diff --git a/crates/weaver-app/assets/styling/inline-theme-editor.css b/crates/weaver-app/assets/styling/inline-theme-editor.css
new file mode 100644
index 0000000..9aa5c01
--- /dev/null
+++ b/crates/weaver-app/assets/styling/inline-theme-editor.css
@@ -0,0 +1,89 @@
+/* Inline theme editor for notebook settings */
+
+.inline-theme-editor {
+    display: flex;
+    flex-direction: column;
+    gap: 1rem;
+    padding: 1rem;
+    background: var(--color-surface);
+    border: 1px solid var(--color-border);
+}
+
+.inline-theme-editor-heading {
+    margin: 0;
+    font-size: 1rem;
+    font-weight: 600;
+    color: var(--color-text);
+}
+
+.inline-theme-editor-presets {
+    display: flex;
+    flex-direction: column;
+    gap: 0.25rem;
+}
+
+.inline-theme-editor-presets label {
+    font-size: 0.875rem;
+    color: var(--color-muted);
+}
+
+.inline-theme-editor-presets select {
+    padding: 0.5rem;
+    border: 1px solid var(--color-border);
+    background: var(--color-base);
+    color: var(--color-text);
+    font-family: var(--font-ui);
+    font-size: 0.875rem;
+}
+
+.inline-theme-editor-presets select:focus {
+    outline: none;
+    border-color: var(--color-primary);
+}
+
+.inline-theme-editor-colours {
+    display: grid;
+    grid-template-columns: repeat(2, 1fr);
+    gap: 0.75rem;
+}
+
+.inline-theme-editor-code-theme,
+.inline-theme-editor-mode {
+    display: flex;
+    flex-direction: column;
+    gap: 0.25rem;
+}
+
+.inline-theme-editor-code-theme label,
+.inline-theme-editor-mode label {
+    font-size: 0.875rem;
+    color: var(--color-muted);
+}
+
+.inline-theme-editor-code-theme select {
+    padding: 0.5rem;
+    border: 1px solid var(--color-border);
+    background: var(--color-base);
+    color: var(--color-text);
+    font-family: var(--font-ui);
+    font-size: 0.875rem;
+}
+
+.inline-theme-editor-code-theme select:focus {
+    outline: none;
+    border-color: var(--color-primary);
+}
+
+.inline-theme-editor-mode {
+    gap: 0.5rem;
+}
+
+.inline-theme-editor-full-link {
+    font-size: 0.875rem;
+    color: var(--color-link);
+    text-decoration: none;
+}
+
+.inline-theme-editor-full-link:hover {
+    text-decoration: underline;
+}
diff --git a/crates/weaver-app/src/components/inline_theme_editor.rs b/crates/weaver-app/src/components/inline_theme_editor.rs
new file mode 100644
index 0000000..d2147d1
--- /dev/null
+++ b/crates/weaver-app/src/components/inline_theme_editor.rs
@@ -0,0 +1,219 @@
+//! Inline theme editor for notebook settings.
+//!
+//! Provides core 4 colour pickers (background, text, primary, link) plus code theme selector.
+
+use dioxus::prelude::*;
+use weaver_renderer::themes::{BUILTIN_CODE_THEMES, BUILTIN_COLOUR_SCHEMES};
+
+use crate::components::toggle_group::{ToggleGroup, ToggleItem};
+use crate::components::HexColourInput;
+
+/// Strip leading # or 0x from hex colour strings.
+fn strip_hex_prefix(s: &str) -> String {
+    s.trim_start_matches('#')
+        .trim_start_matches("0x")
+        .trim_start_matches("0X")
+        .to_uppercase()
+}
+
+/// Convert mode string to toggle index.
+fn mode_to_index(mode: &str) -> std::collections::HashSet<usize> {
+    let idx = match mode {
+        "light" => 1,
+        "dark" => 2,
+        _ => 0, // "auto" or default
+    };
+    std::collections::HashSet::from([idx])
+}
+
+/// Convert toggle index to mode string.
+fn index_to_mode(idx: usize) -> &'static str {
+    match idx {
+        1 => "light",
+        2 => "dark",
+        _ => "auto",
+    }
+}
+
+const INLINE_THEME_EDITOR_CSS: Asset = asset!("/assets/styling/inline-theme-editor.css");
+
+/// Theme values being edited.
+#[derive(Debug, Clone, PartialEq, Default)]
+pub struct InlineThemeValues {
+    pub background: String,
+    pub text: String,
+    pub primary: String,
+    pub link: String,
+    pub code_theme: String,
+    pub default_mode: String, // "light", "dark", or "auto"
+}
+
+/// Props for InlineThemeEditor.
+#[derive(Props, Clone, PartialEq)]
+pub struct InlineThemeEditorProps {
+    /// Current theme values.
+    pub values: InlineThemeValues,
+    /// Callback when any value changes.
+    pub onchange: EventHandler<InlineThemeValues>,
+}
+
+/// Inline theme editor with core colour pickers and code theme selector.
+#[component]
+pub fn InlineThemeEditor(props: InlineThemeEditorProps) -> Element {
+    let values = props.values.clone();
+
+    // Filter code themes by current mode for the selector.
