fix(tui): address CodeRabbit review on the theme catalog

- CHANGELOG: reconcile the --theme bullet with the named themes (was still
  documenting {auto|dark|light}).
- /theme usage string advertises the list and auto forms (/theme list is still
  accepted) so /help matches the command surface.
- Theme-persistence test parses the written config and asserts preferences.theme
  directly instead of a raw substring, so a wrong-key regression fails.

CHANGELOG.md

@@ -11,7 +11,14 @@ tagged. Until then, source builds report the version `dev`.
 ### Added
 - `SECURITY.md` with a private vulnerability-reporting path, `CODE_OF_CONDUCT.md`, this changelog, and
   GitHub issue/PR templates.
-- `--theme {auto|dark|light}` flag for the TUI (previously only the `ZERO_THEME` env var existed).
+- Interactive `/theme` picker: bare `/theme` opens a popup that live-previews each palette as you move
+  and applies on select (Esc reverts).
+- Ten built-in color themes alongside the `dark`/`light` built-ins — `dracula`, `nord`, `gruvbox`,
+  `tokyo-night`, `catppuccin`, `one-dark`, `solarized-dark`, `rose-pine`, `everforest`, and
+  `solarized-light` — selectable via `/theme <name>`, `--theme <name>`, or `ZERO_THEME`. Every palette
+  is contrast-audited to WCAG AA. The built-in light theme was reworked for legibility.
+- `--theme <name>` flag for the TUI, accepting `auto` or any registered theme (previously only the
+  `ZERO_THEME` env var existed).
 - "Accessibility / Appearance" section in the README documenting `NO_COLOR`, `ZERO_THEME`, `/theme`,
   and `ZERO_NO_FADE`.
 

README.md

@@ -254,9 +254,9 @@ zero update           check for newer releases
 | Control | Effect |
 |---|---|
 | `NO_COLOR=<anything>` | disables color output |
-| `ZERO_THEME=auto|dark|light` | selects the startup theme |
-| `--theme auto|dark|light` | selects the TUI theme from the CLI |
-| `/theme auto|dark|light` | switches theme inside the TUI |
+| `ZERO_THEME=<name>` | selects the startup theme (`auto`, `dark`, `light`, or a color theme like `dracula`, `nord`, `gruvbox`, `tokyo-night`, `catppuccin`, `one-dark`, `solarized-dark`, `rose-pine`, `everforest`, `solarized-light`) |
+| `--theme <name>` | selects the TUI theme from the CLI (same names) |
+| `/theme` | opens the theme picker inside the TUI (live preview; `/theme <name>` switches directly) |
 | `ZERO_NO_FADE=1` | disables streaming fade animation |
 
 Meaning does not rely on color alone; diffs, permissions, and statuses also use

internal/cli/app.go

@@ -217,9 +217,9 @@ func runWithDeps(args []string, stdout io.Writer, stderr io.Writer, deps appDeps
 	if err != nil {
 		return writeAppError(stderr, err.Error(), 1)
 	}
-	// --theme {auto|dark|light} selects the TUI palette non-interactively (populates
-	// tui.Options.Theme, which resolveThemeMode prefers over ZERO_THEME). Re-split
-	// --add-dir afterward so it may appear on either side of --theme.
+	// --theme <name> selects the TUI palette non-interactively (auto or any registered
+	// theme; populates tui.Options.Theme, which resolveThemeMode prefers over
+	// ZERO_THEME). Re-split --add-dir afterward so it may appear on either side of --theme.
 	theme, args, err := splitLeadingThemeFlag(args)
 	if err != nil {
 		return writeAppError(stderr, err.Error(), 1)
@@ -641,6 +641,7 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 	return deps.runTUI(context.Background(), tui.Options{
 		Cwd:                  workspaceRoot,
 		Theme:                theme,
+		SavedTheme:           resolved.Preferences.Theme,
 		UserConfigPath:       userConfigPath,
 		DoctorUserConfigPath: doctorUserConfigPath,
 		ProjectConfigPath:    projectConfigPath,
@@ -1033,9 +1034,10 @@ func splitLeadingAddDirFlags(args []string) ([]string, []string, error) {
 	return addDirs, args, nil
 }
 
-// splitLeadingThemeFlag strips a leading --theme {auto|dark|light} (space or =form)
-// from the root argument list and validates it. The last occurrence wins. A value
-// outside the allowed set is a loud error rather than a silent fallback.
+// splitLeadingThemeFlag strips a leading --theme <auto|theme-name> (space or =form)
+// from the root argument list and validates it against the registered themes. The
+// last occurrence wins. A value outside the allowed set is a loud error rather than
+// a silent fallback.
 func splitLeadingThemeFlag(args []string) (string, []string, error) {
 	theme := ""
 	for len(args) > 0 {
@@ -1043,7 +1045,7 @@ func splitLeadingThemeFlag(args []string) (string, []string, error) {
 		switch {
 		case args[0] == "--theme":
 			if len(args) < 2 {
-				return "", nil, errors.New("--theme requires a value (auto, dark, or light)")
+				return "", nil, errors.New("--theme requires a value (auto or a theme name; try --theme auto)")
 			}
 			value = strings.TrimSpace(args[1])
 			args = args[2:]
@@ -1053,12 +1055,10 @@ func splitLeadingThemeFlag(args []string) (string, []string, error) {
 		default:
 			return theme, args, nil
 		}
-		switch strings.ToLower(value) {
-		case "auto", "dark", "light":
-			theme = strings.ToLower(value)
-		default:
-			return "", nil, fmt.Errorf("--theme must be auto, dark, or light (got %q)", value)
+		if !tui.ValidThemeArg(value) {
+			return "", nil, fmt.Errorf("--theme must be auto or a registered theme name (got %q)", value)
 		}
+		theme = strings.ToLower(value)
 	}
 	return theme, args, nil
 }

internal/cli/app_test.go

@@ -1397,7 +1397,7 @@ func TestRunThemeFlagRejectsBadValue(t *testing.T) {
 	if launched {
 		t.Fatal("the TUI must not launch on a bad --theme value")
 	}
-	if !strings.Contains(stderr.String(), "--theme must be auto, dark, or light") {
+	if !strings.Contains(stderr.String(), "--theme must be auto or a registered theme name") {
 		t.Fatalf("expected a clear --theme error, got %q", stderr.String())
 	}
 }

internal/config/resolver.go

@@ -195,6 +195,9 @@ func mergeConfig(dst *FileConfig, src FileConfig) {
 	if src.Preferences.Recaps != nil {
 		dst.Preferences.Recaps = src.Preferences.Recaps
 	}
+	if strings.TrimSpace(src.Preferences.Theme) != "" {
+		dst.Preferences.Theme = strings.TrimSpace(src.Preferences.Theme)
+	}
 	mergeLocalControlConfig(&dst.LocalControl, src.LocalControl)
 }
 

internal/config/types.go

@@ -97,6 +97,10 @@ type ToolsConfig struct {
 
 type PreferencesConfig struct {
 	FavoriteModels []string `json:"favoriteModels,omitempty"`
+	// Theme is the persisted TUI palette preference — "auto" or a registered theme
+	// name (e.g. "dracula"). Applied at startup below the --theme flag and
+	// ZERO_THEME, so a /theme choice survives restart. Empty = unset (defaults auto).
+	Theme string `json:"theme,omitempty"`
 	// Recaps is a tri-state: nil (unset) defaults to ON; an explicit false means
 	// the user turned post-turn recaps off. A *bool is its own tri-state, so no
 	// custom unmarshal is needed (unlike ToolsConfig.DeferThreshold's int).

internal/config/writer.go

@@ -154,6 +154,28 @@ func SetRecapsEnabled(path string, enabled bool) (FileConfig, error) {
 	return cfg, nil
 }
 
+// SetTheme persists the TUI theme preference, mirroring SetFavoriteModels
+// (read-modify-atomic-write). A blank theme clears the stored preference.
+func SetTheme(path string, theme string) (FileConfig, error) {
+	path = strings.TrimSpace(path)
+	if path == "" {
+		return FileConfig{}, fmt.Errorf("config path is required")
+	}
+	cfg := FileConfig{}
+	if data, err := os.ReadFile(path); err == nil {
+		if err := json.Unmarshal(data, &cfg); err != nil {
+			return FileConfig{}, fmt.Errorf("invalid config JSON %s: %w", path, err)
+		}
+	} else if !os.IsNotExist(err) {
+		return FileConfig{}, fmt.Errorf("read config %s: %w", path, err)
+	}
+	cfg.Preferences.Theme = strings.TrimSpace(theme)
+	if err := writeConfigFile(path, cfg); err != nil {
+		return FileConfig{}, err
+	}
+	return cfg, nil
+}
+
 func normalizeFavoriteModels(models []string) []string {
 	seen := map[string]bool{}
 	favorites := make([]string, 0, len(models))

internal/config/writer_test.go

@@ -272,6 +272,39 @@ func TestSetFavoriteModelsPersistsUserPreferences(t *testing.T) {
 	}
 }
 
+func TestSetThemePersistsUserPreference(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "zero.json")
+	writeConfigFixture(t, path, FileConfig{
+		ActiveProvider: "openai",
+		Providers: []ProviderProfile{
+			{Name: "openai", ProviderKind: ProviderKindOpenAI, Model: "gpt-4.1"},
+		},
+	}, 0o600)
+
+	cfg, err := SetTheme(path, "  dracula  ")
+	if err != nil {
+		t.Fatalf("SetTheme() error = %v", err)
+	}
+	if cfg.Preferences.Theme != "dracula" {
+		t.Fatalf("Theme = %q, want dracula (trimmed)", cfg.Preferences.Theme)
+	}
+	persisted := readConfigFixture(t, path)
+	if persisted.Preferences.Theme != "dracula" {
+		t.Fatalf("persisted Theme = %q, want dracula", persisted.Preferences.Theme)
+	}
+	if persisted.ActiveProvider != "openai" || len(persisted.Providers) != 1 {
+		t.Fatalf("provider config was not preserved by SetTheme: %#v", persisted)
+	}
+
+	// A blank value clears the stored preference.
+	if cfg, err = SetTheme(path, ""); err != nil {
+		t.Fatalf("SetTheme(\"\") error = %v", err)
+	}
+	if cfg.Preferences.Theme != "" {
+		t.Fatalf("SetTheme(\"\") should clear the theme, got %q", cfg.Preferences.Theme)
+	}
+}
+
 func TestRecapsPreferenceRoundTrips(t *testing.T) {
 	// Default (unset) is ON.
 	if !(PreferencesConfig{}).RecapsEnabled() {

internal/tools/exec_command.go

@@ -28,8 +28,17 @@ const (
 	completedSessionRetention = 30 * time.Second
 	maxExecSessions           = 64
 	recentExecOutputBytes     = 4096
-	execSessionStopTimeout    = 3 * time.Second
-	execSessionEvictedMessage = "[zero] session evicted: too many background terminals\n"
+	// maxExecOutputBufferBytes caps the undrained output an unpolled session can
+	// accumulate. Without a cap, a long-lived background session nobody polls
+	// again (e.g. a dev server left running after its initiating run was
+	// cancelled) grows this buffer forever as long as the process keeps writing
+	// output, with no ceiling — this previously ran a session's memory into the
+	// tens of gigabytes over several hours and got the whole zero process
+	// OOM-killed by the OS.
+	maxExecOutputBufferBytes         = 2 * 1024 * 1024
+	execSessionStopTimeout           = 3 * time.Second
+	execSessionEvictedMessage        = "[zero] session evicted: too many background terminals\n"
+	execOutputBufferTruncatedMessage = "[zero] output buffer truncated: undrained output exceeded 2MiB, oldest output dropped"
 )
 
