Add shell completion

.gitignore

@@ -0,0 +1 @@
+diple

README.md

@@ -59,6 +59,29 @@ diple --repo owner/repository \
   --endpoint https://github.example.com/api/graphql
 ```
 
+## Shell completion
+
+`diple` generates completion scripts without contacting GitHub or loading the
+configuration. Choose the command for your shell:
+
+```sh
+# Bash: current session
+source <(diple completion bash)
+
+# Zsh: current session
+source <(diple completion zsh)
+
+# Fish: install for the current user
+diple completion fish > ~/.config/fish/completions/diple.fish
+```
+
+For persistent Bash completion, write the generated output to a directory
+loaded by your distribution's `bash-completion` package. For persistent Zsh
+completion, write it to a file named `_diple` in a directory on `$fpath`, then
+run `compinit`. `diple completion --help` lists the supported shells, while
+`diple --help` shows grouped command-line options, defaults, configuration
+precedence, and authentication behavior.
+
 ## Configuration
 
 The optional TOML configuration is loaded from
@@ -74,7 +97,7 @@ cache directories remain fallback locations when their new `diple`
 counterparts do not yet exist.
 
 ```toml
-theme = "dark"                 # dark, light, high-contrast, or no-color
+theme = "dark"                 # built-in name, "custom", or an accessibility mode
 refresh_interval = "10s"
 repository = ""               # optional owner/repository default
 show_all = false              # requires repository
@@ -192,6 +215,40 @@ repeat_find = [";"]
 repeat_find_reverse = [","]
 ```
 
+Themes are compiled into `diple`; they do not require a separate download.
+Available names are `dark`, `light`, `catppuccin` (`catppuccin-mocha`),
+`catppuccin-latte`, `gruvbox` (`gruvbox-dark`), `gruvbox-light`,
+`one-dark-pro`, `github` (`github-dark`), `github-light`, `high-contrast`,
+and `no-color`.
+
+Set `theme = "custom"` to inherit a built-in palette and replace only the
+roles you care about:
+
+```toml
+theme = "custom"
+
+[custom_theme]
+base = "catppuccin-mocha"       # defaults to "dark"
+mode = "dark"                   # "dark" or "light"; controls Markdown rendering
+title = "#F5C2E7"
+active_foreground = "#1E1E2E"
+active_background = "#89B4FA"
+selection_background = "#313244"
+author_palette = ["#89B4FA", "#CBA6F7", "#94E2D5", "#F9E2AF"]
+syntax_theme = "catppuccin-mocha"
+```
+
+Every color override uses `#RRGGBB`. The complete set of roles is `title`,
+`dim`, `text`, `active_foreground`, `active_background`, `success`, `warning`,
+`error`, `editor_foreground`, `editor_background`, `pane_inactive`,
+`pane_active`, `quote`, `selection_background`,
+`suggestion_remove_background`, `suggestion_add_background`,
+`changed_remove_background`, and `changed_add_background`.
+`author_palette` accepts one or more colors. `syntax_theme` accepts an installed
+Chroma style name; invalid colors, bases, and syntax styles are reported as
+configuration errors at startup. The `[custom_theme]` table is ignored unless
+`theme = "custom"`.
+
 Every command binding accepts one or more Bubble Tea key names. Omitted
 settings retain their defaults, while an explicitly configured action replaces
 its default keys. Printable keys remain text in Insert mode, reply drafts, and

cli.go

@@ -0,0 +1,238 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"strings"
+)
+
+var completionShells = []string{"bash", "zsh", "fish"}
+
+func handleCompletionCommand(args []string, output io.Writer) (bool, error) {
+	if len(args) == 0 || args[0] != "completion" {
+		return false, nil
+	}
+	if len(args) == 2 && (args[1] == "-h" || args[1] == "--help") {
+		_, err := fmt.Fprintln(output, completionHelp)
+		return true, err
+	}
+	if len(args) != 2 {
+		return true, fmt.Errorf("usage: diple completion <bash|zsh|fish>")
+	}
+	var script string
+	switch args[1] {
+	case "bash":
+		script = bashCompletion
+	case "zsh":
+		script = zshCompletion
+	case "fish":
+		script = fishCompletion
+	default:
+		return true, fmt.Errorf(
+			"unsupported shell %q; choose %s",
+			args[1], strings.Join(completionShells, ", "),
+		)
+	}
+	_, err := io.WriteString(output, script)
+	return true, err
+}
+
+const completionHelp = `Generate a shell completion script.
+
+Usage:
+  diple completion <shell>
+
+Available shells:
+  bash
+  zsh
+  fish
+
+Run 'diple completion <shell>' and source or install the generated script.
+See the README for shell-specific installation paths.`
+
+func writeCLIHelp(output io.Writer, defaults Config, configPath string) {
+	fmt.Fprintf(output, `diple — review and manage GitHub pull requests from the terminal
+
+Usage:
+  diple [options]
+  diple completion <bash|zsh|fish>
+  diple help
+
+Pull-request selection:
+  --repo OWNER/REPOSITORY   Limit results to one repository (or use GH_REPO).
+  --all[=BOOL]              Include every open PR in --repo. Default: %t.
+  --limit NUMBER            Maximum PRs to load, from 1 to 1000. Default: %d.
+
+GitHub and refresh:
+  --poll DURATION           Base refresh interval, at least 2s. Default: %s.
+  --endpoint URL            GitHub GraphQL endpoint.
+                            Default: %s.
+
+Appearance and navigation:
+  --theme NAME              dark, light, catppuccin, catppuccin-latte,
+                            gruvbox, gruvbox-light, one-dark-pro, github,
+                            github-light, high-contrast, no-color, or custom.
+                            Default: %s.
+  --dashboard-mode MODE     hotkey or intermediate. Default: %s.
+  --thread-list-width N     List width in percent, from 20 to 60. Default: %d.
+  --fold-resolved[=BOOL]    Start resolved threads folded. Default: %t.
+  --compact-reviews[=BOOL]  Aggregate submitted-review history. Default: %t.
+  --path-scroll[=BOOL]      Scroll truncated file paths. Default: %t.
+  --path-scroll-interval D  Path scroll step interval. Default: %s.
+  --editor-mode MODE        vim or standard. Default: %s.
+
+Local state:
+  --config FILE             TOML configuration file.
+                            Default: %s.
+  --cache[=BOOL]            Enable instant cached startup and offline fallback.
+                            Default: %t.
+  --cache-max-age DURATION  Maximum offline cache age; 0 disables expiry.
+                            Default: %s.
+  --cache-dir DIRECTORY     Override the operating-system cache directory.
+
+Other:
+  -h, --help                Show this help and exit.
+
+Boolean options accept explicit values, for example --cache=false.
+Command-line options override TOML settings. GH_REPO is used only when
+--repo is absent. DIPLE_CONFIG selects a configuration file; GH_THREADS_CONFIG
+is retained as a migration fallback.
+
+Authentication uses GH_TOKEN or GITHUB_TOKEN when set, otherwise the active
+credential from 'gh auth login'. Run 'diple completion --help' for completion
+installation guidance.
