Anthropic has just released Claude Opus 4.6, its most capable AI model to date. Whether you’re a developer, researcher, or enterprise team, Opus 4.6 represents a significant leap in reasoning, coding, and agentic capabilities. In this post, we’ll cover what’s new, how it compares to older Claude models, and — most importantly — how to connect it to your terminal and unlock its full power with Claude Code.

What Is Claude Opus 4.6?

Claude Opus 4.6 is Anthropic’s flagship model, released on February 5, 2026. It sits at the top of the Claude model family (Opus 4.6 > Sonnet 4.5 > Haiku 4.5) and is designed for the most demanding tasks in software engineering, financial analysis, scientific reasoning, and long-context document work.

Key specs at a glance:

  • 1 million token context window — the first Opus-class model to support this
  • 128,000 token output — generate entire codebases, reports, or analyses in a single response
  • Adaptive thinking — the model dynamically adjusts how much reasoning effort to invest based on the complexity of your prompt
  • Agent Teams — coordinate multiple AI agents that split large tasks and work in parallel
  • Same pricing as Opus 4.5: $5 / $25 per million input/output tokens

What Makes Opus 4.6 Different from Older Claude Models?

vs. Claude 3.5 Sonnet

Claude 3.5 Sonnet was a breakthrough model when it launched, but Opus 4.6 is a generational leap:

Capability Claude 3.5 Sonnet Claude Opus 4.6
Context Window 200K tokens 1M tokens
Max Output 8,192 tokens 128,000 tokens
Long-context retrieval (MRCR v2) ~18.5% 76%
Agentic coding Basic tool use Full agent teams, parallel coordination
Adaptive reasoning Not available 4-level effort control
Financial analysis (Real-World Finance) Baseline +23 percentage points improvement

vs. Claude Opus 4.5

Even compared to its direct predecessor, Opus 4.6 brings substantial improvements:

  • Better planning and debugging — Opus 4.6 plans more carefully before writing code, catches its own mistakes more often, and sustains complex agentic tasks for longer
  • Agent Teams (new) — for the first time, multiple Claude agents can coordinate directly with each other, splitting larger tasks into segments
  • Adaptive Thinking (new) — the model uses contextual clues to decide how much reasoning to apply, and developers can control this via the effort parameter (low, medium, high, max)
  • Context Compaction — automatically summarizes prior context during long-running sessions so it can work indefinitely without hitting context limits
  • Lower over-refusal rate — Opus 4.6 has the lowest rate of unnecessary refusals of any Claude model, meaning it’s more helpful and less likely to block legitimate requests

Benchmark Highlights

  • ARC AGI 2: 68.8% — solving problems easy for humans but hard for AI
  • Terminal-Bench 2.0: Highest score — agentic coding in real terminal environments
  • Humanity’s Last Exam: Top score — expert-level multidisciplinary reasoning
  • BrowseComp: Best in industry — information retrieval across the web
  • Finance Agent: 60.7% (state-of-the-art) — autonomous financial research
  • TaxEval: 76.0% — tax analysis and compliance reasoning

How to Connect Claude Opus 4.6 to Your Terminal

The most powerful way to use Opus 4.6 is through Claude Code, Anthropic’s official command-line interface. Here’s how to set it up:

Step 1: Install Claude Code

npm install -g @anthropic-ai/claude-code

Requirements: Node.js 18+ and an Anthropic API key.

Step 2: Authenticate

claude

On first run, Claude Code will prompt you to log in with your Anthropic account or enter your API key. Follow the on-screen instructions.

Step 3: Start Using It

Navigate to any project directory and simply run:

cd your-project/
claude

Claude Code will now have full context of your project and can read files, edit code, run terminal commands, search your codebase, and much more.

Using Subagents for Parallel Work

One of the most powerful features of Claude Code is subagents — specialized AI agents that handle specific types of tasks in their own context window.

What Are Subagents?

Subagents are independent Claude instances that the main agent can delegate work to. Each subagent gets:

  • Its own context window (so your main conversation stays clean)
  • A custom system prompt tailored to its specialty
  • Specific tool access and permissions

Built-in Subagent Types

Claude Code ships with several built-in subagent types:

  • Explore — quickly scans your codebase, finds files by pattern, searches for keywords
  • Plan — designs implementation strategies and identifies critical files
  • Bash — executes terminal commands autonomously
  • General-purpose — handles research, multi-step tasks, and complex queries

Creating Custom Subagents

You can create your own subagents by adding Markdown files to your project:

.claude/agents/my-reviewer.md

Each file uses YAML frontmatter for configuration, followed by the system prompt:

---
name: code-reviewer
description: Reviews code for bugs, security issues, and best practices
tools:
  - Read
  - Grep
  - Glob
---

You are a senior code reviewer. Analyze the provided code for:
1. Security vulnerabilities (OWASP Top 10)
2. Performance issues
3. Code style and readability
4. Potential bugs

Provide actionable feedback with specific line references.

