diff --git a/.arcanist/memories/364cb094.md b/.arcanist/memories/364cb094.md
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+---
+id: mem-364cb094
+type: gotcha
+context_hint: Operators or transforms that cache results and process dataclass objects
+referenced_files:
+  - nons/operators/deterministic.py
+source_pr_url: https://github.com/shreypjain/non/pull/16
+source_session_id: 9db00177-844e-4c98-8cbd-e0c7354f9f04
+---
+
+When modifying dataclass objects inside operator `transform()` methods (or any caching pipeline), never mutate fields in-place — use `dataclasses.replace()` to create a new instance. In-place mutation changes the object's hash, corrupting cache keys and causing unbounded cache growth.
diff --git a/.arcanist/memories/394fab9e.md b/.arcanist/memories/394fab9e.md
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+---
+id: mem-394fab9e
+type: gotcha
+context_hint: Checking Optional fields on Pydantic models using hasattr
+referenced_files:
+  - nons/core/agents/agent.py
+source_pr_url: https://github.com/shreypjain/non/pull/16
+source_session_id: 9db00177-844e-4c98-8cbd-e0c7354f9f04
+---
+
+When checking if a Pydantic BaseModel field is set/truthy, never use `hasattr()` — all declared fields always have the attribute. Use an explicit `is not None` check (or `is not None` + not-empty) instead. E.g., `decision.params if decision.params is not None else {}`.