diff --git a/.github/config/conan/profiles/android.jinja b/.github/config/conan/profiles/android.jinja
index 7c851aa89..a5cc98e69 100644
--- a/.github/config/conan/profiles/android.jinja
+++ b/.github/config/conan/profiles/android.jinja
@@ -24,7 +24,7 @@ arch={{arch}}
 build_type=Release
 compiler=clang
 compiler.version=17
-compiler.cppstd=20
+compiler.cppstd=23
 compiler.libcxx=c++_shared
 
 [conf]
diff --git a/.github/config/conan/profiles/apple.jinja b/.github/config/conan/profiles/apple.jinja
index 550ac77de..89e7fd3bf 100644
--- a/.github/config/conan/profiles/apple.jinja
+++ b/.github/config/conan/profiles/apple.jinja
@@ -19,7 +19,7 @@ os.version={{os_version}}
 build_type=Release
 compiler=apple-clang
 compiler.version=17
-compiler.cppstd=20
+compiler.cppstd=23
 compiler.libcxx=libc++
 
 [conf]
diff --git a/.github/config/conan/profiles/emscripten-wasm b/.github/config/conan/profiles/emscripten-wasm
index 7854be44c..5367b470c 100644
--- a/.github/config/conan/profiles/emscripten-wasm
+++ b/.github/config/conan/profiles/emscripten-wasm
@@ -17,7 +17,7 @@ build_type=Release
 compiler=emcc
 compiler.version={{emsdk_version}}
 compiler.libcxx=libc++
-compiler.cppstd=20
+compiler.cppstd=23
 
 [options]
 # No sockets and no threads in a browser; the CLI has no meaning here either.
diff --git a/.github/config/conan/profiles/macos-15-armv8-clang-14 b/.github/config/conan/profiles/macos-15-armv8-clang-14
index 64b597da4..bb64de343 100644
--- a/.github/config/conan/profiles/macos-15-armv8-clang-14
+++ b/.github/config/conan/profiles/macos-15-armv8-clang-14
@@ -3,7 +3,7 @@ arch=armv8
 build_type=Release
 compiler=apple-clang
 compiler.version=14
-compiler.cppstd=20
+compiler.cppstd=23
 compiler.libcxx=libc++
 os=Macos
 
diff --git a/.github/config/conan/profiles/macos-26-armv8-clang-14 b/.github/config/conan/profiles/macos-26-armv8-clang-14
index 64b597da4..bb64de343 100644
--- a/.github/config/conan/profiles/macos-26-armv8-clang-14
+++ b/.github/config/conan/profiles/macos-26-armv8-clang-14
@@ -3,7 +3,7 @@ arch=armv8
 build_type=Release
 compiler=apple-clang
 compiler.version=14
-compiler.cppstd=20
+compiler.cppstd=23
 compiler.libcxx=libc++
 os=Macos
 
diff --git a/.github/config/conan/profiles/ubuntu-24.04-clang-18 b/.github/config/conan/profiles/ubuntu-24.04-clang-18
index fafeefc8c..ae904e043 100644
--- a/.github/config/conan/profiles/ubuntu-24.04-clang-18
+++ b/.github/config/conan/profiles/ubuntu-24.04-clang-18
@@ -3,7 +3,7 @@ arch=x86_64
 build_type=Release
 compiler=clang
 compiler.version=18
-compiler.cppstd=20
+compiler.cppstd=23
 compiler.libcxx=libstdc++11
 os=Linux
 
diff --git a/.github/config/conan/profiles/ubuntu-24.04-gcc-14 b/.github/config/conan/profiles/ubuntu-24.04-gcc-14
index c7df6917c..47a08c060 100644
--- a/.github/config/conan/profiles/ubuntu-24.04-gcc-14
+++ b/.github/config/conan/profiles/ubuntu-24.04-gcc-14
@@ -3,7 +3,7 @@ arch=x86_64
 build_type=Release
 compiler=gcc
 compiler.version=14
-compiler.cppstd=20
+compiler.cppstd=23
 compiler.libcxx=libstdc++11
 os=Linux
 
diff --git a/.github/config/conan/profiles/windows-2022-msvc-1940 b/.github/config/conan/profiles/windows-2022-msvc-1940
index 4a74ff921..32d5eed36 100644
--- a/.github/config/conan/profiles/windows-2022-msvc-1940
+++ b/.github/config/conan/profiles/windows-2022-msvc-1940
@@ -3,7 +3,7 @@ arch=x86_64
 build_type=Release
 compiler=msvc
 compiler.version=194
-compiler.cppstd=20
+compiler.cppstd=23
 compiler.runtime=dynamic
 os=Windows
 
diff --git a/AGENTS.md b/AGENTS.md
index 73a5c4601..a6762bc23 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -5,10 +5,10 @@ user-facing docs see [`README.md`](README.md) and [`docs/`](docs/README.md).
 
 ## What this is
 
-`odr` (a.k.a. `odrcore`) is a **C++20 library that decodes documents and renders
+`odr` (a.k.a. `odrcore`) is a **C++23 library that decodes documents and renders
 them to HTML**. It reads many formats (ODF, OOXML, legacy MS binary, PDF, CSV, …)
 behind one abstract document model and a generic HTML renderer. It is the backend
-for OpenDocument.droid / .ios. Build: **CMake + Conan**; standard: **C++20**.
+for OpenDocument.droid / .ios. Build: **CMake + Conan**; standard: **C++23**.
 
