diff --git a/docs/architecture/legacy-commands.md b/docs/architecture/legacy-commands.md
new file mode 100644
index 0000000..7ce552b
--- /dev/null
+++ b/docs/architecture/legacy-commands.md
@@ -0,0 +1,136 @@
+# Legacy Command Catalog
+
+This file lists the command keys available under `legacy/hwe/sammo/Command/`.
+Command keys match class names and file names; they are the values stored in
+`general_turn.action` and `nation_turn.action`.
+
+## Command Resolution
+
+- General: `buildGeneralCommandClass($type)` in `legacy/hwe/func_converter.php`
+- Nation: `buildNationCommandClass($type)` in `legacy/hwe/func_converter.php`
+- `null` or empty `type` defaults to `휴식`
+- Post-req turn cooldowns are stored in:
+  - `next_execute` KV (per general)
+  - `nation_env` KV (per nation)
+
+## Execution Semantics (BaseCommand)
+
+- Conditions are checked via constraint sets (permission/min/full).
+- `getPreReqTurn()` is enforced by `LastTurn` term stacking.
+- `getPostReqTurn()` is enforced by `next_execute` (cooldown).
+- If `run()` returns `false`, `getAlternativeCommand()` may be used.
+
+## Command Prefixes and Scenarios
+
+Command keys are scenario-driven. The prefixes (e.g. `che_`, `cr_`, `event_`)
+identify the rule set or scenario extension, and the active scenario chooses
+which commands are available via `GameConst` overrides. See
+`docs/architecture/legacy-scenarios.md` for details.
+
+## General Commands (`legacy/hwe/sammo/Command/General/`)
+
+| Key | Display name (actionName) |
+| --- | --- |
+| `che_NPC능동` | `NPC능동` |
+| `che_강행` | `강행` |
+| `che_거병` | `거병` |
+| `che_건국` | `건국` |
+| `che_견문` | `견문` |
+| `che_군량매매` | `군량매매` |
+| `che_귀환` | `귀환` |
+| `che_기술연구` | `기술 연구` |
+| `che_내정특기초기화` | `내정 특기 초기화` |
+| `che_농지개간` | `농지 개간` |
+| `che_단련` | `단련` |
+| `che_등용` | `등용` |
+| `che_등용수락` | `등용 수락` |
+| `che_랜덤임관` | `무작위 국가로 임관` |
+| `che_모반시도` | `모반시도` |
+| `che_모병` | `모병` |
+| `che_무작위건국` | `무작위 도시 건국` |
+| `che_물자조달` | `물자조달` |
+| `che_방랑` | `방랑` |
+| `che_사기진작` | `사기진작` |
+| `che_상업투자` | `상업 투자` |
+| `che_선동` | `선동` |
+| `che_선양` | `선양` |
+| `che_성벽보수` | `성벽 보수` |
+| `che_소집해제` | `소집해제` |
+| `che_수비강화` | `수비 강화` |
+| `che_숙련전환` | `숙련전환` |
+| `che_요양` | `요양` |
+| `che_은퇴` | `은퇴` |
+| `che_이동` | `이동` |
+| `che_인재탐색` | `인재탐색` |
+| `che_임관` | `임관` |
+| `che_장비매매` | `장비매매` |
+| `che_장수대상임관` | `장수를 따라 임관` |
+| `che_전투태세` | `전투태세` |
+| `che_전투특기초기화` | `전투 특기 초기화` |
+| `che_접경귀환` | `접경귀환` |
+| `che_정착장려` | `정착 장려` |
+| `che_주민선정` | `주민 선정` |
+| `che_증여` | `증여` |
+| `che_집합` | `집합` |
+| `che_징병` | `징병` |
+| `che_첩보` | `첩보` |
+| `che_출병` | `출병` |
+| `che_치안강화` | `치안 강화` |
+| `che_탈취` | `탈취` |
+| `che_파괴` | `파괴` |
+| `che_하야` | `하야` |
+| `che_해산` | `해산` |
+| `che_헌납` | `헌납` |
+| `che_화계` | `화계` |
