v0.4.9e — five of six playtest bugs: one button per train, and a load that has to go somewhere

Gameplay testing on 0.4.9d returned six reports. Five are fixed; the sixth could not be
reproduced and is written up in TODO.md with the two questions that would pin it down.

TWO TRAINS AT ONE PLATFORM ANSWERED TO ONE BUTTON. `porter.board` and `porter.detrain`
carried no tray, so there was one button per platform however many trains stood at it and
the reducer filled the first empty coach on the A/D tracks. `check` and the reducer were not
even asking the same question: `check` skipped a train whose card refuses passenger work and
the reducer did not. Both intents now carry an optional `trayId`, one function resolves the
train and the coach for check/execute/reduce alike, `legal.ts` offers one candidate per train,
and the label names it.

A LOAD COULD BE MADE AND BROKEN WITHOUT GOING ANYWHERE. A Freight House could unload the
boxcar it had just loaded; a platform could detrain the passengers it had just boarded. Full
Revenue at both ends for a movement that never happened. Jesse's rule: a load made anywhere in
an Office Area may not be broken anywhere in that Office Area, ever — it has to be carried to
another district. The load carries the seat that made it (`RollingStock.origin`), stripped by
`pooled` at every yard push. Measured at -0.60 +/- 0.10 Revenue a game (t = -6.1) over 400
paired deals: 78 worse, 3 better, 319 unchanged — free Revenue coming off the board, not a nerf.

THE GROCER'S WAREHOUSE SHIPPED AND THE REFINERY RECEIVED. Both were `flow: 'both'` on the
reading that "Freight House" was a collective term for exactly those two, and therefore what
§9.3 described. The engine has dealt a Freight House CARD since before v0.4.9, so §9.3 names
it and the argument goes. The card set agrees: all three Refinery modifiers grant +1 outbound.
Refinery outbound-only, Grocer's inbound-only, Freight House the one two-way industry — which
leaves exactly the one same-district pairing the rule above refuses.

NOT REPRODUCED: cars left behind when backing up over them. Five layouts tried, including cars
spotted at an industry; every one couples the lot. Three are pinned in `apply.test.ts`. One way
to create such cars was closed anyway — `flyingSwitch` wrote its cut past `carsOn`.

Both published replays that had gone dead were re-recorded; a rules change retires a save, and
`harness.test.ts` is what catches it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011nbvwWMef8CuEP6t5cgkTv

CHANGELOG.md

@@ -19,6 +19,143 @@ page as `v0.1.0 · <sha> · <date>`, so what is deployed can always be identifie
 
