diff --git a/ChangeLog b/ChangeLog
index 53b6bbbeb..3d43dfbd3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,25 @@
+2025-11-09  G. Branden Robinson <g.branden.robinson@gmail.com>
+
+	* src/libs/libgroff/color.cpp (color::get_rgb, color::get_cmy)
+	(color::get_cmyk, color::get_gray):
+	* src/preproc/eqn/pile.cpp (pile_box::output)
+	(matrix_box::output, column::debug_print)
+	* src/preproc/eqn/common.cpp (common_output::rounded_box):
+	* src/preproc/pic/lex.cpp (get_delimited):
+	* src/preproc/pic/object.cpp (object_spec::position_rectangle)
+	(object_spec::make_move, object_spec::make_line)
+	(object_spec::make_object):
+	* src/preproc/pic/tex.cpp (tex_output::spline)
+	(tex_output::circle, tex_output::ellipse):
+	* src/preproc/pic/troff.cpp (simple_output::line)
+	(simple_output::ellipse, simple_output::circle):
+	* src/preproc/refer/command.cpp (check_args):
+	* src/preproc/refer/label.ypp (format_serial)
+	(extractor_expr::evaluate):
+	* src/utils/hpftodit/hpftodit.cpp (main):
+	* src/utils/lkbib/lkbib.cpp (main): Replace `assert(0)` calls
+	with communicative predicates.
+
 2025-11-09  G. Branden Robinson <g.branden.robinson@gmail.com>
 
 	* src/preproc/pic/lex.cpp (get_delimited): Drop `switch` case
diff --git a/src/libs/libgroff/color.cpp b/src/libs/libgroff/color.cpp
index 0a8c9a946..2f8ba830a 100644
--- a/src/libs/libgroff/color.cpp
+++ b/src/libs/libgroff/color.cpp
@@ -249,7 +249,7 @@ color::get_rgb(unsigned int *r, unsigned int *g, unsigned int *b) const
     *r = *g = *b = Gray;
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of color scheme");
     break;
   }
 }
@@ -280,7 +280,7 @@ color::get_cmy(unsigned int *c, unsigned int *m, unsigned int *y) const
     *c = *m = *y = MAX_COLOR_VAL - Gray;
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of color scheme");
     break;
   }
 }
@@ -330,7 +330,7 @@ void color::get_cmyk(unsigned int *c, unsigned int *m,
     *k = MAX_COLOR_VAL - Gray;
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of color scheme");
     break;
   }
 }
@@ -355,7 +355,7 @@ void color::get_gray(unsigned int *g) const
     *g = Gray;
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of color scheme");
     break;
   }
 }
diff --git a/src/preproc/eqn/pile.cpp b/src/preproc/eqn/pile.cpp
index 30203231d..515646337 100644
--- a/src/preproc/eqn/pile.cpp
+++ b/src/preproc/eqn/pile.cpp
@@ -79,7 +79,7 @@ void pile_box::output()
 	       uid, col.p[i]->uid);
 	break;
       default:
-	assert(0);
+	assert(0 == "unhandled case of column alignment");
       }
       col.p[i]->output();
       printf("\\h'-\\n[" WIDTH_FORMAT "]u'", col.p[i]->uid);
@@ -95,7 +95,7 @@ void pile_box::output()
 	       col.p[i]->uid, uid);
 	break;
       default:
-	assert(0);
+	assert(0 == "unhandled case of column alignment");
       }
       if (i != col.len - 1)
 	printf("\\v'\\n[" BASELINE_SEP_FORMAT "]u'", uid);
@@ -117,7 +117,7 @@ void pile_box::output()
       av = "center";
       break;
     default:
-      assert(0);
+      assert(0 == "unhandled case of column alignment");
     }
     printf("<mtable columnalign='%s'>", av);
     for (int i = 0; i < col.len; i++) {
@@ -216,7 +216,7 @@ void matrix_box::output()
 		 uid, i, p[i]->p[j]->uid);
 	  break;
 	default:
-	  assert(0);
+	  assert(0 == "unhandled case of column alignment");
 	}
 	p[i]->p[j]->output();
 	printf("\\h'-\\n[" WIDTH_FORMAT "]u'", p[i]->p[j]->uid);
@@ -232,7 +232,7 @@ void matrix_box::output()
 		 p[i]->p[j]->uid, uid, i);
 	  break;
 	default:
-	  assert(0);
+	  assert(0 == "unhandled case of column alignment");
 	}
 	if (j != p[i]->len - 1)
 	  printf("\\v'\\n[" BASELINE_SEP_FORMAT "]u'", uid);
@@ -263,7 +263,7 @@ void matrix_box::output()
 	  av = "center";
 	  break;
 	default:
-	  assert(0);
+	  assert(0 == "unhandled case of column alignment");
 	}
 	printf("<mtd columnalign='%s'>", av);
 	p[j]->p[i]->output();
@@ -349,7 +349,7 @@ void column::debug_print(const char *s)
     c = 'c';
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of column alignment");
   }
   fprintf(stderr, "%c%s %d { ", c, s, space);
   list_debug_print(" above ");
diff --git a/src/preproc/pic/common.cpp b/src/preproc/pic/common.cpp
index e61df9323..bc434288e 100644
--- a/src/preproc/pic/common.cpp
+++ b/src/preproc/pic/common.cpp
@@ -342,7 +342,7 @@ void common_output::rounded_box(const position &cent, const distance &dim,
     solid_rounded_box(cent, dim, rad, lt);
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of line type");
   }
 }
 
