From dcfa1a53485f357bceeb158e26090a855c06cd8e Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Wed, 30 Oct 2024 09:25:19 +0900
Subject: [PATCH 01/15] feat(helper/proxy): introduce proxy helper

---
 src/helper/proxy/index.test.ts | 112 +++++++++++++++++++++++++++++++++
 src/helper/proxy/index.ts      |  85 +++++++++++++++++++++++++
 2 files changed, 197 insertions(+)
 create mode 100644 src/helper/proxy/index.test.ts
 create mode 100644 src/helper/proxy/index.ts

diff --git a/src/helper/proxy/index.test.ts b/src/helper/proxy/index.test.ts
new file mode 100644
index 000000000..16afd6eaa
--- /dev/null
+++ b/src/helper/proxy/index.test.ts
@@ -0,0 +1,112 @@
+import { Hono } from '../../hono'
+import { proxyFetch } from '.'
+
+describe('Proxy Middleware', () => {
+  describe('proxyFetch', () => {
+    beforeEach(() => {
+      global.fetch = vi.fn().mockResolvedValue(
+        new Response('ok', {
+          headers: {
+            'Content-Encoding': 'gzip',
+            'Content-Length': '100',
+            'Content-Range': '100-200',
+            'X-Response-Id': '456',
+          },
+        })
+      )
+    })
+
+    it('simple proxy', async () => {
+      const app = new Hono()
+      app.get('/proxy/:path', (c) =>
+        proxyFetch(
+          new Request(`https://example.com/${c.req.param('path')}`, {
+            headers: {
+              'X-Request-Id': '123',
+              'Accept-Encoding': 'gzip',
+            },
+          })
+        )
+      )
+      const res = await app.request('/proxy/test')
+      const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
+
+      expect(req.url).toBe('https://example.com/test')
+      expect(req.headers.get('X-Request-Id')).toBe('123')
+      expect(req.headers.get('Accept-Encoding')).toBeNull()
+
+      expect(res.status).toBe(200)
+      expect(res.headers.get('X-Response-Id')).toBe('456')
+      expect(res.headers.get('Content-Encoding')).toBeNull()
+      expect(res.headers.get('Content-Length')).toBeNull()
+      expect(res.headers.get('Content-Range')).toBeNull()
+    })
+
+    it('proxySetRequestHeaders option', async () => {
+      const app = new Hono()
+      app.get('/proxy/:path', (c) =>
+        proxyFetch(
+          new Request(`https://example.com/${c.req.param('path')}`, {
+            headers: {
+              'X-Request-Id': '123',
+              'X-To-Be-Deleted': 'to-be-deleted',
+              'Accept-Encoding': 'gzip',
+            },
+          }),
+          {
+            proxySetRequestHeaders: {
+              'X-Request-Id': 'abc',
+              'X-Forwarded-For': '127.0.0.1',
+              'X-Forwarded-Host': 'example.com',
+              'X-To-Be-Deleted': undefined,
+            },
+          }
+        )
+      )
+      const res = await app.request('/proxy/test')
+      const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
+
+      expect(req.url).toBe('https://example.com/test')
+      expect(req.headers.get('X-Request-Id')).toBe('abc')
+      expect(req.headers.get('X-Forwarded-For')).toBe('127.0.0.1')
+      expect(req.headers.get('X-Forwarded-Host')).toBe('example.com')
+      expect(req.headers.get('X-To-Be-Deleted')).toBeNull()
+      expect(req.headers.get('Accept-Encoding')).toBeNull()
+
+      expect(res.status).toBe(200)
+      expect(res.headers.get('X-Response-Id')).toBe('456')
+      expect(res.headers.get('Content-Encoding')).toBeNull()
+      expect(res.headers.get('Content-Length')).toBeNull()
+      expect(res.headers.get('Content-Range')).toBeNull()
+    })
+
+    it('proxySetRequestHeaders option', async () => {
+      const app = new Hono()
+      app.get('/proxy/:path', (c) =>
+        proxyFetch(
+          new Request(`https://example.com/${c.req.param('path')}`, {
+            headers: {
+              'X-Request-Id': '123',
+              'Accept-Encoding': 'gzip',
+            },
+          }),
+          {
+            proxyDeleteResponseHeaderNames: ['X-Response-Id'],
+          }
+        )
+      )
+      const res = await app.request('/proxy/test')
+      const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
+
+      expect(req.url).toBe('https://example.com/test')
+      expect(req.headers.get('X-Request-Id')).toBe('123')
+      expect(req.headers.get('Accept-Encoding')).toBeNull()
+
+      expect(res.status).toBe(200)
+      expect(res.headers.get('X-Response-Id')).toBeNull()
+      expect(res.headers.get('Content-Encoding')).toBeNull()
+      expect(res.headers.get('Content-Length')).toBeNull()
+      expect(res.headers.get('Content-Range')).toBeNull()
+    })
+  })
+})
diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
new file mode 100644
index 000000000..4f4f0ad2f
--- /dev/null
+++ b/src/helper/proxy/index.ts
@@ -0,0 +1,85 @@
+/**
+ * @module
+ * Proxy Helper for Hono.
+ */
+
+/*
+ * The following headers will be deleted from the response:
+ * * Content-Encoding
+ * * Content-Length
+ * * Content-Range
+ */
+const forceDeleteResponseHeaderNames = ['Content-Encoding', 'Content-Length', 'Content-Range']
+
+// Typical header names for requests for proxy use
+type ProxyRequestHeaderName = 'X-Forwarded-For' | 'X-Forwarded-Proto' | 'X-Forwarded-Host'
+
+interface ProxyRequestInit extends RequestInit {
+  /**
+   * Headers that are overwritten in requests to the origin server.
+   * Specify undefined to delete the header.
+   */
+  proxySetRequestHeaders?: Partial<Record<ProxyRequestHeaderName, string>> &
+    Record<string, string | undefined>
+  /**
+   * Headers included in the response from the origin server that should be removed in the response to the client.
+   */
+  proxyDeleteResponseHeaderNames?: string[]
+}
+
+interface ProxyFetch {
+  (input: RequestInfo | URL, init?: ProxyRequestInit): Promise<Response>
+  (input: string | URL | globalThis.Request, init?: ProxyRequestInit): Promise<Response>
+}
+
+/**
+ * Fetch API wrapper for proxy.
+ * The parameters and return value are the same as for `fetch` (except for the proxy-specific options).
+ *
+ * The “Accept-Encoding” header is replaced with an encoding that the current runtime can handle.
+ * Unnecessary response headers are deleted and a Response object is returned that can be returned
+ * as is as a response from the handler.
+ *
+ * @example
+ * ```ts
+ * app.get('/proxy/:path', (c) => {
+ *   return proxyFetch(new Request(`http://${originServer}/${c.req.param('path')}`, c.req.raw), {
+ *     proxySetRequestHeaders: {
+ *       'X-Forwarded-For': '127.0.0.1',
+ *       'X-Forwarded-Host': c.req.header('host'),
+ *       Authorization: undefined, // do not propagate request headers contained in c.req.raw
+ *     },
+ *     proxyDeleteResponseHeaderNames: ['Cookie'],
+ *   })
+ * })
+ * ```
+ */
+export const proxyFetch: ProxyFetch = async (input, proxyInit) => {
+  const {
+    proxySetRequestHeaders = {},
+    proxyDeleteResponseHeaderNames = [],
+    ...requestInit
+  } = proxyInit ?? {}
+
+  const req = new Request(input, requestInit)
+  req.headers.delete('accept-encoding')
+
+  for (const [key, value] of Object.entries(proxySetRequestHeaders)) {
+    if (value !== undefined) {
+      req.headers.set(key, value)
+    } else {
+      req.headers.delete(key)
+    }
+  }
+
+  const res = await fetch(req)
+  const resHeaders = new Headers(res.headers)
+  for (const key of forceDeleteResponseHeaderNames.concat(proxyDeleteResponseHeaderNames)) {
+    resHeaders.delete(key)
+  }
+
+  return new Response(res.body, {
+    ...res,
+    headers: resHeaders,
+  })
+}

