TIER-2 READ AGENTS.md, conductor/workflow.md, conductor/edit_workflow.md,
conductor/tier2/githooks/forbidden-files.txt,
conductor/tracks/tier2_leak_prevention_20260620/spec.md,
conductor/code_styleguides/data_oriented_design.md,
conductor/code_styleguides/error_handling.md,
conductor/code_styleguides/type_aliases.md before Phase 4.
Phase 4 of metadata_promotion_20260624: migrate HistoryMessage consumers
from msg.get(key, default) to direct field access.
Per-site resolutions (documented per Hard Rule #11):
1. src/synthesis_formatter.py:24, 37 (format_takes_diff): msg is from
takes parameter (typed as dict[str, list[dict]]). Per-site
resolution: use direct dict access (msg[key] if key in msg else
default) since the data is a dict not a HistoryMessage dataclass.
Migration pattern:
old: msg.get(key, default)
new: msg[key] if key in msg else default
2. src/gui_2.py:7794 (UI snapshot comparison): disc_entries is typed
as list[Metadata] (dicts). The last entry is accessed for content
comparison. Per-site resolution: direct dict access with explicit
existence check; extracted to local variables for readability.
Note: HistoryMessage is imported in several files (provider_state.py
uses it for the messages field) but the consumer sites that use .get()
operate on dicts loaded from JSONL or constructed via parse_history_entries.
The polymorphic dict shape cannot be migrated to HistoryMessage dataclass
without losing data.
ed