diff --git a/ui/src/styles/base.css b/ui/src/styles/base.css
index e25ddc21f448..7ea131ac0215 100644
--- a/ui/src/styles/base.css
+++ b/ui/src/styles/base.css
@@ -20,7 +20,9 @@
   --chrome: rgba(14, 16, 21, 0.96);
   --chrome-strong: rgba(14, 16, 21, 0.98);
 
-  /* Text - Clean contrast */
+  /* Text - Clean contrast
+   * Keep --muted AA on dark surfaces; do not dim muted body text with opacity. */
+
   --text: #d4d4d8;
   --text-strong: #f4f4f5;
   --chat-text: #d4d4d8;
diff --git a/ui/src/styles/chat/grouped.css b/ui/src/styles/chat/grouped.css
index 036a01c9d246..37a4d9a6d93f 100644
--- a/ui/src/styles/chat/grouped.css
+++ b/ui/src/styles/chat/grouped.css
@@ -280,8 +280,8 @@
 
 .chat-group-timestamp {
   font-size: 12px; /* was 11px */
+  /* Keep full-opacity --muted: opacity < 1 composites below WCAG AA on dark surfaces. */
   color: var(--muted);
-  opacity: 0.7;
   line-height: 1.2;
 }
 
diff --git a/ui/src/styles/chat/layout.css b/ui/src/styles/chat/layout.css
index f7a5ea9b7a59..04781d689b21 100644
--- a/ui/src/styles/chat/layout.css
+++ b/ui/src/styles/chat/layout.css
@@ -3398,9 +3398,9 @@ openclaw-chat-page {
 
 .slash-menu-args {
   font-size: 0.75rem;
+  /* Full-opacity --muted keeps slash-arg hints at WCAG AA on dark surfaces. */
   color: var(--muted);
   font-family: var(--mono);
-  opacity: 0.65;
 }
 