+`,
+		defaults.ShowAll,
+		defaults.Limit,
+		defaults.RefreshInterval.Duration,
+		defaults.Endpoint,
+		defaults.Theme,
+		defaults.Display.DashboardMode,
+		defaults.Display.ThreadListWidthPercent,
+		defaults.Display.FoldResolved,
+		defaults.Display.CompactReviews,
+		defaults.Paths.Scroll,
+		defaults.Paths.ScrollInterval.Duration,
+		defaults.Editing.Mode,
+		configPath,
+		defaults.Cache.Enabled,
+		defaults.Cache.MaxAge.Duration,
+	)
+}
+
+const bashCompletion = `# bash completion for diple
+_diple_completion() {
+    local current previous
+    current="${COMP_WORDS[COMP_CWORD]}"
+    previous="${COMP_WORDS[COMP_CWORD-1]}"
+
+    if [[ ${COMP_CWORD} -eq 1 && ${current} != -* ]]; then
+        COMPREPLY=($(compgen -W "completion help" -- "${current}"))
+        return
+    fi
+    if [[ ${COMP_WORDS[1]} == completion ]]; then
+        COMPREPLY=($(compgen -W "bash zsh fish" -- "${current}"))
+        return
+    fi
+    if [[ ${COMP_WORDS[1]} == help ]]; then
+        COMPREPLY=()
+        return
+    fi
+
+    case "${previous}" in
+        --theme)
+            COMPREPLY=($(compgen -W "dark light catppuccin catppuccin-mocha catppuccin-latte gruvbox gruvbox-dark gruvbox-light one-dark-pro github github-dark github-light high-contrast no-color custom" -- "${current}"))
+            return
+            ;;
+        --dashboard-mode)
+            COMPREPLY=($(compgen -W "hotkey intermediate" -- "${current}"))
+            return
+            ;;
+        --editor-mode)
+            COMPREPLY=($(compgen -W "vim standard" -- "${current}"))
+            return
+            ;;
+        --config|--cache-dir)
+            COMPREPLY=($(compgen -f -- "${current}"))
+            return
+            ;;
+    esac
+
+    local options="--repo --all --limit --poll --endpoint --theme --dashboard-mode --thread-list-width --fold-resolved --compact-reviews --path-scroll --path-scroll-interval --editor-mode --config --cache --cache-max-age --cache-dir --help -h"
+    COMPREPLY=($(compgen -W "${options}" -- "${current}"))
+}
+complete -F _diple_completion diple
+`
+
+const zshCompletion = `#compdef diple
+
+_diple() {
+  local -a themes
+  themes=(dark light catppuccin catppuccin-mocha catppuccin-latte gruvbox gruvbox-dark gruvbox-light one-dark-pro github github-dark github-light high-contrast no-color custom)
+
+  if (( CURRENT == 2 )) && [[ ${PREFIX} != -* ]]; then
+    _values 'command' \
+      'completion[generate shell completion]' \
+      'help[show command-line help]'
+    return
+  fi
+  if [[ ${words[2]} == completion ]]; then
+    _values 'shell' bash zsh fish
+    return
+  fi
+  if [[ ${words[2]} == help ]]; then
+    return
+  fi
+
+  _arguments -s \
+    '--repo[limit results to one repository]:owner/repository:' \
+    '--all=[include every open PR in the repository]:boolean:(true false)' \
+    '--limit[maximum pull requests to load]:number:' \
+    '--poll[base GitHub refresh interval]:duration:' \
+    '--endpoint[GitHub GraphQL endpoint]:url:' \
+    '--theme[UI and syntax color theme]:theme:($themes)' \
+    '--dashboard-mode[dashboard navigation mode]:mode:(hotkey intermediate)' \
+    '--thread-list-width[thread-list width percentage]:percent:' \
+    '--fold-resolved=[start resolved threads folded]:boolean:(true false)' \
+    '--compact-reviews=[aggregate submitted reviews]:boolean:(true false)' \
+    '--path-scroll=[scroll truncated paths]:boolean:(true false)' \
+    '--path-scroll-interval[path scrolling interval]:duration:' \
+    '--editor-mode[description editor mode]:mode:(vim standard)' \
+    '--config[TOML configuration file]:file:_files' \
+    '--cache=[enable local read cache]:boolean:(true false)' \
+    '--cache-max-age[maximum offline cache age]:duration:' \
+    '--cache-dir[local read-cache directory]:directory:_directories' \
+    '(-h --help)'{-h,--help}'[show help]'
+}
+
+if (( ! ${+functions[compdef]} )); then
+  autoload -Uz compinit
+  compinit -D
+fi
+compdef _diple diple
+`
+
+const fishCompletion = `# fish completion for diple
+complete -c diple -f
+complete -c diple -n '__fish_use_subcommand' -a completion -d 'Generate shell completion'
+complete -c diple -n '__fish_use_subcommand' -a help -d 'Show help'
+complete -c diple -n '__fish_seen_subcommand_from completion' -a 'bash zsh fish'
+complete -c diple -l repo -d 'Limit results to owner/repository'
+complete -c diple -l all -d 'Include every open PR in --repo'
+complete -c diple -l limit -x -d 'Maximum pull requests to load'
+complete -c diple -l poll -x -d 'Base GitHub refresh interval'
+complete -c diple -l endpoint -x -d 'GitHub GraphQL endpoint'
+complete -c diple -l theme -x -a 'dark light catppuccin catppuccin-mocha catppuccin-latte gruvbox gruvbox-dark gruvbox-light one-dark-pro github github-dark github-light high-contrast no-color custom' -d 'UI and syntax color theme'
+complete -c diple -l dashboard-mode -x -a 'hotkey intermediate' -d 'Dashboard navigation mode'
+complete -c diple -l thread-list-width -x -d 'Thread-list width percentage'
+complete -c diple -l fold-resolved -d 'Start resolved threads folded'
+complete -c diple -l compact-reviews -d 'Aggregate submitted reviews'
+complete -c diple -l path-scroll -d 'Scroll truncated paths'
+complete -c diple -l path-scroll-interval -x -d 'Path scrolling interval'
+complete -c diple -l editor-mode -x -a 'vim standard' -d 'Description editor mode'
+complete -c diple -l config -r -F -d 'TOML configuration file'
+complete -c diple -l cache -d 'Enable local read cache'
+complete -c diple -l cache-max-age -x -d 'Maximum offline cache age'
+complete -c diple -l cache-dir -r -a '(__fish_complete_directories)' -d 'Local read-cache directory'
+complete -c diple -s h -l help -d 'Show help'
+`

cli_test.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestCompletionCommandGeneratesSupportedShells(t *testing.T) {
+	for _, shell := range completionShells {
+		t.Run(shell, func(t *testing.T) {
+			var output bytes.Buffer
+			handled, err := handleCompletionCommand([]string{"completion", shell}, &output)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !handled || output.Len() == 0 ||
+				!strings.Contains(output.String(), "diple") {
+				t.Fatalf("completion output = %q, handled=%t", output.String(), handled)
+			}
+		})
+	}
+}
+
+func TestZshCompletionRegistersWithoutCallingCompletionFunction(t *testing.T) {
+	var output bytes.Buffer
+	handled, err := handleCompletionCommand([]string{"completion", "zsh"}, &output)
+	if err != nil {
+		t.Fatal(err)
+	}
+	script := output.String()
+	if !handled || !strings.Contains(script, "compdef _diple diple") {
+		t.Fatalf("Zsh completion does not register _diple:\n%s", script)
+	}
+	if strings.Contains(script, `_diple "$@"`) {
+		t.Fatalf("Zsh completion invokes _diple while being sourced:\n%s", script)
+	}
+}
+
+func TestCompletionCommandRejectsUnknownShell(t *testing.T) {
+	var output bytes.Buffer
+	handled, err := handleCompletionCommand(
+		[]string{"completion", "powershell"}, &output,
+	)
+	if !handled || err == nil || !strings.Contains(err.Error(), "unsupported shell") {
+		t.Fatalf("handled=%t error=%v", handled, err)
+	}
+}
+
+func TestCompletionCommandDoesNotClaimNormalInvocation(t *testing.T) {
+	handled, err := handleCompletionCommand([]string{"--repo", "owner/repo"}, &bytes.Buffer{})
