diff --git a/.ai/README.md b/.ai/README.md
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+# .ai
+
+Store repository-local AI artifacts here.
+
+Examples:
+
+- prompts
+- notes
+- plans
+- generated scratch files
+
+This directory is gitignored on non-`ai` branches in this repo.
diff --git a/.gitignore b/.gitignore
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+++ b/.gitignore
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 # Tempfiles created by git-spell-check
 docs-dictionary-*
 temp_file-*
-
-# Local AI working files live here. Keep ignored on non-ai branches.
-.ai/
-AGENTS.md
diff --git a/AGENTS.md b/AGENTS.md
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+# AGENTS.md
+
+This repository keeps AI-specific working files in the project-local `.ai/` directory, and keeps the repository-level `AGENTS.md` as a local AI control file.
+
+Rules:
+
+1. Keep all AI notes, prompts, plans, transcripts, and generated helper artifacts under `.ai/`.
+2. Keep `AGENTS.md` as a local AI instruction file for this repository.
+3. On main development branches, both `.ai/` and `AGENTS.md` must remain gitignored so they can exist locally without affecting normal commits.
+4. If AI files need to be versioned, do that work on a branch named `ai`, where `.ai/` and `AGENTS.md` can be tracked intentionally.
+5. When switching between `ai` and non-`ai` branches, preserve local AI files unless the user explicitly asks to remove them.
+6. Any commit created by Codex in this repository must set the git author identity on the `git commit` command itself using `--author="Codex <codex@local>"`.
+
+Practical workflow:
+
+- Use `.ai/` for persistent local AI context in this working tree.
+- Keep `.gitignore` on non-`ai` branches configured to ignore both `.ai/` and `AGENTS.md`.
+- If the `ai` branch should track these files, remove or override those ignore rules on the `ai` branch before committing.
+- Do not rely on global git config for Codex-authored commits in this repository; pass the author explicitly on each commit command.