From 65ac76bb2780bad121a40aa16de95f242256156a Mon Sep 17 00:00:00 2001
From: Roberto Bianchi <roberto.bianchi@spendesk.com>
Date: Thu, 19 Mar 2026 18:25:03 +0100
Subject: [PATCH 1/2] fix(qs): preserve fromParameters query params

Signed-off-by: Roberto Bianchi <roberto.bianchi@spendesk.com>
---
 index.js     | 12 +++++++-----
 test/test.js | 25 +++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/index.js b/index.js
index 10375c9..fcc063d 100644
--- a/index.js
+++ b/index.js
@@ -605,29 +605,31 @@ async function fastifyHttpProxy (fastify, opts) {
       }
 
       dest = dest.replace(prefixPathWithVariables, rewritePrefixWithVariables)
-      if (queryParams) {
-        dest += `?${qs.stringify(queryParams)}`
-      }
     } else {
       dest = dest.replace(prefix, rewritePrefix)
     }
 
+    if (queryParams) {
+      dest += `?${qs.stringify(queryParams)}`
+    }
+
     return { url: dest || '/', options: replyOpts }
   }
 
   function handler (request, reply) {
     const { url, options } = fromParameters(request.url, request.params, this.prefix)
+    const dest = url.split('?')[0]
 
     if (request.raw[kWs]) {
       reply.hijack()
       try {
-        wsProxy.handleUpgrade(request, url, noop)
+        wsProxy.handleUpgrade(request, dest, noop)
       } /* c8 ignore start */ catch (err) {
         request.log.warn({ err }, 'websocket proxy error')
       } /* c8 ignore stop */
       return
     }
-    reply.from(url, options)
+    reply.from(dest, options)
   }
 
   fastify.decorateReply('fromParameters', fromParameters)
diff --git a/test/test.js b/test/test.js
index 30d2829..7996dad 100644
--- a/test/test.js
+++ b/test/test.js
@@ -38,6 +38,10 @@ async function run () {
     return 'this is /api2/a'
   })
 
+  origin.get('/api2/echo-query', async (request) => {
+    return `query: ${JSON.stringify(request.query)}`
+  })
+
   origin.get('/variable-api/:id/endpoint', async (request) => {
     return `this is "variable-api" endpoint with id ${request.params.id}`
   })
@@ -900,6 +904,27 @@ async function run () {
     }
   })
 
+  test('fromParameters should preserve query params with non-parameterized prefix', async t => {
+    let fromParametersUrl
+    const server = Fastify()
+    server.register(proxy, {
+      upstream: `http://localhost:${origin.server.address().port}`,
+      prefix: '/api',
+      rewritePrefix: '/api2',
+      preHandler (request, reply, done) {
+        const { url } = reply.fromParameters(request.url, request.params, '/api')
+        fromParametersUrl = url
+        done()
+      }
+    })
+
+    await server.listen({ port: 0 })
+    t.after(() => server.close())
+
+    await fetch(`http://localhost:${server.server.address().port}/api/echo-query?foo=bar&baz=qux`)
+    t.assert.strictEqual(fromParametersUrl, '/api2/echo-query?foo=bar&baz=qux')
+  })
+
   test('preRewrite handler', async t => {
     const proxyServer = Fastify()
 

From ad38e08388f3a6b490ef2d333901c79ae2e8b7ed Mon Sep 17 00:00:00 2001
From: Roberto Bianchi <rbianchidev@gmail.com>
Date: Thu, 19 Mar 2026 20:08:44 +0100
Subject: [PATCH 2/2] Update index.js
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Gürgün Dayıoğlu <hey@gurgun.day>
Signed-off-by: Roberto Bianchi <rbianchidev@gmail.com>
---
 index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/index.js b/index.js
index fcc063d..7be5933 100644
--- a/index.js
+++ b/index.js
@@ -618,7 +618,7 @@ async function fastifyHttpProxy (fastify, opts) {
 
   function handler (request, reply) {
     const { url, options } = fromParameters(request.url, request.params, this.prefix)
-    const dest = url.split('?')[0]
+    const dest = url.split('?', 1)[0]
 
     if (request.raw[kWs]) {
       reply.hijack()