Model comparison
GPT-5.6 Terra vs Grok 4.20
Head-to-head evidence from 5 shared benchmark results across 4 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.6 Terra #11 (Estimated); Grok 4.20 #88 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.6 Terra and Grok 4.20 share 5 comparable benchmark results. 3 of 8 categories are comparable. 39 results are unique to GPT-5.6 Terra; 13 to Grok 4.20.
Updated July 23, 2026- Shared results
- 5
- GPT-5.6 Terra only
- 39
- Grok 4.20 only
- 13
- Comparable categories
- 3 / 8
Pick GPT-5.6 Terra if you want the stronger benchmark profile. Grok 4.20 only becomes the better choice if coding is the priority or you want the cheaper token bill.
Confidence note. This is a partial-evidence comparison with 5 shared benchmark results across 4 evidence categories; 3 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
GPT-5.6 Terra is clearly ahead on the BenchAlign aggregate, 72.57 to 54.68. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.6 Terra's sharpest advantage is in agentic, where it averages 87.4 against 47.1. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 87.4% to 47.1%. Grok 4.20 does hit back in coding, so the answer changes if that is the part of the workload you care about most.
GPT-5.6 Terra is also the more expensive model on tokens at $2.50 input / $15.00 output per 1M tokens, versus $2.00 input / $6.00 output per 1M tokens for Grok 4.20. That is roughly 2.5x on output cost alone. Grok 4.20 gives you the larger context window at 2M, compared with 1M for GPT-5.6 Terra.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | GPT-5.6 Terra | Δ | Grok 4.20 |
|---|---|---|---|
| Agentic | GPT-5.6 Terra87.4 | Margin← 40.3 | Grok 4.2047.1 |
| Multimodal | GPT-5.6 Terra80.7 | Margin← 10.6 | Grok 4.2070.1 |
| Coding | GPT-5.6 Terra63.4 | Margin→ 3.7 | Grok 4.2067.1 |
| Reasoning | GPT-5.6 TerraNot measured | MarginNo overlap | Grok 4.2053.3 |
| Knowledge | GPT-5.6 Terra92.9 | MarginNo overlap | Grok 4.20Not measured |
| Math | GPT-5.6 Terra80.8 | MarginNo overlap | Grok 4.20Not measured |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
Terminal-Bench 2.0
AgenticA 87.4%B 47.1%Winner: GPT-5.6 TerraΔ 40.3Terminal-Bench 2.0: GPT-5.6 Terra scored 87.4%; Grok 4.20 scored 47.1%. GPT-5.6 Terra wins this benchmark. - Source ↗
SWE-bench Pro
CodingA 63.4%B 51.8%Winner: GPT-5.6 TerraΔ 11.6SWE-bench Pro: GPT-5.6 Terra scored 63.4%; Grok 4.20 scored 51.8%. GPT-5.6 Terra wins this benchmark. - Source ↗
MMMU-Pro
MultimodalA 80.7%B 75.2%Winner: GPT-5.6 TerraΔ 5.5MMMU-Pro: GPT-5.6 Terra scored 80.7%; Grok 4.20 scored 75.2%. GPT-5.6 Terra wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.6 Terra | Grok 4.20 | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.6 Terra$2.5 input / $15 output | Grok 4.20$2 input / $6 output | Grok 4.20 has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.6 TerraNot available | Grok 4.20233 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.6 TerraNot available | Grok 4.2010.33 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.6 Terra1M | Grok 4.202M | Grok 4.20 lists the larger context window. |
Benchmark Deep Dive
AgenticGPT-5.6 Terra wins19 benchmarks
| Benchmark | GPT-5.6 Terra | Grok 4.20 | Result |
|---|---|---|---|
| Terminal-Bench 2.0Source | 87.4% | 47.1% | GPT-5.6 Terra leads |
| BrowseCompSource | 87.5% | — | Not comparable |
| OSWorld 2.0Source | 50.2% | — | Not comparable |
| CyberGymSource | 81.8% | — | Not comparable |
| ExploitGymSource | 23.2% | — | Not comparable |
| ToolathlonSource | 53.1% | — | Not comparable |
| AA Agentic IndexSource | 47.4% | — | Not comparable |
| τ²-bench resultsSource | 86.3% | — | Not comparable |