diff --git a/src/preproc/pic/lex.cpp b/src/preproc/pic/lex.cpp
index 623634927..56e0a5376 100644
--- a/src/preproc/pic/lex.cpp
+++ b/src/preproc/pic/lex.cpp
@@ -1392,7 +1392,7 @@ int get_delimited()
 	state = IN_STRING_QUOTED;
       break;
     default:
-      assert(0);
+      assert(0 == "unhandled case of lexical analyzer state");
     }
     if (state == DELIM_END)
       break;
diff --git a/src/preproc/pic/object.cpp b/src/preproc/pic/object.cpp
index a8e079be0..35a22d3ca 100644
--- a/src/preproc/pic/object.cpp
+++ b/src/preproc/pic/object.cpp
@@ -902,7 +902,7 @@ int object_spec::position_rectangle(rectangle_object *p,
     motion.x = p->width()/2.0;
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of motion direction");
   }
   if (flags & HAS_AT) {
     pos = at;
@@ -1205,7 +1205,7 @@ graphic_object *object_spec::make_move(position *curpos, direction *dirp)
 	segment_pos.x = segment_width;
 	break;
       default:
-	assert(0);
+	assert(0 == "unhandled case of motion direction");
       }
     }
   }
@@ -1567,7 +1567,7 @@ linear_object *object_spec::make_line(position *curpos, direction *dirp)
 	segment_pos.x = segment_width;
 	break;
       default:
-	assert(0);
+	assert(0 == "unhandled case of motion direction");
       }
   }
   segment_list = new segment(segment_pos, segment_is_absolute, segment_list);
@@ -1693,7 +1693,7 @@ linear_object *object_spec::make_line(position *curpos, direction *dirp)
     p->set_vertex_number(vertex_number);
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of picture object type");
   }
   have_last_line = 1;
   last_line = endpos - startpos;
@@ -2045,7 +2045,7 @@ object *object_spec::make_object(position *curpos, direction *dirp)
   case MARK_OBJECT:
   case OTHER_OBJECT:
   default:
-    assert(0);
+    assert(0 == "unhandled case of picture object type");
     break;
   }
   if (obj) {
diff --git a/src/preproc/pic/tex.cpp b/src/preproc/pic/tex.cpp
index 04d469b78..a386970d1 100644
--- a/src/preproc/pic/tex.cpp
+++ b/src/preproc/pic/tex.cpp
@@ -239,7 +239,7 @@ void tex_output::spline(const position &start, const position *v, int n,
     printf(" %.3f", lt.dash_width/scale);
     break;
   case line_type::invisible:
-    assert(0);
+    assert(0 == "unhandled case of line type");
   }
   fputs("}%\n", stdout);
 }
@@ -312,7 +312,7 @@ void tex_output::circle(const position &cent, double rad,
     dotted_circle(cent, rad, lt);
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of line type");
   }
 }
 
