Merge pull request 'feat: v0.20.0 — ISS-021 move On board to left pane, widen left 360/280' (#31) from feat/onboard-left-pane into master

Part A: r(F) = k(We + rho*F) L/km, k calibrated so a full tank burns exactly
the old constant; closed forms in lib/sim/movement.ts (fuelAtWeighted,
requiredFuelFor, burnRateConstant, FUEL_DENSITY_KG_PER_L). Catalog gains
emptyWeightKg (ATR72 OEW 9300 kg), exposed in the snapshot. All three burn
call sites (engine landing, state live fuel, fly validation) moved to the
weighted model; old constant-rate fuelAt removed.

Part B: POST /api/planes/{planeId}/refuel takes an optional body
{mode:'full'|'forFlight', packageId} — no body keeps today's fill-to-full
behavior exactly (fuel lands bit-exact on maxFuel); forFlight adds just
enough for the loaded package's destination leg (409 not-loaded/expired/
doesn't-fit, 400 bad body). UI: per-cargo-row 'Refuel' button
(refuel-for-{pkg.id}), market button renamed 'Refuel to full'.

OpenAPI: RefuelRequest schema + optional requestBody + 400 on refuel, fly's
409 description updated, CatalogEntry.emptyWeightKg. Tests: new weighted-burn
suite, forFlight action/route cases (incl. ~7670 km UNNT<->LPPD doesn't-fit),
openapi guards; landing-fuel assertions in engine.test.ts + e2e/actions.spec.ts
use the closed form; the e2e 'return leg unfuelable' scenario reworked — a full
tank now covers the EDDF<->LEZL round trip, so the 409 moves to the second
outbound. New e2e: row Refuel deducts exactly L*price / raises fuel by exactly
L via the endpoint's own response snapshot.

AGENTS.md

@@ -1,18 +1,16 @@
 # Flight Simulator — Workflow Rules
 
 ## Change process (mandatory)
-1. **Small, incremental changes** — work is done one change at a time, in smaller parts; each part must be tested thoroughly with unit and e2e tests covering it before moving on.
+1. **Small, incremental changes** — work is done one change at a time, in smaller parts; each part must be tested thoroughly with unit and e2e tests covering it before moving on. Connected issues/tasks that reference the same part of code MAY be done together on one branch/PR with a single version bump (e.g. two UI tweaks to the same panel).
 2. **Feature branch + PR** — every change lands on a feature branch off `master` (no direct pushes to master). The branch carries the commits below; open a pull request to `master`.
 3. **Changelog entry** — every such change is listed in `CHANGELOG.md` with date, time and version (format: `## v<version> — YYYY-MM-DD HH:MM`, then bullet points of what changed).
 4. **Version bump** — the version is updated in `package.json`.
-5. **CI must pass** — the PR's pipeline (build → unit tests → e2e, `.gitea/workflows/ci.yml`) must be green before merging. CI never deploys to production; its e2e runs against an isolated stack inside dind.
+5. **CI must pass** — enforced by branch protection on `master` (required status check `CI / build + unit + e2e (pull request)`): the PR cannot be merged until CI is green. Merge via auto-merge (`POST /repos/{owner}/{repo}/pulls/{n}/merge` with body `{"do":"merge","merge_style":"merge","merge_when_checks_succeed":true}`) so it merges automatically once CI passes. CI never deploys to production; its e2e runs against an isolated stack inside dind.
 6. **Tag + manual deploy after merge** — once merged, tag the version on `master` (e.g. `v0.13.0`). Production (`https://flight.dev.kkhost.pl`) is updated manually afterwards: `docker compose up -d --build` on the host.
 
 ## E2E tests (mandatory)
-1. **Docker compose instance is the app under test** — e2e always runs against a docker-compose build, never a local `next dev` on :3000 (dev builds don't render for non-loopback clients, and a second instance splits state). Locally that means the Traefik-routed instance at `https://flight.dev.kkhost.pl`; in CI it is an isolated stack inside dind (`docker-compose.ci.yml`) — **CI never deploys to or modifies production**.
+1. **CI-only** — e2e runs ONLY in CI, against an isolated docker stack inside dind built from `docker-compose.ci.yml` (project name `flight-ci`, app container on a static IP; see `.gitea/workflows/ci.yml`). There are NO local e2e runs at all: locally you verify with `tsc --noEmit` + `npx vitest run` + `npx playwright test --list` (typecheck, unit suite, specs compile and list), and the full e2e suite is verified by CI on every PR. **CI never deploys to or modifies production.**
-2. **Update before testing (local)** — deploy current code first: `docker compose up -d --build`, then run the suite with plain `npx playwright test`. The config's webServer block is off by default; set `E2E_DEPLOY_CMD` to have Playwright itself run a deploy command and wait for readiness.
+2. **CI env vars** (`playwright.config.ts`, all optional) — `E2E_BASE_URL` (app under test; CI sets it to the in-network app host, so the config's default of the live Traefik instance at `https://flight.dev.kkhost.pl` is never used), `E2E_DEPLOY_CMD` (runs as Playwright webServer: deploys the stack and waits for readiness before tests start; CI uses build + `up -d` + `logs -f`), `PW_REMOTE_BROWSER=0` (CI runs local chromium because the shared remote browser server at 192.168.1.4 cannot reach a stack inside dind — when unset, the config defaults to that remote server and to the live instance as baseURL), and `E2E_COMPOSE_ARGS`, read by `e2e/state.spec.ts` for its mid-run `docker compose restart flight` (CI points it at `-f docker-compose.ci.yml -p flight-ci`).
-3. **Remote browsers** — local runs drive browsers through the shared Playwright server at `192.168.1.4:3000` (Docker image tag must match this repo's @playwright/test version, pinned in devDependencies). Set `PW_REMOTE_BROWSER=0` to run local chromium instead — CI does, because the remote server cannot reach a stack inside dind.
-4. **CI env vars** (`playwright.config.ts`, all optional; defaults preserve the local flow) — `E2E_BASE_URL` (app under test), `E2E_DEPLOY_CMD` (webServer deploy command), `PW_REMOTE_BROWSER=0` (local browsers); `e2e/state.spec.ts` reads `E2E_COMPOSE_ARGS` for its mid-run container restart.
 
