diff --git a/develop/untests.lua b/develop/untests.lua
index 7388572..7af682b 100644
--- a/develop/untests.lua
+++ b/develop/untests.lua
@@ -3859,3 +3859,212 @@ do
         assert(sum_removed_components == 0)
     end
 end
+
+do
+    local f1, f2, f3, f4, f5 = evo.id(5)
+
+    local e1 = evo.entity():set(f1, 11):build()
+    local e2 = evo.entity():set(f1, 21):set(f2, 22):build()
+    local e3 = evo.entity():set(f1, 31):set(f2, 32):set(f3, 33):build()
+    local e4 = evo.entity():set(f1, 41):set(f2, 42):set(f3, 43):set(f4, 44):build()
+
+    assert(evo.get(e1, f1) == 11 and evo.get(e1, f2) == nil and evo.get(e1, f3) == nil)
+    assert(evo.get(e2, f1) == 21 and evo.get(e2, f2) == 22 and evo.get(e2, f3) == nil)
+    assert(evo.get(e3, f1) == 31 and evo.get(e3, f2) == 32 and evo.get(e3, f3) == 33)
+    assert(evo.get(e4, f1) == 41 and evo.get(e4, f2) == 42 and evo.get(e4, f3) == 43 and evo.get(e4, f4) == 44)
+
+    do
+        local q = evo.query():include(f1):build()
+        assert(evo.batch_multi_assign(q, {}) == 0)
+        assert(evo.batch_multi_assign(q, { f5 }) == 0)
+    end
+
+    do
+        local q = evo.query():include(f3):build()
+
+        assert(evo.batch_multi_assign(q, { f4 }, { 54 }) == 1)
+        assert(evo.get(e3, f3) == 33 and evo.get(e3, f4) == nil)
+        assert(evo.get(e4, f3) == 43 and evo.get(e4, f4) == 54)
+    end
+
+    do
+        local q = evo.query():include(f2):build()
+
+        assert(evo.batch_multi_assign(q, { f1 }, { 51, 52 }) == 3)
+        assert(evo.get(e1, f1) == 11 and evo.get(e1, f2) == nil and evo.get(e1, f3) == nil)
+        assert(evo.get(e2, f1) == 51 and evo.get(e2, f2) == 22 and evo.get(e2, f3) == nil)
+        assert(evo.get(e3, f1) == 51 and evo.get(e3, f2) == 32 and evo.get(e3, f3) == 33)
+        assert(evo.get(e4, f1) == 51 and evo.get(e4, f2) == 42 and evo.get(e4, f3) == 43 and evo.get(e4, f4) == 54)
+
+        assert(evo.batch_multi_assign(q, { f2, f3 }, { 52, 53 }) == 3)
+        assert(evo.get(e1, f1) == 11 and evo.get(e1, f2) == nil and evo.get(e1, f3) == nil)
+        assert(evo.get(e2, f1) == 51 and evo.get(e2, f2) == 52 and evo.get(e2, f3) == nil)
+        assert(evo.get(e3, f1) == 51 and evo.get(e3, f2) == 52 and evo.get(e3, f3) == 53)
+        assert(evo.get(e4, f1) == 51 and evo.get(e4, f2) == 52 and evo.get(e4, f3) == 53 and evo.get(e4, f4) == 54)
+    end
+end
+
+do
+    local f1, f2, f3, f4, f5 = evo.id(4)
+
+    evo.set(f2, evo.DEFAULT, 41)
+    evo.set(f3, evo.TAG)
+
+    local e1 = evo.entity():set(f1, 11):build()
+    local e2 = evo.entity():set(f1, 21):set(f2, 22):build()
+    local e3 = evo.entity():set(f1, 31):set(f2, 32):set(f3, 33):build()
+    local e4 = evo.entity():set(f1, 41):set(f2, 42):set(f3, 43):set(f4, 44):build()
+
+    assert(evo.get(e1, f1) == 11 and evo.get(e1, f2) == nil and evo.get(e1, f3) == nil)
+    assert(evo.get(e2, f1) == 21 and evo.get(e2, f2) == 22 and evo.get(e2, f3) == nil)
+    assert(evo.get(e3, f1) == 31 and evo.get(e3, f2) == 32 and evo.get(e3, f3) == nil)
+    assert(evo.get(e4, f1) == 41 and evo.get(e4, f2) == 42 and evo.get(e4, f3) == nil and evo.get(e4, f4) == 44)
+
+    do
+        local q = evo.query():include(f1):build()
+        assert(evo.batch_multi_assign(q, {}) == 0)
+        assert(evo.batch_multi_assign(q, { f5 }) == 0)
+    end
+
+    do
+        local q = evo.query():include(f3):build()
+
+        assert(evo.batch_multi_assign(q, { f4 }, { 54 }) == 1)
+        assert(evo.get(e1, f1) == 11 and evo.get(e1, f2) == nil and evo.get(e1, f3) == nil)
+        assert(evo.get(e2, f1) == 21 and evo.get(e2, f2) == 22 and evo.get(e2, f3) == nil)
+        assert(evo.get(e3, f1) == 31 and evo.get(e3, f2) == 32 and evo.get(e3, f3) == nil)
+        assert(evo.get(e4, f1) == 41 and evo.get(e4, f2) == 42 and evo.get(e4, f3) == nil and evo.get(e4, f4) == 54)
+    end
+
+    do
+        local q = evo.query():include(f2):build()
+
+        assert(evo.batch_multi_assign(q, { f1 }, { 51, 52 }) == 3)
+        assert(evo.get(e1, f1) == 11 and evo.get(e1, f2) == nil and evo.get(e1, f3) == nil)
+        assert(evo.get(e2, f1) == 51 and evo.get(e2, f2) == 22 and evo.get(e2, f3) == nil)
+        assert(evo.get(e3, f1) == 51 and evo.get(e3, f2) == 32 and evo.get(e3, f3) == nil)
+        assert(evo.get(e4, f1) == 51 and evo.get(e4, f2) == 42 and evo.get(e4, f3) == nil and evo.get(e4, f4) == 54)
+
+        assert(evo.batch_multi_assign(q, { f2, f3 }, { 52, 53 }) == 3)
