switch guide · updated 2026-10-26

Switch from Braintrust to TokenZero in one line

Braintrust is an evaluation and logging platform with an AI proxy. TokenZero is a BYOK savings gateway: you keep evals and datasets; only the base URL in the proxy path changes, and every request comes back with a signed receipt for what it saved.

The change

OPENAI_BASE_URL=https://tokenzero.sh/w//v1
ANTHROPIC_BASE_URL=https://tokenzero.sh/w/
# provider keys stay in your code exactly as they are; nothing else changes

Create the workspace first:

curl -s -X POST https://tokenzero.sh/v1/signup -d '{}'   # workspace + key, no form
npx -y @tokenzero/cli init                                # or: audits the repo, writes .env

What differs from Braintrust

  • TokenZero's shadow-parity monitor is an in-production eval of cascade routing: a sample of routed requests is re-run on the original model and the pair is auto-disabled when parity drops.
  • Receipts, not logs: metadata only, signed.

What TokenZero does

  • Bring your own key. Provider keys pass through untouched; TokenZero never holds them.
  • Four engines. Prompt-cache formatting (Anthropic breakpoints, OpenAI prompt_cache_key / 12h retention), exact and semantic response cache, calibrated cascade routing with a shadow-parity breaker, and a signed savings ledger.
  • Measured, not claimed. Gateway overhead and the audit corpus are published on /benchmarks with the scripts that produced them.
  • Free up to $500/month of routed spend; paid plans are a share of verified savings with a 3x-ROI-or-$0 rule.

Verified, not reported

Every request through the gateway gets an Ed25519-signed receipt with list-price baseline, actual provider cost and the difference, chained per workspace (seq, prev_receipt_hash), verifiable offline with npx -y @tokenzero/cli verify --chain.

Questions

Can I evaluate TokenZero's routing with Braintrust?
Yes. Set X-TokenZero-Cascade: advise, read the recommendation header, and run your Braintrust eval on the recommended model before switching to auto.

Is there a migration tool?
No tool is needed: change the base URL (or the /w/<key>/ prefix) and keep your provider keys. Run npx -y @tokenzero/cli audit first to see what the gateway will act on.