From 64cdd4133c11a0f9a8e338c0c3bc6a403a7b3c1c Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Wed, 30 Oct 2024 18:16:58 +0900
Subject: [PATCH 02/15] chore(helper/proxy): expose proxy helper

---
 jsr.json     | 1 +
 package.json | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/jsr.json b/jsr.json
index 09c22785b..9d253f8ea 100644
--- a/jsr.json
+++ b/jsr.json
@@ -79,6 +79,7 @@
     "./testing": "./src/helper/testing/index.ts",
     "./dev": "./src/helper/dev/index.ts",
     "./ws": "./src/helper/websocket/index.ts",
+    "./proxy": "./src/helper/proxy/index.ts",
     "./utils/body": "./src/utils/body.ts",
     "./utils/buffer": "./src/utils/buffer.ts",
     "./utils/color": "./src/utils/color.ts",
diff --git a/package.json b/package.json
index 77b62e787..a1452a93c 100644
--- a/package.json
+++ b/package.json
@@ -383,6 +383,11 @@
       "types": "./dist/types/helper/conninfo/index.d.ts",
       "import": "./dist/helper/conninfo/index.js",
       "require": "./dist/cjs/helper/conninfo/index.js"
+    },
+    "./proxy": {
+      "types": "./dist/types/helper/proxy/index.d.ts",
+      "import": "./dist/helper/proxy/index.js",
+      "require": "./dist/cjs/helper/proxy/index.js"
     }
   },
   "typesVersions": {
@@ -587,6 +592,9 @@
       ],
       "conninfo": [
         "./dist/types/helper/conninfo"
+      ],
+      "proxy": [
+        "./dist/types/helper/proxy"
       ]
     }
   },

From ad17d90a6e295e3ac1eaaa159b89036a24fda8eb Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Wed, 30 Oct 2024 22:22:16 +0900
Subject: [PATCH 03/15] test(helper/proxy): fix test name

---
 src/helper/proxy/index.test.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/helper/proxy/index.test.ts b/src/helper/proxy/index.test.ts
index 16afd6eaa..1262b2f35 100644
--- a/src/helper/proxy/index.test.ts
+++ b/src/helper/proxy/index.test.ts
@@ -80,7 +80,7 @@ describe('Proxy Middleware', () => {
       expect(res.headers.get('Content-Range')).toBeNull()
     })
 
-    it('proxySetRequestHeaders option', async () => {
+    it('proxySetRequestHeaderNames option', async () => {
       const app = new Hono()
       app.get('/proxy/:path', (c) =>
         proxyFetch(

From 5998770200b3e4101243c95b44498be3a33b7985 Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Thu, 31 Oct 2024 06:23:41 +0900
Subject: [PATCH 04/15] fix(helper/proxy): return Content-Range header as it is

