diff --git a/src/tui.zig b/src/tui.zig
index 48e50c2..8e595f1 100644
--- a/src/tui.zig
+++ b/src/tui.zig
@@ -152,6 +152,96 @@ pub const StyledLine = struct {
     cell_styles: ?[]const vaxis.Style = null,
 };
 
+/// Pre-resolved row in the help overlay: a key string (possibly
+/// comma-joined for multiple bindings) plus its label. Used by
+/// `buildHelpLines` so the renderer is a pure function over already-
+/// resolved data and doesn't need access to the keymap or tab modules.
+pub const HelpRow = struct {
+    keys: []const u8,
+    label: []const u8,
+};
+
+/// One `key label` fragment of the dynamic status-hint line. Used by
+/// `formatStatusHint` to compose the full hint as ` | `-joined fragments.
+pub const StatusHintFragment = struct {
+    key: []const u8,
+    label: []const u8,
+};
+
+/// Format the dynamic default status hint from pre-resolved key /
+/// label fragments. Each fragment renders as `key label`; fragments
+/// are joined with ` | `. Pure function — no App access.
+pub fn formatStatusHint(
+    arena: std.mem.Allocator,
+    fragments: []const StatusHintFragment,
+) ![]const u8 {
+    if (fragments.len == 0) return "";
+    var pieces: std.ArrayListUnmanaged([]const u8) = .empty;
+    for (fragments) |f| {
+        try pieces.append(arena, try std.fmt.allocPrint(arena, "{s} {s}", .{ f.key, f.label }));
+    }
+    return std.mem.join(arena, " | ", pieces.items);
+}
+
+/// Pre-resolved data passed to `buildHelpLines`. Comprises the
+/// global section's rows, the active tab section's rows, and the
+/// active tab's display name (without the registry-position prefix).
+pub const HelpData = struct {
+    globals: []const HelpRow,
+    tab_rows: []const HelpRow,
+    active_tab_name: []const u8,
+};
+
+/// Render the help overlay's styled lines from pre-resolved data.
+/// Pure function — no App access, no keymap lookup. Easy to test
+/// with fixture rows.
+pub fn buildHelpLines(
+    arena: std.mem.Allocator,
+    th: theme.Theme,
+    data: HelpData,
+) ![]const StyledLine {
+    var lines: std.ArrayListUnmanaged(StyledLine) = .empty;
+
+    try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
+    try lines.append(arena, .{ .text = "  zfin TUI -- Keybindings", .style = th.headerStyle() });
+    try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
+
+    try lines.append(arena, .{ .text = "  Global", .style = th.headerStyle() });
+    for (data.globals) |row| {
+        try lines.append(arena, .{
+            .text = try std.fmt.allocPrint(arena, "    {s:<20}  {s}", .{ row.keys, row.label }),
+            .style = th.contentStyle(),
+        });
+    }
+
+    try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
+    try lines.append(arena, .{
+        .text = try std.fmt.allocPrint(arena, "  Active Tab: {s}", .{data.active_tab_name}),
+        .style = th.headerStyle(),
+    });
+    if (data.tab_rows.len == 0) {
+        try lines.append(arena, .{
+            .text = "    (no tab-local actions)",
+            .style = th.mutedStyle(),
+        });
+    } else {
+        for (data.tab_rows) |row| {
+            try lines.append(arena, .{
+                .text = try std.fmt.allocPrint(arena, "    {s:<20}  {s}", .{ row.keys, row.label }),
+                .style = th.contentStyle(),
+            });
+        }
+    }
+
+    try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
+    try lines.append(arena, .{ .text = "  Mouse: click tabs, scroll wheel, click rows", .style = th.mutedStyle() });
+    try lines.append(arena, .{ .text = "  Config: ~/.config/zfin/keys.srf | theme.srf", .style = th.mutedStyle() });
+    try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
+    try lines.append(arena, .{ .text = "  Press any key to close.", .style = th.dimStyle() });
+
+    return lines.toOwnedSlice(arena);
+}
+
 // ── Tab-specific types ───────────────────────────────────────────
 // These logically belong to individual tab files, but live here because
 // App's struct fields reference them and Zig requires field types to be
@@ -1623,7 +1713,7 @@ pub const App = struct {
     /// the active tab's `status_hints` actions resolved against its
     /// current bindings. Each fragment is `key label`.
     fn buildDefaultStatusHint(self: *App, arena: std.mem.Allocator) ![]const u8 {
-        var fragments: std.ArrayList([]const u8) = .empty;
+        var fragments: std.ArrayListUnmanaged(StatusHintFragment) = .empty;
 