 ## API
 1. **Live base URL** — `https://flight.dev.kkhost.pl` (the docker-compose build behind Traefik).

CHANGELOG.md

@@ -1,5 +1,79 @@
 # Changelog
 
+## v0.20.0 — 2026-09-19 19:21
+- **On board moved to the left pane (ISS-021).** The "On board" section (per-plane blocks with loaded/expired cargo rows, Refuel-for-leg / Fly-to / Abandon + penalty preview) now renders in `components/LeftPane.tsx` between Fleet and Time — wallet stays on top. The JSX moved verbatim (same testids: `onboard-{planeId}`, `onboard-package-{pkg.id}`, `refuel-for-*`, `fly-to-*`, `abandon-*` + penalty preview), along with the `onboard` computation (`planes.filter(flying || slotsUsedFor > 0)`) and per-plane cargo filter. All onboard e2e locators are global testids, so existing specs work unchanged
+- **Left pane widened: grid swapped to 360/1fr/280.** `.app-shell` in `app/globals.css` goes from `280px minmax(0, 1fr) 360px` to `360px minmax(0, 1fr) 280px` — total fixed width stays 640 px, so the map column is pixel-identical (map.spec.ts clicks via dynamic `map.project()`). Stale comments updated (on-board blocks now in the left pane; Relocate row comment reflects the 280 px right pane)
+- **Shared action runner hook.** RightPane's local `runAction` (busy gate, inline pane error + shell toast on failure, full post-action snapshot pushed via `applySnapshot`) extracted to new `lib/useGameAction.ts`: `useGameAction(state, applySnapshot, onError) → { runAction, busy, actionError }`, exact semantics kept incl. the non-2xx throw/catch and inline-error auto-clear on the next snapshot. Used in BOTH panes; LeftPane receives `applySnapshot` from the shell (`app/page.tsx`). RightPane keeps `[data-testid="right-error"]`; LeftPane gains a matching `[data-testid="left-action-error"]`. Pure helpers `slotsUsedFor` / `loadEligiblePlanes` stay exported from RightPane (unit tests import them there; LeftPane imports `slotsUsedFor` from it); the Market Relocate row + `/api/airports` fetch stay in RightPane
+- Tests: e2e — `panes.spec.ts` first test now also asserts the "On board" heading is visible inside `[data-testid="left-pane"]` and absent from the right pane; stale header comments updated in `actions.spec.ts` / `right-pane.spec.ts`. No unit-test changes (baseline 283)
+- Verified: `tsc --noEmit` clean; unit suite green locally; e2e not run locally by design — CI verifies against an isolated stack
+- **On-board cargo rows are two lines (ISS-028).** Each `onboard-package-*` row now stacks a full-width "Fly to <airport>" button on its own line above Refuel + Abandon side by side: `components/LeftPane.tsx` moves the fly-to button out of `.contract-main` into the row root and wraps refuel-for + abandon in a new `.onboard-actions` div — all testids, label text, penalty preview and disabled states unchanged. Long destination names in the fly-to label truncate with an ellipsis instead of overflowing: the label's inner span gets `min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap`, full name preserved via a `title` attribute (CSS in `app/globals.css`: `.onboard-block .contract-row` becomes flex-column, new `.onboard-fly-btn` / `.onboard-fly-label` / `.onboard-actions`). No e2e changes — specs locate everything by testid and assert no layout or button order; no version bump (part 2 of v0.20.0)
+
+## v0.19.2 — 2026-09-19 20:06
+- **AGENTS.md "Change process" item 1** — connected issues/tasks that reference the same part of code may now be done together on one branch/PR with a single version bump (e.g. two UI tweaks to the same panel)
+- **AGENTS.md "E2E tests" section rewritten to match current reality** — e2e runs ONLY in CI, against an isolated docker stack inside dind (`docker-compose.ci.yml`); there are NO local e2e runs at all (local verification = `tsc --noEmit` + `npx vitest run` + `npx playwright test --list`; the full suite is verified by CI on every PR). Dropped the stale local-run instructions (deploying to the Traefik-routed instance before testing, driving browsers through the remote Playwright server at 192.168.1.4:3000); kept and reworded the CI env vars that actually exist in `playwright.config.ts` (`E2E_BASE_URL`, `E2E_DEPLOY_CMD`, `PW_REMOTE_BROWSER=0`, `E2E_COMPOSE_ARGS`)
+
+## v0.19.1 — 2026-09-19 18:48
+- AGENTS.md: document that CI-green is enforced on master by branch protection (required status check) and that merges use auto-merge (`merge_when_checks_succeed`) so PRs merge automatically once CI passes
+
+## v0.19.0 — 2026-09-19 18:05
+- **Auto-slow to 1× when all planes have landed (ISS-011).** When the last plane in flight lands, the sim slows down on its own so an idle fleet doesn't sit at 1000×. Server-side and authoritative: `tickOnce` (`lib/sim/engine.ts`) now remembers how many planes `deliverPackages` finalized during a tick, and when ≥1 plane landed this tick AND no plane remains with status `'flying'` AND the sim is not paused, it persists `timeScale = 1` on the same `sim_state` write as the clock — so the UI slider reflects it on the very next snapshot (no API or OpenAPI change: timeScale is still set via the existing `POST /api/sim`, and `clampTimeScale` semantics are untouched since 1 is a valid ladder value)
+- **Arrival-triggered, not idle-enforced.** The trigger fires only on the tick that processes a landing — a grounded fleet at high scale with no flight ever happening is left alone (this keeps the existing slider e2e in `panes.spec.ts` green: it sets 1000× and expects the server to confirm it while nothing is flying). Paused state is untouched: while paused no landings are processed, so a paused sim never auto-slows
+- **No auto-restore by design.** The previous scale is not remembered — once the game slows to 1× after the last landing, the player speeds up manually again (slider or `POST /api/sim`). Deliberately minimal scope: no "resume my old speed" behavior
+- Tests: unit — new `describe('auto-slow …')` block in `lib/sim/engine.test.ts`: last plane lands → stored timeScale becomes 1; a landing while another plane is still flying → no change; already at 1× → stays 1; paused sim with all planes landed → no change. e2e — new `e2e/auto-slow.spec.ts` (serial mode, SCALE=1000, self-heal fly-home in afterEach like relocation.spec.ts): sets 1000× via the API, dispatches plane-starter on the shortest leg from its hub (EDDF → nearest airport), waits for the landing and asserts the server's `timeScale` is exactly 1 in that snapshot, then proves manual override still works (`POST /api/sim {timeScale: 1000}` confirmed by response + fresh snapshot)
+- **e2e suite adapted to the new behavior.** Every existing spec that flies out-and-back relied on 1000× persisting across a landing — with ISS-011 it no longer does, so each return leg now re-sets SCALE explicitly: `flyHomeViaApi` in actions/relocation/right-pane/hover (re-set before the repositioning flight after waiting for an in-flight leg to land) and the restore legs inside the test bodies of actions.spec.ts (core loop, expired packages, validation paths ×2), right-pane.spec.ts (fly-to-destination, refuel-for-leg) and hover.spec.ts (flying-plane route highlight). map-interactions.spec.ts needed no change — its `loadAndFly` helper already re-sets SCALE before every landing wait
+- Verified: `tsc --noEmit` clean; unit suite green locally; e2e not run locally by design — CI verifies against an isolated stack
+
+## v0.18.0 — 2026-09-19 16:02
+- **Relocate a grounded (empty) plane to any airport (ISS-010).** `flyPlane` has allowed pure repositioning since v0.12.0, but the UI only exposed flying for planes that carried cargo — an empty grounded plane had no fly control anywhere. Two new surfaces now drive the EXISTING `POST /api/planes/{id}/fly {destIcao}` endpoint (no API or OpenAPI change):
+  - **Right-pane market row** (`components/RightPane.tsx`): a fourth `.market-row` with `[data-testid="relocate-plane"]` (grounded planes, "ATR 72-600 — EDDF" labels), `[data-testid="relocate-dest"]` (all airports from a one-time `GET /api/airports` fetch per page life — same promise-ref pattern as Map.tsx — sorted by name for stable e2e selection) and the `[data-testid="relocate-go"]` "Relocate" button, disabled while busy or until both selects have a value. Same effective-selection + `runAction` pattern as the buy/sell/refuel rows (first grounded plane / first airport preselected); the row wraps (`market-row-relocate`) since two selects don't fit one 360 px line
+  - **Airport popup Relocate row** (`components/Map.tsx`): after the name/ICAO/local-time/weather lines, a `.popup-relocate` block with `[data-testid="airport-popup-plane"]` (grounded planes from the latest polled snapshot at click time) and `[data-testid="airport-popup-relocate"]` "Relocate here" — disabled until a plane is picked; on click it POSTs fly to the clicked airport, pushes the response snapshot through the shell's `applySnapshot` (new Map prop, same callback RightPane receives), and reports success/failure in `[data-testid="airport-popup-relocate-status"]`. With no grounded planes the row shows `[data-testid="airport-popup-no-planes"]` instead. Popups are plain HTML, not React — controls wired via `popup.getElement().querySelector(...)` after `.addTo(map)`
+- **Bigger airport markers (ISS-010).** The r=3 dots were hard to click: `airports-circles` paint in `components/Map.tsx` goes from radius 3 / stroke 1 to radius 5 / stroke 1.5, and the hover highlight ring follows (r=8 → r=9). Paint-only — no data or interaction changes
+- No server or OpenAPI changes — both surfaces reuse the existing fly endpoint (validations unchanged: 404 unknown plane / 409 flying or insufficient fuel / 400 unknown ICAO, strict unknown-field rejection kept)
+- Tests: e2e — new `e2e/relocation.spec.ts` (serial mode, SCALE=1000, self-heal fly-home in afterEach like actions.spec.ts): market-row test ensures plane-starter grounded at the hub via API, picks it + the nearest non-hub airport (shortest leg) and asserts `/api/state` shows `flying` with that destIcao after clicking Relocate; popup test clicks the isolated LFRS marker (projected-center pattern from map.spec.ts), asserts the select lists "ATR 72-600 — EDDF" and the button is disabled until a plane is picked, then relocates via the popup. Marker-size regression gate = the existing map.spec.ts click tests keep passing
+- Verified: `tsc --noEmit` clean; unit suite green locally (no lib/ changes — flyPlane's zero-package case already covered by actions.test.ts); e2e not run locally by design — CI verifies against an isolated stack
+- **Fix (CI run #50): POPUP_AIRPORT scoping in the popup relocation e2e.** The LFRS marker click passed `POPUP_AIRPORT` into a `page.evaluate(() => …)` callback that runs in the BROWSER, where Node-scope constants don't exist — deterministic `ReferenceError: POPUP_AIRPORT is not defined` (relocation.spec.ts popup test, both attempts of run #50). The constant is now passed as an evaluate argument (`page.evaluate(({lon, lat}) => …, POPUP_AIRPORT)`); the other evaluate in the file only touches browser globals and needed no change. Test-only — no app code touched
+- **Fix (CI run #51): strict-mode locator in the popup relocation e2e.** `expect(planeSel.locator('option')).toContainText(…)` resolved to BOTH options (placeholder + plane) → strict mode violation (relocation.spec.ts popup test, both attempts of run #51; the app rendered correctly). The assertion now targets `option[value="plane-starter"]` specifically with `toHaveText`. Test-only — no app code touched
+
+## v0.17.0 — 2026-09-19 14:49
+- **Bottom-right toasts for action errors (ISS-008).** Error messages like "insufficient funds: a ATR 72-600 costs 200000, you have 62721" now appear as toasts in the bottom-right corner — new `lib/useToasts.ts` hook (`useToasts() → {toasts, push(kind, msg), dismiss(id)}`, auto-dismiss after ~5 s, queue capped at 4 dropping the oldest; pure core `pushToast` unit-tested) and new `components/Toasts.tsx` `<ToastStack>` (fixed container `.toasts`, items `[data-testid="toast"]` with class `toast toast-error|toast-info` + a × dismiss button). Wired into BOTH error paths: `RightPane.runAction`'s catch now calls the shell's `onError` in addition to keeping the inline `[data-testid="right-error"]` pane error, and `LeftPane.applySimControls`'s catch (previously console.error-only) reports "Failed to update time controls (…)" through the same callback. The shell (`app/page.tsx`) owns the hook and renders the stack; CSS in `app/globals.css`
+- **Event messages via snapshot diffing.** No server event feed exists, so new pure `lib/deriveEvents.ts` — `diffSnapshots(prev: StateSnapshot | null, next) → {kind:'info', message}[]` — derives human-readable events from the fields already in `/api/state`: plane landing (`flying→available`, "ATR 72-600 landed at Frankfurt"), package delivery (`loaded→delivered`, "Package delivered: +€X" with the reward), expiry (`open|loaded→expired`, "Package expired: A → B"), new packages (id only in next, "New package available: A → B") and planes bought/sold (plane id set changed, "Bought/Sold {model}"). The shell keeps a `prevRef` and diffs on every snapshot change, pushing each event as an info toast; the first snapshot after load emits nothing (no baseline — no page-load spam)
+- **Browser notifications when the window is not focused.** Each derived event also fires `new Notification('Flight Ops', {body})` when `document.hidden && 'Notification' in window && Notification.permission === 'granted'`. The left-pane Time section gains an explicit opt-in button (`[data-testid="enable-notifications"]`) calling `Notification.requestPermission()`; its label reflects the result ("Enable notifications" → "Notifications enabled"/"Notifications blocked"), and it renders disabled with a tooltip title when the API is absent. SSR-safe: permission state starts null and is read in an effect after hydration