+        assert(evo.get(e1, f1) == 11 and evo.get(e1, f2) == nil and evo.get(e1, f3) == nil)
+        assert(evo.get(e2, f1) == 51 and evo.get(e2, f2) == 52 and evo.get(e2, f3) == nil)
+        assert(evo.get(e3, f1) == 51 and evo.get(e3, f2) == 52 and evo.get(e3, f3) == nil)
+        assert(evo.get(e4, f1) == 51 and evo.get(e4, f2) == 52 and evo.get(e4, f3) == nil and evo.get(e4, f4) == 54)
+    end
+
+    do
+        local q = evo.query():include(f1):build()
+
+        assert(evo.batch_multi_assign(q, { f1 }) == 4)
+        assert(evo.get(e1, f1) == true and evo.get(e1, f2) == nil and evo.get(e1, f3) == nil)
+        assert(evo.get(e2, f1) == true and evo.get(e2, f2) == 52 and evo.get(e2, f3) == nil)
+        assert(evo.get(e3, f1) == true and evo.get(e3, f2) == 52 and evo.get(e3, f3) == nil)
+        assert(evo.get(e4, f1) == true and evo.get(e4, f2) == 52 and evo.get(e4, f3) == nil and evo.get(e4, f4) == 54)
+
+        assert(evo.batch_multi_assign(q, { f2 }) == 3)
+        assert(evo.get(e1, f1) == true and evo.get(e1, f2) == nil and evo.get(e1, f3) == nil)
+        assert(evo.get(e2, f1) == true and evo.get(e2, f2) == 41 and evo.get(e2, f3) == nil)
+        assert(evo.get(e3, f1) == true and evo.get(e3, f2) == 41 and evo.get(e3, f3) == nil)
+        assert(evo.get(e4, f1) == true and evo.get(e4, f2) == 41 and evo.get(e4, f3) == nil and evo.get(e4, f4) == 54)
+    end
+end
+
+do
+    local f1, f2, f3 = evo.id(3)
+
+    evo.set(f2, evo.DEFAULT, 42)
+    evo.set(f3, evo.TAG)
+
+    local sum_entity = 0
+    local last_assign_entity = 0
+    local last_assign_new_component = 0
+    local last_assign_old_component = 0
+
+    evo.set(f1, evo.ON_ASSIGN, function(e, f, nc, oc)
+        assert(f == f1)
+        sum_entity = sum_entity + e
+        last_assign_entity = e
+        last_assign_new_component = nc
+        last_assign_old_component = oc
+    end)
+
+    evo.set(f2, evo.ON_ASSIGN, function(e, f, nc, oc)
+        assert(f == f2)
+        sum_entity = sum_entity + e
+        last_assign_entity = e
+        last_assign_new_component = nc
+        last_assign_old_component = oc
+    end)
+
+    evo.set(f3, evo.ON_ASSIGN, function(e, f, nc, oc)
+        assert(f == f3)
+        sum_entity = sum_entity + e
+        last_assign_entity = e
+        last_assign_new_component = nc
+        last_assign_old_component = oc
+    end)
+
+    local e1 = evo.entity():set(f1, 11):build()
+    local e2 = evo.entity():set(f1, 21):set(f2, 22):build()
+    local e3 = evo.entity():set(f1, 31):set(f2, 32):set(f3, 33):build()
+
+    do
+        local q = evo.query():include(f3):build()
+
+        sum_entity = 0
+        last_assign_entity = 0
+        last_assign_new_component = 0
+        last_assign_old_component = 0
+
+        assert(evo.batch_multi_assign(q, { f2 }, {}) == 1)
+        assert(sum_entity == e3)
+        assert(last_assign_entity == e3)
+        assert(last_assign_new_component == 42)
+        assert(last_assign_old_component == 32)
+    end
+
+    do
+        local q = evo.query():include(f1):build()
+
+        sum_entity = 0
+        last_assign_entity = 0
+        last_assign_new_component = 0
+        last_assign_old_component = 0
+
+        assert(evo.batch_multi_assign(q, { f1 }, { 51 }) == 3)
+        assert(sum_entity == e1 + e2 + e3)
+        assert(last_assign_entity == e3)
+        assert(last_assign_new_component == 51)
+        assert(last_assign_old_component == 31)
+    end
+
+    do
+        local q = evo.query():include(f1):build()
+
+        sum_entity = 0
+        last_assign_entity = 0
+        last_assign_new_component = 0
+        last_assign_old_component = 0
+
+        assert(evo.batch_multi_assign(q, { f1, f1 }, { 61, 61 }) == 3)
+        assert(sum_entity == e1 + e2 + e3 + e1 + e2 + e3)
+        assert(last_assign_entity == e3)
+        assert(last_assign_new_component == 61)
+        assert(last_assign_old_component == 61)
+    end
+
+    do
+        local q = evo.query():include(f1):build()
+
+        sum_entity = 0
+        last_assign_entity = 0
+        last_assign_new_component = 0
+        last_assign_old_component = 0
+
+        assert(evo.batch_multi_assign(q, { f3 }, { 63 }) == 1)
+        assert(sum_entity == e3)
+        assert(last_assign_entity == e3)
+        assert(last_assign_new_component == nil)
+        assert(last_assign_old_component == nil)
+    end
+end
diff --git a/evolved.lua b/evolved.lua
index 80a2311..bb48af6 100644
--- a/evolved.lua
+++ b/evolved.lua
