Molang: the language, what vanilla uses server-side, and how to implement it in TypeScript

Scope: Mojang's Molang specification, the subset the vanilla Bedrock behavior pack uses on the server, the semantics an evaluator must match, how entity filters differ, a review of existing implementations, and design input for a TypeScript evaluator. Researched 2026-10-24 against MicrosoftDocs/minecraft-creator at 4432fb62a8e0ce5c785bd2bf02a6f981dcffbbe8 (synced 2026-10-20), Mojang's engine-generated documentation/Molang.html in Mojang/bedrock-samples tag v1.26.50.4 (46ba6ea985fb5a92d79a9419198f10dda14c199d), the BDS 1.26.51.1 behavior packs and definitions/ described in bedrock-data-extraction.md, and the source of the implementations in section 5 at pinned commits. Every claim names the source that owns it. Nothing in this note was executed from the third-party libraries; their behavior is read from source.

Summary

• Two Mojang texts describe the language. The Learn pages (creator/Documents/molang/syntax-guide.md, MolangReference/.../QueryFunctions.md, MathFunctions.md) are the maintained reference; the engine-generated documentation/Molang.html in bedrock-samples is the only one with the operator precedence table and lists 13 more queries (deprecated or internal ones the Learn pages dropped).
• Molang is case-insensitive except inside strings. Every value is a float; booleans are 0.0 and 1.0; errors (division by zero, missing variables, null references) evaluate to 0.0 and raise a content error in development builds. Strings support only == and !=.
• The vanilla behavior pack composed from the 56 BDS layers plus the server-root definitions/ contains 537 Molang strings (82 distinct expressions) in 331 files. They use 35 distinct identifiers: 21 query.*, 7 math.*, 6 variable.*, 1 context.*. Loot tables, trade tables, spawn rules and recipes contain none.
• Every server-side vanilla expression is a single statement. None uses ;, return, loop, for_each, ??, temp., arrays or structs. One pattern uses -> (context.other->query.remaining_durability in the seven spear items) and one uses this (query.anger_level(this) in the warden).
• Feature rules and features hold 342 of the 537 strings: query.heightmap, query.above_top_solid, query.noise, query.has_biome_tag, query.any_tag, math.random, and the engine-supplied variable.worldx, worldz, originx, originz, is_legacy. The docs say x, y and z are "evaluated each iteration" and scatter_chance once.
• Of the 306 queries on the Learn index, vanilla parity needs 21 server-side today. 66 are render or client-session queries. Mojang labels four as server side only (anger_level, scoreboard, server_memory_tier, had_component_group) and 13 as client only.
• Precedence rules are versioned by the containing pack's min_engine_version: ternary associativity changed at 1.18.10, && over || and comparison over equality at 1.18.20. 39 vanilla expressions live in layers older than 1.18.20, all of them single-operator; the five expressions that mix &&, || or nest ?: are fully parenthesized, so both rule sets agree on vanilla.
• Filters (test, subject, operator, value, all_of, any_of, none_of) are a separate JSON predicate system with 108 documented tests. Filters never contain Molang and Molang never contains filters. Entity properties are where they meet: Molang writes them through set_property, and both systems read them.
• Neither JavaScript library should be a dependency. Both bridge-core/molang (TypeScript, MIT) and JannisX11/molangjs (JavaScript, MIT) bind || tighter than &&, which is the pre-1.18.20 rule; bridge-core also misnames math.lerprotate, lacks math.sign, copy_sign, inverse_lerp and the 30 easing functions, and loops forever in math.die_roll; molangjs lowercases string contents, strips whitespace inside strings, and has no ->, for_each, arrays or structs. Neither has a version switch.
• Write a small package: Pratt parser, AST compiled once at pack load into closures over a typed scope, a query registry with declared contexts (entity, block, item, placement, world), unknown identifiers reported at load and evaluated as 0.0 at run time as vanilla does, and a version selected from the pack manifest.

1. The Molang specification

Sources

Source	Pin	What it contributes
creator/Documents/molang/syntax-guide.md (Learn: molang/syntax-guide)	commit 4432fb62, ms.date 08/13/2025	Keywords, values, variables, aliases, structs, strings, scopes, conditionals, loop, break, continue, ??, versioned changes. No precedence table.
creator/Documents/molang/introduction.md, practical-molang.md	same	Tutorials; the only Learn text on render-controller arrays.
creator/Reference/Content/MolangReference/Examples/MolangConcepts/QueryFunctions.md plus 306 subpages	same, ms.date 02/11/2025	Query index with one-line meanings; subpages add format-version notes.
.../MathFunctions.md plus 61 subpages	same	Math function index.
documentation/Molang.html in Mojang/bedrock-samples	v1.26.50.4	Engine-generated. Has "Operator Precedence", ->, for_each, render-controller arrays, 319 queries with "Available on the Server only" or "Client (Resource Packs) only" labels, and a versioned-changes row for 1.21.100 the Learn page lacks.
creator/Documents/IntroductionToEntityProperties.md	same commit	Molang in property defaults and set_property, range clamping, deferred application, query.property errors.

bedrock.dev republishes the generated HTML (arexon/nolana's README links bedrock.dev/docs/stable/Molang); this note reads the bedrock-samples copy, which Mojang publishes.

Lexical structure

From Molang.html "Lexical Structure" and the syntax guide: C-like syntax; an expression is one value or calculation, or several sub-expressions. A simple expression has no ; and returns its value. A complex expression terminates every statement with ;, including the last, and "evaluates to 0.0 unless there is a return statement". The syntax guide: "If you leave off the return statement, the return value will be 0.0". bridge-core's test file records the consequence: return 1 without ; evaluates to 0 and return 1; to 1 ("Your typical Minecraft quirk", __tests__/tests.ts line 17).

"All things in Molang are case-insensitive, with the exception of strings, which maintain the case provided." Vanilla relies on this: Math.Random(1,3), Math.Min(...) and Math.die_roll(...) appear in entity files next to lowercase math.clamp. Number literals accept a trailing f (0.5f), shown in bridge-core's and molangjs's tests and in vanilla's query.main_hand_item_use_duration > 0.0f (attachables, client side).

Keywords

The syntax guide: "All identifiers not in a scope listed below are reserved for future use."

Keyword	Meaning (Mojang's wording, shortened)
1.23	Numerical constant
! || && < <= >= > == !=	Logical operators
* / + -	Basic math operators
( )	Evaluation order
{ }	Execution scope
??	Null coalescing, "for handling missing variables or stale actor references"
geometry., material., texture.	References to resources named in the client entity definition
math.	Math functions
query.	"Access to an entity's properties"
variable.	Read/write storage on an actor
temp.	Read/write temporary storage
context.	Read-only storage "provided by the game in certain scenarios"
A ? B	Binary conditional
A ? B : C	Ternary conditional
this	"The current value that this expression will ultimately write to (context specific)"
return	Evaluate the following statement, stop, return it
->	Arrow operator, "for accessing data from a different entity"
loop, for_each, break, continue	Loops
[ ]	Array access

Aliases: c. for context., q. for query., t. for temp., v. for variable.; "left and right sides function identically" and may be mixed in one expression.

Operator precedence

Reproduced from Molang.html "Operator Precedence": "Operators that are higher in this table are evaluated first, while operators on the same row are evaluated with the same priority. When operators have the same priority, they are evaluated left-to-right, except for the Ternary conditional operator, which is evaluated right-to-left. ... This should match the behavior of C or C++."

Rank	Group	Operators	Note
1 (highest)	Logical not	!
2	Multiplication and division	* /
3	Addition and subtraction	+ -
4	Comparisons	< <= > >=	Versioned (1.18.20)
5	Equality	== !=	Versioned (1.18.20)
6	Logical and	&&	Versioned (1.18.20)
7	Logical or	||	Versioned (1.18.20)
8	Ternary conditional	? :	Right to left; versioned (1.18.10)
9 (lowest)	Null coalescing	??

The table omits unary minus, assignment =, function call, -> and [ ]. The docs give no rank for them; the only statement is C/C++ likeness. Section 6 proposes the ranks an implementation should use.

Values

From Molang.html "Values" and the syntax guide: "All numerical values are floats." Booleans "are converted and stored as a float value of either 0.0 or 1.0". "For boolean tests, a float value equivalent to 0.0 is false, and anything not equal to 0.0 is true." "For array indices, floats are C-style-cast to ints, and clamped at zero for negative values or wrapped by the array size for large values." "Errors (such as divide by zero, missing variables, null references, etc) generally return a value of 0.0." Other types: Geometry, Texture, Material, Actor Reference, Actor Reference Array, String, Struct.

Variables

Three lifetimes (syntax guide "Variables"):

• temp.: "valid for the scope they are defined in, as per C rules. For performance reasons their lifetime is global to the current expression execution and may return a valid value outside of the outermost scope they are defined in".
• variable.: "store their value on the entity for the lifetime of that entity. Note that these are currently not saved, so quitting and reloading the world will re-initialize these."
• context.: "read-only, defined by Minecraft itself rather than your code, and valid for the expression they are run on. Details on what variables are in each will be available in the documentation of the area where that Molang expression exists".

Public variables: another entity may read a variable only if the owning client entity definition lists it under scripts.variables as "public". This is a resource-pack feature.

Structs, strings, this

Structs "are implicitly defined by usage" (v.location.x = 1;), nest arbitrarily, and can be copied across ->. Strings use single quotes, cannot contain ' ("no support for escape characters"), and "String operations only support == and != at this time". this is the value the expression writes to; vanilla's server-side use is query.anger_level(this), where this is the entity.

Conditionals, scopes and loops

A ? B runs B only when A is true; A ? B : C returns B or C. { } groups statements. loop(count, expression): "The maximum loop counter is 1024 for safety reasons." for_each(variable, array, expression) iterates an actor array such as the result of query.get_nearby_entities (the HTML example; that query is not on either index, so it is an undocumented or removed query). break "exits the innermost active loop"; continue "skips to the next iteration", "currently supported in loop and for_each".

Arrow and null coalescing

-> (HTML "Arrow Operator"): "in the case where the left-hand side of the -> operator has an error (value is null, the entity was killed previously, or some other issue), the expression will not evaluate the right-hand side and will return 0."

