minecraft_protocol/versions/1.21.md

# Java Edition 1.21.x — "Tricky Trials" and the Long Patch Series

**Protocol numbers:** 767 (1.21/1.21.1) · 768 (1.21.2/1.21.3) · 769 (1.21.4) · 770 (1.21.5) · 771 (1.21.6) · 772 (1.21.7/1.21.8) · 773 (1.21.9/1.21.10) · 774 (1.21.11)

**Release span:** June 13, 2024 (1.21) — December 9, 2025 (1.21.11) — 8 distinct protocol versions across 11 game releases.

Sources:
- MCWIKI: `https://minecraft.wiki/w/Java_Edition_1.21[.X]` (fetched 2026-06-19)
- VV: `/tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_20_5to1_21/` … `v1_21_9to1_21_11/` (Protocol*.java + packet enums)
- VV-LOG: `git -C /tmp/mcproto-refs/ViaVersion log --oneline -- common/.../protocols/<pkg>` (fetched 2026-06-19)
- MD: `/tmp/mcproto-refs/minecraft-data/data/pc/1.21[.x]/version.json`

---

## Headline

1.21 "Tricky Trials" (June 2024) was the major combat/adventure update: trial chambers, breeze mob, mace weapon, wind charge, crafter block, copper and tuff block variants, four new status effects. Patch releases after it were unusually numerous — 10 patches over 18 months spanning the "Wild West" (1.21.2: bundles), "Winter Drop" (1.21.4: pale garden/creaking), animal variants (1.21.5), "Chase the Skies" (1.21.6: happy ghasts, dialog system), "Copper Age" (1.21.9: copper golem/equipment), and "Mounts of Mayhem" (1.21.11: spears, nautilus, dimension attribute overhaul). Each sub-update bumped the protocol, producing 8 distinct wire versions inside a single major release line.

---

## Protocol bump summary

| Protocol | MC versions | Released | Key protocol change |
|---|---|---|---|
| 767 | 1.21, 1.21.1 | 2024-06-13, 2024-08-08 | First 1.21 wire (attribute UUID→ID remap, `PROJECTILE_POWER` scalar) |
| 768 | 1.21.2, 1.21.3 | 2024-10-22, 2024-10-23 | Major: `ENTITY_POSITION_SYNC` + `MOVE_MINECART_ALONG_TRACK` new; serverbound `CLIENT_TICK_END` + `BUNDLE_ITEM_SELECTED`; full item component rebuild; new entity types (Salmon sizes, etc.) |
| 769 | 1.21.4 | 2024-12-03 | `PICK_ITEM` split into `PICK_ITEM_FROM_BLOCK`/`PICK_ITEM_FROM_ENTITY`; `LEVEL_PARTICLES` gets `always_show` field; `CUSTOM_MODEL_DATA` format extended (`1_21_4`); `PROFILE_ACTIONS_ENUM` gains "show hat" bit |
| 770 | 1.21.5 | 2025-03-25 | `ADD_EXPERIENCE_ORB` removed (merged into `ADD_ENTITY`); `PLAYER_ROTATION` packet added; `PLAYER_CHAT` gets message-index prefix; serverbounds: `SET_TEST_BLOCK` + `TEST_INSTANCE_BLOCK_ACTION` (test framework); `PLAYER_LOADED` new; large item component churn (`UNBREAKABLE`, `ENCHANTMENTS`, `ATTRIBUTE_MODIFIERS`, `EQUIPPABLE`, `INSTRUMENT`, `JUKEBOX_PLAYABLE`, `TRIM`, many variants bump to `1_21_5`) |
| 771 | 1.21.6 | 2025-06-17 | Dialog system: `CLEAR_DIALOG` + `SHOW_DIALOG` new (play + config); `CUSTOM_CLICK_ACTION` new serverbound (play + config); `TRACKED_WAYPOINT` new; `CHANGE_DIFFICULTY` changes type (unsigned byte → varint); `CHANGE_GAME_MODE` new serverbound; sneak/shift actions removed from `PLAYER_COMMAND` (now absorbed into `PLAYER_INPUT`); `ATTRIBUTE_MODIFIERS` → `1_21_6`, `EQUIPPABLE` → `1_21_6` |
| 772 | 1.21.7, 1.21.8 | 2025-06-30, 2025-07-17 | Incremental: entity/item data remapping only (block/item ID changes); no new packet types; 1.21.8 was graphics bug-fix only |
| 773 | 1.21.9, 1.21.10 | 2025-09-30, 2025-10-07 | `ADD_ENTITY` velocity field type changed (short×3 → `LOW_PRECISION_VECTOR`); `SET_ENTITY_MOTION` same; `PLAYER_ROTATION` gets "relative" boolean fields; four new `DEBUG_*` packets (`DEBUG_BLOCK_VALUE`, `DEBUG_CHUNK_VALUE`, `DEBUG_ENTITY_VALUE`, `DEBUG_EVENT`); `GAME_EVENT_TEST_HIGHLIGHT_POS` new; `EXPLODE` restructured (radius+count fields moved to `PROJECTILE_POWER`); config: `CODE_OF_CONDUCT` added; copper golem entity + copper equipment block/item IDs |
| 774 | 1.21.11 | 2025-12-09 | `HORSE_SCREEN_OPEN` → `MOUNT_SCREEN_OPEN` rename; new entity types (`zombie_nautilus`, new mounts); `zombie_nautilus_variant` + `timeline` registries injected at FINISH_CONFIGURATION; massive `dimension_type` field migration (many fields → `attributes` NBT compound); `worldgen/biome` similarly gains `attributes`; new item components: `ATTACK_RANGE`, `USE_EFFECTS`, `MINIMUM_ATTACK_CHARGE`, `DAMAGE_TYPE`, `PIERCING_WEAPON`, `KINETIC_WEAPON`, `SWING_ANIMATION`, `ZOMBIE_NAUTILUS_VARIANT` |

