refactor: move NotProvided/NotProvidedType from Options to Core

NotProvidedType and NotProvided are now defined in CTBase.Core as the
canonical ecosystem-wide sentinel. CTBase.Options re-exports both names
unchanged — no user-visible API change.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ocots

BREAKINGS.md

@@ -2,6 +2,13 @@
 
 This document outlines all breaking changes introduced in CTBase v0.18.0-beta compared to v0.17.4. Use this guide to migrate your code and understand the impact of these changes.
 
+## Non-breaking note (0.24.1-beta)
+
+- **NotProvided moved to Core**: `NotProvidedType` and `NotProvided` are now defined in
+  `CTBase.Core`; `CTBase.Options` re-exports them. All existing `CTBase.Options.NotProvided`
+  and `using CTBase.Options` consumers continue to work unchanged.
+- `CTBase.Core.NotProvided` is now the canonical ecosystem-wide sentinel.
+
 ## Non-breaking note (0.24.0-beta)
 
 - **Differentiation module**: Added comprehensive AD backend infrastructure for computing gradients

CHANGELOGS.md

@@ -5,6 +5,14 @@ All notable changes to CTBase will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.24.1-beta] - 2026-06-26
+
+### 🔄 Refactoring
+
+- **NotProvided moved to Core**: `NotProvidedType` and `NotProvided` are now defined in
+  `CTBase.Core` instead of `CTBase.Options`. `CTBase.Options` re-exports both names
+  unchanged — no user-visible API change.
+
 ## [0.24.0-beta] - 2026-06-25
 
 ### ✨ New Features

Project.toml

@@ -1,6 +1,6 @@
 name = "CTBase"
 uuid = "54762871-cc72-4466-b8e8-f6c8b58076cd"
-version = "0.24.0-beta"
+version = "0.24.1-beta"
 authors = ["Olivier Cots <olivier.cots@irit.fr>", "Jean-Baptiste Caillau <caillau@univ-cotedazur.fr>"]
 
 [deps]

src/Core/Core.jl

@@ -13,6 +13,7 @@ import DocStringExtensions: TYPEDEF, TYPEDSIGNATURES
 include("types.jl")
 include("tags.jl")
 include("caches.jl")
+include("not_provided.jl")
 include("default.jl")
 
 # Private utilities
@@ -27,6 +28,7 @@ include("display.jl")
 # Export public API
 export ctNumber, matrix2vec, to_out_of_place, make_coerce, @ensure
 export AbstractTag, AbstractCache
+export NotProvided, NotProvidedType
 export Style, Palette
 export DEFAULT_PALETTE, MONOCHROME_PALETTE, HIGH_CONTRAST_PALETTE
 export current_palette, set_palette!, set_color!, reset_palette!, show_palette

src/Core/not_provided.jl

@@ -0,0 +1,39 @@
+"""
+$(TYPEDEF)
+
+Singleton type marking the absence of a provided value.
+
+Ecosystem-wide sentinel for "no default / argument not given". The canonical
+value is [`NotProvided`](@ref).
+
+See also: [`NotProvided`](@ref).
+"""
+struct NotProvidedType end
+
+"""
+    NotProvided
+
+Singleton instance of [`NotProvidedType`](@ref).
+
+The canonical "not provided" sentinel used across the control-toolbox ecosystem
+(option defaults, optional variable parameters, optional AD backends, …).
+
+# Example
+```julia-repl
+julia> using CTBase.Core
+
+julia> x = NotProvided
+NotProvided
+
+julia> x isa NotProvidedType
+true
+
+julia> x === NotProvided
+true
+```
+
+See also: [`NotProvidedType`](@ref).
+"""
+const NotProvided = NotProvidedType()
+
+Base.show(io::IO, ::NotProvidedType) = print(io, "NotProvided")

src/Options/not_provided.jl

@@ -1,69 +1,5 @@
-# NotProvided sentinel type
-#
-# Singleton type representing the absence of a default value for an option.
-
-"""
-$(TYPEDEF)
-
-Singleton type representing the absence of a default value for an option.
-
-This type is used to distinguish between:
-- `default = NotProvided`: No default value, option must be provided by user or not stored
-- `default = nothing`: The default value is explicitly `nothing`
-
-# Example
-```julia
-# Option with no default - won't be stored if not provided
-opt1 = OptionDefinition(
-    name = :minimize,
-    type = Union{Bool, Nothing},
-    default = NotProvided,
-    description = "Whether to minimize"
-)
-
-# Option with explicit nothing default - will be stored as nothing
-opt2 = OptionDefinition(
-    name = :backend,
-    type = Union{Nothing, KernelAbstractions.Backend},
-    default = nothing,
-    description = "Execution backend"
-)
-```
-
-See also: `OptionDefinition`, `extract_options`
-"""
-struct NotProvidedType end
-
-"""
-    NotProvided
-
-Singleton instance of `NotProvidedType`.
-
-Use this as the default value in `OptionDefinition` to indicate
-that an option has no default value and should not be stored if not provided
-by the user.
-
-# Example
-```julia-repl
-julia> using CTBase.Options
-
-julia> def = OptionDefinition(
-           name = :optional_param,
-           type = Any,
-           default = NotProvided,
-           description = "Optional parameter"
-       )
-
-julia> # If user doesn't provide it, it won't be stored
-julia> opts, _ = extract_options((other=1,), [def])
-julia> haskey(opts, :optional_param)
-false
-```
-"""
-const NotProvided = NotProvidedType()
-
-# Pretty printing
-Base.show(io::IO, ::NotProvidedType) = print(io, "NotProvided")
+# NotProvided is defined in CTBase.Core and re-exported from here for backward compatibility.
+using CTBase.Core: NotProvided, NotProvidedType
 
 """
 $(TYPEDEF)
@@ -78,21 +14,20 @@ default and was not provided by the user.
 This type is internal to the Options module and should not be used directly by users.
 Use `NotProvided` instead.
 
-See also: `NotProvided`, `extract_option`
+See also: [`NotProvided`](@ref), [`extract_option`](@ref).
 """
 struct NotStoredType end
 
 """
     NotStored
 
-Internal singleton instance of `NotStoredType`.
+Internal singleton instance of [`NotStoredType`](@ref).
 
 Used internally by the option extraction system to signal that an option should not
 be stored. This is distinct from `nothing` which is a valid option value.
 
-See also: `NotProvided`, `extract_option`
+See also: [`NotProvided`](@ref), [`extract_option`](@ref).
 """
 const NotStored = NotStoredType()
 
-# Pretty printing
 Base.show(io::IO, ::NotStoredType) = print(io, "NotStored")