diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3755047e..313f70a7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -131,10 +131,12 @@ tagged. Until then, source builds report the version `dev`.
   GitHub issue/PR templates.
 - 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.
+- Twelve built-in color themes alongside the `dark`/`light` built-ins — `dracula`, `nord`, `gruvbox`,
+  `tokyo-night`, `catppuccin`, `one-dark`, `solarized-dark`, `rose-pine`, `everforest`,
+  `solarized-light`, `dune`, and `neon` — selectable via `/theme <name>`, `--theme <name>`, or
+  `ZERO_THEME`. Every palette is contrast-audited to WCAG AA, and the new presets are additionally
+  audited after xterm-256 downsampling; see [docs/THEMES.md](docs/THEMES.md). 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`,
diff --git a/README.md b/README.md
index 86ce5d13..2fdc8ea5 100644
--- a/README.md
+++ b/README.md
@@ -322,7 +322,7 @@ manifest.
 | Control | Effect |
 |---|---|
 | `NO_COLOR=<anything>` | disables color output |
-| `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`) |
+| `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`, `neon`, `solarized-light`, `dune`) |
 | `--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 |
@@ -350,6 +350,7 @@ go run ./cmd/zero-release build --goos windows --goarch amd64 --output dist/zero
 
 - [Install](docs/INSTALL.md)
 - [Update flow](docs/UPDATE.md)
+- [Themes](docs/THEMES.md)
 - [Stream-JSON protocol](docs/STREAM_JSON_PROTOCOL.md)
 - [Specialists](docs/SPECIALISTS.md)
 - [GitHub Action](docs/GITHUB_ACTION.md)
diff --git a/README_ZH.md b/README_ZH.md
index 014697ef..bab0968f 100644
--- a/README_ZH.md
+++ b/README_ZH.md
@@ -252,7 +252,7 @@ zero update           检查更新版本
 | 控制 | 效果 |
 |---|---|
 | `NO_COLOR=<任意值>` | 禁用颜色输出 |
-| `ZERO_THEME=<名称>` | 选择启动主题（`auto`、`dark`、`light`，或颜色主题如 `dracula`、`nord`、`gruvbox`、`tokyo-night`、`catppuccin`、`one-dark`、`solarized-dark`、`rose-pine`、`everforest`、`solarized-light`） |
+| `ZERO_THEME=<名称>` | 选择启动主题（`auto`、`dark`、`light`，或颜色主题如 `dracula`、`nord`、`gruvbox`、`tokyo-night`、`catppuccin`、`one-dark`、`solarized-dark`、`rose-pine`、`everforest`、`neon`、`solarized-light`、`dune`） |
 | `--theme <名称>` | 从 CLI 选择 TUI 主题（相同名称） |
 | `/theme` | 在 TUI 中打开主题选择器（实时预览；`/theme <名称>` 直接切换） |
 | `ZERO_NO_FADE=1` | 禁用流式淡入动画 |
@@ -279,6 +279,7 @@ go run ./cmd/zero-release build --goos windows --goarch amd64 --output dist/zero
 
 - [安装](docs/INSTALL.md)
 - [更新流程](docs/UPDATE.md)
+- [主题](docs/THEMES.md)
 - [Stream-JSON 协议](docs/STREAM_JSON_PROTOCOL.md)
 - [专家](docs/SPECIALISTS.md)
 - [GitHub Action](docs/GITHUB_ACTION.md)
diff --git a/docs/THEMES.md b/docs/THEMES.md
new file mode 100644
index 00000000..d5d14d16
--- /dev/null
+++ b/docs/THEMES.md
@@ -0,0 +1,39 @@
+# TUI Themes
+
+Zero's TUI ships a set of built-in color themes. Pick one with `--theme <name>`,
+the `ZERO_THEME` environment variable, or the `/theme <name>` command while
+running. `auto` (the default) follows the terminal's detected background.
+
+Run `/theme` with no argument to open a picker: move through the list to
+live-preview each theme, press Enter to apply the highlighted one, or Esc to
+cancel and restore the previously active theme. Run `/theme list` to print
+the active theme and the registered names without opening the picker.
+
+## Dune (`dune`)
+
+A warm sand-and-cream palette: sand/cream surface, charcoal ink, and a soft
+amber accent.
+
+## Neon (`neon`)
+
+A neon-on-black palette: pitch-black surface, bright green ink, and a cyan accent.
