Cursor reduced token costs by 7% with no drop in agent quality, through tighter prompts, selective tool loading, better caching, and reading fewer line numbers when scanning files.
Cursor announced on September 23 that changes across its agent harness cut token costs by 7% with no drop in agent quality. The system prompt and tool definitions, sent every turn, were among the biggest controllable costs, so tightening them cut cold cache misses by 20%.
Another fix targeted file reads: instead of numbering every line, the agent now numbers only every tenth, still enough to cite code accurately, cutting cache-read tokens by 1.6%. Longer agent runs also delegate more work to subagents that start with fresh context windows.
Key Capabilities:
- Trimmed context: Tighter system prompts and selective tool loading cut cold cache misses by 20%.
- Smarter file reads: Numbering only every tenth line cut cache-read tokens by 1.6%.
- No quality trade-off: All changes were validated to preserve agent output quality.