Claude Code v2.1.277 reads AGENTS.md when a project has no CLAUDE.md

Archive entry: this covers an event from September 18, 2026, and we published it on November 8, 2026. The details come from sources dated at the time and may have changed since.

On September 18, 2026, Anthropic released Claude Code v2.1.277, as recorded in the v2.1.277 release notes on GitHub. The version added support for AGENTS.md project instruction files, which Claude Code reads when a project has no CLAUDE.md. The same release removed the deprecated TaskOutput tool.

What changed in v2.1.277

• The AGENTS.md behavior can be changed under 'Project instructions' in /config.
• At release, AGENTS.md support was not available on Bedrock, Vertex or Foundry.
• The deprecated TaskOutput tool was removed. Claude reads a background task's output file with the Read tool instead.
• The taskOutputMaxChars setting and TASK_MAX_OUTPUT_LENGTH stopped having any effect.
• The background Haiku auto-title request was removed from claude -p runs launched outside an SDK or IDE.

What it means for people who build with AI

Repositories that already keep agent instructions in AGENTS.md for other coding tools work in Claude Code without a duplicate CLAUDE.md. Teams on Bedrock, Vertex or Foundry should note that the AGENTS.md fallback was not available on those platforms at release. Configurations that set taskOutputMaxChars or TASK_MAX_OUTPUT_LENGTH could be cleaned up, since neither had any effect after this release.

Sources

• Release v2.1.277 · anthropics/claude-code · GitHub (Anthropic (GitHub), September 18, 2026, official)

Written with AI assistance, strictly from the sources listed above. Before it went live, automated checks verified its dates, sources and every language edition.