proxy-mcp

proxy-mcp is an MCP server that runs an explicit HTTP/HTTPS MITM proxy (L7). It captures requests/responses, lets you modify traffic in-flight (headers/bodies/mock/forward/drop), supports upstream proxy chaining, and records TLS fingerprints for connections to the proxy (JA3/JA4) plus optional upstream server JA3S. Ships "interceptors" to route a stealth browser (cloakbrowser, source-patched Chromium), CLI tools, Docker containers, and Android devices/apps through the proxy, plus Playwright-driven browser automation with locator-based click, typing, scroll, and ARIA snapshots.

71 tools + 6 resources + 3 resource templates. Built on mockttp and cloakbrowser.

Table of Contents

• Setup
• HTTP Proxy Configuration
• Boundaries
• TLS ClientHello Passthrough
• Pairs well with CDP/Playwright
• Mobile Capture (Transparent Proxy)
• Tools Reference
  • Lifecycle
  • Upstream Proxy
  • Interception Rules
  • Traffic Capture
  • Modification Shortcuts
  • TLS Fingerprinting
  • Interceptors
  • Browser DevTools-equivalents
  • Sessions
  • Humanizer
• Resources
• Usage Example
• Architecture
• Testing
• Credits

Setup

Quick install (Claude Code)

claude mcp add proxy-mcp -- npx -y proxy-mcp@latest

This installs proxy-mcp as an MCP server using stdio transport. It auto-updates on every Claude Code restart.

Scopes:

# Per-user (available in all projects)
claude mcp add --scope user proxy-mcp -- npx -y proxy-mcp@latest

# Per-project (shared via .mcp.json, commit to repo)
claude mcp add --scope project proxy-mcp -- npx -y proxy-mcp@latest

Prerequisites

• Node.js 22+

From source (development)

git clone https://github.com/yfe404/proxy-mcp.git
cd proxy-mcp
npm install
npm run build

# stdio transport (default) — used by MCP clients like Claude Code
node dist/index.js

# Streamable HTTP transport — exposes /mcp endpoint for scripting
node dist/index.js --transport http --port 3001

--transport and --port also accept env vars TRANSPORT and PORT.

Manual MCP configuration

Claude Code CLI:

# stdio (default)
claude mcp add proxy-mcp -- npx -y proxy-mcp@latest

# From local clone
claude mcp add proxy-mcp -- node /path/to/proxy-mcp/dist/index.js

# HTTP transport for scripting
claude mcp add --transport http proxy-mcp http://127.0.0.1:3001/mcp

.mcp.json (project-level, commit to repo):

{
  "mcpServers": {
    "proxy": {
      "command": "npx",
      "args": ["-y", "proxy-mcp@latest"]
    }
  }
}

Streamable HTTP transport:

{
  "mcpServers": {
    "proxy": {
      "type": "streamable-http",
      "url": "http://127.0.0.1:3001/mcp"
    }
  }
}

HTTP Proxy Configuration

1) Start proxy and get endpoint

proxy_start

Use the returned port and endpoint http://127.0.0.1:<port>.

2) Browser setup (recommended: interceptor)

Use the browser interceptor so proxy flags and cert trust are configured automatically. Launches cloakbrowser — a stealth-patched Chromium with source-level C++ fingerprint patches and humanize mode on by default:

interceptor_browser_launch --url "https://example.com"

Drive the page with Playwright-backed tools (no CDP, no sidecar — target_id is all you need):

interceptor_browser_navigate --target_id "browser_<id>" --url "https://apify.com"
interceptor_browser_snapshot  --target_id "browser_<id>"
interceptor_browser_screenshot --target_id "browser_<id>" --file_path "/tmp/shot.png"

3) Browser setup (manual fallback)

If launching a browser manually, pass the proxy flag yourself:

google-chrome --proxy-server="http://127.0.0.1:<port>"

4) CLI/process setup

Route any process through proxy-mcp by setting proxy env vars:

export HTTP_PROXY="http://127.0.0.1:<port>"
export HTTPS_PROXY="http://127.0.0.1:<port>"
export NO_PROXY="localhost,127.0.0.1"

If the client verifies TLS, trust the proxy-mcp CA certificate (see proxy_get_ca_cert) or use the Terminal interceptor (interceptor_spawn) which sets proxy env vars plus common CA env vars (curl, Node, Python requests, Git, npm/yarn, etc.):

interceptor_spawn --command curl --args '["-s","https://example.com"]'

Explicit curl examples:

curl --proxy http://127.0.0.1:<port> http://example.com
curl --proxy http://127.0.0.1:<port> https://example.com

5) Upstream proxy chaining

Set optional proxy chaining from proxy-mcp to another upstream proxy (for geolocation, auth, or IP reputation):

Client/app  →  proxy-mcp (local explicit proxy)  →  upstream proxy (optional chaining layer)

proxy_set_upstream --proxy_url "socks5://user:pass@upstream.example:1080"

Supported upstream URL schemes: socks4://, socks5://, http://, https://, pac+http://.

