Claude Code v2.1.172–v2.1.173: Nested Sub-Agents Up to 5 Levels Deep
Anthropic
Two releases landed on June 10–11. v2.1.172 enables sub-agents to spawn their own sub-agents up to 5 levels deep, adds a marketplace plugin search bar, exposes a model attribute on OTEL lines-of-code metrics, and fixes multiple bugs (1M-context sessions stuck on usage credits, repeated image-processing errors, agents-view UI lag, background sub-agents staying stuck as active). Amazon Bedrock now reads AWS region from ~/.aws config when AWS_REGION is unset. v2.1.173 strips the [1m] suffix from Fable 5 model names automatically and fixes a spurious 'sandbox dependencies missing' startup warning on Windows.
Why it matters
Recursive sub-agent spawning up to 5 levels is a meaningful architectural upgrade for complex agentic workflows. Fable 5 name normalization removes friction for teams upgrading to the new model family.
Importance: 3/5
Notable Claude Code release; recursive sub-agent spawning is a significant agentic capability addition; follows v2.1.170 from June 9.