diff --git a/src/atm/calibrate.py b/src/atm/calibrate.py
index a1cd115..13530ac 100644
--- a/src/atm/calibrate.py
+++ b/src/atm/calibrate.py
@@ -158,16 +158,19 @@ def _image_looks_blank(pil_img, dark_thresh: int = 10) -> bool:
 def _capture_fullscreen_region():
     """Grab the entire virtual desktop and let the user drag a rectangle.
 
-    Returns a cropped PIL RGB Image. The underlying desktop-snapshot is taken
-    BEFORE the Tk overlay opens, so what the user sees = what gets saved.
+    Returns (cropped PIL RGB Image, (origin_x, origin_y, width, height)) in
+    virtual-desktop coordinates. Runtime capture crops the same region.
     """
     import mss  # type: ignore[import-untyped]
     import tkinter as tk
     from PIL import Image, ImageTk
 
     with mss.mss() as sct:
-        shot = sct.grab(sct.monitors[0])  # virtual screen (all monitors)
+        virt = sct.monitors[0]  # virtual screen (all monitors combined)
+        shot = sct.grab(virt)
     full_img = Image.frombytes("RGB", shot.size, shot.rgb)
+    virt_left = int(virt["left"])
+    virt_top = int(virt["top"])
 
     root = tk.Tk()
     root.title("Select chart region")
@@ -203,6 +206,7 @@ def _capture_fullscreen_region():
     result: dict = {"img": None}
 
     def on_press(e):
+        state["started"] = True
         state["x0"], state["y0"] = e.x, e.y
         state["x1"], state["y1"] = e.x, e.y
         if state["rect_id"] is not None:
@@ -217,7 +221,7 @@ def _capture_fullscreen_region():
             canvas.coords(state["rect_id"], state["x0"], state["y0"], e.x, e.y)
 
     def on_ok(_=None):
-        if state["x0"] is None:
+        if not state["started"]:
             return
         x0 = int(min(state["x0"], state["x1"]) / scale)
         y0 = int(min(state["y0"], state["y1"]) / scale)
@@ -226,6 +230,8 @@ def _capture_fullscreen_region():
         if x1 - x0 < 100 or y1 - y0 < 100:
             return  # too small, ignore
         result["img"] = full_img.crop((x0, y0, x1, y1))
+        # Convert back to virtual-desktop absolute coordinates.
+        result["region"] = (virt_left + x0, virt_top + y0, x1 - x0, y1 - y0)
         root.destroy()
 
     def on_cancel(_=None):
@@ -242,7 +248,7 @@ def _capture_fullscreen_region():
     root.mainloop()
     if result["img"] is None:
         raise ValueError("Region selection cancelled")
-    return result["img"]
+    return result["img"], result["region"]
 
 
 def _capture_window(title_substr: str):
@@ -375,6 +381,7 @@ def run_calibration(out_dir: Path, screenshot: Path | None = None) -> Path:
     # 1. Acquire image + window title
     # ------------------------------------------------------------------
     pil_img: "Image.Image"
+    chart_region: tuple[int, int, int, int] | None = None
     if screenshot is not None:
         pil_img = Image.open(screenshot).convert("RGB")
         root0 = tk.Tk(); root0.withdraw()
@@ -398,9 +405,10 @@ def run_calibration(out_dir: Path, screenshot: Path | None = None) -> Path:
             raise ValueError("Window title is required to proceed.")
 