?? (syntax guide): "Normally, if your Molang expression references a variable that hasn't been defined yet, your code will stop with a content error." a ?? b returns a if it resolves, else b; it works for variable., temp. and context. holding numbers or entity references "but not resources such as materials, textures, or geometries". "The standing rule of thumb in Molang is that if something would error or be a bad value, it is converted to 0.0, and generally throws a content error on screen in non-published builds."

Arrays and resources

Render controllers declare array.name lists of textures, materials or geometries and index them with index = max(0, expression_result) % array_size (HTML "Array Expressions"). Resource expressions must return one resource of the right type. Animations and animation controllers "have access to everything in the language except material, texture, and geometry types". All of this is client only; the server never sees geometry., material., texture. or array..

Math functions

61 functions, identical lists in MathFunctions.md and Molang.html (diffed). Descriptions are Mojang's; "Doc gap" marks what neither text specifies.

Function	Mojang's semantics	Doc gap
math.abs(v)	Absolute value
math.acos(v), math.asin(v), math.atan(v)	Inverse trig	Result unit not stated; sin/cos take degrees, so degrees is the consistent reading. Both JS libraries return degrees.
math.atan2(y, x)	"arctan of y/x. NOTE: the order of arguments!"	Unit as above
math.ceil(v), math.floor(v)	Round up / down to nearest integral
math.clamp(v, min, max)	Clamp inclusive	Behavior when min > max
math.copy_sign(A, B)	A with the sign of B	Sign of zero
math.cos(v), math.sin(v)	"Cosine (in degrees) of value", "Sine (in degrees) of value"
math.die_roll(num, low, high)	Sum of num random floats in [low, high]; "not integers like normal dice"	Rounding of a fractional num; vanilla passes query.equipment_count, an integer
math.die_roll_integer(num, low, high)	Sum of num random integers in [low, high]
math.exp(v)	e to the power v
math.hermite_blend(t)	3t^2 - 2t^3; "works best in the range [0, 1]"
math.inverse_lerp(start, end, v)	Normalized progress of v between start and end	Format version 1.21.120 or later
math.lerp(a, b, t)	a + (b - a) * t with t "in the range [0, 1]"	Whether t is clamped (bridge-core clamps, molangjs does not)
math.lerprotate(a, b, t)	Interpolate "around a circle in the shortest direction from a degrees to b degrees"
math.ln(v)	Natural logarithm
math.max(A, B), math.min(A, B)	Highest / lowest of two	Only two arguments are documented
math.min_angle(v)	"Minimize angle magnitude (in degrees) into the range [-180, 180)"
math.mod(v, d)	"Return the remainder of value / denominator"	Sign of the result for negative operands. C fmod keeps the dividend's sign; both JS libraries use %, which does the same.
math.pi	Float pi; takes no parentheses
math.pow(base, exp)	base to the exp power
math.random(low, high)	"Random value between low and high inclusive"	Seeding; the docs say nothing, so each evaluation draws fresh
math.random_integer(low, high)	"Random integer value between low and high inclusive"	Distribution of the endpoints (bridge-core rounds a float, which halves the odds of the endpoints; molangjs draws uniformly)
math.round(v)	Nearest integral	Half-way rounding
math.sign(v)	"Returns 1 if value is positive, -1 otherwise"	Zero returns -1 by this wording
math.sqrt(v)	Square root
math.trunc(v)	Round toward zero
math.ease_in_*, math.ease_out_*, math.ease_in_out_* for back, bounce, circ, cubic, elastic, expo, quad, quart, quint, sine (30 functions, (start, end, 0_to_1))	Output goes from start to end along the named curve	Format version 1.21.120 or later; exact coefficients unstated. molangjs implements them from the common Penner formulas (src/easing.js).

Vanilla server-side files use seven: math.random (116, nearly all as Math.Random), math.ceil (4), math.clamp (3), math.die_roll (3), math.trunc (3), math.max (1), math.min (1).

Versioned changes

Syntax guide "Versioned changes": "Molang uses the min_engine_version from the manifest.json of the resource or behavior pack that contains each Molang expression to determine which version of the rules to apply. ... Molang change versions apply to each expression separately, so it's possible to have different versions active if multiple packs are loaded." Any change "with a version less than or equal to that version number will be in effect."

Pack min_engine_version	Change (Mojang's wording, shortened)	BDS MolangVersion enumerator (EndstoneMC/endstone src/bedrock/shared_types/molang/molang_version.h at bb0475b6)
1.17.0	Versioning introduced	Initial = 1
1.17.30	query.item_remaining_use_duration ticks to seconds fixed; normalization goes 1 to 0	FixedItemRemainingUseDurationQuery = 2
1.17.40	Content errors for invalid expressions such as 'text' + 1	ExpressionErrorMessages = 3
1.17.40	Errors for too many operators (1+(2 3)) and unknown tokens	UnexpectedOperatorErrors = 4
1.18.10	Ternary associativity: A ? B : C ? D : E is A ? B : (C ? D : E), previously (A ? B : C) ? D : E	ConditionalOperatorAssociativity = 5
1.18.20	&& before ||; comparison before equality. HTML example: A && B || C is (A && B) || C "instead of A && (B || C)"	ComparisonAndLogicalOperatorPrecedence = 6
1.19.60	Division by a dynamically determined negative variable no longer divides by its absolute value	DivideByNegativeValue = 7
1.20.0	query.cape_flap_amount uses body rotation	FixedCapeFlapAmountQuery = 8
1.20.10	block_property renamed block_state, has_block_property renamed has_block_state	QueryBlockPropertyRenamedToState = 9
1.20.40	Old names deprecated	DeprecateOldBlockQueryNames = 10
1.20.50	HTML: dash_cooldown_progress removed; is_scenting, is_rising, is_feelingHappy removed, use timer_flag_1..3. The Learn page says block_property is removed here instead; the two texts disagree.	DeprecatedSnifferAndCamelQueries = 11
1.20.70	Surface particle queries treat leaves as supporting blocks	LeafSupportingInFirstSolidBlockBelow = 12
1.21.100 (HTML only)	query.is_carrying_block works for all entities and returns 1.0 for air	CarryingBlockQueryAllActors = 13; Latest = 13, HardcodedMolang = 13

The enum also has BeforeVersioning = 0, which is what a pack with min_engine_version below 1.17.0 gets. The base vanilla layer declares [1, 13, 0]; vanilla_1.17.0 and later declare their own version, so a composed vanilla pack carries expressions under 0, 1, 5, 6 and 13 at once. Section 2 shows this does not change any vanilla result.

2. Queries

The documented lists

The Learn index (QueryFunctions.md) has 306 distinct query.* names. Molang.html has 319; the 13 extra are block_property, has_block_property, cardinal_block_face_placed_on, dash_cooldown_progress, debug_output, get_equipped_item_name, get_name, owner_identifier, is_feeling_happy, lod_index, overlay_alpha, texture_frame_index, unhappy_counter, all deprecated, removed or internal. Nothing is on the Learn index and missing from the HTML. query.is_daytime and query.get_default_bonemeal_block appear in neither.

Mojang labels six queries by side in the HTML text: anger_level "Available on the Server only"; scoreboard "Available only with behavior packs"; server_memory_tier "Available on the server side (Behavior Packs) only"; had_component_group "Usable only in behavior packs when determining the default value for an entity's Property"; is_local_player "Always returns 0.0 if used in a behavior pack"; last_hit_by_player "If called by the client always returns 0.0". Thirteen carry "Available on the Client (Resource Packs) only": client_max_render_distance, client_memory_tier, get_pack_setting, graphics_mode_is_any, heartbeat_phase, is_pack_setting_enabled, is_pack_setting_selected, last_input_mode_is_any, surface_particle_color, surface_particle_texture_coordinate, surface_particle_texture_size, time_since_last_vibration_detection, touch_only_affects_hotbar. Every other query is documented without a side; the "context" column in the table at the end of this section is this note's classification from each description.

What vanilla uses server-side

Method: compose the 56 vanilla* layers (later layer wins by member name) into /tmp/bds-research-molang/composed/vanilla_bp, add the server-root definitions/features, definitions/feature_rules and definitions/spawn_groups, then walk every JSON string value for query., q., math., variable., v., temp., t., context., c. identifiers, case-insensitively. 15 of the 3524 files are unreadable because they are \x7fMCB binaries (23 items, all trading, shapes, item catalog); the same files from bedrock-samples v1.26.50.4 were scanned as plain JSON and add nothing new (items: context.other, query.max_durability, query.remaining_durability, query.all_tags; trading, loot tables, spawn rules, recipes: zero expressions). Attachables and persona files under definitions/ are client content and are excluded.

Result: 537 strings, 82 distinct expressions, 331 files, 35 identifiers.

