Module proxy 

mcpr-proxy

Proxy engine for mcpr: request routing, upstream forwarding, SSE streaming, and widget CSP rewriting.

This crate contains the core proxy logic that sits between clients and upstream MCP servers. It handles request classification, HTTP forwarding, SSE stream management, and response rewriting for widget security (CSP).

Responsibilities

• Request routing (router): Classify incoming HTTP requests into typed variants: MCP JSON-RPC POST, MCP SSE GET, widget HTML, widget assets, OAuth callbacks, or passthrough.

• Upstream forwarding (forwarding): HTTP client with connection pooling, semaphore-based concurrency limiting, configurable timeouts, and header forwarding (auth, content-type, MCP session ID).

• SSE handling (sse): Extract JSON from SSE-wrapped responses, re-wrap JSON as SSE, and split upstream URLs into (base, path) components.

• Widget CSP rewriting (csp, rewrite): Rewrite MCP response metadata to inject proxy domains into widget CSP arrays and widgetDomain fields. Supports both OpenAI and Claude widget metadata formats, with Extend and Override CSP modes.

• Proxy state (state): Shared runtime state tracking MCP upstream health, tunnel status, widget discovery, cloud sync, and request counters. Used by the admin API, health checks, and future mcpr proxy view TUI.

Module Structure

mcpr-proxy/src/
+-- lib.rs          # Crate root, re-exports
+-- router.rs       # ClassifiedRequest enum, classify() dispatcher
+-- forwarding.rs   # UpstreamClient, forward_request(), build_response()
+-- sse.rs          # SSE extract/wrap helpers, split_upstream()
+-- csp.rs          # CspMode enum, parse_csp_mode()
+-- rewrite.rs      # RewriteConfig, rewrite_response() for widget metadata
+-- state.rs        # ProxyState, ConnectionStatus, SharedProxyState

Re-exports

pub use csp::CspMode;

pub use csp::parse_csp_mode;

pub use rewrite::RewriteConfig;

pub use rewrite::rewrite_response;

pub use state::ConnectionStatus;

pub use state::ProxyState;

pub use state::SharedProxyState;

pub use state::lock_state;

pub use state::new_shared_state;

Modules

csp

forwarding

rewrite

router

sse

state

Proxy runtime state — shared across the proxy process.