---

## 767 — 1.21 / 1.21.1 (June 13 / August 8, 2024)

### Gameplay headline
Tricky Trials: trial chambers, breeze mob, mace+heavy core, wind charge, crafter block, copper/tuff variant blocks, four status effects (Wind Charged, Weaving, Oozing, Infested). First release requiring 64-bit OS and Java 21+. [MCWIKI 1.21](https://minecraft.wiki/w/Java_Edition_1.21)

**1.21.1** hotfixed two security exploits (update suppression block-entity swap; server crash via malicious command-completion target selector causing stack exhaustion) plus two gameplay bugs. Same protocol 767. Servers running 1.21.1 are compatible with 1.21 clients. [MCWIKI 1.21.1](https://minecraft.wiki/w/Java_Edition_1.21.1)

### Protocol changes (766→767)
VV package: `v1_20_5to1_21/` ([`Protocol1_20_5To1_21.java`](/tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_20_5to1_21/Protocol1_20_5To1_21.java))

**Play state — clientbound (0x00–0x7B):** Packet set identical in count/IDs to 1.20.5 (`ClientboundPackets1_21` enum ends at `SERVER_LINKS` 0x7B = 124 entries). Notable: `PROJECTILE_POWER` (0x79) already existed as of 1.20.5 but its payload changed — 1.21 converts the separate x/y/z doubles (three fields) into a single `acceleration_power` scalar (magnitude of the velocity vector). VV does this inline: `Protocol1_20_5To1_21.java:registerPackets()` reads the three doubles, computes `sqrt(x²+y²+z²)`, writes one double. [VV `Protocol1_20_5To1_21.java:registerPackets()`]

**Attribute modifiers:** UUID-keyed modifiers in `UPDATE_ATTRIBUTES` replaced by string IDs. VV maps UUID→string via `AttributeModifierMappings1_21`. Bidirectional mapping: server sends string IDs, old clients need UUIDs, VV translates. [VV `Protocol1_20_5To1_21.java:registerPackets()`, `AttributeModifierMappings1_21`]

**Chat type holder:** `DISGUISED_CHAT` and `PLAYER_CHAT` chat-type field changed from plain varint to `Holder<ChatType>` (inline or registry reference). VV wraps the varint into `ChatType.TYPE` holder. [VV `Protocol1_20_5To1_21.java:registerPackets()`]

**Item components:** The 1.20.5 component set carries forward. VV's `VersionedTypes.V1_21.structuredData` filler enumerates which components exist at this version — all keys use `1_20_5`-suffixed variants except `FOOD1_21`, `JUKEBOX_PLAYABLE1_21`, `ATTRIBUTE_MODIFIERS1_21`. [VV `Protocol1_20_5To1_21.java:onMappingDataLoaded()`]

**New entity tags:** `blocks_wind_charge_explosions` (block), several entity tags (`can_turn_in_boats`, `deflects_projectiles`, `immune_to_infested`, `immune_to_oozing`, `no_anger_from_wind_charge`). Enchantment tags added (`curse`, `double_trade_price`, `in_enchanting_table`, etc.). [VV `Protocol1_20_5To1_21.java:onMappingDataLoaded()`]

---

## 768 — 1.21.2 / 1.21.3 (October 22 / October 23, 2024)

### Gameplay headline
Bundles (dyeable, store up to 64 mixed items), new banner patterns (field masoned, bordure indented). Experimental content: Minecart Improvements, Redstone Experiments, Winter Drop (pale garden biome, creaking mob) gated behind feature flags. Significant ender pearl chunk-loading change. [MCWIKI 1.21.2](https://minecraft.wiki/w/Java_Edition_1.21.2)

**1.21.3** hotfixed salmon size regression (small salmon incorrectly downsized on world load) and Realms resource-pack failure. Same protocol 768. [MCWIKI 1.21.3](https://minecraft.wiki/w/Java_Edition_1.21.3)

MD confirms: `data/pc/1.21.3/version.json` = `768`.

