Tunnel Doctor

Tunnel Doctor

Diagnose and fix conflicts when Tailscale coexists with proxy/VPN tools on macOS, with specific guidance for SSH access to WSL instances.

Five Conflict Layers

Proxy/VPN tools on macOS create conflicts at five independent layers. Layers 1-3 affect Tailscale connectivity; Layer 4 affects SSH git operations; Layer 5 affects VM/container runtimes:

Diagnostic Workflow

Step 1: Identify the Symptom

Determine which scenario applies:

• Browser returns HTTP 503, but curl and SSH both work → System proxy bypass conflict (Step 2C)
• local.<domain> fails in browser/default curl, but direct/no-proxy request works → Local vanity domain proxy interception (Step 2C-1)
• Tailscale ping works, SSH works, but curl/HTTP times out → HTTP proxy env var conflict (Step 2A)
• Tailscale ping works, SSH/TCP times out → Route conflict (Step 2B)
• Remote dev server auth redirects to localhost → browser can't follow → SSH tunnel needed (Step 2D)
• make status / scripts curl to localhost fail with proxy → localhost proxy interception (Step 2E)
• git push/pull fails with FATAL: failed to begin relaying via HTTP → SSH double tunnel (Step 2F)
• docker build RUN apk/apt fails with Connection refused instantly → OrbStack transparent proxy + TUN conflict (Step 2G-1, fix: --network host)
• docker pull fails with TLS handshake timeout → VM proxy misconfiguration (Step 2G-2, fix: docker.json with host.internal)
• Container healthcheck (unhealthy) but app runs fine → Lowercase proxy env var leak (Step 2G-4, fix: clear http_proxy+HTTP_PROXY)
• docker build can't fetch base images → VM/container proxy propagation (Step 2G)
• git clone fails with Connection closed by 198.18.x.x → TUN DNS hijack for SSH (Step 2H)
• SSH connects but operation not permitted → Tailscale SSH config issue (Step 4)
• SSH connects but be-child ssh exits code 1 → WSL snap sandbox issue (Step 5)
• TCP port 22 reachable (nc -z succeeds) but SSH fails with kex_exchange_identification: Connection closed → Tailscale SSH proxy intercept on WSL (Step 5A)
• tailscale ssh returns "not available on App Store builds" → Wrong Tailscale distribution on macOS (Step 5B)

Key distinctions:

• SSH does NOT use http_proxy/NO_PROXY env vars. If SSH works but HTTP doesn't → Layer 2.
• curl uses http_proxy env var, NOT the system proxy. Browser uses system proxy (set by VPN). If curl works but browser doesn't → Layer 3.
• If tailscale ping works but regular ping doesn't → Layer 1 (route table corrupted).
• If ssh -T git@github.com works but git push fails intermittently → Layer 4 (double tunnel).
• If host curl https://... works but docker pull times out → Layer 5 (VM proxy propagation).
• If docker pull works but docker build RUN apk add fails instantly with Connection refused → OrbStack transparent proxy broken by TUN (Step 2G-1).
• If container healthcheck shows (unhealthy) but app works → lowercase http_proxy leaked into container (Step 2G-4).
• If DNS resolves to 198.18.x.x virtual IPs → TUN DNS hijack (Step 2H).
• If nc -z succeeds on port 22 but SSH gets no banner (kex_exchange_identification) → Tailscale SSH proxy intercept (Step 5A). Confirm with tcpdump -i any port 22 on the remote — 0 packets means Tailscale intercepts above the kernel.
• If tailscale ssh fails with "not available on App Store builds" → install Standalone Tailscale (Step 5B).

Fast Path: Run Automated Checks

For common macOS conflicts (env proxy, system proxy exceptions, direct/proxy path split, local TLS trust), run:

python3 scripts/quick_diagnose.py --host local.claude4.dev --url https://local.claude4.dev/health

Optional route ownership check for a Tailscale destination:

python3 scripts/quick_diagnose.py --host <target-host> --url http://<target-host>:<port>/health --tailscale-ip <100.x.x.x>

Interpretation:

• direct=PASS + forced_proxy=FAIL = host must bypass proxy (skip-proxy + NO_PROXY).
• strict_tls=FAIL + direct=PASS = path is reachable; trust issue only (install/trust local CA).
• host in scutil exceptions: no = browser/system clients still likely proxied.

Step 2A: Fix HTTP Proxy Environment Variables

Check if proxy env vars are intercepting Tailscale HTTP traffic:

env | grep -i proxy

Broken output — proxy is set but NO_PROXY doesn't exclude Tailscale:

http_proxy=http://127.0.0.1:1082
https_proxy=http://127.0.0.1:1082
NO_PROXY=localhost,127.0.0.1          ← Missing Tailscale!

