Claude Fable 5.1 vs DeepSeek-V3 (Legacy API Alias)

Side-by-side technical and economic comparison between Anthropic's Claude Fable 5.1 and DeepSeek's DeepSeek-V3 (Legacy API Alias).

Verdict: DeepSeek-V3 (Legacy API Alias) is about 99% cheaper than Claude Fable 5.1 at a typical 3:1 input-to-output mix ($0.175 vs $20.00 per 1M blended tokens). Claude Fable 5.1 offers the larger context window (1M tokens).

Endpoint Availability & Transition Notice

• DeepSeek-V3 (Legacy API Alias): Classified as a Legacy Reference model (Legacy Reference (API Aliased)).

Claude Fable 5.1 vs DeepSeek-V3 (Legacy API Alias) Pricing & Specs

Metric	Claude Fable 5.1	DeepSeek-V3 (Legacy API Alias)	Advantage
Provider Organization	Anthropic	DeepSeek	—
Standard Input / 1M	$10.00	$0.14	DeepSeek-V3 (Legacy API Alias) (99% lower)
Cached Input / 1M	$0.25	$0.014	DeepSeek-V3 (Legacy API Alias) lower
Output / 1M	$50.00	$0.28	DeepSeek-V3 (Legacy API Alias) lower
Context Window	1M	128k	Claude Fable 5.1 (1M)
Max Generation Tokens	32k	8.2k	Claude Fable 5.1
Tokenizer Family	Anthropic Claude BPE (~65k vocabulary)	DeepSeek Byte-level BPE (~128k vocabulary)	—

Monthly Cost: Claude Fable 5.1 vs DeepSeek-V3 (Legacy API Alias)

Workload (per month)	Claude Fable 5.1	DeepSeek-V3 (Legacy API Alias)
Chatbot10k requests · 500 in / 200 out	$150.00	$1.26
RAG app100k requests · 8,000 in / 1,200 out	$14,000.00	$145.60
Coding agent100k requests · 12,000 in / 2,000 out	$22,000.00	$224.00

Standard rates, no caching or batch discounts. Model your own numbers below.

Interactive Side-by-Side Cost Simulator

Live Delta

Input Tokens / Req2,500

Output Tokens / Req800

Daily Requests10,000

Claude Fable 5.1

$15,843.75 / month

$0.0528 / request

DeepSeek-V3 (Legacy API Alias)LOWER COST

$124.95 / month

$0.00042 / request

Selecting DeepSeek-V3 (Legacy API Alias) saves $15,718.80 / month (99.2% savings) over Claude Fable 5.1.

When to Choose Claude Fable 5.1

Opt for Claude Fable 5.1 when your engineering requirements prioritize Anthropic's ecosystem, specific tokenizer efficiencies (Calibrated Claude Tokenizer (±3%)), or when your expected prompt-to-completion ratios favor its $10/M input rate.

Claude Fable 5.1 Specs & Documentation

When to Choose DeepSeek-V3 (Legacy API Alias)

Opt for DeepSeek-V3 (Legacy API Alias) when looking for DeepSeek's tooling integration, specific context window depth (128k tokens), or when output generation volume favors its $0.28/M rate.

DeepSeek-V3 (Legacy API Alias) Specs & Documentation

Claude Fable 5.1 vs DeepSeek-V3 (Legacy API Alias) FAQ

Is Claude Fable 5.1 cheaper than DeepSeek-V3 (Legacy API Alias)?

At a typical 3:1 input-to-output token mix, DeepSeek-V3 (Legacy API Alias) is about 99% cheaper than Claude Fable 5.1. Claude Fable 5.1 costs $10 per 1M input and $50 per 1M output tokens; DeepSeek-V3 (Legacy API Alias) costs $0.14 and $0.28.

Which has a larger context window, Claude Fable 5.1 or DeepSeek-V3 (Legacy API Alias)?

Claude Fable 5.1 has the larger context window: 1M tokens vs 128k.

Do Claude Fable 5.1 and DeepSeek-V3 (Legacy API Alias) support prompt caching?

Claude Fable 5.1: yes, cached input costs $0.25/1M. DeepSeek-V3 (Legacy API Alias): yes, cached input costs $0.014/1M.