codex-team/editor.js · error · Error

Incorrect index

Error message

Incorrect index

What it means

BlockCollection.replace(index, block) swaps a block in the internal array; if blocks[index] is undefined (index past the end or negative) it throws 'Incorrect index'. Reached via internal flows like beautifyShortcut and isNodeEmpty handling.

Source

Thrown at src/components/blocks.ts:232

      const nextBlock = this.blocks[index + 1];

      if (nextBlock) {
        this.insertToDOM(block, 'beforebegin', nextBlock);
      } else {
        this.insertToDOM(block);
      }
    }
  }

  /**
   * Replaces block under passed index with passed block
   *
   * @param index - index of existed block
   * @param block - new block
   */
  public replace(index: number, block: Block): void {
    if (this.blocks[index] === undefined) {
      throw Error('Incorrect index');
    }

    const prevBlock = this.blocks[index];

    prevBlock.holder.replaceWith(block.holder);

    this.blocks[index] = block;
  }

  /**
   * Inserts several blocks at once
   *
   * @param blocks - blocks to insert
   * @param index - index to insert blocks at
   */
  public insertMany(blocks: Block[], index: number ): void {
    const fragment = new DocumentFragment();

View on GitHub (pinned to 5f45dabbe5)

Solutions

1. Refresh the index immediately before calling replace instead of caching it
2. Ensure index < blocks.length before replace
3. Serialize structural block operations so removals can't interleave

Example fix

// before
blockCollection.replace(staleIndex, newBlock);
// after
if (blockCollection.blocks[staleIndex] !== undefined) {
  blockCollection.replace(staleIndex, newBlock);
}

if (blockCollection.blocks[index] !== undefined) { blockCollection.replace(index, newBlock); }

const isValidBlockIndex = (blocks: Block[], i: number): boolean => Number.isInteger(i) && i >= 0 && i < blocks.length;

try { blockCollection.replace(index, block); } catch (e) { if (e instanceof Error && e.message === 'Incorrect index') { /* recompute index and retry */ } throw e; }

When it happens

Trigger: An internal operation calling replace with an index no longer valid because blocks were removed concurrently (undo/redo race, rapid deletion), or an out-of-range index computed from a stale count.

Common situations: Race conditions between keyboard shortcuts (beautify/enter handling) and asynchronous block removal; bugs in custom code reaching into BlockManager.replace with stale indices.

Related errors

• Index should be greater than or equal to 0
• Unable to move Block down since it is already the last
• Unable to move Block up since it is already the first
• Index should be a number

AI-assisted analysis of codex-team/editor.js@5f45dabbe5 (2026-08-27). Data as JSON: /api/errors/362ebd9688fa9778. Report an issue: GitHub.