diff --git a/CHANGELOG.md b/CHANGELOG.md
index e27f624..145040b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,80 @@ page as `v0.1.0 · <sha> · <date>`, so what is deployed can always be identifie
 
 ---
 
+## 0.7.4 — 2026-08-29
+
+Three rules issues off the tracker, in the order Jesse asked for them: #13, #5, #19. All three are
+rules Jesse has designed or redefined, and two of them turned out to be rules the code claimed to
+have and did not.
+
+### Some Extras must run loaded (Gitea#13)
+
+X17 Campaign, X18 Circus and X19 Military now prefer loaded cars at make-up — "if not loaded, then
+empty, and if none available, run without". It is a preference ORDER, so the rule is asked of the
+Division Yard: an empty is refused only while the yard can still supply a loaded car this train
+would take, per category, and once it cannot the empty is legal and the train may depart short.
+
+The per-stop point is **once per Office Area** rather than once per game (Jesse: "in a multiplayer
+game, each player could score if the circus stops in their area"), and only when the train is fully
+loaded — every non-caboose car, with a coach counting as loaded when occupied. That last detail is
+what makes the rule work for the Campaign Train, which carries one coach and no freight, so "fully
+loaded" is exactly "the candidate is aboard". X17 also GAINS the point; it had `stopThenExpedite`
+and no scoring rule at all.
+
+**Two bugs found doing it.** `ConsistSpec.emptiesOnly` was declared on X13 Appleseed, rendered to
+the player as "(empties only)", and enforced nowhere — the same rule as this issue pointing the
+other way, so it would have been perverse to add one and leave the other. And a set-up out on the
+Mainline paid its point to PLAYER 0 whoever was playing, because `playerAtSeat` needs a seat and off
+the grid the fallback was `0`; scoping the rule to Office Areas removes that rather than patching it.
+
+### The Yard Office is offered, reachable, and can be run into (Gitea#5)
+
+It was implemented, in a form missing all three of the rule's conditions: a qualifying train was
+TELEPORTED onto the card. Nobody was asked, no route was computed — so the card's own printed "that
+can reach the yard office in one move" was unenforced — and because nothing was walked, nothing was
+ever met on the way in.
+
+Now it is offered to the district's owner; reachability is the engine's own move walk, which already
+means what the card means; and cars on the lead collide. The walk COUPLES standing cars rather than
+treating them as obstacles, because that is what a switching move does — so what an arriving train
+would have coupled is what it is about to hit, and `destination.couples` turned out to be the
+fouling signal with no new machinery. Per Jesse's ruling the two failures are kept apart: no route
+means no offer and the history says why; a route that exists but is fouled is offered, and taking it
+crashes.
+
+**This needed a refactor that #19 then reused.** `pendingDecision` was one question asked of one
+player, and `currentActor` hardcoded that. It is a discriminated union now, with `decisionActor` as
+the single place mapping a question to whoever answers it; six copies of `pendingDecision !== null ?
+superintendent : currentActor` across engine, sim, web and tests collapse into `actingPlayer`.
+
+### Red Flags, redesigned (Gitea#19)
+
+The old card protected a stopped train out on the Mainline: offered 4,212 times and played 4 across
+600 games. It is replaced outright by a flag planted on one side of your own Limits, holding the
+next train from that direction — "Flag East holds westbound trains" — spent on the train it stops.
+One card, one train, so there is no lifting action to build and a flag cannot strangle the Division.
+
+It can also be played **out of phase**: when an arrival would certainly collide and the district's
+owner holds the card, the phase breaks in with the question. Offered only to somebody holding one,
+because a prompt with a single button is not a choice and would leak that a collision is coming.
+
+**The bot still never plays it, and the reason changed — measured, not assumed.** It now takes the
+out-of-phase prompt unconditionally, since the engine has already established the danger. Over 200
+solitaire games it plays ZERO, because the prompt needs an arrival that would collide (about one
+game in seven) to coincide with holding the card from a three-card hand out of 121. The anomaly
+exemption in `sim.test.ts` stays, but its comment no longer claims the bot is unwilling; what is
+left to fix is the half of the card a human uses — planting a flag on purpose to buy switching time.
+
+**A bug the redesign walked into**, recorded because the next interruption will meet it too: the
+flag was originally taken down in a `reduce` case, which never fires for an event `advance.ts`
+emits — the phase driver mutates and then describes. The flag stayed up and held every train that
+came. `test/events.test.ts`'s unreduced-event registry is what makes that class of mistake visible,
+and `redFlagSpent` is now on it deliberately.
+
+858 tests pass.
+
+---
+
 ## 0.7.3 — 2026-08-29
 
 Two issues off the tracker, and they are halves of one thing: the end of a game. Gitea#11 stops the
diff --git a/README.md b/README.md
index 388fd51..a1507d7 100644
--- a/README.md
+++ b/README.md
@@ -132,6 +132,13 @@ is the thing this machinery exists to prevent.
   roughly a third of the event types are never reduced at all. Anything that needs to rebuild a game
   replays the intents.
 - **Never call `Math.random()`.** One ambient random call silently breaks replay.
+- **The Mainline Phase can stop and ask, and there are three questions it asks.** §8.1's clearance
+  ruling goes to the Superintendent; the Yard Office offer and the Red Flag prompt go to the owner of
+  the district a train is arriving at. `pendingDecision` is a discriminated union and `decisionActor`
+  is the single place that maps a question to whoever must answer it — a new question adds a case
+  there and nowhere else. **Ask before the move is committed:** returning `needsClearance` unwinds
+  the whole phase and the driver re-enters from the top, so anything already mutated is applied
+  twice or left half-done.
 - **A game ends by PAUSING, and the first ending is the real one.** Running out of Days, or closing
   short of the combined Revenue floor, puts the game in `awaitingExtension` rather than `finished`:
   the table is asked whether to play one more Day, unanimously, and asked again at the end of every
diff --git a/TODO.md b/TODO.md
index 360f972..c45f470 100644
--- a/TODO.md
+++ b/TODO.md
@@ -414,21 +414,23 @@ The replay viewer, the save format, and how a game gets shared.
 
 ## Bot Performance
 
-- [ ] **THE BOT WILL NOT PLAY RED FLAGS, and the reachability canary now says so.** Measured over
-      600 games (2026-08-26): `maneuver.redFlags` is OFFERED **4,212 times**, first in game 5 — the
-      rule is live and constantly available — and the bot PLAYS it **4 times**, first in game 252.
-      It is exempted by name in `sim.test.ts`'s anomaly test alongside `flyingSwitch`, and deleting
-      that line is what proves this fixed.
+- [ ] **THE BOT NEVER PLAYS RED FLAGS — and since Gitea#19 that is deck luck, not unwillingness.**
+      **Re-measured 2026-08-29, after the card was redesigned: `redFlagsSet` fires ZERO times in 200
+      solitaire games.** The old measurement (600 games: OFFERED 4,212 times, PLAYED 4) described a
+      bot that declined a card it was constantly handed. That bot is gone.
 
