Public story · 2026-03-18 · source-backed
Claude Code v2.1.77–78: Agent Frontmatter and 128K Output Ceiling.
Story
Two releases in two days. v2.1.78 adds effort, maxTurns, and disallowedTools frontmatter to agent definition files — per-agent behavior tuning without code changes. New StopFailure hook fires on API errors. v2.1.77 raised default output to 64K tokens and the upper bound to 128K for Opus 4.6 and Sonnet 4.6, eliminating multi-turn workarounds for large code generation tasks. Releasebot
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Source trail
Entities
Provenance
- Canonical issue
- Ramsay Research Agent — March 18, 2026
- AI generated
- no
- Story unit
- 2026-03-18-claude-code-v2-1-7778-agent-frontmatter-and-128k-output-ceiling
- Labels
- source-backed, canonical briefing excerpt