Co-authored-by: Haochen M. Kotoi-Xie <haochenx@acm.org>
---
 src/helper/proxy/index.test.ts | 8 ++++----
 src/helper/proxy/index.ts      | 3 +--
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/src/helper/proxy/index.test.ts b/src/helper/proxy/index.test.ts
index 1262b2f35..1bcbc16ec 100644
--- a/src/helper/proxy/index.test.ts
+++ b/src/helper/proxy/index.test.ts
@@ -9,7 +9,7 @@ describe('Proxy Middleware', () => {
           headers: {
             'Content-Encoding': 'gzip',
             'Content-Length': '100',
-            'Content-Range': '100-200',
+            'Content-Range': 'bytes 0-2/1024',
             'X-Response-Id': '456',
           },
         })
@@ -39,7 +39,7 @@ describe('Proxy Middleware', () => {
       expect(res.headers.get('X-Response-Id')).toBe('456')
       expect(res.headers.get('Content-Encoding')).toBeNull()
       expect(res.headers.get('Content-Length')).toBeNull()
-      expect(res.headers.get('Content-Range')).toBeNull()
+      expect(res.headers.get('Content-Range')).toBe('bytes 0-2/1024')
     })
 
     it('proxySetRequestHeaders option', async () => {
@@ -77,7 +77,7 @@ describe('Proxy Middleware', () => {
       expect(res.headers.get('X-Response-Id')).toBe('456')
       expect(res.headers.get('Content-Encoding')).toBeNull()
       expect(res.headers.get('Content-Length')).toBeNull()
-      expect(res.headers.get('Content-Range')).toBeNull()
+      expect(res.headers.get('Content-Range')).toBe('bytes 0-2/1024')
     })
 
     it('proxySetRequestHeaderNames option', async () => {
@@ -106,7 +106,7 @@ describe('Proxy Middleware', () => {
       expect(res.headers.get('X-Response-Id')).toBeNull()
       expect(res.headers.get('Content-Encoding')).toBeNull()
       expect(res.headers.get('Content-Length')).toBeNull()
-      expect(res.headers.get('Content-Range')).toBeNull()
+      expect(res.headers.get('Content-Range')).toBe('bytes 0-2/1024')
     })
   })
 })
diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index 4f4f0ad2f..e1ac48b91 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -7,9 +7,8 @@
  * The following headers will be deleted from the response:
  * * Content-Encoding
  * * Content-Length
- * * Content-Range
  */
-const forceDeleteResponseHeaderNames = ['Content-Encoding', 'Content-Length', 'Content-Range']
+const forceDeleteResponseHeaderNames = ['Content-Encoding', 'Content-Length']
 
 // Typical header names for requests for proxy use
 type ProxyRequestHeaderName = 'X-Forwarded-For' | 'X-Forwarded-Proto' | 'X-Forwarded-Host'

From 3a5ef0f4844b67a5bdcf8d5039b76aee8bf4bf3a Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Thu, 31 Oct 2024 06:44:08 +0900
Subject: [PATCH 05/15] refactor(helper/proxy): return the original
 content-length if the response is uncompressed

---
 src/helper/proxy/index.test.ts | 74 ++++++++++++++++++++++++++--------
 src/helper/proxy/index.ts      | 14 +++----
 2 files changed, 63 insertions(+), 25 deletions(-)

diff --git a/src/helper/proxy/index.test.ts b/src/helper/proxy/index.test.ts
index 1bcbc16ec..a60ece09e 100644
--- a/src/helper/proxy/index.test.ts
+++ b/src/helper/proxy/index.test.ts
@@ -4,19 +4,34 @@ import { proxyFetch } from '.'
 describe('Proxy Middleware', () => {
   describe('proxyFetch', () => {
     beforeEach(() => {
-      global.fetch = vi.fn().mockResolvedValue(
-        new Response('ok', {
-          headers: {
-            'Content-Encoding': 'gzip',
-            'Content-Length': '100',
-            'Content-Range': 'bytes 0-2/1024',
-            'X-Response-Id': '456',
-          },
-        })
-      )
+      global.fetch = vi.fn().mockImplementation((req) => {
+        if (req.url === 'https://example.com/compressed') {
+          return Promise.resolve(
+            new Response('ok', {
+              headers: {
+                'Content-Encoding': 'gzip',
+                'Content-Length': '1',
+                'Content-Range': 'bytes 0-2/1024',
+                'X-Response-Id': '456',
+              },
+            })
+          )
+        } else if (req.url === 'https://example.com/uncompressed') {
+          return Promise.resolve(
+            new Response('ok', {
+              headers: {
+                'Content-Length': '2',
+                'Content-Range': 'bytes 0-2/1024',
+                'X-Response-Id': '456',
+              },
+            })
+          )
+        }
+        return Promise.resolve(new Response('not found', { status: 404 }))
+      })
     })
 
-    it('simple proxy', async () => {
+    it('compressed', async () => {
       const app = new Hono()
       app.get('/proxy/:path', (c) =>
         proxyFetch(
@@ -28,10 +43,10 @@ describe('Proxy Middleware', () => {
           })
         )
       )
-      const res = await app.request('/proxy/test')
+      const res = await app.request('/proxy/compressed')
       const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
 
-      expect(req.url).toBe('https://example.com/test')
+      expect(req.url).toBe('https://example.com/compressed')
       expect(req.headers.get('X-Request-Id')).toBe('123')
       expect(req.headers.get('Accept-Encoding')).toBeNull()
 
@@ -42,6 +57,31 @@ describe('Proxy Middleware', () => {
       expect(res.headers.get('Content-Range')).toBe('bytes 0-2/1024')
     })
 
+    it('uncompressed', async () => {
+      const app = new Hono()
+      app.get('/proxy/:path', (c) =>
+        proxyFetch(
+          new Request(`https://example.com/${c.req.param('path')}`, {
+            headers: {
+              'X-Request-Id': '123',
+              'Accept-Encoding': 'gzip',
+            },
+          })
+        )
+      )
+      const res = await app.request('/proxy/uncompressed')
+      const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
+
+      expect(req.url).toBe('https://example.com/uncompressed')
+      expect(req.headers.get('X-Request-Id')).toBe('123')
+      expect(req.headers.get('Accept-Encoding')).toBeNull()
+
+      expect(res.status).toBe(200)
+      expect(res.headers.get('X-Response-Id')).toBe('456')
+      expect(res.headers.get('Content-Length')).toBe('2')
+      expect(res.headers.get('Content-Range')).toBe('bytes 0-2/1024')
+    })
+
     it('proxySetRequestHeaders option', async () => {
       const app = new Hono()
       app.get('/proxy/:path', (c) =>
@@ -63,10 +103,10 @@ describe('Proxy Middleware', () => {
           }
         )
       )
-      const res = await app.request('/proxy/test')
+      const res = await app.request('/proxy/compressed')
       const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
 
