Oath Keeper

"Cron is for things you plan. Oath Keeper is for things you promise."

An agent that keeps its word — automatically.

What it does

Agents make promises they can't keep. "I'll get back to you" becomes "I forgot." Oath Keeper passively detects when agents make follow-up promises and makes them follow through — automatically, in the same conversation, with full tool access.

No human prompting required. No agent cooperation required.

Demo

User: Can you check if the build is passing and let me know?

Agent: I'll look into that and get back to you with the CI status.

(5 minutes pass — the agent has moved on to other things)

Agent (automatically re-engaged by Oath Keeper): [Oath Delivered] The build is currently passing. I checked the CI pipeline — all 47 tests pass on the latest commit (a3f2b1c). The only flaky test (test_network_timeout) passed on retry.

User: Can you investigate the memory bloat issue?

Agent: I'll dig into that and report back what I find.

(5 minutes later, unprompted)

Agent (automatically re-engaged): [Oath Delivered] The memory bloat is coming from node_modules in the memory directory — 16,813 files being indexed by the scanner. I've added a .gitignore and deleted the bloated directory. Memory index size dropped from 193MB to 12MB.

The agent never called a scheduling tool. It never set a reminder. It just made a promise in natural language, and Oath Keeper held it to its word.

How it works

1. Agent says: "I'll get back to you on that."
2. Oath Keeper detects the promise passively (polls conversation every 15s)
3. Oath created with a 5-minute countdown
4. Timer expires — Oath Keeper posts a delivery prompt to the conversation
5. Agent re-engages with full tool access and delivers

User asks question
    → Agent responds with "I'll get back to you..."
        → Oath Keeper detects promise (passive, no agent action)
            → 5-minute timer starts
                → Timer fires → agent re-engaged → delivers answer

Installation

letta install npm:@letta-ai/oath-keeper

Then run /reload in Letta Code.

The mod auto-discovers conversation and agent IDs from the tool context on first use. For headless/polling-only setups where tools never fire, you can optionally create ~/.letta/extensions/oath-env.json:

{
  "LETTA_AGENT_ID": "your-agent-id",
  "LETTA_CONVERSATION_ID": "your-conversation-id"
}

Usage

Just talk to your agent. When it says "I'll follow up" or "I'll get back to you," Oath Keeper catches it automatically.

Check tracked oaths:

list_oaths

Promise detection

Oath Keeper catches natural-language promises without any agent cooperation:

• "I'll get back to you on that"
• "I'll follow up"
• "I'll check on this"
• "I'll look into that and report back"
• "I'll let you know"
• "I'll circle back"
• "I'll update you"
• "I'll have results for you"
• 15+ patterns total

Anti-false-positive: code blocks, inline code, blockquotes, and quoted text are stripped before scanning.

Architecture

• Detection: setInterval polls the conversation API every 15s for new assistant messages
• Delivery: POST to conversation API endpoint with retry on 409 (busy conversation). Up to 5 retries with 15s backoff
• State: Local JSON at ~/.letta/mods/oath-keeper.state.json
• Capabilities: Works with { tools: true } only — no events required

Why not cron?

Cron requires explicit scheduling. Oath Keeper catches promises the agent made implicitly — "I'll get back to you" — without the agent calling any scheduling tool.

Cron is for things you plan. Oath Keeper is for things you promise.

Safety

• Uses only the public tools API and fetch()
• Does not modify turn input or tool arguments
• Recursion prevention: skips its own messages
• All timers cleaned up on unload

Demo

Watch the full flow: agent makes a promise → moves on to other work → Oath Keeper re-engages it to deliver.