From 369e3db5f9d000f6e4622c237ae6c3a2fc590b7c Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 16:42:37 -0600
Subject: [PATCH 01/13] drop json3 dependency

---
 Project.toml | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/Project.toml b/Project.toml
index 3f89ed780..92a99ab66 100644
--- a/Project.toml
+++ b/Project.toml
@@ -12,7 +12,7 @@ DocStringExtensions = "ffbed154-4ef7-542d-bbb7-c09d3a79fcae"
 H5Zblosc = "c8ec2601-a99c-407f-b158-e79c03c2f5f7"
 HDF5 = "f67ccb44-e63f-5c2f-98bd-6dc0ccc4ba2f"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
-JSON3 = "0f8b85d8-7281-11e9-16c2-39a750bddbf1"
+JSON = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
 Mustache = "ffc61752-8dc7-55ee-8c37-f3e9cdd09e70"
@@ -24,7 +24,6 @@ SHA = "ea8e919c-243c-51af-8825-aaa63cd721ce"
 SQLite = "0aa819cd-b072-5ff4-a722-6bc24af294d9"
 Serialization = "9e88b42a-f829-5b0c-bbe9-9e923198166b"
 StringTemplates = "59c22e0c-4e04-425f-9782-11a552c58a8d"
-StructTypes = "856f2bd8-1eba-4b0a-8007-ebc267875bd4"
 TOML = "fa267f1f-6049-4f14-aa54-33bafae1ed76"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
 TerminalLoggers = "5d786b92-1e48-4d6f-9151-6b4477ca9bed"
@@ -42,7 +41,7 @@ DocStringExtensions = "0.8, 0.9"
 H5Zblosc = "0.1"
 HDF5 = "0.17"
 InteractiveUtils = "1"
-JSON3 = "^1.11"
+JSON = "^1.5"
 LinearAlgebra = "1"
 Logging = "1"
 Mustache = "1"
@@ -54,7 +53,6 @@ SHA = "0.7"
 SQLite = "^1.6"
 Serialization = "1"
 StringTemplates = "0.1.0"
-StructTypes = "^1.9"
 TOML = "1"
 Tables = "^1.11"
 TerminalLoggers = "~0.1"

From a28cc5a6053d34fe1e8a7ad9afe676ba78d8847f Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 16:43:32 -0600
Subject: [PATCH 02/13] change API

---
 src/abstract_time_series.jl        |  4 ++--
 src/serialization.jl               | 16 ++++++++--------
 src/time_series_metadata_store.jl  | 12 ++++++------
 src/time_series_parser.jl          |  2 +-
 src/utils/generate_struct_files.jl |  8 ++------
 src/utils/generate_structs.jl      |  2 +-
 src/utils/recorder_events.jl       |  6 +++---
 src/validation.jl                  |  2 +-
 8 files changed, 24 insertions(+), 28 deletions(-)

diff --git a/src/abstract_time_series.jl b/src/abstract_time_series.jl
index 4a6029d4f..94fa2d478 100644
--- a/src/abstract_time_series.jl
+++ b/src/abstract_time_series.jl
@@ -17,13 +17,13 @@ end
 function make_features_string(features::Dict{String, Union{Bool, Int, String}})
     key_names = sort!(collect(keys(features)))
     data = [Dict(k => features[k]) for k in key_names]
-    return JSON3.write(data)
+    return JSON.json(data)
 end
 
 function make_features_string(; features...)
     key_names = sort!(collect(string.(keys(features))))
     data = [Dict(k => features[Symbol(k)]) for (k) in key_names]
-    return JSON3.write(data)
+    return JSON.json(data)
 end
 
 abstract type ForecastMetadata <: TimeSeriesMetadata end
diff --git a/src/serialization.jl b/src/serialization.jl
index 8afccc317..1fb0777d7 100644
--- a/src/serialization.jl
+++ b/src/serialization.jl
@@ -33,10 +33,10 @@ function to_json(obj::T; pretty = false, indent = 2) where {T <: InfrastructureS
     try
         if pretty
             io = IOBuffer()
-            JSON3.pretty(io, serialize(obj), JSON3.AlignmentContext(; indent = indent))
+            JSON.json(io, serialize(obj); pretty = indent)
             return take!(io)
         else
-            return JSON3.write(serialize(obj))
+            return JSON.json(serialize(obj))
         end
     catch e
         @error "Failed to serialize $(summary(obj))"
@@ -52,9 +52,9 @@ function to_json(
 ) where {T <: InfrastructureSystemsType}
     data = serialize(obj)
     if pretty
-        res = JSON3.pretty(io, data, JSON3.AlignmentContext(; indent = indent))
+        res = JSON.json(io, data; pretty = indent)
     else
-        res = JSON3.write(io, data)
+        res = JSON.json(io, data)
     end
 
     return res
@@ -73,7 +73,7 @@ end
 Deserializes a InfrastructureSystemsType from String or IO.
 """
 function from_json(io::Union{IO, String}, ::Type{T}) where {T <: InfrastructureSystemsType}
-    return deserialize(T, JSON3.read(io, Dict))
+    return deserialize(T, JSON.parse(io; dicttype = Dict{String, Any}))
 end
 
 """
@@ -271,7 +271,7 @@ deserialize(::Type{Dates.DateTime}, val::AbstractString) = Dates.DateTime(val)
 # The next methods fix serialization of UUIDs. The underlying type of a UUID is a UInt128.
 # JSON tries to encode this as a number in JSON. Encoding integers greater than can
 # be stored in a signed 64-bit integer sometimes does not work - at least when using
-# JSON3. The number gets converted to a float in scientific notation, and so
+# JSON. The number gets converted to a float in scientific notation, and so
 # the UUID is truncated and essentially lost. These functions cause JSON to encode UUIDs as
 # strings and then convert them back during deserialization.
 
