[BUG] manifest.opensteamtool.com returns 403 Forbidden — all downloads fail with "no internet" error

[prettysurest]

Prerequisites

• I have searched existing issues and confirmed this has not been reported.
• I am using the latest build version from the releases page.

Steam client version

1782257239

Windows version

Sürüm 25H2 (İS Derlemesi 26200.8655)

Describe the bug

The manifest provider at https://manifest.opensteamtool.com appears to return
HTTP 403 Forbidden for certain IP ranges (likely datacenter IPs, VPN exit nodes,
or specific ISP ranges blocked by Cloudflare). Since this is the hardcoded default
provider, affected users cannot download any game and Steam reports a generic
"no internet connection" error.

Steps to reproduce

1. Place opensteamtoold.dll, dwmapi.dll, xinput1_4.dll in Steam root directory
2. Launch Steam and attempt to download any game configured via addappid()
3. Observe "no internet connection" or download failure error
4. Alternatively, run: curl -I https://manifest.opensteamtool.com/7759922098115499616
   → Returns: HTTP/2 403

Expected behavior

https://manifest.opensteamtool.com/ should return the manifest request code as a
plain uint64 string with HTTP 200, allowing the game download to proceed.

Actual behavior

https://manifest.opensteamtool.com returns HTTP 403 Forbidden from certain IPs
(confirmed: datacenter/cloud IPs receive 403, residential IPs receive correct uint64 response).

From affected IP:
curl -I https://manifest.opensteamtool.com/7759922098115499616
→ HTTP/2 403

From unaffected IP:
curl https://manifest.opensteamtool.com/7759922098115499616
→ 9230506510738152619 (correct response)

Log files

No response

Lua configuration (if relevant)

-- MAIN APPLICATION
addappid(3551340, 1, "052016d88278aada4bc94cc5d3fbef162105991acf65634e80e5fb0fb5fd3304") -- Football Manager 26
-- MAIN APP DEPOTS
addappid(3551341, 1, "a4f9c46a0797978fa0b278dac08a0f473872fc74c6b6d9bf45b30d56e33a42c7") -- Depot 3551341

addappid(3551342, 1, "31edad03a3daebca77afad83adb899f2ff6611d949738ad3d15e708da8f2c7ca") -- Depot 3551342

addappid(3551343, 1, "5ff6a006dff3e4ea6364310a8390ffc5f4754c3928150ea5719009c21074a607") -- Depot 3551343

-- DLCS WITHOUT DEDICATED DEPOTS
addappid(3551410) -- Football Manager 26 In-Game Editor

Additional context

No response