[msc] make playersettings more efficient

apps/chat/package.json

@@ -17,6 +17,7 @@
 	},
 	"dependencies": {
 		"@2toad/profanity": "3.3.0",
+		"@repo/domain": "workspace:*",
 		"@repo/hono-helpers": "workspace:*",
 		"@repo/jwt": "workspace:*",
 		"@standard-community/standard-json": "0.3.5",

apps/chat/src/chat.app.ts

@@ -2,6 +2,7 @@ import { Hono } from 'hono'
 import { describeRoute, openAPIRouteHandler } from 'hono-openapi'
 import { useWorkersLogger } from 'workers-tagged-logger'
 
+import { mergePlayerSettings as mergeStoredPlayerSettings, readPlayerSettings } from '@repo/domain'
 import { logger, withCleanSpec, withNotFound, withOnError } from '@repo/hono-helpers'
 import { validateAndGetAccountId } from '@repo/jwt'
 
@@ -201,10 +202,7 @@ async function getPlayerSettings(
 	env: Env,
 	accountId: number
 ): Promise<Record<string, string> | null> {
-	return env.RECFLARE_PLAYER_SETTINGS.get<Record<string, string>>(
-		`player:${accountId}`,
-		'json'
-	).catch(() => null)
+	return readPlayerSettings(env.RECFLARE_PLAYER_SETTINGS, accountId).catch(() => null)
 }
 
 /**
@@ -251,15 +249,15 @@ async function writeChatPrivacy(
  * Merge keys into the player's settings map, the way the `playersettings` worker's own PUT
  * does. Never a whole-map write: the bag holds every setting the player has (OOBE state,
  * tutorial mask, …) and storing one key on its own would wipe the rest. Values are strings,
- * which is what that worker stores and what its GET serves back.
+ * which is what that worker stores and what its GET serves back. Nothing is written when
+ * the patch changes no value — the client re-posts its privacy settings freely.
  */
 async function mergePlayerSettings(
 	env: Env,
 	accountId: number,
 	patch: Record<string, string>
 ): Promise<void> {
-	const merged: Record<string, string> = { ...(await getPlayerSettings(env, accountId)), ...patch }
-	await env.RECFLARE_PLAYER_SETTINGS.put(`player:${accountId}`, JSON.stringify(merged))
+	await mergeStoredPlayerSettings(env.RECFLARE_PLAYER_SETTINGS, accountId, patch)
 }
 
 /**

apps/chat/src/test/integration/api.test.ts

@@ -956,6 +956,17 @@ describe('PUT /thread/chatPrivacySetting', () => {
 		})
 	})
 
+	// Re-posting the stored value writes nothing to KV — writes are the cost, and the client
+	// posts these freely. The raw value is seeded with whitespace JSON.stringify never
+	// produces; surviving the PUT untouched means no write happened.
+	it('does not write KV when the value is already stored', async () => {
+		const padded = '{ "Recroom.OOBE": "77", "directMessagePrivacySetting": "Favorites" }'
+		await env.RECFLARE_PLAYER_SETTINGS.put('player:887010', padded)
+		const res = await put(887010, { directMessagePrivacySetting: 'Favorites' })
+		expect(await res.json()).toMatchObject({ directMessagePrivacySetting: 1 })
+		expect(await env.RECFLARE_PLAYER_SETTINGS.get('player:887010', 'text')).toBe(padded)
+	})
+
 	it('accepts the enum by ordinal too, and is case-insensitive about the name', async () => {
 		expect(await (await put(887005, { directMessagePrivacySetting: '2' })).json()).toMatchObject({
 			directMessagePrivacySetting: 2,