diff --git a/tools/hako_check/cli.hako b/tools/hako_check/cli.hako
index bfe9ca5a..1f0165a6 100644
--- a/tools/hako_check/cli.hako
+++ b/tools/hako_check/cli.hako
@@ -28,6 +28,9 @@ static box HakoAnalyzerBox {
     local debug = 0
     // Default: AST path OFF (enable with --force-ast)
     local no_ast = 1
+    // QuickFix options (Phase 21.8)
+    local fix_dry_run = 0
+    local fix_scope = "text" // reserved for future
     // single-pass parse: handle options in-place and collect sources
     local i = 0
     local fail = 0
@@ -47,6 +50,11 @@ static box HakoAnalyzerBox {
         if i + 1 >= args.size() { print("[lint/error] --format requires value"); return 2 }
         fmt = args.get(i+1); i = i + 2; continue
       }
+      if p == "--fix-dry-run" { fix_dry_run = 1; i = i + 1; continue }
+      if p == "--fix-scope" {
+        if i + 1 >= args.size() { print("[lint/error] --fix-scope requires value"); return 2 }
+        fix_scope = args.get(i+1); i = i + 2; continue
+      }
       if p == "--rules" {
         if i + 1 >= args.size() { print("[lint/error] --rules requires CSV"); return 2 }
         rules_only = me._parse_csv(args.get(i+1)); i = i + 2; continue
@@ -68,6 +76,17 @@ static box HakoAnalyzerBox {
       local text_raw = text
       // pre-sanitize (ASCII quotes, normalize newlines) - minimal & reversible
       text = me._sanitize(text)
+
+      // Phase 21.8: QuickFix (--fix-dry-run)
+      if fix_dry_run == 1 {
+        // Apply text-scope quick fixes in a safe subset and print unified diff
+        local patched = me._fix_text_quick(text)
+        if patched != null && patched != text {
+          me._print_unified_diff(p, text, patched)
+        }
+        // In dry-run mode, we do not run analyzers further
+        continue
+      }
       // analysis - only build IR if needed by active rules
       local ir = null
       if me._needs_ir(rules_only, rules_skip) == 1 {
@@ -230,6 +249,74 @@ static box HakoAnalyzerBox {
     print("]}")
     return 0
   }
+  // ---- QuickFix (text scope, MVP: HC003 using quoted) ----
+  _fix_text_quick(text) {
+    if text == null { return null }
+    // Only HC003: using 非引用→引用化
+    local lines = me._split_lines(text)
+    local changed = 0
+    local out = new ArrayBox()
+    local i = 0
+    while i < lines.size() {
+      local ln = lines.get(i)
+      local ltrim = me._ltrim(ln)
+      if ltrim.indexOf("using ") == 0 && ltrim.indexOf('using "') != 0 {
+        // rewrite: using X ... -> using "X" ...（X は最初の空白/セミコロン/"as" まで）
+        local prefix_len = ln.indexOf("using ")
+        if prefix_len < 0 { prefix_len = 0 }
+        local head = ln.substring(0, prefix_len)
+        local rest = ln.substring(prefix_len)
+        // rest starts with 'using '
+        local after = rest.substring(6)
+        // Find boundary
+        local b = 0; local n = after.length()
+        while b < n {
+          local ch = after.substring(b,b+1)
+          // stop at space, semicolon or before ' as '
+          if ch == " " || ch == ";" { break }
+          b = b + 1
+        }
+        local name = after.substring(0,b)
+        local tail = after.substring(b)
+        // If tail starts with ' as ' but name had trailing spaces, we already stopped at space
+        // Wrap name with quotes if not already
+        if name.length() > 0 {
+          local newline = head + "using \"" + name + "\"" + tail
+          if newline != ln { changed = 1; out.push(newline) } else { out.push(ln) }
+        } else { out.push(ln) }
+      } else {
+        out.push(ln)
+      }
+      i = i + 1
+    }
+    if changed == 0 { return text }
+    // Join with \n
+    local j = 0; local buf = ""; while j < out.size() { buf = buf + out.get(j); if j < out.size()-1 { buf = buf + "\n" } j = j + 1 }
+    return buf
+  }
+  _print_unified_diff(path, before, after) {
+    if before == null || after == null || before == after { return 0 }
+    // Minimal unified diff for whole file replacement（MVP）
+    print("--- " + path)
+    print("+++ " + path)
+    print("@@")
+    // Print lines with +/-; this MVP prints only changed lines as + and original as - when they differ line-wise
+    local bl = me._split_lines(before); local al = me._split_lines(after)
+    local max = bl.size(); if al.size() > max { max = al.size() }
+    local i = 0
+    while i < max {
+      local b = i < bl.size() ? bl.get(i) : null
+      local a = i < al.size() ? al.get(i) : null
+      if b == a {
+        print(" " + (a==null?"":a))
+      } else {
+        if b != null { print("-" + b) }
+        if a != null { print("+" + a) }
+      }
+      i = i + 1
+    }
+    return 0
+  }
   _needs_ast(only, skip) {
     // Parse AST when duplicate_method is explicitly requested (needs method spans/definitions precision).
     if only != null {