diff --git a/meshterm/services/monitor_service.py b/meshterm/services/monitor_service.py
index 88bae1e..d7c353c 100644
--- a/meshterm/services/monitor_service.py
+++ b/meshterm/services/monitor_service.py
@@ -80,6 +80,9 @@ class MonitorService:
         # "total" is this plus what we capture this session (this process is the only
         # writer during an interactive session), avoiding a DB count on every repaint.
         self._start_total = ctx.repo.observation_count()
+        # The minute this session began: buckets at or after it hold live traffic,
+        # older ones the seeded history — the boundary the activity charts colour by.
+        self._start_bucket = int(time.time() // ACTIVITY_BUCKET_S)
         self._seed_from_history()
 
     def _seed_from_history(self) -> None:
@@ -131,6 +134,20 @@ class MonitorService:
         bucket = int(time.time() // ACTIVITY_BUCKET_S)
         return tuple(self._activity.get(bucket - i, 0) for i in range(ACTIVITY_BUCKETS))
 
+    def activity_session_flags(self) -> tuple[bool, ...]:
+        """Whether each histogram bucket holds this session's own traffic.
+
+        Aligned with :meth:`activity_histogram` (newest first): ``True`` for buckets
+        at or after the session's first minute, ``False`` for the seeded history —
+        the split the activity charts use to draw live traffic green and a previous
+        session's grey.
+
+        Returns:
+            :data:`ACTIVITY_BUCKETS` flags, newest first.
+        """
+        bucket = int(time.time() // ACTIVITY_BUCKET_S)
+        return tuple(bucket - i >= self._start_bucket for i in range(ACTIVITY_BUCKETS))
+
     def kind_counts(self) -> dict[str, int]:
         """Tallies by packet class: advert/telemetry/packet, message, ack.
 
diff --git a/meshterm/ui/braillechart.py b/meshterm/ui/braillechart.py
index bddc081..f6c2e96 100644
--- a/meshterm/ui/braillechart.py
+++ b/meshterm/ui/braillechart.py
@@ -85,6 +85,7 @@ def timeline_rows(
     span: Optional[tuple[float, float]] = None,
     style: CellStyle = "ok",
     baseline_style: str = "faint",
+    column_styles: Optional[Sequence[str]] = None,
 ) -> list[Text]:
     """Render a chronological series as a braille bar chart, newest at the right.
 
@@ -103,6 +104,10 @@ def timeline_rows(
         style: Style for lit cells: a Rich style name, or a callable given each
             cell's present readings (for per-slice colouring).
         baseline_style: Style for the zero line where nothing covers it.
+        column_styles: Optional per-column styles, aligned with ``values``,
+            overriding ``style`` — how the activity charts dim history recorded by
+            an earlier session. A cell straddling two styles takes its newer
+            (right) lit column's.
 
     Returns:
         ``rows`` :class:`Text` lines, top row first, ``ceil(len(values)/2)``
@@ -124,7 +129,7 @@ def timeline_rows(
         else:
             height = max(1, round(value / lo * down))
             bars.append((base - height + 1, base))
-    return _assemble(bars, list(values), rows, base, style, baseline_style)
+    return _assemble(bars, list(values), rows, base, style, baseline_style, column_styles)
 
 
 def activity_sparkline(
@@ -133,6 +138,7 @@ def activity_sparkline(
     buckets: int,
     *,
     style: str = "ok",
+    column_styles: Optional[Sequence[str]] = None,
 ) -> Text:
     """A one-row activity sparkline over a newest-first histogram, "now" rightmost.
 
@@ -148,16 +154,25 @@ def activity_sparkline(
         levels: Ascending count thresholds for bar heights 1..4.
         buckets: How many buckets to draw (half this many characters).
         style: Style for lit cells.
+        column_styles: Optional per-bucket styles aligned with ``histogram``
+            (newest first, reversed here alongside it), overriding ``style`` —
+            how the header pulse dims buckets recorded by an earlier session.
 
