fix(webapp): fetch run-scoped trace subtrees for large traces

Large traces capped by row limits could leave child runs with an empty trace
view when their span fell outside the first time-ordered slice. Fetch the
anchor span subtree for the dashboard and trace API, surface truncation in
the UI, and document the run-scoped response shape.

Author: kathiekiwi

.server-changes/fetch-ancestors-outside-anchor-window.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: fix
+---
+
+Fix run-scoped trace subtree fetching so ancestor spans are loaded regardless of the anchor run's time window. Ancestors start before the anchor run and are fetched by explicit span IDs, so applying the anchor's `startCreatedAt` filter wrongly excluded them — which meant cancellation/error overrides from an ancestor never propagated down to the anchor subtree (e.g. a child span stayed PARTIAL when its parent run was cancelled). Ancestor fetches now skip the time window.

.server-changes/trace-view-large-runs-subtree.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: fix
+---
+
+Fix empty trace views for child and nested runs in very large traces. The dashboard and retrieve-trace API now return the requested run's span subtree.

apps/webapp/app/presenters/v3/RunPresenter.server.ts

@@ -1,6 +1,7 @@
 import { millisecondsToNanoseconds, RunAnnotations } from "@trigger.dev/core/v3";
 import { createTreeFromFlatItems, flattenTree } from "~/components/primitives/TreeView/TreeView";
 import { prisma, type PrismaClient } from "~/db.server";
+import { logger } from "~/services/logger.server";
 import { createTimelineSpanEventsFromSpanEvents } from "~/utils/timelineSpanEvents";
 import { getUsername } from "~/utils/username";
 import { SpanSummary } from "~/v3/eventRepository/eventRepository.types";
@@ -179,16 +180,49 @@ export class RunPresenter {
       run.runtimeEnvironment.organizationId
     );
 
-    // get the events
+    const traceTimeBounds = {
+      startCreatedAt: run.rootTaskRun?.createdAt ?? run.createdAt,
+      endCreatedAt: run.completedAt ?? undefined,
+    };
+
+    // Fast path: full trace summary. Slow path: subtree fetch when the anchor
+    // span fell past the row cap (large traces ordered by start_time ASC).
     let traceSummary = await repository.getTraceSummary(
       getTaskEventStoreTableForRun(run),
       run.runtimeEnvironment.id,
       run.traceId,
-      run.rootTaskRun?.createdAt ?? run.createdAt,
-      run.completedAt ?? undefined,
+      traceTimeBounds.startCreatedAt,
+      traceTimeBounds.endCreatedAt,
       { includeDebugLogs: showDebug }
     );
 
+    let isTruncated = traceSummary?.isTruncated ?? false;
+    const hasAnchorSpan = traceSummary?.spans.some((span) => span.id === run.spanId) ?? false;
+
+    if (traceSummary && !hasAnchorSpan) {
+      logger.warn("Trace summary missing anchor span, falling back to subtree fetch", {
+        runId: run.friendlyId,
+        spanId: run.spanId,
+        traceId: run.traceId,
+        spanCount: traceSummary.spans.length,
+      });
+
+      const subtreeSummary = await repository.getTraceSubtreeSummary(
+        getTaskEventStoreTableForRun(run),
+        run.runtimeEnvironment.id,
+        run.traceId,
+        run.spanId,
+        traceTimeBounds.startCreatedAt,
+        traceTimeBounds.endCreatedAt,
+        { includeDebugLogs: showDebug }
+      );
+
+      if (subtreeSummary) {
+        traceSummary = subtreeSummary;
+        isTruncated = subtreeSummary.isTruncated ?? false;
+      }
+    }
+
     if (!traceSummary) {
       const spanSummary: SpanSummary = {
         id: run.spanId,
@@ -241,6 +275,18 @@ export class RunPresenter {
 
     //this tree starts at the passed in span (hides parent elements if there are any)
     const tree = createTreeFromFlatItems(traceSummary.spans, run.spanId);
+    const missingAnchor = !traceSummary.spans.some((span) => span.id === run.spanId) || !tree;
+
+    if (missingAnchor) {
+      logger.warn("Trace view anchor span not found in trace summary", {
+        runId: run.friendlyId,
+        spanId: run.spanId,
+        traceId: run.traceId,
+        spanCount: traceSummary.spans.length,
+      });
+
+      isTruncated = true;
+    }
 
     //we need the start offset for each item, and the total duration of the entire tree
     const treeRootStartTimeMs = tree ? tree?.data.startTime.getTime() : 0;
@@ -312,6 +358,8 @@ export class RunPresenter {
           : undefined,
         overridesBySpanId: traceSummary.overridesBySpanId,
         linkedRunIdBySpanId,
+        isTruncated,
+        missingAnchor,
       },
       maximumLiveReloadingSetting: repository.maximumLiveReloadingSetting,
     };

apps/webapp/app/routes/_app.orgs.$organizationSlug.projects.$projectParam.env.$envParam.runs.$runParam/route.tsx

