Claude Haiku 4.5 vs GPT-5 Codex
Wins 1 of 7 areas
Long documents
Wins 5 of 7 areas
Coding · Agents · Reasoning · Images and charts · Following instructions
GPT-5 Codex is the stronger all-rounder.Claude Haiku 4.5 is cheaper and better at long documents.
Scores updated · 17 tests both models report · How we compare
Where each one wins
Tests won in each of the seven areas where both have results. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- ReasoningHard problems that need careful thinking03GPT-5 Codex3 of 3 tests
- CodingWriting and fixing software12GPT-5 Codex2 of 3 tests
- AgentsCarrying out multi-step tasks on its own01GPT-5 Codex1 of 1 test
- Images and chartsUnderstanding pictures, charts and video01GPT-5 Codex1 of 1 test
- Following instructionsDoing exactly what it is asked01GPT-5 Codex1 of 1 test
- Long documentsFinding answers in very long texts10Claude Haiku 4.51 of 1 test
- FactsGetting facts right instead of making them up11Even1 each
Agents, images and charts, long documents and following instructions rest on a single test each.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
Claude Haiku 4.5 costs 47% less for the same work.
The biggest differences
The three tests each model wins by the widest margin. Scores are out of 100.
Where GPT-5 Codex pulls ahead
- Real work tasks from 44 professionsGDPVal+24points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+20.7points ahead
- Follows unfamiliar, precisely checkable instructionsIFBench+19.8points ahead
Where Claude Haiku 4.5 pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+48.1points ahead
- Reasons across sets of long documentsAA-LCR+2.6points ahead
- Code for real scientific research problemsSciCode+1.3points ahead
Every test, side by side
All 17 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingGPT-5 Codex
- Terminal-Bench HardGPT-5 Codex by 10.627.337.9+10.6
- SciCodeClaude Haiku 4.5 by 1.342.240.9+1.3
- SWE-bench VerifiedGPT-5 Codex by 1.273.374.5+1.2
ReasoningGPT-5 Codex
- Humanity's Last ExamGPT-5 Codex by 17.410.427.8+17.4
- GPQA DiamondGPT-5 Codex by 16.567.283.7+16.5
- CritPtGPT-5 Codex by 5.105.1+5.1
FactsEven
- AA-Omniscience · Non-hallucinationClaude Haiku 4.5 by 48.172.724.6+48.1
- AA-Omniscience · AccuracyGPT-5 Codex by 20.71838.7+20.7
Following instructionsGPT-5 Codex
- IFBenchGPT-5 Codex by 19.854.374.1+19.8
Other results5 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- AA Agentic IndexGPT-5 Codex by 42.410.352.7+42.4
- τ²-Bench Telecom (AA run)GPT-5 Codex by 32.154.786.8+32.1
- AA IntelligenceGPT-5 Codex by 816.924.9+8
- Artificial Analysis Coding IndexClaude Haiku 4.5 by 543.938.9+5
- AA-OmniscienceClaude Haiku 4.5 by 3.1-4.4-7.5+3.1
Questions people ask
Which is better, Claude Haiku 4.5 or GPT-5 Codex?
GPT-5 Codex wins five of the seven areas where both have results: coding, agents, reasoning, images and charts and following instructions. Claude Haiku 4.5 wins long documents, and costs 47% less. They are level on facts.
Which is better for coding?
GPT-5 Codex. It wins 2 of the 3 coding tests both models report; Claude Haiku 4.5 wins 1.
Which is cheaper?
Claude Haiku 4.5 costs $1.00 per million input tokens and $5.00 per million output tokens; GPT-5 Codex costs $1.25 and $10.00. That makes Claude Haiku 4.5 about 47% cheaper for the same work.
How do you compare the two?
We use the 17 benchmark tests both models have published scores on. The verdict counts the 12 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 5 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.