al-Redha, false Imam ?

Muhammad Ibn Yahya, from Ahmad Ibn Muhammad, from Ibn Mahbub, from al-Hussein Ibn Nu'aym al-Sahaf who said: "Hisham Ibn al-Hakam, Ali Ibn Yaqtin and I were in Baghdad. Ali Ibn Yaqtin said, I was in the presence of the pious servant (of Allah) and his son Ali (al-Redha) came. He then said to me, O Ali Ibn Yaqtin, this is Ali, the sayyid (leader, master) of my children and I have gifted him with my own Kunya. Hisham tapped his forehead with his palm and said, Fie up on you! How did you say it? Ali Ibn Yaqtin said, I heard, by Allah, from him just as I said. Hisham said, He (Imam Musa) informed you that after him the task will be with him (his son)."

 محمد بن يحيى، عن أحمد بن محمد، عن ابن محبوب، عن الحسين بن نعيم الصحاف قال: كنت وأنا وهشام بن الحكم وعلي بن يقطين ببغداد، فقال علي بن يقطين: كنت عند العبد الصالح جالسا فدخل عليه ابنه علي فقال لي: يا علي بن يقطين هذا علي سيد ولدي، أما إني قد نحلته كنيتي، فضرب هشام بن الحكم براحته جبهته، ثم قال: ويحك كيف قلت؟ فقال علي بن يقطين: سمعت والله منه كما قلت، فقال هشام: أخبرك أن الامر فيه من بعده.

- Usul al-Kafi, Vol.1, Page 311, Hadith Number 1

Authentfication :

Muhammad Ibn Yahyah:
Scholar from our compagnon, Thiqah Ayn. شيخ أصحابنا في زمانه ثقة عين - Rijal al-Najashi, Page 353.

Ahmad Ibn Muhammad:
Thiqah. ثقة - Rijal al-Tusi, Page 351.

Ibn Mahbub:
Thiqah. ثقة - Rijal al-Tusi, Page 334.

al-Hussein Ibn Nu'aym al-Sahaf:
Thiqah and his brothers are Ali and Muhammad. ثقة و أخواه علي و محمد  - Rijal al-Najashi, Page 54.

Ali Ibn Yaqtin:
Thiqah Jahlil his statut, he have a great position to Abi al-Hassan Musa (as) great is his place in our sect. : ثقة جليل القدر له منزلة عظيمة عند أبي الحسن موسى عليه السلام عظيم المكان في الطائفة  - Fihrist al-Tusi, Page 271.

The chain is Sahih.

'Allamah Baqir al-Majlissi: Sahih in Mirat al-'Uqool.
Mirza Jawad al-Tabrizi: Sahih in al-Nusus al-Sahiha.