diff --git a/datasette/views/database.py b/datasette/views/database.py
index cf7a6db3..99e85d2b 100644
--- a/datasette/views/database.py
+++ b/datasette/views/database.py
@@ -851,6 +851,8 @@ class QueryView(View):
 
             return await stream_csv(datasette, fetch_data_for_csv, request, db.name)
         elif format_ in datasette.renderers.keys():
+            if not sql:
+                raise DatasetteError("?sql= is required", status=400)
             data = {"ok": True, "rows": rows, "columns": columns}
             extras = extra_names_from_request(request)
             if extras:
diff --git a/existing-api.md b/existing-api.md
index 8c6e1c4e..9947edeb 100644
--- a/existing-api.md
+++ b/existing-api.md
@@ -486,8 +486,9 @@ queries section).
     HTTP 400 `{"ok": false, "error": "<message>", "rows": [], "truncated": false}`.
   - Time limit → 400 titled `"SQL Interrupted"` (the `error` value contains
     an HTML fragment).
-  - `?sql=` omitted → 200 `{"ok": true, "rows": [], "truncated": false}`
-    (the CSV format instead errors 400 `"?sql= is required"`).
+  - `?sql=` omitted or blank → 400 `"?sql= is required"` for all data
+    formats (`.json`, `.csv`, plugin formats). The HTML page remains the
+    SQL editor.
 - `.csv` streams CSV; unknown extensions → 404.
 
 ### GET /\<database\>/-/query/parameters
diff --git a/stable-api-recommendations.md b/stable-api-recommendations.md
index 273a272c..11f0a75d 100644
--- a/stable-api-recommendations.md
+++ b/stable-api-recommendations.md
@@ -338,9 +338,11 @@ Concerns:
    `is_trusted` — an actor with `delete-query` can delete a config-defined
    trusted query via the API (it will resync on restart, making the
    behavior confusing rather than catastrophic). Align delete with update.
-2. **GET `/db/-/query` with no `?sql=` returns 200 `{"ok": true, "rows":
+2. ~~**GET `/db/-/query` with no `?sql=` returns 200 `{"ok": true, "rows":
    []}`** while `.csv` on the same request returns 400 `"?sql= is
-   required"`. The JSON behavior masks caller bugs; return 400 on both.
+   required"`. The JSON behavior masks caller bugs; return 400 on both.~~
+   ✅ **Done** — all data formats now return 400; the HTML SQL editor page
+   is unchanged.
 3. **`_shape=object` HTTP 200 error** (§1b) — almost certainly unintended.
 4. ~~**Row delete 500** (§1c) — inconsistent with every sibling endpoint.~~
    ✅ Done — now 400.
diff --git a/tests/test_error_shape.py b/tests/test_error_shape.py
index 49b2c314..9d4a566c 100644
--- a/tests/test_error_shape.py
+++ b/tests/test_error_shape.py
@@ -483,3 +483,27 @@ async def test_token_when_signed_tokens_disabled_returns_401(tmp_path_factory):
         assert "not enabled" in data["error"]
     finally:
         ds.close()
+
+
+# GET /db/-/query without SQL: 400 for data formats, HTML editor stays 200
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "path",
+    (
+        "/fixtures/-/query.json",
+        "/fixtures/-/query.json?sql=",
+    ),
+)
+async def test_query_json_without_sql_is_400(ds_client, path):
+    response = await ds_client.get(path)
+    data = assert_canonical_error(response, 400)
+    assert data["errors"] == ["?sql= is required"]
+
+
+@pytest.mark.asyncio
+async def test_query_html_without_sql_is_still_the_editor(ds_client):
+    response = await ds_client.get("/fixtures/-/query")
+    assert response.status_code == 200
+    assert response.headers["content-type"].startswith("text/html")
diff --git a/tests/test_table_api.py b/tests/test_table_api.py
index c8ba31b7..41c89f39 100644
--- a/tests/test_table_api.py
+++ b/tests/test_table_api.py
@@ -180,9 +180,11 @@ def test_query_extra_query_reports_bound_params():
         assert response.json["query"]["params"] == {}
 
 
-def test_query_extra_query_does_not_echo_querystring_without_sql():
+def test_query_extra_query_does_not_echo_querystring():
     with make_app_client() as client:
-        response = client.get("/fixtures/-/query.json?_extra=query&foo=bar")
+        response = client.get(
+            "/fixtures/-/query.json?sql=select+1&_extra=query&foo=bar"
+        )
         assert response.status == 200
         assert response.json["query"]["params"] == {}