After the previous commit (99ac3d0) moved attribute lookup from a hardcoded
dictionary to the dynamic RegistryData, MCC would crash immediately upon
joining a vanilla 1.20.6 server with:
System.ArgumentException: An item with the same key has already been added.
Key: unknown
Root cause: When KnownDataPacks negotiation tells the server that MCC already
has the "minecraft" data pack, the server skips sending RegistryData for
registries it considers "known" — including minecraft:attribute. This left
the dynamic attribute map empty, so every VarInt attribute ID resolved to
"unknown". The EntityProperties packet often contains multiple attributes
(e.g. armor, max_health, movement_speed), and `keys.Add("unknown", ...)` on
the second "unknown" attribute threw ArgumentException.
Two fixes applied:
1. World.GetAttributeNameById(): When the dynamic attribute map is empty
(server didn't send the registry), automatically load the vanilla 1.20.6
default attribute order (22 entries matching Attributes.java registration
order). This mirrors the pattern used for dimensions where defaults are
loaded when RegistryData is not sent. If a modded server sends a custom
attribute registry, the dynamic map takes precedence.
2. Protocol18.cs EntityProperties handler: Change `keys.Add(propertyKey,
propertyValue2)` to `keys[propertyKey] = propertyValue2` to tolerate
duplicate keys defensively, in case an unknown attribute ID still appears.
Tested: MCC now connects to a vanilla 1.20.6 offline-mode server, stays
online for 6+ minutes with no crashes or disconnections. Verified: chat
messages received, inventory listing (item names/counts correct), entity
detection, TPS query, and health query all work correctly.
Made-with: Cursor
In 1.20.6+, EntityProperties packets reference attributes by VarInt registry
IDs instead of string names. Previously, a hardcoded dictionary of 22 attribute
entries (matching the vanilla 1.20.6 registry) was used to map these IDs back
to names. This works for vanilla servers but would fail silently for modded
servers that add custom attributes — any unknown ID would be reported as
"unknown".
This commit replaces the hardcoded attribute dictionary with dynamic registry
parsing, following the same pattern already used for dimension_type and
chat_type registries:
- World.cs: Add static `attributeIdMap` field, `SetAttributeIdMap()` and
`GetAttributeNameById()` methods for storing/querying attribute names by
their VarInt registry IDs.
- Protocol18.cs (RegistryData handler): When the server sends a
`minecraft:attribute` registry during the Configuration phase, parse all
entries and store the ID→name mapping. The `minecraft:` prefix is stripped
from entry names to match the format used in EntityProperties packets
(e.g. "minecraft:generic.armor" → "generic.armor").
- Protocol18.cs (EntityProperties handler): Remove the hardcoded 22-entry
`attributeDictionary` and use `World.GetAttributeNameById()` instead.
Unknown IDs still fall back to "unknown" for safety.
Also closes issue #4 (Disconnect packet extra boolean) — verified that both
Play and Configuration phase Disconnect handlers already use `ReadNextChat()`
(NBT format since 1.20.4+), matching the 1.20.6 protocol spec. No code
changes needed; updated tracking document to mark as closed.
Made-with: Cursor
The JoinGame and Respawn packet handlers for 1.20.6+ used hardcoded
switch expressions to map dimension type VarInt IDs to names:
0 => overworld, 1 => overworld_caves, 2 => the_end, 3 => the_nether
This only works for vanilla servers with exactly 4 default dimensions.
Modded servers (Forge/Fabric/NeoForge) or servers with custom
datapacks can register additional dimensions with IDs beyond 0-3,
causing the switch to fall through to the default "overworld" for
any non-vanilla dimension. This means players in modded dimensions
would have incorrect world parameters (height, lighting, etc.).
Fix: Replace both hardcoded switch expressions with
World.GetDimensionNameById(), which looks up the VarInt ID in
the dimension ID map populated during the RegistryData phase.
Also fixes two pre-existing issues in the SetDimension dispatch:
- JoinGame (pre-1.20.2 path): The `case < MC_1_20_6_Version` guard
was technically correct within its enclosing `if` block, but
changed to `default` for clarity and future-proofing.
- Respawn: The `case <= MC_1_20_6_Version` guard excluded protocol
versions above 766 (e.g. 1.21 / protocol 767), meaning
SetDimension was never called for those versions. Changed to
`default` so all versions >= 1.19 properly update the dimension.