Typical geo-routing examples:

# Route ALL outgoing traffic from proxy-mcp via a geo proxy
proxy_set_upstream --proxy_url "socks5://user:pass@fr-exit.example.net:1080"

# Bypass upstream for local/internal hosts
proxy_set_upstream --proxy_url "http://user:pass@proxy.example.net:8080" --no_proxy '["localhost","127.0.0.1",".corp.local"]'

# Route only one hostname via a dedicated upstream (overrides global)
proxy_set_host_upstream --hostname "api.example.com" --proxy_url "https://user:pass@us-exit.example.net:443"

# Remove overrides when done
proxy_remove_host_upstream --hostname "api.example.com"
proxy_clear_upstream

For HTTPS MITM, the proxy CA must be trusted in the target environment (proxy_get_ca_cert).

6) Validate and troubleshoot quickly

proxy_list_traffic --limit 20
proxy_search_traffic --query "example.com"

Common issues:

• Traffic from the wrong browser instance (fix: always pass target_id from interceptor_browser_launch)
• HTTPS cert trust missing on target
• NO_PROXY bypassing expected hosts
• First launch is slow: cloakbrowser downloads a ~200 MB stealth Chromium binary on first use (cached afterwards)

7) HAR import + replay

Import HAR into a persisted session, then analyze with existing session query/findings tools:

proxy_import_har --har_file "/path/to/capture.har" --session_name "imported-run"
proxy_list_sessions
proxy_query_session --session_id SESSION_ID --hostname_contains "api.example.com"
proxy_get_session_handshakes --session_id SESSION_ID

Replay defaults to dry-run (preview only). Execute requires explicit mode:

# Preview what would be replayed
proxy_replay_session --session_id SESSION_ID --mode dry_run --limit 20

# Execute replay against original hosts
proxy_replay_session --session_id SESSION_ID --mode execute --limit 20

# Optional: override target host/base URL while preserving path+query
proxy_replay_session --session_id SESSION_ID --mode execute --target_base_url "http://127.0.0.1:8081"

Note: imported HAR entries (and entries created by proxy_replay_session) do not carry JA3/JA4/JA3S handshake metadata. Use live proxy-captured traffic to analyze handshake fingerprints.

Mobile Capture (Transparent Proxy)

For mobile apps with custom HTTP stacks that ignore the system proxy (most modern Android apps — Shopee, SHEIN, TikTok, banking, etc.) the explicit proxy won't see their traffic. proxy-mcp ships a transparent listener that sits behind an iptables REDIRECT and MITMs using the TLS SNI — no CONNECT tunnel required.

Pairs with proxy-ap-card — a XIAO ESP32-S3 that broadcasts a WiFi AP (proxy-ap SSID by default) and presents to the laptop as a USB-NCM ethernet adapter. That repo handles the AP + NAPT side; proxy-mcp handles the laptop side.

Prerequisites

• Laptop: Linux with iptables, sysctl, nmcli (NetworkManager), ip (iproute2), adb. sudo for network configuration (one command per session).
• Hardware router: a proxy-ap-card (XIAO ESP32-S3) with firmware flashed. Or any USB-ethernet / USB-WiFi combo where the laptop NATs traffic for the phone's subnet — pass --ap_iface / --ap_subnet to override defaults.
• Target device: Android with root (Magisk / KernelSU). Root is required to inject the CA into the system cert store. Android 14-16 additionally need the zygote mount-namespace injection which this tool does automatically.
• ADB access: the target device must appear in adb devices (USB at minimum, wireless after pairing).

First-time walkthrough

1. Flash + plug in the proxy-ap-card

Follow the proxy-ap-card README to build + flash the XIAO. On replug the laptop should show a cdc_ncm interface (verify: ls /sys/class/net/*/device/uevent | xargs grep DRIVER | grep cdc_ncm).

2. Connect the target device to the laptop via USB

Only needed the first time per device, to push the CA. Verify with adb devices. Copy the serial.

3. Run the setup tool

proxy_mobile_setup --android_serial <serial>

Optional arguments:

Param	Default	When to override
ap_iface	auto-detect (cdc_ncm)	Using a different USB-ethernet bridge
ap_address	192.168.99.2/24	Matches default proxy-ap-card firmware
ap_subnet	192.168.4.0/24	Matches default proxy-ap-card firmware
egress_iface	auto-detect from default route	Multi-homed host, or wanting traffic to exit via a specific iface
explicit_port	8080	Port collision
transparent_port	8443	Port collision
block_quic	true	Need QUIC/HTTP3 (no MITM available then)
upstream_proxy_url	—	Route outbound through a residential/ISP proxy — see below
android_serial	—	Omit to skip CA injection (remote-only setups)
inject_cert	true if android_serial set	Set false to re-use a prior install

The response is JSON with three key bits:

{
  "ap_iface": "enp195s0f3u1u4",
  "cert_injected": true,
  "android_target_id": "adb_HQ63C81CB2",
  "sudo_command": "sudo bash /tmp/proxy-mcp-mobile-setup-<hex>.sh"
}

Keep android_target_id around — you'll need it for teardown.

