Zeir Anpin's First and Second Maturity.
First Maturity = standard intensity. Second Maturity = higher intensity. The cosmic government's two regular operational modes.
Op. 129 unfolds the operational specifics of Z"A's First and Second Maturity. The chapter is structural; it specifies what each maturity does operationally.
First Maturity: Z"A operates with its full Mental Powers (Tzelem-completed) at standard intensity. The cosmic-government's deed-relevant operations occur — service is performed, response flows, the cycle's middle-phase work proceeds.
Second Maturity: Z"A operates at higher intensity. The cosmic government's deed-relevant operations occur with greater radiance, deeper coupling, more expansive operational reach. Shabbat is the regular instance — the cosmic government's higher operational mode that recurs every seven days.
The distinction has operational implications. Service performed during First Maturity has standard cosmic effect; service performed during Second Maturity has higher cosmic effect (the rabbinic doctrine that Shabbat-prayer reaches higher than weekday-prayer is the operational form of this).
The two maturities are both present throughout the cycle's middle phase; they alternate regularly. The cosmic government has built-in oscillation, not constant single-intensity operation.
Op. 131 (different times of ascent and descent — the macro-temporal architecture). Op. 138 (the closing operational mechanism — operating with both maturities active).