         // Always-shown globals. Each fragment uses the FIRST bound
         // key for the action; full lists go to the help overlay.
@@ -1639,11 +1729,7 @@ pub const App = struct {
         for (globals) |g| {
             const keys = try self.keysForGlobal(arena, g.action);
             if (keys.len == 0) continue;
-            try fragments.append(arena, try std.fmt.allocPrint(
-                arena,
-                "{s} {s}",
-                .{ keys[0], g.label },
-            ));
+            try fragments.append(arena, .{ .key = keys[0], .label = g.label });
         }
 
         // Active tab's status_hints — comptime walk to get the right
@@ -1657,16 +1743,12 @@ pub const App = struct {
                     if (keys.len == 0) continue;
                     const label = Module.tab.action_labels.get(hint_action);
                     if (label.len == 0) continue;
-                    try fragments.append(arena, try std.fmt.allocPrint(
-                        arena,
-                        "{s} {s}",
-                        .{ keys[0], label },
-                    ));
+                    try fragments.append(arena, .{ .key = keys[0], .label = label });
                 }
             }
         }
 
-        return std.mem.join(arena, " | ", fragments.items);
+        return formatStatusHint(arena, fragments.items);
     }
 
     pub fn freePortfolioSummary(self: *App) void {
@@ -1973,78 +2055,57 @@ pub const App = struct {
     // ── Help ─────────────────────────────────────────────────────
 
     fn buildHelpStyledLines(self: *App, arena: std.mem.Allocator) ![]const StyledLine {
-        const th = self.theme;
-        var lines: std.ArrayList(StyledLine) = .empty;
-
-        try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
-        try lines.append(arena, .{ .text = "  zfin TUI -- Keybindings", .style = th.headerStyle() });
-        try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
-
-        // ── GLOBAL section ─────────────────────────────────────
-        try lines.append(arena, .{ .text = "  Global", .style = th.headerStyle() });
-
+        // Resolve the help-overlay data upfront (key strings + labels)
+        // so the renderer is a pure function over the pre-resolved data.
+        // Active-tab section requires a comptime walk to dispatch on
+        // `self.active_tab`'s local Action enum; the data we collect
+        // is type-erased to `[]const HelpRow`.
+        var globals: std.ArrayListUnmanaged(HelpRow) = .empty;
         const global_actions = comptime std.enums.values(keybinds.Action);
         for (global_actions) |action| {
             const keys = try self.keysForGlobal(arena, action);
             if (keys.len == 0) continue;
-            const keys_str = try std.mem.join(arena, ", ", keys);
-            const label = keybinds.action_labels.get(action);
-            try lines.append(arena, .{
-                .text = try std.fmt.allocPrint(arena, "    {s:<20}  {s}", .{ keys_str, label }),
-                .style = th.contentStyle(),
+            try globals.append(arena, .{
+                .keys = try std.mem.join(arena, ", ", keys),
+                .label = keybinds.action_labels.get(action),
             });
         }
 