+| `che_훈련` | `훈련` |
+| `cr_건국` | `건국` |
+| `cr_맹훈련` | `맹훈련` |
+| `휴식` | `휴식` |
+
+## Nation Commands (`legacy/hwe/sammo/Command/Nation/`)
+
+| Key | Display name (actionName) |
+| --- | --- |
+| `che_감축` | `감축` |
+| `che_국기변경` | `국기변경` |
+| `che_국호변경` | `국호변경` |
+| `che_급습` | `급습` |
+| `che_몰수` | `몰수` |
+| `che_무작위수도이전` | `무작위 수도 이전` |
+| `che_물자원조` | `원조` |
+| `che_발령` | `발령` |
+| `che_백성동원` | `백성동원` |
+| `che_부대탈퇴지시` | `부대 탈퇴 지시` |
+| `che_불가침수락` | `불가침 수락` |
+| `che_불가침제의` | `불가침 제의` |
+| `che_불가침파기수락` | `불가침 파기 수락` |
+| `che_불가침파기제의` | `불가침 파기 제의` |
+| `che_선전포고` | `선전포고` |
+| `che_수몰` | `수몰` |
+| `che_의병모집` | `의병모집` |
+| `che_이호경식` | `이호경식` |
+| `che_종전수락` | `종전 수락` |
+| `che_종전제의` | `종전 제의` |
+| `che_증축` | `증축` |
+| `che_천도` | `천도` |
+| `che_초토화` | `초토화` |
+| `che_포상` | `포상` |
+| `che_피장파장` | `피장파장` |
+| `che_필사즉생` | `필사즉생` |
+| `che_허보` | `허보` |
+| `cr_인구이동` | `인구이동` |
+| `event_극병연구` | `극병 연구` |
+| `event_대검병연구` | `대검병 연구` |
+| `event_무희연구` | `무희 연구` |
+| `event_산저병연구` | `산저병 연구` |
+| `event_상병연구` | `상병 연구` |
+| `event_원융노병연구` | `원융노병 연구` |
+| `event_음귀병연구` | `음귀병 연구` |
+| `event_화륜차연구` | `화륜차 연구` |
+| `event_화시병연구` | `화시병 연구` |
+| `휴식` | `휴식` |
+
+## Open Questions / Follow-ups
+
+- Prefix semantics (`che_`, `cr_`, `event_`) are not documented here and may be
+  scenario- or mode-specific.
diff --git a/docs/architecture/legacy-engine-execution.md b/docs/architecture/legacy-engine-execution.md
new file mode 100644
index 0000000..4102323
--- /dev/null
+++ b/docs/architecture/legacy-engine-execution.md
@@ -0,0 +1,121 @@
+# Legacy Engine Execution Flow
+
+This document summarizes how the legacy engine advances turns and executes
+commands. It focuses on the execution pipeline, RNG seeding, and state writes
+based on `legacy/hwe/sammo/API/Global/ExecuteEngine.php`,
+`legacy/hwe/sammo/TurnExecutionHelper.php`, and `legacy/hwe/sammo/Command/BaseCommand.php`.
+
+## Entry Point: ExecuteEngine API
+
+- Endpoint: `legacy/hwe/sammo/API/Global/ExecuteEngine.php`
+- Session: no session required (`NO_SESSION`)
+- Optional `serverID` guard via `UniqueConst::$serverID`
+- Calls `TurnExecutionHelper::executeAllCommand($updated, $locked)`
+- Returns `{ updated, locked, lastExecuted }`
+
+## Global Turn Loop (`TurnExecutionHelper::executeAllCommand`)
+
+1. **Time gate**
+   - If `now < game_env.turntime`, return without executing.
+2. **Locking**
+   - `tryLock()` on `plock` row (`type='GAME'`).
+   - If locked or `isunited` in `2|3`, return (frozen state).
+3. **Pre-turn maintenance**
+   - Cache game env, `checkDelay()`, `updateOnline()`, `CheckOverhead()`.
+4. **Catch-up monthly loop**
+   - Compute `prevTurn = cutTurn(turntime, turnterm)` and `nextTurn = addTurn(prevTurn)`.