Count	Identifier	Where, with an example
176	variable.worldx	Feature rule distribution.x/y/z and y.extent: query.heightmap(variable.worldx, variable.worldz)
176	variable.worldz	As above
162	query.heightmap	129 rules set y to it, 37 use it inside y.extent; .../mangrove_swamp_mangrove_tree_feature.json: math.max(query.above_top_solid(variable.worldx, variable.worldz), query.heightmap(variable.worldx, variable.worldz) - 4)
116	math.random	100 in minecraft:experience_reward (on_bred: "Math.Random(1,7)", on_death: "query.last_hit_by_player ? Math.Random(1,3) : 0"), 13 in feature rule and feature iterations ("Math.Random(48, 96)" dripstone cluster, "Math.Random(204, 250)" sculk vein, "Math.Random(104, 157)" glow lichen), 2 in eyeblossom_feature_rules.json x and z ("math.random(-8, 8)"), 1 in breeze.json reflect_projectiles.azimuth_angle ("180.0 + Math.random(-20.0, 20.0)")
113	query.any_tag	Block filters in features: may_replace, may_grow_on, may_grow_through, block_intersection.block_allowlist ("query.any_tag('minecraft:leaves')", "query.any_tag('dirt', 'sand', 'gravel')"); navigation.walk.blocks_to_avoid in breeze.json ("query.any_tag('trapdoors')")
89	query.last_hit_by_player	experience_reward.on_death in 86 files (the six root-level copies included)
28	variable.is_legacy	Feature rule scatter_chance and iterations: "variable.is_legacy ? 0.0 : 100.0", "variable.is_legacy == 0.0 ? 1 : 0"
24	query.equipment_count	on_death: "query.last_hit_by_player ? 5 + (query.equipment_count * Math.Random(1,3)) : 0" (bogged, skeletons, zombies)
16	query.block_state	The 9 permutations[].condition strings of shelf_mushroom_block.json: "query.block_state('growth') == 1 && query.block_state('minecraft:cardinal_direction') == 'east'"
15	query.is_baby	ambient_sound_interval.event_names[].condition, behavior.eat_block.success_chance ("query.is_baby ? 0.02 : 0.001", sheep), inside on_death
15	query.noise	Feature rule iterations and scatter_chance: "math.ceil((query.noise(variable.originx / 80.0, variable.originz / 80.0) + 0.3) * 160.0)" (bamboo), "(query.noise((variable.originx + 8) / 200.0, (variable.originz + 8) / 200.0) < -0.8) ? 5 : 10"
15	variable.originx, variable.originz (15 each)	Only with query.noise
14	query.above_top_solid	Feature rule y: "query.above_top_solid(variable.worldx, variable.worldz)" (grove pine, mangrove)
9	query.has_any_family	rideable.seats[].rotate_rider_by in boat and chest boat: "query.has_any_family('blaze', 'creeper', ..., 'happy_ghast') ? -90 : 0"
9	query.has_biome_tag	definitions/features/optional_beehive_feature.json scatter_chance: a nested ternary over has_biome_tag('bee_habitat'), 'plains', 'flower_forest', 'birch_forest'... returning 5.0, 3.0 or smaller percentages
7	context.other	Spear items repairable.repair_items[].repair_amount: "context.other->query.remaining_durability"
7	query.all_tags	behavior.pickup_items.excluded_items[].tags ("q.all_tags('minecraft:is_spear')"), behavior.tempt.items[].tags, repairable.repair_items[].items[].tags
7	query.head_is_in_water	ambient_sound_interval conditions (axolotl, drowned)
7	query.max_durability	Spear repair_amount: "query.max_durability * 0.25"
7	query.remaining_durability	With context.other above
5	query.anger_level	warden.json: anger_level.on_increase_sounds[].condition "query.anger_level(this) >= 40", ambient_sound_interval "query.anger_level(this) >= 80", heartbeat.interval "2.0 - math.clamp(query.anger_level / 80 * 1.5, 0, 1.5)"
4	math.ceil	Bamboo iterations
4	variable.sea_level	hell.biome.json surface_material_adjustments.adjustments[].height_range: "variable.sea_level - 3", "variable.sea_level + 2"
3	math.clamp	Warden heartbeat; creaking set_property; bamboo
3	math.die_roll	on_death of pillager, vindicator, witch: "query.last_hit_by_player ? (query.is_baby ? 12 : 5) + (Math.die_roll(query.equipment_count,1,3)) : 0"
3	math.trunc	definitions/feature_rules/bamboo_jungle_after_surface_bamboo_feature.json: "math.clamp(math.trunc(math.ceil((query.noise(math.trunc(variable.originx / 80), math.trunc(variable.originz / 80)) + 0.3) * 160)), 15, 160)"
2	query.is_using_item	Allay ambient sound conditions
2	query.variant	on_death: "query.last_hit_by_player ? query.variant : 0" (magma cube, slime)
1	math.max	Mangrove y above
1	math.min	player.json on_death: "Math.Min(query.player_level * 7, 100)"
1	query.had_component_group	bee.json description.properties.minecraft:has_nectar.default: "query.had_component_group('has_nectar')"
1	query.is_on_ground	Breeze ambient sound "!query.is_on_ground"
1	query.player_level	Player on_death above
1	query.property	creaking.json event set_property: "math.clamp(query.property('minecraft:creaking_swaying_ticks') + 1, 0, 6)"

Occurrences by folder: feature_rules 158 in 130 files, entities 157 in 82, features 121 in 56, definitions/feature_rules 62 in 48, items 16 in 7, blocks 9 in 1, biomes 4 in 1, definitions/features 1 in 1, plus 9 in six entity files that sit at the root of layers vanilla_1.20.10 and vanilla_1.19.60 (donkey, horse, llama, mule, trader_llama, tropicalfish) rather than under entities/; whether the engine reads those is not verified.

By pack layer, the Molang-bearing files come from vanilla_1.26.50 (80), vanilla_1.21.60 (72), definitions (48), vanilla_1.26.30 (26), vanilla_1.18.0 (23), and smaller numbers from 17 other layers; the base vanilla layer contributes one file (hell.biome.json). 39 strings live in layers with min_engine_version below 1.18.20 (vanilla 4, vanilla_1.17.0 1, vanilla_1.18.0 25, vanilla_1.18.10 9); each is a single operator or a bare query, so the pre-1.18.20 rules cannot change them. The five expressions that mix && with ||, nest ?:, or combine == with >= (bee habitat, three bamboo rules, the pillager family on_death) are fully parenthesized. The definitions/ files have no manifest; which version the engine applies to them is an open question.

Fields that carry Molang, by JSON path (component groups and feature types normalized): feature rule distribution.y 129, distribution.y.extent[] 37, distribution.iterations 28, distribution.scatter_chance 24, legacy root-level y 9, scatter_chance 1 and iterations 1 (pre-1.21.20 format), distribution.x 1, distribution.z 1; feature may_replace[].tags 36, may_grow_on[].tags 32, may_grow_through[].tags 31, constraints.block_intersection.block_allowlist[].tags 10, base_cluster.may_replace[].tags 2; entity experience_reward.on_death 90 and on_bred 33, ambient_sound_interval.event_names[].condition 20, rideable.seats[].rotate_rider_by 9, behavior.pickup_items.excluded_items[].tags 5, anger_level.on_increase_sounds[].condition 2, reflect_projectiles.azimuth_angle 1, navigation.walk.blocks_to_avoid[].tags 1, heartbeat.interval 1, behavior.eat_block.success_chance 1, behavior.tempt.items[].tags 1, event set_property 1, description.properties.*.default 1; item repairable.repair_items[].repair_amount 14 and .items[].tags 2; block permutations[].condition 9; biome surface_material_adjustments.adjustments[].height_range[] 4. iterations is documented as "Integer number" yet 13 vanilla rules give it Math.Random(a, b), a float; how the engine rounds it is unstated.

The docs confirm these fields are Molang: minecraft:experience_reward on_bred and on_death are typed "Molang" (EntityComponents/minecraftComponent_experience_reward.md); ambient_sound_interval.event_names[].condition is "The condition that must be satisfied to select the given ambient sound"; feature_rule_definition.md says iterations "Can be an integer or a Molang expression", scatter_chance "(0.0 to 1.0 or Molang expression). If not triggered, no iterations will run", and x, y, z "(evaluated each iteration). Can be an integer, range object, or Molang expression"; minecraft_scatter_feature.md says "The scatter_chance check happens once, so either all placements will run or none will"; BlockStatesAndPermutations.md says a permutation condition is "A Molang expression that evaluates to true or false ... you are limited to using one Molang query: query.block_state()"; minecraft:repairable repair_amount accepts a "Legacy Molang Expression" object with expression and version (an explicit per-expression version override, also offered for on_bred and on_death); minecraft_conditional_list.md types feature condition as "Molang". The tree-feature may_replace, may_grow_on and may_grow_through pages type the fields only as "Array of strings"; the 1.26.50 changelog cited in the extraction note describes the query.any_tag('minecraft:leaves') form. variable.worldx, worldz, originx, originz, is_legacy and sea_level are documented nowhere in the reference; variable.worldx and worldz appear only in the feature tutorials (Documents/FeaturesTutorial_1.md, world-generation.md).

What the client uses, for contrast

The same scan over bedrock-samples v1.26.50.4 resource_pack/ (animations, animation controllers, render controllers, client entities, attachables, particles; 1014 files) finds 5602 strings and 908 identifiers: 169 query.*, 22 math.*, 695 variable.*, 18 temp.*, 4 context.*. The most used are query.life_time (359), math.cos (350), variable.particle_random_1 (343), query.is_baby (294), math.sin (289), query.modified_move_speed (269). Only six queries are used on both sides: equipment_count, is_baby, is_on_ground, is_using_item, property, variant. The server-side subset is 21 queries; the client subset is 169 and needs temp., ->, arrays, structs and resources.

The query list

Context is this note's reading of each description: entity (needs an entity; the server has these entities), entity, server only and server only (Mojang's labels), item (needs an item stack), block (needs a block and its permutation), placement (feature placement position), world (level state), tags (item or block tag test), pure (no game state), client (render, camera, animation, particle, input or pack-setting state the server never has). "BP" marks use in the vanilla behavior pack or definitions/; "RP" marks use in the vanilla resource pack. Meanings are the first sentence of the Learn description.

