Version number ${input.versionNumber} already exists for MCP

Error message

Version number ${input.versionNumber} already exists for MCP server ${input.mcpServerId}

What it means

createVersion() enforces a composite uniqueness constraint on (mcpServerId, versionNumber): each MCP server may only have one version record with a given versionNumber. Even with unique ids, re-registering the same numeric version for the same server is rejected.

Source

Thrown at packages/core/src/storage/domains/mcp-servers/inmemory.ts:186

      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);
  }

  async getVersion(id: string): Promise<MCPServerVersion | null> {
    const version = this.db.mcpServerVersions.get(id);
    return version ? this.deepCopyVersion(version) : null;
  }

View on GitHub (pinned to 75dd419e61)

Solutions

Increment versionNumber before inserting a new version
Query existing versions for the mcpServerId and use max(versionNumber)+1
Catch the error and return the already-existing version for idempotent publishes

Example fix

// before
await storage.createVersion({ id: newId, mcpServerId, versionNumber: 1 }); // second publish throws
// after
const { versions } = await storage.listVersions(mcpServerId, { perPage: 1 });
const next = (versions[0]?.versionNumber ?? 0) + 1;
await storage.createVersion({ id: crypto.randomUUID(), mcpServerId, versionNumber: next });

Defensive patterns

Strategy: try-catch

Validate before calling

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

Try / catch

try {
  await storage.createVersion(input);
} catch (e) {
  if (e instanceof Error && e.message.includes('already exists for MCP server')) {
    return getExistingVersion(mcpServerId, input.versionNumber); // idempotent publish
  }
  throw e;
}

Prevention

Derive versionNumber as max(existing)+1 instead of trusting request input
Bump versionNumber on every publish in CI
Serialize publishes per mcpServerId (lock or queue) to avoid races

When it happens

Trigger: Calling createVersion() with a (mcpServerId, versionNumber) pair that already exists — e.g. publishing an MCP server again without incrementing versionNumber, or two concurrent creates of the same version racing.

Common situations: CI publishing an MCP server twice without a version bump; unique ids avoided but version numbers reused; concurrent workers creating the same version.

Related errors

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/4b58944fbf34b8a7. Report an issue: GitHub.