core/config: split agent system_prompt and tool_directives

src/plyngent/cli/editor.py

@@ -29,8 +29,9 @@ _MINIMAL_CONFIG = """\
 # # url = ":memory:"
 
 # [agent]
-# # system_prompt defaults to the built-in coding-agent guide when omitted.
-# # system_prompt = ""  # disable; or multi-line '''...''' to override
+# # system_prompt = persona (omit → built-in). tool_directives = tool playbook.
+# # system_prompt = "" / tool_directives = "" disable each part; both "" → no system.
+# # Or multi-line '''...''' to override.
 # max_tool_result_chars = 32000
 # parallel_tools = true
 # confirm_destructive = true

src/plyngent/cli/state.py

@@ -169,9 +169,13 @@ class ReplState:
 
     def _make_agent(self) -> ChatAgent:
         from plyngent.cli.limits import prompt_continue_limit_async
+        from plyngent.config import compose_agent_system_content
 
         agent_cfg = self.config.agent_config
-        system_prompt = agent_cfg.system_prompt or None
+        system_prompt = compose_agent_system_content(
+            agent_cfg.system_prompt,
+            agent_cfg.tool_directives,
+        )
         on_limit = prompt_continue_limit_async if self.interactive_limits else None
         return ChatAgent(
             self.client,

src/plyngent/config/__init__.py

@@ -6,6 +6,7 @@ import tomlkit
 from tomlkit.exceptions import TOMLKitError
 
 from .models import DEFAULT_SYSTEM_PROMPT as DEFAULT_SYSTEM_PROMPT
+from .models import DEFAULT_TOOL_DIRECTIVES as DEFAULT_TOOL_DIRECTIVES
 from .models import AgentConfig as AgentConfig
 from .models import AnthropicProvider as AnthropicProvider
 from .models import DatabaseConfig as DatabaseConfig
@@ -15,6 +16,7 @@ from .models import ModelConfig as ModelConfig
 from .models import OpenAICompatibleProvider as OpenAICompatibleProvider
 from .models import OpenAIProvider as OpenAIProvider
 from .models import ProviderConfig as ProviderConfig
+from .models import compose_agent_system_content as compose_agent_system_content
 from .path import get_default_path as _get_default_path
 from .store import ConfigFormatError as ConfigFormatError
 from .store import ConfigStore as ConfigStore

src/plyngent/config/models.py

@@ -2,12 +2,16 @@ from typing import Any
 
 from msgspec import Struct, field
 
-# Built-in agent system prompt when ``[agent].system_prompt`` is omitted.
-# Set ``system_prompt = ""`` in TOML to disable. Override with a multi-line
-# TOML literal (prefer '''...''' so nested " quotes are fine).
+# Built-in persona when ``[agent].system_prompt`` is omitted.
+# Set ``system_prompt = ""`` to omit the persona block only.
+# Override with a multi-line TOML literal (prefer ''' so nested " is fine).
 DEFAULT_SYSTEM_PROMPT = """\
 You are a professional coding agent in a workspace-bound tool environment.
+"""
 
+# Built-in tool playbook when ``[agent].tool_directives`` is omitted.
+# Set ``tool_directives = ""`` to omit this block only.
+DEFAULT_TOOL_DIRECTIVES = """\
 ### Workspace
 - Explore with `tree`/`listdir`/`glob_paths`/`grep_files`/`read_file` when unsure.
 - Stay under the workspace (or a path from `new_temporary_workspace`). Respect path denylists.
@@ -41,6 +45,21 @@ pop the group). Open items mean unfinished work.
 """
 
 
+def compose_agent_system_content(
+    system_prompt: str,
+    tool_directives: str,
+) -> str | None:
+    """Join persona + tool playbook into one system body, or ``None`` if both empty.
+
+    Non-empty parts are stripped and joined with a blank line. Either field may
+    be ``""`` to disable that part while keeping the other.
+    """
+    parts = [part.strip() for part in (system_prompt, tool_directives) if part and part.strip()]
+    if not parts:
+        return None
+    return "\n\n".join(parts)
+
+
 class DatabaseConfig(Struct, omit_defaults=True):
     """Database connection configuration.
 
@@ -58,7 +77,10 @@ class DatabaseConfig(Struct, omit_defaults=True):
 class AgentConfig(Struct, omit_defaults=True):
     """Single-user agent profile defaults."""
 
+    # Persona / role (omit → DEFAULT_SYSTEM_PROMPT; "" disables persona only).
     system_prompt: str = DEFAULT_SYSTEM_PROMPT
+    # Tool how-to (omit → DEFAULT_TOOL_DIRECTIVES; "" disables playbook only).
+    tool_directives: str = DEFAULT_TOOL_DIRECTIVES
     max_tool_result_chars: int = 32_000
     parallel_tools: bool = True
     confirm_destructive: bool = True