Fix inline header/footer border color when falling back to line

InitTheme was called before the runtime coerced BorderInline to
BorderLine, so HeaderBorder / FooterBorder inherited from ListBorder
even when the effective shape was 'line'. Mirror the coercion so
color inheritance matches the rendered shape.

src/terminal.go

@@ -1167,10 +1167,14 @@ func NewTerminal(opts *Options, eventBox *util.EventBox, executor *util.Executor
 	if baseTheme == nil {
 		baseTheme = renderer.DefaultTheme()
 	}
-	// This should be called before accessing tui.Color*
+	// If the list border can't host an inline separator, the runtime later coerces
-	headerInline := opts.HeaderBorderShape == tui.BorderInline || opts.HeaderLinesShape == tui.BorderInline
+	// BorderInline to BorderLine. Mirror that here so theme color inheritance matches
-	footerInline := opts.FooterBorderShape == tui.BorderInline
+	// the final rendering rather than the user's requested shape.
+	inlineListSupported := opts.ListBorderShape.HasTop() && opts.ListBorderShape.HasBottom()
+	headerInline := inlineListSupported && (opts.HeaderBorderShape == tui.BorderInline || opts.HeaderLinesShape == tui.BorderInline)
+	footerInline := inlineListSupported && opts.FooterBorderShape == tui.BorderInline
 	hasHeader := opts.HeaderBorderShape.Visible() || opts.HeaderLinesShape.Visible()
+	// This should be called before accessing tui.Color*
 	tui.InitTheme(opts.Theme, baseTheme, opts.Bold, opts.Black, opts.InputBorderShape.Visible(), hasHeader, headerInline, footerInline)
 
 	// Gutter character

test/lib/common.rb

@@ -130,6 +130,11 @@ class Tmux
     go(%W[capture-pane -p -J -t #{win}]).map(&:rstrip).reverse.drop_while(&:empty?).reverse
   end
 
+  # Raw pane capture with ANSI escape sequences preserved.
+  def capture_ansi
+    go(%W[capture-pane -p -J -e -t #{win}])
+  end
+
   # 3-bit ANSI bg code (40..47) -> color name used in --color options.
   BG_NAMES = %w[black red green yellow blue magenta cyan white].freeze
 

test/test_layout.rb

@@ -1466,6 +1466,31 @@ class TestLayout < TestInteractive
     tmux.send_keys 'Escape'
   end
 
+  # Regression: when --header-border=inline falls back to `line` because the
+  # list border can't host an inline separator, the header-border color must
+  # inherit from `border`, not `list-border`. The effective shape is `line`,
+  # so color inheritance must match what `line` rendering would use.
+  def test_inline_fallback_does_not_inherit_list_border_color
+    # Marker attribute (bold) on list-border. If HeaderBorder wrongly inherits
+    # from ListBorder, the header separator characters will carry the bold
+    # attribute. --info=hidden and --no-separator strip other separator lines
+    # so the only row of `─` chars is the header separator.
+    tmux.send_keys %(seq 5 | #{FZF} --list-border=none --header HEADER --header-border=inline --info=hidden --no-separator --color=bg:-1,list-border:red:bold), :Enter
+    sep_row = nil
+    tmux.until do |_|
+      sep_row = tmux.capture_ansi.find do |row|
+        stripped = row.gsub(/\e\[[\d;]*m/, '').rstrip
+        stripped.match?(/\A─+\z/)
+      end
+      !sep_row.nil?
+    end
+    # Bold (1) or red fg (31) on the header separator means it inherited from
+    # list-border even though the effective shape is `line` (non-inline).
+    refute_match(/\e\[(?:[\d;]*;)?(?:1|31)(?:;[\d;]*)?m─/, sep_row,
+                 "header separator inherited list-border attr: #{sep_row.inspect}")
+    tmux.send_keys 'Escape'
+  end
+
   # Invalid inline combinations must be rejected at startup.
   def test_inline_rejected_on_unsupported_options
     [