Agentic
Not comparable- Claude Mythos Preview
- Not ranked
- Claude Opus 5.5
- 82.7
- Supported · #1/156
- Basis
- BenchAlign lane · 2 vs 11 public rows
- Reading
- Not comparable
Claude Mythos Preview vs Claude Opus 5.5
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 resting on Estimated evidence or different benchmark sets are marked directional and do not name a winner.
Updated September 22, 2026. We do not rank this pair: at least one has no public score. Public scores include evidence status and uncertainty.
Both of these models will change. Get the price, version and retirement notices for the pair, each with its source. Follow model changes
Share or export
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 5.5
Claude Opus 5.5 has the lower estimated token cost for this stated workload. Costs use the listed standard API rates.
Confidence: listed-rates
Cache-heavy agent loop cost
200K cached + 20K fresh input + 10K output tokens
Claude Opus 5.5
Claude Opus 5.5 has the lower estimated token cost for this stated workload. Claude Mythos Preview has no published cached-input rate, so cached tokens use its listed input rate.
Confidence: rate-fallback
Show secondary and unsupported calls
Repository review cost
50K fresh input + 3K output tokens
Claude Opus 5.5
Claude Opus 5.5 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
Claude Mythos Preview is not ranked on the public lane for coding, so no winner is named for coding.
Confidence: limited
Agentic work
Tool use, computer use, and multi-step task completion
Not enough matched evidence
Claude Mythos Preview is not ranked on the public lane for agentic, so no winner is named for agentic.
Confidence: limited
Long documents
Prompts that approach the documented context limit
Not enough matched evidence
A complete context comparison is not sourced.
Confidence: limited
Which one for a specific job
Choose a job from the LLM Selector's task catalog to see the category row it rests on, under the same basis rules as the table below. A directional row stays directional; choosing a job never creates a winner.
The same task catalog as the LLM Selector. Each job names the evidence surface it rests on; nothing here adds a new score.
—Claude Mythos Preview76.0Claude Opus 5.5
Not comparable · BenchAlign
The coding row is not comparable on the public lane: at least one model is not measured or not ranked there.
Coding scores combine specific tasks and setups. Match the editor, harness, and effort to your workflow.
What is actually comparable
Shared results can support a head-to-head reading. Results present for only one model describe coverage, not superiority.
2 Claude Mythos Preview only
48 Claude Opus 5.5 only
- Shared results
- 0
- Claude Mythos Preview only
- 2
- Claude Opus 5.5 only
- 48
- Like-for-like categories
- 0 / 8
Category results, on a stated basis
Each row shows the public-lane category score for both models: the BenchAlign lane for agentic, coding, and knowledge, and the weighted public rows elsewhere, with the same rank each model page reports. A row is like-for-like only when both scores rest on Supported evidence or the same weighted set. Directional and not-comparable rows remain visible, but they never receive a winner.
Coding
Not comparable- Claude Mythos Preview
- Not ranked
- Claude Opus 5.5
- 76.0
- Estimated · #4/159
- Basis
- BenchAlign lane · 0 vs 9 public rows
- Reading
- Not comparable
Reasoning
Not comparable- Claude Mythos Preview
- Not ranked
- Claude Opus 5.5
- 78.5
- #4/19
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Multimodal
Not comparable- Claude Mythos Preview
- Not ranked
- Claude Opus 5.5
- 88.8
- #3/50
- Basis
- Provisional lane · 0 vs 1 weighted rows
- Reading
- Not comparable
Knowledge
Not comparable- Claude Mythos Preview
- Not ranked
- Claude Opus 5.5
- 81.5
- Estimated · #3/187
- Basis
- BenchAlign lane · 0 vs 17 public rows
- Reading
- Not comparable
Multilingual
Not comparable- Claude Mythos Preview
- Not ranked
- Claude Opus 5.5
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Instruction following
Not comparable- Claude Mythos Preview
- Not ranked
- Claude Opus 5.5
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Math
Not comparable- Claude Mythos Preview
- Not ranked
- Claude Opus 5.5
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
| Category | Claude Mythos Preview | Claude Opus 5.5 | Basis | Reading |
|---|---|---|---|---|
| Agentic | Not ranked | 82.7Supported · #1/156 | Not comparableBenchAlign lane · 2 vs 11 public rows | Not comparable |
| Coding | Not ranked | 76.0Estimated · #4/159 | Not comparableBenchAlign lane · 0 vs 9 public rows | Not comparable |
| Reasoning | Not ranked | 78.5#4/19 | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
| Multimodal | Not ranked | 88.8#3/50 | Not comparableProvisional lane · 0 vs 1 weighted rows | Not comparable |
| Knowledge | Not ranked | 81.5Estimated · #3/187 | Not comparableBenchAlign lane · 0 vs 17 public rows | Not comparable |
| Multilingual | Not ranked | Not ranked | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
| Instruction following | Not ranked | Not ranked | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
| Math | Not ranked | Not ranked | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
Ranks count the models scored in each category’s lane, so the agentic, coding, and knowledge denominators (BenchAlign) differ from the provisional-lane categories. Unranked scores sit on the lane’s scale but never name a winner. Like-for-like rows within 0.5 points read as a practical tie.
