diff --git a/packages/config/src/index.ts b/packages/config/src/index.ts
index 6838140..d64e29a 100644
--- a/packages/config/src/index.ts
+++ b/packages/config/src/index.ts
@@ -118,8 +118,17 @@ export const envSchema = z.object({
     .string()
     .transform((v) => v === "true")
     .default("false"),
-  PCAT_SOURCE_DB_URL: z.string().url().optional(),
-  EMEX_SOURCE_DB_URL: z.string().optional(), // mysql://... — not a strict URL per WHATWG
+  // docker-compose's `${VAR:-}` substitution always sets the env, even if to
+  // an empty string. zod's `.optional()` only accepts undefined, so a chained
+  // `.url()` would reject "" and crash boot — preprocess "" → undefined first.
+  PCAT_SOURCE_DB_URL: z.preprocess(
+    (v) => (typeof v === "string" && v.trim() === "" ? undefined : v),
+    z.string().url().optional(),
+  ),
+  EMEX_SOURCE_DB_URL: z.preprocess(
+    (v) => (typeof v === "string" && v.trim() === "" ? undefined : v),
+    z.string().optional(),
+  ), // mysql://... — not a strict URL per WHATWG
   // Per-source kill switches under the master CATALOG_SOURCE_DB_ENABLED.
   // EMEX_SOURCE_DB_ENABLED keeps the connection pool alive but, per the
   // 2026-06-01 safety audit, fetchCategoryParts ALWAYS returns null unless the