Theming Reference

Theming in the coding agent: schema, loading, runtime behavior, and failure modes.

What the theme system controls

The theme system drives:

• foreground/background color tokens used across the TUI
• markdown styling adapters (getMarkdownTheme())
• selector/editor/settings list adapters (getSelectListTheme(), getEditorTheme(), getSettingsListTheme())
• symbol preset + symbol overrides (unicode, nerd, ascii)
• syntax highlighting colors used by native highlighter (@veyyon/natives)
• status line segment colors

Primary implementation: src/modes/theme/theme.ts.

Theme JSON shape

Theme files are JSON objects validated against the runtime schema in theme.ts (themeJsonSchema) and mirrored by src/modes/theme/theme-schema.json.

Top-level fields:

• name (required)
• colors (required; all color tokens required)
• vars (optional; reusable color variables)
• export (optional; HTML export colors)
• symbols (optional)
  • preset (optional: unicode | nerd | ascii)
  • overrides (optional: key/value overrides for SymbolKey)

Color values accept:

• hex string ("#RRGGBB")
• 256-color index (0..255)
• variable reference string (resolved through vars)
• empty string ("") meaning terminal default (\x1b[39m fg, \x1b[49m bg)

Required color tokens (current)

All tokens below are required in colors.

Core text and borders (11)

accent, border, borderAccent, borderMuted, success, error, warning, muted, dim, text, thinkingText

Background blocks (7)

selectedBg, userMessageBg, customMessageBg, toolPendingBg, toolSuccessBg, toolErrorBg, statusLineBg

Message/tool text (5)

userMessageText, customMessageText, customMessageLabel, toolTitle, toolOutput

Markdown (10)

mdHeading, mdLink, mdLinkUrl, mdCode, mdCodeBlock, mdCodeBlockBorder, mdQuote, mdQuoteBorder, mdHr, mdListBullet

Tool diff + syntax highlighting (12)

toolDiffAdded, toolDiffRemoved, toolDiffContext, syntaxComment, syntaxKeyword, syntaxFunction, syntaxVariable, syntaxString, syntaxNumber, syntaxType, syntaxOperator, syntaxPunctuation

Mode/thinking borders (8)

thinkingOff, thinkingMinimal, thinkingLow, thinkingMedium, thinkingHigh, thinkingXhigh, bashMode, pythonMode

Status line segment colors (13)

statusLineSep, statusLineModel, statusLinePath, statusLineGitClean, statusLineGitDirty, statusLineContext, statusLineSpend, statusLineStaged, statusLineDirty, statusLineUntracked, statusLineOutput, statusLineCost, statusLineSubagents

Optional tokens

Purpose accents (5, optional)

sessionAccent, modeAccent, shareAccent, infoAccent, matchHighlight

These color the “cool arc” of the design language: session identity segments use sessionAccent, mode labels (plan, vibe, goal, loop) use modeAccent, share and collab segments use shareAccent, informational callouts such as the welcome tip label use infoAccent, and fuzzy-filter hit characters in select lists use matchHighlight. A theme that omits them still loads: each falls back to a sensible existing token (sessionAccent and modeAccent to accent, shareAccent to link then accent, infoAccent to muted, matchHighlight to warning). The built-in titanium theme binds them to its Daybreak palette (teal, violet, indigo, rose, gold).

composerBg (optional)

The tonal ground painted under the composer’s input rows and the padding rows above and below them (the “quiet card”). The padding rows carry the same ground so the card has a visible body rather than a single tinted line.

A theme that omits composerBg gets an unpainted composer: the input area renders directly on the terminal’s own background. Inheriting statusLineBg here used to render the composer band as a gray slab on mismatched terminals, so the default is no paint. A theme that wants a painted composer card must set composerBg explicitly, and an explicit value is painted.

export section (optional)

Used for HTML export theming helpers:

• export.pageBg
• export.cardBg
• export.infoBg

If omitted, export code derives defaults from resolved theme colors.

symbols section (optional)

• symbols.preset sets a theme-level default symbol set.
• symbols.overrides can override individual SymbolKey values.
• symbols.spinnerFrames overrides the loading spinner frames. Accepts either a flat string[] (applied to the status and activity spinners) or an object { "status"?: string[], "activity"?: string[], "thinking"?: string[] } to override each type independently. Any type not specified falls back to the symbol preset’s default frames. status drives the ~12.5fps spinner used by loaders and tool-execution indicators; activity drives the ~30fps spinner used by markdown progress bars and similar high-frequency UI; thinking drives the starburst pulse shown in place of hidden reasoning while a model thinks (a single-frame array renders it static, with no animation timer).

