Is there an existing issue for this?

• [x] I have searched the existing issues

Are you using any gamescope patches or a forked version of gamescope?

• [x] The issue occurs on upstream gamescope without any modifications

Current Behavior

When streaming Gaming Mode via Steam Link to a phone client, the session works for the first ~5 seconds, then the video output hard-freezes for 5–10 seconds, followed by a ~1 second burst of stuttering video as it "catches up," then freezes again — repeating in a cycle. This happens before any game is launched, i.e. it reproduces in the Big Picture / Gaming Mode UI itself.

During the freeze:

Audio continues with no delay
Input (touch/virtual controller from the phone) is still being received — the mouse cursor visibly moves on screen even while the frame is frozen
Ping and packet loss reported by the Steam Link overlay are normal (0% loss, ~5ms direct ping)
Hardware encoding is active throughout (VAAPI HEVC), not falling back to software

Steps To Reproduce

1. Boot SteamOS into Gaming Mode
2. Connect to the machine remotely using the Steam Link app on a phone (same LAN, 5GHz Wi-Fi, direct connection, wired-equivalent low latency confirmed via overlay)
3. Observe the Big Picture UI (no game running) over the Steam Link stream
4. Cyclic freeze/stutter begins within the first ~5 seconds and continues indefinitely

Isolation steps already performed

• Desktop Mode streaming is completely unaffected — identical hardware, identical network path, Steam Link to Desktop Mode is flawless. This points at something specific to Gamescope's remote-play/input path rather than PipeWire/VAAPI/network/encoder.
• Using a controller plugged directly into the host PC (no remote client) is completely smooth — video streams perfectly to the phone as long as input is coming from the local controller, not from the remote Steam Link client.
• The freeze is specifically triggered by receiving input events from the remote client. When input arrives from the phone (touch/virtual controller), the freeze cycle begins; local-only input does not trigger it.
• Ruled out: Wi-Fi power save (disabled via iw dev wlan0 set power_save off, no change), gyro/motion input (disabled in Steam Link app, no change), DSU/gyro service contention (would also affect Desktop Mode, which is unaffected), thermal/hardware issues (system stable under heavy local load), recent SteamOS/driver updates (issue predates and persists across several updates), network jitter/bufferbloat/DFS channel switching (fixed non-DFS channel, clean ping/packet-loss stats throughout).

Hardware information

Distro: SteamOS (desktop build, not Steam Deck)
CPU: AMD Ryzen 9600X
GPU: AMD Radeon RX 9060 XT (RDNA4)
Motherboard: ASRock A620AI Mini-ITX
RAM: 32GB DDR5-5200 (EXPO)

Software information

Session type: Gamescope (Gaming Mode) — DRM/KMS embedded session
Client: Steam Link app on Android/iOS phone, same LAN, 5GHz Wi-Fi, direct connection
Gamescope version: 3.16.23.4 (gcc 15.1.1)
Kernel version: 6.16.12-valve24.5-1-neptune-616-gb2f7cfe85e45
Desktop environment: plasmashell 6.4.3
Session type: wayland

Which gamescope backends have the issue you are reporting?

• [x] Wayland (default for nested gamescope)
• [ ] DRM (default for embedded gamescope, i.e. gamescope-session)
• [ ] SDL
• [ ] OpenVR

Logging, screenshots, or anything else

No response