feat(core): allow parallel tool calls and stop asking for exactly one tool call per turn

strix/agents/prompts/system_prompt.jinja

@@ -44,7 +44,7 @@ INTERACTIVE BEHAVIOR:
 - If you end a turn on plain text and the nudge arrives, your words already reached the user. Do not repeat them: call wait_for_user.
 - You can narrate while you work — plain text is shown to the user as you go. Narrating is free; wait_for_user is specifically the act of WAITING for the user, so do not call it just to give a status update.
 - Respond naturally when the user asks questions or gives instructions.
-- While actively working on a task, every turn should carry exactly one tool call — use think to plan, the appropriate tool to act, and wait_for_user only when you genuinely need the user.
+- While actively working on a task, every turn should carry a tool call (independent calls can go in the same turn) — use think to plan, the appropriate tool to act, and wait_for_user only when you genuinely need the user.
 - Never loop through think or other tools just to prepare, polish, confirm, or announce an answer. Once you know the answer, write it and call wait_for_user.
 {% else %}
 AUTONOMOUS BEHAVIOR:

strix/core/execution.py

@@ -1004,7 +1004,7 @@ async def _append_tool_required_message(
         message = (
             "Your previous message ended a turn without a tool call. Plain text never ends "
             "execution and never hands control to the user: it is shown to the user, and the "
-            "run continues. Continue immediately and call exactly one tool. "
+            "run continues. Continue immediately and call a tool. "
             "If you have nothing to do until the user replies, call wait_for_user; your "
             "text already reached them, so do not repeat it. "
             "If you are blocked waiting for another agent, call wait_for_agents. "
@@ -1016,7 +1016,7 @@ async def _append_tool_required_message(
         message = (
             "Your previous response ended the autonomous run without a lifecycle tool "
             "call. That is invalid in non-interactive mode; plain text final answers are "
-            "ignored. Continue immediately and call exactly one tool. "
+            "ignored. Continue immediately and call a tool. "
             f"If your work is complete, call {finish_tool}. "
             "If you are blocked waiting for another agent, call wait_for_agents. "
             "Otherwise use the appropriate execution or planning tool. "

strix/core/inputs.py

@@ -255,7 +255,7 @@ def make_model_settings(
 ) -> ModelSettings:
     headers = _request_headers(model_name, extra_headers)
     model_settings = ModelSettings(
-        parallel_tool_calls=False if has_tools else None,
+        parallel_tool_calls=True if has_tools else None,
         retry=DEFAULT_MODEL_RETRY,
         include_usage=True,
         extra_args=request_timeout_extra_args(request_timeout),

tests/test_inputs.py

@@ -310,8 +310,8 @@ def test_make_model_settings_forces_required_for_anyllm_routed_openai_model() ->
     assert settings.tool_choice == "required"
 
 
-def test_make_model_settings_disables_parallel_tool_calls_by_default() -> None:
-    assert make_model_settings("none", model_name="gpt-4o").parallel_tool_calls is False
+def test_make_model_settings_enables_parallel_tool_calls_by_default() -> None:
+    assert make_model_settings("none", model_name="gpt-4o").parallel_tool_calls is True
 
 
 def test_make_model_settings_omits_parallel_tool_calls_without_tools() -> None: