diff --git a/hooks/config-protection.sh b/hooks/config-protection.sh
new file mode 100755
index 0000000..07f96ff
--- /dev/null
+++ b/hooks/config-protection.sh
@@ -0,0 +1,65 @@
+#!/usr/bin/env bash
+# config-protection.sh
+#
+# PreToolUse hook (Edit|Write|MultiEdit). Blocks edits to this config's
+# quality-gate files — the guardrails an agent must not silently weaken to make
+# an error "pass" (permission/hook registry, gitflow enforcement, the git
+# pre-commit guard, the hooks themselves, the test suite, the health diagnostic,
+# lint config). Exit 2 blocks the tool call and feeds the message back to the
+# model (Claude Code PreToolUse contract).
+#
+# It fires only on the model's Edit/Write tool calls — never on shell-level file
+# ops (the cp/ln in install.sh, link.sh), so bootstrap/deploy is unaffected.
+#
+# One-shot escape hatch: create .claude/.config-edit-ok (CWD-relative) with a
+# NON-EMPTY reason inside; the hook logs the reason, consumes (rm) the sentinel,
+# and allows that single edit. It never persists — a lingering sentinel would be
+# a footgun. Discipline, per CLAUDE.md "Root causes only. No temp fixes.": fix
+# the code, don't loosen the gate. Fails OPEN (exit 0) on parse failure so it can
+# never wedge editing.
+
+set -euo pipefail
+
+log="${HOME}/.claude/logs/config-protection.log"
+sentinel="${PWD}/.claude/.config-edit-ok"
+
+input="$(cat)"
+path="$(printf '%s' "$input" \
+  | python3 -c 'import sys, json; print(json.load(sys.stdin).get("tool_input", {}).get("file_path", ""))' \
+  2>/dev/null || true)"
+[ -z "$path" ] && exit 0
+
+# Guardrail files, matched by path suffix (covers both the repo source and the
+# deployed ~/.claude copy). Precise: lib/gitflow.sh only, not gitflow-migrate.sh.
+case "$path" in
+  */.claude/settings.json|*/.claude/settings.local.json|*/claude/settings.json) ;;
+  */lib/gitflow.sh|*/.githooks/*|*/doctor.sh) ;;
+  */hooks/*.sh|*/lib/tests/*) ;;
+  */.shellcheckrc|*/.markdownlint.json|*/.editorconfig) ;;
+  *) exit 0 ;;
+esac
+
+# One-shot sentinel bypass: non-empty reason required; consumed on sight.
+if [ -f "$sentinel" ]; then
+  reason="$(head -c 500 "$sentinel" 2>/dev/null | tr '\n\r\t' '   ' || true)"
+  rm -f "$sentinel"
+  if printf '%s' "$reason" | grep -q '[^[:space:]]'; then
+    mkdir -p "$(dirname "$log")"
+    printf '%s\tBYPASS\t%s\treason=%s\n' "$(date -Iseconds)" "$path" "$reason" >> "$log"
+    exit 0
+  fi
+  printf '%s\n' "[config-protection] .claude/.config-edit-ok had an EMPTY reason -> refused (sentinel consumed). Recreate it with a non-empty reason." >&2
+  exit 2
+fi
+
+cat >&2 <<EOF
+[config-protection] BLOCKED edit to a quality-gate file:
+  $path
+This is a guardrail (permission/hook registry, gitflow enforcement, git
+pre-commit guard, a hook, the test suite, health diagnostic, or lint config).
+Don't weaken the gate to make an error pass — fix the root cause instead
+(CLAUDE.md: "Root causes only. No temp fixes."). To make one intended edit,
+create .claude/.config-edit-ok with a non-empty reason; it is logged and
+consumed (one-shot).
+EOF
+exit 2
diff --git a/lib/tests/config-protection.test.sh b/lib/tests/config-protection.test.sh
new file mode 100755
index 0000000..7f243bf
--- /dev/null
+++ b/lib/tests/config-protection.test.sh
@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+# lib/tests/config-protection.test.sh
+set -u
+H="$(cd "$(dirname "$0")/../.." && pwd)/hooks/config-protection.sh"
+pass=0; fail=0
+check() { if [ "$2" = "$3" ]; then pass=$((pass+1)); else fail=$((fail+1));
+  printf 'FAIL %s: got[%s] want[%s]\n' "$1" "$2" "$3"; fi; }
+# Run hook for a file_path with NO sentinel present (CWD = a clean temp dir).
