diff --git a/HyperDRM.manifest.json b/HyperDRM.manifest.json
index 29a926a..239de8a 100644
--- a/HyperDRM.manifest.json
+++ b/HyperDRM.manifest.json
@@ -1,15 +1,15 @@
 {
   "id": "org.webosbrew.histogramhyperion",
-  "version": "0.13.2",
+  "version": "0.13.3",
   "type": "web",
   "title": "HyperDRM",
   "appDescription": "Ambient lighting for webOS, Hyperion and HyperHDR",
   "iconUri": "https://gitea.adnau.de/matze19999/HyperDRM/raw/branch/main/app/icon.png",
   "sourceUrl": "https://gitea.adnau.de/matze19999/HyperDRM",
   "rootRequired": true,
-  "ipkUrl": "https://gitea.adnau.de/matze19999/HyperDRM/raw/branch/main/HyperDRM_0.13.2_arm.ipk",
+  "ipkUrl": "https://gitea.adnau.de/matze19999/HyperDRM/raw/branch/main/HyperDRM_0.13.3_arm.ipk",
   "ipkHash": {
-    "sha256": "d83eed088b5a1cc8a90d96bc781359db219aa50f51218e3ae3c2ef52510f6ed7"
+    "sha256": "acb0978100796e8765e586a91183599ef4eb783631d8b68205d716621790e232"
   },
-  "ipkSize": 1207844
+  "ipkSize": 1208120
 }
diff --git a/HyperDRM_0.13.2_arm.ipk b/HyperDRM_0.13.3_arm.ipk
similarity index 92%
rename from HyperDRM_0.13.2_arm.ipk
rename to HyperDRM_0.13.3_arm.ipk
index 7df99f9..25035b7 100644
Binary files a/HyperDRM_0.13.2_arm.ipk and b/HyperDRM_0.13.3_arm.ipk differ
diff --git a/README.md b/README.md
index c6187d6..faeb85f 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,7 @@ Only the own service is modified. Optional Auto PicCap can configure its receive
 
 ## Installation
 
-The current package is [HyperDRM_0.13.2_arm.ipk](HyperDRM_0.13.2_arm.ipk). Install it using the TV's webOS/Homebrew package installation workflow.
+The current package is [HyperDRM_0.13.3_arm.ipk](HyperDRM_0.13.3_arm.ipk). Install it using the TV's webOS/Homebrew package installation workflow.
 
 Elevate the installed own service through Homebrew Channel:
 
@@ -235,3 +235,5 @@ receiver-output and simulated service-lifecycle tests with ASan/UBSan. These hos
 tests do not replace real LG capture and remote-control validation on a TV.
 
