Python: fix: DevUI list[Message] input for declarative ToolAgent entry (#6533)

[anneheartrecord]

When a declarative ToolAgent is created, its entry JoinExecutor declares input_types = [dict | str | list[Message] | ...]. DevUI called select_primary_input_type which returned bare Message instead of list[Message], passing a single Message to an executor that expects a list -- causing 'cannot handle message of type Message'.

Root cause: select_primary_input_type iterated over message_types without searching inside the union for list[Message].

Changes:

• _is_list_message_type: detect list[Message] via get_origin/get_args
• _find_chat_message_type: recursively searches union members, prefers list[Message] over bare Message
• select_primary_input_type: use _find_chat_message_type so list[Message] is returned correctly
• generate_input_schema: return {type: string} for list[Message] so DevUI shows a text box
• _looks_like_message_dict: distinguish serialised Message payloads from structured workflow inputs
• parse_input_for_type: handle list[Message] target -- wrap strings/Messages, convert lists of dicts item-by-item, pass structured workflow inputs through unchanged

12 regression tests added; 57 total pass.

Closes #6533

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR improves DevUI handling of declarative entry executors whose input union includes list[Message], ensuring the UI presents a simple text box while runtime input parsing wraps user text into the expected list[Message] shape.

Changes:

• Add recursive detection of list[Message] vs Message in select_primary_input_type.
• Render list[Message] input schemas as a plain JSON {"type":"string"} and parse raw inputs into list[Message].
• Add regression tests covering schema generation and parse_input_for_type behavior for list[Message].

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
python/packages/devui/agent_framework_devui/_utils.py	Adds list[Message] detection, schema rendering as string, and input parsing logic to wrap/convert into list[Message].
python/packages/devui/tests/devui/test_server.py	Adds regression tests for select_primary_input_type and parse_input_for_type with list[Message].
python/packages/devui/tests/devui/test_schema_generation.py	Adds regression test ensuring list[Message] generates a simple string schema.

Comments suppressed due to low confidence (2)

python/packages/devui/agent_framework_devui/_utils.py:476

• generate_input_schema and parse_input_for_type accept and are now called with list[Message], which is a types.GenericAlias (not a type) in modern Python. Keeping the parameter annotations as type is misleading for callers and type checkers, and isinstance(input_data, target_type) will raise TypeError for other generic aliases (e.g., list[str]) if they ever get passed in. Updating these signatures to accept Any (or type[Any] | object) and guarding isinstance (only call it when target_type is a real type) would make this API safer and more accurate.

def generate_input_schema(input_type: type) -> dict[str, Any]:

python/packages/devui/agent_framework_devui/_utils.py:536

• generate_input_schema and parse_input_for_type accept and are now called with list[Message], which is a types.GenericAlias (not a type) in modern Python. Keeping the parameter annotations as type is misleading for callers and type checkers, and isinstance(input_data, target_type) will raise TypeError for other generic aliases (e.g., list[str]) if they ever get passed in. Updating these signatures to accept Any (or type[Any] | object) and guarding isinstance (only call it when target_type is a real type) would make this API safer and more accurate.

def parse_input_for_type(input_data: Any, target_type: type) -> Any: