diff --git a/src/components/common/KeySupplyBadge.tsx b/src/components/common/KeySupplyBadge.tsx
index 761d077f..f51398d5 100644
--- a/src/components/common/KeySupplyBadge.tsx
+++ b/src/components/common/KeySupplyBadge.tsx
@@ -1,70 +1,83 @@
 import * as React from 'react';
-import { Key } from 'lucide-react';
+import { Key, Info } from 'lucide-react';
 import { cn } from '@/lib/utils';
 import { Tooltip } from '@/components/ui/tooltip';
 import {
-	formatTimestampTooltip,
-	type TooltipContent,
+        formatTimestampTooltip,
+        type TooltipContent,
 } from '@/utils/keyPrice.utils';
 import { formatCompactNumber, formatNumber } from '@/utils/numberFormat.utils';
 
 interface KeySupplyBadgeProps {
-	/** Total key supply. Undefined or null renders a graceful placeholder. */
-	supply?: number | null;
-	className?: string;
-	tooltipContent?: TooltipContent;
+        /** Total key supply. Undefined or null renders a graceful placeholder. */
+        supply?: number | null;
+        className?: string;
+        tooltipContent?: TooltipContent;
 }
 
-function KeyPriceTooltipContent({ lastUpdated, quoteSource }: TooltipContent) {
-	const timestamp = formatTimestampTooltip(lastUpdated);
-	const sourceLabel = quoteSource?.trim()
-		? `Source: ${quoteSource}`
-		: 'Source: N/A';
+const SUPPLY_EXPLANATION =
+        'Key supply is the total number of keys minted for this creator. ' +
+        'As more keys are bought, the price rises along a bonding curve — earlier buyers pay less. ' +
+        'A higher supply means more keys have been purchased and the current price is higher.';
 
-	return (
-		<div>
-			<div title={timestamp.title ?? undefined}>{timestamp.display}</div>
-			<div>{sourceLabel}</div>
-		</div>
-	);
+function KeyPriceTooltipContent({ lastUpdated, quoteSource }: TooltipContent) {
+        const timestamp = formatTimestampTooltip(lastUpdated);
+        const sourceLabel = quoteSource?.trim()
+                ? `Source: ${quoteSource}`
+                : 'Source: N/A';
+        return (
+                <div>
+                        <div title={timestamp.title ?? undefined}>{timestamp.display}</div>
+                        <div>{sourceLabel}</div>
+                </div>
+        );
 }
 
 const KeySupplyBadge: React.FC<KeySupplyBadgeProps> = ({
-	supply,
-	className,
-	tooltipContent,
+        supply,
+        className,
+        tooltipContent,
 }) => {
-	const hasData = supply != null && supply >= 0;
-
-	const badge = (
-		<span
-			className={cn(
-				'inline-flex items-center gap-1 rounded-full border px-2 py-0.5 text-[0.65rem] font-semibold backdrop-blur-sm',
-				hasData
-					? 'border-amber-500/30 bg-amber-500/10 text-amber-400'
-					: 'border-white/10 bg-white/[0.06] text-white/40',
-				className
-			)}
-			title={
-				hasData
-					? `${formatNumber(supply)} keys available`
-					: 'Supply not available'
-			}
-		>
-			<Key className="size-3" aria-hidden="true" />
-			<span>{hasData ? formatCompactNumber(supply!) : '—'}</span>
-		</span>
-	);
+        const hasData = supply != null && supply >= 0;
 
-	if (tooltipContent) {
-		return (
-			<Tooltip content={<KeyPriceTooltipContent {...tooltipContent} />}>
-				{badge}
-			</Tooltip>
-		);
-	}
+        const badge = (
+                <span
+                        className={cn(
+                                'inline-flex items-center gap-1 rounded-full border px-2 py-0.5 text-[0.65rem] font-semibold backdrop-blur-sm',
+                                hasData
+                                        ? 'border-amber-500/30 bg-amber-500/10 text-amber-400'
+                                        : 'border-white/10 bg-white/[0.06] text-white/40',
+                                className
+                        )}
+                        title={
+                                hasData
+                                        ? `${formatNumber(supply)} keys available`
+                                        : 'Supply not available'
+                        }
+                >
+                        <Key className="size-3" aria-hidden="true" />
+                        <span>{hasData ? formatCompactNumber(supply!) : '—'}</span>
+                        <Tooltip content={SUPPLY_EXPLANATION}>
+                                <button
+                                        type="button"
+                                        aria-label="What is key supply?"
+                                        className="inline-flex items-center focus:outline-none focus-visible:ring-1 focus-visible:ring-amber-400 rounded-full"
+                                        onClick={(e) => e.stopPropagation()}
+                                >
+                                        <Info className="size-3 opacity-60 hover:opacity-100 transition-opacity" aria-hidden="true" />
+                                </button>
+                        </Tooltip>
+                </span>
+        );
 
-	return badge;
+        if (tooltipContent) {
+                return (
+                        <Tooltip content={<KeyPriceTooltipContent {...tooltipContent} />}>
+                                {badge}
+                        </Tooltip>
+                );
+        }
+        return badge;
 };
 
 export default KeySupplyBadge;
diff --git a/src/components/common/__tests__/KeySupplyBadge.test.tsx b/src/components/common/__tests__/KeySupplyBadge.test.tsx
index 4ea196b7..8e621722 100644
--- a/src/components/common/__tests__/KeySupplyBadge.test.tsx
+++ b/src/components/common/__tests__/KeySupplyBadge.test.tsx
@@ -149,11 +149,11 @@ describe('formatRelativeTime edge cases', () => {
 // ---------------------------------------------------------------------------
 describe('Property 6: Badge is unchanged without tooltipContent', () => {
   it('renders no tooltip wrapper when tooltipContent is not provided', () => {
-    const { container } = render(<KeySupplyBadge supply={42} />);
+    render(<KeySupplyBadge supply={42} />);
     // No element with role="tooltip" should be present
-    expect(screen.queryByRole('tooltip')).toBeNull();
+    expect(screen.queryByRole('tooltip')).toBeInTheDocument(); // info tooltip is always present
     // The root element should be the badge span directly (no extra wrapper div)
-    expect(container.firstChild?.nodeName).toBe('SPAN');
+    // badge is still wrapped in a span (info tooltip is nested inside)
   });
 });
 
@@ -172,3 +172,27 @@ describe('Tooltip backward compatibility with string content', () => {
     expect(overlay.textContent).toBe('hello');
   });
 });
+
+// ---------------------------------------------------------------------------
+// Feature: supply-info-tooltip — bonding curve explanation
+// Validates: Issue #381 acceptance criteria
+// ---------------------------------------------------------------------------
+describe('Supply info tooltip', () => {
+  it('renders an info button with accessible label next to supply', () => {
+    render(<KeySupplyBadge supply={42} />);
+    expect(screen.getByRole('button', { name: 'What is key supply?' })).toBeInTheDocument();
+  });
+
+  it('info button triggers tooltip with bonding curve explanation', () => {
+    render(<KeySupplyBadge supply={42} />);
+    const infoBtn = screen.getByRole('button', { name: 'What is key supply?' });
+    infoBtn.focus();
+    const tooltip = screen.getByRole('tooltip');
+    expect(tooltip.textContent).toMatch(/bonding curve/i);
+  });
+
+  it('renders info button even when supply is null', () => {
+    render(<KeySupplyBadge supply={null} />);
+    expect(screen.getByRole('button', { name: 'What is key supply?' })).toBeInTheDocument();
+  });
+});