@@ -1364,7 +1364,108 @@ end
 ---@param components evolved.component[]
 ---@return integer assigned_count
 local function __chunk_multi_assign(chunk, fragments, components)
-    error('not implemented yet', 2)
+    if __defer_depth <= 0 then
+        error('batched chunk operations should be deferred', 2)
+    end
+
+    local fragment_count = #fragments
+
+    if fragment_count == 0 then
+        return 0
+    end
+
+    if not __chunk_has_any_fragment_list(chunk, fragments) then
+        return 0
+    end
+
+    local chunk_entities = chunk.__entities
+    local chunk_size = #chunk_entities
+
+    local chunk_fragment_set = chunk.__fragment_set
+    local chunk_component_indices = chunk.__component_indices
+    local chunk_component_storages = chunk.__component_storages
+
+    for i = 1, fragment_count do
+        local fragment = fragments[i]
+        if chunk_fragment_set[fragment] then
+            if chunk.__has_set_or_assign_hooks and __fragment_has_set_or_assign_hooks(fragment) then
+                local component_index = chunk_component_indices[fragment]
+                if component_index then
+                    local component_storage = chunk_component_storages[component_index]
+                    if chunk.__has_defaults_or_constructs and __fragment_has_default_or_construct(fragment) then
+                        local new_component = components[i]
+
+                        if new_component == nil then
+                            new_component = evolved.get(fragment, evolved.DEFAULT)
+                        end
+
+                        if new_component == nil then
+                            new_component = true
+                        end
+
+                        for place = 1, chunk_size do
+                            local entity = chunk_entities[place]
+                            local old_component = component_storage[place]
+                            component_storage[place] = new_component
+                            __fragment_call_set_and_assign_hooks(entity, fragment, new_component, old_component)
+                        end
+                    else
+                        local new_component = components[i]
+
+                        if new_component == nil then
+                            new_component = true
+                        end
+
+                        for place = 1, chunk_size do
+                            local entity = chunk_entities[place]
+                            local old_component = component_storage[place]
+                            component_storage[place] = new_component
+                            __fragment_call_set_and_assign_hooks(entity, fragment, new_component, old_component)
+                        end
+                    end
+                else
+                    for place = 1, chunk_size do
+                        local entity = chunk_entities[place]
+                        __fragment_call_set_and_assign_hooks(entity, fragment)
+                    end
+                end
+            else
+                local component_index = chunk_component_indices[fragment]
+                if component_index then
+                    local component_storage = chunk_component_storages[component_index]
+                    if chunk.__has_defaults_or_constructs and __fragment_has_default_or_construct(fragment) then
+                        local new_component = components[i]
+
+                        if new_component == nil then
+                            new_component = evolved.get(fragment, evolved.DEFAULT)
+                        end
+
+                        if new_component == nil then
+                            new_component = true
+                        end
+
+                        for place = 1, chunk_size do
+                            component_storage[place] = new_component
+                        end
+                    else
+                        local new_component = components[i]
+
+                        if new_component == nil then
+                            new_component = true
+                        end
+
+                        for place = 1, chunk_size do
+                            component_storage[place] = new_component
+                        end
+                    end
+                else
+                    -- nothing
+                end
+            end
+        end
+    end
+
+    return chunk_size
 end
 
 ---@param chunk evolved.chunk