### Protocol changes (767→768)
VV package: `v1_21to1_21_2/` ([`Protocol1_21To1_21_2.java`](/tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_21to1_21_2/Protocol1_21To1_21_2.java))

This is the most substantial bump in the 1.21 line.

#### New clientbound play packets
- **`ENTITY_POSITION_SYNC` (0x20):** New packet for authoritative entity position sync (replaces the indirect position-via-teleport path for most entities). All subsequent packet IDs shift up by 1. [VV `ClientboundPackets1_21_2.java:0x20`]
- **`MOVE_MINECART_ALONG_TRACK` (0x31):** New dedicated minecart movement packet for the experimental Minecart Improvements feature. [VV `ClientboundPackets1_21_2.java:0x31`]
- **`SET_CURSOR_ITEM` (0x5A):** Sends the item on the cursor (held item in inventory GUI). Was previously implicit. [VV `ClientboundPackets1_21_2.java:0x5A`]
- **`SET_HELD_SLOT` (0x63):** Replaces `SET_CARRIED_ITEM` rename. [VV `ClientboundPackets1_21_2.java:0x63`]
- **`SET_PLAYER_INVENTORY` (0x66):** Sends a specific slot of the player inventory. [VV `ClientboundPackets1_21_2.java:0x66`]

Total play clientbound count grows from 124 (0x7B) to 131 (0x82).

#### New serverbound play packets
- **`BUNDLE_ITEM_SELECTED` (0x02):** Client reports which item inside a bundle was selected. VV cancels this (no equivalent in 1.21). [VV `Protocol1_21To1_21_2.java:cancelServerbound()`]
- **`CLIENT_TICK_END` (0x0B):** Client sends at end of each tick. VV cancels. [VV `Protocol1_21To1_21_2.java:cancelServerbound()`]

#### Packet field changes
- **`LOGIN_FINISHED` (login state):** `strict_error_handling` boolean field removed. VV reads and discards it. [VV `Protocol1_21To1_21_2.java:registerPackets()`]
- **`SET_TIME`:** `doDaylightCycle` was encoded as negative day-time; now explicit `doDaylightCycle: boolean` field added. VV converts the sign-encoding to explicit field. [VV `Protocol1_21To1_21_2.java:registerPackets()`]
- **`PLAYER_INFO_UPDATE`:** `PROFILE_ACTIONS_ENUM` updated to `1_21_2` variant. Display-name entries now include component rewriting. [VV `Protocol1_21To1_21_2.java:replaceClientbound()`]
- **`UPDATE_ATTRIBUTES`:** Attribute modifier format: UUID field removed, modifiers now have string ID only (already done in 767 serverside, now serverbound clean-up). VV tracks `generic.max_health` to compute max health for 1.21 clients. [VV `Protocol1_21To1_21_2.java:appendClientbound()`]

#### Item component changes (notable)
- `DAMAGE_RESISTANT` → `DAMAGE_RESISTANT1_21_2` (format change)
- `FOOD` → `FOOD1_21_2` (split into food + consumable components)
- `CONSUMABLE1_21_2`, `USE_COOLDOWN`, `EQUIPPABLE1_21_2`, `ITEM_MODEL`, `GLIDER`, `TOOLTIP_STYLE`, `DEATH_PROTECTION` added
- `REPAIRABLE`, `ENCHANTABLE` added
- `LOCK` → `LOCK1_21_2`, `POTION_CONTENTS` → `POTION_CONTENTS1_21_2`, `INSTRUMENT` → `INSTRUMENT1_21_2`, `TRIM` → `TRIM1_21_2`

[VV `Protocol1_21To1_21_2.java:onMappingDataLoaded()`]

#### Damage types added
`ender_pearl` and `mace_smash` damage types added to registry. [VV `Protocol1_21To1_21_2.java:registryDataRewriter()`]

#### Chunk-load workaround
1.21.2 introduced a rendering bug: if a loaded chunk received new data without being unloaded first, it wouldn't render correctly. VV injects a `ChunkLoadTracker` that forces chunk unload before re-send, only for 1.21.2 clients (not 1.21.3 which got the 1.21.2 packet set, as 1.21.4 fixed the bug). [VV `Protocol1_21To1_21_2.java:init()`]

#### `CLIENT_INFORMATION`
New `particle_status` varint field added at end. VV reads and discards it when translating to 1.21. [VV `Protocol1_21To1_21_2.java:clientInformation()`]

---

## 769 — 1.21.4 (December 3, 2024)

### Gameplay headline
Pale garden biome + pale oak wood set; creaking heart block; creaking mob (freezes when observed); eyeblossom; resin blocks. Spawn damage immunity removed. Water Breathing/Conduit Power now restore oxygen. [MCWIKI 1.21.4](https://minecraft.wiki/w/Java_Edition_1.21.4)

### Protocol changes (768→769)
VV package: `v1_21_2to1_21_4/` ([`Protocol1_21_2To1_21_4.java`](/tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_21_2to1_21_4/Protocol1_21_2To1_21_4.java))

Relatively lightweight protocol bump — no new packet types, primarily field changes and item-component format updates.

