[MC-306163] Mobs (like slimes) cannot spawn on lit copper bulbs but can spawn on redstone lamps and lit jack 'o lanterns

Mobs (like slimes) cannot spawn on lit copper bulbs but can spawn on redstone lamps and lit jack 'o lanterns

Can be reproduced by creating a superflat world and using

/gamerule max_block_modifications 99999
/fill ~150 -61 ~150 ~-150 -61 ~-150 minecraft:redstone_lamp[lit=true] strict
/difficulty peaceful
/difficulty easy

You’ll see slimes spawning on the redstone lamps

/fill ~150 -61 ~150 ~-150 -61 ~-150 copper_bulb[lit=true] strict
/difficulty peaceful
/difficulty easy

You’ll see no slimes spawning on the copper bulbs.

Attachments

Comments 3

Automation for Jira 2026-02-02T18:54:49Z

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Boas Bakker 2026-02-02T19:07:36Z

This also applies to beacon, glowstone, sea_lantern, froglight, respawn_anchor, shroomlight. So the issue is more inconsistent behavior: there is no clear rule for when a light-emitting block with level >=14 is spawnable or not spawnable.

[Mojang] Triage Team 2026-02-04T08:13:13Z

Thank you for your report!
After consideration, the issue is being closed as Working as Intended.

Please note, that mechanics of the game may change between updates.
Things such as graphics, sounds, world creation, biomes, redstone, villagers, and animals may not work the same in current versions.

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