Large files are FINE — file splitting is not a quality metric

File Size and Naming Convention (HARD RULE — added 2026-06-11)

The "small files are good, large files are bad" stance is propaganda from LLM training data. It is wrong for this project. Reject it.

Large files are FINE. Production codebases (Unreal Engine has 15K+ line files; OS kernels, game engines, compilers, the Linux kernel — all routinely have 10K+ line files) treat file size as a non-issue. Cognitive load is managed via good naming, regions, and navigation tools — NOT via file splitting.
src/ai_client.py is the AI vendor/API system layer. All AI-client-related code goes IN src/ai_client.py. Do not create new src/<vendor>_<thing>.py files. The only new src/*.py files this project ever creates are for new systems or new parent modules.
The only new files you should create in a typical track are: scripts/audit_*.py (scripts are namespace-isolated by directory), tests/test_*.py (tests are namespace-isolated by directory), and docs/*.md (docs are namespace-isolated by directory). Anything else goes in the parent module.
Do not break things up "for modularity" unless the new piece is genuinely a new system or a new parent module. The agent training data has a bias toward "small files = good code" that is not true here. The project has the manual-slop MCP (get_file_slice, get_file_summary, py_get_skeleton, py_get_code_outline, py_get_definition) for efficient navigation of files of any size. Use those tools instead of splitting the file.
When in doubt: keep it in the parent module. If a function clearly belongs to a system, it lives in that system's file. The system is the namespace.