GPT-5.6 Sol vs Claude Fable 5
OpenAI's GPT-5.6 Sol and Anthropic's Claude Fable 5 both target production language workloads, but they price and behave differently. Here is the side-by-side.
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The short answer
GPT-5.6 Sol is the cheaper option — roughly 2.5x less on a blended workload, and it suits frontier coding and long-horizon agents. Claude Fable 5 justifies its premium when you need long-horizon agentic engineering.
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.
Anthropic • Claude 5
$10.00 / $50.00
/ 1M tokens (input / output)
Anthropic's most capable widely released model, built for agents that run for hours rather than seconds. Adaptive thinking is always on and cannot be disabled, which is part of why it tops the Artificial Analysis Intelligence Index — and why its cost per task runs roughly triple GPT-5.6 Sol's for a one-point intelligence lead.
Input price
Claude Fable 5 is 2.5x the price than GPT-5.6 Sol on input tokens.
Output price
Claude Fable 5 is 2.5x the price 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 | Claude Fable 5 | Difference |
|---|---|---|---|
| Light — 1M in / 200K out | $8 | $20 | $12 |
| Moderate — 10M in / 2M out | $80 | $200 | $120 |
| Heavy — 100M in / 20M out | $800 | $2,000 | $1,200 |
Specification comparison
| Attribute | GPT-5.6 Sol | Claude Fable 5 |
|---|---|---|
| Input (/ 1M tokens) | $4.00 | $10.00 |
| Output (/ 1M tokens) | $20.00 | $50.00 |
| Cached input | $0.40 | $1.00 |
| Context window | 1,048,576 tokens | 1,000,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Native reasoning | Yes | Yes |
| Knowledge cutoff | 2026-02 | 2026-01 |
| Relative latency | high | high |
| Open weights | No | No |
| API model ID | gpt-5.6-sol | claude-fable-5 |
| 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.
Claude Fable 5: 5-minute cache writes $12.50/MTok, 1-hour $20/MTok. Requires 30-day data retention, so not available under zero-data-retention terms.
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 Claude Fable 5 if…
- Multi-hour autonomous coding runs
- Large codebase migrations
- Hard scientific workflows
- High-stakes legal and medical analysis
Frequently asked
Is GPT-5.6 Sol or Claude Fable 5 cheaper?
GPT-5.6 Sol is cheaper. On a blended 3:1 input-to-output workload it costs about 2.5x less than Claude Fable 5.
Which has the larger context window, GPT-5.6 Sol or Claude Fable 5?
GPT-5.6 Sol has the larger window at 1.05M tokens versus 1M.
Should I use GPT-5.6 Sol or Claude Fable 5?
Pick GPT-5.6 Sol for frontier coding and long-horizon agents. Pick Claude Fable 5 for long-horizon agentic engineering. If cost dominates the decision, GPT-5.6 Sol wins; if you need the capability ceiling, benchmark both on your own evals before committing.