+   - While `nextTurn <= now`:
+     - `executeGeneralCommandUntil(nextTurn, limitActionTime, year, month)`
+     - `updateTraffic()`
+     - Monthly pipeline:
+       - `runEventHandler(PreMonth)`
+       - `preUpdateMonthly()`
+       - `turnDate(nextTurn)`
+       - `checkStatistic()` (only if `month == 1`)
+       - `runEventHandler(Month)`
+       - `postUpdateMonthly($monthlyRng)`
+     - Advance `prevTurn`, `nextTurn`, update `game_env.turntime`.
+5. **Current partial month**
+   - `turnDate(prevTurn)`
+   - `executeGeneralCommandUntil(now, limitActionTime, year, month)`
+6. **Post-turn maintenance**
+   - `processTournament()`
+   - `processAuction()`
+   - Reset cache, `unlock()`.
+
+`limitActionTime` is derived from `max_execution_time` (roughly 2/3 of the
+configured limit). If time runs out mid-loop, it returns early and keeps
+`game_env.turntime` at the most recent executed value.
+
+## Per-General Execution (`executeGeneralCommandUntil`)
+
+For each general with `turntime < targetDate` (ordered by `turntime, no`):
+
+1. **Load state**
+   - `General::createObjFromDB()` and `KVStorage` for `game_env`.
+2. **Nation command (if officer_level >= 5)**
+   - Pull `nation_turn` row for `turn_idx = 0`.
+   - Build `NationCommand` with `LastTurn` stored in `nation_env`.
+3. **AI/autorun**
+   - NPCs (`npc >= 2`) or players past `autorun_limit` use `GeneralAI`.
+   - AI can replace both nation and general commands.
+4. **Preprocess triggers**
+   - RNG seed: `hiddenSeed + 'preprocess' + year + month + generalID`.
+   - `preprocessCommand()` merges action triggers + `che_부상경감`, `che_병력군량소모`.
+5. **Blocked users**
+   - `processBlocked()` consumes `killturn` and logs if `block >= 2`.
+6. **Execute nation command**
+   - RNG seed: `hiddenSeed + 'nationCommand' + year + month + generalID + commandKey`.
+   - `processNationCommand()` checks conditions, term stack, `run()`.
+   - If `run()` fails and `getAlternativeCommand()` exists, it retries.
+   - Updates `nation_env` with `LastTurn` result.
+7. **Execute general command**
+   - Load from `general_turn` (`turn_idx = 0`), default to `휴식`.
+   - RNG seed: `hiddenSeed + 'generalCommand' + year + month + generalID + commandKey`.
+   - `processCommand()` checks conditions, term stack, `run()`.
+   - Updates `killturn` based on NPC status, autorun, or `휴식`.
+8. **Queue maintenance & turntime**
+   - `pullNationCommand()` / `pullGeneralCommand()` advance queues.
+   - `updateTurnTime()` handles deletion/retirement and sets next `turntime`.
+   - Persist via `General::applyDB()`.
+
+## Command Semantics (BaseCommand)
+
+- **Constraints**: permission/min/full conditions are evaluated via
+  `Constraint::testAll()` with `general/city/nation/dest*` context.
+- **Pre-turn requirement**: `getPreReqTurn()` uses `LastTurn` to accumulate
+  term stack (`addTermStack()`), logging "수행중" until the term completes.
+- **Post-turn requirement**: `getPostReqTurn()` uses `next_execute` storage
+  (general: `next_execute`, nation: `nation_env`) to block early execution.
+- **Run flow**: `run($rng)` returns `true` when completed; `false` can chain to
+  `getAlternativeCommand()`.
+
+## Turntime & Lifecycle (`updateTurnTime`)
+
+- **Inactivity**: if `killturn <= 0`:
+  - NPC-owned characters can detach (owner -> NPC) if `deadyear` not reached.
+  - Otherwise the general is deleted (`kill()`).
+- **Retirement**: if `age >= retirementYear` and not NPC, `CheckHall()` and
+  `rebirth()` are invoked.
+- **Scheduling**: next `turntime` is `addTurn(current, turnterm)` with
+  optional `nextTurnTimeBase` override (aux var).
