diff --git a/.changeset/clever-deer-wander.md b/.changeset/clever-deer-wander.md
new file mode 100644
index 000000000..14709e09e
--- /dev/null
+++ b/.changeset/clever-deer-wander.md
@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 640
+---
+**`gsd-tools query summary-extract` no longer drops snake_case `requirements_completed`** — the reader now accepts both the kebab `requirements-completed` and the snake `requirements_completed` key forms (the snake form is what the tool's own JSON output and the milestone audit `--pick` emit), so a round-tripped requirements field is no longer silently read back as empty.
diff --git a/src/commands.cts b/src/commands.cts
index b23c9ae80..a269e0a5a 100644
--- a/src/commands.cts
+++ b/src/commands.cts
@@ -750,7 +750,11 @@ function cmdSummaryExtract(cwd: string, summaryPath: string | undefined, fields:
     tech_added: (techStack && techStack['added']) || [],
     patterns: fm['patterns-established'] || [],
     decisions: parseDecisions(fm['key-decisions']),
-    requirements_completed: fm['requirements-completed'] || [],
+    // Tolerate both key forms: the template/reader use kebab `requirements-completed`,
+    // but the tool's own JSON output and the milestone audit `--pick` use snake
+    // `requirements_completed`. Reading both prevents a snake-keyed SUMMARY (the form the
+    // tool emits) from being silently dropped to []. See #628.
+    requirements_completed: fm['requirements-completed'] ?? fm['requirements_completed'] ?? [],
   };
 
   // If fields specified, filter to only those fields
diff --git a/tests/commands.test.cjs b/tests/commands.test.cjs
index e4424fe35..96052db29 100644
--- a/tests/commands.test.cjs
+++ b/tests/commands.test.cjs
@@ -424,6 +424,61 @@ one-liner: Minimal summary
     assert.deepStrictEqual(output.requirements_completed, [], 'requirements_completed defaults to empty');
   });
 
+  test('reads requirements in snake_case form the tool itself emits (#628)', () => {
+    // Regression: the tool's JSON output key and the milestone-audit `--pick` both use the
+    // snake form `requirements_completed`, so operators naturally write that into SUMMARY
+    // frontmatter. The reader must accept it, not silently drop it to [].
+    const phaseDir = path.join(tmpDir, '.planning', 'phases', '01-foundation');
+    fs.mkdirSync(phaseDir, { recursive: true });
+
+    fs.writeFileSync(
+      path.join(phaseDir, '01-01-SUMMARY.md'),
+      `---
+one-liner: Snake-keyed summary
+requirements_completed:
+  - REQ-1
+  - REQ-2
+---
+
+# Summary
+`
+    );
+
+    const result = runGsdTools('summary-extract .planning/phases/01-foundation/01-01-SUMMARY.md', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+
+    const output = JSON.parse(result.output);
+    assert.deepStrictEqual(output.requirements_completed, ['REQ-1', 'REQ-2'],
+      'snake-case requirements_completed should be read, not dropped to []');
+  });
+
+  test('prefers kebab requirements-completed when both key forms are present (#628)', () => {
+    // kebab is the documented template form and must win the tolerance fallback.
+    const phaseDir = path.join(tmpDir, '.planning', 'phases', '01-foundation');
+    fs.mkdirSync(phaseDir, { recursive: true });
+
+    fs.writeFileSync(
+      path.join(phaseDir, '01-01-SUMMARY.md'),
+      `---
+one-liner: Both key forms present
+requirements-completed:
+  - KEBAB-1
+requirements_completed:
+  - SNAKE-1
+---
+
+# Summary
+`
+    );
+
+    const result = runGsdTools('summary-extract .planning/phases/01-foundation/01-01-SUMMARY.md', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+
+    const output = JSON.parse(result.output);
+    assert.deepStrictEqual(output.requirements_completed, ['KEBAB-1'],
+      'kebab key should take precedence over snake when both are present');
+  });
+
   test('parses key-decisions with rationale', () => {
     const phaseDir = path.join(tmpDir, '.planning', 'phases', '01-foundation');
     fs.mkdirSync(phaseDir, { recursive: true });