NIHAR MALALI

While GitHub Copilot excels at inline suggestions and chat-based assistance, Claude Code takes a fundamentally different approach: it operates as an autonomous coding agent that can plan, execute, and iterate on multi-file changes directly from your terminal. When combined with Instruction Driven Development and the AGENTS.md file, Claude Code becomes a powerful partner for complex software engineering tasks.

How Claude Code Differs from Copilot

• Terminal-Native Agent — Claude Code runs in your terminal and interacts with your codebase through file reads, writes, and shell commands. It does not live inside an IDE; it operates alongside your entire development environment.
• Autonomous Multi-Step Execution — Rather than suggesting one line or one file at a time, Claude Code can plan a multi-file refactoring, execute each step, run tests to verify, and iterate on failures — all in a single session.
• Full Repository Context — Claude Code can read any file in your repository, understand the relationships between modules, and make changes that are consistent across the entire codebase.
• Tool Use — Claude Code can execute shell commands, run tests, query databases, and interact with APIs as part of its development workflow. This makes it capable of true end-to-end development tasks.

AGENTS.md — The Agent Instruction File

The AGENTS.md file is the Claude Code equivalent of Copilot’s instruction files. Placed at the repository root or in specific directories, it provides Claude Code with the context it needs to work effectively on your project.

• Project Overview — High-level description of the application, its architecture, and key design decisions. This orients Claude Code before it reads any source files.
• Workflow Instructions — Step-by-step procedures for common tasks like adding a new feature, fixing a bug, or running the test suite. Claude Code follows these as checklists when executing tasks.
• Constraints and Guardrails — Explicit rules about what Claude Code should never do: never modify migration files directly, never push to main, never delete test fixtures. These prevent the agent from making well-intentioned but destructive changes.
• Testing Expectations — Define what “done” looks like. “All changes must pass existing tests and include new tests for added functionality” ensures Claude Code does not skip the verification step.

Claude Code in Practice — The Task Tracker Example

In the task-tracker-copilot-md repository, the AGENTS.md file provides Claude Code with the complete monorepo layout, shared type system architecture, API endpoint patterns, and testing strategy. When asked to implement a new feature, Claude Code reads AGENTS.md first, then examines existing implementations for patterns, and finally generates code that is consistent with the existing codebase.

• Adding an API Endpoint — Claude Code reads the AGENTS.md workflow, creates the route handler in the correct directory, adds Zod validation using the shared schema, writes the service layer with proper error handling, and creates test files — all following the documented patterns.
• Refactoring Across Packages — When renaming a shared type, Claude Code propagates the change through the shared library, backend services, frontend components, and test files, running the type checker after each change to catch errors early.
• Bug Investigation — Claude Code can read logs, examine failing tests, trace the execution path through your code, and propose targeted fixes — all guided by the AGENTS.md context about your project’s debugging procedures.

Combining Copilot and Claude Code

The most effective approach uses both tools. Copilot handles inline coding and quick suggestions within your IDE, guided by .github/copilot-instructions.md. Claude Code handles larger, multi-file tasks from the terminal, guided by AGENTS.md. Both tools benefit from IDD instruction files, and the instruction files benefit from both tools’ usage patterns — creating a virtuous cycle where better documentation leads to better AI output, which leads to more investment in documentation.

Claude Code with AGENTS.md brings the agent paradigm to software development. Instead of autocompleting individual lines, it reasons about your project holistically and executes complex tasks end-to-end. When paired with well-structured IDD instruction files, it approaches the productivity of having an experienced junior developer who knows your entire codebase.