Google GenAI SDK: cascade routing in one line
Prompts the deterministic classifier scores as simple are routed to the cheaper sibling of the model you asked for, inside the same provider, with a shadow-parity breaker. Here is the change for Google GenAI SDK, the switch that turns it on, and the arithmetic on gemini-3.8-flash.
Google GenAI SDK reaches TokenZero with one base-URL argument and keeps your gemini key. The cascade sibling of gemini-3.8-flash is gemini-3.5-flash-lite at $0.00135 per reference call against $0.00262; if every call were simple that is $128 a month on 100,000 calls, and a 99.8% parity floor with shadow evaluation decides whether a pair stays enabled.
· Source: pricing table 2026-10-26; overhead from the published benchmark on /benchmarks
At a glance
- Framework
- Google GenAI SDK (Python)
- Capability
- cascade routing
- Change
- client.py: base URL argument
- Request shape
- Gemini native generateContent
- Turn it on
- X-TokenZero-Cascade: auto
- Workspace setting
- cascade: auto, shadowEval: true
- Reference model
- gemini-3.8-flash ($0.75 in / $3.75 out per 1M, table 2026-10-26)
- Cascade saving if every simple call moves
- $128/month to gemini-3.5-flash-lite (computed)
- Gateway overhead (measured)
- 1.52 ms p50, 3.42 ms p95
- Parity floor
- 99.8%
- Free tier
- $500/month routed spend
Reference workload on gemini-3.8-flash: 2,000 input (1,500 static) / 300 output tokens, 100,000 calls per month, table 2026-10-26
| Scenario | Per call | Per month | Delta |
|---|---|---|---|
| List price, no gateway | $0.00262 | $263 | — |
| Static prefix cached (prompt compression) | $0.00161 | $161 | $101 (39%) |
| 20% exact-cache repeats | $0.00210 | $210 | $53 (20%) |
| All calls cascaded to gemini-3.5-flash-lite | $0.00135 | $135 | $128 (49%) |
| Budget guardrail at $500/month | — | capped at $500.00 | 402 after 190,476 calls |
The change
1. Point Google GenAI SDK at the gateway (client.py):
-client = genai.Client()
+client = genai.Client(http_options={"base_url": "https://tokenzero.sh"})
r = client.models.generate_content(model="gemini-3.8-flash", contents=prompt)The native /v1beta generateContent and streamGenerateContent paths are proxied; x-goog-api-key passes through.
2. Turn on cascade routing. Per request: X-TokenZero-Cascade: auto (default advise: the recommendation is returned in X-TokenZero-Cascade-Recommendation and nothing moves). Per workspace (applies to every call without touching code): PATCH /v1/workspaces/settings {cascade: auto, shadowEval: true} or the dashboard toggle.
3. Prove it. npx -y @tokenzero/cli doctor checks the gateway, the signer, the pricing table and your key; then watch routed share and parity per pair on the scorecard.
Questions people ask
How do I point Google GenAI SDK at TokenZero?
Pass base_url / baseURL = https://tokenzero.sh where Google GenAI SDK builds its client (client.py) and keep your gemini key; nothing else changes.
What does cascade routing save on gemini-3.8-flash?
The cascade sibling of gemini-3.8-flash is gemini-3.5-flash-lite at $0.00135 per reference call against $0.00262; if every call were simple that is $128 a month on 100,000 calls, and a 99.8% parity floor with shadow evaluation decides whether a pair stays enabled.
Does cascade routing change the model's output?
Only when a prompt is scored simple and the pair is above the 99.8% parity floor; shadow evaluation re-runs a sample on the original model, and a pair that drops below the floor is auto-disabled. Everything else goes to the model you asked for.
What does TokenZero cost?
Free up to $500 per month of routed spend; then 15% of verified savings with a 3x-ROI-or-$0 rule, capped plans available. Gateway overhead measured at 1.52 ms p50.