Fix — add Tailscale MagicDNS domain + CIDR to NO_PROXY:

export NO_PROXY=localhost,127.0.0.1,.ts.net,100.64.0.0/10,192.168.*,10.*,172.16.*

Two layers complement each other: .ts.net handles domain-based access, 100.64.0.0/10 handles direct IP access.

NO_PROXY syntax pitfalls — see references/proxy_conflict_reference.md for the compatibility matrix.

Go net/http CIDR caveat: Go's standard net/http does NOT support CIDR notation in NO_PROXY. Setting NO_PROXY=100.64.0.0/10 works for curl and Python, but Go programs (including Tailscale-adjacent tooling) will still send traffic through the proxy. The fix is to use MagicDNS hostnames (e.g., workstation-4090-wsl) instead of raw IPs, or add explicit hostnames to NO_PROXY:

# WRONG for Go programs — CIDR is silently ignored
NO_PROXY=100.64.0.0/10 go-program http://100.101.102.103:8002/health  # → goes through proxy

# CORRECT — use hostname (matched as suffix) or explicit IP
export NO_PROXY=localhost,127.0.0.1,.ts.net,workstation-4090-wsl,100.101.102.103,192.168.*,10.*,172.16.*

This is especially relevant when accessing Tailscale services from Go-based tools (e.g., custom CLIs, Go test suites hitting remote APIs).

Verify the fix:

# Both must return HTTP 200:
NO_PROXY="...(new value)..." curl -s --connect-timeout 5 http://<host>.ts.net:<port>/health -w "HTTP %{http_code}\n"
NO_PROXY="...(new value)..." curl -s --connect-timeout 5 http://<tailscale-ip>:<port>/health -w "HTTP %{http_code}\n"

Then persist in shell config (~/.zshrc or ~/.bashrc).

Step 2B: Detect Route Conflicts

Check if a proxy tool hijacked the Tailscale CGNAT range:

route -n get <tailscale-ip>

Healthy output — traffic goes through Tailscale interface:

destination: 100.64.0.0
interface: utun7    # Tailscale interface (utunN varies)

Broken output — proxy hijacked the route:

destination: 100.64.0.0
gateway: 192.168.x.1    # Default gateway
interface: en0           # Physical interface, NOT Tailscale

Important: Not all utun interfaces are Tailscale's. Verify which utun belongs to Tailscale before concluding the route is correct:

# Find Tailscale's utun interface (has a 100.x.x.x IP)
ifconfig | grep -A2 'inet 100\.'

Quick indicators by MTU:

• MTU 1280 → typically Tailscale
• MTU 4064 → typically Shadowrocket TUN

If route -n get shows traffic going to a utun with MTU 4064, it is hitting Shadowrocket's TUN, not Tailscale — this is still a route conflict even though the interface name starts with utun.

Confirm with full route table:

netstat -rn | grep 100.64

Two competing routes indicate a conflict:

100.64/10  192.168.x.1   UGSc  en0       ← Proxy added this (wins)
100.64/10  link#N        UCSI  utun7     ← Tailscale route (loses)

Root cause: On macOS, UGSc (Static Gateway) takes priority over UCSI (Cloned Static Interface) for the same prefix length.

Step 2C: Fix System Proxy Bypass (Browser 503)

Symptom: Browser shows HTTP 503 for http://<tailscale-ip>:<port>, but both curl --noproxy '*' and curl (with proxy env var) return 200. SSH also works.

Root cause: The browser uses the system proxy configured by the VPN profile (Shadowrocket/Clash/Surge). The proxy matches IP-CIDR,100.64.0.0/10,DIRECT and tries to connect directly — but "directly" means via the Wi-Fi interface (en0), NOT through Tailscale's utun interface. The proxy process itself doesn't have a route to Tailscale IPs, so the connection fails with 503.

Diagnosis:

# curl with proxy env var works (curl connects to proxy port, but traffic flows differently)
curl -s -o /dev/null -w "%{http_code}" http://<tailscale-ip>:<port>/
# → 200

# Browser gets 503 because it goes through the VPN system proxy, not http_proxy env var

Fix — add Tailscale CGNAT range to skip-proxy in the proxy tool config:

For Shadowrocket, in [General]:

skip-proxy = 192.168.0.0/16, 10.0.0.0/8, 172.16.0.0/12, 100.64.0.0/10, localhost, *.local, captive.apple.com

skip-proxy tells the system "bypass the proxy entirely for these addresses." The browser then connects directly through the OS network stack, where Tailscale's routing table correctly handles the traffic.