- **`PICK_ITEM` split:** Serverbound `PICK_ITEM` (0x22) split into `PICK_ITEM_FROM_BLOCK` (0x22) and `PICK_ITEM_FROM_ENTITY` (0x23). VV provides a `PickItemProvider` to handle the split. [VV `Protocol1_21_2To1_21_4.java:register()`]
- **`LEVEL_PARTICLES`:** `always_show` boolean field added after `override_limiter`. VV writes `false` for it when translating down. [VV `Protocol1_21_2To1_21_4.java:registerPackets()` `replaceClientbound(LEVEL_PARTICLES)`]
- **`PLAYER_INFO_UPDATE`:** `PROFILE_ACTIONS_ENUM` → `1_21_4` variant (adds "show hat" action). VV writes `true` by default. [VV `Protocol1_21_2To1_21_4.java:registerPackets()`]
- **Item components:** `CUSTOM_MODEL_DATA` → `1_21_4` (format extended), `TRIM` → `1_21_4`.
- **`PLAYER_LOADED` serverbound:** Added at protocol **769 (1.21.4)** — `ServerboundPackets1_21_4.java` includes it at 0x2A, and `EntityPacketRewriter1_21_4.java:63` cancels it downward (`protocol.cancelServerbound(ServerboundPackets1_21_4.PLAYER_LOADED)`), confirming 769 is the introduction boundary. It is not present in the 1.21.2 (768) serverbound enum (0x2A there is `RECIPE_BOOK_CHANGE_SETTINGS`). In 1.21.5 it shifts to 0x2A in the new numbering (`ServerboundPackets1_21_5.java:64`). Source: ViaVersion `v1_21_2to1_21_4/rewriter/EntityPacketRewriter1_21_4.java:63`, `v1_21_2to1_21_4/packet/ServerboundPackets1_21_4.java:64`, `v1_21to1_21_2/packet/ServerboundPackets1_21_2.java` (no PLAYER_LOADED entry).
- VV does NOT add a `ChunkLoadTracker` for 1.21.4 clients — Mojang fixed the rendering bug in this release. [VV `Protocol1_21To1_21_2.java:init()` comment]

---

## 770 — 1.21.5 (March 25, 2025)

### Gameplay headline
Farm animal variants (cold/warm/temperate pigs, cows, chickens with biome-based spawning), new decorative plants (leaf litter, wildflowers, bushes, firefly bushes), wolf sound variants (7). Game test framework (`/test` command, test blocks). Text components switch from JSON to SNBT. [MCWIKI 1.21.5](https://minecraft.wiki/w/Java_Edition_1.21.5)

### Protocol changes (769→770)
VV package: `v1_21_4to1_21_5/` ([`Protocol1_21_4To1_21_5.java`](/tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_21_4to1_21_5/Protocol1_21_4To1_21_5.java))

This is one of the larger protocol bumps: packet added/removed and major item-component churn.

#### Packet additions and removals

**Clientbound play:**
- **`ADD_EXPERIENCE_ORB` removed.** Experience orbs now spawn via the regular `ADD_ENTITY` packet (entity type `experience_orb`). All subsequent IDs shift. [VV `ClientboundPackets1_21_5.java` — no `ADD_EXPERIENCE_ORB` entry; 1.21 enum had it at 0x02]
- **`PLAYER_ROTATION` (0x42) added:** Server sends player rotation authoritative update. Separate from `PLAYER_POSITION`. [VV `ClientboundPackets1_21_5.java:0x42`]
- **`TEST_INSTANCE_BLOCK_STATUS` (0x77):** New packet for the game test framework. [VV `ClientboundPackets1_21_5.java:0x77`]

**Serverbound play (vs 1.21.4):**
- `PICK_ITEM_FROM_BLOCK` (0x22), `PICK_ITEM_FROM_ENTITY` (0x23) — carried from 769
- **`PLAYER_LOADED` (0x2A):** New — client signals it has loaded the world. [VV `ServerboundPackets1_21_5.java:0x2A`]
- **`SET_TEST_BLOCK` (0x39):** Test framework. VV cancels. [VV `Protocol1_21_4To1_21_5.java:cancelServerbound()`]
- **`TEST_INSTANCE_BLOCK_ACTION` (0x3D):** Test framework. VV cancels. [VV `Protocol1_21_4To1_21_5.java:cancelServerbound()`]

#### Packet field changes
- **`PLAYER_CHAT`:** Message-index varint added as first field. VV synthesizes this using `MessageIndexStorage` (tracks per-connection index). [VV `Protocol1_21_4To1_21_5.java:replaceClientbound(PLAYER_CHAT)`, `MessageIndexStorage`]
- **`CHAT_COMMAND_SIGNED` and `CHAT` (serverbound):** `checksum: byte` field added at end. VV reads and drops it. [VV `Protocol1_21_4To1_21_5.java:registerServerbound(CHAT_COMMAND_SIGNED)`, `registerServerbound(CHAT)`]
- **`wolf_variant` registry:** `assets` field restructured — `wild_texture`, `tame_texture`, `angry_texture` moved under `assets` compound; `biomes` field removed. VV remaps on registry send. [VV `Protocol1_21_4To1_21_5.java:registryDataRewriter` handler for `wolf_variant`]