+
+## Deterministic RNG Seeds
+
+RNG uses `LiteHashDRBG` with `UniqueConst::$hiddenSeed`:
+
+- Preprocess: `('preprocess', year, month, generalID)`
+- Nation command: `('nationCommand', year, month, generalID, commandKey)`
+- General command: `('generalCommand', year, month, generalID, commandKey)`
+- Monthly: `('monthly', year, month)`
+
+These seeds make command outcomes and monthly updates reproducible for
+validation.
+
+## Open Questions / Follow-ups
+
+- `preUpdateMonthly()`, `postUpdateMonthly()`, `turnDate()`, `checkStatistic()`
+  are defined outside this flow; see `legacy/hwe/func_time_event.php` for
+  economic updates and population calculations.
+- `updateTraffic()`, `checkDelay()`, `updateOnline()` logic lives in
+  `legacy/hwe/func.php` and related utility files.
diff --git a/docs/architecture/legacy-engine-general.md b/docs/architecture/legacy-engine-general.md
new file mode 100644
index 0000000..18b3731
--- /dev/null
+++ b/docs/architecture/legacy-engine-general.md
@@ -0,0 +1,91 @@
+# Legacy General Model and Action Stack
+
+This document captures how `General` aggregates modifiers, computes stats, and
+exposes trigger hooks. The main reference is `legacy/hwe/sammo/General.php`.
+
+## Construction and Core State
+
+- `General` builds from raw DB rows (general, city, nation, rank, access log).
+- `last_turn` is parsed into `LastTurn`, and a separate `resultTurn` is
+  maintained for updates.
+- `penalty` JSON is decoded into `PenaltyKey -> value` map.
+- Rank data is tracked with:
+  - `rankVarRead` (current read view)
+  - `rankVarIncrease` (increment queue)
+  - `rankVarSet` (explicit set queue)
+
+## Action Objects (`iAction`)
+
+`General` composes action sources into a single list:
+
+1. Nation type (`buildNationTypeClass`)
+2. Officer level (`TriggerOfficerLevel`)
+3. Domestic special (`buildGeneralSpecialDomesticClass`)
+4. War special (`buildGeneralSpecialWarClass`)
+5. Personality (`buildPersonalityClass`)
+6. Crew type (`GameUnitConst::byID`)
+7. Inheritance buff (`TriggerInheritBuff`)
+8. Scenario effect (`buildScenarioEffectClass`)
+9. Items: horse / weapon / book / item (`buildItemClass`)
+
+`getActionList()` returns this merged list and is the core entry point for
+modifiers and triggers.
+
+## Stat Computation
+
+`getStatValue()` applies layered modifiers:
+
+- Base stat from raw value
+- Injury multiplier
+- Cross-stat adjust (strength/intel + 1/4 of the other stat)
+- Clamp to `GameConst::$maxLevel`
+- `onCalcStat()` from every action object
+- Cached by `(statName, injury, action, adjust)` tuple
+
+Convenience wrappers:
+- `getLeadership()`, `getStrength()`, `getIntel()`
+
+## Turn Reservation and LastTurn
+
+- `getReservedTurn(turnIdx)` reads from `general_turn`.
+- When no entry exists, `buildGeneralCommandClass(null)` creates `휴식`.
+- `LastTurn` holds `{ command, arg, term, seq }` and is used by
+  `BaseCommand::addTermStack()` to advance multi-turn commands.
+- `applyDB()` persists updated fields and writes `last_turn` if it changed.
+
+## Trigger and Modifier Hooks
+
+`General` delegates calculations and trigger lists through action objects:
+
+- Economy/strategy: `onCalcDomestic`, `onCalcStrategic`,
+  `onCalcNationalIncome`
+- Combat modifiers: `onCalcStat`, `onCalcOpposeStat`, `getWarPowerMultiplier`
+- Arbitrary actions: `onArbitraryAction` (used in city conquest)
+
+Turn-prep triggers:
+
+- `getPreTurnExecuteTriggerList()` merges trigger lists from every action
+  object. `TurnExecutionHelper::preprocessCommand()` adds
+  `che_부상경감` + `che_병력군량소모` on top.
+
+Battle triggers:
+
+- `getBattleInitSkillTriggerList()` merges per-action battle-init triggers.