@@ -348,7 +348,7 @@ void tex_output::ellipse(const position &cent, const distance &dim,
     dotted_ellipse(cent, dim / scale, lt);
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of line type");
   }
 }
 
diff --git a/src/preproc/pic/troff.cpp b/src/preproc/pic/troff.cpp
index 2bd1ed861..e8397bc93 100644
--- a/src/preproc/pic/troff.cpp
+++ b/src/preproc/pic/troff.cpp
@@ -135,7 +135,7 @@ void simple_output::line(const position &start, const position *v,
     case line_type::invisible:
       break;
     default:
-      assert(0);
+      assert(0 == "unhandled case of line type");
     }
     pos = v[i];
   }
@@ -190,7 +190,7 @@ void simple_output::circle(const position &cent, double rad,
     simple_circle(0, cent, rad);
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of line type");
   }
 }
 
@@ -218,7 +218,7 @@ void simple_output::ellipse(const position &cent, const distance &dim,
     simple_ellipse(0, cent, dim);
     break;
   default:
-    assert(0);
+    assert(0 == "unhandled case of line type");
   }
 }
 
diff --git a/src/preproc/refer/command.cpp b/src/preproc/refer/command.cpp
index f24a08111..5cd2dfe86 100644
--- a/src/preproc/refer/command.cpp
+++ b/src/preproc/refer/command.cpp
@@ -739,7 +739,7 @@ static int check_args(const char *types, const char *name,
       }
       break;
     default:
-      assert(0);
+      assert(0 == "unhandled case of command type");
     }
     if (types[1] == '?')
       types += 2;
diff --git a/src/preproc/refer/label.ypp b/src/preproc/refer/label.ypp
index 35fe9cd11..44202b8f8 100644
--- a/src/preproc/refer/label.ypp
+++ b/src/preproc/refer/label.ypp
@@ -620,7 +620,7 @@ static const char *format_serial(char c, int n)
       break;
     }
   default:
-    assert(0);
+    assert(0 == "unhandled case of register format");
   }
   return buf;
 }
@@ -715,7 +715,7 @@ void extractor_expr::evaluate(int tentative, const reference &ref,
 	result.append(end, temp.contents() + temp.length() - end);
       break;
     default:
-      assert(0);
+      assert(0 == "unhandled case of part in expression evaluator");
     }
   }
 }
diff --git a/src/utils/hpftodit/hpftodit.cpp b/src/utils/hpftodit/hpftodit.cpp
index 617a76abe..b29a04dc3 100644
--- a/src/utils/hpftodit/hpftodit.cpp
+++ b/src/utils/hpftodit/hpftodit.cpp
@@ -340,7 +340,7 @@ main(int argc, char **argv)
       exit(2);
       break;
     default:
-      assert(0);
+      assert(0 == "unhandled case of command-line option");
     }
 
   if (debug_flag && argc - optind < 1)
diff --git a/src/utils/lkbib/lkbib.cpp b/src/utils/lkbib/lkbib.cpp
index 419972cbf..a69a57250 100644
--- a/src/utils/lkbib/lkbib.cpp
+++ b/src/utils/lkbib/lkbib.cpp
@@ -119,7 +119,7 @@ int main(int argc, char **argv)
       exit(2);
       break;
     default:
-      assert(0);
+      assert(0 == "unhandled case of command-line option");
     }
   if (optind >= argc) {
     usage(stderr);