diff --git a/apps/api/src/template/http-schemas/template.schema.ts b/apps/api/src/template/http-schemas/template.schema.ts
index d6fb81ea5f..df9eb26d90 100644
--- a/apps/api/src/template/http-schemas/template.schema.ts
+++ b/apps/api/src/template/http-schemas/template.schema.ts
@@ -37,10 +37,15 @@ export const GetTemplatesListResponseSchema = z.object({
 export type GetTemplatesListResponse = z.infer<typeof GetTemplatesListResponseSchema>;
 
 export const GetTemplateByIdParamsSchema = z.object({
-  id: z.string().openapi({
-    description: "Template ID",
-    example: "akash-network-cosmos-omnibus-agoric"
-  })
+  // Template ids never contain a path separator (they're built by collapsing "/" and "\" to "-"),
+  // so rejecting them here blocks path traversal before the id reaches the filesystem.
+  id: z
+    .string()
+    .regex(/^[^/\\]+$/, "Invalid template ID")
+    .openapi({
+      description: "Template ID",
+      example: "akash-network-cosmos-omnibus-agoric"
+    })
 });
 
 export const GetTemplateByIdResponseSchema = z.object({ data: TemplateSchema });
diff --git a/apps/api/src/template/routes/templates/templates.router.ts b/apps/api/src/template/routes/templates/templates.router.ts
index afd86cac67..4b4cea11eb 100644
--- a/apps/api/src/template/routes/templates/templates.router.ts
+++ b/apps/api/src/template/routes/templates/templates.router.ts
@@ -55,6 +55,9 @@ const getTemplateByIdRoute = createRoute({
         }
       }
     },
+    400: {
+      description: "Invalid template ID"
+    },
     404: {
       description: "Template not found"
     }
diff --git a/apps/api/src/template/services/template-gallery/template-gallery.service.spec.ts b/apps/api/src/template/services/template-gallery/template-gallery.service.spec.ts
index fb804e235e..45cdc3c2db 100644
--- a/apps/api/src/template/services/template-gallery/template-gallery.service.spec.ts
+++ b/apps/api/src/template/services/template-gallery/template-gallery.service.spec.ts
@@ -323,6 +323,18 @@ describe(TemplateGalleryService.name, () => {
         })
       );
     });
+
+    it("reads the correct file for a legit id containing dots", async () => {
+      const { service, fsMock } = setup();
+      const template = { id: "akash-network-awesome-akash-DeepSeek-V3.1", name: "DeepSeek" };
+
+      fsMock.readFile.mockResolvedValue(JSON.stringify({ data: template }));
+
+      const result = await service.getTemplateById("akash-network-awesome-akash-DeepSeek-V3.1");
+
+      expect(result).toEqual(template);
+      expect(fsMock.readFile).toHaveBeenCalledWith("/data/templates/v1/templates/akash-network-awesome-akash-DeepSeek-V3.1.json", "utf8");
+    });
   });
 
   function setup(input?: { getTagsConfig?: () => TemplateTagsConfig }) {
diff --git a/apps/api/test/functional/__snapshots__/docs.spec.ts.snap b/apps/api/test/functional/__snapshots__/docs.spec.ts.snap
index 7c8ea9c89d..cc2bc245fe 100644
--- a/apps/api/test/functional/__snapshots__/docs.spec.ts.snap
+++ b/apps/api/test/functional/__snapshots__/docs.spec.ts.snap
@@ -14583,6 +14583,7 @@ exports[`API Docs > GET /v1/doc > returns docs with all routes expected 1`] = `
             "schema": {
               "description": "Template ID",
               "example": "akash-network-cosmos-omnibus-agoric",
+              "pattern": "^[^/\\\\]+$",
               "type": "string",
             },
           },
@@ -14659,6 +14660,9 @@ exports[`API Docs > GET /v1/doc > returns docs with all routes expected 1`] = `
             },
             "description": "Return a template by id",
           },
+          "400": {
+            "description": "Invalid template ID",
+          },
           "404": {
             "description": "Template not found",
           },
diff --git a/apps/api/test/functional/templates.spec.ts b/apps/api/test/functional/templates.spec.ts
new file mode 100644
index 0000000000..4874d6e278
--- /dev/null
+++ b/apps/api/test/functional/templates.spec.ts
@@ -0,0 +1,43 @@
+import { app, initDb } from "@src/rest-app";
+
+describe("Templates", () => {
+  let isDbInitialized = false;
+
+  const setup = async () => {
+    if (isDbInitialized) {
+      return;
+    }
+
+    await initDb();
+    isDbInitialized = true;
+  };
+
+  describe("GET /v1/templates/{id} path traversal", () => {
+    // An encoded separator (%2F -> "/", %5C -> "\") survives Hono routing as a single segment and is
+    // only decoded when the param is read, so the id schema sees the real separator and rejects it
+    // with a 400 before any file is read. A double-encoded payload decodes to a literal "%2F"/"%5C"
+    // (no separator), so it passes validation and resolves to a missing file -> 404. Either way no
+    // file contents leak (CON-428). The schema blocks both "/" and "\", so both are exercised here.
+    [
+      { encodedId: "..%2F..%2F..%2Fetc%2Fpasswd", expectedStatus: 400 }, // ../../../etc/passwd
+      { encodedId: "%2Fetc%2Fpasswd", expectedStatus: 400 }, // /etc/passwd (absolute escape)
+      { encodedId: "..%2F..%2Fsecret", expectedStatus: 400 },
+      { encodedId: "..%252F..%252Fsecret", expectedStatus: 404 }, // double-encoded: stays a literal "%2F"
+      { encodedId: "..%5C..%5Csecret", expectedStatus: 400 }, // ..\..\secret (backslash separator)
+      { encodedId: "..%255C..%255Csecret", expectedStatus: 404 } // double-encoded: stays a literal "%5C"
+    ].forEach(({ encodedId, expectedStatus }) => {
+      it(`rejects traversal attempt "${encodedId}" with ${expectedStatus} and no leaked file contents`, async () => {
+        await setup();
+
+        const response = await app.request(`/v1/templates/${encodedId}`, {
+          method: "GET",
+          headers: new Headers({ "Content-Type": "application/json" })
+        });
+
+        expect(response.status).toBe(expectedStatus);
+        const body = await response.text();
+        expect(body).not.toContain("root:x:"); // /etc/passwd marker — proves no file contents are returned
+      });
+    });
+  });
+});