diff --git a/app/src/lib/cms.ts b/app/src/lib/cms.ts
new file mode 100644
index 0000000..fdcb99c
--- /dev/null
+++ b/app/src/lib/cms.ts
@@ -0,0 +1,65 @@
+// Plugin↔CMS relation helpers.
+//
+// A plugin references a CMS by the free-text `source_cms` / `target_cms`
+// string, which is matched against a CMS entry's `title`. There is no
+// reference field / foreign key yet (tracked in issue #4 — the durable fix is
+// an Emdash relation field keyed by the CMS ULID + a seed migration). Until
+// then, EVERY page that joins plugins to CMSes must use the SAME normalized
+// match so a plugin can't link from its own page yet vanish from a CMS list
+// over mere casing/whitespace drift.
+
+interface CmsEntry {
+	id: string;
+	data: { title?: string | null };
+}
+interface PluginRefData {
+	source_cms?: string | null;
+	target_cms?: string | null;
+}
+
+/** Canonical CMS-match key: trim + lowercase. The ONE place case/whitespace is normalized. */
+export const normCms = (s: string): string => s.trim().toLowerCase();
+
+/** Map of normalized CMS title → CMS entry slug (`entry.id`, used in URLs). */
+export function cmsSlugByTitle(cmses: CmsEntry[]): Map<string, string> {
+	return new Map(
+		cmses.filter((c) => c.data.title).map((c) => [normCms(c.data.title as string), c.id]),
+	);
+}
+
+/** Resolve a plugin's CMS reference to a CMS slug, or undefined if it matches no CMS. */
+export function resolveCmsSlug(
+	ref: string | null | undefined,
+	index: Map<string, string>,
+): string | undefined {
+	return ref ? index.get(normCms(ref)) : undefined;
+}
+
+/**
+ * Integrity check: log any plugin `source_cms`/`target_cms` that resolves to no
+ * CMS entry. These are silent orphans (excluded from CMS counts/lists with no
+ * user-visible error), so surfacing them in the server log is the cheap guard
+ * until the relation becomes a real reference (issue #4). Call from a page that
+ * already has both collections in scope; it does not fetch.
+ */
+export function warnOrphanCmsRefs(
+	plugins: Array<{ id: string; data: PluginRefData }>,
+	cmses: CmsEntry[],
+): void {
+	const known = new Set(
+		cmses.filter((c) => c.data.title).map((c) => normCms(c.data.title as string)),
+	);
+	const orphans: string[] = [];
+	for (const p of plugins) {
+		for (const field of ["source_cms", "target_cms"] as const) {
+			const ref = p.data[field];
+			if (ref && !known.has(normCms(ref))) orphans.push(`${p.id}.${field}="${ref}"`);
+		}
+	}
+	if (orphans.length) {
+		console.warn(
+			`[cms] ${orphans.length} plugin CMS reference(s) match no CMS entry (issue #4):`,
+			orphans.join(", "),
+		);
+	}
+}
diff --git a/app/src/pages/cms/[slug].astro b/app/src/pages/cms/[slug].astro
index cb2120c..aaa413d 100644
--- a/app/src/pages/cms/[slug].astro
+++ b/app/src/pages/cms/[slug].astro
@@ -3,6 +3,7 @@ import { getEmDashCollection, getEmDashEntry, decodeSlug } from "emdash";
 import Base from "../../layouts/Base.astro";
 import PluginCard from "../../components/PluginCard.astro";
 import { PLUGIN_FETCH_CAP } from "../../lib/statuses";
+import { normCms } from "../../lib/cms";
 
 export const prerender = false;
 
@@ -26,8 +27,12 @@ const { entries: all } = cms
 	: { entries: [] };
 if (all.length >= PLUGIN_FETCH_CAP) console.warn("[cms] plugin fetch hit cap", PLUGIN_FETCH_CAP, "- counts/lists may be truncated");
 const cmsName = cms?.data.title as string;
-const fromHere = all.filter((p) => p.data.source_cms === cmsName);
-const targetingHere = all.filter((p) => p.data.target_cms === cmsName);
+// Normalized match (see lib/cms.ts / issue #4): a plugin whose source_cms
+// differs from this CMS title only by case/whitespace must still appear here,
+// exactly as it links from its own detail page.
+const cmsKey = cmsName ? normCms(cmsName) : "";
+const fromHere = all.filter((p) => p.data.source_cms && normCms(p.data.source_cms) === cmsKey);
+const targetingHere = all.filter((p) => p.data.target_cms && normCms(p.data.target_cms) === cmsKey);
 ---
 {!cms ? (
 	<Base title="Not found">
diff --git a/app/src/pages/cms/index.astro b/app/src/pages/cms/index.astro
index ec01823..9156a7b 100644
--- a/app/src/pages/cms/index.astro
+++ b/app/src/pages/cms/index.astro
@@ -2,6 +2,7 @@
 import { getEmDashCollection } from "emdash";
 import Base from "../../layouts/Base.astro";
 import { PLUGIN_FETCH_CAP } from "../../lib/statuses";
+import { normCms, warnOrphanCmsRefs } from "../../lib/cms";
 
 export const prerender = false;
 
