Did Mirza Ghulam Ahmad claim to be the Mahdi, who was foretold in 20+ hadith reports?  This is a sketchy topic.  The fact is, in MGA’s first two books of 1891, “Victory of Islam” and “Elucidation of Objectives” he never mentioned anything about any Mahdi.  Further, from 1839 to early-1891, MGA and his team of writers never mentioned the Mahdi at all.  MGA seems to have been silent on this topic.  However, as we all know, MGA affiliated with the “Ahl-e-Hadith”, in english, “the people of hadith” aka the Wahabbis of India.  Further, in 1884, when MGA got married to Nusrat Jehan, a famous Ahle-Hadith cleric read the Nikkah.  Moreover, new research from Afzal Upal proves that MGA was very fond of the Ahle-hadith camp and seems to have been working with them.  However, behind the scenes, MGA was slowly adopting the beliefs of Sir Syed, who also denied all hadith on the Mahdi back in the 1870’s.

The news reports of the eclipses in 1894 changed MGA and his teams mind
From the summer of 1891 to the early part of 1894, MGA denied all the hadith on the Mahdi, in total.  He wrote this specifically, however, his team read the news reports of impending eclipses and promptly found a hadith from Dar-e-Qutni which seems to have matched up.  However, they were wrong, the hadith from Dar-e-Qutni (which isnt authentic, nor does it trace back to Muhammad (saw), says that this type of eclipses has never happened before in the history of the world.  Ahmadiyya ghost-writers seem to have initially agreed, however, later on, they found out that it happens every 22 years and quickly wrote an amendment to their argument, i.e. that this eclipses had never happened before.

See here for the full explanation of the eclipses

Mirza Tahir Ahmad confirms that MGA didnt claim to be the Mahdi initially

Watch the full video by Mirza Tahir Ahmad here

Additional research needed
When MGA claimed to be the Promised Messiah…he made an announcement, and wrote a book, when MGA claimed prophethood in 1901, it was through an announcement.  However, his claim of being the Mahdi didnt warrant an announcement from MGA.  FACT.

The hadith report from Dar-e-Qutni
Narrated Amr son of Shamir, quoting Jabir, who quoted Mohammad bin ‘Ali:

“For our Mahdi, two signs are given which never occurred in the past from the creation of the heavens and the earth. One is that a lunar eclipse will occur on the first night of Ramadhan and the second sign is that a solar eclipse will occur in the middle of Ramadhan and these signs had never happened from the creation of the heavens and the earth.” (Dar-e-Qatni, Vol. 1, P. 188)

From 1894 to  MGA and his team wrote that these types of eclipses had never happened ever before or would ever happen after

“This has never happened and absolutely never happened, except in my time, since the beginning of universe till now, that lunar and solar eclipse had gathered in the month of Ramadhan in such a manner that some claimant of messengership or prophethood or muhaddathiyat (one who converse with God) had also been present.”
  (Roohani Khazain, Vol. 9, P. 50)

“Combination of lunar and solar eclipse in Ramadhan has never taken place in the time of any Prophet or Messenger or muhaddith and since the birth of universe during the time of any claimant of messengership or prophethood or muhaddithiyat lunar and solar has never combined. Combination of Lunar and Solar eclipse and Mahdi is an unnatural phenomenon.”  (Roohani Khazain, Vol. 9, P. 84)

“The meaning of prophecy is that this sign has not been to any other claimant, whether true or false. Only given to the Promised Mahdi. If these tyrant molvis (Muslim scholars) can present a similar occurrence of lunar and solar eclipse in the time of some other claimant then please do it; then I will no doubt become a liar.”
(Roohani Khazain, Vol. 11, P. 332)

“One Hadith of Dar-e-Qatni also proves that the Promised Mahdi will appear at the head of 14th Century; and that hadith is this ….translation of the whole hadith is:

‘There are two signs of our Mahdi; since the creation of earth and heaven this sign has not been revealed for any appointed and prophet and messenger; and those signs are that moon will eclipse in the first night of its fixed nights of eclipse and sun will get eclipsed in the middle of the fixed days for its eclipse, during the month of Ramadhan.’

…this hadith clearly fixes 14th Century.”  (Roohani Khazain, Vol. 17, P. 331)