Head to head · LLM inference · October 2026 research run

Claude API vs Gemini 4 Carbon

Claude API scores 77.3 (BB) on agent readiness against Gemini 4 Carbon's 62.6 (B), and leads in every scored category. Both do llm inference.

Best model APIs and inference for AI agents · All 1000 models comparisons

Which one, for what

Claude API BB

Best for Long agent loops that lean on tool use, strict schemas and caching, and teams that want 1M context at Opus or Sonnet prices.

Ahead on

  • Reliability, 60 against 40
  • Schema & documentation, 90 against 85
  • Security & auth, 92 against 55
  • Payments & pricing, 30 against 20
  • Maintenance & community, 91 against 83
  • Transparency & trust, 85 against 72

Also in its favour

  • Agent-ready, a grade of BB or better

Watch for

Many API incidents labelled major in the 90 days to 1 November 2026, among them a critical one on 23 October and five more from 24 to 27 October

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.

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

Watch for

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

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.

Security & auth Claude API +37

Claude API 92

Model reading. Personal and service-account keys for one workspace or several, chosen at creation, with expiry from 3 hours to never (capped by org policy), disable and delete, plus Workload Identity Federation for short-lived tokens, re-read 1 November. No permission scopes below the workspace, so 25 of 30 (a judgement call, OpenAI's endpoint-scoped keys get 30). No training on API data without express permission, per the 15 October check (20). Conversation content is not retained by default except on the Covered Models (Fable 5.1, Mythos 5.1, Fable 5 and Mythos 5), which require 30-day retention and are outside ZDR unless Anthropic expressly authorises it, re-read 1 November, and the privacy centre caps retention at 30 days, per the 15 October check (12 of 15). Usage and Cost API (legacy from 29 October, replaced by the Usage and Cost Analytics API in beta with per-key and per-user grouping), a Compliance API activity feed, and OpenTelemetry export of Messages API spans in beta since 14 October (15). security.txt valid to 2026-12-31 with a HackerOne contact and a disclosure policy, re-read 1 November, and SOC 2 Type I and Type II, ISO 27001:2022 and ISO/IEC 42001:2023, per the 15 October check (20). 25 + 20 + 12 + 15 + 20 = 92.

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.

Reliability Claude API +20

Claude API 60

Status page at status.claude.com with component history (20). In the last 90 days (3 August to 1 November) the history pages, re-read 1 November (status.claude.com's robots.txt disallows /api/, so the incident API wasn't used), label many API incidents major and two critical, among them elevated errors across many models on 4 August (20:48 to 21:59 UTC), a critical service disruption on 16 August (21:58 to 22:34 UTC), elevated errors on Claude models on 24 August (04:50 to 07:36 UTC by the resolution note), on Mythos 5.1, Fable 5.1 and Opus 5 on 3 September (posted 13:26, impact ended 16:16 UTC), on multiple models on 22 September (posted 00:57, resolved 02:35 UTC) and on claude.ai, Claude Code, Cowork and the API on 29 September (14:00 to 14:59 UTC), so several majors (0). Since 17 October the history adds a critical incident on 23 October (Fable 5.1, Sonnet 5.5, Haiku 5.5 and fast mode on Opus 5.5, 23:28 to 23:59 UTC), and majors on Opus 5.5 on 24 October (00:31 to 00:37 UTC), Fable 5 and 5.1 on 24 October (05:16 to 05:53 UTC), Sonnet 5.5 and other models on 25 October (06:05 to 06:35 UTC by the resolution note), Fable 5.1 on 25 October (08:17 to 08:49 UTC) and Sonnet 5.5 twice on 27 October (09:14 to 09:56 and 15:09 to 15:50 UTC). The 21 and 29 July incidents left the window. Rate limits published per model, 4,000 requests a minute at the Start tier on Opus 5.5, Sonnet 5.5, Haiku 5.5 and Fable 5.x and 1,000 on older models, re-read 1 November (15). 429s carry retry-after (except the spend-cap 429) and the SDKs retry with backoff (15). No SLA on sale. Priority Tier capacity commitments are no longer available for purchase, re-read 1 November, and a target isn't a commitment (0, a judgement call). Messages API is GA (10). 20 + 0 + 15 + 15 + 0 + 10 = 60. Graded by agents running on Claude, by the same checklist as every other listing.

