kettu-builder · Oct 31, 2026 · Oct 31, 2026
diff --git a/README.md b/README.md
@@ -7,11 +7,12 @@ Color themes for [Kettu](https://github.com/KettuAI/Kettu). Kettu lists them in
 | [Catppuccin](themes/catppuccin.json)   | Latte and Mocha | [Catppuccin](https://github.com/catppuccin/catppuccin)           | MIT     |
 | [Gruvbox](themes/gruvbox.json)         | Light and dark  | [Pavel Pertsev](https://github.com/morhetz/gruvbox)              | MIT     |
 | [Nord](themes/nord.json)               | Light and dark  | [Arctic Ice Studio](https://github.com/nordtheme/nord)           | MIT     |
+| [Paper](themes/paper.json)             | Light and dark  | [Kettu](https://github.com/KettuAI/Kettu)                        | MIT     |
 | [Rosé Pine](themes/rose-pine.json)     | Dawn and Main   | [Rosé Pine](https://github.com/rose-pine/rose-pine-theme)        | MIT     |
 | [Solarized](themes/solarized.json)     | Light and dark  | [Ethan Schoonover](https://github.com/altercation/solarized)     | MIT     |
 | [Tokyo Night](themes/tokyo-night.json) | Light and Night | [enkia](https://github.com/tokyo-night/tokyo-night-vscode-theme) | MIT     |
 
-Each keeps its palette's published colors. Where one is too faint for text on its own surfaces, under 4.5:1, the theme uses the same hue a shade lighter or darker for text. Solarized keeps its body text tone, so Kettu marks its tile with a contrast warning.
+Paper is Kettu's former built-in look: warm paper colors with Source Serif 4 for prose and headings and Inter for the interface. The others each keep their palette's published colors. Where one is too faint for text on its own surfaces, under 4.5:1, the theme uses the same hue a shade lighter or darker for text. Solarized keeps its body text tone, so Kettu marks its tile with a contrast warning.
 
 ## Adding a theme
 
@@ -42,6 +43,7 @@ A theme here needs a license that lets anyone use and share it, and names the pa
 ```
 
 - A color a variant leaves out keeps Kettu's own.
+- `fonts`, which both variants share, may name a face for `ui`, `prose` (the agent's replies and headings) and `code`: `system`, `inter`, `source-serif-4` or `jetbrains-mono`, and for `code` only `system` or `jetbrains-mono`. Kettu ships each of them; a role left out keeps Kettu's own.
 - Colors are hex, `rgb()`, `hsl()`, `oklch()`, `oklab()` or `transparent`; nothing else, such as `var()` or color names.
 - A file is at most 256 KB.
 

diff --git a/index.json b/index.json
@@ -106,6 +106,41 @@
         }
       }
     },
+    {
+      "id": "paper",
+      "name": "Paper",
+      "author": "Kettu",
+      "version": "1.0.0",
+      "license": "MIT",
+      "file": "themes/paper.json",
+      "sha256": "4b0680014dc9a51acb67353dfca6e61ee3e6038d22caf6bb10c2181c19480bb1",
+      "preview": {
+        "light": {
+          "bg-app": "#fdfcf9",
+          "bg-sidebar": "#efede6",
+          "bg-surface": "#ffffff",
+          "bg-subtle": "#f2f0e9",
+          "bg-selected": "rgb(28 27 24 / 7.5%)",
+          "border-default": "rgb(28 27 24 / 12%)",
+          "border-subtle": "rgb(28 27 24 / 7.5%)",
+          "border-strong": "rgb(28 27 24 / 20%)",
+          "primary-from": "#2e2d29",
+          "primary-to": "#1c1b18"
+        },
+        "dark": {
+          "bg-app": "#1c1b18",
+          "bg-sidebar": "#121110",
+          "bg-surface": "#262521",
+          "bg-subtle": "#2a2925",
+          "bg-selected": "rgb(244 243 238 / 9%)",
+          "border-default": "rgb(244 243 238 / 10%)",
+          "border-subtle": "rgb(244 243 238 / 6.5%)",
+          "border-strong": "rgb(244 243 238 / 18%)",
+          "primary-from": "#f4f3ee",
+          "primary-to": "#e3e1d9"
+        }
+      }
+    },
     {
       "id": "rose-pine",
       "name": "Rosé Pine",

diff --git a/scripts/build-index.mjs b/scripts/build-index.mjs
@@ -66,6 +66,7 @@ const TOKENS = new Set([
   'mark',
   'checker',
   'agent-opencode',
+  'agent-pi',
   'agent-other',
   'heat-hue',
   'heat-0',
@@ -112,7 +113,23 @@ const PREVIEW_TOKENS = [
   'primary-to',
 ]
 
-const FIELDS = ['kettuTheme', 'name', 'author', 'version', 'license', 'source', 'light', 'dark']
+const FIELDS = [
+  'kettuTheme',
+  'name',
+  'author',
+  'version',
+  'license',
+  'source',
+  'fonts',
+  'light',
+  'dark',
+]
+// The faces a theme may choose for each kind of text, all of them shipped with Kettu.