+	if handled || err != nil {
+		t.Fatalf("handled=%t error=%v", handled, err)
+	}
+}
+
+func TestCLIHelpIsGroupedAndActionable(t *testing.T) {
+	var output bytes.Buffer
+	writeCLIHelp(&output, defaultConfig(), "/tmp/diple/config.toml")
+	help := output.String()
+	for _, expected := range []string{
+		"Usage:",
+		"Pull-request selection:",
+		"GitHub and refresh:",
+		"Appearance and navigation:",
+		"Local state:",
+		"diple completion <bash|zsh|fish>",
+		"--repo OWNER/REPOSITORY",
+		"--cache=false",
+		"gh auth login",
+		"/tmp/diple/config.toml",
+	} {
+		if !strings.Contains(help, expected) {
+			t.Fatalf("help does not contain %q:\n%s", expected, help)
+		}
+	}
+}

config.go

@@ -25,18 +25,44 @@ func (d *configDuration) UnmarshalText(text []byte) error {
 }
 
 type Config struct {
-	Theme           string         `toml:"theme"`
+	Theme           string            `toml:"theme"`
-	RefreshInterval configDuration `toml:"refresh_interval"`
+	RefreshInterval configDuration    `toml:"refresh_interval"`
-	Repository      string         `toml:"repository"`
+	Repository      string            `toml:"repository"`
-	ShowAll         bool           `toml:"show_all"`
+	ShowAll         bool              `toml:"show_all"`
-	Limit           int            `toml:"limit"`
+	Limit           int               `toml:"limit"`
-	Endpoint        string         `toml:"endpoint"`
+	Endpoint        string            `toml:"endpoint"`
-	Display         DisplayConfig  `toml:"display"`
+	Display         DisplayConfig     `toml:"display"`
-	Paths           PathConfig     `toml:"paths"`
+	Paths           PathConfig        `toml:"paths"`
-	Threads         ThreadConfig   `toml:"threads"`
+	Threads         ThreadConfig      `toml:"threads"`
-	Cache           CacheConfig    `toml:"cache"`
+	Cache           CacheConfig       `toml:"cache"`
-	Editing         EditingConfig  `toml:"editing"`
+	Editing         EditingConfig     `toml:"editing"`
-	KeyBindings     KeyBindings    `toml:"keybindings"`
+	CustomTheme     CustomThemeConfig `toml:"custom_theme"`
+	KeyBindings     KeyBindings       `toml:"keybindings"`
+}
+
+type CustomThemeConfig struct {
+	Base                       string   `toml:"base"`
+	Mode                       string   `toml:"mode"`
+	Title                      string   `toml:"title"`
+	Dim                        string   `toml:"dim"`
+	Text                       string   `toml:"text"`
+	ActiveForeground           string   `toml:"active_foreground"`
+	ActiveBackground           string   `toml:"active_background"`
+	Success                    string   `toml:"success"`
+	Warning                    string   `toml:"warning"`
+	Error                      string   `toml:"error"`
+	EditorForeground           string   `toml:"editor_foreground"`
+	EditorBackground           string   `toml:"editor_background"`
+	PaneInactive               string   `toml:"pane_inactive"`
+	PaneActive                 string   `toml:"pane_active"`
+	Quote                      string   `toml:"quote"`
+	SelectionBackground        string   `toml:"selection_background"`
+	SuggestionRemoveBackground string   `toml:"suggestion_remove_background"`
+	SuggestionAddBackground    string   `toml:"suggestion_add_background"`
+	ChangedRemoveBackground    string   `toml:"changed_remove_background"`
+	ChangedAddBackground       string   `toml:"changed_add_background"`
+	AuthorPalette              []string `toml:"author_palette"`
+	SyntaxTheme                string   `toml:"syntax_theme"`
 }
 
 type DisplayConfig struct {
@@ -160,10 +186,8 @@ func loadConfig(path string, required bool) (Config, error) {
 }
 
 func validateConfig(config Config) error {
-	switch config.Theme {
+	if _, err := resolveThemePalette(config.Theme, config.CustomTheme); err != nil {
-	case "dark", "light", "no-color", "high-contrast":
+		return err
-	default:
-		return fmt.Errorf("theme must be dark or light")
 	}
 	if config.RefreshInterval.Duration < 2*time.Second {
 		return fmt.Errorf("refresh_interval must be at least 2s")

config_test.go

@@ -87,6 +87,39 @@ up = ["ctrl+k"]
 	}
 }
 
+func TestLoadConfigParsesCustomTheme(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "config.toml")
+	content := `
+theme = "custom"
+
+[custom_theme]
+base = "catppuccin-mocha"
+mode = "dark"
+title = "#112233"
+selection_background = "#223344"
+author_palette = ["#334455", "#445566"]
+syntax_theme = "gruvbox"
+`
+	if err := os.WriteFile(path, []byte(content), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	got, err := loadConfig(path, true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := validateConfig(got); err != nil {
+		t.Fatal(err)
+	}
+	if got.Theme != "custom" ||
+		got.CustomTheme.Base != "catppuccin-mocha" ||
+		got.CustomTheme.Title != "#112233" ||
+		got.CustomTheme.SelectionBackground != "#223344" ||
+		len(got.CustomTheme.AuthorPalette) != 2 ||
+		got.CustomTheme.SyntaxTheme != "gruvbox" {
+		t.Fatalf("custom theme config = %#v", got.CustomTheme)
+	}
+}
+
 func TestValidateConfigRejectsEmptyKeyBinding(t *testing.T) {
 	config := defaultConfig()
 	config.KeyBindings.Navigation.Down = nil

highlight.go

@@ -3,11 +3,11 @@ package main
 import (
 	"bytes"
 	"fmt"
-	"path/filepath"
 	"regexp"
 	"strconv"
 	"strings"
 
+	"github.com/alecthomas/chroma/v2/lexers"
 	"github.com/alecthomas/chroma/v2/quick"
 )
 
@@ -252,9 +252,9 @@ func highlightedSource(lexer, source string) string {
 }
 
 func lexerForPath(path string) string {
-	ext := strings.TrimPrefix(filepath.Ext(path), ".")
+	lexer := lexers.Match(path)
-	if ext == "" {
+	if lexer == nil {
-		return "plaintext"
+		return ""
 	}
-	return ext
+	return lexer.Config().Name
 }

highlight_lexer_test.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alecthomas/chroma/v2/lexers"
+)
+
+func TestLexerForPathUsesCompleteFilename(t *testing.T) {
+	tests := []struct {
+		path string
+		want string
+	}{
+		{"Dockerfile", "Docker"},
+		{"Makefile", "Makefile"},
+		{"src/component.tsx", "TypeScript"},
+		{"scripts/check.py", "Python"},
+		{".github/workflows/test.yml", "YAML"},
+	}
+	for _, test := range tests {
+		t.Run(test.path, func(t *testing.T) {
+			got := lexerForPath(test.path)
+			lexer := lexers.Get(got)
+			if lexer == nil {
+				t.Fatalf("lexerForPath(%q) = %q, which is not registered", test.path, got)
+			}
+			if lexer.Config().Name != test.want {
+				t.Fatalf("lexerForPath(%q) selected %q, want %q", test.path, lexer.Config().Name, test.want)
+			}
+		})
+	}
+}
+
+func TestLexerForUnknownPathAllowsContentAnalysis(t *testing.T) {
+	if got := lexerForPath("LICENSE.unknown-extension"); got != "" {
+		t.Fatalf("unknown path selected %q instead of allowing content analysis", got)
+	}
+}

main.go

@@ -11,31 +11,47 @@ import (
 )
 
 func main() {
+	if handled, err := handleCompletionCommand(os.Args[1:], os.Stdout); handled {
+		if err != nil {
+			exitf("%v", err)
+		}
+		return
+	}
 	defaults := defaultConfig()
 	defaultConfigPath, err := configPath()
 	if err != nil {
 		exitf("configuration: %v", err)
 	}
+	flag.Usage = func() {
+		writeCLIHelp(flag.CommandLine.Output(), defaults, defaultConfigPath)
+	}
+	if len(os.Args) == 2 && os.Args[1] == "help" {
+		flag.Usage()
+		return
+	}
 	var (
 		configFile     = flag.String("config", defaultConfigPath, "TOML configuration file")
