A new side-by-side measurement shows Claude Code ships roughly 33,000 tokens of system prompt, tool schemas, and scaffolding before your prompt even arrives — about 4.7x the ~7,000 tokens OpenCode sends on the same setup. The bigger cost surprise is next: Claude Code re-wrote up to 54x more prompt-cache tokens per session, and cache writes bill at a premium.
How the test was run
The benchmark (published by Systima) spliced a logging proxy between each harness and the model endpoint, capturing the exact request payload and the API's usage block. Both harnesses were pinned to the same conditions:
Claude Code 2.1.207 and OpenCode 1.17.18, both pointed at claude-sonnet-4-5
Fresh config directories, empty workspace, no MCP servers, no instruction files, permissions bypassed