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 5.5
- $0.014
- Fits in one request
Claude Opus 5.5 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 5.5
- $0.26
- Fits in one request
Claude Opus 5.5 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 5.5
- $0.32
- Fits in one request
Claude Opus 5.5 has the lower modeled cost
Claude Mythos Preview 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.
SpecificationClaude Mythos PreviewClaude Opus 5.5
Context window
Maximum documented context; output-token limits may be lower.
Claude Mythos Preview
Not sourced
Anthropic Project GlasswingClaude Opus 5.5
API model ID
Claude Mythos Preview
claude-mythos-preview
Anthropic Project GlasswingClaude Opus 5.5
claude-opus-5-5
Anthropic Claude Opus 5.5 model documentationCached-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 GlasswingClaude Opus 5.5
$0.2 per 1M cached input tokens
Claude Opus 5.5 model documentationDocumented inputs
Claude Mythos Preview
Not sourced
Claude Opus 5.5
Documented outputs
Claude Mythos Preview
Not sourced
Claude Opus 5.5
Provider availability
Claude Mythos Preview
Limited Access · Project Glasswing participants
Anthropic Project GlasswingClaude Opus 5.5
Generally Available · Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry, Claude Platform on AWS
Anthropic Claude Opus 5.5 model documentationReasoning profile
Claude Mythos Preview
Reasoning
Claude Opus 5.5
Reasoning
Weight access
Claude Mythos Preview
Proprietary
Claude Opus 5.5
Proprietary
License
Claude Mythos Preview
Proprietary
Claude Opus 5.5
Proprietary
Release date
Claude Mythos Preview
2026-04-07
Claude Opus 5.5
2026-09-22
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
- Repository review: $1.63 vs $0.26. Cache-heavy agent loop: $6.75 vs $0.32.
- 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 evidence50 rows
Agentic
CyberGym
Claude Mythos Preview83.1%SourceClaude Opus 5.5—Not directly comparable
ExploitGym
Claude Mythos Preview17.5%SourceClaude Opus 5.5—Not directly comparable
Terminal-Bench 4.0
Claude Mythos Preview—Claude Opus 5.566.40%SourceNot directly comparable
Terminal-Bench-Science 0.1
Claude Mythos Preview—Claude Opus 5.558.7%SourceNot directly comparable
AutomationBench
Claude Mythos Preview—Claude Opus 5.540.0%SourceNot directly comparable
HLE w/ tools
Claude Mythos Preview—Claude Opus 5.567.7%SourceNot directly comparable
OSWorld 2.0
Claude Mythos Preview—Claude Opus 5.548.7%SourceNot directly comparable
LAB all-pass (Harvey held-out)
Claude Mythos Preview—Claude Opus 5.58.3%SourceNot directly comparable
LAB criterion-pass (Harvey held-out)
Claude Mythos Preview—Claude Opus 5.591.2%SourceNot directly comparable
Toolathlon-Verified
Claude Mythos Preview—Claude Opus 5.577.8%SourceNot directly comparable
Toolathlon Verified Pass@3
Claude Mythos Preview—Claude Opus 5.582.4%SourceNot directly comparable
Toolathlon Verified Pass³
Claude Mythos Preview—Claude Opus 5.572.2%SourceNot directly comparable
Toolathlon Verified avg. turns
Claude Mythos Preview—Claude Opus 5.526.9 turnsSourceNot directly comparable
Coding
FrontierCode 1.1 Main
Claude Mythos Preview—Claude Opus 5.554.4%SourceNot directly comparable
cursorBench40
Claude Mythos Preview—Claude Opus 5.557.8%SourceNot directly comparable
SWE-bench Pro
Claude Mythos Preview—Claude Opus 5.589.9%SourceNot directly comparable
SWE Multilingual
Claude Mythos Preview—Claude Opus 5.593.9%SourceNot directly comparable
SWE Multimodal
Claude Mythos Preview—Claude Opus 5.561.4%SourceNot directly comparable
DeepSWE
Claude Mythos Preview—Claude Opus 5.574.2%SourceNot directly comparable
