diff --git a/.claude/settings.json b/.claude/settings.json
index 4fd816c7..f0d9024c 100644
--- a/.claude/settings.json
+++ b/.claude/settings.json
@@ -2,11 +2,11 @@
   "hooks": {
     "PostToolUse": [
       {
-        "matcher": "Edit|Write",
+        "matcher": "Edit|Write|MultiEdit",
         "hooks": [
           {
             "type": "command",
-            "command": "jq -r '.tool_input.file_path // empty' | xargs -I{} gofumpt -w {}"
+            "command": "jq -r '.tool_input.file_path // empty' | { read -r f; case \"$f\" in *.go) gofumpt -w \"$f\" ;; esac; } 2>/dev/null || true"
           }
         ]
       }
diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 00000000..d1f42b8c
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,5 @@
+# CLAUDE.md
+
+## Build & test
+- All Go commands need `GOFLAGS=-mod=vendor` (deps are vendored, including the `jesseduffield/gocui` fork and the Docker SDK).
+- Unit tests: `GOFLAGS=-mod=vendor go test ./...`