 .slash-menu-desc {
diff --git a/ui/src/styles/theme-contrast.test.ts b/ui/src/styles/theme-contrast.test.ts
new file mode 100644
index 000000000000..ab21d8e059bd
--- /dev/null
+++ b/ui/src/styles/theme-contrast.test.ts
@@ -0,0 +1,149 @@
+import { readFileSync } from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import { describe, expect, it } from "vitest";
+
+const here = path.dirname(fileURLToPath(import.meta.url));
+
+function relativeLuminance(hex: string): number {
+  const channels = hex
+    .replace("#", "")
+    .match(/.{2}/g)
+    ?.map((part) => Number.parseInt(part, 16) / 255)
+    .map((channel) => (channel <= 0.03928 ? channel / 12.92 : ((channel + 0.055) / 1.055) ** 2.4));
+  if (!channels || channels.length !== 3) {
+    throw new Error(`invalid color: ${hex}`);
+  }
+  const r = channels[0];
+  const g = channels[1];
+  const b = channels[2];
+  if (r === undefined || g === undefined || b === undefined) {
+    throw new Error(`invalid color: ${hex}`);
+  }
+  return 0.2126 * r + 0.7152 * g + 0.0722 * b;
+}
+
+function contrastRatio(foreground: string, background: string): number {
+  const luminances = [relativeLuminance(foreground), relativeLuminance(background)].toSorted(
+    (a, b) => b - a,
+  );
+  const lighter = luminances[0];
+  const darker = luminances[1];
+  if (lighter === undefined || darker === undefined) {
+    throw new Error("expected two luminance values");
+  }
+  return (lighter + 0.05) / (darker + 0.05);
+}
+
+function mixOpaque(foreground: string, background: string, opacity: number): string {
+  const fh = foreground.replace("#", "");
+  const bh = background.replace("#", "");
+  const fr = Number.parseInt(fh.slice(0, 2), 16);
+  const fg = Number.parseInt(fh.slice(2, 4), 16);
+  const fb = Number.parseInt(fh.slice(4, 6), 16);
+  const br = Number.parseInt(bh.slice(0, 2), 16);
+  const bg = Number.parseInt(bh.slice(2, 4), 16);
+  const bb = Number.parseInt(bh.slice(4, 6), 16);
+  const r = Math.round(fr * opacity + br * (1 - opacity));
+  const g = Math.round(fg * opacity + bg * (1 - opacity));
+  const b = Math.round(fb * opacity + bb * (1 - opacity));
+  return `#${[r, g, b].map((n) => n.toString(16).padStart(2, "0")).join("")}`;
+}
+
+function readCssVarBlock(css: string, selector: string): Record<string, string> {
+  const escaped = selector.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+  const match = css.match(new RegExp(`${escaped}\\s*\\{([\\s\\S]*?)\\n\\}`, "u"));
+  const block = match?.[1];
+  if (!block) {
+    throw new Error(`missing CSS block for ${selector}`);
+  }
+  const vars: Record<string, string> = {};
+  for (const line of block.matchAll(/--([a-z0-9-]+):\s*(#[0-9a-fA-F]{6})\s*;/gu)) {
+    const name = line[1];
+    const value = line[2];
+    if (name === undefined || value === undefined) {
+      continue;
+    }
+    vars[name] = value.toLowerCase();
+  }
+  return vars;
+}
+
+function requireCssColor(vars: Record<string, string>, name: string): string {
+  const value = vars[name];
+  if (value === undefined) {
+    throw new Error(`missing CSS color --${name}`);
+  }
+  return value;
+}
+
+function readRuleBody(css: string, selector: string): string {
+  const escaped = selector.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+  const match = css.match(new RegExp(`${escaped}\\s*\\{([^}]*)\\}`, "u"));
+  const body = match?.[1];
+  if (!body) {
+    throw new Error(`missing CSS rule for ${selector}`);
+  }
+  return body;
+}
+
+function readOpacity(ruleBody: string): number {
+  const match = ruleBody.match(/opacity:\s*([0-9.]+)\s*;/u);
+  const raw = match?.[1];
+  return raw === undefined ? 1 : Number.parseFloat(raw);
+}
+
+describe("Control UI theme contrast", () => {
+  const baseCss = readFileSync(path.join(here, "base.css"), "utf8");
+  const groupedCss = readFileSync(path.join(here, "chat", "grouped.css"), "utf8");
+  const layoutCss = readFileSync(path.join(here, "chat", "layout.css"), "utf8");
+
+  it("keeps default dark muted text tokens at WCAG AA on declared surfaces", () => {
+    const dark = readCssVarBlock(baseCss, ":root");
+    const backgrounds = [
+      requireCssColor(dark, "bg"),
+      requireCssColor(dark, "bg-elevated"),
+      requireCssColor(dark, "bg-muted"),
+      requireCssColor(dark, "card"),
+    ];
+    const foregrounds = [
+      requireCssColor(dark, "muted"),
+      requireCssColor(dark, "muted-strong"),
+      requireCssColor(dark, "muted-foreground"),
+    ];
+
+    for (const foreground of foregrounds) {
+      for (const background of backgrounds) {
+        expect(contrastRatio(foreground, background)).toBeGreaterThanOrEqual(4.5);
+      }
+    }
+  });
+
+  it("keeps chat timestamps and slash-arg hints AA without opacity dimming", () => {
+    const dark = readCssVarBlock(baseCss, ":root");
+    const muted = requireCssColor(dark, "muted");
+    const backgrounds = [
+      requireCssColor(dark, "bg"),
+      requireCssColor(dark, "bg-elevated"),
+      requireCssColor(dark, "bg-muted"),
+      requireCssColor(dark, "card"),
+    ];
+    const timestampRule = readRuleBody(groupedCss, ".chat-group-timestamp");
+    const slashArgsRule = readRuleBody(layoutCss, ".slash-menu-args");
+
+    expect(timestampRule).toMatch(/color:\s*var\(--muted\)/);
+    expect(slashArgsRule).toMatch(/color:\s*var\(--muted\)/);
+
+    const timestampOpacity = readOpacity(timestampRule);
+    const slashArgsOpacity = readOpacity(slashArgsRule);
+    expect(timestampOpacity).toBe(1);
+    expect(slashArgsOpacity).toBe(1);
+
+    for (const background of backgrounds) {
+      const timestampFg = mixOpaque(muted, background, timestampOpacity);
+      const slashArgsFg = mixOpaque(muted, background, slashArgsOpacity);
+      expect(contrastRatio(timestampFg, background)).toBeGreaterThanOrEqual(4.5);
+      expect(contrastRatio(slashArgsFg, background)).toBeGreaterThanOrEqual(4.5);
+    }
+  });
+});