diff --git a/lib/kamal/cli/proxy/reboot.rb b/lib/kamal/cli/proxy/reboot.rb
index a3fe1b324..6a56f26c9 100644
--- a/lib/kamal/cli/proxy/reboot.rb
+++ b/lib/kamal/cli/proxy/reboot.rb
@@ -38,6 +38,7 @@ def pull_image
     def replace_container
       execute *proxy.ensure_proxy_directory
       execute *proxy.ensure_apps_config_directory
+      sync_proxy_secrets
 
       if proxy.port_holder?
         replace_generation
@@ -46,18 +47,26 @@ def replace_container
       end
     end
 
-    # Phase 1 replacement: stop the old container, start the new one. Brief gap.
-    def stop_and_replace
-      info "Stopping and removing kamal-proxy on #{host}, if running..."
-      execute *proxy.stop(timeout: KAMAL.config.drain_timeout + 10), raise_on_non_zero_exit: false
-      execute *proxy.remove_container
-
+    # Every replacement path below launches a container that reads
+    # --env-file at docker run, so the secrets must be on disk before ANY
+    # generation starts. This used to live inside stop_and_replace only, and
+    # the port-holder paths launched their generation without it — a
+    # port-holder reboot on a host without the file died with
+    # "open .kamal/proxy/secrets.env: no such file or directory".
+    def sync_proxy_secrets
       if (run_config = proxy.proxy_run_config)&.secrets?
         upload! run_config.secrets_io, run_config.secrets_path, mode: "0600"
       else
         # A host keeps no secrets it no longer needs.
         execute *proxy.remove_proxy_secrets_file, raise_on_non_zero_exit: false
       end
+    end
+
+    # Phase 1 replacement: stop the old container, start the new one. Brief gap.
+    def stop_and_replace
+      info "Stopping and removing kamal-proxy on #{host}, if running..."
+      execute *proxy.stop(timeout: KAMAL.config.drain_timeout + 10), raise_on_non_zero_exit: false
+      execute *proxy.remove_container
 
       execute *proxy.run(digest: drift.expected_digest)
     end
diff --git a/test/cli/proxy_test.rb b/test/cli/proxy_test.rb
index e04aadefb..70dc938a0 100644
--- a/test/cli/proxy_test.rb
+++ b/test/cli/proxy_test.rb
@@ -49,6 +49,23 @@ class CliProxyTest < CliTestCase
     end
   end
 
+  # Regression: the port-holder replacement paths start a generation that
+  # reads --env-file at docker run, but only the legacy stop_and_replace path
+  # uploaded the secrets file — a port-holder reboot on a fresh host died with
+  # "open .kamal/proxy/secrets.env: no such file or directory".
+  test "port-holder reboot uploads the acme credentials before starting the new generation" do
+    with_test_secrets("secrets" => "CF_API_TOKEN=zone-rewriting-token") do
+      uploads = capture_uploads
+
+      run_command("reboot", "-y", fixture: :with_proxy_acme_port_holder).tap do |output|
+        assert_match "--env-file .kamal/proxy/secrets.env", output
+        assert_no_match(/zone-rewriting-token/, output)
+      end
+
+      assert_equal [ [ "CF_API_TOKEN=zone-rewriting-token\n", ".kamal/proxy/secrets.env", "0600" ] ], uploads
+    end
+  end
+
   test "boot delivers the cache store through the secrets env file, never printing the URL" do
     uploads = capture_uploads
 
diff --git a/test/fixtures/deploy_with_proxy_acme_port_holder.yml b/test/fixtures/deploy_with_proxy_acme_port_holder.yml
new file mode 100644
index 000000000..13ae29f7f
--- /dev/null
+++ b/test/fixtures/deploy_with_proxy_acme_port_holder.yml
@@ -0,0 +1,22 @@
+service: app
+image: dhh/app
+servers:
+  web:
+    - "1.1.1.1"
+registry:
+  username: user
+  password: pw
+builder:
+  arch: amd64
+proxy:
+  host: example.com
+  ssl: true
+  run:
+    port_holder: true
+    acme:
+      email: admin@example.com
+      dns_provider: cloudflare
+      prefer_wildcard: true
+      http_fallback: false
+      credentials:
+        - CF_API_TOKEN