+- No server or OpenAPI changes — diffing uses only existing snapshot fields (verified: planes by id/status/locationName, packages by id/status/reward/origin+dest names)
+- Tests: unit — new `lib/deriveEvents.test.ts` suite pins every event format (landing, delivery with reward, expiry from open and loaded, new-package appearance, bought/sold, identical snapshots → [], first snapshot → [], non-events like takeoff/load ignored); `lib/useToasts.test.ts` covers the queue cap. e2e — new `e2e/toasts.spec.ts`: deterministic insufficient-funds path (select the most expensive model in `[data-testid="market-buy-model"]`, click Buy, expect a visible error toast matching /insufficient funds/ AND the inline `right-error` still showing; skips only if cash already covers the plane on a long-lived local instance) and the notifications opt-in (unsupported → disabled + title; otherwise fresh context shows "Enable notifications" and after clicking the label reflects the result — soft, since headless CI may deny permission)
+- Verified: `tsc --noEmit` clean; unit suite green locally; e2e not run locally by design — CI verifies against an isolated stack
+- **Fix (CI runs #44/#47): sim-control POSTs are retried before surfacing the error.** A dropped `POST /api/sim` on the runner's flaky uplink left the UI optimistic while the server kept the old scale — panes.spec.ts:74 timed out with timeScale stuck at 1000 (run #47). `applySimControls` now retries each commit up to 3× total (~500 ms backoff) before surfacing the error toast; a newer intent arriving mid-retry supersedes the in-flight body instead of waiting out its retries (last-wins queueing kept), and the endpoint's set-semantics make re-sending an already-applied value idempotent. Pure retry core `retrySimPost` exported from LeftPane + unit-tested. Also run #47: toasts.spec.ts Part B is now permission-state-aware — headless Chromium reports `Notification.permission` as 'denied' (not 'default'), so the test branches on the actual state (denied → assert blocked label without clicking; granted → enabled label; default → prompt, click, accept either resulting label)
+
+## v0.16.1 — 2026-09-19 14:00
+- **Smooth client-side sim clock with per-snapshot re-sync (ISS-007).** The left-pane "Time" display used to jump once per 1 s poll because it rendered the snapshot's `clockMs` verbatim. It now ticks smoothly on the client between polls: new hook `lib/useSimClock.ts` keeps an anchor `{clockMs, at, timeScale, paused}` and re-derives the display clock every ~100 ms as `anchor.clockMs + (now − at) × timeScale` — exactly the server's own tick model (`tickOnce`: real-time × timeScale), so client extrapolation mirrors authoritative game time. Every new snapshot re-anchors to server truth, bounding any drift by network latency only; while paused the display is frozen at the anchor value (advance 0). The pure core `advanceSimClock(anchor, nowMs)` is exported and unit-tested in node
+- **LeftPane consumes it for the `sim-clock` paragraph ONLY** (`components/LeftPane.tsx`): fed with EFFECTIVE controls `{timeScale: pendingScale ?? snapshot scale, paused}` so a slider drag or pause click takes effect on click/drag without waiting for a confirming snapshot; the `(paused)` suffix keeps coming from the effective paused flag. Right-pane deadline/penalty previews are untouched — they stay computed from the snapshot's `clockMs` (deterministic against server truth)
+- No server or OpenAPI changes — display-only client work
+- Tests: unit — new suite in `lib/useSimClock.test.ts` pins the extrapolation math (exact elapsed × scale advance, frozen while paused at any scale, zero-elapsed identity, clock-skew clamp never goes backwards, mirrors the tickOnce formula under the 2 s clamp). e2e (`panes.spec.ts`) — new test: at scale 1000 sample `sim-clock` three times ~1.3 s apart real time and assert the displayed clock strictly advances between CONSECUTIVE samples (with poll-only rendering a pair could straddle zero snapshots and not change), plus format check and a total-advance sanity bound
+- Verified: `tsc --noEmit` clean; unit suite green locally; e2e not run locally by design — CI verifies against an isolated stack
+
+## v0.16.0 — 2026-09-19 12:18
+- **Weight-proportional fuel burn (ISS-005, part A).** Fuel no longer burns at a constant L/km — the instantaneous rate is proportional to total weight, `r(F) = k·(We + ρF)` L/km with We the empty weight and ρ = 0.8 kg/L (Jet-A1), so a heavier plane burns more per km and a tank gets lighter as it empties. The constant `k` is calibrated so a FULL tank burns exactly the catalog's old `burnPerKm`, keeping full-tank departure behavior identical to before; divergence only grows in flight as fuel drops off. Closed forms of `dF/dx = −k(We + ρF)` live in `lib/sim/movement.ts` (single source of truth):
+  - `fuelAtWeighted(startFuel, burnPerKm, emptyWeightKg, maxFuel, distanceKm, progress)` — fuel remaining after flying `progress` of the leg (replaces the old constant-rate `fuelAt`, which is removed)
+  - `requiredFuelFor(burnPerKm, emptyWeightKg, maxFuel, distanceKm)` — liters needed to cover the distance arriving empty, independent of starting load; a leg is flyable iff current fuel ≥ this and fits at all iff it ≤ tank capacity
+  - `burnRateConstant(...)` + exported `FUEL_DENSITY_KG_PER_L` (0.8)
+- **Catalog gains `emptyWeightKg`** (`lib/game/catalog.ts`, ATR 72-600 OEW ≈ 9300 kg), exposed in the snapshot's `catalog[]` so clients can mirror the model; OpenAPI `CatalogEntry` follows
+- **All three burn call sites moved to the weighted model**: landing fuel on arrival (`lib/sim/engine.ts`), live in-flight fuel in the state snapshot (`lib/game/state.ts`), and fly validation (`lib/game/actions.ts` — a leg now needs `requiredFuelFor`, not `burnPerKm × km`)
+- **Refuel "just enough for the loaded package" (ISS-005, part B).** `POST /api/planes/{planeId}/refuel` takes an OPTIONAL JSON body `{ mode?: 'full' | 'forFlight', packageId?: string }`: no body or `mode:'full'` is exactly today's fill-to-max behavior; `mode:'forFlight'` adds just enough fuel to fly that loaded package's destination leg — liters = `requiredFuelFor(haversine(plane → pkg.destIcao)) − current fuel`, 409 if the package isn't loaded on this plane / is expired, or the leg doesn't fit even a full tank; bad bodies (unknown field/mode, forFlight without packageId) are 400. OpenAPI gains `RefuelRequest` + the 400
+- **UI** (`components/RightPane.tsx`): each on-board cargo row gets a "Refuel" button (`refuel-for-{pkg.id}` → `{mode:'forFlight', packageId}`, disabled while flying or busy, mirroring fly-to/abandon); the market fill-up button is renamed **"Refuel to full"** (testid `market-refuel` and behavior unchanged)
+- Tests: unit — new weighted-burn suite in `lib/sim/movement.test.ts` (full-tank calibration ≈ old constant, closed form vs numeric integration of r(F), F_req monotonic + empty-arrival identity, lighter-start burns less, clamping); `refuelPlane` forFlight cases in `lib/game/actions.test.ts` (exact liters/cost, no-op when enough, 409 not-loaded/expired/doesn't-fit via the ~7670 km UNNT↔LPPD pair, 404 unknown package, 400 missing packageId); refuel route body-validation tests; `lib/openapi.test.ts` updated (optional RefuelRequest, errorCodes `['400','404','409']`, CatalogEntry.emptyWeightKg). Adjusted where the model legitimately shifts numbers: landing-fuel assertions in `lib/sim/engine.test.ts` and `e2e/actions.spec.ts` now use the weighted closed form; the e2e "return leg unfuelable" scenario is reworked — under weight-proportional burn a full tank covers the EDDF↔LEZL round trip (the plane lightens as it flies), so the 409 insufficient-fuel assertion moves to the SECOND outbound after landing back with a partial tank
+- e2e (`right-pane.spec.ts`): new test — fly the longest hub leg on a full tank, load a package back to the hub at the far end, click the row "Refuel" and assert via the endpoint's own response snapshot that cash drops by exactly L×price and fuel rises by exactly L (L from the mirrored closed form); also asserts the market button label is "Refuel to full". `e2e/api.spec.ts` path list unchanged
+- Verified: `tsc --noEmit` clean; unit suite green locally; e2e not run locally by design — CI verifies against an isolated stack
+- **Fix (CI run #40): forFlight refuel leaves an exactly-feasible tank, and the new e2e's premise corrected.** The right-pane e2e picked the dataset's absolute farthest airport from EDDF — UNNT at ~4803 km, whose leg needs ~6955 L > the 6300 L tank (max range from empty is ~4436 km) — so the full-tank fly rightly 409'd; `farthestToHub` becomes `farthestFlyableToHub`, picking the farthest airport whose leg still fits a full tank (UWUU, ~3195 km). Server hardening in the same area: forFlight now sets fuel to EXACTLY `requiredFuelFor(...)` instead of `fuel + liters` — that sum is not guaranteed ≥ R in IEEE754 (`f + fl(R − f)` can round a hair below), and flyPlane's strict comparison would then 409 on an otherwise-feasible leg; cost math unchanged (still the added liters × price). New unit regression test: forFlight on an empty-ish tank → immediate `flyPlane` to the package destination succeeds
+- **E2e flake hardening (runs #36/#41): full-core-loop Load/Fly precondition races** — test mechanics only, no app code changes. Two independent races in `e2e/actions.spec.ts`: (1) the Fly click fires its POST asynchronously (`runAction` is fire-and-forget from the test's view), so the immediate `getState` could race ahead of it and still see status 'available' — now an `expect.poll` waits until the server shows 'flying' with the expected destIcao before proceeding; (2) `flyHomeViaApi` made its repositioning decision from a snapshot taken BEFORE waiting for a leftover in-flight leg to land — while flying, locationIcao stays at the departure airport, so a plane that landed away from home was still believed to be home and never repositioned (run #41 retry: starter stranded at EDFH) — state is now re-read after landing; plus an explicit server-side precondition poll (starter grounded at the package origin) before clicking Load
+
+## v0.15.1 — 2026-09-19 11:04
+- **Right pane widened, "On board" wrapping fixed (ISS-004).** The 3-pane shell grid (`app/globals.css` `.app-shell`) moves from `300px / 1fr / 320px` to `280px / 1fr / 360px` — the map column absorbs the delta (MapLibre sizes itself from its container, no JS change). Three wrap offenders in the right pane's "On board" blocks are fixed:
+  - In-flight leg header (`components/RightPane.tsx`, `.contract-route` span): the class already had `white-space: nowrap; overflow: hidden; text-overflow: ellipsis`, but as a flex item with default `min-width: auto` it could not shrink below its full text width, so long routes (e.g. "Frankfurt → Madrid–Barajas") overflowed instead of ellipsizing — `.contract-route` now has `min-width: 0`
+  - Cargo-row buttons ("Fly to {dest}" / "Abandon −€X" in `.contract-main`): labels wrapped mid-text at the old width — `.pane-btn` now has `white-space: nowrap`
+  - Cargo sub-line route span had no white-space rule and wrapped mid-route — it now carries the existing `contract-route` class (nowrap + ellipsis)
+- **Left pane sanity-checked at its new 280px**: fleet-row location span (`.plane-loc`) already had nowrap+ellipsis but lacked `min-width: 0`, so a long in-flight leg would have overflowed instead of truncating — same one-line guard added. Fuel/loadout spans are short fixed strings and need no guard
+- Verified: `tsc --noEmit` clean; unit suite **238/238** green locally (no lib changes); e2e not run locally by design — CI verifies against an isolated stack
+- **Unrelated test-stability fix included on this branch to unblock the pipeline** (`e2e/map-interactions.spec.ts`, no app changes): the mid-flight marker click now targets the plane's RENDERED position — it polls up to ~5 s for the rendered feature via `window.__flightMap.queryRenderedFeatures` on layers `planes-flying`/`planes-grounded` and projects that feature's coordinates, instead of fetching a fresh `/api/state`. With the sim paused the server position is static, but the map renders from its own ~1 s poll — right after the freeze confirmation the last rendered frame can still be up to one poll interval stale (tens of px at scale 1000 on EDDF→LEMD), so a click projected from a fresh fetch misses the small circle layer: the render-lag race that flaked CI run #37. Pause + freeze confirmation, popup assertions and resume are unchanged
+
 ## v0.15.0 — 2026-09-19 09:35
 - **Hover visualization from the side panels (ISS-002).** Hovering a fleet row in the left pane, an "On board" block (including its cargo rows) or an open-package row in the right pane now highlights the matching object on the map. The shared `HoverTarget` type (`components/hoverTypes.ts`: `{kind:'plane', id}` | `{kind:'package', originIcao, destIcao}`) is owned by the shell as a single `useState` and prop-drilled down — panes report via an `onHover` callback, `<Map>` consumes it. No React contexts introduced; the established prop-drilling pattern is kept
 - **Three top-most highlight layers** (`components/Map.tsx`, added inside idempotent `ensureLayers()` so they survive every `setStyle`): `planes-highlight` (circle over both plane layers, filter `['==',['get','id'],<planeId>]`, r=10, #38bdf8 fill + white stroke), `routes-highlight` (line over `routes-legs`, filter on the leg's `planeId`, width 6, #ef4444) and `airports-highlight` (circle ring over `airports-circles`, filter matching the hovered package's two ICAOs via `['any', …]`, r=8 stroke-only). All start filtered to match nothing — an empty-string sentinel no feature can have. Consumption follows the existing ref + effect pattern: a `[hovered]` effect calls `map.setFilter(...)` on the three layers (guarded by `getLayer`), and `ensureLayers` re-applies the current filter at its end so a hover outliving a style switch stays highlighted