     Returns:
         A styled Rich :class:`Text` of ``buckets / 2`` braille characters.
     """
     window = (tuple(histogram) + (0,) * buckets)[:buckets]
+    per_column: Optional[list[str]] = None
+    if column_styles is not None:
+        padded = (list(column_styles) + [style] * buckets)[:buckets]
+        per_column = list(reversed(padded))
     bars: list[Optional[tuple[int, int]]] = []
     for count in reversed(window):
         height = bisect_right(levels, count)
         bars.append((0, height - 1) if height else None)
-    return _assemble(bars, [float(c) for c in reversed(window)], 1, 0, style, "faint")[0]
+    return _assemble(
+        bars, [float(c) for c in reversed(window)], 1, 0, style, "faint", per_column
+    )[0]
 
 
 #: The meter's fill glyphs, ``(full step, half step)``, by profile. A *full-height*
@@ -323,6 +338,7 @@ def _assemble(
     base: int,
     style: CellStyle,
     baseline_style: str,
+    column_styles: Optional[Sequence[str]] = None,
 ) -> list[Text]:
     """Assemble bar spans into styled braille rows (the shared cell walk).
 
@@ -339,6 +355,9 @@ def _assemble(
         base: The zero baseline's dot row.
         style: Fixed style, or per-cell callable (see :data:`CellStyle`).
         baseline_style: Style for baseline-only cells.
+        column_styles: Per-column style overrides aligned with ``bars``; a cell
+            takes its right column's style when that column is lit, else its
+            left's (the newer reading wins the shared cell).
 
     Returns:
         ``rows`` :class:`Text` lines, top row first.
@@ -357,7 +376,9 @@ def _assemble(
             right = _column_bits(bars[i + 1], floor, _RIGHT_BITS)
             if left or right:
                 mask = left | right | base_bit_left | base_bit_right
-                if callable(style):
+                if column_styles is not None and i + 1 < len(column_styles):
+                    cell_style = column_styles[i + 1] if right else column_styles[i]
+                elif callable(style):
                     present = [v for v in values[i : i + 2] if v is not None]
                     cell_style = style(present) if present else baseline_style
                 else:
diff --git a/meshterm/ui/menu.py b/meshterm/ui/menu.py
index 5ee9903..1aa9ea6 100644
--- a/meshterm/ui/menu.py
+++ b/meshterm/ui/menu.py
@@ -155,9 +155,17 @@ def _header(ctx: AppContext, cache: dict, width: int) -> Text:
     # Two dot columns per cell: every cell left of the row's edge shows two minutes.
     room = width - header.cell_len
     if room > 0:
+        # Buckets seeded from a previous session's stored history draw grey; only
+        # traffic this session actually heard pulses green.
+        styles = [
+            "ok" if live else "muted" for live in ctx.monitor.activity_session_flags()
+        ]
         header.append_text(
             activity_sparkline(
-                ctx.monitor.activity_histogram(), _HEADER_ACTIVITY_LEVELS, room * 2
+                ctx.monitor.activity_histogram(),
+                _HEADER_ACTIVITY_LEVELS,
+                room * 2,
+                column_styles=styles,
             )
         )
     return header
diff --git a/tests/test_header.py b/tests/test_header.py
index f37c8b2..567cb53 100644
--- a/tests/test_header.py
+++ b/tests/test_header.py
@@ -12,7 +12,10 @@ def _ctx(histogram=(), unread=0, alerts=0) -> SimpleNamespace:
     return SimpleNamespace(
         mock=True,
         chat=SimpleNamespace(unread_total=lambda: unread),
-        monitor=SimpleNamespace(activity_histogram=lambda: tuple(histogram)),
+        monitor=SimpleNamespace(
+            activity_histogram=lambda: tuple(histogram),
+            activity_session_flags=lambda: (True,) * len(tuple(histogram)),
+        ),
         watchtower=SimpleNamespace(unacked_count=lambda: alerts),
     )