 ---
 
+## 0.4.9e — 2026-08-22
+
+Six bugs came back from a gameplay-testing session on 0.4.9d. Five are fixed here; the sixth could not
+be reproduced and is written up in `TODO.md` with the two questions that would pin it down. Patched
+onto the 0.4.9d line, and applied to the 0.5/0.6 line as the same change.
+
+### Two trains at one platform answered to one button
+
+**REPORTED:** "Operating two trains in a station: the select button does not work. Regardless of which
+you pick, it is always one train, not the other."
+
+It did not work because there was nothing for it to do. `porter.board` and `porter.detrain` carried
+**no tray at all** — `{ type, at }` and nothing else — so there was one "board passengers at (0,0)"
+button however many trains were standing at the platform, and the reducer walked `adOccupancy` and
+filled the first empty coach it met. The roster chip the player clicked chose which crew the board
+DREW and nothing else. Two independent things were wrong at once:
+
+- `check` asked whether SOME train at the Office had an empty coach, skipping any whose card refuses
+  passenger work (`refusesPassengers`, `refusesThisOffice`). The reducer did not skip those. So with a
+  Military train and an ordinary one at the same platform, `check` said yes on behalf of the ordinary
+  one and the reducer boarded the Military.
+- The action list collapses identical labels, and "board passengers at (0,0)" describes both trains —
+  the same trap that once ate a turnout's second rotation and a Department discard.
+
+Both intents now carry an optional `trayId`, one function (`passengerWork`) resolves which train and
+which coach for `check`, `execute` and the reducer alike, `legal.ts` enumerates one candidate per
+train standing at the Office, and the label names it: *"board passengers at (0,0) onto Train 9"*.
+`trayId` is OPTIONAL for the reason `switch.move`'s `via` is — intents are the canonical record every
+save and undo replay against, and absent still means "the first eligible train".
+
+The events carry `trayId` and `coachIndex` rather than leaving the reducer to find them again, which
+is the lesson `unloadBegan`'s `carIndex` already taught: a reducer that re-derives the target is a
+second implementation of the rule, and it disagreed with the first.
+
+### A load could be made and broken without going anywhere
+
+**REPORTED, twice over:** "Freight House: boxcars loaded cannot be immediately unloaded. In the game
+we'll put the chip upside down in the tray to indicate." And: "Passenger stations: passengers just
+boarded cannot be immediately unloaded."
+
+They could. A Freight House permits both directions, so the boxcar its own Laborers had just loaded
+was standing on its own industry track, loaded, with an empty of that type in the Division Yard and a
+free red box — every gate said yes. Passengers were worse: `porter.board` filled a coach and
+`porter.detrain` looked for "a loaded coach on a train at the Office", which is the coach that had
+just been filled. Full Revenue at both ends of a movement that never happened, for one Porter action.
+
+**Jesse's rule, and it is wider than the report:** freight or passengers loaded anywhere in an Office
+Area may not be unloaded anywhere in that same Office Area — not at another facility, not in a later
+Stage. A train has to carry them to a different district. So a load carries a stamp naming the SEAT
+that made it (`RollingStock.origin`), and the stamp never expires; `laborer.beginUnload` and
+`porter.detrain` refuse a car stamped with the district they are standing in, with a rejection code of
+its own (`LOADED_IN_THIS_DISTRICT`) because "the car is loaded, the Laborer is free, the boxes are
+clear, and the only thing wrong is where it came from" deserves better than "wrong car".
+
+**A seat, not a player**, because Employee Rotation moves players between chairs and the district
+stays with the chair. **Undefined, not −1**, for "no origin": the Division Yard opens with loaded cars
+and loaded coaches out of the common supply, and those are exactly the inbound traffic a solitaire
+district lives on — a sentinel inside `SeatIndex`'s own range is not a sentinel. And `pooled` strips
+the stamp at every yard push, because the stamp belongs to the LOAD: a train can retire at a Division
+Point with freight still aboard, and that car must not carry a district it left three Days ago into
+whatever train is made up from it next.
+
+**Measured: −0.60 ± 0.10 Revenue a game** (t = −6.1) over 400 paired deals — 78 deals worse, 3 better,
+319 unchanged. That shape is the point. This is not a nerf spread across the game; it is a narrow
+piece of free Revenue coming off the board, and on four deals in five the bot never took it.
+
+The screen's version of the upside-down chip: a car or coach loaded by this district reads *"loaded
+boxcar (loaded here)"* on the card, in the tray and in the facility panel.
+
+### The Grocer's Warehouse shipped, and the Refinery received
+
