diff --git a/rust/crates/langsmith-tracing-client/src/client/blocking/processor.rs b/rust/crates/langsmith-tracing-client/src/client/blocking/processor.rs
index 2063516bf..bb23cd858 100644
--- a/rust/crates/langsmith-tracing-client/src/client/blocking/processor.rs
+++ b/rust/crates/langsmith-tracing-client/src/client/blocking/processor.rs
@@ -1,3 +1,4 @@
+use std::collections::HashMap;
 use std::sync::mpsc::{Receiver, Sender};
 use std::sync::{mpsc, Arc, Mutex};
 use std::time::{Duration, Instant};
@@ -97,6 +98,62 @@ impl RunProcessor {
         Ok(())
     }
 
+    // If we have a `QueuedRun::Create` and `QueuedRun::Update` for the same run ID in the batch,
+    // combine the update data into the create so we can send just one operation instead of two.
+    fn combine_batch_operations(batch: Vec<QueuedRun>) -> Vec<QueuedRun> {
+        let mut output = Vec::with_capacity(batch.len());
+        let mut id_to_index = HashMap::with_capacity(batch.len());
+
+        for queued_run in batch {
+            match queued_run {
+                QueuedRun::Create(ref run_create_extended) => {
+                    // Record the `Create` operation's ID and index,
+                    // in case we need to modify it later.
+                    let RunCreateExtended { run_create, .. } = run_create_extended;
+                    let run_id = run_create.common.id.clone();
+                    let index = output.len();
+                    id_to_index.insert(run_id, index);
+                    output.push(queued_run);
+                }
+                QueuedRun::Update(run_update_extended) => {
+                    let run_id = run_update_extended.run_update.common.id.as_str();
+                    if let Some(create_index) = id_to_index.get(run_id) {
+                        // This `run_id` matches a `Create` in this batch.
+                        // Merge the `Update` data into the `Create` and
+                        // drop the separate `Update` operation from the batch.
+                        let RunUpdateExtended { run_update, io, attachments } = run_update_extended;
+                        let QueuedRun::Create(matching_create) = &mut output[*create_index] else {
+                            panic!("index {create_index} did not point to a Create operation in {output:?}");
+                        };
+                        debug_assert_eq!(
+                            run_update.common.id, matching_create.run_create.common.id,
+                            "Create operation at index {create_index} did not have expected ID {}: {matching_create:?}",
+                            run_update.common.id,
+                        );
+
+                        matching_create.run_create.common.merge(run_update.common);
+                        matching_create.run_create.end_time = Some(run_update.end_time);
+                        matching_create.io.merge(io);
+                        if let Some(mut _existing_attachments) =
+                            matching_create.attachments.as_mut()
+                        {
+                            unimplemented!("figure out how to merge attachments -- in Python they are a dict but here they are a Vec");
+                        } else {
+                            matching_create.attachments = attachments;
+                        }
+                    } else {
+                        // No matching `Create` operations for this `Update`, add it as-is.
+                        output.push(QueuedRun::Update(run_update_extended));
+                    }
+                }
+                // Allow other operations to pass through unchanged.
+                _ => output.push(queued_run),
+            }
+        }
+
+        output
+    }
+
     #[expect(unused_variables)]
     fn send_batch(&self, batch: Vec<QueuedRun>) -> Result<(), TracingClientError> {
         //println!("Handling a batch of {} runs", batch.len());
@@ -104,6 +161,8 @@ impl RunProcessor {
         let mut json_data = Vec::new();
         let mut attachment_parts = Vec::new();
 
+        let batch = Self::combine_batch_operations(batch);
+
         let start_iter = Instant::now();
         for queued_run in batch {
             match queued_run {
diff --git a/rust/crates/langsmith-tracing-client/src/client/run.rs b/rust/crates/langsmith-tracing-client/src/client/run.rs
index b5308bc71..4750c1028 100644
--- a/rust/crates/langsmith-tracing-client/src/client/run.rs
+++ b/rust/crates/langsmith-tracing-client/src/client/run.rs
@@ -24,6 +24,18 @@ pub struct RunIO {
     pub outputs: Option<Vec<u8>>,
 }
 
+impl RunIO {
+    #[inline]
+    pub(crate) fn merge(&mut self, other: RunIO) {
+        if other.inputs.is_some() {
+            self.inputs = other.inputs;
+        }
+        if other.outputs.is_some() {
+            self.outputs = other.outputs;
+        }
+    }
+}
+
 #[derive(Serialize, Deserialize, PartialEq, Debug)]
 pub struct RunCommon {
     pub id: String,
@@ -39,6 +51,36 @@ pub struct RunCommon {
     pub session_name: Option<String>,
 }
 
+impl RunCommon {
+    #[inline]
+    pub(crate) fn merge(&mut self, other: RunCommon) {
+        if other.parent_run_id.is_some() {
+            self.parent_run_id = other.parent_run_id;
+        }
+        if other.extra.is_some() {
+            self.extra = other.extra;
+        }
+        if other.error.is_some() {
+            self.error = other.error;
+        }
+        if other.serialized.is_some() {
+            self.serialized = other.serialized;
+        }
+        if other.events.is_some() {
+            self.events = other.events;
+        }
+        if other.tags.is_some() {
+            self.tags = other.tags;
+        }
+        if other.session_id.is_some() {
+            self.session_id = other.session_id;
+        }
+        if other.session_name.is_some() {
+            self.session_name = other.session_name;
+        }
+    }
+}
+
 #[derive(Serialize, Deserialize, PartialEq, Debug)]
 pub struct RunCreate {
     #[serde(flatten)]