World Dimension Loader 1.3.0

Major update from WDL 1.2.2

WDL 1.3.0 is a major runtime, reset, gate-control, compatibility, and configuration update.

This release introduces a new Runtime Reset architecture, timestamp-based physical generations, Timed Dimensions, Forced Exit handling, per-Dimension environment controls, Gate reopen cooldowns, expanded diagnostics, and major safety improvements for modded environments such as Valkyrien Skies and Distant Horizons.

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⚠️ IMPORTANT: Existing WDL Dimension Data May Require Manual Migration

WDL 1.3.0 changes how imported worlds are prepared and managed.

If you are upgrading from WDL 1.2.2 or older and want to preserve the latest state of a WDL Dimension that has already been played, manual world-data migration may be required.

Why is this necessary?

In WDL 1.2.2 and older, the active/playable WDL Dimension data was stored inside the Minecraft save.

Typical singleplayer location:

.minecraft/saves/<save-name>/dimensions/worlddimensionloader/<dimension-id>/

Typical dedicated-server location:

<server-world-folder>/dimensions/worlddimensionloader/<dimension-id>/

This Dimension data may contain changes made after the world was originally imported, including:

• explored and generated chunks;
• placed or removed blocks;
• player-built structures;
• terrain changes;
• entities;
• other Dimension world state.

WDL 1.3.0 prepares imported Dimensions from the source world stored under:

WDL_custom_dimensions/<dimension-id>/

If the copy in WDL_custom_dimensions/ is older than the Dimension that was actually played in WDL 1.2.2, those newer changes may not be present after upgrading.

Recommended migration method

1. Stop Minecraft / the server completely

Do not perform the migration while the world or server is running.

2. Back up the existing source world

Before changing anything, back up:

WDL_custom_dimensions/<dimension-id>/

Example:

WDL_custom_dimensions/dungeon_world/

Keep this backup until the entire migration has been tested successfully.

It is also strongly recommended to back up the Minecraft save containing the old WDL Dimension.

3. Locate the latest WDL 1.2.2-or-older Dimension data

Example:

saves/MyWorld/dimensions/worlddimensionloader/dungeon_world/

General location:

<save>/dimensions/worlddimensionloader/<dimension-id>/

4. Copy the contents of the old Dimension into the existing WDL source folder

Copy the contents of:

<save>/dimensions/worlddimensionloader/<dimension-id>/

into:

WDL_custom_dimensions/<dimension-id>/

When matching files or folders already exist, allow the newer old-WDL Dimension data to overwrite the corresponding world data.

Example:

Old WDL 1.2.2 Dimension

saves/MyWorld/dimensions/worlddimensionloader/dungeon_world/
                          ↓
Copy its contents
                          ↓
Overwrite matching world data inside
                          ↓
WDL_custom_dimensions/dungeon_world/

This is intended to update the source copy with the latest state that existed in the playable WDL Dimension.

⚠️ Do Not Delete the Destination Folder First

Do not delete:

WDL_custom_dimensions/<dimension-id>/

before copying the old Dimension data into it.

The existing source folder may contain files required for WDL to recognize and prepare the world correctly.

The recommended migration is therefore:

Back up existing source
        ↓
Keep the existing source folder
        ↓
Copy old WDL Dimension contents over it
        ↓
Overwrite matching world data

rather than:

Delete source folder
        ↓
Replace it blindly with old Dimension folder

⚠️ Keep a Valid level.dat

After the overwrite migration, make sure the resulting source world still contains:

WDL_custom_dimensions/<dimension-id>/level.dat

directly inside the registered folder.

The old WDL Dimension folder may not contain every file required for a standalone WDL source world.

If the old Dimension data does not contain a suitable level.dat, keep the valid level.dat already present in:

WDL_custom_dimensions/<dimension-id>/

If your file manager specifically asks whether to overwrite level.dat, keeping the existing valid source level.dat is the safer choice unless you have independently confirmed that the replacement is a valid full-world level.dat.

Example final structure:

WDL_custom_dimensions/dungeon_world/
├─ level.dat
├─ region/
├─ entities/
├─ poi/
├─ data/
└─ ...

The goal is to preserve the valid source-world structure while updating its Dimension data to the latest state from WDL 1.2.2 or older.

When is migration required?

