diff --git a/src/lib/server/compose-validate/effective-compose.ts b/src/lib/server/compose-validate/effective-compose.ts
index ed40145..de79a68 100644
--- a/src/lib/server/compose-validate/effective-compose.ts
+++ b/src/lib/server/compose-validate/effective-compose.ts
@@ -19,10 +19,12 @@
  */
 
 import { spawn } from 'node:child_process';
-import { chmod, mkdtemp, rm, writeFile } from 'node:fs/promises';
+import { chmod, mkdir, mkdtemp, rm, writeFile } from 'node:fs/promises';
 import { tmpdir } from 'node:os';
-import { join } from 'node:path';
+import { dirname, join } from 'node:path';
 import { resolveComposeDockerHost, buildComposeBaseArgs } from '../compose-docker-args';
+import { parseCompose } from './parse';
+import { extractMaterializableEnvFiles } from './env-file-paths';
 import type { Finding } from './types';
 
 const CONFIG_TIMEOUT_MS = 20_000;
@@ -58,6 +60,22 @@ export async function renderEffectiveCompose(
 		const file = join(dir, 'docker-compose.yml');
 		await writeFile(file, composeContent, 'utf8');
 
+		// Pre-create referenced env_file(s) as empty files so `docker compose config` resolves
+		// them. The user's real env file lives in their stack dir, not this scratch dir, so
+		// without this a valid `env_file: - .env` is falsely reported "env file ... not found".
+		// Only temp-dir-safe relative paths are materialized; interpolation values still come
+		// from envVars (passed as process env), so empty files don't skew other findings.
+		try {
+			const parsed = parseCompose(composeContent);
+			for (const rel of extractMaterializableEnvFiles(parsed.doc)) {
+				const target = join(dir, rel);
+				await mkdir(dirname(target), { recursive: true });
+				await writeFile(target, '', { flag: 'wx' }).catch(() => undefined); // don't overwrite
+			}
+		} catch {
+			// A compose that won't parse is handled by the local parser; config will report it too.
+		}
+
 		const composeDockerHost = resolveComposeDockerHost(dockerHost, undefined);
 		const base = buildComposeBaseArgs(stackName, composeDockerHost); // ['docker', ('-H' host)?, 'compose', '-p', name]
 		// `--format json` renders the FULLY effective compose as JSON: interpolation,
diff --git a/src/lib/server/compose-validate/env-file-paths.ts b/src/lib/server/compose-validate/env-file-paths.ts
new file mode 100644
index 0000000..45b9e3c
--- /dev/null
+++ b/src/lib/server/compose-validate/env-file-paths.ts
@@ -0,0 +1,55 @@
+/**
+ * Extract the `env_file` paths a compose references, keeping only those safe to MATERIALIZE
+ * inside a scratch validation dir. `docker compose config` fails "env file <path> not found"
+ * when a referenced env_file is absent from the cwd it runs in - but Compose Validate runs in a
+ * throwaway temp dir that has only the compose file, so a perfectly valid `env_file: - .env` is
+ * falsely rejected. We pre-create these files (empty) so config resolves.
+ *
+ * We only return paths that stay INSIDE the temp dir: a relative path with no `..` segment and
+ * not absolute. Absolute paths and `../` escapes are left alone (we can't/shouldn't write them;
+ * config's error for those is arguably legitimate).
+ */
+
+/** Normalize the compose `env_file` value (string | string[] | {path,required?}[]) to paths. */
+function envFileEntriesToPaths(value: unknown): string[] {
+	const out: string[] = [];
+	const push = (v: unknown) => {
+		if (typeof v === 'string') {
+			if (v.trim()) out.push(v.trim());
+		} else if (v && typeof v === 'object' && typeof (v as { path?: unknown }).path === 'string') {
+			const p = (v as { path: string }).path.trim();
+			if (p) out.push(p);
+		}
+	};
+	if (typeof value === 'string') push(value);
+	else if (Array.isArray(value)) value.forEach(push);
+	return out;
+}
+
+/** True when `p` is a relative path that stays inside its base dir (no absolute, no `..`). */
+function isInsideRelative(p: string): boolean {