app/api/planes/[planeId]/refuel/route.test.ts

@@ -5,7 +5,11 @@ import { eq } from 'drizzle-orm';
 import { afterAll, beforeAll, describe, expect, it } from 'vitest';
 import * as schema from '@/lib/db/schema';
 import { getGameDb } from '@/lib/db/client';
+import { loadAirportsGeoJson } from '@/lib/airports';
+import { haversineKm } from '@/lib/geo';
+import { requiredFuelFor } from '@/lib/sim/movement';
 import { FUEL_PRICE_PER_L, PLANE_TYPES } from '@/lib/game/catalog';
+import { HUB_ICAO } from '@/lib/game/seed';
 import { POST } from './route';
 
 let dir: string;
@@ -22,7 +26,15 @@ afterAll(async () => {
   await fs.rm(dir, { recursive: true, force: true });
 });
 
-const post = (planeId: string) => POST(new Request(`http://localhost/api/planes/${planeId}/refuel`), { params: Promise.resolve({ planeId }) });
+const post = (planeId: string, body?: unknown) =>
+  POST(
+    new Request(`http://localhost/api/planes/${planeId}/refuel`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: body === undefined ? undefined : JSON.stringify(body),
+    }),
+    { params: Promise.resolve({ planeId }) },
+  );
 
 describe('POST /api/planes/:planeId/refuel', () => {
   it('rejects an unknown id with 404', async () => {
@@ -74,4 +86,76 @@ describe('POST /api/planes/:planeId/refuel', () => {
     expect(res.status).toBe(409);
     expect(((await res.json()) as { error: string }).error).toMatch(/insufficient funds/i);
   });
+
+  it('accepts an explicit {mode:"full"} body exactly like no body', async () => {
+    const { db } = await getGameDb();
+    await db.update(schema.account).set({ cash: 50_000 }); // previous test left the account poor
+    await db.update(schema.planes).set({ fuel: 1_000 }).where(eq(schema.planes.id, 'plane-starter'));
+
+    const res = await post('plane-starter', { mode: 'full' });
+    expect(res.status).toBe(200);
+    const body = (await res.json()) as { planes: Array<{ id: string; fuel: number }> };
+    expect(body.planes.find((p) => p.id === 'plane-starter')!.fuel).toBe(PLANE_TYPES.atr72.maxFuel);
+  });
+
+  it('rejects an unknown mode with 400', async () => {
+    const res = await post('plane-starter', { mode: 'half' });
+    expect(res.status).toBe(400);
+    expect(((await res.json()) as { error: string }).error).toMatch(/mode/);
+  });
+
+  it('rejects forFlight without a packageId with 400', async () => {
+    const res = await post('plane-starter', { mode: 'forFlight' });
+    expect(res.status).toBe(400);
+    expect(((await res.json()) as { error: string }).error).toMatch(/packageId/);
+  });
+
+  it('rejects an unknown body field with 400', async () => {
+    const res = await post('plane-starter', { liters: 100 });
+    expect(res.status).toBe(400);
+    expect(((await res.json()) as { error: string }).error).toMatch(/unknown field/);
+  });
+
+  it('rejects invalid JSON with 400', async () => {
+    const res = await POST(
+      new Request(`http://localhost/api/planes/plane-starter/refuel`, { method: 'POST', body: '{nope' }),
+      { params: Promise.resolve({ planeId: 'plane-starter' }) },
+    );
+    expect(res.status).toBe(400);
+  });
+
+  it('forFlight tops up exactly the liters needed for the loaded package leg', async () => {
+    const { db } = await getGameDb();
+    await db.update(schema.account).set({ cash: 50_000 });
+    // A loaded EDDF → LEMD package on the starter (direct row — loadPackage is covered in actions tests).
+    await db.insert(schema.packages).values({
+      id: 'p-ff-api', originIcao: HUB_ICAO, destIcao: 'LEMD', reward: 1_000, cargoType: 'Mail', cargoCount: 4,
+      deadlineSimTime: Date.now() + 24 * 3_600_000, status: 'loaded', planeId: 'plane-starter', createdSimTime: Date.now(),
+    });
+
+    const fc = await loadAirportsGeoJson();
+    const from = fc.features.find((f) => f.properties.icao === HUB_ICAO)!.properties;
+    const to = fc.features.find((f) => f.properties.icao === 'LEMD')!.properties;
+    const km = haversineKm(from.lat, from.lon, to.lat, to.lon);
+    const type = PLANE_TYPES.atr72;
+    const required = requiredFuelFor(type.burnPerKm, type.emptyWeightKg, type.maxFuel, km);
+
+    const startFuel = Math.round(required / 2); // partial tank so L > 0
+    await db.update(schema.planes).set({ fuel: startFuel }).where(eq(schema.planes.id, 'plane-starter'));
+    const cashBefore = (await db.select().from(schema.account))[0].cash;
+
+    const res = await post('plane-starter', { mode: 'forFlight', packageId: 'p-ff-api' });
+    expect(res.status).toBe(200);
+
+    const body = (await res.json()) as {
+      account: { cash: number };
+      planes: Array<{ id: string; fuel: number }>;
+    };
+    const cost = Math.round((required - startFuel) * FUEL_PRICE_PER_L * 100) / 100;
+    expect(body.account.cash).toBeCloseTo(cashBefore - cost, 6);
+    expect(body.planes.find((p) => p.id === 'plane-starter')!.fuel).toBeCloseTo(required, 6);
+
+    // Clean up the test package.
+    await db.delete(schema.packages).where(eq(schema.packages.id, 'p-ff-api'));
+  });
 });

