small updates

modules/capabilities/ai.nix

@@ -69,5 +69,39 @@ in
         pkgs.llm-agents.herdr
         pkgs.ctx7
       ];
+
+      home.file.".codex/AGENTS.md".text = ''
+        # Environment
+
+        This is Nix; use `nix run` for missing commands.
+
+        - Default Nix commands to `--quiet`; inspect logs only for failing derivations.
+        - Never emit full package, derivation, closure, GC, or store-tree listings. Capture them in `/tmp`, summarize or filter, then inspect targeted excerpts.
+        - For store sources, locate files first, then read exact ranges; avoid broad `rg -C` searches.
+
+        # Work
+
+        - Inspect the relevant implementation and follow project conventions.
+        - Prefer the simplest complete solution.
+        - Identify and address root causes rather than masking symptoms.
+        - Prefer existing capabilities and defaults. Add custom code, wrappers, helpers, defensive checks, fallbacks, compatibility layers, or abstractions only for a concrete need.
+        - Delete unnecessary code; keep related logic together.
+        - Use types, schemas, and interfaces to prevent invalid states where practical.
+        - Keep changes focused; preserve behavior unless requested or fixing a confirmed defect.
+        - Verify unfamiliar, version-sensitive, or consequential APIs against current documentation; prefer context7.
+        - Run the most relevant checks; report only verification performed.
+
+        # Reviews and refactoring
+
+        - Inspect complete relevant context, not just the obvious file or diff.
+        - Find unnecessary or duplicated code, redundant state, avoidable checks, reimplemented capabilities, and repeated defaults.
+        - Ask whether defensive code protects a realistic state or hides an unclear invariant.
+        - Optimize conceptual complexity, not line count.
+        - Separate confirmed problems from optional improvements; explain important tradeoffs.
+
+        # Context
+
+        Every action must justify its context. Minimize tools and skills; prefer targeted queries and bounded output. Ask for readily available large output instead of retrieving it.
+      '';
     };
 }