#### Item component changes (major churn)
Many component keys changed to `1_21_5`-suffixed variants:
- `UNBREAKABLE` → `1_21_5`, `ENCHANTMENTS` → `1_21_5`, `STORED_ENCHANTMENTS` → `1_21_5`
- `DYED_COLOR` → `1_21_5`, `TRIM` → `1_21_5`, `ATTRIBUTE_MODIFIERS` → `1_21_5`
- `EQUIPPABLE` → `1_21_5`, `TOOL` → `1_21_5`, `INSTRUMENT` → `1_21_5`, `JUKEBOX_PLAYABLE` → `1_21_5`
- **New components added:** `BLOCKS_ATTACKS1_21_5` (shield-like), `PROVIDES_BANNER_PATTERNS1_21_5`, `TOOLTIP_DISPLAY`, `WEAPON`, `POTION_DURATION_SCALE`, `PROVIDES_TRIM_MATERIAL1_21_5`, `BREAK_SOUND`
- **Mob-variant components as items:** `VILLAGER_VARIANT`, `WOLF_VARIANT`, `WOLF_COLLAR`, `FOX_VARIANT`, `SALMON_SIZE`, `PARROT_VARIANT`, `TROPICAL_FISH_*`, `MOOSHROOM_VARIANT`, `RABBIT_VARIANT`, `PIG_VARIANT`, `FROG_VARIANT`, `HORSE_VARIANT`, `PAINTING_VARIANT`, `LLAMA_VARIANT`, `AXOLOTL_VARIANT`, `CAT_VARIANT`, `CAT_COLLAR`, `SHEEP_COLOR`, `SHULKER_COLOR`, `COW_VARIANT`, `CHICKEN_VARIANT1_21_5`, `WOLF_SOUND_VARIANT` — all bucket/spawn-egg entity variant data is now carried as item components.

[VV `Protocol1_21_4To1_21_5.java:onMappingDataLoaded()`]

#### Smithing trim recipe slot display change
Trim pattern slot display format changed — VV substitutes a placeholder (holder index 0) when translating smithing-trim recipe packets down. [VV `Protocol1_21_4To1_21_5.java` `recipeRewriter` anonymous class]

---

## 771 — 1.21.6 (June 17, 2025)

### Gameplay headline
"Chase the Skies" — rideable happy ghasts (up to 4 riders, colored harnesses); locator bar (shows other players' direction/distance in HUD); mob-to-mob leads; craftable saddles; waypoints. Dialog system (server-controlled modal UI). [MCWIKI 1.21.6](https://minecraft.wiki/w/Java_Edition_1.21.6)

### Protocol changes (770→771)
VV package: `v1_21_5to1_21_6/` ([`Protocol1_21_5To1_21_6.java`](/tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_21_5to1_21_6/Protocol1_21_5To1_21_6.java))

#### New packets

**Clientbound play:**
- **`TRACKED_WAYPOINT` (0x83):** Waypoint tracking for the locator bar feature. [VV `ClientboundPackets1_21_6.java:0x83`]
- **`CLEAR_DIALOG` (0x84):** Dismiss the current server dialog. [VV `ClientboundPackets1_21_6.java:0x84`]
- **`SHOW_DIALOG` (0x85):** Display a dialog to the player. [VV `ClientboundPackets1_21_6.java:0x85`]

**Configuration state — clientbound:**
- **`CLEAR_DIALOG` (0x11)** and **`SHOW_DIALOG` (0x12)** also appear in Configuration state — dialogs can be shown during config phase. [VV `ClientboundConfigurationPackets1_21_6.java:0x11,0x12`]

**Serverbound play:**
- **`CHANGE_GAME_MODE` (0x04):** New packet for switching game mode. VV translates this to `CHAT_COMMAND` (`/gamemode <name>`) for 1.21.5 servers. [VV `Protocol1_21_5To1_21_6.java:registerServerbound(CHANGE_GAME_MODE)`]
- **`CUSTOM_CLICK_ACTION` (0x41):** New serverbound packet sent when a player interacts with a dialog element. VV cancels (no equivalent). [VV `Protocol1_21_5To1_21_6.java:cancelServerbound(CUSTOM_CLICK_ACTION)`]

