Auto-switch Claude Code model (opus/sonnet) based on remaining token usage

claude_model_switcher.py

#!/usr/bin/env python3
"""
claude_model_switcher.py — Auto-switch Claude Code model based on token usage.

Reads remaining tokens from Anthropic API, then writes the chosen model
("opus" or "sonnet") into ~/.claude/settings.json.

Logic:
  - Use opus  if  token_remaining% > 30  AND  token_remaining% >= time_remaining%
  - Otherwise use sonnet (to conserve tokens)

Usage:
  python claude_model_switcher.py          # switch and show result
  python claude_model_switcher.py --dry-run # show decision, don't write

Setup:
  Requires a valid ~/.claude/.credentials.json with a Claude Pro OAuth token.
"""

import json
import sys
import urllib.request
from datetime import datetime, timezone
from pathlib import Path

SETTINGS_FILE = Path.home() / ".claude" / "settings.json"
CREDENTIALS_FILE = Path.home() / ".claude" / ".credentials.json"


def fetch_usage() -> dict:
    token = json.loads(CREDENTIALS_FILE.read_text())["claudeAiOauth"]["accessToken"]
    req = urllib.request.Request(
        "https://api.anthropic.com/api/oauth/usage",
        headers={"Authorization": f"Bearer {token}", "anthropic-beta": "oauth-2025-04-20"},
    )
    with urllib.request.urlopen(req, timeout=10) as resp:
        return json.loads(resp.read())


def pick_model(data: dict) -> tuple[str, int, int]:
    token_rem = 100 - round(data["seven_day"]["utilization"])
    reset_at = datetime.fromisoformat(data["seven_day"]["resets_at"])
    remaining_sec = max(0, (reset_at - datetime.now(timezone.utc)).total_seconds())
    time_rem = round(remaining_sec / (7 * 24 * 3600) * 100)
    model = "opus" if token_rem > 30 and token_rem >= time_rem else "sonnet"
    return model, token_rem, time_rem


def set_model(model: str):
    settings = json.loads(SETTINGS_FILE.read_text()) if SETTINGS_FILE.exists() else {}
    settings["model"] = model
    SETTINGS_FILE.write_text(json.dumps(settings, indent=2, ensure_ascii=False))


def main():
    dry_run = "--dry-run" in sys.argv

    try:
        data = fetch_usage()
    except Exception as e:
        print(f"Error fetching usage: {e}", file=sys.stderr)
        sys.exit(1)

    model, token_rem, time_rem = pick_model(data)
    print(f"token remaining: {token_rem}%, time remaining: {time_rem}% -> {model}")

    if not dry_run:
        set_model(model)
        print(f"Written to {SETTINGS_FILE}: model = {model!r}")
    else:
        print("(dry-run, no changes written)")


if __name__ == "__main__":
    main()