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Head to head · LLM inference · October 2026 research run

Claude Mythos 5.2 vs Gemini 4 Carbon

Claude Mythos 5.2 scores 76.1 (BB) on agent readiness against Gemini 4 Carbon's 62.6 (B), and leads in 6 of 7 scored categories. Both do llm inference.

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

Claude Mythos 5.2Anthropic · Model API BB76.1/100#51 of 1518 Gemini 4 CarbonGoogle · Model API B62.6/100#555 of 1518

Which one, for what

Claude Mythos 5.2 BB

Best for Security and life-science teams whose organisation Anthropic has verified, who want Fable 5.2's capability without the classifiers that send high-risk cyber and biology requests to older models.

Ahead on

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

Also in its favour

  • Agent-ready, a grade of BB or better

Watch for

Only for organisations Anthropic verifies, so an agent can't start on it alone

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 Mythos 5.2 +37

Claude Mythos 5.2 92

Model reading for claude-mythos-5-2 on the Claude API. Platform facts are the Claude API listing's (anthropic-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. Workspace-scoped keys with expiry and Workload Identity Federation, no scopes below the workspace (25 of 30). No training on API data without express permission (20). The model requires 30-day retention, is a Covered Model and is outside ZDR unless Anthropic expressly authorises it, per the model page read 9 November, the same as Fable 5.1 (12 of 15). Usage and cost analytics, Compliance API and OpenTelemetry export (15). security.txt, HackerOne and SOC 2, ISO 27001 and ISO 42001 (20). Thinking blocks work only in the account that produced them or one linked to it, per the model page. 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 Mythos 5.2 +20

Claude Mythos 5.2 60

Model reading for claude-mythos-5-2 on the Claude API. Platform facts are the Claude API listing's (anthropic-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. Status page at status.claude.com with component history (20). The last 90 days carry several major and two critical API incidents, among them Fable 5.1 and Mythos 5.1 on 3 September and Fable 5.1 on 23 and 25 October, so 0 for incident history. Rate limits published per model, Fable 5.x at 4,000 requests a minute at the Start tier (15). 429s with retry-after and SDK retries with backoff (15). No SLA on sale (0). The model page lists it as a current model with no preview label (10). 20 + 0 + 15 + 15 + 0 + 10 = 60. Graded by an agent 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 Mythos 5.2 +13

Claude Mythos 5.2 85

Model reading for claude-mythos-5-2 on the Claude API. Platform facts are the Claude API listing's (anthropic-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. Commercial Terms with named contracting parties and Apache 2.0 SDKs (15). Retention stated two ways across the docs and the privacy centre, though for this model the model page is plain that 30 days is required (20 of 30, kept at the platform's reading). Deprecation page with dates, and this model's retirement floor on its page (20). Processing countries and subprocessors named (20). The benchmark figures are Anthropic's own, with no third-party run of this model found on 9 November. 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.

Maintenance & community Claude Mythos 5.2 +8

Claude Mythos 5.2 91

Model reading for claude-mythos-5-2 on the Claude API. Platform facts are the Claude API listing's (anthropic-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. Released 9 November 2026 beside dated release notes several times a week (30). 60 days' minimum notice for retirements, and the model page says retirement not sooner than 9 November 2027 (8 of 12, the Claude API's reading). Model shutdowns kept to notice (8). Support centre and dated notes (15). The sampled SDK issue without a reply, per the 1 October check (5 of 10). Current SDKs (15). Runtimes stated (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 Mythos 5.2 +5

Claude Mythos 5.2 90

Model reading for claude-mythos-5-2 on the Claude API. Platform facts are the Claude API listing's (anthropic-api, re-read 1 November), carried over as RULES.md allows for a model on an already graded platform. The SDK-bundled OpenAPI file as half a contract (15 of 25, the Claude API listing's judgement call). llms.txt with Markdown twins (10). The model page, what's new and the migration guide say what changed from Fable 5.1 and what to send and not send (forced tool choice, sampling parameters, computer_20251124 returning 400 except on Bedrock), read 9 November (20). Structured outputs and strict tools GA (15). Documented error types with request_id (15). anthropic-version and dated release notes (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 Mythos 5.2Gemini 4 CarbonEdge
Reliability16%206040Claude Mythos 5.2 +20
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.29085Claude Mythos 5.2 +5
Agent ergonomics13%16.29593Claude Mythos 5.2 +2
Security & auth14%17.59255Claude Mythos 5.2 +37
Payments & pricing10%12.52020even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.89183Claude Mythos 5.2 +8
Transparency & trust7%8.88572Claude Mythos 5.2 +13
Negative events≤1500
TotalBB 76.1/100B 62.6/100

Facts side by side

FactClaude Mythos 5.2Gemini 4 Carbon
KindModel APIModel API
VendorAnthropicGoogle
Hosted endpointhttps://api.anthropic.com/v1https://generativelanguage.googleapis.com/v1beta
Transports
AuthAPI keyAPI key
PricingPay per usePay per use
x402nono
LicenceClosed model, used through the Claude API and cloud platforms under Anthropic's Commercial Terms of ServiceClosed model, used through the Gemini API and Google's apps under Google's terms
Read-only variant documentednono
llms.txtyesyes
Last release2026-11-092026-11-10
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

Verdicts

Claude Mythos 5.2

Fable 5.2 without Fable's stronger cyber and biology safeguards, for verified security and life-science teams, on the same mature API at $8 and $40 per million tokens. Most agents can't use it, since access depends on Anthropic approving the organisation, and it requires 30-day retention.

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 Mythos 5.2

  1. Confirm your organisation is verified before routing work here; otherwise use claude-fable-5-2
  2. Call https://api.anthropic.com/v1/messages with model claude-mythos-5-2 and your key
  3. Steer thinking with the effort parameter (default high); don't send temperature, top_p or top_k
  4. Don't force a tool with tool_choice any or tool; describe the tool and let the model choose
  5. Thinking blocks from it are read only by Fable 5.2 and Mythos 5.2, so keep them out of other models' context
  6. Check data retention before sending regulated data, since 30 days is required

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 Mythos 5.2 or Gemini 4 Carbon?

Claude Mythos 5.2 scores 76.1 (BB) on agent readiness against Gemini 4 Carbon's 62.6 (B), and leads in 6 of 7 scored categories.

Do Claude Mythos 5.2 and Gemini 4 Carbon need an API key?

Both need an API key.

Can an agent call Claude Mythos 5.2 and Gemini 4 Carbon without installing anything?

Yes. Claude Mythos 5.2 has a hosted endpoint at https://api.anthropic.com/v1 and Gemini 4 Carbon at https://generativelanguage.googleapis.com/v1beta.

Other comparisons with Claude Mythos 5.2 or Gemini 4 Carbon

Disclosure

Anthropic makes the models this research run and the review panel run on. This listing was graded by an agent running on Claude, by the same published checklist as every other listing, from Anthropic's own pages and the Claude API listing's platform readings, with every judgement call written in the note. The panel reviews Anthropic's listings 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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