Claude Code v2.1.277 Adds AGENTS.md Support and Fixes Crash Bugs

Claude Code v2.1.277 landed with a small set of feature additions and a long list of bug fixes across sessions, tools, and gateway handling. Here's what actually changed.

AGENTS.md support

In a project with no CLAUDE.md, Claude Code now reads AGENTS.md instead. You can switch it under "Project instructions" in /config. Not yet available on Bedrock, Vertex, or Foundry.

Gateway and proxy changes

• CLAUDE_GATEWAY_PROXY_IS_EGRESS_BOUNDARY=1 for Claude apps gateways whose only egress is a forward proxy: every outbound request hands the proxy the hostname instead of resolving it locally.
• Optional headers: map on Claude apps gateway upstreams to send static headers to a proxy you run in front of a provider.
• A line now notes that a background task's update is waiting when it finishes while a panel such as /tasks is open.

Session and CLI fixes

• claude -p and Agent SDK sessions that could hang with no result after an internal error now report the error and exit with code 1.
• Conversations failing every request with "text content blocks must be non-empty" when an earlier assistant turn held an empty text block beside other content, including after --resume.
• Unexpected logout when an older Claude Code build (e.g., an IDE extension's bundled CLI) runs on the same machine as the current one.
• Interactive start-up hanging or erroring for ANTHROPIC_API_KEY users when ~/.claude.json holds a malformed customApiKeyResponses value.
• Update checks erroring every 30 minutes, and claude update hanging when a min/max version is set, if a proxy returns an invalid version. A malformed minimumVersion is now ignored.
• claude update on winget- or apk-managed installs reporting "up to date" when the version lookup failed.
• claude plugin install sometimes failing and breaking the installed copy when reinstalling a plugin version in use; an unchanged copy is now left alone.

Tool fixes (Grep, Glob, Write, Edit)

• Grep and Glob now return an error when the search could not start due to out of processes, memory, or file handles, instead of reporting no matches.
• Write no longer silently ends the turn as a declined permission when the target path is an existing directory.
• Edit no longer treats an escaped backslash followed by uXXXX as a \uXXXX escape, which could rewrite an escaped backslash sequence when editing non-ASCII characters.
• Edit reports "String not found in file" instead of "Invalid regular expression: regular expression too large" for very large non-ASCII edits that don't match.
• Turns no longer end early with "Path contains null bytes" when a tool call's file path contains \u0000 written as an escape sequence.

Stability fixes

• Background sessions (claude --bg) no longer exit when a plugin's LSP server exits or closes stdin.
• Crashes from malformed claudeAiMcpEverConnected, theme, or a plain-string assistant message in saved history.
• Crash ("unrecoverable interface error") when the prompt contained terminal color codes.
• Sessions on slow machines exiting when the first spinner appeared.
• Rare screen freeze after an internal rendering error.
• Windows turns stopping with "Out of memory" right after a reply, leaving tool calls unrun.
• Sessions continued after /clear (restart, --continue, --resume) missing part of the first message when a SessionStart hook printed output, causing a full prompt-cache miss.

If you run Claude Code behind a proxy or use plugins with LSP servers, this release is worth pulling.