What hurts coding productivity most isn't slow speed — it's inconsistency: completions return instantly in the morning, then the same tool spins for ages at night. On cross-border networks there is almost always an explanation for this, and almost always a fix in switching route type.

Long-lived connections and web browsing fail in different ways

Web browsing uses short connections: opening a page fires dozens of parallel requests, each finishing within a few hundred milliseconds. Lose a packet or two along the way and TCP retransmits it — all the user notices is a slight delay.

AI coding tools work differently. Cursor completions, Copilot chat and CLI assistants all use HTTPS long-lived connections with streaming responses (SSE): the server pushes results back token by token, and a single connection stays open for tens of seconds or even minutes. If that connection stutters, the symptom isn't slowness — it's a completion that stops mid-sentence, a chat with no reply, and nothing to do but regenerate.

Worse, packet loss gets amplified by the protocol. The moment TCP decides a packet is lost, it halves the congestion window and the streaming output immediately slows down; by the time the window grows back, the completion is already over. So judging whether a route suits coding isn't about peak speed — it's about jitter and packet loss.

Two more things that often get overlooked:

How this test works: three dimensions, one reproducible set of checks

First, what "tested" means here. This article doesn't hand you a set of fixed latency numbers — numbers that look good today may not hold up in tomorrow's peak hours, so their value is limited. What you get instead are three dimensions and checks you can reproduce yourself.

  1. Connection hold: fire off streaming requests back to back and see how long a single connection lasts, and whether the client reconnects automatically after a drop.
  2. CLI proxy: whether your terminal, Git, package managers and Docker actually go through the proxy, rather than only the browser.
  3. Peak-hour performance: repeat the same set of operations between 19:00 and 23:00 and compare drops and retransmissions.

Of the three, the first two decide whether a route is usable at all; the third decides whether it stays usable. Most complaints that "this tool doesn't work" come down to one of them.

Connection hold: the three steps where long connections usually break

Step one: connection setup — DNS resolution and the TLS handshake

On a direct public-internet route, DNS resolution and the TLS handshake each take extra round trips, stretching out time to first byte. In the editor you feel it like this: you trigger a completion, it spins for two seconds, and only then does text start appearing. If resolution is still handled by your local ISP, you may get an address far from your current egress and wait for nothing.

Step two: idle — heartbeats and timeout reclamation

Intermediary devices reclaim connections based on idle time. If the client's heartbeat interval is too long, the connection looks alive but is already dead, and the next request has to handshake again. This is a common reason the first completion after stepping away feels especially slow.

Step three: congestion — packet loss and window shrinkage

Cross-border public internet at peak hours is shared bandwidth, and packet loss and jitter rise together. This is where differences in route quality show up most clearly, and where dedicated lines pull away from relay and direct routes.

Route type How traffic is carried Packet loss & jitter Long-connection behaviour Best for
IEPL dedicated line The cross-border leg runs over a carrier's dedicated channel, not public internet egress Low Long connection hold times, little variation at peak hours AI completions, live chat, remote desktop
Relay Traffic lands on a relay node first, which then connects to the cross-border leg Medium Steadier than direct, cheaper than a dedicated line Package pulls, builds, repo sync, docs
Direct Runs straight over public internet egress High, and clearly worse at peak hours Fine for short requests; long connections drop easily Quick lookups and latency-tolerant tasks
Takeaway: putting AI coding tools on an IEPL dedicated line while sending large downloads and package managers over relay or direct routes is the combination developers reach for most — long connections stay intact, and download jobs don't eat the dedicated line's bandwidth.

CLI proxy: how terminals, Git and package managers get routed

The proxy switch in your editor and the one in your terminal are two different things. This is why so many people get stuck on "the browser works but the terminal keeps timing out": the client only enabled the system proxy, and command-line tools don't read system proxy settings by default.

There are three ways to get the command line through a proxy:

  1. Environment variables: they apply only to the current terminal window — the lightest option, good for one-off use; a new window needs them set again, and GUI apps won't read them at all.
  2. The client's TUN / virtual adapter mode: it takes over all system traffic, covering the terminal, Docker, SSH and background processes at once — at the cost of needing higher system privileges.
  3. Routing rules: send AI tool domains and code hosting through the proxy, and keep package manager sources and the corporate intranet direct — it saves traffic and stops internal services from being routed out.