Using Subagents in Practice

When Claude Code encounters a complex task, it automatically delegates to subagents. For example, if you ask it to refactor an authentication system, it might:

  1. Spawn an Explore agent to map all auth-related files
  2. Use a Plan agent to design the refactoring strategy
  3. Execute changes in the main context
  4. Launch a Bash agent to run tests

You can also manage subagents interactively using the /agents command within a Claude Code session.

Plan Mode: Think Before You Code

Plan Mode is a built-in feature that lets Claude Code design an implementation strategy before writing any code. This is essential for complex tasks where the wrong approach could waste significant time.

How Plan Mode Works

  1. Claude enters plan mode — either automatically for complex tasks or when you ask it to plan first
  2. Explores your codebase — reads relevant files, searches for patterns, understands your architecture
  3. Designs an approach — identifies which files to modify, what patterns to follow, and what trade-offs exist
  4. Presents the plan for your approval — you review the strategy before any code is written
  5. Executes on approval — only after you approve does Claude begin implementing

When to Use Plan Mode

  • Adding new features that touch multiple files
  • Refactoring existing code where multiple approaches are valid
  • Architectural decisions (choosing patterns, libraries, or strategies)
  • Any task where you want to review the approach before implementation

Triggering Plan Mode

You can ask Claude Code to plan explicitly:

> Plan how to add user authentication to this app

Or Claude Code will proactively enter plan mode when it detects that a task is complex enough to benefit from upfront planning.

Custom Instructions with CLAUDE.md

CLAUDE.md files are how you give Claude Code persistent, project-specific instructions. Think of them as a “developer README” that Claude reads every time it starts working on your project.

Where to Place CLAUDE.md

Claude Code reads instructions from multiple locations, in order of priority:

Location Scope Use Case
~/.claude/CLAUDE.md Global (all projects) Your personal preferences, coding style
./CLAUDE.md Project root Project-wide conventions, architecture notes
./.claude/CLAUDE.md Project (alternative) Same as above, hidden in .claude directory
./src/CLAUDE.md Subdirectory Module-specific instructions

What to Include

Here’s an example CLAUDE.md for a TypeScript project:

# Project Instructions

## Tech Stack
- TypeScript 5.x with strict mode
- React 19 with Server Components
- PostgreSQL with Drizzle ORM
- Tailwind CSS v4

## Coding Conventions
- Use functional components with hooks, never class components
- Prefer named exports over default exports
- All API routes must validate input with Zod schemas
- Error messages should be user-friendly, not technical

## Testing
- Write tests for all new features using Vitest
- Place test files next to the source file: `foo.ts` → `foo.test.ts`
- Minimum 80% coverage for new code

## Architecture
- Follow the repository pattern for database access
- Keep business logic in `/src/services/`, never in route handlers
- All dates must be stored and transmitted in UTC

## Do NOT
- Do not use `any` type — use `unknown` and narrow
- Do not add console.log statements in production code
- Do not modify the database schema without creating a migration

Tips for Effective Custom Instructions

  1. Be specific — “Use Zod for validation” is better than “validate inputs”
  2. Include examples — show the pattern you want, not just the rule
  3. Keep it concise — Claude reads this every session; don’t write a novel
  4. Update regularly — as your project evolves, update the instructions
  5. Use subdirectory CLAUDE.md — for module-specific conventions that don’t apply everywhere

Quick Reference: Essential Claude Code Commands

Command What It Does
claude Start an interactive session
claude "fix the login bug" Start with a specific task
claude --model opus Use a specific model
/plan Enter plan mode
/agents Manage subagents
/help Show all available commands
/clear Clear conversation history
Ctrl+C Cancel current operation
Escape Exit Claude Code

Why This Matters

Claude Opus 4.6 isn’t just an incremental update — it represents a shift in how developers can work with AI. The combination of a 1M token context window, agent teams, adaptive thinking, and deep terminal integration through Claude Code means you can tackle projects that were previously too complex for AI assistance.

Whether you’re debugging a massive codebase, planning a system architecture, or automating repetitive development tasks, Opus 4.6 with Claude Code gives you a capable partner that understands your entire project and works the way you do — in the terminal.

For more information, visit the official Anthropic announcement or the Claude Code documentation.