3 ms·

Does anyone have an understanding - or intuition - of what the agentic loop looks like in the popular coding agents? Is it purely a “while 1: call_llm(system, a

Does anyone have an understanding - or intuition - of what the agentic loop looks like in the popular coding agents? Is it purely a “while 1: call_llm(system, assistant)”, or is there complex orchestration? I’m trying to understand if the value for Claude Code (for example) is purely in Sonnet/Haiku + the tool system prompt, or if there’s more secret sauce - beyond the “sugar” of instruction file inclusion via commands, tools, skills etc.

CraftThatBlock 11mo ago
Generally, that's pretty much it. More advanced tools like Claude Code will also have context compaction (which sometimes isn't very good), or possibly RAG on code (unsure about this, I haven't used any tools that did this). Context compaction, to my understanding, is just passing all the previous context into a call which summarizes it, then that becomes to new context starting point.
colonCapitalDee 11mo ago
I thought this was informative: https://minusx.ai/blog/decoding-claude-code/ https://minusx.ai/blog/decoding-claude-code/
mrkurt 11mo ago
Claude Code is an obfuscated javascript app. You can point Claude Code at it's own package and it will pretty reliably tell you how it works. I think Claude Code's magic is that Anthropic is happy to burn tokens. The loop itself is not all that interesting. What is interesting is how they manage the context window over a long chat. And I think a fair amount of that is serverside.
- AdieuToLogic 11mo ago
  > Claude Code is an obfuscated javascript app. You can point Claude Code at it's own package and it will pretty reliably tell you how it works. This is why I keep coming back to Hacker News. If the above is not a quintessential "hack", then I've never seen one. Bravo!
  - simonw 11mo ago
    I've been running the obfuscated code through Prettier first, which I think makes it a bit easier for Claude Code to run grep against.
PhilippGille 11mo ago
No need to take guesses - the VS Code GitHub Copilot extension is open source amnd has an agent mode with tool calling: https://github.com/microsoft/vscode-copilot-chat/blob/4f7ffdf08d013c282090b2bdafe47f1f001cd82f/src/extension/intents/node/toolCallingLoop.ts#L170 https://github.com/microsoft/vscode-copilot-chat/blob/4f7ffd...
jeremy_k 11mo ago
https://github.com/sst/opencode https://github.com/sst/opencode opencode is open source. Here's a session I started but haven't had time to get back to which is using opencode to ask it about how the loop works https://opencode.ai/s/4P4ancv4 https://opencode.ai/s/4P4ancv4 The summary is The beauty is in the simplicity: 1. One loop - while (true) 2. One step at a time - stopWhen: stepCountIs(1) 3. One decision - "Did LLM make tool calls? → continue : exit" 4. Message history accumulates tool results automatically 5. LLM sees everything from previous iterations This creates emergent behavior where the LLM can: - Try something - See if it worked - Try again if it failed - Keep iterating until success - All without explicit retry logic!
nl 11mo ago
Have a look at https://github.com/anthropics/claude-code/tree/main/plugins/feature-dev https://github.com/anthropics/claude-code/tree/main/plugins/... to see how a fairly complex workflow is implemented
simonw 11mo ago
You can reverse engineer Claude Code by intercepting its HTTP traffic. It's pretty fascinating - there are a bunch of ways to do this, I use this one: https://simonwillison.net/2025/Jun/2/claude-trace/ https://simonwillison.net/2025/Jun/2/claude-trace/
- nylonstrung 11mo ago
  Wow it seems almost designed to burn through tokens. I wish we had a version that was optimized around token/cost efficiency

CraftThatBlock 11mo ago

Generally, that's pretty much it. More advanced tools like Claude Code will also have context compaction (which sometimes isn't very good), or possibly RAG on code (unsure about this, I haven't used any tools that did this). Context compaction, to my understanding, is just passing all the previous context into a call which summarizes it, then that becomes to new context starting point.

colonCapitalDee 11mo ago

I thought this was informative: https://minusx.ai/blog/decoding-claude-code/ https://minusx.ai/blog/decoding-claude-code/

mrkurt 11mo ago

Claude Code is an obfuscated javascript app. You can point Claude Code at it's own package and it will pretty reliably tell you how it works. I think Claude Code's magic is that Anthropic is happy to burn tokens. The loop itself is not all that interesting. What is interesting is how they manage the context window over a long chat. And I think a fair amount of that is serverside.

AdieuToLogic 11mo ago
> Claude Code is an obfuscated javascript app. You can point Claude Code at it's own package and it will pretty reliably tell you how it works. This is why I keep coming back to Hacker News. If the above is not a quintessential "hack", then I've never seen one. Bravo!
- simonw 11mo ago
  I've been running the obfuscated code through Prettier first, which I think makes it a bit easier for Claude Code to run grep against.

PhilippGille 11mo ago

No need to take guesses - the VS Code GitHub Copilot extension is open source amnd has an agent mode with tool calling: https://github.com/microsoft/vscode-copilot-chat/blob/4f7ffdf08d013c282090b2bdafe47f1f001cd82f/src/extension/intents/node/toolCallingLoop.ts#L170 https://github.com/microsoft/vscode-copilot-chat/blob/4f7ffd...

jeremy_k 11mo ago

https://github.com/sst/opencode https://github.com/sst/opencode opencode is open source. Here's a session I started but haven't had time to get back to which is using opencode to ask it about how the loop works https://opencode.ai/s/4P4ancv4 https://opencode.ai/s/4P4ancv4 The summary is The beauty is in the simplicity: 1. One loop - while (true) 2. One step at a time - stopWhen: stepCountIs(1) 3. One decision - "Did LLM make tool calls? → continue : exit" 4. Message history accumulates tool results automatically 5. LLM sees everything from previous iterations This creates emergent behavior where the LLM can: - Try something - See if it worked - Try again if it failed - Keep iterating until success - All without explicit retry logic!

nl 11mo ago

Have a look at https://github.com/anthropics/claude-code/tree/main/plugins/feature-dev https://github.com/anthropics/claude-code/tree/main/plugins/... to see how a fairly complex workflow is implemented

simonw 11mo ago

You can reverse engineer Claude Code by intercepting its HTTP traffic. It's pretty fascinating - there are a bunch of ways to do this, I use this one: https://simonwillison.net/2025/Jun/2/claude-trace/ https://simonwillison.net/2025/Jun/2/claude-trace/

nylonstrung 11mo ago
Wow it seems almost designed to burn through tokens. I wish we had a version that was optimized around token/cost efficiency