washed out/overexposed output with macvk + gpu-next

mpv Information

mpv v0.40.0-357-g17a3ac4cf-dirty Copyright © 2000-2025 mpv/MPlayer/mplayer2 projects
 built on Oct  4 2025 18:54:12
libplacebo version: v7.356.0 (v7.351.0-80-g76c7076c)
FFmpeg version: 8.0
FFmpeg library versions:
   libavcodec      62.11.100
   libavdevice     62.1.100
   libavfilter     11.4.100
   libavformat     62.3.100
   libavutil       60.8.100
   libswresample   6.1.100
   libswscale      9.1.100

Other Information

- macOS version: 15.6.1
- Source of mpv: master build
- Latest known working version: N/A
- Issue started after the following happened: update of libplacebo to master

Reproduction Steps

any video with mpv --no-config

Expected Behavior

same output as current nightly build with libplacebo 7.351

Actual Behavior

output is washed out/overexposed. behavior with --no-config
top left with libplacebo 7.351 (expcted)
top right with libplacebo master (slightly overexposed)
bottom left libplacebo master + --target-trc=bt.1886 --target-prim=bt.709 (overexposed)
bottom right libplacebo master + --target-trc=bt.1886 --target-prim=bt.709 --target-colorspace-hint=yes (slightly overexposed)
smaller window on the right vo=libmpv (same output as top left)

same as above just with my current config (without no-config)

Log File

with no-config:
log libplacebo 7.351 (working): placebo-7.351.log
log libplacebo master (broken): placebo-master.log

without no-config:
log libplacebo 7.351 (working): placebo-7.351.log
log libplacebo master (broken): placebo-master.log

Sample Files

No response

I carefully read all instruction and confirm that I did the following:

• I tested with the latest mpv version to validate that the issue is not already fixed.
• I produced the log file with the exact same set of files, parameters, and conditions used in "Reproduction Steps", with the addition of --log-file=output.txt.
• I produced the log file while the behaviors described in "Actual Behavior" were actively observed.
• I attached the full, untruncated log file.
• I attached the backtrace in the case of a crash.
• I provided all required information including system and mpv version.

Start by reproducing the issue with mpv --no-config and comparing the attached placebo-7.351.log and placebo-master.log files, using the reported macOS and libplacebo versions. Trace the macOS gpu-next rendering path and verify that output with libplacebo master matches the working 7.351 behavior without regressing vo=libmpv.