-        // ── ACTIVE TAB section ─────────────────────────────────
-        try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
-        const active_label = tabLabel(self.active_tab);
-        // tabLabel returns " {N}:{Name} " with surrounding spaces;
-        // trim for the header.
-        const trimmed_label = std.mem.trim(u8, active_label, " ");
-        const without_number = trimmed_label[std.mem.findScalar(u8, trimmed_label, ':').? + 1 ..];
-        try lines.append(arena, .{
-            .text = try std.fmt.allocPrint(arena, "  Active Tab: {s}", .{without_number}),
-            .style = th.headerStyle(),
-        });
-
-        // Comptime walk to dispatch to the active tab's Action enum.
+        var tab_rows: std.ArrayListUnmanaged(HelpRow) = .empty;
         inline for (std.meta.fields(@TypeOf(tab_modules))) |field| {
             if (std.mem.eql(u8, field.name, @tagName(self.active_tab))) {
                 const Module = @field(tab_modules, field.name);
                 const tab_actions = comptime std.enums.values(Module.Action);
-                if (tab_actions.len == 0) {
-                    try lines.append(arena, .{
-                        .text = "    (no tab-local actions)",
-                        .style = th.mutedStyle(),
-                    });
-                } else {
-                    inline for (tab_actions) |action| {
-                        const action_name = @tagName(action);
-                        const label = Module.tab.action_labels.get(action);
-                        // Skip empty labels (placeholder tabs).
-                        if (label.len > 0) {
-                            const keys = try self.keysForTabAction(arena, field.name, action_name);
-                            const keys_str = if (keys.len == 0)
-                                try arena.dupe(u8, "(unbound)")
-                            else
-                                try std.mem.join(arena, ", ", keys);
-                            try lines.append(arena, .{
-                                .text = try std.fmt.allocPrint(arena, "    {s:<20}  {s}", .{ keys_str, label }),
-                                .style = th.contentStyle(),
-                            });
-                        }
+                inline for (tab_actions) |action| {
+                    const action_name = @tagName(action);
+                    const label = Module.tab.action_labels.get(action);
+                    if (label.len > 0) {
+                        const keys = try self.keysForTabAction(arena, field.name, action_name);
+                        const keys_str = if (keys.len == 0)
+                            try arena.dupe(u8, "(unbound)")
+                        else
+                            try std.mem.join(arena, ", ", keys);
+                        try tab_rows.append(arena, .{
+                            .keys = keys_str,
+                            .label = label,
+                        });
                     }
                 }
             }
         }
 
-        try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
-        try lines.append(arena, .{ .text = "  Mouse: click tabs, scroll wheel, click rows", .style = th.mutedStyle() });
-        try lines.append(arena, .{ .text = "  Config: ~/.config/zfin/keys.srf | theme.srf", .style = th.mutedStyle() });
-        try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
-        try lines.append(arena, .{ .text = "  Press any key to close.", .style = th.dimStyle() });
+        // Active tab name (without the registry-position prefix) for
+        // the section header.
+        const active_tab_label = tabLabel(self.active_tab);
+        const trimmed = std.mem.trim(u8, active_tab_label, " ");
+        const colon_pos = std.mem.indexOfScalar(u8, trimmed, ':') orelse 0;
+        const active_tab_name = if (colon_pos > 0) trimmed[colon_pos + 1 ..] else trimmed;
 
-        return lines.toOwnedSlice(arena);
+        return buildHelpLines(arena, self.theme, .{
+            .globals = globals.items,
+            .tab_rows = tab_rows.items,
+            .active_tab_name = active_tab_name,
+        });
     }
 