Query	Context	Meaning	Vanilla use
query.above_top_solid	placement	Returns the height of the block immediately above the highest solid block at the input (x,z) position.	BP
query.actor_count	client	Returns the number of entities (actors) rendered in the last frame.
query.all	pure	Evaluates the first argument, then returns 1.0 if all of the following arguments evaluate to the same value as the first.
query.all_animations_finished	client	Returns 1.0 if all animations in the current animation controller state have played through at least once, else it returns 0.0.	RP
query.all_tags	tags	Returns if the item or block has all of the tags specified.	BP
query.anger_level	entity, server only	Mojang: server only. Returns the anger level of the entity [0,n).	BP
query.anim_time	client	Returns the time in seconds since the current animation started, else 0.0 if not called within an animation.	RP
query.any	pure	Evaluates the first argument, then returns 1.0 if any of the following arguments evaluate to the same value as the first.
query.any_animation_finished	client	Returns 1.0 if any animation in the current animation controller state has played through at least once, else it returns 0.0.	RP
query.any_tag	tags	Returns if the item or block has any of the tags specified.	BP
query.approx_eq	pure	Returns 1.0 if all of the arguments are within the smallest unit of measurement possible for the computer running this query of each other, else 0.0.
query.armor_color_slot	entity	Takes the armor slot index as a parameter, and returns the color of the armor in the requested slot.	RP
query.armor_damage_slot	entity	Takes the armor slot index as a parameter, and returns the damage value of the requested slot.
query.armor_material_slot	entity	Takes the armor slot index as a parameter, and returns the armor material type in the requested armor slot.
query.armor_texture_slot	client	Takes the armor slot index as a parameter, and returns the texture type of the requested slot.	RP
query.average_frame_time	client	Returns the time in seconds of the average frame time over the last 'n' frames.
query.base_swing_duration	client	Returns the duration of the mob's swing/attack animation, determined by the carried item and unmodified by effects applied on the mob.
query.blocking	entity	Returns 1.0 if the entity is blocking, else it returns 0.0.	RP
query.block_face	block	Returns the block face for this (only valid for certain triggers such as placing blocks, or interacting with block) (Down=0.0, Up=1.0, North=2.0, S...
query.block_has_all_tags	block	Takes a world-origin-relative position and one or more tag names, and returns either 0 or 1 based on if the block at that position has all of the t...
query.block_has_any_tag	block	Takes a world-origin-relative position and one or more tag names, and returns either 0 or 1 based on if the block at that position has any of the t...
query.block_neighbor_has_all_tags	block	Takes a block-relative position and one or more tag names, and returns either 0 or 1 based on if the block at that position has all of the tags pro...
query.block_neighbor_has_any_tag	block	Takes a block-relative position and one or more tag names, and returns either 0 or 1 based on if the block at that position has any of the tags pro...
query.block_state	block	Returns the value of the associated block's block state.	BP
query.body_x_rotation	entity	Returns the body pitch rotation if called on an entity, else it returns 0.0.	RP
query.body_y_rotation	entity	Returns the body yaw rotation if called on an entity, else it returns 0.0.	RP
query.bone_aabb	client	Returns the axis aligned bounding box of a bone as a structure with members '.min', '.max', along with '.x', '.y', and '.z' values for each.	RP
query.bone_orientation_matrix	client	Returns the bone orientation (as a matrix) of the desired bone provided it exists in the queryable geometry of the mob, else this returns the ident...
query.bone_orientation_trs	client	Returns the bone orientation matrix decomposed into the component translation/rotation/scale (TRS) parts of the desired bone provided it exists in...
query.bone_origin	client	Returns the initial (from the .geo) pivot of a bone as a structure with members '.x', '.y', and '.z'.	RP
query.bone_rotation	client	Returns the initial (from the .geo) rotation of a bone as a structure with members '.x', '.y', and '.z' in degrees.	RP
query.camera_distance_range_lerp	client	Takes two distances (any order) and return a number from 0 to 1 based on the camera distance between the two ranges clamped to that range.
query.camera_rotation	client	Returns the rotation of the camera.	RP
query.can_climb	entity	Returns 1.0 if the entity can climb, else it returns 0.0.
query.can_damage_nearby_mobs	entity	Returns 1.0 if the entity can damage nearby mobs, else it returns 0.0.	RP
query.can_dash	entity	Returns 1.0 if the entity can dash, else it returns 0.0
query.can_fly	entity	Returns 1.0 if the entity can fly, else it returns 0.0.
query.can_power_jump	entity	Returns 1.0 if the entity can power jump, else it returns 0.0.
query.can_swim	entity	Returns 1.0 if the entity can swim, else it returns 0.0.
query.can_walk	entity	Returns 1.0 if the entity can walk, else it returns 0.0.
query.cape_flap_amount	client	Returns value between 0.0 and 1.0 with 0.0 meaning cape is fully down and 1.0 is cape is fully up.	RP
query.cardinal_facing	entity	Returns the current facing of the player (Down=0.0, Up=1.0, North=2.0, South=3.0, West=4.0, East=5.0, Undefined=6.0).
query.cardinal_facing_2d	entity	Returns the current facing of the player ignoring up/down part of the direction (North=2.0, South=3.0, West=4.0, East=5.0, Undefined=6.0).
query.cardinal_player_facing	entity	Returns the current facing of the player (Down=0.0, Up=1.0, North=2.0, South=3.0, West=4.0, East=5.0, Undefined=6.0).
query.client_max_render_distance	client	Mojang: client only. Returns the max render distance in chunks of the current client.
query.client_memory_tier	client	Mojang: client only. Returns a number representing the client RAM memory tier, 0 = 'SuperLow', 1 = 'Low', 2 = 'Mid', 3 = 'High', or 4 = 'SuperHigh'.
query.combine_entities	pure	Combines any valid entity references from all arguments into a single array.
query.cooldown_time	item	Returns the total cooldown time in seconds for the item held or worn by the specified equipment slot name (and if required second numerical slot id...
query.cooldown_time_remaining	item	Returns the cooldown time remaining in seconds for specified cooldown type or the item held or worn by the specified equipment slot name (and if re...
query.count	pure	Counts the number of things passed to it (arrays are counted as the number of elements they contain; non-arrays count as 1).
query.current_squish_value	client	Returns the squish value for the current entity, or 0.0 if this doesn't make sense.	RP
query.day	world	Returns the day of the current world.
query.death_ticks	entity	Returns the elapsed ticks since the mob started dying.	RP
query.delta_time	client	Returns the time in seconds since the previous frame.	RP
query.distance_from_camera	client	Returns the distance of the root of this entity or particle emitter from the camera.
query.effect_emitter_count	client	Returns the total number of active emitters of the callee's particle effect type.
query.effect_particle_count	client	Returns the total number of active particles of the callee's particle effect type.
query.entity_biome_has_all_tags	entity	Compares the biome the entity is standing in with one or more tag names, and returns either 0 or 1 based on if all of the tag names match.
query.entity_biome_has_any_identifier	entity	Compares the biome the entity is standing in with one or more identifier names, and returns either 0 or 1 based on if any of the identifier names m...
query.entity_biome_has_any_tags	entity	Compares the biome the entity is standing in with one or more tag names, and returns either 0 or 1 based on if any of the tag names match.
query.equipment_count	entity	Returns the number of equipped armor pieces for an entity from 0 to 5, not counting items held in hands.	BP, RP
query.equipped_item_all_tags	entity	Takes a slot name followed by any tag you want to check for in the form of 'tag_name' and returns 1 if all of the tags are on that equipped item, 0...
query.equipped_item_any_tag	entity	Takes a slot name followed by any tag you want to check for in the form of 'tag_name' and returns 0 if none of the tags are on that equipped item o...	RP
query.equipped_item_is_attachable	client	Takes the desired hand slot as a parameter (0 or 'main_hand' for main hand, 1 or 'off_hand' for off hand), and returns whether the item is an attac...
query.eye_target_x_rotation	entity	Returns the X eye rotation of the entity, else it returns 0.0.	RP
query.eye_target_y_rotation	entity	Returns the Y eye rotation of the entity, else it returns 0.0.	RP
query.facing_target_to_range_attack	entity	Returns 1.0 if the entity is attacking from range (i.e.	RP
query.frame_alpha	client	Returns the ratio (from 0 to 1) of how much between AI ticks this frame is being rendered.	RP
query.fuse_time	entity	Returns the remaining fuse time of the entity.	RP
query.get_actor_info_id	item	Returns the integer id of an entity (actor) by its string name.
query.get_animation_frame	client	Returns the current texture of an item whose appearance can change (such as a drawn bow).	RP
query.get_default_bone_pivot	client	Gets specified axis of the specified bone orientation pivot.	RP
query.get_level_seed_based_fraction	world	Returns a value in range [0.0, 1.0] based on the level seed.
query.get_locator_offset	client	Gets specified axis of the specified locator offset.
query.get_pack_setting	client	Mojang: client only. Returns value of Pack Setting slider, parameter is name of slider.
query.get_root_locator_offset	client	Gets specified axis of the specified locator offset of the root model.	RP
query.graphics_mode_is_any	client	Mojang: client only. If the graphics mode of the client matches any of the arguments, return 1.0.
query.ground_speed	entity	Returns the ground speed of the entity in meters/second.	RP
query.had_component_group	entity, server only	If the entity is being loaded from data that was last saved with a component_group with the specified name, returns 1.0, otherwise returns 0.0.	BP
query.has_all_biome_tags	placement	Returns 1.0 if the biome at the current placement position has all of the specified tags, else 0.0.
query.has_any_biome_tags	placement	Returns 1.0 if the biome at the current placement position has at least one of the specified tags, else 0.0.
query.has_any_family	entity	Returns 1 if the entity has any of the specified type families, else 0.	BP
query.has_any_leashed_entity_of_type	entity	Returns whether or not the entity is currently leashing other entities of the designated types.	RP
query.has_armor_slot	entity	Takes the armor slot index as a parameter, and returns 1.0 if the entity has armor in the requested slot, else it returns 0.0.
query.has_biome_tag	placement	Returns whether or not a block placement target has a specific biome tag.	BP
query.has_block_state	block	Returns 1.0 if the associated block has the given block state or 0.0 if not.
query.has_cape	entity	Returns 1.0 if the player has a cape, else it returns 0.0.
query.has_collision	entity	Returns 1.0 if the entity has collisions enabled, else it returns 0.0.
query.has_dash_cooldown	entity	Returns 1.0 if the entity has cooldown on its dash, else it returns 0.0	RP
query.has_gravity	entity	Returns 1.0 if the entity is affected by gravity, else it returns 0.0.
query.has_head_gear	entity	Returns boolean whether an entity has an item in their head armor slot or not, or false if no entity in current context	RP
