diff --git a/TODO.md b/TODO.md
new file mode 100644
index 0000000..3f75f60
--- /dev/null
+++ b/TODO.md
@@ -0,0 +1,14 @@
+# TODO — Streams dense layout toggle
+
+- [ ] Add density state + toggle UI in `app/streams/StreamsPageContent.tsx` with localStorage persistence (`streampay.density`)
+- [ ] Pass density to `app/components/StreamRow.tsx` and apply compact class
+- [ ] Add compact CSS rules in `app/globals.css` (reduce padding/gaps for `.stream-row--compact` and related layouts)
+- [ ] Update `app/streams/page.test.tsx` to cover:
+  - [ ] comfortable mode (default) -> non-compact
+  - [ ] compact mode -> compact class
+  - [ ] toggle interaction updates localStorage
+  - [ ] keyboard accessibility (role="switch" + aria-checked)
+- [ ] Run `npm test -- app/streams/page.test.tsx` and ensure passing
+- [ ] Commit changes with message: `feat: add dense-mode toggle to streams list`
+- [ ] Provide manual visual testing notes for PR
+
diff --git a/app/components/StreamRow.tsx b/app/components/StreamRow.tsx
index 7638d42..69f20cb 100644
--- a/app/components/StreamRow.tsx
+++ b/app/components/StreamRow.tsx
@@ -28,9 +28,13 @@ export type StreamRowData = {
 
 type StreamRowProps = {
   stream: StreamRowData;
+  density?: "compact" | "comfortable";
 };
 
-export function StreamRow({ stream }: StreamRowProps) {
+export function StreamRow({ stream, density = "comfortable" }: StreamRowProps) {
+  // Density is controlled by StreamsPageContent and affects only layout spacing.
+  // Keeping it as a prop avoids extra re-renders beyond StreamRow itself.
+
   const [isProcessing, setIsProcessing] = useState(false);
   const [error, setError] = useState<StreamPayError | null>(null);
   const [isIncidentMode] = useState(false);
@@ -101,7 +105,10 @@ export function StreamRow({ stream }: StreamRowProps) {
   };
 
   return (
-    <article className="stream-row" aria-labelledby={`${stream.id}-recipient`}>
+    <article
+      className={`stream-row ${density === "compact" ? "stream-row--compact" : ""}`}
+      aria-labelledby={`${stream.id}-recipient`}
+    >
       {/* Dynamic polite status messenger announcement node layer for assistive tech */}
       <div className="sr-only" aria-live="polite" role="status">
         {srAnnouncement}
@@ -158,7 +165,7 @@ export function StreamRow({ stream }: StreamRowProps) {
         />
       )}
 
-      <div style={{ display: "flex", flexDirection: "column", gap: "0.5rem", alignItems: "flex-end" }}>
+      <div className="stream-row__action-wrap">
         <button
           ref={actionButtonRef}
           className={`button button--secondary stream-row__action ${isProcessing ? "button--busy" : ""}`}
diff --git a/app/globals.css b/app/globals.css
index 28f475b..4dbc613 100644
--- a/app/globals.css
+++ b/app/globals.css
@@ -400,11 +400,113 @@ a:hover {
   line-height: 1.5;
 }
 
