# Claude vs GPT for coding and how to build AI agents

> Source: <https://promptcube3.com/en/posts/9312/>
> Published: 2026-09-13 15:45:38+00:00

# Claude vs GPT for coding and how to build AI agents

[Claude](/en/tags/claude/) 3.5 Sonnet currently beats GPT-4o for complex coding tasks because it handles large context windows with less "forgetfulness" and writes more concise, less repetitive boilerplate. It wins on architectural reasoning; GPT-4o wins on raw speed and ecosystem integration.

## Which one actually ships code faster?

I spent three weeks in February switching my primary workflow between Claude 3.5 Sonnet and GPT-4o for a TypeScript project. The result wasn't about who is "smarter," but who hallucinated fewer imports.

GPT-4o has a habit of inventing npm packages that don't exist when you ask for a niche utility. I hit this three times while trying to implement a specific PDF parsing logic. Claude, on the other hand, tends to be more honest about what it doesn't know, or it will actually suggest a vanilla JS implementation instead of lying about a library.

| Feature | Claude 3.5 Sonnet | GPT-4o |

| :--- | :--- | :--- |

| Refactoring | Exceptional (keeps state) | Good (occasionally forgets files) |

| Boilerplate | Clean, modern | Verbose, "AI-style" comments |

| Speed | Moderate | Fast |

| Logic Errors | Rare in small-medium files | Occasional "lazy" skips |

The real pain point with GPT-4o is "lazy coding." You'll ask it to update a 200-line function, and it gives you `// ... rest of code remains the same ...`. That's a productivity killer when you're trying to copy-paste quickly. Claude generally gives me the full block or very clear markers.

## How do you actually build AI agents that don't loop infinitely?

Build AI agents by implementing a "Reasoning-Action-Observation" loop (ReAct) where the LLM is forced to write its thought process before calling a tool.

Most beginners just throw a prompt at an LLM and hope it acts like an agent. That's not an agent; that's just a chatbot. A real agent needs a loop. I tried building a simple GitHub issue resolver last month. It kept getting stuck in a loop: reading the file, deciding to fix it, then reading the file again without actually writing the change.

The fix was forcing a "Plan" step.

1. **Plan**: The agent writes a 3-step bullet list of what it needs to do.

2. **Act**: It executes one tool (e.g., `read_file`).

3. **Observe**: It sees the output of the tool.

4. **Update**: It updates the plan based on the observation.

If you use a framework like LangGraph or CrewAI, this is handled for you, but if you're coding it from scratch in Python, you need a while-loop that breaks only when a specific `<FINAL_ANSWER>` tag is detected in the LLM output.

To avoid the "infinite loop of death," I set a hard limit of 10 iterations per task. If it hasn't solved the bug by then, the agent kills itself and alerts me. It's cheaper than letting a runaway agent burn through $15 of API credits in five minutes.

## Why bother with a specialized AI Discord alternative?

You need a dedicated AI community or platform when Discord's noise-to-signal ratio makes it impossible to find a specific, working prompt for a niche library.

Discord is great for chatting, but it's a graveyard for technical knowledge. Searching for a specific "[Cursor](/en/tags/cursor/) rules" configuration in a Discord channel is a nightmare. You scroll through 500 messages of "hello" and "help me" before finding one snippet.

I shifted my technical prompt storage to the [PromptCube homepage](/en/) because I needed a place where prompts are categorized by version and model, not buried in a chat history. When you're fighting a bug at 11 PM, you don't want to "discuss" a solution; you want to find the exact prompt that worked for someone else on a similar stack.

## Managing the "Context Window" nightmare

The wild part is that "200k context" doesn't mean the AI remembers everything. It's called the "lost in the middle" phenomenon.

When I fed a 50-file codebase into Claude, it remembered the first file and the last file perfectly. The stuff in the middle? It started guessing. To stop this, I stopped uploading the whole folder and started using a `.cursorrules` file or a project map.

If you're building agents, don't just dump everything into the prompt. Use a [RAG](/en/tags/rag/) (Retrieval-Augmented Generation) pipeline.

**My current stack for this:**

- **Vector DB:** Pinecone (for speed) or pgvector (if I'm already using Postgres).
- **Embedding Model:**`text-embedding-3-small` (cheap enough for most tasks).
- **Orchestration:** Simple Python scripts.

I found that chunking my code by function rather than by line count reduced hallucinations by about 30%. If you chunk by 500 characters, you often cut a function in half, and the AI loses the context of the return type.

## Where to find actually useful prompts?

Stop guessing and start using proven patterns. The most effective way to improve your AI coding output isn't by "talking" to the AI more, but by using structured prompts that define the AI's persona and constraints.

I've spent hours refining prompts for "TDD-style" code generation—where the AI writes the test first, then the code. You can find a lot of these curated patterns in [Prompt Sharing](/en/category/prompts/), which saves me from having to rediscover the same "system prompt" tweaks every time I start a new project.

For example, adding "Avoid over-engineering; prefer standard library over third-party dependencies" to a system prompt reduces the number of unnecessary packages I have to install by a surprising amount.

## The cost of running agentic workflows

If you're building agents, keep a close eye on your token usage. An agent that "thinks" through a problem for 5 minutes might make 12 API calls.

On GPT-4o, that's negligible for one person. But if you scale that to a team, you're looking at thousands of dollars in "reasoning tokens" that aren't actually producing code. I recommend using a smaller model (like GPT-4o-mini or Claude Haiku) for the "Observation" and "Routing" steps, and only calling the "Big" model for the final code synthesis.

This hybrid approach cut my API bill by 60% without a noticeable drop in code quality.

[Next Stop debating if AI can write code and start asking if it can maintain a production →](/en/threads/9262/)

[a library of Claude prompt techniques](https://tanyan888.com/), with plenty of directly applicable cases.