4. Run the emitted sudo script

sudo bash /tmp/proxy-mcp-mobile-setup-<hex>.sh

This is the only sudo required. The script is idempotent, safe to re-run. It plumbs the routing that iptables needs root for:

# Static IP on the AP iface (skipped if already configured).
ip addr add 192.168.99.2/24 dev <ap_iface>

# Forwarding + dedicated nat chain.
sysctl -w net.ipv4.ip_forward=1
iptables -t nat -N PROXY_MCP_PREROUTING
iptables -t nat -A PROXY_MCP_PREROUTING -p tcp --dport 80  -j REDIRECT --to-ports 8080
iptables -t nat -A PROXY_MCP_PREROUTING -p tcp --dport 443 -j REDIRECT --to-ports 8443
iptables -t nat -A PREROUTING -i <ap_iface> -j PROXY_MCP_PREROUTING

# Block QUIC so apps fall back to TCP/TLS.
iptables -A FORWARD -i <ap_iface> -p udp --dport 443 -j DROP

# Masquerade out through the real egress.
iptables -t nat -A POSTROUTING -s 192.168.4.0/24 -o <egress_iface> -j MASQUERADE

Why a script and not direct execution? MCP runs as your user; iptables needs root; sudo from an MCP tool would require NOPASSWD or polkit policy (fragile, distro-specific). Emitting a script is auditable, reproducible, and portable.

5. Connect the phone to the proxy-ap WiFi

Credentials are set in the proxy-ap-card firmware (default SSID proxy-ap, default password shown in that repo). After connecting, the phone can be unplugged from USB — future sessions don't need it.

6. Start capturing

Every HTTP/HTTPS request from the phone now lands in proxy-mcp's ring buffer:

proxy_list_traffic --source_filter transparent   # iptables-redirected HTTPS
proxy_list_traffic --source_filter explicit      # absolute-URL HTTP that arrived on :80
proxy_get_exchange --exchange_id <id>            # full headers + body preview
proxy_search_traffic --query "api.example.com"   # full-text search

Each entry carries source: "explicit" | "transparent" + TLS fingerprints (ja3, ja4).

Subsequent sessions (phone already paired)

Skip step 2. Run:

proxy_mobile_setup                                # skip android_serial — cert already installed
sudo bash /tmp/proxy-mcp-mobile-setup-<hex>.sh

Then phone joins the AP and capture resumes.

Upstream chaining

Set upstream_proxy_url to route outbound traffic through a residential/ISP proxy — the target servers see that proxy's IP, not your laptop's:

proxy_mobile_setup \
  --upstream_proxy_url "http://user:pass@proxy.example.com:8000" \
  --android_serial <serial>

Applies to BOTH listeners. Use proxy_set_upstream after the fact to change it without restarting.

Verifying each step

Check	Command	Expected
Listeners up	proxy_status	running: true, transparentProxy.running: true
Iface detected	proxy_mobile_detect_iface	found: true, iface name
Cert injected	adb shell "su -c 'nsenter --mount=/proc/\$(pidof zygote64)/ns/mnt -- ls /apex/com.android.conscrypt/cacerts/ | wc -l'"	144 (or 143 + 1)
iptables wired	sudo iptables -t nat -L PROXY_MCP_PREROUTING -v -n	2 REDIRECT rules, non-zero pkts after phone generates traffic
Forwarding on	cat /proc/sys/net/ipv4/ip_forward	1
Phone sees AP	phone Settings → WiFi shows proxy-ap connected, IP in 192.168.4.0/24
Traffic flowing	proxy_list_traffic --limit 5 after opening any app	source: "transparent" entries with status 200

Teardown

proxy_mobile_teardown --android_target_id <from-setup>
sudo bash /tmp/proxy-mcp-mobile-teardown-<hex>.sh

The MCP call stops both listeners and deactivates the Android target. The sudo script removes the iptables rules, disables ip_forward, and hands the AP iface back to NetworkManager. Phone stays connected to the AP until you forget it in phone WiFi settings.

