Claude API “credit balance is too low” / 402 insufficient_quota — the fix

Confirm it's balance, not auth

401 = key problem; 400 "credit balance too low" / 402 insufficient_quota = money problem. Don't rotate keys for a billing error — the new key reads the same empty wallet.

Top up, then verify with one cheap call

Balances apply immediately on both Anthropic and Kunavo — no redeploy needed. Verify with a minimal request before unpausing your workers:

curl -s https://api.kunavo.com/v1/chat/completions \
  -H "Authorization: Bearer $KUNAVO_API_KEY" \
  -H "content-type: application/json" \
  -d '{"model":"claude-haiku-4-5","max_tokens":8,"messages":[{"role":"user","content":"ok?"}]}'

Seeing it in Claude Code?

Claude Code prints this message when it runs on an Anthropic API key whose Console balance is empty — a Pro or Max login runs into usage limits instead and never shows it. Top up the Console, or keep working on a pay-as-you-go endpoint: Claude Code reads ANTHROPIC_BASE_URL natively, so the switch is a few environment variables. Keep the four model lines — Claude Code's default and its opus and sonnet aliases follow Anthropic's newest models, and the sonnet alias asks for Sonnet 5.5, which Kunavo does not serve.

export ANTHROPIC_BASE_URL=https://api.kunavo.com
export ANTHROPIC_AUTH_TOKEN=sk-kn-...
export ANTHROPIC_MODEL=claude-sonnet-5
export ANTHROPIC_DEFAULT_OPUS_MODEL=claude-opus-5-5
export ANTHROPIC_DEFAULT_SONNET_MODEL=claude-sonnet-5
export ANTHROPIC_DEFAULT_HAIKU_MODEL=claude-haiku-4-5

Make the next one boring

Set a low-balance alert (email) and, if your provider supports it, auto-reload with a sane monthly cap. Fail-closed billing is correct — you just want the warning before the wall, not the wall.

On Kunavo: read the 402, or let it top itself up

A Kunavo wallet 402 says so in machine-readable form: error.code is insufficient_balance, error.balance_usd and error.needed_usd give the gap, and error.topup_url and error.auto_recharge_url open the billing page with the fix preselected — neither link charges anything. With optional auto-recharge on, the wallet tops itself up by an amount you choose, from $10 and within a monthly cap you set, whenever it falls below your threshold, so a request that would have been refused is served instead — as long as the charge goes through and the cap has room. While such a top-up is still in flight the 402 carries Retry-After: retry after it, and stop retrying on a 402 without it.

I topped up — why am I still getting the error?

Check you funded the same account/workspace that minted the key, and that a monthly spend cap isn't the real blocker. Balance application itself is immediate on both Anthropic and Kunavo.

Does Claude's API have a free tier?

No — Anthropic bills every API call from the first token (Claude.ai consumer plans are separate from API credit). Gateways are also pay-as-you-go; Kunavo starts at a $10 top-up with rates under list.

“Credit balance is too low” in Claude Code — but I pay for Pro. Why?

Because Claude Code is using an API key, not your subscription. While ANTHROPIC_API_KEY or ANTHROPIC_AUTH_TOKEN is set, Claude Code bills the key and parks the Pro or Max login, and that key draws on a separate prepaid Console balance. Run /status to see which credential is live; unset the variable to go back to the plan, or top up the key's balance.

OpenClaw says “API provider returned a billing error” — is that the same thing?

Yes. That is OpenClaw's wording for a billing refusal from the model provider: the API key has run out of credits or has an insufficient balance. Top up that provider, or switch OpenClaw to a different one — the related guides below compare the options.