diff --git a/docs/re/mission-phase-timers.md b/docs/re/mission-phase-timers.md
index f6a82b08..26d58cc3 100644
--- a/docs/re/mission-phase-timers.md
+++ b/docs/re/mission-phase-timers.md
@@ -74,8 +74,46 @@ It also reframes the arrival timetable: the routes' `t=170` entry
 same kind of thing — **the mission is substantially a timeline**, with unit
 predicates deciding *what* happens at each scheduled point rather than *when*.
 
+## ✅ Stage 02 phase 1, as a timeline — and what arms the clock
+
+Disassembling all 25 triggers in threshold order turns the phase into a script
+you can read:
+
+```
+timer5 @   0.0s  fade in
+timer5 @   0.5s  play_bgm(0x3ED)
+timer5 @   1.0s  damage_unit(TCN131, 0)
+timer5 @   4.0s  timer_set(1200, 180) ; timer_resume ; set_flag(0)   <-- arms timer 0
+timer0 @   1.0s  radio 0x52, 0x53
+timer0 @  30.0s  deploy + move_order(TCN105 group) ; radio 0x55
+timer0 @  60.0s  radio 0x56
+timer0 @  90.0s  deploy + move_order(idx 0x08) ; radio 0x57
+timer0 @ 120.0s  deploy + move_order(idx 0x43) + objective_marker ; radio 0x58, 0x59
+timer0 @ 170.0s  deploy + move_order(idx 0x01 = ADN110) ; radio 0x5A, 0x5B
+timer0 @ 210.0s  deploy + move_order(idx 0x33) + objective_marker
+timer0 @ 240.0s  deploy + move_order(idx 0x19)
+timer0 @ 270/300/330 s   radio only
+timer0 @ 1020/1080/1140/1170 s   radio only
+```
+
+### ✅ What arms the clock — the open question, answered
+
+**`timer_set(1200, 180)` then `timer_resume`, at 4.0 s on the phase-intro
+clock.** So timer 0 is started by the phase's own intro coroutine, with a
+**1200-second limit**; timer 5 is already running when the phase begins. That
+closes "which built-in arms or resets each timer" for the common case.
+
+### ✅ It independently confirms the arrival measurement
+
+The `timer0 @ 170.0s` trigger deploys **symbol index 0x01 = `ADN110`** — the
+first of the three squadrons the phase-1 condition polls. The live run measured
+those three flipping to *active* at roughly **155–165 s of mission time**
+([mission-wave-arrivals](mission-wave-arrivals.md)), against a route table that
+also says `170`. Three independent sources — the route table, this trigger
+table, and the running game — agree.
+
 ## 🟡 Not settled
 
-* **Which built-in arms or resets each timer.** Indices 0 and 5 are named from
-  the `+= dt` accumulator and the threshold magnitudes, not from a writer.
-* Whether a coroutine started this way can *re-arm* its own trigger.
+* Whether a coroutine started this way can **re-arm** its own trigger.
+* `timer_set`'s second argument (`180`) — a limit and a warning threshold is the
+  obvious reading, but it is **not** established.