fix(logs): resume the withheld-span fallback from the retained spans' structure budget

Author: waleedlatif1

apps/sim/lib/logs/execution/trace-secret-projection.test.ts

@@ -1149,6 +1149,33 @@ describe('projectTraceSpansForSecrets whole-trace content budget', () => {
     expect(countSpans(projected)).toBeLessThanOrEqual(100_000)
   })
 
+  it('keeps the structure a whole-trace fallback would for the span that crossed the budget', async () => {
+    const toolCall = (index: number) => ({
+      name: `tool-${index}`,
+      duration: 0,
+      startTime: '2026-07-01T00:00:00.000Z',
+      endTime: '2026-07-01T00:00:00.000Z',
+      status: 'success' as const,
+    })
+    const projected = await projectTraceSpansForSecrets(
+      [
+        heavySpan('span-a', 'first', {
+          children: Array.from({ length: 30_000 }, (_, index) => createSpan({ id: `a-${index}` })),
+        }),
+        createSpan({
+          id: 'span-b',
+          output: { items: Array.from({ length: 70_000 }, (_, index) => `row-${index}`) },
+          toolCalls: Array.from({ length: 50_000 }, (_, index) => toolCall(index)),
+        }),
+      ],
+      { registry: SECRET_REGISTRY, store: STORE, allowLargeValueWrites: false }
+    )
+
+    expect(projected[0].output?.marker).toBe('first')
+    expect(projected[1]).not.toHaveProperty('output')
+    expect(projected[1].toolCalls).toHaveLength(50_000)
+  })
+
   it('withholds the whole top-level span whose descendant crossed the budget', async () => {
     const projected = await projectTraceSpansForSecrets(
       [

apps/sim/lib/logs/execution/trace-secret-projection.ts

@@ -1681,6 +1681,7 @@ export async function projectTraceSpansForSecrets(
     assertTraceStructureArrayFits(traceSpans, state)
     const assertContentIsSafe = createSpanContentAssertion(traceSpans, context)
     for (let index = 0; index < traceSpans.length; index += 1) {
+      const retainedStructureNodes = state.nodes
       try {
         projected.push(
           await sanitizeTraceSpan(traceSpans[index], context, 0, state, assertContentIsSafe)
@@ -1690,7 +1691,8 @@ export async function projectTraceSpansForSecrets(
         /**
          * Every span already returned was sanitized and then passed the whole-trace check,
          * descendants included, so only the span that crossed the budget and those after it
-         * lose their content. The walk stops here, so the budget still bounds it.
+         * lose their content. The fallback resumes the structure budget where the retained
+         * spans left it, so the trace keeps exactly the structure a whole-trace fallback would.
          */
         logger.warn(
           'Trace content exceeded the projection budget; withholding the remaining spans',
@@ -1701,7 +1703,13 @@ export async function projectTraceSpansForSecrets(
             failure: describeProjectionFailure(error),
           }
         )
-        return [...projected, ...structuralOnlyTraceSpans(traceSpans.slice(index), state)]
+        return [
+          ...projected,
+          ...structuralOnlyTraceSpans(traceSpans.slice(index), {
+            nodes: retainedStructureNodes,
+            truncated: false,
+          }),
+        ]
       }
     }
     return projected