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Head to head · LLM inference · October 2026 research run

Gemini 4 Carbon vs Gemini 4 Hydrogen

Gemini 4 Hydrogen scores 64.9 (B) on agent readiness against Gemini 4 Carbon's 63.9 (B), and leads in 3 of 7 scored categories. Gemini 4 Carbon leads on security & auth. Both do llm inference.

Best model APIs and inference for AI agents · All 1044 models comparisons

Gemini 4 CarbonGoogle · Model API B63.9/100#599 of 1524 Gemini 4 HydrogenGoogle · Model API B64.9/100#546 of 1524

Which one, for what

Gemini 4 Carbon B

Best for Agents on the hardest long tasks (multi-step debugging, large codebases, open-ended research, security work) that can pay frontier prices and already use the Gemini API.

Ahead on

  • Security & auth, 55 against 50

Watch for

Paid tier only, with no free tier to try it on

Gemini 4 Hydrogen B

Best for Agents doing everyday coding, tool calls and document work at volume on the Gemini API, including ones that need to start on a free key, or as the executor beside Carbon or Argon.

Ahead on

  • Reliability, 45 against 40
  • Payments & pricing, 40 against 30

Watch for

temperature, top_p and top_k are ignored, and thinking_budget, MINIMAL, penalties and extra candidates return a 400

Why the edge

Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.

Payments & pricing Gemini 4 Hydrogen +10

Gemini 4 Carbon 30

Model reading for gemini-4-carbon on the Gemini API. Platform facts are the Gemini API listing's (gemini-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. No machine payment protocol (0). Introductory prices published in Google's 28 October announcement without a login, $2 and $10, then $4 and $20; the Gemini API pricing page as read on 10 November showed no Carbon row, so the figures rest on the announcement (20). No free tier: Google's developer post puts Carbon on the paid tier (0). A Google account and AI Studio for a key (0). 0 + 20 + 0 + 0 = 20. Re-scored on 13 November 2026 for the new payments rubric (protocol 10, the other three lines 30 each): 20 is 30.

Gemini 4 Hydrogen 40

Model reading for gemini-4-hydrogen on the Gemini API. Platform facts are the Gemini API listing's (gemini-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. No machine payment protocol (0). Prices published in Google's announcement without a login, $1.50 input and $7.50 output per million tokens, flat across the window; the Gemini API pricing page, now at aistudio.google.com, is still to be read for Hydrogen's row (20). A free tier with no card: Google's announcement puts Hydrogen on all tiers of the Gemini API, and the free tier needs no billing account per the gemini-api listing; its limits for Hydrogen are on that pricing page (20). A Google account and AI Studio for a key (0). 0 + 20 + 20 + 0 = 40.

Reliability Gemini 4 Hydrogen +5

Gemini 4 Carbon 40

Model reading for gemini-4-carbon on the Gemini API. Platform facts are the Gemini API listing's (gemini-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. Status page at aistudio.google.com/status with no readable components or history (10 of 20) and no readable incident record (5 of 30). Rate-limit tiers and spend limits published, per-model limits in AI Studio (5 of 15). Backoff guidance for 429 and 503 and SDK retries (15). No SLA (0). Carbon's launch stage isn't stated in Google's developer post, the Antigravity post or the Cloud developer guide read on 10 November, and the model ID carries no preview label, so half (5 of 10, a judgement call; Argon's GA earned the platform 10). 10 + 5 + 5 + 15 + 0 + 5 = 40.

Gemini 4 Hydrogen 45

Model reading for gemini-4-hydrogen on the Gemini API. Platform facts are the Gemini API listing's (gemini-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. Status page at aistudio.google.com/status with no readable components or history (10 of 20) and no readable incident record (5 of 30). Rate-limit tiers and spend limits published, per-model limits in AI Studio (5 of 15). Backoff guidance for 429 and 503 and SDK retries (15). No SLA (0). Google Cloud's release notes and model page call Hydrogen generally available, a short-term release, under the same model ID; the Gemini API pages read don't name a stage, so full marks rest on Cloud's statement (10, a judgement call; Carbon, with no stage stated anywhere, got 5). 10 + 5 + 5 + 15 + 0 + 10 = 45.

Security & auth Gemini 4 Carbon +5

Gemini 4 Carbon 55

Model reading for gemini-4-carbon on the Gemini API. Platform facts are the Gemini API listing's (gemini-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. Keys bound to a service account and restricted to the Gemini API, with no scopes and a token accepted in the URL (15 of 30, the platform's deduction). Carbon is on the paid tier only, and Google's terms say paid-tier content isn't used to improve products; AI Studio use under a Google AI Ultra subscription falls under terms we didn't read, so 15 of 20 (a judgement call; the platform's 10 is for its free tier). Abuse retention with no number, and new paid projects store requests by default since 26 October (5 of 15). Request logs for billed projects (15). security.txt and a reward programme, no certification naming the API (5 of 20). 15 + 15 + 5 + 15 + 5 = 55.

