[dlin-wandb]

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JIRA/GH Issues(s)

Paste links to relevant JIRA/GH issues here, one per line e.g.

• https://coreweave.atlassian.net/browse/WB-39260

Description

Preserves section info of runset grouping keys when loading Reports V2.

Previously, deserialization only kept the key name

groupby=[expr.to_frontend_name(k.name) for k in model.grouping],

And on subsequent saves, the names with dots would get reparsed incorrectly

• Before: {section: "config", name: "algo_backbone.value"}
• After: {section: "algo_backbone", name: "value"}

This produced invalid persisted keys and could cause the frontend to throw keyToServerPath error.

Testing

How was this PR tested?
Repro notebook:
https://colab.research.google.com/drive/1EP1swfBuNQV-QR22JSPj1jaqks0f0Lpq?usp=sharing
Fix notebook:
https://colab.research.google.com/drive/1o186fqyBLjpP3UiZQ5IK4vpIUrTExI4r?usp=sharing

State	print debug	recording
Before	['algo_backbone.value']	Screen.Recording.2026-10-05.at.12.22.03.PM.mov
After	['config.algo_backbone.value']	Screen.Recording.2026-10-05.at.1.55.03.PM.mov

• Added unit tests : regression tests covering config, summary, aliased run, and dotted run keys.
• Manual testing (include description)
• N/A (include explanation)

Server compatibility

• Requires a minimum W&B Server version (label requires-server/X.Y+ applied)
• SaaS only — not yet in any tagged W&B Server release (label requires-server/unreleased applied)
• N/A — works on all currently supported servers