Model comparison

GPT-5.6 Terra vs GPT-6 Astra

Two OpenAI tiers compared on the figures that decide which one a workload actually needs.

Catalog record checked September 5, 2026Individual provider fields may changeEvidence confidence: High — see receipts below

OpenAI

GPT-5.6 Terra

Balanced

OpenAI

GPT-6 Astra

Frontier

AI model capability comparison
Specification	GPT-5.6 Terra	GPT-6 Astra
Provider	OpenAI	OpenAI
Tier	Balanced	Frontier
Context window	1.05M	1.05M
Max output	128K	128K
Input / 1M tokens	Winner: $2	$10
Output / 1M tokens	Winner: $12	$50
Weights	Closed	Closed
Parameters	mid-tier reasoning model	computer-use flagship
Reasoning levels	none, low, medium, high, xhigh, max	low, medium, high, xhigh, max
Modalities	text, image	text, image
API model id	gpt-5.6-terra	gpt-6-astra
Released	July 9, 2026	September 3, 2026
Artificial Analysis Intelligence Index [high] (2026-08-14)	50	Not verifiedUnverified
Artificial Analysis Intelligence Index [max] (2026-09-03)	Not verifiedUnverified	61.2
SWE-bench Verified (2026-09-01)	95.4	Not verifiedUnverified
Terminal-Bench 2.1 (2026-07-09)	87.4	Winner: 89.9
LiveBench (2026-09-05)	77.9	Not verifiedUnverified
DeepSWE 1.1 (2026-09-03)	Not verifiedUnverified	74.1
OSWorld 2.0 (offline) (2026-09-03)	Not verifiedUnverified	72.6
GPQA Diamond (2026-09-03)	Not verifiedUnverified	96
Humanity's Last Exam (2026-09-03)	Not verifiedUnverified	57.2

Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

2026-09-05: Artificial Analysis Terminal-Bench v2.1 (independent, Terminus 2 harness — conflicts with tbench.ai 87.4; harness difference preserved)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
2026-09-05: LiveBench official leaderboard (benchmark-owned), max effortContamination-resistant general capability across reasoning, coding, math, data analysis, and language, with monthly question refreshes. Comparability: comparable with caveat — Rolling question set: observations months apart measure different question mixes. Record the measurement date and compare within ~1 month windows.
2026-09-03: Terminal-Bench official leaderboard (independent, native harness, high effort; captured 2026-09-03 — the live board has since moved to Terminal-Bench 4.0)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
2026-09-03: OpenAI GPT-6 Astra launch chart (vendor, with tools; transcribed by Vellum)Agentic software engineering: pass@1 on real repo tasks with reported cost per completed task. Comparability: directly comparable
2026-09-03: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
2026-09-01: vals.ai SWE-bench Verified leaderboard (independent, mini-swe-agent bash-only) (independent; official SWE-bench not published)Real GitHub issue resolution: does the model's patch pass the hidden tests. Comparability: comparable with caveat — Post-audit vendor claims and pre-audit scores sit on different task trust levels; scaffolding (agent harness, compute budget) also dominates results. Never aggregate across scaffolds.
2026-07-09: OpenAI GPT-5.6 announcement (vendor; chart transcribed by Vellum)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.

Pricing tiers: GPT-5.6 Terra: Launch list was $2.50/$15; cut to $2/$12 on 2026-07-30. Cached input $0.20/MTok; batch $1/$6. · GPT-6 Astra: Standard $10/$50 per MTok (≤272K context); >272K input billed $20/$75 (Fast mode output $100). Cached input $1/MTok; Fast mode is 2x price for ~2.5x speed. Knowledge cutoff Apr 30 2026. Rolling out over several days from 2026-09-03; Enterprise tenants get it disabled by default.

BalancedRecord checked September 3, 2026

GPT-5.6 Terra

GPT-5.6 Terra delivers roughly GPT-5.5-class quality at about half the cost, with the full 1.05M-token context.

Best for

Cost-sensitive production
Mixed reasoning workloads
High-volume agents

Watch out

Quality trails Sol on the hardest tasks; route frontier work to Sol when it matters.

FrontierRecord checked September 5, 2026

GPT-6 Astra

GPT-6 Astra is OpenAI's computer-use flagship — the first model it gates at the Preparedness Framework's 'Critical' cybersecurity threshold, trained on >100,000 GPUs at Stargate.

