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OpenAI vs Together AI
Closed GPT models against the broadest open-model platform. The decision turns on whether you need closed frontier quality or control over weights, training and serving.
By The Subconscious Team · Updated
OpenAI vs Together AI: key differences
This is the closed-versus-open choice in its clearest form. OpenAI rents access to GPT-6 Astra and the GPT-5.6 family, and the weights stay with OpenAI. Together AI serves more than thirty open models, including DeepSeek V4, Kimi K3, GLM 5.2 and Qwen 3.8, and lets a team fine-tune them with LoRA or full-parameter SFT from $0.48 per million training tokens, then serve the checkpoint on the same platform. Together lists migrating off closed APIs through its OpenAI-compatible endpoint as a core use case, so testing the swap is mostly a base URL change.
OpenAI keeps the edge on frontier computer use and coding with Astra, and on the size of its tooling ecosystem. Together wins on ownership and deployment range: serverless, batch at up to 50% off, provisioned throughput with a 99% SLA, dedicated deployments and raw H100 clusters from $3.19 an hour reserved. Budget carefully on the Together side, since there is no free tier and dedicated inference costs more per GPU hour than a raw cluster on the same silicon. On OpenAI, the budget risk sits in long prompts past 272K, which bill input at 2x.
What OpenAI and Together AI do
OpenAI
OpenAI runs the most widely adopted closed-model API. Its September 2026 lineup has GPT-6 Astra at the top for computer use, coding and long agentic runs, priced at $10 in and $50 out per million tokens. Below it sits the GPT-5.6 family: Sol for hard professional work, Terra as the balanced default, and Luna for high-volume jobs at $0.20 in and $1.20 out. All of them carry a 1.05M token context window with up to 128K output.
Example models: GPT-6 Astra, GPT-5.6 Terra
Full OpenAI profileTogether AI
Together AI is the broadest open-model platform in the category. One bill covers per-token serverless inference, batch at up to 50% off, provisioned throughput with a 99% SLA, dedicated deployments, raw GPU clusters, managed fine-tuning and code sandboxes for agents. The text catalog runs past thirty open models, including DeepSeek V4, Kimi K3, GLM 5.2, Qwen 3.8 and MiniMax M3, plus image, video, speech and embedding models. Token prices sit at parity with Fireworks and Baseten.
Example models: Kimi K3, DeepSeek V4 Pro
Full Together AI profileShould you choose OpenAI or Together AI?
OpenAI
Choose OpenAI for
- Frontier computer use and coding without managing models
- Products built on the largest SDK and integration ecosystem
- Hosted agent tools out of the box
Together AI
Choose Together AI for
- Fine-tuning or RL on proprietary data, then serving the checkpoint
- Avoiding closed-model lock-in with open weights
- Teams that also need reserved GPU clusters for training
OpenAI vs Together AI at a glance
| Attribute | OpenAI | Together AI |
|---|---|---|
| Model access | Closed, plus open gpt-oss | Open weights |
| Flagship models | GPT-6 Astra, GPT-5.6 Sol, Terra, Luna | Kimi K3, DeepSeek V4, GLM 5.2, Qwen 3.8 |
| Speed | Fast mode: up to 2.5x at 2x price | 0.99s TTFT on DeepSeek V4 Pro |
| Price | $0.20–$10 in, $1.20–$50 out per 1M | Parity with Fireworks and Baseten |
| Customization | N/A | LoRA and full SFT; RL in beta |
| Deployment | API, Azure OpenAI, Bedrock | Serverless, dedicated, GPU clusters |
| Long context | 1.05M; 2x input past 272K | 512K on DeepSeek V4 Pro |
Frequently asked questions
What is the difference between OpenAI and Together AI?
Closed GPT models against the broadest open-model platform. The decision turns on whether you need closed frontier quality or control over weights, training and serving.
When should I choose OpenAI over Together AI?
Frontier computer use and coding without managing models; Products built on the largest SDK and integration ecosystem; Hosted agent tools out of the box.
When should I choose Together AI over OpenAI?
Fine-tuning or RL on proprietary data, then serving the checkpoint; Avoiding closed-model lock-in with open weights; Teams that also need reserved GPU clusters for training.
Is OpenAI or Together AI cheaper?
OpenAI: $0.20–$10 in, $1.20–$50 out per 1M. Together AI: Parity with Fireworks and Baseten. The cheaper choice depends on the model and workload.
Which has more context, OpenAI or Together AI?
OpenAI: 1.05M; 2x input past 272K. Together AI: 512K on DeepSeek V4 Pro.
Related comparisons
Running long-horizon agents?
If your agents run past 200K tokens, compare both against Subconscious. Our inference stack treats a long-horizon trace as the primary workload, so speed, cost, and accuracy hold up deep into the trace.