 type execSessionManager struct {
@@ -233,6 +242,10 @@ type ExecSessionSnapshot struct {
 	Status       string
 	ExitCode     *int
 	RecentOutput string
+	// OutputTruncated reflects the buffer's last-known truncation state (see
+	// execOutputBuffer.peekTruncated), so a session listing (/ps) still shows
+	// this even if the session is reaped before ever being polled again.
+	OutputTruncated bool
 }
 
 type ExecSessionController interface {
@@ -317,24 +330,26 @@ func (session *execSession) snapshot() ExecSessionSnapshot {
 		status = "exited"
 	}
 	return ExecSessionSnapshot{
-		ID:           session.id,
-		Command:      session.commandText,
-		Cwd:          session.cwd,
-		RelativeCwd:  session.relativeCwd,
-		StartedAt:    startedAt,
-		LastUsedAt:   lastUsedAt,
-		TTY:          session.tty,
-		Status:       status,
-		ExitCode:     copiedExit,
-		RecentOutput: session.output.recentString(),
+		ID:              session.id,
+		Command:         session.commandText,
+		Cwd:             session.cwd,
+		RelativeCwd:     session.relativeCwd,
+		StartedAt:       startedAt,
+		LastUsedAt:      lastUsedAt,
+		TTY:             session.tty,
+		Status:          status,
+		ExitCode:        copiedExit,
+		RecentOutput:    session.output.recentString(),
+		OutputTruncated: session.output.peekTruncated(),
 	}
 }
 
 type execOutputBuffer struct {
-	mu     sync.Mutex
-	data   []byte
-	recent []byte
-	notify chan struct{}
+	mu        sync.Mutex
+	data      []byte
+	recent    []byte
+	truncated bool
+	notify    chan struct{}
 }
 
 func newExecOutputBuffer() *execOutputBuffer {
@@ -344,6 +359,10 @@ func newExecOutputBuffer() *execOutputBuffer {
 func (buffer *execOutputBuffer) Write(p []byte) (int, error) {
 	buffer.mu.Lock()
 	buffer.data = append(buffer.data, p...)
+	if len(buffer.data) > maxExecOutputBufferBytes {
+		buffer.data = buffer.data[len(buffer.data)-maxExecOutputBufferBytes:]
+		buffer.truncated = true
+	}
 	buffer.recent = append(buffer.recent, p...)
 	if len(buffer.recent) > recentExecOutputBytes {
 		buffer.recent = buffer.recent[len(buffer.recent)-recentExecOutputBytes:]
@@ -373,6 +392,34 @@ func (buffer *execOutputBuffer) drainString() string {
 	return out
 }
 
+// consumeTruncated reports whether the buffer has dropped output to stay
+// within maxExecOutputBufferBytes since the last call, resetting the flag.
+// Kept as an out-of-band signal rather than text embedded in drainString's
+// result: an earlier version prefixed a notice directly into the drained
+// string, but that notice always sat ~maxExecOutputBufferBytes (2MiB) before
+// the end of the combined output, far outside the byte-budget head/tail
+// window truncateExecOutput keeps afterward (at most 400KB even at the
+// tool's maximum max_output_tokens) — so the notice was reliably swallowed
+// or chopped by that second, unrelated truncation pass. Surfacing it as a
+// separate bool lets the caller report it regardless of where in the byte
+// stream the overflow happened.
+func (buffer *execOutputBuffer) consumeTruncated() bool {
+	buffer.mu.Lock()
+	defer buffer.mu.Unlock()
+	truncated := buffer.truncated
+	buffer.truncated = false
+	return truncated
+}
+
+// peekTruncated reports the buffer's last-known truncation state without
+// clearing it, for status views (e.g. /ps) that shouldn't consume the signal
+// a subsequent poll is still meant to report via consumeTruncated.
+func (buffer *execOutputBuffer) peekTruncated() bool {
+	buffer.mu.Lock()
+	defer buffer.mu.Unlock()
+	return buffer.truncated
+}
+
 type execCommandTool struct {
 	baseTool
 	workspaceRoot string
@@ -485,25 +532,28 @@ func (tool execCommandTool) run(ctx context.Context, args map[string]any, engine
 	if err != nil {
 		return errorResult("Error starting exec_command: " + err.Error())
 	}
-	output := session.collect(ctx, time.Duration(yieldTimeMS)*time.Millisecond)
+	output, outputTruncated := session.collect(ctx, time.Duration(yieldTimeMS)*time.Millisecond)
 	if ctx != nil && ctx.Err() != nil && !session.doneClosed() {
 		session.terminate()
-		output += session.collect(context.Background(), time.Second)
+		more, moreTruncated := session.collect(context.Background(), time.Second)
+		output += more
+		outputTruncated = outputTruncated || moreTruncated
 	}
 	exitCode, exited := session.exitStatus()
 	if exited {
 		tool.manager.remove(session.id)
 	}
 	return execToolResult(execToolResultInput{
-		commandText:     commandText,
-		output:          output,
-		sessionID:       session.id,
-		exitCode:        exitCode,
-		exited:          exited,
-		relativeCwd:     relativeCwd,
-		tty:             session.tty,
-		plan:            session.plan,
-		maxOutputTokens: maxOutputTokens,
+		commandText:           commandText,
+		output:                output,
+		outputBufferTruncated: outputTruncated,
+		sessionID:             session.id,
+		exitCode:              exitCode,
+		exited:                exited,
+		relativeCwd:           relativeCwd,
+		tty:                   session.tty,
+		plan:                  session.plan,
+		maxOutputTokens:       maxOutputTokens,
 	})
 }
 
@@ -558,26 +608,39 @@ func (tool execCommandTool) startSession(commandText string, absoluteCwd string,
 	return session, nil
 }
 
-func (session *execSession) collect(ctx context.Context, wait time.Duration) string {
+// collect drains the session's output buffer, returning the accumulated text
+// and whether the buffer ever had to drop output to stay within
+// maxExecOutputBufferBytes since the last collect call.
+func (session *execSession) collect(ctx context.Context, wait time.Duration) (string, bool) {
 	if ctx == nil {
 		ctx = context.Background()
 	}
 	deadline := time.Now().Add(wait)
 	var builder strings.Builder
+	truncated := false
+	finish := func() (string, bool) {
+		if session.output.consumeTruncated() {
+			truncated = true
+		}
+		return builder.String(), truncated
+	}
 	for {
 		if chunk := session.output.drainString(); chunk != "" {
 			builder.WriteString(chunk)
+			if session.output.consumeTruncated() {
+				truncated = true
+			}
 			continue
 		}
 		if session.doneClosed() {
 			if chunk := session.output.drainString(); chunk != "" {
 				builder.WriteString(chunk)
 			}
-			return builder.String()
+			return finish()
 		}
 		remaining := time.Until(deadline)
 		if remaining <= 0 {
-			return builder.String()
+			return finish()
 		}
 		timer := time.NewTimer(remaining)
 		select {
@@ -602,9 +665,9 @@ func (session *execSession) collect(ctx context.Context, wait time.Duration) str
 				default:
 				}
 			}
-			return builder.String()
+			return finish()
 		case <-timer.C:
-			return builder.String()
+			return finish()
 		}
 	}
 }
@@ -701,22 +764,23 @@ func (tool writeStdinTool) RunWithOptions(ctx context.Context, args map[string]a
 			}
 		}
 	}
-	output := session.collect(ctx, time.Duration(yieldTimeMS)*time.Millisecond)
+	output, outputTruncated := session.collect(ctx, time.Duration(yieldTimeMS)*time.Millisecond)
 	exitCode, exited := session.exitStatus()
 	if exited {
 		tool.manager.remove(session.id)
 	}
 	return execToolResult(execToolResultInput{
-		commandText:     session.commandText,
-		output:          output,
-		sessionID:       session.id,
-		exitCode:        exitCode,
-		exited:          exited,
-		relativeCwd:     session.relativeCwd,
-		tty:             session.tty,
-		interrupted:     interrupted,
-		plan:            session.plan,
-		maxOutputTokens: maxOutputTokens,
+		commandText:           session.commandText,
+		output:                output,
+		outputBufferTruncated: outputTruncated,
+		sessionID:             session.id,
+		exitCode:              exitCode,
+		exited:                exited,
+		relativeCwd:           session.relativeCwd,
+		tty:                   session.tty,
+		interrupted:           interrupted,
+		plan:                  session.plan,
+		maxOutputTokens:       maxOutputTokens,
 	})
 }
 
@@ -741,16 +805,22 @@ func shouldInterruptExecSession(chars string, tty bool) bool {
 }
 
 type execToolResultInput struct {
-	commandText     string
-	output          string
-	sessionID       int
-	exitCode        int
-	exited          bool
-	relativeCwd     string
-	tty             bool
-	interrupted     bool
-	plan            zeroSandbox.CommandPlan
-	maxOutputTokens int
+	commandText string
+	output      string
+	// outputBufferTruncated is true when the session's undrained output buffer
+	// had to drop bytes to stay within maxExecOutputBufferBytes since it was
+	// last collected — data that is gone for good, unlike the head/tail
+	// truncation below (which the caller can recover by polling again or
+	// raising max_output_tokens).
+	outputBufferTruncated bool
+	sessionID             int
+	exitCode              int
+	exited                bool
+	relativeCwd           string
+	tty                   bool
+	interrupted           bool
+	plan                  zeroSandbox.CommandPlan
+	maxOutputTokens       int
 }
 
 func execToolResult(input execToolResultInput) Result {
@@ -771,16 +841,26 @@ func execToolResult(input execToolResultInput) Result {
 	} else {
 		meta["session_id"] = strconv.Itoa(input.sessionID)
 	}
+	if input.outputBufferTruncated {
+		meta["output_buffer_truncated"] = "true"
+	}
 
 	status := StatusOK
 	if input.exited && ((input.exitCode != 0 && !input.interrupted) || meta[SandboxLikelyDeniedMeta] == "true") {
 		status = StatusError
 	}
 	body := formatExecCommandOutput(output, input.sessionID, input.exited, input.exitCode, input.interrupted)
+	if input.outputBufferTruncated {
+		// Appended after truncateExecOutput's own head/tail slicing, not
+		// embedded in the text that goes through it — a marker inside that
+		// text can land in the discarded middle or get chopped at a small
+		// max_output_tokens budget. Appending here guarantees it survives.
+		body += "\n" + execOutputBufferTruncatedMessage
+	}
 	return Result{
 		Status:    status,
 		Output:    body,
-		Truncated: truncated,
+		Truncated: truncated || input.outputBufferTruncated,
 		Meta:      meta,
 		Display: Display{
 			Summary: execDisplaySummary(input.commandText, input.sessionID, input.exited, input.exitCode),

internal/tools/exec_command_test.go

@@ -363,6 +363,93 @@ func TestStartExecProcessFallsBackAfterPTYStartMutation(t *testing.T) {
 	}
 }
 
