Grok 4.6 vs GPT-5.6 Terra

head-to-head

what do the benchmarks actually say?

On SWE-bench Verified — real, human-validated GitHub issues resolved end-to-end — Grok 4.6 posts 95.6% against 95.4% for GPT-5.6 Terra, a 0.2-point gap. Verified is the closest public proxy for "can it fix a real bug in a real repo without help", which is why it anchors our ranking.

A few points either way is real but not decisive: within that band, the agent scaffolding around the model — how it retrieves files, runs tests, and retries — often matters as much as the base model. Treat the gap as a lean, not a verdict.

which is cheaper to run?

Both list at $2 per 1M input tokens, so the sticker price is a wash — output rates ($6 vs $12) and token efficiency decide the real bill. Coding workloads are output-heavy — agents write diffs, tests and retries — so weight the output rate more than the input rate when you estimate a monthly bill.

when to pick each

how were these scores verified?

We only print a number once it's confirmed against a primary source or an independent evaluation, and each row on our leaderboard records which kind it is:

• Grok 4.6: Independent (vals.ai, benchmark updated 2026-08-12, mini-swe-agent bash-only harness): SWE-bench Verified 95.60% ±0.92. Entered ranked 2026-08-13, one day after launch, and it enters near the top: 4th of the 82 systems vals.ai has run, behind Claude Opus 5 (97.00% ±0.76), DeepSeek V4 Pro 0813 (96.40% ±0.83) and GPT-5.6 Sol (96.20% ±0.86). Read the gap to Claude Fable 5 below it (95.00% ±0.98) as a tie: 0.6 points against a pooled SEM of about 1.34 is well inside the margin of error, and we rank Grok 4.6 higher only because it scored higher. Same against Sol above it, a 0.6-point gap. This is the second time running that xAI shipped a Grok with no SWE-bench Verified number of its own and vals.ai supplied one: Grok 4.5 waited nine days, Grok 4.6 waited one. SpaceXAI still publishes no SWE-bench Verified or SWE-bench Pro figure, so the ranked score here is entirely vals.ai's measurement with no vendor claim to disclose against. What xAI did publish, all vendor-reported on its own table: AA Intelligence Index 61, CursorBench v3.2 69.9%, DeepSWE v1.1 65.9%, FrontierCode v1.1 Extended 61.3%, APEX-Agents 57.5%, APEX-SWE 56.4%, Terminal-Bench v3.0 26%, GDPVal-AA v2 1753, AA-Briefcase 1577, Harvey LAB (Vals) 15.8%. That table's shape still holds and is worth reading against this score: Grok 4.6 takes the best result on the three knowledge-work evals and loses the two hardest agentic-coding ones by wide margins (DeepSWE 65.9% vs Sol's 73%, Terminal-Bench v3.0 26% vs Sol's 34.6%). Terminal-Bench v3.0 is NOT comparable to the 83.3% TB2.1 figure on the Grok 4.5 row: on v3.0 Grok 4.5 scores 15.7% and the whole field tops out near 34%. On cost it is the standout of the top five, $0.78 per test against $1.29 for Opus 5, $1.15 for Sol and $2.05 for Fable 5, though it is also the slowest of them at 604s. Pricing unchanged from Grok 4.5 at $2/$6 per 1M. See /p/grok-4-6-frontier-benchmarks-terminal-bench-gap/.
• GPT-5.6 Terra: Independent (vals.ai, re-evaluated, mini-swe-agent bash-only harness): SWE-bench Verified 95.4% ±0.94, 5th of 86 systems. CORRECTION, 2026-08-20: this row previously carried 75.2% ±1.93 (32nd of 75), the figure vals.ai published on Jul 22 2026 and which we added Jul 27, 2026. A routine sweep found vals.ai had re-run the model and revised the score up by 20.2 points; the old figure and the reading we built on it, that Terra was the weakest of the three GPT-5.6 tiers, are both withdrawn. A jump that large on an unchanged model points at the first run rather than the model, so read 95.4% as the corrected measurement and not as an improvement. Terra now sits second among the GPT-5.6 tiers, behind Sol at 96.2% and ahead of Luna at 93.0%. Treat it as tied with GLM-5.3 (also 95.4% ±0.94), Grok 4.6 (95.6%) and Claude Fable 5 (95.0%): pooled SEM across those rows is about 1.3 points and every gap is smaller than that. Cheapest of the 95%-plus cluster on measured cost per test at $0.40, against $1.15 for Sol and $2.05 for Fable 5. Repriced Aug 1, 2026: OpenAI cut Terra 20% on Jul 30, 2026, from $2.50/$15 to $2/$12 per 1M (vendor-announced, reported by BleepingComputer and VentureBeat). Cached input $0.25 at launch, not re-confirmed after the cut. Context ~1.05M, max output 128k. Released Jul 9, 2026.

Full reviewsGrok 4.6, decoded

Ranked on our AI Coding Leaderboard, updated 2026-08-20. Scores are confirmed against primary sources; prices are per 1M input tokens and can change.