 ## Big picture: how a file becomes HTML
 
@@ -202,6 +202,28 @@ Dispatch `release.yml` against main, publish the draft that appears —
 - **Formatting**: clang-format (LLVM-based, `.clang-format`); run `scripts/format`
   or use the `scripts/setup` git hook. `clang-tidy` per `.clang-tidy`. CI enforces
   both.
+- **C++23, but three separate ceilings sit under it.** Check a facility against
+  all three before reaching for it, and check it by building an **object file**
+  — `-fsyntax-only` misses the codegen bugs.
+  - **The standard library is capped by `emsdk 3.1.73`'s libc++ 18.1**, the
+    oldest in the profile matrix and the newest emsdk conan-center packages.
+    `std::ranges::to`, `std::expected`, `std::string::resize_and_overwrite`,
+    `views::zip`, `ranges::fold_left` and the monadic `std::optional` are there;
+    **`views::enumerate`, `std::generator`, `std::move_only_function` and
+    `std::flat_map` are not**. `std::mdspan` fails from the other side —
+    libstdc++ has no `<mdspan>`, so the gcc-14 job would not build it.
+  - **`std::format` is unusable, on every slice** — the apple deployment target
+    gates it, and `fmt` is what we format with instead. See *Format numbers*
+    below.
+  - **Deducing `this` is fine on accessors, not on a capturing recursive
+    lambda.** NDK 28.1's clang 19 segfaults on `[&](this auto self, …)` that
+    recurses (`cannot compile this l-value expression yet`). The Y-combinator
+    form — pass the lambda to itself — is what `ooxml_text_list` still uses.
+- **The public headers stay C++20**: nothing propagates the standard to a
+  consumer — no `target_compile_features(odr PUBLIC …)`, no `cppstd` in
+  `package_info` — so `src/odr/*.hpp` must keep compiling under C++20. C++23 is
+  for `internal/`, `cli/` and the bindings. `conanfile.py`'s `check_min_cppstd`
+  sits in `validate_build`, which constrains building `odr` and not using it.
 - **Fail fast**: where the spec dictates what to expect, **throw** on unexpected
   input (`std::runtime_error` or the typed exceptions in `src/odr/exceptions.hpp`)
   rather than silently degrading. Only pass through (return empty / skip) values
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f8f9a1e93..1f6a4d2de 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,10 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- **Breaking**: building `odr` from source now needs a **C++23** compiler. Using
+  it does not — the public headers still compile as C++20, and the package
+  forces no standard on a consumer.
+
 - **Breaking**: the drawing elements `Rect`, `Line`, `Circle` and `CustomShape`
   are gone, with their `ElementType` values and `Element::as_rect`/`as_line`/
   `as_circle`/`as_custom_shape`. Every shape is a `Frame` now, naming itself
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 750555b87..6d9fb9759 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,7 +6,7 @@ if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.24.0")
 endif ()
 
 project(odr LANGUAGES C CXX)
-set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
diff --git a/conanfile.py b/conanfile.py
index bbd418fcb..5c8fd6ae1 100644
--- a/conanfile.py
+++ b/conanfile.py
@@ -70,7 +70,7 @@ def build_requirements(self):
 
     def validate_build(self):
         if self.settings.get_safe("compiler.cppstd"):
-            check_min_cppstd(self, 20)
+            check_min_cppstd(self, 23)
 
     def configure(self):
         if self.options.shared:
diff --git a/src/odr/internal/common/element_registry.hpp b/src/odr/internal/common/element_registry.hpp
index cc07aaada..0b428ead7 100644
--- a/src/odr/internal/common/element_registry.hpp
+++ b/src/odr/internal/common/element_registry.hpp
@@ -33,37 +33,21 @@ template <typename T> class SideTable final {
     return m_entries.insert_or_assign(id, std::move(value)).first->second;
   }
 
-  [[nodiscard]] T *find(const ElementIdentifier id) {
-    return find_(m_entries, id);
-  }
-  [[nodiscard]] const T *find(const ElementIdentifier id) const {
-    return find_(m_entries, id);
-  }
-
-  [[nodiscard]] T &at(const ElementIdentifier id) { return at_(*this, id); }
-  [[nodiscard]] const T &at(const ElementIdentifier id) const {
-    return at_(*this, id);
-  }
-
-private:
-  std::unordered_map<ElementIdentifier, T> m_entries;
-
-  /// One body for both constnesses: the argument carries the const and the
-  /// deduced return takes it on.
-  template <typename Entries>
-  static auto *find_(Entries &entries, const ElementIdentifier id) {
-    const auto it = entries.find(id);
-    return it != std::end(entries) ? &it->second : nullptr;
+  [[nodiscard]] auto *find(this auto &self, const ElementIdentifier id) {
+    const auto it = self.m_entries.find(id);
+    return it != std::end(self.m_entries) ? &it->second : nullptr;
   }
 