Troubleshooting

Symptom	Likely cause	Fix
proxy_mobile_detect_iface returns found: false	proxy-ap-card not plugged in, or cdc_ncm driver missing	lsusb | grep '303a:'; dmesg | grep cdc_ncm; re-plug the card
setup errors No such file or directory: /sys/class/net/.../device/uevent	iface name passed explicitly but doesn't exist	Use auto-detect or verify with ip link
Phone connects to AP but zero traffic in proxy_list_traffic	sudo script not run; or phone on a different WiFi	Verify cat /proc/sys/net/ipv4/ip_forward returns 1; check phone's active SSID
Phone says "no internet" on proxy-ap	Forward + MASQUERADE rules missing, OR egress iface down	Re-run the sudo script; check ip route show default
HTTPS fails with "connection not private" or similar	Cert not trusted by the app (Chrome bundles its own CAs and ignores system trust, app has cert pinning)	Use another app to verify chain works; Chrome is the exception not the rule (see limitations below)
Some apps capture, others don't	Cert pinning in the apps that fail	See limitations below; Frida/LSPosed unpinning module needed
Ports 20346/20443/other custom ports not captured	Only :80 and :443 are redirected	Add extra REDIRECT rules in the sudo script, or pair redsocks to CONNECT-tunnel arbitrary ports through the explicit listener
cert_injected: false or zygote nsenter failed	Device not rooted, or SELinux chcon rejected	adb shell su -c 'id' must return uid=0; confirm zygisksu / Magisk is active
Wireless ADB port changes every session	Android's Wireless Debugging randomises the port	Re-pair; or keep phone plugged in for control plane

Without the proxy-ap-card

Any USB-NCM or USB-ethernet bridge that the phone can route through works:

proxy_mobile_setup --ap_iface eth1 --ap_address 10.0.0.1/24 --ap_subnet 10.0.0.0/24

Or use a laptop-hosted WiFi AP via hostapd on a USB WiFi adapter (MT76x2U, RTL8812AU, etc.) — pass the wlanN interface as ap_iface.

Limitations

• Cert pinning — apps that pin specific public keys (Instagram, WhatsApp, banking, Shopee homepage feed, etc.) will refuse our mockttp cert even with CA trust installed. You see partial capture (tracking / static / unpinned endpoints succeed, pinned API calls fail). Fix: Frida or LSPosed unpinning module for that specific app. See interceptor_frida_attach in the tool reference, or morrownr's USB-WiFi guides for common patterns.
• Chrome on Android — Chrome ships its own Mozilla CA bundle and enforces Certificate Transparency. Our CA is self-signed and not in any CT log, so Chrome rejects it regardless of system trust. Use any other app (or any OkHttp/Conscrypt-based browser) to verify the pipeline.
• QUIC / HTTP3 — the transparent listener is TCP/TLS only. By default we drop UDP/443 so apps fall back to TCP. Set block_quic: false if you want QUIC to pass through uncaptured (QUIC content won't appear in traffic logs).
• Non-standard ports — the default iptables rules only redirect TCP/80 and TCP/443. Shopee's :20346, custom gaming protocols, etc. will bypass. Add more REDIRECT rules in the sudo script (or chain redsocks to issue CONNECT tunnels through the explicit listener).
• Native TLS pinning — some apps use BoringSSL/OpenSSL directly via JNI with pins embedded in the .so. Java-layer Frida hooks won't catch these; native hooks needed.
• Root required — the system-trust CA overlay requires root. Non-rooted Android only trusts user-installed CAs for apps that explicitly opt in via network_security_config — which no shipping app does. There's no bypass for that without root.

Boundaries

• Only sees traffic configured to route through it (not a network tap or packet sniffer)
• Spoofs outgoing JA3 + HTTP/2 fingerprint + header order (via impit — native Rust TLS impersonation), not JA4 (JA4 is capture-only)
• Can add, overwrite, or delete HTTP headers; outgoing header order can be controlled via fingerprint spoofing
• Returns its own CA certificate — does not expose upstream server certificate chains

TLS ClientHello Passthrough (browser via interceptor)

When cloakbrowser is launched via interceptor_browser_launch, proxy-mcp forwards the browser's original TLS ClientHello to the upstream server for document loads and same-origin sub-resource requests. The target server sees an authentic Chrome TLS fingerprint — not the proxy's.

This is a key difference from typical MITM proxies (mitmproxy, Charles, Fiddler) which re-terminate TLS with their own fingerprint, making MITM trivially detectable by anti-bot systems via JA3/JA4 analysis.