-.stream-list {
+ .stream-list {
   display: grid;
   gap: 1rem;
 }
 
+/* ─── Streams Dense Layout (density toggle) ─────────────────────────────── */
+.stream-row--compact {
+  padding: 0.875rem;
+  gap: 0.75rem;
+  border-radius: 1.1rem;
+}
+
+.stream-list--compact {
+  gap: 0.75rem;
+}
+
+.stream-row--compact .stream-row__primary {
+  gap: 0.5rem;
+}
+
+.stream-row--compact .stream-row__recipient {
+  font-size: 1.0rem;
+  margin-bottom: 0.25rem;
+}
+
+.stream-row--compact .stream-row__schedule {
+  line-height: 1.35;
+}
+
+.stream-row--compact .stream-row__meta {
+  gap: 0.5rem;
+}
+
+.stream-row--compact .stream-row__meta dt {
+  font-size: 0.75rem;
+  margin-bottom: 0.25rem;
+}
+
+.stream-row--compact .stream-row__meta dd {
+  font-size: 0.9rem;
+}
+
+.stream-row--compact .stream-row__action-wrap {
+  gap: 0.25rem;
+}
+
+.density-toggle {
+  align-items: center;
+  display: inline-flex;
+  gap: 0.5rem;
+}
+
+.density-toggle__label {
+  color: var(--muted);
+  font-size: 0.75rem;
+  font-weight: 700;
+  text-transform: uppercase;
+}
+
+.density-toggle__switch {
+  background-color: var(--border);
+  border: none;
+  border-radius: 999px;
+  cursor: pointer;
+  height: 24px;
+  width: 44px;
+  padding: 0;
+  position: relative;
+  transition: background-color 160ms ease;
+}
+
+.density-toggle__switch:focus-visible {
+  outline: 2px solid var(--accent);
+  outline-offset: 4px;
+}
+
+.density-toggle__switch--compact {
+  background-color: var(--accent);
+}
+
+.density-toggle__thumb {
+  background-color: white;
+  border-radius: 50%;
+  height: 20px;
+  left: 2px;
+  position: absolute;
+  top: 2px;
+  transition: transform 160ms ease-in-out;
+  width: 20px;
+}
+
+.density-toggle__switch--compact .density-toggle__thumb {
+  transform: translateX(20px);
+  background-color: var(--accent-strong);
+  border: 2px solid var(--accent);
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .density-toggle__thumb,
+  .density-toggle__switch { transition: none !important; }
+}
+
+@media (max-width: 47.9375rem) {
+  .density-toggle__label { display: none; }
+}
+
+
 .stream-row {
   background: linear-gradient(180deg, var(--panel-elevated), var(--panel));
   border: 1px solid var(--border);
diff --git a/app/streams/StreamsPageContent.test.tsx b/app/streams/StreamsPageContent.test.tsx
new file mode 100644
index 0000000..73a74fc
--- /dev/null
+++ b/app/streams/StreamsPageContent.test.tsx
@@ -0,0 +1,48 @@
+/**
+ * @jest-environment jsdom
+ */
+
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { StreamsPageContent } from "./StreamsPageContent";
+
+const STORAGE_KEY = "streampay.density";
+
+describe("StreamsPageContent density toggle", () => {
+  beforeEach(() => {
+    window.localStorage.clear();
+  });
+
+  it("defaults to comfortable when no localStorage value exists", () => {
+    render(<StreamsPageContent state="populated" />);
+
+    const compactSwitch = screen.getByRole("switch", { name: /streams list density/i });
+    expect(compactSwitch).toHaveAttribute("aria-checked", "false");
+
+    // Should not mark rows compact.
+    expect(document.querySelectorAll(".stream-row--compact").length).toBe(0);
+  });
+
+  it("uses compact mode when localStorage is set", () => {
+    window.localStorage.setItem(STORAGE_KEY, "compact");
+
+    render(<StreamsPageContent state="populated" />);
+
+    const compactSwitch = screen.getByRole("switch", { name: /streams list density/i });
+    expect(compactSwitch).toHaveAttribute("aria-checked", "true");
+
+    expect(document.querySelectorAll(".stream-row--compact").length).toBeGreaterThan(0);
+  });
+
+  it("toggle persists per device via localStorage", async () => {
+    const user = userEvent.setup();
+    render(<StreamsPageContent state="populated" />);
+
+    const compactSwitch = screen.getByRole("switch", { name: /streams list density/i });
+    await user.click(compactSwitch);
+
+    expect(window.localStorage.getItem(STORAGE_KEY)).toBe("compact");
+    expect(compactSwitch).toHaveAttribute("aria-checked", "true");
+  });
+});
+
diff --git a/app/streams/StreamsPageContent.tsx b/app/streams/StreamsPageContent.tsx
index 3a38cb9..0de19e2 100644
--- a/app/streams/StreamsPageContent.tsx
+++ b/app/streams/StreamsPageContent.tsx
@@ -1,7 +1,11 @@
+"use client";
+
+import { useEffect, useState } from "react";
 import { EmptyState } from "../components/EmptyState";
 import { PageError } from "../components/PageError";
 import { StreamRow, type StreamRowData } from "../components/StreamRow";
 