Migration is important when:

• the WDL Dimension was entered and played in 1.2.2 or older;
• chunks were explored or generated;
• players built or destroyed blocks;
• terrain or entities changed;
• or you otherwise want to preserve the latest played state.

Migration may not be necessary when:

• the Dimension was never used after import;
• or the existing WDL_custom_dimensions/<dimension-id>/ already represents the exact state you want WDL 1.3.0 to use.

Verify the migration

After copying the old Dimension data into WDL_custom_dimensions/, start WDL 1.3.0 and verify that:

• the imported Dimension appears as READY;
• the expected explored areas are present;
• player builds are present;
• expected terrain changes are present;
• other important Dimension data is present;
• the configured Gate can enter the migrated Dimension normally.

Keep the old WDL 1.2.2 Dimension data and your backup until the migrated world has been verified successfully.

Do not delete the old data immediately after copying it.

After verification, WDL 1.3.0 will manage the imported Dimension using its current Runtime storage architecture.

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⚠️ IMPORTANT: Config Regeneration Is Strongly Recommended

WDL 1.3.0 includes substantial changes to the generated Config structure, available options, defaults, comments, migration behavior, and Gate selection rules.

Existing Config files are NOT automatically overwritten by WDL.

Because of this, simply replacing the 1.2.2 JAR with 1.3.0 may leave you using an older Config layout that does not show the new options, new safety warnings, or current recommended settings.

Why regenerate the Config?

Compared with 1.2.2, WDL 1.3.0 adds or changes:

• Runtime Reset and physical-generation settings;

• Deferred cleanup and Startup GC settings;

• Timed Dimension / Forced Exit settings;

• Per-Dimension Environment settings;

• Gate reopen cooldown;

• new Reset safety warnings;

• new STARTUP ONLY settings;

• new canonical cleanup Config keys;

• Dimension ID validation;

• Gate selection behavior when selection_mode is omitted;

• runtime.max_loaded_dimensions default from 4 to 8;

• generated Config organization into:

  • ALL OPTIONS;
  • practical/minimal examples;
  • LEGACY COMPATIBILITY.

Old Config files can still be read where compatibility is supported, but they do not automatically gain the new comments or recommended values.

Recommended complete upgrade procedure

1. Stop Minecraft / the server completely.

2. Back up:

   • your save/world;
   • config/worlddimensionloader/;
   • WDL_custom_dimensions/;
   • any important existing WDL 1.2.2 Dimension data.

3. For every WDL 1.2.2-or-older Dimension whose latest played state you want to preserve, locate:

<save>/dimensions/worlddimensionloader/<dimension-id>/

1. Back up the corresponding existing source:

WDL_custom_dimensions/<dimension-id>/

1. Copy the contents of the old WDL Dimension into the existing:

WDL_custom_dimensions/<dimension-id>/

1. Allow matching Dimension world-data files and folders to be overwritten.

2. Do not delete the destination source folder before copying.

3. Confirm that a valid:

WDL_custom_dimensions/<dimension-id>/level.dat

still exists.

1. Keep all migration backups until the migrated Dimension has been verified.

2. Move or rename the old:

config/worlddimensionloader/

1. Install WDL 1.3.0 and start Minecraft/the server once.

2. WDL will generate fresh:

common.toml
dimensions.toml
gates.toml

1. Stop Minecraft/the server again.

2. Copy only your intentional custom Dimension/Gate definitions and custom overrides into the new files.

3. Do not simply overwrite the newly generated 1.3.0 Config with the complete old 1.2.2 Config.

4. Check all Gates that use dimensions = [...], especially if selection_mode was previously omitted.

5. Start Minecraft/the server again and verify with:

/wdl scan
/wdl list
/wdl status

1. Confirm that migrated Dimensions are READY.

2. Enter and verify important migrated worlds before deleting any old WDL 1.2.2 data or migration backups.

Some settings are STARTUP ONLY.

/wdl scan cannot change those settings for an already running process, so a full restart is required.

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✨ Major New Features

♻️ Runtime Reset System

WDL 1.3.0 adds a full Runtime Reset system for imported Dimensions.

Per Dimension:

[dimensions.runtime]
reset_on_empty = false
reset_delay_seconds = 30

When reset_on_empty = true, a WDL Dimension can be rebuilt from its original imported source after it has been used and becomes empty.

This makes repeatable dungeons, challenge worlds, loot instances, adventure maps, and other resettable content possible without modifying the original imported world.

