docs: exit_reason's tool result is not always last_message

docs-website/docs/pipeline-components/agents-1/agent.mdx

@@ -66,7 +66,7 @@ The `exit_reason` output tells you why the agent stopped, which makes it easy to
 - `"text"`: the model returned a complete reply with no tool calls.
 - `"length"`: the model reached its output-token limit. `last_message` may contain a partial response.
 - `"content_filter"`: a content filter stopped the model response. `last_message` may contain a partial response.
-- the name of the tool that satisfied a tool exit condition. In this case `last_message` is that tool's result — a tool-result `ChatMessage` whose `text` is empty — so `exit_reason` tells you how to consume it.
+- the name of the tool that satisfied a tool exit condition. Its result is the last tool-result `ChatMessage` in `messages` whose `tool_call_result.origin.tool_name` matches `exit_reason`; read it from `tool_call_result.result`. When the model calls several tools in one reply, this may not be `last_message`.
 - `"max_agent_steps"`: the agent reached `max_agent_steps` before meeting an exit condition.
 - a custom reason set by a hook through the `stop_run` state key, such as `"token_budget_exceeded"` from the [`TokenBudgetHook`](./token-budget.mdx).
 

docs-website/versioned_docs/version-3.2/pipeline-components/agents-1/agent.mdx

@@ -66,7 +66,7 @@ The `exit_reason` output tells you why the agent stopped, which makes it easy to
 - `"text"`: the model returned a complete reply with no tool calls.
 - `"length"`: the model reached its output-token limit. `last_message` may contain a partial response.
 - `"content_filter"`: a content filter stopped the model response. `last_message` may contain a partial response.
-- the name of the tool that satisfied a tool exit condition. In this case `last_message` is that tool's result — a tool-result `ChatMessage` whose `text` is empty — so `exit_reason` tells you how to consume it.
+- the name of the tool that satisfied a tool exit condition. Its result is the last tool-result `ChatMessage` in `messages` whose `tool_call_result.origin.tool_name` matches `exit_reason`; read it from `tool_call_result.result`. When the model calls several tools in one reply, this may not be `last_message`.
 - `"max_agent_steps"`: the agent reached `max_agent_steps` before meeting an exit condition.
 - a custom reason set by a hook through the `stop_run` state key, such as `"token_budget_exceeded"` from the [`TokenBudgetHook`](./token-budget.mdx).
 

haystack/components/agents/agent.py

@@ -866,9 +866,10 @@ def run(
             - "exit_reason": Why the Agent stopped, useful for routing the output downstream (e.g. with a
               `ConditionalRouter`). One of: `"text"` (the model returned a complete reply with no tool calls),
               `"length"` or `"content_filter"` (the model returned an incomplete reply, which may contain partial
-              text), the name of the tool that satisfied a tool exit condition (in which case `last_message` is that
-              tool's result), or `"max_agent_steps"` (the Agent hit `max_agent_steps` before meeting an exit
-              condition), or a custom reason a hook supplied through the `stop_run` state key.
+              text), the name of the tool that satisfied a tool exit condition (its result is the last tool message in
+              `messages` whose `tool_call_result.origin.tool_name` matches it, which may not be `last_message` when
+              the model called several tools at once), or `"max_agent_steps"` (the Agent hit `max_agent_steps` before
+              meeting an exit condition), or a custom reason a hook supplied through the `stop_run` state key.
             - Any additional keys defined in the `state_schema`.
         """
         agent_inputs = {"messages": messages, "streaming_callback": streaming_callback, **kwargs}
@@ -952,9 +953,10 @@ async def run_async(
             - "exit_reason": Why the Agent stopped, useful for routing the output downstream (e.g. with a
               `ConditionalRouter`). One of: `"text"` (the model returned a complete reply with no tool calls),
               `"length"` or `"content_filter"` (the model returned an incomplete reply, which may contain partial
-              text), the name of the tool that satisfied a tool exit condition (in which case `last_message` is that
-              tool's result), or `"max_agent_steps"` (the Agent hit `max_agent_steps` before meeting an exit
-              condition), or a custom reason a hook supplied through the `stop_run` state key.
+              text), the name of the tool that satisfied a tool exit condition (its result is the last tool message in
+              `messages` whose `tool_call_result.origin.tool_name` matches it, which may not be `last_message` when
+              the model called several tools at once), or `"max_agent_steps"` (the Agent hit `max_agent_steps` before
+              meeting an exit condition), or a custom reason a hook supplied through the `stop_run` state key.
             - Any additional keys defined in the `state_schema`.
         """
         agent_inputs = {"messages": messages, "streaming_callback": streaming_callback, **kwargs}

test/components/agents/test_agent.py

@@ -1111,7 +1111,6 @@ def test_exit_condition_exits(self, weather_tool):
         assert "last_message" in result
         assert isinstance(result["last_message"], ChatMessage)
         assert result["messages"][-1] == result["last_message"]
-        # The exit reason is the tool that triggered the exit, and `last_message` is that tool's result.
         assert result["exit_reason"] == "weather_tool"
 
     def test_exit_condition_on_tool_provided_at_runtime(self, weather_tool):
@@ -1254,6 +1253,7 @@ def test_tool_exit_reports_the_first_matching_tool(self, weather_tool, component
         )
         result = agent.run([ChatMessage.from_user("Go")])
         assert result["exit_reason"] == "parrot"
+        assert result["last_message"].tool_call_result.origin.tool_name == "weather_tool"
 
     def test_max_steps_exit(self, weather_tool, caplog):
         """Exhausting `max_agent_steps` before meeting an exit condition reports `"max_agent_steps"`."""