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BenchLM
Model A
Claude Mythos Preview

Anthropic

—

Evidence status unavailable

90% interval unavailable

Claude Mythos Preview vs Claude Opus 4.5

Updated August 13, 2026. Public scores include evidence status and uncertainty. They are not guarantees for a specific workload.

Model B
Claude Opus 4.5

Anthropic

63.4/100

Supported · Public rank #41

90% interval 49.7–77.0

Decision reading

At least one model is not scored in the current public ranking lane, so the page does not name an overall quality winner.

1 results are shared. Category rows based on different benchmark sets are marked directional and do not name a winner.

Which one for your work

Recommendations appear only when a shared evidence basis or an explicit operating constraint supports the call. Secondary and unsupported use cases stay disclosed below the initial list.

  • Chat turn cost

    1K fresh input + 500 output tokens

    Claude Opus 4.5

    Claude Opus 4.5 has the lower estimated token cost for this stated workload. Costs use the listed standard API rates.

    Confidence: listed-rates

Show secondary and unsupported calls

  • Repository review cost

    50K fresh input + 3K output tokens

    Claude Opus 4.5

    Claude Opus 4.5 has the lower estimated token cost for this stated workload. Costs use the listed standard API rates.

    Confidence: listed-rates

  • Coding work

    Code generation, repair, and software-engineering tasks

    Not enough matched evidence

    No shared weighted benchmark basis supports a winner.

    Confidence: limited

  • Agentic work

    Tool use, computer use, and multi-step task completion

    Not enough matched evidence

    No shared weighted benchmark basis supports a winner.

    Confidence: limited

  • Long documents

    Prompts that approach the documented context limit

    Not enough matched evidence

    A complete context comparison is not sourced.

    Confidence: limited

  • Cache-heavy agent loop cost

    200K cached + 20K fresh input + 10K output tokens

    Not enough matched evidence

    The page does not recommend a cost winner because at least one model cannot fit the stated workload in one request. Claude Opus 4.5 does not fit this workload in one request. Claude Mythos Preview has no published cached-input rate, so cached tokens use its listed input rate. Claude Opus 4.5 has no published cached-input rate, so cached tokens use its listed input rate.

    Confidence: rate-fallback

What is actually comparable

Shared results can support a head-to-head reading. Results present for only one model describe coverage, not superiority.

Shared results
1
Claude Mythos Preview only
1
Claude Opus 4.5 only
44
Like-for-like categories
0 / 8

Category results, on a stated basis

Each row states whether both averages use the same weighted benchmark set. Directional and not-comparable rows remain visible, but they never receive a winner in this template.

Agentic

Not comparable
Claude Mythos Preview
Not measured
Claude Opus 4.5
62.6
Weighted basis
0 vs 2 rows
Reading
Not comparable

Coding

Not comparable
Claude Mythos Preview
Not measured
Claude Opus 4.5
71.7
Weighted basis
0 vs 2 rows
Reading
Not comparable

Reasoning

Not comparable
Claude Mythos Preview
Not measured
Claude Opus 4.5
64.4
Weighted basis
0 vs 1 rows
Reading
Not comparable

Knowledge

Not comparable
Claude Mythos Preview
Not measured
Claude Opus 4.5
58.1
Weighted basis
0 vs 4 rows
Reading
Not comparable

Math

Not comparable
Claude Mythos Preview
Not measured
Claude Opus 4.5
57.5
Weighted basis
0 vs 4 rows
Reading
Not comparable

Multilingual

Not comparable
Claude Mythos Preview
Not measured
Claude Opus 4.5
85.7
Weighted basis
0 vs 1 rows
Reading
Not comparable

Multimodal

Not comparable
Claude Mythos Preview
Not measured
Claude Opus 4.5
69.9
Weighted basis
0 vs 2 rows
Reading
Not comparable

Instruction following

Not comparable
Claude Mythos Preview
Not measured
Claude Opus 4.5
69.5
Weighted basis
0 vs 2 rows
Reading
Not comparable

Shape of the matched evidence

Only shared public evidence is shown. Sparse evidence stays a ruled list rather than being closed into a radar shape.

A shared-evidence shape is not available.

BenchLM does not draw a radar or infer missing axes when the matched evidence is too sparse.

What each workload costs

Three fixed token mixes turn per-token rates into comparable decisions. Each scenario states context fit and whether cached input had to fall back to the published list-input rate.

Chat turn

1K fresh input + 500 output tokens

Claude Mythos Preview
$0.0875
Fit state unavailable
Claude Opus 4.5
$0.0175
Fits in one request

Claude Opus 4.5 has the lower modeled cost

Costs use the listed standard API rates.

Repository review

50K fresh input + 3K output tokens

Claude Mythos Preview
$1.63
Fit state unavailable
Claude Opus 4.5
$0.325
Fits in one request

Claude Opus 4.5 has the lower modeled cost

Costs use the listed standard API rates.

