[BUG] increase_robot_speed.lua error when decreasing speed

[JesseHawkins]

What happened?

Reducing bot speed from max generates error.

Steps to reproduce

1. Use slider to increase bot speed to max.
2. Close admin window.
3. Open admin window.
4. Reduce slider from 50 to zero. Error seems to appear at 48 when moving to 47.

Expected

Any value could be set.

Quick facts

• Factorio: steam, space-age v2.0.69 (build 84148 expansion, win64)
• facc: v3.7.2
• Mode: Singleplayer / Did not test multiplayer
• OS: Windows

Other mods

• I can reproduce with only facc enabled

Evidence

• factorio-current.log
• 2025-10-13 - Big Game.zip

Checklist

• I'm on the latest facc release
• I provided clear steps or a minimal save
• I attached factorio-current.log

[github-actions]

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[louanfontenele]

Hello, I'll check it out.

[louanfontenele]

@JesseHawkins Do you get any error screen? If yes, please attach here.

[JesseHawkins]

[louanfontenele]

@JesseHawkins Please, copy the error, and send it to me, please.

[Jvella94]

Hi, I think I figured out the issue with some print statements.

Since the bonus isn't run on save load, if something happens to reset the speed to a lower one by a different mod (or factorio does a consistency check), when you lower the value in the slider, you're actually able to push the base value of the robot speed below 0.

What you probably need to do is just change whatever the current speed modifier is to the new value rather than comparing the old. It's neater the way you've done it but I don't believe there's a way to be sure what the current speed is unless you can add it as a custom bonus.

-- Clamp the slider bonus itself within [0, MAX_BONUS]
local slider_bonus = math.max(0, math.min(new, MAX_BONUS))
player.print(slider_bonus)
-- Apply new slider bonus
force.worker_robots_speed_modifier = slider_bonus