+// TestExecOutputBufferCapsUndrainedData: a session nobody polls must not grow
+// its undrained buffer without bound — a long-lived background process that
+// keeps writing while unpolled previously ran a session's memory into the
+// tens of gigabytes and got the whole zero process OOM-killed by the OS.
+func TestExecOutputBufferCapsUndrainedData(t *testing.T) {
+	buffer := newExecOutputBuffer()
+
+	chunk := strings.Repeat("x", 1024)
+	writes := (maxExecOutputBufferBytes / len(chunk)) + 10 // comfortably over the cap
+	for i := 0; i < writes; i++ {
+		if _, err := buffer.Write([]byte(chunk)); err != nil {
+			t.Fatalf("Write: %v", err)
+		}
+	}
+
+	buffer.mu.Lock()
+	dataLen := len(buffer.data)
+	buffer.mu.Unlock()
+	if dataLen > maxExecOutputBufferBytes {
+		t.Fatalf("undrained buffer grew to %d bytes, want <= %d", dataLen, maxExecOutputBufferBytes)
+	}
+
+	out := buffer.drainString()
+	// drainString itself carries no truncation marker: a marker embedded in
+	// the drained text would always sit ~maxExecOutputBufferBytes before the
+	// end of the string, past any realistic head/tail truncation window a
+	// caller applies afterward (see execToolResult), so it's reliably lost.
+	// The signal lives out of band on consumeTruncated/peekTruncated instead.
+	if !strings.HasSuffix(out, chunk) {
+		t.Fatal("drained output should keep the most recent bytes, not the oldest")
+	}
+	if len(out) > maxExecOutputBufferBytes {
+		t.Fatalf("drained output = %d bytes, want <= %d (no marker text mixed in)", len(out), maxExecOutputBufferBytes)
+	}
+
+	if !buffer.peekTruncated() {
+		t.Fatal("peekTruncated should report the overflow without clearing it")
+	}
+	if !buffer.peekTruncated() {
+		t.Fatal("a second peekTruncated call should still report it — peek must not consume")
+	}
+	if !buffer.consumeTruncated() {
+		t.Fatal("consumeTruncated should report the overflow")
+	}
+	if buffer.consumeTruncated() {
+		t.Fatal("consumeTruncated should reset after being read once")
+	}
+	if buffer.peekTruncated() {
+		t.Fatal("peekTruncated should reflect the reset state after consumeTruncated")
+	}
+
+	// A second drain with no intervening writes must be empty.
+	if got := buffer.drainString(); got != "" {
+		t.Fatalf("drainString after a full drain = %q, want empty", got)
+	}
+}
+
+// TestExecToolResultSurfacesBufferTruncationOutsideByteBudget: an earlier
+// version embedded the truncation notice directly in the drained text, which
+// a review found sits ~maxExecOutputBufferBytes before the end of the
+// string — far past the head/tail window truncateExecOutput keeps even at
+// the tool's smallest allowed max_output_tokens, so the notice was reliably
+// swallowed or chopped. The notice must survive regardless of how small the
+// byte budget is, and it must not count against that budget.
+func TestExecToolResultSurfacesBufferTruncationOutsideByteBudget(t *testing.T) {
+	hugeOutput := strings.Repeat("y", maxExecOutputBufferBytes+1024)
+
+	result := execToolResult(execToolResultInput{
+		commandText:           "cmd",
+		output:                hugeOutput,
+		outputBufferTruncated: true,
+		sessionID:             1,
+		exited:                false,
+		maxOutputTokens:       1, // the schema's own declared minimum
+	})
+
+	if !strings.Contains(result.Output, execOutputBufferTruncatedMessage) {
+		t.Fatalf("result output should contain the buffer-truncation notice even at the smallest max_output_tokens, got %q", result.Output[:min(len(result.Output), 200)])
+	}
+	if result.Meta["output_buffer_truncated"] != "true" {
+		t.Fatalf("result meta should flag output_buffer_truncated, got %#v", result.Meta)
+	}
+	if !result.Truncated {
+		t.Fatal("result should report Truncated when the buffer dropped output")
+	}
+}
+
 // resilientTempDir is like t.TempDir() but tolerates the Windows handle-release
 // lag: a SIGKILL'd child process that had the dir as its cwd may not have
 // released it the instant it is reaped, so the immediate RemoveAll t.TempDir()

internal/tui/background_terminals.go

@@ -146,6 +146,9 @@ func formatBackgroundTerminalRow(session tools.ExecSessionSnapshot, now time.Tim
 	}
 	preview := compactCommandOutputText(session.RecentOutput)
 	prefix := fmt.Sprintf("%d · %s · %s · %s", session.ID, session.Status, age, cwd)
+	if session.OutputTruncated {
+		prefix += " · output truncated"
+	}
 	if preview != "" {
 		return prefix + " · " + command + " · " + preview
 	}

internal/tui/commands.go

@@ -281,9 +281,9 @@ var commandDefinitions = []commandDefinition{
 	},
 	{
 		name:        "/theme",
-		usage:       "/theme [auto|dark|light]",
+		usage:       "/theme [list|auto|name]",
 		group:       commandGroupSession,
-		description: "Switch or show the color theme (auto-detects terminal background).",
+		description: "Pick a color theme (no arg opens the picker; auto detects the terminal background).",
 		kind:        commandTheme,
 	},
 	{

internal/tui/model.go

@@ -678,7 +678,7 @@ func newModel(ctx context.Context, options Options) model {
 		permissionMode:         permissionMode,
 		reasoningEffort:        options.ReasoningEffort,
 		responseStyle:          defaultedResponseStyle(options.ResponseStyle),
-		themeMode:              resolveThemeMode(options.Theme, os.Getenv("ZERO_THEME")),
+		themeMode:              resolveThemeMode(options.Theme, os.Getenv("ZERO_THEME"), options.SavedTheme),
 		hasDarkBg:              true,
 		userAgent:              options.UserAgent,
 		usageTracker:           usageTracker,
@@ -1047,6 +1047,11 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				if m.picker.kind == pickerModel {
 					m.clearModelPickerLoadState()
 				}
+				if m.picker.kind == pickerTheme {
+					// A live theme preview was applied while navigating; restore the
+					// committed palette since Esc dismisses without choosing.
+					m.restoreCommittedTheme()
+				}
 				m.picker = nil
 				return m, nil
 			}
@@ -1181,6 +1186,9 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 					return m, nil
 				}
 				m.picker.deleteQueryRune()
+				// Editing the filter changes which row is highlighted; keep the
+				// theme preview in sync with it (no-op for other pickers).
+				m.previewSelectedTheme()
 				return m, nil
 			}
 			// On an empty composer, Backspace removes the last attachment chip
@@ -1253,7 +1261,7 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				if m.modelPickerIsLoading() {
 					return m, nil
 				}
-				m.picker.move(1)
+				m.pickerMoved(1)
 				return m, nil
 			}
 			if m.suggestionsActive() {
@@ -1295,7 +1303,7 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				if m.modelPickerIsLoading() {
 					return m, nil
 				}
-				m.picker.move(-1)
+				m.pickerMoved(-1)
 				return m, nil
 			}
 			if m.suggestionsActive() {
@@ -1354,6 +1362,9 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 			}
 			if keyPrintable(msg) {
 				m.picker.appendQuery(keyRunes(msg))
+				// Filtering changes the highlighted row; keep the theme preview in
+				// sync with it (no-op for other pickers).
+				m.previewSelectedTheme()
 			}
 			return m, nil
 		}
@@ -1934,6 +1945,17 @@ func (m model) View() tea.View {
 
 	view := tea.NewView(content)
 	view.AltScreen = m.altScreen
+	// Paint the whole frame with the active theme's surface. Zero never paints the
+	// terminal's own canvas, so without this a theme's text falls on the terminal
+	// background — fine when they share polarity, but a light theme's dark text on a
+	// dark terminal (or vice versa) is invisible, and a color theme never shows its
+	// real surface. Painting the panel makes every theme self-contained and legible
+	// on any terminal, and fills the transparent popup interiors (e.g. the /theme
+	// picker) too. Alt-screen only, so inline output never leaves a painted
+	// background behind in the user's scrollback after exit.
+	if m.altScreen {
+		view.BackgroundColor = zeroTheme.bgPanel
+	}
 	view.ReportFocus = m.notifier != nil
 	if m.wantsMouseCapture() {
 		// AllMotion (not CellMotion) is required for hover highlighting: it
@@ -3265,6 +3287,11 @@ func (m model) choosePicker() (tea.Model, tea.Cmd) {
 	}
 	item, ok := picker.current()
 	if !ok {
+		if picker.kind == pickerTheme {
+			// No selectable row (e.g. the filter matched nothing): undo any live
+			// preview so the palette matches the committed m.themeMode.
+			m.restoreCommittedTheme()
+		}
 		return m, nil
 	}
 	switch picker.kind {
@@ -3289,6 +3316,18 @@ func (m model) choosePicker() (tea.Model, tea.Cmd) {
 		if text != "" {
 			m.transcript = reduceTranscript(m.transcript, transcriptAction{kind: actionAppendSystem, text: text})
 		}
+	case pickerTheme:
+		// The hovered palette is already live from the preview; handleThemeCommand
+		// records the choice (m.themeMode) and re-applies it, and reports the switch.
+		text := ""
+		m, text = m.handleThemeCommand(item.Value)
+		m.transcript = reduceTranscript(m.transcript, transcriptAction{kind: actionAppendSystem, text: text})
+		if m.themeMode == themeAuto {
+			// Re-probe the terminal background so a committed `auto` re-detects
+			// light/dark instead of reusing the preview's reading — mirrors the
+			// text /theme dispatch (M17).
+			return m, tea.RequestBackgroundColor
+		}
 	}
 	return m, nil
 }
@@ -3544,6 +3583,13 @@ func (m model) handleSubmit() (tea.Model, tea.Cmd) {
 		m.transcript = reduceTranscript(m.transcript, transcriptAction{kind: actionAppendSystem, text: text})
 		return m, nil
 	case commandTheme:
+		// Bare `/theme` opens the popup picker (live preview on move, apply on
+		// Enter), matching /model and /effort. An explicit `/theme auto|dark|light`
+		// (or `/theme list`) still runs the text handler directly.
+		if strings.TrimSpace(command.text) == "" {
+			m.picker = m.newThemePicker()
+			return m, nil
+		}
 		text := ""
 		m, text = m.handleThemeCommand(command.text)
 		m.transcript = reduceTranscript(m.transcript, transcriptAction{kind: actionAppendSystem, text: text})

internal/tui/mouse.go

@@ -130,7 +130,7 @@ func (m model) handleMouse(msg tea.MouseMsg) (tea.Model, tea.Cmd) {
 			if m.modelPickerIsLoading() {
 				return m, nil
 			}
-			m.picker.move(-1)
+			m.pickerMoved(-1)
 			return m, nil
 		}
 		if m.suggestionsActive() {
@@ -162,7 +162,7 @@ func (m model) handleMouse(msg tea.MouseMsg) (tea.Model, tea.Cmd) {
 			if m.modelPickerIsLoading() {
 				return m, nil
 			}
-			m.picker.move(1)
+			m.pickerMoved(1)
 			return m, nil
 		}
 		if m.suggestionsActive() {
@@ -441,6 +441,9 @@ func (m *model) selectGenericPickerAtMouse(msg tea.MouseMsg) (mouseSelectionTarg
 		if hit.y == line {
 			index := start + offset
 			m.picker.selected = index
+			// Clicking (or hovering onto) a row live-previews it, like arrow keys,
+			// so the theme picker repaints before the confirming second click.
+			m.previewSelectedTheme()
 			return mouseSelectionTarget{Scope: "picker", Kind: int(m.picker.kind), Value: item.Value, Index: index}, true
 		}
 		line++

internal/tui/options.go

@@ -51,10 +51,14 @@ type Options struct {
 	PermissionMode  agent.PermissionMode
 	ReasoningEffort modelregistry.ReasoningEffort
 	ResponseStyle   string
-	// Theme is the operator's palette preference: "auto" (default), "dark", or
-	// "light". Set from the --theme flag; falls back to ZERO_THEME then auto.
-	Theme     string
-	UserAgent string
+	// Theme is the operator's palette preference: "auto" (default), a built-in
+	// ("dark"/"light"), or a registered color theme. Set from the --theme flag;
+	// falls back to ZERO_THEME, then the persisted SavedTheme, then auto.
+	Theme string
+	// SavedTheme is the theme persisted in user config (Preferences.Theme). Applied
+	// at startup below --theme and ZERO_THEME, so a /theme choice survives restart.
+	SavedTheme string
+	UserAgent  string
 
