TokenSave
TokenSave Data · Dataset
What Claude Code sends before you type: baseline tokens by version
Every Claude Code request starts with a fixed block of instructions and tool definitions. Between mid-2025 and May 2026 that block grew by 86%, from 19,498 tokens in 2025-07 to 36,309 in 2026-05, then came back down: version 2.1.306 sends 18,304 tokens before you type anything, half the peak. We installed 46 versions from npm and sent each the one-letter prompt “a”.
Measured 2026-10-21 · 46 versions, 2025-07 to 2026-10 · Claude Haiku 5.5 · License CC BY 4.0 · Related: Claude Code harness cost
DOI 10.5281/zenodo.23527278 · Also on Hugging Face · GitHub
Key findings
- Ten months of growth. Version 1.0.60 (2025-07-24) sent 19,498 tokens with the prompt “a”. By 2.1.150 (2026-05-23) it was 36,309 (+86%). Built-in tools went from 15 to 27 along the way: plan mode, task lists, scheduled tasks, worktrees and more.
- The biggest single change was a cut. Between 2.1.292 (2026-10-06) and 2.1.293 (2026-10-07) the baseline fell from 29,701 to 18,055 tokens (-39%), with the same number of tools. Today’s 18,304 is about where it was in mid-2025.
- Connected apps once came along in full. Apps connected to a claude.ai account (connectors) are also available in Claude Code. In versions 2.1.83 to 2.1.140 (2026-03-24 to 2026-05-12), all of their tools were sent with every request: with the 13 connected apps on our account that was 420–426 extra tools and about 395,332 tokens for the prompt “a”, roughly 11 times the baseline. 2.1.81 and earlier did not load them; by 2.1.145 they were loaded only when needed, and the baseline is now the same with them on or off.
- The numbers are exact and repeatable. Three runs of the same version gave the same count every time.
Baseline by version
Input tokens of the first model request (uncached + cache read + cache write) for the prompt “a”, Claude Haiku 5.5, MCP off. “With connectors on” is the same request with the 13 connected claude.ai apps of our account enabled (one run). Change is against the previous row.
| Version | Released | Baseline tokens | Change | Built-in tools | With connectors on |
|---|---|---|---|---|---|
| 1.0.60 | 2025-07-24 | 19,498 | 15 | 19,498 | |
| 1.0.70 | 2025-08-06 | 18,951 | -3% | 14 | 18,951 |
| 1.0.80 | 2025-08-13 | 19,744 | +4% | 16 | 19,744 |
| 1.0.90 | 2025-08-24 | 19,710 | ±0% | 16 | 19,710 |
| 1.0.120 | 2025-09-19 | 19,959 | +1% | 15 | 19,959 |
| 2.0.0 | 2025-09-29 | 19,420 | -3% | 15 | 19,420 |
| 2.0.25 | 2025-10-21 | 19,987 | +3% | 16 | 19,987 |
| 2.0.50 | 2025-11-21 | 21,340 | +7% | 16 | 21,340 |
| 2.0.70 | 2025-12-15 | 23,465 | +10% | 17 | 23,465 |
| 2.1.0 | 2026-01-07 | 23,957 | +2% | 17 | 23,957 |
| 2.1.25 | 2026-01-29 | 25,120 | +5% | 18 | 25,120 |
| 2.1.50 | 2026-02-20 | 26,491 | +5% | 18 | 26,491 |
| 2.1.75 | 2026-03-13 | 29,648 | +12% | 23 | 29,648 |
| 2.1.80 | 2026-03-19 | 30,066 | +1% | 23 | 30,066 |
| 2.1.81 | 2026-03-20 | 30,124 | ±0% | 23 | 30,124 |
| 2.1.83 | 2026-03-24 | 33,778 | +12% | 23 | 420,697 |
| 2.1.84 | 2026-03-25 | 33,421 | -1% | 23 | 391,137 |
| 2.1.85 | 2026-03-26 | 33,421 | ±0% | 23 | 391,137 |
| 2.1.89 | 2026-03-31 | 33,546 | ±0% | 23 | 391,774 |
| 2.1.92 | 2026-04-04 | 33,546 | ±0% | 23 | 391,788 |
| 2.1.96 | 2026-04-08 | 33,543 | ±0% | 23 | 391,785 |
| 2.1.100 | 2026-04-10 | 33,305 | -1% | 23 | 391,547 |
| 2.1.101 | 2026-04-10 | 34,857 | +5% | 24 | 394,102 |
| 2.1.126 | 2026-04-30 | 35,656 | +2% | 24 | 394,900 |
| 2.1.131 | 2026-05-06 | 35,703 | ±0% | 24 | 395,055 |
