SQR: Fix datasource-template runtime routing for multi-select fan-out

[harisrozajac]

This PR fixes runtime execution for panels using a datasource variable with multiple selected values.

Previously, when a datasource variable (for example ${ds}) had multiple selected values, runtime could execute only one datasource query path (effectively the first), instead of running across all selected datasources.

This change ensures runtime routes templated datasource execution through the Mixed datasource path so all selected datasource values are executed.

The demo below shows v1 dashboards, but i've verified that this also fixes it for v2 dashboards.

Current behavior:

Screen.Recording.2026-04-02.at.9.30.06.AM.mov

With the fix:

Screen.Recording.2026-04-02.at.9.23.41.AM.mov

Fixes: grafana/grafana#121324

📦 Published PR as canary version: 7.3.8--canary.1416.23913328165.0

✨ Test out this PR locally via:

npm install @grafana/scenes@7.3.8--canary.1416.23913328165.0
npm install @grafana/scenes-react@7.3.8--canary.1416.23913328165.0
# or 
yarn add @grafana/scenes@7.3.8--canary.1416.23913328165.0
yarn add @grafana/scenes-react@7.3.8--canary.1416.23913328165.0

[Copilot]

Pull request overview

This PR updates SceneQueryRunner runtime datasource resolution so panels using a templated datasource variable (e.g. ${ds}) can correctly fan out execution when the variable has multiple selected values, by routing execution through the Mixed datasource path.

Changes:

• Add runtime detection logic to decide when to use the Mixed datasource for query execution based on datasource templating and variable selection count.
• Preserve the original templated datasource ref on request targets when executing via Mixed, so Mixed can perform the fan-out.
• Extend unit tests to cover single-selection, multi-selection, and “ambiguous” templated datasource UID cases; update snapshot accordingly.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/scenes/src/querying/SceneQueryRunner.ts	Adds Mixed-runtime routing decision logic and adjusts request target datasource assignment to preserve templated refs when running via Mixed.
packages/scenes/src/querying/SceneQueryRunner.test.ts	Adds unit tests verifying Mixed vs non-Mixed runtime datasource selection behavior for templated datasource variables.
packages/scenes/src/querying/__snapshots__/SceneQueryRunner.test.ts.snap	Updates snapshot output due to additional tests affecting requestId counter progression.

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[kristinademeshchik]

I tested this on different combinations v1/v2 with/without panel level ds works well!

[scenes-repo-bot-access-token]

🚀 PR was released in v7.3.8 🚀