fix(lens): show the first user message as the run input (#44958)

* fix(traces): use the first user message for the run input preview

* test(traces): cover first user message as the input preview

* test(traces): check fixture previews against the first user message

* fix(lens): show the whole input preview on one line in the runs table

* test(lens): cover multi-line input previews in the runs table

litellm-rust/crates/traces/src/normalize/messages.rs

@@ -422,11 +422,10 @@ pub(super) fn event_payload(events: &[(bool, Value)], output: bool) -> Option<St
     (!values.is_empty()).then(|| canonical(&encode(&values)))
 }
 
-/// The latest user message with text.
+/// The first user message with text.
 pub(super) fn preview(messages: &[Message]) -> String {
     messages
         .iter()
-        .rev()
         .find(|message| message.role == "user" && !message.content.is_empty())
         .map_or("", |message| message.content.as_str())
         .chars()
@@ -434,7 +433,7 @@ pub(super) fn preview(messages: &[Message]) -> String {
         .collect()
 }
 
-/// The latest user message when `input` is a conversation, else the input itself.
+/// The first user message when `input` is a conversation, else the input itself.
 pub(super) fn input_preview(input: &str) -> String {
     match serde_json::from_str::<Value>(input)
         .ok()
@@ -597,7 +596,7 @@ mod tests {
     use serde_json::Value;
 
     #[rstest]
-    #[case::latest_user(r#"{"messages":[{"role":"user","content":"first"},{"role":"assistant","content":"reply"},{"role":"user","content":"last"}]}"#, Some("last"))]
+    #[case::first_user(r#"{"messages":[{"role":"user","content":"first"},{"role":"assistant","content":"reply"},{"role":"user","content":"last"}]}"#, Some("first"))]
     #[case::malformed("not-json", None)]
     #[case::missing("{}", None)]
     #[case::not_messages(r#"{"messages":[{"role":"user"}]}"#, None)]

litellm-rust/crates/traces/tests/normalization_formats.rs

@@ -502,6 +502,25 @@ fn existing_formats_win_over_new_formats(span: Span, #[case] kind: &str) {
     assert_eq!(decoded.normalized.observation_type, ObservationType::Llm);
 }
 
+#[rstest]
+fn input_preview_is_the_first_user_message(span: Span) {
+    let conversation = json!([
+        {"role": "system", "content": "sys"},
+        {"role": "user", "content": "initial question"},
+        {"role": "assistant", "content": "answer"},
+        {"role": "user", "content": "follow up"},
+    ])
+    .to_string();
+    let decoded = decode(
+        span,
+        "custom",
+        &[("gen_ai.input.messages", &conversation)],
+        vec![],
+    )
+    .unwrap();
+    assert_eq!(decoded.normalized.input_preview, "initial question");
+}
+
 #[rstest]
 #[case::messages(&[("gen_ai.input.messages", r#"[{"role":"user","content":"modern"}]"#)], "modern")]
 #[case::indexed(&[("gen_ai.prompt.0.role", "user"), ("gen_ai.prompt.0.content", "indexed")], "indexed")]

litellm-rust/crates/traces/tests/normalize.rs

@@ -82,7 +82,7 @@ fn assert_invariants(span: &DecodedSpan) {
     }
     assert!(normalized.input_preview.chars().count() <= 240);
     if let Ok(Value::Array(messages)) = serde_json::from_str(&normalized.input) {
-        let user = messages.iter().rev().find_map(|message| {
+        let user = messages.iter().find_map(|message| {
             (message.get("role")?.as_str()? == "user")
                 .then(|| {
                     message

ui/litellm-dashboard/src/components/lens/traces/list/AgentTracesTable.test.tsx

@@ -165,6 +165,26 @@ describe("AgentTracesTable cost cell", () => {
   });
 });
 
+describe("AgentTracesTable input cell", () => {
+  it("shows the whole preview on one line instead of only its first line", () => {
+    const template = (traceList as TracePage).data[0] as TraceSummary;
+    renderWithProviders(
+      inList(
+        <AgentTracesTable
+          traces={[{ ...template, input_preview: "CURRENT USER REQUEST:\n\n- add feedback to Lens" }]}
+          findings={new Map()}
+          isLoading={false}
+          error={null}
+          hasMore={false}
+          onLoadMore={vi.fn()}
+          onSetUpTracing={vi.fn()}
+        />,
+      ),
+    );
+    expect(screen.getByText("CURRENT USER REQUEST: - add feedback to Lens")).toBeInTheDocument();
+  });
+});
+
 describe("AgentTracesTable column picker", () => {
   const runs = (traceList as TracePage).data as TraceSummary[];
   const renderRuns = () =>

ui/litellm-dashboard/src/components/lens/traces/list/AgentTracesTable.tsx

@@ -69,7 +69,7 @@ function CostCell({ run }: { run: TraceSummary }) {
   );
 }
 
-const firstLine = (text: string): string => text.split("\n")[0] ?? text;
+const singleLine = (text: string): string => text.replace(/\s+/g, " ").trim();
 const runKey = (run: TraceSummary): string => run.trace_ref || run.trace_id;
 
 const PREFETCH_MARGIN = "0px 0px 480px 0px";
@@ -96,7 +96,7 @@ function InputCell({ run }: { run: TraceSummary }) {
   return (
     <div className="flex min-w-0 items-center gap-2">
       <span className="truncate text-foreground">
-        {firstLine(previewText(run.input_preview)) || traceDisplayName(run)}
+        {singleLine(previewText(run.input_preview)) || traceDisplayName(run)}
       </span>
       {run.resolution_limited && (
         <span