| 2.1.136 | 2026-05-08 | 35,744 | ±0% | 24 | 395,096 |
| 2.1.137 | 2026-05-09 | 35,744 | ±0% | 24 | 395,096 |
| 2.1.138 | 2026-05-09 | 35,744 | ±0% | 24 | 395,096 |
| 2.1.139 | 2026-05-11 | 35,941 | +1% | 24 | 395,293 |
| 2.1.140 | 2026-05-12 | 36,125 | +1% | 24 | 395,477 |
| 2.1.145 | 2026-05-19 | 36,262 | ±0% | 27 | 36,262 |
| 2.1.150 | 2026-05-23 | 36,309 | ±0% | 27 | 36,309 |
| 2.1.175 | 2026-06-12 | 31,348 | -14% | 28 | 31,348 |
| 2.1.200 | 2026-07-03 | 31,718 | +1% | 27 | 31,718 |
| 2.1.225 | 2026-08-07 | 31,851 | ±0% | 27 | 31,851 |
| 2.1.250 | 2026-08-27 | 28,451 | -11% | 28 | 28,451 |
| 2.1.275 | 2026-09-17 | 28,906 | +2% | 25 | 28,906 |
| 2.1.280 | 2026-09-22 | 28,890 | ±0% | 24 | 28,890 |
| 2.1.285 | 2026-09-29 | 29,331 | +2% | 24 | 29,331 |
| 2.1.290 | 2026-10-05 | 29,566 | +1% | 24 | 29,566 |
| 2.1.291 | 2026-10-06 | 29,566 | ±0% | 24 | 29,566 |
| 2.1.292 | 2026-10-06 | 29,701 | ±0% | 24 | 29,701 |
| 2.1.293 | 2026-10-07 | 18,055 | -39% | 24 | 18,055 |
| 2.1.294 | 2026-10-08 | 18,055 | ±0% | 24 | 18,055 |
| 2.1.295 | 2026-10-08 | 18,067 | ±0% | 24 | 18,067 |
| 2.1.306 | 2026-10-21 | 18,304 | +1% | 24 | 18,304 |
What to take from it
- The baseline is paid on every request, but after the first one it is usually read from the prompt cache at a tenth of the input price or less. It matters most for short sessions, subagents (each starts with its own copy) and after the cache expires (see our coffee-break measurement).
- If you used Claude Code between late March and May 2026 with many apps connected on claude.ai, sessions started with hundreds of thousands of tokens. Updating removes that cost.
- Your own number will be higher than ours: CLAUDE.md files, MCP servers, plugins, skills and hooks all add to it (see what the harness costs and CLAUDE.md size).
Method
- Each version was installed with
npm install @anthropic-ai/claude-code@<version>into its own folder on one Windows laptop and run asclaude -p "a" --model claude-haiku-5-5 --output-format stream-json --verbose, in an empty folder, with auto-update off and a fresh config folder holding only the login (no user settings, CLAUDE.md, plugins or skills). MCP was off (--strict-mcp-configwith an empty config,ENABLE_CLAUDEAI_MCP_SERVERS=false); the second set left our account’s claude.ai connectors on. - We count the usage of the first assistant message in the log, because some older versions made a second request for the same prompt and their final total counts both.
- Release dates are npm publish dates. Three runs per version with MCP off, one with connectors on, on 2026-10-21.
Limitations
- Versions 0.2.50, 0.2.100, 1.0.0, 1.0.30 would not install on Windows (early Claude Code required WSL), so the series starts in July 2025.
- One model (Haiku 5.5), one prompt, one machine. Tool definitions and the system prompt can differ by model, operating system and account features, so other setups will see other absolute numbers; the trend is what this shows.
- Old versions were run against today’s API and account. Features the server switches on per account may make an old version send more or less than it did at release.
- The connector numbers depend on how many apps are connected; ours had 13.
How to cite
Free to use, quote and republish with attribution under CC BY 4.0. Please link to this page.
TokenSave (2026). Claude Code baseline tokens by version: what every request carries before you type [Data set]. Zenodo. https://doi.org/10.5281/zenodo.23527278
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