Best for

Computer-use agents
Agentic coding
Hard reasoning

Watch out

Gated at the 'Critical' cyber threshold and disabled by default for Enterprise; long-context work bills $20/$75 above 272K input tokens.

When the cheaper one wins

GPT-5.6 Terra is cheaper on output at $12 per million tokens against $50 for GPT-6 Astra — about 4.2×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.

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Evidence confidence: High

How strong and complete the evidence behind this comparison is — not a prediction of which model is better.

Pricing verified on both sides — Input and output rates are verified for both models.
5/5 core specs verified on both sides — All core specifications verified for both models.
2 shared named benchmarks with differing scores — Measured on: Artificial Analysis Intelligence Index, Terminal-Bench 2.1.
Verified within the last 90 days — Newest catalog check was 6 days ago.
Both models carry source citations — Each side has at least two catalog sources on record.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

GPT-5.6 Terra: OpenAI — GPT-5.6 (accessed 2026-08-29)
GPT-5.6 Terra: OpenAI API pricing (gpt-5.6-terra $2/$12) (accessed 2026-08-29)
GPT-6 Astra: OpenAI — Introducing GPT-6 Astra (accessed 2026-09-03)
GPT-6 Astra: OpenAI API pricing (gpt-6-astra $10/$50) (accessed 2026-09-03)
GPT-6 Astra: CNBC — OpenAI launches GPT-6 Astra (accessed 2026-09-03)
GPT-6 Astra: OpenAI model docs — gpt-6-astra (128K max output, effort levels) (accessed 2026-09-05)

Related comparisons

Diving deeper on one model? GPT-5.6 Terra · GPT-6 Astra

Common questions

GPT-5.6 Terra vs GPT-6 Astra

Answered from the verified figures on this page rather than general guidance.

Is GPT-5.6 Terra or GPT-6 Astra cheaper for input?

GPT-5.6 Terra is cheaper at $2 per million input tokens, against $10 for GPT-6 Astra — roughly 5.0× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.6 Terra has tiered pricing: Launch list was $2.50/$15; cut to $2/$12 on 2026-07-30. Cached input $0.20/MTok; batch $1/$6. GPT-6 Astra has tiered pricing: Standard $10/$50 per MTok (≤272K context); >272K input billed $20/$75 (Fast mode output $100). Cached input $1/MTok; Fast mode is 2x price for ~2.5x speed. Knowledge cutoff Apr 30 2026. Rolling out over several days from 2026-09-03; Enterprise tenants get it disabled by default.

Is GPT-5.6 Terra or GPT-6 Astra cheaper for output?

GPT-5.6 Terra is cheaper at $12 per million output tokens, against $50 for GPT-6 Astra — roughly 4.2× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.6 Terra has tiered pricing: Launch list was $2.50/$15; cut to $2/$12 on 2026-07-30. Cached input $0.20/MTok; batch $1/$6. GPT-6 Astra has tiered pricing: Standard $10/$50 per MTok (≤272K context); >272K input billed $20/$75 (Fast mode output $100). Cached input $1/MTok; Fast mode is 2x price for ~2.5x speed. Knowledge cutoff Apr 30 2026. Rolling out over several days from 2026-09-03; Enterprise tenants get it disabled by default.

Which has the larger context window, GPT-5.6 Terra or GPT-6 Astra?

Both accept about 1.05M tokens of context, so document length will not decide between them.

Do GPT-5.6 Terra and GPT-6 Astra support the same reasoning levels?

GPT-5.6 Terra exposes none, low, medium, high, xhigh, max, while GPT-6 Astra exposes low, medium, high, xhigh, max.

Should I use GPT-5.6 Terra or GPT-6 Astra?

GPT-5.6 Terra is the balanced tier and GPT-6 Astra the frontier tier. The useful question is whether your hardest task actually fails on the cheaper one — most production volume such as classification, extraction and summarisation does not.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

Input price: GPT-5.6 Terra costs $2 per 1M tokens versus $10 for GPT-6 Astra — a 5x difference at the headline tier.
Measured capability: GPT-6 Astra leads Artificial Analysis Intelligence Index 61.2 to 50 (measured 2026-08-14).
Positioning: GPT-5.6 Terra sits in the balanced tier, GPT-6 Astra in the frontier tier — most production volume (classification, extraction, summarisation) does not need the pricier tier.

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