-  template <typename Self>
-  static auto &at_(Self &self, const ElementIdentifier id) {
+  [[nodiscard]] auto &at(this auto &self, const ElementIdentifier id) {
     auto *entry = self.find(id);
     if (entry == nullptr) {
       throw std::out_of_range("SideTable::at: identifier not found");
     }
     return *entry;
   }
+
+private:
+  std::unordered_map<ElementIdentifier, T> m_entries;
 };
 
 /// A per-type payload appended as its elements are created, so the ids only
@@ -80,44 +64,32 @@ class SortedSideTable final {
     return m_entries.emplace_back(static_cast<Id>(id), std::move(value)).second;
   }
 
-  [[nodiscard]] T *find(const ElementIdentifier id) {
-    return find_(m_entries, id);
-  }
-  [[nodiscard]] const T *find(const ElementIdentifier id) const {
-    return find_(m_entries, id);
+  [[nodiscard]] auto *find(this auto &self, const ElementIdentifier id) {
+    const auto it =
+        std::ranges::lower_bound(self.m_entries, id, {}, &Entry::first);
+    return it != std::end(self.m_entries) && it->first == id ? &it->second
+                                                             : nullptr;
   }
 
-  [[nodiscard]] T &at(const ElementIdentifier id) { return at_(*this, id); }
-  [[nodiscard]] const T &at(const ElementIdentifier id) const {
-    return at_(*this, id);
+  [[nodiscard]] auto &at(this auto &self, const ElementIdentifier id) {
+    auto *entry = self.find(id);
+    if (entry == nullptr) {
+      throw std::out_of_range("SortedSideTable::at: identifier not found");
+    }
+    return *entry;
   }
 
-  [[nodiscard]] auto begin() const noexcept { return m_entries.begin(); }
-  [[nodiscard]] auto end() const noexcept { return m_entries.end(); }
-  [[nodiscard]] auto begin() noexcept { return m_entries.begin(); }
-  [[nodiscard]] auto end() noexcept { return m_entries.end(); }
+  [[nodiscard]] auto begin(this auto &self) noexcept {
+    return self.m_entries.begin();
+  }
+  [[nodiscard]] auto end(this auto &self) noexcept {
+    return self.m_entries.end();
+  }
 
 private:
   using Entry = std::pair<Id, T>;
 
   std::deque<Entry> m_entries;
-
-  /// One body for both constnesses: the argument carries the const and the
-  /// deduced return takes it on.
-  template <typename Entries>
-  static auto *find_(Entries &entries, const ElementIdentifier id) {
-    const auto it = std::ranges::lower_bound(entries, id, {}, &Entry::first);
-    return it != std::end(entries) && it->first == id ? &it->second : nullptr;
-  }
-
-  template <typename Self>
-  static auto &at_(Self &self, const ElementIdentifier id) {
-    auto *entry = self.find(id);
-    if (entry == nullptr) {
-      throw std::out_of_range("SortedSideTable::at: identifier not found");
-    }
-    return *entry;
-  }
 };
 
 /// The flat store an engine builds its element tree in: an id is the index
@@ -132,14 +104,9 @@ class ElementRegistry {
 
   [[nodiscard]] std::size_t size() const noexcept { return m_elements.size(); }
 
-  [[nodiscard]] Element &element_at(const ElementIdentifier id) {
-    check_element_id(id);
-    return m_elements[id - 1];
-  }
-
-  [[nodiscard]] const Element &element_at(const ElementIdentifier id) const {
-    check_element_id(id);
-    return m_elements[id - 1];
+  [[nodiscard]] auto &element_at(this auto &self, const ElementIdentifier id) {
+    self.check_element_id(id);
+    return self.m_elements[id - 1];
   }
 
   void append_child(const ElementIdentifier parent_id,
diff --git a/src/odr/internal/font/cff_builder.cpp b/src/odr/internal/font/cff_builder.cpp
index 278b63b18..fb45997ac 100644
--- a/src/odr/internal/font/cff_builder.cpp
+++ b/src/odr/internal/font/cff_builder.cpp
@@ -3,6 +3,7 @@
 #include <odr/internal/util/byte_string.hpp>
 
 #include <cstdint>
+#include <ranges>
 #include <string>
 #include <vector>
 
@@ -108,11 +109,10 @@ std::string cff::build_cff(const std::string_view name,
   // String INDEX: every glyph name gets a custom SID (391 + position). Glyph 0
   // is the implicit `.notdef` (SID 0), so its name is not stored; the charset
   // lists SIDs for glyphs 1..n-1.
-  std::vector<std::string> strings;
-  for (std::size_t i = 1; i < glyphs.size(); ++i) {
-    strings.push_back(glyphs[i].name);
-  }
-  const std::string string_index = build_index(strings);
+  const std::string string_index =
+      build_index(glyphs | std::views::drop(1) |
+                  std::views::transform(&BuilderGlyph::name) |
+                  std::ranges::to<std::vector<std::string>>());
 
