Claude Code’s September 18, 2026 update introduces support for AGENTS.md as a fallback for project instructions. According to the changelog, in projects with no CLAUDE.md file, Claude Code will now read AGENTS.md instead, with configuration available under “Project instructions” in /config. This feature is not yet available on Bedrock, Vertex, or Foundry platforms.
Beyond this core feature addition, the update includes substantial improvements to gateway configuration and infrastructure. A new environment variable, CLAUDE_GATEWAY_PROXY_IS_EGRESS_BOUNDARY=1, has been added for Claude apps gateways whose only egress is a forward proxy, allowing every outbound request to hand the proxy the hostname instead of resolving it locally. Claude apps gateway upstreams now support an optional headers:map to send static headers to a proxy running in front of a provider.
The release addresses numerous stability issues affecting user sessions. Fixed bugs include sessions that could hang with no result after internal errors, conversations failing with “text content blocks must be non-empty” errors when previous assistant turns contained empty text blocks, and unexpected logouts when older Claude Code builds run alongside the current version. The update also resolves issues with interactive startup hanging for users with ANTHROPIC_API_KEY when ~/.claude.json contains malformed customApiKeyResponses values.
Updating mechanisms have been improved. Claude update now properly handles cases where a proxy returns invalid versions, and the command no longer hangs when minimum or maximum versions are set. Plugin management has been corrected to prevent installations from failing or breaking when reinstalling a plugin version already in use by another session.
The update fixes multiple tool-related issues: the Write tool now reports clear errors instead of silently declining permissions when the target path is a directory, and the Edit tool no longer mishandles escaped backslashes or produces overly broad error messages on large edits containing non-ASCII text. Background sessions are more stable, crashing less frequently from LSP server exits or malformed configuration values.
Additional fixes improve file handling, terminal behavior, sandbox functionality, and marketplace policy enforcement. The update also improves session startup performance for SDK and headless use, eliminating unnecessary per-directory CLAUDE.md lookups on first turn.
Key facts
- Claude Code now reads AGENTS.md if no CLAUDE.md file exists in a project, configurable under “Project instructions” in /config
- New CLAUDE_GATEWAY_PROXY_IS_EGRESS_BOUNDARY environment variable enables gateway egress through forward proxies
- Fixed sessions hanging after internal errors and conversations failing with empty text block issues
- Improved Claude update command to handle invalid version lookups from proxies
- Write tool now reports clear errors instead of silently declining when target is a directory
- Background sessions are more stable, with fixes for LSP server exits and malformed configuration crashes