How to verify passthrough is working:

proxy_list_tls_fingerprints --hostname_filter "example.com"

• JA3 varies across requests to the same host — this is expected; Chrome randomizes cipher suite order per-connection (feature since Chrome 110+)
• JA4 stays stable — same cipher/extension set, just different ordering
• JA3 variation + JA4 stability = authentic Chrome TLS passthrough confirmed

When passthrough applies vs. when spoofing is needed:

Traffic source	TLS behavior	Action needed
cloakbrowser via interceptor_browser_launch (document loads, same-origin)	Browser's native ClientHello forwarded (passthrough)	None — fingerprint is authentic
cloakbrowser via interceptor_browser_launch (cross-origin sub-resources, when spoof active)	Re-issued via impit with spoofed TLS	proxy_set_fingerprint_spoof with a browser preset
Non-browser clients (curl, Python, interceptor_spawn)	Proxy's own TLS	proxy_set_fingerprint_spoof or proxy_set_ja3_spoof required
HAR replay (proxy_replay_session)	Proxy's own TLS	proxy_set_fingerprint_spoof required

Built on cloakbrowser + Playwright

Browser automation uses cloakbrowser — a stealth-patched Chromium with source-level C++ fingerprint patches — driven via Playwright. There is no CDP surface, no sidecar, no hand-rolled stealth script. One target_id from interceptor_browser_launch is everything downstream tools need.

Capability	proxy-mcp
See/modify DOM, run JS in page	Via interceptor_browser_snapshot + interceptor_browser_list_storage_keys (also reachable from custom scripts via page.evaluate)
Read cookies, localStorage, sessionStorage	Yes — interceptor_browser_list_cookies, interceptor_browser_list_storage_keys
Capture HTTP request/response bodies	Via the MITM proxy (4 KB preview cap by default; full capture profile on persisted sessions stores complete bodies)
Modify requests in-flight (headers, body, mock, drop)	Yes (declarative rules, hot-reload)
Upstream proxy chaining (geo, auth)	Global + per-host upstreams across all clients (SOCKS4/5, HTTP, HTTPS, PAC)
TLS fingerprint capture (JA3/JA4/JA3S)	Yes
JA3 + HTTP/2 fingerprint spoofing	Proxy-side (impit re-issues matching requests with spoofed TLS 1.3, HTTP/2 frames, and header order)
Intercept non-browser traffic (curl, Python, Android apps)	Yes (interceptors)
Human-like mouse/keyboard/scroll input	humanizer_* tools: Bezier curves + Fitts's law for mouse, WPM + bigram + typo model for typing, eased wheel scroll — layered on top of cloakbrowser's built-in humanize mode
Locator-based interaction	humanizer_click accepts CSS/XPath selector, ARIA role + name, visible text, or form label — no pixel guessing

Standard flow:

1. Call proxy_start
2. Optionally enable outbound fingerprint spoofing for cross-origin sub-resources: proxy_set_fingerprint_spoof --preset chrome_136
3. Call interceptor_browser_launch --url "https://example.com"
4. Drive the page: interceptor_browser_navigate, interceptor_browser_snapshot, humanizer_click --selector "...", humanizer_type --text "..."
5. Inspect traffic: proxy_search_traffic --query "<hostname>"

Tools Reference

Lifecycle (4)

Tool	Description
proxy_start	Start MITM proxy, auto-generate CA cert
proxy_stop	Stop proxy (traffic/cert retained)
proxy_status	Running state, port, rule/traffic counts
proxy_get_ca_cert	CA certificate PEM + SPKI fingerprint

Transparent / Mobile Capture (6)

Tool	Description
proxy_start_transparent	Start second MITM listener (SNI-based, no CONNECT) on a parallel port; shares CA + rules + ring buffer with the explicit listener
proxy_stop_transparent	Stop the transparent listener
proxy_transparent_status	Running state + port + dedicated traffic count
proxy_mobile_setup	One-command mobile capture: start both listeners, inject CA into Android system store via adb (tmpfs overlay + zygote ns for Android 14+), emit a sudo-runnable iptables/sysctl/nmcli script
proxy_mobile_teardown	Reverse setup: deactivate Android target, stop transparent listener, emit teardown script
proxy_mobile_detect_iface	Probe /sys/class/net for a cdc_ncm USB interface (matches the proxy-ap-card firmware)

Upstream Proxy (4)

Tool	Description
proxy_set_upstream	Set global upstream proxy
proxy_clear_upstream	Remove global upstream
proxy_set_host_upstream	Per-host upstream override
proxy_remove_host_upstream	Remove per-host override

Interception Rules (7)

Tool	Description
proxy_add_rule	Add rule with matcher + handler
proxy_update_rule	Modify existing rule
proxy_remove_rule	Delete rule
proxy_list_rules	List all rules by priority
proxy_test_rule_match	Test which rules would match a simulated request or captured exchange, with detailed diagnostics
proxy_enable_rule	Enable a disabled rule
proxy_disable_rule	Disable without removing

Quick debugging examples:

# Simulate a request and see which rule would win
proxy_test_rule_match --mode simulate --request '{"method":"GET","url":"https://example.com/api/v1/items","headers":{"accept":"application/json"}}'

# Evaluate a real captured exchange by ID
proxy_test_rule_match --mode exchange --exchange_id "ex_abc123"

Traffic Capture (4)

