GPT-5.6 Sol vs DeepSeek V4-Flash
OpenAI's GPT-5.6 Sol and DeepSeek's DeepSeek V4-Flash both target production language workloads, but they price and behave differently. Here is the side-by-side.
Pricing checked against provider documentation on . How we verify
The short answer
DeepSeek V4-Flash is the cheaper option — roughly 24.2x less on a blended workload, and it suits the cheapest capable open-weight option. GPT-5.6 Sol justifies its premium when you need frontier coding and long-horizon agents.
OpenAI • GPT-5.6
$4.00 / $20.00
/ 1M tokens (input / output)
OpenAI's flagship tier and the current state of the art on agentic coding benchmarks. Reasoning effort is tunable from none through max, and an `ultra` setting coordinates parallel subagents across workstreams. Sol reaches near-Fable-5 intelligence while spending markedly fewer output tokens, which is why its cost per finished task lands well below its sticker price.
DeepSeek • DeepSeek V4
$0.22 / $0.66
/ 1M tokens (input / output)
A 284B-parameter MoE with only 13B active, which is why it runs fast and prices low. Notable for a 384K maximum output — far beyond the 128K most frontier models cap at — and for supporting both thinking and non-thinking modes, so you can switch reasoning off on easy requests rather than paying for it.
Input price
DeepSeek V4-Flash is 95% cheaper than GPT-5.6 Sol on input tokens.
Output price
DeepSeek V4-Flash is 97% cheaper than GPT-5.6 Sol on output tokens — usually the side that dominates the bill.
Monthly cost at three workload sizes
Standard (non-batch, non-cached) rates. Reasoning models will exceed these figures because thinking tokens bill as output.
| Workload | GPT-5.6 Sol | DeepSeek V4-Flash | Difference |
|---|---|---|---|
| Light — 1M in / 200K out | $8 | $0 | $8 |
| Moderate — 10M in / 2M out | $80 | $4 | $76 |
| Heavy — 100M in / 20M out | $800 | $35 | $765 |
Specification comparison
| Attribute | GPT-5.6 Sol | DeepSeek V4-Flash |
|---|---|---|
| Input (/ 1M tokens) | $4.00 | $0.22 |
| Output (/ 1M tokens) | $20.00 | $0.66 |
| Cached input | $0.40 | $0.01 |
| Context window | 1,048,576 tokens | 1,000,000 tokens |
| Max output | 128,000 tokens | 384,000 tokens |
| Native reasoning | Yes | Yes |
| Knowledge cutoff | 2026-02 | 2026-03 |
| Relative latency | high | low |
| Open weights | No | MIT |
| API model ID | gpt-5.6-sol | deepseek-v4-flash |
| Status | stable | stable |
GPT-5.6 Sol: Promotional pricing (down from $5/$30) held at least through 2026-11-21. Prompts above 272K input tokens bill at higher rates; 'fast' processing is 2x.
DeepSeek V4-Flash: Off-peak rate shown. Peak rates double ($0.44 / $1.32) during 01:00–04:00 and 06:00–10:00 UTC on weekdays. Superseded the earlier flat-rate pricing of $0.14 / $0.28 that many comparison sites still quote.
Choose GPT-5.6 Sol if…
- Long-running autonomous coding agents
- Large-scale refactors and migrations
- Agentic browsing and computer use
- Scientific and financial analysis
Choose DeepSeek V4-Flash if…
- High-volume classification and extraction
- Very long generated outputs
- Budget coding agents
- Local deployment on modest hardware
Frequently asked
Is GPT-5.6 Sol or DeepSeek V4-Flash cheaper?
DeepSeek V4-Flash is cheaper. On a blended 3:1 input-to-output workload it costs about 24.2x less than GPT-5.6 Sol.
Which has the larger context window, GPT-5.6 Sol or DeepSeek V4-Flash?
GPT-5.6 Sol has the larger window at 1.05M tokens versus 1M.
Should I use GPT-5.6 Sol or DeepSeek V4-Flash?
Pick GPT-5.6 Sol for frontier coding and long-horizon agents. Pick DeepSeek V4-Flash for the cheapest capable open-weight option. If cost dominates the decision, DeepSeek V4-Flash wins; if you need the capability ceiling, benchmark both on your own evals before committing.