Claude Opus 5.5 vs ChatGPT 6 Astra Make A Minecraft Mod From Scratch

Summary
Content creator LanceyPoo tests Anthropic's Claude Opus 5.5 against OpenAI's GPT-6 Astra by prompting both frontier models to autonomously build a full-featured Minecraft Java Edition mod from scratch. After evaluating the generated code in-game, LanceyPoo reviews the custom weapons, mobs, boss fights, structures, and animations, concluding that Claude Opus 5.5 produced a far superior, fully realized mod compared to GPT-6 Astra.

What is shown

• Prompting Claude Opus 5.5 [00:26]: In the Claude Code desktop UI, Lancey sets model effort to "Max" (rather than UltraCode) and submits a prompt instructing it to create an impressive Forge 65.1.0 mod for Minecraft Java Edition 26.2 using Java 25 with complete creative freedom.
• Opus 5.5 Mod Showcase ("Riftfall") [01:00]: After approximately 1.5 hours of autonomous coding, Lancey launches Minecraft to test Opus 5.5's mod, titled Riftfall.
• Custom Equipment & Weapons [01:28 – 05:04]: Testing Voidsteel armor (granting double jump, speed buffs, and hostile wall-vision), the interactive Rift Codex guide UI with built-in showcase triggers, the Oblivion blade with wide visual wave attacks, the Phase Scythe, the Gravity Maul ground-slam hammer, and the Starcaller Scepter.
• Custom Mobs & Flying Mounts [05:20 – 06:55]: Spawning the rideable Sky Manta, the item-stealing Hoarder goblin, and a player clone called Rift Echo.
• Floating Structure & Boss Fight [07:31 – 11:10]: Navigating to an autonomously generated floating structure called the Shattered Citadel using a Rift Compass, activating an elevator beam, placing three Astral Sigils into the Eclipse Altar, and triggering an animated multi-phase boss fight against Voraxis, the Star-Eater.
• Rift Storm Event & Astral Wings [11:14 – 15:20]: Gliding with boostable Astral Wings, triggering a multi-wave Rift Storm event that spawns the Rift Herald, and throwing Singularity Grenades that create collapsing black holes.
• Prompting GPT-6 Astra [15:46]: In the ChatGPT Codex desktop app, Lancey sets effort to "Extra High" and submits the identical prompt to GPT-6 Astra.
• Astra Mod Showcase ("Eclipse Protocol") [16:07 – 18:30]: After 49 minutes of run time, Astra produces Eclipse Protocol. Lancey tests the mod's items (Event Horizon hammer, Zenith Lance, Gravity Gauntlet) and mobs (Glass Cantor, Null Bulwark), finding basic flat 2D textures, buggy attack behaviors, and lack of cohesive 3D models or complex multi-phase events.

Claims & numbers

• LanceyPoo notes that Claude Opus 5.5 ran for approximately 1.5 hours to write and compile the Riftfall mod [00:58].
• GPT-6 Astra took 49 minutes to generate its Eclipse Protocol mod under the "Extra High" effort setting [16:07].
• Both models were tasked with building a standalone Forge 65.1.0 mod targeting Minecraft Java Edition 26.2 and Java 25 [00:40, 16:01].

Notable quotes

• "Dude, this is the most creative mod I've ever seen. Wow." — LanceyPoo [02:46]
• "This is what Voraxis the final boss looks like... This is just the coolest thing ever." — LanceyPoo [10:41, 15:43]
• "Opus 5.5 destroyed Astra, I can already tell you." — LanceyPoo [16:56]

Assessment
This is an independent hands-on review and comparison demo. The gameplay showcases actual mod jar files running inside Minecraft Forge, with cuts used only to skip compilation wait times (1.5 hours for Claude Opus 5.5 and 49 minutes for GPT-6 Astra).

Described by gemini-3.8-flash on 2026-09-29 from the video's audio and frames.