# Claude Fable 5 vs GPT-5.3 Codex

> Side-by-side benchmark comparison for Claude Fable 5 and GPT-5.3 Codex across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-fable-vs-gpt-5-3-codex
- Last updated: September 4, 2026

- Shared sourced benchmarks: 4
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Pick Claude Fable 5 if you want the stronger benchmark profile. GPT-5.3 Codex only makes more sense when its price, context window, or workload-specific category wins matter more than the overall score.

## Summary

- Claude Fable 5 leads overall 80.9 to 65.22.
- The clearest category separation is in knowledge, where the averages are 83.5 for Claude Fable 5 and 66.3 for GPT-5.3 Codex.
- The biggest single benchmark swing is SWE-bench Pro in Coding, with scores of 80% and 56.8%.
- GPT-5.3 Codex is the cheaper option on output tokens, which matters if you expect large responses or heavy interactive use.
- Claude Fable 5 also has the larger context window at 1M+.

## Model Snapshot

| Property | Claude Fable 5 | GPT-5.3 Codex |
|----------|----------|----------|
| Creator | Anthropic | OpenAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 1M+ | 400K |
| Overall Score | 80.9 | 65.22 |
| Benchmarks Covered | 18 | 8 |
| Pricing (input/output) | $10.00 / $50.00 | $1.75 / $14.00 |

## Category Breakdown

### Agentic

- Winner: Coming soon
- Claude Fable 5 public-lane score: 74.8 (Supported · #3/151)
- GPT-5.3 Codex public-lane score: 62.3 (Estimated · #19/151)

| Benchmark | Claude Fable 5 | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 3.0 | 34.0% | Coming soon | Coming soon |
| Terminal-Bench 2.0 | 84.3% | 77.3% | Claude Fable 5 |
| OSWorld-Verified | 85% | 64.7% | Claude Fable 5 |
| Terminal-Bench 2.1 (Vals) | 80.5% | Coming soon | Coming soon |
| Gert Labs | Coming soon | 57.47% | Coming soon |
| JobBench | Coming soon | 33.7% | Coming soon |

### Coding

- Winner: Claude Fable 5
- Claude Fable 5 public-lane score: 76.9 (Supported · #2/183)
- GPT-5.3 Codex public-lane score: 62.7 (Supported · #16/183)

| Benchmark | Claude Fable 5 | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Verified | 95% | 85% | Claude Fable 5 |
| SWE-bench Pro | 80% | 56.8% | Claude Fable 5 |
| FrontierSWE v2 | 48.0% | Coming soon | Coming soon |
| FrontierCode 1.1 Main | 53.5% | Coming soon | Coming soon |
| Terminal-Bench 2.0 | 84.3% | Coming soon | Coming soon |
| cursorBench31 | 70.6% | Coming soon | Coming soon |
| cursorBench32 | 70.5% | Coming soon | Coming soon |
| VulcanBench v3 | 89.5% | Coming soon | Coming soon |
| LiveCodeBench (Vals) | 89.8% | Coming soon | Coming soon |
| SWE-bench (Vals) | 95.0% | Coming soon | Coming soon |
| SWE-Rebench | Coming soon | 58.2% | Coming soon |
| Vibe Code Bench | Coming soon | 61.77% | Coming soon |

### Multimodal & Grounded

- Winner: Coming soon
- Claude Fable 5 public-lane score: 62.5 (Unranked · 2 rankable rows)
- GPT-5.3 Codex public-lane score: 75.6 (Unranked · 1 rankable row)

| Benchmark | Claude Fable 5 | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| Blueprint-Bench 2 | 38.6% | Coming soon | Coming soon |
| OfficeQA Pro | 57.9% | Coming soon | Coming soon |

### Reasoning

- Winner: Coming soon
- Claude Fable 5 public-lane score: 76.2 (#11/22)
- GPT-5.3 Codex public-lane score: 77.3 (Unranked · 2 rankable rows)

### Knowledge

- Winner: Coming soon
- Claude Fable 5 public-lane score: 83.5 (Supported · #2/181)
- GPT-5.3 Codex public-lane score: 66.3 (Estimated · #22/181)

| Benchmark | Claude Fable 5 | GPT-5.3 Codex | Winner |
|-----------|-----------|-----------|--------|
| GPQA Diamond (Vals) | 93.2% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 91.5% | Coming soon | Coming soon |

### Instruction Following

- Winner: Coming soon
- Claude Fable 5 public-lane score: 78.3 (#54/120)
- GPT-5.3 Codex public-lane score: 92.3 (#15/120)

## FAQ

### Which is better overall, Claude Fable 5 or GPT-5.3 Codex?

Claude Fable 5 is ahead overall on BenchLM right now.

### Where is the biggest gap between Claude Fable 5 and GPT-5.3 Codex?

The widest category gap is in knowledge, where the averages are 83.5 for Claude Fable 5 and 66.3 for GPT-5.3 Codex.

### How many benchmarks does Claude Fable 5 cover on BenchLM?

Claude Fable 5 currently has 18 sourced benchmark scores on BenchLM.

### How many benchmarks does GPT-5.3 Codex cover on BenchLM?

GPT-5.3 Codex currently has 8 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Claude Fable 5 vs Claude Fable 5.1](/compare/claude-fable-vs-claude-fable-5-1)
- [GPT-5.3 Codex vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-gpt-5-3-codex)
- [Claude Fable 5 vs GPT-5.3-Codex-Spark](/compare/claude-fable-vs-gpt-5-3-codex-spark)
- [GPT-5.3 Codex vs GPT-5.3-Codex-Spark](/compare/gpt-5-3-codex-vs-gpt-5-3-codex-spark)

## Explore More

- [Claude Fable 5 profile](/models/claude-fable)
- [GPT-5.3 Codex profile](/models/gpt-5-3-codex)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)