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Model comparison

Claude Sonnet 5.5 vs DeepSeek R1

Anthropic against DeepSeek, compared on context, price, and attributed benchmark results.

Claude Sonnet 5.5: profile checked October 25, 2026DeepSeek R1: profile checked October 25, 2026Individual provider fields may changeEvidence confidence: Insufficient data — see receipts below

Anthropic

Claude Sonnet 5.5

Balanced

vs

DeepSeek

DeepSeek R1

Balanced · Open weights

AI model capability comparison
SpecificationClaude Sonnet 5.5DeepSeek R1
ProviderAnthropicDeepSeek
TierBalancedBalanced
Context windowWinner: 1M128K
Max output128KNot verifiedUnverified
Input / 1M tokens$2Not verifiedUnverified
Output / 1M tokens$10Not verifiedUnverified
WeightsClosedOpen
ParametersNot verifiedUnverified671B total / 37B active (MoE)
Reasoning levelslow, medium, high, xhigh, maxNot verifiedUnverified
Modalitiestext, imagetext
LicenseNot verifiedUnverifiedMIT
API model idclaude-sonnet-5-5Not verifiedUnverified
ReleasedSeptember 28, 2026January 20, 2025
Artificial Analysis Intelligence Index [max] · source date Claude Sonnet 5.5: 2026-10-0156Not verifiedUnverified
Terminal-Bench 4.0 [max] · source date Claude Sonnet 5.5: 2026-10-0163.6Not verifiedUnverified
Terminal-Bench 4.0 · source date Claude Sonnet 5.5: 2026-10-0170.6Not verifiedUnverified
CursorBench 4.0 [max] · source date Claude Sonnet 5.5: 2026-10-0155.5Not verifiedUnverified
Humanity's Last Exam · source date Claude Sonnet 5.5: 2026-10-0164.5Not verifiedUnverified
FrontierCode 1.1 (Main) [xhigh] · source date Claude Sonnet 5.5: 2026-10-0152.1Not verifiedUnverified
OSWorld 2.1 · source date Claude Sonnet 5.5: 2026-10-0180.1Not verifiedUnverified

Dates beside benchmark scores refer to the linked source’s publication or capture date unless that source explicitly states when it measured the result. A shared URL alone does not establish comparable runs; unverified setups are marked. Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

Where each score comes from, and how far it can be compared across models.

  • Source date2026-10-01
    Anthropic (vendor-reported) (partial task set)
  • Source date2026-10-01
    Anthropic (vendor-reported)
  • Source date2026-10-01
    Anthropic (vendor-reported) (with tools)

    Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise.

    Comparable with caveatSubset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.

  • Source date2026-10-01
    Cursor (vendor-run coding agent)
  • Source date2026-10-01
    Artificial Analysis (independent, mini-swe-agent)

    Agentic terminal work: long multi-step tasks executed in a sandboxed shell environment.

    Comparable with caveatDo not directly compare scores across Terminal-Bench versions: 4.0 revises and prunes the 3.0 task set and changes environment resources, requiring fresh trials. Within 4.0, harness, time limit, tools, sampling and resource settings must match; maintainer-agent and Artificial Analysis runs are not interchangeable.

  • Source date2026-10-01
    Anthropic (vendor-reported)

    Agentic terminal work: long multi-step tasks executed in a sandboxed shell environment.

    Comparable with caveatDo not directly compare scores across Terminal-Bench versions: 4.0 revises and prunes the 3.0 task set and changes environment resources, requiring fresh trials. Within 4.0, harness, time limit, tools, sampling and resource settings must match; maintainer-agent and Artificial Analysis runs are not interchangeable.

  • Source date2026-10-01
    Artificial Analysis (Claude Sonnet 5.5 (max with fallback))

    Composite index blending reasoning, knowledge, and coding evals into one 0–100 score.

    Comparable with caveatOnly same-version scores are comparable. v4.3.2 was rebaselined (the top score fell from 66 on v4.1.1 to ~58), so v4.1.1 figures must not be compared with v4.3.2 figures — check the cited source and its date.

