GPT-5.5 Instant vs GPT-5.6 Terra
Wins 0 of 8 areas
—
Wins 6 of 8 areas
Coding · Agents · Reasoning · Images and charts · Math · Long documents
GPT-5.6 Terra is the stronger all-rounder.
Scores updated · 26 tests both models report · How we compare
Where each one wins
Tests won in each of the eight areas we test. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- CodingWriting and fixing software03GPT-5.6 Terra3 of 3 tests
- AgentsCarrying out multi-step tasks on its own03GPT-5.6 Terra3 of 3 tests
- ReasoningHard problems that need careful thinking03GPT-5.6 Terra3 of 3 tests
- Images and chartsUnderstanding pictures, charts and video03GPT-5.6 Terra3 of 3 tests
- MathCompetition and research-level math02GPT-5.6 Terra2 of 2 tests
- Long documentsFinding answers in very long texts01GPT-5.6 Terra1 of 1 test
- FactsGetting facts right instead of making them up11Even1 each · 1 tie
- Following instructionsDoing exactly what it is asked00Even0 each · 1 tie
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.
GPT-5.6 Terra costs 60% less for the same work.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where GPT-5.6 Terra pulls ahead
- Extremely hard research-level math problemsFrontierMath Tier 4+65.9points ahead
- Unpublished advanced math problemsFrontierMath Tiers 1-3 (v2)+59.7points ahead
- Command-line tasks in a real terminalTerminal-Bench 2.1+53.2points ahead
Where GPT-5.5 Instant pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+22.6points ahead
Every test, side by side
All 26 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingGPT-5.6 Terra
- Terminal-Bench 2.1GPT-5.6 Terra by 53.234.888+53.2
- Terminal-Bench HardGPT-5.6 Terra by 15.242.457.6+15.2
- SciCodeGPT-5.6 Terra by 2.552.555+2.5
AgentsGPT-5.6 Terra
- GDPValGPT-5.6 Terra by 47.7047.7+47.7
- τ-Bench V3 · BankingGPT-5.6 Terra by 28.411.840.2+28.4
- Terminal-Bench 4.0GPT-5.6 Terra by 22.812.635.4+22.8
ReasoningGPT-5.6 Terra
- CritPtGPT-5.6 Terra by 27.42.630+27.4
- Humanity's Last ExamGPT-5.6 Terra by 21.321.642.9+21.3
- GPQA DiamondGPT-5.6 Terra by 7.984.692.5+7.9
FactsEven
- AA-Omniscience · Non-hallucinationGPT-5.5 Instant by 22.634.712.1+22.6
- SimpleQA VerifiedGPT-5.6 Terra by 5.23843.2+5.2
- AA-Omniscience · Accuracytie46.346.8tie
Images and chartsGPT-5.6 Terra
- MMMU-ProGPT-5.6 Terra by 4.77680.7+4.7
- CharXiv (RQ)GPT-5.6 Terra by 4.381.685.9+4.3
- LMArena · VisionGPT-5.6 Terra by 21 rating points12501271+21 rating
MathGPT-5.6 Terra
- FrontierMath Tier 4GPT-5.6 Terra by 65.92.468.3+65.9
- FrontierMath Tiers 1-3 (v2)GPT-5.6 Terra by 59.726.386+59.7
Other results7 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.
- Artificial Analysis Coding IndexGPT-5.6 Terra by 37.339.476.7+37.3
- τ²-Bench Telecom (AA run)GPT-5.6 Terra by 36.949.486.3+36.9
- AA Agentic IndexGPT-5.6 Terra by 24.519.243.7+24.5
- AA IntelligenceGPT-5.6 Terra by 19.422.742.1+19.4
- HealthBench ProfessionalGPT-5.6 Terra by 19.338.457.7+19.3
- AA-OmniscienceGPT-5.5 Instant by 11.111.20.1+11.1
- HealthBenchGPT-5.6 Terra by 5.651.457+5.6
Questions people ask
Which is better, GPT-5.5 Instant or GPT-5.6 Terra?
GPT-5.6 Terra wins six of the eight areas we test: coding, agents, reasoning, images and charts, math and long documents. GPT-5.5 Instant wins none. They are level on facts and following instructions.
Which is better for coding?
GPT-5.6 Terra. It wins 3 of the 3 coding tests both models report; GPT-5.5 Instant wins none.
Which is cheaper?
GPT-5.5 Instant costs $5.00 per million input tokens and $30.00 per million output tokens; GPT-5.6 Terra costs $2.00 and $12.00. That makes GPT-5.6 Terra about 60% cheaper for the same work.
How do you compare the two?
We use the 26 benchmark tests both models have published scores on. The verdict counts the 19 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 7 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.