vercel/next.js · error

Source at index ${sourceIndex} not found

Error message

Source at index ${sourceIndex} not found

What it means

Thrown by computeTreemapLayoutFromAnalyzeInternal when analyzeData.source(sourceIndex) returns undefined, meaning the source index is out of bounds for the analyze header's sources array (analyze-data.ts:240 just does sources[index]). It is an internal-consistency error: the treemap traversal (either the root index passed to computeTreemapLayoutFromAnalyze or a child index returned by sourceChildren) referenced a source that does not exist in the loaded analyze data. In a well-formed analyze report this never happens, so hitting it indicates a corrupt/mismatched @next/analyze report or an out-of-band index computed elsewhere.

Source

Thrown at apps/bundle-analyzer/lib/treemap-layout.ts:119

  for (const rootIdx of roots) {
    processDirectory(rootIdx)
  }

  return metadata
}

// Internal function that uses precomputed metadata
function computeTreemapLayoutFromAnalyzeInternal(
  analyzeData: AnalyzeData,
  sourceIndex: SourceIndex,
  foldedPath: string,
  rect: LayoutRect,
  metadata: SourceMetadata[],
  sizeMode: SizeMode
): LayoutNode {
  const source = analyzeData.source(sourceIndex)
  if (!source) {
    throw new Error(`Source at index ${sourceIndex} not found`)
  }

  const isDirectory = source.path.endsWith('/') || !source.path

  const childrenIndices = analyzeData.sourceChildren(sourceIndex)

  // Fold single-child directories
  if (
    childrenIndices.length === 1 &&
    isDirectory &&
    (foldedPath + source.path).length <= 40
  ) {
    const childIndex = childrenIndices[0]
    const child = analyzeData.source(childIndex)
    if (child?.path.endsWith('/')) {
      return computeTreemapLayoutFromAnalyzeInternal(
        analyzeData,
        childIndex,

View on GitHub (pinned to 0ae8c72462)

Solutions

1. Regenerate the analyze report with the matching bundle-analyzer version (re-run the build's analyze step) so the tree structure and sources list agree.
2. Before computing the layout, guard the requested sourceIndex against analyzeData.sourceCount() and the children indices against the same bound; surface a clearer error about which index is stale.
3. If consuming reports from multiple sources, validate the analyze header once on load (sources length, every child index < sources.length) instead of letting the layout crash deep in recursion.
4. If you built AnalyzeData by hand, audit the code that fills analyzeHeader.sources and the parent->child index maps for off-by-one or stale-reference bugs.

Example fix

// before
const root = computeTreemapLayoutFromAnalyze(analyzeData, requestedIndex, rect, filter, sizeMode)

// after
if (requestedIndex < 0 || requestedIndex >= analyzeData.sourceCount()) {
  throw new Error(
    `sourceIndex ${requestedIndex} out of range [0, ${analyzeData.sourceCount()})`
  )
}
const root = computeTreemapLayoutFromAnalyze(analyzeData, requestedIndex, rect, filter, sizeMode)

function isValidSourceIndex(analyzeData: AnalyzeData, idx: number): boolean {
  return Number.isInteger(idx) && idx >= 0 && idx < analyzeData.sourceCount()
}

// before computing any layout:
const roots = analyzeData.sourceRoots()
for (const r of roots) {
  if (!isValidSourceIndex(analyzeData, r)) throw new Error(`stale root index ${r}`)
  for (const c of analyzeData.sourceChildren(r)) {
    if (!isValidSourceIndex(analyzeData, c)) throw new Error(`stale child ${c} of root ${r}`)
  }
}

function isAnalyzable(data: AnalyzeData, idx: number): data is AnalyzeData & { sourceIndex: number } {
  return data.source(idx) !== undefined
}

try {
  return computeTreemapLayoutFromAnalyze(analyzeData, sourceIndex, rect, filter, sizeMode)
} catch (err) {
  if (err instanceof Error && err.message.startsWith('Source at index')) {
    // regenerate the report rather than render a half-broken treemap
    throw new Error('Analyze report is inconsistent — regenerate it with the matching analyzer version', { cause: err })
  }
  throw err
}

When it happens

Trigger: Calling computeTreemapLayoutFromAnalyze (treemap-layout.ts:271) with a sourceIndex >= analyzeData.sourceCount(), or a child index returned by analyzeData.sourceChildren(idx) that points past the end of the sources array. Also reachable via the single-child directory fold at lines 127-144 and the recursive children walk at 247-256 when the analyze header's tree links are inconsistent with its sources list.

Common situations: Loading an analyze report produced by a different/older @next/build-analyzer or webpack-bundle-analyzer plugin version whose tree format differs; manually constructing or hand-editing an AnalyzeData instance and passing a stale sourceIndex; a partial/truncated report JSON where the sources array was cut off but child references remained.

Related errors

• Failed to fetch ${url}

AI-assisted analysis of vercel/next.js@0ae8c72462 (2026-08-06). Data as JSON: /api/errors/3c10ac35b87f646c. Report an issue: GitHub.