query.has_owner	entity	Returns true if the entity has an owner ID else it returns false.
query.has_player_rider	entity	Returns 1 if the entity has a player riding it in any seat, else it returns 0.	RP
query.has_property	entity	Returns 1.0 if a property with the given name exists, 0 otherwise.
query.has_rider	entity	Returns 1.0 if the entity has a rider, else it returns 0.0	RP
query.has_target	entity	Returns 1.0 if the entity has a target, else it returns 0.0	RP
query.head_is_in_water	entity	Returns 1.0 if the entity's head is in water, else it returns 0.0.	BP
query.head_roll_angle	client	Returns the roll angle of the head of the entity if it makes sense, else it returns 0.0.	RP
query.head_x_rotation	entity	Returns the nth head x rotation of the entity if it makes sense, else it returns 0.0.	RP
query.head_y_rotation	entity	Returns the nth head y rotation of the entity if it makes sense, else it returns 0.0.	RP
query.health	entity	Returns the health of the entity, or 0.0 if it doesn't make sense to call on this entity.	RP
query.heartbeat_interval	entity	Returns the heartbeat interval of the entity in seconds.
query.heartbeat_phase	client	Mojang: client only. Returns the heartbeat phase of the entity.	RP
query.heightmap	placement	Returns the world height (Y value) of the terrain at the specified position.	BP
query.hurt_direction	entity	Returns the hurt direction for the entity, otherwise returns 0.	RP
query.hurt_time	entity	Returns the hurt time for the entity, otherwise returns 0.	RP
query.invulnerable_ticks	entity	Returns the number of ticks of invulnerability the entity has left if it makes sense, else it returns 0.0.	RP
query.in_range	pure	If the first argument is between the minimum and maximum (inclusive), returns 1.0.
query.is_admiring	entity	Returns 1.0 if the entity is admiring, else it returns 0.0.	RP
query.is_alive	entity	Returns 1.0 if the entity is alive, and 0.0 if it's dead.	RP
query.is_angry	entity	Returns 1.0 if the entity is angry, else it returns 0.0.	RP
query.is_attached	entity	Returns 1.0 if the entity is attached to another entity (such as being held or worn), else it will return 0.0.
query.is_attached_to_entity	entity	Returns 1.0 if the entity is attached to another entity, else it will return 0.0.	RP
query.is_avoiding_block	entity	Returns 1.0 if the entity is fleeing from a block, else it returns 0.0.
query.is_avoiding_mobs	entity	Returns 1.0 if the entity is fleeing from mobs, else it returns 0.0.
query.is_baby	entity	Returns 1.0 if the entity has a is_baby component, else it returns 0.0.	BP, RP
query.is_breathing	entity	Returns 1.0 if the entity is breathing, else it returns 0.0.
query.is_bribed	entity	Returns 1.0 if the entity has been bribed, else it returns 0.0.
query.is_carrying_block	entity	Returns 1.0 if the entity is carrying a block, else it returns 0.0.	RP
query.is_casting	entity	Returns 1.0 if the entity is casting, else it returns 0.0.	RP
query.is_celebrating	entity	Returns 1.0 if the entity is celebrating, else it returns 0.0.	RP
query.is_celebrating_special	entity	Returns 1.0 if the entity is doing a special celebration, else it returns 0.0.	RP
query.is_charged	entity	Returns 1.0 if the entity has the is_charged component, else it returns 0.0.	RP
query.is_charging	entity	Returns 1.0 if the entity is charging, else it returns 0.0.	RP
query.is_chested	entity	Returns 1.0 if the entity has chests attached to it (has the is_chested component), else it returns 0.0.	RP
query.is_cooldown_category	item	Returns 1.0 if the specified held or worn item has the specified cooldown category, otherwise returns 0.0.
query.is_crawling	entity	Returns 1.0 if the entity is crawling, else it returns 0.0	RP
query.is_critical	entity	Returns 1.0 if the entity is at a critical level of damage, else it returns 0.0.
query.is_croaking	entity	Returns 1.0 if the entity is croaking, else it returns 0.0.	RP
query.is_dancing	entity	Returns 1.0 if the entity is dancing, else it returns 0.0.	RP
query.is_delayed_attacking	entity	Returns 1.0 if the entity is attacking using the delayed attack, else it returns 0.0.	RP
query.is_digging	entity	Returns 1.0 if the entity is digging, else it returns 0.0.	RP
query.is_eating	entity	Returns 1.0 if the entity is eating, else it returns 0.0.	RP
query.is_eating_mob	entity	Returns 1.0 if the entity is eating a mob, else it returns 0.0.	RP
query.is_elder	entity	Returns 1.0 if the entity is an elder version of it, else it returns 0.0.	RP
query.is_emerging	entity	Returns 1.0 if the entity is emerging, else it returns 0.0.	RP
query.is_emoting	client	Returns 1.0 if the entity is emoting, else it returns 0.0.	RP
query.is_enchanted	item	Returns 1.0 if the entity is enchanted, else it returns 0.0.
query.is_fire_immune	entity	Returns 1.0 if the entity is immune to fire (has the fire_immune component), else it returns 0.0.
query.is_first_person	client	Returns 1.0 if the entity is being rendered in first person mode, else it returns 0.0.
query.is_ghost	entity	Returns 1.0 if an entity is a ghost, else it returns 0.0.	RP
query.is_gliding	entity	Returns 1.0 if the entity is gliding, else it returns 0.0.	RP
query.is_grazing	entity	Returns 1.0 if the entity is grazing, or 0.0 if not.	RP
query.is_idling	entity	Returns 1.0 if the entity is idling, else it returns 0.0.
query.is_ignited	entity	Returns 1.0 if the entity is ignited (has the is_ignited component), else it returns 0.0.
query.is_illager_captain	entity	Returns 1.0 if the entity is an illager captain (has the is_illager_captain component), else it returns 0.0.
query.is_interested	entity	Returns 1.0 if the entity is interested, else it returns 0.0.	RP
query.is_invisible	entity	Returns 1.0 if the entity is invisible (using render controllers), else it returns 0.0.	RP
query.is_in_contact_with_water	entity	Returns 1.0 if the entity is in contact with any water (water, rain, splash water bottle), else it returns 0.0.
query.is_in_lava	entity	Returns 1.0 if the entity is in lava, else it returns 0.0.	RP
query.is_in_love	entity	Returns 1.0 if the entity is in love (has a love-hearts animation), else it returns 0.0.
query.is_in_ui	client	Returns 1.0 if the entity is rendered as part of the UI, else it returns 0.0.	RP
query.is_in_water	entity	Returns 1.0 if the entity is in water, else it returns 0.0.	RP
query.is_in_water_or_rain	entity	Returns 1.0 if the entity is in water or rain, else it returns 0.0.
query.is_item_equipped	entity	Takes one optional hand slot as a parameter (0 or 'main_hand' for main hand, 1 or 'off_hand' for off hand), and returns 1.0 if there is an item in...	RP
query.is_item_name_any	entity	Returns 1.0 if an item in the specified slot has any of the specified names, otherwise returns 0.0.	RP
query.is_jumping	entity	Returns 1.0 if the entity is jumping, else it returns 0.0.	RP
query.is_jump_goal_jumping	client	Returns 1.0 if the entity is doing a jump goal jump, else it returns 0.0.	RP
query.is_laying_down	entity	Returns 1.0 if the entity is laying down, else it returns 0.0.
query.is_laying_egg	entity	Returns 1.0 if the entity is laying an egg, else it returns 0.0.	RP
query.is_leashed	entity	Returns 1.0 if the entity is leashed to something, else it returns 0.0.	RP
query.is_levitating	entity	Returns 1.0 if the entity is levitating, else it returns 0.0.	RP
query.is_lingering	entity	Returns 1.0 if the potion type or effect is lingering, else it returns 0.0.
query.is_local_player	client	Returns 1.0 if the entity is the local player for the current game window, else it returns 0.0.
query.is_moving	entity	Returns 1.0 if the entity is moving, else it returns 0.0.	RP
query.is_name_any	entity	Takes one or more arguments.
query.is_onfire	entity	Returns 1.0 if the entity is on fire, else it returns 0.0.
query.is_on_fire	entity	Returns 1.0 if the entity is on fire, else it returns 0.0.
query.is_on_ground	entity	Returns 1.0 if the entity is on the ground, else it returns 0.0.	BP, RP
query.is_on_screen	client	Returns 1.0 if this is called on an entity at a time when it is known if it is on screen, else it returns 0.0.
query.is_orphaned	entity	Returns 1.0 if the entity is orphaned, else it returns 0.0.
query.is_owner_identifier_any	entity	Returns whether the root entity identifier is any of the specified strings.
query.is_pack_setting_enabled	client	Mojang: client only. Returns 1.0 if the Pack Setting toggle is enabled, parameter is name of toggle.
query.is_pack_setting_selected	client	Mojang: client only. Returns 1.0 if the Pack Setting dropdown or multiselect (first parameter) matches the string value of the second parameter (selection).
query.is_persona_or_premium_skin	client	Returns 1.0 if the player has a persona or premium skin, else it returns 0.0.	RP
query.is_playing_dead	entity	Returns 1.0 if the entity is playing dead, else it returns 0.0.	RP
query.is_powered	entity	Returns 1.0 if the entity is powered, else it returns 0.0.	RP
query.is_pregnant	entity	Returns 1.0 if the entity is pregnant, else it returns 0.0.	RP
query.is_ram_attacking	entity	Returns 1.0 if the entity is using a ram attack, else it returns 0.0.
query.is_resting	entity	Returns 1.0 if the entity is resting, else it returns 0.0.	RP
query.is_riding	entity	Returns 1.0 if the entity is riding, else it returns 0.0.	RP
query.is_riding_any_entity_of_type	entity	Returns whether or not the entity is currently riding an entity of any of the designated types.	RP
query.is_rising	entity	Deprecated. Returns 1.0 if behavior.timer_flag_2 is running, else it returns 0.0.
query.is_roaring	entity	Returns 1.0 if the entity is currently roaring, else it returns 0.0.	RP
query.is_rolling	entity	Returns 1.0 if the entity is rolling, else it returns 0.0.
query.is_saddled	entity	Returns 1.0 if the entity has a saddle (has the is_saddled component), else it returns 0.0.	RP
query.is_scared	entity	Returns 1.0 if the entity is scared, else it returns 0.0.	RP
query.is_scenting	entity	Deprecated. Returns 1.0 if behavior.timer_flag_1 is running, else it returns 0.0.
query.is_searching	entity	Returns 1.0 if the entity is searching, else it returns 0.0.	RP
query.is_selected_item	entity	Returns true if the player has selected an item in the inventory, else it returns 0.0.
query.is_shaking	entity	Returns 1.0 if the entity is shaking, else it returns 0.0.	RP
query.is_shaking_wetness	entity	Returns 1.0 if the entity is shaking water off, else it returns 0.0.	RP
query.is_sheared	entity	Returns 1.0 if the entity is able to be sheared and is sheared, else it returns 0.0.	RP
query.is_shield_powered	entity	Returns 1.0 if the entity has an active powered shield if it makes sense, else it returns 0.0.	RP
query.is_silent	entity	Returns 1.0 if the entity is silent, else it returns 0.0.
query.is_sitting	entity	Returns 1.0 if the entity is sitting, else it returns 0.0.	RP
query.is_sleeping	entity	Returns 1.0 if the entity is sleeping, else it returns 0.0.	RP
query.is_sneaking	entity	Returns 1.0 if the entity is sneaking, else it returns 0.0.	RP
query.is_sneezing	entity	Returns 1.0 if the entity is sneezing, else it returns 0.0.
query.is_sniffing	entity	Returns 1.0 if the entity is sniffing, else it returns 0.0.	RP
query.is_sonic_boom	entity	Returns 1.0 if the entity is using sonic boom, else it returns 0.0.	RP
query.is_spectator	entity	Returns 1.0 if the entity (player) is in spectator mode, else it returns 0.0.	RP
query.is_sprinting	entity	Returns 1.0 if the entity is sprinting, else it returns 0.0.
query.is_stackable	entity	Returns 1.0 if the entity is stackable (has the is_stackable component), else it returns 0.0.
query.is_stalking	entity	Returns 1.0 if the entity is stalking, else it returns 0.0.	RP
