diff --git a/.claude/rules/bash-style.md b/.claude/rules/bash-style.md
index 3227323..36c50b3 100644
--- a/.claude/rules/bash-style.md
+++ b/.claude/rules/bash-style.md
@@ -20,7 +20,7 @@ Complements CLAUDE.md. Does not repeat rules already defined there.
 
 ## Naming
 
-- `UPPER_CASE` — exported env vars and constants
+- `UPPER_CASE` — exported env vars and constants; use `readonly` for true constants
 - `snake_case` — local variables and function names
 - `verb_noun` pattern for functions: `set_ps1_prompt`, `docker_aws_login`
 - Meaningful names, no single letters except loop counters (`i`, `f`)
@@ -51,6 +51,15 @@ function do_thing() {
 - Single quotes for literals that must not expand
 - `printf` over `echo` when output contains escapes or format strings
 
+## Resource Cleanup
+
+- Consider `trap cleanup EXIT` with `mktemp` when scripts create temporary files/dirs or acquire resources; skip when it would add unnecessary complexity (short scripts, no temp state)
+
+## Structured Data
+
+- Prefer `jq` for JSON and `yq` for YAML over ad-hoc `grep`/`awk`/string splitting
+- Treat parser errors as fatal; check exit status before using results
+
 ## Commands
 
 - Long options for clarity: `--recursive` not `-r` (common test flags `-f`, `-d`, `-e` are fine)