fix(workflow): guard on_tool_execution stdout traces behind DEBUG

[MRZHUH]

Summary

DifyWorkflowCallbackHandler.on_tool_execution was the only callback in the DifyAgentCallbackHandler family that wrote to stdout without the if dify_config.DEBUG: guard that every sibling method uses (on_tool_start, on_tool_end, on_tool_error, on_agent_start, on_agent_finish, on_datasource_start; ignore_agent returns not dify_config.DEBUG). This wraps its print_text(...) calls in the same guard.

Two improvements when DEBUG is off (the default):

• No unconditional stdout output — the calls use a raw print() that bypasses LOG_LEVEL, so they were emitted in every deployment.
• tool_output.model_dump_json() is no longer invoked just to build a 1000-char preview, removing avoidable full serialization of large tool outputs on a hot path.

Functional behavior is unchanged — outputs are still yielded; only the debug printing is gated.

Local checks: ruff check is clean on the changed files and tests/unit_tests/core/callback_handler/test_workflow_tool_callback_handler.py passes (10 passed), with a new case covering the DEBUG-off short-circuit.

Fixes #38199

Screenshots

Before	After
N/A — backend stdout/logging behavior	N/A

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint && make type-check (backend) and cd web && pnpm exec vp staged (frontend) to appease the lint gods — ran ruff check (clean) and the affected unit tests (10 passed); full make type-check not run locally

[github-actions]

Pyrefly Diff

base → PR

--- /tmp/pyrefly_base.txt	2026-06-30 07:06:00.034157800 +0000
+++ /tmp/pyrefly_pr.txt	2026-06-30 07:05:45.775067530 +0000
@@ -4238,13 +4238,13 @@
 ERROR Argument `None` is not assignable to parameter `dataset_id` with type `str` in function `core.callback_handler.index_tool_callback_handler.DatasetIndexToolCallbackHandler.on_query` [bad-argument-type]
   --> tests/unit_tests/core/callback_handler/test_index_tool_callback_handler.py:72:32
 ERROR Argument `list[DummyToolInvokeMessage]` is not assignable to parameter `tool_outputs` with type `Iterable[ToolInvokeMessage]` in function `core.callback_handler.workflow_tool_callback_handler.DifyWorkflowCallbackHandler.on_tool_execution` [bad-argument-type]
-  --> tests/unit_tests/core/callback_handler/test_workflow_tool_callback_handler.py:47:30
+  --> tests/unit_tests/core/callback_handler/test_workflow_tool_callback_handler.py:55:30
 ERROR Argument `list[DummyToolInvokeMessage]` is not assignable to parameter `tool_outputs` with type `Iterable[ToolInvokeMessage]` in function `core.callback_handler.workflow_tool_callback_handler.DifyWorkflowCallbackHandler.on_tool_execution` [bad-argument-type]
-  --> tests/unit_tests/core/callback_handler/test_workflow_tool_callback_handler.py:79:30
+  --> tests/unit_tests/core/callback_handler/test_workflow_tool_callback_handler.py:89:30
 ERROR Argument `list[DummyToolInvokeMessage]` is not assignable to parameter `tool_outputs` with type `Iterable[ToolInvokeMessage]` in function `core.callback_handler.workflow_tool_callback_handler.DifyWorkflowCallbackHandler.on_tool_execution` [bad-argument-type]
-   --> tests/unit_tests/core/callback_handler/test_workflow_tool_callback_handler.py:139:30
+   --> tests/unit_tests/core/callback_handler/test_workflow_tool_callback_handler.py:174:30
 ERROR Argument `list[DummyToolInvokeMessage]` is not assignable to parameter `tool_outputs` with type `Iterable[ToolInvokeMessage]` in function `core.callback_handler.workflow_tool_callback_handler.DifyWorkflowCallbackHandler.on_tool_execution` [bad-argument-type]
-   --> tests/unit_tests/core/callback_handler/test_workflow_tool_callback_handler.py:181:30
+   --> tests/unit_tests/core/callback_handler/test_workflow_tool_callback_handler.py:218:30
 ERROR Class member `ConcreteDatasourcePlugin.datasource_provider_type` overrides a member in a parent class but is missing an `@override` decorator [missing-override-decorator]
   --> tests/unit_tests/core/datasource/__base/test_datasource_plugin.py:15:9
 ERROR Class member `ConcreteDatasourcePluginProviderController.get_datasource` overrides a member in a parent class but is missing an `@override` decorator [missing-override-decorator]

[github-actions]

Pyrefly Type Coverage

Metric	Base	PR	Delta
Type coverage	51.49%	51.49%	-0.01%
Strict coverage	51.01%	51.00%	-0.01%
Typed symbols	30,861	30,864	+3
Untyped symbols	29,350	29,359	+9
Modules	2932	2932	0

[hjlarry]

LGTM