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Claude Code Updates Auto Mode and Adds AGENTS.md Support

Claude Code has updated its auto mode to default to a server-side classifier for API and Enterprise users, and on Bedrock, Vertex, Foundry, and gateways, while also introducing support for AGENTS.md in projects.

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Source · Sep 19, 2026, 3:10 AM · On Illumora · Sep 19, 2026, 3:17 AM

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Read the source →Claude Code What's New + releases — Claude Code changelog - Claude Code Docs
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Claude Code has implemented changes to its auto mode, now defaulting to a server-side classifier for Claude API and Enterprise users, as well as for deployments on Bedrock, Vertex, Foundry, and gateways. This update aims to avoid charging for classifier overhead. Users can opt out of this server-side default by setting CLAUDE_CODE_AUTO_MODE_SERVER=0 on Bedrock, Vertex, Foundry, and gateways. The system will issue a warning if a billed fallback occurs.

Additionally, Claude Code now supports AGENTS.md. In projects without a CLAUDE.md file, Claude Code will read AGENTS.md instead. This setting can be modified under "Project instructions" in /config, though this feature is not yet available on Bedrock, Vertex, or Foundry.

Key Points

  • Claude API and Enterprise users, along with those on Bedrock, Vertex, Foundry, and gateways, now default to a server-side classifier in auto mode.
  • The server-side classifier does not incur charges for classifier overhead.
  • Users can opt out of the server-side classifier by setting CLAUDE_CODE_AUTO_MODE_SERVER=0 on Bedrock, Vertex, Foundry, and gateways.
  • A warning will be issued if a billed fallback occurs.
  • A new "Auto mode server" row has been added to /status to indicate if the session's auto mode classifier runs on the server.
  • AGENTS.md is now supported; Claude Code will read this file if CLAUDE.md is absent in a project.
  • The AGENTS.md feature is configurable under "Project instructions" in /config but is not yet available on Bedrock, Vertex, or Foundry.

Context

According to the Claude Code changelog, these updates are part of ongoing improvements and bug fixes. The changes to auto mode and the introduction of AGENTS.md support are documented in the release notes for Claude Code.

Why It Matters

The shift to a server-side classifier for auto mode could impact cost management for developers and enterprises utilizing Claude Code by potentially reducing classifier overhead charges. The addition of AGENTS.md provides an alternative for defining project instructions, offering more flexibility in project configuration.

What To Do

  • Review the /status page to check if your session's auto mode classifier is running on the server.
  • Note the CLAUDE_CODE_AUTO_MODE_SERVER=0 option if you need to opt out of the server-side classifier on Bedrock, Vertex, Foundry, or gateways.
  • Consider using AGENTS.md for project instructions if CLAUDE.md is not present in your projects, especially if not deploying on Bedrock, Vertex, or Foundry.
  • Check the /config page under "Project instructions" to manage AGENTS.md settings.

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