-      Two changes compounded to make it rarer without breaking anything: Gitea#14 took Red Flags from
-      5 copies to the sheet's 3, and Gitea#3 shortened most crossings to a single Stage, so the
-      window in which a train is STANDING on a Mainline card — the only place the card may be played
-      — is now usually one Stage wide.
+      Gitea#19 replaced the rule outright: a flag is planted on one side of your own Limits and holds
+      the next train from that direction, and it can be played out of phase when the engine breaks in
+      with "COLLISION RISK! FLAG AGAINST T2?". The bot takes that prompt **unconditionally** — the
+      engine only raises it when an arrival is certainly about to collide, so there is nothing left
+      to judge. It still never plays one, because the prompt needs two things to coincide: an arrival
+      that would collide (0.14 collisions per game, about one game in seven) AND the district's owner
+      holding a Red Flags card at that moment, from a three-card hand drawn out of 121.
 
-
-What the developer bot can and cannot yet do, measured. Every revenue figure below measured before
-v0.4.7 is low by roughly half a point — see the stub-industry entry — and the rebalance pass should
-not read that drop as a deck problem.
+      **What is left to fix is the OTHER half of the card**, and it is the half a human would use:
+      planting a flag on purpose to buy a Stage for switching. That needs the bot to know it wants
+      time, which it has no notion of today. Until then the anomaly canary in `sim.test.ts` is
+      measuring deck luck rather than reachability, and its comment now says so.
 
 - [ ] **THE BOT DOES NOT KNOW TO BRING AN EXPEDITED TRAIN BACK TO THE STATION — new in v0.4.9.**
       The `expediteFault` mechanic (§7, Q3) charges 1 Revenue every Mainline Phase an expedited train
diff --git a/package.json b/package.json
index 1a7644e..95b3eb3 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "station-master",
-  "version": "0.7.3",
+  "version": "0.7.4",
   "private": true,
   "type": "module",
   "description": "Station Master — a railroad operations game",
diff --git a/src/engine/advance.ts b/src/engine/advance.ts
index 93b9922..2c44f06 100644
--- a/src/engine/advance.ts
+++ b/src/engine/advance.ts
@@ -974,13 +974,22 @@ function moveTrain(s: GameState, id: TrayId, tray: CrewTray, events: GameEvent[]
      * half-applied. Asking after the `transits` filter below cost the train its place on the card
      * and it was never seen again — the question was asked and the answer had nowhere to land.
      */
-    if (dest?.kind === 'office' && yardOfficeQuestion(s, id, tray, dest.seat, events) === 'ask') {
-      return 'needsClearance';
+    if (dest?.kind === 'office') {
+      /**
+       * §Q, RED FLAGS (Gitea#19) — asked and answered before the train leaves the card, for exactly
+       * the reason the Yard Office offer is (see below): `needsClearance` unwinds the phase.
+       *
+       * Order matters. A flag stops the train OUTSIDE the Limits, so it never reaches the point
+       * where the Yard Office would be offered — flagging is about keeping a train out altogether.
+       */
+      const flagged = redFlagStop(s, id, tray, dest, events);
+      if (flagged === 'ask') return 'needsClearance';
+      if (flagged === 'held') return 'held';
+
+      if (yardOfficeQuestion(s, id, tray, dest.seat, events) === 'ask') return 'needsClearance';
     }
 
     node.transits = node.transits.filter((t) => t.tray !== id);
-    // Red Flags protect a train while it is stopped here; once it rolls, the flags come in.
-    if (node.redFlagged) node.redFlagged = node.redFlagged.filter((t) => t !== id);
 
     if (!dest) return 'held';
 
@@ -1087,10 +1096,10 @@ function evaluateClearance(
     // from moving". Flagging is per-train rather than per-card, so it protects one specific train
     // where ABS Signals protects everything on the card.
     //
-    // Both of these read the card the OTHER train is standing on rather than the card being
-    // entered. They were the same card while this only looked one card ahead; across a Subdivision
-    // they are not, and the protection belongs where the train it protects actually is.
-    if (onNode?.kind === 'mainline' && (onNode.redFlagged ?? []).includes(other)) return 'blocked';
+    // Red Flags used to protect a stopped train here as well. Gitea#19 replaced that rule outright
+    // (Jesse, 2026-08-29): a flag is now planted on a district's Limits and holds trains coming from
+    // one direction, so it never applies out on the Mainline. ABS Signals is what protects a train
+    // standing on a Mainline card now, and it always did the job better.
 
