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    AI Coding Assistant Account Bans: A Practical Zero DNS Leak Networking Guide

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    When teams use overseas AI coding assistants and large-model APIs, newly created accounts are sometimes restricted shortly after activation, top-up, or after only a few days of use. This article treats the issue as an engineering problem rather than a “ban mystery.” It does not discuss evading provider risk-control systems. It explains the four common technical root causes—DNS resolution leakage, mixed egress IPs, residual local sessions and credentials, and abrupt usage patterns—and provides a zero-DNS-leak network design, configuration examples, verification scripts, troubleshooting guidance, and a pre-launch checklist.

    Introduction: Turning the “Instant Ban” Narrative into an Engineering Problem

    In cross-border network environments, using overseas AI coding tools and calling overseas large-model services is part of daily work for many engineering teams. However, community reports often mention the same pattern: an account is newly created, topped up, or used for only a few days before receiving a restriction notice. In response, many people try fingerprint browsers, change system language and time zone, or purchase shared accounts from unclear sources. The problem often remains.

    This article does not discuss techniques for evading risk-control systems. A large amount of network troubleshooting and frontline development experience shows that most account issues can be reduced to four engineering factors:

    1. DNS resolution leakage: Queries that should be encrypted and completed through an overseas network path are visible to, or interfered with by, the local network.
    2. Mixed egress IPs: Multiple users share the same proxy egress.
    3. Residual local sessions and credentials: Old login states, caches, and device identifiers are not cleaned up.
    4. Abrupt usage behavior: A new account generates high concurrency, bulk requests, or automation-like traffic within a short period.

    Correspondingly, the solution can be divided into three layers:

    • Build a network foundation with zero DNS leakage, stable egress, and a consistent access path.
    • Isolate browser configuration, caches, and login credentials.
    • Use the service with gradual ramp-up and controlled request rates.

    The following sections expand on these layers and provide reproducible configuration examples and self-check scripts, followed by a pre-launch checklist.

    1. Problem Model: Four Root Causes Behind Account Issues

    To solve a problem, first locate it. A complete request path from an AI service can be divided into four layers:

    1. Application / browser / CLI tool
    2.       │
    3.       ▼
    4. ① DNS resolution layer: resolve a domain name to an IP address
    5.    (plaintext UDP/TCP, or encrypted DoH / DoT)
    6.       │
    7.       ▼
    8. ② Network egress layer: the request exits through a proxy or dedicated line
    9.    and reaches the target service from an overseas node
    10.       │
    11.       ▼
    12. ③ Application session layer: login credentials, cookies, caches, device identifiers
    13.       │
    14.       ▼
    15. ④ Usage behavior layer: request frequency, concurrency, and traffic volume over time

    Each layer has typical failure modes:

    Layer Typical failure mode Possible consequence
    ① DNS resolution layer The proxy does not take over DNS, browser encrypted DNS bypasses the proxy, or IPv6 resolves independently Resolution is polluted, connections fail or fall back to direct access, and query content is exposed
    ② Network egress layer Shared nodes, abused data-center IPs, logins from multiple regions, or inconsistent egress across devices Accounts become associated, triggering extra verification or restrictions
    ③ Application session layer Multiple accounts share a browser, and old credentials or caches are not cleaned Accounts become associated, and local state becomes inconsistent
    ④ Usage behavior layer A new account makes bulk calls or generates excessive concurrency in a short time The traffic is classified as abnormal automation

    It is worth noting that each provider’s risk-control logic is not publicly disclosed, and a single factor does not necessarily lead to restriction. However, the more abnormal signals stack up, the higher the probability of triggering extra verification or restriction. The goal is not to “win” against risk control, but to eliminate avoidable abnormal signals.

    Also, settings such as system language and time zone mainly affect local display formats. They are not the primary basis for determining whether an account is abnormal.

    2. Three Common Misconceptions: Why Does the Problem Persist After Changing the Environment?

    Misconception 1: The system language or time zone is the problem

    Some users believe that changing the system to English and setting the time zone to the target service region will make the account “look like a local user.” In practice, the server side pays more attention to the source network of requests, the resolution path, session consistency, and usage behavior. System display settings do not change these underlying signals. Changing them does not address the root cause, so the problem remains.