+const FONTS = {
+  ui: ['system', 'inter', 'source-serif-4', 'jetbrains-mono'],
+  prose: ['system', 'inter', 'source-serif-4', 'jetbrains-mono'],
+  code: ['system', 'jetbrains-mono'],
+}
 const VERSION = /^\d+\.\d+\.\d+(?:-[0-9A-Za-z.-]+)?(?:\+[0-9A-Za-z.-]+)?$/
 const CODE_THEME = /^[a-z0-9-]{1,64}$/
 const CONTROL = /[\u0000-\u001f\u007f]/
@@ -203,6 +220,16 @@ function checkTheme(fileName, raw) {
     throw new Error('has a source that is not an https URL')
   }
 
+  if (raw.fonts !== undefined) {
+    if (!isRecord(raw.fonts)) throw new Error('fonts is not an object')
+    for (const [role, face] of Object.entries(raw.fonts)) {
+      if (!Object.hasOwn(FONTS, role)) throw new Error(`fonts.${role} is not text Kettu sets`)
+      if (!FONTS[role].includes(face)) {
+        throw new Error(`fonts.${role} is not one of ${FONTS[role].join(', ')}`)
+      }
+    }
+  }
+
   const preview = {}
   for (const mode of MODES) {
     const variant = raw[mode]

diff --git a/themes/paper.json b/themes/paper.json
@@ -0,0 +1,183 @@
+{
+  "kettuTheme": 1,
+  "name": "Paper",
+  "author": "Kettu",
+  "version": "1.0.0",
+  "license": "MIT",
+  "source": "https://github.com/KettuAI/Kettu",
+  "fonts": {
+    "ui": "inter",
+    "prose": "source-serif-4",
+    "code": "jetbrains-mono"
+  },
+  "light": {
+    "colors": {
+      "bg-app": "#fdfcf9",
+      "bg-sidebar": "#efede6",
+      "bg-surface": "#ffffff",
+      "bg-subtle": "#f2f0e9",
+      "bg-code-inline": "rgb(28 27 24 / 6.5%)",
+      "bg-code-block": "#f7f5ef",
+      "bg-hover": "rgb(28 27 24 / 5%)",
+      "bg-selected": "rgb(28 27 24 / 7.5%)",
+      "queue-back": "#f2f0ea",
+      "border-default": "rgb(28 27 24 / 12%)",
+      "border-subtle": "rgb(28 27 24 / 7.5%)",
+      "border-strong": "rgb(28 27 24 / 20%)",
+      "text-primary": "#1c1b18",
+      "text-secondary": "#55534c",
+      "text-tertiary": "#68655d",
+      "text-placeholder": "#6e6b63",
+      "text-disabled": "#a9a69d",
+      "icon-default": "#68655d",
+      "attention": "#a3441c",
+      "attention-dot": "#d2622f",
+      "danger": "#ac3b2d",
+      "success": "#2e7550",
+      "merged": "#6f4c8e",
+      "info": "#2d5e91",
+      "warning": "#8a6212",
+      "link": "#2d5e91",
+      "link-hover": "#234a73",
+      "danger-tint": "#fbf6f6",
+      "danger-border": "#eed8d5",
+      "success-tint": "#f2f7f5",
+      "info-tint": "#f2f5f8",
+      "warning-tint": "#f8f6f1",
+      "info-tint-hover": "#eaeff4",
+      "focus": "rgb(45 94 145 / 55%)",
+      "selection": "rgb(45 94 145 / 18%)",
+      "edit-ring": "#2a79d7",
+      "edit-selection": "#b3d6fe",
+      "primary-from": "#2e2d29",
+      "primary-to": "#1c1b18",
+      "primary-hover-from": "#3b3934",
+      "primary-hover-to": "#292824",
+      "primary-ring": "#1c1b18",
+      "primary-highlight": "rgb(255 255 255 / 12%)",
+      "primary-foreground": "#ffffff",
+      "scrollbar-thumb": "rgb(28 27 24 / 20%)",
+      "scrim": "rgb(28 27 24 / 14%)",
+      "viewer-scrim": "oklch(0.14 0.004 85 / 92%)",
+      "mark": "oklch(0.88 0.14 92 / 55%)",
+      "checker": "rgb(28 27 24 / 5%)",
+      "agent-opencode": "oklch(0.6 0.008 85)",
+      "agent-pi": "oklch(0.852 0.114 83.4)",
+      "agent-other": "oklch(0.8 0.008 85)",
+      "heat-hue": "#55534c",
+      "heat-0": "rgb(28 27 24 / 5.5%)",
+      "context-1": "oklch(0.52 0.09 250)",
+      "context-2": "oklch(0.56 0.07 190)",
+      "context-3": "oklch(0.52 0.09 310)",
+      "context-4": "oklch(0.68 0.11 75)",
+      "context-5": "oklch(0.56 0.09 155)",
+      "context-6": "oklch(0.56 0.1 25)",
+      "context-7": "oklch(0.6 0.02 85)",
+      "terminal-background": "#fdfcf9",
+      "terminal-foreground": "#1c1b18",
+      "terminal-cursor": "#1c1b18",