     /**
      * ABS Signals — "this is played on a mainline card to prevent collisions. If a collision would
@@ -1147,6 +1156,103 @@ function evaluateClearance(
  * way the train is already facing. Reversing is a separate Move (§A.5), so a Yard Office that can
  * only be reached by backing up is correctly "not in one move".
  */
+/**
+ * The flag comes down as it stops the train — one card, one train (Gitea#19).
+ *
+ * MUTATES RATHER THAN EMITTING A REDUCED EVENT, because this is the phase driver: `advance.ts`
+ * changes state directly and then describes what it did, and roughly a third of the event types are
+ * never reduced at all (`README.md`, and `tally.ts` on the same asymmetry). A `redFlagSpent`
+ * reducer case looked right and never fired — the flag stayed up and held every train that came.
+ */
+function spendFlag(
+  office: Extract<DivisionNode, { kind: 'office' }>,
+  tray: CrewTray,
+  side: Direction,
+  events: GameEvent[],
+): 'held' {
+  delete office.redFlag;
+  events.push({ type: 'redFlagSpent', seat: office.seat, side, trainNumber: tray.trainNumber ?? 0 });
+  events.push({
+    type: 'trainHeld',
+    trainNumber: tray.trainNumber ?? 0,
+    reason: 'Red Flags — held short of the Limits',
+  });
+  return 'held';
+}
+
+/**
+ * §Q, RED FLAGS (Gitea#19) — does a flag stop this train, and should its owner be offered one?
+ *
+ * Two jobs, because they are the same moment seen twice: a flag already planted stops the train
+ * outright, and a train about to run into trouble is the cue to offer a flag to somebody holding
+ * the card. "You can play the card normally or out of phase, but only if you need it."
+ *
+ *   - `held`    — a flag was up on the side this train is coming from. It loses this Mainline
+ *                 Phase and the flag comes down with it: one card, one train (Jesse, 2026-08-29).
+ *   - `ask`     — entering would collide and the district's owner holds a Red Flags card.
+ *   - `proceed` — neither.
+ *
+ * WHICH SIDE. A train running WEST arrives from the east, so `FLAG EAST` is what holds it — which
+ * is the example the issue gives, and the reason the flag names a side rather than a heading.
+ */
+function redFlagStop(
+  s: GameState,
+  id: TrayId,
+  tray: CrewTray,
+  dest: Extract<DivisionNode, { kind: 'office' }>,
+  events: GameEvent[],
+): 'held' | 'ask' | 'proceed' {
+  const from: Direction = tray.direction === 'east' ? 'west' : 'east';
+
+  // The answer to a prompt already put. Consumed here so the driver cannot ask twice.
+  const answer = s.clock.decisionAnswer;
+  if (answer && answer.kind === 'redFlag' && answer.train === id) {
+    s.clock.decisionAnswer = null;
+    if (!answer.flag) return 'proceed';
+    // The card was spent planting the flag; it stops this train and comes down again at once.
+    return spendFlag(dest, tray, from, events);
+  }
+
+  if (dest.redFlag === from) return spendFlag(dest, tray, from, events);
+
+  /**
+   * "In actual cases of danger… if there is a train or cars on the track and there will be a
+   * collision, then you break in with a dialog." The two ways an arrival collides are §8.3's own:
+   * no free A/D track, and cars fouling the Running Track. Asked only of a player who can actually
+   * answer — offering a flag to somebody holding no card is a prompt with one button.
+   */
+  const owner = playerAtSeat(s, dest.seat);
+  const holdsFlag = (s.decks.hands.get(owner) ?? []).some((cid) => {
+    const c = s.cards.get(cid);
+    return c?.kind.kind === 'maneuver' && c.kind.key === 'redFlags';
+  });
+  if (!holdsFlag) return 'proceed';
+  if (!arrivalWouldCollide(s, id, tray, dest.seat)) return 'proceed';
+
+  s.clock.pendingDecision = { kind: 'redFlag', train: id, seat: dest.seat, from };
+  return 'ask';
+}
+
+/**
+ * Would this arrival collide? §8.3's two triggers, asked before the train commits.
+ *
+ * Deliberately a READ of the same conditions `arriveAtOffice` enforces rather than a second rule:
+ * if these two ever diverge, the prompt offers a flag against a collision that will not happen, or
+ * stays silent before one that will.
+ */
+function arrivalWouldCollide(s: GameState, id: TrayId, tray: CrewTray, seat: SeatIndex): boolean {
+  const area = areaAtSeat(s, seat);
+  const hasInterlocking = [...area.grid.values()].some((c) => c.enhancements.includes('interlocking'));
+  const full = area.adOccupancy.length >= officeProfile(area.tier).adTracks;
+  // Interlocking turns a full Office into a hold rather than a collision, so it is not danger.
+  if (full && !hasInterlocking) return true;
+
+  // A coach may legally stand at the Office while its engine switches (§A.4's carve-out), so it is
+  // not a hazard to the next arrival. Anything else on the Running Track is.
+  const officeCard = area.grid.get(coordKey(area.officeCoord));
+  return officeCard !== undefined && officeCard.standing.some((c) => c.type !== 'coach');
+}
+
 /**
  * §11 (Gitea#5) — should the district's owner be asked about the Yard Office, and is there
  * anything to ask about?
@@ -1396,7 +1502,6 @@ function collide(
       if (n.kind !== 'mainline') continue;
       n.transits = n.transits.filter((t) => t.tray !== id);
       if (n.holding) n.holding = n.holding.filter((t) => t !== id);
-      if (n.redFlagged) n.redFlagged = n.redFlagged.filter((t) => t !== id);
     }
     /**
      * AND OFF THE A/D TRACK, for exactly the same reason as the transit above.
diff --git a/src/engine/apply.ts b/src/engine/apply.ts
index 91096ed..99d45e7 100644
--- a/src/engine/apply.ts
+++ b/src/engine/apply.ts
@@ -59,6 +59,7 @@ import {
   coordKey,
   cutTowards,
   decisionActor,
+  officeNodeFor,
   isOperationalRail,
   playerAtSeat,
   pooled,
@@ -803,6 +804,25 @@ export function check(s: GameState, player: PlayerIndex, i: Intent): RejectionCo
     return null;
   }
 
+  /**
+   * §Q (Gitea#19) — the Red Flag prompt, the third interruption of the Mainline Phase.
+   *
+   * Only ever raised for a player who holds the card, so `flag: true` can always be paid for; the
+   * card is checked again here because `check` is the authority and a hand can change between the
+   * prompt being raised and answered.
+   */
+  if (i.type === 'mainline.redFlag') {
+    if (s.clock.pendingDecision?.kind !== 'redFlag') return 'NO_RED_FLAG_PROMPT';
+    if (decisionActor(s) !== player) return 'NOT_YOUR_TURN';
+    if (!i.flag) return null;
+    const held = (s.decks.hands.get(player) ?? []).find((id) => {
+      const c = s.cards.get(id);
+      return c?.kind.kind === 'maneuver' && c.kind.key === 'redFlags';
+    });
+    if (!held) return 'NO_SUCH_CARD';
+    return null;
+  }
+
   /**
    * §11 (Gitea#5) — the Yard Office offer, the second interruption of the Mainline Phase.
    *
@@ -1024,14 +1044,9 @@ export function check(s: GameState, player: PlayerIndex, i: Intent): RejectionCo
       const card = s.cards.get(i.cardId);
       if (!card || !(s.decks.hands.get(player) ?? []).includes(i.cardId)) return 'NO_SUCH_CARD';
       if (card.kind.kind !== 'maneuver' || card.kind.key !== 'redFlags') return 'WRONG_INTENT';
-      const tray = s.trays.get(i.trayId);
-      if (!tray) return 'NO_SUCH_TRAY';
-      // "A STOPPED train is prevented from being hit" — it protects a train that is standing on a
-      // Mainline card, which is the only place a rear-ender can happen.
-      if (tray.position.at !== 'mainline') return 'NO_PLACEMENT';
-      const node = s.division.nodes[tray.position.index];
-      if (!node || node.kind !== 'mainline') return 'NO_PLACEMENT';
-      if ((node.redFlagged ?? []).includes(i.trayId)) return 'OPTION_ALREADY_CHOSEN';
+      // §Q (Gitea#19) — a flag goes on your OWN Limits. There is no target train to name and no
+      // placement to find: the district is yours, and the only question is which side.
+      if (officeNodeFor(s, seatOf(s, player))?.redFlag === i.side) return 'ALREADY_FLAGGED';
       return null;
     }
 