+**REPORTED:** "Grocer's warehouse should be receive only, does not ship anything out." And:
+"Refinery: only ships out tanks, does not receive anything."
+
+Both were `flow: 'both'` in `content.ts`, put there deliberately and for a reason that has since
+collapsed. `card-reference.md` read: *"'Freight House' is not a card. It is the collective term for a
+freight facility that loads and unloads — the Grocer's Warehouse and the Oil Refinery."* If that were
+true, §9.3's "Passenger Facilities and Freight Houses permit cars to move each direction" named
+exactly those two, and they had to be two-way. But the engine has dealt a `freightHouse` card since
+before v0.4.9 — 6 copies, one slot each direction — so §9.3 names it, and the argument evaporates.
+
+The card set says the same thing without needing the rules text. All three Refinery modifiers —
+Pipelines, Oil Depot, Viscosity Breakers — grant **+1 outbound**; a two-way Refinery would be the only
+industry in the game with no card able to raise one of its two directions.
+`StationMaster-Home-Deck-v0.4.5.md` prints "Refinery · Outbound · 1 out / 0 in" and "Grocer's
+Warehouse · Inbound · 0 out / 1 in".
+
+So the Refinery ships and the Grocer's receives, and the **Freight House is the one two-way industry**
+— which also means the only same-district load-and-unload the district rule above has to refuse is a
+Freight House unloading its own work. The two fixes meet exactly where the report said they would.
+
+A consequence worth naming rather than discovering: an **Ice House beside a Grocer's Warehouse is now
+a dead card**, its +1 outbound dropped on a direction the host does not have. That is the design, not
+an oversight — the Home Deck sheet says so outright, and names the Truck Dock's inbound grant beside
+the outbound-only Packing Sheds as the other example. `suppressedGrants` already reports it on the
+page. It does mean the v0.4.7 note in `TODO.md` that opened these two facilities up was half wrong,
+and it is annotated there rather than deleted: the *machinery* it built (an industry's printed flow is
+absolute; drop the grant, never open the direction) is exactly what makes this correction land.
+
+### Not reproduced: cars left behind when backing up over them
+
+**REPORTED:** "When I back up to collect standing cars and, further down the tracks, the caboose, I
+get the caboose but the cars remain. I can later drive right through them."
+
+Not found, and not for want of looking. Cars on plain track on the way; cars spotted at an INDUSTRY on
+the way (Jesse's own guess at the shape); the train's own cut on the square it is pulling out of; a
+stale `standingWest`; an industry locked by MEN AT WORK. Every one couples the lot, and the last
+correctly blocks the whole route rather than letting the crew past. Three of them are now pinned in
+`apply.test.ts` so the case, when it is found, is somewhere none of them cover.
+
+The reason it is hard to make happen is structural: coupling is mandatory (§A.4) and `exploreMoves`
+accumulates what it meets card by card, so a route that reaches the caboose has already met everything
+between. `carsOn` is the single answer to "what is standing here", and the movement walk, the sweep in
+`carsCoupled` and every renderer all ask it — so cars a train can drive through would have to be cars
+that are on screen and not in `carsOn`, and there is no such place.
+
+There was one way to MAKE such a place, and it is closed: `flyingSwitch`'s reducer wrote the cut
+straight into `industryTrack`, which is not where `carsOn` looks on a Passenger Facility. `check`
+refuses a non-freight target so it never fired, but a trap that needs another rule to stay unsprung is
+still a trap; it goes through `carsOn` now.
+
+`TODO.md` carries the two questions that would settle it: was there a second route to the caboose, and
+what did the move button say it would couple. The label names every car, so "couples caboose" and
+"couples 2 boxcars, caboose" are different bugs — the first is route selection, the second the sweep.
+
+### Also
+
+- **An unload never checks the facility's commodity** — found reading `laborer.beginUnload` for the
+  district rule, not from play. It gates on `allows.inbound`, a loaded car, a matching empty in the
+  yard and room in the red box, but never on `facilityCarTypes`, which `freightAgent.stockOutbound`
+  does check. So a Freight House will unload a hopper. Left alone and logged: the district rule now
+  refuses the one same-Office pairing that made it easy to reach, and the fix is a rule question about
+  what an industry will accept, not a one-line guard.
+- **Both published replays that had gone dead were re-recorded** (`save-replay.ts 400 --top 3`). A save
+  is a save from a particular ruleset, so a rules change retires the files that no longer replay —
+  `harness.test.ts` catches it, which is what that test is for.
+
 ## 0.4.9d — 2026-08-21
 
 Three bugs from the same playtest session, patched directly onto 0.4.9a rather than the in-progress