FrontierCode 1.1 Extended
Claude Mythos Preview—Claude Opus 5.563.6%SourceNot directly comparable
FrontierSWE v2
Claude Mythos Preview—Claude Opus 5.562.3%SourceNot directly comparable
ProgramBench
Claude Mythos Preview—Claude Opus 5.591.2%SourceNot directly comparable
Multimodal
Chartography (tools)
Claude Mythos Preview—Claude Opus 5.589.0%SourceNot directly comparable
Chartography (no tools)
Claude Mythos Preview—Claude Opus 5.564.4%SourceNot directly comparable
BenchCAD Vision2Code (no tools)
Claude Mythos Preview—Claude Opus 5.50.730SourceNot directly comparable
BenchCAD Vision2Code (tools)
Claude Mythos Preview—Claude Opus 5.50.962SourceNot directly comparable
Biomedical image analysis
Claude Mythos Preview—Claude Opus 5.571.4%SourceNot directly comparable
OfficeQA
Claude Mythos Preview—Claude Opus 5.578.9%SourceNot directly comparable
OfficeQA Pro
Claude Mythos Preview—Claude Opus 5.567.7%SourceNot directly comparable
Knowledge
HLE
Claude Mythos Preview—Claude Opus 5.567.7%SourceNot directly comparable
HLE w/o tools
Claude Mythos Preview—Claude Opus 5.564.4%SourceNot directly comparable
HealthBench (raw)
Claude Mythos Preview—Claude Opus 5.568.1%SourceNot directly comparable
HealthBench (length-adjusted)
Claude Mythos Preview—Claude Opus 5.560.6%SourceNot directly comparable
HealthBench Professional
Claude Mythos Preview—Claude Opus 5.565.6%SourceNot directly comparable
HealthBench Professional (raw)
Claude Mythos Preview—Claude Opus 5.577.1%SourceNot directly comparable
BioMysteryBench (human-solvable)
Claude Mythos Preview—Claude Opus 5.589.3%SourceNot directly comparable
BioMysteryBench (human-difficult)
Claude Mythos Preview—Claude Opus 5.550.0%SourceNot directly comparable
SpatialBench Verified
Claude Mythos Preview—Claude Opus 5.572.0%SourceNot directly comparable
SingleCellBench
Claude Mythos Preview—Claude Opus 5.561.2%SourceNot directly comparable
Morphology-to-molecule matching
Claude Mythos Preview—Claude Opus 5.534.0%SourceNot directly comparable
Medicinal chemistry
Claude Mythos Preview—Claude Opus 5.563.5%SourceNot directly comparable
Protein Design
Claude Mythos Preview—Claude Opus 5.560.2%SourceNot directly comparable
Protein Design library ranking
Claude Mythos Preview—Claude Opus 5.556.0%SourceNot directly comparable
De novo protein-binder design
Claude Mythos Preview—Claude Opus 5.582.6%SourceNot directly comparable
Protocols (troubleshooting)
Claude Mythos Preview—Claude Opus 5.573.7%SourceNot directly comparable
Protocols (understanding)
Claude Mythos Preview—Claude Opus 5.569.0%SourceNot directly comparable
Multilingual
Math
Questions
Which is better, Claude Mythos Preview or Claude Opus 5.5?
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 Mythos Preview or Claude Opus 5.5?
Claude Mythos Preview is not ranked on the public lane for coding, so no winner is named for coding.
Which is better for agentic tasks, Claude Mythos Preview or Claude Opus 5.5?
Claude Mythos Preview is not ranked on the public lane for agentic tasks, so no winner is named for agentic tasks.
Which costs less, Claude Mythos Preview or Claude Opus 5.5?
For the stated presets, chat costs $0.0875 on Claude Mythos Preview and $0.014 on Claude Opus 5.5; repository review costs $1.63 and $0.26; the cache-heavy agent loop costs $6.75 and $0.32. Claude Mythos Preview 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 5.5?
A complete documented context-window comparison is not available.
Related comparisons
Last updated September 22, 2026
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