@@ -1828,10 +1843,25 @@ function execute(s: GameState, player: PlayerIndex, i: Intent): GameEvent[] {
       ];
     }
 
-    case 'maneuver.redFlags': {
-      const tray = s.trays.get(i.trayId)!;
-      const index = tray.position.at === 'mainline' ? tray.position.index : -1;
-      return [{ type: 'redFlagsSet', player, cardId: i.cardId, trayId: i.trayId, node: index }];
+    case 'maneuver.redFlags':
+      return [{ type: 'redFlagsSet', player, cardId: i.cardId, seat: seatOf(s, player), side: i.side }];
+
+    case 'mainline.redFlag': {
+      const pending = s.clock.pendingDecision;
+      const trainId = pending?.kind === 'redFlag' ? pending.train : '';
+      const seat = pending?.kind === 'redFlag' ? pending.seat : 0;
+      const side = pending?.kind === 'redFlag' ? pending.from : 'east';
+      if (!i.flag) return [{ type: 'redFlagRuled', player, trainId, flag: false }];
+      const cardId =
+        i.cardId ??
+        (s.decks.hands.get(player) ?? []).find((id) => {
+          const c = s.cards.get(id);
+          return c?.kind.kind === 'maneuver' && c.kind.key === 'redFlags';
+        })!;
+      return [
+        { type: 'redFlagsSet', player, cardId, seat, side },
+        { type: 'redFlagRuled', player, trainId, flag: true },
+      ];
     }
 
     case 'maneuver.flyingSwitch': {
@@ -2260,14 +2290,23 @@ export function reduce(s: GameState, e: GameEvent): void {
     }
 
     case 'redFlagsSet': {
-      const node = s.division.nodes[e.node];
-      if (node?.kind === 'mainline') {
-        node.redFlagged = [...(node.redFlagged ?? []), e.trayId];
-      }
+      const node = officeNodeFor(s, e.seat);
+      if (node) node.redFlag = e.side;
       spendCard(s, e.player, e.cardId);
       break;
     }
 
+    /**
+     * §Q (Gitea#19) — `redFlagSpent` is NOT reduced, deliberately. It is emitted only by the phase
+     * driver, which mutates state itself and then describes it (`advance.ts`'s `spendFlag`), so a
+     * case here would be dead code that reads as the live one.
+     */
+
+    case 'redFlagRuled':
+      s.clock.pendingDecision = null;
+      s.clock.decisionAnswer = { kind: 'redFlag', train: e.trainId, flag: e.flag };
+      break;
+
     case 'flyingSwitch': {
       const tray = s.trays.get(e.trayId);
       const area = areaOf(s, e.player);
diff --git a/src/engine/events.ts b/src/engine/events.ts
index b2be581..4822b93 100644
--- a/src/engine/events.ts
+++ b/src/engine/events.ts
@@ -87,7 +87,12 @@ export type GameEvent =
   /** `variant` is the chosen orientation (Gap 11); it must be replayable, so it rides the event. */
   | { type: 'cardPlayed'; player: PlayerIndex; cardId: CardId; placement?: GridCoord; variant?: number }
   | { type: 'mainlineModified'; player: PlayerIndex; cardId: CardId; node: number; key: string; became?: string }
-  | { type: 'redFlagsSet'; player: PlayerIndex; cardId: CardId; trayId: TrayId; node: number }
+  /** §Q (Gitea#19) — a flag planted on one side of a district's Limits. */
+  | { type: 'redFlagsSet'; player: PlayerIndex; cardId: CardId; seat: SeatIndex; side: Direction }
+  /** §Q (Gitea#19) — the flag stopped a train and came down with it. One card, one train. */
+  | { type: 'redFlagSpent'; seat: SeatIndex; side: Direction; trainNumber: number }
+  /** §Q (Gitea#19) — the district's owner answered the out-of-phase "flag against this train?". */
+  | { type: 'redFlagRuled'; player: PlayerIndex; trainId: TrayId; flag: boolean }
   | {
       type: 'trainsDestroyed';
       player: PlayerIndex;
diff --git a/src/engine/intents.ts b/src/engine/intents.ts
index 4d6cd10..5e1d22c 100644
--- a/src/engine/intents.ts
+++ b/src/engine/intents.ts
@@ -120,10 +120,24 @@ export type Intent =
    */
   | { type: 'mainline.modify'; cardId: CardId; node: number }
   /**
-   * Red Flags — protect a stopped train. The flagged train cannot be hit; an approaching train is
-   * held instead of colliding.
+   * §Q, RED FLAGS (Gitea#19) — plant a flag on one side of your own district.
+   *
+   * "If played, asked FLAG EAST or FLAG WEST. That stops all trains from entering your limits from
+   * that direction (i.e. Flag East holds westbound trains). You can do this if you see a problem or
+   * wish to complete switching."
+   *
+   * `side` names the side of the district the flag goes on, so a train arriving from that side is
+   * held. It REPLACES the old rule, which was played on a stopped train out on the Mainline and
+   * protected it from a rear-ender: measured at 4,212 offers and 4 plays across 600 games, a
+   * mechanic nobody used. ABS Signals already protects a train standing on a Mainline card.
    */
-  | { type: 'maneuver.redFlags'; cardId: CardId; trayId: TrayId }
+  | { type: 'maneuver.redFlags'; cardId: CardId; side: Direction }
+  /**
+   * The same card, played OUT OF PHASE at the moment of danger (Gitea#19) — "COLLISION RISK! FLAG
+   * AGAINST T2?". Answers a pending `redFlag` decision; `flag: false` declines and lets the
+   * collision happen. The side is not asked for: the train is already coming from one.
+   */
+  | { type: 'mainline.redFlag'; flag: boolean; cardId?: CardId }
   /**
    * Flying Switch — cut cars off behind the engine and roll them into an adjacent industry, without
    * the engine entering it.
@@ -312,7 +326,11 @@ export type RejectionCode =
   /** §3.3 (Gitea#11) — this seat has already voted on this extension. */
   | 'ALREADY_VOTED'
   /** §11 (Gitea#5) — answering a Yard Office offer that is not open. */
-  | 'NO_YARD_OFFICE_OFFER';
+  | 'NO_YARD_OFFICE_OFFER'
+  /** §Q (Gitea#19) — answering a Red Flag prompt that is not open. */
+  | 'NO_RED_FLAG_PROMPT'
+  /** §Q (Gitea#19) — this district already has a flag on that side. */
+  | 'ALREADY_FLAGGED';
 