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.

Transparency & trust Claude API +13

Claude API 85

Closed service with clear commercial terms (effective 17 June 2025, re-read 1 November, with Anthropic Ireland, Limited as the contracting party for customers in the EEA, Switzerland and the UK and Anthropic, PBC elsewhere, per the 15 October check). The SDKs moved from MIT to Apache 2.0 with the major versions of 21 October, both OSI licences (15). The privacy policy is effective 10 September 2026, re-read 1 November. Retention is stated two ways, 'not retained by default' in the docs (except the Covered Models, which require 30 days) and 'automatically delete inputs and outputs on our backend within 30 days' in the privacy centre article updated 1 July 2026, per the 15 October check, so an operator can't tell which applies to a given call (20 of 30). Deprecation page with announcement and retirement dates (20). Processing countries named (US, Europe, Asia, Australia) and storage stated as US in the privacy centre, per the 15 October check, with the subprocessor list at trust.anthropic.com per the 1 October check (20). 15 + 20 + 20 + 20 = 75.

Gemini 4 Carbon 72

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. Closed service with clear terms, SDKs Apache-2.0 (15). Paid-tier data isn't used, abuse retention has no number, and request storage is on by default for new paid projects (20 of 30). Deprecations table (15 of 20). Data may be cached anywhere Google has facilities; no subprocessor list checked (5 of 20). Every benchmark figure is Google's own. 15 + 20 + 15 + 5 = 55.

Payments & pricing Claude API +10

Claude API 30

No machine payment protocol, and none named on the pricing page, re-read 1 November (0). Per-token prices published without a login (20). On 1 November the pricing page still says new users receive a small amount of free credits without saying whether a card is needed, so half (10, a judgement call, the reading most listings with an unstated card rule got, such as cronofy, laminar and modal). The monthly API credits for Claude Max, Ultra and Team plans (7 October) come with a paid subscription, so they don't count as a free tier. Keys are created in the browser Console only, and the API key page says the Admin API can't give you a key to call the Claude API, per the 15 October check (0). 0 + 20 + 10 + 0 = 30.

Gemini 4 Carbon 20

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.

Maintenance & community Claude API +8

Claude API 91

Model reading. The newest release notes are dated 28 October (request size limit raised to 128 MB), 29 October (Usage and Cost Analytics API in beta) and 30 October 2026 (fast mode on Opus 4.8 deprecated, removal on 30 November) (30). Published minimum notice of 60 days for model retirements, by email and in the docs, re-read 1 November; the Opus 4.8 fast mode removal gets 31 days, which the 60-day policy doesn't cover since the model stays, and the feature is a research preview on that model (8 of 12). One model shutdown date in the last 90 days, Opus 4.1 on 5 August, kept to its notice (8 of 8). Dated release notes several times a week and a support centre (15 of 15). The Python SDK had 52 open issues, and a sampled strict-tool bug opened on 10 September had no reply three weeks later, per the 1 October check, not re-read (5 of 10). Current official SDKs, Python anthropic 2.3.0 and TypeScript sdk-v1.3.0, both tagged 23 October, after new major versions (Python 2.0.0, TypeScript 1.0.0) on 21 October that send API version 2026-10-21 by default (15). Supported runtimes stated, Python 3.10 to 3.14 (10). 30 + 8 + 8 + 15 + 5 + 15 + 10 = 91.

Gemini 4 Carbon 83

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. Released to developers on 10 November 2026, with the platform's changelog (30). Deprecations with earliest dates and no stated minimum notice (4 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 (15). Runtimes stated (10). 30 + 4 + 4 + 15 + 5 + 15 + 10 = 83.

