feat: preserve planner context across task steps

runtime/planner_config.py

@@ -11,6 +11,7 @@ DEFAULT_MODEL_BY_PROVIDER = {
     "openai_compatible": "local-model",
 }
 DEFAULT_TIMEOUT_SECONDS = 30.0
+DEFAULT_HISTORY_MAX_TURNS = 20
 
 ENABLED_ENV = "AI_PLANNER_ENABLED"
 PROVIDER_ENV = "AI_PLANNER_PROVIDER"
@@ -20,6 +21,7 @@ THINKING_BUDGET_ENV = "AI_PLANNER_THINKING_BUDGET_TOKENS"
 API_KEY_ENV = "AI_PLANNER_API_KEY"
 BASE_URL_ENV = "AI_PLANNER_BASE_URL"
 MULTIMODAL_ENV = "AI_PLANNER_MULTIMODAL"
+HISTORY_MAX_TURNS_ENV = "AI_PLANNER_HISTORY_MAX_TURNS"
 
 SUPPORTED_PROVIDERS = frozenset(DEFAULT_MODEL_BY_PROVIDER)
 
@@ -34,6 +36,7 @@ class PlannerConfig:
     api_key: str | None = None
     base_url: str | None = None
     multimodal: bool = False
+    history_max_turns: int = DEFAULT_HISTORY_MAX_TURNS
 
     def resolved_model(self) -> str:
         return self.model or DEFAULT_MODEL_BY_PROVIDER[self.provider]
@@ -50,6 +53,10 @@ def load_config(env: Mapping[str, str] | None = None) -> PlannerConfig:
         api_key=values.get(API_KEY_ENV) or _provider_key(values),
         base_url=values.get(BASE_URL_ENV) or None,
         multimodal=_parse_bool(values.get(MULTIMODAL_ENV), default=False),
+        history_max_turns=_parse_positive_int(
+            values.get(HISTORY_MAX_TURNS_ENV),
+            default=DEFAULT_HISTORY_MAX_TURNS,
+        ),
     )
 
 
@@ -88,6 +95,16 @@ def _parse_thinking_budget(value: str | None) -> int | None:
     return budget if budget > 0 else None
 
 
+def _parse_positive_int(value: str | None, *, default: int) -> int:
+    if value is None:
+        return default
+    try:
+        parsed = int(value)
+    except ValueError:
+        return default
+    return parsed if parsed > 0 else default
+
+
 def _provider_key(values: Mapping[str, str]) -> str | None:
     provider = (values.get(PROVIDER_ENV) or DEFAULT_PROVIDER).strip().lower()
     if provider == "openai":