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KAIROS

Kairos (ancient Greek: the opportune moment) is the unreleased always-on autonomous agent mode for claude-code. Unlike standard Claude Code which waits for user input, KAIROS keeps the agent alive between turns, acting at the right moment rather than on a schedule. It is gated behind compile-time flags (PROACTIVE and KAIROS) and is completely absent from external builds via Bun dead-code elimination.

The Tick Loop

In normal Claude Code, the message queue empties when the model finishes responding. KAIROS changes this: when the queue is empty, it injects a <tick> message containing the current local time.

const scheduleProactiveTick =
  feature('PROACTIVE') || feature('KAIROS')
    ? () => {
        setTimeout(() => {
          const tickContent = `<${TICK_TAG}>${new Date().toLocaleTimeString()}</${TICK_TAG}>`
          enqueue({ mode: 'prompt', value: tickContent, priority: 'later', isMeta: true })
          void run()
        }, 0)
      }
    : undefined

The setTimeout(0) yields to the Node.js event loop first, so user input always takes priority over tick messages. The system prompt on each tick:

"You are running autonomously. You will receive <tick> prompts that keep you alive between turns — just treat them as 'you're awake, what now?' The time in each <tick> is the user's current local time."

SleepTool

Every tick without useful work is a wasted API call. SleepTool lets the agent yield control explicitly. Only available in proactive mode. The tool description surfaces the cost trade-off directly:

"Each wake-up costs an API call, but the prompt cache expires after 5 minutes of inactivity — balance accordingly."

The agent decides its own rhythm — how long to sleep, when to wake early, when to wait for a slow process.

15-Second Blocking Budget

ASSISTANT_BLOCKING_BUDGET_MS = 15_000. If a shell command runs longer than 15 seconds, it is automatically moved to a background task. The agent gets control back immediately; nothing is killed. The command continues in the background and the agent is notified on completion.

Append-Only Daily Logs

Standard Claude Code rewrites MEMORY.md in-place. KAIROS can't — sessions are perpetual, and rewriting from a continuously-running agent would corrupt intermediate states. Instead, it writes append-only to date-named log files:

logs/YYYY/MM/YYYY-MM-DD.md

When the date rolls over mid-session, the agent silently starts appending to a new file. The system prompt: "Do not rewrite or reorganize the log — it is append-only. A separate nightly process distills these logs." That nightly process is auto-dream.

SendUserMessage

In background mode, stdout is unmonitored. KAIROS uses SendUserMessage (internally BriefTool) as its explicit output channel. The status field tags intent: 'normal' for replies, 'proactive' for unsolicited updates — enabling downstream routing to push or silently log.

Exclusive Tools

Three tools are only available in KAIROS mode, not in regular sessions: - SendUserFile — deliver files to the user - PushNotification — push alerts - SubscribePR — monitor pull request activity autonomously

Relationship to ULTRAPLAN

KAIROS handles ambient, continuous operations (memory accumulation, background monitoring, proactive nudges). ultraplan handles episodic deep deliberation (30-minute architectural planning in remote Cloud Container Runtime). The community drew the parallel to Kahneman's System 1 / System 2 — fast intuitive processing vs. slow deliberate reasoning.

Willow Mode

KAIROS includes an inactivity detection system called Willow Mode that activates when users return after extended absence. It re-orients context by reading accumulated daily logs and memory files to brief the returning user.

Key Claims

Sources