#### Packet field changes
- **`CHANGE_DIFFICULTY`:** Difficulty value changes type from `unsigned byte` to `varint`. VV converts both directions. [VV `Protocol1_21_5To1_21_6.java:registerClientbound(CHANGE_DIFFICULTY)`, `registerServerbound(CHANGE_DIFFICULTY)`]
- **`PLAYER_COMMAND`:** `press_shift_key` (action 0) and `release_shift_key` (action 1) removed — sneak is now a `PLAYER_INPUT` flag. All remaining actions shift down by 2. VV synthesizes `press_shift_key`/`release_shift_key` from `PLAYER_INPUT`'s sneak flag, using `SneakStorage` to track state changes. [VV `EntityPacketRewriter1_21_6.java:registerServerbound(PLAYER_COMMAND)`, `registerServerbound(PLAYER_INPUT)`]

#### Configuration: dialog registry injection
At `FINISH_CONFIGURATION`, VV synthesizes a `minecraft:dialog` registry entry (`server_links` dialog type) and sends it as `REGISTRY_DATA` — vanilla servers don't send this so older clients wouldn't see server links dialogs. [VV `EntityPacketRewriter1_21_6.java:appendClientbound(FINISH_CONFIGURATION)`]

#### Dimension type: cloud_height defaults
VV patches dimension-type registry entries to inject a default `cloud_height: 192` for overworld-like dimensions, since 1.21.6 clients render clouds based on this field. [VV `Protocol1_21_5To1_21_6.java:registryDataRewriter` handler for `dimension_type`]

#### Item components
- `ATTRIBUTE_MODIFIERS` → `1_21_6`, `EQUIPPABLE` → `1_21_6`

[VV `Protocol1_21_5To1_21_6.java:onMappingDataLoaded()`]

---

## 772 — 1.21.7 / 1.21.8 (June 30 / July 17, 2025)

### Gameplay headline
**1.21.7:** New music disc "Lava Chicken" (Hyper Potions, from chicken jockey kill); new painting "Dennis" (3×3, A Minecraft Movie tie-in). 16 bug fixes (AMD/Qualcomm rendering, texture atlas leaks). [MCWIKI 1.21.7](https://minecraft.wiki/w/Java_Edition_1.21.7)

**1.21.8:** Graphics bug-fix only — Intel Gen11 shading errors, inventory item-color glitches on Intel integrated graphics. Same protocol 772. [MCWIKI 1.21.8](https://minecraft.wiki/w/Java_Edition_1.21.8)

### Protocol changes (771→772)
VV package: `v1_21_6to1_21_7/` ([`Protocol1_21_6To1_21_7.java`](/tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_21_6to1_21_7/Protocol1_21_6To1_21_7.java))

Purely incremental — **no new packet types**. Same clientbound/serverbound enum as 771. VV's `Protocol1_21_6To1_21_7` class has an empty `registerPackets()` body; translation is limited to block/item/entity ID remapping and dialog-packet item rewriting. [VV `Protocol1_21_6To1_21_7.java:registerPackets()`]

The `git log` shows `6b74116ff Handle item changes in dialog packets` as the main content commit — items embedded in `SHOW_DIALOG` / `CLEAR_DIALOG` needed remapping for the new block/item IDs. [VV-LOG `v1_21_6to1_21_7`]

---

## 773 — 1.21.9 / 1.21.10 (September 30 / October 7, 2025)

### Gameplay headline
"The Copper Age" — copper golem mob, copper tools/armor (stone-tier, high enchantability), copper chests (with oxidation), shelves (all wood types), copper lanterns/chains/bars. Chat drafts persist. New game rules (portal control, mob spawn). [MCWIKI 1.21.9](https://minecraft.wiki/w/Java_Edition_1.21.9)

**1.21.10:** Five bug fixes from 1.21.9 (wind charge collision, TP chunk loading, piston/cobweb entity clip). Same protocol 773. [MCWIKI 1.21.10](https://minecraft.wiki/w/Java_Edition_1.21.10)

### Protocol changes (772→773)
VV package: `v1_21_7to1_21_9/` ([`Protocol1_21_7To1_21_9.java`](/tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_21_7to1_21_9/Protocol1_21_7To1_21_9.java))

This is a notably large bump: movement encoding overhaul, explosion restructure, debug packet additions.

#### Entity velocity encoding change
- **`ADD_ENTITY`:** Entity initial velocity previously encoded as three signed shorts (`velX`, `velY`, `velZ` — each = velocity × 8000, clamped). Now encoded as `LOW_PRECISION_VECTOR` (a compact 3-component float vector type). VV translates: reads the old shorts, reconstructs the vector. [VV `EntityPacketRewriter1_21_9.java:replaceClientbound(ADD_ENTITY)`]
- **`SET_ENTITY_MOTION`:** Same change — shorts → `LOW_PRECISION_VECTOR`. [VV `EntityPacketRewriter1_21_9.java:registerClientbound(SET_ENTITY_MOTION)`]
- **`PLAYER_ROTATION`:** Gets two `relative: boolean` flags (one per axis). VV writes `false` for both when translating down. [VV `EntityPacketRewriter1_21_9.java:registerClientbound(PLAYER_ROTATION)`]