@@ -36,6 +36,7 @@ import { AdminDebugTooltip } from "~/components/admin/debugTooltip";
 import { PageBody } from "~/components/layout/AppLayout";
 import { Badge } from "~/components/primitives/Badge";
 import { Button, LinkButton } from "~/components/primitives/Buttons";
+import { Callout } from "~/components/primitives/Callout";
 import { CopyableText } from "~/components/primitives/CopyableText";
 import { DateTimeShort } from "~/components/primitives/DateTime";
 import { Dialog, DialogTrigger } from "~/components/primitives/Dialog";
@@ -599,8 +600,16 @@ function TraceView({
     return <></>;
   }
 
-  const { events, duration, rootSpanStatus, rootStartedAt, queuedDuration, overridesBySpanId } =
-    trace;
+  const {
+    events,
+    duration,
+    rootSpanStatus,
+    rootStartedAt,
+    queuedDuration,
+    overridesBySpanId,
+    isTruncated = false,
+    missingAnchor = false,
+  } = trace;
 
   const changeToSpan = useDebounce((selectedSpan: string) => {
     replaceSearchParam("span", selectedSpan, { replace: true });
@@ -647,31 +656,44 @@ function TraceView({
           id={resizableSettings.parent.main.id}
           min={resizableSettings.parent.main.min}
         >
-          <TasksTreeView
-            selectedId={selectedSpanId}
-            key={events[0]?.id ?? "-"}
-            events={events}
-            onSelectedIdChanged={(selectedSpan) => {
-              //instantly close the panel if no span is selected
-              if (!selectedSpan) {
-                replaceSearchParam("span");
-                return;
-              }
-
-              changeToSpan(selectedSpan);
-            }}
-            totalDuration={duration}
-            rootSpanStatus={rootSpanStatus}
-            rootStartedAt={rootStartedAt ? new Date(rootStartedAt) : undefined}
-            queuedDuration={queuedDuration}
-            environmentType={run.environment.type}
-            shouldLiveReload={isLiveReloading}
-            maximumLiveReloadingSetting={maximumLiveReloadingSetting}
-            rootRun={run.rootTaskRun}
-            parentRun={run.parentTaskRun}
-            isCompleted={run.completedAt !== null}
-            treeSnapshot={resizable.tree as ResizableSnapshot}
-          />
+          <div className="flex h-full flex-col overflow-hidden">
+            {isTruncated && (
+              <div className="shrink-0 border-b border-charcoal-700 px-3 py-2">
+                <Callout variant="warning" className="text-sm">
+                  {missingAnchor
+                    ? "Trace too large to display completely."
+                    : "This run's trace is partially displayed because it exceeds the view limit."}
+                </Callout>
+              </div>
+            )}
+            <div className="min-h-0 flex-1">
+              <TasksTreeView
+                selectedId={selectedSpanId}
+                key={events[0]?.id ?? "-"}
+                events={events}
+                onSelectedIdChanged={(selectedSpan) => {
+                  //instantly close the panel if no span is selected
+                  if (!selectedSpan) {
+                    replaceSearchParam("span");
+                    return;
+                  }
+
+                  changeToSpan(selectedSpan);
+                }}
+                totalDuration={duration}
+                rootSpanStatus={rootSpanStatus}
+                rootStartedAt={rootStartedAt ? new Date(rootStartedAt) : undefined}
+                queuedDuration={queuedDuration}
+                environmentType={run.environment.type}
+                shouldLiveReload={isLiveReloading}
+                maximumLiveReloadingSetting={maximumLiveReloadingSetting}
+                rootRun={run.rootTaskRun}
+                parentRun={run.parentTaskRun}
+                isCompleted={run.completedAt !== null}
+                treeSnapshot={resizable.tree as ResizableSnapshot}
+              />
+            </div>
+          </div>
         </ResizablePanel>
         <ResizableHandle
           id={resizableSettings.parent.handleId}

apps/webapp/app/routes/api.v1.runs.$runId.trace.ts

@@ -93,10 +93,11 @@ export const loader = createLoaderApiRoute(
       authentication.environment.organization.id
     );
 
-    const traceSummary = await eventRepository.getTraceDetailedSummary(
+    const traceSummary = await eventRepository.getTraceDetailedSubtreeSummary(
       getTaskEventStoreTableForRun(run),
       authentication.environment.id,
       run.traceId,
+      run.spanId,
       run.createdAt,
       run.completedAt ?? undefined
     );