     // ── Tab navigation ───────────────────────────────────────────
@@ -2529,3 +2590,129 @@ test "Tab label" {
     try testing.expectEqualStrings(" 1:Portfolio ", tabLabel(.portfolio));
     try testing.expectEqualStrings(" 6:Analysis ", tabLabel(.analysis));
 }
+
+test "buildHelpLines: header, global section, active-tab section, footer" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+
+    const data: HelpData = .{
+        .globals = &.{
+            .{ .keys = "q, ctrl+c", .label = "Quit" },
+            .{ .keys = "j", .label = "Select next" },
+        },
+        .tab_rows = &.{
+            .{ .keys = "enter", .label = "Expand position" },
+            .{ .keys = "s, space", .label = "Select symbol" },
+        },
+        .active_tab_name = "Portfolio",
+    };
+
+    const lines = try buildHelpLines(arena, theme.default_theme, data);
+
+    var all: std.ArrayListUnmanaged(u8) = .empty;
+    for (lines) |l| {
+        try all.appendSlice(arena, l.text);
+        try all.append(arena, '\n');
+    }
+    const text = all.items;
+
+    // Title + section headers.
+    try testing.expect(std.mem.indexOf(u8, text, "zfin TUI -- Keybindings") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "  Global") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "  Active Tab: Portfolio") != null);
+
+    // Global rows.
+    try testing.expect(std.mem.indexOf(u8, text, "q, ctrl+c") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "Quit") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "Select next") != null);
+
+    // Tab rows.
+    try testing.expect(std.mem.indexOf(u8, text, "Expand position") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "s, space") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "Select symbol") != null);
+
+    // Footer.
+    try testing.expect(std.mem.indexOf(u8, text, "Mouse: click tabs") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "~/.config/zfin/keys.srf") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "Press any key to close") != null);
+}
+
+test "buildHelpLines: empty tab_rows shows '(no tab-local actions)'" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+
+    const data: HelpData = .{
+        .globals = &.{.{ .keys = "q", .label = "Quit" }},
+        .tab_rows = &.{},
+        .active_tab_name = "Earnings",
+    };
+
+    const lines = try buildHelpLines(arena, theme.default_theme, data);
+    var all: std.ArrayListUnmanaged(u8) = .empty;
+    for (lines) |l| {
+        try all.appendSlice(arena, l.text);
+        try all.append(arena, '\n');
+    }
+    const text = all.items;
+
+    try testing.expect(std.mem.indexOf(u8, text, "Active Tab: Earnings") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "(no tab-local actions)") != null);
+}
+
+test "buildHelpLines: empty globals still renders title and section headers" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+
+    const data: HelpData = .{
+        .globals = &.{},
+        .tab_rows = &.{.{ .keys = "x", .label = "Do thing" }},
+        .active_tab_name = "Quote",
+    };
+
+    const lines = try buildHelpLines(arena, theme.default_theme, data);
+    var all: std.ArrayListUnmanaged(u8) = .empty;
+    for (lines) |l| {
+        try all.appendSlice(arena, l.text);
+        try all.append(arena, '\n');
+    }
+    const text = all.items;
+
+    try testing.expect(std.mem.indexOf(u8, text, "  Global") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "Active Tab: Quote") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "Do thing") != null);
+}
+
+test "formatStatusHint: joins fragments with ' | '" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+
+    const fragments = [_]StatusHintFragment{
+        .{ .key = "h", .label = "tabs" },
+        .{ .key = "j", .label = "select" },
+        .{ .key = "/", .label = "symbol" },
+        .{ .key = "?", .label = "help" },
+    };
+    const out = try formatStatusHint(arena, &fragments);
+    try testing.expectEqualStrings("h tabs | j select | / symbol | ? help", out);
+}
+
+test "formatStatusHint: empty fragments returns empty string" {
+    const out = try formatStatusHint(testing.allocator, &.{});
+    try testing.expectEqualStrings("", out);
+}
+
+test "formatStatusHint: single fragment has no separator" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+
+    const fragments = [_]StatusHintFragment{
+        .{ .key = "ctrl+s", .label = "save" },
+    };
+    const out = try formatStatusHint(arena, &fragments);
+    try testing.expectEqualStrings("ctrl+s save", out);
+}
diff --git a/src/tui/history_tab.zig b/src/tui/history_tab.zig
index 92c7ca7..4b57306 100644
--- a/src/tui/history_tab.zig
+++ b/src/tui/history_tab.zig
@@ -497,14 +497,63 @@ fn setSelectionStatus(state: *const State, app: *App) void {
     defer arena_state.deinit();
     const arena = arena_state.allocator();
     const c_keys = app.keysForTabAction(arena, "history", "compare_commit") catch return;
-    const c_key = c_keys[0];
     var buf: [128]u8 = undefined;
-    const msg = switch (n) {
-        1 => std.fmt.bufPrint(&buf, "Selected 1 row — select one more + press '{s}' to compare", .{c_key}) catch return,
-        2 => std.fmt.bufPrint(&buf, "Selected 2 rows — press '{s}' to compare", .{c_key}) catch return,
+    const msg = formatSelectionStatus(&buf, n, c_keys[0]) catch return;
+    app.setStatus(msg);
+}
+
+/// Format the selection-count status message. Pure function over
+/// (count, commit_key). Returns a slice of `buf`.
+pub fn formatSelectionStatus(buf: []u8, count: usize, commit_key: []const u8) std.fmt.BufPrintError![]const u8 {
+    return switch (count) {
+        1 => std.fmt.bufPrint(buf, "Selected 1 row — select one more + press '{s}' to compare", .{commit_key}),
+        2 => std.fmt.bufPrint(buf, "Selected 2 rows — press '{s}' to compare", .{commit_key}),
         else => unreachable,
     };
-    app.setStatus(msg);
+}
+
+/// Format the "select N rows" status hint shown by `commitCompare`
+/// when the user presses commit with too few rows selected. Pure
+/// function over (count, select_key, commit_key).
+pub fn formatCompareNeedMore(buf: []u8, count: usize, select_key: []const u8, commit_key: []const u8) std.fmt.BufPrintError![]const u8 {
+    return if (count == 0)
+        std.fmt.bufPrint(buf, "Select two rows with '{s}' (or space), then press '{s}' to compare", .{ select_key, commit_key })
+    else
+        std.fmt.bufPrint(buf, "Select one more row with '{s}' (or space), then press '{s}' to compare", .{ select_key, commit_key });
+}
+
+/// Format the "Comparing — ... to return" status set when a
+/// compare view becomes active. Pure function over the two keys.
+pub fn formatCompareActiveStatus(buf: []u8, cancel_key: []const u8, commit_key: []const u8) std.fmt.BufPrintError![]const u8 {
+    return std.fmt.bufPrint(buf, "Comparing — {s} or '{s}' to return to timeline", .{ cancel_key, commit_key });
+}
+
+/// Format the parenthetical key hint shown in the recent-snapshots
+/// table header. Pure function over the resolved keys; allocates
+/// in `arena`.
+pub fn formatTableHeaderHint(
+    arena: std.mem.Allocator,
+    j_key: []const u8,
+    k_key: []const u8,
+    enter_key: []const u8,
+    select_key: []const u8,
+    commit_key: []const u8,
+) ![]const u8 {
+    return std.fmt.allocPrint(
+        arena,
+        "({s}/{s}: move, {s}: expand/collapse, {s}/space: select, {s}: compare)",
+        .{ j_key, k_key, enter_key, select_key, commit_key },
+    );
+}
+
+/// Format the footer hint shown at the bottom of an active compare
+/// view. Pure function; allocates in `arena`.
+pub fn formatCompareFooterHint(
+    arena: std.mem.Allocator,
+    cancel_key: []const u8,
+    commit_key: []const u8,
+) ![]const u8 {
+    return std.fmt.allocPrint(arena, "  {s} or '{s}' to return to timeline", .{ cancel_key, commit_key });
 }
 
