diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..5aee0f7
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+
+# Claude Code worktrees. These are other sessions' checkouts living inside this
+# repo; `git add -A` will otherwise commit them as embedded git repositories.
+.claude/worktrees/
diff --git a/infra/.claude/skills/key-gaps/SKILL.md b/infra/.claude/skills/key-gaps/SKILL.md
index 3896d72..f243540 100644
--- a/infra/.claude/skills/key-gaps/SKILL.md
+++ b/infra/.claude/skills/key-gaps/SKILL.md
@@ -34,8 +34,18 @@ Gather the key names over SSH (never the values), then audit. Hosts/keys per INF
 K=~/.ssh/thermograph_agent_ed25519
 # sudo: /etc/thermograph.env is root-owned (0640). On prod `agent` can read it
 # directly too, but sudo works uniformly on both boxes.
-ssh -i $K agent@169.58.46.181 'sudo grep -oE "^[A-Z_]+=" /etc/thermograph.env' > /tmp/prod.keys  # prod
-ssh -i $K agent@75.119.132.91  'sudo grep -oE "^[A-Z_]+=" /etc/thermograph.env' > /tmp/beta.keys  # beta
+#
+# The character class must allow DIGITS. This was `^[A-Z_]+=` until 2026-07-24,
+# which silently skipped every key whose name contains a digit — in this estate
+# that is all six *_S3_* keys. Prod audited as 26 keys against 32 real ones, and
+# the audit reported the S3 credentials as missing from both hosts. They were
+# present the whole time, and the phantom was independently "confirmed" twice by
+# people re-running the same pattern. An audit that under-reports is worse than
+# no audit: the invented finding sends someone to provision a credential that
+# already exists, and it was briefly recorded as a root cause of a real bug.
+# The match still stops at the `=`, so no value is ever read.
+ssh -i $K agent@169.58.46.181 'sudo grep -oE "^[A-Z][A-Z0-9_]*=" /etc/thermograph.env' > /tmp/prod.keys  # prod
+ssh -i $K agent@75.119.132.91  'sudo grep -oE "^[A-Z][A-Z0-9_]*=" /etc/thermograph.env' > /tmp/beta.keys  # beta
 python3 .claude/skills/key-gaps/key_gaps.py prod=/tmp/prod.keys beta=/tmp/beta.keys
 ```
 
diff --git a/infra/.claude/skills/key-gaps/key_gaps.py b/infra/.claude/skills/key-gaps/key_gaps.py
index 775f7ab..a32df73 100755
--- a/infra/.claude/skills/key-gaps/key_gaps.py
+++ b/infra/.claude/skills/key-gaps/key_gaps.py
@@ -17,7 +17,7 @@ It reads only KEY NAMES, never values — safe to run anywhere. Sources per envi
   * a SOPS-encrypted YAML (deploy/secrets/<env>.yaml) — keys are plaintext even when
     encrypted, so no age key or decryption is needed; or
   * a plain key-list file (one KEY per line, or KEY=... lines) — e.g. the output of
-    `ssh <box> 'grep -oE "^[A-Z_]+=" /etc/thermograph.env'` for a live audit.
+    `ssh <box> 'grep -oE "^[A-Z][A-Z0-9_]*=" /etc/thermograph.env'` for a live audit.
 
 Usage:
   key_gaps.py prod=deploy/secrets/prod.yaml beta=deploy/secrets/beta.yaml