-		repo           = flag.String("repo", "", "optional GitHub repository filter as owner/name (or GH_REPO)")
+		repo           = flag.String("repo", "", "limit pull requests to an owner/repository")
-		poll           = flag.Duration("poll", defaults.RefreshInterval.Duration, "refresh interval")
+		poll           = flag.Duration("poll", defaults.RefreshInterval.Duration, "base interval between GitHub refreshes")
-		showAll        = flag.Bool("all", defaults.ShowAll, "show all open PRs in --repo, not only PRs assigned to you")
+		showAll        = flag.Bool("all", defaults.ShowAll, "show every open PR in --repo instead of only assigned PRs")
-		limit          = flag.Int("limit", defaults.Limit, "maximum open PRs to load (1-1000)")
+		limit          = flag.Int("limit", defaults.Limit, "maximum number of open pull requests to load")
-		endpoint       = flag.String("endpoint", defaults.Endpoint, "GitHub GraphQL endpoint")
+		endpoint       = flag.String("endpoint", defaults.Endpoint, "GitHub GraphQL API endpoint")
-		theme          = flag.String("theme", defaults.Theme, "color theme: dark, light, high-contrast, or no-color")
+		theme          = flag.String("theme", defaults.Theme, "built-in or custom color theme")
-		foldResolved   = flag.Bool("fold-resolved", defaults.Display.FoldResolved, "start resolved threads folded")
+		foldResolved   = flag.Bool("fold-resolved", defaults.Display.FoldResolved, "start resolved review threads folded")
-		listWidth      = flag.Int("thread-list-width", defaults.Display.ThreadListWidthPercent, "thread list width as terminal percentage (20-60)")
+		listWidth      = flag.Int("thread-list-width", defaults.Display.ThreadListWidthPercent, "thread-list width as a percentage of the terminal")
-		dashboardMode  = flag.String("dashboard-mode", defaults.Display.DashboardMode, "dashboard navigation: intermediate or hotkey")
+		dashboardMode  = flag.String("dashboard-mode", defaults.Display.DashboardMode, "open the dashboard by hotkey or as an intermediate screen")
-		compactReviews = flag.Bool("compact-reviews", defaults.Display.CompactReviews, "aggregate submitted review history")
+		compactReviews = flag.Bool("compact-reviews", defaults.Display.CompactReviews, "aggregate repeated submitted-review entries")
-		pathScroll     = flag.Bool("path-scroll", defaults.Paths.Scroll, "scroll truncated paths")
+		pathScroll     = flag.Bool("path-scroll", defaults.Paths.Scroll, "scroll file paths that do not fit")
-		pathScrollRate = flag.Duration("path-scroll-interval", defaults.Paths.ScrollInterval.Duration, "path scrolling interval")
+		pathScrollRate = flag.Duration("path-scroll-interval", defaults.Paths.ScrollInterval.Duration, "interval between file-path scroll steps")
-		cacheEnabled   = flag.Bool("cache", defaults.Cache.Enabled, "enable local read cache fallback")
+		cacheEnabled   = flag.Bool("cache", defaults.Cache.Enabled, "enable the local read cache and offline fallback")
-		cacheMaxAge    = flag.Duration("cache-max-age", defaults.Cache.MaxAge.Duration, "maximum offline cache age (0 disables expiry)")
+		cacheMaxAge    = flag.Duration("cache-max-age", defaults.Cache.MaxAge.Duration, "oldest cache entry accepted for offline fallback")
-		cacheDir       = flag.String("cache-dir", defaults.Cache.Directory, "local read cache directory")
+		cacheDir       = flag.String("cache-dir", defaults.Cache.Directory, "local read-cache directory")
-		editorMode     = flag.String("editor-mode", defaults.Editing.Mode, "description editor mode: standard or vim")
+		editorMode     = flag.String("editor-mode", defaults.Editing.Mode, "description editor mode")
 	)
 	flag.Parse()
+	if flag.NArg() != 0 {
+		exitf("unexpected argument %q; run 'diple --help' for usage", flag.Arg(0))
+	}
 
 	visited := map[string]bool{}
 	flag.Visit(func(item *flag.Flag) { visited[item.Name] = true })
@@ -109,7 +125,7 @@ func main() {
 		}
 		owner, name = parts[0], parts[1]
 	}
-	if err := applyTheme(config.Theme); err != nil {
+	if err := applyTheme(config.Theme, config.CustomTheme); err != nil {
 		exitf("configuration: %v", err)
 	}
 	token, err := resolveToken(config.Endpoint)

markdown.go

@@ -5,6 +5,7 @@ import (
 	"sync"
 
 	"github.com/charmbracelet/glamour"
+	glamouransi "github.com/charmbracelet/glamour/ansi"
 	"github.com/charmbracelet/glamour/styles"
 	"github.com/charmbracelet/lipgloss"
 )
@@ -79,12 +80,7 @@ func commentMarkdownRenderer(width int) (*glamour.TermRenderer, error) {
 	if cached, ok := commentMarkdownRenderers.Load(width); ok {
 		return cached.(*glamour.TermRenderer), nil
 	}
-	style := styles.DarkStyleConfig
+	style := markdownStyleForTheme()
-	if markdownStyleName == "light" {
-		style = styles.LightStyleConfig
-	} else if markdownStyleName == "notty" {
-		style = styles.NoTTYStyleConfig
-	}
 	zero := uint(0)
 	style.Document.Margin = &zero
 	style.Code.Prefix = ""
@@ -103,6 +99,70 @@ func commentMarkdownRenderer(width int) (*glamour.TermRenderer, error) {
 	return actual.(*glamour.TermRenderer), nil
 }
 
+func markdownStyleForTheme() glamouransi.StyleConfig {
+	if markdownStyleName == "notty" {
+		return styles.NoTTYStyleConfig
+	}
+	style := styles.DarkStyleConfig
+	if themeIsLight {
+		style = styles.LightStyleConfig
+	}
+	palette := editorMarkdownTheme
+	color := func(value string) *string { return &value }
+	truth := func(value bool) *bool { return &value }
+
+	style.Document.Color = color(palette.Text)
+	// Leave Text unset so inline text inherits the surrounding heading, link,
+	// quote, or paragraph color instead of flattening every Markdown token to
+	// the document foreground.
+	style.Text.Color = nil
+	style.Paragraph.Color = color(palette.Text)
+	style.Heading.Color = color(palette.Title)
+	style.H1.Color = color(palette.ActiveForeground)
+	style.H1.BackgroundColor = color(palette.ActiveBackground)
+	style.H2.Color = color(palette.Title)
+	style.H3.Color = color(palette.Title)
+	style.H4.Color = color(palette.Title)
+	style.H5.Color = color(palette.Title)
+	style.H6.Color = color(palette.Title)
+	style.HorizontalRule.Color = color(palette.Dim)
+	style.Item.Color = color(palette.Title)
+	style.Enumeration.Color = color(palette.Title)
+	style.Task.Color = color(palette.Text)
+	style.BlockQuote.Color = color(palette.Quote)
+	style.Strong.Color = color(palette.Text)
+	style.Strong.Bold = truth(true)
+	style.Emph.Color = color(palette.Text)
+	style.Link.Color = color(themeAuthorColor(palette, 0))
+	style.LinkText.Color = color(themeAuthorColor(palette, 1))
+	style.Image.Color = color(themeAuthorColor(palette, 0))
+	style.ImageText.Color = color(palette.Dim)
+	style.Code.Color = color(palette.Success)
+	style.Code.BackgroundColor = color(palette.EditorBackground)
+	style.CodeBlock.Color = color(palette.EditorForeground)
+	style.CodeBlock.BackgroundColor = color(palette.EditorBackground)
+	style.CodeBlock.Theme = palette.SyntaxTheme
+	style.CodeBlock.Chroma = nil
+	style.Table.Color = color(palette.Text)
+	style.Table.CenterSeparator = stringPointer("─")
+	style.Table.ColumnSeparator = stringPointer("│")
+	style.Table.RowSeparator = stringPointer("─")
+	style.DefinitionTerm.Color = color(palette.Title)
+	style.DefinitionDescription.Color = color(palette.Text)
+	return style
+}
+
+func themeAuthorColor(palette themePalette, index int) string {
+	if len(palette.AuthorPalette) == 0 {
+		return palette.Text
+	}