-      expect(req.url).toBe('https://example.com/test')
+      expect(req.url).toBe('https://example.com/compressed')
       expect(req.headers.get('X-Request-Id')).toBe('abc')
       expect(req.headers.get('X-Forwarded-For')).toBe('127.0.0.1')
       expect(req.headers.get('X-Forwarded-Host')).toBe('example.com')
@@ -95,10 +135,10 @@ describe('Proxy Middleware', () => {
           }
         )
       )
-      const res = await app.request('/proxy/test')
+      const res = await app.request('/proxy/compressed')
       const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
 
-      expect(req.url).toBe('https://example.com/test')
+      expect(req.url).toBe('https://example.com/compressed')
       expect(req.headers.get('X-Request-Id')).toBe('123')
       expect(req.headers.get('Accept-Encoding')).toBeNull()
 
diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index e1ac48b91..fbe9220ab 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -3,13 +3,6 @@
  * Proxy Helper for Hono.
  */
 
-/*
- * The following headers will be deleted from the response:
- * * Content-Encoding
- * * Content-Length
- */
-const forceDeleteResponseHeaderNames = ['Content-Encoding', 'Content-Length']
-
 // Typical header names for requests for proxy use
 type ProxyRequestHeaderName = 'X-Forwarded-For' | 'X-Forwarded-Proto' | 'X-Forwarded-Host'
 
@@ -73,7 +66,12 @@ export const proxyFetch: ProxyFetch = async (input, proxyInit) => {
 
   const res = await fetch(req)
   const resHeaders = new Headers(res.headers)
-  for (const key of forceDeleteResponseHeaderNames.concat(proxyDeleteResponseHeaderNames)) {
+  if (resHeaders.has('content-encoding')) {
+    resHeaders.delete('content-encoding')
+    // Content-Length is the size of the compressed content, not the size of the original content
+    resHeaders.delete('content-length')
+  }
+  for (const key of proxyDeleteResponseHeaderNames) {
     resHeaders.delete(key)
   }
 

From b6eb510285c2fb040433cc95ba60dfc07ed2dce9 Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Sun, 26 Jan 2025 11:39:29 +0900
Subject: [PATCH 06/15] feat(middleware): enable to pass `...c.req` to init
 options

---
 src/helper/proxy/index.test.ts | 81 +++++++++-------------------------
 src/helper/proxy/index.ts      | 67 +++++++++++++++-------------
 2 files changed, 56 insertions(+), 92 deletions(-)

diff --git a/src/helper/proxy/index.test.ts b/src/helper/proxy/index.test.ts
index a60ece09e..331416039 100644
--- a/src/helper/proxy/index.test.ts
+++ b/src/helper/proxy/index.test.ts
@@ -4,7 +4,7 @@ import { proxyFetch } from '.'
 describe('Proxy Middleware', () => {
   describe('proxyFetch', () => {
     beforeEach(() => {
-      global.fetch = vi.fn().mockImplementation((req) => {
+      global.fetch = vi.fn().mockImplementation(async (req) => {
         if (req.url === 'https://example.com/compressed') {
           return Promise.resolve(
             new Response('ok', {
@@ -26,6 +26,8 @@ describe('Proxy Middleware', () => {
               },
             })
           )
+        } else if (req.url === 'https://example.com/post' && req.method === 'POST') {
+          return Promise.resolve(new Response(`request body: ${await req.text()}`))
         }
         return Promise.resolve(new Response('not found', { status: 404 }))
       })
@@ -82,71 +84,28 @@ describe('Proxy Middleware', () => {
       expect(res.headers.get('Content-Range')).toBe('bytes 0-2/1024')
     })
 
-    it('proxySetRequestHeaders option', async () => {
+    it('POST request', async () => {
       const app = new Hono()
-      app.get('/proxy/:path', (c) =>
-        proxyFetch(
-          new Request(`https://example.com/${c.req.param('path')}`, {
-            headers: {
-              'X-Request-Id': '123',
-              'X-To-Be-Deleted': 'to-be-deleted',
-              'Accept-Encoding': 'gzip',
-            },
-          }),
-          {
-            proxySetRequestHeaders: {
-              'X-Request-Id': 'abc',
-              'X-Forwarded-For': '127.0.0.1',
-              'X-Forwarded-Host': 'example.com',
-              'X-To-Be-Deleted': undefined,
-            },
-          }
-        )
-      )
-      const res = await app.request('/proxy/compressed')
-      const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
-
-      expect(req.url).toBe('https://example.com/compressed')
-      expect(req.headers.get('X-Request-Id')).toBe('abc')
-      expect(req.headers.get('X-Forwarded-For')).toBe('127.0.0.1')
-      expect(req.headers.get('X-Forwarded-Host')).toBe('example.com')
-      expect(req.headers.get('X-To-Be-Deleted')).toBeNull()
-      expect(req.headers.get('Accept-Encoding')).toBeNull()
-
-      expect(res.status).toBe(200)
-      expect(res.headers.get('X-Response-Id')).toBe('456')
-      expect(res.headers.get('Content-Encoding')).toBeNull()
-      expect(res.headers.get('Content-Length')).toBeNull()
-      expect(res.headers.get('Content-Range')).toBe('bytes 0-2/1024')
-    })
-
-    it('proxySetRequestHeaderNames option', async () => {
-      const app = new Hono()
-      app.get('/proxy/:path', (c) =>
-        proxyFetch(
-          new Request(`https://example.com/${c.req.param('path')}`, {
-            headers: {
-              'X-Request-Id': '123',
-              'Accept-Encoding': 'gzip',
-            },
-          }),
-          {
-            proxyDeleteResponseHeaderNames: ['X-Response-Id'],
-          }
-        )
-      )
-      const res = await app.request('/proxy/compressed')
+      app.all('/proxy/:path', (c) => {
+        return proxyFetch(`https://example.com/${c.req.param('path')}`, {
+          ...c.req,
+          headers: {
+            ...c.req.header(),
+            'X-Request-Id': '123',
+            'Accept-Encoding': 'gzip',
+          },
+        })
+      })
+      const res = await app.request('/proxy/post', {
+        method: 'POST',
+        body: 'test',
+      })
       const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
 
