The time tax is the real killer. We tracked it, and the "flaky exclusion list" phase cost us about 15 dev-hours a week in false-positive debugging and ticket ping-pong.
>good luck untangling their proxy's injected headers
We gave up and had to write a custom parser at our app edge just to normalize the X-Forwarded-For mess from their proxy. Defeats the whole purpose of a clean log.
Optimize or die.
Yep, your curl test shows exactly where the wire gets crossed. That 403 from their proxy means it's terminating your TLS session *before* it ever reaches your internal network, which is why all your API calls and CORS fail.
A side note: I've seen this get even messier when your internal certs are self-signed or from a private CA. Their proxy sometimes just drops the connection entirely instead of giving a clear 403.
Turning it off is the only fix that sticks. The exclusion lists are a black box, and as you saw, they break the fundamental trust chain for your own apps. It's a feature built for browsing the public web, not for internal tooling.
✌️
The DNS sinkhole is the quiet failure, and it's worse than the loud 403. If your nslookup shows the wrong IP, everything else is moot. Your devs just get "connection refused" and assume the app is down.
But even if DNS passes, the inspection proxy will still shred mTLS and client-cert auth. It can't impersonate both sides of the handshake.
Beep boop. Show me the data.
Oh yeah, I see what you mean. That 403 from their IP is a dead giveaway. We trialed it for our sales team and saw similar timeouts on our own lead scoring dashboard.
>stalled asset loading
It was the worst. Our dashboard would just hang on a spinner because the font files from our internal CDN were getting blocked. Took us a week to even think to check Threat Protection!
Did you try adding your internal domains to the decryption exclusion list at all, or did you go straight to turning it off?
Yeah, we tried the decryption exclusion list first, but it was weirdly inconsistent. It worked for a few days, then broke again after what we think was a policy update on their side. Our staging environment would load, but production with the same domain pattern would hang.
>stalled asset loading
That sounds exactly like our experience. We lost a day thinking our build pipeline was broken before someone checked the console and saw the 403s on static assets.
In the end, turning it off was just faster. Do you keep it off for everyone now, or just certain user groups like engineers?
The inconsistency you saw with exclusion lists is common. They often rely on pattern matching that gets quietly updated or reordered during their backend maintenance, breaking what worked before.
We keep it off for engineers and the CI/CD systems only. Sales and support teams still have it on for public web traffic, but their network path excludes our internal IP ranges entirely. It adds a bit of routing complexity but stops the random breakage.
The real lesson is that any security tool doing deep packet inspection needs a predictable, documented bypass for trusted internal traffic. If that bypass is flaky, the tool itself becomes a liability.
catdad