diff --git a/packages/cli-kit/src/private/node/api/urls.test.ts b/packages/cli-kit/src/private/node/api/urls.test.ts
index 59def344dab..62492fb2eb7 100644
--- a/packages/cli-kit/src/private/node/api/urls.test.ts
+++ b/packages/cli-kit/src/private/node/api/urls.test.ts
@@ -45,4 +45,38 @@ describe('sanitizeURL', () => {
     // Then
     expect(sanitizedUrl).toBe('https://example.com/?subject_token=****&other_param=def456')
   })
+
+  test.each([
+    'access_token',
+    'refresh_token',
+    'id_token',
+    'subject_token',
+    'actor_token',
+    'device_code',
+    'client_secret',
+    'code',
+    'token',
+  ])('sanitizes %s query parameter', (param) => {
+    // Given
+    const url = `https://example.com?${param}=secret-value`
+
+    // When
+    const sanitizedUrl = sanitizeURL(url)
+
+    // Then
+    expect(sanitizedUrl).toBe(`https://example.com/?${param}=****`)
+  })
+
+  test('sanitizes all sensitive query parameters together', () => {
+    // Given
+    const url = 'https://example.com?access_token=a&refresh_token=b&device_code=c&subject_token=d&other=keep'
+
+    // When
+    const sanitizedUrl = sanitizeURL(url)
+
+    // Then
+    expect(sanitizedUrl).toBe(
+      'https://example.com/?access_token=****&refresh_token=****&device_code=****&subject_token=****&other=keep',
+    )
+  })
 })
diff --git a/packages/cli-kit/src/private/node/api/urls.ts b/packages/cli-kit/src/private/node/api/urls.ts
index c2e0da6a5e8..fd1297f7c58 100644
--- a/packages/cli-kit/src/private/node/api/urls.ts
+++ b/packages/cli-kit/src/private/node/api/urls.ts
@@ -1,3 +1,19 @@
+// Query-string parameter names that may carry sensitive credentials and must
+// not be written to logs, verbose debug output, or any other user-visible
+// destination. Covers OAuth 2.0 / device-authorization / token-exchange
+// parameters.
+const SENSITIVE_QUERY_PARAMS = [
+  'access_token',
+  'refresh_token',
+  'id_token',
+  'subject_token',
+  'actor_token',
+  'device_code',
+  'client_secret',
+  'code',
+  'token',
+]
+
 /**
  * Removes the sensitive data from the url and outputs them as a string.
  * @param url - HTTP headers.
@@ -5,11 +21,10 @@
  */
 export function sanitizeURL(url: string): string {
   const parsedUrl = new URL(url)
-  if (parsedUrl.searchParams.has('subject_token')) {
-    parsedUrl.searchParams.set('subject_token', '****')
-  }
-  if (parsedUrl.searchParams.has('token')) {
-    parsedUrl.searchParams.set('token', '****')
+  for (const param of SENSITIVE_QUERY_PARAMS) {
+    if (parsedUrl.searchParams.has(param)) {
+      parsedUrl.searchParams.set(param, '****')
+    }
   }
   return parsedUrl.toString()
 }
diff --git a/packages/cli-kit/src/private/node/session/exchange.test.ts b/packages/cli-kit/src/private/node/session/exchange.test.ts
index b0b1f0a7dc0..d0f2c95c97e 100644
--- a/packages/cli-kit/src/private/node/session/exchange.test.ts
+++ b/packages/cli-kit/src/private/node/session/exchange.test.ts
@@ -271,8 +271,10 @@ describe.each(tokenExchangeMethods)(
     test(`Executing ${tokenExchangeMethod.name} returns access token and user ID for a valid CLI token`, async () => {
       // Given
       let capturedUrl = ''
+      let capturedInit: {method?: string; headers?: Record<string, string>; body?: string} = {}
       vi.mocked(shopifyFetch).mockImplementation(async (url, options) => {
         capturedUrl = url.toString()
+        capturedInit = (options ?? {}) as typeof capturedInit
         return Promise.resolve(
           new Response(
             JSON.stringify({
@@ -292,12 +294,21 @@ describe.each(tokenExchangeMethods)(
       await expect(getLastSeenUserIdAfterAuth()).resolves.toBe(userId)
       await expect(getLastSeenAuthMethod()).resolves.toBe('partners_token')
 
-      // Assert token exchange parameters are correct
+      // Request is sent as POST form-encoded body (not query string), so the
+      // URL must not contain any OAuth parameters.
       const actualUrl = new URL(capturedUrl)
       expect(actualUrl).toBeDefined()
-      expect(actualUrl.href).toContain('https://fqdn.com/oauth/token')
+      expect(actualUrl.href).toBe('https://fqdn.com/oauth/token')
+      expect(actualUrl.search).toBe('')
 
-      const params = actualUrl.searchParams
+      expect(capturedInit.method).toBe('POST')
+      expect(capturedInit.headers).toMatchObject({
+        'Content-Type': 'application/x-www-form-urlencoded',
+      })
+      expect(typeof capturedInit.body).toBe('string')
+
+      // Assert token exchange parameters are correct and sent in the body.
+      const params = new URLSearchParams(capturedInit.body)
       expect(params.get('grant_type')).toBe(grantType)
       expect(params.get('requested_token_type')).toBe(accessTokenType)
       expect(params.get('subject_token_type')).toBe(accessTokenType)
diff --git a/packages/cli-kit/src/private/node/session/exchange.ts b/packages/cli-kit/src/private/node/session/exchange.ts
index 8ddf858eb86..e5a60bac820 100644
--- a/packages/cli-kit/src/private/node/session/exchange.ts
+++ b/packages/cli-kit/src/private/node/session/exchange.ts
@@ -226,10 +226,19 @@ async function tokenRequest(
   params: Record<string, string>,
 ): Promise<Result<TokenRequestResult, {error: string; store?: string}>> {
   const fqdn = await identityFqdn()
-  const url = new URL(`https://${fqdn}/oauth/token`)
-  url.search = new URLSearchParams(Object.entries(params)).toString()
+  const url = `https://${fqdn}/oauth/token`
 
-  const res = await shopifyFetch(url.href, {method: 'POST'})
+  // Send OAuth parameters in the request body (per RFC 6749) rather than the
+  // URL query string. This prevents sensitive credentials (subject_token,
+  // refresh_token, device_code, client_id, etc.) from being written to
+  // verbose CLI debug output or otherwise leaking through URLs.
+  const body = new URLSearchParams(Object.entries(params)).toString()
+
+  const res = await shopifyFetch(url, {
+    method: 'POST',
+    headers: {'Content-Type': 'application/x-www-form-urlencoded'},
+    body,
+  })
   try {
     const responseText = await res.text()