All thoughts

Agent OS, Part 2: The harness

Stages 3 and 4: the control surface around the model, a stop on the loop, then trace and eval before anything ships.

How it works

Day ~185 · Jun 2026 Put a harness on it, and a stop on the loop

Day ~185: a harness and a loop with a stopThe memory platform and the agent platform. On the agent deck, two tool blocks sit on a dashed loop around the agent, and a small stop post on the loop is lit in amber: the end-loop guardrail.Memory3 pillars + gateAgenttools + a stop

Harness is a buzzword until you draw it. It's the control surface around the model (tools, connectors, permissions, defaults) so the horse doesn't run random.

The loop is the other half: call tools until an end-loop guardrail fires, then reply. Without a stop condition you get permission stalls and actions that keep firing. When the ending is unclear, ask the user: do all of them, or only list them. If the agent is stuck on a permission, it should notify you instead of sitting silent.

Day ~190 · Jul 2026 Trace it, eval it, then ship

Day ~190: trace and eval on topTwo new platforms above the agent: Trace, with a small terminal whose screen is lit, and Eval, with a lit gate. A dashed line on the left runs from Eval back down to the agent: diagnose, then fix.diagnose → fixMemory3 pillars + gateAgenttools + a stopTracewhat ranEvalhealthy? good?

A harness without health checks is incomplete. Any agent that claims to improve itself without an eval has a gap.

One agent run is the user's ask, the tool loop, then the reply. Trace that tree: retrievals, tool calls, latency, tokens. Evaluate health and quality. Diagnose. Then ship a better prompt or config, or fix the bug and re-run.

My take

What I learnedA harness rides the LLM horse, and every loop needs an end condition.

What I learned"Self-improving" without eval is cosplay.

Try this

  1. List the tools your agent may call. Anything irreversible (send, pay, publish, delete) sits behind an approval. Prep is automatic, the action waits. Then write the end-loop rule in one sentence.
  2. Keep one dashboard or log that answers two questions. Was this run healthy, and was it good? Hold ship until Pass.

Sources