 	// Notify configures completion / awaiting-input notifications.
 	Notify config.NotifyConfig

internal/tui/picker.go

@@ -23,6 +23,7 @@ const (
 	pickerModel pickerKind = iota
 	pickerEffort
 	pickerSession
+	pickerTheme
 )
 
 // pickerItem is one selectable row: Label is shown, Value is passed to the
@@ -726,3 +727,44 @@ func (m model) newEffortPicker() *commandPicker {
 	}
 	return &commandPicker{kind: pickerEffort, title: "select reasoning effort", items: items, selected: selected}
 }
+
+// newThemePicker lists `auto` plus every registered theme as a popup, grouped into
+// Dark/Light sections (the registry is ordered dark-then-light so the group header
+// changes exactly once), preselecting the active preference. Bare `/theme` opens the
+// same overlay /model and /effort use. Moving the cursor live-previews each palette
+// (previewSelectedTheme); Enter commits the highlighted theme (choosePicker) and Esc
+// restores the previous one (Update's picker-cancel path). Items stay 1:1 with
+// themeModes and in the same order, so the popup and /theme state list agree.
+func (m model) newThemePicker() *commandPicker {
+	items := make([]pickerItem, 0, len(themeModes))
+	selected := 0
+	// `auto` sits at the top with an empty Group, so it renders header-less above
+	// the Dark/Light sections.
+	items = append(items, pickerItem{Label: string(themeAuto), Value: string(themeAuto), Meta: "match terminal"})
+	for _, entry := range themeRegistry {
+		group := "Light"
+		if entry.IsDark {
+			group = "Dark"
+		}
+		items = append(items, pickerItem{Group: group, Label: entry.Label, Value: entry.Name})
+		if entry.Name == string(m.themeMode) {
+			selected = len(items) - 1
+		}
+	}
+	// allItems lets the query filter restore rows on Backspace (one-way narrowing
+	// otherwise, since applyQuery falls back to the current items without it).
+	return &commandPicker{kind: pickerTheme, title: "select theme", items: items, allItems: append([]pickerItem{}, items...), selected: selected}
+}
+
+// pickerMoved advances the open picker's cursor by delta and live-previews the new
+// selection where the picker supports it — stepping through the /theme popup
+// repaints the UI in the hovered palette. Safe to call with no picker open. Callers
+// mutate through m.picker (a pointer) and the global theme, so the value receiver
+// is fine.
+func (m model) pickerMoved(delta int) {
+	if m.picker == nil {
+		return
+	}
+	m.picker.move(delta)
+	m.previewSelectedTheme()
+}

internal/tui/picker_test.go

@@ -639,14 +639,17 @@ func TestEffortPickerOpensForSupportedModel(t *testing.T) {
 	}
 }
 
-func TestThemeCommandOpensNoPicker(t *testing.T) {
-	// /theme keeps the existing shell-only message; no picker opens.
+func TestThemeCommandOpensPicker(t *testing.T) {
+	// Bare /theme opens the theme popup (live preview on move, apply on Enter),
+	// like /model and /effort. Full preview/commit/cancel behavior is covered in
+	// theme_picker_test.go; here we just pin that the no-arg command opens it.
+	defer applyTheme(themeDark, true)
 	m := newModel(context.Background(), Options{})
 	m.input.SetValue("/theme")
 	updated, _ := m.Update(testKey(tea.KeyEnter))
 	m = updated.(model)
-	if m.picker != nil {
-		t.Fatal("/theme should not open a picker")
+	if m.picker == nil || m.picker.kind != pickerTheme {
+		t.Fatalf("expected the theme picker to open, got %#v", m.picker)
 	}
 }
 

internal/tui/streaming_fade_test.go

@@ -32,9 +32,9 @@ func TestStreamingFadePaletteMonotonic(t *testing.T) {
 	// so per-bucket comparisons are byte-stable. The endpoint byte
 	// values are the contract — the hex strings are not.
 	fresh := rgbaOf(t, palette[0])
-	// Sanity: palette[0] must equal the accent endpoint (#759523).
-	if fresh.R != 0x75 || fresh.G != 0x95 || fresh.B != 0x23 {
-		t.Errorf("palette[0] RGBA = %v, want {R:0x75, G:0x95, B:0x23} (accent)", fresh)
+	// Sanity: palette[0] must equal the accent endpoint (#caff3f).
+	if fresh.R != 0xca || fresh.G != 0xff || fresh.B != 0x3f {
+		t.Errorf("palette[0] RGBA = %v, want {R:0xca, G:0xff, B:0x3f} (accent)", fresh)
 	}
 	last := rgbaOf(t, palette[streamingFadeSteps-1])
 	if last == fresh {

internal/tui/theme.go

@@ -12,7 +12,8 @@ import (
 // may be swapped at startup (background detection / ZERO_THEME / --theme) or live
 // via /theme. Colors are truecolor hex; lipgloss downsamples on limited displays
 // and renders plain text when there is no TTY (tests). Every renderer consumes
-// these named styles — no hex literal may appear outside this file.
+// these named styles — no hex literal may appear outside theme_palettes.go (the
+// palette tables + theme registry).
 type tuiTheme struct {
 	// Base tokens.
 	ink        lipgloss.Style // primary text
@@ -92,9 +93,10 @@ type tuiTheme struct {
 }
 
 // palette is the raw color-token table for one theme. buildTheme turns it into a
-// resolved tuiTheme. darkPalette and lightPalette are the ONLY place hex literals
-// live. All dark tints stay darker than ink so every pairing survives 256-color
-// downsampling; the light set is dark-on-light with the same intent inverted.
+// resolved tuiTheme. The palette literals and the ordered theme registry live in
+// theme_palettes.go (the only place hex literals live). Dark palettes keep tints
+// darker than ink so every pairing survives 256-color downsampling; light palettes
+// are dark-on-light with the same intent inverted.
 type palette struct {
 	panel     string // card backgrounds (the terminal canvas itself is never painted full-bleed)
 	promptBg  string // submitted user prompt background
@@ -125,81 +127,6 @@ type palette struct {
 	cardPerm  string // permission card border (amber mixed into line)
 }
 
-// darkPalette is the original Lime palette: a near-black chat surface with one
-// lime accent. bg (#070708) is the terminal's own canvas — deliberately never
-// painted — so no token references it.
-var darkPalette = palette{
-	panel:    "#0e0e10",
-	promptBg: "#262626",
-	line:     "#242429",
-	line2:    "#414147",
-	ink:      "#ececee",
-	muted:    "#9a9aa2", // secondary text — lifted so it clearly out-ranks faint
-	faint:    "#8a8a92", // hints/metadata — nudged up to separate from faintest
-	faintest: "#7c7c82", // line numbers/separators — pinned at the WCAG-AA floor on the dark panel
-	// Brand lime, softened from the original #caff3f (L 62%, S 100% — fully
-	// saturated, which read as glaring/neon everywhere it filled a block or
-	// bold-text surface: the composer prompt glyph, the permission popup's
-	// focused-option badge, the text-selection highlight). Two prior passes
-	// (#ade619 at L50/S80, #8db620 at L42/S70) were each confirmed too subtle
-	// in turn; settled at L 36%/S 62% — a darker, more olive lime. Contrast
-	// vs both black (onAccent) and the near-black panel stays comfortably
-	// above WCAG AA (~6.1:1 and ~5.6:1) with real margin to spare.
-	accent:    "#759523",
-	green:     "#5dd1a4",
-	red:       "#ff7a7a",
-	amber:     "#ffc25c",
-	blue:      "#7db4ff",
-	gitAdd:    "#7db87a",
-	gitDel:    "#b87a7a",
-	addBg:     "#18352c",
-	delBg:     "#241819",
-	addBgWord: "#2e654d", // changed span within an added line — brighter green (sep 1.83 vs addBg, addInk 7.1:1)
-	delBgWord: "#502d30", // changed span within a deleted line — brighter red (sep 1.44 vs delBg, delInk 7.7:1)
-	permBg:    "#1c1915",
-	selBg:     "#32401b", // selected row bg — brightened from #1d2114 so the highlighted row separates from the panel (sep 1.18→1.73) while ink label contrast stays ~9.4:1
-	addInk:    "#bdeed7",
-	delInk:    "#f2c4c4",
-	onAccent:  "#000000",
-	cardRun:   "#5a6b2e",
-	cardErr:   "#6b3434",
-	cardPerm:  "#6b5a2e",
-}
-
-// lightPalette is dark-on-light: light-gray surfaces with near-black ink. The
-// muted/faint/faintest grays get progressively LIGHTER (toward the surface) so the
-// same text hierarchy reads on white; the lime accent is darkened to keep contrast
-// against a light background, and the diff/permission tints become light surfaces.
-var lightPalette = palette{
-	panel:     "#ececed", // card backgrounds (slightly off-white)
-	promptBg:  "#dcdce0", // submitted prompt background
-	line:      "#cfcfd5", // default borders
-	line2:     "#b0b0b8", // emphasized borders
-	ink:       "#1b1b1d", // primary text (near-black)
-	muted:     "#4a4a52", // secondary text — darkened so it clearly out-ranks faint on light
-	faint:     "#57575f", // hints, metadata — nudged down to separate from faintest
-	faintest:  "#646469", // line numbers, separators — pinned at the WCAG-AA floor on the light panel
-	accent:    "#477006", // brand lime, darkened to AA contrast on light
-	green:     "#1c7a4a", // success / diff add
-	red:       "#c0322c", // errors / diff del
-	amber:     "#8f6200", // permission / warnings
-	blue:      "#1d5fd6", // grep locations
-	gitAdd:    "#2f7a3a", // footer PR diff additions
-	gitDel:    "#a83a3a", // footer PR diff deletions
-	addBg:     "#e2f3e6", // diff added-line bg (light green)
-	delBg:     "#fbe6e6", // diff deleted-line bg (light red)
-	addBgWord: "#97d3ab", // changed span within an added line — deeper green (sep 1.49 vs addBg, addInk 4.7:1)
-	delBgWord: "#f1b3b3", // changed span within a deleted line — deeper red (sep 1.48 vs delBg, delInk 4.6:1)
-	permBg:    "#fbf0d8", // permission card bg (light amber)
-	selBg:     "#cfe78f", // selected row bg (light accent) — deepened from #e7f2cd so it separates from the near-white panel (sep 1.01→1.15); ink label stays >12:1, faint ~5:1
-	addInk:    "#1d5b37", // added-line text
-	delInk:    "#8e2d2d", // deleted-line text
-	onAccent:  "#ffffff", // text on the (dark) accent/amber fills
-	cardRun:   "#94ad60", // running card border
-	cardErr:   "#cf9a9a", // errored card border
-	cardPerm:  "#c9ad7d", // permission card border
-}
-
 // buildTheme resolves a palette into the styles every renderer uses.
 func buildTheme(p palette) tuiTheme {
 	col := func(s string) color.Color { return lipgloss.Color(s) }

