StacDev · divyanshub024 · Aug 20, 2026 · Aug 17, 2026 · Aug 17, 2026 · Aug 18, 2026
diff --git a/AGENTS.md b/AGENTS.md
@@ -85,7 +85,7 @@ Status legend: ⬜ Todo · ✅ Done
 | 18 | Suggestion & Suggestion Group | plain & outlined rows; scroll, wrap, column | ✅ |
 | 19 | Confirmation | default, approved, rejected | ⬜ |
 | 20 | Error state | | ⬜ |
-| 21 | Code block | | ⬜ |
+| 21 | Code block | built-in synchronous highlighter; languages host-extensible | ✅ |
 | 22 | Thinking indicator | turning, breathing asterisk + shimmer label; active & settled | ✅ |
 | 23 | Shimmer | text only; sweeping highlight, static when settled | ✅ |
 

diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,15 @@
 
 ## 0.2.0 (unreleased)
 
+- **Code block** — `FlowCodeBlock`, and a `FlowCodePart` message part
+  rendered by `FlowMessage`/`FlowThread` with copy intent surfaced on
+  `onCodeCopy`. Highlighting is built in and synchronous (Dart, JSON,
+  JavaScript/TypeScript, Python, shell, YAML, HTML, CSS and SQL;
+  host-extensible via `FlowCodeLanguage.register`), colored by new
+  `FlowSyntaxColors` theme tokens. The package now also bundles Geist Mono (three weights, SIL OFL)
+  behind new `code` / `codeInline` typography roles — `withFontFamily()`
+  no longer touches the mono roles; swap those with
+  `withCodeFontFamily()`.
 - **Breaking**: migrated from `package:flutter/material.dart` to
   `package:material_ui` (Material's home since Flutter 3.47) — no API
   changes, but the two Materials are distinct types, so the host app must

diff --git a/CLAUDE.md b/CLAUDE.md
@@ -8,7 +8,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 Two hard constraints shape everything here:
 
-- **No third-party dependencies.** `dependencies:` in `pubspec.yaml` contains only the Flutter SDK and Flutter's own first-party packages — `material_ui` (Material's home since Flutter 3.47) and its transitive set, all published by flutter.dev. Nothing outside that. Dev dependencies (`flutter_test`, `flutter_lints`) are fine. Bundled *assets* are not dependencies: the package ships Figtree (`fonts/`, SIL OFL) because the design system is set in it, declared under `flutter: fonts:` and referenced as `package: 'flow_ui'`.
+- **No third-party dependencies.** `dependencies:` in `pubspec.yaml` contains only the Flutter SDK and Flutter's own first-party packages — `material_ui` (Material's home since Flutter 3.47) and its transitive set, all published by flutter.dev. Nothing outside that. Dev dependencies (`flutter_test`, `flutter_lints`) are fine. Bundled *assets* are not dependencies: the package ships Figtree and Geist Mono (`fonts/`, SIL OFL) because the design system is set in them, declared under `flutter: fonts:` and referenced as `package: 'flow_ui'`.
 - **Nothing model-facing.** Components render state passed in and report intent out through callbacks. No prompts, schemas, provider/network calls, or any LLM awareness — that belongs to the layers built on top.
 
 The theme, the conversation components (message, thread, streaming text, actions, loading), the composer and its menus, attachments with their preview, suggestions, and the chat surface are implemented; the roadmap below tracks the rest. Message content is modeled as typed parts (`lib/src/models/`) — sealed `FlowMessagePart` subtypes rendered by `FlowMessage`, with `FlowCustomPart` + `FlowCustomPartBuilder` as the extension seam for host-injected content.
@@ -87,7 +87,7 @@ Values come from the Flow UI Figma file. Role names follow Material 3's `ColorSc
 | 18 | Suggestion & Suggestion Group | plain & outlined rows; scroll, wrap, column | ✅ |
 | 19 | Confirmation | default, approved, rejected | ⬜ |
 | 20 | Error state | | ⬜ |
-| 21 | Code block | | ⬜ |
+| 21 | Code block | built-in synchronous highlighter; languages host-extensible | ✅ |
 | 22 | Thinking indicator | turning, breathing asterisk + shimmer label; active & settled | ✅ |
 | 23 | Shimmer | text only; sweeping highlight, static when settled | ✅ |
 