@@ -298,14 +298,14 @@ function serialize_julia_info()
 end
 
 """
-Perform a test to see if JSON3 can convert this value so that the code can give the user a
+Perform a test to see if JSON can convert this value so that the code can give the user a
 a comprehensible corrective action.
 """
 function is_ext_valid_for_serialization(value)
     isnothing(value) && return true
     is_valid = true
     try
-        JSON3.write(value)
+        JSON.json(value)
     catch
         is_valid = false
     end
diff --git a/src/time_series_metadata_store.jl b/src/time_series_metadata_store.jl
index 73d429601..7ad76da49 100644
--- a/src/time_series_metadata_store.jl
+++ b/src/time_series_metadata_store.jl
@@ -123,7 +123,7 @@ function _load_metadata_into_memory!(store::TimeSeriesMetadataStore)
             elseif field == :time_series_uuid
                 data[field] = Base.UUID(val)
             elseif field == :features
-                features_array = JSON3.read(val, Array)
+                features_array = JSON.parse(val; dicttype = Dict{String, Any})
                 features_dict = Dict{String, Union{Bool, Int, String}}()
                 for obj in features_array
                     length(obj) != 1 && error("Invalid features: $obj")
@@ -134,7 +134,7 @@ function _load_metadata_into_memory!(store::TimeSeriesMetadataStore)
                 data[field] = features_dict
             elseif field == :scaling_factor_multiplier
                 if !ismissing(val)
-                    val2 = JSON3.read(val, Dict{String, Any})
+                    val2 = JSON.parse(val; dicttype = Dict{String, Any})
                     data[field] = deserialize(Function, val2)
                 end
             else
@@ -294,7 +294,7 @@ function _create_migrated_row(metadata::SingleTimeSeriesMetadata, row)
         row.owner_type,
         row.owner_category,
         row.features,
-        isnothing(sfm) ? missing : JSON3.write(serialize(sfm)),
+        isnothing(sfm) ? missing : JSON.json(serialize(sfm)),
         get_uuid(metadata),
         missing,
     )
@@ -317,7 +317,7 @@ function _create_migrated_row(metadata::ForecastMetadata, row)
         row.owner_type,
         row.owner_category,
         row.features,
-        isnothing(sfm) ? missing : JSON3.write(serialize(sfm)),
+        isnothing(sfm) ? missing : JSON.json(serialize(sfm)),
         get_uuid(metadata),
         missing,
     )
@@ -503,7 +503,7 @@ function add_metadata!(
         owner_category,
         _convert_ts_type_to_string(time_series_type),
         features,
-        isnothing(sfm) ? missing : JSON3.write(serialize(sfm)),
+        isnothing(sfm) ? missing : JSON.json(serialize(sfm)),
     )
     params = chop(repeat("?,", length(vals)))
     _execute_cached(
@@ -1612,7 +1612,7 @@ _convert_ts_type_to_string(::Type{<:Probabilistic}) = _PROBABILISTIC_AS_STRING
 _convert_ts_type_to_string(::Type{<:Scenarios}) = _SCENARIOS_AS_STRING
 
 function _deserialize_metadata(text::String)
-    val = JSON3.read(text, Dict)
+    val = JSON.parse(text; dicttype = Dict{String, Any})
     return deserialize(get_type_from_serialization_data(val), val)
 end
 
diff --git a/src/time_series_parser.jl b/src/time_series_parser.jl
index a248fb9a0..e827ffab4 100644
--- a/src/time_series_parser.jl
+++ b/src/time_series_parser.jl
@@ -76,7 +76,7 @@ function read_time_series_file_metadata(file_path::AbstractString)
     if endswith(file_path, ".json")
         metadata = open(file_path) do io
             metadata = Vector{TimeSeriesFileMetadata}()
-            data = JSON3.read(io, Array)
+            data = JSON.parse(io; dicttype = Dict{String, Any})
             for item in data
                 parsed_resolution = Dates.Millisecond(Dates.Second(item["resolution"]))
                 normalization_factor = item["normalization_factor"]
diff --git a/src/utils/generate_struct_files.jl b/src/utils/generate_struct_files.jl
index 64f1b625d..7a6c568f7 100644
--- a/src/utils/generate_struct_files.jl
+++ b/src/utils/generate_struct_files.jl
@@ -147,10 +147,6 @@ function StructDefinition(;
     return StructDefinition(struct_name, fields, supertype, docstring)
 end
 
-# These allow JSON3 serialization of the structs.
-StructTypes.StructType(::Type{StructDefinition}) = StructTypes.Struct()
-StructTypes.StructType(::Type{StructField}) = StructTypes.Struct()
-
 """
 Generate a Julia source code file for one struct from a `StructDefinition`.
 
@@ -204,7 +200,7 @@ function generate_struct_files(definitions; filename = nothing, output_directory
     end
 
     data = open(filename, "r") do io
-        JSON3.read(io, Dict)
+        JSON.parse(io; dicttype = Dict{String, Any})
     end
 
     # The user might run this multiple times and so we need to remove existing entries.
@@ -224,7 +220,7 @@ function generate_struct_files(definitions; filename = nothing, output_directory
     end
 
     open(filename, "w") do io
-        JSON3.pretty(io, data, JSON3.AlignmentContext(; indent = 2))
+        JSON.json(io, data; pretty = 2)
     end
 
     @info "Added $(length(definitions)) structs to $filename"
diff --git a/src/utils/generate_structs.jl b/src/utils/generate_structs.jl
index 5dd0552d5..63e1156f9 100644
--- a/src/utils/generate_structs.jl
+++ b/src/utils/generate_structs.jl
@@ -79,7 +79,7 @@ end
 
 function read_json_data(filename::String)
     return open(filename) do io
-        data = JSON3.read(io, Dict)
+        data = JSON.parse(io; dicttype = Dict{String, Any})
         if data isa Array
             return data
         elseif data isa Dict && haskey(data, "auto_generated_structs")
diff --git a/src/utils/recorder_events.jl b/src/utils/recorder_events.jl
index aae2827a7..14189f84d 100644
--- a/src/utils/recorder_events.jl
+++ b/src/utils/recorder_events.jl
@@ -34,9 +34,9 @@ function serialize(event::T) where {T <: AbstractRecorderEvent}
     return data
 end
 
-to_json(event::AbstractRecorderEvent) = JSON3.write(serialize(event))
+to_json(event::AbstractRecorderEvent) = JSON.json(serialize(event))
 from_json(::Type{T}, text::AbstractString) where {T <: AbstractRecorderEvent} =
-    deserialize(T, JSON3.read(text, Dict))
+    deserialize(T, JSON.parse(text; dicttype = Dict{String, Any}))
 
 function deserialize(::Type{T}, data::Dict) where {T <: AbstractRecorderEvent}
     name = pop!(data, "name")
@@ -151,7 +151,7 @@ end
 function _record_event(name::Symbol, event::AbstractRecorderEvent)
     # Key is not checked. Callers must use @record and not call this directly.
     recorder = g_recorders[name]
-    write(recorder.io, JSON3.write(serialize(event)))
+    write(recorder.io, JSON.json(serialize(event)))
     return write(recorder.io, "\n")
 end
 
diff --git a/src/validation.jl b/src/validation.jl
index d423da3c3..e465c73bc 100644
--- a/src/validation.jl
+++ b/src/validation.jl
@@ -16,7 +16,7 @@ function read_validation_descriptor(filename::AbstractString)
         end
     elseif occursin(r"(\.json)"i, filename)
         data = open(filename) do file
-            return JSON3.read(file, Dict)
+            return JSON.parse(file; dicttype = Dict{String, Any})
         end
     else
         error("Filename is not a YAML or JSON file.")