The imported source under:

WDL_custom_dimensions/<world-id>/

is not used as the live Runtime world and is not deleted by the Reset process.

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🔄 Stable Logical Dimension + Fresh Physical Generations

WDL 1.3.0 separates the public/logical Dimension identity from the physical Runtime generation.

Example logical ID:

worlddimensionloader:test_world_01

Example physical Runtime generation:

dimensions/wdl/test_world_01/20260822123000/

A Reset can create a completely fresh physical generation while preserving the same logical WDL Dimension identity.

New generations use WDL-generated timestamps:

dimensions/wdl/<world-id>/<YYYYMMDDHHMMSS>/

If more than one generation is allocated during the same second, deterministic suffixes are added:

20260822123000
20260822123000a
20260822123000b
...
20260822123000z
20260822123000aa
...

The physical generation number is also retained internally for lifecycle/recovery tracking.

This architecture allows WDL to replace a Runtime world without changing the public Dimension identity used by Config, Gate destinations, policies, history, and player-facing behavior.

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⏱️ Timed Dimensions / Timed Sessions

WDL 1.3.0 adds per-Dimension time limits.

Example:

[dimensions.time_limit]
minutes = 10
exit_destination = "PREVIOUS"

Supported duration types:

• seconds
• minutes
• hours
• minecraft_days

Use exactly one duration type.

Supported exit destinations:

• PREVIOUS
• OVERWORLD

Default:

exit_destination = "PREVIOUS"

A Timed Session is shared for the active timed Dimension session rather than being a simple per-player countdown.

WDL also handles expiration while players are offline.

If a player logs back in after an applicable Timed Session has expired, WDL can complete the required Forced Exit safely.

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🚪 Forced Exit System

Timed Dimensions include a dedicated Forced Exit system.

When a Timed Session expires, WDL attempts to evacuate participating players to the configured destination.

PREVIOUS

WDL attempts to return the player to the trusted previous location captured for the Timed Session.

If the previous destination can no longer be used safely, WDL can fall back to the Overworld.

OVERWORLD

The player is returned directly to the Overworld using WDL's safe return handling.

Forced Exit is intentionally separate from ordinary Gate activation and does not create a new Timed Session simply because the player is being evacuated.

When Inventory Policy restrictions would otherwise permanently block emergency evacuation, the Forced Exit cleanup path may remove violating stacks according to the safe cleanup plan.

Use Inventory restrictions carefully in timed loot/challenge Dimensions.

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🌍 Per-Dimension Environment Controls

WDL 1.3.0 adds configurable Environment behavior for imported Dimensions.

Example:

[dimensions.environment]
game_mode = "ADVENTURE"
fixed_time = 18000
difficulty = "HARD"

Supported game modes:

• INHERIT
• SURVIVAL
• CREATIVE
• ADVENTURE
• SPECTATOR

Supported difficulty values:

• INHERIT
• PEACEFUL
• EASY
• NORMAL
• HARD

fixed_time may be set from 0 to 23999.

If omitted, normal time progression is used.

SPECTATOR warning: normal Gate or Return Scroll interaction may not always be available while Spectator mode is forced.

Provide another recovery method before using this setting in production.

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🌀 Gate Reopen Cooldown

Physical Gates can now have an independent reopen cooldown.

reopen_cooldown_seconds = 0

Default:

0 = disabled

Cooldown identity is tracked for the physical Gate while preserving the correct logical WDL source identity across Runtime generation rotation.

This allows permanent or frequently reusable Gates to be rate-limited without changing the normal Gate open duration.

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🧭 Improved Gate Selection UX

WDL 1.3.0 changes how omitted selection_mode is interpreted.

New behavior

[[gates]]
id = "example_gate"
dimensions = ["test_world_01"]

Now means:

LIST

Selection rules:

• explicit LIST + destinations → LIST
• explicit ALL → ALL
• omitted mode + non-empty dimensions → LIST
• omitted mode + empty/omitted dimensions → legacy-compatible ALL
• explicit invalid mode → Gate rejected

This makes the minimal targeted Gate much easier to configure.

IMPORTANT migration note

Older WDL parsing could treat a Gate with omitted selection_mode as ALL even when dimensions = [...] was present.

If an existing 1.2.2 Gate intentionally relied on that old ALL behavior, add:

selection_mode = "ALL"

explicitly.