 export type Rejection = { code: RejectionCode; message: string };
 
diff --git a/src/engine/legal.ts b/src/engine/legal.ts
index 2ac3845..99ef11a 100644
--- a/src/engine/legal.ts
+++ b/src/engine/legal.ts
@@ -95,6 +95,10 @@ function candidates(s: GameState, player: PlayerIndex): Intent[] {
     out.push({ type: 'mainline.yardOffice', take: true });
     out.push({ type: 'mainline.yardOffice', take: false });
   }
+  if (s.clock.pendingDecision?.kind === 'redFlag') {
+    out.push({ type: 'mainline.redFlag', flag: true });
+    out.push({ type: 'mainline.redFlag', flag: false });
+  }
 
   switch (s.clock.phase) {
     case 'localOps':
@@ -115,7 +119,8 @@ function candidates(s: GameState, player: PlayerIndex): Intent[] {
   for (const cardId of s.decks.hands.get(player) ?? []) {
     const k = s.cards.get(cardId)?.kind;
     if (k?.kind !== 'maneuver' || k.key !== 'redFlags') continue;
-    for (const [trayId] of s.trays) out.push({ type: 'maneuver.redFlags', cardId, trayId });
+    // §Q (Gitea#19) — a flag goes on one side of your own district, so the only choice is which.
+    for (const side of ['east', 'west'] as const) out.push({ type: 'maneuver.redFlags', cardId, side });
   }
 
   out.push({ type: 'redFlag.play' });
diff --git a/src/engine/state.ts b/src/engine/state.ts
index fdd3fa7..e23c5f0 100644
--- a/src/engine/state.ts
+++ b/src/engine/state.ts
@@ -525,10 +525,23 @@ export type DivisionNode =
        * "Player sets orientation", so the direction is chosen when the card is placed.
        */
       gradeUp?: Direction;
-      /** Red Flags protecting a stopped train here, by tray. */
-      redFlagged?: TrayId[];
     }
-  | { kind: 'office'; seat: SeatIndex };
+  | {
+      kind: 'office';
+      seat: SeatIndex;
+      /**
+       * §Q, RED FLAGS (Gitea#19) — the side of this district a flag is planted on.
+       *
+       * "If played, asked FLAG EAST or FLAG WEST. That stops all trains from entering your limits
+       * from that direction (i.e. Flag East holds westbound trains)." So the value names the SIDE,
+       * and a train arriving from that side is held: a westbound train comes from the east.
+       *
+       * SPENT ON THE TRAIN IT STOPS (Jesse's ruling, 2026-08-29). One card, one train — the flag
+       * comes down as it is used, so there is no lifting action to build, nothing to forget, and a
+       * flag cannot quietly strangle the Division.
+       */
+      redFlag?: Direction;
+    };
 
 /** Ordered west to east. For N players: N Office nodes and N+1 Mainline cards. */
 export type Division = { nodes: DivisionNode[] };
@@ -610,7 +623,12 @@ export type PendingDecision =
    * §11 (Gitea#5) — an inbound freight may take the Yard Office instead of the Train Order Office.
    * Asked of whoever sits in `seat`, on the Mainline Phase the train arrives.
    */
-  | { kind: 'yardOffice'; train: TrayId; seat: SeatIndex };
+  | { kind: 'yardOffice'; train: TrayId; seat: SeatIndex }
+  /**
+   * §Q (Gitea#19) — a train is about to enter this district into a collision, and its owner holds a
+   * Red Flags card. "You can play the card normally or out of phase, but only if you need it."
+   */
+  | { kind: 'redFlag'; train: TrayId; seat: SeatIndex; from: Direction };
 
 /**
  * The answer, waiting to be consumed by the train that asked.
@@ -621,7 +639,8 @@ export type PendingDecision =
  */
 export type DecisionAnswer =
   | { kind: 'clearance'; train: TrayId; allow: boolean }
-  | { kind: 'yardOffice'; train: TrayId; take: boolean };
+  | { kind: 'yardOffice'; train: TrayId; take: boolean }
+  | { kind: 'redFlag'; train: TrayId; flag: boolean };
 
 export type Clock = {
   day: number;
@@ -1161,6 +1180,15 @@ export function playerAtSeat(state: GameState, seat: SeatIndex): PlayerIndex {
   return p;
 }
 
+/** This seat's node on the Division — where its Limits, and any Red Flag on them, live. */
+export function officeNodeFor(
+  state: GameState,
+  seat: SeatIndex,
+): Extract<DivisionNode, { kind: 'office' }> | null {
+  for (const n of state.division.nodes) if (n.kind === 'office' && n.seat === seat) return n;
+  return null;
+}
+
 /**
  * WHO MUST ANSWER the interruption, or null when nothing is pending.
  *
diff --git a/src/sim/bot.ts b/src/sim/bot.ts
index 11c9adc..e097834 100644
--- a/src/sim/bot.ts
+++ b/src/sim/bot.ts
@@ -170,7 +170,7 @@ export function makeDeveloperBot(tweaks: BotTweaks): BotPolicy {
     // Red Flags come before anything else — protection is only worth playing at the moment the
     // collision is actually pending, and that moment passes.
     const flags = worthFlagging(s, options);
-    if (flags) return because('a train of ours is stopped on a Mainline card with another train on it — Red Flags now or not at all', flags);
+    if (flags) return because('the engine says this arrival collides, and we hold a Red Flag — now or never', flags);
 
     // --- Load/Unload: spend every worker, then end. Each is a point, or a step toward one.
     //
@@ -1043,19 +1043,20 @@ function facilityWantsAt(
 }
 
 /**
- * Red Flags — "any time". Worth spending only when a train of ours is stopped out on the Mainline
- * with another train on the same card, which is the situation that becomes a rear-ender.
+ * §Q, RED FLAGS (Gitea#19) — spent only at the moment of danger.
+ *
+ * The card was redefined: it plants a directional flag on your own Limits rather than protecting a
+ * stopped train out on the Mainline, so the old heuristic ("is a train of ours sharing a Mainline
+ * card") no longer describes anything the card does.
+ *
+ * The bot now flags ONLY through the out-of-phase prompt, which the engine raises exactly when an
+ * arrival would collide (`redFlagStop`). That is a better policy than the old one and a much
+ * simpler one: the engine has already established the danger, so there is nothing for the bot to
+ * judge. It never plants a flag speculatively — it cannot tell whether it wants time to switch, and
+ * a flag spent early is a flag not there when a train is actually bearing down.
  */
-function worthFlagging(s: GameState, options: Intent[]): Intent | null {
-  for (const i of options) {
-    if (i.type !== 'maneuver.redFlags') continue;
-    const tray = s.trays.get(i.trayId);
-    if (!tray || tray.position.at !== 'mainline') continue;
-    const node = s.division.nodes[tray.position.index];
-    if (node?.kind !== 'mainline') continue;
-    if (node.transits.length > 1) return i;
-  }
-  return null;
+function worthFlagging(_s: GameState, options: Intent[]): Intent | null {
+  return options.find((i) => i.type === 'mainline.redFlag' && i.flag === true) ?? null;
 }
 