From d7ee6cc75dfa56537e74e714ab251dd4592e4a8b Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 16:44:03 -0600
Subject: [PATCH 03/13] change imports

---
 src/InfrastructureSystems.jl       | 3 +--
 src/utils/test.jl                  | 2 +-
 src/utils/utils.jl                 | 9 +++------
 test/InfrastructureSystemsTests.jl | 2 +-
 4 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/src/InfrastructureSystems.jl b/src/InfrastructureSystems.jl
index bbf1fa251..1c9428226 100644
--- a/src/InfrastructureSystems.jl
+++ b/src/InfrastructureSystems.jl
@@ -13,7 +13,7 @@ import CSV
 import DataFrames
 import DataFrames: DataFrame
 import Dates
-import JSON3
+import JSON
 import Logging
 import Random
 import Pkg
@@ -21,7 +21,6 @@ import PrettyTables
 import Printf: @sprintf
 import SHA
 import StringTemplates
-import StructTypes
 import TerminalLoggers: TerminalLogger, ProgressLevel
 import TimeSeries
 import TimerOutputs
diff --git a/src/utils/test.jl b/src/utils/test.jl
index 72e4bfba4..d35b0fa5e 100644
--- a/src/utils/test.jl
+++ b/src/utils/test.jl
@@ -51,7 +51,7 @@ supports_time_series(::AdditionalTestComponent) = true
 supports_time_series(::SimpleTestComponent) = false
 
 function from_json(io::IO, ::Type{TestComponent})
-    data = JSON3.read(io, Dict)
+    data = JSON.parse(io; dicttype = Dict{String, Any})
     return deserialize(TestComponent, data)
 end
 
diff --git a/src/utils/utils.jl b/src/utils/utils.jl
index 8a485a89d..ef4457f5b 100644
--- a/src/utils/utils.jl
+++ b/src/utils/utils.jl
@@ -1,6 +1,6 @@
 import InteractiveUtils
 import SHA
-import JSON3
+import JSON
 
 const HASH_FILENAME = "check.sha256"
 const COMPARE_VALUES_SENTINEL = :(!NOUPGRADE)  # A Symbol that can't be a field name
@@ -364,7 +364,6 @@ macro scoped_enum(T, args...)
     blk = esc(
         :(
             module $(Symbol("$(T)Module"))
-            using JSON3
             import InfrastructureSystems
             export $T
             struct $T
@@ -393,11 +392,9 @@ macro scoped_enum(T, args...)
             Base.show(io::IO, e::$T) =
                 print(io, string($T, ".", string(e), " = ", e.value))
             Base.propertynames(::Type{$T}) = _ALL_NAMES
-            JSON3.StructType(::Type{$T}) = JSON3.StructTypes.StringType()
 
             InfrastructureSystems.serialize(val::$T) = Base.string(val)
-            InfrastructureSystems.deserialize(::Type{$T}, val) =
-                JSON3.StructTypes.constructfrom($T, val)
+            InfrastructureSystems.deserialize(::Type{$T}, val) = $T(val)
 
             Base.convert(::Type{$T}, val::Integer) = $T(val)
             Base.isless(val::$T, other::$T) = isless(val.value, other.value)
@@ -726,7 +723,7 @@ function compute_file_hash(path::String, files::Vector{String})
     end
 
     open(joinpath(path, HASH_FILENAME), "w") do io
-        JSON3.write(io, data)
+        JSON.json(io, data)
     end
 end
 
diff --git a/test/InfrastructureSystemsTests.jl b/test/InfrastructureSystemsTests.jl
index 54ea69a6a..98ad5afe0 100644
--- a/test/InfrastructureSystemsTests.jl
+++ b/test/InfrastructureSystemsTests.jl
@@ -6,7 +6,7 @@ using Dates
 import TerminalLoggers: TerminalLogger
 import TimeSeries
 import UUIDs
-import JSON3
+import JSON
 import HDF5
 using DataStructures: SortedDict
 using DataFrames

From 0ece622345e231daac5e6d6440c79e962a2e98cf Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 16:44:10 -0600
Subject: [PATCH 04/13] update testing

---
 test/Project.toml             |  2 +-
 test/test_function_data.jl    |  6 +++++-
 test/test_generate_structs.jl |  2 +-
 test/test_recorder.jl         |  2 +-
 test/test_serialization.jl    | 19 ++++++++++++++-----
 test/test_time_series.jl      |  4 ++--
 6 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/test/Project.toml b/test/Project.toml
index 8015a777c..e11f25865 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -8,7 +8,7 @@ Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 HDF5 = "f67ccb44-e63f-5c2f-98bd-6dc0ccc4ba2f"
 InfrastructureSystems = "2cd47ed4-ca9b-11e9-27f2-ab636a7671f1"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
-JSON3 = "0f8b85d8-7281-11e9-16c2-39a750bddbf1"
+JSON = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"
 Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
 Mustache = "ffc61752-8dc7-55ee-8c37-f3e9cdd09e70"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
diff --git a/test/test_function_data.jl b/test/test_function_data.jl
index e6a1bf444..4cf8c1576 100644
--- a/test/test_function_data.jl
+++ b/test/test_function_data.jl
@@ -613,7 +613,11 @@ end
     for fd in get_test_function_data()
         for do_jsonify in (false, true)
             serialized = IS.serialize(fd)
-            do_jsonify && (serialized = JSON3.read(JSON3.write(serialized), Dict))
+            do_jsonify &&
+                (
+                    serialized =
+                        JSON.parse(JSON.json(serialized); dicttype = Dict{String, Any})
+                )
             @test typeof(serialized) <: AbstractDict
             deserialized = IS.deserialize(typeof(fd), serialized)
             @test deserialized == fd
diff --git a/test/test_generate_structs.jl b/test/test_generate_structs.jl
index 169669da1..220209aa7 100644
--- a/test/test_generate_structs.jl
+++ b/test/test_generate_structs.jl
@@ -30,7 +30,7 @@ end
         )
     end
     data = open(descriptor_file, "r") do io
-        JSON3.read(io, Dict)
+        JSON.parse(io; dicttype = Dict{String, Any})
     end
 
     @test data["auto_generated_structs"][end]["struct_name"] == "MyComponent"
diff --git a/test/test_recorder.jl b/test/test_recorder.jl
index 018e00c80..6318b9072 100644
--- a/test/test_recorder.jl
+++ b/test/test_recorder.jl
@@ -12,7 +12,7 @@
         @test isfile(filename)
         lines = readlines(filename)
         @test length(lines) == 1
-        data = JSON3.read(lines[1], Dict)
+        data = JSON.parse(lines[1]; dicttype = Dict{String, Any})
         @test data["name"] == "TestEvent"
         @test data["val1"] == "a"
         @test data["val2"] == 1
diff --git a/test/test_serialization.jl b/test/test_serialization.jl
index b6fcc8810..3b371d66e 100644
--- a/test/test_serialization.jl
+++ b/test/test_serialization.jl
@@ -4,7 +4,7 @@ function validate_serialization(sys::IS.SystemData; time_series_read_only = fals
     IS.prepare_for_serialization_to_file!(sys, filename; force = true)
     data = IS.serialize(sys)
     open(filename, "w") do io
-        JSON3.write(io, data)
+        JSON.json(io, data)
     end
 