   // Format-0 charset: SID per glyph 1..n-1.
   std::string charset;
diff --git a/src/odr/internal/iwork/iwork_element_registry.hpp b/src/odr/internal/iwork/iwork_element_registry.hpp
index aed11335e..769601c3b 100644
--- a/src/odr/internal/iwork/iwork_element_registry.hpp
+++ b/src/odr/internal/iwork/iwork_element_registry.hpp
@@ -90,46 +90,29 @@ class ElementRegistry final
   std::tuple<ElementIdentifier, Element &, Cell &>
   create_cell_element(ElementType type);
 
-  [[nodiscard]] Text &text_element_at(const ElementIdentifier id) {
-    return m_texts.at(id);
+  [[nodiscard]] auto &text_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_texts.at(id);
   }
-  [[nodiscard]] Frame &frame_element_at(const ElementIdentifier id) {
-    return m_frames.at(id);
+  [[nodiscard]] auto &frame_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_frames.at(id);
   }
-  [[nodiscard]] Slide &slide_element_at(const ElementIdentifier id) {
-    return m_slides.at(id);
+  [[nodiscard]] auto &slide_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_slides.at(id);
   }
-  [[nodiscard]] Table &table_element_at(const ElementIdentifier id) {
-    return m_tables.at(id);
+  [[nodiscard]] auto &table_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_tables.at(id);
   }
-  [[nodiscard]] Sheet &sheet_element_at(const ElementIdentifier id) {
-    return m_sheets.at(id);
+  [[nodiscard]] auto &sheet_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_sheets.at(id);
   }
-  [[nodiscard]] Cell &cell_element_at(const ElementIdentifier id) {
-    return m_cells.at(id);
-  }
-
-  [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
-    return m_texts.at(id);
-  }
-  [[nodiscard]] const Frame &
-  frame_element_at(const ElementIdentifier id) const {
-    return m_frames.at(id);
-  }
-  [[nodiscard]] const Slide &
-  slide_element_at(const ElementIdentifier id) const {
-    return m_slides.at(id);
-  }
-  [[nodiscard]] const Table &
-  table_element_at(const ElementIdentifier id) const {
-    return m_tables.at(id);
-  }
-  [[nodiscard]] const Sheet &
-  sheet_element_at(const ElementIdentifier id) const {
-    return m_sheets.at(id);
-  }
-  [[nodiscard]] const Cell &cell_element_at(const ElementIdentifier id) const {
-    return m_cells.at(id);
+  [[nodiscard]] auto &cell_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_cells.at(id);
   }
 
   /// Links @p column_id into @p table_id's column chain. Columns are not
diff --git a/src/odr/internal/markdown/markdown_element_registry.hpp b/src/odr/internal/markdown/markdown_element_registry.hpp
index 3a97f1bc4..c093f024c 100644
--- a/src/odr/internal/markdown/markdown_element_registry.hpp
+++ b/src/odr/internal/markdown/markdown_element_registry.hpp
@@ -57,16 +57,15 @@ class ElementRegistry final
   std::tuple<ElementIdentifier, Element &, TableCell &>
   create_table_cell_element();
 
-  [[nodiscard]] Text &text_element_at(const ElementIdentifier id) {
-    return m_texts.at(id);
+  [[nodiscard]] auto &text_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_texts.at(id);
   }
-  [[nodiscard]] Table &table_element_at(const ElementIdentifier id) {
-    return m_tables.at(id);
+  [[nodiscard]] auto &table_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_tables.at(id);
   }
 
-  [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
-    return m_texts.at(id);
-  }
   [[nodiscard]] const Link &link_element_at(const ElementIdentifier id) const {
     return m_links.at(id);
   }
@@ -77,10 +76,6 @@ class ElementRegistry final
   list_item_element_at(const ElementIdentifier id) const {
     return m_list_items.at(id);
   }
-  [[nodiscard]] const Table &
-  table_element_at(const ElementIdentifier id) const {
-    return m_tables.at(id);
-  }
   [[nodiscard]] const TableCell &
   table_cell_element_at(const ElementIdentifier id) const {
     return m_table_cells.at(id);
diff --git a/src/odr/internal/odf/odf_chart.cpp b/src/odr/internal/odf/odf_chart.cpp
index 92b99f1ea..94a8663ca 100644
--- a/src/odr/internal/odf/odf_chart.cpp
+++ b/src/odr/internal/odf/odf_chart.cpp
@@ -9,6 +9,7 @@
 #include <cmath>
 #include <cstring>
 #include <numbers>
+#include <ranges>
 #include <string>
 #include <string_view>
 #include <unordered_map>
@@ -282,11 +283,8 @@ class ChartWriter {
 
   [[nodiscard]] static std::vector<std::string>
   read_row_text(const pugi::xml_node row) {
-    std::vector<std::string> result;
-    for (const pugi::xml_node cell : read_row(row)) {
-      result.emplace_back(read_text(cell));
-    }
-    return result;
+    return read_row(row) | std::views::transform(read_text) |
+           std::ranges::to<std::vector<std::string>>();
   }
 
   /// A missing data point is written `office:value="NaN"`.
diff --git a/src/odr/internal/odf/odf_element_registry.hpp b/src/odr/internal/odf/odf_element_registry.hpp
index db1794229..e638ed5d4 100644
--- a/src/odr/internal/odf/odf_element_registry.hpp
+++ b/src/odr/internal/odf/odf_element_registry.hpp
@@ -112,27 +112,19 @@ class ElementRegistry final
   create_sheet_cell_element(pugi::xml_node node, const TablePosition &position,
                             bool is_repeated);
 