internal/tui/theme_palettes.go

@@ -0,0 +1,457 @@
+package tui
+
+import "strings"
+
+// theme_palettes.go is the sole home of raw color hex in the TUI: every palette
+// literal and the ordered theme registry live here, so theme.go stays hex-free
+// (just the palette struct, buildTheme, and the resolved tuiTheme). Adding a theme
+// is a new palette{...} literal plus one themeRegistry entry — nothing else.
+//
+// Contrast discipline: every palette must satisfy the same WCAG invariants the
+// built-ins do (asserted across the whole registry in theme_select_test.go): ink
+// and faintest ≥ AA on panel; onAccent ≥ AA on accent; addInk/delInk readable on
+// their diff bands and word spans; the muted>faint>faintest ramp monotonic toward
+// the surface; and selBg visibly separated from panel while its label stays legible.
+
+// darkPalette is the original Lime palette: a near-black chat surface with one
+// lime accent. bg (#070708) is the terminal's own canvas — deliberately never
+// painted — so no token references it.
+var darkPalette = palette{
+	panel:     "#0e0e10",
+	promptBg:  "#262626",
+	line:      "#242429",
+	line2:     "#414147",
+	ink:       "#ececee",
+	muted:     "#9a9aa2", // secondary text — lifted so it clearly out-ranks faint
+	faint:     "#8a8a92", // hints/metadata — nudged up to separate from faintest
+	faintest:  "#7c7c82", // line numbers/separators — pinned at the WCAG-AA floor on the dark panel
+	accent:    "#caff3f", // original bright lime (the brand accent)
+	green:     "#5dd1a4",
+	red:       "#ff7a7a",
+	amber:     "#ffc25c",
+	blue:      "#7db4ff",
+	gitAdd:    "#7db87a",
+	gitDel:    "#b87a7a",
+	addBg:     "#18352c",
+	delBg:     "#241819",
+	addBgWord: "#2e654d", // changed span within an added line — brighter green (sep 1.83 vs addBg, addInk 7.1:1)
+	delBgWord: "#502d30", // changed span within a deleted line — brighter red (sep 1.44 vs delBg, delInk 7.7:1)
+	permBg:    "#1c1915",
+	selBg:     "#32401b", // selected row bg — brightened from #1d2114 so the highlighted row separates from the panel (sep 1.18→1.73) while ink label contrast stays ~9.4:1
+	addInk:    "#bdeed7",
+	delInk:    "#f2c4c4",
+	onAccent:  "#000000",
+	cardRun:   "#5a6b2e",
+	cardErr:   "#6b3434",
+	cardPerm:  "#6b5a2e",
+}
+
+// draculaPalette — the Dracula scheme (dracula.com): muted-violet surface, purple
+// accent, high-chroma pink/green/cyan signals.
+var draculaPalette = palette{
+	panel:     "#282a36",
+	promptBg:  "#383c4d",
+	line:      "#363a4b",
+	line2:     "#484c62",
+	ink:       "#f8f8f2",
+	muted:     "#b9bccb",
+	faint:     "#a2a5b8",
+	faintest:  "#9195ac",
+	accent:    "#bd93f9",
+	green:     "#50fa7b",
+	red:       "#ff5555",
+	amber:     "#ffb86c",
+	blue:      "#8be9fd",
+	gitAdd:    "#77c58c",
+	gitDel:    "#d98d8d",
+	addBg:     "#1c3b2a",
+	delBg:     "#3a2026",
+	addBgWord: "#235035",
+	delBgWord: "#5e333b",
+	permBg:    "#322a1e",
+	selBg:     "#504482",
+	addInk:    "#cbf2dd",
+	delInk:    "#f4c9c9",
+	onAccent:  "#000000",
+	cardRun:   "#7c6aa6",
+	cardErr:   "#98505a",
+	cardPerm:  "#9a7c62",
+}
+
+// nordPalette — the Nord scheme (nordtheme.com): cool polar-night slate with a
+// frost-blue accent and desaturated aurora signals.
+var nordPalette = palette{
+	panel:     "#3b4252",
+	promptBg:  "#464f62",
+	line:      "#434c5e",
+	line2:     "#4c566a",
+	ink:       "#eceff4",
+	muted:     "#c8cfda",
+	faint:     "#b4bdcb",
+	faintest:  "#a5afc1",
+	accent:    "#88c0d0",
+	green:     "#a3be8c",
+	red:       "#bf616a",
+	amber:     "#d08770",
+	blue:      "#81a1c1",
+	gitAdd:    "#8ba077",
+	gitDel:    "#b0757d",
+	addBg:     "#37433a",
+	delBg:     "#45383d",
+	addBgWord: "#456d46",
+	delBgWord: "#6d4650",
+	permBg:    "#47413a",
+	selBg:     "#40688a",
+	addInk:    "#d6ecca",
+	delInk:    "#f0c6cb",
+	onAccent:  "#000000",
+	cardRun:   "#4c6672",
+	cardErr:   "#6b4a51",
+	cardPerm:  "#6a564d",
+}
+
+// gruvboxPalette — Gruvbox dark (medium): warm retro browns with an olive-green
+// accent and high-contrast cream ink.
+var gruvboxPalette = palette{
+	panel:     "#32302f",
+	promptBg:  "#3c3836",
+	line:      "#504945",
+	line2:     "#665c54",
+	ink:       "#ebdbb2",
+	muted:     "#c9b99a",
+	faint:     "#b7a78d",
+	faintest:  "#a89984",
+	accent:    "#8ec07c",
+	green:     "#b8bb26",
+	red:       "#fb4934",
+	amber:     "#fabd2f",
+	blue:      "#83a598",
+	gitAdd:    "#98971a",
+	gitDel:    "#cc241d",
+	addBg:     "#2f3a29",
+	delBg:     "#3b2b29",
+	addBgWord: "#3e5236",
+	delBgWord: "#593733",
+	permBg:    "#38331e",
+	selBg:     "#3d4e30",
+	addInk:    "#c5e6b0",
+	delInk:    "#f0c0bb",
+	onAccent:  "#000000",
+	cardRun:   "#6f8460",
+	cardErr:   "#a5493d",
+	cardPerm:  "#a5833a",
+}
+
+// tokyoNightPalette — Tokyo Night (storm): deep indigo surface, soft blue accent,
+// cool high-contrast ink.
+var tokyoNightPalette = palette{
+	panel:     "#1e2030",
+	promptBg:  "#2c3149",
+	line:      "#262a3d",
+	line2:     "#3b4261",
+	ink:       "#c8d3f5",
+	muted:     "#a9b1d0",
+	faint:     "#9099b2",
+	faintest:  "#838ba8",
+	accent:    "#82aaff",
+	green:     "#c3e88d",
+	red:       "#ff757f",
+	amber:     "#ffc777",
+	blue:      "#86e1fc",
+	gitAdd:    "#96bf7d",
+	gitDel:    "#c77e85",
+	addBg:     "#20303b",
+	delBg:     "#37222c",
+	addBgWord: "#2b5a4a",
+	delBgWord: "#5c2e3a",
+	permBg:    "#2a2419",
+	selBg:     "#2a385b",
+	addInk:    "#b8e4d3",
+	delInk:    "#f3c4cb",
+	onAccent:  "#000000",
+	cardRun:   "#4b5d8b",
+	cardErr:   "#7d4857",
+	cardPerm:  "#7d6954",
+}
+
+// catppuccinPalette — Catppuccin Mocha: soft lavender surface with a mauve accent
+// and pastel signals.
+var catppuccinPalette = palette{
+	panel:     "#1e1e2e",
+	promptBg:  "#34364b",
+	line:      "#313244",
+	line2:     "#45475a",
+	ink:       "#cdd6f4",
+	muted:     "#a6adc8",
+	faint:     "#9399b2",
+	faintest:  "#83889f",
+	accent:    "#cba6f7",
+	green:     "#a6e3a1",
+	red:       "#f38ba8",
+	amber:     "#f9e2af",
+	blue:      "#89b4fa",
+	gitAdd:    "#8cbf8a",
+	gitDel:    "#cc8a9b",
+	addBg:     "#24312b",
+	delBg:     "#3c2a32",
+	addBgWord: "#2f5140",
+	delBgWord: "#56333f",
+	permBg:    "#29261b",
+	selBg:     "#322e46",
+	addInk:    "#c4ecd6",
+	delInk:    "#f4cdd6",
+	onAccent:  "#000000",
+	cardRun:   "#7a6a99",
+	cardErr:   "#8a5b72",
+	cardPerm:  "#8d8274",
+}
+
+// oneDarkPalette — Atom One Dark: slate-gray surface with a blue accent.
+var oneDarkPalette = palette{
+	panel:     "#2e323b",
+	promptBg:  "#3a3f4a",
+	line:      "#393f4a",
+	line2:     "#4b525f",
+	ink:       "#abb2bf",
+	muted:     "#a2a9b6",
+	faint:     "#9aa1af",
+	faintest:  "#969cab",
+	accent:    "#61afef",
+	green:     "#98c379",
+	red:       "#e06c75",
+	amber:     "#e5c07b",
+	blue:      "#56b6c2",
+	gitAdd:    "#82a06a",
+	gitDel:    "#bd8087",
+	addBg:     "#2c382b",
+	delBg:     "#3a2d2f",
+	addBgWord: "#3d5a3a",
+	delBgWord: "#5c3e40",
+	permBg:    "#3c3826",
+	selBg:     "#354256",
+	addInk:    "#cdeab3",
+	delInk:    "#f0c3c7",
+	onAccent:  "#000000",
+	cardRun:   "#496c8c",
+	cardErr:   "#7c515b",
+	cardPerm:  "#7e735e",
+}
+
+// solarizedDarkPalette — Solarized Dark (Ethan Schoonover): the signature teal
+// base03/base02 surface with a cyan accent and the fixed accent wheel.
