diff --git a/tests/openapi-body-field-analysis.test.ts b/tests/openapi-body-field-analysis.test.ts
new file mode 100644
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--- /dev/null
+++ b/tests/openapi-body-field-analysis.test.ts
@@ -0,0 +1,87 @@
+// @ts-expect-error -- bun:test is a runtime built-in with no types installed
+import { describe, expect, test } from 'bun:test';
+import { analyzeHandlerBody } from '../scripts/openapi/lib';
+
+// Gate 7 (body-field drift) compares these extracted fields against the @openapi
+// body: annotation. The extraction must see BOTH destructuring and member access,
+// and must NOT count a write to a local variable that happens to be named `body`.
+describe('analyzeHandlerBody: request-body field extraction', () => {
+	test('destructured fields', () => {
+		const a = analyzeHandlerBody(`const { name, count } = await request.json();`);
+		expect(a.bodyFields).toEqual(['count', 'name']);
+	});
+
+	test('member access (body.foo / body?.foo) is detected', () => {
+		const a = analyzeHandlerBody(`
+			const flags = body.backupFlags ?? body.restoreFlags;
+			if (body?.mode === 'x') return;
+		`);
+		expect(a.bodyFields).toContain('backupFlags');
+		expect(a.bodyFields).toContain('restoreFlags');
+		expect(a.bodyFields).toContain('mode');
+	});
+
+	test('mixes destructure + member access', () => {
+		const a = analyzeHandlerBody(`
+			const { destinationId } = await request.json();
+			const s = body.snapshotId;
+		`);
+		expect(a.bodyFields).toEqual(['destinationId', 'snapshotId']);
+	});
+
+	test('a WRITE to a local var named body is NOT a request field (the preview-env false positive)', () => {
+		// This is the real shape from src/routes/api/git/preview-env: an error-response
+		// object literally named `body`. Its assignments must not be read as body fields.
+		const a = analyzeHandlerBody(`
+			const body: Record<string, unknown> = { error: outcome.message };
+			if (outcome.vars) body.vars = outcome.vars;
+			if (outcome.sources) body.sources = outcome.sources;
+			return json(body, { status: 400 });
+		`);
+		expect(a.bodyFields).not.toContain('vars');
+		expect(a.bodyFields).not.toContain('sources');
+	});
+
+	test('a comparison (body.x ===) IS a read, still counted', () => {
+		const a = analyzeHandlerBody(`if (body.mode === 'in-place') {}`);
+		expect(a.bodyFields).toContain('mode');
+	});
+
+	test('request.body stream members are still captured here (Gate 7 filters them out separately)', () => {
+		// analyzeHandlerBody is naive about `request.body.getReader()`; the STREAM_BODY_MEMBERS
+		// allowlist in the drift checker is what prevents these from being flagged.
+		const a = analyzeHandlerBody(`const r = request.body.getReader();`);
+		expect(a.bodyFields).toContain('getReader');
+	});
+
+	test('compound / logical assignment to a local body is a WRITE, not a read', () => {
+		// A local var named `body` mutated with +=, ??=, ||=, &&=, *= must not be counted
+		// as a request-body read (would spuriously hard-fail the drift gate).
+		const a = analyzeHandlerBody(`
+			const body: Record<string, unknown> = {};
+			body.count += 1;
+			body.flag ??= true;
+			body.acc ||= [];
+			body.on &&= false;
+			body.total *= 2;
+		`);
+		for (const f of ['count', 'flag', 'acc', 'on', 'total']) {
+			expect(a.bodyFields).not.toContain(f);
+		}
+	});
+
+	test('destructuring a NESTED object off body.member does not leak nested keys as top-level', () => {
+		// `const { setting } = body.config;` reads config.setting, NOT a top-level `setting`.
+		const a = analyzeHandlerBody(`const { setting } = body.config;`);
+		expect(a.bodyFields).not.toContain('setting');
+		// body.config itself IS a real top-level read
+		expect(a.bodyFields).toContain('config');
+	});
+
+	test('a real field named like a Body method (body.text) IS captured (not masked here)', () => {
+		// The extractor must surface body.text; only the narrowed STREAM_BODY_MEMBERS in
+		// the drift checker skips true stream methods, and `text` is no longer in it.
+		const a = analyzeHandlerBody(`const t = body.text;`);
+		expect(a.bodyFields).toContain('text');
+	});
+});