What causes "Version with id ${input.id} already exists" in mastra-ai/mastra?

Generate a fresh unique id (crypto.randomUUID()) per version

Version with id ${input.id} already exists

Error message

Version with id ${input.id} already exists

What it means

createVersion() enforces primary-key uniqueness for MCP server versions: an entry with the same version id already exists in mcpServerVersions. Versions are keyed by explicit input.id, so re-submitting the same id collides.

Source

Thrown at packages/core/src/storage/domains/mcp-servers/inmemory.ts:180

    const { offset, perPage: perPageForResponse } = calculatePagination(page, perPageInput, perPage);

    return {
      mcpServers: clonedConfigs.slice(offset, offset + perPage),
      total: clonedConfigs.length,
      page,
      perPage: perPageForResponse,
      hasMore: offset + perPage < clonedConfigs.length,
    };
  }

  // ==========================================================================
  // MCP Server Version Methods
  // ==========================================================================

  async createVersion(input: CreateMCPServerVersionInput): Promise<MCPServerVersion> {
    // Check if version with this ID already exists
    if (this.db.mcpServerVersions.has(input.id)) {
      throw new Error(`Version with id ${input.id} already exists`);
    }

    // Check for duplicate (mcpServerId, versionNumber) pair
    for (const version of this.db.mcpServerVersions.values()) {
      if (version.mcpServerId === input.mcpServerId && version.versionNumber === input.versionNumber) {
        throw new Error(`Version number ${input.versionNumber} already exists for MCP server ${input.mcpServerId}`);
      }
    }

    const version: MCPServerVersion = {
      ...input,
      createdAt: new Date(),
    };

    // Deep clone before storing
    this.db.mcpServerVersions.set(input.id, this.deepCopyVersion(version));
    return this.deepCopyVersion(version);
  }

View on GitHub (pinned to 75dd419e61)

Solutions

Generate a fresh unique id (crypto.randomUUID()) per version
Check existence first via listVersions and skip or update instead of insert
Catch the error and treat it as an idempotent no-op if the existing version matches

Example fix

// before
await storage.createVersion({ id: 'v1', mcpServerId: id, versionNumber: 1 });
await storage.createVersion({ id: 'v1', mcpServerId: id, versionNumber: 1 }); // throws
// after
await storage.createVersion({ id: crypto.randomUUID(), mcpServerId: id, versionNumber: 1 });

Defensive patterns

Strategy: try-catch

Validate before calling

const { versions } = await storage.listVersions(mcpServerId);
if (versions.some(v => v.id === input.id)) {
  throw new ConflictError(`version ${input.id} already exists`);
}

Try / catch

try {
  await storage.createVersion(input);
} catch (e) {
  if (e instanceof Error && e.message.startsWith('Version with id')) {
    return; // idempotent no-op: already registered
  }
  throw e;
}

Prevention

Always generate ids with crypto.randomUUID(), never reuse client ids
Make seed/import scripts idempotent by checking existence first
On retry, reuse the same id and treat duplicates as success

When it happens

Trigger: Calling createVersion() (directly or via create()) with an input.id that already exists in the store, e.g. re-running an import/seed script or retrying a request without a fresh unique id.

Common situations: Idempotency mistakes in seed scripts; retry logic reusing the request body without generating a new id; importing the same MCP server definition twice.

Related errors

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/1d0ff4f13eebb3bb. Report an issue: GitHub.