Rare case: Verify reports unsnapped slider repeat/end after adding repeats

[LianSheng197]

Type

Game behaviour

Bug description

Description

I encountered an unusual Verify warning related to slider repeats that I have not seen before, despite mapping for a long time.

In this case, a slider was placed and snapped normally, and Verify initially reported no issues.
At a later point, after adjusting the repeat count, Verify started reporting timing errors:

• Slider repeat is unsnapped by XX ms
• Slider end is unsnapped by XX ms

What makes this noteworthy is that this does not appear to be a common or easily reproducible case.
The exact trigger conditions are currently unclear.

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Steps to Reproduce

The exact triggering conditions are unclear -- by this I mean that, aside from the slider shown in the video, I don't know how to create another slider that results in the same behavior.

However, I'm providing the complete map file from when the issue occurred. The problem can be reproduced on my machine, but I have not tested it on other computers.

I'm not sure whether the file would be modified after being uploaded to osu!, so I'm providing the original file here. Since GitHub does not allow the .osz file extension, I'm using .zip instead, even though we all know they're the same format.

osu-repeat-slider-weird-problem-00m32s593ms.zip

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Expected Behavior

If a slider is initially snapped correctly, adjusting the repeat count should not introduce Verify warnings unless an actual timing mismatch exists.

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Actual Behavior

Verify reports unsnapped slider repeat and end timing after modifying repeat count, despite no obvious desync introduced by the mapper.

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Additional Notes

• This may be an extremely rare edge case.
• A screen recording is attached for context.

Screenshots or videos

osu-repeat-slider-weird-problem.mp4

Observations

Initial state (repeat slider x4)

• A slider is placed and snapped to the timing grid.
• After placement, Verify remains clean with no timing warnings.
• No visible timing adjustments, re-snapping, or micro-movements are made.

Repeat modification

• The only change made to the slider is increasing its repeat count.
• This action is NOT accompanied by:
  • moving the slider start or end
  • changing timing points
  • changing beat divisor or snap settings

Verify result after repeat change

• After modifying the repeat count and reopening Verify:
  • Verify reports
    • Slider repeat is unsnapped by XX ms
    • Slider end is unsnapped by XX ms
• These warnings appear only after the repeat count change.
• Visually, the slider alignment doesn't appear to change.

Notable characteristics

• The issue doesn't occur at initial slider placement.
• The Verify warnings appear to be temporally correlated with modifying the repeat count.
• From the recorded interaction, no user action clearly introduces an unsnap condition.

Version

2025.1218.0-lazer

Logs

Because the guidelines explicitly state that complete logs must be attached, there are cases where the automatically generated compressed-logs.zip from the game exceeds 25 MB and cannot be uploaded. In such situations, the GitHub interface only displays a minimal message like <!-- Failed to upload "compressed-logs.zip" -->. The specific cause of the failure can only be identified by checking the official documentation or by inspecting the Network request response via the browser developer tools (F12).

Therefore, the attachments below were created by extracting the original compressed-logs.zip and then recompressing the contents into multiple smaller archives.

compressed-logs-part1.zip
compressed-logs-part2.zip

It's also recommended to improve the description related to logs in the Issue template.

[cihe13375]

I encountered this before, which was caused by accumulation of sub-millisecond errors. For example, let's say the beat length is 100ms, and the silder length of a single reverse is 99.5ms. So the first reverse point is unsnapped by 0.5ms, the second by 1.0, the third by 1.5 etc. The fourth is unsnapped by 2.0 which would trigger the error (>=2ms).

This is kinda confusing in lazer, because sometimes you apprently fixed it, but after the map upload (i.e. stable export) the problem appears again. The solution is to adjust the slider length.