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🧩 Much Smaller Minimum Config

The canonical minimum imported Dimension definition is now:

[[dimensions]]
id = "test_world_01"

The canonical minimum targeted Gate is:

[[gates]]
id = "test_world_01_gate"
dimensions = ["test_world_01"]

Defaults are resolved by WDL when omitted.

New Dimension definition IDs should use a bare WDL path such as:

test_world_01

Namespaced definition IDs such as:

worlddimensionloader:test_world_01

are rejected early.

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📊 Expanded Runtime Diagnostics

The WDL admin/debug commands now expose more lifecycle and Runtime information.

Useful commands include:

/wdl scan
/wdl list
/wdl status
/wdl loaded
/wdl probe <id>

/wdl loaded and /wdl probe can expose current physical-generation and resident/lifecycle information where applicable.

This makes Reset, loading, staging, capacity, and compatibility problems easier to diagnose from logs and command output.

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♻️ Runtime Reset Behavior and Important Warnings

This section is especially important for server owners and modpack developers.

Default Safe Reset Flow

The recommended/default cleanup setting is:

[runtime]
defer_dimension_cleanup_until_restart = true
resident_gc_backup = false
resident_retired_generation_limit = 100

With the default safe behavior:

Current generation
↓
Dimension becomes eligible for Reset
↓
Reset delay / GRACE
↓
Fresh physical generation is created
↓
Fresh generation becomes current
↓
Old generation becomes RETIRED
↓
Old generation remains present during gameplay
↓
Minecraft/server is restarted
↓
Startup GC verifies ownership and safety
↓
Old RETIRED generation is deleted

This intentionally avoids deleting an old Runtime Dimension while other mods may still hold references to it.

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⚠️ Reset Deletes Runtime Changes

If:

reset_on_empty = true

is enabled, the next Runtime generation is rebuilt from the imported source copy.

Therefore, changes made inside the Runtime Dimension can be lost on Reset, including for example:

• placed or removed blocks;
• player-built structures;
• modified terrain;
• entities;
• dropped items;
• other Runtime-only world state.

Use Reset only for Dimensions that are intended to be disposable/repeatable.

The imported source under:

WDL_custom_dimensions/<world-id>/

is kept separate and is not deleted by Runtime Reset.

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⚠️ Temporary Disk Usage Can Increase Significantly

The default cleanup policy prioritizes safety.

Old generations are kept until the next restart.

Therefore, if a large Dimension is reset repeatedly without restarting Minecraft/the server, temporary storage may look like:

current generation
+ retired generation 1
+ retired generation 2
+ retired generation 3
+ ...

For large imported worlds, this can temporarily consume several gigabytes or more.

If you use frequent automatic Reset, monitor available disk space.

Restarting Minecraft/the server allows Startup GC to process safely retired generations.

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⚠️ Live Cleanup Exists but Is Not Recommended

Advanced setting:

defer_dimension_cleanup_until_restart = false

may allow WDL to attempt live unload/delete behavior during gameplay.

This can reduce temporary disk growth, but it is not the recommended mode.

Live Dimension removal can conflict with mods that retain references to Runtime Dimensions and may cause:

• Reset failure;
• unload problems;
• crashes;
• invalid/stale references;
• mod compatibility problems;
• world/runtime data inconsistency.

For normal use, keep:

defer_dimension_cleanup_until_restart = true

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🛡️ Valkyrien Skies Safety Override

Runtime Dimension removal was found to be unsafe with the tested Valkyrien Skies environment.

WDL 1.3.0 therefore does not use the abandoned dynamic-removal approach as the normal VS Reset path.

When Valkyrien Skies is detected, WDL forces effective deferred cleanup for safety, even if the Config requests live cleanup.

The final Reset strategy is:

Generation Rotation + Resident Compatibility + Startup GC

The old physical generation may remain resident while a fresh physical generation becomes the current generation for the same logical WDL Dimension.

This avoids removing a VS-referenced Runtime Dimension during active gameplay.

Compatibility work was primarily validated against:

Valkyrien Skies 2.4.11

Future or unknown versions are not automatically guaranteed.

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🧹 Startup GC Safety

Startup GC only removes a retired physical generation after WDL can prove that it is safe to remove.

Safety checks include protection against deleting:

• the current physical generation;
• an active/recovery target;
• a live ServerLevel;
• an unproven/non-WDL Runtime path;
• conflicting recovery authority;
• unsafe/symlink-ambiguous paths.