+	return palette.AuthorPalette[index%len(palette.AuthorPalette)]
+}
+
+func stringPointer(value string) *string {
+	return &value
+}
+
 func stripQuoteMarker(line string) (string, bool) {
 	trimmed := strings.TrimLeft(line, " \t")
 	if !strings.HasPrefix(trimmed, ">") {

markdown_editor_highlight.go

@@ -124,43 +124,30 @@ func editorMarkdownStyleStart(style editorMarkdownStyle) string {
 			return ""
 		}
 	}
-	if currentThemeName == "light" {
+	authors := editorMarkdownTheme.AuthorPalette
-		switch style {
+	author := func(index int) string {
-		case editorMarkdownHeading:
+		if len(authors) == 0 {
-			return "\x1b[1;38;2;154;103;0m"
+			return editorMarkdownTheme.Text
-		case editorMarkdownStrong:
-			return "\x1b[1;38;2;130;80;223m"
-		case editorMarkdownEmphasis:
-			return "\x1b[3;38;2;87;96;106m"
-		case editorMarkdownCode:
-			return "\x1b[38;2;17;99;41m"
-		case editorMarkdownLink:
-			return "\x1b[4;38;2;9;105;218m"
-		case editorMarkdownDestination:
-			return "\x1b[38;2;10;112;111m"
-		case editorMarkdownQuote:
-			return "\x1b[38;2;154;103;0m"
-		case editorMarkdownComment:
-			return "\x1b[2;38;2;101;109;118m"
 		}
+		return authors[index%len(authors)]
 	}
 	switch style {
 	case editorMarkdownHeading:
-		return "\x1b[1;38;2;240;183;47m"
+		return "\x1b[1m" + foregroundSequence(editorMarkdownTheme.Title)
 	case editorMarkdownStrong:
-		return "\x1b[1;38;2;198;120;221m"
+		return "\x1b[1m" + foregroundSequence(author(1))
 	case editorMarkdownEmphasis:
-		return "\x1b[3;38;2;215;218;232m"
+		return "\x1b[3m" + foregroundSequence(editorMarkdownTheme.Text)
 	case editorMarkdownCode:
-		return "\x1b[38;2;152;195;121m"
+		return foregroundSequence(editorMarkdownTheme.Success)
 	case editorMarkdownLink:
-		return "\x1b[4;38;2;97;175;239m"
+		return "\x1b[4m" + foregroundSequence(author(0))
 	case editorMarkdownDestination:
-		return "\x1b[38;2;86;182;194m"
+		return foregroundSequence(author(2))
 	case editorMarkdownQuote:
-		return "\x1b[38;2;229;192;123m"
+		return foregroundSequence(editorMarkdownTheme.Warning)
 	case editorMarkdownComment:
-		return "\x1b[2;38;2;119;119;119m"
+		return "\x1b[2m" + foregroundSequence(editorMarkdownTheme.Dim)
 	default:
 		return ""
 	}
@@ -168,15 +155,8 @@ func editorMarkdownStyleStart(style editorMarkdownStyle) string {
 
 func editorMarkdownStyleEnd(active bool) string {
 	foreground := "\x1b[39m"
-	if active {
+	if active && colorEnabled {
-		switch currentThemeName {
+		foreground = foregroundSequence(editorMarkdownTheme.EditorForeground)
-		case "dark":
-			foreground = "\x1b[38;2;215;218;232m"
-		case "light":
-			foreground = "\x1b[38;2;36;41;47m"
-		case "high-contrast":
-			foreground = "\x1b[38;2;255;255;255m"
-		}
 	}
 	return "\x1b[22;23;24m" + foreground
 }

markdown_test.go

@@ -22,6 +22,10 @@ func TestCommentMarkdownDistinguishesQuoteAndReply(t *testing.T) {
 }
 
 func TestCommentMarkdownStylesInlineCode(t *testing.T) {
+	defer applyTheme("dark")
+	if err := applyTheme("dark"); err != nil {
+		t.Fatal(err)
+	}
 	rendered := strings.Join(renderCommentMarkdown(
 		"Use `list_comparison` for this value.", 60,
 	), "\n")
@@ -32,11 +36,30 @@ func TestCommentMarkdownStylesInlineCode(t *testing.T) {
 	if strings.Contains(plain, "Use  list_comparison  for") {
 		t.Fatalf("inline code added surrounding spaces: %q", plain)
 	}
-	if !strings.Contains(rendered, "48;5;236m") {
+	if !strings.Contains(rendered, "48;2;44;48;69m") {
 		t.Fatalf("inline code has no distinct background: %q", rendered)
 	}
 }
 
+func TestCommentMarkdownUsesActiveThemePalette(t *testing.T) {
+	defer applyTheme("dark")
+	if err := applyTheme("catppuccin-mocha"); err != nil {
+		t.Fatal(err)
+	}
+	rendered := strings.Join(renderCommentMarkdown(
+		"## Heading\n\nUse `value` and [link](https://example.com).\n\n```python\nif ready:\n    return 1\n```",
+		80,
+	), "\n")
+	for _, sequence := range []string{
+		"38;2;203;166;247", // Catppuccin mauve heading/link.
+		"38;2;166;227;161", // Catppuccin green inline code/string.
+	} {
+		if !strings.Contains(rendered, sequence) {
+			t.Fatalf("Markdown did not use active palette color %q:\n%q", sequence, rendered)
+		}
+	}
+}
+
 func TestWrappedQuoteKeepsRailOnEveryLine(t *testing.T) {
 	const width = 28
 	lines := renderCommentMarkdown(

suggestions_test.go

@@ -88,8 +88,8 @@ func TestDetailRendersSuggestionAsRemovalAndAddition(t *testing.T) {
 func TestSuggestionBackgroundIsDirectionalWithoutTextUnderline(t *testing.T) {
 	removed := suggestionHighlight("  - ", "old", 12, '-')
 	added := suggestionHighlight("  + ", "new", 12, '+')
-	if !strings.Contains(removed, "\x1b[48;5;52m") ||
+	if !strings.Contains(removed, suggestionRemoveBackground) ||
-		!strings.Contains(added, "\x1b[48;5;22m") {
+		!strings.Contains(added, suggestionAddBackground) {
 		t.Fatalf("suggestion decorations missing: removed=%q added=%q", removed, added)
 	}
 	if strings.Contains(removed, "\x1b[4m") || strings.Contains(added, "\x1b[4m") ||
@@ -100,8 +100,8 @@ func TestSuggestionBackgroundIsDirectionalWithoutTextUnderline(t *testing.T) {
 	if ansi.StringWidth(removed) != 12 || ansi.StringWidth(added) != 12 {
 		t.Fatal("suggestion backgrounds do not fill the row")
 	}
-	if !strings.Contains(removed, "\x1b[0m\x1b[48;5;52m     ") ||
+	if !strings.Contains(removed, "\x1b[0m"+suggestionRemoveBackground+"     ") ||
-		!strings.Contains(added, "\x1b[0m\x1b[48;5;22m     ") {
+		!strings.Contains(added, "\x1b[0m"+suggestionAddBackground+"     ") {
 		t.Fatal("padded row remainder is still underlined")
 	}
 }

theme.go

@@ -2,97 +2,329 @@ package main
 
 import (
 	"fmt"
+	"strconv"
+	"strings"
 
+	"github.com/alecthomas/chroma/v2/styles"
 	"github.com/charmbracelet/lipgloss"
 )
 
-var currentThemeName = "dark"
+type themePalette struct {
+	Mode                       string
+	Title, Dim, Text           string
+	ActiveForeground           string
+	ActiveBackground           string
+	Success, Warning, Error    string
+	EditorForeground           string
+	EditorBackground           string
+	PaneInactive, PaneActive   string
+	Quote                      string
+	SelectionBackground        string
+	SuggestionRemoveBackground string
+	SuggestionAddBackground    string
+	ChangedRemoveBackground    string
+	ChangedAddBackground       string
+	AuthorPalette              []string
+	SyntaxTheme                string
+	NoColor                    bool
+	HighContrast               bool
+}
 
-func applyTheme(name string) error {
+var (
-	colorEnabled = true
+	currentThemeName    = "dark"
-	switch name {
+	themeIsLight        bool
-	case "dark":
+	editorMarkdownTheme themePalette
-		titleStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#F0B72F"))
+)
-		dimStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#777777"))
+
-		activeStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#FFFFFF")).Background(lipgloss.Color("#3B4261"))
+func applyTheme(name string, custom ...CustomThemeConfig) error {
-		okStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#67C587"))
+	var configured CustomThemeConfig
-		warnStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#E5C07B"))
+	if len(custom) > 0 {
-		badStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#E06C75"))
+		configured = custom[0]
-		editorLineStyle = lipgloss.NewStyle().
+	}
-			Foreground(lipgloss.Color("#D7DAE8")).