| GDPval-AASource | 54.1% | — | Not comparable |
| GDPval-AASource | 1581 | — | Not comparable |
| AA Harvey LABSource | 85.2% | — | Not comparable |
| AA ITBenchSource | 51.0% | — | Not comparable |
| AA Tau3 BankingSource | 31.8% | — | Not comparable |
| AA AutomationBenchSource | 45.6% | — | Not comparable |
| terminalBenchHardSource | 57.6% | — | Not comparable |
| aaTerminalBench21Source | 88% | — | Not comparable |
| APEX-Agents-AASource | 38.9% | — | Not comparable |
| DeepSearchQASource | — | 62.8% | Not comparable |
| Gert LabsSource | — | 38.36% | Not comparable |
CodingGrok 4.20 wins10 benchmarks
| Benchmark | GPT-5.6 Terra | Grok 4.20 | Result |
|---|---|---|---|
| SWE-bench ProSource | 63.4% | 51.8% | GPT-5.6 Terra leads |
| Terminal-Bench 2.0Source | 87.4% | — | Not comparable |
| deepSweSource | 69.6% | — | Not comparable |
| FrontierCode 1.1 ExtendedSource | 55.8% | — | Not comparable |
| cursorBench32Source | 64.9% | — | Not comparable |
| AA Coding IndexSource | 76.7% | — | Not comparable |
| AA-SciCodeSource | 53.9% | — | Not comparable |
| LiveCodeBench ProSource | — | 74.2% | Not comparable |
| SWE-bench VerifiedSource | — | 76.7% | Not comparable |
| Vibe Code BenchSource | — | 4.06% | Not comparable |
Reasoning4 benchmarks
Knowledge12 benchmarks
| Benchmark | GPT-5.6 Terra | Grok 4.20 | Result |
|---|---|---|---|
| GPQASource | 92.9% | — | Not comparable |
| GPQA-DSource | 92.9% | 88.5% | GPT-5.6 Terra leads |
| HealthBench ProfessionalSource | 57.7% | — | Not comparable |
| HealthBench HardSource | 32.7% | 20.3% | GPT-5.6 Terra leads |
| Artificial Analysis Intelligence IndexSource | 55.0% | — | Not comparable |
| AA-GPQA DiamondSource | 92.5% | — | Not comparable |
| AA-HLESource | 41.8% | — | Not comparable |
| AA-Omniscience IndexSource | -0.2% | — | Not comparable |
| AA-Omniscience AccuracySource | 45.9% | — | Not comparable |
| AA-Omniscience Hallucination RateSource | 85.2% | — | Not comparable |
| HLE w/o toolsSource | — | 31.6% | Not comparable |
| MedXpertQA (Text)Source | — | 50.2% | Not comparable |
Math3 benchmarks
MultimodalGPT-5.6 Terra wins8 benchmarks
| Benchmark | GPT-5.6 Terra | Grok 4.20 | Result |
|---|---|---|---|
| MMMU-ProSource | 80.7% | 75.2% | GPT-5.6 Terra leads |
| MMMU-Pro w/ PythonSource | 82% | — | Not comparable |
| AA-MMMU-ProSource | 80.7% | — | Not comparable |
| CharXivSource | — | 60.9% | Not comparable |
| ERQASource | — | 54.1% | Not comparable |
| SimpleVQASource | — | 57.4% | Not comparable |
| MedXpertQA (MM)Source | — | 65.8% | Not comparable |
| Design Arena WebsiteSource | — | 1257 | Not comparable |
Inst. Following1 benchmarks
| Benchmark | GPT-5.6 Terra | Grok 4.20 | Result |
|---|---|---|---|
| AA-IFBenchSource | 71.2% | — | Not comparable |
Frequently Asked Questions (4)
Which is better, GPT-5.6 Terra or Grok 4.20?
GPT-5.6 Terra is ahead on BenchLM's BenchAlign leaderboard, 72.57 to 54.68. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 87.4% and 47.1%.
Which is better for coding, GPT-5.6 Terra or Grok 4.20?
Grok 4.20 has the edge for coding in this comparison, averaging 67.1 versus 63.4. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.
Which is better for agentic tasks, GPT-5.6 Terra or Grok 4.20?
GPT-5.6 Terra has the edge for agentic tasks in this comparison, averaging 87.4 versus 47.1. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
Which is better for multimodal and grounded tasks, GPT-5.6 Terra or Grok 4.20?
GPT-5.6 Terra has the edge for multimodal and grounded tasks in this comparison, averaging 80.7 versus 70.1. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
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