+
+## Adding a theme
+
+Every theme is a `palette` (a table of color hex tokens) plus one entry in
+`themeRegistry`, both in `internal/tui/theme_palettes.go`. `buildTheme` in
+`internal/tui/theme.go` turns a `palette` into the resolved `lipgloss.Style`
+set every renderer reads from the active `zeroTheme`. Adding a theme means
+adding a new `palette{...}` literal, a `themeRegistry` entry, and test
+coverage for the new palette (see below).
+
+Registry-wide tests in `internal/tui/theme_select_test.go` assert the basic
+WCAG AA text tokens, the gray-ramp order, the diff word-span pairs, and the
+selected-row band for every entry. The rendered-surface invariants beyond
+those (permission surfaces, selected-row secondary text, diff gutters, and
+the xterm-256 downsampling checks) are asserted per palette, not against the
+whole registry: `TestExtendedThemeContrastInvariants` and
+`TestExtendedThemeANSI256Contrast` enumerate the palettes they cover. A new
+theme must be added to those tests (or given equivalent palette-specific
+assertions), or CI can stay green while its permission, selected-row, and
+diff surfaces ship unreadable.
diff --git a/internal/tui/theme_palettes.go b/internal/tui/theme_palettes.go
index 7230a5f1..054dfdd1 100644
--- a/internal/tui/theme_palettes.go
+++ b/internal/tui/theme_palettes.go
@@ -333,6 +333,38 @@ var everforestPalette = palette{
 	cardPerm:  "#96896b",
 }
 
+// neonPalette is a neon-on-black color scheme: pitch-black surface with
+// neon green ink and a cyan accent.
+var neonPalette = palette{
+	panel:     "#050b06",
+	promptBg:  "#0c180d",
+	line:      "#1c3820",
+	line2:     "#2c5230",
+	ink:       "#c9ffd2",
+	muted:     "#80db8f",
+	faint:     "#6eca7d",
+	faintest:  "#74c468", // brightened from #58af69 so line numbers quantize to #87d75f and stay AA on the xterm-green addBg (#005f00); still dimmer than faint, keeping the ramp monotonic
+	accent:    "#00e5c8",
+	green:     "#39ff6a",
+	red:       "#ff4d6d",
+	amber:     "#f4ff3a",
+	blue:      "#22e0ff",
+	gitAdd:    "#4fdc6a",
+	gitDel:    "#ff6f80",
+	addBg:     "#083c10", // quantizes to xterm green #005f00 instead of the same gray as delBg, keeping add/del rows distinct on 256-color terminals
+	delBg:     "#3c0810", // quantizes to xterm red #5f0000 (see addBg)
+	addBgWord: "#147828", // quantizes to xterm green #008700, distinct from both addBg's #005f00 and delBgWord's red
+	delBgWord: "#74202e", // quantizes to xterm red #870000 (see addBgWord)
+	permBg:    "#2a2a0c",
+	selBg:     "#123a1e",
+	addInk:    "#ecffdc", // quantizes to #ffffd7, which keeps AA on addBgWord's xterm #008700 (the old #c8ffcf quantized to #d7ffd7 at 4.29:1)
+	delInk:    "#ffd0d6",
+	onAccent:  "#001410",
+	cardRun:   "#1f8a6e",
+	cardErr:   "#9a4042", // raised from #8a2f42 for the 3:1 non-text border threshold against the panel (2.43:1 before), holding after xterm-256 quantization too
+	cardPerm:  "#8a8a1f",
+}
+
 // 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
@@ -401,6 +433,38 @@ var solarizedLightPalette = palette{
 	cardPerm:  "#c4ae63",
 }
 
+// dunePalette is a warm sand-and-cream color scheme: sand/cream surface,
+// charcoal ink, and a soft amber accent.