+    let mode = &values.default_mode;
+    let relevant_code_themes: Vec<_> = BUILTIN_CODE_THEMES
+        .iter()
+        .filter(|t| mode == "auto" || t.variant == mode)
+        .collect();
+
+    rsx! {
+        document::Stylesheet { href: INLINE_THEME_EDITOR_CSS }
+
+        div { class: "inline-theme-editor",
+            h4 { class: "inline-theme-editor-heading", "Theme" }
+
+            // Preset selector.
+            div { class: "inline-theme-editor-presets",
+                label { "Start from preset:" }
+                select {
+                    onchange: {
+                        let onchange = props.onchange.clone();
+                        let code_theme = props.values.code_theme.clone();
+                        move |e: Event<FormData>| {
+                            let preset_id = e.value();
+                            if let Some(scheme) = BUILTIN_COLOUR_SCHEMES.iter().find(|s| s.id == preset_id) {
+                                onchange.call(InlineThemeValues {
+                                    background: strip_hex_prefix(&scheme.colours.base),
+                                    text: strip_hex_prefix(&scheme.colours.text),
+                                    primary: strip_hex_prefix(&scheme.colours.primary),
+                                    link: strip_hex_prefix(&scheme.colours.link),
+                                    code_theme: code_theme.clone(),
+                                    default_mode: scheme.variant.to_string(),
+                                });
+                            }
+                        }
+                    },
+                    option { value: "", "Custom" }
+                    for scheme in BUILTIN_COLOUR_SCHEMES.iter() {
+                        option {
+                            value: "{scheme.id}",
+                            "{scheme.name}"
+                        }
+                    }
+                }
+            }
+
+            // Colour pickers.
+            div { class: "inline-theme-editor-colours",
+                HexColourInput {
+                    label: Some("Background".to_string()),
+                    value: values.background.clone(),
+                    onchange: {
+                        let values = props.values.clone();
+                        let onchange = props.onchange.clone();
+                        move |val| {
+                            let mut v = values.clone();
+                            v.background = val;
+                            onchange.call(v);
+                        }
+                    },
+                }
+                HexColourInput {
+                    label: Some("Text".to_string()),
+                    value: values.text.clone(),
+                    onchange: {
+                        let values = props.values.clone();
+                        let onchange = props.onchange.clone();
+                        move |val| {
+                            let mut v = values.clone();
+                            v.text = val;
+                            onchange.call(v);
+                        }
+                    },
+                }
+                HexColourInput {
+                    label: Some("Primary".to_string()),
+                    value: values.primary.clone(),
+                    onchange: {
+                        let values = props.values.clone();
+                        let onchange = props.onchange.clone();
+                        move |val| {
+                            let mut v = values.clone();
+                            v.primary = val;
+                            onchange.call(v);
+                        }
+                    },
+                }
+                HexColourInput {
+                    label: Some("Link".to_string()),
+                    value: values.link.clone(),
+                    onchange: {
+                        let values = props.values.clone();
+                        let onchange = props.onchange.clone();
+                        move |val| {
+                            let mut v = values.clone();
+                            v.link = val;
+                            onchange.call(v);
+                        }
+                    },
+                }
+            }
+
+            // Code theme selector.
+            div { class: "inline-theme-editor-code-theme",
+                label { "Code theme:" }
+                select {
+                    value: "{values.code_theme}",
+                    onchange: {
+                        let values = props.values.clone();
+                        let onchange = props.onchange.clone();
+                        move |e: Event<FormData>| {
+                            let mut v = values.clone();
+                            v.code_theme = e.value();
+                            onchange.call(v);
+                        }
+                    },
+                    for theme in relevant_code_themes {
+                        option {
+                            value: "{theme.id}",
+                            "{theme.name}"
+                        }
+                    }
+                }
+            }
+
+            // Default mode toggle group.
+            // Indexes: 0 = auto, 1 = light, 2 = dark
+            div { class: "inline-theme-editor-mode",
+                label { "Default mode:" }
+                ToggleGroup {
+                    horizontal: true,
+                    default_pressed: mode_to_index(&values.default_mode),
+                    on_pressed_change: {
+                        let values = props.values.clone();
+                        let onchange = props.onchange.clone();
+                        move |pressed: std::collections::HashSet<usize>| {
+                            if let Some(&idx) = pressed.iter().next() {
+                                let mut v = values.clone();
+                                v.default_mode = index_to_mode(idx).to_string();
+                                onchange.call(v);
+                            }
+                        }
+                    },
+                    ToggleItem { index: 0usize, "Auto" }
+                    ToggleItem { index: 1usize, "Light" }
+                    ToggleItem { index: 2usize, "Dark" }
+                }
+            }
+
+            // Link to full editor.
+            // TODO: Enable once theme page exists
+            // a { href: "/{ident}/themes", class: "inline-theme-editor-full-link",
+            //     "Edit full theme ->"
+            // }
+        }
+    }
+}
diff --git a/crates/weaver-app/src/components/mod.rs b/crates/weaver-app/src/components/mod.rs
index ea3da4e..c74756b 100644
--- a/crates/weaver-app/src/components/mod.rs
+++ b/crates/weaver-app/src/components/mod.rs
@@ -362,3 +362,6 @@ pub mod tooltip;
 
 mod hex_colour_input;
 pub use hex_colour_input::HexColourInput;
+
+mod inline_theme_editor;
+pub use inline_theme_editor::{InlineThemeEditor, InlineThemeValues};