Pricing tiers

Claude Sonnet 5.5: Standard USD/MTok input/output $2/$10 with no long-context surcharge; cache reads $0.10, 5-minute writes $2.50, 1-hour writes $4. Batch $1/$5. US-only inference adds 10% to input/output and cache reads/writes on Anthropic-operated routes where supported; Foundry uses US Data Zone Standard. Bedrock and Google-managed Google Cloud have independent regional prices. Batch 300K output requires output-300k-2026-03-24; standard output stays 128K. Knowledge cutoff June 2026; retirement not sooner than September 28, 2027. Server-side tools can add usage fees; tool schemas/results and thinking consume billable tokens.

DeepSeek R1: No current first-party API. The original deepseek-reasoner alias moved to R1-0528 on May 28, 2025 and V3.1 on August 21, 2025, before the alias retired July 24, 2026 at 15:59 UTC. Historical launch tariffs are not verified here; hosts charge their own rates for the MIT weights.

BalancedRecord checked October 25, 2026

Claude Sonnet 5.5

Anthropic’s newer Sonnet model for everyday coding and knowledge work at the same $2/$10 token rates as Sonnet 5.

Best for

  • Everyday coding
  • Document and slide creation
  • Fast iteration

Watch out

Vendor scores keep their original evaluation setup and dates. between_tools turns off up-front thinking only at low/medium/high effort; xhigh/max requires adaptive thinking. Changing effort per message while between_tools is active returns an error. Forced tool use, temperature/top_p/top_k, older computer_20251124 on Claude API/Google-managed Google Cloud, and some advisor pairings are rejected. Thinking blocks are model/conversation-bound; progress text needs a display setting that returns it. Haiku 5.5 has now released separately; its capabilities and scores are not inherited.

BalancedOpen weightsRecord checked October 25, 2026

DeepSeek R1

DeepSeek R1 is the January 2025 open-weight (MIT) reasoning model — now open weights only, with no first-party API.

Best for

  • Harder reasoning on a budget
  • Open-weight deployments
  • Agentic coding

Watch out

Original January R1 MIT weights remain available. The first-party alias moved to R1-0528 on May 28, 2025 and later to other models before its July 24, 2026 retirement. Pin the exact checkpoint; no current first-party tariff, hard native output cap or selectable hosted effort menu is established for this original profile. Distilled Qwen/Llama variants have additional base-model licence terms.

When the cheaper one wins

One of these rows is missing a verified output price, so this page will not name a cheaper winner. Run the model picker against the actual job instead of guessing.

Run the model picker

Evidence confidence: Insufficient data

How strong and complete the evidence behind this comparison is — not a prediction of which model is better. Hard limitations apply: missing pricing; evidence too sparse.

  • Pricing incomplete — No verified token pricing for DeepSeek R1.
  • 2/5 core specs verified on both sides — Not published for at least one side: max output, parameter count, reasoning levels.
  • No directly aligned benchmark setup — No benchmark has matching cited sources, source dates, units, effort and recorded run details on both models.
  • Verified within the last 90 days — Older of the two catalog checks was 1 day ago.
  • Both models carry source citations — Each side has at least two catalog sources on record.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

Related comparisons

Diving deeper on one model? Claude Sonnet 5.5 · DeepSeek R1

Common questions

Claude Sonnet 5.5 vs DeepSeek R1

Answered from the verified figures on this page rather than general guidance.

Which has the larger context window, Claude Sonnet 5.5 or DeepSeek R1?
Claude Sonnet 5.5 accepts 1M tokens against 128K for DeepSeek R1. This only matters if you routinely send very long documents or large codebases.
Should I use Claude Sonnet 5.5 or DeepSeek R1?
Both are classified in our balanced tier; this editorial grouping does not imply equal capability. Claude Sonnet 5.5 is a candidate for everyday coding; DeepSeek R1 is a candidate for harder reasoning on a budget. Compare accuracy, tool reliability, latency and cost on representative tasks.
Can I self-host Claude Sonnet 5.5 or DeepSeek R1?
DeepSeek R1 publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. Claude Sonnet 5.5 is a closed model whose supported access paths are controlled by its provider.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

  • Context: Claude Sonnet 5.5 takes 1M against 128K for DeepSeek R1 — only decisive if your prompts approach the smaller window.
  • Deployment: DeepSeek R1 publishes weights you can self-host; the other is API-only.
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