Why skip-proxy works but tun-excluded-routes doesn't:

• skip-proxy: Bypasses the HTTP proxy layer only. Traffic still flows through the TUN interface and Tailscale utun handles it. Safe.
• tun-excluded-routes: Removes the CIDR from the TUN routing entirely. This creates a competing en0 route that overrides Tailscale. Breaks everything.

Step 2C-1: Fix Local Vanity Domain Interception (local.<domain>)

Symptom: https://local.<domain> fails in browser or default curl, but succeeds with direct/no-proxy command:

env -u http_proxy -u https_proxy curl -k -I https://local.<domain>/health
# -> 200
curl -I https://local.<domain>/health
# -> proxy CONNECT then TLS reset/failure

Root cause: The domain is routed through system/shell proxy instead of local direct path.

Fix:

1. Add domain to proxy app bypass list (skip-proxy for Shadowrocket).
2. Add domain to shell bypass list (NO_PROXY/no_proxy).
3. If local TLS uses internal CA, trust the local root certificate.

# ~/.zshrc
export NO_PROXY=localhost,127.0.0.1,.ts.net,100.64.0.0/10,192.168.*,10.*,172.16.*,local.<domain>,www.local.<domain>
export no_proxy="$NO_PROXY"

Verification:

python3 scripts/quick_diagnose.py --host local.<domain> --url https://local.<domain>/health

Expected:

• host in NO_PROXY: yes
• host in scutil exceptions: yes
• ambient=PASS and direct=PASS

Step 2D: Fix Auth Redirect for Remote Dev (SSH Tunnel)

Symptom: Dev server runs on a remote machine (e.g., Mac Mini via Tailscale). You access http://<tailscale-ip>:3010 in the browser. Login/signup works, but after auth, the app redirects to http://localhost:3010/ which fails — localhost on your machine isn't running the dev server.

Root cause: The app's APP_URL (or equivalent) is set to http://localhost:3010. Auth libraries (Better-Auth, NextAuth, etc.) use this URL for callback redirects. Changing APP_URL to the Tailscale IP introduces Shadowrocket proxy conflicts and breaks local development on the remote machine.

Fix — SSH local port forwarding. This avoids all three conflict layers entirely:

# Forward local port 3010 to remote machine's localhost:3010
ssh -NL 3010:localhost:3010 <tailscale-ip>

# Or with autossh for auto-reconnect (recommended for long sessions)
autossh -M 0 -f -N -L 3010:localhost:3010 \
    -o "ServerAliveInterval=30" \
    -o "ServerAliveCountMax=3" \
    -o "ExitOnForwardFailure=yes" \
    <tailscale-ip>

Now access http://localhost:3010 in the browser. Auth redirects to localhost:3010 → tunnel → remote dev server → works correctly.

Why this is the best approach:

• No .env changes needed — APP_URL=http://localhost:3010 works everywhere
• No Shadowrocket conflicts — localhost is always in skip-proxy
• No code changes — same behavior as local development
• Industry standard — VS Code Remote SSH, GitHub Codespaces use the same pattern

Install autossh: brew install autossh (macOS) or apt install autossh (Linux)

Kill background tunnel: pkill -f 'autossh.*<tailscale-ip>'

Step 2E: Fix localhost Proxy Interception in Scripts

Symptom: Makefile targets or scripts that curl localhost (health checks, warmup routes) fail or timeout when http_proxy is set globally in the shell.

Root cause: http_proxy=http://127.0.0.1:1082 is set in ~/.zshrc but no_proxy doesn't include localhost. All curl commands send localhost requests through the proxy.

Fix — add --noproxy localhost to all localhost curl commands in scripts:

# WRONG — fails when http_proxy is set
@curl -sf http://localhost:9000/minio/health/live && echo "OK"

# CORRECT — always bypasses proxy for localhost
@curl --noproxy localhost -sf http://localhost:9000/minio/health/live && echo "OK"

Alternatively, set no_proxy globally in ~/.zshrc:

export no_proxy=localhost,127.0.0.1

Step 2F: Fix SSH ProxyCommand Double Tunnel (git push/pull failures)

Symptom: ssh -T git@github.com succeeds consistently, but git push or git pull fails intermittently with:

FATAL: failed to begin relaying via HTTP.
Connection closed by UNKNOWN port 65535

Small operations (auth, fetch metadata) work; large data transfers fail.

Root cause: When Shadowrocket TUN is active, it already routes all TCP traffic through its VPN tunnel. If SSH config also uses ProxyCommand connect -H, data flows through two proxy layers — the landing proxy drops large/long-lived HTTP CONNECT connections.