-  [[nodiscard]] Text &text_element_at(const ElementIdentifier id) {
-    return m_texts.at(id);
+  [[nodiscard]] auto &text_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_texts.at(id);
   }
-  [[nodiscard]] Table &table_element_at(const ElementIdentifier id) {
-    return m_tables.at(id);
+  [[nodiscard]] auto &table_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_tables.at(id);
   }
-  [[nodiscard]] Sheet &sheet_element_at(const ElementIdentifier id) {
-    return m_sheets.at(id);
+  [[nodiscard]] auto &sheet_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_sheets.at(id);
   }
 
-  [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
-    return m_texts.at(id);
-  }
-  [[nodiscard]] const Table &
-  table_element_at(const ElementIdentifier id) const {
-    return m_tables.at(id);
-  }
-  [[nodiscard]] const Sheet &
-  sheet_element_at(const ElementIdentifier id) const {
-    return m_sheets.at(id);
-  }
   [[nodiscard]] const SheetCell &
   sheet_cell_element_at(const ElementIdentifier id) const {
     return m_sheet_cells.at(id);
diff --git a/src/odr/internal/oldms/presentation/ppt_element_registry.hpp b/src/odr/internal/oldms/presentation/ppt_element_registry.hpp
index db4000267..e4d49b820 100644
--- a/src/odr/internal/oldms/presentation/ppt_element_registry.hpp
+++ b/src/odr/internal/oldms/presentation/ppt_element_registry.hpp
@@ -36,26 +36,17 @@ class ElementRegistry final
   std::tuple<ElementIdentifier, Element &, Frame &> create_frame_element();
   std::tuple<ElementIdentifier, Element &, Image &> create_image_element();
 
-  [[nodiscard]] Text &text_element_at(const ElementIdentifier id) {
-    return m_texts.at(id);
+  [[nodiscard]] auto &text_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_texts.at(id);
   }
-  [[nodiscard]] Frame &frame_element_at(const ElementIdentifier id) {
-    return m_frames.at(id);
+  [[nodiscard]] auto &frame_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_frames.at(id);
   }
-  [[nodiscard]] Image &image_element_at(const ElementIdentifier id) {
-    return m_images.at(id);
-  }
-
-  [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
-    return m_texts.at(id);
-  }
-  [[nodiscard]] const Frame &
-  frame_element_at(const ElementIdentifier id) const {
-    return m_frames.at(id);
-  }
-  [[nodiscard]] const Image &
-  image_element_at(const ElementIdentifier id) const {
-    return m_images.at(id);
+  [[nodiscard]] auto &image_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_images.at(id);
   }
 
   /// Character style of a span or paragraph element, as an index into the
diff --git a/src/odr/internal/oldms/presentation/ppt_io.cpp b/src/odr/internal/oldms/presentation/ppt_io.cpp
index c69708931..cb41d61fc 100644
--- a/src/odr/internal/oldms/presentation/ppt_io.cpp
+++ b/src/odr/internal/oldms/presentation/ppt_io.cpp
@@ -72,9 +72,11 @@ std::u16string presentation::read_raw_text_chars(std::istream &in,
 std::string presentation::read_raw_text_bytes(std::istream &in,
                                               const std::uint32_t rec_len) {
   std::string buffer;
-  buffer.resize(rec_len);
-  in.read(buffer.data(), static_cast<std::streamsize>(rec_len));
-  buffer.resize(static_cast<std::size_t>(in.gcount()));
+  // The record length is only a claim, so the buffer is cut to what was read.
+  buffer.resize_and_overwrite(rec_len, [&](char *out, const std::size_t size) {
+    in.read(out, static_cast<std::streamsize>(size));
+    return static_cast<std::size_t>(in.gcount());
+  });
   return buffer;
 }
 
diff --git a/src/odr/internal/oldms/spreadsheet/xls_element_registry.hpp b/src/odr/internal/oldms/spreadsheet/xls_element_registry.hpp
index b4d477e4f..4f515ee7b 100644
--- a/src/odr/internal/oldms/spreadsheet/xls_element_registry.hpp
+++ b/src/odr/internal/oldms/spreadsheet/xls_element_registry.hpp
@@ -47,26 +47,17 @@ class ElementRegistry final
   std::tuple<ElementIdentifier, Element &, SheetCell &>
   create_sheet_cell_element(const TablePosition &position);
 
-  [[nodiscard]] Text &text_element_at(const ElementIdentifier id) {
-    return m_texts.at(id);
+  [[nodiscard]] auto &text_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_texts.at(id);
   }
-  [[nodiscard]] Sheet &sheet_element_at(const ElementIdentifier id) {
-    return m_sheets.at(id);
+  [[nodiscard]] auto &sheet_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_sheets.at(id);
   }
-  [[nodiscard]] SheetCell &sheet_cell_element_at(const ElementIdentifier id) {
-    return m_sheet_cells.at(id);
-  }
-
-  [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
-    return m_texts.at(id);
-  }
-  [[nodiscard]] const Sheet &
-  sheet_element_at(const ElementIdentifier id) const {
-    return m_sheets.at(id);
-  }
-  [[nodiscard]] const SheetCell &
-  sheet_cell_element_at(const ElementIdentifier id) const {
-    return m_sheet_cells.at(id);
+  [[nodiscard]] auto &sheet_cell_element_at(this auto &self,
+                                            const ElementIdentifier id) {
+    return self.m_sheet_cells.at(id);
   }
 
