#4472·sing-box

Trailing comma in json config causes ‘configure tun interface: invalid argument’

Author: AgentConDierCreated Aug 31, 2026Updated Sep 17, 2026

Operating system

Android

System version

Android 10 (Huawei EMUI 12)

Installation type

sing-box for Android Graphical Client

If you are using a graphical client, please provide the version of the client.

1.14.5-rc5

Version

bash

Description

I have a minimal tun configuration that works fine (see below).

If I add a trailing comma anywhere (in the example, inside the dns server definition), sing-box fails to start:

This is easily fixed using the Format button in the editor, but that is not apparent from the error message.

Also, this is a regression since previous SFA releases did support trailing commas, and should be fixed so upgrading doesn't break existing configs.

Reproduction

Working json config

json

{
  "dns": {
    "servers": [
      {
        "type": "local",
        "tag": "local-dns"
      }
    ],
    "final": "local-dns"
  },
  "inbounds": [
    {
      "type": "tun",
      "tag": "tun-in",
      "mtu": 1380,
      "address": [
        "172.29.254.189/30",
        "fd77:e057:ac0c:8dac:319b:b6e2:4a8b:7c00/126"
      ],
      "auto_route": true,
      "include_package": [
        "com.termux",
        "io.nekohasekai.sfa"
      ],
      "stack": "system"
    }
  ],
  "outbounds": [
    {
      "type": "direct",
      "tag": "direct-out"
    }
  ],
  "route": {
    "rules": [
      {
        "inbound": "tun-in",
        "ip_cidr": [
          "172.29.254.189/30",
          "fd77:e057:ac0c:8dac:319b:b6e2:4a8b:7c00/126"
        ],
        "port": 53,
        "action": "hijack-dns"
      },
      {
        "inbound": "tun-in",
        "ip_cidr": [
          "172.29.254.189/30",
          "fd77:e057:ac0c:8dac:319b:b6e2:4a8b:7c00/126"
        ],
        "action": "reject"
      }
    ],
    "final": "direct-out",
    "auto_detect_interface": true,
    "default_domain_resolver": "local-dns"
  }
}

Broken json config

json

{
  "dns": {
    "servers": [
      {
        "type": "local",
        "tag": "local-dns",
      }
    ],
    "final": "local-dns"
  },
  "inbounds": [
    {
      "type": "tun",
      "tag": "tun-in",
      "mtu": 1380,
      "address": [
        "172.29.254.189/30",
        "fd77:e057:ac0c:8dac:319b:b6e2:4a8b:7c00/126"
      ],
      "auto_route": true,
      "include_package": [
        "com.termux",
        "io.nekohasekai.sfa"
      ],
      "stack": "system"
    }
  ],
  "outbounds": [
    {
      "type": "direct",
      "tag": "direct-out"
    }
  ],
  "route": {
    "rules": [
      {
        "inbound": "tun-in",
        "ip_cidr": [
          "172.29.254.189/30",
          "fd77:e057:ac0c:8dac:319b:b6e2:4a8b:7c00/126"
        ],
        "port": 53,
        "action": "hijack-dns"
      },
      {
        "inbound": "tun-in",
        "ip_cidr": [
          "172.29.254.189/30",
          "fd77:e057:ac0c:8dac:319b:b6e2:4a8b:7c00/126"
        ],
        "action": "reject"
      }
    ],
    "final": "direct-out",
    "auto_detect_interface": true,
    "default_domain_resolver": "local-dns"
  }
}

Logs

bash

- stderr is empty -

Supporter

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Integrity requirements

I confirm that I have read the documentation, understand the meaning of all the configuration items I wrote, and did not pile up seemingly useful options or default values.
I confirm that I have provided the server and client configuration files and process that can be reproduced locally, instead of a complicated client configuration file that has been stripped of sensitive data.
I confirm that I have provided the simplest configuration that can be used to reproduce the error I reported, instead of depending on remote servers, TUN, graphical interface clients, or other closed-source software.
I confirm that I have provided the complete configuration files and logs, rather than just providing parts I think are useful out of confidence in my own intelligence.

Source: SagerNet/sing-box

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