Cleanup is performed at the whole physical-generation directory level.

Example:

dimensions/wdl/test_world_01/20260822123000/

WDL does not intentionally clean only selected pieces such as:

region/
entities/
poi/
data/

from a generation that is still considered active.

The management root:

dimensions/wdl/

is retained.

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💾 Optional Resident GC Backup

Config:

resident_gc_backup = false

Default is false.

When false:

• Startup GC still works normally;
• no new GC backup ZIP is created;
• existing old WDL backup archives are not automatically removed.

When true:

resident_gc_backup = true

WDL creates the latest successful pre-GC backup at:

WDL_backups/resident_gc/<save-id>/latest.zip

The backup is validated before deletion is authorized.

If the backup transaction fails, that startup's candidate deletion set is aborted.

Disk usage warning: enabling this option can require additional storage comparable to the size of the retired generations being archived.

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🧱 Retired Generation Safety Limit

Config:

resident_retired_generation_limit = 100

Default:

100

This is a safety/headroom limit for retired/resident generation state and rotation reservations.

Setting it to 0 prevents same-process resident rotation from using retired-generation headroom and can require restart/offline Reset progression.

This is an advanced setting and normally should be left at its default.

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🛠️ Bug Fixes, Stability, and Recovery Improvements

WDL 1.3.0 contains extensive Runtime lifecycle hardening beyond the visible new features.

Fixed stale Rotation recovery blocking newer generations

An old physical-rotation completion receipt could previously conflict with a newer Reset/current-generation authority during restart recovery.

1.3.0 now classifies old receipts before attempting obsolete filesystem recovery.

Older/superseded receipts no longer incorrectly block a newer valid generation.

Conflicting or malformed durable authority continues to fail closed instead of guessing.

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Fixed Reset GRACE state being lost across restart

A Dimension that had entered Reset GRACE and was then shut down could previously return to an incorrect idle state after restart.

Persisted safe GRACE state can now continue into restart-deferred Reset processing.

This allows:

GRACE
→ shutdown
→ restart
→ RESET_PENDING
→ offline/fresh Reset

instead of silently abandoning the scheduled Reset.

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Fixed Gate / Timed Session ordering at Reset deadline

A Gate activation at the end of Reset GRACE could previously create a Timed Session before Reset ownership was established, causing the Dimension to block its own Reset.

WDL now gives the expired Reset lifecycle priority before ordinary Gate cost, Igniter, Gate, and Timed Session mutation.

A genuinely pre-existing Timed Session can still correctly block Reset when required.

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Improved Timed Session / Forced Exit recovery

Timed Session and Forced Exit handling was hardened for:

• logout during a Timed Session;
• expiration while offline;
• login after expiration;
• PREVIOUS destination resolution;
• safe Overworld fallback;
• avoiding accidental creation/restart of another Timed Session during Forced Exit.

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Stronger physical-generation authority tracking

WDL now persists exact physical generation identity in lifecycle/recovery state.

Recovery uses the exact physical ResourceLocation instead of guessing which Runtime folder should be considered current.

Untracked or contradictory physical generations fail closed rather than being silently treated as safe.

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Logical identity preserved across physical generation rotation

Systems that should survive physical-generation replacement now operate on the stable logical WDL identity where appropriate.

This protects behavior such as:

• Gate Travel History;
• Travel Policy comparisons;
• physical Gate cooldown identity;
• Timed Session semantic identity;
• PREVIOUS return logic;
• respawn/bed handling;
• player/session state.

Internal physical IDs remain internal Runtime implementation details.

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Stronger Gate and Config validation

WDL 1.3.0 includes stricter early validation for:

• invalid Dimension definition IDs;
• namespaced Dimension definition IDs;
• explicit invalid selection_mode;
• LIST Gates without destinations;
• ambiguous physical Gate definitions.

Unsafe or ambiguous definitions fail closed rather than being silently guessed.

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🔌 Mod Compatibility Improvements

Valkyrien Skies

The earlier idea of dynamically removing an active Runtime Dimension was abandoned for the supported 1.3.0 VS path after runtime testing exposed unsafe behavior, including physics/lifecycle failures.

WDL 1.3.0 uses the safer Resident Generation Rotation architecture instead.

Test/compatibility focus:

Valkyrien Skies 2.4.11

---

Distant Horizons

Runtime Reset and Dimension lifecycle handling were hardened around Distant Horizons world/provider/database lifecycle behavior.

