# What starts a phase's coroutines: a timer table, scanned every frame

Status: ✅ mechanism and table format, verified against the disassembly and all
28 scripts. This answers the question every phase experiment has been circling.

## ✅ The scanner

`sub_822748D0`, called from `ScriptPhase::Update` each frame:

```
822748e0  lwz  r11, 240(r30)     ; the table at [phase+240]
822748e4  lwz  r10,   4(r11)     ; record count
822748f4  addi r31, r11, 20      ; first record (+8 header, +12 into it)
822748fc  lwz  r11,   0(r31)     ; TIMER INDEX      (rec+20)
82274900  lfs  f0,   -8(r31)     ; THRESHOLD, f32   (rec+12)
82274904  lwz  r10, 104(r30)     ; PREVIOUS timers  [phase+104]
82274910  fcmpu f13, f0 / bgt    ;   skip if prev  >  thr
82274918  lwz  r10,  88(r30)     ; CURRENT timers   [phase+88]
82274920  fcmpu f0, f13 / bge    ;   skip if thr >= cur
8227492c  lwz  r5, -16(r31)      ; COROUTINE OFFSET (rec+4)
82274930  lwz  r4, 232(r30)      ; phase code base
82274934  bl   0x822737C8        ; START THE COROUTINE
8227493c  addi r31, r31, 24      ; stride 24
```

So each record says: **when timer *i* crosses *t* seconds, start the coroutine at
`codebase + off`** — a **rising-edge** test, `prev ≤ t < cur`, so it fires once.

`[phase+88]` and `[phase+104]` are the current and previous copies of the
32-entry float register file; `sub_822710D0(phase, dt)` copies cur→prev and adds
`dt` to the running ones each frame. **They are timers, in seconds.**

## ✅ The table, and where it comes from

The mission-level bytecode's `begin_phase` (op `0x83`) carries five operands; the
fourth is this table's offset and the fifth is the phase's end-event routine.
`sub_82270DF8` stores them as `[phase+240] = base + w4` and `[phase+236] = w5`.

On disc the table is tagged constants, same `<len><op>` shape as the bytecode
(tags `0x819` = int, `0x81A` = float — both past the ISL dispatcher's
`cmplwi 0x18` bound, so they are data and never execute):

```
tbl+0  : 0819 <count>
rec+0  : 0819 <coroutine offset>
rec+8  : 081A <threshold seconds, f32>
rec+16 : 0819 <timer index>
```

Verified here on Stage 02's three phases — counts **25 / 13 / 18**, and the tag
triple `(0x819, 0x81A, 0x819)` correct in **25/25, 13/13, 18/18** records:

```
phase 1  base 0xE4      tbl 0x14848  end 0x1482C
   rec0: off 0x2B20 thr 0.0 timer 5
   rec1: off 0x2B88 thr 0.5 timer 5
   rec2: off 0x2BFC thr 1.0 timer 5
```

Only two timers are ever used corpus-wide: **0** (thresholds 1–1170 s — the
mission clock) and **5** (0/0.5/1/4/5 s — a phase-intro clock).

## 🔑 Why this matters: it explains the poke results

Two experiments set a squadron's state to "destroyed" and watched nothing happen
([script-runtime-probe](script-runtime-probe.md)). The leading explanation was
that the condition coroutine "is not polling" — **this is why.** A phase's
coroutines are **started on a schedule**, by timer crossings. They are not
running continuously waiting to notice a state change, so writing state between
firings changes data nobody is looking at.

It also reframes the arrival timetable: the routes' `t=170` entry
([mission-wave-arrivals](mission-wave-arrivals.md)) and these thresholds are the
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

* 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.~~
  ✅ **SETTLED (2026-08-27), and the obvious reading is REFUTED —
  [structures/isl-mission-timer](structures/isl-mission-timer.md).** `180` is a
  **second countdown that starts only after the first reaches zero**, not a
  threshold on the first: `sub_822639B8` never compares `[phase+312]` with
  `[phase+308]`, it *decrements* it, and only in the `A <= 0` arm. It is 180 in
  all 29 `timer_set` sites on the disc while the first argument varies
  (600 ×19, 1200 ×8, 900, 1800).

  🔴 **And this page conflates two clocks.** "timer 0 is started by
  `timer_set(1200, 180)` then `timer_resume`" merges the **mission timer**
  (`[phase+304…320]`, armed by 127 and started by 123) with **stopwatch 0**
  (`[phase+88][0]`, started by `set_flag(0)` — [structures/isl-timers](structures/isl-timers.md)).
  The three calls sit one instruction apart in the same intro coroutine, so the
  two clocks read almost the same value and the merge was invisible. The
  timeline's `kind = 0` reads the **stopwatch**; the 1200-second limit belongs to
  the **mission timer** and is not stopwatch 0's limit.