app/api/planes/[planeId]/refuel/route.ts

@@ -1,11 +1,47 @@
 import { performAction, refuelPlane } from '@/lib/game/actions';
 
-// POST /api/planes/:planeId/refuel (v0.8.0) — no body. Fills a grounded plane to
+// POST /api/planes/:planeId/refuel (v0.8.0; optional body v0.16.0) — fills a grounded
-// maxFuel at the fuel price per missing liter; deducts the cost from cash. 404
+// plane at the fuel price per added liter and deducts the cost from cash. The body is
-// unknown id; 409 if the plane is flying or cash is insufficient. On success
+// OPTIONAL: no body, {} or {mode:'full'} fill to maxFuel (the original behavior);
-// returns the full state snapshot (fuel back to max, cash reduced by the cost).
+// {mode:'forFlight', packageId} adds just enough for that loaded package's destination
+// leg. 400 bad body (unknown field, unknown mode, forFlight without packageId); 404
+// unknown plane/package id; 409 if the plane is flying, the package isn't loaded on it
+// (or is expired), the leg doesn't fit a full tank, or cash is insufficient. On success
+// returns the full state snapshot (fuel raised by exactly the added liters).
 
-export async function POST(_req: Request, ctx: { params: Promise<{ planeId: string }> }) {
+export async function POST(req: Request, ctx: { params: Promise<{ planeId: string }> }) {
   const { planeId } = await ctx.params;
-  return performAction((inst) => refuelPlane(inst, planeId));
+
+  let body: unknown;
+  try {
+    const text = await req.text();
+    body = text ? JSON.parse(text) : {};
+  } catch {
+    return Response.json({ error: 'invalid JSON body' }, { status: 400 });
+  }
+  if (typeof body !== 'object' || body === null || Array.isArray(body)) {
+    return Response.json({ error: 'body must be a JSON object' }, { status: 400 });
+  }
+  const input = body as Record<string, unknown>;
+  for (const key of Object.keys(input)) {
+    if (key !== 'mode' && key !== 'packageId') {
+      return Response.json({ error: `unknown field "${key}"` }, { status: 400 });
+    }
+  }
+  const mode = input.mode ?? 'full';
+  if (mode !== 'full' && mode !== 'forFlight') {
+    return Response.json({ error: 'mode must be "full" or "forFlight"' }, { status: 400 });
+  }
+  let packageId: string | undefined;
+  if (input.packageId !== undefined) {
+    if (typeof input.packageId !== 'string' || input.packageId.length === 0) {
+      return Response.json({ error: 'packageId must be a non-empty string' }, { status: 400 });
+    }
+    packageId = input.packageId;
+  }
+  if (mode === 'forFlight' && !packageId) {
+    return Response.json({ error: 'packageId is required when mode is "forFlight"' }, { status: 400 });
+  }
+
+  return performAction((inst) => refuelPlane(inst, planeId, { mode, packageId }));
 }

app/globals.css

@@ -68,10 +68,46 @@ body {
   color: #cbd5e1;
 }
 
-/* v0.9.0 — single-screen 3-pane shell: left Assets / center map / right Jobs & Market */
+/* ISS-010 (v0.18.0) — Relocate row inside the airport popup (plain HTML, not React). */
+.popup-relocate {
+  margin-top: 8px;
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  flex-wrap: wrap;
+}
+
+.popup-relocate select {
+  font-size: 12px;
+  padding: 3px 6px;
+  border-radius: 4px;
+  border: 1px solid rgba(148, 163, 184, 0.4);
+}
+
+.popup-relocate button {
+  font-size: 12px;
+  padding: 3px 10px;
+  border-radius: 4px;
+  border: 1px solid rgba(148, 163, 184, 0.4);
+  cursor: pointer;
+}
+
+.popup-relocate button:disabled {
+  opacity: 0.5;
+  cursor: default;
+}
+
+[data-testid='airport-popup-relocate-status'] {
+  font-size: 11px;
+  color: #334155;
+}
+
+/* v0.9.0 — single-screen 3-pane shell: left Assets / center map / right Jobs & Market.
+   ISS-021 (v0.20.0): left widened to 360px (it now carries the On board section), right
+   narrowed to 280px — total fixed width stays 640px, so the map column is unchanged. */
 .app-shell {
   display: grid;
-  grid-template-columns: 300px minmax(0, 1fr) 320px;
+  grid-template-columns: 360px minmax(0, 1fr) 280px;
   height: 100%;
 }
 
@@ -201,6 +237,7 @@ body {
 }
 
 .plane-loc {
+  min-width: 0;
   overflow: hidden;
   text-overflow: ellipsis;
   white-space: nowrap;
@@ -265,6 +302,7 @@ body {
 }
 
 .contract-route {
+  min-width: 0;
   font-weight: 600;
   color: #f1f5f9;
   overflow: hidden;
@@ -284,6 +322,7 @@ body {
 
 .pane-btn {
   flex-shrink: 0;
+  white-space: nowrap;
   font-size: 12px;
   padding: 3px 10px;
   border-radius: 4px;
@@ -324,6 +363,12 @@ body {
   padding: 4px 0;
 }
 
+/* ISS-010 (v0.18.0) — the Relocate row carries TWO selects, so let it wrap instead of
+   squeezing both below their readable width in the 280 px right pane (ISS-021 v0.20.0). */
+.market-row-relocate {
+  flex-wrap: wrap;
+}
+
 .market-preview {
   font-size: 12px;
   color: #f8fafc;
@@ -331,7 +376,7 @@ body {
   font-variant-numeric: tabular-nums;
 }
 
-/* v0.12.0 — on-board blocks (per plane) in the right pane */
+/* v0.12.0 — on-board blocks (per plane); moved to the left pane in ISS-021 (v0.20.0) */
 .onboard-block {
   background: rgba(30, 41, 59, 0.6);
   border-radius: 6px;
@@ -339,8 +384,101 @@ body {
   margin-bottom: 8px;
 }
 
+/* ISS-028 (v0.20.0 part 2) — on-board cargo rows are two lines: a full-width fly-to button,
+   then refuel + abandon side by side below it; long destination names truncate with an ellipsis. */
 .onboard-block .contract-row {
   background: transparent;
   padding: 6px 0 0;
   border-top: 1px solid rgba(148, 163, 184, 0.2);
+  display: flex;
+  flex-direction: column;
+  gap: 5px;
+}
+
+.onboard-block .contract-row .contract-sub {
+  margin-top: 0; /* row spacing comes from the container's gap */
+}
+
+.onboard-fly-btn {
+  width: 100%;
+}
+
+.onboard-fly-label {
+  display: block;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.onboard-actions {
+  display: flex;
+  gap: 6px;
+}
+
+/* v0.17.0 — ISS-008: bottom-right toast stack (action errors + game events) */
+.toasts {
+  position: fixed;
+  bottom: 12px;
+  right: 12px;
+  z-index: 50; /* above map popups/controls and the app header */
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  max-width: 340px;
+}
+
+.toast {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 10px;
+  padding: 8px 12px;
+  border-radius: 6px;
+  font-size: 13px;
+  background: rgba(15, 23, 42, 0.95);
+  color: #e2e8f0;
+  border: 1px solid rgba(148, 163, 184, 0.4);
+}
+
+.toast-error {
+  border-color: rgba(239, 68, 68, 0.7);
+  color: #fecaca;
+}
+
+.toast-info {
+  border-color: rgba(148, 163, 184, 0.5);
+}
+
+.toast-close {
+  flex-shrink: 0;
+  font-size: 14px;
+  line-height: 1;
+  padding: 2px 6px;
+  border-radius: 4px;
+  border: none;
+  background: transparent;
+  color: #94a3b8;
+  cursor: pointer;
+}
+
+.toast-close:hover {
+  color: #e2e8f0;
+}
+
+/* ISS-008 — the Time section's notifications opt-in button (same look as .time-controls buttons) */
+.notif-toggle {
+  margin-top: 8px;
+  font-size: 12px;
+  padding: 4px 10px;
+  border-radius: 4px;
+  border: 1px solid rgba(148, 163, 184, 0.4);
+  background: rgba(30, 41, 59, 0.9);
+  color: #e2e8f0;
+  cursor: pointer;
+}
+
+.notif-toggle:disabled {
+  opacity: 0.5;
+  cursor: default;
 }

