diff --git a/tests/unittests/test_ai_client.c b/tests/unittests/test_ai_client.c
index 4a40b0d4..516fcb7f 100644
--- a/tests/unittests/test_ai_client.c
+++ b/tests/unittests/test_ai_client.c
@@ -614,6 +614,24 @@ test_ai_set_provider_setting(void** state)
     assert_null(ai_get_provider_setting("p_set_settings", "nonexistent_setting"));
 }
 
+void
+test_ai_set_provider_setting_reserved_key(void** state)
+{
+    ai_add_provider("p_reserved_keys", "https://example.test/rk/");
+
+    /* Reserved payload keys are rejected (would duplicate fixed fields) */
+    assert_false(ai_set_provider_setting("p_reserved_keys", "model", "x"));
+    assert_false(ai_set_provider_setting("p_reserved_keys", "messages", "[]"));
+    assert_false(ai_set_provider_setting("p_reserved_keys", "stream", "true"));
+    assert_null(ai_get_provider_setting("p_reserved_keys", "model"));
+
+    /* Ordinary keys still work */
+    assert_true(ai_set_provider_setting("p_reserved_keys", "temperature", "0.7"));
+    auto_gchar gchar* temp = ai_get_provider_setting("p_reserved_keys", "temperature");
+    assert_non_null(temp);
+    assert_string_equal("0.7", temp);
+}
+
 void
 test_ai_get_provider_setting(void** state)
 {
@@ -919,22 +937,22 @@ test_ai_parse_response_openai_content(void** state)
 }
 
 void
-test_ai_parse_response_perplexity_text(void** state)
+test_ai_parse_response_legacy_text_format_unsupported(void** state)
 {
+    /* Legacy Perplexity /v1/agent format: "content" is an array, not a string.
+     * Dropped with the chat-completions alignment, so parsing yields NULL. */
     const gchar* json = "{\"output\":[{\"content\":[{\"text\":\"Search result\",\"type\":\"output_text\"}]}]}";
-    auto_gchar gchar* out = ai_parse_response(json);
-    assert_non_null(out);
-    assert_string_equal("Search result", out);
+    assert_null(ai_parse_response(json));
 }
 
 void
-test_ai_parse_response_text_preferred_over_content(void** state)
+test_ai_parse_response_content_preferred_over_text(void** state)
 {
-    /* When both formats are present, "text" wins (Perplexity path tried first). */
+    /* Chat-completions "content" is extracted; a stray "text" field is ignored. */
     const gchar* json = "{\"text\":\"from text field\",\"content\":\"from content field\"}";
     auto_gchar gchar* out = ai_parse_response(json);
     assert_non_null(out);
-    assert_string_equal("from text field", out);
+    assert_string_equal("from content field", out);
 }
 
 void
diff --git a/tests/unittests/test_ai_client.h b/tests/unittests/test_ai_client.h
index e99c355d..6bf2062e 100644
--- a/tests/unittests/test_ai_client.h
+++ b/tests/unittests/test_ai_client.h
@@ -43,6 +43,7 @@ void test_ai_providers_find_case_insensitive(void** state);
 void test_ai_set_provider_default_model(void** state);
 void test_ai_get_provider_default_model(void** state);
 void test_ai_set_provider_setting(void** state);
+void test_ai_set_provider_setting_reserved_key(void** state);
 void test_ai_get_provider_setting(void** state);
 /* Model caching tests */
 void test_ai_models_are_fresh_initial(void** state);
@@ -64,8 +65,8 @@ int ai_client_teardown_with_prefs(void** state);
 
 /* Chat response parser tests (ai_parse_response) */
 void test_ai_parse_response_openai_content(void** state);
-void test_ai_parse_response_perplexity_text(void** state);
-void test_ai_parse_response_text_preferred_over_content(void** state);
+void test_ai_parse_response_legacy_text_format_unsupported(void** state);
+void test_ai_parse_response_content_preferred_over_text(void** state);
 void test_ai_parse_response_escaped_quote(void** state);
 void test_ai_parse_response_newline_escape(void** state);
 void test_ai_parse_response_empty_content(void** state);
diff --git a/tests/unittests/unittests.c b/tests/unittests/unittests.c
index ca1a7d1e..cf01788e 100644
--- a/tests/unittests/unittests.c
+++ b/tests/unittests/unittests.c
@@ -752,6 +752,7 @@ main(int argc, char* argv[])
         cmocka_unit_test_setup_teardown(test_ai_set_provider_default_model, ai_client_setup, ai_client_teardown),
         cmocka_unit_test_setup_teardown(test_ai_get_provider_default_model, ai_client_setup, ai_client_teardown),
         cmocka_unit_test_setup_teardown(test_ai_set_provider_setting, ai_client_setup, ai_client_teardown),
+        cmocka_unit_test_setup_teardown(test_ai_set_provider_setting_reserved_key, ai_client_setup, ai_client_teardown),
         cmocka_unit_test_setup_teardown(test_ai_get_provider_setting, ai_client_setup, ai_client_teardown),
         /* Model caching tests */
         cmocka_unit_test_setup_teardown(test_ai_models_are_fresh_initial, ai_client_setup, ai_client_teardown),
@@ -774,8 +775,8 @@ main(int argc, char* argv[])
         cmocka_unit_test(test_ai_json_escape_backslash_quote),
         /* Chat response parser */
         cmocka_unit_test(test_ai_parse_response_openai_content),
-        cmocka_unit_test(test_ai_parse_response_perplexity_text),
-        cmocka_unit_test(test_ai_parse_response_text_preferred_over_content),
+        cmocka_unit_test(test_ai_parse_response_legacy_text_format_unsupported),
+        cmocka_unit_test(test_ai_parse_response_content_preferred_over_text),
         cmocka_unit_test(test_ai_parse_response_escaped_quote),
         cmocka_unit_test(test_ai_parse_response_newline_escape),
         cmocka_unit_test(test_ai_parse_response_empty_content),