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opencode/context/development/ai/mastra-ai/guides/modular-building.md

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+<!-- Context: development/modular-building | Priority: high | Version: 1.0 | Updated: 2026-02-15 -->
+
+# Guide: Modular Mastra Building
+
+**Purpose**: Best practices for structuring a large-scale Mastra implementation.
+
+**Last Updated**: 2026-01-09
+
+---
+
+## Core Idea
+Modular building ensures that as the project grows, components remain testable, reusable, and easy to navigate. This is achieved by separating logic into specialized directories and using a central registry.
+
+## Key Points
+- **Component Separation**: Keep `agents`, `tools`, `workflows`, and `scorers` in their own top-level directories within `src/mastra/`.
+- **Shared Services**: Use a `shared.ts` file to instantiate services (DB, repositories) to prevent circular dependencies between workflows and the main Mastra instance.
+- **Central Registry**: Register all components in `src/mastra/index.ts`. This is the single source of truth for the Mastra instance.
+- **Feature-Based Steps**: Group related workflow steps into sub-directories (e.g., `src/mastra/workflows/v3/steps/`) to keep workflow files clean.
+
+## Quick Example
+```typescript
+// src/mastra/shared.ts
+export const services = createServices();
+
+// src/mastra/index.ts
+import { services } from './shared';
+export const mastra = new Mastra({
+  workflows: { myWorkflow },
+  agents: { myAgent },
+  // ...
+});
+```
+
+**Reference**: `src/mastra/index.ts`, `src/mastra/shared.ts`
+**Related**:
+- concepts/core.md
+- guides/workflow-step-structure.md