Diagnosis:

# 1. Confirm Shadowrocket TUN is active
ifconfig | grep '^utun'

# 2. Check SSH config for ProxyCommand
grep -A5 'Host github.com' ~/.ssh/config

# 3. Confirm: removing ProxyCommand fixes push
GIT_SSH_COMMAND="ssh -o ProxyCommand=none" git push origin main

Fix — remove ProxyCommand and switch to ssh.github.com:443. See references/proxy_conflict_reference.md § SSH ProxyCommand and Git Operations for the full SSH config, why port 443 helps, and fallback options when VPN is off.

Step 2G: Fix VM/Container Runtime Proxy Propagation (Docker pull/build failures)

Symptom: docker pull or docker build fails with net/http: TLS handshake timeout, Connection refused from Alpine/Debian repos, or Internal Server Error from auth.docker.io, while host curl to the same URLs works fine.

Applies to: OrbStack, Docker Desktop, or any VM-based Docker runtime on macOS with Shadowrocket/Clash TUN active.

Root cause: VM-based Docker runtimes (OrbStack, Docker Desktop) run the Docker daemon inside a lightweight VM. The VM's outbound traffic takes a different network path than host processes:

Host process (curl):   Process → TUN (Shadowrocket) → landing proxy → internet ✅
VM process (Docker):   Docker daemon → VM bridge → host network → TUN → ??? ❌

The TUN handles host-originated traffic correctly but may drop or delay VM-bridged traffic (different TCP stack, MTU, keepalive behavior).

Critical distinction: docker pull vs docker build use different proxy paths:

Fixing docker.json alone will NOT fix docker build — the RUN commands inside the build container don't inherit daemon proxy settings.

Diagnosis — identify which sub-problem:

# 1. Can the Docker daemon pull images?
docker pull --quiet alpine:latest 2>&1

# 2. Can a RUN command inside a build reach the internet?
docker build --no-cache - <<'EOF' 2>&1
FROM alpine:latest
RUN apk update && echo "APK OK"
EOF

# 3. Can a running container reach the internet?
docker run --rm alpine:latest sh -c "apk update 2>&1 | head -3"

Four sub-problems and their fixes:

2G-1: docker build fails but host works (most common with OrbStack + Shadowrocket)

Symptom: RUN apk add or RUN apt-get install inside docker build fails with Connection refused instantly (< 0.2s), even though host curl to the same URL works.

Root cause: OrbStack's network_proxy: auto creates a transparent proxy inside the VM that intercepts all HTTPS traffic. When Shadowrocket TUN is also active, the transparent proxy's upstream connection breaks — it redirects HTTPS to 127.0.0.1 inside the VM, which has nothing listening.

Diagnosis:

# Verify: inside the container, HTTPS goes to 127.0.0.1 (broken transparent proxy)
docker run --rm alpine:latest sh -c "wget -q --timeout=5 -O /dev/null https://dl-cdn.alpinelinux.org/ 2>&1"
# → "wget: can't connect to remote host (127.0.0.1): Connection refused"
#                                        ^^^^^^^^^^^^ This is the smoking gun

# Verify: --network host bypasses the VM bridge and works
docker run --rm --network host alpine:latest sh -c "apk update 2>&1 | head -3"
# → "v3.23.x ... OK: 27431 distinct packages available"  ← Works!

Fix — use --network host for docker build:

docker build --network host -f Dockerfile -t myimage .

This bypasses OrbStack's VM network bridge entirely. The build container uses the host's network stack directly, where Shadowrocket TUN correctly handles traffic.

Trade-off: --network host disables build-time network isolation. For CI/CD, prefer fixing the proxy config (2G-2). For local development, --network host is the pragmatic fix.

Permanent fix — if all your builds need this, add to ~/.docker/daemon.json or use a shell alias:

# Shell alias (add to ~/.zshrc)
alias docker-build='docker build --network host'

2G-2: OrbStack auto-detects and caches proxy config

OrbStack's network_proxy: auto reads http_proxy from the shell environment and configures the Docker daemon. The config is stored in ~/.orbstack/config/docker.json.

