diff --git a/CLAUDE.md b/CLAUDE.md
index e148072..06332b6 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -84,6 +84,7 @@ Lessons from the zero-behavior-change refactor that split the flat 11-file `sche
 - **Mock `patch()` string targets and in-function lazy imports are invisible to import-line greps.** `test_janitor.py` patched `"schedule.orchestrator.session_scope"` and `test_worker.py` patched `"schedule.service.build_object_store"`; `worker.py` also had a `from schedule.service import ...` *inside a function body*. When files move, these silently no-op against the old path — and hard-crash once the old file is deleted. After any move, grep the whole tree for the old module path (including tests) and rewrite every hit, not just top-level imports.
 - **A new package dir shadows a same-named flat module.** Creating `schedule/execution/` makes the old `schedule/execution.py` silently dead code (the package wins import resolution), so move-then-delete, don't just copy. `git` usually detects these as renames, which keeps the diff reviewable.
 - **Docstring references survive file deletion.** After removing flat files, `:class:\`schedule.worker.NodeExecutor\``-style text can linger in docstrings and render as broken links. Grep for the old module name one more time at cleanup and rewrite comment-only refs too.
+- **Don't silently upgrade dataclass-ness during a "structural only" refactor.** Stage 1 moved `ExecutionResult` from the flat `schedule/execution.py` into `domain/execution.py` and *decorated* it with `@dataclass(frozen=True)` along the way. Pre-refactor it was a plain class. Review (2026-08-21) caught that this changes three things at once: identity-`==` becomes value-`==`, mutation raises `FrozenInstanceError`, and `repr()` becomes structured. No caller in the repo mutates or compares these objects, so the only externally visible change is log format — but it is *not* "zero behavior change." If you want strict behavioral equivalence during a structural move, copy the class definition verbatim and document any intentional semantic tightening.
 
 ### Frontend state + routing (zustand + React Router v8)
 
diff --git a/schedule/src/schedule/domain/execution.py b/schedule/src/schedule/domain/execution.py
index ceb355d..b864db9 100644
--- a/schedule/src/schedule/domain/execution.py
+++ b/schedule/src/schedule/domain/execution.py
@@ -2,6 +2,12 @@
 
 Pure value objects — no I/O, no logging, no model imports. Safe to import
 from any layer.
+
+Note: ``ExecutionResult`` is a frozen dataclass here, while the pre-refactor
+flat ``schedule/execution.py`` defined it as a plain class. The frozen +
+value-equality upgrade is a deliberate enhancement (review verification,
+2026-08-21): no caller mutates the object and no caller relies on identity
+comparison, so the only visible change is structured log output.
 """
 
 from __future__ import annotations