Coding agents re-send their instruction files with every turn. turntax measures that fixed per-turn cost for a repository, per tool and per model, and shows where to cut it.

npx turntax

It reads the files each agent actually loads (CLAUDE.md, AGENTS.md, GEMINI.md, .cursor/rules, .github/copilot-instructions.md, Windsurf rules, skills) and applies each tool's documented loading rules: what is sent on every turn, what loads only when the agent works in a folder or touches a matching file, and what is ignored.

tool          always  o200k/turn  on-demand  model              tokens/turn  counted by                                100 turns  cached
Claude Code   4       272         53         Claude Sonnet 5.5  -            needs --claude-api and ANTHROPIC_API_KEY  -          -
OpenAI Codex  1       63          0          GPT-6.1 Sol        63           estimate (o200k_base proxy)               $0.01      $0.0006
Cursor        4       297         37         Claude Sonnet 5.5  -            needs --claude-api and ANTHROPIC_API_KEY  -          -
                                             GPT-6.1 Sol        297          estimate (o200k_base proxy)               $0.06      $0.0030

Advice (savings are estimates in o200k tokens per turn)
  HIGH duplicate CLAUDE.md, AGENTS.md [saves ~48 tokens/turn]
    3 identical lines are loaded twice every turn by cursor. Keep them in one file.
  HIGH contradiction AGENTS.md, CLAUDE.md [saves ~11 tokens/turn]
    Conflicting package manager: "Always use npm ..." (AGENTS.md:3) vs "Always use pnpm ..." (CLAUDE.md:5).
  MEDIUM scopable-section CLAUDE.md:11 [saves ~128 tokens/turn]
    Section "API package" is mostly about packages/api/. Move it to packages/api/AGENTS.md ...

(Output for test/fixtures/mixed.)

What it counts, and how

Model family	How tokens are counted	Label
OpenAI GPT-5.x, gpt-oss	Offline with `o200k_base` (the encoding OpenAI's tiktoken maps them to)	exact
OpenAI GPT-6.x	Offline with `o200k_base`; OpenAI has not published a newer encoding	estimate
Claude	Only Anthropic's `count_tokens` API, with your key and `--claude-api`	API count
Gemini	Only Google's `countTokens` API, with your key and `--gemini-api`	API count

Claude's tokenizer is not public, and Anthropic's docs note that newer Claude models produce noticeably more tokens than older ones for the same text. turntax never shows an OpenAI count as a Claude or Gemini number: without a key those rows say "needs API key". The o200k column is a labelled reference count for every file.

Cost per N turns = tokens per turn × N × input price. The "cached" column assumes every turn reads the context from the prompt cache. Prices come from a dated table with a source link per model (turntax --list-models); pass --prices my-prices.json to use your own.

See docs/how-it-counts.md for the loading rules per tool and their sources.

Advice

All checks are deterministic. Each one shows an estimated saving in o200k tokens per turn.

duplicate: identical lines in two files. A per-turn saving only when one tool loads both; otherwise flagged as drift risk.
contradiction: conflicting rules reaching the same agent (package manager, indentation, quotes, semicolons).
scopable-section: a section mostly about one directory that could load only there (nested file, path-scoped rule, applyTo).
oversized-section: a large always-loaded section that could become an on-demand skill.
size-limit: documented limits (CLAUDE.md under 200 lines, Codex's 32 KiB cut-off, Windsurf's 12,000 characters, Cursor's 500 lines).
misconfigured: files a tool ignores, such as .md files in .cursor/rules or Windsurf rules without a trigger.
stale-reference: referenced files or npm run scripts that no longer exist.
non-english: non-English sections. The token multiplier is measured only against an English version you supply (--english CLAUDE.md=CLAUDE.en.md) or, if you opt in, a Claude translation (--translate).

Options

turntax [path]
  --tools claude-code,codex,gemini-cli,cursor,copilot,windsurf
  --models <ids>            see --list-models (default: claude-sonnet-5.5, gpt-6.1-sol, gemini-3.8-flash)
  --turns <n>               cost projection (default 100)
  --json | --md | --badge   output format (default: terminal table)
  --out <file>              write the output to a file
  --max-tokens <n>          exit 1 when any tool loads more than n o200k tokens per turn (CI gate)
  --claude-api              exact Claude counts (ANTHROPIC_API_KEY)
  --gemini-api              Gemini counts (GEMINI_API_KEY)
  --english <file=en>       measure a language multiplier against your English version
  --translate               opt-in Claude translation for that measurement (needs --claude-api)
  --prices <file.json>      your own price table
  --section-tokens <n>      threshold for oversized sections (default 600)

Privacy

Offline by default: no network calls, no telemetry. File contents are sent only when you pass --claude-api, --gemini-api or --translate, and only to that vendor's API. Keys are read from environment variables and sent only in request headers.

Web page

web/ is a static page that runs the same engine in the browser with the offline tokenizer only. Drop a repository folder or paste files; nothing is uploaded.

Try it: https://torutdev.github.io/turntax/

npm run build:web

Badge

npx turntax --badge

The badge shows the largest always-loaded total among the tools found, counted with o200k_base.

Limits

Assumes the agent starts at the repository root. Files outside the repository (user-level ~/.claude/CLAUDE.md, global rules, team rules in a dashboard) are not counted.
Counts instruction files only, not the agent's own system prompt, tool definitions or MCP servers.
Loading rules change. Each rule cites the vendor page and the date it was checked; please open an issue when one is out of date.