+var solarizedDarkPalette = palette{
+	panel:     "#073642",
+	promptBg:  "#0b3b46",
+	line:      "#123f48",
+	line2:     "#4b636c",
+	ink:       "#cdd6d6",
+	muted:     "#a9b3b3",
+	faint:     "#9ba5a5",
+	faintest:  "#929c9c",
+	accent:    "#3bb3a6", // solarized cyan, brightened to clear AA on the lifted base02 panel
+	green:     "#859900",
+	red:       "#dc322f",
+	amber:     "#b58900",
+	blue:      "#268bd2",
+	gitAdd:    "#93a05e",
+	gitDel:    "#c67b71",
+	addBg:     "#123f31",
+	delBg:     "#45302e",
+	addBgWord: "#1e5c44",
+	delBgWord: "#6a3f3a",
+	permBg:    "#2e2a18",
+	selBg:     "#17505a",
+	addInk:    "#c3ecd6",
+	delInk:    "#f2cbc6",
+	onAccent:  "#000000",
+	cardRun:   "#1d6b6c",
+	cardErr:   "#6d393d",
+	cardPerm:  "#5b6028",
+}
+
+// rosePinePalette — Rosé Pine (main): muted rose-quartz base with a soft-rose
+// accent and cool pine/foam signals.
+var rosePinePalette = palette{
+	panel:     "#1f1d2e",
+	promptBg:  "#2f2b47",
+	line:      "#2b2840",
+	line2:     "#403d52",
+	ink:       "#e0def4",
+	muted:     "#a8a3c0",
+	faint:     "#928ea9",
+	faintest:  "#8985a0",
+	accent:    "#ebbcba",
+	green:     "#31748f",
+	red:       "#eb6f92",
+	amber:     "#f6c177",
+	blue:      "#9ccfd8",
+	gitAdd:    "#5e88a2",
+	gitDel:    "#d589a7",
+	addBg:     "#1f2d3a",
+	delBg:     "#3a1f2d",
+	addBgWord: "#274b5e",
+	delBgWord: "#763a4f",
+	permBg:    "#4a3e3d",
+	selBg:     "#44415a",
+	addInk:    "#cfe8ef",
+	delInk:    "#f6c9cd",
+	onAccent:  "#000000",
+	cardRun:   "#7c6673",
+	cardErr:   "#7c4662",
+	cardPerm:  "#806857",
+}
+
+// everforestPalette — Everforest dark (medium): warm forest-gray surface with a
+// sage-green accent.
+var everforestPalette = palette{
+	panel:     "#333c43",
+	promptBg:  "#3d484d",
+	line:      "#414b52",
+	line2:     "#55636b",
+	ink:       "#d3c6aa",
+	muted:     "#b0bab0",
+	faint:     "#a4aea3",
+	faintest:  "#9ca99b",
+	accent:    "#a7c080",
+	green:     "#83c092",
+	red:       "#e67e80",
+	amber:     "#dbbc7f",
+	blue:      "#7fbbb3",
+	gitAdd:    "#8faa78",
+	gitDel:    "#c08888",
+	addBg:     "#2c3f37",
+	delBg:     "#3e3234",
+	addBgWord: "#324e3b",
+	delBgWord: "#573a3c",
+	permBg:    "#3c382d",
+	selBg:     "#3b482e",
+	addInk:    "#cfead0",
+	delInk:    "#f4cfcd",
+	onAccent:  "#000000",
+	cardRun:   "#798b6b",
+	cardErr:   "#9c676b",
+	cardPerm:  "#96896b",
+}
+
+// lightPalette is dark-on-light: a warm cream surface (so cards lift off the
+// terminal page, which Zero never paints) with near-black ink and an olive-lime
+// accent that keeps the brand identity while clearing AA on the light panel. The
+// muted/faint/faintest grays get progressively LIGHTER toward the surface; diff and
+// permission tints are light surfaces. Replaces the old flat cool-gray light set
+// whose muddy panel, sub-AA diff spans, and near-invisible selBg read as broken.
+var lightPalette = palette{
+	panel:     "#efebd4",
+	promptBg:  "#e3ddc2",
+	line:      "#d8d2bd",
+	line2:     "#b7b199",
+	ink:       "#22201a",
+	muted:     "#4b5149",
+	faint:     "#575e55",
+	faintest:  "#636a61",
+	accent:    "#54700a",
+	green:     "#1e725c",
+	red:       "#c02434",
+	amber:     "#8a5f00",
+	blue:      "#1f66c0",
+	gitAdd:    "#3d6f46",
+	gitDel:    "#a34a4a",
+	addBg:     "#ddf0df",
+	delBg:     "#f8dcdc",
+	addBgWord: "#a2daae",
+	delBgWord: "#f2b6b6",
+	permBg:    "#f7ebc6",
+	selBg:     "#d4e08f",
+	addInk:    "#0c4026",
+	delInk:    "#641a1d",
+	onAccent:  "#ffffff",
+	cardRun:   "#b0be7e",
+	cardErr:   "#d8b0a8",
+	cardPerm:  "#d6c496",
+}
+
+// solarizedLightPalette — Solarized Light: the base3/base2 cream surface with the
+// same fixed accent wheel as Solarized Dark, dark-on-light.
+var solarizedLightPalette = palette{
+	panel:     "#eee8d5",
+	promptBg:  "#e1d9be",
+	line:      "#d8d1bc",
+	line2:     "#c0b89e",
+	ink:       "#304049",
+	muted:     "#495b61",
+	faint:     "#506469",
+	faintest:  "#576b72",
+	accent:    "#0c665c", // solarized cyan, darkened for AA on the cream panel (with white onAccent)
+	green:     "#859900",
+	red:       "#dc322f",
+	amber:     "#7a5c00", // solarized yellow, darkened so white onAccent works on amber fills
+	blue:      "#268bd2",
+	gitAdd:    "#788d34",
+	gitDel:    "#ac4f50",
+	addBg:     "#dde8c6",
+	delBg:     "#f1ddd2",
+	addBgWord: "#b9d488", // deepened so the changed span separates from addBg (sep 1.28)
+	delBgWord: "#edc4b4",
+	permBg:    "#f0e6bd",
+	selBg:     "#a6d6c4",
+	addInk:    "#38480a",
+	delInk:    "#6f1614",
+	onAccent:  "#ffffff", // white — accent and amber are both dark on this light theme
+	cardRun:   "#7fbaaf",
+	cardErr:   "#d8837a",
+	cardPerm:  "#c4ae63",
+}
+
+// themeEntry is one registered theme: Name is the /theme value + ZERO_THEME/--theme
+// token (lowercase, kebab), Label is the picker display text, and IsDark groups the
+// picker (Dark/Light sections) and drives which built-in `auto` resolves to.
+type themeEntry struct {
+	Name    string
+	Label   string
+	Palette palette
+	IsDark  bool
+}
+
+// themeRegistry is the ordered source of truth for every selectable theme. Order is
+// the picker order: all Dark themes first, then all Light, with the brand
+// dark/light built-ins leading their groups. themeModes (theme_select.go) prepends
+// `auto` to this. Append here to add a theme — nothing else needs editing.
+var themeRegistry = []themeEntry{
+	{Name: "dark", Label: "dark", Palette: darkPalette, IsDark: true},
+	{Name: "dracula", Label: "Dracula", Palette: draculaPalette, IsDark: true},
+	{Name: "nord", Label: "Nord", Palette: nordPalette, IsDark: true},
+	{Name: "gruvbox", Label: "Gruvbox", Palette: gruvboxPalette, IsDark: true},
+	{Name: "tokyo-night", Label: "Tokyo Night", Palette: tokyoNightPalette, IsDark: true},
+	{Name: "catppuccin", Label: "Catppuccin", Palette: catppuccinPalette, IsDark: true},
+	{Name: "one-dark", Label: "One Dark", Palette: oneDarkPalette, IsDark: true},
+	{Name: "solarized-dark", Label: "Solarized Dark", Palette: solarizedDarkPalette, IsDark: true},
+	{Name: "rose-pine", Label: "Rosé Pine", Palette: rosePinePalette, IsDark: true},
+	{Name: "everforest", Label: "Everforest", Palette: everforestPalette, IsDark: true},
+	{Name: "light", Label: "light", Palette: lightPalette, IsDark: false},
+	{Name: "solarized-light", Label: "Solarized Light", Palette: solarizedLightPalette, IsDark: false},
+}
+
+// themeByName indexes the registry by lowercased name for O(1) lookup. Built as a
+// var initializer (not init()) so it is ready before themeModes' package-var
+// initializer calls themeNames().
+var themeByName = func() map[string]themeEntry {
+	byName := make(map[string]themeEntry, len(themeRegistry))
+	for _, entry := range themeRegistry {
+		byName[entry.Name] = entry
+	}
+	return byName
+}()
+
+// lookupTheme resolves a theme name (case/space-insensitive) to its entry.
+func lookupTheme(name string) (themeEntry, bool) {
+	entry, ok := themeByName[strings.ToLower(strings.TrimSpace(name))]
+	return entry, ok
+}
+
+// themeNames returns every registered theme name in registry (picker) order.
+func themeNames() []string {
+	names := make([]string, len(themeRegistry))
+	for index, entry := range themeRegistry {
+		names[index] = entry.Name
+	}
+	return names
+}

