Model comparison

Claude Fable 5.1 vs Claude Haiku 5.5

Two Anthropic tiers compared on the figures that decide which one a workload actually needs.

Claude Fable 5.1: profile checked October 25, 2026Claude Haiku 5.5: profile checked October 25, 2026Individual provider fields may changeEvidence confidence: Medium — see receipts below

Anthropic

Claude Fable 5.1

Frontier

Anthropic

Claude Haiku 5.5

Budget

AI model capability comparison
Specification	Claude Fable 5.1	Claude Haiku 5.5
Provider
Provider	Anthropic	Anthropic
Tier
Tier	Frontier	Budget
Context window
Context window	1M	1M
Max output
Max output	128K	128K
Input / 1M tokens
Input / 1M tokens	$10	Winner: $0.10
Output / 1M tokens
Output / 1M tokens	$50	Winner: $0.50
Weights
Weights	Closed	Not verifiedUnverified
Parameters
Parameters	Not verifiedUnverified	Not verifiedUnverified
Reasoning levels
Reasoning levels	low, medium, high, xhigh, max	Not verifiedUnverified
Modalities
Modalities	text, image	text, image
API model id
API model id	claude-fable-5-1	claude-haiku-5-5
Released
Released	September 1, 2026	October 7, 2026
Artificial Analysis Intelligence Index [max] · source date Claude Fable 5.1: 2026-10-01
Artificial Analysis Intelligence Index [max] · source date Claude Fable 5.1: 2026-10-01	53	Not verifiedUnverified
Humanity's Last Exam · source date Claude Fable 5.1: 2026-09-01
Humanity's Last Exam · source date Claude Fable 5.1: 2026-09-01	65	Not verifiedUnverified
Terminal-Bench 2.1 · source date Claude Fable 5.1: 2026-09-26
Terminal-Bench 2.1 · source date Claude Fable 5.1: 2026-09-26	91.4	Not verifiedUnverified
DeepSWE 1.1 · source date Claude Fable 5.1: 2026-09-03
DeepSWE 1.1 · source date Claude Fable 5.1: 2026-09-03	67.4	Not verifiedUnverified

Dates beside benchmark scores refer to the linked source’s publication or capture date unless that source explicitly states when it measured the result. A shared URL alone does not establish comparable runs; unverified setups are marked. Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

Where each score comes from, and how far it can be compared across models.

Source date2026-10-01
Artificial Analysis (Claude Fable 5.1 (max with fallback))
Composite index blending reasoning, knowledge, and coding evals into one 0–100 score.
Comparable with caveatOnly same-version scores are comparable. v4.3.2 was rebaselined (the top score fell from 66 on v4.1.1 to ~58), so v4.1.1 figures must not be compared with v4.3.2 figures — check the cited source and its date.
Source date2026-09-26
Artificial Analysis Terminal-Bench 2.1 (independent, Terminus 2, max effort)
Agentic terminal work: multi-step tasks executed in a sandboxed shell environment.
Comparable with caveatNot comparable with Terminal-Bench 3.0 or 4.0 (different task sets) or v1; harness configuration (container, time limits) also shifts results.
Source date2026-09-03
OpenAI GPT-6 Astra launch table quoting a cross-provider result; not a direct Datacurve row (Cross-provider quotation; Fable harness, effort and experiment date unverified)
Agentic software engineering: pass@1 on real repo tasks with reported cost per completed task.
Directly comparable
Source date2026-09-01
Anthropic Fable 5.1 announcement (vendor, with tools; 60.9 no tools) — Anthropic's later Opus 5.5 table lists 65.6; conflict preserved
Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise.
Comparable with caveatSubset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.

Pricing tiers

Claude Fable 5.1: Standard USD/MTok input/output $10/$50 with no long-context surcharge; cache reads $0.25 versus Fable 5's $1, 5-minute writes $12.50, 1-hour writes $20. Batch $5/$25. US-only inference adds 10% to input/output and cache reads/writes on Anthropic-operated routes where supported; Foundry uses US Data Zone Standard. Bedrock and Google-managed Google Cloud have independent regional prices. Adaptive thinking is always on; default effort high. Knowledge cutoff June 2026; retirement not sooner than September 1, 2027. Server-side tools can add usage fees; tool schemas/results and thinking consume billable tokens.

Claude Haiku 5.5: Base rates apply to prompts up to 100,000 tokens. Above 100,000 tokens, input is $0.50 and output $2.50 per MTok. Cache reads are $0.01/$0.05; 5-minute writes $0.125/$0.625 and 1-hour writes $0.20/$1 for short/long prompts. Batch input/output receives a 50% discount. Standard output is 128K; 300K Batch output requires the documented beta header. Adaptive thinking defaults to medium effort.

FrontierRecord checked October 25, 2026

Claude Fable 5.1

Claude Fable 5.1 is Anthropic's model for the most demanding reasoning and long-horizon agentic work at $10/$50 — Anthropic now recommends Opus 5.5 as the default for most workloads.

Best for

Frontier agents
Hardest reasoning work
Fable 5 workloads at the same price

Watch out

Standard token rates are 2.5x Opus 5.5's. Forced tool use errors; thinking blocks are model/conversation-bound, so editing earlier turns or switching models can invalidate them. Display updates and per-message effort are beta. Match benchmark settings and evaluate pinned workloads before migrating.

BudgetRecord checked October 25, 2026

Claude Haiku 5.5

Anthropic positions Haiku 5.5 for high-volume classification, extraction, routing and subagent tasks, with adaptive thinking and a 1M-token context window.