+	palette, err := resolveThemePalette(name, configured)
-			Background(lipgloss.Color("#2C3045"))
+	if err != nil {
-		paneInactiveColor = lipgloss.Color("#50566F")
+		return err
-		paneActiveColor = lipgloss.Color("#F0B72F")
+	}
-		authorPalette = []lipgloss.Color{
+	colorEnabled = !palette.NoColor
-			"#61AFEF", "#C678DD", "#56B6C2", "#E5C07B",
+	themeIsLight = palette.Mode == "light"
-			"#E06C75", "#98C379", "#D19A66", "#7FC8FF",
+	editorMarkdownTheme = palette
-		}
+
-		codeHighlightTheme = "github-dark"
+	if palette.NoColor {
-		markdownStyleName = "dark"
+		titleStyle, dimStyle = lipgloss.NewStyle(), lipgloss.NewStyle()
-		quoteRailStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#777777"))
-		selectedLineBackground = "\x1b[48;5;24m"
-		suggestionRemoveBackground = "\x1b[48;5;52m"
-		suggestionAddBackground = "\x1b[48;5;22m"
-		changedRemoveBackground = "\x1b[48;2;55;0;0m"
-		changedAddBackground = "\x1b[48;2;0;55;0m"
-	case "light":
-		titleStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#9A6700"))
-		dimStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#656D76"))
-		activeStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#FFFFFF")).Background(lipgloss.Color("#0969DA"))
-		okStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#1A7F37"))
-		warnStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#9A6700"))
-		badStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#CF222E"))
-		editorLineStyle = lipgloss.NewStyle().
-			Foreground(lipgloss.Color("#24292F")).
-			Background(lipgloss.Color("#DDE8FF"))
-		paneInactiveColor = lipgloss.Color("#8C959F")
-		paneActiveColor = lipgloss.Color("#0969DA")
-		authorPalette = []lipgloss.Color{
-			"#0550AE", "#8250DF", "#0A706F", "#9A6700",
-			"#CF222E", "#116329", "#953800", "#0969DA",
-		}
-		codeHighlightTheme = "github"
-		markdownStyleName = "light"
-		quoteRailStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#656D76"))
-		selectedLineBackground = "\x1b[48;5;153m"
-		suggestionRemoveBackground = "\x1b[48;5;224m"
-		suggestionAddBackground = "\x1b[48;5;194m"
-		changedRemoveBackground = "\x1b[48;2;255;170;170m"
-		changedAddBackground = "\x1b[48;2;170;230;170m"
-	case "high-contrast":
-		titleStyle = lipgloss.NewStyle().Bold(true).Underline(true).Foreground(lipgloss.Color("#FFFF00"))
-		dimStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#FFFFFF"))
-		activeStyle = lipgloss.NewStyle().Bold(true).Reverse(true)
-		okStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#00FF00"))
-		warnStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#FFFF00"))
-		badStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#FF5555"))
-		editorLineStyle = lipgloss.NewStyle().
-			Foreground(lipgloss.Color("#FFFFFF")).
-			Reverse(true)
-		paneInactiveColor, paneActiveColor = lipgloss.Color("#FFFFFF"), lipgloss.Color("#FFFF00")
-		authorPalette = []lipgloss.Color{"#00FFFF", "#FF55FF", "#FFFF00", "#00FF00", "#FFFFFF"}
-		codeHighlightTheme, markdownStyleName = "github-dark", "dark"
-		quoteRailStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("#FFFFFF"))
-		selectedLineBackground = "\x1b[7m"
-		suggestionRemoveBackground, suggestionAddBackground = "\x1b[48;5;88m", "\x1b[48;5;28m"
-		changedRemoveBackground, changedAddBackground = "\x1b[48;5;88m", "\x1b[48;5;28m"
-	case "no-color":
-		colorEnabled = false
-		titleStyle = lipgloss.NewStyle()
-		dimStyle = lipgloss.NewStyle()
 		activeStyle = lipgloss.NewStyle().Reverse(true)
 		okStyle, warnStyle, badStyle = lipgloss.NewStyle(), lipgloss.NewStyle(), lipgloss.NewStyle()
 		editorLineStyle = lipgloss.NewStyle().Reverse(true)
 		paneInactiveColor, paneActiveColor = "", ""
 		authorPalette = []lipgloss.Color{""}
-		codeHighlightTheme, markdownStyleName = "github", "notty"
 		quoteRailStyle = lipgloss.NewStyle()
 		selectedLineBackground, suggestionRemoveBackground, suggestionAddBackground = "", "", ""
 		changedRemoveBackground, changedAddBackground = "", ""
-	default:
+		codeHighlightTheme, markdownStyleName = "github", "notty"
-		return fmt.Errorf("unknown theme %q", name)
+	} else {
+		titleStyle = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color(palette.Title))
+		dimStyle = lipgloss.NewStyle().Foreground(lipgloss.Color(palette.Dim))
+		activeStyle = lipgloss.NewStyle().Bold(true).
+			Foreground(lipgloss.Color(palette.ActiveForeground)).
+			Background(lipgloss.Color(palette.ActiveBackground))
+		okStyle = lipgloss.NewStyle().Foreground(lipgloss.Color(palette.Success))
+		warnStyle = lipgloss.NewStyle().Foreground(lipgloss.Color(palette.Warning))
+		badStyle = lipgloss.NewStyle().Foreground(lipgloss.Color(palette.Error))
+		editorLineStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color(palette.EditorForeground)).
+			Background(lipgloss.Color(palette.EditorBackground))
+		paneInactiveColor = lipgloss.Color(palette.PaneInactive)
+		paneActiveColor = lipgloss.Color(palette.PaneActive)
+		quoteRailStyle = lipgloss.NewStyle().Foreground(lipgloss.Color(palette.Quote))
+		authorPalette = make([]lipgloss.Color, len(palette.AuthorPalette))
+		for index, color := range palette.AuthorPalette {
+			authorPalette[index] = lipgloss.Color(color)
+		}
+		selectedLineBackground = backgroundSequence(palette.SelectionBackground)
+		suggestionRemoveBackground = backgroundSequence(palette.SuggestionRemoveBackground)
+		suggestionAddBackground = backgroundSequence(palette.SuggestionAddBackground)
+		changedRemoveBackground = backgroundSequence(palette.ChangedRemoveBackground)
+		changedAddBackground = backgroundSequence(palette.ChangedAddBackground)
+		codeHighlightTheme = palette.SyntaxTheme
+		markdownStyleName = "dark"
+		if themeIsLight {
+			markdownStyleName = "light"
+		}
+		if palette.HighContrast {
+			titleStyle = titleStyle.Underline(true)
+			activeStyle = lipgloss.NewStyle().Bold(true).Reverse(true)
+			okStyle, warnStyle, badStyle = okStyle.Bold(true), warnStyle.Bold(true), badStyle.Bold(true)
+			editorLineStyle = lipgloss.NewStyle().
+				Foreground(lipgloss.Color(palette.EditorForeground)).Reverse(true)
+			quoteRailStyle = quoteRailStyle.Bold(true)
+			selectedLineBackground = "\x1b[7m"
+		}
 	}
 	currentThemeName = name
 	commentMarkdownRenderers.Clear()
 	return nil
 }
+
+func resolveThemePalette(name string, custom CustomThemeConfig) (themePalette, error) {
+	if name == "custom" {
+		base := custom.Base
+		if base == "" {
+			base = "dark"
+		}
+		if base == "custom" {
+			return themePalette{}, fmt.Errorf("custom_theme.base cannot be custom")
+		}
+		palette, err := resolveThemePalette(base, CustomThemeConfig{})
+		if err != nil {
+			return themePalette{}, fmt.Errorf("custom_theme.base: %w", err)
+		}
+		applyCustomTheme(&palette, custom)
+		if err := validateThemePalette(palette); err != nil {
+			return themePalette{}, fmt.Errorf("custom_theme: %w", err)
+		}
+		return palette, nil
+	}
+	palette, ok := builtinThemePalettes()[name]
+	if !ok {
+		return themePalette{}, fmt.Errorf(
+			"unknown theme %q; use dark, light, catppuccin, catppuccin-latte, "+
+				"gruvbox, gruvbox-light, one-dark-pro, github, github-light, "+
+				"high-contrast, no-color, or custom", name,
+		)
+	}
+	return palette, nil
+}
+
+func applyCustomTheme(palette *themePalette, custom CustomThemeConfig) {
+	set := func(target *string, value string) {
+		if value != "" {
+			*target = value
+		}
+	}
+	set(&palette.Mode, custom.Mode)
+	set(&palette.Title, custom.Title)
+	set(&palette.Dim, custom.Dim)
+	set(&palette.Text, custom.Text)
+	set(&palette.ActiveForeground, custom.ActiveForeground)
+	set(&palette.ActiveBackground, custom.ActiveBackground)
+	set(&palette.Success, custom.Success)
+	set(&palette.Warning, custom.Warning)
+	set(&palette.Error, custom.Error)
+	set(&palette.EditorForeground, custom.EditorForeground)
+	set(&palette.EditorBackground, custom.EditorBackground)
+	set(&palette.PaneInactive, custom.PaneInactive)
+	set(&palette.PaneActive, custom.PaneActive)
+	set(&palette.Quote, custom.Quote)
+	set(&palette.SelectionBackground, custom.SelectionBackground)
+	set(&palette.SuggestionRemoveBackground, custom.SuggestionRemoveBackground)
+	set(&palette.SuggestionAddBackground, custom.SuggestionAddBackground)
+	set(&palette.ChangedRemoveBackground, custom.ChangedRemoveBackground)
+	set(&palette.ChangedAddBackground, custom.ChangedAddBackground)
+	set(&palette.SyntaxTheme, custom.SyntaxTheme)
+	if len(custom.AuthorPalette) > 0 {
+		palette.AuthorPalette = append([]string(nil), custom.AuthorPalette...)
