Session switch crashes: _system_prompt role not handled in Context.restore()

[pablopda]

Bug Description

Switching sessions via /sessions crashes with a Pydantic validation error when the target session's context.jsonl contains a {"role": "_system_prompt", ...} entry.

Steps to Reproduce

1. Start a kimi session and use it normally
2. Run /sessions and select a different session to switch to
3. Crash occurs during session restore

Error

pydantic_core._pydantic_core.ValidationError: 1 validation error for Message
role
  Input should be 'system', 'user', 'assistant' or 'tool' [type=literal_error, input_value='_system_prompt', input_type=str]

Root Cause

In kimi_cli/soul/context.py, the restore() method (line ~41-48) filters out internal metadata roles _usage and _checkpoint before passing messages to Message.model_validate(), but does not filter _system_prompt:

# Current code in restore()
if line_json["role"] == "_usage":
    self._token_count = line_json["token_count"]
    continue
if line_json["role"] == "_checkpoint":
    self._next_checkpoint_id = line_json["id"] + 1
    continue
message = Message.model_validate(line_json)  # crashes on _system_prompt

The same issue exists in revert_to() (~line 128-134).

Proposed Fix

Add a catch-all for any internal role (prefixed with _) so that future internal roles are also handled gracefully:

# In restore()
if line_json["role"] == "_usage":
    self._token_count = line_json["token_count"]
    continue
if line_json["role"] == "_checkpoint":
    self._next_checkpoint_id = line_json["id"] + 1
    continue
if line_json["role"].startswith("_"):
    continue
message = Message.model_validate(line_json)
self._history.append(message)

# In revert_to()
if line_json["role"] == "_usage":
    self._token_count = line_json["token_count"]
elif line_json["role"] == "_checkpoint":
    self._next_checkpoint_id = line_json["id"] + 1
elif not line_json["role"].startswith("_"):
    message = Message.model_validate(line_json)
    self._history.append(message)

Environment

• kimi-cli version: 1.12.0
• kosong version: 0.42.0
• Python: 3.13.5
• OS: Linux (Ubuntu)

[pablopda]

This is already fixed on the main branch (context.py now handles _system_prompt role properly). The fix was missing in version 1.12.0. Closing — just need to upgrade to the latest release.