 /** A one-line account of which Load/Unload action was taken, and why it ranked first. */
diff --git a/src/sim/narrate.ts b/src/sim/narrate.ts
index 0aaf06e..85680ec 100644
--- a/src/sim/narrate.ts
+++ b/src/sim/narrate.ts
@@ -218,10 +218,19 @@ export function narrate(e: GameEvent, ctx: NarrateContext = {}): Narration {
           ? `Realignment: Mainline card ${e.node} converted to ${e.became}`
           : `Played ${e.key} on Mainline card ${e.node}`,
       };
+    case 'redFlagSpent':
+      return {
+        tone: 'good',
+        text: `RED FLAG — Train ${e.trainNumber} stopped short of the ${e.side === 'east' ? 'Eastern' : 'Western'} Limits. The flag comes down with it.`,
+      };
+    case 'redFlagRuled':
+      return e.flag
+        ? { tone: 'plain', text: `Player ${e.player} flagged the approaching train` }
+        : { tone: 'plain', text: `Player ${e.player} waved the train through` };
     case 'redFlagsSet':
       return {
         tone: 'good',
-        text: `Red Flags set out to protect train ${e.trayId} on Mainline card ${e.node} — an approaching train must stop`,
+        text: `RED FLAGS set out on the ${e.side === 'east' ? 'Eastern' : 'Western'} Limits — the next train from that way is held short`,
       };
     case 'flyingSwitch':
       return {
diff --git a/src/sim/view.ts b/src/sim/view.ts
index 04c4822..e2cffb1 100644
--- a/src/sim/view.ts
+++ b/src/sim/view.ts
@@ -1043,7 +1043,15 @@ export function describeIntent(s: GameState, i: Intent): string {
       return `${cardName(s, i.cardId)} on ${shortWhere} — ${where}${effect ? `; ${effect}` : ''}`;
     }
     case 'maneuver.redFlags':
-      return `set Red Flags to protect ${trainName(s, i.trayId)} — an approaching train must stop short`;
+      return (
+        `FLAG ${i.side === 'east' ? 'EAST' : 'WEST'} — hold the next ${i.side === 'east' ? 'westbound' : 'eastbound'} ` +
+        'train short of your Limits, so you can finish switching'
+      );
+    // §Q, the out-of-phase play (Gitea#19) — "COLLISION RISK! FLAG AGAINST T2?"
+    case 'mainline.redFlag':
+      return i.flag
+        ? 'FLAG IT — stop the train short of your Limits, spending a Red Flags card'
+        : 'wave it through — let it come in';
     /**
      * §11, the Yard Office (Gitea#5). The offer interrupts the Mainline Phase, so the label has to
      * carry the whole question — there is no surrounding context on screen to lean on, and the
@@ -1109,7 +1117,15 @@ export function describeIntent(s: GameState, i: Intent): string {
     case 'redFlag.play':
       return 'play your red flag';
     case 'maneuver.redFlags':
-      return `set Red Flags to protect ${trainName(s, i.trayId)} — an approaching train must stop short`;
+      return (
+        `FLAG ${i.side === 'east' ? 'EAST' : 'WEST'} — hold the next ${i.side === 'east' ? 'westbound' : 'eastbound'} ` +
+        'train short of your Limits, so you can finish switching'
+      );
+    // §Q, the out-of-phase play (Gitea#19) — "COLLISION RISK! FLAG AGAINST T2?"
+    case 'mainline.redFlag':
+      return i.flag
+        ? 'FLAG IT — stop the train short of your Limits, spending a Red Flags card'
+        : 'wave it through — let it come in';
     /**
      * §11, the Yard Office (Gitea#5). The offer interrupts the Mainline Phase, so the label has to
      * carry the whole question — there is no surrounding context on screen to lean on, and the
diff --git a/test/events.test.ts b/test/events.test.ts
index 6813abf..2df40da 100644
--- a/test/events.test.ts
+++ b/test/events.test.ts
@@ -48,6 +48,15 @@ const KNOWN_UNREDUCED = [
   'dispatchBonusUsed',
   'expediteFault',
   'phaseBegan',
+  /**
+   * §Q, Red Flags (Gitea#19). The flag comes down inside the phase driver as it stops a train, so
+   * this is described rather than reduced like everything else here.
+   *
+   * ADDED DELIBERATELY, and it cost a bug first: the flag was originally taken down in a `reduce`
+   * case, which never fires for an event `advance.ts` emits — so it stayed up and held every train
+   * that came. That is precisely the failure this list exists to make visible.
+   */
+  'redFlagSpent',
   // Employee Rotation moves `seating` in the phase driver and then describes what it did, which is
   // the pattern every entry on this list follows.
   'seatsRotated',
diff --git a/test/mainline-cards.test.ts b/test/mainline-cards.test.ts
index 3fdee5e..bd6718b 100644
--- a/test/mainline-cards.test.ts
+++ b/test/mainline-cards.test.ts
@@ -28,7 +28,7 @@ import {
 import { createGame } from '../src/engine/setup.ts';
 import type { GameEvent } from '../src/engine/events.ts';
 import type { GameConfig, GameState, GridCoord, TrackCard } from '../src/engine/state.ts';
-import { coordKey, turnOf } from '../src/engine/state.ts';
+import { coordKey, decisionActor, turnOf } from '../src/engine/state.ts';
 import { snapshot } from '../src/sim/view.ts';
 
 const config: GameConfig = {
@@ -317,77 +317,177 @@ describe('Realignment converts one Mainline type to another', () => {
   });
 });
 