+	}
+	palette.NoColor, palette.HighContrast = false, false
+}
+
+func validateThemePalette(palette themePalette) error {
+	if palette.Mode != "dark" && palette.Mode != "light" {
+		return fmt.Errorf("mode must be dark or light")
+	}
+	colors := map[string]string{
+		"title": palette.Title, "dim": palette.Dim, "text": palette.Text,
+		"active_foreground": palette.ActiveForeground,
+		"active_background": palette.ActiveBackground,
+		"success":           palette.Success, "warning": palette.Warning, "error": palette.Error,
+		"editor_foreground": palette.EditorForeground,
+		"editor_background": palette.EditorBackground,
+		"pane_inactive":     palette.PaneInactive, "pane_active": palette.PaneActive,
+		"quote": palette.Quote, "selection_background": palette.SelectionBackground,
+		"suggestion_remove_background": palette.SuggestionRemoveBackground,
+		"suggestion_add_background":    palette.SuggestionAddBackground,
+		"changed_remove_background":    palette.ChangedRemoveBackground,
+		"changed_add_background":       palette.ChangedAddBackground,
+	}
+	for name, value := range colors {
+		if !validHexColor(value) {
+			return fmt.Errorf("%s must be a #RRGGBB color", name)
+		}
+	}
+	if len(palette.AuthorPalette) == 0 {
+		return fmt.Errorf("author_palette must contain at least one color")
+	}
+	for _, color := range palette.AuthorPalette {
+		if !validHexColor(color) {
+			return fmt.Errorf("author_palette contains invalid color %q", color)
+		}
+	}
+	if _, ok := styles.Registry[palette.SyntaxTheme]; !ok {
+		return fmt.Errorf("unknown Chroma syntax_theme %q", palette.SyntaxTheme)
+	}
+	return nil
+}
+
+func validHexColor(value string) bool {
+	if len(value) != 7 || value[0] != '#' {
+		return false
+	}
+	_, err := strconv.ParseUint(value[1:], 16, 24)
+	return err == nil
+}
+
+func backgroundSequence(color string) string {
+	value, err := strconv.ParseUint(strings.TrimPrefix(color, "#"), 16, 24)
+	if err != nil {
+		return ""
+	}
+	return fmt.Sprintf(
+		"\x1b[48;2;%d;%d;%dm", (value>>16)&0xff, (value>>8)&0xff, value&0xff,
+	)
+}
+
+func foregroundSequence(color string) string {
+	value, err := strconv.ParseUint(strings.TrimPrefix(color, "#"), 16, 24)
+	if err != nil {
+		return ""
+	}
+	return fmt.Sprintf(
+		"\x1b[38;2;%d;%d;%dm", (value>>16)&0xff, (value>>8)&0xff, value&0xff,
+	)
+}
+
+func builtinThemePalettes() map[string]themePalette {
+	dark := palette(
+		"dark", "#F0B72F", "#777777", "#D7DAE8", "#FFFFFF", "#3B4261",
+		"#67C587", "#E5C07B", "#E06C75", "#D7DAE8", "#2C3045",
+		"#50566F", "#F0B72F", "#777777", "#18344F", "#370000", "#003700",
+		"#370000", "#003700", "onedark",
+		"#61AFEF", "#C678DD", "#56B6C2", "#E5C07B", "#E06C75", "#98C379", "#D19A66", "#7FC8FF",
+	)
+	light := palette(
+		"light", "#9A6700", "#656D76", "#24292F", "#FFFFFF", "#0969DA",
+		"#1A7F37", "#9A6700", "#CF222E", "#24292F", "#DDE8FF",
+		"#8C959F", "#0969DA", "#656D76", "#ADD6FF", "#FFD7D5", "#CCFFD8",
+		"#FFAAAA", "#AAE6AA", "github",
+		"#0550AE", "#8250DF", "#0A706F", "#9A6700", "#CF222E", "#116329", "#953800", "#0969DA",
+	)
+	catMocha := palette(
+		"dark", "#CBA6F7", "#6C7086", "#CDD6F4", "#1E1E2E", "#CBA6F7",
+		"#A6E3A1", "#F9E2AF", "#F38BA8", "#CDD6F4", "#313244",
+		"#45475A", "#CBA6F7", "#6C7086", "#313244", "#452B36", "#23402E",
+		"#512B3A", "#254936", "catppuccin-mocha",
+		"#89B4FA", "#CBA6F7", "#94E2D5", "#F9E2AF", "#F38BA8", "#A6E3A1", "#FAB387",
+	)
+	catLatte := palette(
+		"light", "#8839EF", "#8C8FA1", "#4C4F69", "#EFF1F5", "#8839EF",
+		"#40A02B", "#DF8E1D", "#D20F39", "#4C4F69", "#DCE0E8",
+		"#9CA0B0", "#8839EF", "#8C8FA1", "#CCD0DA", "#F2CDCD", "#C9E7CA",
+		"#EFB8C0", "#B8DDB5", "catppuccin-latte",
+		"#1E66F5", "#8839EF", "#179299", "#DF8E1D", "#D20F39", "#40A02B", "#FE640B",
+	)
+	gruvbox := palette(
+		"dark", "#FABD2F", "#928374", "#EBDBB2", "#282828", "#458588",
+		"#B8BB26", "#FABD2F", "#FB4934", "#EBDBB2", "#3C3836",
+		"#665C54", "#D3869B", "#928374", "#3C3836", "#4C2828", "#324028",
+		"#5A2929", "#354929", "gruvbox",
+		"#83A598", "#D3869B", "#8EC07C", "#FABD2F", "#FB4934", "#B8BB26", "#FE8019",
+	)
+	gruvboxLight := palette(
+		"light", "#D79921", "#928374", "#3C3836", "#FBF1C7", "#458588",
+		"#98971A", "#D79921", "#CC241D", "#3C3836", "#EBDBB2",
+		"#A89984", "#B16286", "#928374", "#D5C4A1", "#F2C8C5", "#D8E0B0",
+		"#E9B9B3", "#C9D59A", "gruvbox-light",
+		"#458588", "#B16286", "#689D6A", "#D79921", "#CC241D", "#98971A", "#D65D0E",
+	)
+	oneDark := palette(
+		"dark", "#E5C07B", "#5C6370", "#ABB2BF", "#FFFFFF", "#3E4451",
+		"#98C379", "#E5C07B", "#E06C75", "#ABB2BF", "#2C313C",
+		"#4B5263", "#61AFEF", "#5C6370", "#2C313C", "#4B2B31", "#2D4032",
+		"#562D35", "#314A35", "onedark",
+		"#61AFEF", "#C678DD", "#56B6C2", "#E5C07B", "#E06C75", "#98C379", "#D19A66",
+	)
+	githubDark := palette(
+		"dark", "#D29922", "#8B949E", "#E6EDF3", "#FFFFFF", "#1F6FEB",
+		"#3FB950", "#D29922", "#F85149", "#E6EDF3", "#161B22",
+		"#30363D", "#58A6FF", "#8B949E", "#1F2937", "#4A2028", "#183D2A",
+		"#5A222C", "#1C4A30", "github-dark",
+		"#58A6FF", "#BC8CFF", "#39C5CF", "#D29922", "#F85149", "#3FB950", "#DB6D28",
+	)
+	highContrast := palette(
+		"dark", "#FFFF00", "#FFFFFF", "#FFFFFF", "#FFFFFF", "#000000",
+		"#00FF00", "#FFFF00", "#FF5555", "#FFFFFF", "#000000",
+		"#FFFFFF", "#FFFF00", "#FFFFFF", "#000080", "#5F0000", "#005F00",
+		"#5F0000", "#005F00", "github-dark",
+		"#00FFFF", "#FF55FF", "#FFFF00", "#00FF00", "#FFFFFF",
+	)
+	highContrast.HighContrast = true
+	noColor := dark
+	noColor.NoColor = true
+	return map[string]themePalette{
+		"dark": dark, "light": light,
+		"catppuccin": catMocha, "catppuccin-mocha": catMocha,
+		"catppuccin-latte": catLatte,