Tool	Description
proxy_list_traffic	Paginated traffic list with filters
proxy_get_exchange	Full exchange details by ID
proxy_search_traffic	Full-text search across traffic
proxy_clear_traffic	Clear capture buffer

Modification Shortcuts (3)

Tool	Description
proxy_inject_headers	Add/overwrite/delete headers on matching traffic (set value to null to remove a header)
proxy_rewrite_url	Rewrite request URLs
proxy_mock_response	Return mock response for matched requests

TLS Fingerprinting (9)

Tool	Description
proxy_get_tls_fingerprints	Get JA3/JA4 client fingerprints + JA3S for a single exchange
proxy_list_tls_fingerprints	List unique JA3/JA4 fingerprints across all traffic with counts
proxy_set_ja3_spoof	Legacy: enable JA3 spoofing (deprecated, use proxy_set_fingerprint_spoof)
proxy_clear_ja3_spoof	Disable fingerprint spoofing
proxy_get_tls_config	Return current TLS config (server capture, JA3 spoof state)
proxy_enable_server_tls_capture	Toggle server-side JA3S capture (monkey-patches tls.connect)
proxy_set_fingerprint_spoof	Enable full TLS + HTTP/2 fingerprint spoofing via impit. Supports browser presets.
proxy_list_fingerprint_presets	List available browser fingerprint presets (e.g. chrome_131, chrome_136, chrome_136_linux, firefox_133)
proxy_check_fingerprint_runtime	Check fingerprint spoofing backend readiness

Fingerprint spoofing works by re-issuing the request from the proxy via impit (native Rust TLS/HTTP2 impersonation via rustls). TLS 1.3 and HTTP/2 fingerprints (SETTINGS, WINDOW_UPDATE, PRIORITY frames) match real browsers by construction. The origin server sees the proxy's spoofed TLS, HTTP/2, and header order — not the original client's. When a user_agent is set (including via presets), proxy-mcp also normalizes Chromium UA Client Hints headers (sec-ch-ua*) to match the spoofed User-Agent (forwarding contradictory hints is a common bot signal). Browser exception: when cloakbrowser is launched via interceptor_browser_launch, document loads and same-origin requests use the browser's native TLS (no impit), preserving fingerprint consistency for bot detection challenges. Only cross-origin sub-resource requests are re-issued with spoofed TLS. Non-browser clients (curl, spawn, HAR replay) get full TLS + UA spoofing on all requests. Use proxy_set_fingerprint_spoof with a browser preset for one-command setup. proxy_set_ja3_spoof is kept for backward compatibility but custom JA3 strings are ignored (the preset's impit browser target is used instead). JA4 fingerprints are captured (read-only) but spoofing is not supported.

Interceptors (17)

Interceptors configure targets (browsers, processes, devices, containers) to route their traffic through the proxy automatically.

Discovery (3)

Tool	Description
interceptor_list	List all interceptors with availability and active target counts
interceptor_status	Detailed status of a specific interceptor
interceptor_deactivate_all	Emergency cleanup: kill all active interceptors across all types

Browser (3)

Tool	Description
interceptor_browser_launch	Launch cloakbrowser (stealth Chromium) with proxy flags, SPKI cert trust, built-in humanize mode
interceptor_browser_navigate	Navigate the bound page via Playwright page.goto and verify proxy capture
interceptor_browser_close	Close a browser instance by target ID

Stealth is source-level: cloakbrowser ships 48+ C++ patches so ja3n/ja4/akamai match real Chrome, navigator.webdriver is false, audio/canvas/WebGL fingerprints match real hardware. No JS stealth injection needed. First launch downloads a ~200 MB Chromium binary (cached afterwards).

Terminal / Process (2)

Tool	Description
interceptor_spawn	Spawn a command with proxy env vars pre-configured (HTTP_PROXY, SSL certs, etc.)
interceptor_kill	Kill a spawned process and retrieve stdout/stderr

Sets 18+ env vars covering curl, Node.js, Python requests, Deno, Git, npm/yarn.

Android ADB (4)

Tool	Description
interceptor_android_devices	List connected Android devices via ADB
interceptor_android_activate	Full interception: inject CA cert, ADB reverse tunnel, optional Wi-Fi proxy
interceptor_android_deactivate	Remove ADB tunnel and clear Wi-Fi proxy
interceptor_android_setup	Quick setup: push CA cert + ADB reverse tunnel (no Wi-Fi proxy)

Caveats: CA cert injection requires root access. Supports Android 14+ (/apex/com.android.conscrypt/cacerts/). Wi-Fi proxy is opt-in (default off).

Android Frida (3)

Tool	Description
interceptor_frida_apps	List running apps on device via Frida
interceptor_frida_attach	Attach to app and inject SSL unpinning + proxy redirect scripts
interceptor_frida_detach	Detach Frida session from app

Caveats: Requires frida-server running on device. Uses frida-js (pure JS, no native binaries on host). SSL unpinning covers OkHttp, BoringSSL, TrustManager, system TLS — but may not work against QUIC or custom TLS stacks.