+
 export type StreamsViewState = "empty" | "loading" | "populated" | "error";
 
 const streamListCopy = {
@@ -102,6 +106,29 @@ export function StreamsPageContent({
   errorMessage,
   onRetry,
 }: StreamsPageContentProps) {
+  type DensityMode = "compact" | "comfortable";
+
+  const DENSITY_STORAGE_KEY = "streampay.density";
+
+  const [density, setDensity] = useState<DensityMode>(() => {
+    if (typeof window === "undefined") return "comfortable";
+
+    try {
+      const value = window.localStorage.getItem(DENSITY_STORAGE_KEY);
+      return value === "compact" || value === "comfortable" ? value : "comfortable";
+    } catch {
+      return "comfortable";
+    }
+  });
+
+  useEffect(() => {
+    // Keep localStorage in sync with state.
+    try {
+      window.localStorage.setItem(DENSITY_STORAGE_KEY, density);
+    } catch {
+      // Ignore storage errors (private mode, blocked storage, etc.)
+    }
+  }, [density]);
   const isEmpty = state === "empty" || streams.length === 0;
 
   return (
@@ -112,10 +139,23 @@ export function StreamsPageContent({
           <h1 className="page-hero__title">Manage every stream from one list.</h1>
           <p className="page-hero__description">{streamListCopy.description}</p>
         </div>
-        <div style={{ display: "flex", gap: "0.75rem", flexWrap: "wrap" }}>
+        <div style={{ display: "flex", gap: "0.75rem", flexWrap: "wrap", alignItems: "center" }}>
           <button className="button button--secondary" type="button">
             Export History
           </button>
+          <div className="density-toggle" aria-label="Streams list density">
+            <span className="density-toggle__label">Density</span>
+            <button
+              type="button"
+              className={`density-toggle__switch ${density === "compact" ? "density-toggle__switch--compact" : ""}`}
+              role="switch"
+              aria-checked={density === "compact"}
+              onClick={() => setDensity((d) => (d === "compact" ? "comfortable" : "compact"))}
+            >
+              <span className="density-toggle__thumb" aria-hidden="true" />
+              <span className="sr-only">{density === "compact" ? "Compact density" : "Comfortable density"}</span>
+            </button>
+          </div>
           <button className="button button--primary" type="button">
             {streamListCopy.primaryCta}
           </button>
@@ -154,9 +194,9 @@ export function StreamsPageContent({
             title={streamListCopy.empty.title}
           />
         ) : (
-          <section aria-label="Streams list" className="stream-list">
+          <section aria-label="Streams list" className={`stream-list ${density === "compact" ? "stream-list--compact" : ""}`}>
             {streams.map((stream) => (
-              <StreamRow key={stream.id} stream={stream} />
+              <StreamRow key={stream.id} stream={stream} density={density} />
             ))}
           </section>
         )}
diff --git a/app/streams/page.test.tsx b/app/streams/page.test.tsx
index 7482f7f..b2113ed 100644
--- a/app/streams/page.test.tsx
+++ b/app/streams/page.test.tsx
@@ -6,7 +6,14 @@ import { render } from "@testing-library/react";
 const { screen } = require("@testing-library/react") as any;
 import { StreamsPageContent } from "./StreamsPageContent";
 
+const STORAGE_KEY = "streampay.density";
+
+
 describe("StreamsPageContent", () => {
+  beforeEach(() => {
+    window.localStorage.clear();
+  });
+
   it("renders the empty state", () => {
     render(<StreamsPageContent state="empty" streams={[]} />);