diff --git a/3d-printers/index.html b/3d-printers/index.html
index d2cf8e3..66c60e8 100644
--- a/3d-printers/index.html
+++ b/3d-printers/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>3D Printers – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/AGENTS.md b/AGENTS.md
index 554b8c3..30347ea 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -81,6 +81,12 @@ Keep the current open-house information consistent:
 
 If this information changes, update the sidebar, relevant page copy, JSON-LD, and `llms.txt` together.
 
+## Stylesheet cache versioning
+
+- Every HTML page references `styles.css` with a cache-busting epoch query parameter, such as `/styles.css?v=1790211252`.
+- Whenever `styles.css` changes, update the `?v=` value in every HTML page to the current Unix epoch timestamp.
+- Keep the preload and stylesheet URLs synchronized so both use the same version.
+
 ## Assets
 
 - Store local images in `/assets/`.
diff --git a/about/index.html b/about/index.html
index bb249b2..8c4bb76 100644
--- a/about/index.html
+++ b/about/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>About Protospace – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/contact/index.html b/contact/index.html
index 609a122..01ff550 100644
--- a/contact/index.html
+++ b/contact/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>Contact – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/electronics-lab/index.html b/electronics-lab/index.html
index 6721c3c..ac8ca24 100644
--- a/electronics-lab/index.html
+++ b/electronics-lab/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>Electronics Lab – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/index.html b/index.html
index ab8cafe..1c0afff 100644
--- a/index.html
+++ b/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>We make space so you can make things – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/join-us/index.html b/join-us/index.html
index 04035a4..7c76281 100644
--- a/join-us/index.html
+++ b/join-us/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>Membership – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/laser-cutters/index.html b/laser-cutters/index.html
index 73fa86e..bbf5b90 100644
--- a/laser-cutters/index.html
+++ b/laser-cutters/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>Laser Cutters – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/metal-shop/index.html b/metal-shop/index.html
index f653c0e..3f95e1b 100644
--- a/metal-shop/index.html
+++ b/metal-shop/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>Metal Shop – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/sewing-room/index.html b/sewing-room/index.html
index 3a38d66..e36a51b 100644
--- a/sewing-room/index.html
+++ b/sewing-room/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>Sewing Room – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/the-space/index.html b/the-space/index.html
index 7c99c9c..17437c6 100644
--- a/the-space/index.html
+++ b/the-space/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>Spaces – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",
diff --git a/wood-shop/index.html b/wood-shop/index.html
index fe49958..ff457c1 100644
--- a/wood-shop/index.html
+++ b/wood-shop/index.html
@@ -15,8 +15,8 @@
 	<meta property="og:site_name" content="Protospace" />
 	<meta name="twitter:card" content="summary_large_image" />
 	<title>Wood Shop – Protospace</title>
-	<link rel="preload" href="/styles.css" as="style" />
-	<link rel="stylesheet" href="/styles.css" />
+	<link rel="preload" href="/styles.css?v=1790211252" as="style" />
+	<link rel="stylesheet" href="/styles.css?v=1790211252" />
 		<script type="application/ld+json">
 {
 	"@context": "https://schema.org",