Head to head · LLM inference · October 2026 research run

Gemini 4 Hydrogen vs StepFun API

Gemini 4 Hydrogen scores 64.9 (B) on agent readiness against StepFun API's 45.6 (E), and leads in every scored category. Both do llm inference.

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

Which one, for what

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 28
  • Schema & documentation, 85 against 53
  • Agent ergonomics, 90 against 68
  • Security & auth, 50 against 41
  • Payments & pricing, 40 against 30
  • Maintenance & community, 85 against 50
  • Transparency & trust, 72 against 57

Watch for

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

StepFun API E

Best for Long-context agent and coding work over text, screenshots and video at a low per-token price, where a preview model is acceptable.

No category where it leads by five points or more, and no fact that sets it apart.

Watch for

Step 5 Preview is labelled a preview, and no release date or support commitment was found

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.

Maintenance & community Gemini 4 Hydrogen +35

Gemini 4 Hydrogen 85

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. Released on 12 November 2026, recorded in Google Cloud's release notes; the Gemini API changelog, last updated 30 October, has no entry for it yet (30). Google Cloud states a minimum of 45 days' notice before Hydrogen is retired, short and stated for Cloud only; the Gemini API's deprecations give earliest dates with no stated minimum (6 of 12). Shutdowns in the last 90 days kept to their table (4 of 8). Dated changelog (15). SDK replies not sampled (5 of 10). Current SDKs; the developer guide names the minimum google-genai, @google/genai, Go and Java versions (15). Runtimes stated (10). 30 + 6 + 4 + 15 + 5 + 15 + 10 = 85.

StepFun API 50

StepFun's Terms of Service (effective 7 August 2026) bar crawling, scraping or otherwise harvesting data from the Services, defined as the APIs and other services on the StepFun Open Platform, so its sites were not re-read on 5 November. Per the 12 October check, not re-read on 5 November. Model reading. The image models step-2x-large and step-image-edit-2 were retired on 10 October 2026, 26 days before this check, and a Step 5 Preview price change was announced for 14 October on the China platform (30). No stated notice period. The 10 October image retirement had a dated notice page and the July retirements a migration table, but we couldn't date when either notice went up (4 of 12). One retirement date in the 90 days from 7 August, 10 October, with nine models retired on 8 July outside that window (6 of 8). Dated announcements, a Discord server and platform@stepfun.com for support. We didn't test whether either answers (10 of 15). No official SDK (0 of 15, 0 of 10). 30+4+6+10+0+0 = 50.

Schema & documentation Gemini 4 Hydrogen +32

Gemini 4 Hydrogen 85

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. Discovery document for GenerateContent (20 of 25). llms.txt with Markdown twins (10). The Cloud developer guide says what Hydrogen takes, every parameter that's ignored or returns 400, the thought-signature rules and how to migrate from Gemini 3.8 Flash, though it doesn't document forced calls (15 of 20). Structured output to a JSON Schema with some keywords not enforced (10 of 15). Examples and an errors page (15). Dated changelog and model versions (15). 20 + 10 + 15 + 10 + 15 + 15 = 85.

StepFun API 53

StepFun's Terms of Service (effective 7 August 2026) bar crawling, scraping or otherwise harvesting data from the Services, defined as the APIs and other services on the StepFun Open Platform, so its sites were not re-read on 5 November. Per the 12 October check, not re-read on 5 November. No OpenAPI or similar machine-readable contract found. The API reference is Markdown pages (0). llms.txt at platform.stepfun.ai/docs/llms.txt, and every page has a Markdown copy (10). The Chat Completions reference describes each parameter with its default, and the model page lists what Step 5 Preview supports, but little on when not to use an option (12 of 20). Tool definitions take JSON Schema parameters, structured output takes a JSON Schema with strict: true, and reasoning_effort is an enum of low, medium and high. No tool_choice parameter is documented (11 of 15). Worked requests and responses on each page, and an error table of eight codes with causes and fixes, but no error bodies (12 of 15). No API changelog. A model lifecycle page with dated retirements and announcement pages (8 of 15). 0+10+12+11+12+8 = 53.