app/page.tsx

@@ -1,11 +1,14 @@
 'use client';
 
 import dynamic from 'next/dynamic';
-import { useState } from 'react';
+import { useEffect, useRef, useState } from 'react';
 import LeftPane from '@/components/LeftPane';
 import RightPane from '@/components/RightPane';
+import ToastStack from '@/components/Toasts';
 import type { HoverTarget } from '@/components/hoverTypes';
 import { useGameState } from '@/lib/useGameState';
+import { useToasts } from '@/lib/useToasts';
+import { diffSnapshots } from '@/lib/deriveEvents';
 
 const Map = dynamic(() => import('@/components/Map'), { ssr: false });
 
@@ -19,12 +22,36 @@ export default function Home() {
   // either pane highlights the matching plane/route/airports on the map.
   const [hovered, setHovered] = useState<HoverTarget | null>(null);
 
+  // ISS-008 (v0.17.0): bottom-right toasts — action errors from both panes plus game events
+  // derived by diffing consecutive snapshots (no server event feed exists).
+  const { toasts, push, dismiss } = useToasts();
+  const onError = (message: string) => push('error', message);
+
+  // Diff each new snapshot against the previous one → info toasts. When the window is hidden
+  // and notifications are granted, mirror them as browser notifications too.
+  const prevSnapshotRef = useRef<typeof state>(null);
+  useEffect(() => {
+    if (state === null) return;
+    for (const event of diffSnapshots(prevSnapshotRef.current, state)) {
+      push('info', event.message);
+      if (document.hidden && 'Notification' in window && Notification.permission === 'granted') {
+        new Notification('Flight Ops', { body: event.message });
+      }
+    }
+    prevSnapshotRef.current = state;
+  }, [state, push]);
+
   return (
     <div className="app-shell">
-      <LeftPane state={state} loading={loading} error={error} onRefresh={refresh} onHover={setHovered} />
+      {/* ISS-021 (v0.20.0) — applySnapshot also reaches the left pane: its On board section's
-      {/* v0.11.0 — the same polled snapshot drives the map's plane markers + route lines */}
+          refuel/fly/abandon actions push their response snapshot into the shared state */}
-      <Map state={state} hovered={hovered} />
+      <LeftPane state={state} loading={loading} error={error} onRefresh={refresh} applySnapshot={applySnapshot} onHover={setHovered} onError={onError} />
-      <RightPane state={state} loading={loading} applySnapshot={applySnapshot} onHover={setHovered} />
+      {/* v0.11.0 — the same polled snapshot drives the map's plane markers + route lines;
+          ISS-010 (v0.18.0) — applySnapshot lets the airport popup's Relocate row push its
+          action response into the shared state, exactly like RightPane does */}
+      <Map state={state} hovered={hovered} applySnapshot={applySnapshot} />
+      <RightPane state={state} loading={loading} applySnapshot={applySnapshot} onHover={setHovered} onError={onError} />
+      <ToastStack toasts={toasts} onDismiss={dismiss} />
     </div>
   );
 }

components/LeftPane.tsx

@@ -3,8 +3,12 @@
 import { useCallback, useEffect, useRef, useState, type ChangeEvent } from 'react';
 import type { PlaneState, StateSnapshot } from '@/lib/game/state';
 import { PLANE_TYPES } from '@/lib/game/catalog';
-import { formatCash, formatFuel, formatSimClock } from '@/lib/format';
+import { abandonPenalty } from '@/lib/game/penalty';
+import { formatCash, formatDeadlineRelative, formatFuel, formatSimClock } from '@/lib/format';
 import { TIME_SCALES, scaleToSlider, sliderToScale } from '@/lib/timeScale';
+import { useGameAction } from '@/lib/useGameAction';
+import { useSimClock } from '@/lib/useSimClock';
+import { slotsUsedFor } from './RightPane';
 import type { HoverTarget } from './hoverTypes';
 
 interface LeftPaneProps {
@@ -13,8 +17,13 @@ interface LeftPaneProps {
   error: string | null;
   // The shell's single-poll refresh — called after a sim-control POST so the pane updates immediately.
   onRefresh: () => void;
+  // ISS-021 (v0.20.0): push the full snapshot returned by an action endpoint into the shared shell
+  // state — needed now that the On board section's refuel/fly/abandon actions live in this pane.
+  applySnapshot: (snapshot: StateSnapshot) => void;
   // ISS-002 (v0.15.0): report fleet-row hovers to the shell so the map can highlight the plane.
   onHover: (target: HoverTarget | null) => void;
+  // ISS-008 (v0.17.0): report a failed sim-control POST to the shell as an error toast.
+  onError?: (message: string) => void;
 }
 
 // Discrete ladder slider (v0.9.2, values reworked in v0.14.0): position t ∈ [0,1] → nearest
@@ -45,16 +54,55 @@ export function pendingScaleConfirmed(pendingScale: number | null, serverTimeSca
   return pendingScale !== null && serverTimeScale === pendingScale;
 }
 
-export default function LeftPane({ state, loading, error, onRefresh, onHover }: LeftPaneProps) {
+// ISS-008 fix (v0.17.0, CI runs #44/#47): bounded retry for POST /api/sim — a commit dropped by
+// the runner's flaky uplink used to leave the UI optimistic while the server kept the old scale.
+// Up to maxAttempts tries with delayMs between them; stops early once superseded() flips (a newer
+// intent arrived and the caller's loop sends it instead). post is idempotent set-semantics, so
+// re-sending a body whose response was lost cannot double-apply. Pure core — unit-tested in node.
+export const SIM_POST_MAX_ATTEMPTS = 3;
+export const SIM_POST_RETRY_DELAY_MS = 500;
+
+export type SimPostRetryResult =
+  | { ok: true }
+  | { ok: false; reason: 'exhausted'; error: unknown }
+  | { ok: false; reason: 'superseded' };
+
+export async function retrySimPost(
+  post: () => Promise<void>,
+  superseded: () => boolean,
+  sleep: (ms: number) => Promise<void> = (ms) => new Promise((r) => setTimeout(r, ms)),
+  maxAttempts: number = SIM_POST_MAX_ATTEMPTS,
+  delayMs: number = SIM_POST_RETRY_DELAY_MS,
+): Promise<SimPostRetryResult> {
+  let lastError: unknown;
+  for (let attempt = 1; attempt <= maxAttempts; attempt++) {
+    if (superseded()) return { ok: false, reason: 'superseded' }; // a newer intent takes over — don't even send this body
+    try {
+      await post();
+      return { ok: true };
+    } catch (err) {
+      lastError = err;
+      if (superseded()) return { ok: false, reason: 'superseded' }; // a newer intent arrived during the attempt — don't wait out the backoff
+      if (attempt < maxAttempts) await sleep(delayMs);
+    }
+  }
+  return { ok: false, reason: 'exhausted', error: lastError };
+}
+
+export default function LeftPane({ state, loading, error, onRefresh, applySnapshot, onHover, onError }: LeftPaneProps) {
   const [busy, setBusy] = useState(false);
 
-  // POST /api/sim, then refetch the full snapshot immediately so the pane reflects the new
+  // ISS-021 (v0.20.0): shared action runner for the On board section (moved here from RightPane).
-  // controls without waiting for the next poll tick. On failure keep the stale UI — the
+  const { runAction, busy: actionsBusy, actionError } = useGameAction(state, applySnapshot, onError);
-  // running poll retries on its own and surfaces the error state. A commit that lands while
+
-  // another POST is in flight is held in a single slot (last intent wins) and flushed by the
+  // POST /api/sim (retried up to SIM_POST_MAX_ATTEMPTS× on failure — CI runs #44/#47), then
-  // in-flight call, so every user intent reaches the server (the [1,1000] clamp stays as backstop).
+  // refetch the full snapshot immediately so the pane reflects the new controls without waiting
-  // The gate is a REF, not React state: closures never see a stale "busy" value, which used to
+  // for the next poll tick. After the final attempt fails keep the stale UI and surface an error
-  // let a flush re-queue instead of send and silently drop a commit.
+  // toast (the running poll retries on its own). A commit that lands while another POST is in
+  // flight — including mid-retry — is held in a single slot (last intent wins) and supersedes
+  // the in-flight body, so every user intent reaches the server (the [1,1000] clamp stays as
+  // backstop). The gate is a REF, not React state: closures never see a stale "busy" value,
+  // which used to let a flush re-queue instead of send and silently drop a commit.
   const queuedRef = useRef<{ timeScale?: number; paused?: boolean } | null>(null);
   const busyRef = useRef(false);
 