-      expect(req.url).toBe('https://example.com/compressed')
-      expect(req.headers.get('X-Request-Id')).toBe('123')
-      expect(req.headers.get('Accept-Encoding')).toBeNull()
+      expect(req.url).toBe('https://example.com/post')
 
       expect(res.status).toBe(200)
-      expect(res.headers.get('X-Response-Id')).toBeNull()
-      expect(res.headers.get('Content-Encoding')).toBeNull()
-      expect(res.headers.get('Content-Length')).toBeNull()
-      expect(res.headers.get('Content-Range')).toBe('bytes 0-2/1024')
+      expect(await res.text()).toBe('request body: test')
     })
   })
 })
diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index fbe9220ab..759b0f435 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -3,20 +3,8 @@
  * Proxy Helper for Hono.
  */
 
-// Typical header names for requests for proxy use
-type ProxyRequestHeaderName = 'X-Forwarded-For' | 'X-Forwarded-Proto' | 'X-Forwarded-Host'
-
 interface ProxyRequestInit extends RequestInit {
-  /**
-   * Headers that are overwritten in requests to the origin server.
-   * Specify undefined to delete the header.
-   */
-  proxySetRequestHeaders?: Partial<Record<ProxyRequestHeaderName, string>> &
-    Record<string, string | undefined>
-  /**
-   * Headers included in the response from the origin server that should be removed in the response to the client.
-   */
-  proxyDeleteResponseHeaderNames?: string[]
+  raw?: Request
 }
 
 interface ProxyFetch {
@@ -35,35 +23,55 @@ interface ProxyFetch {
  * @example
  * ```ts
  * app.get('/proxy/:path', (c) => {
- *   return proxyFetch(new Request(`http://${originServer}/${c.req.param('path')}`, c.req.raw), {
- *     proxySetRequestHeaders: {
+ *   return proxyFetch(`http://${originServer}/${c.req.param('path')}`, {
+ *     headers: {
+ *       ...c.req.header(), // optional, specify only when header forwarding is truly necessary.
+ *       'X-Forwarded-For': '127.0.0.1',
+ *       'X-Forwarded-Host': c.req.header('host'),
+ *       Authorization: undefined, // do not propagate request headers contained in c.req.header('Authorization')
+ *     },
+ *   }).then((res) => {
+ *     res.headers.delete('Cookie')
+ *     return res
+ *   })
+ * })
+ * 
+ * app.any('/proxy/:path', (c) => {
+ *   return proxyFetch(`http://${originServer}/${c.req.param('path')}`, {
+ *     ...c.req,
+ *     headers: {
+ *       ...c.req.header(),
  *       'X-Forwarded-For': '127.0.0.1',
  *       'X-Forwarded-Host': c.req.header('host'),
- *       Authorization: undefined, // do not propagate request headers contained in c.req.raw
+ *       Authorization: undefined, // do not propagate request headers contained in c.req.header('Authorization')
  *     },
- *     proxyDeleteResponseHeaderNames: ['Cookie'],
  *   })
  * })
  * ```
  */
 export const proxyFetch: ProxyFetch = async (input, proxyInit) => {
   const {
-    proxySetRequestHeaders = {},
-    proxyDeleteResponseHeaderNames = [],
+    raw,
     ...requestInit
   } = proxyInit ?? {}
 
-  const req = new Request(input, requestInit)
-  req.headers.delete('accept-encoding')
-
-  for (const [key, value] of Object.entries(proxySetRequestHeaders)) {
-    if (value !== undefined) {
-      req.headers.set(key, value)
-    } else {
-      req.headers.delete(key)
-    }
+  const requestInitRaw: RequestInit & { duplex?: 'half' } = raw
+    ? {
+        method: raw.method,
+        body: raw.body,
+        headers: raw.headers,
+      }
+    : {}
+  if (requestInitRaw.body) {
+    requestInitRaw.duplex = 'half'
   }
 
+  const req = new Request(input, {
+    ...requestInitRaw,
+    ...requestInit,
+  })
+  req.headers.delete('accept-encoding')
+
   const res = await fetch(req)
   const resHeaders = new Headers(res.headers)
   if (resHeaders.has('content-encoding')) {
@@ -71,9 +79,6 @@ export const proxyFetch: ProxyFetch = async (input, proxyInit) => {
     // Content-Length is the size of the compressed content, not the size of the original content
     resHeaders.delete('content-length')
   }
-  for (const key of proxyDeleteResponseHeaderNames) {
-    resHeaders.delete(key)
-  }
 
   return new Response(res.body, {
     ...res,

From fb54227f9b861c3376032c0ed503ecd13b6bce55 Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Sun, 26 Jan 2025 11:42:09 +0900
Subject: [PATCH 07/15] refactor(middleware/proxy): rename `proxyFetch` to
 `proxy`

---
 src/helper/proxy/index.test.ts | 10 +++++-----
 src/helper/proxy/index.ts      | 13 +++++--------
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/src/helper/proxy/index.test.ts b/src/helper/proxy/index.test.ts
index 331416039..079ba7a5b 100644
--- a/src/helper/proxy/index.test.ts
+++ b/src/helper/proxy/index.test.ts
@@ -1,8 +1,8 @@
 import { Hono } from '../../hono'
-import { proxyFetch } from '.'
+import { proxy } from '.'
 