     # Make sure the code supports the files changing directories.
@@ -23,7 +23,7 @@ function validate_serialization(sys::IS.SystemData; time_series_read_only = fals
     end
 
     data = open(path) do io
-        return JSON3.read(io, Dict)
+        return JSON.parse(io; dicttype = Dict{String, Any})
     end
 
     orig = pwd()
@@ -159,7 +159,10 @@ end
 @testset "Test JSON string" begin
     component = IS.SimpleTestComponent("Component1", 1)
     text = IS.to_json(component)
-    IS.deserialize(IS.SimpleTestComponent, JSON3.read(text, Dict)) == component
+    IS.deserialize(
+        IS.SimpleTestComponent,
+        JSON.parse(text; dicttype = Dict{String, Any}),
+    ) == component
 end
 
 @testset "Test pretty-print JSON IO" begin
@@ -168,13 +171,19 @@ end
     IS.to_json(io, component; pretty = false)
     text = String(take!(io))
     @test !occursin(" ", text)
-    IS.deserialize(IS.SimpleTestComponent, JSON3.read(text, Dict)) == component
+    IS.deserialize(
+        IS.SimpleTestComponent,
+        JSON.parse(text; dicttype = Dict{String, Any}),
+    ) == component
 
     io = IOBuffer()
     IS.to_json(io, component; pretty = true)
     text = String(take!(io))
     @test occursin(" ", text)
-    IS.deserialize(IS.SimpleTestComponent, JSON3.read(text, Dict)) == component
+    IS.deserialize(
+        IS.SimpleTestComponent,
+        JSON.parse(text; dicttype = Dict{String, Any}),
+    ) == component
 end
 
 @testset "Test ext serialization" begin
diff --git a/test/test_time_series.jl b/test/test_time_series.jl
index 3d0f1ef22..65c61c45b 100644
--- a/test/test_time_series.jl
+++ b/test/test_time_series.jl
@@ -3922,7 +3922,7 @@ function _setup_for_migration_tests_from_IS_v2_3()
                         string(nameof(typeof(component))),
                         owner_category,
                         features,
-                        JSON3.write(IS.serialize(metadata)),
+                        JSON.json(IS.serialize(metadata)),
                     )
                 SQLite.DBInterface.execute(stmt, params)
             end
@@ -3948,7 +3948,7 @@ function _setup_for_migration_tests_from_IS_v2_4()
                     (
                         missing,
                         string(IS.get_uuid(metadata)),
-                        JSON3.write(IS.serialize(metadata)),
+                        JSON.json(IS.serialize(metadata)),
                     )
                 SQLite.DBInterface.execute(stmt, params)
             end

From 1d893ff4a540ca83e043e424925911f5c165bb38 Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 17:00:15 -0600
Subject: [PATCH 05/13] remove support for function deserialization in Ext

---
 src/serialization.jl | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/src/serialization.jl b/src/serialization.jl
index 1fb0777d7..5f50e211d 100644
--- a/src/serialization.jl
+++ b/src/serialization.jl
@@ -302,20 +302,39 @@ Perform a test to see if JSON can convert this value so that the code can give t
 a comprehensible corrective action.
 """
 function is_ext_valid_for_serialization(value)
-    isnothing(value) && return true
-    is_valid = true
+    is_valid = _is_ext_value_basic(value)
+    if !is_valid
+        @error "Failed to serialize an 'ext' value. Please ensure that the " *
+               "contents follow the rules provided in the documentation. Generally, only " *
+               "basic types are allowed - strings and numbers and arrays, dictionaries, and " *
+               "structs of those." value
+        return false
+    end
     try
         JSON.json(value)
     catch
-        is_valid = false
-    end
-
-    if !is_valid
         @error "Failed to serialize an 'ext' value. Please ensure that the " *
                "contents follow the rules provided in the documentation. Generally, only " *
                "basic types are allowed - strings and numbers and arrays, dictionaries, and " *
                "structs of those." value
+        return false
     end
+    return true
+end
 
-    return is_valid
+# JSON.jl will happily serialize Functions, Modules, Tasks, IO handles, etc. by
+# introspecting their fields, but those values are not meaningful JSON content and
+# cannot be reliably deserialized. Restrict 'ext' values to genuine data types.
+_is_ext_value_basic(::Union{Nothing, Missing, Number, AbstractString, Symbol, Bool}) = true
+_is_ext_value_basic(x::AbstractArray) = all(_is_ext_value_basic, x)
+_is_ext_value_basic(x::Tuple) = all(_is_ext_value_basic, x)
+_is_ext_value_basic(x::AbstractDict) =
+    all(_is_ext_value_basic, keys(x)) && all(_is_ext_value_basic, values(x))
+_is_ext_value_basic(::Union{Function, Module, Task, IO, Ptr, Base.RefValue}) = false
+function _is_ext_value_basic(x::T) where {T}
+    isstructtype(T) || return false
+    for name in fieldnames(T)
+        _is_ext_value_basic(getfield(x, name)) || return false
+    end
+    return true
 end

From eda5359f52c9b79ba77a951a3a11b8cd7bab4209 Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 22 Apr 2026 00:00:11 -0700
Subject: [PATCH 06/13] update serialize/deserialize code for the scoped enums

---
 src/utils/utils.jl | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/utils/utils.jl b/src/utils/utils.jl
index ef4457f5b..b37b6f656 100644
--- a/src/utils/utils.jl
+++ b/src/utils/utils.jl
@@ -394,7 +394,11 @@ macro scoped_enum(T, args...)
             Base.propertynames(::Type{$T}) = _ALL_NAMES
 
             InfrastructureSystems.serialize(val::$T) = Base.string(val)
+            InfrastructureSystems.serialize(vals::Vector{$T}) =
+                InfrastructureSystems.serialize.(vals)
             InfrastructureSystems.deserialize(::Type{$T}, val) = $T(val)
+            InfrastructureSystems.deserialize(::Type{Vector{$T}}, vals::Vector) =
+                [InfrastructureSystems.deserialize($T, v) for v in vals]
 
             Base.convert(::Type{$T}, val::Integer) = $T(val)
             Base.isless(val::$T, other::$T) = isless(val.value, other.value)

From 0327bc996a370b318455fd1fefa7776e90e367f2 Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 16:42:37 -0600
Subject: [PATCH 07/13] drop json3 dependency

