Coding
Like-for-like- Claude Fable 5
- 76.9
- Supported · #2/183
- Mercury 2
- 25.5
- Supported · #177/183
- Basis
- BenchAlign lane · 10 vs 0 public rows
- Reading
- Claude Fable 5 leads
Claude Fable 5 vs Mercury 2
Updated September 4, 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 resting on Estimated evidence or different benchmark sets are marked directional and do not name a winner.
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.
Coding work
Code generation, repair, and software-engineering tasks
Claude Fable 5
Claude Fable 5 leads on the public coding lane, 76.9 to 25.5, with Supported evidence for both models and non-overlapping 90% intervals.
Confidence: stronger
Long documents
Prompts that approach the documented context limit
Claude Fable 5
Claude Fable 5 has the larger documented context window.
Confidence: documented
Chat turn cost
1K fresh input + 500 output tokens
Mercury 2
Mercury 2 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 2
Mercury 2 has the lower estimated token cost for this stated workload. Costs use the listed standard API rates.
Confidence: listed-rates
Agentic work
Tool use, computer use, and multi-step task completion
Not enough matched evidence
Mercury 2 is scored on Estimated evidence for agentic, so the reading is directional rather than like-for-like.
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. Mercury 2 does not fit this workload in one request.
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.
18 Claude Fable 5 only
- Shared results
- 0
- Claude Fable 5 only
- 18
- Mercury 2 only
- 0
- Like-for-like categories
- 1 / 8
1 category rests on Estimated evidence or different evidence sets. Those rows remain visible for coverage context but do not name a winner.
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.
Agentic
Directional only- Claude Fable 5
- 74.8
- Supported · #3/151
- Mercury 2
- 42.7
- Estimated · #112/151
- Basis
- BenchAlign lane · 4 vs 0 public rows
- Reading
- Directional only
Reasoning
Not comparable- Claude Fable 5
- 76.2
- #11/22
- Mercury 2
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Knowledge
Not comparable- Claude Fable 5
- 83.5
- Supported · #2/181
- Mercury 2
- Not ranked
- Basis
- BenchAlign lane · 2 vs 0 public rows
- Reading
- Not comparable
Math
Not comparable- Claude Fable 5
- Not ranked
- Mercury 2
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Multilingual
Not comparable- Claude Fable 5
- Not ranked
- Mercury 2
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Multimodal
Not comparable- Claude Fable 5
- 62.5
- Unranked · 2 rankable rows
- Mercury 2
- Not ranked
- Basis
- Provisional lane · 1 vs 0 weighted rows
- Reading
- Not comparable
Instruction following
Not comparable- Claude Fable 5
- 78.3
- #54/120
- Mercury 2
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
| Category | Claude Fable 5 | Mercury 2 | Basis | Reading |
|---|---|---|---|---|
| Coding | 76.9Supported · #2/183 | 25.5Supported · #177/183 | Like-for-likeBenchAlign lane · 10 vs 0 public rows | Claude Fable 5 leads |
| Agentic | 74.8Supported · #3/151 | 42.7Estimated · #112/151 | Directional onlyBenchAlign lane · 4 vs 0 public rows | Directional only |
| Reasoning | 76.2#11/22 | Not ranked | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
| Knowledge | 83.5Supported · #2/181 | Not ranked | Not comparableBenchAlign lane · 2 vs 0 public rows | Not comparable |
| Math | Not ranked | Not ranked | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
| Multilingual | Not ranked | Not ranked | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
| Multimodal | 62.5Unranked · 2 rankable rows | Not ranked | Not comparableProvisional lane · 1 vs 0 weighted rows | Not comparable |
| Instruction following | 78.3#54/120 | 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 Fable 5
- $0.035
- Fits in one request
- Mercury 2
- $0.00063
- Fits in one request
Mercury 2 has the lower modeled cost
Costs use the listed standard API rates.
Repository review
50K fresh input + 3K output tokens
- Claude Fable 5
- $0.65
- Fits in one request
- Mercury 2
- $0.01475
- Fits in one request
Mercury 2 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
- $0.9
- Fits in one request
- Mercury 2
- $0.0175
- Does not fit in one request
Mercury 2 does not fit this workload in one request.
