diff --git a/src/app/api/ai-summary/route.ts b/src/app/api/ai-summary/route.ts
index b31dd1a2..fb9e1516 100644
--- a/src/app/api/ai-summary/route.ts
+++ b/src/app/api/ai-summary/route.ts
@@ -4,20 +4,22 @@ import { getSummary } from "~/queries/page.server"
 export async function GET(req: Request): Promise<Response> {
   const query = getQuery(req)
   const res = new NextServerResponse()
-  if (!query.cid || typeof query.cid !== "string") {
+  if (!query.cid) {
     return res.status(400).json({ error: "Missing cid" })
   }
-  if (!query.lang || typeof query.lang !== "string") {
-    return res.status(400).json({ error: "Missing lang" })
-  }
 
   try {
     const summary = await getSummary({
       cid: query.cid,
-      lang: query.lang,
+      lang: String(query.lang),
     })
     return res.status(200).json({ summary })
   } catch (error) {
-    return res.status(500).json({ error: "Could not get summary" })
+    return res.status(500).json({
+      error:
+        "Could not get summary for" + query.cid + query.lang
+          ? " in " + query.lang
+          : "",
+    })
   }
 }
diff --git a/src/app/api/summary/route.ts b/src/app/api/summary/route.ts
deleted file mode 100644
index 68498545..00000000
--- a/src/app/api/summary/route.ts
+++ /dev/null
@@ -1,18 +0,0 @@
-import { getQuery, NextServerResponse } from "~/lib/server-helper"
-import { getSummary } from "~/queries/page.server"
-
-export async function GET(req: Request): Promise<Response> {
-  let { cid, lang } = getQuery(req)
-  const res = new NextServerResponse()
-
-  if (!cid) {
-    return res.status(400).send("Bad Request")
-  }
-
-  return res.status(200).json({
-    data: await getSummary({
-      cid,
-      lang,
-    }),
-  })
-}
diff --git a/src/app/api/translate-note/route.ts b/src/app/api/translate-note/route.ts
index 39a696d4..7c517a65 100644
--- a/src/app/api/translate-note/route.ts
+++ b/src/app/api/translate-note/route.ts
@@ -6,6 +6,7 @@ import { PromptTemplate } from "langchain/prompts"
 import { Metadata } from "@prisma/client"
 
 import { languageNames } from "~/i18n"
+import { detectLanguage } from "~/lib/detect-lang"
 import { toGateway } from "~/lib/ipfs-parser"
 import { llmModelSwitcherByTextLength } from "~/lib/llm-model-switcher-by-text-length"
 import prisma from "~/lib/prisma.server"
@@ -38,10 +39,17 @@ if (process.env.OPENAI_API_KEY) {
 type ChainKeyType = `${4 | 16}k_${Language}` // e.g. "4k_en" | "4k_zh" | "4k_zh-TW" | "4k_ja" | "16k_en" | "16k_zh" | "16k_zh-TW" | "16k_ja"
 const translationChains = new Map<ChainKeyType, LLMChain>()
 
-const getOriginalTranslation = async (
-  cid: string,
-  targetLang: Language,
-): Promise<ContentTranslation | undefined> => {
+const getOriginalTranslation = async ({
+  cid,
+  toLang,
+  fromLang,
+}: {
+  cid: string
+  toLang: Language
+  fromLang?: Language
+}): Promise<ContentTranslation | undefined> => {
+  if (fromLang === toLang) return
+
   if (!translationModel4K || !translationModel16K) return
 
   try {
@@ -49,19 +57,21 @@ const getOriginalTranslation = async (
       await fetch(toGateway(`ipfs://${cid}`))
     ).json()
 
-    console.time(`fetching translation ${cid}, ${targetLang}`)
+    if (!fromLang && detectLanguage(title + content) === toLang) return
+
+    console.time(`fetching translation ${cid}, ${toLang}`)
     const { modelSize, tokens } = llmModelSwitcherByTextLength(content, {
-      includeResponse: { lang: targetLang },
+      includeResponse: { lang: toLang },
     })
 
     if (!modelSize) {
       console.error(
-        `|__ Error: Content too long for translation: ${cid}, ${targetLang}. (Tokens: ${tokens})`,
+        `|__ Error: Content too long for translation: ${cid}, ${toLang}. (Tokens: ${tokens})`,
       )
       return
     }
 
-    let chain = translationChains.get(`${modelSize}_${targetLang}`)
+    let chain = translationChains.get(`${modelSize}_${toLang}`)
 
     if (!chain) {
       const template = `
@@ -81,7 +91,7 @@ You are a Markdown translation expert. During the translation process, you need
 
 IMPORTANT: ONLY RETURN TRANSLATED TEXT AND NOTHING ELSE.
 