Setting the environment variables (the examples below use local mixed port 7890; use whatever port your client shows):

# Applies to the current terminal window only
export http_proxy="http://127.0.0.1:7890"
export https_proxy="http://127.0.0.1:7890"

# Make Git use the proxy too
git config --global http.proxy http://127.0.0.1:7890

# Unset when you're done
unset http_proxy https_proxy
git config --global --unset http.proxy

Always verify after configuring: open the site's What's My IP page in your terminal and check whether the egress region matches the one selected in the client. If the browser shows Japan while the terminal still shows your local ISP, the terminal's traffic isn't going through the proxy at all.

What a subscription link is: a single address the client uses to pull your route configuration. Import it once and the client keeps updating from the route list it contains; when you switch devices, just paste the same subscription link into the new client's subscription field — no need to copy server addresses one by one. For how subscriptions map to protocols, see Routes & Protocols; import steps for each platform's client are on the Guides page.

Peak hours and DNS: two things that are easy to overlook

Peak hours: run your checks between 19:00 and 23:00

Congestion on the cross-border public internet follows a clear daily pattern. A route that tests smoothly during the day may start dropping packets at night, because everyone is using the same public egress. To judge whether a route suits coding, watch the peak-hour window: if completions stutter repeatedly during those hours, the thing to change is the route type, not the editor.

DNS leaks: local resolution sends requests the long way round

If DNS resolution is still handled by your local ISP, you may get an address far from your egress even when traffic goes through the proxy, adding a pointless wait to time to first byte. Checking is simple: with the proxy on, visit any DNS leak test page and see whether the resolving server follows your egress region. If it doesn't, hand DNS queries to the proxy in your client as well.

Checking only the browser isn't enough. Your editor, terminal and Docker may each leave through a different egress, so run the DNS leak test in the same environment where your AI tools actually run.

Routing rules: three categories are enough to start

There are three common rule types: by domain suffix (DOMAIN-SUFFIX), by IP range (IP-CIDR) and by geo database (GEOIP). For development work, getting these three right solves most problems:

Choosing routes by scenario: four combinations developers use most

Scenario Recommended route Why
Completions and chat (Cursor, Copilot, CLI assistants) IEPL dedicated line, Japan or Singapore Long connections are the most sensitive to packet loss, and a dedicated line has less jitter
Package pulls, builds, repo sync Relay or direct, in a high-bandwidth region Throughput comes first; the occasional retransmission doesn't change the end result
Remote desktop, video calls IEPL dedicated line, nearest region Jitter hurts the experience more than speed does — frozen video is the hardest to put up with
Reading docs, searching for answers Any stable route Short connections are tolerant, so there's no need to use up dedicated-line bandwidth

On route coverage, KimiVPN spans 110+ countries and 150+ routes; to see which route types are available in a given region, filter by country on the Routes page before deciding. Clients cover five platforms — Windows, Android, iOS, macOS and Linux — and one account has no device limit: laptop, desktop and tablet can be online at the same time, with no extra charge for multiple devices.

Takeaway: pick the route type by purpose first, then choose the region by physical distance. Sending completions and chat over a dedicated line and downloads and builds over relay or direct is far more stable than pushing all traffic through a single route.

Check these before you buy

Development work demands more from a client and its route information than everyday browsing does. Compare the points below one by one:

110+ Countries & regions covered
150+ Routes available, including IEPL dedicated lines
5 Platform clients: Windows / Android / iOS / macOS / Linux
7 days No-questions-asked refund

On pricing, monthly plans start at ¥9.9 and come in tiers by data volume; if you're unsure how much you'll use in a month, start monthly and add a data pack later — data packs never expire.

FAQ

Cursor completions are stalling — check the route first or the tool?

Look at the timing first. If it only happens at peak hours, it's most likely the route — switch to an IEPL dedicated line and test again. If it stalls all day, first confirm that your terminal and editor really are going through the proxy, then check whether DNS resolution follows your egress region.

How many devices can one account use at the same time?

This service has no device limit. The laptop, desktop and tablet you use day to day can be online at once, with no extra charge for multiple devices.

Do I need to reconfigure routes when I switch devices?

No. Paste the same subscription link into the new client's subscription field and update once — you get every route, and your routing rules come along with them.

Does it need to stay on all the time?

No. With routing rules in place, direct traffic never goes through the proxy anyway; you can switch it on only when using AI tools or looking things up.