Model comparison

Claude Fable 5.1 vs Claude Opus 5.5

Anthropic's Claude Fable 5.1 against Anthropic's Claude Opus 5.5: vendor list prices, limits, abilities and the Artificial Analysis indexes side by side - and what OpenSmartRoute does when both are available.

CheaperClaude Opus 5.5

Claude Opus 5.5 lists at $8.00 per million tokens blended against $20 for Claude Fable 5.1 - 2.5x less.

Stronger on intelligenceClaude Opus 5.5

Claude Opus 5.5 scores 58 on the intelligence index against 53 - 4 points apart.

Side by side

Vendor list prices per million tokens and published limits; indexes are Artificial Analysis composites (0-100).

Specification	Claude Fable 5.1	Claude Opus 5.5
Input price / 1M tokens	$10.0	$4.00
Output price / 1M tokens	$50.0	$20.0
Blended (3 in : 1 out)	$20.0	$8.00
Cached input / 1M	$0.25	$0.20
Context window	1M	1M
Max output	128K	128K
Input	text, image, file	text, image, file
Output	text	text
Tool calls
Structured output
Reasoning
Open weights
Intelligence index	53	58
Coding index	82	-
Agentic index	58	-
Released	Sep 1, 2026	Sep 22, 2026
Available on this deployment

What a month costs

List price times tokens for three typical workloads; your mix of input and output decides which model's pricing suits you.

Workload	Claude Fable 5.1	Claude Opus 5.5	Difference
Support chat20M tokens in, 5M out a month - a help desk answering a few thousand conversations.	$450	$180	$270 less on Claude Opus 5.5
Document summaries100M in, 5M out - long inputs, short answers.	$1,250	$500	$750 less on Claude Opus 5.5
Coding assistant60M in, 20M out - a team's editor assistant, output-heavy.	$1,600	$640	$960 less on Claude Opus 5.5

What the router does with the pair

Claude Opus 5.5 is both cheaper and stronger on the intelligence index, so with both in the catalogue the router sends it almost everything; Claude Fable 5.1 earns a request only on something it alone offers - a longer context, a modality, a data boundary or a region your rules require.

Price a request Playground

yaml

# targets.yaml - both models as routing targets (metadata.model links each to the catalogue entry)
targets:
  - { id: claude-opus-5.5, kind: llm, metadata: { model: anthropic/claude-opus-5.5 } }
  - { id: claude-fable-5.1, kind: llm, metadata: { model: anthropic/claude-fable-5.1 } }

# rules.yaml - the cheaper model by default, the stronger one when the request is hard
rules:
  - name: simple-requests-stay-cheap
    when: { max_complexity: 0.45 }
    prefer: [claude-opus-5.5]
    weight: 0.8
  - name: hard-requests-escalate
    when: { min_complexity: 0.45 }
    prefer: [claude-fable-5.1]
    weight: 0.8

Frequently asked

Is Claude Fable 5.1 cheaper than Claude Opus 5.5?: No. Claude Fable 5.1 lists at $10.0 in / $50.0 out per million tokens, Claude Opus 5.5 at $4.00 in / $20.0 out; blended, Claude Opus 5.5 is the cheaper one.
Which is better, Claude Fable 5.1 or Claude Opus 5.5?: On the Artificial Analysis intelligence index Claude Opus 5.5 scores higher (58 against 53). "Better" depends on the task: the coding and agentic indexes below and the abilities row may point the other way for your requests.
Which has the longer context window?: Both accept 1M tokens.
Can I use Claude Fable 5.1 and Claude Opus 5.5 together?: Yes. Declare both as targets and OpenSmartRoute picks one per request on quality for the task, price and your rules - the cheaper model for the requests it can answer, the stronger one for the rest - and records why in the trace.

Also compared

Every Anthropic and Anthropic model, with prices, is on the vendor pages; the rankings show what the router actually picks.

For the business

What it means for which models you pay for.

