Choose AI21: Jamba Large 1.7 if…
- cost matters at scale — it is 65% cheaper on a typical 3:1 input/output mix ($310 vs $875 a month for 50,000 support chats)
AI21: Jamba Large 1.7 vs Anthropic: Claude Fable 5.1 (batch)
Neither wins outright: AI21: Jamba Large 1.7 is the pick when cost matters at scale, Anthropic: Claude Fable 5.1 (batch) when you need to fit long inputs in one request.
Key numbers
| Spec | AI21: Jamba Large 1.7 | Anthropic: Claude Fable 5.1 (batch) |
|---|---|---|
| Provider | AI21 | Anthropic |
| Input price (per 1M tokens) | $2.00 | $5.00 |
| Output price (per 1M tokens) | $8.00 | $25.00 |
| Blended price (3:1 input/output) | $3.50 | $10.00 |
| Cheaper than … of all models we track | 18% | 5% |
| Context window | 256K tokens (~384 pages) | 1M tokens (~1,500 pages) |
| Larger context than … of all models | 45% | 69% |
| Max output per response | 4K tokens (~3,100 words) | 128K tokens (~96,000 words) |
| Input types | text | text, image, file |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2025-08-08 | 2026-09-01 |
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What it costs for real workloads
Monthly cost at list price for five common workloads. Token counts per unit are stated so you can scale them to your own traffic. A workload that does not fit a model's context window is marked rather than priced.
| Workload (per month) | AI21: Jamba Large 1.7 | Anthropic: Claude Fable 5.1 (batch) | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $310 | $875 | AI21: Jamba Large 1.7 saves $565 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $320 | $850 | AI21: Jamba Large 1.7 saves $530 |
| Coding / tool-using agent 2,000 tasks — each a multi-step task with tool calls and file context (60,000 in / 6,000 out tokens) | $336 | $900 | AI21: Jamba Large 1.7 saves $564 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $208 | $550 | AI21: Jamba Large 1.7 saves $342 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $108 | $275 | AI21: Jamba Large 1.7 saves $167 |
Capabilities side by side
| Capability | AI21: Jamba Large 1.7 | Anthropic: Claude Fable 5.1 (batch) | What it lets you do |
|---|---|---|---|
| Tool / function calling | ✓ Yes | ✓ Yes | call your APIs and run agent loops |
| Structured output (JSON schema) | ✓ Yes | ✓ Yes | return JSON that validates against your schema |
| Reasoning / thinking mode | — | ✓ Yes | spend extra tokens thinking before answering hard problems |
| Image input | — | ✓ Yes | read screenshots, charts and scanned pages |
| Audio input | — | — | take speech or audio directly |
| File / PDF input | — | ✓ Yes | accept documents without your own parsing step |
| Image output | — | — | generate images, not just text |
| Built-in web search | — | ✓ Yes | answer from live web results |
| Seed (reproducible sampling) | — | — | repeat a generation for tests and evals |
| Log-probabilities | — | — | read token confidence for classification and scoring |
From each model's published parameters and input/output types. “—” means not advertised, not proven absent.
Price history
- AI21: Jamba Large 1.7: price unchanged since we started tracking it on 2026-03-10.
- Anthropic: Claude Fable 5.1 (batch): price unchanged since we started tracking it on 2026-09-03.
Which should you choose?
Choose Anthropic: Claude Fable 5.1 (batch) if…
- you need to fit long inputs in one request — 1M tokens is roughly 1,500 pages, against 384
- you need reasoning / thinking mode — to spend extra tokens thinking before answering hard problems; AI21: Jamba Large 1.7 does not advertise it
- you need image input — to read screenshots, charts and scanned pages; AI21: Jamba Large 1.7 does not advertise it
- you need file / PDF input — to accept documents without your own parsing step; AI21: Jamba Large 1.7 does not advertise it
- you need built-in web search — to answer from live web results; AI21: Jamba Large 1.7 does not advertise it
- you generate long outputs in one go — up to 128K tokens (about 96,000 words) per response
- you want the newer model — released 2026-09-01, 13 months after the other
Frequently asked questions
Is AI21: Jamba Large 1.7 better than Anthropic: Claude Fable 5.1 (batch)?
Neither wins outright: AI21: Jamba Large 1.7 is the pick when cost matters at scale, Anthropic: Claude Fable 5.1 (batch) when you need to fit long inputs in one request. In short: AI21: Jamba Large 1.7 when cost matters at scale; Anthropic: Claude Fable 5.1 (batch) when you need to fit long inputs in one request, you need reasoning / thinking mode, you need image input, you need file / PDF input, you need built-in web search, you generate long outputs in one go, you want the newer model.
Which is cheaper, AI21: Jamba Large 1.7 or Anthropic: Claude Fable 5.1 (batch)?
AI21: Jamba Large 1.7 is cheaper: $3.50 vs $10.00 per 1M tokens at a typical 3:1 input/output mix, 65% less. For 50,000 support conversations a month that is $310 against $875.
How much do AI21: Jamba Large 1.7 and Anthropic: Claude Fable 5.1 (batch) cost per million tokens?
AI21: Jamba Large 1.7 costs $2.00 per 1M input tokens and $8.00 per 1M output tokens; Anthropic: Claude Fable 5.1 (batch) costs $5.00 input and $25.00 output. Output tokens are billed separately, so long answers shift the gap.
Which has the bigger context window, AI21: Jamba Large 1.7 or Anthropic: Claude Fable 5.1 (batch)?
Anthropic: Claude Fable 5.1 (batch): 1M tokens, about 1,500 pages, against 256K (about 384 pages) for AI21: Jamba Large 1.7.
Do AI21: Jamba Large 1.7 and Anthropic: Claude Fable 5.1 (batch) support function calling and JSON output?
Tool calling — AI21: Jamba Large 1.7: yes, Anthropic: Claude Fable 5.1 (batch): yes. JSON-schema structured output — AI21: Jamba Large 1.7: yes, Anthropic: Claude Fable 5.1 (batch): yes.
Can AI21: Jamba Large 1.7 or Anthropic: Claude Fable 5.1 (batch) read images?
Only Anthropic: Claude Fable 5.1 (batch) accepts image input; AI21: Jamba Large 1.7 is text-only for input.
Is AI21: Jamba Large 1.7 or Anthropic: Claude Fable 5.1 (batch) free to use?
No free variant is listed for either; both are pay-per-token.
What is the maximum output length of AI21: Jamba Large 1.7 and Anthropic: Claude Fable 5.1 (batch)?
AI21: Jamba Large 1.7 can write up to 4K tokens (about 3,100 words) per response; Anthropic: Claude Fable 5.1 (batch) up to 128K (about 96,000 words).
When were AI21: Jamba Large 1.7 and Anthropic: Claude Fable 5.1 (batch) released?
AI21: Jamba Large 1.7 was listed on 2025-08-08; Anthropic: Claude Fable 5.1 (batch) on 2026-09-01.
About the two models
AI21: Jamba Large 1.7
Jamba Large 1.7 is the latest model in the Jamba open family, offering improvements in grounding, instruction-following, and overall efficiency. Built on a hybrid SSM-Transformer architecture with a 256K context...
Full AI21: Jamba Large 1.7 specs →Anthropic: Claude Fable 5.1 (batch)
Claude Fable 5.1 improves on Claude Fable 5 across the board, with the biggest gains in agentic coding, long-running agentic workflows, and knowledge work: long code refactors, front-end and visual...
Full Anthropic: Claude Fable 5.1 (batch) specs →