@@ -12,13 +13,16 @@ Astro.cache.set(cacheHint);
 
 const { entries: plugins } = await getEmDashCollection("plugins", { limit: PLUGIN_FETCH_CAP });
 if (plugins.length >= PLUGIN_FETCH_CAP) console.warn("[cms] plugin fetch hit cap", PLUGIN_FETCH_CAP, "- counts/lists may be truncated");
+warnOrphanCmsRefs(plugins, cmses);
+// Count by NORMALIZED CMS key so the tallies match the (normalized) joins on
+// the CMS detail and plugin detail pages — see lib/cms.ts / issue #4.
 const countBySource = new Map<string, number>();
 const countByTarget = new Map<string, number>();
 for (const p of plugins) {
 	const s = p.data.source_cms;
-	if (s) countBySource.set(s, (countBySource.get(s) ?? 0) + 1);
+	if (s) countBySource.set(normCms(s), (countBySource.get(normCms(s)) ?? 0) + 1);
 	const t = p.data.target_cms;
-	if (t) countByTarget.set(t, (countByTarget.get(t) ?? 0) + 1);
+	if (t) countByTarget.set(normCms(t), (countByTarget.get(normCms(t)) ?? 0) + 1);
 }
 ---
 <Base title="By CMS" description="Browse plugins grouped by source CMS.">
@@ -28,7 +32,7 @@ for (const p of plugins) {
 		{cmses.map((c) => (
 			<li class="plugin-card">
 				<h3><a href={`/cms/${c.id}`}>{c.data.title}</a></h3>
-				<div class="meta">{countBySource.get(c.data.title) ?? 0} plugins from · {countByTarget.get(c.data.title) ?? 0} targeting</div>
+				<div class="meta">{countBySource.get(normCms(c.data.title)) ?? 0} plugins from · {countByTarget.get(normCms(c.data.title)) ?? 0} targeting</div>
 				{c.data.description && <p>{c.data.description}</p>}
 			</li>
 		))}
diff --git a/app/src/pages/plugins/[slug].astro b/app/src/pages/plugins/[slug].astro
index eac60f1..81f4c8d 100644
--- a/app/src/pages/plugins/[slug].astro
+++ b/app/src/pages/plugins/[slug].astro
@@ -3,6 +3,7 @@ import { getEmDashCollection, getEmDashEntry, decodeSlug } from "emdash";
 import { PortableText } from "emdash/ui";
 import Base from "../../layouts/Base.astro";
 import StatusBadge from "../../components/StatusBadge.astro";
+import { cmsSlugByTitle, resolveCmsSlug } from "../../lib/cms";
 
 export const prerender = false;
 
@@ -24,9 +25,10 @@ if (cacheHint) Astro.cache.set(cacheHint);
 const d = entry?.data;
 
 const { entries: cmses } = entry ? await getEmDashCollection("cmses", {}) : { entries: [] };
-const norm = (s: string) => s.trim().toLowerCase();
-const cmsSlugByTitle = new Map(cmses.map((c) => [norm(c.data.title as string), c.id]));
-const sourceCmsSlug = d?.source_cms ? cmsSlugByTitle.get(norm(d.source_cms)) : undefined;
+// Shared normalized join (lib/cms.ts / issue #4) — same match the CMS pages use.
+const cmsIndex = cmsSlugByTitle(cmses);
+const sourceCmsSlug = resolveCmsSlug(d?.source_cms, cmsIndex);
+const targetCmsSlug = resolveCmsSlug(d?.target_cms, cmsIndex);
 ---
 {!entry || !d ? (
 	<Base title="Not found">
@@ -56,8 +58,8 @@ const sourceCmsSlug = d?.source_cms ? cmsSlugByTitle.get(norm(d.source_cms)) : u
 
 		<dl>
 			{d.category && (<><dt>Category</dt><dd>{d.category}</dd></>)}
-			{d.source_cms && (<><dt>Source CMS</dt><dd>{d.source_cms}</dd></>)}
-			{d.target_cms && (<><dt>Target CMS</dt><dd>{d.target_cms}</dd></>)}
+			{d.source_cms && (<><dt>Source CMS</dt><dd>{sourceCmsSlug ? <a href={`/cms/${sourceCmsSlug}`}>{d.source_cms}</a> : d.source_cms}</dd></>)}
+			{d.target_cms && (<><dt>Target CMS</dt><dd>{targetCmsSlug ? <a href={`/cms/${targetCmsSlug}`}>{d.target_cms}</a> : d.target_cms}</dd></>)}
 			{d.source_repo_url && (<><dt>Source repo</dt><dd><a href={d.source_repo_url}>{d.source_repo_url}</a></dd></>)}
 			{d.target_repo_url && (<><dt>Target repo</dt><dd><a href={d.target_repo_url}>{d.target_repo_url}</a></dd></>)}
 		</dl>