-Translate the following text to ${languageNames[targetLang]} language:
+Translate the following text to ${languageNames[toLang]} language:
 
 {text}
 `
@@ -96,7 +106,7 @@ Translate the following text to ${languageNames[targetLang]} language:
 
       chain = new LLMChain({ llm: translateModel, prompt })
 
-      translationChains.set(`${modelSize}_${targetLang}`, chain)
+      translationChains.set(`${modelSize}_${toLang}`, chain)
     }
 
     const t =
@@ -109,7 +119,7 @@ Translate the following text to ${languageNames[targetLang]} language:
         ? { text: "" }
         : await chain.call({ text: content })
 
-    console.timeEnd(`fetching translation ${cid}, ${targetLang}`)
+    console.timeEnd(`fetching translation ${cid}, ${toLang}`)
 
     return {
       title: t.text,
@@ -117,23 +127,19 @@ Translate the following text to ${languageNames[targetLang]} language:
     }
   } catch (error) {
     console.error(error)
-    console.timeEnd(`fetching translation ${cid}, ${targetLang}`)
+    console.timeEnd(`fetching translation ${cid}, ${toLang}`)
   }
 }
 
 async function getTranslation({
   cid,
+  toLang,
   fromLang,
-  toLang = "en",
 }: {
   cid: string
+  toLang: Language
   fromLang?: Language
-  toLang?: Language
 }): Promise<ContentTranslation | undefined> {
-  if (fromLang === toLang) {
-    return undefined
-  }
-
   const translatedContent = (await cacheGet({
     key: ["translation", cid, toLang],
     allowEmpty: true,
@@ -159,7 +165,11 @@ async function getTranslation({
         if (translatedJson) {
           result = translatedJson
         } else {
-          const newTranslation = await getOriginalTranslation(cid, toLang)
+          const newTranslation = await getOriginalTranslation({
+            cid,
+            toLang,
+            fromLang,
+          })
           if (newTranslation) {
             /**
              * e.g.
@@ -215,7 +225,11 @@ export async function GET(req: Request): Promise<Response> {
   const res = new NextServerResponse()
 
   if (!cid) {
-    return res.status(400).send("Bad Request")
+    return res.status(400).json({ error: "Missing cid" })
+  }
+
+  if (!toLang) {
+    return res.status(400).json({ error: "Missing toLang" })
   }
 
   return res.status(200).json({
diff --git a/src/queries/page.server.ts b/src/queries/page.server.ts
index 0211c3c4..61ab12c5 100644
--- a/src/queries/page.server.ts
+++ b/src/queries/page.server.ts
@@ -7,7 +7,8 @@ import removeMarkdown from "remove-markdown"
 import { Metadata } from "@prisma/client"
 import { QueryClient } from "@tanstack/react-query"
 
-import { defaultLocale, locales } from "~/i18n"
+import { locales } from "~/i18n"
+import { detectLanguage } from "~/lib/detect-lang"
 import { toGateway } from "~/lib/ipfs-parser"
 import prisma from "~/lib/prisma.server"
 import { cacheGet } from "~/lib/redis.server"
@@ -85,7 +86,13 @@ if (process.env.OPENAI_API_KEY) {
 }
 const chains = new Map<string, AnalyzeDocumentChain>()
 
-const getOriginalSummary = async (cid: string, lang: string) => {
+const getOriginalSummary = async ({
+  cid,
+  lang,
+}: {
+  cid: string
+  lang?: string
+}) => {
   if (!model) return
   try {
     let { content } = await (await fetch(toGateway(`ipfs://${cid}`))).json()
@@ -96,12 +103,13 @@ const getOriginalSummary = async (cid: string, lang: string) => {
     if (content?.length < 200) {
       return
     } else if (content) {
-      console.time(`fetching summary ${cid}, ${lang}`)
+      const summaryLang = lang ?? detectLanguage(content)
+      console.time(`fetching summary ${cid}, ${summaryLang}`)
 
-      let chain = chains.get(lang)
+      let chain = chains.get(summaryLang)
       if (!chain) {
         const prompt = new PromptTemplate({
-          template: `Summarize this in "${lang}" language:
+          template: `Summarize this in "${summaryLang}" language:
         "{text}"
         CONCISE SUMMARY:`,
           inputVariables: ["text"],
@@ -117,7 +125,7 @@ const getOriginalSummary = async (cid: string, lang: string) => {
           combineDocumentsChain: combineDocsChain,
         })
 
-        chains.set(lang, chain)
+        chains.set(summaryLang, chain)
       }
 
       const res = await chain.call({
@@ -138,7 +146,7 @@ const lock = new AsyncLock()
 
 export async function getSummary({
   cid,
-  lang = defaultLocale,
+  lang,
 }: {
   cid: string
   lang?: string
@@ -149,7 +157,7 @@ export async function getSummary({
     noUpdate: true,
     noExpire: true,
     getValueFun: async () => {
-      if (locales.includes(lang as Language)) {
+      if (!lang || locales.includes(lang as Language)) {
         let result
         await lock.acquire(cid, async () => {
           const meta = await prisma.metadata.findFirst({
@@ -157,12 +165,12 @@ export async function getSummary({
               uri: `ipfs://${cid}`,
             },
           })
-          const key = `ai_summary_${lang.replace("-", "").toLowerCase()}`
+          const key = `ai_summary_${lang?.replace("-", "").toLowerCase()}`
           if (meta) {
             if (meta?.[key as keyof Metadata]) {
               result = meta?.[key as keyof Metadata]
             } else {
-              const summary = await getOriginalSummary(cid, lang)
+              const summary = await getOriginalSummary({ cid, lang })
               if (summary) {
                 await prisma.metadata.update({
                   where: {
@@ -176,7 +184,7 @@ export async function getSummary({
               }
             }
           } else {
-            const summary = await getOriginalSummary(cid, lang)
+            const summary = await getOriginalSummary({ cid, lang })
             if (summary) {
               await prisma.metadata.create({
                 data: {