GPT-5.5 vs Claude Fable 5: Pricing, Benchmarks, and Which Model to Use
June 2026 has an embarrassment of riches in the frontier AI model space. OpenAI's GPT-5.5 and Anthropic's Claude Fable 5 both launched within weeks of each other, each claiming state-of-the-art performance in coding, reasoning, and agentic tasks.
If you're trying to decide which one to use for your project — or whether the premium is worth it over GPT-5.4, Claude Opus 4.8, or Gemini 3.5 Flash — here's a practical head-to-head.
Pricing at a Glance
| Model | Input (per 1M tokens) | Cached Input | Output (per 1M tokens) | Batch (50% off) | |-------|----------------------|-------------|----------------------|----------------| | GPT-5.5 | $5.00 | $0.50 | $30.00 | $2.50 / $15.00 | | GPT-5.4 | $2.50 | $0.25 | $15.00 | $1.25 / $7.50 | | GPT-5.4 Mini | $0.75 | $0.075 | $4.50 | $0.375 / $2.25 | | Claude Fable 5 | $10.00 | TBD | $50.00 | TBD | | Claude Opus 4.8 | $5.00 | — | $25.00 | 50% off | | Claude Sonnet 4.6 | $3.00 | — | $15.00 | 50% off |
Key takeaway: GPT-5.5 is 2x cheaper than Claude Fable 5 on input and 1.67x cheaper on output. But raw price isn't everything — you need to consider task-specific accuracy and token efficiency.
How GPT-5.5 and Claude Fable 5 Compare on Benchmarks
OpenAI published a detailed benchmark comparison at GPT-5.5's launch (April 23, 2026). Here are the highlights — Claude Fable 5 data is from Anthropic's launch materials and independent evals:
| Benchmark | GPT-5.5 | GPT-5.4 | Claude Fable 5 | Claude Opus 4.7/4.8 | |-----------|---------|---------|----------------|---------------------| | Terminal-Bench 2.0 | 82.7% | 75.1% | — | 69.4% | | Expert-SWE (internal) | 73.1% | 68.5% | — | — | | GDPval (wins or ties) | 84.9% | 83.0% | — | 80.3% | | OSWorld-Verified | 78.7% | 75.0% | — | 78.0% | | Toolathlon | 55.6% | 54.6% | — | 48.8% | | BrowseComp | 84.4% | 82.7% | — | 79.3% | | FrontierMath Tier 1-3 | 51.7% | 47.6% | — | 43.8% | | FrontierMath Tier 4 | 35.4% | 27.1% | — | 22.9% |
Anthropic hasn't released direct benchmarks for Claude Fable 5 on all the same evals, but their launch materials emphasized that Fable 5 represents their most capable widely released model, with a 1M token context window and "adaptive thinking" always enabled.
What the numbers tell us: GPT-5.5 appears to be the stronger model for agentic coding and complex tool use based on available benchmarks. The 82.7% on Terminal-Bench 2.0 is notably strong — that eval tests complex command-line workflows requiring planning, iteration, and tool coordination.
Token Efficiency Matters
One claim that cuts both ways: OpenAI says GPT-5.5 uses significantly fewer tokens to complete the same Codex tasks compared to GPT-5.4, making it more efficient operationally.
This is a meaningful point in the cost comparison. If GPT-5.5 averages 30-40% fewer output tokens for the same task compared to Claude Fable 5, the effective cost gap narrows significantly.
Context Windows and Output Limits
| Feature | GPT-5.5 | Claude Fable 5 | |---------|---------|----------------| | Context window | 270K tokens (standard) | 1M tokens | | Max output | 128K tokens | 128K tokens | | Extended thinking | Via reasoning_effort | Adaptive thinking (always on) | | Batch API | Yes (50% off) | Yes (50% off) |
Context window advantage: Claude Fable 5's 1M token context is a genuine differentiator for tasks that require processing very long documents, entire codebases, or large conversation histories.
Practical Recommendations
Choose GPT-5.5 when:
• You need the best agentic coding performance
• Cost is a primary concern (especially at scale)
• You're already in the OpenAI ecosystem (Codex, ChatGPT)
• Your context needs fit within 270K tokens
• You want Prompt Caching (cached input at $0.50/1M vs $10 uncached)
Choose Claude Fable 5 when:
• You need the full 1M token context window
• Tasks involve very long documents or codebases
• You value Anthropic's safety architecture (constitutional AI)
• You need integration with AWS Bedrock, GCP Vertex AI, or Microsoft Foundry
• Price sensitivity is lower (enterprise budgets)
The Pragmatic Approach: Use Both
Many serious AI builders are adopting a multi-model strategy: use GPT-5.5 for the heaviest coding and agentic tasks, Claude Fable 5 for long-context analysis and safety-sensitive applications, and GPT-5.4 Mini (at $0.75/1M input) for high-volume, lower-stakes tasks.
With Batch API pricing, GPT-5.5 drops to $2.50/1M input and $15/1M output — affordable enough for large-scale offline processing. Claude Fable 5's batch pricing hasn't been announced separately, but if it follows the usual 50% discount pattern, it would be $5/$25 per 1M tokens.