diff --git a/.gitignore b/.gitignore
index 107511d..bbfc8b3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -261,3 +261,32 @@ backend/data/wormhole_stdout.log
 
 # Compressed snapshot archives (can be 100 MB+)
 *.json.gz
+
+# ──────────────────────────────────────────────────────────────────────
+# AI assistant / coding-agent scratch
+# ──────────────────────────────────────────────────────────────────────
+# Per-tool config + scratch directories. These are private to whichever
+# coding agent the operator happens to be using and have no business in
+# the repo. If a tool's instructions need to be canonical for the project,
+# we'll put them in docs/ explicitly — not let the agent dump them at the
+# repo root.
+
+# OpenAI Codex CLI
+.codex/
+.codex-app-schema/
+.codex-app-ts/
+
+# Per-agent instruction files dropped at repo root by various tools.
+# These are operator-side preferences, not part of the project contract.
+AGENTS.md
+GEMINI.md
+CLAUDE.md
+.github/copilot-instructions.md
+
+# Stale AI-generated test file that referenced fields that don't exist in
+# the current `_parse_carrier_positions_from_news` implementation. Kept
+# ignored so it doesn't accidentally get committed if it shows up again
+# from a tool that's working off an out-of-date understanding of the
+# module. If a real test for that function is needed, write it under a
+# meaningful name in tests/test_carrier_tracker_quality.py.
+backend/tests/test_carrier_tracker_region_centers.py