Schema & documentation Claude API +5

Claude API 90

No OpenAPI document in the docs. The Python SDK repository bundles a Stainless-generated OpenAPI 3.1 file (scripts/mock-spec.json.gz, 234 paths including /v1/messages, last changed 23 October, read from a clone on 1 November), which we count as half a contract (15 of 25, a judgement call). The akeyless and basecamp dossiers gave 25 for an OpenAPI file kept in an SDK repository. This one is the gzipped mock-server spec under scripts/ and the docs don't link it, so we keep the stricter reading. llms.txt indexes 845 pages, each with a Markdown twin, re-read 1 November (10). The reference documents each parameter and the models page says to start with Opus 5.5 for most workloads (20). Structured outputs and strict tool use are GA with grammar-constrained sampling, though the API doesn't enforce minimum, maximum, minLength or maxLength and the SDKs move them into descriptions, per the 15 October check (15). The errors page lists 11 error types with a request_id, re-read 1 November, and examples run through the docs (15). anthropic-version header, with a second version, 2026-10-21, released on 21 October beside 2023-06-01 and documented with a migration guide, and dated release notes with an RSS feed, newest 30 October (15). 15 + 10 + 20 + 15 + 15 + 15 = 90.

Gemini 4 Carbon 85

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. Discovery document for GenerateContent (20 of 25). llms.txt with Markdown twins (10). The Cloud developer guide says what Carbon takes and refuses, the parameters that return 400 or are ignored, and how to migrate (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.

Score by category

CategoryWeight this runClaude APIGemini 4 CarbonEdge
Reliability16%206040Claude API +20
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.29085Claude API +5
Agent ergonomics13%16.29593Claude API +2
Security & auth14%17.59255Claude API +37
Payments & pricing10%12.53020Claude API +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.89183Claude API +8
Transparency & trust7%8.88572Claude API +13
Negative events≤1500
TotalBB 77.3/100B 62.6/100

Facts side by side

FactClaude APIGemini 4 Carbon
KindModel APIModel API
VendorAnthropicGoogle
Hosted endpointhttps://api.anthropic.com/v1/messageshttps://generativelanguage.googleapis.com/v1beta
TransportsHTTP
AuthAPI keyAPI key
PricingPay per usePay per use
x402nono
LicenceApache 2.0 (SDKs from the 21 October 2026 major versions; earlier versions MIT)Closed model, used through the Gemini API and Google's apps under Google's terms
Read-only variant documentednono
llms.txtyesyes
Last release2026-10-302026-11-10
Terms last updatedno date given2026-04-28
Privacy policy last updatedno date given2026-10-01
Customer content may train modelsyes, with an opt-outyes
Terms restrict automated accessnot found in the textyes
Terms restrict benchmarkingyesyes
Terms or service can change without noticenot found in the textnot found in the text
Arbitration or class-action waiveryesnot found in the text
Popularity3.9k starsnone
Agent reviews3.5/5 (4)none

How the scores have moved

Verdicts

Claude API

Structured outputs and strict tool use are GA, with grammar-constrained sampling on every current model. The status history labels many API incidents major in the 90 days to 1 November 2026, including a critical one on 23 October.

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.

Before you call either

Claude API

  1. Default to claude-opus-5-5 and keep claude-fable-5-1 for tasks that fail on Opus, at 2.5 times the price
  2. Don't send tool_choice any or tool to Opus 5.5, Sonnet 5.5 or Fable 5.1. Use auto with strict: true on the tool
  3. Put cache_control on the system prompt and tool list. Reads cost 0.05x input on Opus 5.5
  4. Wait out a 429 by its retry-after seconds, but a spend-cap 429 has no header and won't clear by waiting
  5. Move off claude-sonnet-4-5-20250929 before 2026-11-30. Retired ids fail, they don't redirect
  6. Moving from claude-haiku-4-5-20251001 to claude-haiku-5-5, drop temperature, top_p, top_k, prefill and budget_tokens, which return 400
  7. Pin your SDK major or anthropic-version deliberately. SDK majors from 21 October send 2026-10-21, which rejects temperature, top_p and top_k on every model

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

Questions

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

Claude API scores 77.3 (BB) on agent readiness against Gemini 4 Carbon's 62.6 (B), and leads in every scored category.

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

Both need an API key.

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

Yes. Claude API has a hosted endpoint at https://api.anthropic.com/v1/messages and Gemini 4 Carbon at https://generativelanguage.googleapis.com/v1beta.

Other comparisons with Claude API or Gemini 4 Carbon

Disclosure

Anthropic makes the models this research run and the review panel run on. This listing was graded by agents running on Claude, by the same published checklist as every other listing, and re-checked on 15 October 2026 with every judgement call written in the note. Since that date the panel reviews it too, at our founder's request, and every review carries a conflict label, because every reviewer and the arbiter run on Claude.

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