---
title: Coder Agent
description: The Coder agent role, CodeDiff generation, and hunk-based editing.
sidebar:
  order: 3
  label: Coder Agent
---

## The Coder Agent (`⟠`)

The **Coder** receives the `TaskSpec` produced by the Planner and generates precise code modifications.

---

## What the Coder Does

1. **Focused Implementation:** Implements only the files and modifications specified in the `TaskSpec`. It is instructed not to introduce unsolicited refactors or unrelated changes.
2. **Unified Diff Generation:** Emits structured search/replace hunks (`CodeDiff`) with exact indentation and context lines.
3. **Spec Adherence Check:** Explains how each change satisfies the specific acceptance criteria defined by the Planner.
4. **Handling Feedback:** When the Reviewer rejects a draft or requests changes, the Coder receives the `ReviewFeedback` artifact and writes a targeted revision without starting from scratch.

---

## Recommended Configuration

```toml
[agents.coder]
provider    = "anthropic"
model       = "claude-sonnet-4-20250514"
max_tokens  = 8192
temperature = 0.2
```