I can't reproduce this error when running cd tools/js && npm test locally from this branch. Also my # of tests run don't match the github actions output.

Locally I get

1663 passing (1m)
1 pending

Github says

1690 passing (2m)
1 pending
1 failing

1. protocol yaml
   should be valid and in sync with json:
   Error: 1.21.8 (1.21.8) / protocol.json is desynced from yaml, please run 'npm run build'

I could use some advice on how to ensure my local environment testing matches the CI/CD

Your local branch is out of date, it's not listing all the tests (1663 vs 1690). I just merged master into here, pull the latest commit and run it again

Ok thanks. I regenerated the json and it found .8 and .9 were out of sync. I can submit a PR to fix.

It looks like the bot changed the .8 proto.yaml in this branch even though this PR is for .9. Is that correct?

This bot updates to .8 are here.
dd11e71

PR to fix is here
#1117

Protocol data is not correct https://github.com/PrismarineJS/mineflayer/actions/runs/19987084418/job/57322609224?pr=3754

🐛 Protocol Issues Found in 1.21.9 protocol.json

I've been testing the 1.21.9 data with a vanilla 1.21.9 server and found two critical packet definition errors that cause connection failures:

1. packet_spawn_position - Missing dimension field

Current (incorrect):

"packet_spawn_position": [
  "container",
  [
    { "name": "location", "type": "position" },
    { "name": "angle", "type": "f32" }
  ]
]

Should be (same as 1.21.8 and 1.21.11):

"packet_spawn_position": [
  "container",
  [
    { "name": "dimension", "type": "string" },
    { "name": "location", "type": "position" },
    { "name": "yaw", "type": "f32" },
    { "name": "pitch", "type": "f32" }
  ]
]

Evidence: Server sends 37 bytes but only 13 were being read. Buffer analysis shows:

• VarInt length prefix
• String "minecraft:overworld" (19 chars)
• Position (8 bytes)
• yaw + pitch floats (8 bytes)

2. packet_spawn_entity - Wrong format for movement data

Current (incorrect):

"packet_spawn_entity": [
  "container",
  [
    { "name": "entityId", "type": "varint" },
    { "name": "objectUUID", "type": "UUID" },
    { "name": "type", "type": "varint" },
    { "name": "x", "type": "f64" },
    { "name": "y", "type": "f64" },
    { "name": "z", "type": "f64" },
    { "name": "pitch", "type": "i8" },
    { "name": "yaw", "type": "i8" },
    { "name": "headPitch", "type": "i8" },
    { "name": "objectData", "type": "varint" },
    { "name": "velocityX", "type": "i16" },
    { "name": "velocityY", "type": "i16" },
    { "name": "velocityZ", "type": "i16" }
  ]
]

Should be (same as 1.21.8):

"packet_spawn_entity": [
  "container",
  [
    { "name": "entityId", "type": "varint" },
    { "name": "objectUUID", "type": "UUID" },
    { "name": "type", "type": "varint" },
    { "name": "x", "type": "f64" },
    { "name": "y", "type": "f64" },
    { "name": "z", "type": "f64" },
    { "name": "movement", "type": "restBuffer" }
  ]
]

Error: PartialReadError: Read error for undefined : undefined at Object.reader [as i16] - trying to read velocity fields that don't exist in the actual packet data.

✅ Test Results After Fixes

After applying both fixes locally, a mineflayer bot successfully:

• Logged into vanilla 1.21.9 server
• Spawned without errors
• Read position correctly: Vec3 { x: 127.5, y: 70, z: -40.5 }

These packets should match the 1.21.8 format since protocol version 773 (1.21.9/1.21.10) didn't change these specific packet structures.

🔧 Ready-to-Apply Patch for Protocol Fixes

Following up on the bug report above, here's the exact patch that fixes both issues in data/pc/1.21.9/protocol.json:

diff --git a/data/pc/1.21.9/protocol.json b/data/pc/1.21.9/protocol.json
--- a/data/pc/1.21.9/protocol.json
+++ b/data/pc/1.21.9/protocol.json
@@ -4730,32 +4730,8 @@
               "type": "f64"
             },
             {
-              "name": "pitch",
-              "type": "i8"
-            },
-            {
-              "name": "yaw",
-              "type": "i8"
-            },
-            {
-              "name": "headPitch",
-              "type": "i8"
-            },
-            {
-              "name": "objectData",
-              "type": "varint"
-            },
-            {
-              "name": "velocityX",
-              "type": "i16"
-            },
-            {
-              "name": "velocityY",
-              "type": "i16"
-            },
-            {
-              "name": "velocityZ",
-              "type": "i16"
+              "name": "movement",
+              "type": "restBuffer"
             }
           ]
         ],
@@ -7304,12 +7280,20 @@
         "packet_spawn_position": [
           "container",
           [
+            {
+              "name": "dimension",
+              "type": "string"
+            },
             {
               "name": "location",
               "type": "position"
             },
             {
-              "name": "angle",
+              "name": "yaw",
+              "type": "f32"
+            },
+            {
+              "name": "pitch",
               "type": "f32"
             }
           ]

Summary of Changes:

Verification

• ✅ Tested with vanilla Minecraft 1.21.9 server (downloaded from Mojang)
• ✅ Bot successfully connected and received spawn position
• ✅ Entity spawning works correctly with mineflayer

To apply: git apply protocol-fix.patch or manually edit the file.

cc @rom1504 @extremeheat

/makerelease