API cost decision in 10 seconds

NewUnion Alpha vs Claude Opus 5 (Fast)

Pick Union Alpha for lower cost; pick Claude Opus 5 (Fast) only if the larger context window matters more.

Page updated: 2026-09-16T15:08:45Z Data confirmed: 2026-09-16T16:08:25Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick Union Alpha for lower cost; pick Claude Opus 5 (Fast) only if the larger context window matters more.

On the standard 1M input plus 500K output workload, Union Alpha is estimated at $0 vs $35 for Claude Opus 5 (Fast), saving $35 (100% lower).

Cost-first pickUnion Alpha

Context-first pickClaude Opus 5 (Fast)

Sample savings$35100%

10x traffic gap$350

Claude Opus 5 (Fast) has more context, but Union Alpha saves $35 on the standard workload. At 10x that traffic, the same price gap is about $350. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

Union Alpha stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shape	Token mix	Better pick	Union Alpha	Claude Opus 5 (Fast)
Input-heavy / RAG	5M input + 500K output	Union Alpha	$0	$75
Balanced workload	1M input + 1M output	Union Alpha	$0	$60
Output-heavy chatbot	1M input + 5M output	Union Alpha	$0	$260

Cheaper input Union Alpha $0 vs $10 / 1M

Union Alpha is free for input tokens while Claude Opus 5 (Fast) costs $10 per 1M tokens.

Cheaper output Union Alpha $0 vs $50 / 1M

Union Alpha is free for output tokens while Claude Opus 5 (Fast) costs $50 per 1M tokens.

Larger context Claude Opus 5 (Fast) 262.14K vs 1M

Claude Opus 5 (Fast) has 737.86K more context (3.81x larger).

Sample workload Union Alpha $0 vs $35

Union Alpha is free for the standard workload while the other model is estimated at $35.

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

Union Alpha Calculating… Estimated API cost

Claude Opus 5 (Fast) Calculating… Estimated API cost

Cheaper for this workload Calculating… Difference: calculating…

This estimate uses normalized public API pricing per 1M tokens. It is a planning aid, not a billing quote. Verify provider pricing, limits, and terms before production use.

Quick Decision

Verdict

Union Alpha has the lower input price; Union Alpha has the lower output price; Claude Opus 5 (Fast) offers the larger context window. For the 1M input plus 500K output sample, Union Alpha is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $0 for Union Alpha and $35 for Claude Opus 5 (Fast).

Best Fit

Choose Union Alpha when you care most about lower input-token price, and lower output-token price.

Choose Claude Opus 5 (Fast) when you care most about larger context window.

Decision Notes

On the standard 1M input plus 500K output workload, Union Alpha is estimated at $0 vs $35 for Claude Opus 5 (Fast), saving $35 (100% lower).
Union Alpha is free for the standard workload while the other model is estimated at $35.
Union Alpha is free for input tokens while Claude Opus 5 (Fast) costs $10 per 1M tokens.
Union Alpha is free for output tokens while Claude Opus 5 (Fast) costs $50 per 1M tokens.
Claude Opus 5 (Fast) has 737.86K more context (3.81x larger).

Head-to-Head Specs

Feature	NewUnion Alpha (stealth)	Claude Opus 5 (Fast) (Anthropic)
Input Price prompt tokens per 1M	$0	$10
Completion Price per 1M tokens	$0	$50
Sample Workload Cost 1M input + 500K output	$0	$35
Context Window	262.14K	1M
Release Date	2026-09-16	2026-07-24

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	Union Alpha	On the standard 1M input plus 500K output workload, Union Alpha is estimated at $0 vs $35 for Claude Opus 5 (Fast), saving $35 (100% lower).
High-volume input processing	Union Alpha	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	Union Alpha	Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document work	Claude Opus 5 (Fast)	A larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Same-provider lower-cost swaps

Claude 3 Haiku can replace Claude Opus 5 (Fast) when lower sample workload cost matters most: $0.88.
Claude Haiku 4.5 (batch) can replace Claude Opus 5 (Fast) when lower sample workload cost matters most: $1.75.
Claude 3.5 Haiku can replace Claude Opus 5 (Fast) when lower sample workload cost matters most: $2.8.
Claude Sonnet 5 (batch) can replace Claude Opus 5 (Fast) when lower sample workload cost matters most: $3.5.

Larger context near this budget

Grok 4.20 Multi-Agent offers 2M context with $2.5 sample workload cost.
Grok 4.20 offers 2M context with $2.5 sample workload cost.
DeepSeek V4 Flash 0731 offers 1.31M context with $0.12 sample workload cost.
GLM 5.3 Flash offers 1.31M context with $0.24 sample workload cost.

Popular competitors

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DeepSeek V4 Flash 0731 · DeepSeek · #4

Cheaper alternatives

Review low-cost models sorted by a standard 1M input plus 500K output workload.

Open cheapest models

Larger context alternatives

Find models with larger context windows for RAG, long documents, and codebase review.

Open largest context models

Provider catalogs

Compare models within provider hubs before choosing a final API vendor.

Open provider hubs

stealth catalog

Review all tracked stealth models before deciding whether this matchup is the right shortlist.

Open stealth models

Anthropic catalog

Check other Anthropic models with comparable pricing, context, or release timing.

Open Anthropic models

Union Alpha

Union Alpha is a multimodal model built for research, coding, and agentic workflows, while delivering frontier-level performance across a broad range of general-purpose tasks. Union Alpha is a stealth model....

Claude Opus 5 (Fast)

Fast-mode variant of [Opus 5](/anthropic/claude-opus-5) - identical capabilities with higher output speed at 2x pricing relative to regular Opus 5. Learn more in Anthropic's docs: https://platform.claude.com/docs/en/build-with-claude/fast-mode