Runtime precedence:

1. settings symbolPreset override (if set)
2. theme JSON symbols.preset
3. fallback "unicode"

Invalid override keys are ignored and logged (logger.debug).

Box-drawing borders

All outlined chrome, tool-result frames, overlays, code fences, the editor, the welcome banner, and markdown tables draw with the boxSharp.* tokens (┌┐└┘─│├┤┬┴┼).

Override behavior follows from that:

• boxSharp.{topLeft,topRight,bottomLeft,bottomRight} restyle corners everywhere, markdown tables included.
• boxSharp.{horizontal,vertical} restyle edges and rules.
• boxSharp.{cross,teeDown,teeUp,teeRight,teeLeft} restyle dividers and junctions.
• The boxRound.* tokens (rounded corners ╭╮╰╯) remain in the symbol schema, but no shipped surface consumes them today; setting them changes nothing.

Built-in vs custom theme sources

Theme lookup order (loadThemeJson):

1. built-in embedded themes (dark.json, light.json, and all defaults/*.json compiled into defaultThemes)
2. custom theme file: <customThemesDir>/<name>.json

Custom themes directory comes from getCustomThemesDir():

• default: ~/.veyyon/profiles/default/agent/themes: profile-aware: under a named profile (--profile <name> / VEYYON_PROFILE) this resolves to ~/.veyyon/profiles/<name>/agent/themes
• overridden by VEYYON_CODING_AGENT_DIR: $VEYYON_CODING_AGENT_DIR/themes

getAvailableThemes() returns merged built-in + custom names, sorted, with built-ins taking precedence on name collision.

Loading, validation, and resolution

For custom theme files:

1. read JSON
2. parse JSON
3. validate against themeJsonSchema
4. resolve vars references recursively
5. convert resolved values to ANSI by terminal capability mode

Validation behavior:

• missing required color tokens: explicit grouped error message
• bad token types/values: validation errors with JSON path
• unknown theme file: Theme not found: <name>

Var reference behavior:

• supports nested references
• throws on missing variable reference
• throws on circular references

Terminal color mode behavior

Color mode detection (detectColorMode):

• COLORTERM=truecolor|24bit => truecolor
• WT_SESSION => truecolor
• TERM in dumb, linux, or empty => 256color
• otherwise => truecolor

Conversion behavior:

• hex -> Bun.color(..., "ansi-16m" | "ansi-256")
• numeric -> 38;5 / 48;5 ANSI
• "" -> default fg/bg reset

Runtime switching behavior

Initial theme (initTheme)

main.ts initializes theme with settings:

• symbolPreset
• colorBlindMode
• theme.dark
• theme.light

Auto theme slot selection uses terminal appearance in this order:

1. terminal-reported OSC 11 background luminance, unless the macOS/Zellij fallback path is active
2. COLORFGBG background index (< 8 => dark, >= 8 => light)
3. macOS appearance fallback only for the known-broken macOS/Zellij OSC 11 path
4. dark slot fallback

Current defaults from settings schema:

• theme.dark = "titanium"
• theme.light = "light"
• symbolPreset = "unicode"
• colorBlindMode = false

Explicit switching (setTheme)

• loads selected theme
• updates global theme singleton
• optionally starts watcher
• triggers onThemeChange callback

On failure:

• falls back to built-in dark
• returns { success: false, error }

Preview switching (previewTheme)

• applies temporary preview theme to global theme
• does not change persisted settings by itself
• returns success/error without fallback replacement

Settings UI uses this for live preview and restores prior theme on cancel.

Watchers and live reload

When watcher is enabled (setTheme(..., true) / interactive init):

• watches <customThemesDir>/<currentTheme>.json only when that file exists
• built-ins are effectively not watched; built-in theme lookup also takes precedence over same-name custom files
• matching file changes schedule a debounced reload; reload errors or temporary file absence keep the last successfully loaded theme
• the watcher does not perform a delete/rename fallback; it waits for a future successful reload or explicit theme switch

Auto mode also reevaluates dark/light slot mapping from terminal appearance changes, SIGWINCH, and the macOS fallback observer when active.

Color-blind mode behavior

colorBlindMode changes only one token at runtime:

• toolDiffAdded is HSV-adjusted (green shifted toward blue)
• adjustment is applied only when resolved value is a hex string

Other tokens are unchanged.