    Misconception 2: A fingerprint browser or a cloud virtual machine is enough

    Browser fingerprint isolation tools can reduce browser-level feature correlation, but they cannot solve DNS resolution and egress IP issues:

    • If the proxy only covers the browser, CLI tools, plugins, and scripts may still use direct connections.
    • If a virtual machine does not route all traffic through a controlled proxy, its DNS queries may still be visible to the local network.

    Nesting more layers into the setup only increases path complexity and failure points, making troubleshooting harder. The correct order is to fix the network foundation first, then consider browser isolation only when needed.

    Misconception 3: If an account is restricted, just create a new one

    If the root cause is in the network path or usage behavior, a new account in the same environment will soon encounter the same problem. The account is only the carrier; the environment and behavior are the root causes.

    3. Root Cause 1: DNS Leakage—the Most Hidden and Most Dangerous Issue

    3.1 What Is DNS Leakage?

    DNS translates domain names into IP addresses. Leakage occurs when a system or application does not perform resolution through a controlled encrypted channel, but instead sends queries directly to a DNS server in the local network. Leakage creates two risks:

    • Privacy risk: Plaintext queries expose which services are being accessed and when.
    • Correctness risk: In cross-border network environments, local resolution results may be modified by intermediate devices, which is commonly referred to as DNS pollution. The client receives an unreachable or redirected address, causing application errors, timeouts, or fallback to a non-ideal direct path.

    A common misconception is that “if the target website opens, the configuration must be fine.” In fact, if the local DNS has ever resolved the target domain, the query has already occurred. More importantly, operating systems and browsers often cache resolution results. During the cache period, subsequent requests may reuse old results and may even bypass the proxy.

    3.2 Seven Common Leak Scenarios

    1. The proxy only takes over system DNS: The browser has its own “secure DNS” or DoH feature enabled, so resolution requests bypass the proxy rules and go directly to a remote server.
    2. TUN mode is not enabled: Direct requests from CLI tools, plugins, or scripts are not captured.
    3. Only IPv4 is handled: IPv6 traffic bypasses the proxy and is resolved or sent directly.
    4. DNS fallback: After an overseas resolution attempt fails, the system falls back to a local DNS resolver and receives a polluted result.
    5. Application built-in resolution or hard-coded IP addresses: Some runtimes and frameworks resolve domains themselves or connect directly to fixed addresses, unaffected by system settings.
    6. Virtual machines, containers, or multi-NIC environments: Traffic resolved inside a VM or container may be sent through the host’s local DNS.
    7. Enterprise intranet DNS hijacking: An office network forces DNS to an internal server, overriding endpoint configuration.

    3.3 Target Architecture: Zero Leakage in One Diagram

    Zero leakage is not mysterious. It can be summarized in one sentence: All DNS queries ultimately exit through only one controlled egress, and failed queries fail directly instead of falling back.

    1. ┌──────────────── Local device ────────────────┐
    2. │  Applications / browsers / CLI tools         │
    3. │  (including containers and virtual machines) │
    4. │                  │                           │
    5. │          TUN virtual NIC captures all traffic│
    6. │                  ▼                           │
    7. │          ┌──────────────┐                    │
    8. │          │ Built-in DNS │ ← hijacks all port 53 queries
    9. │          │ resolver     │ ← browser DoH is also captured
    10. │          └──────┬───────┘                    │
    11. └─────────────────┼─────────────────────────────┘
    12.                   │ Encrypted tunnel
    13.                   ▼
    14.         ┌───────────────────────┐
    15.         │ Dedicated overseas     │ ← only egress, fixed long term
    16.         │ egress node            │
    17.         └─────────┬─────────────┘
    18.                   ▼
    19.         Encrypted overseas DNS resolver → AI service

    The key points are:

    • Locally, only virtual IP mappings are retained; real resolution results are not cached.
    • If overseas resolution fails, the request fails directly instead of falling back to local DNS.
    • All devices share the same stable egress.
    • Internal domains follow direct rules so normal office access is not affected.