+- `getBattlePhaseSkillTriggerList()` includes base phase triggers:
+  - `che_필살시도`, `che_필살발동`
+  - `che_회피시도`, `che_회피발동`
+  - `che_계략시도`, `che_계략발동`, `che_계략실패`
+  - plus any action-specific additions.
+
+## Rank and Access Log Updates
+
+- `increaseRankVar()` / `setRankVar()` queue updates until `applyDB()`.
+- `applyDB()` updates `general` and `rank_data`, then flushes logs.
+- `checkStatChange()` uses `*_exp` thresholds to increase/decrease stats and
+  logs level changes.
+
+## Open Questions / Follow-ups
+
+- `PenaltyKey` effects and how penalties are applied are outside this file.
+- `GeneralBase` and `LazyVarAndAuxUpdater` may contain additional state
+  conventions for new code to mirror.
diff --git a/docs/architecture/legacy-engine-war.md b/docs/architecture/legacy-engine-war.md
new file mode 100644
index 0000000..e59b3d5
--- /dev/null
+++ b/docs/architecture/legacy-engine-war.md
@@ -0,0 +1,109 @@
+# Legacy Battle and War Resolution
+
+This document summarizes the legacy battle pipeline centered on
+`legacy/hwe/process_war.php`, `legacy/hwe/sammo/WarUnit.php`,
+`legacy/hwe/sammo/WarUnitGeneral.php`, and `legacy/hwe/sammo/WarUnitCity.php`.
+
+## Entry Point: `processWar`
+
+Inputs:
+
+- `warSeed` (string): battle RNG seed
+- `attackerGeneral`: `General`
+- `rawAttackerNation`: nation row (snapshot)
+- `rawDefenderCity`: city row (snapshot)
+
+Setup steps:
+
+1. Initialize RNG with `warSeed` (`LiteHashDRBG`).
+2. Load defender nation row (or default neutral nation if `nation = 0`).
+3. Build `WarUnitGeneral` (attacker) and `WarUnitCity` (defender city).
+4. Collect defender generals in the city, filter with `extractBattleOrder()`.
+5. Optionally append city as defender if city order > 0.
+6. Sort defenders by battle order, iterate via `getNextDefender()`.
+7. Run `processWar_NG()`; update DB and nation/city stats.
+
+## Battle Order (`extractBattleOrder`)
+
+For defender generals:
+
+- Must have crew > 0
+- Must have rice > crew/100
+- `train` and `atmos` must meet `defence_train`
+- Battle order uses:
+  - `totalStat = (realStat + fullStat) / 2`
+  - `totalCrew = crew / 1_000_000 * (train * atmos) ^ 1.5`
+  - `totalStat + totalCrew / 100`
+
+For cities:
+
+- Uses attacker `onCalcOpposeStat('cityBattleOrder', -1)`.
+
+## Battle Loop (`processWar_NG`)
+
+1. Log start, include seed in battle logs.
+2. If no defenders remain, set defender = city and switch to siege.
+3. **Initial engagement**
+   - `setOppose()` for attacker/defender
+   - `addTrain(1)` for both
+   - Fire battle-init triggers
+4. **Per phase**
+   - `beginPhase()` computes war power
+   - Fire battle-phase triggers
+   - `calcDamage()` on both sides
+   - Clamp damage if it exceeds HP ratios
+   - Apply damage, increase killed/dead counters
+   - Log phase results
+5. **Continuation checks**
+   - `continueWar()` fails on no rice or HP <= 0
+   - On retreat/defeat: log, apply win/lose, try wound
+   - If defender removed, move to next defender (or city siege)
+6. **Finish**
+   - `logBattleResult()` for last phase if needed
+   - `finishBattle()` for attacker/defender
+   - City conflict tracking and history logs
+
+## Post-Battle Updates (`processWar`)
+
+After `processWar_NG()`:
+
+- Apply attacker DB updates
+- Update nation rice (supply and siege rules)
+- Distribute city `dead` counts (40% attacker city, 60% defender city)
+- Increase nation tech based on killed/dead and nation size adjustments
+- Update `diplomacy.dead` for both sides
+- If city conquered: call `ConquerCity()`
+
+## `WarUnitGeneral` Highlights
+
+- Train/atmos bonuses depend on city level and attacker/defender role.
