Kimi K3.1 Pro vs Opus 5.5 on Scores and Access

Kimi K3.1 Pro from Moonshot AI opened on the API on October 23, 2026 with a published Terminal-Bench 4.0 mark of 65.7%, 0.7 points under Claude Opus 5.5’s 66.4% in the same week’s circulating scorecards. Buyers shopping coding and agent runs now treat four named options as the shortlist: Moonshot’s MoE, Anthropic’s Opus tier, OpenAI’s GPT-6 Astra, and Alibaba’s Qwen3.8-Max.

65.7% Terminal-Bench for Kimi K3.1 Pro

Moonshot’s own launch materials frame Kimi K3.1 Pro as a 2.8T-parameter mixture-of-experts model with a 1M-token context window, API access on day one, and open weights promised for November 4, 2026. The official @Kimi_Moonshot announcement carried that package into the week’s high-engagement threads.

Terminal-Bench 4.0 at 65.7% is the number people pasted next to Opus screenshots. It is a terminal-agent harness score, not a chat preference win and not a latency claim.

Judgement: take Kimi first when you want API access now plus a dated open-weights path on the same model family, and you can live with a sub-point gap on that one public agent bench.

66.4% Terminal-Bench for Claude Opus 5.5

Opus 5.5 sits 0.7 points above Kimi on the same Terminal-Bench 4.0 figure that drove the comparison posts. Anthropic still sells Claude through its paid products and API; the public pricing surface for Opus-class models lives on Anthropic’s pricing page, which is the clean place to read current input and output rates without inferring them from social screenshots.

What Opus does not advertise in this week’s Kimi threads is a matching open-weights date. Closed weights stay the product.

Judgement: pick Opus when you already standardize on Anthropic tooling and want the published Terminal-Bench edge, even if that edge is thinner than the hype ratio suggests.

GPT-6 Astra in the third column of those scorecards

GPT-6 Astra shows up in the same X comparison grids as Kimi K3.1 Pro and Opus 5.5, which is why it belongs on this field map. What those grids often skip is a single, cited Terminal-Bench 4.0 cell for Astra that matches the Moonshot and Anthropic pair above. Absent that matched cell, Astra is a product-and-access reference, not a third scored bar on this particular bench.

OpenAI’s Astra rollout has been gradual for orgs in prior coverage on this site. That access pattern is a differentiator even when the screenshot set treats all three names as peers.

Judgement: keep Astra on the shortlist for shops already inside OpenAI’s org gates, and refuse to rank it on Terminal-Bench 4.0 until a sourced score appears beside the 65.7 / 66.4 pair.

$2 input and $6 output on Qwen3.8-Max

Qwen3.8-Max enters as the price-named open-weight competitor Alibaba put on a public API card at $2 per million input tokens and $6 per million output tokens in its launch materials, with open weights on a short follow-on timetable. It is not Moonshot’s 2.8T MoE, and it is not Anthropic’s Opus stack.

Independent indexes such as Artificial Analysis remain the place to watch for cross-lab quality and price composites once more labs publish matched agent runs. Until a Terminal-Bench 4.0 number for Qwen sits next to 65.7 and 66.4 with the same citation trail, treat the $2/$6 card as the concrete differentiator, not a win claim on that harness.

Judgement: Qwen is the buy when the rate card and open-weight timeline matter more than matching Moonshot’s or Anthropic’s Terminal-Bench screenshot this week.

November 4 open weights without a matched day-one harness card

What’s underappreciated here: none of these four options ships a single public artifact that combines (1) the live API model id, (2) the Terminal-Bench 4.0 score used in this week’s threads, (3) a stable $/M token row, and (4) downloadable weights under one checksum on the same calendar day. Moonshot splits API-now from weights-on-November-4. Anthropic keeps weights closed. Astra’s Terminal-Bench cell is missing from the viral grids. Qwen’s loudest public figure this cycle is the rate card, not a 65.7-class Terminal-Bench citation next to Kimi and Opus.

That empty slot is a buyer problem. Teams that need to justify a switch want one printable page. The field still makes them assemble four tabs.

Moonshot’s Kimi K3.1 Pro API is live as of October 23, 2026, with the 65.7% Terminal-Bench 4.0 figure and the November 4 open-weights date stated in the same launch package.