query.is_standing	entity	Returns 1.0 if the entity is standing, else it returns 0.0.	RP
query.is_stunned	entity	Returns 1.0 if the entity is currently stunned, else it returns 0.0.	RP
query.is_swimming	entity	Returns 1.0 if the entity is swimming, else it returns 0.0.	RP
query.is_tamed	entity	Returns 1.0 if the entity is tamed, else it returns 0.0.	RP
query.is_transforming	entity	Returns 1.0 if the entity is transforming, else it returns 0.0.
query.is_using_item	entity	Returns 1.0 if the entity is using an item, else it returns 0.0.	BP, RP
query.is_wall_climbing	entity	Returns 1.0 if the entity is climbing a wall, else it returns 0.0.
query.item_in_use_duration	item	Returns the amount of time an item has been in use in seconds up to the maximum duration, else 0.0 if it doesn't make sense.
query.item_is_charged	item	Takes one optional hand slot as a parameter (0 or 'main_hand' for main hand, 1 or 'off_hand' for off hand), and returns 1.0 if the item is charged...	RP
query.item_max_use_duration	item	Returns the maximum amount of time the item can be used, else 0.0 if it doesn't make sense.
query.item_remaining_use_duration	item	Returns the amount of time an item has left to use, else 0.0 if it doesn't make sense.	RP
query.item_slot_to_bone_name	client	This function returns the name of the bone this entity has mapped to that slot.	RP
query.key_frame_lerp_time	client	Returns the ratio between the previous and next key frames.	RP
query.kinetic_weapon_damage_duration	entity	Returns the "max_duration" value of "damage_conditions" from the main-hand item's "minecraft:kinetic_weapon" component, or 0 if the component is no...	RP
query.kinetic_weapon_delay	entity	Returns the "delay" value from the main-hand item's "minecraft:kinetic_weapon" component, or 0 if the component is not present.	RP
query.kinetic_weapon_dismount_duration	entity	Returns the "max_duration" value of "dismount_conditions" from the main-hand item's "minecraft:kinetic_weapon" component, or 0 if the component is...	RP
query.kinetic_weapon_knockback_duration	entity	Returns the "max_duration" value of "knockback_conditions" from the main-hand item's "minecraft:kinetic_weapon" component, or 0 if the component is...	RP
query.last_frame_time	client	Returns the time in seconds of the last frame.
query.last_hit_by_player	entity	Returns 1.0 if the entity was last hit by the player, else it returns 0.0.	BP
query.last_input_mode_is_any	client	Mojang: client only. Takes one or more arguments ('keyboard_and_mouse', 'touch', or 'gamepad').
query.leashed_entity_count	entity	Returns the number of entities for which this entity is the leash holder.
query.lie_amount	entity	Returns the lie down amount for the entity.	RP
query.life_span	entity	Returns the limited life span of an entity, or 0.0 if it lives forever.	RP
query.life_time	client	Returns the time in seconds since the current animation started, else 0.0 if not called within an animation.	RP
query.log	pure	Debug log a value to the content file.
query.main_hand_item_max_duration	item	Returns the use time maximum duration for the main hand item if it makes sense, else it returns 0.0.	RP
query.main_hand_item_use_duration	item	Returns the use time for the main hand item.	RP
query.mark_variant	entity	Returns the entity's mark variant value, if the entity has the mark_variant component.	RP
query.maximum_frame_time	client	Returns the time in seconds of the most expensive frame over the last 'n' frames.
query.max_durability	item	Returns the max durability an item can take.	BP
query.max_health	entity	Returns the maximum health of the entity, or 0.0 if it doesn't make sense to call on this entity.
query.max_trade_tier	entity	Returns the maximum trade tier of the entity if it can perform trades, else it returns 0.0
query.minimum_frame_time	client	Returns the time in seconds of the least expensive frame over the last 'n' frames.
query.model_scale	entity	Returns the scale of the current entity.	RP
query.modified_distance_moved	client	Returns the total distance the entity has moved horizontally in meters (since the entity was last loaded, not necessarily since it was originally c...	RP
query.modified_move_speed	client	Returns the current walk speed of the entity.	RP
query.modified_swing_duration	client	Returns the duration of the mob's swing/attack animation, determined by the carried item and modified by effects applied on the mob.
query.moon_brightness	world	Returns the brightness of the moon (FULL_MOON=1.0, WANING_GIBBOUS=0.75, FIRST_QUARTER=0.5, WANING_CRESCENT=0.25, NEW_MOON=0.0, WAXING_CRESCENT=0.25...
query.moon_phase	world	Returns the phase of the moon (FULL_MOON=0, WANING_GIBBOUS=1, FIRST_QUARTER=2, WANING_CRESCENT=3, NEW_MOON=4, WAXING_CRESCENT=5, LAST_QUARTER=6, WA...
query.movement_direction	client	Returns the specified axis of the normalized position delta of the entity.	RP
query.noise	placement	Queries a Perlin Noise Map.	BP
query.on_fire_time	entity	Returns the time that the entity is on fire, else it returns 0.0.
query.out_of_control	entity	Returns 1.0 if the entity is out of control (has the out_of_control component), else it returns 0.0.
query.player_level	entity	Returns the players level if the entity is a player, otherwise returns 0.	BP
query.position	entity	Returns the absolute position of an entity.
query.position_delta	entity	Returns the position delta for an entity.	RP
query.previous_squish_value	client	Returns the previous squish value for the current entity, or 0.0 if this doesn't make sense.	RP
query.property	entity	Returns the value of that property if it exists, else 0.0 if not.	BP, RP
query.relative_block_has_all_tags	entity	Takes an entity-relative position and one or more tag names, and returns either 0 or 1 based on if the block at that position has all of the tags p...
query.relative_block_has_any_tag	entity	Takes an entity-relative position and one or more tag names, and returns either 0 or 1 based on if the block at that position has any of the tags p...
query.remaining_durability	item	Returns how much durability an item has remaining.	BP
query.rider_body_x_rotation	entity	Returns the body pitch world-rotation of a valid rider at the provided index if called on an entity, else it returns 0.0.
query.rider_body_y_rotation	entity	Returns the body yaw world-rotation of a valid rider at the provided index if called on an entity, else it returns 0.0.
query.rider_head_x_rotation	entity	Returns the head x world-rotation of the rider entity at the provided index, else it returns 0.0.
query.rider_head_y_rotation	entity	Returns the head y world-rotation of the rider entity at the provided index, else it returns 0.0.
query.ride_body_x_rotation	entity	Returns the body pitch world-rotation of the ride an entity, else it returns 0.0.
query.ride_body_y_rotation	entity	Returns the body yaw world-rotation of the ride of on an entity, else it returns 0.0.
query.ride_head_x_rotation	entity	Returns the head x world-rotation of the ride of an entity, else it returns 0.0.
query.ride_head_y_rotation	entity	Returns the head y world-rotation of the ride of an entity, else it returns 0.0.
query.roll_counter	entity	Returns the roll counter of the entity.	RP
query.rotation_to_camera	client	Returns the rotation required to aim at the camera.
query.scoreboard	entity, server only	Mojang: server only. Returns the specified scoreboard value for this entity.
query.server_memory_tier	server only	Mojang: server only. Returns a number representing the server RAM memory tier, 0 = 'SuperLow', 1 = 'Low', 2 = 'Mid', 3 = 'High', or 4 = 'SuperHigh'.
query.shake_angle	entity	Returns the shaking angle of the entity if it makes sense, else it returns 0.0.	RP
query.shake_time	entity	Returns the shake time of the entity.	RP
query.shield_blocking_bob	client	Returns the how much the offhand shield should translate down when blocking and being hit.
query.show_bottom	entity	Returns 1.0 if we render the entity's bottom, else it returns 0.0.	RP
query.sit_amount	entity	Returns the current sit amount of the entity.	RP
query.skin_id	entity	Returns the entity's skin ID (related to the skin_id component).	RP
query.sleep_rotation	entity	Returns the rotation of the bed the player is sleeping on.	RP
query.sneeze_counter	entity	Returns the sneeze counter of the entity.	RP
query.spellcolor	client	Returns a struct representing the entity spell color for the specified entity.
query.standing_scale	entity	Returns the scale of how standing up the entity is.	RP
query.state_time	client	Returns the time in seconds in the current animation controller state.
query.structural_integrity	entity	Returns the structural integrity for the entity, otherwise returns 0.	RP
query.surface_particle_color	client	Mojang: client only. Returns the particle color for the block located in the surface below the entity (scanned up to 10 blocks down).	RP
query.surface_particle_texture_coordinate	client	Mojang: client only. Returns the texture coordinate for generating particles for the block located in the surface below the entity (scanned up to 10 blocks down) in a s...	RP
query.surface_particle_texture_size	client	Mojang: client only. Returns the texture size for generating particles for the block located in the surface below the entity (scanned up to 10 blocks down).	RP
query.swelling_dir	entity	Returns the swelling direction of the entity if it makes sense, else it returns 0.0.	RP
query.swell_amount	entity	Returns how swollen an entity is.	RP
query.swim_amount	entity	Returns the amount the current entity is swimming.	RP
query.tail_angle	entity	Returns the angle of the tail of the entity if it makes sense, else it returns 0.0.	RP
query.target_x_rotation	entity	Returns the x rotation required to aim at the entity's current target if it has one, else it returns 0.0.	RP
query.target_y_rotation	entity	Returns the y rotation required to aim at the entity's current target if it has one, else it returns 0.0.	RP
query.ticks_since_last_kinetic_weapon_hit	entity	Returns the number of ticks elapsed since the user last hit something while using a kinetic weapon.	RP
query.timer_flag_1	entity	Returns 1.0 if behavior.timer_flag_1 is running, else it returns 0.0.	RP
query.timer_flag_2	entity	Returns 1.0 if behavior.timer_flag_2 is running, else it returns 0.0.	RP
query.timer_flag_3	entity	Returns 1.0 if behavior.timer_flag_3 is running, else it returns 0.0.	RP
query.time_of_day	world	Returns the time of day (midnight=0.0, sunrise=0.25, noon=0.5, sunset=0.75) of the dimension the entity is in.
query.time_since_last_vibration_detection	client	Mojang: client only. Returns the time in seconds since the last vibration detected by the entity.	RP
query.time_stamp	world	Returns the current time stamp of the level.	RP
query.total_emitter_count	client	Returns the total number of active emitters in the world.
query.total_particle_count	client	Returns the total number of active particles in the world.
query.touch_only_affects_hotbar	client	Mojang: client only. Returns 1.0 if the touch input only affects the touchbar, otherwise returns 0.0.
query.trade_tier	entity	Returns the trade tier of the entity if it makes sense, else it returns 0.0.	RP
query.variant	entity	Returns the entity's variant index.	BP, RP
query.vertical_speed	entity	Returns the speed of the entity up or down in meters/second, where positive is up.	RP
query.walk_distance	client	Returns the total distance traveled by an entity while on the ground and not sneaking.	RP
query.wing_flap_position	entity	Returns the wing flap position of the entity, or 0.0 if this doesn't make sense.	RP
query.wing_flap_speed	entity	Returns the wing flap speed of the entity, or 0.0 if this doesn't make sense.	RP
query.yaw_speed	entity	Returns the entity's yaw speed.