    4. Network Foundation: Building a Zero DNS Leak Environment

    4.1 Egress Node Planning

    • Prefer dedicated, fixed egress IPs: Public shared nodes are often used by many strangers. If some of them perform abusive behavior such as scraping, credential stuffing, or bulk registration, the IP range may be classified as high risk. The same egress may also host many seemingly unrelated accounts, increasing association risk.
    • Self-hosted nodes should be hardened: If you run a proxy service on a long-lived overseas cloud host, the egress is used only by you. Apply basic security measures:
      • Run the proxy process as a non-root user.
      • Allow only necessary ports in the firewall.
      • Use SSH key authentication for management ports and disable password login.
    • Enterprise connectivity options: Enterprise users may choose cloud-provider connectivity services, such as dedicated cross-border interconnect, cloud enterprise networks, or global acceleration capabilities, where available. These options usually provide more stable, manageable, and auditable egress paths.
    • One account, one egress: Plan different egress IPs for different accounts to avoid multiple accounts logging in from the same address.
    • Do not mix proxy traffic: Traffic for AI services should, as much as possible, not share proxy rules with daily development, downloads, or other traffic. This reduces the chance of accidentally triggering rate limits.

    4.2 Core Client Configuration

    The following is an example configuration for a mainstream TUN-mode client. Field names may vary between clients; refer to the documentation for the client you use. IP addresses and domains below are reserved documentation values and should be replaced with actual values.

    1. # ① TUN mode: capture all device traffic to prevent CLI tools, plugins, and scripts from bypassing the proxy
    2. tun:
    3.   enable: true
    4.   stack: gvisor            # User-space protocol stack to reduce intrusion into the system network
    5.   auto-route: true         # Automatically take over the default route
    6.   strict-route: true       # Block connections that bypass routing rules and handle multi-NIC environments
    7.   dns-hijack:              # Hijack port 53 queries sent to any address and pass them to the built-in resolver
    8.     - any:53
    10. # ② DNS policy: virtual IP mapping + encrypted DNS only + no fallback
    11. dns:
    12.   enable: true
    13.   enhanced-mode: fake-ip   # Applications receive virtual IPs; real addresses are visible only inside the resolver and tunnel
    14.   fake-ip-range: 198.18.0.1/16
    15.   fake-ip-filter:          # Return real IPs for internal and local domains to avoid affecting internal services
    16.     - "*.corp.example.com"
    17.     - "+.local"
    18.   default-nameserver:      # Used only for plaintext bootstrap resolution of encrypted DNS server domains
    19.     - 192.0.2.53
    20.   proxy-server-nameserver: # Resolve node domains over the proxy path to prevent a chicken-and-egg loop
    21.     - 192.0.2.53
    22.   nameserver:              # Business resolution uses encrypted DNS
    23.     - https://dns.example.com/dns-query
    24.   fallback: []             # Empty means no fallback; if resolution fails, it fails
    25.   respect-rules: true      # DNS queries themselves follow routing rules
    27. # ③ Routing rules: internal traffic first, then AI service traffic through the overseas egress
    28. rules:
    29.   - DOMAIN-SUFFIX,corp.example.com,DIRECT
    30.   - IP-CIDR,10.0.0.0/8,DIRECT,no-resolve
    31.   - DOMAIN-SUFFIX,ai-provider.example.com,overseas   # Replace with the actual AI service domain
    32.   - MATCH,overseas

    4.2.1 TUN Mode: Ensure No Traffic Escapes

    TUN mode creates a virtual network interface and takes over the default route. All applications, including tools that do not read system proxy settings, enter the proxy core and are routed according to rules. strict-route blocks connections that deliberately bypass routing and helps reduce cases where some traffic bypasses TUN in multi-NIC environments.

    4.2.2 Virtual IP Mapping and Encrypted DNS Bootstrap

    In normal proxy mode, the proxy core fills the real resolution result back to the application, and the application connects directly using the real IP. In this case, DNS queries may be encrypted, but the real address is briefly exposed locally.