Gemini 4 Hydrogen 50

Model reading for gemini-4-hydrogen on the Gemini API. Platform facts are the Gemini API listing's (gemini-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. Keys bound to a service account and restricted to the Gemini API, with no scopes and a token accepted in the URL (15 of 30, the platform's deduction). Hydrogen is on the free tier, where Google's terms say content is used to improve products and may be read by humans; paid-tier content isn't (10 of 20, the platform's reading; Carbon, paid tier only, got 15). Abuse retention has no number and new paid projects store requests by default since 26 October; Google's prompt-injection figure (2.3 times more resilient on Gray Swan's benchmark) is its own, and the model card says jailbreak resistance is still being improved (5 of 15). Request logs for billed projects (15). security.txt and a reward programme, no certification naming the API (5 of 20). 15 + 10 + 5 + 15 + 5 = 50.

Score by category

CategoryWeight this runGemini 4 CarbonGemini 4 HydrogenEdge
Reliability16%204045Gemini 4 Hydrogen +5
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28585even
Agent ergonomics13%16.29390Gemini 4 Carbon +3
Security & auth14%17.55550Gemini 4 Carbon +5
Payments & pricing10%12.53040Gemini 4 Hydrogen +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88385Gemini 4 Hydrogen +2
Transparency & trust7%8.87272even
Negative events≤1500
TotalB 63.9/100B 64.9/100

Facts side by side

FactGemini 4 CarbonGemini 4 Hydrogen
KindModel APIModel API
VendorGoogleGoogle
Hosted endpointhttps://generativelanguage.googleapis.com/v1betahttps://generativelanguage.googleapis.com/v1beta
Transports
AuthAPI keyAPI key
PricingPay per usePay per use
x402nono
LicenceClosed model, used through the Gemini API and Google's apps under Google's termsClosed model, used through the Gemini API and Google's apps under Google's terms
Read-only variant documentednono
llms.txtyesyes
Last release2026-11-102026-11-12
Terms last updated2026-04-282026-04-28
Privacy policy last updated2026-10-012026-10-01
Customer content may train modelsyesyes
Terms restrict automated accessyesyes
Terms restrict benchmarkingyesyes
Terms or service can change without noticenot found in the textnot found in the text
Arbitration or class-action waivernot found in the textnot found in the text

How the scores have moved

Gemini 4 Carbon

Gemini 4 Hydrogen

No score change since it was listed.

Verdicts

Gemini 4 Carbon

Google's strongest model on the same Gemini API as Argon, with a 1M-token budget, function calling and structured output, at an introductory $2 and $10 per million tokens. Paid tier only, sampling parameters are ignored or refused, its launch stage isn't stated, and the price rises to $4 and $20 at a date Google hasn't given.

Gemini 4 Hydrogen

Google's fast Gemini 4 model, on every tier of the Gemini API including the free one, at $1.50 and $7.50 per million tokens with a 1M-token budget, four thinking levels, function calling and structured output. Sampling parameters are ignored, explicit caching isn't supported, it's a short-term release with 45 days' notice on Cloud, and the benchmarks are Google's.

Before you call either

Gemini 4 Carbon

  1. Call generateContent at https://generativelanguage.googleapis.com/v1beta with model gemini-4-carbon and an x-goog-api-key on a billed project
  2. Set thinking_level (LOW, MEDIUM or HIGH) instead of thinking_budget, and don't send temperature, top_p or top_k
  3. Count output against the same 1,048,576-token limit as the input, and set max_output_tokens for long answers
  4. Put static prompt content first so implicit caching applies; explicit caches aren't supported
  5. Use gemini-4-argon for most coding and knowledge work, and Carbon for the hardest long tasks, as Google suggests

Gemini 4 Hydrogen

  1. Call generateContent at https://generativelanguage.googleapis.com/v1beta with model gemini-4-hydrogen and an x-goog-api-key
  2. Set thinking_level instead of thinking_budget; the default is HIGH, so set MEDIUM to keep 3.8 Flash's latency
  3. Don't send temperature, top_p, top_k, penalties or candidate_count above 1
  4. Pass every thought_signature back in its original part, on the first parallel functionCall only, or the call returns a 400
  5. Put static content of 4,096 tokens or more first so implicit caching applies, and keep confidential prompts off the free tier

Questions

Which is better for AI agents, Gemini 4 Carbon or Gemini 4 Hydrogen?

Gemini 4 Hydrogen scores 64.9 (B) on agent readiness against Gemini 4 Carbon's 63.9 (B), and leads in 3 of 7 scored categories. Gemini 4 Carbon leads on security & auth.

Do Gemini 4 Carbon and Gemini 4 Hydrogen need an API key?

Both need an API key.

Can an agent call Gemini 4 Carbon and Gemini 4 Hydrogen without installing anything?

Yes. Gemini 4 Carbon has a hosted endpoint at https://generativelanguage.googleapis.com/v1beta and Gemini 4 Hydrogen at https://generativelanguage.googleapis.com/v1beta.

Other comparisons with Gemini 4 Carbon or Gemini 4 Hydrogen

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