+var dunePalette = palette{
+	panel:     "#f2e9d8",
+	promptBg:  "#e9dcbf",
+	line:      "#d9c7a3",
+	line2:     "#c2a97c",
+	ink:       "#2b241a",
+	muted:     "#473e32",
+	faint:     "#554a3a",
+	faintest:  "#655648",
+	accent:    "#724028", // darkened from #8f5215 for AA on selBg (5.46:1) that also survives ANSI-256 downsampling (quantizes to #444444, 6.47:1 on quantized selBg; the previous #7c4712 quantized to #875f00 at 3.81:1)
+	green:     "#38572a",
+	red:       "#872d24", // darkened from #963328 so delBg contrast survives ANSI-256 downsampling (true 6.57:1, 256 7.86:1)
+	amber:     "#6d4600",
+	blue:      "#2f5680", // darkened from #3d6a9e for AA on selBg (was 3.61:1, now 4.90:1)
+	gitAdd:    "#38572a",
+	gitDel:    "#963328",
+	addBg:     "#dcecd0",
+	delBg:     "#f5dbd5",
+	addBgWord: "#b9dc9e",
+	delBgWord: "#eebba9",
+	permBg:    "#f0dfae",
+	selBg:     "#e0cf98",
+	addInk:    "#264018",
+	delInk:    "#5c1810",
+	onAccent:  "#fdf6ea",
+	cardRun:   "#b08a4a",
+	cardErr:   "#b57560",
+	cardPerm:  "#c2a04a",
+}
+
 // 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.
@@ -426,8 +490,10 @@ var themeRegistry = []themeEntry{
 	{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: "neon", Label: "Neon", Palette: neonPalette, IsDark: true},
 	{Name: "light", Label: "light", Palette: lightPalette, IsDark: false},
 	{Name: "solarized-light", Label: "Solarized Light", Palette: solarizedLightPalette, IsDark: false},
+	{Name: "dune", Label: "Dune", Palette: dunePalette, IsDark: false},
 }
 
 // themeByName indexes the registry by lowercased name for O(1) lookup. Built as a
diff --git a/internal/tui/theme_select_test.go b/internal/tui/theme_select_test.go
index cb8e0ef9..d586fdde 100644
--- a/internal/tui/theme_select_test.go
+++ b/internal/tui/theme_select_test.go
@@ -1,6 +1,7 @@
 package tui
 
 import (
+	"fmt"
 	"math"
 	"strconv"
 	"strings"
@@ -261,6 +262,225 @@ func TestHandleThemeCommand(t *testing.T) {
 	}
 }
 
+func TestNewThemePresetsWired(t *testing.T) {
+	neon, ok := lookupTheme("neon")
+	if !ok {
+		t.Fatal("theme 'neon' is not registered")
+	}
+	if !neon.IsDark {
+		t.Error("theme 'neon' should be marked as dark")
+	}
+
+	dune, ok := lookupTheme("dune")
+	if !ok {
+		t.Fatal("theme 'dune' is not registered")
+	}
+	if dune.IsDark {
+		t.Error("theme 'dune' should be marked as light")
+	}
+
+	for _, name := range []string{"neon", "dune"} {
+		if !validThemeMode(name) {
+			t.Errorf("%q should be a valid --theme/ZERO_THEME value", name)
+		}
+	}
+
+	if !contains(themeModes, "neon") || !contains(themeModes, "dune") {
+		t.Errorf("themeModes = %v, want it to include neon and dune (the /theme picker list)", themeModes)
+	}
+}
+
+// The --theme flag and ZERO_THEME both resolve through resolveThemeMode, and
+// applyTheme must actually swap zeroTheme to the resolved preset's own palette,
+// not silently fall back to a built-in.
+func TestNewThemePresetsResolveThroughCLIAndEnvPath(t *testing.T) {
+	defer applyTheme(themeDark, true)
+
+	if got := resolveThemeMode("dune", ""); got != themeMode("dune") {
+		t.Fatalf(`resolveThemeMode("dune", "") = %q, want "dune"`, got)
+	}
+	if got := resolveThemeMode("", "neon"); got != themeMode("neon") {
+		t.Fatalf(`resolveThemeMode("", "neon") = %q, want "neon"`, got)
+	}
+
+	applyTheme(themeMode("dune"), true)
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r != mustR(t, dunePalette.ink) {
+		t.Error("applying \"dune\" did not swap zeroTheme to the dune palette")
+	}
+
+	applyTheme(themeMode("neon"), true)
+	if r, _, _, _ := zeroTheme.inkColor.RGBA(); r != mustR(t, neonPalette.ink) {
+		t.Error("applying \"neon\" did not swap zeroTheme to the neon palette")
+	}
+}
+
+func TestExtendedThemeContrastInvariants(t *testing.T) {
+	// Skip validation for old built-in themes if they have established, non-compliant palettes,
+	// but enforce strict compliance on the newly introduced 'neon' and 'dune' themes.