Specification differences
Sourced differences are shown directly. Missing facts stay explicit instead of being inferred from a model name or family.
SpecificationClaude Fable 5Mercury 2
Context window
Maximum documented context; output-token limits may be lower.
Claude Fable 5
Mercury 2
128K
API model ID
Claude Fable 5
claude-fable-5
Anthropic model overviewMercury 2
Not sourced
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 per 1M cached input tokens
Claude API pricingMercury 2
$0.025 per 1M cached input tokens
Documented inputs
Claude Fable 5
text, image
Anthropic model overviewMercury 2
Not sourced
Documented outputs
Claude Fable 5
Mercury 2
Not sourced
Provider availability
Claude Fable 5
Generally Available · Claude API
Anthropic model overviewMercury 2
Not sourced
Reasoning profile
Claude Fable 5
Reasoning
Mercury 2
Reasoning
Weight access
Claude Fable 5
Proprietary
Mercury 2
Proprietary
License
Claude Fable 5
Proprietary
Mercury 2
Proprietary
Release date
Claude Fable 5
2026-06-09
Mercury 2
2026-02-24
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
- The public evidence has no benchmark result shared by both models, so it does not support a quality verdict.
- Workload cost
- Repository review: $0.65 vs $0.01475. Cache-heavy agent loop: $0.9 vs $0.0175.
- Context tradeoff
- Claude Fable 5 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 evidence18 rows
Agentic
Terminal-Bench 3.0
Claude Fable 534.0%SourceMercury 2—Not directly comparable
Terminal-Bench 2.0
Claude Fable 584.3%SourceMercury 2—Not directly comparable
OSWorld-Verified
Claude Fable 585%SourceMercury 2—Not directly comparable
Terminal-Bench 2.1 (Vals)
Claude Fable 580.5%SourceMercury 2—Not directly comparable
Coding
SWE-bench Verified
Claude Fable 595%SourceMercury 2—Not directly comparable
SWE-bench Pro
Claude Fable 580%SourceMercury 2—Not directly comparable
FrontierSWE v2
Claude Fable 548.0%SourceMercury 2—Not directly comparable
FrontierCode 1.1 Main
Claude Fable 553.5%SourceMercury 2—Not directly comparable
Terminal-Bench 2.0
Claude Fable 584.3%SourceMercury 2—Not directly comparable
cursorBench31
Claude Fable 570.6%SourceMercury 2—Not directly comparable
cursorBench32
Claude Fable 570.5%SourceMercury 2—Not directly comparable
VulcanBench v3
Claude Fable 589.5%SourceMercury 2—Not directly comparable
LiveCodeBench (Vals)
Claude Fable 589.8%SourceMercury 2—Not directly comparable
SWE-bench (Vals)
Claude Fable 595.0%SourceMercury 2—Not directly comparable
Knowledge
Multimodal
Frequently asked questions
Which is better, Claude Fable 5 or Mercury 2?
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 Fable 5 or Mercury 2?
Claude Fable 5 leads the public coding lane, 76.9 to 25.5, with Supported evidence for both models and non-overlapping 90% intervals.
Which is better for agentic tasks, Claude Fable 5 or Mercury 2?
Claude Fable 5 scores higher for agentic tasks on the public lane, 74.8 to 42.7. Mercury 2 is scored on Estimated evidence for agentic tasks, so the reading is directional rather than like-for-like. BenchLM does not name a winner for agentic tasks from a directional reading; read the shared benchmark rows directly and test the models on the same task set.
Which costs less, Claude Fable 5 or Mercury 2?
For the stated presets, chat costs $0.035 on Claude Fable 5 and $0.00063 on Mercury 2; repository review costs $0.65 and $0.01475; the cache-heavy agent loop costs $0.9 and $0.0175. Mercury 2 does not fit this workload in one request.
Which has the larger context window, Claude Fable 5 or Mercury 2?
Claude Fable 5 has the larger documented context window: 1M, compared with 128K.
Related comparisons
Last updated September 4, 2026
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