Use Claude Code with a custom API endpoint

Claude Code reads its endpoint from two environment variables. Set them once and every session routes through your own key — billed at whatever rate your provider charges.

In short: Claude Code reads ANTHROPIC_BASE_URL and ANTHROPIC_API_KEY from the environment. Set both in your shell profile, restart the terminal completely, and every session routes through your own key. Verify with one curl before trusting it with real work.

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Quick self-check. Before wiring anything into your app, confirm the key works. This lists every model your account can call — it costs nothing and works from any machine:

curl https://aicomp.ai/v1/models \
  -H "Authorization: Bearer sk-your-gateway-key"

You should get back a JSON list of model IDs. If you see Invalid token, the key is wrong or was not copied in full.

Step 1 — get your key and base URL

After signing up, open the dashboard and generate an API key. The dashboard also shows your API base URL. It looks like https://aicomp.ai/v1. You need both values.

Step 2 — set the environment variables

Add these to ~/.zshrc or ~/.bashrc:

export ANTHROPIC_BASE_URL="https://aicomp.ai/v1"
export ANTHROPIC_API_KEY="sk-your-gateway-key"

Then reload your shell:

source ~/.zshrc

If you would rather not touch your profile permanently, prefix a single session instead:

ANTHROPIC_BASE_URL="https://aicomp.ai/v1" \
ANTHROPIC_API_KEY="sk-your-gateway-key" \
claude

Step 3 — verify it actually works

Before you trust it with real work, confirm the endpoint responds:

curl https://aicomp.ai/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{"model":"claude-sonnet-5","max_tokens":64,
       "messages":[{"role":"user","content":"say OK"}]}'

A normal completion response means you are routing correctly.

Troubleshooting

Symptom	Cause
401 authentication error	Key is wrong, or belongs to a different account. Regenerate it.
404 on `/v1/messages`	Path doubling. If your base URL already ends in `/v1`, do not add it again.
Model not found	The gateway may use a slightly different model ID. Check its model list.
Still billed by Anthropic	The variable is not in the environment Claude Code actually reads. Restart the terminal completely.

Why bother

Claude Code is the single heaviest token consumer most developers run, because it resends accumulated context on every turn. Whatever your monthly bill is today, the per-token rate is the only lever that scales with it. See the Claude Code cost calculator for your own number.

What it costs

Claude models used with Claude Code — gateway rate vs official list
Model	Gateway rate in / out per 1M tokens	Official list in / out per 1M tokens	Diff
claude-haiku-4-5	$0.5 / $2.5	$1 / $5	50%
claude-sonnet-5	$1 / $5	$2 / $10	50%
claude-opus-5	$2.5 / $12.5	$5 / $25	50%

Rates checked 2026-09-16. Gateway rates move with upstream promotions — verify the current number in your dashboard before committing to a budget.

Model choice matters more here than anywhere else, because agent loops resend context on every turn. The full breakdown is in what Claude Code costs per month.

FAQ

Does Claude Code really work with a custom endpoint?

Yes. Claude Code reads ANTHROPIC_BASE_URL and ANTHROPIC_API_KEY from the environment, so setting those two variables routes every session through the endpoint you choose — no change to how you use the tool.

Which model should I point Claude Code at?

Sonnet-class is the default choice for agent work; Haiku-class is worth it for mechanical edits, and Opus-class for the hardest debugging. The spread between them is large enough to change your monthly bill by a factor of several — see the table above.

How much does it cost per month?

It is pure token spend, driven mostly by how much context each turn resends rather than by message count. See the dedicated breakdown in what Claude Code costs per month, or use the Claude Code cost calculator with your real session length.

Why am I still being billed by Anthropic?

The variables are not reaching the process. Export them from your shell profile and restart the terminal completely — a reloaded profile in an already-running shell is the usual cause.

Can I switch back?

Yes. Unset the two variables, or keep them in a separate profile file you source only when you want the alternate route. Nothing about your project changes.

Claude Sonnet 5 pricing — the usual default for agent coding
Claude Opus 5 pricing — for the hardest reasoning
Do the same in Cursor
Eight ways to cut the bill

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