Flow Lens — Hopper Inspector

Flow Lens — Hopper Inspector

Find the blockage in a hopper route.

Look at a hopper, press a key, and see its output route highlighted in the world. A compact HUD explains the first issue found; a details screen shows the inspected positions and reasons.

Live inspection (requires 1.1.0)

Press V while aiming at a hopper to turn live inspection on. The compact HUD refreshes every second while you keep looking at that hopper, so freeing space in a full chest can change the result without another key press.

Look away or open a menu to pause requests; look back to resume. Press V again for a snapshot, or H to stop and clear. Shift + V checks the current item in your main hand on each refresh. LIVE / PAUSED and the result age keep the current state visible. All keys are rebindable.

Live inspection repeats read-only snapshots of one outlet route; it does not measure item throughput. Server permissions and cooldown still apply.

Features

• Trace up to 32 nodes through a vanilla hopper route.
• Use the first item in the starting hopper, or hold Shift while inspecting to test the item in your main hand.
• Locate supported issues such as powered hoppers, full destinations, rejected insertion, loops, and missing destinations.
• Follow colored outlines that respect world depth and read the result without leaving the world.
• Open a detailed result screen when you need more context.
• English and Thai text, with rebindable controls.
• Adjustable compact HUD size and optional world outlines in the client configuration.

How to use

1. Look at a vanilla hopper and press G.
2. Read the compact HUD and follow the outlines. To test a specific item, hold it in your main hand and press Shift + G.
3. Press O for details or H to clear the result.

Aim at a hopper within eight blocks. G takes a snapshot; inspect again after changing your build, or enable V live mode in 1.1.0. Results expire after 20 seconds without an update, including when live mode stays paused.

Installation

Minecraft 1.21.1 · NeoForge 21.1.264+ in the 21.1 series · Java 21

Install the release JAR on both client and server. For singleplayer, install it in your game instance. No additional library mods are required.

The local singleplayer owner can inspect without cheats. By default, other players, including LAN guests, need operator permission. Server owners may allow non-operators with operatorsOnly = false in flowlens-server.toml. Owners should check their own inventory privacy and protection setup before enabling access for everyone. A client with the mod can still join a server without it, but inspections need server support.

Scope

Flow Lens follows a single outlet route, up to the configured node limit, through vanilla hoppers, chests, trapped chests, barrels, furnaces, blast furnaces and smokers. It recognizes a hopper below a powered hopper pulling items downward. Other branches are not exhaustively traced: a blocked outlet does not mean the entire build has stopped.

It does not move items, change blocks, load chunks, or repair circuits. Locked containers and unopened loot inventories stay private. It does not measure throughput or diagnose arbitrary modded machine recipes. Compatibility with every storage and protection mod is not guaranteed.

Client configuration: config/flowlens-client.toml (hudScale, showWorldOutlines, and liveRefreshMillis in 1.1.0). Live refresh defaults to 1,000 ms and can be set from 1,000 to 10,000 ms; server cooldown can slow updates further. The details screen focuses the first reported issue.

MIT license. Original icon and artwork. Created for Hibrownson with AI-assisted development and review.