inspector/specification/v2_tech_stack.md

Inspector V2 Tech Stack

Brief | V1 Problems | V2 Scope | V2 Tech Stack

UX: Overview | Features | Handlers | Screenshots

Table of Contents

• Web Client
  • Language and Framework
  • Components and theme
• Proxy Server
  • Language and Runtime
  • Transport Operation
  • Logging

Web Client

Language and Framework

• Typescript
• React

Components and Theme

Let's choose a feature-rich component set with easy theming control

• -[ ] Mantine
• -[x] Shadcn

Shadcn Rationale

Shadcn is recommended based on evaluation of both prototype implementations (v2/prototype/shadcn and v2/prototype/mantine).

Why Shadcn over Mantine:

Requirement	Shadcn	Mantine
Component ownership	Yes - Copy to codebase	No - npm dependency
Styling approach	Tailwind CSS	CSS-in-JS (emotion)
Bundle size	Minimal - Only used components	Larger - Full library
Customization	Full control - Edit source directly	Theme config only
Dark mode	CSS variables	Context provider

Benefits:

1. Component Ownership - Components are copied into your project, not installed as dependencies. This means:

   • More control over implementation details
   • Easier to modify for project-specific needs

2. Tailwind CSS Integration:

   • Theme customization via CSS variables
   • Smaller production bundles (unused styles purged)

3. Simpler Theme Architecture - CSS variables for theming:

   • Light/dark mode via CSS class toggle
   • Easy to extend with custom color schemes
   • Works seamlessly with Tailwind

4. Developer Experience from Prototype:

   • Faster iteration when modifying components
   • More readable component code
   • Easier debugging (source is in your project)

Tradeoffs:

• Initial setup - Requires adding components individually (vs Mantine's single install)
• Less "batteries included" - Some advanced features need additional work (e.g., date pickers, rich text)
• Documentation - Mantine has more extensive API docs for each prop

Prototype Comparison:

Both prototypes implement the same V2 UX spec. Key observations:

Aspect	Shadcn Prototype	Mantine Prototype
Code clarity	Component code visible in project	Abstracted in node_modules
Theme toggle	CSS class swap	useMantineColorScheme hook
Custom styling	Add Tailwind classes directly	Override with sx prop or styles API
Component modification	Edit the file	Create wrapper or fork

Proxy Server

Language and Runtime

• Typescript
• Node

Transport Operation

Let's consider how to operate the server transports.

• -[x] Hono
• -[ ] Express
• -[ ] Node:http

Hono Rationale

Hono is selected based on community consensus (PR #945 discussion) for alignment with modern web standards and the TypeScript SDK v2 direction.

Why Hono over Express:

Requirement	Hono	Express
Bundle size	12kb	~1mb
Web Standards (Request/Response)	Yes - Native	No - Shimmed
TypeScript native	Yes	No - @types package
Tree-shakable	Yes - Fully	No
HTTP/2 support	Yes	No (SPDY dropped)
Built-in middleware	Yes - Body parsing, auth, etc.	No - Requires plugins
Edge/serverless deployment	Yes - Native	Partial - Requires adapters

Benefits:

1. Web Standards Alignment - Uses native Request/Response objects, enabling deployment across Node, Deno, Bun, serverless, and edge environments
2. TypeScript Native - Full type safety without external type packages, no monkey-patching of request objects
3. Future-proofing - HTTP/2 support enables potential gRPC transport; aligns with TypeScript SDK v2 plans
4. Developer Experience - Simpler API, type-safe context, smaller learning curve
5. Bundle Efficiency - Dramatically smaller footprint benefits both development and deployment

Logging

Let's step up our logging capability with an advanced logger:

• -[ ] Winston
• -[x] Pino
• -[ ] Morgan
• -[ ] Log4js
• -[ ] Bunyan

Pino Rationale

Pino is selected for synergy with the History Screen feature. The log file serves dual purposes:

1. Server diagnostics - Standard application logging
2. History persistence - Request/response replay source

Why Pino over Winston:

Requirement	Pino	Winston
Default JSON format	Yes - NDJSON	No - Text (needs config)
Line-by-line parsing	Yes - Native	No - Extra work
High-throughput logging	Yes - Very fast	Partial - Slower
Log rotation	Yes - pino-roll	Yes - winston-daily-rotate
Dev-friendly output	Yes - pino-pretty	Yes - Built-in

Architecture:

┌─────────────────────────────────────────────────────────────────┐
│                         Proxy Server                            │
│                                                                 │
│  MCP Request ──▶ Pino Logger ──┬──▶ history.ndjson (file)       │
│                                │                                │
│                                └──▶ Console (pino-pretty)       │
│                                                                 │
│  History API: GET /api/history?method=tools/call&limit=50       │
│  (parses history.ndjson, returns filtered JSON)                 │
└─────────────────────────────────────────────────────────────────┘

Log Entry Schema:

Each MCP operation logs a request/response pair:

{"ts":1732987200000,"level":"info","type":"mcp_request","method":"tools/call","target":"echo","params":{"message":"hello"},"requestId":"abc123","serverId":"my-server"}
{"ts":1732987200045,"level":"info","type":"mcp_response","requestId":"abc123","result":{"content":[{"type":"text","text":"hello"}]},"duration":45,"success":true}

Schema fields:

Field	Description
ts	Unix timestamp (ms)
level	Log level (info, error)
type	mcp_request or mcp_response
method	MCP method (tools/call, resources/read, prompts/get, etc.)
target	Tool name, resource URI, or prompt name
params	Request parameters
requestId	Correlation ID linking request to response
serverId	Server identifier
result	Response data (for mcp_response)
error	Error message (for failed requests)
duration	Response time in ms
success	Boolean success indicator

Dependencies:

• pino - Core logger
• pino-pretty - Dev console formatting
• pino-roll - Log rotation (optional)
• pino-http - Express integration