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| license: cc-by-4.0 |
| tags: |
| - pixel-canary |
| - callstack-apex |
| - stealth-model |
| - stealthmark |
| - coding |
| - reasoning |
| thumbnail: https://stealthmodels.com/pixel-canary/assets/social-card-v3.png |
| --- |
| |
| <img src="https://huggingface.co/stealth-model/pixel-canary/resolve/main/panels/hero.webp" alt="Golden Pixel Canary building a small app beside the words 'Revealed as Callstack Apex'."> |
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| **Our reasoning study pointed to Qwen two days before Callstack revealed Pixel Canary as Apex, a Qwen-based coding model built for React Native.** |
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| By [Stealth Models](https://stealthmodels.com/). |
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| <img src="https://huggingface.co/stealth-model/pixel-canary/resolve/main/panels/verdict.webp" alt="StealthMark 1.8.10 results for Pixel Canary (Callstack Apex): benchmark score 49.5, General Intelligence 40.4, Visual Intelligence 59.6. Strongest at characters that interact: 76.8 on Raccoon."> |
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| <img src="https://huggingface.co/stealth-model/pixel-canary/resolve/main/panels/results.webp" alt="Every StealthMark result of Pixel Canary (Callstack Apex): Raccoon 76.8, Selfie 74.1, Beach 61.4, Mona Lisa 45.9, Ground Truth 44.1, Newton's Mirror 32.7, Latch 100.0 (partial run, 1 of 5 levels). Not tested yet: Foresight."> |
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| [Compare it with the Qwen 3.8 family](https://stealthmodels.com/benchmarks?models=qwen3.8-max-0902,qwen3.8-27b,pixel-canary,qwen3.8-flash,qwen3.6-27b) |
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| <img src="https://huggingface.co/stealth-model/pixel-canary/resolve/main/panels/case.webp" alt="The case file. First seen 25 Sep 2026, revealed 1 Oct 2026, developer Callstack (Poland), context 262,144 tokens, input Text, tool calls unknown, speed in our tests about 255 tok/s. 26 Sep 2026: A tokenizer study by AI時短ラボ links its vocabulary to Qwen. 29 Sep 2026, our finding: Our reasoning study puts Qwen3.8-Flash closest, two days before the reveal. 1 Oct 2026: Callstack reveals Apex: a Qwen foundation with React Native post-training."> |
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| [See our reasoning study](https://stealthmodels.com/pixel-canary#reasoning-comparison) |
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| <details><summary>Facts as text</summary> |
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| | Fact | Value | |
| |---|---| |
| | First seen | 25 Sep 2026 | |
| | Revealed | 1 Oct 2026 | |
| | Developer | Callstack (Poland) | |
| | Context | 262,144 tokens | |
| | Input | Text | |
| | Tool calls | unknown | |
| | Speed in our tests | about 255 tok/s | |
| | Access | Active as a hosted API | |
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| </details> |
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| ## Run it |
| Callstack serves Apex as a hosted model, so there are no weights to download. |
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| --- |
| [StealthMark leaderboard](https://huggingface.co/spaces/stealth-model/stealthmark)<br> |
| Text and images: CC BY 4.0, stealthmodels.com. |
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