 // ── Compare commit ───────────────────────────────────────────
@@ -519,13 +568,8 @@ fn commitCompare(state: *State, app: *App) void {
         const arena = arena_state.allocator();
         const s_keys = app.keysForTabAction(arena, "history", "compare_select") catch return;
         const c_keys = app.keysForTabAction(arena, "history", "compare_commit") catch return;
-        const s_key = s_keys[0];
-        const c_key = c_keys[0];
         var buf: [192]u8 = undefined;
-        const msg = if (sel_count == 0)
-            std.fmt.bufPrint(&buf, "Select two rows with '{s}' (or space), then press '{s}' to compare", .{ s_key, c_key }) catch return
-        else
-            std.fmt.bufPrint(&buf, "Select one more row with '{s}' (or space), then press '{s}' to compare", .{ s_key, c_key }) catch return;
+        const msg = formatCompareNeedMore(&buf, sel_count, s_keys[0], c_keys[0]) catch return;
         app.setStatus(msg);
         return;
     }
@@ -684,7 +728,7 @@ fn buildCompareFromSelections(state: *State, app: *App, sel_a: usize, sel_b: usi
     const cancel_keys = try app.keysForTabAction(arena, "history", "compare_cancel");
     const commit_keys = try app.keysForTabAction(arena, "history", "compare_commit");
     var status_buf: [128]u8 = undefined;
-    const msg = std.fmt.bufPrint(&status_buf, "Comparing — {s} or '{s}' to return to timeline", .{ cancel_keys[0], commit_keys[0] }) catch "Comparing — return to timeline";
+    const msg = formatCompareActiveStatus(&status_buf, cancel_keys[0], commit_keys[0]) catch "Comparing — return to timeline";
     app.setStatus(msg);
 }
 
@@ -1059,7 +1103,7 @@ pub fn buildStyledLines(state: *State, app: *App, arena: std.mem.Allocator) ![]c
         // cursor state remains sensible if the user exits back.
         const cancel_keys = try app.keysForTabAction(arena, "history", "compare_cancel");
         const commit_keys = try app.keysForTabAction(arena, "history", "compare_commit");
-        const footer = try std.fmt.allocPrint(arena, "  {s} or '{s}' to return to timeline", .{ cancel_keys[0], commit_keys[0] });
+        const footer = try formatCompareFooterHint(arena, cancel_keys[0], commit_keys[0]);
         return renderCompareLines(arena, app.theme, cv, footer);
     }
 