diff --git a/README.md b/README.md
@@ -39,6 +39,7 @@
 | [`FlowStreamingText`](https://flowui.stac.dev/components/streaming-text) | Animated text reveal while a reply arrives |
 | [`FlowThinkingIndicator`](https://flowui.stac.dev/components/thinking-indicator) | Turning, breathing asterisk with a shimmering label |
 | [`FlowShimmerText`](https://flowui.stac.dev/components/shimmer-text) | Sweeping text highlight, static once settled |
+| [`FlowCodeBlock`](https://flowui.stac.dev/components/code-block) | Fenced code with built-in synchronous highlighting, a header label, and a copy affordance — languages host-extensible |
 | [`FlowMessageActions`](https://flowui.stac.dev/components/message-actions) | Copy / regenerate / edit / feedback row under a message |
 | [`FlowComposer`](https://flowui.stac.dev/components/composer) | Multiline input with send/stop, attachments strip, and leading/trailing action slots |
 | [`FlowMenu`](https://flowui.stac.dev/components/menu) | Icon-triggered menu with groups, submenus, and toggles — anchored card on desktop, bottom sheet on phones |

diff --git a/docs/src/content/docs/components/code-block.mdx b/docs/src/content/docs/components/code-block.mdx
@@ -0,0 +1,168 @@
+---
+title: Code block
+description: Fenced code on its own ground — built-in synchronous highlighting, a header label, and a copy affordance that reports intent.
+sidebar:
+  order: 13
+---
+
+import FlowDemo from '../../../components/FlowDemo.astro';
+
+`FlowCodeBlock` renders a fenced snippet on its own washed ground, under a
+header that names the content and offers copy. Highlighting is built in
+and synchronous — no setup call, no assets, nothing async. `language`
+picks a rule table (Dart, JSON, JavaScript/TypeScript, Python, shell,
+YAML, HTML, CSS and SQL ship in the box); unknown ids render plain,
+never an error. Token inks come from the theme's `FlowSyntaxColors`, so
+code recolors with the rest of the palette in both themes.
+
+In a message, code arrives as a `FlowCodePart` and `FlowMessage` renders
+the block for you — copy intent surfaces on `FlowThread.onCodeCopy` with
+the part in hand.
+
+## Dart
+
+<FlowDemo demo="codeBlock" variant="dart" height={620} title="Dart" />
+
+```dart title="The block reports intent; the host owns the clipboard"
+FlowCodeBlock(
+  code: source,
+  language: 'dart',
+  filename: 'point.dart',
+  copyTooltip: 'Copy code',
+  copied: copied,
+  onCopy: () async {
+    await Clipboard.setData(ClipboardData(text: source));
+    setState(() => copied = true);
+    // Hold `copied` for a beat, then clear it — the affordance shows a
+    // primary-tinted check for as long as the host says so.
+  },
+)
+```
+
+## JSON
+
+Keys read apart from string values, and long lines scroll horizontally
+inside the block (`wrap: true` wraps them instead):
+
+<FlowDemo demo="codeBlock" variant="json" height={420} title="JSON" />
+
+```dart title="A payload with a long line"
+FlowCodeBlock(
+  code: payload,
+  language: 'json',
+  filename: 'screen.json',
+  copyTooltip: 'Copy code',
+  onCopy: () => copy(payload),
+)
+```
+
+## Plain
+
+No `language` — or one the registry doesn't know — renders plain ink;
+the header can still carry a filename:
+
+<FlowDemo demo="codeBlock" variant="plain" height={300} title="Plain" />
+
+```dart title="Logs, output, anything unhighlightable"
+FlowCodeBlock(
+  code: log,
+  filename: 'build.log',
+  copyTooltip: 'Copy',
+  onCopy: () => copy(log),
+)
+```
+
+## Streaming
+
+While `isStreaming` is true the copy affordance hides — there is nothing
+complete to copy — and each delivery renders whole, with no per-character
+reveal (streamed code arrives re-highlighted as often as appended, which
+a reveal would restart on). In a thread this is automatic while the
