mermaid-js/mermaid · error · Error

Configuration is required in layout data

Error message

Configuration is required in layout data

What it means

Second guard in validateLayoutData: `data` itself is truthy but `data.config` is missing. The cose-bilkent layout needs the MermaidConfig to drive cytoscape options, so a LayoutData without its config block is rejected before cytoscape is created. Thrown at layout.ts:61.

Source

Thrown at packages/mermaid/src/rendering-util/layout-algorithms/cose-bilkent/layout.ts:61

    };
  } catch (error) {
    log.error('Error in cose-bilkent layout algorithm:', error);
    throw error;
  }
}

/**
 * Validate layout data structure
 * @param data - The data to validate
 * @returns True if data is valid, throws error otherwise
 */
export function validateLayoutData(data: LayoutData): boolean {
  if (!data) {
    throw new Error('Layout data is required');
  }

  if (!data.config) {
    throw new Error('Configuration is required in layout data');
  }

  if (!data.rootNode) {
    throw new Error('Root node is required');
  }

  if (!data.nodes || !Array.isArray(data.nodes)) {
    throw new Error('No nodes found in layout data');
  }

  if (!Array.isArray(data.edges)) {
    throw new Error('Edges array is required in layout data');
  }

  return true;
}

View on GitHub (pinned to d93e9c88c0)

Solutions

1. Attach the active MermaidConfig to data.config before calling the layout (the standard render path does this automatically — use it instead of calling executeCoseBilkentLayout directly).
2. If building LayoutData manually, spread the config in: { ...rest, config: mermaidConfig }.
3. Add a unit-test fixture that includes a minimal valid config object.
4. Log data.config at the call site to confirm it is populated.

Example fix

// before
{ rootNode, nodes, edges, layoutAlgorithm: 'cose-bilkent' }
// after
{ rootNode, nodes, edges, layoutAlgorithm: 'cose-bilkent', config: mermaidConfig }

if (!data?.config) throw new Error('LayoutData.config missing — attach the active MermaidConfig');

function hasConfig(d: any): d is { config: object } { return d && typeof d.config === 'object' && d.config !== null; }

try { validateLayoutData(data); } catch (e) { if (/Configuration is required/.test(String(e))) { data.config = mermaidConfig; validateLayoutData(data); } else throw e; }

When it happens

Trigger: A LayoutData object assembled without the config field, e.g. { rootNode, nodes, edges, layoutAlgorithm } with config omitted, or a partial spread that dropped config. Also if a transformer sets config to null explicitly.

Common situations: Custom diagram integrations that hand-build LayoutData and forget to attach the mermaid config; a refactor that moved config to a sibling property; or a mock/fixture used in tests missing the config block.

Related errors

• Layout data is required
• Root node is required
• No nodes found in layout data
• Edges array is required in layout data
• No nodes found in layout data

AI-assisted analysis of mermaid-js/mermaid@d93e9c88c0 (2026-08-12). Data as JSON: /api/errors/0e9eb2270f0b93dc. Report an issue: GitHub.