 describe('Proxy Middleware', () => {
-  describe('proxyFetch', () => {
+  describe('proxy', () => {
     beforeEach(() => {
       global.fetch = vi.fn().mockImplementation(async (req) => {
         if (req.url === 'https://example.com/compressed') {
@@ -36,7 +36,7 @@ describe('Proxy Middleware', () => {
     it('compressed', async () => {
       const app = new Hono()
       app.get('/proxy/:path', (c) =>
-        proxyFetch(
+        proxy(
           new Request(`https://example.com/${c.req.param('path')}`, {
             headers: {
               'X-Request-Id': '123',
@@ -62,7 +62,7 @@ describe('Proxy Middleware', () => {
     it('uncompressed', async () => {
       const app = new Hono()
       app.get('/proxy/:path', (c) =>
-        proxyFetch(
+        proxy(
           new Request(`https://example.com/${c.req.param('path')}`, {
             headers: {
               'X-Request-Id': '123',
@@ -87,7 +87,7 @@ describe('Proxy Middleware', () => {
     it('POST request', async () => {
       const app = new Hono()
       app.all('/proxy/:path', (c) => {
-        return proxyFetch(`https://example.com/${c.req.param('path')}`, {
+        return proxy(`https://example.com/${c.req.param('path')}`, {
           ...c.req,
           headers: {
             ...c.req.header(),
diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index 759b0f435..26035b82b 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -23,7 +23,7 @@ interface ProxyFetch {
  * @example
  * ```ts
  * app.get('/proxy/:path', (c) => {
- *   return proxyFetch(`http://${originServer}/${c.req.param('path')}`, {
+ *   return proxy(`http://${originServer}/${c.req.param('path')}`, {
  *     headers: {
  *       ...c.req.header(), // optional, specify only when header forwarding is truly necessary.
  *       'X-Forwarded-For': '127.0.0.1',
@@ -35,9 +35,9 @@ interface ProxyFetch {
  *     return res
  *   })
  * })
- * 
+ *
  * app.any('/proxy/:path', (c) => {
- *   return proxyFetch(`http://${originServer}/${c.req.param('path')}`, {
+ *   return proxy(`http://${originServer}/${c.req.param('path')}`, {
  *     ...c.req,
  *     headers: {
  *       ...c.req.header(),
@@ -49,11 +49,8 @@ interface ProxyFetch {
  * })
  * ```
  */
-export const proxyFetch: ProxyFetch = async (input, proxyInit) => {
-  const {
-    raw,
-    ...requestInit
-  } = proxyInit ?? {}
+export const proxy: ProxyFetch = async (input, proxyInit) => {
+  const { raw, ...requestInit } = proxyInit ?? {}
 
   const requestInitRaw: RequestInit & { duplex?: 'half' } = raw
     ? {

From e08c602c9ea95a0b5023a67141750db9531e314b Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Sun, 26 Jan 2025 11:55:33 +0900
Subject: [PATCH 08/15] docs(helper/proxy): update example

---
 src/helper/proxy/index.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index 26035b82b..6052b7a2b 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -25,7 +25,7 @@ interface ProxyFetch {
  * app.get('/proxy/:path', (c) => {
  *   return proxy(`http://${originServer}/${c.req.param('path')}`, {
  *     headers: {
- *       ...c.req.header(), // optional, specify only when header forwarding is truly necessary.
+ *       ...c.req.header(), // optional, specify only when forwarding all the request data (including credentials) is necessary.
  *       'X-Forwarded-For': '127.0.0.1',
  *       'X-Forwarded-Host': c.req.header('host'),
  *       Authorization: undefined, // do not propagate request headers contained in c.req.header('Authorization')
@@ -38,7 +38,7 @@ interface ProxyFetch {
  *
  * app.any('/proxy/:path', (c) => {
  *   return proxy(`http://${originServer}/${c.req.param('path')}`, {
- *     ...c.req,
+ *     ...c.req, // optional, specify only when forwarding all the request data (including credentials) is necessary
  *     headers: {
  *       ...c.req.header(),
  *       'X-Forwarded-For': '127.0.0.1',

From eafc02aff50055378b7d87af11d76c84fd9ebeb3 Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Sun, 26 Jan 2025 11:57:19 +0900
Subject: [PATCH 09/15] docs(helper/proxy): fix typo

---
 src/helper/proxy/index.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index 6052b7a2b..0754dbefb 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -38,7 +38,7 @@ interface ProxyFetch {
  *
  * app.any('/proxy/:path', (c) => {
  *   return proxy(`http://${originServer}/${c.req.param('path')}`, {
- *     ...c.req, // optional, specify only when forwarding all the request data (including credentials) is necessary
+ *     ...c.req, // optional, specify only when forwarding all the request data (including credentials) is necessary.
  *     headers: {
  *       ...c.req.header(),
  *       'X-Forwarded-For': '127.0.0.1',

From dc24de31acd6f7e4bde73fc96b9d2e048fc524b3 Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Sun, 26 Jan 2025 12:12:50 +0900
Subject: [PATCH 10/15] refactor(helper/proxy): also accept HonoRequest
 instance as request init

---
 src/helper/proxy/index.ts | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index 0754dbefb..40dea5b08 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -3,13 +3,18 @@
  * Proxy Helper for Hono.
  */
 