   /// Registers a cell with its sheet: sets the cell's parent and adds it to
diff --git a/src/odr/internal/oldms/text/doc_element_registry.hpp b/src/odr/internal/oldms/text/doc_element_registry.hpp
index d1e34ca20..e4ae925ff 100644
--- a/src/odr/internal/oldms/text/doc_element_registry.hpp
+++ b/src/odr/internal/oldms/text/doc_element_registry.hpp
@@ -21,11 +21,9 @@ class ElementRegistry final
   std::tuple<ElementIdentifier, Element &> create_element(ElementType type);
   std::tuple<ElementIdentifier, Element &, Text &> create_text_element();
 
-  [[nodiscard]] Text &text_element_at(const ElementIdentifier id) {
-    return m_texts.at(id);
-  }
-  [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
-    return m_texts.at(id);
+  [[nodiscard]] auto &text_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_texts.at(id);
   }
 
   /// Character style of a span or paragraph element, as an index into the
diff --git a/src/odr/internal/ooxml/presentation/ooxml_presentation_element_registry.hpp b/src/odr/internal/ooxml/presentation/ooxml_presentation_element_registry.hpp
index 43f0aea7e..1b921fc7c 100644
--- a/src/odr/internal/ooxml/presentation/ooxml_presentation_element_registry.hpp
+++ b/src/odr/internal/ooxml/presentation/ooxml_presentation_element_registry.hpp
@@ -34,19 +34,13 @@ class ElementRegistry final
   std::tuple<ElementIdentifier, Element &, Text &>
   create_text_element(pugi::xml_node first_node, pugi::xml_node last_node);
 
-  [[nodiscard]] Table &table_element_at(const ElementIdentifier id) {
-    return m_tables.at(id);
+  [[nodiscard]] auto &table_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_tables.at(id);
   }
-  [[nodiscard]] Text &text_element_at(const ElementIdentifier id) {
-    return m_texts.at(id);
-  }
-
-  [[nodiscard]] const Table &
-  table_element_at(const ElementIdentifier id) const {
-    return m_tables.at(id);
-  }
-  [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
-    return m_texts.at(id);
+  [[nodiscard]] auto &text_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_texts.at(id);
   }
 
   void append_column(ElementIdentifier table_id, ElementIdentifier column_id);
diff --git a/src/odr/internal/ooxml/spreadsheet/ooxml_spreadsheet_element_registry.hpp b/src/odr/internal/ooxml/spreadsheet/ooxml_spreadsheet_element_registry.hpp
index 1d04c4860..7126b2737 100644
--- a/src/odr/internal/ooxml/spreadsheet/ooxml_spreadsheet_element_registry.hpp
+++ b/src/odr/internal/ooxml/spreadsheet/ooxml_spreadsheet_element_registry.hpp
@@ -97,24 +97,18 @@ class ElementRegistry final
                                              const Relations &relations,
                                              const AbsPath &origin);
 
-  [[nodiscard]] Sheet &sheet_element_at(const ElementIdentifier id) {
-    return m_sheets.at(id);
+  [[nodiscard]] auto &sheet_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_sheets.at(id);
   }
-  [[nodiscard]] SheetCell &sheet_cell_element_at(const ElementIdentifier id) {
-    return m_sheet_cells.at(id);
+  [[nodiscard]] auto &sheet_cell_element_at(this auto &self,
+                                            const ElementIdentifier id) {
+    return self.m_sheet_cells.at(id);
   }
 
   [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
     return m_texts.at(id);
   }
-  [[nodiscard]] const Sheet &
-  sheet_element_at(const ElementIdentifier id) const {
-    return m_sheets.at(id);
-  }
-  [[nodiscard]] const SheetCell &
-  sheet_cell_element_at(const ElementIdentifier id) const {
-    return m_sheet_cells.at(id);
-  }
 
   [[nodiscard]] const ElementRelations *
   element_relations(const ElementIdentifier id) const {
diff --git a/src/odr/internal/ooxml/text/ooxml_text_element_registry.hpp b/src/odr/internal/ooxml/text/ooxml_text_element_registry.hpp
index 3743699b2..7e0fc3db8 100644
--- a/src/odr/internal/ooxml/text/ooxml_text_element_registry.hpp
+++ b/src/odr/internal/ooxml/text/ooxml_text_element_registry.hpp
@@ -35,19 +35,13 @@ class ElementRegistry final
   std::tuple<ElementIdentifier, Element &, Text &>
   create_text_element(pugi::xml_node first_node, pugi::xml_node last_node);
 
