---
title: "Build a coding agent with GPT 5.1"
section: "raw"
type: "source"
created: "2026-08-27"
updated: "2026-08-27"
canonical: "https://pyweb.dev/wiki/raw/articles/openai-build-a-coding-agent-gpt-5-1-2025"
---
# Build a coding agent with GPT 5.1

**Author:** Katia Gil Guzman (OpenAI)  
**Published:** 2025-11-13  
**Source:** [OpenAI Cookbook](https://developers.openai.com/cookbook/examples/build_a_coding_agent_with_gpt-5.1)  

---

## Executive Summary & Architecture

This reference implementation details the architecture of an autonomous coding agent built on the OpenAI Agents SDK and the Responses API. The agent can scaffold brand-new applications from user prompts, iterate on codebases through patches, execute terminal build/test commands, and retrieve fresh documentation.

### Core Tool Harness Configuration
- **`apply_patch`**: Structured file editing tool applying unified diffs to project files.
- **`shell` (LocalShellCall / ShellExecutor)**: Executes shell commands in an isolated directory with timeout enforcement and explicit human approval gates.
- **`web_search` (ResponseFunctionWebSearch)**: Retrieves up-to-date documentation and package information.
- **Context7 MCP**: Model Context Protocol integration providing indexed library documentation.

---

## Reference Shell Executor with Safety & Approval Gates

```python
class ShellExecutor:
    """
    Shell executor for coding agent harness.
    - Runs all commands inside isolated `workspace_dir`
    - Captures stdout/stderr
    - Enforces timeout from `action.timeout_ms`
    - Enforces mandatory human approval gate before command execution
    """
    def __init__(self, cwd: Path):
        self.cwd = cwd

    async def __call__(self, request: ShellCommandRequest) -> ShellResult:
        action = request.data.action
        await require_approval(action.commands)
        # executes in isolated subprocess with timeout handling
```

---

## Decision Rules & Loop Controls

- **When configuring shell execution tools for coding agents, do enforce strict workspace directory isolation and human approval gates**, because arbitrary command execution in un-sandboxed environments creates critical security and system destruction risks.
- **When executing multi-step agent workflows, do implement an outer controller loop to handle `MaxTurnsExceeded` and dependency errors**, because agents can exhaust turn limits or enter error loops without harness-level retries.
- **When editing multi-file codebases, do use structured patching tools (`apply_patch`) rather than whole-file rewrites**, because structured diffs minimize token consumption and reduce unintentional code clobbering.

---

## What the Source Does NOT Claim

- Does **NOT** claim that un-sandboxed shell command execution is safe for autonomous agents.
- Does **NOT** claim that single-pass generation can reliably build complex applications without outer feedback loops.

---

## Agent Navigation

### Machine endpoints
- Knowledge graph: https://pyweb.dev/api/graph.json
- Graph analysis: https://pyweb.dev/api/graph-analysis.json
- Context index: https://pyweb.dev/llms.txt