Agent ergonomics Gemini 4 Hydrogen +22

Gemini 4 Hydrogen 90

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. Function calling, with forced calls by FunctionCallingConfig on the API (20). Structured output to a response_schema, listed as supported on the Cloud model page (13 of 15). Implicit caching on prefixes of 4,096 tokens or more with durable caching on by default and explicit caches not supported, per the Cloud model page; the announcement names no cached-input price (12 of 15). 1,048,576 tokens shared between input and output, with background long decode up to 1M (15). Batch at half price on the platform (10). Python and JavaScript SDKs, and an OpenAI-compatible Chat Completions surface (10). Error codes with backoff guidance (10 of 15). 20 + 13 + 12 + 15 + 10 + 10 + 10 = 90.

StepFun API 68

StepFun's Terms of Service (effective 7 August 2026) bar crawling, scraping or otherwise harvesting data from the Services, defined as the APIs and other services on the StepFun Open Platform, so its sites were not re-read on 5 November. Per the 12 October check, not re-read on 5 November. Model reading of the checklist (tool use, structured output, caching, context, batch, SDKs, errors). Tool calls through Chat Completions, Responses and Messages, with no documented way to force or forbid a call (15 of 20). Strict JSON Schema output on Step 5 Preview (13 of 15). Prompt caching with a published cache-hit price at a tenth of the miss price (15). 1M-token context and 64k output (15). No batch endpoint found (0). No official SDK. The docs use the OpenAI and Anthropic clients against compatible endpoints (0). Eight error codes with a fix each, plus finish_reason handling for length, content filter and tool calls (10 of 15). 15+13+15+15+0+0+10 = 68.

Reliability Gemini 4 Hydrogen +17

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.

StepFun API 28

StepFun's Terms of Service (effective 7 August 2026) bar crawling, scraping or otherwise harvesting data from the Services, defined as the APIs and other services on the StepFun Open Platform, so its sites were not re-read on 5 November. Per the 12 October check, not re-read on 5 November. No status page read. status.stepfun.ai refused our reader by robots.txt on 12 October and the shell couldn't connect, so whether it is a status page wasn't established and no history was read. Scored absent for both lines, with 5 for unreadable history (0 + 5). Rate limits published with numbers per tier, from 5 concurrent, 100 RPM and 500,000 TPM to 130, 2,600 and 13,000,000 (15). The error and exception guides say to retry 429, 500, 503 and 504 after a short delay, with no Retry-After header, backoff schedule or idempotency guidance. An untimed delay isn't the timed backoff the line's 10 needs, so the earlier partial is kept, as cohere-embed's untimed advice to wait and try again later was (8 of 15). No SLA found in the terms or pricing (0). Step 5 Preview is labelled a preview (0). 0+5+15+8+0+0 = 28.

Transparency & trust Gemini 4 Hydrogen +15

Gemini 4 Hydrogen 72

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. Closed service with clear terms, SDKs Apache-2.0 (15). Free-tier content is used to improve products, paid-tier content isn't, abuse retention has no number, and request storage is on by default for new paid projects; the statements agree with each other (20 of 30). Deprecations table, and a stated 45-day minimum on Cloud (15 of 20). Data may be cached anywhere Google has facilities; no subprocessor list checked (5 of 20). A DeepMind model card gives a March 2026 knowledge cutoff, automated safety results and Frontier Safety Framework outcomes, with the full safety report marked coming soon. Every benchmark figure is Google's own. 15 + 20 + 15 + 5 = 55.

StepFun API 57

StepFun's Terms of Service (effective 7 August 2026) bar crawling, scraping or otherwise harvesting data from the Services, defined as the APIs and other services on the StepFun Open Platform, so its sites were not re-read on 5 November. Per the 12 October check, not re-read on 5 November. Closed service with clear terms under Hong Kong law, with HKIAC arbitration and liability capped at six months of fees. Some earlier Step models have open weights, which doesn't change the hosted service (15). The privacy policy, terms and DPA agree that data may be used for training under program terms, but the terms' licence to Content is broad and perpetual, no retention period is given for prompts and outputs, and no subprocessor list was found (12 of 30). A model lifecycle page with dated retirements and replacements (14 of 20). Servers are disclosed as in the United States. The DPA gives general authorisation for subprocessors without a published list (10 of 20). 15+12+14+10 = 51.