+import type { HonoRequest } from '../../request'
+
 interface ProxyRequestInit extends RequestInit {
   raw?: Request
 }
 
 interface ProxyFetch {
-  (input: RequestInfo | URL, init?: ProxyRequestInit): Promise<Response>
-  (input: string | URL | globalThis.Request, init?: ProxyRequestInit): Promise<Response>
+  (input: RequestInfo | URL, init?: ProxyRequestInit | HonoRequest): Promise<Response>
+  (
+    input: string | URL | globalThis.Request,
+    init?: ProxyRequestInit | HonoRequest
+  ): Promise<Response>
 }
 
 /**

From 833b8e2496ba0191c3092def7e7b2cf4dc78275d Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Sun, 26 Jan 2025 21:30:49 +0900
Subject: [PATCH 11/15] fix(helper/proxy): remove hop-by-hop headers

---
 src/helper/proxy/index.test.ts | 46 ++++++++++++++++++++++++++++++++++
 src/helper/proxy/index.ts      | 19 ++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/src/helper/proxy/index.test.ts b/src/helper/proxy/index.test.ts
index 079ba7a5b..f12873a10 100644
--- a/src/helper/proxy/index.test.ts
+++ b/src/helper/proxy/index.test.ts
@@ -28,6 +28,14 @@ describe('Proxy Middleware', () => {
           )
         } else if (req.url === 'https://example.com/post' && req.method === 'POST') {
           return Promise.resolve(new Response(`request body: ${await req.text()}`))
+        } else if (req.url === 'https://example.com/hop-by-hop') {
+          return Promise.resolve(
+            new Response('ok', {
+              headers: {
+                'Transfer-Encoding': 'chunked',
+              },
+            })
+          )
         }
         return Promise.resolve(new Response('not found', { status: 404 }))
       })
@@ -107,5 +115,43 @@ describe('Proxy Middleware', () => {
       expect(res.status).toBe(200)
       expect(await res.text()).toBe('request body: test')
     })
+
+    it('remove hop-by-hop headers', async () => {
+      const app = new Hono()
+      app.get('/proxy/:path', (c) => proxy(`https://example.com/${c.req.param('path')}`))
+
+      const res = await app.request('/proxy/hop-by-hop', {
+        headers: {
+          Connection: 'keep-alive',
+          'Keep-Alive': 'timeout=5, max=1000',
+          'Proxy-Authorization': 'Basic 123456',
+        },
+      })
+      const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
+
+      expect(req.headers.get('Connection')).toBeNull()
+      expect(req.headers.get('Keep-Alive')).toBeNull()
+      expect(req.headers.get('Proxy-Authorization')).toBeNull()
+
+      expect(res.headers.get('Transfer-Encoding')).toBeNull()
+    })
+
+    it('specify hop-by-hop header by options', async () => {
+      const app = new Hono()
+      app.get('/proxy/:path', (c) =>
+        proxy(`https://example.com/${c.req.param('path')}`, {
+          headers: {
+            'Proxy-Authorization': 'Basic 123456',
+          },
+        })
+      )
+
+      const res = await app.request('/proxy/hop-by-hop')
+      const req = (global.fetch as ReturnType<typeof vi.fn>).mock.calls[0][0]
+
+      expect(req.headers.get('Proxy-Authorization')).toBe('Basic 123456')
+
+      expect(res.headers.get('Transfer-Encoding')).toBeNull()
+    })
   })
 })
diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index 40dea5b08..6cd37c8fd 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -5,6 +5,17 @@
 
 import type { HonoRequest } from '../../request'
 
+// https://datatracker.ietf.org/doc/html/rfc2616#section-13.5.1
+const hopByHopHeaders = [
+  'connection',
+  'keep-alive',
+  'proxy-authenticate',
+  'proxy-authorization',
+  'te',
+  'trailers',
+  'transfer-encoding',
+]
+
 interface ProxyRequestInit extends RequestInit {
   raw?: Request
 }
@@ -67,6 +78,11 @@ export const proxy: ProxyFetch = async (input, proxyInit) => {
   if (requestInitRaw.body) {
     requestInitRaw.duplex = 'half'
   }
+  if (requestInitRaw.headers) {
+    hopByHopHeaders.forEach((header) => {
+      ;(requestInitRaw.headers as Headers).delete(header)
+    })
+  }
 
   const req = new Request(input, {
     ...requestInitRaw,
@@ -76,6 +92,9 @@ export const proxy: ProxyFetch = async (input, proxyInit) => {
 
   const res = await fetch(req)
   const resHeaders = new Headers(res.headers)
+  hopByHopHeaders.forEach((header) => {
+    resHeaders.delete(header)
+  })
   if (resHeaders.has('content-encoding')) {
     resHeaders.delete('content-encoding')
     // Content-Length is the size of the compressed content, not the size of the original content

From 2e8e2509143aa2841ea35cc8be91a3eb6a0ff43e Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Mon, 27 Jan 2025 09:01:17 +0900
Subject: [PATCH 12/15] refactor(helper/proxy): build request init from request

---
 src/helper/proxy/index.ts | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index 6cd37c8fd..03fd7240d 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -28,6 +28,26 @@ interface ProxyFetch {
   ): Promise<Response>
 }
 
+const buildRequestInitFromRequest = (
+  request: Request | undefined
+): RequestInit & { duplex?: 'half' } => {
+  if (!request) {
+    return {}
+  }
+
+  const headers = new Headers(request.headers)
+  hopByHopHeaders.forEach((header) => {
+    headers.delete(header)
+  })
+
+  return {
+    method: request.method,
+    body: request.body,
+    duplex: request.body ? 'half' : undefined,
+    headers,
+  }
+}
+
 /**
  * Fetch API wrapper for proxy.
  * The parameters and return value are the same as for `fetch` (except for the proxy-specific options).
@@ -68,24 +88,8 @@ interface ProxyFetch {
 export const proxy: ProxyFetch = async (input, proxyInit) => {
   const { raw, ...requestInit } = proxyInit ?? {}
 
