diff --git a/src/content/docs/reference/program-format.mdx b/src/content/docs/reference/program-format.mdx
index d5c13bd..3ebe7a5 100644
--- a/src/content/docs/reference/program-format.mdx
+++ b/src/content/docs/reference/program-format.mdx
@@ -95,19 +95,19 @@ for p in iter_defined(acct.programs):
 
 Source: `enuProgramType.cs`.
 
-### `ProgramCond` (high bits of `cond` / `cond2`)
+### `ConditionFamily` (high bits of `cond` / `cond2`)
 
 | Value | Name | Family |
 |------:|---|---|
-| 0 | `OTHER` | catch-all / miscellaneous |
+| 0 | `OTHER` | misc-conditional (`DARK`, `AC_POWER_OFF`, …) |
 | 4 | `ZONE` | zone-state condition |
-| 8 | `CTRL` | control-unit condition |
+| 8 | `CTRL` | control-unit (light/output) condition |
 | 12 | `TIME` | time-clock condition |
-| 16 | `SEC` | security-mode condition |
+| 16 | `SEC` | security-mode condition (catch-all) |
 
-Source: `enuProgramCond.cs`. The internal bit-split of `cond` (selector vs
-operand within the 16-bit field) is **not yet decoded** — see "What we don't
-yet know" below.
+Family is found by `(cond >> 8) & 0xFC` — bits 2-7 of the high byte.
+Source: `enuProgramCond.cs`. See ["cond / cond2 bit
+split"](#condcond2-bit-split) below for the full per-family decode.
 
 ### `Days` (byte 11)
 
@@ -152,6 +152,67 @@ Decoded as a file record:
 So: "TIMED program firing at 07:15 on weekdays, doing command 0x44 with
 par=3 and pr2=256, gated by the condition pair 0x8d09 / 0x9b09."
 
+## `cond`/`cond2` bit split
+
+The 16-bit `cond` (and `cond2`) field packs **family + selector + operand**.
+The high byte's bits 2-7 (i.e. `(cond >> 8) & 0xFC`) discriminate the family;
+the bottom byte and low bits of the high byte carry the rest.
+
+| Family | Match | Bit layout | Selector | Operand |
+|---|---|---|---|---|
+| `OTHER` | `(cond >> 8) & 0xFC == 0x00` | `....‥‥‥‥ ‥‥‥‥mmmm` | bits 0-3 = `MiscConditional` | (no operand) |
+| `ZONE` | `... == 0x04` | `000001oo zzzzzzzz` | bits 0-7 = zone # | bit 9 = `0`=SECURE, `1`=NOT_READY |
+| `CTRL` | `... == 0x08` | `000010oo uuuuuuuu (+ bit 8 = high u)` | bits 0-8 = unit # | bit 9 = `0`=OFF, `1`=ON |
+| `TIME` | `... == 0x0C` | `000011oo cccccccc` | bits 0-7 = clock # | bit 9 = `0`=DISABLED, `1`=ENABLED |
+| `SEC` | anything else (incl. `0x10`+) | `xmmm aaaa ........` | bits 8-11 = area # (0 = any) | bits 12-14 = `SecurityMode`, bit 15 = arming-transition flag |
+
+Worked examples:
+
+```
+cond = 0x0605  →  ZONE, zone 5, NOT_READY    ("Zone 5 NOT_READY")
+cond = 0x0A0F  →  CTRL, unit 15, ON          ("Unit 15 ON")
+cond = 0x0E03  →  TIME, clock 3, ENABLED     ("Time clock 3 ENABLED")
+cond = 0x000B  →  OTHER, BATTERY_OK
+cond = 0x8100  →  SEC, area 1, mode=OFF      ("Area 1 OFF")
+cond = 0xB100  →  SEC, area 1, ARMING AWAY   (bit 15 + mode=3)
+```
+
+Python usage:
+
+```python
+from omni_pca.programs import Condition, ConditionFamily, Program, ProgramType
+
+p = Program(
+    prog_type=int(ProgramType.TIMED),
+    cond=0x0605,     # "Zone 5 NOT_READY"
+    cond2=0xB100,    # "Area 1 ARMING AWAY"
+)
+c1 = p.condition()
+assert c1.family is ConditionFamily.ZONE
+assert c1.selector == 5 and c1.operand == 1
+assert c1.describe() == "Zone 5 NOT_READY"
+```
+
+`Condition.describe()` does the rendering with index-based labels
+(`"Zone 5"`, `"Unit 12"`) — name lookups need the panel name tables and
+are left to the caller. A future helper that takes a name map would be
+the obvious next step for a UI editor.
+
+A few details worth knowing:
+
+- **`OTHER` ignores high bits.** `cond=0x010B` and `cond=0x000B` both decode
+  to `BATTERY_OK` — PC Access's encoder sometimes leaves high bits set on
+  Other-family conditions; the decoder masks them off.
+- **`SEC` with mode=Off + bit 15** is the plain "Area X is OFF" encoding,
+  NOT an arming transition. The arming-transition rendering kicks in only
+  when bit 15 *and* the mode bits 12-14 are non-zero (per `clsText.cs:2263`).
+- **Area `0` in `SEC`** is the "no specific area" / "any area" form —
+  PC Access renders the area name as blank in this case.
+
+Source: `clsText.GetConditionalText` at clsText.cs:2224-2273 (decode) and
+`frmAutomationEditCondition.cs:615-2550` (encode/UI). The `MiscConditional`
+enum mirrors `enuMiscConditional.cs`.
+
 ## TIMED programs: absolute time vs sunrise/sunset offset
 
 The `hour` byte at offset 12 is **overloaded** as a one-of-three
@@ -258,13 +319,6 @@ specific 16-bit value refers to — is a separate reverse-engineering
 pass. So is the multi-record clausal encoding hinted at by the
 `WHEN/AT/EVERY/AND/OR/THEN` connector values in `ProgramType`. Concretely:
 
-- **`cond` / `cond2` internal bit split.** The high bits encode the
-  `ProgramCond` family (Zone / Ctrl / Time / Sec); we don't yet know
-  where the selector index (zone number, etc.) and the operand
-  ("not ready", "Day mode", …) live in the low bits. None of the 330
-  defined programs in our fixture is enough to triangulate this — we'd
-  need to author known programs in PC Access and diff the exported
-  bytes.
 - **Multi-record clausal encoding.** No program in our live fixture uses
   the `WHEN / AT / EVERY / AND / OR / THEN` ProgType values — so we
   can't yet say whether they reference adjacent slots, use extra bytes