diff --git a/site/AGENTS.md b/site/AGENTS.md
index d89d2959c6..fe43e999b3 100644
--- a/site/AGENTS.md
+++ b/site/AGENTS.md
@@ -117,6 +117,15 @@ Debug logs and pprof dumps use the same job name and commit SHA convention.
 - For JSX boolean props that are `true`, use the shorthand form
   (`<Foo prop />`) instead of `<Foo prop={true} />`. The two are
   equivalent; the shorthand is the React convention and reduces noise.
+- Use **sentence case** for user-facing UI labels: capitalize only the
+  first word and proper nouns (`Personal instructions`, `API key`), not
+  Title Case (`Personal Instructions`, `API Key`). Under
+  `src/pages/AgentsPage`, a Biome GritQL plugin
+  (`biome-rules/use-sentence-case-labels.grit`) enforces this for
+  `label`/`title`/`sectionLabel`/`aria-label` attributes and `label:`/
+  `title:` object properties. It cannot see labels rendered as JSX text
+  or built from variables, so those still need a human eye. Add genuine
+  proper nouns to the allowlist in that file.
 - **Avoid unnecessary indirection.** Inline single-use module-level
   constants, single-use aliases, and one-line helpers that just return a
   single field at the call site. Do not create wrapper hooks that only
diff --git a/site/biome-rules/use-sentence-case-labels.grit b/site/biome-rules/use-sentence-case-labels.grit
new file mode 100644
index 0000000000..b87f1f6d06
--- /dev/null
+++ b/site/biome-rules/use-sentence-case-labels.grit
@@ -0,0 +1,35 @@
+// Enforce sentence case for user-facing UI labels.
+//
+// Flags Title Case in label-bearing JSX attributes (label, title,
+// sectionLabel, aria-label) and object-property labels (label:, title:,
+// sectionLabel:). Sentence case capitalizes only the first word and
+// proper nouns: "Personal instructions", not "Personal Instructions".
+//
+// Heuristic: a space followed by a capitalized word ([A-Z][a-z]). This
+// also catches acronym-prefixed Title Case like "MCP Servers". Genuine
+// multi-word proper nouns (e.g. "VS Code") are false positives and must
+// be added to the allowlist below.
+//
+// Diagnostic-only: Biome GritQL plugins cannot autofix yet.
+language js
+
+or {
+	JsxAttribute(name = $name) as $node where {
+		$name <: r"^(?:label|title|sectionLabel|aria-label)$",
+		$node <: contains JsxString() as $value
+	},
+	JsPropertyObjectMember() as $node where {
+		$node <: contains JsLiteralMemberName() as $key,
+		$key <: r"^(?:label|title|sectionLabel)$",
+		$node <: contains JsStringLiteralExpression() as $value
+	}
+} where {
+	$value <: r".* [A-Z][a-z].*",
+	// Allowlist: proper nouns / product names that are correctly multi-cap.
+	not $value <: r".*(?:VS Code|Coder Agents|GitHub Actions|JetBrains Fleet|Cmd/Ctrl).*",
+	register_diagnostic(
+		span = $value,
+		message = "Use sentence case for UI labels (e.g. \"Personal instructions\"), not Title Case. If this is a proper noun, add it to the allowlist in use-sentence-case-labels.grit.",
+		severity = "warn"
+	)
+}
diff --git a/site/biome.jsonc b/site/biome.jsonc
index 1721a0853c..6df5385abe 100644
--- a/site/biome.jsonc
+++ b/site/biome.jsonc
@@ -3,5 +3,16 @@
 	"files": {
 		"includes": ["!e2e/**/*Generated.ts", "!scripts/*.mjs"]
 	},
+	"overrides": [
+		{
+			"includes": [
+				"src/pages/AgentsPage/**/*.ts",
+				"src/pages/AgentsPage/**/*.tsx",
+				"!**/*.stories.tsx",
+				"!**/*.test.tsx"
+			],
+			"plugins": ["./biome-rules/use-sentence-case-labels.grit"]
+		}
+	],
 	"$schema": "./node_modules/@biomejs/biome/configuration_schema.json"
 }
diff --git a/site/src/pages/AgentsPage/components/ChatModelAdminPanel/ProviderForm.tsx b/site/src/pages/AgentsPage/components/ChatModelAdminPanel/ProviderForm.tsx
index fe817705f7..49678327ed 100644
--- a/site/src/pages/AgentsPage/components/ChatModelAdminPanel/ProviderForm.tsx
+++ b/site/src/pages/AgentsPage/components/ChatModelAdminPanel/ProviderForm.tsx
@@ -256,7 +256,7 @@ export const ProviderForm: FC<ProviderFormProps> = ({
 				>
 					<div className="space-y-5">
 						<ProviderField
-							label="API Key"
+							label="API key"
 							htmlFor={apiKeyInputId}
 							required={requiresAPIKey}
 							description={apiKeyDescription}
diff --git a/site/src/pages/AgentsPage/components/MCPServerAdminPanel.tsx b/site/src/pages/AgentsPage/components/MCPServerAdminPanel.tsx
index c9d67b108f..e6f129251e 100644
--- a/site/src/pages/AgentsPage/components/MCPServerAdminPanel.tsx
+++ b/site/src/pages/AgentsPage/components/MCPServerAdminPanel.tsx
@@ -67,25 +67,25 @@ const TRANSPORT_OPTIONS = [
 const AUTH_TYPE_OPTIONS = [
 	{ value: "none", label: "None" },
 	{ value: "oauth2", label: "OAuth2" },
-	{ value: "api_key", label: "API Key" },
-	{ value: "custom_headers", label: "Custom Headers" },
-	{ value: "user_oidc", label: "User OIDC Identity" },
+	{ value: "api_key", label: "API key" },
+	{ value: "custom_headers", label: "Custom headers" },
+	{ value: "user_oidc", label: "User OIDC identity" },
 ] as const;
 
 const AVAILABILITY_OPTIONS = [
 	{
 		value: "force_on",
-		label: "Force On",
+		label: "Force on",
 		description: "Always injected into every conversation.",
 	},
 	{
 		value: "default_on",
-		label: "Default On",
+		label: "Default on",
 		description: "Pre-selected but users can opt out.",
 	},
 	{
 		value: "default_off",
-		label: "Default Off",
+		label: "Default off",
 		description: "Available but users must opt in.",
 	},
 ] as const;
@@ -784,7 +784,7 @@ const ServerForm: FC<ServerFormProps> = ({
 												disabled={isDisabled}
 											/>
 										</Field>
-										<Field label="API Key" htmlFor={`${formId}-apikey-value`}>
+										<Field label="API key" htmlFor={`${formId}-apikey-value`}>
 											<Input
 												id={`${formId}-apikey-value`}
 												className="h-9 font-mono text-[13px] [-webkit-text-security:disc]"