Docker (2)

Tool	Description
interceptor_docker_attach	Inject proxy env vars and CA cert into running container
interceptor_docker_detach	Remove proxy config from container

Two modes: exec (live injection, existing processes need restart) and restart (stop + restart container). Uses host.docker.internal for proxy URL.

Browser DevTools-equivalents (9)

Playwright-driven tools for the browser target. Each takes a target_id directly — no session binding, no sidecar.

Tool	Description
interceptor_browser_snapshot	ARIA/role YAML snapshot of the page (or selector subtree) — optimized for LLM page reasoning
interceptor_browser_screenshot	Screenshot. Writes to file_path if provided; otherwise reports byte count only
interceptor_browser_list_console	Buffered console messages since launch, with type/text filters and pagination
interceptor_browser_list_cookies	Cookie listing with filters, pagination, truncated value previews
interceptor_browser_get_cookie	Get one cookie by cookie_id (value is capped to keep output bounded)
interceptor_browser_list_storage_keys	localStorage/sessionStorage key listing with value previews
interceptor_browser_get_storage_value	Get one storage value by item_id
interceptor_browser_list_network_fields	Header field listing from proxy-captured traffic since the browser was launched
interceptor_browser_get_network_field	Get one full header field value by field_id

Network data is sourced from the MITM proxy rather than a browser-side protocol — the proxy sees every wire request regardless of what the browser reported.

Sessions (13)

Persistent, queryable on-disk capture for long runs and post-crash analysis.

Tool	Description
proxy_session_start	Start persistent session capture (preview or full-body mode)
proxy_session_stop	Stop and finalize the active persistent session
proxy_session_status	Runtime status for persistence (active session, bytes, disk cap errors)
proxy_import_har	Import a HAR file from disk into a new persisted session
proxy_list_sessions	List recorded sessions from disk
proxy_get_session	Get manifest/details for one session
proxy_query_session	Indexed query over recorded exchanges
proxy_get_session_handshakes	Report JA3/JA4/JA3S handshake metadata availability for session entries
proxy_get_session_exchange	Fetch one exchange from a session (with optional full bodies)
proxy_replay_session	Dry-run or execute replay of selected session requests
proxy_export_har	Export full session or filtered subset to HAR
proxy_delete_session	Delete a stored session
proxy_session_recover	Rebuild indexes from records after unclean shutdown

proxy_get_session_exchange and proxy_export_har automatically decompress response bodies (gzip, deflate, brotli) based on the stored content-encoding header. The returned responseBodyText and responseBodyBase64 contain the decompressed content. Raw compressed bytes are preserved on disk for exact replay fidelity.

Note on proxy_start with persistence_enabled: true: this auto-creates a session. A subsequent proxy_session_start() call returns the existing active session instead of failing — no need to stop and re-start.

Humanizer — Playwright Input (5)

Human-like browser input via Playwright page.mouse / page.keyboard, layered on top of cloakbrowser's built-in humanize mode. Binds to target_id from interceptor_browser_launch.

Tool	Description
humanizer_move	Move mouse along a Bezier curve with Fitts's law velocity scaling and eased timing
humanizer_click	Click a locator (selector / role + name / text / label) or raw x,y. Auto-waits for visible + enabled + stable + in-view before clicking
humanizer_type	Type text with per-character delays modeled on WPM, bigram frequency, shift penalty, word pauses, and optional typo injection
humanizer_scroll	Scroll with easeInOutQuad acceleration/deceleration via multiple wheel events
humanizer_idle	Simulate idle behavior with mouse micro-jitter and occasional micro-scrolls to defeat idle detection

All tools require target_id from a prior interceptor_browser_launch. The engine maintains tracked mouse position across calls, so humanizer_move followed by humanizer_click produces a continuous path.

Behavioral details:

• Mouse paths: Cubic Bezier curves with random control points, Fitts's law distance/size scaling, optional overshoot + correction arc
• Typing: Base delay from WPM, modified by bigram frequency (common pairs like "th" are faster), shift key penalty, word-boundary pauses. Optional typo injection uses QWERTY neighbor map with backspace correction
• Scrolling: Total delta distributed across multiple wheel events following easeInOutQuad velocity curve
• Idle: Periodic micro-jitter (±3px subtle / ±8px normal) and random micro-scrolls at configurable intensity

