fix(yaml): accept empty flow mappings in mapping bodies

src/cli/config_yaml_edit.c

@@ -1266,8 +1266,8 @@ static int yaml_find_comment(const char *data, size_t start, size_t end, size_t
  * The test is positional and deliberately conservative: an indicator is only
  * honoured as one when nothing has appeared before it in the value. `key: *a`
  * is still an alias and still refused; `key: 2 * 3` and `key: a*b` are text.
- * `{`/`}` keep their existing treatment — empty flow mappings are a separate
- * change with its own semantics. */
+ * `{`/`}` keep their existing treatment here; mapping-body validation admits
+ * exact empty flow mappings through a context-specific exception. */
 static int yaml_range_has_unsupported(const char *data, size_t start, size_t end) {
     char quote = '\0';
     /* Last significant character seen, so an indicator can be judged by what
@@ -1387,6 +1387,19 @@ static int yaml_tail_is_explicit_empty_mapping(const char *data, size_t colon, s
     return 0;
 }
 
+static int yaml_mapping_body_line_has_unsupported(const yaml_doc_t *doc, const yaml_line_t *line) {
+    size_t start = line->start + line->indent;
+    size_t colon = 0U;
+    bool empty_mapping = false;
+    if (yaml_find_mapping_colon(doc->data, start, line->text_end, &colon) == 0 &&
+        yaml_tail_is_explicit_empty_mapping(doc->data, colon, line->text_end, &empty_mapping) ==
+            0 &&
+        empty_mapping) {
+        return yaml_range_has_unsupported(doc->data, start, colon + YAML_UNIT);
+    }
+    return yaml_range_has_unsupported(doc->data, start, line->text_end);
+}
+
 static int yaml_value_starts_multiline(const char *data, size_t colon, size_t end) {
     size_t pos = yaml_skip_spaces(data, colon + YAML_UNIT, end);
     return pos < end && (data[pos] == '|' || data[pos] == '>');
@@ -1404,7 +1417,7 @@ static int yaml_validate_mapping_body(const yaml_doc_t *doc, size_t first_line,
             continue;
         }
         if (line->indent < YAML_ENTRY_INDENT || (line->indent & YAML_UNIT) != 0U ||
-            yaml_range_has_unsupported(doc->data, line->start + line->indent, line->text_end)) {
+            yaml_mapping_body_line_has_unsupported(doc, line)) {
             return YAML_ERROR;
         }
         size_t colon = 0U;

tests/test_config_yaml_edit.c

@@ -812,6 +812,107 @@ TEST(config_yaml_edit_goose_extensions_preserve_siblings) {
     PASS();
 }
 