+      "terminal-selection": "rgb(45 94 145 / 18%)",
+      "ansi-black": "#1c1b18",
+      "ansi-red": "#ac3b2d",
+      "ansi-green": "#2e7550",
+      "ansi-yellow": "#8a6212",
+      "ansi-blue": "#2d5e91",
+      "ansi-magenta": "#6f4c8e",
+      "ansi-cyan": "#23707a",
+      "ansi-white": "#6d6a62",
+      "ansi-bright-black": "#75726a",
+      "ansi-bright-red": "#c24e3b",
+      "ansi-bright-green": "#3c8a5e",
+      "ansi-bright-yellow": "#a0761a",
+      "ansi-bright-blue": "#3b74ae",
+      "ansi-bright-magenta": "#8660a6",
+      "ansi-bright-cyan": "#2f8590",
+      "ansi-bright-white": "#a9a69d"
+    }
+  },
+  "dark": {
+    "colors": {
+      "bg-app": "#1c1b18",
+      "bg-sidebar": "#121110",
+      "bg-surface": "#262521",
+      "bg-subtle": "#2a2925",
+      "bg-code-inline": "rgb(244 243 238 / 8.5%)",
+      "bg-code-block": "#181715",
+      "bg-hover": "rgb(244 243 238 / 5.5%)",
+      "bg-selected": "rgb(244 243 238 / 9%)",
+      "queue-back": "#201f1c",
+      "border-default": "rgb(244 243 238 / 10%)",
+      "border-subtle": "rgb(244 243 238 / 6.5%)",
+      "border-strong": "rgb(244 243 238 / 18%)",
+      "text-primary": "#eceae3",
+      "text-secondary": "#bab7ad",
+      "text-tertiary": "#9a978f",
+      "text-placeholder": "#95928a",
+      "text-disabled": "#5e5c56",
+      "icon-default": "#9a978f",
+      "attention": "#e8916a",
+      "attention-dot": "#e8916a",
+      "danger": "#ea8a7d",
+      "success": "#7dc196",
+      "merged": "#b798d4",
+      "info": "#80aada",
+      "warning": "#d9b463",
+      "link": "#80aada",
+      "link-hover": "#a6c4e8",
+      "danger-tint": "#3a2f2a",
+      "danger-border": "#593f39",
+      "success-tint": "#2f352d",
+      "info-tint": "#2f3234",
+      "warning-tint": "#383328",
+      "info-tint-hover": "#34393d",
+      "focus": "rgb(128 170 218 / 60%)",
+      "selection": "rgb(128 170 218 / 28%)",
+      "edit-ring": "#3a8ee6",
+      "edit-selection": "#3f638b",
+      "primary-from": "#f4f3ee",
+      "primary-to": "#e3e1d9",
+      "primary-hover-from": "#ffffff",
+      "primary-hover-to": "#eceae3",
+      "primary-ring": "#d4d1c8",
+      "primary-highlight": "rgb(255 255 255 / 60%)",
+      "primary-foreground": "#262521",
+      "scrollbar-thumb": "rgb(244 243 238 / 20%)",
+      "scrim": "rgb(0 0 0 / 32%)",
+      "viewer-scrim": "oklch(0.14 0.004 85 / 92%)",
+      "mark": "oklch(0.8 0.13 88 / 32%)",
+      "checker": "rgb(244 243 238 / 7%)",
+      "agent-opencode": "oklch(0.74 0.008 85)",
+      "agent-pi": "oklch(0.749 0.115 84.2)",
+      "agent-other": "oklch(0.46 0.008 85)",
+      "heat-hue": "#bab7ad",
+      "heat-0": "rgb(244 243 238 / 6.5%)",
+      "context-1": "oklch(0.72 0.08 250)",
+      "context-2": "oklch(0.74 0.06 190)",
+      "context-3": "oklch(0.72 0.08 310)",
+      "context-4": "oklch(0.78 0.1 75)",
+      "context-5": "oklch(0.74 0.08 155)",
+      "context-6": "oklch(0.74 0.09 25)",
+      "context-7": "oklch(0.7 0.02 85)",
+      "terminal-background": "#1c1b18",
+      "terminal-foreground": "#eceae3",
+      "terminal-cursor": "#eceae3",
+      "terminal-selection": "rgb(128 170 218 / 28%)",
+      "ansi-black": "#3a3833",
+      "ansi-red": "#ea8a7d",
+      "ansi-green": "#7dc196",
+      "ansi-yellow": "#d9b463",
+      "ansi-blue": "#80aada",
+      "ansi-magenta": "#b798d4",
+      "ansi-cyan": "#79c2c2",
+      "ansi-white": "#d9d6cd",
+      "ansi-bright-black": "#6e6b63",
+      "ansi-bright-red": "#f2a497",
+      "ansi-bright-green": "#97d3ac",
+      "ansi-bright-yellow": "#e8c77e",
+      "ansi-bright-blue": "#9dc0e8",
+      "ansi-bright-magenta": "#cbb0e2",
+      "ansi-bright-cyan": "#97d6d6",
+      "ansi-bright-white": "#f4f3ee"
+    }
+  }
+}