Agent harnesses often waste tens of thousands of tokens before processing a single user prompt. A recent comparative benchmark between Claude Code and OpenCode shows that Claude Code injects around 33,000 tokens of system prompt, tool schemas, and scaffolding upfront, whereas OpenCode requires only 7,000 tokens for the exact same task.
The discrepancy becomes even more severe when looking at prompt cache mechanics. OpenCode keeps its request prefix byte-identical across runs, allowing it to pay for cache writes once per session. In contrast, Claude Code frequently invalidates its cache mid-session, resulting in up to 54 times more cache writes. Adding standard configuration files and Model Context Protocol servers can push baseline overhead past 80,000 tokens before execution begins.
Subagents compound this overhead exponentially. When a task is split between two subagents, baseline scaffolding is duplicated across both instances, driving token consumption from 121,000 tokens to over 513,000 tokens.
Efficient agent architecture requires treating context harnesses with the same cache discipline applied to database query engines.




