fix: preserve exploration tool history and cap context budget

tests/unit/test_memory_config.py

@@ -19,6 +19,16 @@ import pytest
 from artemis.config import AgentGlobalConfig, load_agent_config
 
 
+def test_transcript_budget_cannot_exceed_300k_context_ceiling():
+    from pydantic import ValidationError
+    from artemis.config.agent import MemoryTranscriptConfig
+
+    assert MemoryTranscriptConfig().context_budget_tokens == 80_000
+    assert MemoryTranscriptConfig(context_budget_tokens=300_000).context_budget_tokens == 300_000
+    with pytest.raises(ValidationError):
+        MemoryTranscriptConfig(context_budget_tokens=300_001)
+
+
 def test_memory_defaults():
     cfg = AgentGlobalConfig.model_validate({})
     assert cfg.flash.step_summarizer.timeout_seconds == 120.0