#### Explosion restructure
`EXPLODE` packet restructured: the explosion radius and affected-block count (previously sent inline) are now sourced from `PROJECTILE_POWER`'s tracked state. VV emits the old-format explosion packet using values from `LastExplosionPowerStorage`. A new `block_particles` list field appended (VV writes count=0). [VV `Protocol1_21_7To1_21_9.java:replaceClientbound(EXPLODE)`]

#### New debug packets (clientbound play)
Four new debug visualisation packets added (likely tied to the game test framework):
- **`DEBUG_BLOCK_VALUE` (0x1A)**
- **`DEBUG_CHUNK_VALUE` (0x1B)**
- **`DEBUG_ENTITY_VALUE` (0x1C)**
- **`DEBUG_EVENT` (0x1D)**

And **`GAME_EVENT_TEST_HIGHLIGHT_POS` (0x27):** Highlight test positions in the world. [VV `ClientboundPackets1_21_9.java`]

All existing IDs shift up accordingly — packet count goes from 134 (0x85) in 772 to 139 (0x8A) in 773.

#### Configuration state changes
- **`CODE_OF_CONDUCT` (0x13)** added to serverbound Configuration packets (client accepts/rejects). VV cancels `ACCEPT_CODE_OF_CONDUCT` when translating down. [VV `ServerboundConfigurationPackets1_21_9.java:0x09`; `Protocol1_21_7To1_21_9.java:cancelServerbound(ACCEPT_CODE_OF_CONDUCT)`]

#### Debug sample subscription
`DEBUG_SAMPLE_SUBSCRIPTION` serverbound changed: from a single `type: varint` to a list `count: varint` + per-entry `registry_id: varint`. VV maps the new `DEDICATED_SERVER_TICK_TIME` subscription (id=0) back to the old `TICK_TIME` type (0). [VV `Protocol1_21_7To1_21_9.java:registerServerbound(DEBUG_SAMPLE_SUBSCRIPTION)`]

#### `SET_DEFAULT_SPAWN_POSITION`

In **773 (1.21.9)** this packet gained two new fields: a **dimension identifier** (string) prepended before the block position, and a **pitch float** appended after the yaw float. ViaVersion's handler reads `BLOCK_POSITION1_14`, gets the current dimension from `tracker(wrapper.user()).currentWorld()`, writes `GLOBAL_POSITION` (dimension string + block position), passthroughs the yaw float, then writes `pitch=0F`. Old format (≤ 772): `BlockPosition + float yaw`; new format (773+): `String dimension + BlockPosition + float yaw + float pitch`. Source: `v1_21_7to1_21_9/rewriter/EntityPacketRewriter1_21_9.java:80–90`; `GlobalBlockPositionType.java` (dimension written as string before position).

---

## 774 — 1.21.11 (December 9, 2025)

### Gameplay headline
"Mounts of Mayhem" — nautilus (tameable aquatic mount), zombie nautilus (hostile), camel husk, parched (desert skeleton), zombie horseman. Spears (7 material tiers, jab + charge attacks, lunge enchantment). Nautilus armor. Netherite horse armor. Overhaul of dimension type and biome data (environment attributes system). [MCWIKI 1.21.11](https://minecraft.wiki/w/Java_Edition_1.21.11)

### Protocol changes (773→774)
VV package: `v1_21_9to1_21_11/` ([`Protocol1_21_9To1_21_11.java`](/tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_21_9to1_21_11/Protocol1_21_9To1_21_11.java))

This is the most structurally significant bump of the 1.21 line from a proxy standpoint.

#### Packet rename
- **`HORSE_SCREEN_OPEN` → `MOUNT_SCREEN_OPEN`** (same ID 0x28; name change only reflects expanded mount support). VV registers a direct remap. [VV `EntityPacketRewriter1_21_11.java:registerClientbound(HORSE_SCREEN_OPEN → MOUNT_SCREEN_OPEN)`]

#### New entity type
- **`zombie_nautilus`** entity type added. New entity-data type `zombieNautilusVariantType` registered. [VV `EntityPacketRewriter1_21_11.java:registerRewrites()`, `EntityTypes1_21_11`]

#### Registry injection at FINISH_CONFIGURATION
VV injects two entirely new registries before the config-phase completes, so older servers' clients see them:
- **`zombie_nautilus_variant`** registry — VV synthesizes a single entry (`minecraft:pale` with `temperate` asset ID). [VV `Protocol1_21_9To1_21_11.java:registerPackets()`, `appendClientbound(FINISH_CONFIGURATION)`]
- **`timeline`** registry — an experimental feature allowing time-based behavior modifications. VV synthesizes entries from `MAPPINGS.timelineRegistry()`. [VV `Protocol1_21_9To1_21_11.java:registerPackets()`]

#### `dimension_type` registry overhaul (massive)
The `dimension_type` data format was significantly restructured — many fields extracted into a new `attributes` compound NBT sub-object. VV performs full field-level migration for each dimension type entry:
- `fixed_time` → `has_fixed_time` boolean
- `has_raids` → `attributes/"gameplay/can_start_raid"`
- `piglin_safe` → `attributes/"gameplay/piglins_zombify"` (inverted)
- `respawn_anchor_works` → `attributes/"gameplay/respawn_anchor_works"`
- `ultrawarm` → `attributes/"gameplay/fast_lava"` + `"gameplay/water_evaporates"`
- `cloud_height` → `attributes/"visual/cloud_height"` + synthesizes `"visual/cloud_color": "#ccffffff"`
- New fields added: `skybox`, `cardinal_light`, `timelines` list, `attributes/"visual/sky_light_color"`, `attributes/"visual/fog_start_distance"`, `attributes/"visual/fog_end_distance"`, `attributes/"audio/background_music"`, ambient cave sounds.

