mermaid-js/mermaid · error · Error

Trying to create an existing branch. (Help: Either use a new

Error message

Trying to create an existing branch. (Help: Either use a new name if you want create a new branch or try using "checkout ${name}")

What it means

Error "Trying to create an existing branch. (Help: Either use a new name if you want create a new branch or try using "checkout ${name}")" thrown in mermaid-js/mermaid.

Source

Thrown at packages/mermaid/src/diagrams/git/gitGraphAst.ts:141

    parents: state.records.head == null ? [] : [state.records.head.id],
    branch: state.records.currBranch,
  };
  state.records.head = newCommit;
  log.info('main branch', config.mainBranchName);
  if (state.records.commits.has(newCommit.id)) {
    log.warn(`Commit ID ${newCommit.id} already exists`);
  }
  state.records.commits.set(newCommit.id, newCommit);
  state.records.branches.set(state.records.currBranch, newCommit.id);
  log.debug('in pushCommit ' + newCommit.id);
};

export const branch = function (branchDB: BranchDB) {
  let name = branchDB.name;
  const order = branchDB.order;
  name = common.sanitizeText(name, getConfig());
  if (state.records.branches.has(name)) {
    throw new Error(
      `Trying to create an existing branch. (Help: Either use a new name if you want create a new branch or try using "checkout ${name}")`
    );
  }

  state.records.branches.set(name, state.records.head != null ? state.records.head.id : null);
  state.records.branchConfig.set(name, { name, order });
  checkout(name);
  log.debug('in createBranch');
};

export const merge = (mergeDB: MergeDB): void => {
  let otherBranch = mergeDB.branch;
  let customId = mergeDB.id;
  const overrideType = mergeDB.type;
  const customTags = mergeDB.tags;
  const config = getConfig();
  otherBranch = common.sanitizeText(otherBranch, config);
  if (customId) {

View on GitHub (pinned to d93e9c88c0)

When it happens

Trigger: Thrown at packages/mermaid/src/diagrams/git/gitGraphAst.ts:141 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mermaid-js/mermaid@d93e9c88c0 (2026-08-12). Data as JSON: /api/errors/75589ae818299f0b. Report an issue: GitHub.