# Claude Code's week: Sonnet 5.5 by default, Mods and a side agent

https://aycode.ai/blog/claude-code-mods-sonnet-5-5/ · 2026-10-06 · News

Sonnet 5.5 became the default Sonnet, Mods let plugins change how Claude Code behaves, and a built-in side agent flags what you miss.

Seven releases in eight days. Claude Code's changelog from 29 September to today reads like a team that does not sleep, and three changes stand out for anyone who codes with it every day.

## Sonnet 5.5 is the new default Sonnet

Version 2.1.286 (30 September) added Claude Sonnet 5.5 (claude-sonnet-5-5) and made it the default Sonnet, with a 1M token context window at $2 per million input and $10 per million output tokens. One release earlier, 2.1.285 had already moved interactive sessions to the 1M window for Opus 4.7 and later, Sonnet 5 and later, and Fable.

## Mods: plugins that change behavior, not just add tools

Version 2.1.290 (5 October) introduced Claude Mods. Plugins could already add commands, agents and hooks; Mods let them modify deeper behavior and are shared through the plugin directory. 2.1.289 had given mods $.ui.selection(), which returns the text you selected in fullscreen mode, and 2.1.290 adds more data to their hook results.

The first built-in one is called "You should know": a side agent that watches the session and flags things you or Claude might miss. You turn it on with /plugin enable cc-plugin-you-should-know@builtin. The changelog says it is available in first-party sessions with telemetry on.

## The small things that save your afternoon

- /code-review takes --max-findings <n> or all (2.1.289).
- Mid-response API timeouts no longer throw away the answer: non-interactive sessions continue from the partial response (2.1.289).
- A prompt cleared with Ctrl+C can be recovered (2.1.288).
- WebFetch no longer cuts pages silently after 100,000 characters; it says so and offers an offset (2.1.290).
- Scheduled tasks no longer stop running after a conversation is compacted (2.1.290).

## Our take

Mods are the bigger story than another model bump. A side agent that reviews while you work is the kind of thing teams used to build on their own, badly. The catch is the telemetry requirement for the built-in one, which some companies will not accept.

## In AyCode

In AyCode, Sonnet 5.5 is already in the model menu. The usage view shows what each chat costs in tokens, so a bigger context window does not turn into a surprise bill.

Sources:
- Anthropic: Claude Code changelog (https://code.claude.com/docs/en/changelog)