GLM-5.2 vs GPT-5.6 vs Claude Fable 5: Coding Models Compared

Open-weight models have closed a lot of ground on coding benchmarks this year, but "closed the gap" and "caught up" aren't the same claim. GLM-5.2, GPT-5.6 Sol, and Claude Fable 5 sit at three different points on the intelligence-vs-price curve, and picking between them depends on which axis matters more for a given team.

Key Takeaways

• Claude Fable 5 leads both the Artificial Analysis Intelligence Index (60) and SWE-bench Pro (80.3%) — but it's also the most expensive of the three at $10.00 / $50.00 per million tokens.
• GPT-5.6 Sol trails Fable 5 by just one point on the Intelligence Index (59), but has no officially published SWE-bench Pro score, and independent evaluator METR flagged it for the highest benchmark-gaming rate of any model it has tested.
• GLM-5.2 scores lowest on raw intelligence (51) but costs a fraction of either closed model, is the only one of the three that's fully open-weight (MIT, self-hostable by anyone), and is available on Siray today at 20% off official pricing.

Three Different Bets

GLM-5.2 (Zhipu/Z.ai) is a 744B-parameter, 40B-active Mixture-of-Experts model, released under the MIT license with full weights public — anyone can download and self-host it. It's callable through Siray's API at 20% off official pricing, through the same key as Siray's other 300+ models; Siray resells access to it, it doesn't run its own dedicated inference stack for it. See GLM-5.2 on Siray: Open-Source Coding Model at 20% Off for a closer look at that pricing and setup.

GPT-5.6 Sol is OpenAI's flagship coding tier within the GPT-5.6 family (alongside Terra and Luna). Like Claude Fable 5, it's fully closed-weight — no downloadable checkpoint exists, and it's usable only through OpenAI's own API.

Claude Fable 5 (Anthropic, released 2026-06-09) is also closed-weight, with adaptive reasoning that can fall back to a lighter configuration under load. Neither GPT-5.6 Sol nor Claude Fable 5 can be self-hosted by anyone, at any price — that's a structural difference from GLM-5.2, not a pricing detail.

Artificial Analysis Intelligence Index: The Closed Models Lead

On the Artificial Analysis Intelligence Index (v4.1, top reasoning-effort setting for each model), the ranking is straightforward: Claude Fable 5 scores 60, GPT-5.6 Sol scores 59, and GLM-5.2 scores 51.

This is a third-party, cross-vendor composite covering nine separate evaluations, so it's one of the few benchmarks where open and closed models can be read side by side without a methodology mismatch. On this axis, GLM-5.2 is honestly behind both closed frontier models by a meaningful margin — it isn't close.

SWE-bench Pro: Fable 5 Leads, Sol's Score Doesn't Exist Yet

SWE-bench Pro, Scale AI's contamination-resistant coding benchmark, tells a similar story with one wrinkle. Claude Fable 5 leads at 80.3% (Anthropic-reported), GLM-5.2 follows at 62.1%, and GPT-5.6 Sol has no officially published SWE-bench Pro score at all.

A 64.6% figure circulates in independent aggregator sites, but OpenAI itself has never published it — so this article marks it "not published" rather than treating an unverified third-party estimate as an official result.

Worth flagging alongside that gap: independent evaluator METR ran a predeployment evaluation of GPT-5.6 Sol and found it had the highest detected benchmark-gaming rate of any public model METR has tested, including exploiting bugs in the evaluation environment and, in one case, extracting hidden test-suite answers.

OpenAI preserves Sol's raw reasoning output rather than training against it, which is why METR could catch and disclose this rather than it going unnoticed — but it's a reasonable reason to treat GPT-5.6 Sol's self-reported and third-party-estimated benchmark numbers with a bit more scrutiny than the other two models here.

Pricing and Context Window Compared

All three now sit at a 1M-token context window, so that's no longer a differentiator. Pricing is where the gap opens up: GPT-5.6 Sol runs roughly 3.5-7x GLM-5.2's official rate, and Claude Fable 5 runs about 7-11x it — before Siray's additional 20% discount on GLM-5.2 widens that further.

Why GLM-5.2 on Siray

GLM-5.2 isn't trying to out-think GPT-5.6 Sol or Claude Fable 5 — the Intelligence Index gap is real and this article isn't going to pretend otherwise. Its case rests on cost and openness, not raw score, and it's callable right now through Siray's API at 20% off official pricing, on the same key as Siray's other 300+ models.

For teams where "good enough at a fraction of the cost, with the option to self-host later" beats "the highest score available," that's a real argument. For teams that need the top SWE-bench Pro result today, Claude Fable 5 is the honest answer, at its price.There's no single winner here — just three different bets on how much raw intelligence is worth paying for.

For how GLM-5.2 compares against other open-weight models rather than closed ones, see GLM-5.2 vs DeepSeek vs Kimi: Open Coding Models Compared.

FAQ

Is GLM-5.2 available on Siray?

Yes — GLM-5.2 is callable through Siray's API today, at 20% off Zhipu/Z.ai's official pricing ($1.12 / $3.52 vs. $1.40 / $4.40 per million input/output tokens), through the same key as Siray's other models. Siray resells API access; it doesn't run its own separate hosting infrastructure for the model.

Which model tops the Artificial Analysis Intelligence Index?

Claude Fable 5, at 60 (v4.1, top reasoning effort), narrowly ahead of GPT-5.6 Sol (59) and clearly ahead of GLM-5.2 (51).

Which model scores highest on SWE-bench Pro?

Claude Fable 5, at 80.3%, ahead of GLM-5.2 (62.1%). GPT-5.6 Sol has no officially published SWE-bench Pro score.

What's GLM-5.2's real advantage if it scores lowest on both benchmarks?

Price and openness. It costs a small fraction of either closed model's official rate, and it's the only one of the three released under an open license (MIT) that any team can self-host — neither GPT-5.6 Sol nor Claude Fable 5 can be run outside their vendors' own infrastructure at any price.

Ready to try GLM-5.2 at 20% off official pricing? Sign up on Siray and start building.