---
 Project.toml | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/Project.toml b/Project.toml
index e0854dcaf..721adf01e 100644
--- a/Project.toml
+++ b/Project.toml
@@ -12,7 +12,7 @@ DocStringExtensions = "ffbed154-4ef7-542d-bbb7-c09d3a79fcae"
 H5Zblosc = "c8ec2601-a99c-407f-b158-e79c03c2f5f7"
 HDF5 = "f67ccb44-e63f-5c2f-98bd-6dc0ccc4ba2f"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
-JSON3 = "0f8b85d8-7281-11e9-16c2-39a750bddbf1"
+JSON = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
 Mustache = "ffc61752-8dc7-55ee-8c37-f3e9cdd09e70"
@@ -24,7 +24,6 @@ SHA = "ea8e919c-243c-51af-8825-aaa63cd721ce"
 SQLite = "0aa819cd-b072-5ff4-a722-6bc24af294d9"
 Serialization = "9e88b42a-f829-5b0c-bbe9-9e923198166b"
 StringTemplates = "59c22e0c-4e04-425f-9782-11a552c58a8d"
-StructTypes = "856f2bd8-1eba-4b0a-8007-ebc267875bd4"
 TOML = "fa267f1f-6049-4f14-aa54-33bafae1ed76"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
 TerminalLoggers = "5d786b92-1e48-4d6f-9151-6b4477ca9bed"
@@ -42,7 +41,7 @@ DocStringExtensions = "0.8, 0.9"
 H5Zblosc = "0.1"
 HDF5 = "0.17"
 InteractiveUtils = "1"
-JSON3 = "^1.11"
+JSON = "^1.5"
 LinearAlgebra = "1"
 Logging = "1"
 Mustache = "1"
@@ -54,7 +53,6 @@ SHA = "0.7"
 SQLite = "^1.6"
 Serialization = "1"
 StringTemplates = "0.1.0"
-StructTypes = "^1.9"
 TOML = "1"
 Tables = "^1.11"
 TerminalLoggers = "~0.1"

From 6a935fd769751faa0680c576551af760c6e9a221 Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 16:43:32 -0600
Subject: [PATCH 08/13] change API

---
 src/abstract_time_series.jl        |  4 ++--
 src/serialization.jl               | 16 ++++++++--------
 src/time_series_metadata_store.jl  | 12 ++++++------
 src/time_series_parser.jl          |  2 +-
 src/utils/generate_struct_files.jl |  8 ++------
 src/utils/generate_structs.jl      |  2 +-
 src/utils/recorder_events.jl       |  6 +++---
 src/validation.jl                  |  2 +-
 8 files changed, 24 insertions(+), 28 deletions(-)

diff --git a/src/abstract_time_series.jl b/src/abstract_time_series.jl
index 4a6029d4f..94fa2d478 100644
--- a/src/abstract_time_series.jl
+++ b/src/abstract_time_series.jl
@@ -17,13 +17,13 @@ end
 function make_features_string(features::Dict{String, Union{Bool, Int, String}})
     key_names = sort!(collect(keys(features)))
     data = [Dict(k => features[k]) for k in key_names]
-    return JSON3.write(data)
+    return JSON.json(data)
 end
 
 function make_features_string(; features...)
     key_names = sort!(collect(string.(keys(features))))
     data = [Dict(k => features[Symbol(k)]) for (k) in key_names]
-    return JSON3.write(data)
+    return JSON.json(data)
 end
 
 abstract type ForecastMetadata <: TimeSeriesMetadata end
diff --git a/src/serialization.jl b/src/serialization.jl
index 8afccc317..1fb0777d7 100644
--- a/src/serialization.jl
+++ b/src/serialization.jl
@@ -33,10 +33,10 @@ function to_json(obj::T; pretty = false, indent = 2) where {T <: InfrastructureS
     try
         if pretty
             io = IOBuffer()
-            JSON3.pretty(io, serialize(obj), JSON3.AlignmentContext(; indent = indent))
+            JSON.json(io, serialize(obj); pretty = indent)
             return take!(io)
         else
-            return JSON3.write(serialize(obj))
+            return JSON.json(serialize(obj))
         end
     catch e
         @error "Failed to serialize $(summary(obj))"
@@ -52,9 +52,9 @@ function to_json(
 ) where {T <: InfrastructureSystemsType}
     data = serialize(obj)
     if pretty
-        res = JSON3.pretty(io, data, JSON3.AlignmentContext(; indent = indent))
+        res = JSON.json(io, data; pretty = indent)
     else
-        res = JSON3.write(io, data)
+        res = JSON.json(io, data)
     end
 
     return res
@@ -73,7 +73,7 @@ end
 Deserializes a InfrastructureSystemsType from String or IO.
 """
 function from_json(io::Union{IO, String}, ::Type{T}) where {T <: InfrastructureSystemsType}
-    return deserialize(T, JSON3.read(io, Dict))
+    return deserialize(T, JSON.parse(io; dicttype = Dict{String, Any}))
 end
 
 """
@@ -271,7 +271,7 @@ deserialize(::Type{Dates.DateTime}, val::AbstractString) = Dates.DateTime(val)
 # The next methods fix serialization of UUIDs. The underlying type of a UUID is a UInt128.
 # JSON tries to encode this as a number in JSON. Encoding integers greater than can
 # be stored in a signed 64-bit integer sometimes does not work - at least when using
-# JSON3. The number gets converted to a float in scientific notation, and so
+# JSON. The number gets converted to a float in scientific notation, and so
 # the UUID is truncated and essentially lost. These functions cause JSON to encode UUIDs as
 # strings and then convert them back during deserialization.
 