 Histogram near-black handling suppresses colors with a maximum RGB channel of 16 or less, gradually restores brightness between 16 and 32, and preserves brighter colors. This applies only to histogram output; PicCap, receiver calibration and raw calibration samples are unchanged.
+
+Thin letterbox detection compares both edges against lit interior histogram samples and requires a consistently dark upper edge for at least two seconds. Histogram probes cannot determine the exact bar height or guarantee detection on every scene.
diff --git a/VERSION b/VERSION
index 9beb74d..288adf5 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.13.2
+0.13.3
diff --git a/app/appinfo.json b/app/appinfo.json
index e8a6f14..1134cc0 100644
--- a/app/appinfo.json
+++ b/app/appinfo.json
@@ -1,6 +1,6 @@
 {
   "id": "org.webosbrew.histogramhyperion",
-  "version": "0.13.2",
+  "version": "0.13.3",
   "vendor": "Local development",
   "type": "web",
   "main": "index.html",
diff --git a/app/version.js b/app/version.js
index fd9640d..82a0b94 100644
--- a/app/version.js
+++ b/app/version.js
@@ -1,2 +1,2 @@
 'use strict';
-var HYPERDRM_APP_VERSION = '0.13.2';
+var HYPERDRM_APP_VERSION = '0.13.3';
diff --git a/docs/release-0.13.3.md b/docs/release-0.13.3.md
new file mode 100644
index 0000000..e543e62
--- /dev/null
+++ b/docs/release-0.13.3.md
@@ -0,0 +1,3 @@
+# HyperDRM 0.13.3
+
+Detect thinner horizontal black bars using edge-versus-interior contrast, distributed upper-edge support and lower-edge support. Preserve the existing dark-scene rejection, wide-bar rule and two-second stability gate. Regression tests include live G4 measurements, one-sided and isolated dark edges, dim frames and insufficient contrast. This is a histogram heuristic; it does not measure exact bar heights.
diff --git a/native/blackbars.h b/native/blackbars.h
index dee18c3..86a6bbd 100644
--- a/native/blackbars.h
+++ b/native/blackbars.h
@@ -4,14 +4,17 @@
  * or dark frame so darkness alone cannot switch the active capture mode. */
 static inline int letterbox_candidate(const unsigned black[16], const unsigned char color[16][3]) {
     const unsigned interior[] = {2, 6, 10, 15};
-    unsigned lit = 0;
+    unsigned lit = 0, interior_black = 0, interior_peak = 0;
     for (unsigned i = 0; i < 4; i++) {
         unsigned r = interior[i], peak = color[r][0];
         for (unsigned c = 1; c < 3; c++)
             if (color[r][c] > peak)
                 peak = color[r][c];
-        if (black[r] < 20 && peak > 35)
+        if (black[r] < 20 && peak > 35) {
             lit++;
+            interior_black += black[r];
+            interior_peak += peak;
+        }
     }
     if (lit < 2)
         return -1;
@@ -19,6 +22,26 @@ static inline int letterbox_candidate(const unsigned black[16], const unsigned c
     unsigned bottom = (black[1] + black[5] + black[9]) / 3;
     if (top >= 55 && bottom >= 25)
         return 1;
+    /* Thin bars occupy only part of an edge probe. Require a broad upper
+     * dark edge, lower-edge support and contrast against lit interior probes.
+     * This remains a histogram heuristic, not a pixel-accurate crop. */
+    const unsigned top_regions[] = {3, 11, 12};
+    const unsigned bottom_regions[] = {1, 5, 9};
+    unsigned top_support = 0, bottom_support = 0, top_peak = 0;
+    for (unsigned i = 0; i < 3; i++) {
+        unsigned r = top_regions[i], peak = color[r][0];
+        for (unsigned c = 1; c < 3; c++)
+            if (color[r][c] > peak)
+                peak = color[r][c];
+        top_peak += peak;
+        top_support += black[r] >= 12;
+        bottom_support += black[bottom_regions[i]] >= 8;
+    }
+    unsigned baseline = interior_black / lit;
+    if (top_support == 3 && bottom_support >= 2 && top >= 12 && bottom >= 10 &&
+        top >= baseline + 8 && bottom >= baseline + 8 &&
+        (unsigned long)top_peak * lit * 100 <= (unsigned long)interior_peak * 3 * 60)
+        return 1;
     if (top < 20 && bottom < 20)
         return 0;
     return -1;
diff --git a/native/test_blackbars.c b/native/test_blackbars.c
index 8373d0d..a510adb 100644
--- a/native/test_blackbars.c
+++ b/native/test_blackbars.c
@@ -11,5 +11,22 @@ int main(void){
  for(unsigned i=0;i<16;i++)black[i]=100;
  memset(color,0,sizeof(color));assert(letterbox_candidate(black,color)==-1);
  memset(black,0,sizeof(black));assert(letterbox_candidate(black,color)==-1);
- puts("PASS: full frame, measured letterbox, one edge only, black frame, dark frame");
+ unsigned thin_black[16]={12,23,1,21,9,6,6,16,18,12,26,23,23,22,37,8};
+ unsigned char thin_color[16][3]={{57,52,48},{97,94,92},{51,42,35},{25,24,21},
+ {71,65,60},{128,122,118},{84,74,67},{34,32,27},{47,41,36},{59,47,43},
+ {37,29,25},{19,18,15},{22,20,16},{22,19,15},{14,13,11},{78,75,72}};
+ assert(letterbox_candidate(thin_black,thin_color)==1);
+ thin_black[1]=thin_black[5]=thin_black[9]=0;
+ assert(letterbox_candidate(thin_black,thin_color)!=1);
+ thin_black[1]=23;thin_black[5]=6;thin_black[9]=12;
+ thin_black[11]=0;
+ assert(letterbox_candidate(thin_black,thin_color)!=1);
+ thin_black[11]=23;
+ memset(thin_color,10,sizeof(thin_color));
+ assert(letterbox_candidate(thin_black,thin_color)==-1);
+ memset(thin_color,100,sizeof(thin_color));
+ assert(letterbox_candidate(thin_black,thin_color)!=1);
+ memset(thin_black,15,sizeof(thin_black));
+ assert(letterbox_candidate(thin_black,thin_color)!=1);
+ puts("PASS: measured wide/thin bars, full frame, one-sided/isolated edges, dark frame and low contrast");
 }
diff --git a/native/version.h b/native/version.h
index 1263c46..606126d 100644
--- a/native/version.h
+++ b/native/version.h
@@ -1,4 +1,4 @@
 #ifndef HYPERDRM_VERSION_H
 #define HYPERDRM_VERSION_H
-#define HYPERDRM_VERSION "0.13.2"
+#define HYPERDRM_VERSION "0.13.3"
 #endif
diff --git a/package/packageinfo.json b/package/packageinfo.json
index b8bf389..cd94e1b 100644
--- a/package/packageinfo.json
+++ b/package/packageinfo.json
@@ -1,6 +1,6 @@
 {
   "id": "org.webosbrew.histogramhyperion",
-  "version": "0.13.2",
+  "version": "0.13.3",
   "vendor": "Local development",
   "app": "org.webosbrew.histogramhyperion",
   "services": [
diff --git a/service/histogram-service b/service/histogram-service
index 3a0fa27..64658f9 100644
Binary files a/service/histogram-service and b/service/histogram-service differ