simonwDesigning agentic loops
https://simonwillison.net/2025/Sep/30/designing-agentic-loops/
I think this is a strictly worse name than "agentic harness", which is already a term used by open-source agentic IDEs (https://github.com/search?q=repo%3Aopenai%2Fcodex%20harness&... or https://github.com/openai/codex/discussions/1174)
Any reason why you want to rename it?
Edit: to say more about my opinions, "agentic loop" could mean a few things -- it could mean the thing you say, or it could mean calling multiple individual agents in a loop ... whereas "agentic harness" evokes a sort of interface between the LLM and the digital outside world which mediates how the LLM embodies itself in that world. That latter thing is exactly what you're describing, as far as I can tell.
I like "agentic harness" too, but that's not the name of a skill.
"Designing agentic loops" describes a skill people need to develop. "Designing agentic harnesses" sounds more to me like you're designing a tool like Claude Code from scratch.
Plus "designing agentic loops" includes a reference to my preferred definition of the term "agent" itself - a thing that runs tools in a loop to achieve a goal.
Context engineering is another name people have given to same skill?
I think that's actually quite different.
Context engineering is about making sure you've stuffed the context with all of the necessary information - relevant library documentation and examples and suchlike.
Design the agentic loop is about picking the right tools to be provided to the model. The tool descriptions may go in the context but you also need to provide the right implementations of them.
They feel pretty closely connected. For instance: in an agent loop over a series of tool calls, which tool results should stay resident in the context, which should be summarized, which should be committed to a tool-searchable "memory", and which should be discarded? All context engineering questions and all kind of fundamental to the agent loop.
Yeah, "connected" feels right to me.
Those decisions feel to me like problems for the agent harness to solve - Anthropic released a new cookbook about that yesterday: https://github.com/anthropics/claude-cookbooks/blob/main/too...
One thing I'm really fuzzy on is, if you're building a multi-model agent thingy (like, can drive with GPT5 or Sonnet), should you be thinking about context management tools like memory and autoediting as tools the agent provides, or should you be wrapping capabilities the underlying models offer? Memory is really easy to do in the agent code! But presumably Sonnet is better trained to use its own builtins.
It boils down to information loss in compaction driven by LLM's. Either you could carefully design tools that only give compacted output with high information density so models have to auto-compact or organize information only once in a while which eventually is going to be lossy.
Or you just give loads of information without thinking much about it, assuming models will have to do frequent compaction and memory organization and hope its not super lossy.
Right, just so I'm clear here: assume you decide your design should be using a memory tool. Should you make your own with a tool call interface or should you rely on a model feature for it, and how much of a difference does it make?