Cache-heavy agent loop

200K cached + 20K fresh input + 10K output tokens

Claude Mythos Preview
$6.75
Fit state unavailable
Cached input priced at the published list-input rate
Claude Opus 4.5
$1.35
Does not fit in one request
Cached input priced at the published list-input rate

Claude Opus 4.5 does not fit this workload in one request. Claude Mythos Preview has no published cached-input rate, so cached tokens use its listed input rate. Claude Opus 4.5 has no published cached-input rate, so cached tokens use its listed input rate.

Specification differences

Sourced differences are shown directly. Missing facts stay explicit instead of being inferred from a model name or family.

Context window

Maximum documented context; output-token limits may be lower.

Claude Mythos Preview

Not sourced

Claude Opus 4.5

200K

Cached-input rate

A missing cached-input rate falls back to the listed input rate only in the stated workload estimate.

Claude Mythos Preview

Not published

Anthropic Project Glasswing

Claude Opus 4.5

Not published

Documented inputs

Claude Mythos Preview

Not sourced

Claude Opus 4.5

Not sourced

Documented outputs

Claude Mythos Preview

Not sourced

Claude Opus 4.5

Not sourced

Provider availability

Claude Mythos Preview

Not sourced

Claude Opus 4.5

Not sourced

Reasoning profile

Claude Mythos Preview

Reasoning

Claude Opus 4.5

Non-Reasoning

Weight access

Claude Mythos Preview

Proprietary

Claude Opus 4.5

Proprietary

License

Claude Mythos Preview

Proprietary

Claude Opus 4.5

Proprietary

Release date

Claude Mythos Preview

2026-04-07

Claude Opus 4.5

2025-11-01

If you already use one of these models
Deployment change
Both entries list Anthropic as the provider. Confirm endpoint, model ID, limits, and feature support before switching.
Quality signal
At least one model is not scored in the current public ranking lane, so the page does not name an overall quality winner.
Workload cost
Repository review: $1.63 vs $0.325. Cache-heavy agent loop: $6.75 vs $1.35.
Context tradeoff
A complete documented context comparison is not available.

Run the same representative tasks against both endpoints before changing production traffic.

Benchmark evidence

The full public result ledger is available for audit without forcing a wide desktop table onto a phone.