3. Semantics that matter for parity

• Numbers. Every value is a float (Molang.html "Values"). The engine's floats are 32-bit: IntroductionToEntityProperties.md warns that incrementing an int property "will fail when the value exceeds about 16.7 million" because "Molang expressions are evaluated as float values", and 16,777,216 is the float32 integer limit. A JavaScript evaluator using doubles diverges only above that range; Math.fround on arithmetic results would match exactly at a cost. No Molang operator does integer division; / is float division and division by zero yields 0.0.
• Truthiness. 0.0 is false; anything else is true. Comparison and logical operators return 1.0 or 0.0. ! of a nonzero value is 0.0.
• Strings. Single quoted, no escapes, case preserved, == and != only. 'text' + 1 is a content error since 1.17.40. Vanilla compares query.block_state('minecraft:cardinal_direction') == 'east', so block state enum values must compare as strings and booleans as 0.0/1.0 (query.block_state('custom:is_lit') == true in BlockStatesAndPermutations.md).
• Undefined variables. Without ?? the docs describe a content error and a 0.0 result ("Errors (such as divide by zero, missing variables, null references, etc) generally return a value of 0.0"). query.property on a missing property "will send a content error message and return 0" (IntroductionToEntityProperties.md).
• -> short-circuits: a null or dead left side returns 0 without evaluating the right side.
• loop is capped at 1024 iterations. break and continue apply to the innermost loop; a return inside a loop body ends the whole expression (bridge-core's test v.x = 2; loop(10, { return 1; }); return v.x; expects 1).
• Array indices: C-style cast to int, negative clamps to 0, large wraps by size.
• Randomness. math.random, math.random_integer, math.die_roll and math.die_roll_integer are documented as random with no seed, so each evaluation draws a fresh value. Vanilla uses them for experience (on_bred, on_death) and for two feature-rule offsets. Nothing in either text says a feature rule's random is derived from the world seed; query.get_level_seed_based_fraction exists for that purpose ("Returns a value in range [0.0, 1.0] based on the level seed", format version 1.26.10 or later) and vanilla does not use it. A server that wants reproducible worldgen can seed its own generator per chunk and still satisfy the docs.
• query.noise: the Learn page says "Queries a Perlin Noise Map. Pertains to terrain generation."; the HTML says "Returns a Perlin simplex noise value for the given (x, z) position." Neither gives the range, octaves or seed. Vanilla thresholds it at -0.8 and multiplies (noise + 0.3) * 160, which only makes sense for a range near [-1, 1]. Exact parity with vanilla bamboo density is not reachable from the docs.
• query.heightmap returns "the heightmap value at the given (x, z) position" and query.above_top_solid "the height of the block immediately above the highest solid block"; which heightmap (world surface, motion blocking, ocean floor) is unstated. Vanilla puts features at heightmap, heightmap + 32, heightmap * 2, and max(above_top_solid, heightmap - 4).
• Trigonometry is in degrees for sin and cos; lerprotate and min_angle are in degrees. The 30 easing functions and inverse_lerp require format version 1.21.120.
• Rounding: math.round "to nearest integral number" without a tie rule; math.trunc toward zero; math.sign "1 if value is positive, -1 otherwise", so 0 gives -1 by the letter of the text.
• math.mod: "remainder of value / denominator" with no sign rule. C's fmod (sign of the dividend) is the reading consistent with "modeled on the C math library" (syntax guide "Math Functions").
• Evaluation order and caching. Statements run in order; temp. lives for one execution. Feature rules evaluate scatter_chance once per rule per chunk and x, y, z once per iteration in coordinate_eval_order (default xzy), "Should be used when a coordinate depends on another" (feature_rule_definition.md). set_property values are "calculated immediately" and applied "the next time the entity ticks"; int and float properties clamp to their range "without any warning or error" (IntroductionToEntityProperties.md). pre_animation scripts run once per render tick on the client; nothing in the docs describes server-side caching of query results.

4. Filters are not Molang

Entity filters are JSON objects, not expressions. FilterList.md lists 108 tests (has_component, is_family, is_biome, clock_time, bool_property, enum_property, ...). Each test object has test, an optional subject (self, other, target, parent, player, damager, block), an optional operator (==, =, equals, !=, <>, not, <, <=, >, >=; Definitions/NestedTables/operator.md), and a value; all_of, any_of and none_of nest them (Filters/has_component.md). The value is a literal, never an expression. Spawn rules (biome_filter, brightness_filter, difficulty_filter, ...) and feature rules (minecraft:biome_filter) use the same object form.

Where the two meet: components take filters for who or when (minecraft:entity_sensor.subsensors[].event_filters, minecraft:environment_sensor.triggers[].filters, minecraft:interact.interactions[].on_interact.filters, event filters) and Molang for how much (experience_reward, heartbeat.interval, rotate_rider_by, success_chance). Entity properties are readable by both: Molang through query.property, filters through bool_property, int_property, float_property, enum_property and has_property; Molang writes them through set_property (IntroductionToEntityProperties.md, "Entity Properties can be read by two systems to affect how the game behaves: Molang and Filters"). The breeze's environment_sensor in minecraftComponent_environment_sensor.md shows a bool_property filter and on_ground test side by side with no Molang. An implementation needs a filter evaluator and a Molang evaluator as two modules sharing the entity property store.

