Last date label hidden on Time Series X-axis

[aijung0331]

Bug description

In Charts, when the X-axis is set to a Time format, the last date label often fails to display.
This is particularly important for daily or hourly monitoring dashboards where the user needs to confirm the exact "latest" time reflected on the chart at a glance.

Screenshots/recordings

No response

Superset version

master / latest-dev

Python version

I don't know

Node version

I don't know

Browser

Chrome

Additional context

No response

Checklist

• I have searched Superset docs and Slack and didn't find a solution to my problem.
• I have searched the GitHub issue tracker and didn't find a similar bug report.
• I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

[dosubot]

This is a known and actively-discussed issue. You actually raised this same topic in Discussion #39361, where it was explored in detail [1].

Root cause: ECharts' hideOverlap: true setting aggressively suppresses the last label when it detects potential overlap at the axis boundary. Despite several fixes merged in early 2026 (PR #37755, PR #38733, PR #38979), there's a discrepancy between those PRs and the current codebase — showMaxLabel does not appear to be set in the current transformProps.ts [2]. The showMaxLabel approach has a troubled history: it was added, reverted (PR #24995) due to "phantom labels," and subsequent fixes evolved away from it.

Current state: There is no deterministic user-facing configuration that guarantees the last time label is always shown [1]. The available workarounds are:

1. Apply non-zero X-axis label rotation (e.g., 45°) — triggers hideOverlap: false in newer builds
2. Increase chart width to reduce overlap detection
3. Theme-level override (Superset 6.0+) — use echartsOptionsOverridesByChartType to inject showMaxLabel: true globally if you control the deployment
4. Cast date column to STRING at the dataset level and set "X Axis Label Interval → All" to bypass time-scale overlap logic entirely

For your monitoring dashboard use case where the latest timestamp must always be visible, a feature request for an exposed showMaxLabel toggle or a dedicated "Always show last label" control would be well-motivated. The infrastructure partially exists — extending the ECharts Options JS editor (currently available for Evolution chart types) to Time-Series charts would also address this.

To reply, just mention @dosu.

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[Cloud-Architect-Emma]

Hi @aijung0331 , thanks for raising the issue, i'd like to help fix this issue . Can you assign it to me ?