mermaid-js/mermaid · error

align ${hint.direction} lists [${id}] more than once

Error message

align ${hint.direction} lists [${id}] more than once

What it means

Thrown by ArchitectureDB.addLayoutHint when the same id appears more than once in hint.members. The DB walks the members array with a `seen` Set and rejects any repeat. An align chain with a duplicated node would create a degenerate (zero-length) constraint and confuse the layout engine.

Source

Thrown at packages/mermaid/src/diagrams/architecture/architectureDb.ts:277

  public getEdges(): ArchitectureEdge[] {
    return this.edges;
  }

  public addLayoutHint(hint: ArchitectureLayoutHint): void {
    if (hint.members.length < 2) {
      throw new Error(
        `An align directive requires at least two members; got ${hint.members.length}`
      );
    }
    const seen = new Set<string>();
    hint.members.forEach((id) => {
      if (this.registeredIds.get(id) !== 'node') {
        throw new Error(
          `align ${hint.direction} references [${id}], which is not a service or junction`
        );
      }
      if (seen.has(id)) {
        throw new Error(`align ${hint.direction} lists [${id}] more than once`);
      }
      seen.add(id);
    });
    this.layoutHints.push(hint);
  }

  public getLayoutHints(): ArchitectureLayoutHint[] {
    return this.layoutHints;
  }

  /**
   * Returns the current diagram's adjacency list, spatial map, & group alignments.
   * If they have not been created, run the algorithms to generate them.
   * @returns
   */
  public getDataStructures() {
    if (this.dataStructures === undefined) {
      // Tracks how groups are aligned with one another. Generated while creating the adj list

View on GitHub (pinned to d93e9c88c0)

Solutions

1. Remove duplicate ids so each member appears exactly once.
2. Dedupe the members array before calling addLayoutHint.

Example fix

// before
db.addLayoutHint({ direction: 'row', members: ['a', 'a', 'b'] });
// after
db.addLayoutHint({ direction: 'row', members: ['a', 'b'] });

function addLayoutHintSafe(db, hint) {
  if (new Set(hint.members).size !== hint.members.length) {
    throw new Error('align members contains duplicates');
  }
  db.addLayoutHint(hint);
}

const hasNoDuplicates = (arr) => new Set(arr).size === arr.length;

When it happens

Trigger: Calling db.addLayoutHint({ direction: 'row', members: ['a', 'a', 'b'] }). In DSL: `align row: a, a, b`.

Common situations: Copy-paste duplication in a DSL align chain; programmatic array construction that concatenates lists without dedup; refactors that merge two align directives naively.

Related errors

• An align directive requires at least two members; got ${hint
• align ${hint.direction} references [${id}], which is not a s
• Architecture layout failed: a declared `align row|column` di
• No nodes found in layout data
• No nodes available to create tree

AI-assisted analysis of mermaid-js/mermaid@d93e9c88c0 (2026-08-12). Data as JSON: /api/errors/7da669a73f08fbca. Report an issue: GitHub.