+	if (!p || p.startsWith('/') || /^[a-zA-Z]:[\\/]/.test(p)) return false; // absolute (posix / windows)
+	const segs = p.split(/[\\/]/);
+	return !segs.includes('..');
+}
+
+/**
+ * Every distinct, temp-dir-safe env_file path referenced by any service in the parsed compose.
+ * `doc` is the plain object from parseCompose. Returns relative paths (deduped) to create.
+ */
+export function extractMaterializableEnvFiles(doc: unknown): string[] {
+	const services = (doc as { services?: unknown })?.services;
+	if (!services || typeof services !== 'object') return [];
+	const paths = new Set<string>();
+	for (const svc of Object.values(services as Record<string, unknown>)) {
+		if (!svc || typeof svc !== 'object') continue;
+		const ef = (svc as { env_file?: unknown }).env_file;
+		if (ef === undefined) continue;
+		for (const p of envFileEntriesToPaths(ef)) {
+			if (isInsideRelative(p)) paths.add(p);
+		}
+	}
+	// Cap materialization: a validate request should never create an unbounded number of
+	// scratch files. Well past any real compose; the pre-parse already bounds payload size.
+	return [...paths].slice(0, 100);
+}
diff --git a/tests/compose-validate/env-file-paths.test.ts b/tests/compose-validate/env-file-paths.test.ts
new file mode 100644
index 0000000..6be6306
--- /dev/null
+++ b/tests/compose-validate/env-file-paths.test.ts
@@ -0,0 +1,54 @@
+import { describe, test, expect } from 'bun:test';
+import { extractMaterializableEnvFiles } from '../../src/lib/server/compose-validate/env-file-paths';
+
+// Compose Validate runs `docker compose config` in a scratch temp dir. A referenced env_file
+// that lives in the user's stack dir is absent there, so config falsely reports "not found".
+// extractMaterializableEnvFiles finds the temp-dir-safe paths to pre-create as empty files.
+
+describe('extractMaterializableEnvFiles', () => {
+	test('list form: env_file: [.env]', () => {
+		const doc = { services: { web: { env_file: ['.env'] } } };
+		expect(extractMaterializableEnvFiles(doc)).toEqual(['.env']);
+	});
+
+	test('string form: env_file: prod.env', () => {
+		const doc = { services: { web: { env_file: 'prod.env' } } };
+		expect(extractMaterializableEnvFiles(doc)).toEqual(['prod.env']);
+	});
+
+	test('map form: env_file: [{path, required}]', () => {
+		const doc = { services: { web: { env_file: [{ path: 'a.env', required: false }, { path: 'b.env' }] } } };
+		expect(extractMaterializableEnvFiles(doc).sort()).toEqual(['a.env', 'b.env']);
+	});
+
+	test('nested relative path (config/.env) is kept', () => {
+		const doc = { services: { web: { env_file: ['config/.env'] } } };
+		expect(extractMaterializableEnvFiles(doc)).toEqual(['config/.env']);
+	});
+
+	test('dedupes across services', () => {
+		const doc = { services: { a: { env_file: '.env' }, b: { env_file: ['.env', 'x.env'] } } };
+		expect(extractMaterializableEnvFiles(doc).sort()).toEqual(['.env', 'x.env']);
+	});
+
+	test('absolute paths are EXCLUDED (cannot / must not materialize)', () => {
+		const doc = { services: { web: { env_file: ['/etc/app.env', 'C:\\app.env'] } } };
+		expect(extractMaterializableEnvFiles(doc)).toEqual([]);
+	});
+
+	test('parent-escaping paths are EXCLUDED', () => {
+		const doc = { services: { web: { env_file: ['../secret.env', 'a/../../b.env'] } } };
+		expect(extractMaterializableEnvFiles(doc)).toEqual([]);
+	});
+
+	test('no services / no env_file -> empty', () => {
+		expect(extractMaterializableEnvFiles({})).toEqual([]);
+		expect(extractMaterializableEnvFiles({ services: { web: { image: 'nginx' } } })).toEqual([]);
+		expect(extractMaterializableEnvFiles(null)).toEqual([]);
+	});
+
+	test('blank / non-string entries are ignored', () => {
+		const doc = { services: { web: { env_file: ['', '  ', 42, { required: true }] } } };
+		expect(extractMaterializableEnvFiles(doc as any)).toEqual([]);
+	});
+});