Claude Sonnet 5.5

New

anthropic/claude-sonnet-5.5-20260928

Claude Sonnet 5.5 is a model from Anthropic that accepts text, image, and file inputs and generates text outputs. It has a context length of 1,000,000 tokens, supports tool use and reasoning, and is not open-weight. It was released on September 26, 2026.

  • tool use
  • structured outputs
  • reasoning

At a glance

provideranthropic
releasedSep 26, 2026
context1M
input / M$2

Specifications

What the API gives you

Context window
1M tokens
Max output
128K tokens
Input price
$2 / 1M tokens
Output price
$10 / 1M tokens
Cache read
$0.100 / 1M tokens
Modalities
text, image, file → text
Knowledge cutoff
—
Released
Sep 26, 2026

Measured evidence

Public benchmark record

Design Arena Coding
1366 Elo2026-10-16
Design Arena UI
1378 Elo2026-10-16
Design Arena Website
1330 Elo2026-10-16
FrontierMath Tiers 1-3 (Epoch AI)‡
88.8% ± 1.92026-09-29max effort, evaluated 2026-09-29
GPQA Diamond (Epoch AI)‡
95.6% ± 1.42026-09-29max effort, evaluated 2026-09-29
LiveBench Agentic Coding
56.3%2026-10-16
LiveBench Coding
91.4%2026-10-16
LiveBench Data Analysis
59.5%2026-10-16
LiveBench Instruction Following
56.8%2026-10-16
LiveBench Language
78.0%2026-10-16
LiveBench Math
96.1%2026-10-16
LiveBench Reasoning
91.6%2026-10-16
LMArena Agent‡
12.52026-10-14max effort
LMArena Agent Bash Recovery‡
152026-10-08max effort
LMArena Agent Steerability‡
12.32026-10-14max effort
LMArena Agent Task Outcome‡
202026-10-14max effort
LMArena Agent Tool Hallucination‡
0.52026-10-14max effort
LMArena Creative Writing
1467 Elo2026-10-15
LMArena Instruction Following
1488 Elo2026-10-15
LMArena Long Query
1494 Elo2026-10-15
LMArena Math
1499 Elo2026-10-15
LMArena Text
1475 Elo2026-10-15
LMArena Text Factuality
1474 Elo2026-10-15
LMArena Vision
1266 Elo2026-10-09
LMArena Vision Diagrams
1320 Elo2026-10-09
LMArena Vision OCR
1280 Elo2026-10-09
LMArena WebDev
1774 Elo2026-10-13
LMArena WebDev Image-to-Web
1740 Elo2026-10-09
OTIS Mock AIME (Epoch AI)‡
100% ± 02026-09-29max effort, evaluated 2026-09-29
SimpleQA Verified (Epoch AI)‡
46.5% ± 1.62026-09-29max effort, evaluated 2026-09-29
Terminal-Bench (4.0)‡
61.8%2026-10-16Claude Code, max effort, evaluated 2026-10-06

LMArena data licensed CC-BY-4.0. Aider (Apache-2.0) and SWE-bench (MIT) are open. Design Arena uses blind human preference. ‡ Submitted scaffold plus model result. Compare the harness and effort settings, not only the model name.

Task evidence

How broad is the support?

Each status is exact to this model version and the selected task. Official release claims remain provisional.

  • Best LLM for Competition MathEstablished evidence

    100% of intended weighted task evidence across 4 independent sources. 6 of 6 configured evaluation feeds currently have results.

  • Best LLM for Business WritingEstablished evidence

    100% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best LLM for Logic & Problem SolvingEstablished evidence

    100% of intended weighted task evidence across 3 independent sources. 5 of 5 configured evaluation feeds currently have results.

  • Best LLM for Marketing CopyEstablished evidence

    100% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best LLM for Chat & RoleplayEstablished evidence

    100% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best LLM for Creative WritingEstablished evidence

    100% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

Show all 45 tasks
  • Best LLM for Frontend & UIEstablished evidence

    100% of intended weighted task evidence across 3 independent sources. 6 of 6 configured evaluation feeds currently have results.

  • Best LLM for WritingEstablished evidence

    100% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best LLM for Roleplay & CharacterEstablished evidence

    100% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best LLM for Math & ReasoningEstablished evidence

    100% of intended weighted task evidence across 5 independent sources. 7 of 7 configured evaluation feeds currently have results.

  • Best LLM for a General AssistantEstablished evidence

    100% of intended weighted task evidence across 3 independent sources. 6 of 6 configured evaluation feeds currently have results.

  • Best LLM for Code CompletionEstablished evidence

    79% of intended weighted task evidence across 2 independent sources. 3 of 3 configured evaluation feeds currently have results.

  • Best LLM for Autonomous AgentsEstablished evidence

    67% of intended weighted task evidence across 3 independent sources. 6 of 6 configured evaluation feeds currently have results.

  • Best LLM for CodingEstablished evidence

    64% of intended weighted task evidence across 4 independent sources. 7 of 7 configured evaluation feeds currently have results.

  • Best Open-Weight LLM for Self-HostingEstablished evidence

    64% of intended weighted task evidence across 2 independent sources. 2 of 3 configured evaluation feeds currently have results.

  • Best LLM for Image UnderstandingEstablished evidence

    61% of intended weighted task evidence across 2 independent sources. 2 of 3 configured evaluation feeds currently have results.

  • Best LLM for Agentic CodingEstablished evidence

    60% of intended weighted task evidence across 3 independent sources. 7 of 7 configured evaluation feeds currently have results.

  • Best LLM for Fast SummariesEstablished evidence

    58% of intended weighted task evidence across 2 independent sources. 2 of 3 configured evaluation feeds currently have results.