@@ -75,20 +123,32 @@ export default function LeftPane({ state, loading, error, onRefresh, onHover }:
       try {
         let current: { timeScale?: number; paused?: boolean } | null = body;
         while (current !== null) {
+          const target = current; // stable across this retry round
+          const result = await retrySimPost(
+            async () => {
               const res = await fetch('/api/sim', {
                 method: 'POST',
                 headers: { 'Content-Type': 'application/json' },
-            body: JSON.stringify(current),
+                body: JSON.stringify(target),
                 cache: 'no-store',
               });
               if (!res.ok) throw new Error(`POST /api/sim → HTTP ${res.status}`);
+            },
+            () => queuedRef.current !== null, // a newer intent supersedes the in-flight body mid-retry
+          );
+          if (result.ok) {
             onRefresh();
-          if (current === body) sentOwn = true; // object identity — queued bodies are fresh literals
+            if (target === body) sentOwn = true; // object identity — queued bodies are fresh literals
+          } else if (result.reason === 'exhausted') {
+            throw result.error; // only after the final attempt fails → error toast below
+          }
           current = queuedRef.current; // pick up anything that arrived while we were in flight
           queuedRef.current = null;
         }
       } catch (err) {
         console.error('failed to apply sim controls', err);
+        // ISS-008: surface the failure as an error toast too — previously console-only.
+        onError?.(`Failed to update time controls (${err instanceof Error ? err.message : String(err)})`);
         queuedRef.current = null; // don't replay a stale intent after a failed round-trip
       } finally {
         busyRef.current = false;
@@ -96,12 +156,18 @@ export default function LeftPane({ state, loading, error, onRefresh, onHover }:
       }
       return sentOwn ? 'sent' : 'failed';
     },
-    [onRefresh],
+    [onRefresh, onError],
   );
 
   const paused = state?.simState.paused ?? false;
   const timeScale = state?.simState.timeScale ?? 1;
 
+  // On board (v0.12.0, moved from the right pane in ISS-021 v0.20.0): every plane that carries
+  // cargo or is mid-flight gets a block — its loaded/expired packages with fly-to-destination +
+  // abandon controls, and flying planes show their current leg.
+  const clockMs = state?.simState.clockMs ?? 0;
+  const onboard = state ? state.planes.filter((p) => p.status === 'flying' || slotsUsedFor(state, p.id) > 0) : [];
+
   // Slider commit (v0.9.1): the displayed value follows the drag optimistically via
   // pendingScale; POST /api/sim fires after a 250 ms debounce, or immediately when the
   // user releases the slider (browsers fire a native 'change' on release). The server's
@@ -165,8 +231,33 @@ export default function LeftPane({ state, loading, error, onRefresh, onHover }:
     [],
   );
 
+  // ISS-008: browser-notification opt-in. Starts null (SSR-safe — the real permission is read
+  // in an effect after hydration, so server and client render identically) and follows the
+  // result of Notification.requestPermission(). 'unsupported' = no Notification API at all.
+  const [notifPermission, setNotifPermission] = useState<string | null>(null);
+  useEffect(() => {
+    if ('Notification' in window) setNotifPermission(Notification.permission);
+    else setNotifPermission('unsupported');
+  }, []);
+
+  // null (pre-effect) and 'default' both read as the opt-in prompt.
+  const notifLabel: string =
+    notifPermission === 'granted'
+      ? 'Notifications enabled'
+      : notifPermission === 'denied'
+        ? 'Notifications blocked'
+        : notifPermission === 'unsupported'
+          ? 'Notifications unavailable'
+          : 'Enable notifications';
+
   const displayedScale = pendingScale ?? timeScale;
 
+  // ISS-007: the clock ticks client-side between polls, re-syncing to server truth on every
+  // snapshot. Fed with EFFECTIVE controls so a scale drag / pause click takes effect immediately,
+  // not when the confirming snapshot lands. Only the sim-clock paragraph uses this — deadline and
+  // penalty previews stay snapshot-based (deterministic against the server clock).
+  const simClockMs = useSimClock(state, { timeScale: displayedScale, paused });
+
   return (
     <aside data-testid="left-pane" className="pane left-pane">
       <h2 className="pane-title">Assets</h2>
@@ -218,10 +309,100 @@ export default function LeftPane({ state, loading, error, onRefresh, onHover }:
             )}
           </section>
 
+          {/* ISS-021 (v0.20.0): moved here from the right pane — between Fleet and Time. */}
+          <section className="pane-section">
+            <h3 className="pane-heading">On board</h3>
+            {onboard.length === 0 ? (
+              <p className="pane-muted">Nothing on board.</p>
+            ) : (
+              onboard.map((plane) => {
+                const cargo = state.packages.filter(
+                  (pkg) => pkg.planeId === plane.id && (pkg.status === 'loaded' || pkg.status === 'expired'),
+                );
+                return (
+                  // ISS-002: hovering the on-board block (including its cargo rows) highlights the plane.
+                  // Handlers live only on the outer div — React's enter/leave don't fire when moving to a
+                  // child, so this covers the whole block without flicker between sub-elements.
+                  <div
+                    key={plane.id}
+                    data-testid={`onboard-${plane.id}`}
+                    className="onboard-block"
+                    onMouseEnter={() => onHover({ kind: 'plane', id: plane.id })}
+                    onMouseLeave={() => onHover(null)}
+                  >
+                    <div className="contract-main">
+                      <span className="plane-model">{PLANE_TYPES[plane.model]?.name ?? plane.model}</span>
+                      {plane.status === 'flying' ? (
+                        <>
+                          <span className="plane-status status-flying">in flight</span>
+                          {plane.destName && (
+                            <span data-testid={`plane-leg-${plane.id}`} className="contract-route">
+                              {plane.locationName} → {plane.destName}
+                            </span>
+                          )}
+                        </>
+                      ) : (
+                        <span className="plane-status status-available">{plane.locationIcao}</span>
+                      )}
+                    </div>
+                    {cargo.map((pkg) => {
+                      const penalty = abandonPenalty(pkg, clockMs);
+                      return (
+                        <div key={pkg.id} data-testid={`onboard-package-${pkg.id}`} className="contract-row">
+                          <button
+                            type="button"
+                            data-testid={`fly-to-${pkg.id}`}
+                            className="pane-btn onboard-fly-btn"
+                            disabled={actionsBusy || plane.status !== 'available'}
+                            onClick={() => void runAction(`/api/planes/${plane.id}/fly`, { destIcao: pkg.destIcao })}
+                          >
+                            <span className="onboard-fly-label" title={`Fly to ${pkg.destName}`}>
+                              Fly to {pkg.destName}
+                            </span>
+                          </button>
+                          <div className="onboard-actions">
+                            <button
+                              type="button"
+                              data-testid={`refuel-for-${pkg.id}`}
+                              className="pane-btn"
+                              disabled={actionsBusy || plane.status !== 'available'}
+                              onClick={() => void runAction(`/api/planes/${plane.id}/refuel`, { mode: 'forFlight', packageId: pkg.id })}
+                            >
+                              Refuel
+                            </button>
+                            <button
+                              type="button"
+                              data-testid={`abandon-${pkg.id}`}
+                              className="pane-btn"
+                              disabled={actionsBusy || plane.status !== 'available'}
+                              onClick={() => void runAction(`/api/packages/${pkg.id}/abandon`)}
+                            >
+                              Abandon{' '}
+                              <span data-testid={`abandon-penalty-${pkg.id}`}>−{formatCash(penalty)}</span>
+                            </button>
+                          </div>
+                          <div className="contract-sub">
+                            <span className="contract-route">{pkg.originName} → {pkg.destName}</span>
+                            <span>{formatCash(pkg.reward)}</span>
+                            {pkg.status === 'expired' ? (
+                              <span data-testid={`onboard-expired-${pkg.id}`}>expired</span>
+                            ) : (
+                              <span>{formatDeadlineRelative(pkg.deadlineSimTime, clockMs)}</span>
+                            )}
+                          </div>
+                        </div>
+                      );
+                    })}
+                  </div>
+                );
+              })
+            )}
+          </section>
+
           <section className="pane-section">
             <h3 className="pane-heading">Time</h3>
             <p data-testid="sim-clock" className="sim-clock">
-              {formatSimClock(state.simState.clockMs)}
+              {simClockMs !== null && formatSimClock(simClockMs)}
               {paused ? ' (paused)' : ''}
             </p>
             <div className="time-controls">
@@ -246,6 +427,24 @@ export default function LeftPane({ state, loading, error, onRefresh, onHover }:
               />
               <span data-testid="time-scale-value">{displayedScale}×</span>
             </div>
+            {/* ISS-008: explicit opt-in for browser notifications (fired when the window is hidden). */}
+            <button
+              type="button"
+              data-testid="enable-notifications"
+              className="notif-toggle"
+              disabled={notifPermission === 'unsupported'}
+              title={notifPermission === 'unsupported' ? 'This browser does not support notifications' : undefined}
+              onClick={() => {
+                // A rejection (rare — e.g. some headless setups) reads as "blocked".
+                if ('Notification' in window) {
+                  void Notification.requestPermission()
+                    .then(setNotifPermission)
+                    .catch(() => setNotifPermission('denied'));
+                }
+              }}
+            >
+              {notifLabel}
+            </button>
           </section>
 
