--- title: Claude Code 3.0 (New Mods Feature): Anthropic has... description: Claude Code's recent update roundup covers agents.md support (added in v2.1.277, Sept 18) letting the tool read shared cross-agent instruction files, and the... canonical: https://daily.dev/posts/claude-code-3-0-new-mods-feature-anthropic-has-silently-dropped-their-biggest-new-feature--6dk8tfagh twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Claude Code 3.0 (New Mods Feature): Anthropic has SILENTLY dropped their BIGGEST NEW Feature! | daily.dev og:description: Claude Code's recent update roundup covers agents.md support (added in v2.1.277, Sept 18) letting the tool read shared cross-agent instruction files, and the... og:url: https://daily.dev/posts/claude-code-3-0-new-mods-feature-anthropic-has-silently-dropped-their-biggest-new-feature--6dk8tfagh og:image: https://api.daily.dev/og/posts/6dk8tFaGh.png og:image:alt: Claude Code 3.0 (New Mods Feature): Anthropic has SILENTLY dropped their BIGGEST NEW Feature! og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Claude Code 3.0 (New Mods Feature): Anthropic has SILENTLY dropped their BIGGEST NEW Feature! **[AICodeKing](https://daily.dev/sources/aicodeking)** · 7 min read · 0 upvotes · 0 comments ## Summary Claude Code's recent update roundup covers agents.md support (added in v2.1.277, Sept 18) letting the tool read shared cross-agent instruction files, and the new 'mods' plugin system built on function hooks that lets developers customize the harness itself, with four built-in mods (agents.md loader, diff panel, telemetry, org security). Other updates include a redesigned Projects beta that coordinates multi-threaded cloud sessions, background computer use on macOS 15+, a live diff panel, Claude support for the Fable 5.1 model with a 1M token context window, plus /skill doctor and claude plugin eval tools for auditing skills and plugins. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Does Claude Code support the agents.md file for coding agent instructions? Yes, Claude Code gained agents.md support in version 2.1.277, released September 18. By default it uses agents.md only when the project has no Claude-specific instruction file like CLAUDE.md; if both exist, CLAUDE.md takes priority unless you configure loading both files under project instructions in /config. This support is not yet available on Bedrock, Vertex, or Foundry. _Track Claude Code releases like this on daily.dev before switching your project's agent instructions._ ### What are mods in Claude Code and how do they work? Mods are plugins for Claude Code that use function hooks to customize the harness, the software layer around the model that assembles context, calls tools, and displays the session. Early examples include changing interface components and filtering tool output before the model receives it. Four built-in mods exist in the public repository: the agents.md loader, diff panel, telemetry, and an organization security mod; custom mods remain early access and require function hooks to be enabled. _Developers building custom AI coding workflows can follow mods development updates on daily.dev._ ### What model context window does Fable 5.1 support in Claude Code? Fable 5.1 launched September 4 with a 1 million token context window, and Claude Code supports it starting from version 2.1.257, where the normal setup selects it automatically. Claude app gateways are an exception since their alias still points to Fable 5, so a gateway serving 5.1 requires the explicit model name, and usage may draw from separately billed credits depending on plan. _Anyone switching model versions in their coding setup can check compatibility notes like this on daily.dev._ ## Similar posts on daily.dev - [Claude Code 2.5: New Features for Web Developers](https://daily.dev/posts/claude-code-2-5-new-features-for-web-developers-prgjxvmiw) · SitePoint · 0 upvotes · 0 comments --- Tags: [#ai-agents](https://daily.dev/tags/ai-agents), [#anthropic](https://daily.dev/tags/anthropic), [#claude-code](https://daily.dev/tags/claude-code) [View this post on daily.dev](https://daily.dev/posts/claude-code-3-0-new-mods-feature-anthropic-has-silently-dropped-their-biggest-new-feature--6dk8tfagh) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Claude Code 3.0 (New Mods Feature): Anthropic has SILENTLY dropped their BIGGEST NEW Feature!","url":"https://daily.dev/posts/claude-code-3-0-new-mods-feature-anthropic-has-silently-dropped-their-biggest-new-feature--6dk8tfagh","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/claude-code-3-0-new-mods-feature-anthropic-has-silently-dropped-their-biggest-new-feature--6dk8tfagh"},"datePublished":"2026-09-19T09:37:29.131Z","dateModified":"2026-09-19T09:38:27.532Z","description":"Claude Code's recent update roundup covers agents.md support (added in v2.1.277, Sept 18) letting the tool read shared cross-agent instruction files, and the...","image":"https://i.ytimg.com/vi/u1dW4z5Ye90/sddefault.jpg","thumbnailUrl":"https://i.ytimg.com/vi/u1dW4z5Ye90/sddefault.jpg","isAccessibleForFree":true,"articleSection":"AICodeKing","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"AICodeKing","logo":"https://media.daily.dev/image/upload/s--x7nDUfWj--/f_auto,q_auto/v1768208312/logos/aicodeking","url":"https://daily.dev/sources/aicodeking"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/claude-code-3-0-new-mods-feature-anthropic-has-silently-dropped-their-biggest-new-feature--6dk8tfagh","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"ai-agents,anthropic,claude-code","timeRequired":"PT7M","video":{"@type":"VideoObject","name":"Claude Code 3.0 (New Mods Feature): Anthropic has SILENTLY dropped their BIGGEST NEW Feature!","description":"Claude Code's recent update roundup covers agents.md support (added in v2.1.277, Sept 18) letting the tool read shared cross-agent instruction files, and the...","thumbnailUrl":"https://i.ytimg.com/vi/u1dW4z5Ye90/sddefault.jpg","uploadDate":"2026-09-19T09:37:29.131Z","duration":"PT7M","url":"https://api.daily.dev/r/6dk8tFaGh","embedUrl":"https://www.youtube.com/embed/u1dW4z5Ye90"}} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"AICodeKing","item":"https://daily.dev/sources/aicodeking"},{"@type":"ListItem","position":3,"name":"Claude Code 3.0 (New Mods Feature): Anthropic has SILENTLY dropped their BIGGEST NEW Feature!"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/claude-code-3-0-new-mods-feature-anthropic-has-silently-dropped-their-biggest-new-feature--6dk8tfagh#faq","mainEntity":[{"@type":"Question","name":"Does Claude Code support the agents.md file for coding agent instructions?","acceptedAnswer":{"@type":"Answer","text":"Yes, Claude Code gained agents.md support in version 2.1.277, released September 18. 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