Key behaviors:

• network_proxy: auto — OrbStack reads host env, creates transparent proxy in VM
• network_proxy: none — Disables transparent proxy, but VM bridge traffic still routes through TUN (may timeout)
• docker.json — Controls docker pull proxy, NOT docker build RUN commands

Diagnosis:

# Check all three layers
echo "=== OrbStack config ==="
orbctl config get network_proxy

echo "=== docker.json (daemon proxy) ==="
cat ~/.orbstack/config/docker.json

echo "=== Docker info (effective proxy) ==="
docker info | grep -iE "proxy|No Proxy"

Fix — configure docker.json with host.internal (OrbStack resolves this to the host IP):

python3 -c "
import json, os
config = {
    'proxies': {
        'http-proxy': 'http://host.internal:1082',
        'https-proxy': 'http://host.internal:1082',
        'no-proxy': 'localhost,127.0.0.1,::1,192.168.128.0/24,100.64.0.0/10,host.internal,*.local'
    }
}
path = os.path.expanduser('~/.orbstack/config/docker.json')
json.dump(config, open(path, 'w'), indent=2)
print('Written:', path)
"

# Full restart required
orbctl stop && sleep 3 && orbctl start

Important: Use host.internal (OrbStack-specific), NOT 127.0.0.1 (points to VM loopback) and NOT host.docker.internal (may not resolve in all contexts).

Why NOT remove the proxy: When TUN is active, removing the Docker proxy means VM traffic goes directly through the bridge → TUN path, which causes TLS handshake timeouts. The proxy provides a working outbound channel.

2G-3: Removing proxy makes Docker worse (counter-intuitive)

Decision tree:

• docker pull broken → Fix docker.json with host.internal proxy (2G-2)
• docker build broken → Use --network host (2G-1) OR pass --build-arg http_proxy=http://host.internal:1082
• Both broken → Fix both: docker.json + --network host

2G-4: Deploy scripts and container healthchecks probe localhost through proxy

Deploy scripts that curl localhost inside containers or Docker healthchecks that use wget http://localhost will route through the proxy if env vars leak into the container.

Common symptoms:

• Container healthcheck shows (unhealthy) but the app inside is running fine
• wget: can't connect to remote host (127.0.0.1): Connection refused in healthcheck logs (proxy port, not app port)

Root cause: Docker inherits uppercase AND lowercase proxy env vars from the host. Many tools only clear uppercase (HTTP_PROXY=) but forget lowercase (http_proxy=http://127.0.0.1:1082). The healthcheck wget uses lowercase.

Fix in docker-compose.yml — clear BOTH cases:

environment:
  # Must clear both uppercase and lowercase — wget/curl check different vars
  - HTTP_PROXY=
  - HTTPS_PROXY=
  - http_proxy=
  - https_proxy=
  - NO_PROXY=*
  - no_proxy=*

Fix in deploy scripts:

_local_bypass="localhost,127.0.0.1,::1"
export NO_PROXY="${_local_bypass}${NO_PROXY:+,${NO_PROXY}}"
export no_proxy="$NO_PROXY"

# Use 127.0.0.1 instead of localhost in probe URLs (some proxy implementations
# only match exact string "localhost" in no-proxy, not the resolved IP)
curl http://127.0.0.1:3001/health   # ✅ bypasses proxy
curl http://localhost:3001/health    # ❌ may still go through proxy

Verify the fix:

# Docker proxy check (should show proxy + no-proxy)
docker info | grep -iE "proxy|No Proxy"

# Pull test
docker pull --quiet hello-world

# Build test (the real verification)
docker build --network host --no-cache - <<'EOF'
FROM alpine:latest
RUN apk update && echo "BUILD OK"
EOF

# Container env check (no proxy leak)
docker exec <container> env | grep -i proxy
# Expected: all empty or not set

Step 2H: Fix TUN DNS Hijack for SSH/Git (198.18.x.x virtual IPs)

Symptom: git clone/fetch/push fails with Connection closed by 198.18.0.x port 443. ssh -T git@github.com may also fail. DNS resolution returns 198.18.x.x addresses instead of real IPs.

Root cause: Shadowrocket TUN intercepts all DNS queries and returns virtual IPs in the 198.18.0.0/15 range. It then routes traffic to these virtual IPs through the TUN for protocol-aware proxying. HTTP/HTTPS works because the landing proxy understands these protocols, but SSH-over-443 (used by GitHub) gets mishandled — the TUN sees port 443 traffic, expects HTTPS, and drops the SSH handshake.

