Fork without a second runtime.

Jixu is pre-1.0. The public API may change before 1.0.

Why Jixu

Agent loops are easy to start. Resuming one safely is harder: a Tool call may be in flight, the process may stop between writes, or the model may run out of context.

Jixu records the work as ordered Events. State is derived from them, and external work is recorded before it is dispatched. That is what lets a Thread recover, Replay, Fork, or continue later.

Each Harness has one immutable Agent definition. Its Threads hold that Agent's durable history. There is no workflow graph or second execution engine.

Start

Install and open the reference TUI:

npm install -g jixu-ai
jixu

Global installation also works with pnpm add -g jixu-ai and bun add -g jixu-ai. Or run Jixu without installing it:

npx jixu-ai
# pnpm dlx jixu-ai
# yarn dlx jixu-ai
# bunx jixu-ai

The package launcher requires Node.js 22.19.0 or newer. The native TUI supports macOS arm64 and Linux x64 with glibc; Intel macOS is not supported. Bun is not required at runtime.

The TUI uses the same public Agent, Harness, Thread, Store, and Driver APIs as any other Jixu application.

Use Jixu as a framework

npm install jixu-core jixu-llm jixu-store-sqlite

import { createHarness, defineAgent } from "jixu-core";
import {
  createLLMModelDriver,
  resolveLLMModelCapabilities,
} from "jixu-llm";
import { SqliteEventStore } from "jixu-store-sqlite";

const connection = {
  api: "openai-chat-completions" as const,
  apiKey: process.env.MODEL_API_KEY,
  baseURL: "https://api.openai.com/v1",
  model: "gpt-5.6-sol",
};

const modelCapabilities = await resolveLLMModelCapabilities(connection);
const agent = defineAgent({
  instructions: "Be precise and verify your work.",
  model: { provider: "model", model: connection.model },
  modelCapabilities,
  tools: [],
});

const harness = createHarness({
  agent,
  modelDrivers: {
    model: createLLMModelDriver({
      api: connection.api,
      apiKey: connection.apiKey,
      baseURL: connection.baseURL,
      maxOutputTokens: modelCapabilities.maxOutputTokens,
    }),
  },
  store: new SqliteEventStore("./jixu.db"),
});

const thread = await harness.createThread();
const state = await thread.send("Review this design and identify its main risk.");

console.log(state.result);

The Agent definition is immutable. Each send continues the same durable Thread.

Thread operations

The public Harness creates, opens, and lists Threads. A Thread exposes one coherent surface for ordinary work and continuity operations:

One authoritative execution path

durable Event -> pure Reducer -> explicit Effect -> Driver -> durable Event

The Kernel reduces Events into State and Effects without performing I/O. Drivers execute external work and append the result as another Event. Replay only reduces recorded Events; it never calls a live model or Tool.

Jixu retries only when the Effect's delivery contract makes that safe:

• a deterministic Tool failure is recorded and returned to the Agent as a failed Tool result so the same turn can recover or explain;
• an unknown non-idempotent outcome is retained and enters waiting rather than being silently repeated;
• a retained unknown outcome resumes only after an explicit operator decision; that decision is durable context, not an invented Tool result or an automatic retry;
• allow, ask, and deny Tool policy decisions are resolved before Driver dispatch, and approvals are durable decisions for one exact pending Effect.

Jixu does not claim generic exactly-once execution. That guarantee requires an enforceable idempotency contract in the downstream system.

Context engineering

Each model request is assembled from the Thread's durable material: Agent instructions, relevant Events, the active Plan, Skills, Tool schemas, Artifacts, and recent work. A redacted Context Manifest records what was selected and why.

Jixu resolves the model's context window and output limit before Agent creation. If capacity is unknown, it stops instead of guessing. When older work must be compacted, Jixu writes a source-linked Continuity Handoff and keeps a bounded tail of complete recent operations. The underlying Events are not rewritten.

Plans

A Plan is optional Event-backed coordination data. It can record acceptance criteria, steps, evidence, blockers, and the next safe action, but it cannot dispatch Effects, approve a Tool call, or widen user scope.

A Thread has at most one Plan and one active step. Changes are validated and committed before related Effects can dispatch; rejected changes remain visible in Event history. The Plan is a current hypothesis rather than a fixed schedule: completed work and the current step stay protected, while pending steps may be rewritten as evidence changes. If a model returns only Plan or progress control, Jixu durably gives it one execution-only continuation with ordinary Tools and no reserved controls; the control plane cannot loop indefinitely or permanently block the requested work.

Inspectable execution

Jixu keeps operational facts inside the same durable model:

• logical model and Tool calls remain distinct from dispatch attempts;
• reported token usage stays distinct from unavailable values, and unknown pricing remains unknown instead of rendering as zero;
• ordered text and image input is preserved, while image bytes live in verified immutable Artifacts rather than Events;
• Secrets never enter Events, State, Checkpoints, errors, or Signals.

Packages

[!WARNING] Jixu's Bash Tool is not OS-sandboxed and runs with the permissions of the Jixu process. Permission controls approve Tool calls, not individual shell operations. Keep Bash on ASK and use a backed-up or disposable workspace.

Model providers, Tools, Stores, and UIs use the runtime's public ports. Thread state still belongs to the core runtime.

What Jixu is not

Jixu is not a multi-Agent orchestrator, workflow engine, or hosted control plane. It does not add Agent graphs, supervisors, queues, schedulers, or a generic exactly-once guarantee. External systems remain ordinary Tools and do not change the single-Agent model.

Documentation

• Documentation
• Specification
• Contributing
• npm package

License

MIT