Where theme settings are persisted

Theme-related settings are persisted by Settings to global config YAML:

• path: <agentDir>/config.yml
• default agent dir: ~/.veyyon/profiles/default/agent (profile-aware: ~/.veyyon/profiles/<name>/agent under a named profile)
• effective default file: ~/.veyyon/profiles/default/agent/config.yml

Persisted keys:

• theme.dark
• theme.light
• symbolPreset
• colorBlindMode

Legacy migration exists: old flat theme: "name" is migrated to nested theme.dark or theme.light based on luminance detection.

Creating a custom theme (practical)

1. Create file in custom themes dir, e.g. ~/.veyyon/profiles/default/agent/themes/my-theme.json.
2. Include name, optional vars, and all required colors tokens.
3. Optionally include symbols and export.
4. Select the theme in Settings (Appearance -> Dark Theme or Appearance -> Light Theme) depending on which auto slot you want.

Minimal skeleton:

{
  "name": "my-theme",
  "vars": {
    "accent": "#7aa2f7",
    "muted": 244
  },
  "colors": {
    "accent": "accent",
    "border": "#4c566a",
    "borderAccent": "accent",
    "borderMuted": "muted",
    "success": "#9ece6a",
    "error": "#f7768e",
    "warning": "#e0af68",
    "muted": "muted",
    "dim": 240,
    "text": "",
    "thinkingText": "muted",

    "selectedBg": "#2a2f45",
    "userMessageBg": "#1f2335",
    "userMessageText": "",
    "customMessageBg": "#24283b",
    "customMessageText": "",
    "customMessageLabel": "accent",
    "toolPendingBg": "#1f2335",
    "toolSuccessBg": "#1f2d2a",
    "toolErrorBg": "#2d1f2a",
    "toolTitle": "",
    "toolOutput": "muted",

    "mdHeading": "accent",
    "mdLink": "accent",
    "mdLinkUrl": "muted",
    "mdCode": "#c0caf5",
    "mdCodeBlock": "#c0caf5",
    "mdCodeBlockBorder": "muted",
    "mdQuote": "muted",
    "mdQuoteBorder": "muted",
    "mdHr": "muted",
    "mdListBullet": "accent",

    "toolDiffAdded": "#9ece6a",
    "toolDiffRemoved": "#f7768e",
    "toolDiffContext": "muted",

    "syntaxComment": "#565f89",
    "syntaxKeyword": "#bb9af7",
    "syntaxFunction": "#7aa2f7",
    "syntaxVariable": "#c0caf5",
    "syntaxString": "#9ece6a",
    "syntaxNumber": "#ff9e64",
    "syntaxType": "#2ac3de",
    "syntaxOperator": "#89ddff",
    "syntaxPunctuation": "#9aa5ce",

    "thinkingOff": 240,
    "thinkingMinimal": 244,
    "thinkingLow": "#7aa2f7",
    "thinkingMedium": "#2ac3de",
    "thinkingHigh": "#bb9af7",
    "thinkingXhigh": "#f7768e",

    "bashMode": "#2ac3de",
    "pythonMode": "#bb9af7",

    "statusLineBg": "#16161e",
    "statusLineSep": 240,
    "statusLineModel": "#bb9af7",
    "statusLinePath": "#7aa2f7",
    "statusLineGitClean": "#9ece6a",
    "statusLineGitDirty": "#e0af68",
    "statusLineContext": "#2ac3de",
    "statusLineSpend": "#7dcfff",
    "statusLineStaged": "#9ece6a",
    "statusLineDirty": "#e0af68",
    "statusLineUntracked": "#f7768e",
    "statusLineOutput": "#c0caf5",
    "statusLineCost": "#ff9e64",
    "statusLineSubagents": "#bb9af7"
  }
}

Testing custom themes

Use this workflow:

1. Start interactive mode (watcher enabled from startup).
2. Open settings and preview theme values (live previewTheme).
3. For custom theme files, edit the JSON while running and confirm auto-reload on save.
4. Exercise critical surfaces:
   • markdown rendering
   • tool blocks (pending/success/error)
   • diff rendering (added/removed/context)
   • status line readability
   • thinking level border changes
   • bash/python mode border colors
5. Validate both symbol presets if your theme depends on glyph width/appearance.

Real constraints and caveats

• All colors tokens are required for custom themes.
• export and symbols are optional.
• $schema in theme JSON is informational; runtime validation is enforced by an arktype schema in code.
• setTheme failure falls back to dark; previewTheme failure does not replace current theme.
• File watcher reload errors or temporary missing files keep the current loaded theme until a successful reload or explicit theme switch.