Choose AionLabs: Aion 3.5 if…
- cost matters at scale — it is 81% cheaper on a typical 3:1 input/output mix ($345 vs $1,750 a month for 50,000 support chats)
- you want the newer model — released 2026-09-23, 4 months after the other
AionLabs: Aion 3.5 vs Anthropic: Claude Opus 4.8 (Fast)
Neither wins outright: AionLabs: Aion 3.5 is the pick when cost matters at scale, Anthropic: Claude Opus 4.8 (Fast) when you need to fit long inputs in one request.
Key numbers
| Spec | AionLabs: Aion 3.5 | Anthropic: Claude Opus 4.8 (Fast) |
|---|---|---|
| Provider | Aion Labs | Anthropic |
| Input price (per 1M tokens) | $3.00 | $10.00 |
| Output price (per 1M tokens) | $6.00 | $50.00 |
| Blended price (3:1 input/output) | $3.75 | $20.00 |
| Cheaper than … of all models we track | 17% | 3% |
| Context window | 262K tokens (~393 pages) | 1M tokens (~1,500 pages) |
| Larger context than … of all models | 48% | 69% |
| Max output per response | 33K tokens (~24,600 words) | 128K tokens (~96,000 words) |
| Input types | text | text, image, file |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2026-09-23 | 2026-05-27 |
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) | AionLabs: Aion 3.5 | Anthropic: Claude Opus 4.8 (Fast) | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $345 | $1,750 | AionLabs: Aion 3.5 saves $1,405 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $420 | $1,700 | AionLabs: Aion 3.5 saves $1,280 |
| 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) | $432 | $1,800 | AionLabs: Aion 3.5 saves $1,368 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $276 | $1,100 | AionLabs: Aion 3.5 saves $824 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $156 | $550 | AionLabs: Aion 3.5 saves $394 |
Capabilities side by side
| Capability | AionLabs: Aion 3.5 | Anthropic: Claude Opus 4.8 (Fast) | 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 | ✓ 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
- AionLabs: Aion 3.5: price unchanged since we started tracking it on 2026-09-24.
- Anthropic: Claude Opus 4.8 (Fast): price unchanged since we started tracking it on 2026-08-06.
Which should you choose?
Choose Anthropic: Claude Opus 4.8 (Fast) if…
- you need to fit long inputs in one request — 1M tokens is roughly 1,500 pages, against 393
- you need image input — to read screenshots, charts and scanned pages; AionLabs: Aion 3.5 does not advertise it
- you need file / PDF input — to accept documents without your own parsing step; AionLabs: Aion 3.5 does not advertise it
- you need built-in web search — to answer from live web results; AionLabs: Aion 3.5 does not advertise it
- you generate long outputs in one go — up to 128K tokens (about 96,000 words) per response
Frequently asked questions
Is AionLabs: Aion 3.5 better than Anthropic: Claude Opus 4.8 (Fast)?
Neither wins outright: AionLabs: Aion 3.5 is the pick when cost matters at scale, Anthropic: Claude Opus 4.8 (Fast) when you need to fit long inputs in one request. In short: AionLabs: Aion 3.5 when cost matters at scale, you want the newer model; Anthropic: Claude Opus 4.8 (Fast) when you need to fit long inputs in one request, you need image input, you need file / PDF input, you need built-in web search, you generate long outputs in one go.
Which is cheaper, AionLabs: Aion 3.5 or Anthropic: Claude Opus 4.8 (Fast)?
AionLabs: Aion 3.5 is cheaper: $3.75 vs $20.00 per 1M tokens at a typical 3:1 input/output mix, 81% less. For 50,000 support conversations a month that is $345 against $1,750.
How much do AionLabs: Aion 3.5 and Anthropic: Claude Opus 4.8 (Fast) cost per million tokens?
AionLabs: Aion 3.5 costs $3.00 per 1M input tokens and $6.00 per 1M output tokens; Anthropic: Claude Opus 4.8 (Fast) costs $10.00 input and $50.00 output. Output tokens are billed separately, so long answers shift the gap.
Which has the bigger context window, AionLabs: Aion 3.5 or Anthropic: Claude Opus 4.8 (Fast)?
Anthropic: Claude Opus 4.8 (Fast): 1M tokens, about 1,500 pages, against 262K (about 393 pages) for AionLabs: Aion 3.5.
Do AionLabs: Aion 3.5 and Anthropic: Claude Opus 4.8 (Fast) support function calling and JSON output?
Tool calling — AionLabs: Aion 3.5: yes, Anthropic: Claude Opus 4.8 (Fast): yes. JSON-schema structured output — AionLabs: Aion 3.5: yes, Anthropic: Claude Opus 4.8 (Fast): yes.
Can AionLabs: Aion 3.5 or Anthropic: Claude Opus 4.8 (Fast) read images?
Only Anthropic: Claude Opus 4.8 (Fast) accepts image input; AionLabs: Aion 3.5 is text-only for input.
Is AionLabs: Aion 3.5 or Anthropic: Claude Opus 4.8 (Fast) free to use?
No free variant is listed for either; both are pay-per-token.
What is the maximum output length of AionLabs: Aion 3.5 and Anthropic: Claude Opus 4.8 (Fast)?
AionLabs: Aion 3.5 can write up to 33K tokens (about 24,600 words) per response; Anthropic: Claude Opus 4.8 (Fast) up to 128K (about 96,000 words).
When were AionLabs: Aion 3.5 and Anthropic: Claude Opus 4.8 (Fast) released?
AionLabs: Aion 3.5 was listed on 2026-09-23; Anthropic: Claude Opus 4.8 (Fast) on 2026-05-27.
About the two models
AionLabs: Aion 3.5
Aion 3.5 is a multi-model roleplaying and storytelling system from AionLabs, built on the GLM family of models. It uses a collaborative generation process in which multiple specialized models each...
Full AionLabs: Aion 3.5 specs →Anthropic: Claude Opus 4.8 (Fast)
Fast-mode variant of [Opus 4.8](/anthropic/claude-opus-4.8) - identical capabilities with higher output speed at 2x pricing relative to regular Opus 4.8. Learn more in Anthropic's docs: https://platform.claude.com/docs/en/build-with-claude/fast-mode
Full Anthropic: Claude Opus 4.8 (Fast) specs →