Chat turn cost
1K fresh input + 500 output tokens
Mercury 3
Mercury 3 has the lower estimated token cost for this stated workload. Costs use the listed standard API rates.
Confidence: listed-rates
Claude Fable 5.1 vs Mercury 3
Updated October 19, 2026. We do not rank this pair: at least one has no public score. Public scores include evidence status and uncertainty.
Share or export
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 resting on Estimated evidence or different benchmark sets are marked directional and do not name a winner.
- Shared results
- 1
- Claude Fable 5.1 only
- 32
- Mercury 3 only
- 7
- Like-for-like categories
- 0 / 8
Supported: Claude Fable 5.1How the comparison works
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.
Cache-heavy agent loop cost
200K cached + 20K fresh input + 10K output tokens
Mercury 3
Mercury 3 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
Mercury 3
Mercury 3 has the lower estimated token cost for this stated workload. Costs use the listed standard API rates.
Confidence: listed-ratesCoding work
Code generation, repair, and software-engineering tasks
Not enough matched evidence
Mercury 3 is not ranked on the public lane for coding, so no winner is named for coding.
Confidence: limitedAgentic work
Tool use, computer use, and multi-step task completion
Not enough matched evidence
Mercury 3 is not ranked on the public lane for agentic, so no winner is named for agentic.
Confidence: limitedLong documents
Prompts that approach the documented context limit
No clear pick
The documented context windows are equal.
Confidence: documented
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.
76.9Claude Fable 5.1—Mercury 3
Not comparable · BenchAlign v5.8
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.
Same basis rules as the category table below
What is actually comparable
Shared results can support a head-to-head reading. Results present for only one model describe coverage, not superiority.
32 Claude Fable 5.1 only
1 Shared
7 Mercury 3 only
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.
Category results, on a stated basis
Each row shows the public-lane category score for both models: the BenchAlign v5.8 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.
Agentic
Not comparable- Claude Fable 5.1
- 80.8
- Supported · #2/130
- Mercury 3
- Not ranked
- Basis
- BenchAlign v5.8 lane · 12 vs 3 public rows
- Reading
- Not comparable
Coding
Not comparable- Claude Fable 5.1
- 76.9
- Supported · #3/151
- Mercury 3
- Not ranked
- Basis
- BenchAlign v5.8 lane · 11 vs 1 public rows
- Reading
- Not comparable
Reasoning
Not comparable- Claude Fable 5.1
- 85.2
- #5/27
- Mercury 3
- Not ranked
- Basis
- Provisional lane · 1 vs 1 weighted rows
- Reading
- Not comparable
Multimodal
Not comparable- Claude Fable 5.1
- Not ranked
- Mercury 3
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Knowledge
Not comparable- Claude Fable 5.1
- 86.9
- Supported · #2/186
- Mercury 3
- Not ranked
- Basis
- BenchAlign v5.8 lane · 4 vs 1 public rows
- Reading
- Not comparable
Multilingual
Not comparable- Claude Fable 5.1
- Not ranked
- Mercury 3
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Instruction following
Not comparable- Claude Fable 5.1
- Not ranked
- Mercury 3
- Not ranked
- Basis
- Provisional lane · 0 vs 1 weighted rows
- Reading
- Not comparable
Math
Not comparable- Claude Fable 5.1
- 96.8
- Unranked · 2 rankable rows
- Mercury 3
- Not ranked
- Basis
- Provisional lane · 2 vs 0 weighted rows
- Reading
- Not comparable
| Category | Claude Fable 5.1 | Mercury 3 | Basis | Reading |
|---|---|---|---|---|
| Agentic | 80.8Supported · #2/130 | Not ranked | Not comparableBenchAlign v5.8 lane · 12 vs 3 public rows | Not comparable |
| Coding | 76.9Supported · #3/151 | Not ranked | Not comparableBenchAlign v5.8 lane · 11 vs 1 public rows | Not comparable |
| Reasoning | 85.2#5/27 | Not ranked | Not comparableProvisional lane · 1 vs 1 weighted rows | Not comparable |
| Multimodal | Not ranked | Not ranked | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
| Knowledge | 86.9Supported · #2/186 | Not ranked | Not comparableBenchAlign v5.8 lane · 4 vs 1 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 1 weighted rows | Not comparable |
| Math | 96.8Unranked · 2 rankable rows | Not ranked | Not comparableProvisional lane · 2 vs 0 weighted rows | Not comparable |
Ranks count the models scored in each category’s lane, so the agentic, coding, and knowledge denominators (BenchAlign v5.8) differ from the provisional-lane categories. Unranked scores sit on the provisional lane’s scale but never name a winner. Like-for-like rows within 0.5 points read as a practical tie.
Supported evidence per lane · bars run 0–100Methodology
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 Fable 5.1
- $0.035
- Fits in one request
- Mercury 3
- $0.00028
- Fits in one request
Mercury 3 has the lower modeled cost
Costs use the listed standard API rates.
Repository review
50K fresh input + 3K output tokens
- Claude Fable 5.1
- $0.65
- Fits in one request
- Mercury 3
- $0.00605
- Fits in one request
Mercury 3 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 Fable 5.1
- $0.75
- Fits in one request
- Mercury 3
- $0.0075
- Fits in one request
Mercury 3 has the lower modeled cost
Costs use the listed standard API rates.
Cached input falls back to the list input rate only where a cached rate is unpublished
Specification differences
Sourced differences are shown directly. Missing facts stay explicit instead of being inferred from a model name or family.
SpecificationClaude Fable 5.1Mercury 3
Context window
Maximum documented context; output-token limits may be lower.