@@ -298,14 +298,14 @@ function serialize_julia_info()
 end
 
 """
-Perform a test to see if JSON3 can convert this value so that the code can give the user a
+Perform a test to see if JSON can convert this value so that the code can give the user a
 a comprehensible corrective action.
 """
 function is_ext_valid_for_serialization(value)
     isnothing(value) && return true
     is_valid = true
     try
-        JSON3.write(value)
+        JSON.json(value)
     catch
         is_valid = false
     end
diff --git a/src/time_series_metadata_store.jl b/src/time_series_metadata_store.jl
index 73d429601..7ad76da49 100644
--- a/src/time_series_metadata_store.jl
+++ b/src/time_series_metadata_store.jl
@@ -123,7 +123,7 @@ function _load_metadata_into_memory!(store::TimeSeriesMetadataStore)
             elseif field == :time_series_uuid
                 data[field] = Base.UUID(val)
             elseif field == :features
-                features_array = JSON3.read(val, Array)
+                features_array = JSON.parse(val; dicttype = Dict{String, Any})
                 features_dict = Dict{String, Union{Bool, Int, String}}()
                 for obj in features_array
                     length(obj) != 1 && error("Invalid features: $obj")
@@ -134,7 +134,7 @@ function _load_metadata_into_memory!(store::TimeSeriesMetadataStore)
                 data[field] = features_dict
             elseif field == :scaling_factor_multiplier
                 if !ismissing(val)
-                    val2 = JSON3.read(val, Dict{String, Any})
+                    val2 = JSON.parse(val; dicttype = Dict{String, Any})
                     data[field] = deserialize(Function, val2)
                 end
             else
@@ -294,7 +294,7 @@ function _create_migrated_row(metadata::SingleTimeSeriesMetadata, row)
         row.owner_type,
         row.owner_category,
         row.features,
-        isnothing(sfm) ? missing : JSON3.write(serialize(sfm)),
+        isnothing(sfm) ? missing : JSON.json(serialize(sfm)),
         get_uuid(metadata),
         missing,
     )
@@ -317,7 +317,7 @@ function _create_migrated_row(metadata::ForecastMetadata, row)
         row.owner_type,
         row.owner_category,
         row.features,
-        isnothing(sfm) ? missing : JSON3.write(serialize(sfm)),
+        isnothing(sfm) ? missing : JSON.json(serialize(sfm)),
         get_uuid(metadata),
         missing,
     )
@@ -503,7 +503,7 @@ function add_metadata!(
         owner_category,
         _convert_ts_type_to_string(time_series_type),
         features,
-        isnothing(sfm) ? missing : JSON3.write(serialize(sfm)),
+        isnothing(sfm) ? missing : JSON.json(serialize(sfm)),
     )
     params = chop(repeat("?,", length(vals)))
     _execute_cached(
@@ -1612,7 +1612,7 @@ _convert_ts_type_to_string(::Type{<:Probabilistic}) = _PROBABILISTIC_AS_STRING
 _convert_ts_type_to_string(::Type{<:Scenarios}) = _SCENARIOS_AS_STRING
 
 function _deserialize_metadata(text::String)
-    val = JSON3.read(text, Dict)
+    val = JSON.parse(text; dicttype = Dict{String, Any})
     return deserialize(get_type_from_serialization_data(val), val)
 end
 
diff --git a/src/time_series_parser.jl b/src/time_series_parser.jl
index a248fb9a0..e827ffab4 100644
--- a/src/time_series_parser.jl
+++ b/src/time_series_parser.jl
@@ -76,7 +76,7 @@ function read_time_series_file_metadata(file_path::AbstractString)
     if endswith(file_path, ".json")
         metadata = open(file_path) do io
             metadata = Vector{TimeSeriesFileMetadata}()
-            data = JSON3.read(io, Array)
+            data = JSON.parse(io; dicttype = Dict{String, Any})
             for item in data
                 parsed_resolution = Dates.Millisecond(Dates.Second(item["resolution"]))
                 normalization_factor = item["normalization_factor"]
diff --git a/src/utils/generate_struct_files.jl b/src/utils/generate_struct_files.jl
index 64f1b625d..7a6c568f7 100644
--- a/src/utils/generate_struct_files.jl
+++ b/src/utils/generate_struct_files.jl
@@ -147,10 +147,6 @@ function StructDefinition(;
     return StructDefinition(struct_name, fields, supertype, docstring)
 end
 
-# These allow JSON3 serialization of the structs.
-StructTypes.StructType(::Type{StructDefinition}) = StructTypes.Struct()
-StructTypes.StructType(::Type{StructField}) = StructTypes.Struct()
-
 """
 Generate a Julia source code file for one struct from a `StructDefinition`.
 
@@ -204,7 +200,7 @@ function generate_struct_files(definitions; filename = nothing, output_directory
     end
 
     data = open(filename, "r") do io
-        JSON3.read(io, Dict)
+        JSON.parse(io; dicttype = Dict{String, Any})
     end
 
     # The user might run this multiple times and so we need to remove existing entries.
@@ -224,7 +220,7 @@ function generate_struct_files(definitions; filename = nothing, output_directory
     end
 
     open(filename, "w") do io
-        JSON3.pretty(io, data, JSON3.AlignmentContext(; indent = 2))
+        JSON.json(io, data; pretty = 2)
     end
 
     @info "Added $(length(definitions)) structs to $filename"
diff --git a/src/utils/generate_structs.jl b/src/utils/generate_structs.jl
index 5dd0552d5..63e1156f9 100644
--- a/src/utils/generate_structs.jl
+++ b/src/utils/generate_structs.jl
@@ -79,7 +79,7 @@ end
 
 function read_json_data(filename::String)
     return open(filename) do io
-        data = JSON3.read(io, Dict)
+        data = JSON.parse(io; dicttype = Dict{String, Any})
         if data isa Array
             return data
         elseif data isa Dict && haskey(data, "auto_generated_structs")
diff --git a/src/utils/recorder_events.jl b/src/utils/recorder_events.jl
index aae2827a7..14189f84d 100644
--- a/src/utils/recorder_events.jl
+++ b/src/utils/recorder_events.jl
@@ -34,9 +34,9 @@ function serialize(event::T) where {T <: AbstractRecorderEvent}
     return data
 end
 
-to_json(event::AbstractRecorderEvent) = JSON3.write(serialize(event))
+to_json(event::AbstractRecorderEvent) = JSON.json(serialize(event))
 from_json(::Type{T}, text::AbstractString) where {T <: AbstractRecorderEvent} =
-    deserialize(T, JSON3.read(text, Dict))
+    deserialize(T, JSON.parse(text; dicttype = Dict{String, Any}))
 
 function deserialize(::Type{T}, data::Dict) where {T <: AbstractRecorderEvent}
     name = pop!(data, "name")
@@ -151,7 +151,7 @@ end
 function _record_event(name::Symbol, event::AbstractRecorderEvent)
     # Key is not checked. Callers must use @record and not call this directly.
     recorder = g_recorders[name]
-    write(recorder.io, JSON3.write(serialize(event)))
+    write(recorder.io, JSON.json(serialize(event)))
     return write(recorder.io, "\n")
 end
 
diff --git a/src/validation.jl b/src/validation.jl
index d423da3c3..e465c73bc 100644
--- a/src/validation.jl
+++ b/src/validation.jl
@@ -16,7 +16,7 @@ function read_validation_descriptor(filename::AbstractString)
         end
     elseif occursin(r"(\.json)"i, filename)
         data = open(filename) do file
-            return JSON3.read(file, Dict)
+            return JSON.parse(file; dicttype = Dict{String, Any})
         end
     else
         error("Filename is not a YAML or JSON file.")