+message streams:
+
+<FlowDemo demo="codeBlock" variant="streaming" height={620} title="Streaming" />
+
+```dart title="Code parts in a streaming thread"
+FlowThread(
+  messages: messages,
+  codeCopyTooltip: 'Copy code',
+  copiedCodePart: copiedPart,
+  onCodeCopy: (part) async {
+    await Clipboard.setData(ClipboardData(text: part.code));
+    setState(() => copiedPart = part);
+  },
+)
+```
+
+## Languages
+
+Resolution is by id or alias, case-insensitive, and anything unknown
+renders plain — a `rust` fence degrades gracefully rather than erroring:
+
+| Language | id | Aliases |
+|---|---|---|
+| Dart | `dart` | — |
+| JSON | `json` | `jsonc` |
+| JavaScript / TypeScript | `javascript` | `js`, `jsx`, `typescript`, `ts`, `tsx` |
+| Python | `python` | `py` |
+| Shell | `bash` | `sh`, `shell`, `zsh` |
+| YAML | `yaml` | `yml` |
+| HTML | `html` | `xml` |
+| CSS | `css` | `scss`, `less` |
+| SQL | `sql` | `mysql`, `postgres`, `postgresql`, `sqlite` |
+| Plain | `plain` | `text`, `txt` |
+
+YAML, for one, knows that `on:` is a key before it is a boolean:
+
+<FlowDemo demo="codeBlock" variant="yaml" height={520} title="YAML" />
+
+The registry is host-extensible. `FlowCodeLanguage` is an ordered rule
+table — earlier rules win, so comments and strings come first — and
+`register` makes it resolvable from every block. A table like SQL's,
+whose keywords come in either case, sets `caseSensitive: false`:
+
+```dart title="Registering a language"
+FlowCodeLanguage.register(
+  const FlowCodeLanguage(
+    id: 'lisp',
+    rules: [
+      FlowSyntaxRule(FlowSyntaxToken.comment, r';[^\n]*'),
+      FlowSyntaxRule(FlowSyntaxToken.string, r'"(?:\\.|[^"\\])*"'),
+      FlowSyntaxRule(FlowSyntaxToken.punctuation, r'[()]+'),
+    ],
+  ),
+);
+```
+
+## Theming
+
+Token inks are theme tokens. Install a `FlowSyntaxColors` on the theme to
+recolor them; the code face is Geist Mono, bundled with the package, and
+swaps via the typography:
+
+```dart title="Custom syntax palette and mono face"
+FlowTheme(
+  colors: FlowColors.light,
+  syntax: FlowSyntaxColors.light.copyWith(keyword: myBrandAccent),
+  typography: FlowTypography.standard.withCodeFontFamily('JetBrainsMono'),
+)
+```
+
+## Key API
+
+- `FlowCodeBlock` — `code`, `language` (id or alias, case-insensitive),
+  `filename` (header label; falls back to `language`), `onCopy` /
+  `copied` / `copyTooltip` (intent out, host-owned confirmation),
+  `isStreaming`, `wrap`, plus `padding` and `borderRadius` over the
+  design's 16/12 inset and 12px corner.
+- `FlowCodePart` — `code`, `language`, `filename`; rendered by
+  `FlowMessage`, skipped in system messages.
+- `FlowThread` / `FlowMessage` — `onCodeCopy` (handed the tapped part),
+  `copiedCodePart` (pass the instance back while the confirmation lasts),
+  `codeCopyTooltip`.
+- `FlowCodeLanguage` — `find`, `register`, `caseSensitive`, and the
+  built-ins (`dart`, `json`, `javascript`, `python`, `bash`, `yaml`,
+  `html`, `css`, `sql`, `plain`); `FlowSyntaxRule` pairs a regex with a
+  `FlowSyntaxToken`.
+- `FlowSyntaxColors` — eight token roles with light and dark presets, on
+  `FlowTheme.syntax`.
diff --git a/docs/src/content/docs/roadmap.md b/docs/src/content/docs/roadmap.md
@@ -40,7 +40,7 @@ elements and the remaining AI states are on the way.
 | Suggestions | <span class="badge-done">Shipped</span> |
 | Confirmation | <span class="badge-todo">Planned</span> |
 | Error state | <span class="badge-todo">Planned</span> |
-| Code block | <span class="badge-todo">Planned</span> |
+| Code block | <span class="badge-done">Shipped</span> |
 | Thinking indicator | <span class="badge-done">Shipped</span> |
 | Shimmer | <span class="badge-done">Shipped</span> |
 