-describe('Red Flags protect a stopped train', () => {
-  /** A slow train `behind` closing on a stopped train `ahead`, both eastbound on node 1. */
-  function rearEnder(s: GameState) {
-    const node = pinned(s, 1, 'plains');
-    node.transits.push({ tray: 'ahead', stagesRemaining: 2, stagesTotal: 2, direction: 'east' });
-    s.trays.set('ahead', {
-      id: 'ahead', trainNumber: 4, trainIsExtra: false, engineAt: 0,
-      consist: [], direction: 'east', position: { at: 'mainline', index: 1 }, movesUsed: 0,
+describe('Red Flags hold a train out of your Limits (Gitea#19)', () => {
+  /**
+   * REPLACES the old rule outright (Jesse, 2026-08-29). Red Flags used to be played on a stopped
+   * train out on the Mainline and protected it from a rear-ender — measured at 4,212 offers and 4
+   * plays across 600 games, a mechanic nobody used. ABS Signals already does that job better.
+   *
+   * Now: "If played, asked FLAG EAST or FLAG WEST. That stops all trains from entering your limits
+   * from that direction (i.e. Flag East holds westbound trains)." Spent on the train it stops —
+   * one card, one train.
+   */
+
+  /** A westbound train one Stage from entering seat 0's district from the east. */
+  function approaching(s: GameState) {
+    const officeIndex = s.division.nodes.findIndex((n) => n.kind === 'office' && n.seat === 0);
+    const node = pinned(s, officeIndex + 1, 'plains');
+    node.transits.push({ tray: 'inbound', stagesRemaining: 1, stagesTotal: 1, direction: 'west' });
+    s.trays.set('inbound', {
+      id: 'inbound', trainNumber: 9, trainIsExtra: false, engineAt: 0,
+      consist: [{ type: 'hopper', loaded: true }], direction: 'west',
+      position: { at: 'mainline', index: officeIndex + 1 }, movesUsed: 0,
     });
-    s.trays.set('behind', {
-      id: 'behind', trainNumber: 2, trainIsExtra: false, engineAt: 0,
-      consist: [], direction: 'east', position: { at: 'divisionPoint', side: 'west' }, movesUsed: 0,
-    });
-    const dp = s.division.nodes[0];
-    if (dp?.kind === 'divisionPoint') dp.holding.push('behind');
     s.clock.phase = 'mainline';
     s.movedThisPhase = new Set();
-    return node;
+    return s.division.nodes[officeIndex] as Extract<typeof s.division.nodes[0], { kind: 'office' }>;
   }
 
-  it('holds the approaching train instead of letting it close', () => {
+  it('FLAG EAST holds a westbound train short of the Limits', () => {
     const s = game();
-    const node = rearEnder(s);
-    node.redFlagged = ['ahead'];
+    const office = approaching(s);
+    office.redFlag = 'east';
 
     advance(s);
-    assert.deepEqual(
-      s.trays.get('behind')!.position,
-      { at: 'divisionPoint', side: 'west' },
-      'the flagged train must not be approached',
-    );
+    const pos = s.trays.get('inbound')!.position;
+    assert.equal(pos.at, 'mainline', 'the flagged train came in anyway');
+    assert.ok(!areaOf(s, 0).adOccupancy.includes('inbound'), 'it reached an A/D track');
   });
 
-  it('comes in when the protected train rolls', () => {
+  it('is spent on the train it stops — one card, one train', () => {
     const s = game();
-    const node = rearEnder(s);
-    node.redFlagged = ['ahead'];
-    // Bring the protected train to the end of its crossing so it leaves the card.
-    node.transits[0]!.stagesRemaining = 1;
+    const office = approaching(s);
+    office.redFlag = 'east';
 
-    for (let i = 0; i < 12 && (node.redFlagged?.length ?? 0) > 0; i++) advance(s);
-    assert.deepEqual(node.redFlagged, [], 'flags come in once the train moves off');
+    advance(s);
+    assert.equal(office.redFlag, undefined, 'the flag stayed up after stopping a train');
   });
 
-  it('only protects a train out on the Mainline', () => {
+  it('lets the train in on the next Mainline Phase', () => {
+    // "Loses one Mainline Phase" — it buys a Stage to clear the lead, not permanent protection.
+    const s = game();
+    const office = approaching(s);
+    office.redFlag = 'east';
+    advance(s);
+
+    s.clock.phase = 'mainline';
+    s.movedThisPhase = new Set();
+    advance(s);
+    assert.ok(areaOf(s, 0).adOccupancy.includes('inbound'), 'the train never came in');
+  });
+
+  it('does not hold a train coming from the OTHER side', () => {
+    // "Flag East holds westbound trains" — an eastbound train arrives from the west.
+    const s = game();
+    const office = approaching(s);
+    office.redFlag = 'west';
+
+    advance(s);
+    assert.ok(areaOf(s, 0).adOccupancy.includes('inbound'), 'a west flag held a train from the east');
+    assert.equal(office.redFlag, 'west', 'the wrong-side flag was spent');
+  });
+
+  it('is played on a side, not on a train', () => {
     const s = game();
-    rearEnder(s);
     s.clock.phase = 'localOps';
     s.clock.currentActor = 0;
     const cardId = hand(s, 'maneuver', 'redFlags');
 
-    assert.equal(
-      check(s, 0, { type: 'maneuver.redFlags', cardId, trayId: 'behind' }),
-      'NO_PLACEMENT',
-      'a train sitting at a Division Point cannot be rear-ended',
-    );
-    assert.equal(check(s, 0, { type: 'maneuver.redFlags', cardId, trayId: 'ahead' }), null);
+    assert.equal(check(s, 0, { type: 'maneuver.redFlags', cardId, side: 'east' }), null);
+    assert.equal(check(s, 0, { type: 'maneuver.redFlags', cardId, side: 'west' }), null);
   });
 
-  it('will not double-flag the same train', () => {
+  it('will not double-flag the same side', () => {
     const s = game();
-    const node = rearEnder(s);
     s.clock.phase = 'localOps';
     s.clock.currentActor = 0;
     const cardId = hand(s, 'maneuver', 'redFlags');
-    node.redFlagged = ['ahead'];
+    const officeIndex = s.division.nodes.findIndex((n) => n.kind === 'office' && n.seat === 0);
+    const office = s.division.nodes[officeIndex] as { redFlag?: string };
+    office.redFlag = 'east';
 
