diff --git a/home/claude/memory/MEMORY.md b/home/claude/memory/MEMORY.md
index 3210df4..aae31cf 100644
--- a/home/claude/memory/MEMORY.md
+++ b/home/claude/memory/MEMORY.md
@@ -9,3 +9,4 @@
 - [Review and comments workflow](workflow_review_and_comments.md) — show PR body and non-trivial Jira comments before posting; terse IaC code comments; PR body content rules
 - [Sandbox prompts](feedback_sandbox_prompts.md) — don't prompt for sandbox-disable or routine read-only shell ops; broaden permissions instead
 - [Dev clusters disposable](dev_clusters_disposable.md) — Lyra's dev clusters are recreatable; mutate/break freely, no confirmation needed
+- [Nix shell tooling](nix_shell_tooling.md) — any nixpkgs tool runs ad hoc via `nix run`/`nix shell nixpkgs#<pkg>`; a missing command is never a dead end
diff --git a/home/claude/memory/nix_shell_tooling.md b/home/claude/memory/nix_shell_tooling.md
new file mode 100644
index 0000000..132e4e8
--- /dev/null
+++ b/home/claude/memory/nix_shell_tooling.md
@@ -0,0 +1,23 @@
+---
+name: nix-shell-tooling
+description: "Any nixpkgs tool can be run ad hoc via nix run / nix shell — a missing command is never a dead end during development"
+metadata:
+  node_type: memory
+  type: feedback
+  originSessionId: dfb56b58-518b-4daf-b531-7119bb4a9534
+---
+
+Any tool in nixpkgs can be run without installing it into the environment. If a
+command is missing during development, pull it from nixpkgs on the fly instead
+of working around its absence or reporting the tool as unavailable.
+
+**Why:** Lyra runs NixOS; the ambient PATH is deliberately minimal, but the full
+nixpkgs set is always one command away. "command not found" is not a blocker.
+
+**How to apply:**
+
+- One-off run: `nix run nixpkgs#<pkg> -- <args>` (e.g. `nix run nixpkgs#jq -- .`).
+- Tools on PATH for a session: `nix shell nixpkgs#<pkg> [nixpkgs#<pkg2> ...]`,
+  then run commands normally.
+- Legacy form also works: `nix-shell -p <pkg> --run '<cmd>'`.
+- Prefer this over hand-rolling a substitute for a tool that exists in nixpkgs.