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Name	Modified	Size	InfoDownloads / Week
Parent folder
Flecs v4.1.5 source code.tar.gz	2026-03-15	27.7 MB	0
Flecs v4.1.5 source code.zip	2026-03-15	28.7 MB	0
README.md	2026-03-15	24.5 kB	0
Totals: 3 Items		56.5 MB	0

Highlights

New non-fragmenting hierarchy storage which significantly boosts asset hierarchy performance.
Reduced binary footprint of C++ component registration
Lots of hardening bugfixes for issues detected by the AFL fuzzer (1500 new tests since the last release!).
New math and Perlin noise functions for Flecs Script.
Added support for vector type operations in Flecs script:

:::cpp const a = Position: {10, 20} const b = Position: {1, 2} const c: a + b // {a.x + b.x, a.y + b.y}
C++ API improvements:

New function to iterate all entities in the world:

:::cpp
world.each([](flecs::entity e) {
  // ...
});

System components can now be deduced from the each() argument list:

:::cpp
world.system("Move")
  .each([](Position& p, const Velocity& v) {
    // ...
  });

Improved APIs for creating hierarchies:

:::cpp
flecs::entity p = world.entity(world, "p");

// Create child for ChildOf (fragmenting) hierarchy
flecs::entity child_a = world.entity(world, p, "a");

// Create child for Parent (non-fragmenting) hierarchy
flecs::entity child_b = world.entity(world, flecs::Parent{p}, "b");

Release notes

This version includes the following bugfixes:

[core] Fix issue where ref could return wrong value during recursive entity cleanup.
[core] Fix issue with deferred calls to modified() for DontFragment components.
[core] Fix issue where it wasn't possible to inherit from entity with Relationship trait.
[core] Fix issue with cloning entity symbols.
[core] Fix issue with removing sparse pair with recycled target.
[core] Fix issue with overriding existing exclusive relationships.
[core] Fix issue with combining relationship constraints with component disabling.
[core] Return 0 for negative indices in ecs_get_target().
[core] Fix ecs_table_get_target() bounds check to reject negative and >=count indices.
[core] Fix issue with deleting sparse component while deferring is suspended.
[core] Fix issue with using has()/get() from hooks.
[core] Fix issue where deferred setting after removing on a prefab instance could fail.
[core] Fix issues with sparse components and overriding.
[core] Fix race condition in component registration code.
[core] Fix assert when toggling component before adding it to any entity.
[core] Fix issue with removing component in one stage, and setting it in another stage.
[core] Fix issue with determining alignment of 64bit primitive types on 32bit platforms.
[core] Add Prefab to children of entity after adding Prefab.
[core] Fix issue with entity path parsing.
[core] Fix issue where creating entity from path could create cycle.
[queries] Fix issue where queries incorrectly detected if entity variables are used before table variables.
[queries] Fix assert when querying for optional module.
[queries] Fix issue with running the same cached query on multiple threads.
[queries] Fix issue with DontFragment and not terms if no entities have the DontFragment component.
[queries] Fix issue where on_group_delete was called without matching on_group_create.
[queries] Fix issue with cascade and deleting empty tables.
[queries] Fix issue where on_group_create wasn't called for default group.
[observers] Fix incorrect assert in alert builder.
[observers] Fix issue where observer was not always called for deferred set of DontFragment component.
[observers] Fix issue where observers were not always called for deferred DontFragment operations.
[observers] Fix issue where source wasn't correctly populated for optional observer term.
[observers] Fix issue where OrderedChildren OnRemove observer conflicts with cleanup logic.
[observers] Fix cr != NULL assert in observable code.
[cpp] Fix try_get_mut() methods calling get_mut(), get_mut_second() with wrong return type.
[cpp] Fix error when ECS_STRUCT sees struct with only private members.
[cpp] Fix issue with enum reflection on VS 19.44.
[meta] Fix incorrect unit prefix for Femto unit.
[meta] Fix ecs_vec_fini() type mismatch in JSON deserializer.
[meta] Fix issue in JSON serializer where wrong pair string was appended.
[meta] Fix issue where JSON serializer would insert double comma for array member with unit.
[meta] Fix issue with deserializing opaque vector with struct element type in script.
[meta] Fix issue where deserializing recycled anonymous entity into world could cause duplicates.
[meta] Fix issue with serializing named prefab instance children before instance.
[meta] Fix crash when serializing query with only ChildOf term to JSON.
[meta] Fix issue with out-of-bounds copy in meta member parsing.
[meta] Don't crash on invalid recursive type definitions.
[meta] Don't crash on invalid string assignments in meta cursor.
[meta] Don't crash on invalid reflected array/vector element types.
[script] Fix issue in script parser with Windows line endings.
[script] Fix script parser corruption when creating new expression with missing entity statement.
[script] Fix issue where adding multiple tags inside of new expression would fail.
[script] Fix issue with resolving enum type in binary expressions.
[script] Fix script ambiguity between functions and pair syntax.
[script] Fix issues with tokenizing numbers that use scientific notation.
[script] Fix issue where opaque entity types could not be set from scripts.
[script] Make sure that components with on_replace hooks can be assigned from scripts.
[script] Fix crash when writing past the array bounds in initializers.
[script] Fix memory leaks on script parsing errors.
[script] Fix memory leaks when parsing invalid char/string literals.
[script] Fix issues where script error would not throw error message on the command line.
[script] Fix potential invalid free when copying script templates.
[script] Don't crash on deeply nested script scopes.
[script] Don't crash on missing entity for variable component evaluation.
[script] Fix double-free in script template using cleanup.
[script] Fix issue with dereferencing code pointer after parsing invalid comment.
[script] Improve robustness of whitespace/comment parsing.
[script] Improve robustness of script number parsing.
[script] Improve robustness of script comment parsing.
[script] Improve robustness of script visitor depth handling.
[script] Improve robustness of script recursion depth handling.
[script] Harden tokenizer bounds checks for malformed script tokens.
[script] Handle trailing escape in script identifiers.
[rest] Fix issue where emscripten build fails without REST addon.
[rest] Remove duplicate line in rest addon (thanks @ludolpif!).
[rest] Fix issue where build info wasn't accessible for REST API.
[rest] Fix crash when using stats module in low footprint mode.
[http] Bugfixes for HTTP server and strbuf.
[os_api] Fix issue with printing stack trace on Windows.
[os_api] Fix potential crashes where string variables were passed to format string arguments of assert macros.
[os_api] Fix crash in assert if entity name with mismatching template delimiters is also an invalid format string.

