I am still a bit surprised that this is not more widely used. Normal inference + tool calls is effectively composition via serialized natural language, whereas Code Mode / Programmatic Tool Calling is using purpose built languages (aka programming languages) for composition and concurrency. It somewhat feels obvious to me that the latter is way more token and latency efficient.
> The one-line takeaway
> This already ships by default in every claude/codex/opencode session's system prompt