Claude Code Updates: Mods, AGENTS.md, and Multi-Threaded Projects

AICodeKing2026-09-19go watch the original →

the gist

Anthropic has introduced a modular architecture for Claude Code, enabling custom harness behavior, AGENTS.md support for shared project instructions, and cloud-based multi-threaded task coordination.

Modular Customization via Mods

Anthropic is transitioning Claude Code toward a modular architecture called Mods, which allows developers to hook into the underlying harness that manages context, tool execution, and session display. While still in early access, this system enables users to intercept function calls and filter tool outputs before they reach the model. The current implementation includes four built-in mods: the AGENTS.md loader, a diff panel, telemetry, and an organization security module. Developers can inspect these implementations to understand how to build their own custom hooks.

Project Coordination and Context Management

The latest updates focus on improving task execution and context handling across complex workflows. Claude Code now natively supports AGENTS.md files, allowing it to ingest shared project instructions alongside existing claude.md files. For larger tasks, the redesigned Projects beta enables the coordinator to split work into parallel threads, each running in a separate cloud session with its own branch and repository copy. This allows for asynchronous task execution that persists even after the local terminal session closes.

Workflow and Evaluation Tools

New utility commands help developers manage the overhead and effectiveness of their Claude Code configurations:

/skill-doctor: Displays the context cost and usage of active skills, allowing users to disable unnecessary plugins that consume token space.
claude plugin eval: Runs user-defined test cases against a plugin and compares the output against a baseline run without the plugin to quantify performance impact.
/diff: Provides a live, full-screen panel for reviewing file changes, enabling users to select specific lines for subsequent interaction.
/resume: Allows desktop users to restore terminal sessions while maintaining full conversation history and context.

Background Computer Use

For macOS 15 and later, Claude Code now supports background computer use, enabling the model to interact with approved native applications while the user continues to work. This feature requires the desktop application to remain active and is currently available to Pro and Mac subscribers.