    In virtual IP mapping mode, the application only receives a virtual IP from a reserved range. When the proxy core establishes the connection, it performs the real resolution inside the tunnel based on the domain name.

    Note that the domain name of the encrypted DNS server itself needs to be resolved once through ordinary DNS. This is a necessary bootstrap query and can use a self-hosted or trusted recursive resolver.

    4.2.3 Disable Fallback: Fail Directly Instead of Downgrading

    If the system automatically falls back to local DNS after overseas resolution fails, it may receive a polluted result. This is a typical “looks configured, but still leaking” situation. Setting fallback: [] means resolution failure should cause the request to fail rather than silently downgrade to an unsafe path.

    4.2.4 Routing Rules: Internal Direct First, Then Fallback

    Rules are matched from top to bottom. Internal domains and private IP ranges must be placed at the top with direct rules, otherwise internal systems, code repositories, and other office services may become inaccessible. The final rule is the fallback: traffic that cannot be clearly classified should go through the overseas egress to avoid residual direct connections.

    4.3 Three Easily Overlooked Details

    Disable encrypted DNS in the browser. Major browsers such as Chrome, Edge, and Firefox provide a “Use secure DNS” option. When enabled, resolution requests may bypass TUN and proxy rules and go directly from the browser to the specified server. Disable this option in each browser, or set it to use the current system or service provider.

    Handle IPv6. If the client does not provide equivalent proxy and DNS takeover capabilities for IPv6, consider disabling IPv6 resolution and connections in the client configuration. This prevents IPv6 traffic from bypassing the local network. If the target service only provides IPv4 access, also avoid resolving IPv6 addresses, failing, and then retrying.

    Unify DNS for virtual machines and containers. VMs and containers may use the host’s local DNS by default. Configure encrypted DNS explicitly inside them, or point them to a controlled resolver. Also confirm that their traffic is forwarded through the host proxy or host-level TUN.

    5. Verification: Three-Layer Self-Check

    After configuration, verification must be based on facts, not feelings. Check the following three layers.

    Layer 1: Resolution Path Self-Check

    Check the following items:

    • Only encrypted DNS is used: In the proxy client log or query page, resolution records for business domains should be returned through encrypted DNS. Local DNS server addresses should not appear.
    • No fallback: When overseas resolution fails, the request fails directly. The local system does not issue supplementary queries.
    • The browser does not bypass: The resolution path is the same whether browser secure DNS is enabled or disabled.
    • Real IPs are not visible locally: Applications only see virtual IPs, and packet capture on the local machine should not reveal real resolution results.
    • No independent IPv6 resolution: After IPv6 is disabled or taken over, packet capture should not show IPv6 DNS queries.

    Layer 2: Egress Consistency Self-Check

    Check the login source and request egress shown by the service across different devices and networks, such as home broadband and a mobile hotspot. Expected results:

    • Egress remains consistent across devices, or matches the planned egress list one by one.
    • The egress location is broadly consistent with actual usage habits. There should not be rapid “drift” across continents within a short period.
    • IPv4 and IPv6 do not exit through different egress paths.

    Layer 3: Automated Self-Check Script

    The following script uses only the Python standard library. It checks three things:

    • Whether local resolution returns a virtual IP.
    • Whether encrypted resolution through the tunnel works correctly.
    • Whether the egress IP is stable.
    1. import json
    2. import socket
    3. import time
    4. import urllib.request
    6. SERVICE = "ai-provider.example.com"   # Replace with the AI service domain you access
    7. CHECK_URL = "https://check.example.com/api/ip"   # Self-hosted egress IP check endpoint
    8. CHECK_COUNT = 5
    10. def local_resolve(host):
    11.     """Local system resolution: with correct configuration, this should return a virtual IP from a reserved range."""
    12.     try:
    13.         return socket.gethostbyname(host)
    14.     except socket.gaierror:
    15.         return None
    17. def resolve_via_tunnel(host):
    18.     """Encrypted DNS resolution through the proxy tunnel: should return a usable public IP."""
    19.     url = f"https://dns.example.com/resolve?name={host}&type=A"
    20.     try:
    21.         with urllib.request.urlopen(url, timeout=10) as resp:
    22.             data = json.load(resp)
    23.         return [a["data"] for a in data.get("Answer", []) if a.get("type") == 1]
    24.     except Exception as exc:        # In production, record the specific exception type and traceback
    25.         return f"Query failed: {exc}"
    27. def egress_ips(count):
    28.     """Check the egress IP repeatedly: the result should be identical every time."""
    29.     ips = set()
    30.     for _ in range(count):
    31.         try:
    32.             with urllib.request.urlopen(CHECK_URL, timeout=10) as resp:
    33.                 ips.add(json.load(resp).get("ip"))
    34.         except Exception:
    35.             pass
    36.         time.sleep(1)
    37.     return ips
    39. local_ip = local_resolve(SERVICE)
    40. print(f"Local resolution: {local_ip}")
    41. if local_ip and (local_ip.startswith("198.18.")
    42.                  or local_ip.startswith("198.19.")):
    43.     print("[PASS] Local resolution returned a virtual IP; no real DNS resolution leaked")
    44. else:
    45.     print("[CHECK] Local resolution did not return a virtual IP; verify whether fake-IP mapping is enabled")
    47. print(f"Tunnel encrypted DNS resolution: {resolve_via_tunnel(SERVICE)}")
    48. ips = egress_ips(CHECK_COUNT)
    49. print(f"Egress IP: {ips or 'Check failed; confirm that the check endpoint is reachable'}")
    50. if len(ips) == 1:
    51.     print("[PASS] Egress IP is stable and unique")
    52. elif len(ips) > 1:
    53.     print("[WARNING] Egress IP changed; possible multiple egress paths or load balancing")

    When interpreting the results:

    • If local resolution returns an address in the 198.18.0.0/15 range, virtual IP mapping is working normally. If a public address is returned, real resolution may have leaked locally, or virtual IP mapping may not be effective.
    • The address returned by tunnel encrypted DNS should be accessible. If a reserved address or an obviously abnormal address is returned, the resolution result may be polluted.
    • Repeated egress IP checks should return exactly the same address. If multiple egress addresses appear, investigate load balancing, multi-node switching, or routing misconfiguration.

    Troubleshooting Table

    Symptom Possible cause Direction
    The CLI tool can connect, but its egress differs from the browser The tool does not use TUN, or environment variables point to another proxy Enable TUN and strict-route, and unify the egress
    Domain resolution fails or connections are reset Overseas resolution fails and then falls back to local DNS Check and clear the fallback list
    The browser works normally, but local DNS appears in resolution logs Browser encrypted DNS bypasses the proxy Disable the browser’s secure DNS option
    Resolution fails inside a container The container uses the host’s local DNS Explicitly configure a controlled resolver or enable container-level DNS forwarding
    Internal systems are unreachable Routing rules are ordered incorrectly Place internal domains and private IP ranges before direct rules

    6. Root Cause 2: Residual Local Sessions and Credentials

    Fixing the network is only the first step. Old traces on the local machine can also link old and new accounts.

    6.1 What Needs to Be Cleaned

    • Browser layer: Cookies and storage for the target site, including localStorage and IndexedDB, cached data, history records, and cached site certificates.
    • System layer: API keys left in environment variables or configuration files, login tokens and configuration files saved by CLI tools, and unrelated credentials such as SSH keys and certificates.
    • Identity layer: Some clients generate a stable device or instance identifier locally to recognize the “same machine.” Clean the configuration directory or run the client’s reset command to generate a new identifier.
    • Multiple accounts on one browser: If multiple accounts are logged in to the same browser, logging out only clears the current session. Old caches may remain. Use separate browser profiles for different accounts, and enable clearing cookies and site data on exit.

    6.2 Verification After Cleanup

    After cleanup and re-login, confirm:

    • The old account’s login state and cache no longer exist.
    • The new account logs in only from the planned egress.
    • No old API keys or tokens remain locally.