Claude Fable 5.1
API model ID
Claude Fable 5.1
claude-fable-5-1
Anthropic Fable 5.1 and Mythos 5.1 launchMercury 3
Cached-input rate
A missing cached-input rate falls back to the listed input rate only in the stated workload estimate.
Claude Fable 5.1
$0.25 per 1M cached input tokens
Anthropic Fable 5.1 launchMercury 3
$0.01 per 1M cached input tokens
Inception Mercury 3 models page and launch pricingDocumented inputs
Claude Fable 5.1
Not sourced
Mercury 3
Not sourced
Documented outputs
Claude Fable 5.1
Not sourced
Mercury 3
Not sourced
Provider availability
Claude Fable 5.1
Generally Available · Claude API, Claude products, AWS, Google Cloud, Microsoft Azure
Anthropic Fable 5.1 and Mythos 5.1 launchMercury 3
Not sourced
Reasoning profile
Claude Fable 5.1
Reasoning
Mercury 3
Reasoning
Weight access
Claude Fable 5.1
Proprietary
Mercury 3
Proprietary
License
Claude Fable 5.1
Proprietary
Mercury 3
Proprietary
Release date
Claude Fable 5.1
2026-09-01
Mercury 3
2026-10-19
If you already use one of these models
- Deployment change
- The models list different providers, so authentication, endpoint behavior, limits, and feature support may change.
- 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: $0.65 vs $0.00605. Cache-heavy agent loop: $0.75 vs $0.0075.
- Context tradeoff
- Both models list 1M.
Run the same representative tasks against both endpoints before changing production traffic.
Questions
Which is better, Claude Fable 5.1 or Mercury 3?
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 Fable 5.1 or Mercury 3?
Mercury 3 is not ranked on the public lane for coding, so no winner is named for coding.
Which is better for agentic tasks, Claude Fable 5.1 or Mercury 3?
Mercury 3 is not ranked on the public lane for agentic tasks, so no winner is named for agentic tasks.
Which costs less, Claude Fable 5.1 or Mercury 3?
For the stated presets, chat costs $0.035 on Claude Fable 5.1 and $0.00028 on Mercury 3; repository review costs $0.65 and $0.00605; the cache-heavy agent loop costs $0.75 and $0.0075. Costs use the listed standard API rates.
Which has the larger context window, Claude Fable 5.1 or Mercury 3?
Both models list the same context window, 1M.
Benchmark evidence
The full public result ledger is available for audit without forcing a wide desktop table onto a phone.
Browse raw public benchmark evidence40 rows
Agentic
Terminal-Bench 4.0
Claude Fable 5.155.80%SourceMercury 3—Not directly comparable
Terminal-Bench-Science 0.1
Claude Fable 5.152.6%SourceMercury 3—Not directly comparable
OSWorld 2.0
Claude Fable 5.141.7%SourceMercury 3—Not directly comparable
AutomationBench
Claude Fable 5.131.4%SourceMercury 3—Not directly comparable
Toolathlon-Verified
Claude Fable 5.177.8%SourceMercury 3—Not directly comparable
Toolathlon Verified Pass@3
Claude Fable 5.181.5%SourceMercury 3—Not directly comparable
Toolathlon Verified Pass³
Claude Fable 5.173.1%SourceMercury 3—Not directly comparable
Toolathlon Verified avg. turns
Claude Fable 5.123.7 turnsSourceMercury 3—Not directly comparable
Terminal-Bench 2.1 (Vals)
Claude Fable 5.185.0%SourceMercury 3—Not directly comparable
ApprenticeBench
Claude Fable 5.172%SourceMercury 3—Not directly comparable
CWE-bench v1
Claude Fable 5.158.0%SourceMercury 3—Not directly comparable
MazeBench
Claude Fable 5.110%SourceMercury 3—Not directly comparable
τ³-bench results
Claude Fable 5.1—Mercury 330.2%SourceNot directly comparable
BrowseComp+
Claude Fable 5.1—Mercury 355.18%SourceNot directly comparable
DeepSearchQA
Claude Fable 5.1—Mercury 371.3%SourceNot directly comparable
Coding
Bug Hunt Bench
Claude Fable 5.143.0 fixesSourceMercury 3—Not directly comparable
SWE-bench Pro
Claude Fable 5.181.2%SourceMercury 3—Not directly comparable
SWE Multilingual
Claude Fable 5.189.1%SourceMercury 3—Not directly comparable
SWE Multimodal
Claude Fable 5.154.7%SourceMercury 3—Not directly comparable
DeepSWE
Claude Fable 5.167.4%SourceMercury 346.3%SourceClaude Fable 5.1 leads this result
FrontierSWE v2
Claude Fable 5.156.3%SourceMercury 3—Not directly comparable
ProgramBench
Claude Fable 5.187.6%SourceMercury 3—Not directly comparable
CursorBench 3.2
Claude Fable 5.173.4%SourceMercury 3—Not directly comparable
LiveCodeBench (Vals)
Claude Fable 5.190.5%SourceMercury 3—Not directly comparable
CursorBench 4.0
Claude Fable 5.151.8%SourceMercury 3—Not directly comparable
PostTrainBench v1.1
Claude Fable 5.140.2%SourceMercury 3—Not directly comparable
Reasoning
Knowledge
HLE
Claude Fable 5.165%SourceMercury 3—Not directly comparable
HLE w/o tools
Claude Fable 5.160.9%SourceMercury 3—Not directly comparable
GPQA Diamond (Vals)
Claude Fable 5.193.4%SourceMercury 3—Not directly comparable
MMLU-Pro (Vals)
Claude Fable 5.192.4%SourceMercury 3—Not directly comparable
GPQA-D
Claude Fable 5.1—Mercury 389.2%SourceNot directly comparable
Instruction following
Math
40 public results · 1 shared
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Last updated October 19, 2026