Made-with: Cursor
Two critical issues in the 1.20.6 configuration phase that could cause
connection instability and packet desync:
1. RegistryData: The handler used an early `break` when it encountered
a registryId other than "minecraft:dimension_type" or
"minecraft:chat_type". This skipped reading the remaining entries
for that registry, leaving unconsumed data in the packet buffer.
Subsequent packet reads would start at the wrong offset, causing
cascading parse failures and eventual disconnection.
Fix: Always read all entries (entryId + hasData + optional NBT)
for every registry, regardless of whether we process it. For
dimension_type entries, if the server sends inline NBT data (i.e.
non-vanilla dimensions from mods/datapacks), parse and store
the dimension directly via World.StoreOneDimension(). Only fall
back to hardcoded defaults when no dimension data was received.
2. KnownDataPacks: The client echoed back ALL packs the server
listed, including non-vanilla ones. This told the server "I have
these packs cached" when the client actually did not, so the
server would skip sending full registry data for those packs.
The result: incomplete registries for modded/datapack content.
Fix: Filter the response to only include packs with the
"minecraft" namespace. Non-vanilla packs are omitted, forcing
the server to send their full registry data inline.
Also adds supporting methods to World.cs:
- SetDimensionIdMap(): Store VarInt ID -> dimension name mapping
from RegistryData entries (needed by JoinGame/Respawn)
- GetDimensionNameById(): Look up dimension name by numeric ID
- HasAnyDimension(): Check if any dimensions were loaded from
server-provided data
Made-with: Cursor
The 1.20.6 EntityProperties packet sends attribute IDs as VarInts
instead of strings. The existing mapping dictionary had three issues:
1. IDs 5/6/7 used the wrong prefix "generic." but the official
1.20.6 registry uses "player." for these attributes:
- 5: player.block_break_speed (was generic.block_break_speed)
- 6: player.block_interaction_range (was generic.block_interaction_range)
- 7: player.entity_interaction_range (was generic.entity_interaction_range)
2. IDs 22-24 (submerged_mining_speed, sweeping_damage_ratio,
water_movement_efficiency) do not exist in the 1.20.6 attribute
registry — they were introduced in 1.21. Their presence could
cause incorrect attribute resolution.
3. Direct dictionary indexing (attributeDictionary[id]) throws
KeyNotFoundException if the server sends an unknown attribute ID,
crashing the packet handler. Replaced with TryGetValue and a
safe fallback to "unknown".
Made-with: Cursor
* add miscellaneous fixes
* Fixed connecting to server when compression threshold is set to 0
The client assumes that 0 means disabled, when on a notchian (vanilla) server, it is possible to set the compression threshold to 0 (compress all packets).
* Try to capture all exceptions through Sentry
No exceptions are being logged through Sentry, so be more aggressive when sending exceptions
(cherry picked from commit eb1c2f5e771760fb3be32ffea79f8292adca92f1)
* Call OnSpawnPlayer packet when a player is spawned using the SpawnEntity packet
references #2721
(cherry picked from commit ef28ae09ac89e8988dd612de61f2849a9f0e528c)
* Add Sentry Error Tracking
* Omit personally identifiable information and add additional sentry context
* Remove debug message
* Make sentry opt-out and add related notices and strings
Also add Minecraft Version to error context
* Update build to send release info to sentry
* Adjust sentry error tracking
- Send the user-friendly Minecraft Version in the error logs
- Capture exceptions in more parts of the application
We now capture exceptions from the following locations:
- Protocol18 (1.8+) Packet errors
- Errors during client initialization phase (When client is about to start, session keys are NEVER sent to sentry)
* Make Sentry DSN configurable and repository-specific
The Sentry DSN will automatically be filled out on the main repository through the Github Actions build.
* Update build-and-release.yml
Update sed command
* style: change variable name
nitpick, just to make it a little bit more descriptive
* Add Sentry branding in README.
* remove old code (merge conflict)
The fix is to remove the ParseText call from the OnConnectionLost call, as the ReadNextChat function already calls ParseText. Calling ParseText on an unparsable string returns an empty string, therefore the disconnect message never gets propagated to the user.