-  const requestInitRaw: RequestInit & { duplex?: 'half' } = raw
-    ? {
-        method: raw.method,
-        body: raw.body,
-        headers: raw.headers,
-      }
-    : {}
-  if (requestInitRaw.body) {
-    requestInitRaw.duplex = 'half'
-  }
-  if (requestInitRaw.headers) {
-    hopByHopHeaders.forEach((header) => {
-      ;(requestInitRaw.headers as Headers).delete(header)
-    })
-  }
-
   const req = new Request(input, {
-    ...requestInitRaw,
+    ...buildRequestInitFromRequest(raw),
     ...requestInit,
   })
   req.headers.delete('accept-encoding')

From 832532cc16982f0ce8c6dc03616ba1d050a32f20 Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Mon, 27 Jan 2025 20:38:21 +0900
Subject: [PATCH 13/15] fix(helper/proxy): fix type error

Co-authored-by: Yusuke Wada <yusuke@kamawada.com>
---
 src/helper/proxy/index.ts | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index 03fd7240d..6c0f87e6b 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -3,7 +3,7 @@
  * Proxy Helper for Hono.
  */
 
-import type { HonoRequest } from '../../request'
+import type { RequestHeader } from '../../utils/headers'
 
 // https://datatracker.ietf.org/doc/html/rfc2616#section-13.5.1
 const hopByHopHeaders = [
@@ -16,16 +16,17 @@ const hopByHopHeaders = [
   'transfer-encoding',
 ]
 
-interface ProxyRequestInit extends RequestInit {
+interface ProxyRequestInit extends Omit<RequestInit, 'headers'> {
   raw?: Request
+  headers?:
+    | HeadersInit
+    | [string, string][]
+    | Record<RequestHeader, string | undefined>
+    | Record<string, string | undefined>
 }
 
 interface ProxyFetch {
-  (input: RequestInfo | URL, init?: ProxyRequestInit | HonoRequest): Promise<Response>
-  (
-    input: string | URL | globalThis.Request,
-    init?: ProxyRequestInit | HonoRequest
-  ): Promise<Response>
+  (input: string | URL | Request, init?: ProxyRequestInit): Promise<Response>
 }
 
 const buildRequestInitFromRequest = (
@@ -72,7 +73,7 @@ const buildRequestInitFromRequest = (
  *   })
  * })
  *
- * app.any('/proxy/:path', (c) => {
+ * app.all('/proxy/:path', (c) => {
  *   return proxy(`http://${originServer}/${c.req.param('path')}`, {
  *     ...c.req, // optional, specify only when forwarding all the request data (including credentials) is necessary.
  *     headers: {
@@ -88,10 +89,14 @@ const buildRequestInitFromRequest = (
 export const proxy: ProxyFetch = async (input, proxyInit) => {
   const { raw, ...requestInit } = proxyInit ?? {}
 
-  const req = new Request(input, {
-    ...buildRequestInitFromRequest(raw),
-    ...requestInit,
-  })
+  const req = new Request(
+    input,
+    // @ts-expect-error `headers` in `requestInit` is not compatible with HeadersInit
+    {
+      ...buildRequestInitFromRequest(raw),
+      ...requestInit,
+    }
+  )
   req.headers.delete('accept-encoding')
 
   const res = await fetch(req)

From e11a66d4cad9806c6dc0e66b1ed49c2bf3257589 Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Mon, 27 Jan 2025 20:46:58 +0900
Subject: [PATCH 14/15] test(helper/proxy): add test for modify header

---
 src/helper/proxy/index.test.ts | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/src/helper/proxy/index.test.ts b/src/helper/proxy/index.test.ts
index f12873a10..6d3213873 100644
--- a/src/helper/proxy/index.test.ts
+++ b/src/helper/proxy/index.test.ts
@@ -36,6 +36,14 @@ describe('Proxy Middleware', () => {
               },
             })
           )
+        } else if (req.url === 'https://example.com/set-cookie') {
+          return Promise.resolve(
+            new Response('ok', {
+              headers: {
+                'Set-Cookie': 'test=123',
+              },
+            })
+          )
         }
         return Promise.resolve(new Response('not found', { status: 404 }))
       })
@@ -153,5 +161,23 @@ describe('Proxy Middleware', () => {
 
       expect(res.headers.get('Transfer-Encoding')).toBeNull()
     })
+
+    it('modify header', async () => {
+      const app = new Hono()
+      app.get('/proxy/:path', (c) =>
+        proxy(`https://example.com/${c.req.param('path')}`, {
+          headers: {
+            'Set-Cookie': 'test=123',
+          },
+        }).then((res) => {
+          res.headers.delete('Set-Cookie')
+          res.headers.set('X-Response-Id', '456')
+          return res
+        })
+      )
+      const res = await app.request('/proxy/set-cookie')
+      expect(res.headers.get('Set-Cookie')).toBeNull()
+      expect(res.headers.get('X-Response-Id')).toBe('456')
+    })
   })
 })

From 8a816332e3436dcec9c2ae5b6af7da5f92860c4a Mon Sep 17 00:00:00 2001
From: Taku Amano <taku@taaas.jp>
Date: Mon, 27 Jan 2025 21:11:57 +0900
Subject: [PATCH 15/15] fix(helper/proxy): It is generally the Set-Cookie that
 should be removed from the response header

---
 src/helper/proxy/index.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/helper/proxy/index.ts b/src/helper/proxy/index.ts
index 6c0f87e6b..9bfed6f73 100644
--- a/src/helper/proxy/index.ts
+++ b/src/helper/proxy/index.ts
@@ -68,7 +68,7 @@ const buildRequestInitFromRequest = (
  *       Authorization: undefined, // do not propagate request headers contained in c.req.header('Authorization')
  *     },
  *   }).then((res) => {
- *     res.headers.delete('Cookie')
+ *     res.headers.delete('Set-Cookie')
  *     return res
  *   })
  * })