Several desktop copy entry points still called navigator.clipboard directly, which can fail or report success inconsistently in Tauri and browser test contexts. Route those copy actions through the existing textarea execCommand fallback helper and cover the fallback paths for startup diagnostics, markdown copy controls, and workspace file paths.
Constraint: Clipboard API is not reliable in every desktop/browser context.
Rejected: Leave direct navigator.clipboard calls in isolated components | repeats the diagnostics copy failure mode and creates inconsistent copy behavior.
Confidence: high
Scope-risk: narrow
Directive: New desktop copy controls should use copyTextToClipboard or CopyButton instead of calling navigator.clipboard directly.
Tested: cd desktop && bun run lint
Tested: cd desktop && bun run test -- --run src/components/markdown/MarkdownRenderer.test.tsx src/components/layout/StartupErrorView.test.tsx src/components/workspace/WorkspacePanel.test.tsx src/__tests__/diagnosticsSettings.test.tsx src/components/chat/MessageList.test.tsx
Tested: bun run check:desktop
Tested: bun run check:native
Tested: bun run check:coverage
Tested: bun run verify (passed=7 failed=0 skipped=3)
Not-tested: Live provider baseline; not required for this desktop-only clipboard fix.
