From 5d495df91d7a3bff7f4807a36405a8efcb7c735c Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben.bridgewater@datadoghq.com>
Date: Fri, 4 Sep 2026 17:40:53 +0200
Subject: [PATCH 1/2] fix(remote-config): refresh fetcher identity

A resumed process changes its client and runtime identifiers, but an existing fetcher keeps the snapshot identity. Updating the identity in place preserves client and file state for later polls.

Refs: https://github.com/DataDog/dd-trace-js/pull/10067#discussion_r3934876183
---
 libdd-remote-config/src/fetch/single.rs | 68 +++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/libdd-remote-config/src/fetch/single.rs b/libdd-remote-config/src/fetch/single.rs
index bf7ef65228..01f1c7cf6c 100644
--- a/libdd-remote-config/src/fetch/single.rs
+++ b/libdd-remote-config/src/fetch/single.rs
@@ -89,6 +89,13 @@ impl<S: FileStorage, C: HttpClientCapability + SleepCapability> SingleFetcher<S,
         self
     }
 
+    /// Replaces the identity sent on subsequent polls without resetting client or file state.
+    pub fn set_identity(&mut self, client_id: String, runtime_id: String, tags: Vec<String>) {
+        self.client_id = client_id;
+        self.runtime_id = runtime_id;
+        Arc::make_mut(&mut self.target).tags = tags;
+    }
+
     /// Polls the current runtime config files.
     pub async fn fetch_once(&mut self) -> anyhow::Result<Option<Vec<Arc<S::StoredFile>>>> {
         self.fetcher
@@ -194,6 +201,11 @@ where
         self
     }
 
+    /// See [`SingleFetcher::set_identity`].
+    pub fn set_identity(&mut self, client_id: String, runtime_id: String, tags: Vec<String>) {
+        self.fetcher.set_identity(client_id, runtime_id, tags);
+    }
+
     /// Polls for new changes
     pub async fn fetch_changes<R>(&mut self) -> anyhow::Result<Vec<Change<Arc<S::StoredFile>, R>>>
     where
@@ -237,3 +249,59 @@ where
             .set_product_capabilities(products, capabilities);
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::fetch::test_server::RemoteConfigServer;
+    use crate::file_storage::SimpleFileStorage;
+    use libdd_capabilities_impl::NativeCapabilities;
+
+    #[tokio::test]
+    #[cfg_attr(miri, ignore)]
+    async fn updates_identity_without_resetting_client_state() {
+        let server = RemoteConfigServer::spawn();
+        let target = Target::new(
+            "service".to_string(),
+            "env".to_string(),
+            "1.2.3".to_string(),
+            vec!["runtime-id:old-runtime-id".to_string()],
+            vec!["entrypoint.type:script".to_string()],
+        );
+        server.files.lock().unwrap().insert(
+            RemoteConfigPath::parse("employee/APM_TRACING/identity/config").unwrap(),
+            (vec![Arc::new(target.clone())], 1, "v1".to_string()),
+        );
+        let mut fetcher = SingleChangesFetcher::new_no_agentless(
+            SimpleFileStorage::default(),
+            target,
+            "old-runtime-id".to_string(),
+            server.dummy_options(),
+            NativeCapabilities::new_without_connection_pooling(),
+        )
+        .with_client_id("old-client-id".to_string());
+
+        fetcher.fetch_changes::<Vec<u8>>().await.unwrap();
+        fetcher.set_identity(
+            "new-client-id".to_string(),
+            "new-runtime-id".to_string(),
+            vec!["runtime-id:new-runtime-id".to_string()],
+        );
+        fetcher.fetch_changes::<Vec<u8>>().await.unwrap();
+
+        let request = server.last_request.lock().unwrap();
+        let client = request.as_ref().unwrap().client.as_ref().unwrap();
+        let tracer = client.client_tracer.as_ref().unwrap();
+        assert_eq!(client.id, "new-client-id");
+        assert_eq!(tracer.runtime_id, "new-runtime-id");
+        assert_eq!(tracer.service, "service");
+        assert_eq!(tracer.env, "env");
+        assert_eq!(tracer.app_version, "1.2.3");
+        assert_eq!(tracer.tags, ["runtime-id:new-runtime-id"]);
+        assert_eq!(tracer.process_tags, ["entrypoint.type:script"]);
+        assert_eq!(
+            client.state.as_ref().unwrap().backend_client_state,
+            b"some state"
+        );
+    }
+}

From 0e3783aff5586e010a9f1afff048e788eb91b16a Mon Sep 17 00:00:00 2001
From: Bob Weinand <bob.weinand@datadoghq.com>
Date: Fri, 4 Sep 2026 20:05:47 +0200
Subject: [PATCH 2/2] Fully drop unneeded Arc

This comes from a signature change on Fetcher::fetch_once()
---
 libdd-remote-config/src/fetch/single.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libdd-remote-config/src/fetch/single.rs b/libdd-remote-config/src/fetch/single.rs
index 01f1c7cf6c..c0468776b6 100644
--- a/libdd-remote-config/src/fetch/single.rs
+++ b/libdd-remote-config/src/fetch/single.rs
@@ -16,7 +16,7 @@ const DEFAULT_REFRESH_INTERVAL: Duration = Duration::from_secs(5);
 /// Simple implementation
 pub struct SingleFetcher<S: FileStorage, C: HttpClientCapability + SleepCapability> {
     fetcher: ConfigFetcher<S, C>,
-    target: Arc<Target>,
+    target: Target,
     product_capabilities: ConfigProductCapabilities,
     runtime_id: String,
     client_id: String,
@@ -47,7 +47,7 @@ impl<S: FileStorage, C: HttpClientCapability + SleepCapability> SingleFetcher<S,
                 )),
             )
             .await?,
-            target: Arc::new(target),
+            target,
             product_capabilities: ConfigProductCapabilities::new(
                 options.products,
                 options.capabilities,
@@ -73,7 +73,7 @@ impl<S: FileStorage, C: HttpClientCapability + SleepCapability> SingleFetcher<S,
                     http_client,
                 )),
             ),
-            target: Arc::new(target),
+            target,
             product_capabilities: ConfigProductCapabilities::new(
                 options.products,
                 options.capabilities,
@@ -93,7 +93,7 @@ impl<S: FileStorage, C: HttpClientCapability + SleepCapability> SingleFetcher<S,
     pub fn set_identity(&mut self, client_id: String, runtime_id: String, tags: Vec<String>) {
         self.client_id = client_id;
         self.runtime_id = runtime_id;
-        Arc::make_mut(&mut self.target).tags = tags;
+        self.target.tags = tags;
     }
 
     /// Polls the current runtime config files.