What this does

Testing a Create Aeronautics contraption normally means either wrecking your survival world or leaving the server entirely. This mod adds a real, dedicated dimension, fully compatible with Sable's physics, where you can switch to creative mode, build and test freely, and return to survival with your original inventory exactly as you left it.

Every player gets their own private testing area, reached through a portal they build themselves. No shared space, no stepping on anyone else's builds.

How it works

Build a portal. Make a hollow rectangle of Amethyst Block (minimum 2 wide × 3 tall, same size rules as a Nether portal) anywhere in the overworld, then light it with Flint and Steel. Corners are optional, same as a real Nether portal — you don't need to fill them in. This automatically builds a matching portal for you inside the creative dimension, your own private area, not shared with anyone else's portal.

Step through. Walking into the portal works like a real Nether portal: a few seconds standing inside it (instant if you're already in creative mode), with a rainbow screen effect while it charges. Your survival inventory is safely stashed, and you're dropped into creative mode with flight enabled.

Build and test. Anything you gather or build while inside stays inside. Walking back out wipes it, by design, so nothing crosses back into survival. What does carry over automatically is your creative loadout: whatever tools, blocks, and Curios accessories you had set up last time reappear when you come back, so you're not re-gathering a palette every visit. The creative dimension's floor is 50 blocks thick, so tunnel bore contraptions actually have something to dig through.

Walk back out. Same portal, or the analogous one on the other side, and you're returned to the exact spot you left, with your original inventory, gamemode, and position fully restored.

Commands

• /creativedim leave — leave and restore your survival state (works from anywhere, anytime you're inside)
• /creativedim enter — operator-only shortcut to a fixed testing anchor, for quick admin access without needing a portal
• /creativedim restore <player> — operator safety net to force-restore someone's inventory if they get stuck or disconnect mid-visit
• /creativedim debug — operator-only, dumps the portal link registry for troubleshooting
• /creativedim resetlinks — operator-only, clears portal link data if it ever looks stale/corrupted

Requirements

Needs Create, Sable, Create Aeronautics, and Curios API installed alongside it (all required, all linked as dependencies on this page). Built and tested against these exact versions:

• Create 6.0.10
• Sable 2.0.3
• Create Aeronautics (Simulated Project) 1.3.0
• Curios API 9.5.1+1.21.1

Minecraft 1.21.1, NeoForge. Other versions of these mods haven't been tested and may not work.

Notes and known limitations

• Ender Chests are blocked inside the creative dimension. Their contents are tied to the player rather than the location, so leaving them accessible would defeat the whole point of the inventory separation.
• Portal frame detection uses a flood-fill approach rather than an exact port of vanilla's algorithm. Works reliably for a normal rectangular frame; unusual amethyst clusters sitting near a real frame could theoretically confuse it.
• Every overworld portal builds a fixed 2×3 analogous copy on the creative side, regardless of how large the original frame is.

A note on how this was built

This mod was built collaboratively with Claude (Anthropic's AI), through an extended back-and-forth of implementation, testing, and real bug fixes on a live server. I'm sharing that openly rather than passing it off as entirely hand-written. The code has been through genuine, sometimes involved debugging, including two confirmed real exploits (Curios accessory slots and Ender Chests bypassing the inventory separation) that were found through actual use and fixed, not just theorized about. Full development history is in the repo's CHANGELOG if you're curious.

Support

Source is fully open — see the GitHub repo. I use this on my own server, so I'll fix real bugs when I run into them or when they're reported with enough detail to reproduce. I'm not taking requests for new features beyond what's here. If you want to extend it yourself, pull requests are welcome (see CONTRIBUTING.md).