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

Generate a fresh unique id (e.g. `randomUUID()`) per version.

Version with id ${input.id} already exists

Error message

Version with id ${input.id} already exists

What it means

`createVersion` in the in-memory MCP clients domain throws this when a version record with the same version id is already present in `mcpClientVersions`. Version ids must be globally unique within storage.

Source

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

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

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

  // ==========================================================================
  // MCP Client Version Methods
  // ==========================================================================

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

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

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

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

View on GitHub (pinned to 75dd419e61)

Solutions

Generate a fresh unique id (e.g. `randomUUID()`) per version.
Check for the existing version first and reuse/skip it instead of creating.
Clear storage or use a new instance before re-seeding.

Example fix

// before
await mcpClients.createVersion({ id: `${clientId}-v1`, mcpClientId: clientId, versionNumber: 1 });
// after
await mcpClients.createVersion({ id: crypto.randomUUID(), mcpClientId: clientId, versionNumber: 1 });

Defensive patterns

Strategy: validation

Validate before calling

const { versions } = await mcpClients.listVersions(input.mcpClientId, { perPage: false });
if (versions.some(v => v.id === input.id)) {
  throw new Error(`Version ${input.id} already exists; skip createVersion`);
}

Try / catch

try {
  await mcpClients.createVersion(input);
} catch (err) {
  if (err instanceof Error && /already exists/.test(err.message)) return; // idempotent retry
  throw err;
}

Prevention

Use randomUUID() for version ids instead of deterministic templates.
Make createVersion calls idempotent by checking first.
Reset storage before re-running seeds or imports.

When it happens

Trigger: Calling `createVersion({ id, mcpClientId, versionNumber, ... })` where `db.mcpClientVersions.has(input.id)` — a version with that exact id was already created (e.g., re-running seeding, which the SOURCE notes is called by seedAgent).

Common situations: Deterministic ids like `${clientId}-v1` regenerated on re-seed; retrying a createVersion call after a timeout; replaying an event/import twice.

Related errors

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/ff4dd24d0395b06f. Report an issue: GitHub.