diff --git a/README.md b/README.md
index 29d0bfb..6f3278e 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,7 @@
 
 ### Planned Features
 
+- **Support for custom harnesses** — bring your own agent runtime, not just Claude Code and Codex
 - **Full encapsulation hardening** — for worker and CI environments, ensuring complete sandboxing of file system, network, and credentials
 - **ACP integration** via [`dirigate`](https://github.com/dirigence/dirigate) — Agent Communication Protocol support for structured agent orchestration
 
diff --git a/config-layers.svg b/config-layers.svg
index bca6c06..0a31510 100644
--- a/config-layers.svg
+++ b/config-layers.svg
@@ -2,28 +2,28 @@
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     .title { font-size: 15px; font-weight: 600; fill: #24292f; }
-    .layer-label { font-size: 13px; font-weight: 600; fill: #ffffff; }
-    .layer-desc { font-size: 11px; fill: #ffffff; opacity: 0.9; }
+    .layer-label { font-size: 13px; font-weight: 600; }
+    .layer-desc { font-size: 11px; }
     .side-label { font-size: 11px; fill: #57606a; }
     .side-detail { font-size: 10px; fill: #8b949e; }
     .arrow-text { font-size: 11px; fill: #57606a; font-weight: 500; }
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-      <stop offset="0%" stop-color="#c9d1d9"/>
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+      <stop offset="0%" stop-color="#e8ecf0"/>
+      <stop offset="100%" stop-color="#dce1e6"/>
     </linearGradient>
     <linearGradient id="grad2" x1="0" y1="0" x2="1" y2="0">
-      <stop offset="0%" stop-color="#8b949e"/>
-      <stop offset="100%" stop-color="#6e7681"/>
+      <stop offset="0%" stop-color="#a8b2bc"/>
+      <stop offset="100%" stop-color="#94a0ab"/>
     </linearGradient>
     <linearGradient id="grad3" x1="0" y1="0" x2="1" y2="0">
-      <stop offset="0%" stop-color="#D4A574"/>
-      <stop offset="100%" stop-color="#c0895a"/>
+      <stop offset="0%" stop-color="#e8c9a4"/>
+      <stop offset="100%" stop-color="#d4b08a"/>
     </linearGradient>
     <linearGradient id="grad3b" x1="0" y1="0" x2="1" y2="0">
-      <stop offset="0%" stop-color="#b87d4a"/>
-      <stop offset="100%" stop-color="#a06838"/>
+      <stop offset="0%" stop-color="#c9995c"/>
+      <stop offset="100%" stop-color="#b58548"/>
     </linearGradient>
     <linearGradient id="grad4" x1="0" y1="0" x2="1" y2="0">
       <stop offset="0%" stop-color="#8a5c2a"/>
@@ -34,48 +34,51 @@
     </marker>
   </defs>
 
+  <!-- Background panel -->
+  <rect x="10" y="10" width="780" height="400" rx="10" fill="#f6f8fa" stroke="#d0d7de" stroke-width="1"/>
+
   <!-- Title -->
-  <text class="title" x="400" y="30" text-anchor="middle">Configuration Layering</text>
+  <text class="title" x="400" y="35" text-anchor="middle">Configuration Layering</text>
 
   <!-- Priority arrow on the left -->
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   <text class="layer-label" x="390" y="335" text-anchor="middle" fill="#24292f">Compiled Defaults</text>
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-  <text class="layer-label" x="410" y="270" text-anchor="middle">Global Config</text>
-  <text class="layer-desc" x="410" y="288" text-anchor="middle">~/.sandcage/config.toml</text>
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+  <text class="layer-label" x="410" y="270" text-anchor="middle" fill="#ffffff">Global Config</text>
+  <text class="layer-desc" x="410" y="288" text-anchor="middle" fill="#f0f0f0">~/.sandcage/config.toml</text>
   <text class="side-label" x="700" y="270">User-wide</text>
   <text class="side-detail" x="700" y="286">SSH, shell, mounts</text>
 
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