5. Existing implementations

Project	Language, license	Commit read	Approach	Coverage gaps against sections 1 and 3
bridge-core/molang (npm molang 2.0.1, 2022-08-25, repo URL still solvedDev/MoLang; @bridge-editor/molang 2.0.2, 2024-05-23)	TypeScript, MIT	8b4c2bafc502eeab2d7ea414d95b2ac23e5eb9ae (2025-10-11)	Pratt parser (lib/parser/parse.ts), tree-walking AST with static folding, expression cache of 256 entries flushed whole when full (lib/MoLang.ts)	EPrecedence (lib/parser/precedence.ts) orders AND = 7 below OR = 8 and both parselets use parseExpression(this.precedence), so || binds tighter than &&: the pre-1.18.20 rule. ?? (6) binds tighter than the ternary (4); Mojang ranks it lowest. Math table (lib/env/math.ts) spells math.lerp_rotate, omits sign, copy_sign, inverse_lerp and all 30 easings, and dieRoll never increments its counter (while (i < sum) total += random(low, high)), so math.die_roll(n, ...) with n > 0 never returns; vanilla calls it from three on_death expressions. random_integer is Math.round(low + Math.random() * (high - low)). No this, no version switch, no Legacy Molang Expression object. Only query.all, any, count, in_range built in. 12 any in lib/; environment is Record<string, unknown> flattened to dotted keys. Tests: one table of about 90 expressions (__tests__/tests.ts) plus six small files. Has -> (ContextSwitchExpression), loop, for_each, break, continue, arrays, scopes, # comments (not in the spec).
JannisX11/molangjs (npm molangjs 1.7.1, 2026-09-17)	JavaScript, MIT; a 25-line types/index.d.ts	0b17bc32fa12a94c4b77b4602f19a87f15448c04 (2026-09-18)	No tokenizer: parse lowercases the whole input and strips all whitespace, then splits the string on operators by bracket depth (src/molang.js iterateString); result tree is interpreted; 400-entry cache	Lowercasing and whitespace stripping alter string contents, against "strings maintain the case provided". testOp(s, '&&', 11) runs before '||', so the split happens at && first and A && B || C becomes A && (B || C). No ->, for_each, arrays, structs, this, temp. scoping or versioning; ?? works by a flag set when a variable lookup fails. Math is complete for the 61 functions including easings (src/easing.js). randomInt draws uniformly over the inclusive range; lerp does not clamp. 46 assertion lines in tests.js, run as a script.
unnamed/mocha	Java 8+, MIT	eac679c71a1c4211ccf5ec2ff9a31b25c52e7509 (2025-03-14)	Lexer, parser, interpreter, and a compiler to JVM bytecode (runtime/MolangCompiler.java); 91 source files, 26 test files; case-insensitive maps	Not usable from TypeScript; useful as a reference for the compile-once design. Feature list not verified beyond file names.
Ocelot5836/molang-compiler	Java, MIT	bcb00f25c1438a4af29203458f0e9f788e839bc0 (2025-04-21)	Bytecode compiler for per-frame use	README "Limitations": no structs, arrays, strings, ->, for_each, or ?? inside loops; adds non-spec +=, ++, math.triangle_wave.
arexon/nolana	Rust, MIT	7dcd2709e225005b5d394b668a4c26bf7495f413 (2026-03-06)	Parser, AST, semantic checker, code generator; no evaluator	AST (src/ast.rs) covers loop, for_each, arrow, array access, resource expressions, this, ternary and binary conditional, plus non-spec update operators. The most complete grammar read for this note; a good cross-check for a parser's test corpus.
ConcreteMC/MolangSharp	C#, MPL-2.0	fd08e2ccf0754f79d2dcfd05d16f5ef28089fee3 (2026-08-07)	Runtime ported from bedrockk/MoLang (Java, GPL-3.0)	Not read in depth; license mix matters if anything were ported.
hollow-cube/mql	Java, MIT	f68420b12eb1bc870e2836f19b3189a12821db9b (2024-07-30)	Interpreter and JIT for "a subset of MoLang"	README: queries and math/comparison operators only; temp variables listed under future plans.
JannisX11/molang_rs	Rust, MIT	275c367452301db71800a4b181957db1773859e4 (2023-02-25)	Port of molangjs	README: "Experimental and work in progress!"
Blockception/BC-Minecraft-Molang	TypeScript, BSD-3-Clause	f2dc986542b2c2e7ca88cfa700e50ef8be7e207a (2025-09-28)	Data and syntax helpers for a language server, not an evaluator	README: archived, moved into Blockception/minecraft-bedrock-language-server.

Peer servers do not evaluate Molang. AllayMC/Allay's server/.../utils/MolangUtils.java "builds client Molang conditions that select block-state permutations" for custom blocks sent to clients, and its MOLANG_VERSION = 1 is a wire field; df-mc/dragonfly's server/block/customblock/permutations.go and PowerNukkitX's MolangDescriptor serve the same wire purposes (file names from GitHub code search; only Allay's header was read). EndstoneMC/endstone mirrors BDS's MolangVersion enum and MolangVariableMap because it hooks the official binary.

Recommendation: write one. The two JavaScript libraries get the 1.18.20 precedence wrong, which is the one language rule that changes results, and neither models versions, this (vanilla uses it), or the Legacy Molang Expression object. bridge-core would also need its math table fixed and 12 any sites replaced to pass this repository's rule against as casts and any. The vanilla server-side subset is small (21 queries, 7 math functions, single-statement expressions), so a complete parser plus a tested evaluator is a smaller task than auditing and patching a dependency. nolana's AST and molangjs's easing.js are useful references under MIT.

6. Design input

Environment. Bind one MolangScope per evaluation with: the entity (for query.* entity queries, variable.* storage, this), an optional block permutation (query.block_state, query.has_block_state, query.block_face), an optional item stack (query.max_durability, query.remaining_durability, query.any_tag, query.all_tags, query.is_item_name_any), the world or dimension (query.time_of_day, query.day, query.moon_phase, query.moon_brightness, query.time_stamp, query.get_level_seed_based_fraction), and a placement context for feature rules (query.heightmap, query.above_top_solid, query.noise, query.has_biome_tag with its (tag), (tag, x, z) and (tag, x, y, z) forms per the HTML, has_any_biome_tags, has_all_biome_tags, plus the engine variables variable.worldx, worldz, originx, originz, is_legacy). context.* is a read-only map the caller supplies per expression; vanilla needs context.other (the repair item, an entity-like reference for ->). variable.* lives on the entity and is not persisted (docs). temp.* is a map created per execution. Represent values as a discriminated union of number, string, entity reference, entity array and struct, and make queries declare their required context so the loader can reject query.block_state in an entity field at load.

Precompile. Parse each string once when the pack loads, keyed by (expression text, Molang version); keep the AST, then compile it to a closure (scope) => Value with constant subtrees folded ("query.last_hit_by_player ? 10 : 0" folds its branches; "Math.Random(1,7)" cannot fold). Closures avoid new Function and tree-walk overhead; server volume is low (ambient-sound conditions every few seconds, experience on death, feature placement a few hundred times per chunk), so a tree-walker would also do. Do not use a whole-cache flush. Choose the version from the pack's min_engine_version, or from a { "expression", "version" } object where the field allows one, and map it onto BDS's enumerators (section 1); implement the pre- and post-1.18.10 ternary associativity and pre- and post-1.18.20 precedence as parser options, and the 1.19.60 negative-divisor fix as an evaluator option. For operators the precedence table omits, use C ranks: unary minus with !; call, -> and [ ] above !; = below ?? and right-associative.

Unknown identifiers. The docs say unknown tokens are a content error at parse (1.17.40) and that missing variables and other errors evaluate to 0.0 with a content error in development builds. Mirror that: at load, resolve every query.* and math.* against the registry and every context.* against the field's declared context; log each unknown once with pack, file and JSON path; substitute a constant 0.0 so the entity or feature still loads. Offer a strict mode for tests and CI that fails the load instead, and a parity test that asserts the registry covers the 21 queries and 7 math functions in section 2.

What to build first. The parser and evaluator with the full grammar (so resource packs and third-party behavior packs parse), the 61 math functions, the 7 pure queries, the 6 world queries, the 6 placement queries, the 21 vanilla queries, and query.block_state. Entity queries beyond vanilla's 21 can be added as the components that back them land.

Open questions

• query.noise range, octaves and seed are unspecified; vanilla bamboo and sea pickle densities depend on them.
• Which heightmap query.heightmap and query.above_top_solid read is unspecified.
• Whether the engine applies a Molang version to the server-root definitions/ files, which have no manifest.
• Whether feature-rule math.random is seeded from the world seed, and how a float iterations such as Math.Random(48, 96) is rounded; the docs do not say.
• math.round tie rule, math.mod sign, math.sign(0), math.lerp clamping and math.random_integer endpoint handling are undocumented; only the BDS binary settles them.
• Float32 versus float64: the entity-property page implies 32-bit evaluation; whether every operator rounds to float32 is not stated.
• The Learn and HTML texts disagree on the 1.20.50 versioned change; the HTML (engine-generated) is more likely correct.
• Whether the six entity files at layer roots (vanilla_1.20.10/donkey.json and others) are read by the engine.
• query.get_nearby_entities and query.get_relative_block_state appear in the HTML's for_each and -> examples but on neither query index.

Reproduction

# Pinned sources (read-only clones under /tmp/bds-research-molang)
git clone --filter=blob:none --no-checkout --depth 1 https://github.com/MicrosoftDocs/minecraft-creator.git docs/mc-creator
# sparse-checkout creator/Documents/molang creator/Reference/Content/{MolangReference,EntityReference,FeaturesReference,BlockReference,ItemReference,BiomesReference}; HEAD 4432fb62
git clone --filter=blob:none --no-checkout --depth 1 --branch v1.26.50.4 https://github.com/Mojang/bedrock-samples.git samples/bedrock-samples
# sparse-checkout documentation resource_pack/{animations,animation_controllers,render_controllers,entity,attachables,particles} behavior_pack/{entities,blocks,items,trading,loot_tables,spawn_rules,recipes}
for r in bridge-core/molang JannisX11/molangjs unnamed/mocha Ocelot5836/molang-compiler arexon/nolana ConcreteMC/MolangSharp Blockception/BC-Minecraft-Molang hollow-cube/mql JannisX11/molang_rs; do git clone --depth 1 https://github.com/$r.git libs/${r/\//_}; done

# Compose the vanilla behavior pack (later layer wins) and scan for Molang identifiers
node tools/compose.mjs /tmp/bds-research/bds/extracted/behavior_packs composed/vanilla_bp
cp -R /tmp/bds-research/bds/extracted/definitions composed/definitions
# composed/server_only: symlinks to the server-side folders plus definitions/{features,feature_rules,spawn_groups}
node tools/scan-molang.mjs composed/server_only            # tally: 537 strings, 35 identifiers
DUMP=1 node tools/scan-molang.mjs composed/server_only     # every expression with its JSON path
node tools/scan-molang.mjs samples/bedrock-samples/resource_pack   # client contrast

# Precedence table and query labels from Mojang's generated HTML
python3 -I -c 'import re,html,sys; s=open(sys.argv[1]).read(); s=re.sub(r"<[^>]+>"," ",s); print(html.unescape(s))' samples/bedrock-samples/documentation/Molang.html | grep -n -A30 "Operator Precedence"
grep -o "Available on the [A-Za-z (]*only" samples/bedrock-samples/documentation/Molang.html | sort | uniq -c

# Pack versions
for d in /tmp/bds-research/bds/extracted/behavior_packs/vanilla*; do python3 -I -c 'import json,sys; print(sys.argv[1].split("/")[-1], json.load(open(sys.argv[1]+"/manifest.json"))["header"]["min_engine_version"])' $d; done

# Library findings cited above
sed -n 1,20p libs/bridge-core_molang/lib/parser/precedence.ts
grep -n "while (i < sum)" libs/bridge-core_molang/lib/env/math.ts
grep -n "toLowerCase().replace" libs/JannisX11_molangjs/src/molang.js