Best for

Classification and extraction
Routing
High-volume subagent tasks

Watch out

Prices increase fivefold above 100K prompt tokens. The newer tokenizer counts approximately 30% more tokens than Haiku 4.5 for the same text. Omit temperature, top_p and top_k. Thinking blocks are reusable only in the producing account or a linked account. Parameter count and weight availability remain unverified; no predecessor benchmark scores are inherited.

When the cheaper one wins

Claude Haiku 5.5 is cheaper on output at $0.50 per million tokens against $50 for Claude Fable 5.1 — about 100×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. This compares standard short-context token rates, not total cost per accepted task. Include input, cache, context tiers, schedules, retries and review in your pilot.

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Evidence confidence: Medium

How strong and complete the evidence behind this comparison is — not a prediction of which model is better.

Pricing verified on both sides — Input and output rates are verified for both models.
3/5 core specs verified on both sides — Not published for at least one side: parameter count, reasoning levels.
No directly aligned benchmark setup — No benchmark has matching cited sources, source dates, units, effort and recorded run details on both models.
Verified within the last 90 days — Older of the two catalog checks was 1 day ago.
Source citations incomplete — At least one side lacks the two-source citation set.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

Claude Fable 5.1: Whole-record source check: exact model card (accessed 2026-10-25)
Claude Fable 5.1: Whole-record source check: current publisher pricing, controls or access terms (accessed 2026-10-25)
Claude Fable 5.1: Whole-record source check: current publisher pricing, controls or access terms (accessed 2026-10-25)
Claude Fable 5.1: Whole-record source check: current publisher pricing, controls or access terms (accessed 2026-10-25)
Claude Fable 5.1: Anthropic models overview — Fable 5.1 (1M context, 128K output) (accessed 2026-09-03)
Claude Fable 5.1: Anthropic — Claude Fable and Mythos 5.1 announcement (accessed 2026-09-26)
Claude Fable 5.1: Anthropic models overview — Opus 5.5 default; Fable 5.1 for demanding reasoning (accessed 2026-09-26)
Claude Haiku 5.5: Anthropic Haiku 5.5 specifications, release date and scoped pricing (accessed 2026-10-25)

Related comparisons

Diving deeper on one model? Claude Fable 5.1 · Claude Haiku 5.5

Common questions

Claude Fable 5.1 vs Claude Haiku 5.5

Answered from the verified figures on this page rather than general guidance.

Is Claude Fable 5.1 or Claude Haiku 5.5 cheaper for input?

Claude Haiku 5.5 is cheaper at $0.10 per million input tokens, against $10 for Claude Fable 5.1 — roughly 100× the price. Estimate both input and output token volume for your workload. These are base rates; Claude Fable 5.1: Standard USD/MTok input/output $10/$50 with no long-context surcharge; cache reads $0.25 versus Fable 5's $1, 5-minute writes $12.50, 1-hour writes $20. Batch $5/$25. US-only inference adds 10% to input/output and cache reads/writes on Anthropic-operated routes where supported; Foundry uses US Data Zone Standard. Bedrock and Google-managed Google Cloud have independent regional prices. Adaptive thinking is always on; default effort high. Knowledge cutoff June 2026; retirement not sooner than September 1, 2027. Server-side tools can add usage fees; tool schemas/results and thinking consume billable tokens. Claude Haiku 5.5: Base rates apply to prompts up to 100,000 tokens. Above 100,000 tokens, input is $0.50 and output $2.50 per MTok. Cache reads are $0.01/$0.05; 5-minute writes $0.125/$0.625 and 1-hour writes $0.20/$1 for short/long prompts. Batch input/output receives a 50% discount. Standard output is 128K; 300K Batch output requires the documented beta header. Adaptive thinking defaults to medium effort.

Is Claude Fable 5.1 or Claude Haiku 5.5 cheaper for output?

Claude Haiku 5.5 is cheaper at $0.50 per million output tokens, against $50 for Claude Fable 5.1 — roughly 100× the price. Estimate both input and output token volume for your workload. These are base rates; Claude Fable 5.1: Standard USD/MTok input/output $10/$50 with no long-context surcharge; cache reads $0.25 versus Fable 5's $1, 5-minute writes $12.50, 1-hour writes $20. Batch $5/$25. US-only inference adds 10% to input/output and cache reads/writes on Anthropic-operated routes where supported; Foundry uses US Data Zone Standard. Bedrock and Google-managed Google Cloud have independent regional prices. Adaptive thinking is always on; default effort high. Knowledge cutoff June 2026; retirement not sooner than September 1, 2027. Server-side tools can add usage fees; tool schemas/results and thinking consume billable tokens. Claude Haiku 5.5: Base rates apply to prompts up to 100,000 tokens. Above 100,000 tokens, input is $0.50 and output $2.50 per MTok. Cache reads are $0.01/$0.05; 5-minute writes $0.125/$0.625 and 1-hour writes $0.20/$1 for short/long prompts. Batch input/output receives a 50% discount. Standard output is 128K; 300K Batch output requires the documented beta header. Adaptive thinking defaults to medium effort.

Which has the larger context window, Claude Fable 5.1 or Claude Haiku 5.5?

Both accept about 1M tokens of context, so document length will not decide between them.

Should I use Claude Fable 5.1 or Claude Haiku 5.5?

We classify Claude Fable 5.1 in the frontier tier and Claude Haiku 5.5 in the budget tier. Test whether either meets your accuracy, tool-use and latency requirements before choosing on price.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

Input price: Claude Haiku 5.5 costs $0.10 per 1M tokens versus $10 for Claude Fable 5.1 — a 100x difference at the headline tier.
Positioning: Claude Fable 5.1 sits in the frontier tier, Claude Haiku 5.5 in the budget tier. Compare accuracy, reliability, latency, and cost on representative tasks before choosing.

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