    6.3 Enterprise Scenario: Use Identity and Permission Management Instead of Manual Cleanup

    Individual users rely on manual cleanup, but enterprises should avoid residue and mixing from the source:

    • Manage member permissions through unified identity authentication and access control.
    • Store access keys centrally and rotate them regularly.
    • Provide members with operation audit and login anomaly alerts.

    7. Root Cause 3: Usage Behavior—Avoid “Distillation-Style” Ramp-Up

    7.1 What Is “Distillation-Style” Ramp-Up?

    “Distillation-style” ramp-up means a new account performs all high-frequency actions in a very short time: binding a payment method immediately after registration, subscribing to the highest tier right away, using CLI tools to generate or process code in bulk, and frequently switching between multiple projects and directories.

    In a normal user profile, these actions usually occur gradually over a longer period. When concentrated in a short time, they may resemble automated scripts in behavioral characteristics.

    7.2 Gradual Usage Strategy

    1. Light before heavy: In the first few days, use a small amount of conversation and small-scale file operations, then gradually increase usage.
    2. Control concurrency and rate: When processing batch tasks, set concurrency limits and exponential backoff retries for API calls to avoid sudden traffic bursts.
    3. Spread operations across directories: Avoid sending continuous requests for a large number of files in the same directory within a short time. Prefer operating by individual tasks.
    4. Keep a stable rhythm: Usage time and frequency should be close to normal development habits. Avoid frequent alternation between late-night scheduled batch jobs and manual operations.
    5. Consolidate requests: When generating code in bulk, combine multiple small requests into one larger request. This reduces the number of requests and lowers burst peaks.
    6. Manage budgets and quotas: Set internal usage budgets and quotas to prevent runaway scripts from causing abnormal costs or traffic.

    7.3 Usage Monitoring and Alerts

    Use logging, monitoring, and alerting capabilities to build dashboards and threshold alerts for the following metrics:

    • Requests per unit time and concurrency.
    • Token or credit consumption rate.
    • Resolution failure rate and connection failure rate.
    • Number of egress IP changes.

    If consumption rate suddenly increases several times, or multiple egress IPs appear within a short period, receiving an alert and investigating immediately is far more effective than appealing after the fact.

    8. Pre-Launch Checklist

    Network Foundation

    • Use a dedicated, fixed overseas egress node and do not share egress IPs with strangers
    • Egress matches accounts one by one, with no cross-continent drift
    • Enable TUN mode and strict-route, and ensure CLI tools and plugins are included
    • Enable virtual IP mapping and hijack all port 53 queries
    • Use encrypted DNS for business resolution, and keep fallback empty
    • Disable browser encrypted DNS and system-level encrypted DNS
    • Disable or fully take over IPv6
    • Ensure internal domains and private IP ranges are routed directly

    Sessions and Credentials

    • Old cookies, caches, tokens, and API keys are cleaned
    • Local device identifiers are reset
    • Multiple accounts use separate browser profiles, and site data is cleared on exit

    Usage Behavior

    • New accounts use gradual ramp-up without short-term bulk calls
    • API calls have concurrency limits and backoff retries
    • Usage monitoring and anomaly alerts are configured

    Automated Verification

    • All three self-check layers pass, and repeated script runs remain stable

    Conclusion

    Why is an account restricted immediately after activation? The answer is often not superstition, nor system language. It is hidden in easily overlooked details: a DNS query that does not go through an encrypted channel, an egress IP shared with strangers, residual old credentials, and an overly aggressive usage curve.

    A simple method is sufficient for troubleshooting: first model the problem by layer, then verify item by item, and finally turn the process into a checklist. The network foundation determines the lower bound. Session isolation and gradual usage determine the upper bound. Making these practices part of daily workflow makes account stability less dependent on luck.

    Finally, before using any AI service, read and follow its terms of service and applicable laws and regulations. When cross-border data flows are involved, also meet compliance and audit requirements. Stable access is always built on compliance.

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