Exo: Harnesses should see their own code and logs — Alex Krentsel

A genuinely novel architecture for self-modifying agents: split the system into a stateless executor, a protected harness holding secrets and history, and an isolated sandbox — then let the agent edit its own executor code, with a guardian process that tests changes for one step and auto-rolls back. The proof point is concrete: asked to cut spending, Exo rearchitected its own context assembly and reduced Discord adapter costs by 96%.

• Separating stateless compute from protected state is what makes self-modification safe: the executor can be rebuilt at runtime while secrets and history stay out of reach.
• Exo mounts its own executor code in the sandbox; a guardian tests each self-edit for one step and rolls back automatically if the agent breaks itself.
• Annotating conversation logs with per-message costs gives the agent runtime economics data — that's how it found and executed the 96% cost reduction.
• Krentsel argues recursive self-improvement is finally tractable because the medium matches the output: LLMs write code, and the harness is code.

Part of Issue Nº 005: How Unify cut agent costs 95%, and why RL-trained agents break in the wild