diff --git a/src/client/controllers/BuildPreviewController.ts b/src/client/controllers/BuildPreviewController.ts
index ea9338e93..3a9de6cdb 100644
--- a/src/client/controllers/BuildPreviewController.ts
+++ b/src/client/controllers/BuildPreviewController.ts
@@ -163,18 +163,13 @@ export class BuildPreviewController implements Controller {
       }
     }
 
-    // targetingAlly is computed above for state purposes; the renderer's
-    // ghost passes derive their own "warning" visual from canBuild/canUpgrade
-    // if needed. (Leave the variable here so its eslint-no-unused doesn't trip.)
-    void targetingAlly;
-
     this.game
       ?.myPlayer()
       ?.buildables(tileRef, [this.ghostUnit?.buildableUnit.type])
       .then((buildables) => {
         if (!this.ghostUnit) {
           this.pendingConfirm = null;
-          this.emitGhostPreview(tileRef);
+          this.emitGhostPreview(tileRef, targetingAlly);
           return;
         }
 
@@ -187,7 +182,7 @@ export class BuildPreviewController implements Controller {
             canUpgrade: false,
           });
           this.pendingConfirm = null;
-          this.emitGhostPreview(tileRef);
+          this.emitGhostPreview(tileRef, targetingAlly);
           return;
         }
 
@@ -201,7 +196,7 @@ export class BuildPreviewController implements Controller {
           }
         }
 
-        this.emitGhostPreview(tileRef);
+        this.emitGhostPreview(tileRef, targetingAlly);
       });
   }
 
@@ -211,8 +206,11 @@ export class BuildPreviewController implements Controller {
    * the ghost can't be placed. smoothLoop interpolates displayed position
    * toward the target tile each frame.
    */
-  private emitGhostPreview(tileRef: TileRef | undefined): void {
-    const data = this.buildGhostPreviewData(tileRef);
+  private emitGhostPreview(
+    tileRef: TileRef | undefined,
+    targetingAlly: boolean,
+  ): void {
+    const data = this.buildGhostPreviewData(tileRef, targetingAlly);
     if (data === null) {
       this.lastGhostData = null;
       this.view.updateGhostPreview(null);
@@ -302,6 +300,7 @@ export class BuildPreviewController implements Controller {
 
   private buildGhostPreviewData(
     tileRef: TileRef | undefined,
+    targetingAlly: boolean,
   ): GhostPreviewData | null {
     if (!this.ghostUnit) return null;
     if (tileRef === undefined) return null;
@@ -352,6 +351,7 @@ export class BuildPreviewController implements Controller {
       ownerID: myPlayer.smallID(),
       upgradeTargetTile,
       rangeRadius,
+      rangeWarning: targetingAlly,
     };
   }
 
diff --git a/src/client/render/gl/passes/RangeCirclePass.ts b/src/client/render/gl/passes/RangeCirclePass.ts
index 5fb38e805..304f81630 100644
--- a/src/client/render/gl/passes/RangeCirclePass.ts
+++ b/src/client/render/gl/passes/RangeCirclePass.ts
@@ -1,6 +1,7 @@
 /**
- * RangeCirclePass — draws a translucent white circle showing the effective
- * range of a structure during build-mode ghost preview.
+ * RangeCirclePass — draws a translucent circle showing the effective
+ * range of a structure during build-mode ghost preview. White by default,
+ * red when the ghost flags a warning (e.g. nuking would break an alliance).
  *
  * Single quad with circle SDF in the fragment shader.
  * Active only when a ghost preview with rangeRadius > 0 is set.
@@ -20,10 +21,12 @@ export class RangeCirclePass {
   private uCamera: WebGLUniformLocation;
   private uCenter: WebGLUniformLocation;
   private uRadius: WebGLUniformLocation;
+  private uColor: WebGLUniformLocation;
 
   private centerX = 0;
   private centerY = 0;
   private radius = 0;
+  private warning = false;
 
   constructor(gl: WebGL2RenderingContext) {
     this.gl = gl;
@@ -32,6 +35,7 @@ export class RangeCirclePass {
     this.uCamera = gl.getUniformLocation(this.program, "uCamera")!;
     this.uCenter = gl.getUniformLocation(this.program, "uCenter")!;
     this.uRadius = gl.getUniformLocation(this.program, "uRadius")!;
+    this.uColor = gl.getUniformLocation(this.program, "uColor")!;
 
     // Unit quad [0,1]
     this.vao = gl.createVertexArray()!;
@@ -53,8 +57,10 @@ export class RangeCirclePass {
       this.centerX = data.tileX;
       this.centerY = data.tileY;
       this.radius = data.rangeRadius;
+      this.warning = data.rangeWarning;
     } else {
       this.radius = 0;
+      this.warning = false;
     }
   }
 
@@ -66,6 +72,11 @@ export class RangeCirclePass {
     gl.uniformMatrix3fv(this.uCamera, false, cameraMatrix);
     gl.uniform2f(this.uCenter, this.centerX, this.centerY);
     gl.uniform1f(this.uRadius, this.radius);
+    if (this.warning) {
+      gl.uniform3f(this.uColor, 1.0, 0.2, 0.2);
+    } else {
+      gl.uniform3f(this.uColor, 1.0, 1.0, 1.0);
+    }
 
     gl.bindVertexArray(this.vao);
     gl.drawArrays(gl.TRIANGLES, 0, 6);
diff --git a/src/client/render/gl/shaders/range-circle/range-circle.frag.glsl b/src/client/render/gl/shaders/range-circle/range-circle.frag.glsl
index 62744ab37..7c89c77d8 100644
--- a/src/client/render/gl/shaders/range-circle/range-circle.frag.glsl
+++ b/src/client/render/gl/shaders/range-circle/range-circle.frag.glsl
@@ -4,6 +4,7 @@ precision highp float;
 in vec2 vLocal; // [-1, +1]
 
 uniform float uRadius;
+uniform vec3 uColor;
 
 out vec4 fragColor;
 
@@ -23,5 +24,5 @@ void main() {
   float alpha = fill * 0.2 + stroke * 0.5;
   if (alpha < 0.001) discard;
 
-  fragColor = vec4(1.0, 1.0, 1.0, alpha);
+  fragColor = vec4(uColor, alpha);
 }
diff --git a/src/client/render/types/Renderer.ts b/src/client/render/types/Renderer.ts
index 26fb67383..652a5e338 100644
--- a/src/client/render/types/Renderer.ts
+++ b/src/client/render/types/Renderer.ts
@@ -166,6 +166,8 @@ export interface GhostPreviewData {
   upgradeTargetTile: number | null;
   /** Range radius in tiles for the placement circle (0 = no circle). */
   rangeRadius: number;
+  /** True if placing here would carry a penalty (e.g. nuking an ally → traitor). */
+  rangeWarning: boolean;
 }
 
 /** Nuke trajectory preview data — Bezier control points + color thresholds. */