  • Best Value LLMEstablished evidence

    58% of intended weighted task evidence across 2 independent sources. 2 of 3 configured evaluation feeds currently have results.

  • Best LLM for AI AgentsEstablished evidence

    50% of intended weighted task evidence across 3 independent sources. 9 of 9 configured evaluation feeds currently have results.

  • Best LLM for Literary TranslationEstablished evidence

    50% of intended weighted task evidence across 2 independent sources. 3 of 4 configured evaluation feeds currently have results.

  • Best LLM for Everyday TranslationEstablished evidence

    50% of intended weighted task evidence across 2 independent sources. 3 of 4 configured evaluation feeds currently have results.

  • Best LLM for TranslationEstablished evidence

    50% of intended weighted task evidence across 2 independent sources. 3 of 4 configured evaluation feeds currently have results.

  • Best LLM for Hermes AgentEstablished evidence

    48% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best LLM for OpenHandsEstablished evidence

    48% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best LLM for GooseEstablished evidence

    48% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best LLM for OpenClawEstablished evidence

    48% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best Local LLM for CodingEstablished evidence

    47% of intended weighted task evidence across 2 independent sources. 4 of 4 configured evaluation feeds currently have results.

  • Best LLM for Document SummarizationEstablished evidence

    40% of intended weighted task evidence across 2 independent sources. 5 of 6 configured evaluation feeds currently have results.

  • Best LLM for SummarizationEstablished evidence

    40% of intended weighted task evidence across 2 independent sources. 5 of 6 configured evaluation feeds currently have results.

  • Best Cheap LLM for High VolumeEstablished evidence

    40% of intended weighted task evidence across 2 independent sources. 2 of 3 configured evaluation feeds currently have results.

  • Cheapest Capable LLMEstablished evidence

    40% of intended weighted task evidence across 2 independent sources. 2 of 3 configured evaluation feeds currently have results.

  • Best LLM for JSON & Schema OutputEstablished evidence

    35% of intended weighted task evidence across 2 independent sources. 3 of 4 configured evaluation feeds currently have results.

  • Best LLM for Structured Data ExtractionEstablished evidence

    35% of intended weighted task evidence across 2 independent sources. 3 of 4 configured evaluation feeds currently have results.

  • Best LLM for Debugging & Code ReviewEstablished evidence

    33% of intended weighted task evidence across 2 independent sources. 5 of 5 configured evaluation feeds currently have results.

  • Best LLM for Grounded RAGEstablished evidence

    29% of intended weighted task evidence across 2 independent sources. 5 of 7 configured evaluation feeds currently have results.

  • Best LLM for OCR & DocumentsProvisional evidence

    45% of intended weighted task evidence across 1 independent source; broader independent confirmation is still missing from LMArena Document or Structured-output eval. 3 of 5 configured evaluation feeds currently have results.

  • Best LLM for Charts & DiagramsProvisional evidence

    45% of intended weighted task evidence across 1 independent source; broader independent confirmation is still missing from LMArena Document or Structured-output eval. 3 of 5 configured evaluation feeds currently have results.

  • Best LLM for Vision & DocumentsProvisional evidence

    40% of intended weighted task evidence across 1 independent source; broader independent confirmation is still missing from LMArena Document or Structured-output eval. 4 of 6 configured evaluation feeds currently have results.

  • Best LLM for Tool & Function CallingProvisional evidence

    38% of intended weighted task evidence across 1 independent source; broader independent confirmation is still missing from Berkeley Function Calling or LMArena Search. 6 of 7 configured evaluation feeds currently have results.

  • Best LLM for Document ParsingProvisional evidence

    37% of intended weighted task evidence across 1 independent source; broader independent confirmation is still missing from LMArena Document or Structured-output eval. 3 of 5 configured evaluation feeds currently have results. Official release evidence is also tracked provisionally.

  • Best LLM for RAG & Long ContextProvisional evidence

    22% of intended weighted task evidence across 1 independent source; broader independent confirmation is still missing from FACTS Grounding or LMArena Document. 5 of 6 configured evaluation feeds currently have results.

  • Best LLM for High-Volume ExtractionProvisional evidence

    21% of intended weighted task evidence across 1 independent source; broader independent confirmation is still missing from Route reliability or Structured-output eval. 1 of 3 configured evaluation feeds currently have results.

  • Best LLM for Massive ContextProvisional evidence

    20% of intended weighted task evidence across 1 independent source; broader independent confirmation is still missing from LMArena Document or LongBench v2. 2 of 3 configured evaluation feeds currently have results.

  • Best LLM for Computer & Browser UseProvisional evidence

    17% of intended weighted task evidence across 1 independent source; broader independent confirmation is still missing from Berkeley Function Calling or OSWorld Verified. 3 of 3 configured evaluation feeds currently have results.

Official release evidence · provisional

What the launch material actually says

Verbatim claims from the model provider. These help on launch day but do not count as independent confirmation.

Recommendation coverage

Where this model appears

  1. #1Best LLM for Code Completion
  2. #1Best LLM for Debugging & Code Review
  3. #2Best LLM for Coding
  4. #2Best LLM for Autonomous Agents
  5. #2Best LLM for Frontend & UI
  6. #3Best LLM for OpenClaw
  7. #3Best LLM for Agentic Coding
  8. #3Best LLM for Goose
  9. #3Best LLM for OpenHands
  10. #3Best LLM for AI Agents
  11. #3Best LLM for Hermes Agent
  12. #5Best LLM for Math & Reasoning
  13. #6Best LLM for Tool & Function Calling
  14. #6Best LLM for Computer & Browser Use
  15. #6Best LLM for Competition Math
  16. #7Best LLM for Charts & Diagrams
  17. #8Best LLM for Vision & Documents

Compare head to head

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