Features

A quick-reference index of every built-in capability in RelayCore, with a one-line description and a link to the deep-dive doc. Use Ctrl+F to jump to what you need.

Flow interception & rewriting

Capability	Description
Mock Response	Replace the upstream response with a local fake — no server needed
Map Local	Serve a local file in place of an HTTP request
Map Remote	Rewrite the URL to point at another environment or server
Redirect	3xx redirect
Header modification	Add, update, or delete request/response headers
Body modification	Full replace, regex replace, JSONPath set/delete
Intercept breakpoints	Pause live traffic, inspect, modify, then resume or drop
Flow replay	Resend a captured request/response, with optional modifications

Protocols

Capability	Description	Link
HTTP/1.1	Full support	Protocols
HTTP/2	Full support, including HPACK decompression	Protocols
HTTPS / TLS	Dynamic CA + MITM	Certificates
WebSocket	Per-message inspection and modification	Protocols § WebSocket
QUIC / HTTP/3	Default Downgrade, optional Passthrough / ExperimentalMitm	Protocols § QUIC

Operating modes

Capability	Description	Link
Explicit proxy	Client sets the proxy URL	Proxy Modes
Transparent proxy	macOS PF / Linux TPROXY
Upstream proxy	Chained behind a parent proxy
TUI	Terminal real-time inspection and modification	TUI
UDP TPROXY	UDP transparent proxy (Linux only)	Proxy Modes § UDP TPROXY

User surfaces

Surface	Description	Link
TUI	Interactive terminal UI	TUI
CLI	All commands and flags	CLI Reference
HTTP API	REST + SSE	HTTP API
MCP	For AI agents	MCP Server
Tauri plugin	Embed in a Tauri app	Tauri Plugin

Extensions & scripting

Capability	Description	Link
Rule engine	Declarative match + action pipeline	Rule API
Deno scripts	JS/TS for complex logic	Scripting API
Script fetch	HTTP from inside a script (allowlist)	Scripting § fetch

Observability & operations

Capability	Description	Link
Prometheus metrics	Standard text format at `/api/v1/metrics/prometheus`	Monitoring
SSE live event stream	Flows, WebSocket messages, audit, lifecycle	Monitoring
Audit log	Every control-plane change (actor / kind / outcome)	HTTP API § audit
JSONL stream to disk	Every flow appended to a file, for offline analyze	CLI § run
HAR export	Single or batch	HTTP API § flows

Security & privacy

Capability	Description	Link
Header / query redaction	Allowlist fields are masked everywhere	HTTP API § policy
Body redaction	Optional, by content-type	HTTP API § policy
Bearer auth	`--api-token` for the HTTP API	CLI § run
CORS allowlist	`--api-cors`	CLI § run
Secret field masking	Upstream proxy passwords, etc.	Proxy Modes § upstream