diff --git a/fonts/GeistMono-Medium.ttf b/fonts/GeistMono-Medium.ttf
diff --git a/fonts/GeistMono-Regular.ttf b/fonts/GeistMono-Regular.ttf
diff --git a/fonts/GeistMono-SemiBold.ttf b/fonts/GeistMono-SemiBold.ttf
diff --git a/fonts/OFL-GeistMono.txt b/fonts/OFL-GeistMono.txt
@@ -0,0 +1,93 @@
+Copyright 2024 The Geist Project Authors (https://github.com/vercel/geist-font)
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+https://openfontlicense.org
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded, 
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.
diff --git a/lib/flow_ui.dart b/lib/flow_ui.dart
@@ -10,11 +10,13 @@ export 'src/models/flow_attachment.dart';
 export 'src/models/flow_message_data.dart';
 export 'src/models/flow_message_part.dart';
 export 'src/theme/flow_colors.dart';
+export 'src/theme/flow_syntax_colors.dart';
 export 'src/theme/flow_theme.dart';
 export 'src/theme/flow_typography.dart';
 export 'src/widgets/flow_attachment_group.dart';
 export 'src/widgets/flow_attachment_preview.dart';
 export 'src/widgets/flow_chat_screen.dart';
+export 'src/widgets/flow_code_block.dart';
 export 'src/widgets/flow_composer.dart';
 export 'src/widgets/flow_greeting.dart';
 export 'src/widgets/flow_menu.dart';

diff --git a/lib/src/models/flow_message_part.dart b/lib/src/models/flow_message_part.dart
@@ -4,7 +4,7 @@ import 'flow_attachment.dart';
 
 /// One piece of content inside a `FlowMessageData`.
 ///
-/// Sealed so renderers can switch exhaustively. More part types (code, tool)
+/// Sealed so renderers can switch exhaustively. More part types (tool)
 /// arrive alongside their components; [FlowCustomPart] is how hosts inject
 /// arbitrary content today.
 @immutable
@@ -26,6 +26,22 @@ class FlowAttachmentPart extends FlowMessagePart {
   final List<FlowAttachment> attachments;
 }
 
+/// Fenced code, rendered by a `FlowCodeBlock`.
+class FlowCodePart extends FlowMessagePart {
+  const FlowCodePart(this.code, {this.language, this.filename});
+
+  /// The source, verbatim.
+  final String code;
+
+  /// `FlowCodeLanguage` id or alias — usually the fence info string, e.g.
+  /// `'dart'`. Null or unknown renders plain.
+  final String? language;
+
+  /// The block's header label, e.g. a file hint beside the fence. Null
+  /// falls back to [language].
+  final String? filename;
+}
+
 /// Host-defined content, rendered through a `FlowCustomPartBuilder`.
 class FlowCustomPart extends FlowMessagePart {
   const FlowCustomPart({required this.type, this.data});