+- War power:
+  - Base attack/defence from crew type + tech
+  - Adjusted by train/atmos, dex (`getDex()`), crew type coefficients
+  - Experience level scales war power and counter-scales opponent
+  - `General::getWarPowerMultiplier()` applies special multipliers
+- Rice consumption on kills: proportional to damage, tech cost, unit rice
+- Wound chance: 5% unless `부상무효` / `퇴각부상무효` triggered
+- `finishBattle()` updates rank stats, rounds values, and checks stat changes
+
+## `WarUnitCity` Highlights
+
+- Uses `DummyGeneral` with `CREWTYPE_CASTLE`
+- HP = `def * 10`
+- Computed attack/defence = `(def + wall * 9) / 500 + 200`
+- City train/atmos scales with elapsed years since `startYear`
+- Siege state:
+  - Non-siege battle ends after one exchange
+  - Siege continues until HP <= 0
+- `heavyDecreaseWealth()` halves `agri/comm/secu` on supply-based rout
+- `addConflict()` records contribution in `city.conflict` JSON
+
+## Deterministic RNG
+
+- Main battle uses `warSeed` directly.
+- City conquest uses `hiddenSeed + 'ConquerCity' + year + month + nationID + generalID + cityID`.
+
+## Open Questions / Follow-ups
+
+- Detailed conquest outcomes (nation collapse, officer handling) extend beyond
+  the summary here; see `ConquerCity()` in `legacy/hwe/process_war.php`.
diff --git a/docs/architecture/legacy-engine.md b/docs/architecture/legacy-engine.md
index ce3eba9..2f1a3bc 100644
--- a/docs/architecture/legacy-engine.md
+++ b/docs/architecture/legacy-engine.md
@@ -34,3 +34,11 @@ organization rather than endpoint-first routing.
 - "attempt" then "execute" phases
 - Common trigger categories (traits, specials, scenario effects)
 - How triggers combine when multiple sources apply
+
+## Detailed Notes
+
+- Turn execution pipeline: `docs/architecture/legacy-engine-execution.md`
+- General model and action stack: `docs/architecture/legacy-engine-general.md`
+- Battle and war resolution: `docs/architecture/legacy-engine-war.md`
+- Command catalog: `docs/architecture/legacy-commands.md`
+- Scenario system and rule sets: `docs/architecture/legacy-scenarios.md`
diff --git a/docs/architecture/legacy-scenarios.md b/docs/architecture/legacy-scenarios.md
new file mode 100644
index 0000000..6b99716
--- /dev/null
+++ b/docs/architecture/legacy-scenarios.md
@@ -0,0 +1,109 @@
+# Legacy Scenario System
+
+This document explains how scenarios are loaded and how they define the active
+rule set, commands, and effects. Core references include
+`legacy/hwe/sammo/Scenario.php`, `legacy/hwe/sammo/ResetHelper.php`, and
+`legacy/hwe/sammo/GameConstBase.php`.
+
+## Scenario Loading Flow
+
+1. Server reset/init calls `ResetHelper::buildScenario()`.
+2. `Scenario` loads `scenario_{id}.json` and merges defaults (`default.json`).
+3. `Scenario::buildConf()` generates runtime constants:
+   - `d_setting/GameConst.php` from `GameConstBase + scenario.const/map/stat`
+   - `d_setting/CityConst.php` from `scenario/map/{mapName}.php`
+   - `d_setting/GameUnitConst.php` from `scenario/unit/{unitSet}.php`
+4. `Scenario::build()` inserts nations, generals, and events into DB and runs
+   `initialEvents` immediately.
+
+`Scenario::getAllScenarios()` is used for listing scenarios without fully
+building them (lazy init).
+
+## Scenario JSON Structure (Observed)
+
+Common top-level keys (see `legacy/hwe/scenario/frame.json` and actual
+`scenario_*.json` files):
+
+- `title`, `startYear`, `history`, `iconPath`
+- `stat`: default stat totals and bounds
+- `map`: `mapName`, `unitSet`, `scenarioEffect`
+- `const`: overrides for `GameConst` (commands, items, limits, etc.)