Browse raw public benchmark evidence46 rows

Agentic

  • CyberGym

    Shared source
    Claude Mythos Preview83.1%
    Claude Opus 4.550.6%

    Claude Mythos Preview leads this result

  • ExploitGym

    Claude Mythos Preview17.5%
    Source
    Claude Opus 4.5—

    Not directly comparable

  • Terminal-Bench 2.0

    Claude Mythos Preview—
    Claude Opus 4.559.3%
    Source

    Not directly comparable

  • OSWorld-Verified

    Claude Mythos Preview—
    Claude Opus 4.566.3%
    Source

    Not directly comparable

  • OSWorld

    Claude Mythos Preview—
    Claude Opus 4.566.3%
    Source

    Not directly comparable

  • Claw-Eval

    Claude Mythos Preview—
    Claude Opus 4.559.6%
    Source

    Not directly comparable

  • QwenClawBench

    Claude Mythos Preview—
    Claude Opus 4.552.3%
    Source

    Not directly comparable

  • τ³-bench results

    Claude Mythos Preview—
    Claude Opus 4.570.2%
    Source

    Not directly comparable

  • VITA-Bench

    Claude Mythos Preview—
    Claude Opus 4.523.3%
    Source

    Not directly comparable

  • DeepPlanning

    Claude Mythos Preview—
    Claude Opus 4.526.4%
    Source

    Not directly comparable

  • Toolathlon

    Claude Mythos Preview—
    Claude Opus 4.543.5%
    Source

    Not directly comparable

  • MCP Atlas

    Claude Mythos Preview—
    Claude Opus 4.542.3%
    Source

    Not directly comparable

  • MCP-Tasks

    Claude Mythos Preview—
    Claude Opus 4.571.8%
    Source

    Not directly comparable

  • WideResearch

    Claude Mythos Preview—
    Claude Opus 4.576.4%
    Source

    Not directly comparable

  • Gert Labs

    Claude Mythos Preview—
    Claude Opus 4.564.23%
    Source

    Not directly comparable

  • JobBench

    Claude Mythos Preview—
    Claude Opus 4.532.3%
    Source

    Not directly comparable

Coding

  • SWE-bench Verified

    Claude Mythos Preview—
    Claude Opus 4.580.9%
    Source

    Not directly comparable

  • LiveCodeBench v6

    Claude Mythos Preview—
    Claude Opus 4.584.8%
    Source

    Not directly comparable

  • SWE-bench Pro

    Claude Mythos Preview—
    Claude Opus 4.557.1%
    Source

    Not directly comparable

  • SWE Multilingual

    Claude Mythos Preview—
    Claude Opus 4.577.5%
    Source

    Not directly comparable

  • NL2Repo

    Claude Mythos Preview—
    Claude Opus 4.543.2%
    Source

    Not directly comparable

Reasoning

  • LongBench v2

    Claude Mythos Preview—
    Claude Opus 4.564.4%
    Source

    Not directly comparable

  • AI-Needle

    Claude Mythos Preview—
    Claude Opus 4.574%
    Source

    Not directly comparable

Knowledge

  • GPQA

    Claude Mythos Preview—
    Claude Opus 4.587%
    Source

    Not directly comparable

  • SuperGPQA

    Claude Mythos Preview—
    Claude Opus 4.570.6%
    Source

    Not directly comparable

  • MMLU-Pro

    Claude Mythos Preview—
    Claude Opus 4.589.5%
    Source

    Not directly comparable

  • MMLU-Redux

    Claude Mythos Preview—
    Claude Opus 4.596.6%
    Source

    Not directly comparable

  • C-Eval

    Claude Mythos Preview—
    Claude Opus 4.592.2%
    Source

    Not directly comparable

  • HLE

    Claude Mythos Preview—
    Claude Opus 4.530.8%
    Source

    Not directly comparable

Math

  • AIME26

    Claude Mythos Preview—
    Claude Opus 4.595.1%
    Source

    Not directly comparable

  • HMMT Feb 2025

    Claude Mythos Preview—
    Claude Opus 4.592.9%
    Source

    Not directly comparable

  • HMMT Nov 2025

    Claude Mythos Preview—
    Claude Opus 4.593.3%
    Source

    Not directly comparable

  • HMMT Feb 2026

    Claude Mythos Preview—
    Claude Opus 4.585.3%
    Source

    Not directly comparable

  • MMAnswerBench

    Claude Mythos Preview—
    Claude Opus 4.584.0%
    Source

    Not directly comparable

  • FrontierMath v2 (Tiers 1-3)

    Claude Mythos Preview—
    Claude Opus 4.520.690%
    Source

    Not directly comparable

  • FrontierMath v2 (Tier 4)

    Claude Mythos Preview—
    Claude Opus 4.54.167%
    Source

    Not directly comparable

Multilingual

  • MMLU-ProX

    Claude Mythos Preview—
    Claude Opus 4.585.7%
    Source

    Not directly comparable

  • NOVA-63

    Claude Mythos Preview—
    Claude Opus 4.556.7%
    Source

    Not directly comparable

Multimodal

  • MMMU-Pro

    Claude Mythos Preview—
    Claude Opus 4.570.6%
    Source

    Not directly comparable

  • MathVision

    Claude Mythos Preview—
    Claude Opus 4.574.3%
    Source

    Not directly comparable

  • CharXiv

    Claude Mythos Preview—
    Claude Opus 4.568.5%
    Source

    Not directly comparable

  • VideoMMMU

    Claude Mythos Preview—
    Claude Opus 4.584.4%
    Source

    Not directly comparable

  • ScreenSpot Pro

    Claude Mythos Preview—
    Claude Opus 4.545.7%
    Source

    Not directly comparable

  • V*

    Claude Mythos Preview—
    Claude Opus 4.567.0%
    Source

    Not directly comparable

Instruction following

  • IFEval

    Claude Mythos Preview—
    Claude Opus 4.590.9%
    Source

    Not directly comparable

  • IFBench

    Claude Mythos Preview—
    Claude Opus 4.558%
    Source

    Not directly comparable

Frequently asked questions

Which is better, Claude Mythos Preview or Claude Opus 4.5?

At least one model is not scored in the current public ranking lane, so the page does not name an overall quality winner. The page therefore keeps the decision tied to the specific documented workload.

Which is better for coding, Claude Mythos Preview or Claude Opus 4.5?

The published evidence does not provide a shared weighted coding basis for both models, so BenchLM does not name a coding winner.

Which is better for agentic tasks, Claude Mythos Preview or Claude Opus 4.5?

The published evidence does not provide a shared weighted agentic tasks basis for both models, so BenchLM does not name a agentic tasks winner.

Which costs less, Claude Mythos Preview or Claude Opus 4.5?

For the stated presets, chat costs $0.0875 on Claude Mythos Preview and $0.0175 on Claude Opus 4.5; repository review costs $1.63 and $0.325; the cache-heavy agent loop costs $6.75 and $1.35. Claude Opus 4.5 does not fit this workload in one request. Claude Mythos Preview has no published cached-input rate, so cached tokens use its listed input rate. Claude Opus 4.5 has no published cached-input rate, so cached tokens use its listed input rate.

Which has the larger context window, Claude Mythos Preview or Claude Opus 4.5?

A complete documented context-window comparison is not available.

Related comparisons

Compare API pricing Read the methodology Open the model selector

Last updated August 13, 2026

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