-  [[nodiscard]] Text &text_element_at(const ElementIdentifier id) {
-    return m_texts.at(id);
+  [[nodiscard]] auto &text_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_texts.at(id);
   }
-  [[nodiscard]] Table &table_element_at(const ElementIdentifier id) {
-    return m_tables.at(id);
-  }
-
-  [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
-    return m_texts.at(id);
-  }
-  [[nodiscard]] const Table &
-  table_element_at(const ElementIdentifier id) const {
-    return m_tables.at(id);
+  [[nodiscard]] auto &table_element_at(this auto &self,
+                                       const ElementIdentifier id) {
+    return self.m_tables.at(id);
   }
 
   void append_column(ElementIdentifier table_id, ElementIdentifier column_id);
diff --git a/src/odr/internal/ooxml/text/ooxml_text_list.cpp b/src/odr/internal/ooxml/text/ooxml_text_list.cpp
index e2735882a..eac47733a 100644
--- a/src/odr/internal/ooxml/text/ooxml_text_list.cpp
+++ b/src/odr/internal/ooxml/text/ooxml_text_list.cpp
@@ -204,6 +204,8 @@ void resolve_list_numbering(ElementRegistry &registry,
     return node.child("w:pPr").child("w:numPr");
   };
 
+  // Takes itself as a parameter rather than `this auto self`: NDK 28.1's
+  // clang 19 segfaults on a capturing lambda that recurses through one.
   const auto walk = [&](auto &self, const ElementIdentifier id) -> void {
     for (ElementIdentifier child_id = id; child_id != null_element_id;
          child_id = registry.element_at(child_id).next_sibling_id) {
diff --git a/src/odr/internal/pdf/pdf_object.hpp b/src/odr/internal/pdf/pdf_object.hpp
index 4e8f70bc8..e822f3667 100644
--- a/src/odr/internal/pdf/pdf_object.hpp
+++ b/src/odr/internal/pdf/pdf_object.hpp
@@ -257,25 +257,19 @@ class Array final {
   Array &operator=(const Array &) = default;
   Array &operator=(Array &&) = default;
 
-  [[nodiscard]] Holder &holder() { return m_holder; }
-  [[nodiscard]] const Holder &holder() const { return m_holder; }
+  [[nodiscard]] auto &holder(this auto &self) { return self.m_holder; }
 
   [[nodiscard]] std::size_t size() const { return m_holder.size(); }
   [[nodiscard]] bool empty() const { return m_holder.empty(); }
-  [[nodiscard]] Holder::iterator begin() { return m_holder.begin(); }
-  [[nodiscard]] Holder::iterator end() { return m_holder.end(); }
-  [[nodiscard]] Holder::const_iterator begin() const {
-    return m_holder.cbegin();
-  }
-  [[nodiscard]] Holder::const_iterator end() const { return m_holder.cend(); }
+  [[nodiscard]] auto begin(this auto &self) { return self.m_holder.begin(); }
+  [[nodiscard]] auto end(this auto &self) { return self.m_holder.end(); }
 
-  Object &operator[](const std::size_t i) { return m_holder.at(i); }
-  const Object &operator[](const std::size_t i) const { return m_holder.at(i); }
+  [[nodiscard]] auto &operator[](this auto &self, const std::size_t i) {
+    return self.m_holder.at(i);
+  }
 
-  Object &front() { return m_holder.front(); }
-  [[nodiscard]] const Object &front() const { return m_holder.front(); }
-  Object &back() { return m_holder.back(); }
-  [[nodiscard]] const Object &back() const { return m_holder.back(); }
+  [[nodiscard]] auto &front(this auto &self) { return self.m_holder.front(); }
+  [[nodiscard]] auto &back(this auto &self) { return self.m_holder.back(); }
 
   void to_stream(std::ostream &) const;
   [[nodiscard]] std::string to_string() const;
@@ -291,36 +285,25 @@ class Dictionary final {
   Dictionary() = default;
   explicit Dictionary(Holder holder) : m_holder{std::move(holder)} {}
 
-  Holder &holder() { return m_holder; }
-  [[nodiscard]] const Holder &holder() const { return m_holder; }
+  [[nodiscard]] auto &holder(this auto &self) { return self.m_holder; }
 
   [[nodiscard]] std::size_t size() const { return m_holder.size(); }
 
-  using iterator = Holder::iterator;
-  using const_iterator = Holder::const_iterator;
-
-  [[nodiscard]] iterator begin() { return m_holder.begin(); }
-  [[nodiscard]] iterator end() { return m_holder.end(); }
-  [[nodiscard]] const_iterator begin() const { return m_holder.cbegin(); }
-  [[nodiscard]] const_iterator end() const { return m_holder.cend(); }
+  [[nodiscard]] auto begin(this auto &self) { return self.m_holder.begin(); }
+  [[nodiscard]] auto end(this auto &self) { return self.m_holder.end(); }
 
+  /// Inserts a null when the key is absent — `at` is the one that throws.
   Object &operator[](const std::string &name) { return m_holder[name]; }
   const Object &operator[](const std::string &name) const {
     return m_holder.at(name);
   }
 
-  [[nodiscard]] Object &at(const std::string &name) {
-    return m_holder.at(name);
-  }
-  [[nodiscard]] const Object &at(const std::string &name) const {
-    return m_holder.at(name);
+  [[nodiscard]] auto &at(this auto &self, const std::string &name) {
+    return self.m_holder.at(name);
   }
 