Diagnosis:

# DNS returns virtual IP (TUN hijack)
nslookup ssh.github.com
# → 198.18.0.26  ← Shadowrocket virtual IP, NOT real GitHub IP

# Direct IP works (bypasses DNS hijack)
ssh -o HostName=140.82.112.35 -o Port=443 git@github.com
# → "Hi user! You've successfully authenticated"

Fix — use direct IP in SSH config to bypass DNS hijack:

# ~/.ssh/config
Host github.com
    HostName 140.82.112.35    # GitHub SSH server real IP (bypasses TUN DNS hijack)
    Port 443
    User git
    ServerAliveInterval 60
    ServerAliveCountMax 3
    IdentityFile ~/.ssh/id_ed25519

GitHub SSH server IPs (as of 2026, verify with dig +short ssh.github.com @8.8.8.8):

• 140.82.112.35 (primary)
• 140.82.112.36 (alternate)

Trade-off: Hardcoded IPs break if GitHub changes them. Monitor ssh -T git@github.com — if it starts failing, update the IP. A cron job can automate this:

# Weekly check (add to crontab)
0 9 * * 1 dig +short ssh.github.com @8.8.8.8 | head -1 > /tmp/github-ssh-ip.txt

Alternative (if you control Shadowrocket rules): Add GitHub SSH IPs to DIRECT rule so TUN passes them through without protocol inspection:

IP-CIDR,140.82.112.0/24,DIRECT
IP-CIDR,192.30.252.0/22,DIRECT

This is more robust but requires proxy tool config access.

Step 3: Fix Proxy Tool Configuration

Identify the proxy tool and apply the appropriate fix. See references/proxy_conflict_reference.md for detailed instructions per tool.

Key principle: Do NOT use tun-excluded-routes to exclude 100.64.0.0/10. This causes the proxy to add a → en0 route that overrides Tailscale. Instead, let the traffic enter the proxy TUN and use a DIRECT rule to pass it through.

Universal fix — add this rule to any proxy tool:

IP-CIDR,100.64.0.0/10,DIRECT
IP-CIDR,fd7a:115c:a1e0::/48,DIRECT

After applying fixes, verify:

route -n get <tailscale-ip>
# Should show Tailscale utun interface, NOT en0

Step 4: Configure Tailscale SSH ACL

If SSH connects but returns operation not permitted, the Tailscale ACL may require browser authentication for each connection.

At Tailscale ACL admin, ensure the SSH section uses "action": "accept":

"ssh": [
    {
        "action": "accept",
        "src": ["autogroup:member"],
        "dst": ["autogroup:self"],
        "users": ["autogroup:nonroot", "root"]
    }
]

Note: "action": "check" requires browser authentication each time. Change to "accept" for non-interactive SSH access.

Step 5: Fix WSL Tailscale Installation

If SSH connects and ACL passes but fails with be-child ssh exit code 1 in tailscaled logs, the snap-installed Tailscale has sandbox restrictions preventing SSH shell execution.

Diagnosis — check WSL tailscaled logs:

# For snap installs:
sudo journalctl -u snap.tailscale.tailscaled -n 30 --no-pager

# For apt installs:
sudo journalctl -u tailscaled -n 30 --no-pager

Look for:

access granted to user@example.com as ssh-user "username"
starting non-pty command: [/snap/tailscale/.../tailscaled be-child ssh ...]
Wait: code=1

Fix — replace snap with apt installation:

# Remove snap version
sudo snap remove tailscale

# Install apt version
curl -fsSL https://tailscale.com/install.sh | sh

# Start with SSH enabled
sudo tailscale up --ssh

Important: The new installation may assign a different Tailscale IP. Check with tailscale status --self.

Step 5A: Fix Tailscale SSH Proxy Silent Failure on WSL

Symptom: TCP port 22 is reachable (nc -z -w 5 <ip> 22 succeeds), but SSH fails immediately with:

kex_exchange_identification: Connection closed by remote host

No SSH banner is ever received. This happens even with apt-installed Tailscale (not snap).

Root cause: When tailscale up --ssh is enabled on WSL, Tailscale intercepts port 22 connections at the application layer (above the kernel network stack). If Tailscale's built-in SSH proxy malfunctions, it accepts the TCP connection but immediately closes it before sending the SSH banner.

Key diagnostic — on the WSL instance:

# This will show 0 packets even during active SSH attempts
sudo tcpdump -i any port 22 -c 5 -w /dev/null 2>&1

Zero packets means Tailscale is intercepting connections before they reach the kernel network stack. The kernel's sshd never sees the connection.

Distinction from Step 5: Step 5 covers snap sandbox issues where be-child ssh fails. This is a different problem — Tailscale's SSH proxy itself silently fails, regardless of installation method.

Fix — disable Tailscale's SSH proxy and use regular sshd:

# On the WSL instance:
sudo tailscale up --ssh=false

# Verify sshd is running
sudo service ssh status
# If not running:
sudo service ssh start

# Verify from the client machine:
ssh -o ConnectTimeout=10 <user>@<tailscale-ip> 'echo SSH_OK'

After disabling Tailscale SSH, connections go through the kernel network stack to sshd as normal. The Tailscale ACL "action": "accept" in Step 4 is no longer relevant — authentication is handled by sshd using SSH keys or passwords.

