Gemini 3.1 Pro Preview vs Claude Fable 5 vs GPT-5.3 Codex
Gemini 3.1 Pro Preview comes out ahead, 68 to 65 and 64 on our weighted score, and it is the cheaper option too.
- Our pick
GoogleGemini 3.1 Pro Preview
68/100- ECI154.8
- Price$2.00 / $12.00
- Context1.05M
AnthropicClaude Fable 5
65/100- ECI162.2
- Price$10.00 / $50.00
- Context1M
OpenAIGPT-5.3 Codex
64/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
Gemini 3.1 Pro Preview is our pick
Gemini 3.1 Pro Preview is the better all-round choice, scoring 68/100 against Claude Fable 5 (65) and GPT-5.3 Codex (64). It leads on inputs & features. Claude Fable 5 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityClaude Fable 5Capabilities Index (ECI): Claude Fable 5 162.2 · GPT-5.3 Codex 156.8 · Gemini 3.1 Pro Preview 154.8
- Lowest priceGemini 3.1 Pro PreviewGemini 3.1 Pro Preview $4.50 · GPT-5.3 Codex $4.81 · Claude Fable 5 $20.00 per 1M tokens (3:1 blend)
- Longest contextGemini 3.1 Pro PreviewGemini 3.1 Pro Preview 1,048,576 · Claude Fable 5 1,000,000 · GPT-5.3 Codex 400,000 tokens
- Widest inputsGemini 3.1 Pro PreviewGemini 3.1 Pro Preview: Text, Images, PDFs, Audio, Video · Claude Fable 5: Text, Images, PDFs · GPT-5.3 Codex: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Gemini 3.1 Pro Preview | Claude Fable 5 | GPT-5.3 Codex |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 84 | 94 | 87 |
| Price | 25% | 19 | 0 | 18 |
| Inputs & features | 15% | 100 | 80 | 80 |
| Context window | 10% | 61 | 60 | 44 |
| Overall | 100% | 68/100 | 65/100 | 64/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Gemini 3.1 Pro PreviewGoogle | Claude Fable 5Anthropic | GPT-5.3 CodexOpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 154.8 | 162.2 (best) | 156.8 |
| ECI rank | #31 of 148 | #7 of 148 (best) | #18 of 148 |
| GPQA DiamondGraduate-level science questions | 94.4% (best) | 85.9% | — |
| FrontierMath Tiers 1–3Research-level mathematics | 59.7% | 87.0% (best) | — |
| OTIS Mock AIME 2024–2025Competition mathematics | 95.6% | 100% (best) | — |
| SWE-bench VerifiedFixing real GitHub issues | 75.6% (best) | — | 74.8% |
| SimpleQA VerifiedShort factual questions | 73.5% (best) | 70.7% | — |
| Price per million tokens | |||
| Input | $2.00 | $10.00 | $1.75 (best) |
| Output | $12.00 (best) | $50.00 | $14.00 |
| Cached input | $0.20 | $1.00 | $0.175 (best) |
| Blended (3:1) | $4.50 (best) | $20.00 | $4.81 |
| Long-context rate | Over 200K: $4.00 / $18.00 | Same rate | Same rate |
| Price source | Official Google API | Official Anthropic API | Official OpenAI API |
| Limits | |||
| Context window | 1,048,576 tokens (best) | 1,000,000 tokens | 400,000 tokens |
| Max output | 65,536 tokens | 128,000 tokens (best) | 128,000 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | Yes | No | No |
| Video | Yes | No | No |
| Reasoning | Yeslow · medium · high | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gemini-3.1-pro-preview | claude-fable-5 | gpt-5.3-codex |
| API providers | 26 | 38 (best) | 19 |
| Released | Feb 19, 2026 | Jun 9, 2026 | Feb 5, 2026 |
| Knowledge cutoff | Jan 2025 | Jan 31, 2026 | Aug 31, 2025 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Gemini 3.1 Pro Preview$44.00
- Claude Fable 5$200.00
- GPT-5.3 Codex$45.50
Which should you choose?
Which is better: Gemini 3.1 Pro Preview, Claude Fable 5 or GPT-5.3 Codex?
Gemini 3.1 Pro Preview is the better all-round choice, scoring 68/100 against Claude Fable 5 (65) and GPT-5.3 Codex (64). It leads on inputs & features. Claude Fable 5 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Gemini 3.1 Pro Preview, Claude Fable 5 or GPT-5.3 Codex?
Gemini 3.1 Pro Preview is cheaper at $2.00 input / $12.00 output per million tokens (official Google API price). GPT-5.3 Codex costs $1.75 input / $14.00 output per million tokens (official OpenAI API price); Claude Fable 5 costs $10.00 input / $50.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $4.50 per million tokens for Gemini 3.1 Pro Preview versus $4.81 for GPT-5.3 Codex (1.1× as much) and $20.00 for Claude Fable 5 (4.4× as much).
Which scores higher on benchmarks?
Claude Fable 5 scores higher on the Capabilities Index (ECI): Claude Fable 5 162.2 (#7 of 148), GPT-5.3 Codex 156.8 (#18 of 148) and Gemini 3.1 Pro Preview 154.8 (#31 of 148). The confidence ranges of the top two overlap (159.6–166.1 vs 153.5–160.8), so treat the gap as small.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Fable 5 yet, so there is no like-for-like coding score. On overall capability, Claude Fable 5 leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
Gemini 3.1 Pro Preview has the largest context window at 1,048,576 tokens, against 1,000,000 for Claude Fable 5 and 400,000 for GPT-5.3 Codex. Maximum output per response: Gemini 3.1 Pro Preview up to 65,536, Claude Fable 5 up to 128,000, GPT-5.3 Codex up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Gemini 3.1 Pro Preview accepts text, images, PDFs, audio and video; Claude Fable 5 accepts text, images and PDFs; GPT-5.3 Codex accepts text, images and PDFs. Gemini 3.1 Pro Preview handles the widest range of inputs.
Are any of these open source?
No. Gemini 3.1 Pro Preview, Claude Fable 5 and GPT-5.3 Codex are proprietary and only available through APIs and apps.
Which is newer?
Claude Fable 5 is the newest, released Jun 9, 2026. Gemini 3.1 Pro Preview came out Feb 19, 2026; GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: Gemini 3.1 Pro Preview Jan 2025, Claude Fable 5 Jan 31, 2026, GPT-5.3 Codex Aug 31, 2025.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
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