Catalogue of every vendor
The right model, not the famous one
Price, context, abilities and benchmark indexes side by side, with the model that fits each task named.
The rankings
89% less
Lower cost per request
On the 150-prompt benchmark the router spent 89% less than sending every prompt to the reference model, and the judged quality went up, not down.
Read the benchmark
Per million tokens, every model
Prices you can compare
The catalogue prints input and output prices and what three typical monthly workloads cost on each.
The model catalogue

Which LLM is the cheapest for our workload?: The best-for pages rank the live catalogue per task by the index that measures it, and the router picks the cheapest model that meets your quality rule for each request.
How much can we save on our LLM bill?: On the public benchmark the router saved 89% against sending everything to the reference model. Import last month's provider bill on the bill page and the estimate is computed on your own traffic before you change a line of code.
How often do model prices change?: The catalogue is refreshed from the vendors' price lists; each model page shows the date of its data.

Stop choosing between Claude Fable 5.1 and Claude Opus 5.5. Route to both.

Declare the pair as targets and OpenSmartRoute picks per request - the cheaper one where it holds up, the stronger one where it matters - with the comparison in every trace.

Create a free account Try a request

Free plan, no card. Fifteen thousand decisions a month with the full trace.

Specification

Claude Fable 5.1

Claude Opus 5.5

Input price / 1M tokens

$10.0

$4.00

Output price / 1M tokens

$50.0

$20.0

Blended (3 in : 1 out)

$20.0

$8.00

Cached input / 1M

$0.25

$0.20

Context window

Max output

128K

Input

text, image, file

Output

text

Tool calls

Structured output

Reasoning

Open weights

Intelligence index

Coding index

Agentic index

Released

Sep 1, 2026

Sep 22, 2026

Available on this deployment

Workload

Claude Fable 5.1

Claude Opus 5.5

Difference

Support chat20M tokens in, 5M out a month - a help desk answering a few thousand conversations.

$450

$180

$270 less on Claude Opus 5.5

Document summaries100M in, 5M out - long inputs, short answers.

$1,250

$500

$750 less on Claude Opus 5.5

Coding assistant60M in, 20M out - a team's editor assistant, output-heavy.

$1,600

$640

$960 less on Claude Opus 5.5

What the router does with the pair

# targets.yaml - both models as routing targets (metadata.model links each to the catalogue entry) targets: - { id: claude-opus-5.5, kind: llm, metadata: { model: anthropic/claude-opus-5.5 } } - { id: claude-fable-5.1, kind: llm, metadata: { model: anthropic/claude-fable-5.1 } } # rules.yaml - the cheaper model by default, the stronger one when the request is hard rules: - name: simple-requests-stay-cheap when: { max_complexity: 0.45 } prefer: [claude-opus-5.5] weight: 0.8 - name: hard-requests-escalate when: { min_complexity: 0.45 } prefer: [claude-fable-5.1] weight: 0.8

Frequently asked

Is Claude Fable 5.1 cheaper than Claude Opus 5.5?

No. Claude Fable 5.1 lists at $10.0 in / $50.0 out per million tokens, Claude Opus 5.5 at $4.00 in / $20.0 out; blended, Claude Opus 5.5 is the cheaper one.

Which is better, Claude Fable 5.1 or Claude Opus 5.5?

On the Artificial Analysis intelligence index Claude Opus 5.5 scores higher (58 against 53). "Better" depends on the task: the coding and agentic indexes below and the abilities row may point the other way for your requests.

Which has the longer context window?

Both accept 1M tokens.

Can I use Claude Fable 5.1 and Claude Opus 5.5 together?

Yes. Declare both as targets and OpenSmartRoute picks one per request on quality for the task, price and your rules - the cheaper model for the requests it can answer, the stronger one for the rest - and records why in the trace.

Claude Fable 5.1 vs Claude Opus 5.5

Side by side

What a month costs

What the router does with the pair

Frequently asked

Also compared

What it means for which models you pay for.

The right model, not the famous one

Lower cost per request

Prices you can compare

Stop choosing between Claude Fable 5.1 and Claude Opus 5.5. Route to both.

Claude Fable 5.1 vs Claude Opus 5.5

Side by side

What a month costs

What the router does with the pair

Frequently asked

Also compared

What it means for which models you pay for.

The right model, not the famous one

Lower cost per request

Prices you can compare

Stop choosing between Claude Fable 5.1 and Claude Opus 5.5. Route to both.