From d20824cad8519075d4c4b5934d49e3659c378dae Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 16:44:03 -0600
Subject: [PATCH 09/13] change imports

---
 src/InfrastructureSystems.jl       | 3 +--
 src/utils/test.jl                  | 2 +-
 src/utils/utils.jl                 | 9 +++------
 test/InfrastructureSystemsTests.jl | 2 +-
 4 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/src/InfrastructureSystems.jl b/src/InfrastructureSystems.jl
index bbf1fa251..1c9428226 100644
--- a/src/InfrastructureSystems.jl
+++ b/src/InfrastructureSystems.jl
@@ -13,7 +13,7 @@ import CSV
 import DataFrames
 import DataFrames: DataFrame
 import Dates
-import JSON3
+import JSON
 import Logging
 import Random
 import Pkg
@@ -21,7 +21,6 @@ import PrettyTables
 import Printf: @sprintf
 import SHA
 import StringTemplates
-import StructTypes
 import TerminalLoggers: TerminalLogger, ProgressLevel
 import TimeSeries
 import TimerOutputs
diff --git a/src/utils/test.jl b/src/utils/test.jl
index 72e4bfba4..d35b0fa5e 100644
--- a/src/utils/test.jl
+++ b/src/utils/test.jl
@@ -51,7 +51,7 @@ supports_time_series(::AdditionalTestComponent) = true
 supports_time_series(::SimpleTestComponent) = false
 
 function from_json(io::IO, ::Type{TestComponent})
-    data = JSON3.read(io, Dict)
+    data = JSON.parse(io; dicttype = Dict{String, Any})
     return deserialize(TestComponent, data)
 end
 
diff --git a/src/utils/utils.jl b/src/utils/utils.jl
index 8a485a89d..ef4457f5b 100644
--- a/src/utils/utils.jl
+++ b/src/utils/utils.jl
@@ -1,6 +1,6 @@
 import InteractiveUtils
 import SHA
-import JSON3
+import JSON
 
 const HASH_FILENAME = "check.sha256"
 const COMPARE_VALUES_SENTINEL = :(!NOUPGRADE)  # A Symbol that can't be a field name
@@ -364,7 +364,6 @@ macro scoped_enum(T, args...)
     blk = esc(
         :(
             module $(Symbol("$(T)Module"))
-            using JSON3
             import InfrastructureSystems
             export $T
             struct $T
@@ -393,11 +392,9 @@ macro scoped_enum(T, args...)
             Base.show(io::IO, e::$T) =
                 print(io, string($T, ".", string(e), " = ", e.value))
             Base.propertynames(::Type{$T}) = _ALL_NAMES
-            JSON3.StructType(::Type{$T}) = JSON3.StructTypes.StringType()
 
             InfrastructureSystems.serialize(val::$T) = Base.string(val)
-            InfrastructureSystems.deserialize(::Type{$T}, val) =
-                JSON3.StructTypes.constructfrom($T, val)
+            InfrastructureSystems.deserialize(::Type{$T}, val) = $T(val)
 
             Base.convert(::Type{$T}, val::Integer) = $T(val)
             Base.isless(val::$T, other::$T) = isless(val.value, other.value)
@@ -726,7 +723,7 @@ function compute_file_hash(path::String, files::Vector{String})
     end
 
     open(joinpath(path, HASH_FILENAME), "w") do io
-        JSON3.write(io, data)
+        JSON.json(io, data)
     end
 end
 
diff --git a/test/InfrastructureSystemsTests.jl b/test/InfrastructureSystemsTests.jl
index 54ea69a6a..98ad5afe0 100644
--- a/test/InfrastructureSystemsTests.jl
+++ b/test/InfrastructureSystemsTests.jl
@@ -6,7 +6,7 @@ using Dates
 import TerminalLoggers: TerminalLogger
 import TimeSeries
 import UUIDs
-import JSON3
+import JSON
 import HDF5
 using DataStructures: SortedDict
 using DataFrames

From cad71dc0267139500e3fc9d5cbac0281473347b2 Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 16:44:10 -0600
Subject: [PATCH 10/13] update testing

---
 test/Project.toml             |  2 +-
 test/test_function_data.jl    |  6 +++++-
 test/test_generate_structs.jl |  2 +-
 test/test_recorder.jl         |  2 +-
 test/test_serialization.jl    | 19 ++++++++++++++-----
 test/test_time_series.jl      |  4 ++--
 6 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/test/Project.toml b/test/Project.toml
index 8015a777c..e11f25865 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -8,7 +8,7 @@ Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 HDF5 = "f67ccb44-e63f-5c2f-98bd-6dc0ccc4ba2f"
 InfrastructureSystems = "2cd47ed4-ca9b-11e9-27f2-ab636a7671f1"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
-JSON3 = "0f8b85d8-7281-11e9-16c2-39a750bddbf1"
+JSON = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"
 Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
 Mustache = "ffc61752-8dc7-55ee-8c37-f3e9cdd09e70"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
diff --git a/test/test_function_data.jl b/test/test_function_data.jl
index e6a1bf444..4cf8c1576 100644
--- a/test/test_function_data.jl
+++ b/test/test_function_data.jl
@@ -613,7 +613,11 @@ end
     for fd in get_test_function_data()
         for do_jsonify in (false, true)
             serialized = IS.serialize(fd)
-            do_jsonify && (serialized = JSON3.read(JSON3.write(serialized), Dict))
+            do_jsonify &&
+                (
+                    serialized =
+                        JSON.parse(JSON.json(serialized); dicttype = Dict{String, Any})
+                )
             @test typeof(serialized) <: AbstractDict
             deserialized = IS.deserialize(typeof(fd), serialized)
             @test deserialized == fd
diff --git a/test/test_generate_structs.jl b/test/test_generate_structs.jl
index 169669da1..220209aa7 100644
--- a/test/test_generate_structs.jl
+++ b/test/test_generate_structs.jl
@@ -30,7 +30,7 @@ end
         )
     end
     data = open(descriptor_file, "r") do io
-        JSON3.read(io, Dict)
+        JSON.parse(io; dicttype = Dict{String, Any})
     end
 
     @test data["auto_generated_structs"][end]["struct_name"] == "MyComponent"
diff --git a/test/test_recorder.jl b/test/test_recorder.jl
index 018e00c80..6318b9072 100644
--- a/test/test_recorder.jl
+++ b/test/test_recorder.jl
@@ -12,7 +12,7 @@
         @test isfile(filename)
         lines = readlines(filename)
         @test length(lines) == 1
-        data = JSON3.read(lines[1], Dict)
+        data = JSON.parse(lines[1]; dicttype = Dict{String, Any})
         @test data["name"] == "TestEvent"
         @test data["val1"] == "a"
         @test data["val2"] == 1
diff --git a/test/test_serialization.jl b/test/test_serialization.jl
index b6fcc8810..3b371d66e 100644
--- a/test/test_serialization.jl
+++ b/test/test_serialization.jl
@@ -4,7 +4,7 @@ function validate_serialization(sys::IS.SystemData; time_series_read_only = fals
     IS.prepare_for_serialization_to_file!(sys, filename; force = true)
     data = IS.serialize(sys)
     open(filename, "w") do io
-        JSON3.write(io, data)
+        JSON.json(io, data)
     end
 
