The AI Model Tier List, September 2026

Fable 5.1

$10 in$50 out$20 blended1M contextIntelligence index: 66

Released on September 1, 2026, it arrived on the date this list reflects and is both the highest-ranked and most expensive model here. Artificial Analysis scores it at 66, three points ahead of Opus 5 and four ahead of the Fable 5 model it replaces.

Its list price remains unchanged at $10 per million input tokens and $50 per million output tokens. The real price cut is in cache reads, which fell from $1 to $0.25 per million tokens. Anthropic now charges 0.025 times the base input rate, compared with 0.1 times for every other model on its pricing page. Because this tier list excludes cached rates, Anthropic's largest price reduction of the year doesn't appear on the price chip.

Opus 5

$5 in$25 out$10 blended1M contextIntelligence index: 63

Opus 5 gives up only three points to Fable 5.1 while costing half as much, making it the strongest value this close to the top. Anthropic released it on July 24, 2026, and Artificial Analysis found that it delivered comparable intelligence to the previous Fable model at twenty-six percent lower cost per task.

The discount comes with a real tradeoff. In the same evaluation, Opus 5 scored lower than the Fable line on factual knowledge and hallucinated roughly half the time. For long, fact-sensitive work, that is reason enough to pay for Fable 5.1.

The reception in r/ClaudeCode is much colder than the benchmark. One active thread describes Opus 5 as difficult to steer and exhausting to supervise, with users objecting to its long, convoluted answers. These are user reports, not controlled evaluations, but the gap between the score and the day-to-day experience is too wide to ignore.

Grok 4.6

$2 in$6 out$3 blended500K contextIntelligence index: 61

The best price-to-score ratio anywhere above B, and the reason this row isn't just the leftovers. It matches gpt-5.6-sol's index score exactly at $3 against $8. It also has the flattest input-to-output ratio on the list, which makes it unusually cheap for long generation on top of that.

gpt-5.6-sol

$4 in$20 out$8 blended⚠️Promo ends nov 21, 2026400K contextIntelligence index: 61

Five points behind Fable 5.1, two behind Opus 5, and it would still have a case for S+ if Grok 4.6 didn't match it for a third of the money. It's the flagship of the GPT-5.6 family OpenAI shipped on July 9, 2026, which replaced the old unsuffixed naming with three tiers: Sol at the top, Terra in the middle, Luna at the bottom. Sol's own model page says it "roughly corresponds to the unsuffixed model tier used in earlier GPT-5 families", which is the clearest thing anyone has written about that naming scheme.

The $8 is promotional, and the section below says so, but the placement survives the expiry. The rate it was cut from was $5 and $30, which blends to $11.25. What it doesn't survive is a long document: Sol's window is 400K against the million that Fable 5.1, Opus 5 and kimi k3 all give you, and every GPT-5.6 model bills the whole request at double input above 272K tokens.

glm-5.3

$1.40 in$4.40 out$2.15 blended200K contextIntelligence index: 60

glm-5.3 is the clear bargain in this row: it matches kimi k3's index score for roughly a third of the price. Z.ai released the model on August 18, 2026 and published its weights ten days later. Its licence is more restrictive than the plain MIT terms given to glm-5.3-flash, however. Model-as-a-service providers with more than ten billion dollars in revenue must first pass a Z.ai security review.

kimi k3

$3 in$15 out$6 blended1M contextIntelligence index: 60

Three points off the top of the list at thirty percent of the price, and it keeps the full million-token window that Sol gives up. It always reasons, which is why its output rate is five times its input.

It's also, with glm-5.3 beside it, one of two models in this row you can download and run. Moonshot published open weights for a 2.8-trillion-parameter model, which is a strange sentence to be able to write, and it means the price on the chip is a convenience rate rather than the only way to get it.

glm-5.3-flash

$0.15 in$0.50 out$0.24 blended1M contextIntelligence index: 57

The cheapest thing on this list, at roughly half of Luna. Z.ai published its weights on August 26, 2026 under a plain MIT licence, eight days after the larger glm-5.3 and on much friendlier terms.

What keeps it out of the rows above is the word in its name. Flash is slow: around 42 output tokens a second, against a median near 65 for open-weight models its size, and verbose enough that a benchmark suite pulls about a third more output out of it than average. Cheap tokens, expensive minutes. If someone is waiting on it, the price stops being the number that matters.

Gemini 3.7 Flash

$0.75 in$3.75 out$1.50 blended⚠️input doubles jan 1, 20271M contextIntelligence index: 56

A capable budget option priced alongside Luna and DeepSeek Flash. Its input rate is dated, which is its own section below.

gpt-5.6-luna

$0.20 in$1.20 out$0.45 blended400K contextIntelligence index: 52

The cheapest thing OpenAI sells, and until last week the cheapest thing here. Its price was cut by eighty percent on July 30, 2026, which means every comparison written before that date has it at five times what it now costs.

deepseek v4 flash

$0.44 in$1.32 out$0.66 blended1M contextIntelligence index: 52

The third-cheapest blended price on the list, which makes it the DeepSeek sibling worth buying, and the spec sheet below explains exactly how much cheaper that sibling argument is.

Muse Spark 1.2

$1.25 in$4.25 out$2 blended512K contextIntelligence index: 57

Meta's, released August 5, 2026. It scores 57, which is the same number gpt-5.6-terra carries two rows below it and glm-5.3-flash carries one row above, and its price sits between the two of them. Landing exactly between the rows on both axes is what C is for.

Composer 2.5

$0.50 in$2.50 out$1 blended200K contextNo intelligence index

The cheapest model in this row by some way, which is a strange thing to find in D until you notice it isn't really a general model: Cursor's own launch post says it's built on the same open-source checkpoint as Composer 2, Moonshot's Kimi K2.5.

It's also the one model with no number in the index column below. Artificial Analysis rates it on their coding agent index instead, where it placed third. That's a real result, and it's measuring a different thing than every other row here.

gpt-5.6-terra

$2 in$12 out$4.50 blended400K contextIntelligence index: 57

The middle tier of the GPT-5.6 family, and the score column is unkind to it. Two models match its 57 exactly: Muse Spark 1.2 for less than half the price, and glm-5.3-flash for a nineteenth of it.

Sonnet 5

$2 in$10 out$4 blended1M contextIntelligence index: 55

In the same row, and its price has its own story. The $2 in and $10 out rate launched as introductory pricing due to expire on August 31, 2026 and rise to $3 and $15 on September 1. That increase was cancelled. Anthropic's pricing page now states the old rate is the standard one and the scheduled rise "will not occur." If you read almost any comparison written before this week, it has Sonnet 5 at $3 and $15.

deepseek v4 pro

$1.32 in$3.96 out$1.98 blended1M contextIntelligence index: 53

It costs exactly three times its own sibling: DeepSeek v4 Flash is $0.44 in and $1.32 out. Three times the input, three times the output, from the same vendor, released two weeks apart. The index column says what the premium buys: 53 against 52. One point.

Gemini 3.1 Pro

$2 in$12 out$4.50 blended1M contextIntelligence index: 48

The oldest model here by a distance. It was released on February 19, 2026, nearly three months before anything else on this list, and it still prices identically to gpt-5.6-terra. A model holding its launch price while everything around it gets cheaper is a statement about where its vendor's attention has moved.

It also carries the lowest score on the list. Every single model above it is cheaper, better, or both. That's what F is for.