This version includes the following improvements:

[core] New non-fragmenting hierarchy storage.
[core] Detect cycles in prefab instantiation code.
[core] Don't allocate diff builder in flecs_defer_end() if there are no batched commands.
[core] Don't add unnecessary symbols to builtin tags and entities.
[core] Prevent unused allocator chunks by not recycling table columns.
[core] Use OS allocator for allocating table component/column map.
[core] Refactor duplicated hook logic to new type_info API.
[core] Enforce that hooks cannot be called if it has a corresponding INVALID flag set.
[core] Remove doc components from core entities.
[core] Remove Private tag.
[core] Allow ecs_get_target() to be used with value pairs.
[cpp] Call init_builtin_components() at the end of world reset (thanks @60k41p!).
[cpp] Implement world.each([](flecs::entity e) {}) method for iterating all entities.
[cpp] Infer system type from function argument list passed to each().
[cpp] Reduce the binary overhead of component registration (1).
[cpp] Reduce the binary overhead of component registration (2).
[cpp] Update more parts of the API to C++17.
[cpp] Add component tuple getters (thanks @SimonPiCarter!).
[cpp] Add const qualifier to more C++ methods.
[cpp] Add convenience functions for creating hierarchies.
[queries] Add ecs_query_get_groups() function.
[queries] Make query_base constructor const (thanks @Reddy-dev!).
[queries] Allow components to be referred to by typename in query DSL.
[observers] Allow for creation of observers without creating entities.
[systems] Add validation check on whether system .callback or .run is set.
[systems] Add dedicated phase member to ecs_system_desc_t.
[systems] Implement set_group() for systems.
[meta] Implement cycle detector for reflection framework.
[meta] Prevent modifying reflection data after component has been used.
[meta] Update meta utils macros so types can be used with forward declarations.
[meta] Don't create member entities for ECS_STRUCT definitions.
[meta] Don't require creating entities for struct members.
[meta] Don't create member entities when using C++ component::member API.
[meta] Skip recursive runtime type struct member hooks.
[script] Add perlin noise and other math functions to Flecs script.
[script] Implement binary vector operations.
[script] Add dot(), normalize(), length(), length_sq() to script math.
[script] Reject singleton kind on non-singleton script entities.
[rest] Implement type_info endpoint.
[journal] Fix issue where journaling output would write ecs_new_id() instead of ecs_new().
[journal] Add support for tracing value pairs.
[journal] Add operation counter to journaling traces, API for getting counter.
[stats] Add prefab child indices to memory stats, cleanup table memory stats.
[stats] Don't automatically import the units addon when importing stats.
[docs] Add missing comments to Flecs headers.
[docs] Fix incorrect comments in term builder header.
[docs] Fix API doc comments for type_index()/column_index().
[docs] EntitiesComponents.md fixes (thanks @ludolpif!).
[docs] Fix component inheritance example in query manual.
[docs] Update examples in Hierarchy manual to use new API.
[docs] Update outdated example in relationship manual.
[docs] New Hierarchy manual.
[ci] Prevent CI from triggering twice when creating a PR.
[ci] Remove clang 11/12 from CI.

Breaking changes:

[core] delete_all() and remove_all() no longer affect prefab entiites
[meta] Registering reflection data for structs no longer by default creates entities for members
[meta] Modifying reflection data for runtime types is no longer allowed after the type has been instantiated