     # Make sure the code supports the files changing directories.
@@ -23,7 +23,7 @@ function validate_serialization(sys::IS.SystemData; time_series_read_only = fals
     end
 
     data = open(path) do io
-        return JSON3.read(io, Dict)
+        return JSON.parse(io; dicttype = Dict{String, Any})
     end
 
     orig = pwd()
@@ -159,7 +159,10 @@ end
 @testset "Test JSON string" begin
     component = IS.SimpleTestComponent("Component1", 1)
     text = IS.to_json(component)
-    IS.deserialize(IS.SimpleTestComponent, JSON3.read(text, Dict)) == component
+    IS.deserialize(
+        IS.SimpleTestComponent,
+        JSON.parse(text; dicttype = Dict{String, Any}),
+    ) == component
 end
 
 @testset "Test pretty-print JSON IO" begin
@@ -168,13 +171,19 @@ end
     IS.to_json(io, component; pretty = false)
     text = String(take!(io))
     @test !occursin(" ", text)
-    IS.deserialize(IS.SimpleTestComponent, JSON3.read(text, Dict)) == component
+    IS.deserialize(
+        IS.SimpleTestComponent,
+        JSON.parse(text; dicttype = Dict{String, Any}),
+    ) == component
 
     io = IOBuffer()
     IS.to_json(io, component; pretty = true)
     text = String(take!(io))
     @test occursin(" ", text)
-    IS.deserialize(IS.SimpleTestComponent, JSON3.read(text, Dict)) == component
+    IS.deserialize(
+        IS.SimpleTestComponent,
+        JSON.parse(text; dicttype = Dict{String, Any}),
+    ) == component
 end
 
 @testset "Test ext serialization" begin
diff --git a/test/test_time_series.jl b/test/test_time_series.jl
index 4a4623fcf..9239bf0cf 100644
--- a/test/test_time_series.jl
+++ b/test/test_time_series.jl
@@ -3950,7 +3950,7 @@ function _setup_for_migration_tests_from_IS_v2_3()
                         string(nameof(typeof(component))),
                         owner_category,
                         features,
-                        JSON3.write(IS.serialize(metadata)),
+                        JSON.json(IS.serialize(metadata)),
                     )
                 SQLite.DBInterface.execute(stmt, params)
             end
@@ -3976,7 +3976,7 @@ function _setup_for_migration_tests_from_IS_v2_4()
                     (
                         missing,
                         string(IS.get_uuid(metadata)),
-                        JSON3.write(IS.serialize(metadata)),
+                        JSON.json(IS.serialize(metadata)),
                     )
                 SQLite.DBInterface.execute(stmt, params)
             end

From fbba109a8e7703e527f66f42bcdc7a2b7646d75b Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 15 Apr 2026 17:00:15 -0600
Subject: [PATCH 11/13] remove support for function deserialization in Ext

---
 src/serialization.jl | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/src/serialization.jl b/src/serialization.jl
index 1fb0777d7..5f50e211d 100644
--- a/src/serialization.jl
+++ b/src/serialization.jl
@@ -302,20 +302,39 @@ Perform a test to see if JSON can convert this value so that the code can give t
 a comprehensible corrective action.
 """
 function is_ext_valid_for_serialization(value)
-    isnothing(value) && return true
-    is_valid = true
+    is_valid = _is_ext_value_basic(value)
+    if !is_valid
+        @error "Failed to serialize an 'ext' value. Please ensure that the " *
+               "contents follow the rules provided in the documentation. Generally, only " *
+               "basic types are allowed - strings and numbers and arrays, dictionaries, and " *
+               "structs of those." value
+        return false
+    end
     try
         JSON.json(value)
     catch
-        is_valid = false
-    end
-
-    if !is_valid
         @error "Failed to serialize an 'ext' value. Please ensure that the " *
                "contents follow the rules provided in the documentation. Generally, only " *
                "basic types are allowed - strings and numbers and arrays, dictionaries, and " *
                "structs of those." value
+        return false
     end
+    return true
+end
 
-    return is_valid
+# JSON.jl will happily serialize Functions, Modules, Tasks, IO handles, etc. by
+# introspecting their fields, but those values are not meaningful JSON content and
+# cannot be reliably deserialized. Restrict 'ext' values to genuine data types.
+_is_ext_value_basic(::Union{Nothing, Missing, Number, AbstractString, Symbol, Bool}) = true
+_is_ext_value_basic(x::AbstractArray) = all(_is_ext_value_basic, x)
+_is_ext_value_basic(x::Tuple) = all(_is_ext_value_basic, x)
+_is_ext_value_basic(x::AbstractDict) =
+    all(_is_ext_value_basic, keys(x)) && all(_is_ext_value_basic, values(x))
+_is_ext_value_basic(::Union{Function, Module, Task, IO, Ptr, Base.RefValue}) = false
+function _is_ext_value_basic(x::T) where {T}
+    isstructtype(T) || return false
+    for name in fieldnames(T)
+        _is_ext_value_basic(getfield(x, name)) || return false
+    end
+    return true
 end

From 4b22439afb6a83359a24044a3318b491e0d6d808 Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 22 Apr 2026 00:00:11 -0700
Subject: [PATCH 12/13] update serialize/deserialize code for the scoped enums

---
 src/utils/utils.jl | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/utils/utils.jl b/src/utils/utils.jl
index ef4457f5b..b37b6f656 100644
--- a/src/utils/utils.jl
+++ b/src/utils/utils.jl
@@ -394,7 +394,11 @@ macro scoped_enum(T, args...)
             Base.propertynames(::Type{$T}) = _ALL_NAMES
 
             InfrastructureSystems.serialize(val::$T) = Base.string(val)
+            InfrastructureSystems.serialize(vals::Vector{$T}) =
+                InfrastructureSystems.serialize.(vals)
             InfrastructureSystems.deserialize(::Type{$T}, val) = $T(val)
+            InfrastructureSystems.deserialize(::Type{Vector{$T}}, vals::Vector) =
+                [InfrastructureSystems.deserialize($T, v) for v in vals]
 
             Base.convert(::Type{$T}, val::Integer) = $T(val)
             Base.isless(val::$T, other::$T) = isless(val.value, other.value)

From 14e304b06c041c07e113c6310ed395d66591c1e1 Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Wed, 22 Apr 2026 00:35:26 -0700
Subject: [PATCH 13/13] apply recommendation from copilot

---
 src/serialization.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/serialization.jl b/src/serialization.jl
index 5f50e211d..dc85a5faa 100644
--- a/src/serialization.jl
+++ b/src/serialization.jl
@@ -34,7 +34,7 @@ function to_json(obj::T; pretty = false, indent = 2) where {T <: InfrastructureS
         if pretty
             io = IOBuffer()
             JSON.json(io, serialize(obj); pretty = indent)
-            return take!(io)
+            return String(take!(io))
         else
             return JSON.json(serialize(obj))
         end