Tis

Minecraft 1.21.9-pre1

The first Copper Age pre-release is out with several fixes. See the changelog.

Copper Golem

Lightning bolts remove one stage of oxidization from struck copper golems, fixing MC-300257. However, copper golems still do not attract lightning.

Copper golems riding vehicles now only search for neighboring chests (within a 3×3×3 block box).

Copper golems now wait one tick after finding a new target chest.

To reach a chest horizontally, the copper golem’s hitbox must be less than 0.75 blocks from the chest’s hitbox in both the X and Z axes (chessboard distance). While the copper golem is pathfinding to the chest, its range is reduced to 0.5 blocks.

Once the copper golem creates a path to its target chest, it will check if that chest is reachable every tick:

  • If the copper golem was at the end of the path, it would be close enough to interact with the chest (using the 0.75 block horizontal range)
  • If the copper golem was at the end of the path, its center would have line of sight with any of the chest block’s faces (treating the chest as a full block)

If the above conditions are met, the chest is added to the unreachable chests list.

Portals

End portals only prevent fall damage for players. Nether portals also prevent fall damage for players if the playersNetherPortalDefaultDelay game rule is 0.

Debug Properties

Two new debug properties were added: -DMC_DEBUG_VERBOSE_COMMAND_ERRORS and -DMC_DEBUG_DEV_COMMANDS.

-DMC_DEBUG_CHUNKS

No longer crashes on world load.

Shows the following data for each chunk location (requires operator permissions to use on a server):

  • Client: “0n/a” if there is no client chunk at that location, “E” if the client chunk is empty, and nothing otherwise
  • Server: The chunk’s load level
  • St: The chunk’s status in memory
  • Ch: The chunk’s status when it was last written to disk
  • The chunk’s load type (entity ticking, block ticking, border, or inaccessible)

In singleplayer worlds, shows the chunk colormap in the F3 screen.

If the F3 menu is open while loading a singleplayer world, the game will crash.

-DMC_DEBUG_VERBOSE_COMMAND_ERRORS

Instead of printing “An unexpected error occurred trying to execute that command” when an exception is thrown while executing a command, prints the exception message and logs the exception stack trace.

-DMC_DEBUG_DEV_COMMANDS

Enables debug commands.

-DMC_DEBUG_GENERATE_SQUARE_TERRAIN_WITHOUT_NOISE

No longer crashes on world load.

Only generates terrain between (0, 0) and (8207, 1039). In the overworld, generates simplified terrain where:

  • Desert and badlands biomes generate when erosion noise matches certain ranges
  • Snowy taiga biomes generate when continentalness noise matches certain ranges
  • Plains generate everywhere else

-DMC_DEBUG_DONT_SEND_TELEMETRY_TO_BACKEND

Now only disables sending telemetry data if the SharedConstants.isDevelopment (yarn mappings) variable is true.

Debug Commands

These commands are enabled if the -DMC_DEBUG_DEV_COMMANDS flag is set.

/raid

  • /raid start <omenlvl>: Starts a raid with the given omen level at the current location if one doesn’t already exist
  • /raid stop: Stops a raid at the current location
  • /raid check: Prints the current raid’s number of groups spawned, omen level, number of mobs (total raiders alive), and current and total raid health
  • /raid sound local: Plays the raid horn sound at ~5 ~ ~
  • /raid spawnleader: Spawns a pillager captain at the current location
  • /raid setomen <level>: Sets the current raid’s omen level
  • /raid glow: Gives all raiders belonging to the current raid Glowing 2 for 50 seconds

Requires permission level 3. The source executor must be a player.

/debugpath

/debugpath <to> pathfinds from the current location to the target location <to> and reports whether the path could not be found, the target could not be reached, or the target was reached successfully.

The source executor must be a mob.

/debugmobspawning

/debugmobspawning <category> <at> simulates a natural mob spawning attempt for the <category> mob category at the <at> block position.

/warden_spawn_tracker

  • /warden_spawn_tracker set <warning_level>: Sets the current player’s warden warning level to a number 0-4
  • /warden_spawn_tracker clear: Clears the current player’s warden warning level, shrieker cooldown ticks, and ticks since last warning

The source executor must be a player.

/spawn_armor_trims

  • /spawn_armor_trims <pattern>: Spawns armor stands with the given trim pattern and every combination of armor and trim material
  • /spawn_armor_trims *_lag_my_game: Spawns armor stands with every combination of armor, trim pattern, and trim material (and lags your game)

/serverpack

  • /serverpack push <url> [<uuid>] [<hash>]: Tells all connected clients to add a server resource pack with the given <url>, optionally with an ID and hash
  • /serverpack pop <uuid>: Tells all connected clients to remove a server resource pack with the given ID

/debugconfig

  • /debugconfig config <target>: Switches the target player’s connection phase to configuration, removing them from the world
  • /debugconfig unconfig <target>: Switches the target player’s connection phase to play, adding them to the world (<target> only accepts UUIDs)
  • /debugconfig dialog <target> <dialog>: Shows a dialog to the target player, as long as their connection is in configuration phase (<target> only accepts UUIDs)

Only available on dedicated servers. Requires permission level 3.

Edits

Sep 16 2025

  • Clarify that -DMC_DEBUG_GENERATE_SQUARE_TERRAIN_WITHOUT_NOISE only changes biomes in the overworld