Three Flagships in Ten Days: Claude Opus 5.5 vs GPT-6 Astra vs Gemini 4 Argon on LiveBench
Anthropic shipped Claude Opus 5.5 on September 22. Claude Sonnet 5.5 followed on September 28. Google released Gemini 4 Argon on September 30, still under phased rollout for selected users. GPT-6 Astra landed in the same window. Three top labs, four flagship models, ten days.
LiveBench 2.0 now has all three on the same leaderboard with a full suite of results. Here is what the data shows.
LiveBench 2.0 Scores (October 2026)
| Model | Overall | Agentic | Reasoning | Coding | Browser Use | Cost/Task |
|---|---|---|---|---|---|---|
| Claude Opus 5.5 | 86.5 | 85.0 | 92.2 | 96.3 | 80.0 | $4.19 |
| GPT-6 Astra | 86.1 | 82.4 | 92.7 | 93.7 | 84.0 | $3.81 |
| Gemini 4 Argon | 84.1 | 69.9 | 95.1 | 89.7 | 92.0 | $1.80 |
The overall gap between Opus 5.5 and GPT-6 Astra is 0.4 points. Artificial Analysis’s Intelligence Index also has them separated by five points, with Astra and Argon tied at 53 and Opus 5.5 five points ahead. These are not runaway differences. The frontier is genuinely compressed.
Where Each Model Leads
Claude Opus 5.5 leads on coding (96.3) and agentic tasks (85.0). Terminal-Bench 4.0 puts it at 59.6%, marginally ahead of GPT-6 Astra’s 57.9%. Anthropic’s $4/$20 per-million-token pricing makes it the most expensive of the three.
GPT-6 Astra leads on reasoning (92.7) by a narrow margin and places between the other two on most dimensions. At $3.81 per successful LiveBench task, it costs slightly less than Opus 5.5 but substantially more than Argon at intro pricing. It is roughly 5x more expensive per task than GPT-6.1 Sol, which launched the day after Argon at $2/$10 per million tokens.
Gemini 4 Argon has the most distinctive profile. Its reasoning score, 95.1, is the highest of the three and beats both rivals on that dimension. Browser use is 92.0, also the highest of the group. But agentic performance at 69.9 is 12 to 15 points below the other two — a notable gap for a model otherwise performing at frontier level. The clearest differentiator outside benchmarks is LVBench: 91.7% on long-video understanding, well ahead of the field. Argon’s cost-per-task at $1.80 is less than half of either rival at its intro pricing, rising to $4/$20 per million tokens after the intro period ends.
What the Gaps Mean
A 0.4-point overall gap on LiveBench between the top two is within noise for most production use cases. The real decision variables are cost, availability, and specific-task performance.
Argon is still gated to selected users through Google’s Fairwind Program. Opus 5.5 and Astra are broadly available. For developers who can access Argon and are building reasoning-heavy or long-video pipelines, the cost-performance case is strong. For agentic coding workloads, the 15-point agentic gap on LiveBench is a concrete reason to prefer Opus 5.5 or Astra while waiting for independent SWE-bench results for Argon.
None of the three have published SWE-bench Verified scores. The composite agentic scores on Stack Futures’s ticker remain null pending primary benchmark data from an independent harness.