When to keep --ssh enabled: Only if you specifically need Tailscale's SSH features (ACL-based access control, no SSH key management). If standard sshd works, prefer --ssh=false for reliability.

Step 5B: Fix App Store Tailscale on macOS (Missing tailscale ssh)

Symptom: Running tailscale ssh returns:

The 'tailscale ssh' subcommand is not available on macOS builds
distributed through the App Store or TestFlight.

Root cause: The App Store version of Tailscale for macOS is sandboxed and does not include the tailscale ssh subcommand.

Fix — install the Standalone version:

1. Uninstall the App Store version (delete from /Applications)
2. Download the Standalone build from https://pkgs.tailscale.com/stable/#macos
3. Install to /Applications

Post-install CLI setup: The standalone tailscale CLI binary is embedded inside the app bundle. Add an alias to your shell config:

# ~/.zshrc
alias tailscale="/Applications/Tailscale.app/Contents/MacOS/Tailscale"

Verify:

source ~/.zshrc
tailscale version
tailscale ssh <user>@<hostname>   # Should work now

Step 6: Verify End-to-End

Run a complete connectivity test:

# 1. Check route is correct (must show Tailscale's utun, not en0 or Shadowrocket's utun)
route -n get <tailscale-ip>
# Also confirm which utun is Tailscale's:
ifconfig | grep -A2 'inet 100\.'

# 2. Test TCP connectivity
nc -z -w 5 <tailscale-ip> 22

# 3. Test SSH
ssh -o ConnectTimeout=10 -o StrictHostKeyChecking=no <user>@<tailscale-ip> 'echo SSH_OK && hostname && whoami'

All three must pass. If step 1 fails, revisit Step 3. If step 1 shows wrong utun (e.g., Shadowrocket's utun with MTU 4064 instead of Tailscale's with MTU 1280), that is also a route conflict. If step 2 passes but step 3 fails with kex_exchange_identification, revisit Step 5A (Tailscale SSH proxy intercept). If step 2 fails, check WSL sshd or firewall. If step 3 fails with other errors, revisit Steps 4-5.

SOP: Remote Development via Tailscale

Proactive setup guide for remote development over Tailscale with proxy tools. Follow these steps before encountering problems.

Prerequisites

• Tailscale installed and running on both machines
• Proxy tool (Shadowrocket/Clash/Surge) configured with Tailscale compatibility (see Step 3 above)
• SSH access working: ssh <tailscale-ip> 'echo ok'

1. Proxy-Safe Makefile Pattern

Any Makefile target that curls localhost must use --noproxy localhost. This is required because http_proxy is often set globally in ~/.zshrc (common in China), and Make inherits shell environment variables.

## ── Health Checks ─────────────────────────────────────

status:                ## Health check dashboard
	@echo "=== Dev Infrastructure ==="
	@docker exec my-postgres pg_isready -U postgres 2>/dev/null && echo "PostgreSQL: OK" || echo "PostgreSQL: FAIL"
	@curl --noproxy localhost -sf http://localhost:9000/minio/health/live >/dev/null 2>&1 && echo "MinIO: OK" || echo "MinIO: FAIL"
	@curl --noproxy localhost -sf http://localhost:3001/api/status >/dev/null 2>&1 && echo "API: OK" || echo "API: FAIL"

## ── Route Warmup ──────────────────────────────────────

warmup:                ## Pre-compile key routes (run after dev server is ready)
	@echo "Warming up dev server routes..."
	@echo -n "  /api/health → " && curl --noproxy localhost -s -o /dev/null -w '%{http_code} (%{time_total}s)\n' http://localhost:3010/api/health
	@echo -n "  /            → " && curl --noproxy localhost -s -o /dev/null -w '%{http_code} (%{time_total}s)\n' http://localhost:3010/
	@echo "Warmup complete."

