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Is there a tradition that Mashiach will be recognized as such before he does anything?

Not of which I am aware. Or not exactly. The immortal words of Rambam:

3. One should not entertain the notion that the King Moshiach must work miracles and wonders, bring about new phenomena within the world, resurrect the dead, or perform other similar deeds. This is [definitely] not true.
[A proof can be brought from the fact that] that Rabbi Akiva, one of the greatest Sages of the Mishnah, was one of the supporters of King Ben Koziva, and would describe him as the King Moshiach. He and all the Sages of his generation considered him to be the King Moshiach until he was killed because of [his] sins. Once he was killed, they realized that he was not [the Moshiach]. The Sages did not ask him for any signs or wonders.
[Rather,] this is the main thrust of the matter: This Torah, with its statutes and laws, is everlasting. We may neither add to them nor detract from them.
4. If a king will arise from the House of David who delves deeply into the study of the Torah and, like David his ancestor, observes its mitzvos as prescribed by the Written Law and the Oral Law; if he will compel all of Israel to walk in [the way of the Torah] and repair the breaches [in its observance]; and if he will fight the wars of G-d; - we may, with assurance, consider him Moshiach.
If he succeeds in the above, builds the [Beis Ha]Mikdash on its site, and gathers in the dispersed remnant of Israel, he is definitely the Moshiach.
He will then perfect the entire world, [motivating all the nations] to serve G-d together, as it is written [Zephaniah, 3:9], "I will make the peoples pure of speech so that they will all call upon the Name of G-d and serve Him with one purpose."