+- `nation`, `diplomacy`
+- `general`, `general_ex`, `general_neutral`
+- `events`, `initialEvents`
+- `ignoreDefaultEvents` (skip `GameConst::$defaultInitialEvents/$defaultEvents`)
+
+Notes:
+
+- A few files still use `initialActions` or `defaultInitialEvents` keys. The
+  engine currently reads `initialEvents` only.
+- `general` rows use the tuple format from `Scenario::generateGeneral()`:
+  `affinity, name, picture, nationName, city, leadership, strength, intel,
+  officerLevel, birth, death, ego, char, text`.
+
+## How Scenario Chooses Commands and Effects
+
+Scenario config influences runtime rules via `GameConst` and `ScenarioEffect`:
+
+- `const.availableGeneralCommand` / `const.availableChiefCommand` define the
+  commands that appear in UI and can be executed.
+- `const.availableSpecialDomestic/War`, `const.availablePersonality`,
+  `const.allItems`, `const.availableNationType` control selectable traits/items.
+- `map.scenarioEffect` or `const.scenarioEffect` sets
+  `GameConst::$scenarioEffect`, which is injected into each `General` as an
+  `iAction` (`General::getActionList()`).
+- `const.availableInstantAction` merges into
+  `GameConst::$availableInstantAction`.
+
+Because `GameConst` is generated from scenario data, a scenario can swap
+available commands or replace the action pool entirely.
+
+## Command Prefix Conventions
+
+Prefixes are used to separate rule packs and assets:
+
+- `che_`: default rule set (base commands, specials, items, nation types).
+- `cr_`: alternate rule set used by specific scenarios (e.g. `scenario_910`).
+- `event_`: scenario-specific extensions (research, extra unit sets, or special
+  effects).
+
+Example: `scenario_910.json` uses `mapName=cr` and `unitSet=cr` and overrides
+`availableGeneralCommand/availableChiefCommand` to include `cr_건국`,
+`cr_맹훈련`, and `cr_인구이동` alongside `che_` commands.
+
+## Scenario Environment Variants (Current Repo)
+
+These are the map/unit/effect variants referenced by existing scenario files.
+Defaults are `mapName=che` and `unitSet=che` when not specified.
+
+Map sets (`scenario/map/*.php`):
+- `che` (default)
+- `miniche`, `miniche_b`, `miniche_clean`
+- `cr`
+- `chess`
+- `pokemon_v1`
+- `ludo_rathowm`
+
+Unit sets (`scenario/unit/*.php`):
+- `che` (default)
+- `che_except_siege`
+- `cr`
+- `basic`
+- `siegetank`
+- `event_more_crewtype`
+- `ludo_rathowm`
+
+Scenario effects (`sammo/ActionScenarioEffect/*`):
+- `event_StrongAttacker`
+- `event_UnlimitedDefenceThresholdChange`
+- `event_MoreEffect`
+
+## Event Targets
+
+Scenario events are stored in the `event` table and executed via
+`TurnExecutionHelper::runEventHandler()` using `EventTarget` values:
+`PRE_MONTH`, `MONTH`, `OCCUPY_CITY`, `DESTROY_NATION`, `UNITED`.
+
+Most scenario JSON uses lowercase targets (e.g. `"month"`). The DB enum uses
+uppercase values but is case-insensitive, so lowercase targets still match.
+
diff --git a/docs/architecture/todo.md b/docs/architecture/todo.md
index fab775e..99c6e24 100644
--- a/docs/architecture/todo.md
+++ b/docs/architecture/todo.md
@@ -28,3 +28,9 @@ Move items into the main docs once they are finalized.
 
 - "Next-turn intent" (예턴) data schema and lifecycle
 - Profile selection workflow and deployment mapping
+
+## Legacy Engine Docs
+
+- [AI suggestion] Expand monthly pipeline details (`preUpdateMonthly`, `postUpdateMonthly`, `turnDate`, `checkStatistic`) with concrete side effects and tables touched.
+- [AI suggestion] Document `ConquerCity()` resolution paths (nation collapse, officer handling, reward/penalty rules).
+- [AI suggestion] Clarify command prefix semantics (`che_`, `cr_`, `event_`) and add per-command effect summaries.