Claude Opus 5.5 Just Became the Default in Claude Code v2.1.280

Hi everyone, it's Shii-chan! I just went through the latest Claude Code release notes, and there is a lot of exciting stuff packed in there. Let's dive in!

Claude Code Release github.com

What was announced?

The Claude Code Release notes for v2.1.280 just went live, and this one covers everything from a new model to bug fixes, VS Code extension updates, and improvements to Claude Tag (Claude in Slack).

The headline change is that Claude Opus 5.5 (claude-opus-5-5) has been added and is now the default Opus model. On top of that, the default model on Pro and Team Standard plans switched from Sonnet to Opus, matching what Max, Team Premium, and Enterprise already had.

The story so far

Until now, if you were on a Pro or Team Standard plan, Sonnet ran by default, and you had to switch manually if you wanted Opus.

MCP tool descriptions and server instructions also had a fixed 2,048-character cap, so servers with longer descriptions had no choice but to trim them down.

There were also some rough edges in auto mode: when a safety check declined to review an action, Claude Code would keep retrying it over and over, and when a safety check gave no answer at all, it could deny actions repeatedly without any pause.

What changes

First, Claude Opus 5.5 is now available and set as the default Opus model, so you get the benefit of a smarter model without changing anything. It supports up to 1M tokens of context, and pricing is $4 per Mtok for input, $20 per Mtok for output, with cache reads at $0.20 per Mtok.

If you run a lot of MCP servers, you'll like that CLAUDE_CODE_MAX_MCP_DESCRIPTION_LENGTH now lets you raise that 2,048-character description cap yourself, so tools with longer descriptions don't lose information.

Auto mode got safer too: when a safety check declines an action, it's now denied once with a note that retrying won't help, and when a safety check gives no answer, retries back off instead of hammering away, stopping the turn with a message after ten in a row.

The VS Code extension also picked up new dialogs for /status, /sandbox, /chrome, /export, and /plan, so you can check session details or export a conversation without leaving your editor.

Dive Deep

If you want more room for MCP descriptions, you can set the environment variable like this:

export CLAUDE_CODE_MAX_MCP_DESCRIPTION_LENGTH=4096

That raises the cap for every MCP server in the session.

The auto mode safety logic is a small but thoughtful fix: a declined action is now denied exactly once instead of being retried, and unanswered safety checks back off gradually, stopping after ten consecutive attempts with an explanatory message. That is exactly the kind of loop that used to eat your session quietly, so this should help a lot.

There is also a new addition to the hook_execution_complete OpenTelemetry event: hook output sizes and the number of oversized outputs saved to a file, which makes it easier to spot hooks that are getting too heavy.

Wrap-up

• Claude Opus 5.5 (claude-opus-5-5) is added and is now the default Opus model: 1M context, $4 / $20 per Mtok, $0.20/Mtok cache reads
• Pro and Team Standard plans now default to Opus instead of Sonnet
• CLAUDE_CODE_MAX_MCP_DESCRIPTION_LENGTH lets you raise the 2,048-character MCP description cap
• Auto mode's retry and denial loops around safety checks are fixed
• The VS Code extension adds new /status, /sandbox, /chrome, /export, and /plan dialogs
• The hook_execution_complete event now tracks hook output sizes

This update should matter to anyone who uses Claude Code daily, and especially to Pro plan users who never had to think about Opus before!