[VV `Protocol1_21_9To1_21_11.java:registryDataRewriter` `dimension_type` handler]

#### `worldgen/biome` registry overhaul
Biome registry entries similarly gain an `attributes` sub-object with all sound and visual properties migrated:
- `effects.sky_color` → `attributes/"visual/sky_color"` (suppressed for nether biomes)
- `effects.water_fog_color` → `attributes/"visual/water_fog_color"`
- `effects.fog_color` → `attributes/"visual/fog_color"`
- `effects.music` → `attributes/"audio/background_music"`
- `effects.mood_sound`/`additions_sound`/`ambient_sound` → `attributes/"audio/ambient_sounds"`
- `effects.particle` → `attributes/"visual/ambient_particles"`

[VV `Protocol1_21_9To1_21_11.java:registryDataRewriter` `worldgen/biome` handler]

#### New item components
- `ATTACK_RANGE`, `USE_EFFECTS`, `MINIMUM_ATTACK_CHARGE`, `DAMAGE_TYPE1_21_11`, `PIERCING_WEAPON`, `KINETIC_WEAPON`, `SWING_ANIMATION`, `ZOMBIE_NAUTILUS_VARIANT1_21_11`

[VV `Protocol1_21_9To1_21_11.java:onMappingDataLoaded()`]

#### Game time storage
VV adds `GameTimeStorage` to track absolute game time (needed for timeline-based behavior). [VV `Protocol1_21_9To1_21_11.java:init()`]

#### Serverbound: spear cancel
`PLAYER_ACTION` action ID 7 ("stab") added for spear jab — VV cancels these when downgrading. [VV `EntityPacketRewriter1_21_11.java:registerServerbound(PLAYER_ACTION)`]

---

## Proxy and ViaVersion translation impact

| Bump | Translation cost | Key challenge |
|---|---|---|
| 766→767 | Low | Attribute UUID↔ID bidirectional map; `PROJECTILE_POWER` scalar; chat type holder |
| 767→768 | High | 7 new clientbound packets (all IDs shift); 2 new serverbound; full item-component set rebuild; max-health tracking; chunk-load workaround for 1.21.2 clients |
| 768→769 | Medium | `PICK_ITEM` split; `LEVEL_PARTICLES` field insert; profile action enum extension |
| 769→770 | High | `ADD_EXPERIENCE_ORB` removal (XP orbs now `ADD_ENTITY`); message-index synthesis for chat; chat checksum stripping; test-framework packets cancelled; 20+ new item components including all mob-variant data |
| 770→771 | Medium | Dialog packet passthrough (play+config); sneak flag synthesis from `PLAYER_INPUT`; `PLAYER_COMMAND` action re-numbering; `CHANGE_DIFFICULTY` type conversion; dialog registry injection |
| 771→772 | Low | ID remapping only; dialog packet item rewriting |
| 772→773 | High | Entity velocity type change (`LOW_PRECISION_VECTOR` ↔ shorts) for ALL entities; explosion packet restructure; 5 new debug/test packets shifting all IDs; explosion power storage tracking |
| 773→774 | Very high | Full `dimension_type` field migration (many fields → `attributes` compound); full `worldgen/biome` field migration; two new registry types injected during config; new entity type + variant; spear action filtering |

**Proxy notes:**
- **Login state:** `LOGIN_FINISHED` lost `strict_error_handling` (768). If a proxy injects it, strip on the way down.
- **Configuration state:** Dialog packets (`CLEAR_DIALOG`, `SHOW_DIALOG`) appear in both config and play states from 771 onward. Proxies must forward these in both states.
- **`CODE_OF_CONDUCT` (config, 773):** New serverbound; cancel when forwarding to 772 servers.
- **`BUNDLE_ITEM_SELECTED` / `CLIENT_TICK_END` (768):** Cancel toward 767 servers.
- **Chunk-load (768):** 1.21.2 clients need forced chunk unload before re-send; 1.21.3/1.21.4 don't.
- **Item components:** Every bump through 770 added or renamed component keys. A proxy doing item translation must track which component key set the connected client/server uses.
- **`dimension_type` (774):** By far the most complex registry translation in the 1.21 line — the field-level migration is large enough that ViaVersion devotes ~150 lines of registry rewriting code to it alone.