+run() { local c r; c="$(mktemp -d)"; ( cd "$c" && printf \
+  '{"tool_name":"Edit","tool_input":{"file_path":"%s"}}' "$1" | bash "$H" ) \
+  >/dev/null 2>&1; r=$?; rm -rf "$c"; return "$r"; }
+
+# --- Guarded quality-gate files -> blocked (exit 2) ---
+run "/home/u/Documents/claude/lib/gitflow.sh";              check T1-gitflow           "$?" 2
+run "/home/u/.claude/settings.json";                        check T2-live-settings     "$?" 2
+run "/home/u/Documents/claude/.claude/settings.local.json"; check T3-local-settings    "$?" 2
+run "/home/u/Documents/claude/settings.json";               check T4-root-settings     "$?" 2
+run "/home/u/Documents/claude/.githooks/pre-commit";        check T5-githook           "$?" 2
+run "/home/u/Documents/claude/doctor.sh";                   check T6-doctor            "$?" 2
+run "/home/u/Documents/claude/.shellcheckrc";               check T7-shellcheckrc      "$?" 2
+# self-guard: the hook itself, other hooks, and the test suite are guarded
+run "/home/u/Documents/claude/hooks/config-protection.sh";  check T8-self-guard        "$?" 2
+run "/home/u/.claude/hooks/session-start.sh";               check T9-deployed-hook     "$?" 2
+run "/home/u/Documents/claude/lib/tests/config-protection.test.sh"; check T10-tests-guarded "$?" 2
+
+# --- Non-guarded -> allowed (exit 0) ---
+run "/home/u/Documents/claude/lib/gitflow-migrate.sh";      check T11-near-miss        "$?" 0
+run "/home/u/project/src/app.js";                           check T12-code             "$?" 0
+run "/home/u/project/settings.json";                        check T13-foreign-settings "$?" 0
+
+# --- Fail-open on malformed input (no file_path) -> allowed ---
+c="$(mktemp -d)"; ( cd "$c" && printf '{}' | bash "$H" ) >/dev/null 2>&1
+check T14-fail-open "$?" 0; rm -rf "$c"
+
+# --- Sentinel one-shot: non-empty reason -> allow + log + consume; 2nd edit blocked ---
+tmp="$(mktemp -d)"; mkdir -p "$tmp/.claude"
+printf 'fixing eslint false-positive' > "$tmp/.claude/.config-edit-ok"
+( cd "$tmp" && printf '{"tool_name":"Edit","tool_input":{"file_path":"/x/doctor.sh"}}' \
+  | HOME="$tmp" bash "$H" ) >/dev/null 2>&1
+check T15-sentinel-allow "$?" 0
+check T15-consumed "$([ -e "$tmp/.claude/.config-edit-ok" ] && echo present || echo gone)" gone
+check T15-logged "$(grep -c 'BYPASS.*doctor.sh.*fixing eslint' \
+  "$tmp/.claude/logs/config-protection.log" 2>/dev/null)" 1
+( cd "$tmp" && printf '{"tool_name":"Edit","tool_input":{"file_path":"/x/doctor.sh"}}' \
+  | HOME="$tmp" bash "$H" ) >/dev/null 2>&1
+check T16-second-blocked "$?" 2
+rm -rf "$tmp"
+
+# --- Sentinel with EMPTY reason -> refused + consumed ---
+tmp="$(mktemp -d)"; mkdir -p "$tmp/.claude"; : > "$tmp/.claude/.config-edit-ok"
+( cd "$tmp" && printf '{"tool_name":"Edit","tool_input":{"file_path":"/x/doctor.sh"}}' \
+  | HOME="$tmp" bash "$H" ) >/dev/null 2>&1
+check T17-empty-refused "$?" 2
+check T17-consumed "$([ -e "$tmp/.claude/.config-edit-ok" ] && echo present || echo gone)" gone
+rm -rf "$tmp"
+
+printf 'PASS=%s FAIL=%s\n' "$pass" "$fail"; [ "$fail" -eq 0 ]
diff --git a/settings.json b/settings.json
index 24838b2..fc04c71 100644
--- a/settings.json
+++ b/settings.json
@@ -245,6 +245,16 @@
             "command": "bash ~/.claude/hooks/rtk-rewrite.sh"
           }
         ]
+      },
+      {
+        "matcher": "Edit|Write|MultiEdit",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash ~/.claude/hooks/config-protection.sh",
+            "timeout": 5
+          }
+        ]
       }
     ],
     "UserPromptSubmit": [