Agentic
Not comparable- Claude 3.5 Sonnet
- Not measured
- Claude Mythos 5.1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
Claude 3.5 Sonnet vs Claude Mythos 5.1
Updated September 1, 2026. Public scores include evidence status and uncertainty. They are not guarantees for a specific workload.
Decision reading
The public evidence has no benchmark result shared by both models, so it does not support a quality verdict. Use the documented cost, context, and runtime rows instead.
0 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.
Long documents
Prompts that approach the documented context limit
Claude Mythos 5.1
Claude Mythos 5.1 has the larger documented context window.
Confidence: documented
Show secondary and unsupported calls
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
Chat turn cost
1K fresh input + 500 output tokens
Not enough matched evidence
A complete comparable API-rate estimate is not available for both models.
Confidence: listed-rates
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 3.5 Sonnet does not fit this workload in one request. Claude 3.5 Sonnet has no published cached-input rate, so cached tokens use its listed input rate. Claude Mythos 5.1 has no comparable published API token rate.
Confidence: rate-fallback
Repository review cost
50K fresh input + 3K output tokens
Not enough matched evidence
A complete comparable API-rate estimate is not available for both models.
Confidence: listed-rates
What is actually comparable
Shared results can support a head-to-head reading. Results present for only one model describe coverage, not superiority.
4 Claude 3.5 Sonnet only
1 Claude Mythos 5.1 only
- Shared results
- 0
- Claude 3.5 Sonnet only
- 4
- Claude Mythos 5.1 only
- 1
- 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.
Coding
Not comparable- Claude 3.5 Sonnet
- 49.0
- Claude Mythos 5.1
- Not measured
- Weighted basis
- 1 vs 0 rows
- Reading
- Not comparable
Reasoning
Not comparable- Claude 3.5 Sonnet
- Not measured
- Claude Mythos 5.1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
Knowledge
Not comparable- Claude 3.5 Sonnet
- 59.4
- Claude Mythos 5.1
- Not measured
- Weighted basis
- 1 vs 0 rows
- Reading
- Not comparable
Math
Not comparable- Claude 3.5 Sonnet
- 1.6
- Claude Mythos 5.1
- Not measured
- Weighted basis
- 2 vs 0 rows
- Reading
- Not comparable
Multilingual
Not comparable- Claude 3.5 Sonnet
- Not measured
- Claude Mythos 5.1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
Multimodal
Not comparable- Claude 3.5 Sonnet
- Not measured
- Claude Mythos 5.1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
Instruction following
Not comparable- Claude 3.5 Sonnet
- Not measured
- Claude Mythos 5.1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
| Category | Claude 3.5 Sonnet | Claude Mythos 5.1 | Weighted basis | Reading |
|---|---|---|---|---|
| Agentic | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
| Coding | 49.0 | Not measured | Not comparable1 vs 0 rows | Not comparable |
| Reasoning | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
| Knowledge | 59.4 | Not measured | Not comparable1 vs 0 rows | Not comparable |
| Math | 1.6 | Not measured | Not comparable2 vs 0 rows | Not comparable |
| Multilingual | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
| Multimodal | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
| Instruction following | Not measured | Not measured | Not comparable0 vs 0 rows | 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 3.5 Sonnet
- $0.0105
- Fits in one request
- Claude Mythos 5.1
- API rate not published
- Fits in one request
Claude Mythos 5.1 has no comparable published API token rate.
Repository review
50K fresh input + 3K output tokens
- Claude 3.5 Sonnet
- $0.195
- Fits in one request
- Claude Mythos 5.1
- API rate not published
- Fits in one request
Claude Mythos 5.1 has no comparable published API token rate.
Cache-heavy agent loop
200K cached + 20K fresh input + 10K output tokens
- Claude 3.5 Sonnet
- $0.81
- Does not fit in one request
- Cached input priced at the published list-input rate
- Claude Mythos 5.1
- API rate not published
- Fits in one request
- Cached-input rate unavailable
Claude 3.5 Sonnet does not fit this workload in one request. Claude 3.5 Sonnet has no published cached-input rate, so cached tokens use its listed input rate. Claude Mythos 5.1 has no comparable published API token rate.
Specification differences
Sourced differences are shown directly. Missing facts stay explicit instead of being inferred from a model name or family.
SpecificationClaude 3.5 SonnetClaude Mythos 5.1
Context window
Maximum documented context; output-token limits may be lower.
Claude 3.5 Sonnet
200K
Claude Mythos 5.1
API model ID
Claude 3.5 Sonnet
Not sourced
Claude Mythos 5.1
Not sourced
Cached-input rate
A missing cached-input rate falls back to the listed input rate only in the stated workload estimate.
Claude 3.5 Sonnet
Not published
Claude Mythos 5.1
No comparable hosted API rate
Anthropic Fable 5.1 and Mythos 5.1 launchDocumented inputs
Claude 3.5 Sonnet
Not sourced
Claude Mythos 5.1
Not sourced
Documented outputs
Claude 3.5 Sonnet
Not sourced
Claude Mythos 5.1
Not sourced
Provider availability
Claude 3.5 Sonnet
Not sourced
Claude Mythos 5.1
Limited Access · Cyber Verification Program, Life Sciences Verification Program, Claude Security
Anthropic Fable 5.1 and Mythos 5.1 launchReasoning profile
Claude 3.5 Sonnet
Non-Reasoning
Claude Mythos 5.1
Reasoning
Weight access
Claude 3.5 Sonnet
Proprietary
Claude Mythos 5.1
Proprietary
License
Claude 3.5 Sonnet
Proprietary
Claude Mythos 5.1
Proprietary
Release date
Claude 3.5 Sonnet
2024-06-01
Claude Mythos 5.1
2026-09-01
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
- The public evidence has no benchmark result shared by both models, so it does not support a quality verdict.
- Workload cost
- A complete comparable API-rate estimate is not available for both models.
- Context tradeoff
- Claude Mythos 5.1 has the larger documented window (1M).
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 evidence5 rows
Frequently asked questions
Which is better, Claude 3.5 Sonnet or Claude Mythos 5.1?
The public evidence has no benchmark result shared by both models, so it does not support a quality verdict. The page therefore keeps the decision tied to the specific documented workload.
Which is better for coding, Claude 3.5 Sonnet or Claude Mythos 5.1?
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 3.5 Sonnet or Claude Mythos 5.1?
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 3.5 Sonnet or Claude Mythos 5.1?
Both models do not have comparable published API token rates, so this page does not name a universal price winner.
Which has the larger context window, Claude 3.5 Sonnet or Claude Mythos 5.1?
Claude Mythos 5.1 has the larger documented context window: 1M, compared with 200K.
Related comparisons
Last updated September 1, 2026
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