+TEST(config_yaml_edit_goose_accepts_empty_flow_mapping_in_sibling_issue1673) {
+    const char *initial = "extensions:\n"
+                          "  demo:\n"
+                          "    enabled: true\n"
+                          "    type: stdio\n"
+                          "    cmd: /bin/true\n"
+                          "    args:\n"
+                          "    - --serve\n"
+                          "    envs: {}\n"
+                          "    env_keys: []\n"
+                          "    timeout: 300\n"
+                          "GOOSE_THINKING_EFFORT: max\n";
+    const char *block = "    type: stdio\n"
+                        "    cmd: \"/opt/codebase-memory-mcp\"\n"
+                        "    args: []\n"
+                        "    enabled: true\n";
+    const char *expected = "extensions:\n"
+                           "  demo:\n"
+                           "    enabled: true\n"
+                           "    type: stdio\n"
+                           "    cmd: /bin/true\n"
+                           "    args:\n"
+                           "    - --serve\n"
+                           "    envs: {}\n"
+                           "    env_keys: []\n"
+                           "    timeout: 300\n"
+                           "  codebase-memory-mcp:\n"
+                           "    type: stdio\n"
+                           "    cmd: \"/opt/codebase-memory-mcp\"\n"
+                           "    args: []\n"
+                           "    enabled: true\n"
+                           "GOOSE_THINKING_EFFORT: max\n";
+    yaml_fixture_t fixture;
+    ASSERT_EQ(yaml_fixture_init(&fixture, initial), 0);
+
+    ASSERT_EQ(cbm_yaml_upsert_owned_mapping_entry(fixture.path, "extensions", "codebase-memory-mcp",
+                                                  block),
+              CBM_YAML_IDENTITY_EDIT_OK);
+    char *installed = yaml_read_alloc(fixture.path);
+    ASSERT_NOT_NULL(installed);
+    ASSERT_STR_EQ(installed, expected);
+
+    free(installed);
+    th_cleanup(fixture.dir);
+    PASS();
+}
+
+TEST(config_yaml_edit_goose_still_rejects_nonempty_flow_mapping_issue1673) {
+    const char *initial = "extensions:\n"
+                          "  demo:\n"
+                          "    enabled: true\n"
+                          "    type: stdio\n"
+                          "    cmd: /bin/true\n"
+                          "    args: []\n"
+                          "    envs: {FOO: bar}\n"
+                          "    env_keys: []\n"
+                          "    timeout: 300\n";
+    const char *block = "    type: stdio\n"
+                        "    cmd: \"/opt/codebase-memory-mcp\"\n"
+                        "    args: []\n"
+                        "    enabled: true\n";
+    yaml_fixture_t fixture;
+    ASSERT_EQ(yaml_fixture_init(&fixture, initial), 0);
+
+    ASSERT_EQ(cbm_yaml_upsert_owned_mapping_entry(fixture.path, "extensions", "codebase-memory-mcp",
+                                                  block),
+              CBM_YAML_IDENTITY_EDIT_ERROR);
+    char *unchanged = yaml_read_alloc(fixture.path);
+    ASSERT_NOT_NULL(unchanged);
+    ASSERT_STR_EQ(unchanged, initial);
+
+    free(unchanged);
+    th_cleanup(fixture.dir);
+    PASS();
+}
+
+TEST(config_yaml_edit_goose_still_rejects_merge_key_with_empty_mapping_issue1673) {
+    const char *initial = "extensions:\n"
+                          "  demo:\n"
+                          "    type: stdio\n"
+                          "    cmd: /bin/true\n"
+                          "    <<: {}\n";
+    const char *block = "    type: stdio\n"
+                        "    cmd: \"/opt/codebase-memory-mcp\"\n"
+                        "    args: []\n"
+                        "    enabled: true\n";
+    yaml_fixture_t fixture;
+    ASSERT_EQ(yaml_fixture_init(&fixture, initial), 0);
+
+    ASSERT_EQ(cbm_yaml_upsert_owned_mapping_entry(fixture.path, "extensions", "codebase-memory-mcp",
+                                                  block),
+              CBM_YAML_IDENTITY_EDIT_ERROR);
+    char *unchanged = yaml_read_alloc(fixture.path);
+    ASSERT_NOT_NULL(unchanged);
+    ASSERT_STR_EQ(unchanged, initial);
+
+    free(unchanged);
+    th_cleanup(fixture.dir);
+    PASS();
+}
+
 TEST(config_yaml_edit_owned_agent_mapping_installs_idempotently_and_removes_exact_state) {
     struct owned_mapping_case {
         const char *section;
@@ -1592,6 +1693,9 @@ SUITE(config_yaml_edit) {
     RUN_TEST(config_yaml_edit_hermes_mapping_lifecycle);
     RUN_TEST(config_yaml_edit_hermes_creates_missing_section);
     RUN_TEST(config_yaml_edit_goose_extensions_preserve_siblings);
+    RUN_TEST(config_yaml_edit_goose_accepts_empty_flow_mapping_in_sibling_issue1673);
+    RUN_TEST(config_yaml_edit_goose_still_rejects_nonempty_flow_mapping_issue1673);
+    RUN_TEST(config_yaml_edit_goose_still_rejects_merge_key_with_empty_mapping_issue1673);
     RUN_TEST(config_yaml_edit_owned_agent_mapping_installs_idempotently_and_removes_exact_state);
     RUN_TEST(config_yaml_edit_owned_agent_mapping_preserves_foreign_same_name_state);
     RUN_TEST(config_yaml_edit_mapping_remove_first_middle_last);