Rules:

• Every curl http://localhost call MUST include --noproxy localhost
• Docker commands (docker exec) are unaffected by http_proxy — no fix needed
• redis-cli, pg_isready connect via TCP directly — no fix needed

2. SSH Tunnel Makefile Targets

Add these targets for remote development via Tailscale SSH tunnels:

## ── Remote Development ────────────────────────────────

REMOTE_HOST    ?= <tailscale-ip>
TUNNEL_FORWARD ?= -L 3010:localhost:3010

tunnel:                ## SSH tunnel to remote machine (foreground)
	ssh -N $(TUNNEL_FORWARD) $(REMOTE_HOST)

tunnel-bg:             ## SSH tunnel to remote machine (background, auto-reconnect)
	autossh -M 0 -f -N $(TUNNEL_FORWARD) \
		-o "ServerAliveInterval=30" \
		-o "ServerAliveCountMax=3" \
		-o "ExitOnForwardFailure=yes" \
		$(REMOTE_HOST)
	@echo "Tunnel running in background. Kill with: pkill -f 'autossh.*$(REMOTE_HOST)'"

Design decisions:

Install autossh: brew install autossh (macOS) or apt install autossh (Linux/WSL)

3. Multi-Port Tunnels

When the project requires multiple services (dev server + object storage + API gateway):

# Forward multiple ports in one tunnel
make tunnel TUNNEL_FORWARD="-L 3010:localhost:3010 -L 9000:localhost:9000 -L 3001:localhost:3001"

# Or define a project-specific default in Makefile
TUNNEL_FORWARD ?= -L 3010:localhost:3010 -L 9000:localhost:9000

Each -L flag is independent. If one port is already bound locally, ExitOnForwardFailure=yes will abort the entire tunnel — fix the port conflict first.

4. SSH Non-Login Shell Setup

This is a frequent source of "it works interactively but fails in scripts" bugs. SSH non-login shells don't load ~/.zshrc (or ~/.bashrc on Linux), so tools installed via nvm, Homebrew, uv, cargo, or any shell-level manager won't be in $PATH. Proxy env vars set in ~/.zshrc also won't be loaded.

This affects all remote commands run via ssh user@host "command", including CI/CD pipelines, cron-triggered SSH, and Makefile remote targets. Prefix all remote commands with source ~/.zshrc 2>/dev/null; (macOS) or source ~/.bashrc 2>/dev/null; (Linux/WSL).

Common failure: ssh user@host "uv run ..." or ssh user@host "node ..." returns command not found even though the command works in an interactive SSH session.

See references/proxy_conflict_reference.md § SSH Non-Login Shell Pitfall for details and examples.

For Makefile targets that run remote commands:

REMOTE_CMD = ssh $(REMOTE_HOST) 'source ~/.zshrc 2>/dev/null; $(1)'

remote-status:         ## Check remote dev server status
	$(call REMOTE_CMD,curl --noproxy localhost -sf http://localhost:3010/api/health && echo "OK" || echo "FAIL")

5. End-to-End Workflow

First-time setup (remote machine)

# 1. Clone repo and install dependencies
ssh <tailscale-ip>
cd /path/to/project
git clone git@github.com:user/repo.git && cd repo
pnpm install  # Add --registry https://registry.npmmirror.com if in China

# 2. Copy .env from local machine (run on local)
scp .env <tailscale-ip>:/path/to/project/repo/.env

# 3. Start Docker infrastructure
make up && make status

# 4. Run database migrations
bun run db:migrate

# 5. Start dev server
bun run dev

Daily workflow (local machine)

# 1. Start tunnel
make tunnel-bg

# 2. Open browser
open http://localhost:3010

# 3. Auth, coding, testing — everything works as if local

# 4. When done, kill tunnel
pkill -f 'autossh.*<tailscale-ip>'

Why this works

Browser → localhost:3010 → SSH tunnel → Remote localhost:3010 → Dev server
                                     ↓
                              Auth redirects to localhost:3010
                                     ↓
                              Browser follows redirect → same tunnel → works

The key insight: APP_URL=http://localhost:3010 in .env is correct for both local and remote development. The SSH tunnel makes the remote server's localhost accessible as the local machine's localhost. Auth callback redirects to localhost:3010 always resolve correctly.

6. Checklist

Before starting remote development, verify:

• Tailscale connected: tailscale status
• SSH works: ssh <tailscale-ip> 'echo ok'
• Proxy tool configured: [Rule] has IP-CIDR,100.64.0.0/10,DIRECT
• skip-proxy includes 100.64.0.0/10
• tun-excluded-routes does NOT include 100.64.0.0/10
• NO_PROXY includes .ts.net,100.64.0.0/10
• autossh installed: which autossh
• Makefile curl commands have --noproxy localhost
• Remote dev server running: ssh <ip> 'source ~/.zshrc 2>/dev/null; curl --noproxy localhost -sf http://localhost:3010/'
• Tunnel works: make tunnel-bg && curl -sf http://localhost:3010/

References

• references/proxy_conflict_reference.md — Per-tool configuration (Shadowrocket, Clash, Surge), NO_PROXY syntax, SSH ProxyCommand, and conflict architecture