The compatibility work includes safer unload/reset sequencing and additional handling for stale same-process DH repository/JDBC state that could otherwise keep a Runtime world blocked after reopening a world in the same Minecraft process.

Test/compatibility focus:

Distant Horizons 3.2.0-b

Future versions may change their internal lifecycle behavior, so exact compatibility with unknown releases cannot be guaranteed automatically.

---

Forge Dynamic Level Lifecycle

WDL continues to integrate dynamically mounted Runtime Dimensions with Forge level lifecycle behavior and managed teleport handling.

The new generation architecture extends this work so fresh physical generations can be tracked without leaking physical Runtime identity into logical player-facing systems.

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⚙️ Configuration and Compatibility Changes

max_loaded_dimensions default increased

Old default:

max_loaded_dimensions = 4

New default:

max_loaded_dimensions = 8

This limit counts currently used/loaded logical WDL Dimensions.

Retired physical generations retained for compatibility cleanup are not counted as ordinary logical loaded-Dimension slots.

---

Cleanup Config key migration

Canonical 1.3.0 key:

runtime.defer_dimension_cleanup_until_restart

Legacy compatibility input:

runtime.resident_reset_compatibility

The legacy key is only used when the new canonical key is absent.

New Config files should use:

defer_dimension_cleanup_until_restart = true

---

Gate History Config key migration

Canonical key:

gate_history.max_entries

Legacy fallback:

return_history.max_entries

The current key takes priority.

---

Legacy RETURN Gate compatibility

Legacy:

gate_type = "RETURN"

can still be read for compatibility and resolves as an Overworld destination.

New Gate definitions should use the current destination architecture instead of creating new gate_type definitions.

---

Existing Config files are never destructively rewritten

WDL still does not automatically overwrite user Config.

This protects customized servers, but it is also why Config regeneration is strongly recommended for this major update.

---

📚 Documentation and Release Package Improvements

WDL 1.3.0 refreshes the complete Japanese and English public documentation set.

The release includes 20 public documents:

• 10 Japanese
• 10 English

A dedicated Examples / Play Ideas guide now contains ten copy-ready configurations covering:

1. Basic single-world Gate
2. Random LIST Gate
3. Explicit ALL random Gate
4. Rarity/weight selection
5. Timed dungeon
6. Reset-on-empty repeatable dungeon
7. Persistent adventure world
8. Inventory restriction challenge
9. One-way/layered Travel Policy
10. Multiple Gate roles with costs/cooldowns

Generated Config files now act as reference documents and clearly separate:

• ALL OPTIONS
• beginner/practical examples
• LEGACY COMPATIBILITY

Reset data-loss, disk-growth, live-cleanup, Valkyrien Skies, and backup warnings are now documented directly near the relevant settings.

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✅ Summary

WDL 1.3.0 is a major upgrade over 1.2.2.

The largest changes are:

• Runtime Reset
• timestamp Physical Generations
• Generation Rotation
• Resident compatibility mode
• Startup GC
• Timed Dimensions / Timed Sessions
• Forced Exit
• per-Dimension Environment controls
• Gate reopen cooldown
• improved Config UX
• improved recovery and diagnostics
• safer Valkyrien Skies behavior
• stronger Distant Horizons lifecycle handling
• extensive Reset/restart bug fixes
• updated JA/EN documentation and practical examples

Before upgrading an existing WDL installation

If you want to preserve the latest state of Dimensions previously played with WDL 1.2.2 or older:

1. Back up:

WDL_custom_dimensions/<dimension-id>/

1. Locate the old playable Dimension data:

<save>/dimensions/worlddimensionloader/<dimension-id>/

1. Copy the contents of the old Dimension folder into the existing:

WDL_custom_dimensions/<dimension-id>/

1. Allow matching world-data files and folders to be overwritten.

2. Do not delete the destination WDL_custom_dimensions/<dimension-id>/ folder first.

3. Confirm that a valid:

WDL_custom_dimensions/<dimension-id>/level.dat

remains present.

1. Keep the old data and backup until WDL 1.3.0 has been tested and the migrated world has been verified successfully.

Then regenerate:

config/worlddimensionloader/

so the new 1.3.0 options, defaults, comments, and safety warnings are available.

Do not delete your migration backups until the upgraded Dimensions have been confirmed to work correctly.