         # Default: region-select on full desktop (reliable with GPU-rendered apps).
-        # Fallback: try window capture if region-select is cancelled.
+        # Returns (cropped image, virtual-desktop region) so runtime capture can
+        # re-crop the same area without needing pygetwindow to find the chart.
         try:
-            pil_img = _capture_fullscreen_region()
+            pil_img, chart_region = _capture_fullscreen_region()
         except ValueError:
             pil_img = _capture_window(window_title)
 
@@ -433,6 +441,10 @@ def run_calibration(out_dir: Path, screenshot: Path | None = None) -> Path:
     }
     data.setdefault("options", {})
 
+    if chart_region is not None:
+        cx, cy, cw, ch = chart_region
+        data["chart_window_region"] = {"x": cx, "y": cy, "w": cw, "h": ch}
+
     return write_config(data, configs_dir)
 
 
diff --git a/src/atm/config.py b/src/atm/config.py
index bc40c19..3c1856b 100644
--- a/src/atm/config.py
+++ b/src/atm/config.py
@@ -94,6 +94,7 @@ class Config:
     canary: CanaryRegion
     discord: DiscordCfg
     telegram: TelegramCfg
+    chart_window_region: ROI | None = None  # virtual-desktop absolute region; when set, runtime uses full-desktop capture + crop
     debounce_depth: int = 1
     loop_interval_s: float = 5.0
     heartbeat_min: int = 30
@@ -149,6 +150,9 @@ class Config:
             chat_id=str(data["telegram"]["chat_id"]),
         )
         opts = data.get("options", {})
+        region = None
+        if "chart_window_region" in data:
+            region = ROI(**data["chart_window_region"])
         return cls(
             window_title=data["window_title"],
             dot_roi=roi,
@@ -158,6 +162,7 @@ class Config:
             canary=canary,
             discord=discord,
             telegram=telegram,
+            chart_window_region=region,
             debounce_depth=int(opts.get("debounce_depth", 1)),
             loop_interval_s=float(opts.get("loop_interval_s", 5.0)),
             heartbeat_min=int(opts.get("heartbeat_min", 30)),
diff --git a/src/atm/main.py b/src/atm/main.py
index 248412d..d74d611 100644
--- a/src/atm/main.py
+++ b/src/atm/main.py
@@ -277,17 +277,37 @@ def _build_capture(cfg, capture_stub: bool = False):
 
         return _stub_capture
 
-    # Windows live path
+    # Live path — prefer region-based capture if calibrate saved one
     try:
         import mss  # type: ignore[import-untyped]
-        import pygetwindow as gw  # type: ignore[import-untyped]
     except ImportError as exc:
         sys.exit(
-            f"Live screen capture requires 'mss' and 'pygetwindow' (Windows only). "
+            f"Live screen capture requires 'mss' (Windows). "
             f"Use --capture-stub or set ATM_STUB_CAPTURE=1 for testing on Linux. "
             f"Missing: {exc}"
         )
 
+    if cfg.chart_window_region is not None:
+        reg = cfg.chart_window_region
+
+        def _region_capture():
+            with mss.mss() as sct:
+                import cv2  # type: ignore[import-untyped]
+                import numpy as np
+                mon = {"top": reg.y, "left": reg.x, "width": reg.w, "height": reg.h}
+                img = sct.grab(mon)
+                frame = np.array(img)
+                return cv2.cvtColor(frame, cv2.COLOR_BGRA2BGR)
+
+        return _region_capture
+
+    # Legacy: window-title lookup via pygetwindow (unreliable for GPU-rendered apps;
+    # kept as fallback when calibrate was run without region-select).
+    try:
+        import pygetwindow as gw  # type: ignore[import-untyped]
+    except ImportError as exc:
+        sys.exit(f"Fallback window capture needs pygetwindow: {exc}")
+
     def _live_capture():
         wins = gw.getWindowsWithTitle(cfg.window_title)
         if not wins:
@@ -297,10 +317,8 @@ def _build_capture(cfg, capture_stub: bool = False):
             import cv2  # type: ignore[import-untyped]
             import numpy as np
             mon = {
-                "top": win.top,
-                "left": win.left,
-                "width": win.width,
-                "height": win.height,
+                "top": win.top, "left": win.left,
+                "width": win.width, "height": win.height,
             }
             img = sct.grab(mon)
             frame = np.array(img)