core/config: add [agent] section for profile defaults

Parse and sync system_prompt, max_tool_result_chars, and parallel_tools.

src/plyngent/config/__init__.py

@@ -5,6 +5,7 @@ from typing import TYPE_CHECKING
 import tomlkit
 from tomlkit.exceptions import TOMLKitError
 
+from .models import AgentConfig as AgentConfig
 from .models import AnthropicProvider as AnthropicProvider
 from .models import DatabaseConfig as DatabaseConfig
 from .models import DeepseekProvider as DeepseekProvider

src/plyngent/config/models.py

@@ -10,6 +10,14 @@ class DatabaseConfig(Struct, omit_defaults=True):
     password: str | None = None
 
 
+class AgentConfig(Struct, omit_defaults=True):
+    """Single-user agent profile defaults."""
+
+    system_prompt: str = ""
+    max_tool_result_chars: int = 32_000
+    parallel_tools: bool = True
+
+
 class ModelConfig(Struct, omit_defaults=True):
     """Capability flags for a model within a provider."""
 

src/plyngent/config/store.py

@@ -6,7 +6,7 @@ from typing import TYPE_CHECKING, cast
 import msgspec
 import tomlkit
 
-from .models import DatabaseConfig, Provider
+from .models import AgentConfig, DatabaseConfig, Provider
 
 if TYPE_CHECKING:
     from collections.abc import Mapping, MutableMapping
@@ -25,6 +25,14 @@ def _parse_database(raw: dict[str, object]) -> DatabaseConfig:
         return DatabaseConfig()
 
 
+def _parse_agent(raw: dict[str, object]) -> AgentConfig:
+    """Parse the ``[agent]`` section, falling back to defaults."""
+    try:
+        return msgspec.convert(raw, AgentConfig)
+    except msgspec.ValidationError:
+        return AgentConfig()
+
+
 def _parse_providers(
     document: tomlkit.TOMLDocument,
 ) -> tuple[dict[str, Provider], dict[str, object]]:
@@ -73,6 +81,7 @@ class ConfigStore:
     _path: Path
     _document: tomlkit.TOMLDocument
     _database: DatabaseConfig
+    _agent: AgentConfig
     _providers: dict[str, Provider]
     _bad_providers: dict[str, object]
 
@@ -81,6 +90,7 @@ class ConfigStore:
         self._document = document
         raw: dict[str, object] = document.unwrap()
         self._database = _parse_database(cast("dict[str, object]", raw.get("database", {})))
+        self._agent = _parse_agent(cast("dict[str, object]", raw.get("agent", {})))
         self._providers, self._bad_providers = _parse_providers(document)
 
     # -- database (read-only) --
@@ -90,6 +100,18 @@ class ConfigStore:
         """Read-only mapping view of database configuration."""
         return MappingProxyType(msgspec.structs.asdict(self._database))
 
+    # -- agent (read-only) --
+
+    @property
+    def agent(self) -> MappingProxyType[str, object]:
+        """Read-only mapping view of agent profile configuration."""
+        return MappingProxyType(msgspec.structs.asdict(self._agent))
+
+    @property
+    def agent_config(self) -> AgentConfig:
+        """Typed agent profile (system prompt, tool budgets, etc.)."""
+        return self._agent
+
     # -- providers (read/write) --
 
     @property
@@ -128,6 +150,7 @@ class ConfigStore:
             self._document = tomlkit.parse(f.read())
         raw: dict[str, object] = self._document.unwrap()
         self._database = _parse_database(cast("dict[str, object]", raw.get("database", {})))
+        self._agent = _parse_agent(cast("dict[str, object]", raw.get("agent", {})))
         self._providers, self._bad_providers = _parse_providers(self._document)
 
     # -- internal sync helpers --
@@ -138,20 +161,26 @@ class ConfigStore:
             self._document[key] = tomlkit.table()
         return cast("MutableMapping[str, object]", self._document[key])
 
+    def _sync_section(self, key: str, data: object) -> None:
+        raw: dict[str, object] = msgspec.to_builtins(data)
+        if not raw:
+            if key in self._document:
+                del self._document[key]
+            return
+        section = self._toml_table(key)
+        for k in list(section.keys()):
+            if k not in raw:
+                del section[k]
+        for k, v in raw.items():
+            section[k] = v
+
     def _sync_database_section(self) -> None:
         """Sync ``[database]`` to the document."""
-        raw_db: dict[str, object] = msgspec.to_builtins(self._database)
-        if not raw_db:
-            if "database" in self._document:
-                del self._document["database"]
-            return
+        self._sync_section("database", self._database)
 
-        section = self._toml_table("database")
-        for k in list(section.keys()):
-            if k not in raw_db:
-                del section[k]
-        for k, v in raw_db.items():
-            section[k] = v
+    def _sync_agent_section(self) -> None:
+        """Sync ``[agent]`` to the document."""
+        self._sync_section("agent", self._agent)
 
     def _sync_providers_section(self) -> None:
         """Sync ``[providers]`` to the document."""
@@ -174,4 +203,5 @@ class ConfigStore:
     def _sync_to_document(self) -> None:
         """Incrementally sync all sections into the document."""
         self._sync_database_section()
+        self._sync_agent_section()
         self._sync_providers_section()

tests/test_config/test_agent_section.py

@@ -0,0 +1,34 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from plyngent.config import load
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
+def test_agent_section_defaults(tmp_path: Path) -> None:
+    path = tmp_path / "c.toml"
+    _ = path.write_text("", encoding="utf-8")
+    store = load(path)
+    assert store.agent_config.system_prompt == ""
+    assert store.agent_config.max_tool_result_chars == 32_000  # noqa: PLR2004
+    assert store.agent_config.parallel_tools is True
+
+
+def test_agent_section_parse(tmp_path: Path) -> None:
+    path = tmp_path / "c.toml"
+    _ = path.write_text(
+        """
+[agent]
+system_prompt = "Be brief."
+max_tool_result_chars = 100
+parallel_tools = false
+""",
+        encoding="utf-8",
+    )
+    store = load(path)
+    assert store.agent_config.system_prompt == "Be brief."
+    assert store.agent_config.max_tool_result_chars == 100  # noqa: PLR2004
+    assert store.agent_config.parallel_tools is False