Resources

URI	Description
proxy://status	Proxy running state and config
proxy://ca-cert	CA certificate PEM
proxy://traffic/summary	Traffic stats: method/status breakdown, top hostnames, TLS fingerprint stats
proxy://interceptors	All interceptor metadata and activation status
proxy://sessions	Persistent session catalog + runtime persistence status
proxy://browser/primary	Current page URL/title for the most recently launched browser instance
proxy://browser/targets	Current page state for all active browser instances
proxy://sessions/{session_id}/summary	Aggregate stats for one recorded session (resource template)
proxy://sessions/{session_id}/timeline	Time-bucketed request/error timeline (resource template)
proxy://sessions/{session_id}/findings	Top errors/slow exchanges/host error rates (resource template)

Usage Example

# Start the proxy
proxy_start

# Optional: start persistent session recording
proxy_session_start --capture_profile full --session_name "reverse-run-1"

# Configure device to use proxy (Wi-Fi settings or interceptors)
# Install CA cert on device (proxy_get_ca_cert)

# Or use interceptors to auto-configure targets:
interceptor_browser_launch                    # Launch stealth browser with proxy
interceptor_spawn --command curl --args '["https://example.com"]'  # Spawn proxied process
interceptor_android_activate --serial DEVICE_SERIAL               # Android device

# Set upstream proxy for geolocation
proxy_set_upstream --proxy_url socks5://user:pass@geo-proxy:1080

# Mock an API response
proxy_mock_response --url_pattern "/api/v1/config" --status 200 --body '{"feature": true}'

# Inject auth headers (set value to null to delete a header)
proxy_inject_headers --hostname "api.example.com" --headers '{"Authorization": "Bearer token123"}'

# View captured traffic
proxy_list_traffic --hostname_filter "api.example.com"
proxy_search_traffic --query "error"

# TLS fingerprinting
proxy_list_tls_fingerprints                # See unique JA3/JA4 fingerprints
proxy_set_ja3_spoof --ja3 "771,4865-..."   # Spoof outgoing JA3 (for non-browser clients)
proxy_set_fingerprint_spoof --preset chrome_136 --host_patterns '["example.com"]'  # Full fingerprint spoof
proxy_list_fingerprint_presets                  # Available browser presets

# Human-like browser interaction (requires interceptor_browser_launch target)
humanizer_move   --target_id "browser_<id>" --x 500 --y 300
humanizer_click  --target_id "browser_<id>" --selector "#login-button"
humanizer_click  --target_id "browser_<id>" --role "button" --name "Sign in"
humanizer_type   --target_id "browser_<id>" --text "user@example.com" --wpm 45
humanizer_scroll --target_id "browser_<id>" --delta_y 300
humanizer_idle   --target_id "browser_<id>" --duration_ms 2000 --intensity subtle

# Query/export recorded session
proxy_list_sessions
proxy_query_session --session_id SESSION_ID --hostname_contains "api.example.com"
proxy_export_har --session_id SESSION_ID

Architecture

• State: ProxyManager singleton manages mockttp server, rules, traffic
• Rule rebuild: Rules must be set before mockttp start(), so rule changes trigger stop/recreate/restart cycle
• Traffic capture: on('request') + on('response') events, correlated by request ID
• Ring buffer: 1000 entries max, body previews capped at 4KB
• TLS capture: Client JA3/JA4 from mockttp socket metadata; server JA3S via tls.connect monkey-patch
• TLS spoofing: impit (native Rust TLS/HTTP2 impersonation via rustls); in-process, no container needed
• Interceptors: Managed by InterceptorManager, each type registers independently
• Browser: cloakbrowser (stealth Chromium, ~200 MB binary auto-downloaded on first launch) driven via Playwright BrowserContext / Page
• Humanizer: Singleton engine using Playwright's page.mouse / page.keyboard. Custom timing layer (Bezier paths, Fitts's law, bigram typing) feeds Playwright — sits on top of cloakbrowser's built-in humanize: true

Testing

npm test              # All tests (unit + integration)
npm run test:unit     # Unit tests only
npm run test:integration  # Integration tests
npm run test:e2e      # E2E fingerprint tests (requires cloakbrowser + internet)

Credits

Core Libraries

Project	Role
mockttp	MITM proxy engine, rule system, CA generation
impit	Native TLS/HTTP2 fingerprint impersonation (Rust via NAPI-RS)
frida-js	Pure-JS Frida client for Android instrumentation
cloakbrowser	Stealth-patched Chromium with source-level C++ fingerprint patches
playwright-core	Browser automation API driving cloakbrowser
@modelcontextprotocol/sdk	MCP server framework

Vendored Frida Scripts

All scripts in src/frida-scripts/vendor/ are derived from httptoolkit/frida-interception-and-unpinning (MIT):

• config-template.js — proxy/cert config injection
• android-certificate-unpinning.js — TrustManager + OkHttp + BoringSSL hooks
• android-system-certificate-injection.js — runtime cert injection via KeyStore
• android-proxy-override.js — ProxySelector monkey-patch
• native-tls-hook.js — BoringSSL/OpenSSL native hooks
• native-connect-hook.js — libc connect() redirect