+	for _, entry := range themeRegistry {
+		if entry.Name != "neon" && entry.Name != "dune" {
+			continue
+		}
+		name, pal := entry.Name, entry.Palette
+
+		// Finding 1: Permission and status/success surfaces
+		if r := wcagRatio(t, pal.amber, pal.permBg); r < 4.5 {
+			t.Errorf("%s: amber on permBg contrast %.2f < 4.5", name, r)
+		}
+		if r := wcagRatio(t, pal.onAccent, pal.amber); r < 4.5 {
+			t.Errorf("%s: onAccent on amber contrast %.2f < 4.5", name, r)
+		}
+		if r := wcagRatio(t, pal.green, pal.panel); r < 4.5 {
+			t.Errorf("%s: green on panel contrast %.2f < 4.5", name, r)
+		}
+		if r := wcagRatio(t, pal.amber, pal.panel); r < 4.5 {
+			t.Errorf("%s: amber on panel contrast %.2f < 4.5", name, r)
+		}
+		if r := wcagRatio(t, pal.red, pal.panel); r < 4.5 {
+			t.Errorf("%s: red on panel contrast %.2f < 4.5", name, r)
+		}
+
+		// Finding 2: Selected row secondary text
+		if r := wcagRatio(t, pal.faint, pal.selBg); r < 4.5 {
+			t.Errorf("%s: faint on selBg contrast %.2f < 4.5", name, r)
+		}
+		if r := wcagRatio(t, pal.faintest, pal.selBg); r < 4.5 {
+			t.Errorf("%s: faintest on selBg contrast %.2f < 4.5", name, r)
+		}
+
+		// Finding 3: Diff gutter pairings
+		if r := wcagRatio(t, pal.faintest, pal.addBg); r < 4.5 {
+			t.Errorf("%s: faintest on addBg contrast %.2f < 4.5", name, r)
+		}
+		if r := wcagRatio(t, pal.faintest, pal.delBg); r < 4.5 {
+			t.Errorf("%s: faintest on delBg contrast %.2f < 4.5", name, r)
+		}
+		if r := wcagRatio(t, pal.green, pal.addBg); r < 4.5 {
+			t.Errorf("%s: green on addBg contrast %.2f < 4.5", name, r)
+		}
+		if r := wcagRatio(t, pal.red, pal.delBg); r < 4.5 {
+			t.Errorf("%s: red on delBg contrast %.2f < 4.5", name, r)
+		}
+	}
+}
+
+// hexChannels splits a #rrggbb token into its 8-bit channels.
+func hexChannels(t *testing.T, hexColor string) (int, int, int) {
+	t.Helper()
+	h := strings.TrimPrefix(hexColor, "#")
+	v, err := strconv.ParseUint(h, 16, 32)
+	if err != nil || len(h) != 6 {
+		t.Fatalf("bad hex %q", hexColor)
+	}
+	return int((v >> 16) & 0xff), int((v >> 8) & 0xff), int(v & 0xff)
+}
+
+// xterm256Hex returns the nearest xterm-256 color (the 6x6x6 cube plus the
+// 24-step grayscale ramp, by squared RGB distance): how a terminal without
+// truecolor support downsamples the palette's hex tokens before rendering.
+func xterm256Hex(t *testing.T, hexColor string) string {
+	t.Helper()
+	r, g, b := hexChannels(t, hexColor)
+	levels := []int{0, 95, 135, 175, 215, 255}
+	bestR, bestG, bestB := 0, 0, 0
+	bestDistance := math.MaxFloat64
+	try := func(cr, cg, cb int) {
+		d := float64((r-cr)*(r-cr) + (g-cg)*(g-cg) + (b-cb)*(b-cb))
+		if d < bestDistance {
+			bestDistance, bestR, bestG, bestB = d, cr, cg, cb
+		}
+	}
+	for _, cr := range levels {
+		for _, cg := range levels {
+			for _, cb := range levels {
+				try(cr, cg, cb)
+			}
+		}
+	}
+	for i := 0; i < 24; i++ {
+		gray := 8 + 10*i
+		try(gray, gray, gray)
+	}
+	return fmt.Sprintf("#%02x%02x%02x", bestR, bestG, bestB)
+}
+
+// Hex-level AA does not guarantee the rendered pairs hold on a 256-color
+// terminal, which quantizes every token to its nearest xterm entry first.
+// Guard the pairs that regressed: Dune's selected-row affordances (accent
+// caret/favorite star and blue local-model dot over selBg via onSel) and
+// Neon's diff bands, whose previous values all quantized to the same grays.