-    assert.equal(
-      check(s, 0, { type: 'maneuver.redFlags', cardId, trayId: 'ahead' }),
-      'OPTION_ALREADY_CHOSEN',
-    );
+    assert.equal(check(s, 0, { type: 'maneuver.redFlags', cardId, side: 'east' }), 'ALREADY_FLAGGED');
+    assert.equal(check(s, 0, { type: 'maneuver.redFlags', cardId, side: 'west' }), null,
+      'the other side should still be free');
+  });
+});
+
+describe('Red Flags offered at the moment of danger (Gitea#19)', () => {
+  /**
+   * "In actual cases of danger… if there is a train or cars on the track and there will be a
+   * collision, then you break in with a dialog that says COLLISION RISK! FLAG AGAINST T2? This way,
+   * you can play the card normally or out of phase, but only if you need it."
+   *
+   * The engine establishes the danger, so the player is never asked to judge it — which is also why
+   * the bot can now use this card at all. It is offered ONLY to somebody holding one.
+   */
+  function dangerous(s: GameState, giveCard: boolean) {
+    const officeIndex = s.division.nodes.findIndex((n) => n.kind === 'office' && n.seat === 0);
+    const node = pinned(s, officeIndex + 1, 'plains');
+    node.transits.push({ tray: 'inbound', stagesRemaining: 1, stagesTotal: 1, direction: 'west' });
+    s.trays.set('inbound', {
+      id: 'inbound', trainNumber: 9, trainIsExtra: false, engineAt: 0,
+      consist: [{ type: 'hopper', loaded: true }], direction: 'west',
+      position: { at: 'mainline', index: officeIndex + 1 }, movesUsed: 0,
+    });
+    // A hopper fouling the Running Track: §8.3 makes this arrival a collision.
+    const area = areaOf(s, 0);
+    area.grid.get(coordKey(area.officeCoord))!.standing = [{ type: 'hopper', loaded: false }];
+    if (giveCard) hand(s, 'maneuver', 'redFlags');
+    s.clock.phase = 'mainline';
+    s.movedThisPhase = new Set();
+  }
+
+  it('breaks in to offer the flag when an arrival would collide', () => {
+    const s = game();
+    dangerous(s, true);
+    advance(s);
+    assert.equal(s.clock.pendingDecision?.kind, 'redFlag', 'no prompt before a certain collision');
+    assert.equal(decisionActor(s), 0, 'the prompt went to the wrong player');
+  });
+
+  it('flagging holds the train and costs the card', () => {
+    const s = game();
+    dangerous(s, true);
+    advance(s);
+    const before = (s.decks.hands.get(0) ?? []).length;
+
+    const r = applyIntent(s, 0, { type: 'mainline.redFlag', flag: true });
+    assert.ok(r.ok, 'the flag was refused');
+    advance(s);
+
+    assert.equal(s.players[0]!.revenue, 0, 'the collision happened anyway');
+    assert.equal(s.trays.get('inbound')!.position.at, 'mainline', 'the train came in regardless');
+    assert.equal((s.decks.hands.get(0) ?? []).length, before - 1, 'the card was not spent');
+  });
+
+  it('declining lets the collision happen', () => {
+    const s = game();
+    dangerous(s, true);
+    advance(s);
+
+    assert.ok(applyIntent(s, 0, { type: 'mainline.redFlag', flag: false }).ok);
+    advance(s);
+    assert.equal(s.players[0]!.revenue, -5, 'waving it through did not collide');
+  });
+
+  it('does not offer a flag to a player holding none', () => {
+    // A prompt with one button is not a choice, and it leaks that a collision is coming.
+    const s = game();
+    dangerous(s, false);
+    advance(s);
+    assert.equal(s.clock.pendingDecision, null, 'offered a flag to a player with no card');
+    assert.equal(s.players[0]!.revenue, -5, 'the collision should have happened');
+  });
+
+  it('stays quiet when the arrival is safe', () => {
+    const s = game();
+    dangerous(s, true);
+    // Clear the hazard: nothing fouling the Running Track, and room at the Office.
+    const area = areaOf(s, 0);
+    area.grid.get(coordKey(area.officeCoord))!.standing = [];
+    advance(s);
+    assert.equal(s.clock.pendingDecision, null, 'interrupted the phase for a safe arrival');
   });
 });
 
diff --git a/test/sim.test.ts b/test/sim.test.ts
index 6342928..dc49777 100644
--- a/test/sim.test.ts
+++ b/test/sim.test.ts
@@ -363,21 +363,29 @@ describe('end-of-game statistics', () => {
      * and so removing this line is what proves the bot has been fixed.
      */
     /**
-     * RED FLAGS JOINS IT (Gitea#3), and for the same reason — the rule is reachable and the bot will
-     * not take it.
+     * RED FLAGS JOINS IT, and the reason CHANGED with Gitea#19 — the exemption stays, but it no
+     * longer means what it used to.
      *
-     * MEASURED over 600 games: `maneuver.redFlags` is OFFERED 4,212 times, first in game 5 — so the
-     * rule is live and constantly available. The bot PLAYS it 4 times, first in game 252. At 200
-     * games this canary sees nothing and calls it unreachable, which is the opposite of the truth.
+     * IT USED TO MEAN "the bot will not take it": measured over 600 games under the old rule,
+     * `maneuver.redFlags` was OFFERED 4,212 times and PLAYED 4. The card protected a stopped train
+     * out on the Mainline, it was always available, and the bot simply declined it.
      *
-     * It got rarer for two compounding reasons, neither of them a broken rule: Gitea#14 took Red
-     * Flags from 5 copies to the sheet's 3, and Gitea#3 shortened most crossings to a single Stage,
-     * so the window in which a train is STANDING on a Mainline card — the only place the card may be
-     * played — is now usually one Stage wide.
+     * SINCE Gitea#19 the bot would take it every time — `worthFlagging` accepts the out-of-phase
+     * prompt unconditionally, because the engine only raises that prompt when an arrival is
+     * certainly about to collide, so there is nothing left for the bot to judge. It still never
+     * plays one. MEASURED after the redesign, 200 solitaire games: `redFlagsSet` fires ZERO times.
      *
-     * The bot's unwillingness is the thing worth fixing, and it is in TODO.md under Bot Performance.
-     * Exempted BY NAME so the other forty-odd checks stay live, and so deleting this line is what
-     * proves the bot has learned to use it.
+     * The reason is now arithmetic rather than judgement, and it is worth writing down because it
+     * says what would actually change it. The prompt needs two things to coincide — an arrival that
+     * would collide (0.14 collisions per game, so roughly one game in seven) AND the district's
+     * owner holding a Red Flags card at that moment, out of a three-card hand drawn from 121. The
+     * bot also never plants a flag speculatively, which is the other half of the card and the half
+     * a human would use to buy time for switching.
+     *
+     * So this canary is measuring deck luck, not reachability. `test/mainline-cards.test.ts`
+     * exercises both halves of the rule end to end on a hand-built board, which is where the
+     * behaviour is actually pinned. Removing this line still proves something worth proving — that
+     * the bot has learned to plant a flag on purpose rather than only when handed one.
      */
     const KNOWN_UNREACHABLE_BY_THE_BOT = ['event flyingSwitch', 'event redFlagsSet'];
     const found = anomalies(report.perGame);