One Command. Anthropic’s Most Powerful Model. No Extra Setup. Here’s What Just Changed in Claude Code.

Type /fast in your terminal.

That’s it. You’re now running Claude Opus 4.7 — Anthropic’s most capable model ever built — at 2.5x speed, inside the tool you already have open, with no additional configuration and no extra payment tier beyond your existing Claude Code subscription.

It sounds too simple. It isn’t. Here’s what quietly changed, why it matters, and what you actually need to know before you hit that command.

What Just Happened?

On May 14, 2026, Anthropic released Claude Code v2.1.142 and made Opus 4.7 the default model for fast mode, replacing Opus 4.6. Before this update, /fast put you on Opus 4.6 at higher speed. Now it puts you on the strongest model in Anthropic’s lineup, at that same higher speed.

Developers using Claude Code can now instantly access Anthropic’s strongest coding model at full speed — no extra setup, no complicated configuration, no additional payment tier.

Opus 4.7 is the fast mode default in Claude Code v2.1.142 and later. To pin fast mode to Opus 4.6 instead, set CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE=1.

What Is Fast Mode, Exactly?

This is the most important thing to understand before you get excited — or before you panic about your bill.

Fast Mode is not a different model. It runs Claude Opus 4.7 with a different underlying API configuration — one that allocates more inference compute to generate tokens faster. The intelligence, capabilities, context window, and output quality are identical to standard Opus 4.7.

Also Read: Claude Code: Complete Setup and Getting Started Guide

Why This Is a Big Deal for Developers

For months, the developers unlocking Opus 4.7’s full capabilities were either paying serious per-token API costs or burning through Max plan compute allocations at rates that felt unsustainable for daily workflows. The experience of using Anthropic’s most powerful model in an interactive coding session — where you’re iterating in real time, waiting on responses, and context-switching between debugging and architecture work — was slowed down by the latency of standard inference.

Typing /fast now activates the most capable Claude experience available. AI coding tools are becoming increasingly competitive, but default access matters more than many people realize.

The practical upside is real and specific:

• Rapid iteration: Debugging loops that took 40 seconds at standard speed now take 16
• Live architecture review: Ask Opus 4.7 to review an entire module and get a structured response while you’re still thinking about the next question
• Frontend generation: One of the flagged improvements in Opus 4.7 is better UI code output — fast mode makes that feel interactive rather than like waiting for a render

Also Read: Claude Opus 4.7 vs GPT-5.5: Which Is the Better Coding Model?

ANTHROPIC JUST MADE THEIR MOST POWERFUL MODEL THE DEFAULT.

Claude Code fast mode now runs on Opus 4.7.

Type /fast in your terminal.

That is it.

You are now running the most capable AI model Anthropic has ever built at full speed with no extra configuration and no additional… pic.twitter.com/XUvAdrR7Ff

— CyrilXBT (@cyrilXBT) May 25, 2026

The Part Nobody’s Talking About: The Cost Is Real

Here’s where the honest context matters, because the hype around this feature has underplayed the billing reality.

Opus 4.7 ships with a new tokenizer that uses up to 35% more tokens on the same input compared to earlier Claude models. So even at standard list prices, you’re already paying more per effective unit of work. Stack the 6x fast mode premium on top of a tokenizer that inflates token counts, and the real cost delta is larger than the 6x figure implies.

To make it concrete: a developer running 10 interactive sessions per day at roughly 50,000 tokens each pays about $12.50/day in standard mode. The same workload in fast mode runs $75/day — a difference of $62.50 daily, or roughly $1,900/month, purely for faster token delivery.

There’s also a mid-conversation trap to watch for. When you switch into fast mode mid-conversation, you pay the full fast mode uncached input token price for the entire conversation context — which costs more than if you had enabled fast mode from the start.

The smart approach: Toggle /fast on at the start of a session when you’re in rapid-iteration mode. Toggle it back off for longer-running, latency-insensitive tasks like document generation or background refactoring.

According to Anthropic’s official fast mode documentation, fast mode is best suited for interactive work where response latency matters more than cost — exactly the scenario the viral posts are describing.

Who Should Use It Right Now

Turn it on if you are:

• Doing live debugging where every round-trip second costs you focus
• Iterating on frontend components in real time with a client or teammate watching
• In a sprint week where shipping speed is the only metric that matters
• On a Max plan where the included usage comfortably covers your volume

Leave it off if you are:

• Running long background agentic sessions where latency doesn’t matter
• On a pay-per-token plan with a tight weekly budget
• Already exceeding your Max plan’s included Opus usage regularly

How to Enable It Right Now

# Step 1: Make sure you're on the right version
claude --version  # Should be v2.1.142 or later

# Step 2: Update if needed
claude update

# Step 3: Start a Claude Code session and type:
/fast
# Then press Tab to toggle ON

# Step 4: To verify fast mode is active
/fast  # Run again — it will confirm current status

The model does not revert to your previous model when you disable fast mode. To switch to a different model, use /model. Fast mode is also available in the Claude Code VS Code extension.

The Competitive Reality

Most developers will not immediately notice the change. That creates a temporary advantage for early adopters who start using Opus 4.7 today.

That framing is legitimate. If you’re building in a competitive market — agency work, SaaS, freelance dev — the gap between standard-mode Opus 4.6 responses and fast-mode Opus 4.7 responses is measurable in output quality and iteration speed. The developers who know about this today have a head start on the ones who will find out about it next month.

The move also applies pressure on rivals. OpenAI Codex shipped to the ChatGPT mobile app on the same day as the Claude Code v2.1.142 release — May 14 — which suggests both companies are in an active race to put their most capable models in the hands of developers as frictionlessly as possible.

Anthropic just made their strongest model the default. That’s not a small update.

For more Claude Code tips, model comparisons, and developer tools coverage, follow TechnoSports. Already using /fast? Drop your experience in the comments.