mastra-ai/mastra · error · HTTPException

Version with id ${to} not found for prompt block ${promptBlo

Error message

Version with id ${to} not found for prompt block ${promptBlockId}

What it means

Thrown when the 'to' version exists but is owned by a different prompt block (toVersion.blockId !== promptBlockId). Returned as a masked 404 for the same information-hiding reason as the other mismatch errors. The diff/revert operation requires both versions to belong to the addressed block.

Source

Thrown at packages/server/src/server/handlers/prompt-block-versions.ts:473

      const promptBlock = await promptBlockStore.getById(promptBlockId);
      assertStoredResourceScope(promptBlock, await getStoredResourceScope(mastra, requestContext));

      const fromVersion = await promptBlockStore.getVersion(from);
      if (!fromVersion) {
        throw new HTTPException(404, { message: `Version with id ${from} not found` });
      }
      if (fromVersion.blockId !== promptBlockId) {
        throw new HTTPException(404, {
          message: `Version with id ${from} not found for prompt block ${promptBlockId}`,
        });
      }

      const toVersion = await promptBlockStore.getVersion(to);
      if (!toVersion) {
        throw new HTTPException(404, { message: `Version with id ${to} not found` });
      }
      if (toVersion.blockId !== promptBlockId) {
        throw new HTTPException(404, {
          message: `Version with id ${to} not found for prompt block ${promptBlockId}`,
        });
      }

      const fromConfig = extractConfigFromVersion(
        fromVersion as unknown as Record<string, unknown>,
        SNAPSHOT_CONFIG_FIELDS,
      );
      const toConfig = extractConfigFromVersion(
        toVersion as unknown as Record<string, unknown>,
        SNAPSHOT_CONFIG_FIELDS,
      );

      const diffs = computeVersionDiffs(fromConfig, toConfig);

      return {
        diffs,
        fromVersion,

View on GitHub (pinned to 75dd419e61)

Solutions

1. Select 'to' only from the target block's version list.
2. Correct the promptBlockId in the path if the 'to' version's owner is the intended block.
3. Add client-side validation that both from and to versions share the block's id before issuing the request.

Example fix

// before
await post(`/prompt-blocks/${blockA.id}/revert`, { from, to: versionFromBlockB });
// after
const versions = await get(`/prompt-blocks/${blockA.id}/versions`);
const ids = new Set(versions.map(v => v.id));
if (ids.has(from) && ids.has(to)) await post(`/prompt-blocks/${blockA.id}/revert`, { from, to });

const versions = await getBlockVersions(promptBlockId);
if (!versions.some(v => v.id === to)) {
  throw new Error(`'to' version ${to} does not belong to block ${promptBlockId}`);
}

function bothOwned(versions: { id: string; blockId: string }[], from: string, to: string): boolean {
  return [from, to].every(id => versions.some(v => v.id === id && v.blockId === versions[0].blockId));
}

try {
  await revertVersions(promptBlockId, from, to);
} catch (e) {
  if (e.status === 404 && e.message.includes('not found for prompt block')) {
    // 'to' belongs to another block — reselect within this block
  }
  throw e;
}

When it happens

Trigger: Diff/revert request pairing prompt block A in the path with a 'to' version that belongs to prompt block B.

Common situations: Diff tools comparing versions across two blocks, cached 'to' selection from a previous block, or URL construction mixing ids from different API responses.

Related errors

• Version with id ${from} not found for prompt block ${promptB
• ACP connection is not initialized
• Model "${this.options.model}" is not available. Available mo
• ClaudeSDKAgent resumeData.sessionId must be a string.
• ClaudeSDKAgent resumeData.continue must be true when provide

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/3fa7a5269fff17bd. Report an issue: GitHub.