A Claude-Built 3D Terraria Rebuild: What 109 Chats Produced and Where It Falls Short

A post on r/aigamedev describes an AI-rebuilt Terraria in 3D: a Claude project that, according to its title, took 109 chats and covers every boss and event, about 90% of items and 393 enemies. These are the creator's own numbers. The sources available for this article include no playable build or public code for that specific project. Other public Claude-built 3D Terraria attempts suggest what sits behind numbers like these: long task lists, parallel branches, merges resolved by hand and a lot of tuning. That work is easy to miss in a highlight clip.

Who made it, and what do they say they built?

The project belongs to the original poster on r/aigamedev, who shared it in a thread titled "I asked Claude to rebuild Terraria in 3D. 109 chats later...". All credit for the build, the clips and the write-up goes to them. Readers should go to that thread for the footage and the creator's own explanation.

The title makes these claims:

• the project took 109 chats with Claude
• every boss and every event is in the game
• about 90% of Terraria's items are in
• there are 393 enemies
• clips show a boss showcase and general gameplay

The sources behind this article cover the post's title only, not its body or comments. So this piece cannot confirm which engine or tools the creator used, what the project cost, whether they used Claude Code or the chat app, or whether they link a repo or download. It also cannot describe the clips in any detail.

The counts are self-reported. "Every boss" and "393 enemies" are inventory claims. They do not show how close each boss fight comes to the original.

What does 109 chats mean in practice?

The title points to an iterative workflow spread across many sessions. That reading comes from the number alone. The title does not explain how the chats were organised.

A public repository shows what this kind of workflow can leave behind. Pull request #18 on getrekzzz/3D-Terraria is a separate project. Nothing in the sources links it to the Reddit build, so treat it as a comparison only. According to the PR page:

• It merged 474 commits into main on Oct 11, 2026.
• Commits carry a Co-Authored-By trailer naming Claude Opus 5.5, and the PR description credits Claude Code as the tool behind it.
• Commit titles use task IDs such as P2-19 (combat text) and P3-31 (review fixes), plus wave merges such as "Wave W3: merge ovh/laneA". In other words, the work was planned in phases and run in parallel lanes.
• The PR exists because two lines of work had split apart. main had six fix PRs (#12 to #17), while a separate overhaul branch held a new UI, weather and seasons, controller support, bosses, a Dungeon, a town and art. The description says a folder made from main "looked like an old build".

What the merge shows about long AI-driven builds

The PR description lists every place where both branches changed the same system: tree chopping, audio, character models, building, digging and enemy spawning. According to the description, shared files "were resolved by hand". The merge was then checked by listing every line either side added that the merged result lacked.

The merge also exposed a bug. Several furniture models named texture layers (prop:copper, prop:leaves) that did not exist, so those parts drew the "missing" checker texture. The fix added the layers plus an asset-coverage test to catch the same mistake in future.

There was testing too. The PR says GitHub Actions is blocked on the account, so checks ran locally: a solution file builds with 0 errors, Core tests pass, content checks pass, and 24 smoke scripts plus a menu tour pass after a fresh Godot import.

For a deeper look at how agent-heavy projects build up tooling like this, see the Lab Note on an AI-agent decompilation project.

How do other Claude-built 3D Terraria attempts compare?

The Reddit post is not the only project of its kind. Three others turn up in public sources, and each one is built differently.

Some notes on each:

• The Edgex post. A post by Edgex (@SahilExec) on X describes a separate Claude-built 3D Terraria: 8 days, 346K lines of C#, 3,369 items, 313 enemies and bosses, a custom engine, and a creator who says they wrote none of the code. Only the post's preview text was available, so these numbers are second-hand and unverified. The preview also shows a reply arguing that games like this do not appear without a lot of handholding.
• Terraria3D. The Terraria3D repository calls itself an original sandbox "in the spirit of Terraria". It uses non-voxel destructible terrain, and saves store a replayable log of edits.
• 3D-Terraria. Its PR mentions a Blender pipeline that regenerates every humanoid, animation set, hair model, armour piece and portrait, alongside Godot.

The takeaway: "Terraria in 3D" has no fixed definition. One project uses voxel-free browser terrain. Another uses Godot with a Blender asset pipeline. A third uses a custom engine. A count of 393 enemies in one project and 313 "enemies and bosses" in another may not measure the same thing. Treat headline counts as rough marketing for each project, not as numbers you can compare.

Where does it likely fall short?

The Reddit title is the only verified text from the post. This article cannot report any shortfalls the creator lists in the body or comments. If they describe bugs, missing systems or cost, those details are at the original link.

What the title does say is "about 90%" of items. Roughly one item in ten is missing, and the title does not say which.

The wider sources point to a deeper gap than missing items. Counting content is easier than matching how Terraria feels. The 3D-Terraria commit history shows how much tuning sits behind a line like "it has the boss":

• A P3-31 commit reworks Terraria's use-time maths, so weapon prefixes change animations and cooldowns in the same way. It also corrects prefix stats such as Deadly and Celestial.
• A P2-19 commit rebuilds combat text: colours, pop-in, fixed screen size, and green and blue numbers for heals and mana.
• PR #17, merged into the same build, is titled "Calmer nights: fewer enemies at once, spawned at the day's pace". That is a pacing fix made after enemies were already in the game.

The 2D-to-3D problem

Terraria's combat, building and mining all assume a flat side-on plane. Moving to 3D forces new decisions about cameras, targeting, lighting and terrain that the original never had to make.

The 3D-Terraria commits show this in small ways. Damage numbers have to float "in front of the eye in first person". Hits are decided by strike windows and swing curves, with dedicated tests (UseTimingTests, SwingCurveTests). None of this appears in an enemy count, and a short clip can hide it.

Copyright and "rebuild" caveats

Terraria is a commercial game from Re-Logic, first released in 2011. Every project here is a fan recreation. Two things matter and cannot be confirmed for the Reddit build from its title alone:

• whether it uses original art and sound or assets taken from Terraria
• whether the creator plans to release it

The wording matters. Terraria3D's "in the spirit of Terraria" describes an original game influenced by another. "Rebuild Terraria" with "every boss" and "90% of items" describes a copy of a specific commercial game's content. A copy carries more legal risk if it is distributed. Anyone planning a project like this should keep it private or make the design clearly their own.

Verdict: who can learn from this?

Based on the public evidence, long Claude-driven rebuilds suit developers who already know how to:

1. break a large design into tracked tasks with IDs and phases
2. run parallel lines of work and merge them without losing changes
3. write tests and smoke scripts that catch regressions an agent introduces
4. read diffs closely enough to spot a missing texture layer or a wrong formula

The 3D-Terraria PR shows a heavily structured process: phases, waves, review fixes, asset-coverage tests and merges resolved by hand. Casual prompting does not look like that.

The weak reading of these projects is that an AI can "recreate a game" on its own. The sources show many sessions, a human requesting and playing builds, and a lot of manual work to hold the parts together. The 109-chat figure fits the same pattern.

If you want to run a long agent workflow of your own, start with the tooling side:

• the Lab Note on Unity's official Claude Code plugin explains what agents can control in the Unity editor
• the Godot AI playtesting test plan covers checking agent-made builds automatically
• the coding agents tag collects the rest

More community projects are in Specimens.