diff --git a/app/components/DepsStats/DependencyStatsPanel.vue b/app/components/DepsStats/DependencyStatsPanel.vue
index 3b7291a0ed..7dd1cacdea 100644
--- a/app/components/DepsStats/DependencyStatsPanel.vue
+++ b/app/components/DepsStats/DependencyStatsPanel.vue
@@ -34,13 +34,16 @@ const { data: installSize, execute: fetchInstallSize } = useLazyFetch<InstallSiz
   },
 )
 
-watch(
-  resolvedVersion,
-  version => {
-    if (version) fetchInstallSize()
-  },
-  { immediate: true },
-)
+// Client-only: install size walks the whole dependency tree, so never block SSR on it.
+if (import.meta.client) {
+  watch(
+    resolvedVersion,
+    version => {
+      if (version) fetchInstallSize()
+    },
+    { immediate: true },
+  )
+}
 
 const { diff: sizeDiff } = useInstallSizeDiff(
   () => props.packageName,
diff --git a/app/composables/useDependencyAnalysis.ts b/app/composables/useDependencyAnalysis.ts
index d8eee606a2..5de41ee261 100644
--- a/app/composables/useDependencyAnalysis.ts
+++ b/app/composables/useDependencyAnalysis.ts
@@ -2,6 +2,13 @@
  * Shared composable for dependency analysis data (vulnerabilities, deprecated packages).
  * Fetches once and caches the result so multiple components can use it.
  * Before: useVulnerabilityTree - but now we use this for both vulnerabilities and deprecated packages.
+ *
+ * Client-only and lazy: resolving the whole transitive dependency graph (one packument download
+ * per dependency) plus OSV queries is far too slow to block the package page's server render. The
+ * data only drives the vulnerability count and the vulnerability/deprecated trees, none of which
+ * need to be in the server HTML.
+ *
+ * `useFetch` dedupes by key (the request URL), so all consumers share the same request/result.
  */
 export function useDependencyAnalysis(
   packageName: MaybeRefOrGetter<string>,
@@ -10,5 +17,9 @@ export function useDependencyAnalysis(
   return useFetch(
     () =>
       `/api/registry/vulnerabilities/${encodePackageName(toValue(packageName))}/v/${toValue(version)}`,
+    {
+      server: false,
+      lazy: true,
+    },
   )
 }
diff --git a/app/pages/package/[[org]]/[name].vue b/app/pages/package/[[org]]/[name].vue
index 1cb7073cb8..ac88e3c315 100644
--- a/app/pages/package/[[org]]/[name].vue
+++ b/app/pages/package/[[org]]/[name].vue
@@ -128,16 +128,19 @@ const {
   },
 )
 
-// Trigger fetch only when we have the real resolved version
-watch(
-  [resolvedVersion, resolvedStatus],
-  ([version, status]) => {
-    if (version && status === 'success') {
-      fetchInstallSize()
-    }
-  },
-  { immediate: true },
-)
+// Trigger fetch only when we have the real resolved version.
+// Client-only: install size walks the whole dependency tree, so never block SSR on it.
+if (import.meta.client) {
+  watch(
+    [resolvedVersion, resolvedStatus],
+    ([version, status]) => {
+      if (version && status === 'success') {
+        fetchInstallSize()
+      }
+    },
+    { immediate: true },
+  )
+}
 
 const { data: skillsData } = useLazyFetch<SkillsListResponse>(
   () => {
@@ -672,23 +675,28 @@ const showSkeleton = shallowRef(false)
                   <span v-else>-</span>
                 </span>
 
-                <!-- Total install size in parens -->
-                <template v-if="displayVersion?.dist?.unpackedSize !== installSize?.totalSize">
-                  <span class="ms-1">
-                    <span
-                      v-if="installSizeStatus === 'pending'"
-                      class="inline-flex items-center gap-1 text-fg-subtle"
-                    >
-                      (<span class="i-svg-spinners:ring-resize w-3 h-3" aria-hidden="true" />)
-                    </span>
-                    <span v-else-if="installSize?.totalSize" dir="ltr">
-                      <span class="text-fg-subtle">(</span
-                      >{{ bytesFormatter.format(installSize.totalSize)
-                      }}<span class="text-fg-subtle">)</span>
+                <!-- Total install size in parens.
+                     Client-only: the lazy install-size fetch can resolve after the server HTML is
+                     rendered but before the payload is serialized, so the value would be hydrated
+                     even though the server rendered something else (a spinner or '-'). -->
+                <ClientOnly>
+                  <template v-if="displayVersion?.dist?.unpackedSize !== installSize?.totalSize">
+                    <span class="ms-1">
+                      <span
+                        v-if="installSizeStatus === 'pending'"
+                        class="inline-flex items-center gap-1 text-fg-subtle"
+                      >
+                        (<span class="i-svg-spinners:ring-resize w-3 h-3" aria-hidden="true" />)
+                      </span>
+                      <span v-else-if="installSize?.totalSize" dir="ltr">
+                        <span class="text-fg-subtle">(</span
+                        >{{ bytesFormatter.format(installSize.totalSize)
+                        }}<span class="text-fg-subtle">)</span>
+                      </span>
+                      <span v-else class="text-fg-subtle">(-)</span>
                     </span>
-                    <span v-else class="text-fg-subtle">(-)</span>
-                  </span>
-                </template>
+                  </template>
+                </ClientOnly>
               </dd>
             </div>