internal/tui/theme_picker_test.go

@@ -0,0 +1,340 @@
+package tui
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+
+	tea "charm.land/bubbletea/v2"
+)
+
+// A committed theme is written to user config and reloaded at startup (via
+// Options.SavedTheme -> resolveThemeMode), so a /theme choice survives restart.
+func TestThemeChoicePersistsAcrossRestart(t *testing.T) {
+	defer applyTheme(themeDark, true)
+	cfgPath := filepath.Join(t.TempDir(), "config.json")
+
+	// First session: pick a color theme via the /theme command (same commit path the
+	// picker uses).
+	m := newModel(context.Background(), Options{UserConfigPath: cfgPath})
+	m, _ = m.handleThemeCommand("dracula")
+	if m.themeMode != themeMode("dracula") {
+		t.Fatalf("themeMode = %q, want dracula", m.themeMode)
+	}
+	data, err := os.ReadFile(cfgPath)
+	if err != nil {
+		t.Fatalf("theme commit should have written config: %v", err)
+	}
+	var cfg struct {
+		Preferences struct {
+			Theme string `json:"theme"`
+		} `json:"preferences"`
+	}
+	if err := json.Unmarshal(data, &cfg); err != nil {
+		t.Fatalf("config is not valid JSON: %v", err)
+	}
+	if cfg.Preferences.Theme != "dracula" {
+		t.Fatalf("preferences.theme = %q, want dracula", cfg.Preferences.Theme)
+	}
+
+	// Second session: the persisted theme seeds startup (no flag / env).
+	restarted := newModel(context.Background(), Options{UserConfigPath: cfgPath, SavedTheme: "dracula"})
+	if restarted.themeMode != themeMode("dracula") {
+		t.Fatalf("restarted themeMode = %q, want dracula (from saved config)", restarted.themeMode)
+	}
+}
+
+// resolveThemeMode precedence: flag > ZERO_THEME > persisted config > auto.
+func TestResolveThemeModeConfigFallback(t *testing.T) {
+	if got := resolveThemeMode("", "", "nord"); got != themeMode("nord") {
+		t.Errorf("saved-only = %q, want nord", got)
+	}
+	if got := resolveThemeMode("dracula", "", "nord"); got != themeMode("dracula") {
+		t.Errorf("flag should beat saved: got %q, want dracula", got)
+	}
+	if got := resolveThemeMode("", "gruvbox", "nord"); got != themeMode("gruvbox") {
+		t.Errorf("env should beat saved: got %q, want gruvbox", got)
+	}
+	if got := resolveThemeMode("", "", "bogus-theme"); got != themeAuto {
+		t.Errorf("unknown saved theme should fall back to auto, got %q", got)
+	}
+}
+
+// themePickerRowIndex finds the picker row whose Value is name (index-independent,
+// so tests survive registry reordering / additions).
+func themePickerRowIndex(t *testing.T, p *commandPicker, name string) int {
+	t.Helper()
+	for i, item := range p.items {
+		if item.Value == name {
+			return i
+		}
+	}
+	t.Fatalf("theme picker has no row for %q", name)
+	return -1
+}
+
+// assertPreviewMatchesSelection checks the live palette equals the palette of the
+// currently highlighted theme row (the auto row has no palette of its own).
+func assertPreviewMatchesSelection(t *testing.T, m model) {
+	t.Helper()
+	sel := m.picker.items[m.picker.selected]
+	entry, ok := lookupTheme(sel.Value)
+	if !ok {
+		return
+	}
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r != mustR(t, entry.Palette.ink) {
+		t.Errorf("preview of %q did not apply its palette (ink mismatch)", sel.Value)
+	}
+}
+
+// Bare `/theme` opens the popup picker (like /model and /effort) with one row per
+// theme mode, preselecting the active preference. An explicit `/theme <mode>` must
+// keep taking the text path so scripts and the existing state view still work.
+func TestThemePickerOpensOnBareTheme(t *testing.T) {
+	defer applyTheme(themeDark, true)
+	m := newModel(context.Background(), Options{})
+	m.themeMode = themeLight
+	m.input.SetValue("/theme")
+
+	updated, cmd := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if cmd != nil {
+		t.Fatalf("opening the theme picker should not emit a cmd, got %T", cmd)
+	}
+	if m.picker == nil || m.picker.kind != pickerTheme {
+		t.Fatalf("expected the theme picker to open, got %#v", m.picker)
+	}
+	if len(m.picker.items) != len(themeModes) {
+		t.Fatalf("picker has %d items, want %d", len(m.picker.items), len(themeModes))
+	}
+	for i, want := range themeModes {
+		if m.picker.items[i].Value != want {
+			t.Errorf("item %d value = %q, want %q", i, m.picker.items[i].Value, want)
+		}
+	}
+	if got := m.picker.items[m.picker.selected].Value; got != string(themeLight) {
+		t.Errorf("preselected value = %q, want the active mode %q", got, themeLight)
+	}
+}
+
+// An explicit mode argument runs the text handler directly and never opens the
+// popup — guards the dispatch branch and keeps /theme <mode> scriptable.
+func TestThemeArgSkipsPicker(t *testing.T) {
+	defer applyTheme(themeDark, true)
+	m := newModel(context.Background(), Options{})
+	m.input.SetValue("/theme dark")
+
+	updated, _ := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if m.picker != nil {
+		t.Fatalf("explicit /theme dark must not open a picker, got %#v", m.picker)
+	}
+	if m.themeMode != themeDark {
+		t.Fatalf("after /theme dark, mode = %q", m.themeMode)
+	}
+}
+
+// Moving the cursor live-previews each palette: the global zeroTheme swaps as the
+// selection changes, so the whole UI (and the overlay) repaints in the hovered
+// theme without committing the preference.
+func TestThemePickerPreviewsOnMove(t *testing.T) {
+	defer applyTheme(themeDark, true)
+	m := newModel(context.Background(), Options{})
+	m.themeMode = themeDark
+	m.hasDarkBg = true
+	applyTheme(themeDark, true)
+	m.input.SetValue("/theme")
+	updated, _ := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+
+	// Each Down moves to the next theme and live-applies its palette; Up follows back.
+	for i := 0; i < 3; i++ {
+		updated, _ = m.Update(testKey(tea.KeyDown))
+		m = updated.(model)
+		assertPreviewMatchesSelection(t, m)
+	}
+	updated, _ = m.Update(testKey(tea.KeyUp))
+	m = updated.(model)
+	assertPreviewMatchesSelection(t, m)
+
+	// Preview must not have written the committed preference.
+	if m.themeMode != themeDark {
+		t.Errorf("preview mutated the committed mode to %q", m.themeMode)
+	}
+}
+
+// Enter on a fixed mode commits it: the palette stays applied, the preference is
+// recorded, the popup closes, and the switch is noted in the transcript.
+func TestThemePickerCommitAppliesAndRecords(t *testing.T) {
+	defer applyTheme(themeDark, true)
+	m := newModel(context.Background(), Options{})
+	m.themeMode = themeDark
+	m.hasDarkBg = true
+	applyTheme(themeDark, true)
+	m.input.SetValue("/theme")
+	updated, _ := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+
+	// Choose a color theme by locating its row (index-independent), then confirm.
+	m.picker.selected = themePickerRowIndex(t, m.picker, "dracula")
+	updated, cmd := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if cmd != nil {
+		t.Fatalf("committing a fixed theme should not emit a cmd, got %T", cmd)
+	}
+	if m.picker != nil {
+		t.Fatal("committing should close the picker")
+	}
+	if m.themeMode != themeMode("dracula") {
+		t.Fatalf("committed mode = %q, want dracula", m.themeMode)
+	}
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r != mustR(t, draculaPalette.ink) {
+		t.Error("commit did not leave the dracula palette applied")
+	}
+	if !transcriptContains(m.transcript, "active theme") {
+		t.Errorf("commit should record the switch in the transcript:\n%s", transcriptText(m.transcript))
+	}
+}
+
+// Committing `auto` re-probes the terminal background (like the text dispatch) so
+// the palette re-detects light/dark instead of reusing the preview's reading.
+func TestThemePickerAutoCommitReprobesBackground(t *testing.T) {
+	defer applyTheme(themeDark, true)
+	m := newModel(context.Background(), Options{})
+	m.themeMode = themeDark
+	m.input.SetValue("/theme")
+	updated, _ := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+
+	m.picker.selected = 0 // "auto"
+	updated, cmd := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if m.themeMode != themeAuto {
+		t.Fatalf("committed mode = %q, want auto", m.themeMode)
+	}
+	if cmd == nil {
+		t.Fatal("committing auto must return a background re-probe cmd")
+	}
+	if reflect.ValueOf(cmd).Pointer() != reflect.ValueOf(tea.RequestBackgroundColor).Pointer() {
+		t.Error("committing auto must return tea.RequestBackgroundColor")
+	}
+}
+
+// Typing to filter the list re-previews the newly-highlighted mode, so the applied
+// palette never diverges from the row the popup points at. Backspacing back to an
+// empty query re-previews the (restored) selection too.
+func TestThemePickerFilterRePreviews(t *testing.T) {
+	defer applyTheme(themeDark, true)
+	m := newModel(context.Background(), Options{})
+	m.themeMode = themeDark
+	m.hasDarkBg = true
+	applyTheme(themeDark, true)
+	m.input.SetValue("/theme")
+	updated, _ := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+
+	// Preview light by moving, then filter to "light" — the applied palette must
+	// track the filtered highlight (still light here), not lag behind.
+	updated, _ = m.Update(testKey(tea.KeyDown)) // dark -> light preview
+	m = updated.(model)
+	updated, _ = m.Update(testKeyText("l"))
+	m = updated.(model)
+	updated, _ = m.Update(testKeyText("i"))
+	m = updated.(model)
+	if got := m.picker.items[m.picker.selected].Value; got != string(themeLight) {
+		t.Fatalf("filter 'li' should highlight light, got %q", got)
+	}
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r != mustR(t, lightPalette.ink) {
+		t.Error("filtering to light did not keep the light palette previewed")
+	}
+
+	// Re-filter to "dark": highlight and preview must both switch to dark.
+	updated, _ = m.Update(testKey(tea.KeyBackspace))
+	m = updated.(model)
+	updated, _ = m.Update(testKey(tea.KeyBackspace))
+	m = updated.(model)
+	updated, _ = m.Update(testKeyText("d"))
+	m = updated.(model)
+	if got := m.picker.items[m.picker.selected].Value; got != string(themeDark) {
+		t.Fatalf("filter 'd' should highlight dark, got %q", got)
+	}
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r != mustR(t, darkPalette.ink) {
+		t.Error("filtering to dark did not re-preview the dark palette")
+	}
+}
+
+// A filter that matches nothing must not strand the last preview: the palette
+// falls back to the committed theme, and committing (Enter on the empty list) is a
+// clean no-op that leaves the committed mode and palette in agreement.
+func TestThemePickerEmptyFilterRestoresCommitted(t *testing.T) {
+	defer applyTheme(themeDark, true)
+	m := newModel(context.Background(), Options{})
+	m.themeMode = themeDark
+	m.hasDarkBg = true
+	applyTheme(themeDark, true)
+	m.input.SetValue("/theme")
+	updated, _ := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+
+	// Preview another theme by moving, then type a char that matches no theme name
+	// ('q' appears in none) -> the list empties.
+	updated, _ = m.Update(testKey(tea.KeyDown))
+	m = updated.(model)
+	updated, _ = m.Update(testKeyText("q"))
+	m = updated.(model)
+	if len(m.picker.items) != 0 {
+		t.Fatalf("filter 'q' should match no theme, got %d items", len(m.picker.items))
+	}
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r != mustR(t, darkPalette.ink) {
+		t.Error("an empty filter should restore the committed dark palette, not keep the preview")
+	}
+
+	// Enter on the empty list closes the picker without changing the committed
+	// preference, and leaves the palette matching it.
+	updated, _ = m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if m.picker != nil {
+		t.Fatal("Enter on an empty filter should close the picker")
+	}
+	if m.themeMode != themeDark {
+		t.Fatalf("empty-list commit must not change the mode, got %q", m.themeMode)
+	}
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r != mustR(t, darkPalette.ink) {
+		t.Error("after an empty-list commit the palette must match the committed dark mode")
+	}
+}
+
+// Esc dismisses the picker without choosing and restores the committed palette,
+// undoing whatever the live preview applied.
+func TestThemePickerEscRestoresCommittedTheme(t *testing.T) {
+	defer applyTheme(themeDark, true)
+	m := newModel(context.Background(), Options{})
+	m.themeMode = themeDark
+	m.hasDarkBg = true
+	applyTheme(themeDark, true)
+	m.input.SetValue("/theme")
+	updated, _ := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+
+	// Preview another theme by moving, then bail out.
+	updated, _ = m.Update(testKey(tea.KeyDown))
+	m = updated.(model)
+	assertPreviewMatchesSelection(t, m)
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r == mustR(t, darkPalette.ink) {
+		t.Fatal("expected a non-dark preview to be applied before Esc")
+	}
+	updated, _ = m.Update(testKey(tea.KeyEsc))
+	m = updated.(model)
+	if m.picker != nil {
+		t.Fatal("Esc should close the picker")
+	}
+	if m.themeMode != themeDark {
+		t.Fatalf("Esc must not change the committed mode, got %q", m.themeMode)
+	}
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r != mustR(t, darkPalette.ink) {
+		t.Error("Esc did not restore the committed dark palette")
+	}
+}

internal/tui/theme_select.go

@@ -1,6 +1,10 @@
 package tui
 
-import "strings"
+import (
+	"strings"
+
+	"github.com/Gitlawb/zero/internal/config"
+)
 
 // themeMode is the operator's palette preference.
 type themeMode string
@@ -11,34 +15,49 @@ const (
 	themeLight themeMode = "light"
 )
 
-// themeModes lists the values /theme accepts.
-var themeModes = []string{string(themeAuto), string(themeDark), string(themeLight)}
+// themeModes lists the values /theme accepts, in picker order: `auto` first, then
+// every registered theme (theme_palettes.go). It is the single ordered source
+// feeding both the picker and the /theme state list — adding a registry entry
+// extends it automatically.
+var themeModes = append([]string{string(themeAuto)}, themeNames()...)
 
-// resolveThemeMode picks the preference in precedence order: an explicit value
-// (the --theme flag, threaded via Options.Theme), then ZERO_THEME, then auto.
-func resolveThemeMode(flagValue, envValue string) themeMode {
-	for _, v := range []string{flagValue, envValue} {
-		switch strings.ToLower(strings.TrimSpace(v)) {
-		case "dark":
-			return themeDark
-		case "light":
-			return themeLight
-		case "auto":
+// resolveThemeMode picks the first accepted preference from candidates in
+// precedence order — the caller passes them highest-first: the --theme flag, then
+// ZERO_THEME, then the persisted config theme. A value is accepted if it is `auto`
+// or names a registered theme; unrecognized/blank values are skipped, and an empty
+// list (or all-unrecognized) falls back to auto.
+func resolveThemeMode(candidates ...string) themeMode {
+	for _, v := range candidates {
+		s := strings.ToLower(strings.TrimSpace(v))
+		if s == "" {
+			continue
+		}
+		if s == string(themeAuto) {
 			return themeAuto
 		}
+		if _, ok := lookupTheme(s); ok {
+			return themeMode(s)
+		}
 	}
 	return themeAuto
 }
 
-// validThemeMode reports whether s names a theme mode (for /theme validation).
+// validThemeMode reports whether s names a theme mode (for /theme validation):
+// `auto` or any registered theme.
 func validThemeMode(s string) bool {
-	switch themeMode(strings.ToLower(strings.TrimSpace(s))) {
-	case themeAuto, themeDark, themeLight:
+	s = strings.ToLower(strings.TrimSpace(s))
+	if s == string(themeAuto) {
 		return true
 	}
-	return false
+	_, ok := lookupTheme(s)
+	return ok
 }
 
