A study by Systima comparing Claude Code 2.1.207 and OpenCode 1.17.18 on identical tasks through the same Claude Sonnet 4.5 model found that Anthropic’s agent uses 4.7 times more overhead tokens per request — with the bulk of the difference coming from tool descriptions (24K tokens vs 4.8K). Even a minimal “OK” command triggered 27.3K characters of system instructions, 100K characters of tool schemas, and 8K of additional context from Claude Code, versus 9.3K and 20.9K respectively for OpenCode. On a file-summarisation task, Claude Code consumed ~199K input tokens across 6 requests, while OpenCode used ~41K across 4 — both completing the task correctly. The gap narrows when tools are disabled but widens significantly with sub-agents: a task using 121K tokens jumped to 513K with two sub-agents.

[Source: Systima comparison study]