@@ -1071,10 +1115,13 @@ pub fn buildStyledLines(state: *State, app: *App, arena: std.mem.Allocator) ![]c
     const commit_keys = try app.keysForTabAction(arena, "history", "compare_commit");
     const j_keys = try app.keysForGlobal(arena, .select_next);
     const k_keys = try app.keysForGlobal(arena, .select_prev);
-    const table_hint = try std.fmt.allocPrint(
+    const table_hint = try formatTableHeaderHint(
         arena,
-        "({s}/{s}: move, {s}: expand/collapse, {s}/space: select, {s}: compare)",
-        .{ j_keys[0], k_keys[0], enter_keys[0], select_keys[0], commit_keys[0] },
+        j_keys[0],
+        k_keys[0],
+        enter_keys[0],
+        select_keys[0],
+        commit_keys[0],
     );
     const result = try renderHistoryLinesFull(
         arena,
@@ -1591,6 +1638,60 @@ const testing = std.testing;
 const Date = zfin.Date;
 const snapshot = @import("../models/snapshot.zig");
 
+test "formatSelectionStatus: count 1 includes commit key" {
+    var buf: [128]u8 = undefined;
+    const msg = try formatSelectionStatus(&buf, 1, "c");
+    try testing.expectEqualStrings("Selected 1 row — select one more + press 'c' to compare", msg);
+}
+
+test "formatSelectionStatus: count 2 includes commit key" {
+    var buf: [128]u8 = undefined;
+    const msg = try formatSelectionStatus(&buf, 2, "X");
+    try testing.expectEqualStrings("Selected 2 rows — press 'X' to compare", msg);
+}
+
+test "formatCompareNeedMore: count 0 says 'two rows'" {
+    var buf: [192]u8 = undefined;
+    const msg = try formatCompareNeedMore(&buf, 0, "s", "c");
+    try testing.expectEqualStrings("Select two rows with 's' (or space), then press 'c' to compare", msg);
+}
+
+test "formatCompareNeedMore: count 1 says 'one more row'" {
+    var buf: [192]u8 = undefined;
+    const msg = try formatCompareNeedMore(&buf, 1, "x", "y");
+    try testing.expectEqualStrings("Select one more row with 'x' (or space), then press 'y' to compare", msg);
+}
+
+test "formatCompareActiveStatus: includes both keys" {
+    var buf: [128]u8 = undefined;
+    const msg = try formatCompareActiveStatus(&buf, "Esc", "c");
+    try testing.expectEqualStrings("Comparing — Esc or 'c' to return to timeline", msg);
+}
+
+test "formatTableHeaderHint: includes all five keys" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+    const msg = try formatTableHeaderHint(arena, "j", "k", "enter", "s", "c");
+    try testing.expectEqualStrings("(j/k: move, enter: expand/collapse, s/space: select, c: compare)", msg);
+}
+
+test "formatTableHeaderHint: respects rebound keys" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+    const msg = try formatTableHeaderHint(arena, "down", "up", "space", "x", "y");
+    try testing.expectEqualStrings("(down/up: move, space: expand/collapse, x/space: select, y: compare)", msg);
+}
+
+test "formatCompareFooterHint: standard format" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+    const msg = try formatCompareFooterHint(arena, "Esc", "c");
+    try testing.expectEqualStrings("  Esc or 'c' to return to timeline", msg);
+}
+
 test "renderHistoryLines: no series shows no-data message" {
     var arena = std.heap.ArenaAllocator.init(testing.allocator);
     defer arena.deinit();
diff --git a/src/tui/options_tab.zig b/src/tui/options_tab.zig
index 6fac9d9..079370a 100644
--- a/src/tui/options_tab.zig
+++ b/src/tui/options_tab.zig
@@ -428,6 +428,25 @@ fn toggleAllCallsPuts(state: *State, app: *App, is_calls: bool) void {
     }
 }
 
+/// Format the underlying-price header line shown above the option
+/// chains. Pure function over the price, expiration count, current
+/// NTM filter, and the resolved filter_1 / filter_9 key strings;
+/// allocates in `arena`.
+pub fn formatUnderlyingHeader(
+    arena: std.mem.Allocator,
+    price: f64,
+    expiration_count: usize,
+    near_the_money: usize,
+    filter_1_key: []const u8,
+    filter_9_key: []const u8,
+) ![]const u8 {
+    return std.fmt.allocPrint(
+        arena,
+        "  Underlying: {f}    {d} expiration(s)    +/- {d} strikes NTM ({s}..{s} to change)",
+        .{ Money.from(price), expiration_count, near_the_money, filter_1_key, filter_9_key },
+    );
+}
+
 // ── Rendering ─────────────────────────────────────────────────
 
