diff --git a/CLAUDE.md b/CLAUDE.md
index 374fc40..a82ae12 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -112,7 +112,7 @@ Common Lispでは同じパッケージ内で同名関数を再定義すると警
 すべての出力ファイル名生成関数が`opts`を第一引数として受け取るAPIに統一され、
 テストスイートでの検証とバイナリビルドでの動作確認も完了。
 
-#### GIFモードのオプション制限強化
+#### GIFモードのオプション制限強化 ✅ **完了**
 GIFモードで`--input`オプションとの組み合わせエラーが適切に処理されていない問題を修正：
 
 **問題:**
diff --git a/src/package.lisp b/src/package.lisp
index 9f69c1f..39364dc 100644
--- a/src/package.lisp
+++ b/src/package.lisp
@@ -28,15 +28,14 @@
   :validate-codec
   :validate-mono
   :validate-speed
-  :parse-speed-float
   :validate-options
   :validate-output
   :dispatch-validation
 
    ;; util.lisp
    :input-extension
-   :parse-float
-   :safe-parse-float
+   :parse-number
+   :parse-number-or-exit
    :parse-frame-rate
    :resolution-from-key
    :parse-dimensions
diff --git a/src/util.lisp b/src/util.lisp
index 212d0fb..1981b60 100644
--- a/src/util.lisp
+++ b/src/util.lisp
@@ -1,28 +1,28 @@
 (in-package :visp)
 
-(defun parse-float (str)
-  "Parse a string as a float. Returns NIL if not parsable."
-  (handler-case
-      (let ((val (read-from-string str)))
-        (if (floatp val)
-            val
-            (coerce val 'float))) ; int → float に変換
-    (error () nil)))
+(defun parse-number (str)
+  "Parse string to number. Returns nil on failure. Secure version with *read-eval* disabled."
+  (let ((*read-eval* nil))
+    (handler-case
+        (let ((result (with-input-from-string (s str) (read s))))
+          (if (numberp result) result nil))
+      (error () nil))))
+
+(defun parse-number-or-exit (str &optional (context "number"))
+  "Parse string to number. Exit with error message on failure."
+  (let ((result (parse-number str)))
+    (unless result
+      (format t "~a Invalid ~a value: ~a~%" (log-tag "error") context str)
+      (uiop:quit 1))
+    result))
 
-(defun safe-parse-float (str)
-  (let ((val (parse-float str)))
-    (if val
-        val
-        (progn
-          (format t "~a Invalid float value: ~a~%" (log-tag "error") str)
-          (uiop:quit 1)))))
 
 (defun parse-frame-rate (rate)
   (handler-case
       (let ((parts (uiop:split-string rate :separator "/")))
         (if (= (length parts) 2)
-            (/ (parse-float (first parts)) (parse-float (second parts)))
-            (parse-float rate)))
+            (/ (parse-number (first parts)) (parse-number (second parts)))
+            (parse-number rate)))
     (error () nil)))
 
 (defun input-extension (filename)
diff --git a/src/validate.lisp b/src/validate.lisp
index 2ece37c..e2a0891 100644
--- a/src/validate.lisp
+++ b/src/validate.lisp
@@ -285,23 +285,12 @@
       (when (member codec '("prores" "hap") :test #'string=)
         (error "The --mono option is not supported with codec ~A." codec)))))
 
-(defun parse-speed-float (string)
-  "Parse a string as a float for speed validation. Throws an error if not a valid number."
-  (let ((*read-eval* nil)
-        (result nil))
-    (with-input-from-string (s string)
-      (setf result (read s)))
-    ;; 読み取った結果が数値でない場合はエラー
-    (unless (numberp result)
-      (error "Not a valid number: ~a" string))
-    result))
 
 (defun validate-speed (opts)
   "Validate that --speed is a positive number if specified."
   (let ((speed (visp-options-speed opts)))
     (when speed
-      (let ((speedf (handler-case (parse-speed-float speed)
-                      (error () nil))))
+      (let ((speedf (parse-number speed)))
         ;; speedは必ず0より大きい数値
         (unless (and (numberp speedf) (> speedf 0))
           (format t "~a --speed must be a positive number, but got '~a'.~%" 
diff --git a/src/video.lisp b/src/video.lisp
index 3722761..c1850a5 100644
--- a/src/video.lisp
+++ b/src/video.lisp
@@ -25,9 +25,9 @@
          (parts (uiop:split-string output :separator "/")))
     (cond
       ((= (length parts) 2)
-       (/ (safe-parse-float (first parts)) (safe-parse-float (second parts))))
+       (/ (parse-number-or-exit (first parts) "fps") (parse-number-or-exit (second parts) "fps")))
       ((= (length parts) 1)
-       (safe-parse-float (first parts)))
+       (parse-number-or-exit (first parts) "fps"))
       (t
        (format t "~a Failed to extract FPS from input: ~a~%" (log-tag "error") output)
        (uiop:quit 1)))))
@@ -65,7 +65,7 @@
       `(:width ,(when width (parse-integer (cdr width)))
         :height ,(when height (parse-integer (cdr height)))
         :fps ,(when rate (parse-frame-rate (cdr rate)))
-        :duration ,(when duration (parse-float (cdr duration)))
+        :duration ,(when duration (parse-number (cdr duration)))
         :has-audio ,has-audio
         :audio-codec ,(if has-audio audio-codec nil)
         :video-codec ,(when codec (cdr codec))))))
diff --git a/t/test-validate.lisp b/t/test-validate.lisp
index 5ddef44..6da6bb7 100644
--- a/t/test-validate.lisp
+++ b/t/test-validate.lisp
@@ -2,23 +2,23 @@
   (:use :cl :rove)
   (:import-from :visp
                 :make-visp-options
-                :parse-speed-float
+                :parse-number
                 :validate-speed
                 :validate-gif-mode))
 
 (in-package :visp.test.validate)
 
-(deftest parse-speed-float-tests
-  (testing "Parses valid float strings"
-    (ok (= (visp:parse-speed-float "2.0") 2.0))
-    (ok (= (visp:parse-speed-float "0.5") 0.5))
-    (ok (= (visp:parse-speed-float "1") 1.0))
-    (ok (= (visp:parse-speed-float "3.14159") 3.14159)))
+(deftest parse-number-tests
+  (testing "Parses valid number strings"
+    (ok (= (visp:parse-number "2.0") 2.0))
+    (ok (= (visp:parse-number "0.5") 0.5))
+    (ok (= (visp:parse-number "1") 1.0))
+    (ok (= (visp:parse-number "3.14159") 3.14159)))
 
-  (testing "Throws error for invalid strings"
-    (ok (signals (visp:parse-speed-float "invalid")))
-    (ok (signals (visp:parse-speed-float "abc")))
-    (ok (signals (visp:parse-speed-float "")))))
+  (testing "Returns NIL for invalid strings"
+    (ok (null (visp:parse-number "invalid")))
+    (ok (null (visp:parse-number "abc")))
+    (ok (null (visp:parse-number "")))))
 
 (deftest validate-speed-tests
   (testing "Validates positive float values"