-  [[nodiscard]] Holder::iterator find(const std::string &name) {
-    return m_holder.find(name);
-  }
-  [[nodiscard]] Holder::const_iterator find(const std::string &name) const {
-    return m_holder.find(name);
+  [[nodiscard]] auto find(this auto &self, const std::string &name) {
+    return self.m_holder.find(name);
   }
 
   [[nodiscard]] bool has_key(const std::string &name) const {
diff --git a/src/odr/internal/rtf/rtf_element_registry.hpp b/src/odr/internal/rtf/rtf_element_registry.hpp
index c59c12226..032e3d25a 100644
--- a/src/odr/internal/rtf/rtf_element_registry.hpp
+++ b/src/odr/internal/rtf/rtf_element_registry.hpp
@@ -20,11 +20,9 @@ class ElementRegistry final
   std::tuple<ElementIdentifier, Element &> create_element(ElementType type);
   std::tuple<ElementIdentifier, Element &, Text &> create_text_element();
 
-  [[nodiscard]] Text &text_element_at(const ElementIdentifier id) {
-    return m_texts.at(id);
-  }
-  [[nodiscard]] const Text &text_element_at(const ElementIdentifier id) const {
-    return m_texts.at(id);
+  [[nodiscard]] auto &text_element_at(this auto &self,
+                                      const ElementIdentifier id) {
+    return self.m_texts.at(id);
   }
 
 private:
diff --git a/src/odr/internal/rtf/rtf_tokenizer.cpp b/src/odr/internal/rtf/rtf_tokenizer.cpp
index a929ee5df..268bd6d8d 100644
--- a/src/odr/internal/rtf/rtf_tokenizer.cpp
+++ b/src/odr/internal/rtf/rtf_tokenizer.cpp
@@ -73,8 +73,15 @@ std::string Tokenizer::bumpnc(const std::size_t n) {
     const std::size_t offset = result.size();
     const auto m =
         static_cast<std::streamsize>(std::min(chunk_size, n - offset));
-    result.resize(offset + static_cast<std::size_t>(m));
-    if (m_sb->sgetn(result.data() + offset, m) != m) {
+    // The callback must not throw, so a short read reports itself by
+    // shrinking the string back.
+    result.resize_and_overwrite(offset + static_cast<std::size_t>(m),
+                                [&](char *out, const std::size_t size) {
+                                  return m_sb->sgetn(out + offset, m) == m
+                                             ? size
+                                             : offset;
+                                });
+    if (result.size() == offset) {
       m_in->setstate(std::ios::eofbit);
       throw std::runtime_error("unexpected stream exhaust");
     }
diff --git a/src/odr/internal/util/byte_stream_util.cpp b/src/odr/internal/util/byte_stream_util.cpp
index fba64f92a..c39f09db0 100644
--- a/src/odr/internal/util/byte_stream_util.cpp
+++ b/src/odr/internal/util/byte_stream_util.cpp
@@ -53,8 +53,15 @@ std::string byte_stream::read_u8s(std::istream &in, const std::uint64_t n) {
     const std::size_t offset = result.size();
     const auto step =
         static_cast<std::size_t>(std::min(chunk_size, n - offset));
-    result.resize(offset + step);
-    read(in, result.data() + offset, step);
+    // The callback must not throw, so a short read reports itself by
+    // shrinking the string back.
+    result.resize_and_overwrite(
+        offset + step, [&](char *out, const std::size_t size) {
+          return try_read(in, out + offset, step) ? size : offset;
+        });
+    if (result.size() == offset) {
+      throw_exhausted();
+    }
   }
   return result;
 }
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 45577d5f3..959b00176 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -163,3 +163,11 @@ target_link_libraries(odr_test
 )
 
 gtest_add_tests(TARGET odr_test)
+
+# Holds the public headers to C++20. Not a gtest: it compiles or it does not.
+add_library(odr_public_headers_cpp20 OBJECT "public_headers_cpp20.cpp")
+target_link_libraries(odr_public_headers_cpp20 PRIVATE odr)
+set_target_properties(odr_public_headers_cpp20 PROPERTIES
+        CXX_STANDARD 20
+        CXX_STANDARD_REQUIRED ON
+        CXX_EXTENSIONS OFF)
diff --git a/test/public_headers_cpp20.cpp b/test/public_headers_cpp20.cpp
new file mode 100644
index 000000000..d85c538cb
--- /dev/null
+++ b/test/public_headers_cpp20.cpp
@@ -0,0 +1,19 @@
+// Every public header, compiled as a C++20 consumer sees them.
+
+#include <odr/archive.hpp>
+#include <odr/definitions.hpp>
+#include <odr/document.hpp>
+#include <odr/document_element.hpp>
+#include <odr/document_path.hpp>
+#include <odr/exceptions.hpp>
+#include <odr/file.hpp>
+#include <odr/filesystem.hpp>
+#include <odr/font.hpp>
+#include <odr/global_params.hpp>
+#include <odr/html.hpp>
+#include <odr/logger.hpp>
+#include <odr/odr.hpp>
+#include <odr/quantity.hpp>
+#include <odr/style.hpp>
+#include <odr/table_dimension.hpp>
+#include <odr/table_position.hpp>