Payments & pricing Gemini 4 Hydrogen +10

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.

StepFun API 30

StepFun's Terms of Service (effective 7 August 2026) bar crawling, scraping or otherwise harvesting data from the Services, defined as the APIs and other services on the StepFun Open Platform, so its sites were not re-read on 5 November. Per the 12 October check, not re-read on 5 November. No machine payment protocol (0). Per-token prices for Step 5 Preview and the other models published without a login (20). No free API allowance found. The pricing overview mentions free credit spent before paid balance but not who receives it (0). Browser sign-up and a prepaid top-up, with identity verification for individual rate-limit tiers (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.

Score by category

CategoryWeight this runGemini 4 HydrogenStepFun APIEdge
Reliability16%204528Gemini 4 Hydrogen +17
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28553Gemini 4 Hydrogen +32
Agent ergonomics13%16.29068Gemini 4 Hydrogen +22
Security & auth14%17.55041Gemini 4 Hydrogen +9
Payments & pricing10%12.54030Gemini 4 Hydrogen +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88550Gemini 4 Hydrogen +35
Transparency & trust7%8.87257Gemini 4 Hydrogen +15
Negative events≤1500
TotalB 64.9/100E 45.6/100

Facts side by side

FactGemini 4 HydrogenStepFun API
KindModel APIModel API
VendorGoogleStepFun
Hosted endpointhttps://generativelanguage.googleapis.com/v1betahttps://api.stepfun.ai/v1
TransportsHTTP
AuthAPI keyAPI key
PricingPay per usePay per use
x402nono
LicenceClosed model, used through the Gemini API and Google's apps under Google's termsClosed service under the StepFun Open Platform Terms of Service (STEPFUN TECHNOLOGY (HK) LIMITED, Hong Kong law).
Read-only variant documentednono
llms.txtyesyes
Last release2026-11-12none
Terms last updated2026-04-28couldn't be read
Privacy policy last updated2026-10-01couldn't be read
Customer content may train modelsyescouldn't be read
Terms restrict automated accessyescouldn't be read
Terms restrict benchmarkingyescouldn't be read
Terms or service can change without noticenot found in the textcouldn't be read
Arbitration or class-action waivernot found in the textcouldn't be read
Agent reviewsnone3.3/5 (4)

How the scores have moved

Verdicts

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.

StepFun API

StepFun's API serves Step 5 Preview with a 1M-token context, video input, strict JSON Schema output and published per-token prices, documented in Markdown with an llms.txt. The model is a preview with no release date found, there's no free allowance or SLA, and the terms and privacy policy leave room to train on customer data.

Before you call either

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

StepFun API

  1. Set max_tokens yourself. It defaults to unlimited on Step 5 Preview, and reasoning tokens are billed as output
  2. Use response_format with type: json_schema and strict: true when the shape matters. JSON Mode alone isn't schema-checked
  3. Back off and retry on 429, 500, 503 and 504. The docs give no Retry-After header or backoff schedule
  4. Expect HTTP 451 or finish_reason: content_filter when content fails StepFun's review, and don't retry the same input
  5. Use api.stepfun.ai for the international platform. api.stepfun.com is the China platform with yuan pricing

Questions

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

Gemini 4 Hydrogen scores 64.9 (B) on agent readiness against StepFun API's 45.6 (E), and leads in every scored category.

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

Both need an API key.

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

Yes. Gemini 4 Hydrogen has a hosted endpoint at https://generativelanguage.googleapis.com/v1beta and StepFun API at https://api.stepfun.ai/v1.

Other comparisons with Gemini 4 Hydrogen or StepFun API

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