+		"gruvbox":          gruvbox, "gruvbox-dark": gruvbox, "gruvbox-light": gruvboxLight,
+		"one-dark-pro": oneDark, "onedark": oneDark,
+		"github": githubDark, "github-dark": githubDark, "github-light": light,
+		"high-contrast": highContrast, "no-color": noColor,
+	}
+}
+
+func palette(
+	mode, title, dim, text, activeFG, activeBG, success, warning, failure,
+	editorFG, editorBG, paneInactive, paneActive, quote, selection,
+	suggestionRemove, suggestionAdd, changedRemove, changedAdd, syntax string,
+	authors ...string,
+) themePalette {
+	return themePalette{
+		Mode: mode, Title: title, Dim: dim, Text: text,
+		ActiveForeground: activeFG, ActiveBackground: activeBG,
+		Success: success, Warning: warning, Error: failure,
+		EditorForeground: editorFG, EditorBackground: editorBG,
+		PaneInactive: paneInactive, PaneActive: paneActive, Quote: quote,
+		SelectionBackground:        selection,
+		SuggestionRemoveBackground: suggestionRemove,
+		SuggestionAddBackground:    suggestionAdd,
+		ChangedRemoveBackground:    changedRemove, ChangedAddBackground: changedAdd,
+		AuthorPalette: append([]string(nil), authors...), SyntaxTheme: syntax,
+	}
+}

theme_test.go

@@ -3,6 +3,8 @@ package main
 import (
 	"strings"
 	"testing"
+
+	"github.com/charmbracelet/lipgloss"
 )
 
 func TestApplyThemeChangesAllRenderingThemes(t *testing.T) {
@@ -11,6 +13,12 @@ func TestApplyThemeChangesAllRenderingThemes(t *testing.T) {
 			t.Fatal(err)
 		}
 	}()
+	if err := applyTheme("dark"); err != nil {
+		t.Fatal(err)
+	}
+	if codeHighlightTheme != "onedark" {
+		t.Fatalf("dark syntax theme = %q, want onedark", codeHighlightTheme)
+	}
 	if err := applyTheme("light"); err != nil {
 		t.Fatal(err)
 	}
@@ -32,3 +40,110 @@ func TestNoColorThemeDisablesSyntaxColors(t *testing.T) {
 		t.Fatalf("no-color source contains terminal colors: %q", rendered)
 	}
 }
+
+func TestBuiltinThemesApply(t *testing.T) {
+	defer applyTheme("dark")
+	names := []string{
+		"dark", "light",
+		"catppuccin", "catppuccin-mocha", "catppuccin-latte",
+		"gruvbox", "gruvbox-dark", "gruvbox-light",
+		"one-dark-pro", "github", "github-dark", "github-light",
+		"high-contrast", "no-color",
+	}
+	for _, name := range names {
+		t.Run(name, func(t *testing.T) {
+			if err := applyTheme(name); err != nil {
+				t.Fatal(err)
+			}
+			if len(authorPalette) == 0 {
+				t.Fatal("theme has no author colors")
+			}
+		})
+	}
+}
+
+func TestLightBuiltinThemesSelectLightRendering(t *testing.T) {
+	defer applyTheme("dark")
+	for _, name := range []string{"light", "catppuccin-latte", "gruvbox-light", "github-light"} {
+		if err := applyTheme(name); err != nil {
+			t.Fatal(err)
+		}
+		if !themeIsLight || markdownStyleName != "light" {
+			t.Fatalf("%s was not treated as a light theme", name)
+		}
+	}
+}
+
+func TestCustomThemeOverlaysBuiltinBase(t *testing.T) {
+	defer applyTheme("dark")
+	custom := CustomThemeConfig{
+		Base:          "catppuccin-mocha",
+		Title:         "#010203",
+		AuthorPalette: []string{"#112233", "#445566"},
+		SyntaxTheme:   "gruvbox",
+	}
+	if err := applyTheme("custom", custom); err != nil {
+		t.Fatal(err)
+	}
+	if currentThemeName != "custom" ||
+		titleStyle.GetForeground() != lipgloss.Color("#010203") ||
+		codeHighlightTheme != "gruvbox" {
+		t.Fatalf(
+			"custom theme was not applied: name=%q title=%q syntax=%q",
+			currentThemeName, titleStyle.GetForeground(), codeHighlightTheme,
+		)
+	}
+	if len(authorPalette) != 2 ||
+		authorPalette[0] != lipgloss.Color("#112233") ||
+		authorPalette[1] != lipgloss.Color("#445566") {
+		t.Fatalf("custom author palette = %#v", authorPalette)
+	}
+	if selectedLineBackground == "" {
+		t.Fatal("custom theme did not inherit unspecified base colors")
+	}
+}
+
+func TestCustomThemeValidation(t *testing.T) {
+	tests := []struct {
+		name   string
+		custom CustomThemeConfig
+		want   string
+	}{
+		{
+			name:   "invalid color",
+			custom: CustomThemeConfig{Title: "red"},
+			want:   "title must be a #RRGGBB color",
+		},
+		{
+			name:   "invalid syntax theme",
+			custom: CustomThemeConfig{SyntaxTheme: "not-a-chroma-theme"},
+			want:   "unknown Chroma syntax_theme",
+		},
+		{
+			name:   "recursive base",
+			custom: CustomThemeConfig{Base: "custom"},
+			want:   "custom_theme.base cannot be custom",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			_, err := resolveThemePalette("custom", test.custom)
+			if err == nil || !strings.Contains(err.Error(), test.want) {
+				t.Fatalf("error = %v, want it to contain %q", err, test.want)
+			}
+		})
+	}
+}
+
+func TestCatppuccinUsesCanonicalMauveAccent(t *testing.T) {
+	palette, err := resolveThemePalette("catppuccin-mocha", CustomThemeConfig{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if palette.Title != "#CBA6F7" || palette.ActiveBackground != "#CBA6F7" {
+		t.Fatalf(
+			"Catppuccin accent is title=%q active=%q, want mauve",
+			palette.Title, palette.ActiveBackground,
+		)
+	}
+}

tui.go

@@ -2314,6 +2314,7 @@ func (m App) healthLines() []string {
 	components = append(components, refresh)
 	components = append(components, HealthComponent{
 		Name: "configuration", Level: healthOK, Summary: "configuration loaded and validated",
+		Detail: "theme " + currentThemeName,
 	})
 	if m.readState != nil {
 		component := HealthComponent{

tui_test.go

@@ -1704,7 +1704,7 @@ func TestTabHidesListAndHRestoresIt(t *testing.T) {
 
 func TestSelectedBackgroundFillsLine(t *testing.T) {
 	rendered := selectedBackground("code", 12)
-	if !strings.Contains(rendered, "\x1b[48;5;24m") || ansi.StringWidth(rendered) != 12 {
+	if !strings.Contains(rendered, selectedLineBackground) || ansi.StringWidth(rendered) != 12 {
 		t.Fatalf("selected background was not full width: %q", rendered)
 	}
 }