+// ValidThemeArg reports whether s is an acceptable --theme / ZERO_THEME value
+// (`auto` or a registered theme name). Exported so the CLI flag validator shares
+// this one source of truth instead of hardcoding the theme list.
+func ValidThemeArg(s string) bool { return validThemeMode(s) }
+
 // applyTheme swaps the active palette (zeroTheme) and the globals derived from it
 // — the streaming-fade ramp and the static render cache — so a switch repaints
 // every subsequent render. For themeAuto it resolves to dark/light from
@@ -53,12 +72,13 @@ func applyTheme(mode themeMode, hasDarkBackground bool) themeMode {
 			resolved = themeLight
 		}
 	}
-	switch resolved {
-	case themeLight:
-		zeroTheme = buildTheme(lightPalette)
-	default:
-		zeroTheme = buildTheme(darkPalette)
+	// Resolve the (now concrete) mode to its registered palette; an unknown name
+	// falls back to the dark built-in so a bad value can never leave zeroTheme unset.
+	entry, ok := lookupTheme(string(resolved))
+	if !ok {
+		entry, _ = lookupTheme(string(themeDark))
 	}
+	zeroTheme = buildTheme(entry.Palette)
 	rebuildStreamingFadePalette()
 	if defaultRenderCache != nil {
 		defaultRenderCache.clear() // old-palette entries must not be reused
@@ -66,15 +86,45 @@ func applyTheme(mode themeMode, hasDarkBackground bool) themeMode {
 	return resolved
 }
 
-// handleThemeCommand implements /theme [auto|dark|light]: no arg shows state, a
-// valid mode switches the active palette live. Mirrors handleStyleCommand.
+// previewSelectedTheme makes the live palette match the theme picker's current
+// state: the highlighted mode when a row is selectable, or the committed
+// m.themeMode when the filter matches nothing. Called on every change to the
+// picker's selection or filter (arrow/wheel moves, mouse, and query typing) so the
+// whole UI — and the overlay itself — always renders the mode the popup points at,
+// and never strands on a stale preview. It only swaps the global zeroTheme via
+// applyTheme; m.themeMode keeps the committed preference so Esc can restore it. A
+// no-op unless a theme picker is open. Runs on the Update goroutine, like every
+// zeroTheme access.
+func (m model) previewSelectedTheme() {
+	if m.picker == nil || m.picker.kind != pickerTheme {
+		return
+	}
+	if item, ok := m.picker.current(); ok {
+		applyTheme(themeMode(item.Value), m.hasDarkBg)
+		return
+	}
+	// No selectable row (the filter matched nothing): fall back to the committed
+	// theme rather than leaving the previous preview applied.
+	m.restoreCommittedTheme()
+}
+
+// restoreCommittedTheme re-applies m.themeMode after a /theme preview is dismissed
+// without choosing (Esc). Preview never wrote m.themeMode, so it still holds the
+// real preference; re-applying repaints back to it.
+func (m model) restoreCommittedTheme() {
+	applyTheme(m.themeMode, m.hasDarkBg)
+}
+
+// handleThemeCommand implements /theme [name]: `list` shows state, a registered
+// theme name (or `auto`) switches the active palette live. Bare `/theme` opens the
+// picker at the dispatch layer, so it never reaches here empty. Mirrors handleStyleCommand.
 func (m model) handleThemeCommand(args string) (model, string) {
 	arg := strings.ToLower(strings.TrimSpace(args))
 	if arg == "" || arg == "list" {
 		return m, m.themeStateText()
 	}
 	if !validThemeMode(arg) {
-		return m, "Theme\nUnknown theme: " + arg + " (use auto, dark, or light)"
+		return m, "Theme\nUnknown theme: " + arg + " (use /theme with no argument to pick from the list)"
 	}
 	m.themeMode = themeMode(arg)
 	resolved := applyTheme(m.themeMode, m.hasDarkBg)
@@ -82,11 +132,31 @@ func (m model) handleThemeCommand(args string) (model, string) {
 	if m.themeMode == themeAuto {
 		active = "auto (" + string(resolved) + ")"
 	}
-	return m, strings.Join([]string{
+	lines := []string{
 		"Theme",
 		"active theme: " + active,
 		"Already-printed scrollback keeps its previous colors; new output uses the new theme.",
-	}, "\n")
+	}
+	// Commit path (both /theme <name> and the picker route through here): persist the
+	// choice so it survives restart. Previews call applyTheme directly and never reach here.
+	if note := m.persistThemePreference(); note != "" {
+		lines = append(lines, note)
+	}
+	return m, strings.Join(lines, "\n")
+}
+
+// persistThemePreference writes the committed theme to user config so it is applied
+// again at startup (via Options.SavedTheme -> resolveThemeMode). Best-effort: returns
+// a short note to surface on failure, or "" on success / when there is no config
+// path (e.g. tests). Never called from the live-preview path.
+func (m model) persistThemePreference() string {
+	if strings.TrimSpace(m.userConfigPath) == "" {
+		return ""
+	}
+	if _, err := config.SetTheme(m.userConfigPath, string(m.themeMode)); err != nil {
+		return "note: could not save theme preference (" + err.Error() + ")"
+	}
+	return ""
 }
 
 // themeStateText renders the /theme state view.
@@ -109,6 +179,6 @@ func (m model) themeStateText() string {
 				"available: " + strings.Join(themeModes, ", "),
 			},
 		}},
-		Hints: []string{"use /theme <auto|dark|light> to switch this TUI session"},
+		Hints: []string{"run /theme with no argument to open the picker, or /theme <name> to switch directly"},
 	})
 }

internal/tui/theme_select_test.go

@@ -52,24 +52,19 @@ func wcagRatio(t *testing.T, fg, bg string) float64 {
 // The word-level diff's brighter changed-span band must keep its text AA-readable
 // and stay clearly distinct from the base add/del band, on both themes.
 func TestDiffWordSpanContrast(t *testing.T) {
-	for _, c := range []struct {
-		name string
-		pal  palette
-	}{
-		{"dark", darkPalette},
-		{"light", lightPalette},
-	} {
-		if r := wcagRatio(t, c.pal.addInk, c.pal.addBgWord); r < 4.5 {
-			t.Errorf("%s: addInk on addBgWord %.2f < 4.5 (AA)", c.name, r)
+	for _, entry := range themeRegistry {
+		name, pal := entry.Name, entry.Palette
+		if r := wcagRatio(t, pal.addInk, pal.addBgWord); r < 4.5 {
+			t.Errorf("%s: addInk on addBgWord %.2f < 4.5 (AA)", name, r)
 		}
-		if r := wcagRatio(t, c.pal.delInk, c.pal.delBgWord); r < 4.5 {
-			t.Errorf("%s: delInk on delBgWord %.2f < 4.5 (AA)", c.name, r)
+		if r := wcagRatio(t, pal.delInk, pal.delBgWord); r < 4.5 {
+			t.Errorf("%s: delInk on delBgWord %.2f < 4.5 (AA)", name, r)
 		}
-		if sep := wcagRatio(t, c.pal.addBgWord, c.pal.addBg); sep < 1.2 {
-			t.Errorf("%s: addBgWord vs addBg separation %.2f < 1.2 (span not distinct)", c.name, sep)
+		if sep := wcagRatio(t, pal.addBgWord, pal.addBg); sep < 1.2 {
+			t.Errorf("%s: addBgWord vs addBg separation %.2f < 1.2 (span not distinct)", name, sep)
 		}
-		if sep := wcagRatio(t, c.pal.delBgWord, c.pal.delBg); sep < 1.2 {
-			t.Errorf("%s: delBgWord vs delBg separation %.2f < 1.2 (span not distinct)", c.name, sep)
+		if sep := wcagRatio(t, pal.delBgWord, pal.delBg); sep < 1.2 {
+			t.Errorf("%s: delBgWord vs delBg separation %.2f < 1.2 (span not distinct)", name, sep)
 		}
 	}
 }
@@ -78,18 +73,52 @@ func TestDiffWordSpanContrast(t *testing.T) {
 // AND keep its label readable. Guards the regression this fixes: the light
 // selBg (#e7f2cd) sat at 1.01 vs the panel (#ececed) — effectively invisible.
 func TestSelectedRowBandIsVisibleAndReadable(t *testing.T) {
-	for _, c := range []struct {
-		name string
-		pal  palette
-	}{
-		{"dark", darkPalette},
-		{"light", lightPalette},
-	} {
-		if r := wcagRatio(t, c.pal.ink, c.pal.selBg); r < 4.5 {
-			t.Errorf("%s: ink on selBg contrast %.2f < 4.5 — selected-row label unreadable", c.name, r)
+	for _, entry := range themeRegistry {
+		name, pal := entry.Name, entry.Palette
+		if r := wcagRatio(t, pal.ink, pal.selBg); r < 4.5 {
+			t.Errorf("%s: ink on selBg contrast %.2f < 4.5 — selected-row label unreadable", name, r)
 		}
-		if sep := wcagRatio(t, c.pal.selBg, c.pal.panel); sep < 1.10 {
-			t.Errorf("%s: selBg vs panel separation %.2f < 1.10 — selected row does not stand out", c.name, sep)
+		if sep := wcagRatio(t, pal.selBg, pal.panel); sep < 1.10 {
+			t.Errorf("%s: selBg vs panel separation %.2f < 1.10 — selected row does not stand out", name, sep)
+		}
+	}
+}
+
+// Every registered theme — not just the two built-ins — must clear WCAG AA on its
+// text-bearing tokens against the panel and keep the muted>faint>faintest>panel
+// gray ramp monotonic in its polarity (light-on-dark for dark themes, the inverse
+// for light themes). Guards that a newly-added color palette can't ship illegible.
+func TestAllThemesContrastAndHierarchy(t *testing.T) {
+	for _, entry := range themeRegistry {
+		pal := entry.Palette
+		for _, tok := range []struct {
+			name string
+			fg   string
+		}{
+			{"ink", pal.ink}, {"muted", pal.muted}, {"faint", pal.faint},
+			{"faintest", pal.faintest}, {"accent", pal.accent},
+		} {
+			if r := wcagRatio(t, tok.fg, pal.panel); r < 4.5 {
+				t.Errorf("%s %s on panel %.2f < 4.5 (WCAG AA)", entry.Name, tok.name, r)
+			}
+		}
+		if r := wcagRatio(t, pal.onAccent, pal.accent); r < 4.5 {
+			t.Errorf("%s onAccent on accent %.2f < 4.5 (WCAG AA)", entry.Name, r)
+		}
+		// Gray ramp ordered ink -> muted -> faint -> faintest -> panel; luminance
+		// rises toward the surface on light themes, falls on dark themes.
+		chain := []float64{
+			relLum(t, pal.ink), relLum(t, pal.muted), relLum(t, pal.faint),
+			relLum(t, pal.faintest), relLum(t, pal.panel),
+		}
+		for i := 1; i < len(chain); i++ {
+			ok := chain[i] > chain[i-1]
+			if entry.IsDark {
+				ok = chain[i] < chain[i-1]
+			}
+			if !ok {
+				t.Errorf("%s hierarchy not monotonic toward surface at %d: %v", entry.Name, i, chain)
+			}
 		}
 	}
 }

internal/tui/transcript_view.go

@@ -5,6 +5,11 @@ import "strings"
 func (m model) toggleDetailedTranscript() model {
 	m.transcriptDetailed = !m.transcriptDetailed
 	m.clearSuggestions()
+	if m.picker != nil && m.picker.kind == pickerTheme {
+		// Dropping a theme picker mid-preview must undo the live palette, or the
+		// previewed theme would stick while m.themeMode still holds the old one.
+		m.restoreCommittedTheme()
+	}
 	m.picker = nil
 	return m
 }