Fix 1.21.10 packet ID mappings for 4 missing debug packets #1118
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The original protocol.json was generated from an earlier version and was missing 4 new debug packets added in 1.21.10 (protocol 773): - 0x1A: debug_block_value - 0x1B: debug_chunk_value - 0x1C: debug_entity_value - 0x1D: debug_event This caused all packet IDs from 0x1A onwards to be shifted by 4, resulting in wrong parsers being applied to packets. Changes: - Updated packet ID mappings to match wiki (138 packets, 0x00-0x89) - Added placeholder structures (restBuffer) for 4 new debug packets Reference: https://minecraft.wiki/w/Java_Edition_protocol/Packets
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You need to update the yaml version and generate the json from it using the
script in this repo
…On Sat, Dec 6, 2025, 18:54 Micah Stubbs ***@***.***> wrote:
Summary
The original protocol.json was generated from an earlier version and was
missing
4 new debug packets added in 1.21.10 (protocol 773):
- 0x1A: debug_block_value
- 0x1B: debug_chunk_value
- 0x1C: debug_entity_value
- 0x1D: debug_event
This caused all packet IDs from 0x1A onwards to be shifted by +4,
resulting in
wrong parsers being applied to packets.
Changes
- Updated packet ID mappings to match wiki (138 packets, 0x00-0x89)
- Added placeholder structures (restBuffer) for 4 new debug packets
Testing
Tested connection to a 1.21.10 server - bot now successfully connects
through login → configuration → play state.
Reference
https://minecraft.wiki/w/Java_Edition_protocol/Packets (protocol 773)
------------------------------
You can view, comment on, or merge this pull request online at:
#1118
Commit Summary
- 1b101c5
<1b101c5>
Fix 1.21.10 packet ID mappings for 4 missing debug packets
File Changes
(1 file <https://github.com/PrismarineJS/minecraft-data/pull/1118/files>)
- *M* data/pc/1.21.10/protocol.json
<https://github.com/PrismarineJS/minecraft-data/pull/1118/files#diff-eb1285ec47486835a8bbe7654bf750d49b7843d5443118dc7cfdb83117b23d25>
(336)
Patch Links:
- https://github.com/PrismarineJS/minecraft-data/pull/1118.patch
- https://github.com/PrismarineJS/minecraft-data/pull/1118.diff
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micahstubbs
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to micahstubbs/minecraft-data
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Dec 7, 2025
Building on PR PrismarineJS#1118's packet ID mapping fixes, this commit addresses additional packet structure issues discovered during testing: 1. spawn_entity: Remove velocity fields (velocityX/Y/Z) - Server packets are ~5 bytes shorter than expected - Velocity fields appear to be removed or sent differently in 1.21.10 - Use restBuffer to handle any remaining data gracefully 2. entity_velocity: Same treatment for consistency - The i16 velocity fields cause parse errors - Replace with restBuffer to avoid PartialReadError These fixes were discovered while debugging mineflayer/mindcraft bot connectivity to a 1.21.10 server. Raw packet captures confirmed the shorter packet sizes. References: - PR PrismarineJS#1118: Packet ID mapping fixes - Tested with actual 1.21.10 server (protocol 773)
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Summary
The original protocol.json was generated from an earlier version and was missing
4 new debug packets added in 1.21.10 (protocol 773):
This caused all packet IDs from 0x1A onwards to be shifted by +4, resulting in
wrong parsers being applied to packets.
Changes
Testing
Tested connection to a 1.21.10 server - bot now successfully connects through login → configuration → play state.
Reference
https://minecraft.wiki/w/Java_Edition_protocol/Packets (protocol 773)