Editor tab's bottom border briefly use focus color on mouse click

[hecticme]

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.97.2
• OS Version: macOS Sequoia 15.3.1 (24D70)

Steps to Reproduce:

1. Open any file or create a new file.
2. Click on a tab, the bottom border will flicker with the focus border color.

https://github.com/user-attachments/assets/79a3cf3c-8435-4cf4-b8f0-8135ef0135b5

[bpasero]

@hecticme can you share your settings and theme?

[hecticme]

@bpasero Sure, these are my settings:

settings.json

{
  "telemetry.telemetryLevel": "off",
  "update.mode": "manual",
  "security.workspace.trust.enabled": false,
  // Window
  "window.restoreWindows": "none",
  "window.newWindowDimensions": "inherit",
  "window.title": "${rootName}",
  "window.titleBarStyle": "custom",
  "window.experimentalControlOverlay": true,
  "window.dialogStyle": "custom",
  "window.customTitleBarVisibility": "auto",
  "window.commandCenter": true,
  "window.menuBarVisibility": "hidden",
  // Editor
  "editor.cursorSmoothCaretAnimation": "on",
  "editor.cursorBlinking": "solid",
  "editor.bracketPairColorization.enabled": false,
  "editor.minimap.enabled": false,
  "editor.fontFamily": "IBM Plex Mono",
  "editor.fontLigatures": false,
  "editor.fontSize": 14,
  "editor.lineHeight": 1.75,
  "editor.lineNumbers": "off",
  "editor.codeLens": false,
  "editor.guides.indentation": false,
  "editor.matchBrackets": "always",
  "editor.glyphMargin": false,
  "editor.folding": false,
  "editor.overviewRulerBorder": false,
  "editor.tabSize": 2,
  "editor.stickyScroll.enabled": false,
  "editor.find.addExtraSpaceOnTop": false,
  "editor.renderWhitespace": "boundary",
  "editor.renderLineHighlight": "line",
  "editor.lightbulb.enabled": "off",
  "editor.parameterHints.enabled": false,
  "editor.acceptSuggestionOnCommitCharacter": false,
  "editor.acceptSuggestionOnEnter": "off",
  "editor.tabCompletion": "on",
  "editor.colorDecorators": false,
  "editor.wordWrap": "on",
  "editor.gotoLocation.multipleDeclarations": "goto",
  "editor.gotoLocation.multipleDefinitions": "goto",
  "editor.gotoLocation.multipleImplementations": "goto",
  "editor.gotoLocation.multipleReferences": "goto",
  "editor.gotoLocation.multipleTypeDefinitions": "goto",
  // Terminal
  "terminal.integrated.defaultProfile.linux": "zsh",
  "terminal.integrated.persistentSessionReviveProcess": "never",
  "terminal.integrated.cursorStyle": "block",
  "terminal.integrated.cursorBlinking": false,
  "terminal.integrated.stickyScroll.enabled": false,
  "terminal.integrated.shellIntegration.decorationsEnabled": "never",
  "terminal.integrated.initialHint": false,
  // Languages
  "html.autoCreateQuotes": false,
  "javascript.suggest.autoImports": false,
  "typescript.suggest.autoImports": false,
  "javascript.updateImportsOnFileMove.enabled": "never",
  "typescript.updateImportsOnFileMove.enabled": "never",
  "javascript.preferences.importModuleSpecifier": "non-relative",
  "typescript.preferences.importModuleSpecifier": "non-relative",
  // Diff Editor
  "diffEditor.hideUnchangedRegions.enabled": true,
  "diffEditor.ignoreTrimWhitespace": false,
  "diffEditor.renderSideBySide": false,
  // Explorer
  "explorer.compactFolders": false,
  // Files
  "files.insertFinalNewline": true,
  "files.trimFinalNewlines": true,
  "files.trimTrailingWhitespace": true,
  "files.enableTrash": false,
  // Search
  "search.defaultViewMode": "tree",
  "search.exclude": {
    "**/node_modules": true,
    "**/bower_components": true,
    "**/*.code-search": true,
    "**/package-lock.json": true,
    "**/yarn.lock": true,
    "**/pnpm-lock.yaml": true
  },
  // Workbench
  "workbench.startupEditor": "none",
  "workbench.tree.enableStickyScroll": false,
  "workbench.tree.indent": 16,
  "workbench.tree.renderIndentGuides": "none",
  "workbench.editor.closeOnFileDelete": true,
  "workbench.editor.tabSizing": "shrink",
  "workbench.editor.alwaysShowEditorActions": true,
  "workbench.editor.enablePreview": false,
  "workbench.editor.empty.hint": "hidden",
  "workbench.activityBar.location": "top",
  "workbench.layoutControl.enabled": false,
  "workbench.colorTheme": "Manic Pale Night",
  "workbench.colorCustomizations": {
    "editorRuler.foreground": "#0000",
    "scrollbar.shadow": "#0000"
  },
  "workbench.iconTheme": "glyph.legacy",
  "workbench.productIconTheme": "icons-carbon",
  // Source Control
  "git.branchProtectionPrompt": "alwaysCommit",
  "git.openRepositoryInParentFolders": "never",
  "git.suggestSmartCommit": false,
  "git.showActionButton": {
    "commit": true,
    "publish": false,
    "sync": false
  },
  "scm.defaultViewMode": "tree",
  // Extensions
  "extensions.ignoreRecommendations": true,
  "inlineChat.lineNaturalLanguageHint": false,
  "svg.preview.mode": "svg",
  "vue.codeLens.enabled": false,
  "vue.updateImportsOnFileMove.enabled": false,
  "git-graph.commitDetailsView.fileView.type": "File Tree",
  "stylelint.validate": [
    "css",
    "postcss",
    "vue"
  ]
}

But I think you're only interested in:

{
  "workbench.colorCustomizations": {
    "editorRuler.foreground": "#0000",
    "scrollbar.shadow": "#0000"
  },
}

Theme is a custom one of mine (Manic Theme). However, the same thing occured with Default Dark Modern while I was running code --disable-extensions.

https://github.com/user-attachments/assets/06f55f19-da28-46d5-a7cc-ea42dd2989af

[benibenj]

I can confirm. It is mainly noticeable when clicking on the active tab. I believe this is because the tab gets focus for a couple of ms and we have to render the bottom focus border differently

[Pesseto]

Hello @benibenj, I’ve reproduced the bug on my end and would like to work on it if no one else is currently assigned. Thanks, and have a great day!