[trissim]

One line of config: mypy reads Toad's declared source roots, src and tools. It is paired with Core P883. It unblocks Core's debt-src, which currently crashes on every Core PR before comparing anything:

ClientTypeErrors could not check batrachian-toad at 20eac8baf…: tools/performance: error:
Source file found twice under different module names: "tools.performance" and "performance"

(agent-comms run 40800748028, job 123208052787)

 [tool.mypy]
 follow_untyped_imports = true
+mypy_path = ["src", "tools"]

Why this config is the one the checker reads

Core tools/debt_ratchet.py, ClientTypeErrors.checked:

• it runs python -m mypy with cwd=client.checkout, this repository;
• TypeErrors.mypy passes --explicit-package-bases and no --config-file;
• it sets MYPYPATH to Core's archived src plus this checkout's src.

So mypy discovers its config in this checkout. Toad main has pyproject.toml and no mypy.ini, .mypy.ini or setup.cfg, so [tool.mypy] here is the config it selects.

Why it removes the duplicate name

From mypy's find_sources.py:

• the explicit package bases are MYPYPATH + options.mypy_path + [cwd] (get_explicit_package_bases, line 93);
• a source file takes the first base met while crawling up from its directory (_crawl_up_helper, line 186).

With only cwd as a base, tools/performance/*.py (no __init__.py) is named tools.performance.*. Meanwhile tools/acceptance.py:34-36 puts its own directory on sys.path and imports performance.*. With tools as a base, the crawl stops at tools, so the package gets the one name its importer uses. src is listed because it is the other declared root; Core's MYPYPATH already names it.

Scope

• Config only, from fresh main (40bc10482). Toad Input delivery reads through Core's one owner-live operation (agent-comms#3538) #1302's owner-read source is not ported here and stays frozen.
• Input delivery reads through Core's one owner-live operation (agent-comms#3538) #1302 carries the same line (ef21cbf25); when this lands, that commit merges as a no-op.
• No tests or checkers run by the author. Root reviews the diff and hosted gates decide. Not claimed to clear debt-src until the hosted comparison completes.

🤖 Generated with Claude Code

https://claude.ai/code/session_01RnH6dS2Kmg1WxNnAc78YHA

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