 pub fn buildStyledLines(app: *App, arena: std.mem.Allocator) ![]const StyledLine {
@@ -469,7 +488,8 @@ pub fn buildStyledLines(app: *App, arena: std.mem.Allocator) ![]const StyledLine
         // user-rebound keymap shows the actual range.
         const f1_keys = try app.keysForTabAction(arena, "options", "filter_1");
         const f9_keys = try app.keysForTabAction(arena, "options", "filter_9");
-        try lines.append(arena, .{ .text = try std.fmt.allocPrint(arena, "  Underlying: {f}    {d} expiration(s)    +/- {d} strikes NTM ({s}..{s} to change)", .{ Money.from(price), chains.len, state.near_the_money, f1_keys[0], f9_keys[0] }), .style = th.contentStyle() });
+        const text = try formatUnderlyingHeader(arena, price, chains.len, state.near_the_money, f1_keys[0], f9_keys[0]);
+        try lines.append(arena, .{ .text = text, .style = th.contentStyle() });
     }
 
     try lines.append(arena, .{ .text = "", .style = th.contentStyle() });
@@ -541,3 +561,26 @@ pub fn buildStyledLines(app: *App, arena: std.mem.Allocator) ![]const StyledLine
 
     return lines.toOwnedSlice(arena);
 }
+
+// ── Tests ─────────────────────────────────────────────────────
+
+const testing = std.testing;
+
+test "formatUnderlyingHeader: includes price, expirations, NTM, and key range" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+    const text = try formatUnderlyingHeader(arena, 175.42, 7, 5, "ctrl+1", "ctrl+9");
+    try testing.expect(std.mem.indexOf(u8, text, "$175.42") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "7 expiration(s)") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "+/- 5 strikes NTM") != null);
+    try testing.expect(std.mem.indexOf(u8, text, "(ctrl+1..ctrl+9 to change)") != null);
+}
+
+test "formatUnderlyingHeader: respects rebound keys" {
+    var arena_state = std.heap.ArenaAllocator.init(testing.allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+    const text = try formatUnderlyingHeader(arena, 100.0, 3, 1, "F1", "F9");
+    try testing.expect(std.mem.indexOf(u8, text, "(F1..F9 to change)") != null);
+}
diff --git a/src/tui/projections_tab.zig b/src/tui/projections_tab.zig
index 7f775f7..59111cf 100644
--- a/src/tui/projections_tab.zig
+++ b/src/tui/projections_tab.zig
@@ -193,7 +193,7 @@ pub const tab = struct {
                     const arena = arena_state.allocator();
                     const d_keys = app.keysForTabAction(arena, "projections", "as_of_input") catch return;
                     var buf: [128]u8 = undefined;
-                    const msg = std.fmt.bufPrint(&buf, "Overlay only available with --as-of (press {s} to set)", .{d_keys[0]}) catch return;
+                    const msg = formatOverlayUnavailable(&buf, d_keys[0]) catch return;
                     app.setStatus(msg);
                     return;
                 }
@@ -252,6 +252,13 @@ pub const tab = struct {
     }
 };
 
+/// Format the "overlay unavailable" status hint shown when the user
+/// presses the overlay-toggle key while no as-of date is set. Pure
+/// function over the as-of-input key string.
+pub fn formatOverlayUnavailable(buf: []u8, as_of_input_key: []const u8) std.fmt.BufPrintError![]const u8 {
+    return std.fmt.bufPrint(buf, "Overlay only available with --as-of (press {s} to set)", .{as_of_input_key});
+}
+
 // ── Data loading ──────────────────────────────────────────────
 
 pub fn loadData(state: *State, app: *App) void {
@@ -1442,3 +1449,19 @@ fn appendReturnRow(
         .style = style,
     });
 }
+
+// ── Tests ─────────────────────────────────────────────────────
+
+const testing = std.testing;
+
+test "formatOverlayUnavailable: includes resolved as-of-input key" {
+    var buf: [128]u8 = undefined;
+    const msg = try formatOverlayUnavailable(&buf, "d");
+    try testing.expectEqualStrings("Overlay only available with --as-of (press d to set)", msg);
+}
+
+test "formatOverlayUnavailable: respects rebound as-of-input key" {
+    var buf: [128]u8 = undefined;
+    const msg = try formatOverlayUnavailable(&buf, "ctrl+d");
+    try testing.expectEqualStrings("Overlay only available with --as-of (press ctrl+d to set)", msg);
+}