+func TestExtendedThemeANSI256Contrast(t *testing.T) {
+	palettes := map[string]palette{}
+	for _, entry := range themeRegistry {
+		palettes[entry.Name] = entry.Palette
+	}
+	q := func(hexColor string) string { return xterm256Hex(t, hexColor) }
+
+	dune := palettes["dune"]
+	for _, pair := range []struct{ name, fg, bg string }{
+		{"accent on selBg", dune.accent, dune.selBg},
+		{"blue on selBg", dune.blue, dune.selBg},
+		{"faintest on selBg", dune.faintest, dune.selBg},
+		{"ink on selBg", dune.ink, dune.selBg},
+	} {
+		if r := wcagRatio(t, q(pair.fg), q(pair.bg)); r < 4.5 {
+			t.Errorf("dune: %s = %.2f < 4.5 after xterm-256 quantization (%s on %s)", pair.name, r, q(pair.fg), q(pair.bg))
+		}
+	}
+
+	neon := palettes["neon"]
+	greenish := func(hexColor string) bool {
+		r, g, b := hexChannels(t, hexColor)
+		return g > r && g > b
+	}
+	reddish := func(hexColor string) bool {
+		r, g, b := hexChannels(t, hexColor)
+		return r > g && r > b
+	}
+	if q(neon.addBg) == q(neon.delBg) || !greenish(q(neon.addBg)) || !reddish(q(neon.delBg)) {
+		t.Errorf("neon: add/del row bands lose their green/red identity after quantization: addBg %s -> %s, delBg %s -> %s",
+			neon.addBg, q(neon.addBg), neon.delBg, q(neon.delBg))
+	}
+	if q(neon.addBgWord) == q(neon.delBgWord) || !greenish(q(neon.addBgWord)) || !reddish(q(neon.delBgWord)) {
+		t.Errorf("neon: word-span bands lose their green/red identity after quantization: addBgWord %s -> %s, delBgWord %s -> %s",
+			neon.addBgWord, q(neon.addBgWord), neon.delBgWord, q(neon.delBgWord))
+	}
+	if q(neon.addBgWord) == q(neon.addBg) {
+		t.Errorf("neon: changed span is indistinguishable from its add row after quantization (both %s)", q(neon.addBg))
+	}
+	if q(neon.delBgWord) == q(neon.delBg) {
+		t.Errorf("neon: changed span is indistinguishable from its del row after quantization (both %s)", q(neon.delBg))
+	}
+	if r := wcagRatio(t, q(neon.green), q(neon.addBg)); r < 4.5 {
+		t.Errorf("neon: green on addBg = %.2f < 4.5 after quantization", r)
+	}
+	if r := wcagRatio(t, q(neon.red), q(neon.delBg)); r < 4.5 {
+		t.Errorf("neon: red on delBg = %.2f < 4.5 after quantization", r)
+	}
+	// The two rendered diff-content pairs a 256-color terminal actually
+	// shows: line numbers (faintest on addBg/delBg) and highlighted changed
+	// spans (addInk/delInk on their word bands).
+	for _, pair := range []struct{ name, fg, bg string }{
+		{"faintest on addBg", neon.faintest, neon.addBg},
+		{"faintest on delBg", neon.faintest, neon.delBg},
+		{"addInk on addBgWord", neon.addInk, neon.addBgWord},
+		{"delInk on delBgWord", neon.delInk, neon.delBgWord},
+	} {
+		if r := wcagRatio(t, q(pair.fg), q(pair.bg)); r < 4.5 {
+			t.Errorf("neon: %s = %.2f < 4.5 after quantization (%s on %s)", pair.name, r, q(pair.fg), q(pair.bg))
+		}
+	}
+	// Error-card borders are non-text UI components: they need 3:1 against
+	// the panel (WCAG 1.4.11) to be distinguishable at all, in both truecolor
+	// and 256-color renderings.
+	if r := wcagRatio(t, neon.cardErr, neon.panel); r < 3.0 {
+		t.Errorf("neon: cardErr border on panel = %.2f < 3.0", r)
+	}
+	if r := wcagRatio(t, q(neon.cardErr), q(neon.panel)); r < 3.0 {
+		t.Errorf("neon: cardErr border on panel = %.2f < 3.0 after quantization", r)
+	}
+}
+
 func mustR(t *testing.T, hex string) uint32 {
 	t.Helper()
 	r, _, _, _ := lipgloss.Color(hex).RGBA()