OpenAI vs Anthropic
GPT-5.6 against Claude Opus 5 and Sonnet 5, at September 2026 prices. Which provider should your Paperclip agents run on?
OpenAI or Anthropic for AI agents?
Anthropic wins on agent behavior: Claude Sonnet 5 ($2/$10 per 1M tokens) and Opus 5 ($5/$25) follow long, multi-step instructions more reliably and offer extended thinking on every model. OpenAI wins on price spread and ecosystem: the GPT-5.6 family runs from $0.20 (Luna) to $5 (Sol) per 1M input tokens with 1.05M-token context on every tier. At the balanced tier — Terra vs Sonnet 5 — the sticker price is now nearly identical, so the decision comes down to workload: instruction-heavy agents lean Claude, high-volume routed fleets lean OpenAI.
| Feature | OpenAI | Anthropic |
|---|---|---|
| Current family | GPT-5.6 Sol, Terra, Luna (GPT-5.5 Pro for premium reasoning) | Claude Fable 5.1, Opus 5, Sonnet 5, Haiku 4.5 |
| Context window | 1.05M tokens | 1M tokens (Fable 5.1, Opus 5, Sonnet 5), 200K (Haiku 4.5); Fable 5.1 outputs up to 128K |
| Input pricing | Sol $5.00 / 1M input, Terra $2.00, Luna $0.20 (output: $30 / $12 / $1.20) | Fable 5.1 $10.00 / 1M input, Opus 5 $5.00, Sonnet 5 $2.00, Haiku 4.5 $1.00 (output: $50 / $25 / $10 / $5) |
| Output multiplier | 6x input | 5x input |
| Prompt caching | Cached input at 10% | Cache reads at 10% |
| Batch discount | 50% | 50% |
| Function calling | Native | Tool use |
| Extended thinking | Reasoning effort per tier | All models |
What 1M agent runs actually cost
A typical agent run spends about 1,000 input tokens (system prompt, memory, context) and 100 output tokens. One million runs therefore consumes roughly 1M input and 100K output tokens. At September 2026 list prices:
| Model | 1M runs / month |
|---|---|
| GPT-5.6 Luna (high-volume tier) | $0.32 |
| Claude Haiku 4.5 | $1.50 |
| Claude Sonnet 5 | $3.00 |
| GPT-5.6 Terra (balanced tier) | $3.20 |
| Claude Opus 5 | $7.50 |
| GPT-5.6 Sol (flagship) | $8.00 |
| Claude Fable 5.1 (premium flagship) | $11.00 |
Math: 1M × input rate + 0.1M × output rate, before caching and batch discounts. Prompt caching cuts repeat-context input by 90% on both platforms.
OpenAI strengths
- Three-tier family from $0.20 to $5 input
- 1.05M token context on current tiers
- Native function calling and structured outputs
- Widest third-party ecosystem
- Batch API at 50% off
Anthropic strengths
- Exceptional instruction following
- Extended thinking on every model
- Strong safety alignment for critical agents
- Prompt caching from 2.5% of input rate (Fable 5.1; 10% on most Claude models)
- Sonnet 5's $2/$10 price made permanent
Choose OpenAI when
Teams that need the broadest ecosystem, ultra-cheap high-volume tiers, and million-token context at every price point.
Choose Anthropic when
Teams prioritizing instruction following, extended reasoning, and safety-critical agents that run for hours without drifting.
Deploy with either on HostAgentes
Both providers are available on every plan. Switch models without redeploying — or run model routing that sends instruction-heavy runs to Claude and high-volume runs to Luna, and pay one hosted bill instead of two API invoices.
Model lineups and prices verified against OpenAI's public API pricing and Anthropic's public pricing documentation in September 2026. Provider prices change; re-check before committing volume.
Frequently asked questions
Is OpenAI or Anthropic better for AI agents in 2026?
Anthropic is better for long-running, instruction-heavy agents: Claude Sonnet 5 and Opus 5 follow multi-step instructions more reliably and include extended thinking. OpenAI is better when you need ecosystem breadth, function calling everywhere, or a ultra-cheap tier — GPT-5.6 Luna runs high-volume agents at $0.20 per 1M input tokens.
Which is cheaper: OpenAI or Anthropic?
At the balanced tier they now cost nearly the same: GPT-5.6 Terra is $2 input / $12 output and Claude Sonnet 5 is $2 / $10 per 1M tokens. OpenAI's Luna ($0.20/$1.20) undercuts Anthropic's cheapest (Haiku 4.5, $1/$5). Anthropic's Opus 5 ($5/$25) is cheaper than OpenAI's flagship Sol ($5/$30) on output.
How big are the context windows in 2026?
Context is no longer a differentiator. GPT-5.6 tiers offer 1.05M tokens and Claude Opus 5 and Sonnet 5 offer 1M tokens; Haiku 4.5 stays at 200K. OpenAI adds a long-context surcharge above 272K tokens; Anthropic bills its full window at one flat rate.
Which model should a production agent start with?
Start with Claude Sonnet 5 or GPT-5.6 Terra — both cost $2 per 1M input tokens and handle most production agent workloads. Route high-volume simple tasks to Luna or Haiku, and escalate genuinely hard reasoning to Opus 5, Sol, or GPT-5.5 Pro.
Can I use both OpenAI and Anthropic with Paperclip?
Yes. HostAgentes supports both providers. You can switch models without redeploying, or use model routing to pick the best model per request.
Try both models on HostAgentes. Switch at any time without redeploying.
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