           {error && (
@@ -253,6 +452,8 @@ export default function LeftPane({ state, loading, error, onRefresh, onHover }:
               {error}
             </p>
           )}
+          {/* ISS-021 (v0.20.0): inline error from a failed On board action — mirrors right-error. */}
+          {actionError && <p data-testid="left-action-error" className="pane-error">{actionError}</p>}
         </>
       ) : null}
     </aside>

components/Map.tsx

@@ -45,11 +45,14 @@ interface MapProps {
   // ISS-002 (v0.15.0): the side panels' hover target — highlights the matching plane
   // (+ its route leg if flying) or a package's endpoint airports. Null = nothing hovered.
   hovered?: HoverTarget | null;
+  // ISS-010 (v0.18.0): push an action endpoint's full response snapshot into the shared
+  // shell state — same callback RightPane receives, used by the airport popup's Relocate row.
+  applySnapshot: (snapshot: StateSnapshot) => void;
 }
 
 // Named FlightMap (not Map): a component called `Map` would shadow the global
 // Map constructor inside its own body, breaking `new Map(...)` for the airport index.
-export default function FlightMap({ state, hovered }: MapProps) {
+export default function FlightMap({ state, hovered, applySnapshot }: MapProps) {
   const containerRef = useRef<HTMLDivElement>(null);
   const mapRef = useRef<maplibregl.Map | null>(null);
   // /api/airports is fetched at most once per page life: every styledata event
@@ -58,6 +61,12 @@ export default function FlightMap({ state, hovered }: MapProps) {
   // Latest snapshot + airport coordinate index, so the mount effect's styledata wiring
   // and the state-change effect can both push data without prop-drilling into closures.
   const stateRef = useRef<StateSnapshot | null>(null);
+  // ISS-010 (v0.18.0): the shell's applySnapshot is stable (useCallback with no deps), but the
+  // mount effect captures it once — keep a ref so the popup wiring always calls the latest one.
+  const applySnapshotRef = useRef(applySnapshot);
+  useEffect(() => {
+    applySnapshotRef.current = applySnapshot;
+  }, [applySnapshot]);
   const airportsIndexRef = useRef<Map<string, AirportCoord> | null>(null);
   const [airportCount, setAirportCount] = useState<number | null>(null);
   const [styleId, setStyleId] = useState<string>(DEFAULT_STYLE_ID);
@@ -156,16 +165,67 @@ export default function FlightMap({ state, hovered }: MapProps) {
         // deterministic generated weather — no gameplay effects per PLAN.md.
         const w = weatherFor(p.icao);
         const localTime = approxLocalTime(p.lon, Date.now());
-        new maplibregl.Popup({ offset: 10 })
+        // ISS-010 (v0.18.0): Relocate row — grounded planes from the latest snapshot can be
+        // repositioned to this airport via POST /api/planes/{id}/fly (pure repositioning).
+        const st = stateRef.current;
+        const groundedPlanes = st ? st.planes.filter((pl) => pl.status === 'available') : [];
+        const planeLabel = (model: string) => st?.catalog.find((c) => c.model === model)?.label ?? model;
+        const relocateHtml =
+          groundedPlanes.length > 0
+            ? `<select data-testid="airport-popup-plane" aria-label="Plane to relocate here">` +
+              `<option value="">Select a plane\u2026</option>` +
+              groundedPlanes.map(
+                (pl) =>
+                  `<option value="${escapeHtml(pl.id)}">${escapeHtml(planeLabel(pl.model))} \u2014 ${escapeHtml(pl.locationIcao)}</option>`,
+              ).join('') +
+              `</select><button type="button" data-testid="airport-popup-relocate" disabled>Relocate here</button>`
+            : `<span data-testid="airport-popup-no-planes">No grounded planes to relocate.</span>`;
+        const popup = new maplibregl.Popup({ offset: 10 })
           .setLngLat(f.geometry.coordinates as [number, number])
           .setHTML(
             `<div data-testid="airport-popup">` +
               `<strong>${escapeHtml(p.name)}</strong><br/>${escapeHtml(p.icao)}<br/>` +
               `<span data-testid="airport-local-time">${localTime} local (approx)</span><br/>` +
               `<span data-testid="airport-weather">${w.condition}, wind ${w.windDirDeg}\u00B0 / ${w.windKt} kt, vis ${w.visibilityM} m</span>` +
+              `<div class="popup-relocate">` + relocateHtml + `<span data-testid="airport-popup-relocate-status"></span></div>` +
             `</div>`,
           )
           .addTo(map);
+
+        // Popups are plain HTML, not React — the element only exists after addTo, so wire the
+        // controls via querySelector (the select enables the button once a plane is picked).
+        const el = popup.getElement();
+        const select = el?.querySelector<HTMLSelectElement>('[data-testid="airport-popup-plane"]');
+        const button = el?.querySelector<HTMLButtonElement>('[data-testid="airport-popup-relocate"]');
+        // The status span is always in the popup HTML (even with no grounded planes), so it
+        // exists whenever the select/button do.
+        const statusEl = el?.querySelector<HTMLElement>('[data-testid="airport-popup-relocate-status"]');
+        if (select && button && statusEl) {
+          select.addEventListener('change', () => {
+            button.disabled = select.value === '';
+          });
+          button.addEventListener('click', async () => {
+            const planeId = select.value;
+            if (!planeId || button.disabled) return;
+            button.disabled = true;
+            statusEl.textContent = 'Relocating\u2026';
+            try {
+              const res = await fetch(`/api/planes/${planeId}/fly`, {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ destIcao: p.icao }),
+                cache: 'no-store',
+              });
+              const data = (await res.json()) as StateSnapshot & { error?: string };
+              if (!res.ok) throw new Error(data.error ?? `HTTP ${res.status}`);
+              applySnapshotRef.current(data); // shared shell state updates immediately, like the panes' runAction
+              statusEl.textContent = 'Relocation started.';
+            } catch (err) {
+              statusEl.textContent = err instanceof Error ? err.message : String(err);
+              button.disabled = false; // allow retry / picking another plane
+            }
+          });
+        }
       };
 
       const onPlaneClick = (e: maplibregl.MapLayerMouseEvent) => {
@@ -224,9 +284,9 @@ export default function FlightMap({ state, hovered }: MapProps) {
             type: 'circle',
             source: AIRPORTS_SOURCE_ID,
             paint: {
-              'circle-radius': 3,
+              'circle-radius': 5, // ISS-010 (v0.18.0): bigger — the r=3 dots were hard to click
               'circle-color': '#e11d48',
-              'circle-stroke-width': 1,
+              'circle-stroke-width': 1.5,
               'circle-stroke-color': '#ffffff',
             },
           });
@@ -317,7 +377,7 @@ export default function FlightMap({ state, hovered }: MapProps) {
             source: AIRPORTS_SOURCE_ID,
             filter: ['any', ['==', ['get', 'icao'], ''], ['==', ['get', 'icao'], '']],
             paint: {
-              'circle-radius': 8, // ring around the base airport circles (r=3)
+              'circle-radius': 9, // ring around the base airport circles (r=5)
               'circle-color': 'rgba(0, 0, 0, 0)', // transparent fill — stroke-only ring
               'circle-stroke-width': 2.5,
               'circle-stroke-color': '#facc15',

components/RightPane.tsx

@@ -1,10 +1,11 @@
 'use client';
 
-import { useCallback, useEffect, useState } from 'react';
+import { useEffect, useRef, useState } from 'react';
+import type { GeoJsonFeatureCollection } from '@/lib/airports';
 import type { PackageState, PlaneState, StateSnapshot } from '@/lib/game/state';
 import { PLANE_TYPES } from '@/lib/game/catalog';
-import { abandonPenalty } from '@/lib/game/penalty';
 import { formatCash, formatDeadlineRelative } from '@/lib/format';
+import { useGameAction } from '@/lib/useGameAction';
 import type { HoverTarget } from './hoverTypes';
 
 interface RightPaneProps {
@@ -16,6 +17,9 @@ interface RightPaneProps {
   // ISS-002 (v0.15.0): report row hovers to the shell so the map can highlight the plane or
   // the package's endpoint airports.
   onHover: (target: HoverTarget | null) => void;
+  // ISS-008 (v0.17.0): report a failed action to the shell as an error toast — in ADDITION
+  // to the inline pane error, which stays (both surfaces by design).
+  onError?: (message: string) => void;
 }
 
 const planeName = (p: PlaneState): string => PLANE_TYPES[p.model]?.name ?? p.model;
@@ -104,14 +108,10 @@ function LoadControls({
   );
 }
 
-export default function RightPane({ state, loading, applySnapshot, onHover }: RightPaneProps) {
+export default function RightPane({ state, loading, applySnapshot, onHover, onError }: RightPaneProps) {
-  const [busy, setBusy] = useState(false);
+  // ISS-021 (v0.20.0): shared action runner — busy gate, inline pane error + shell toast on
-  // Inline error from a failed action — auto-clears on the next successful poll (the shell's
+  // failure, full post-action snapshot pushed into the shared state on success.
-  // snapshot prop changes every tick) or the next successful action.
+  const { runAction, busy, actionError } = useGameAction(state, applySnapshot, onError);
-  const [actionError, setActionError] = useState<string | null>(null);
-  useEffect(() => {
-    if (state !== null) setActionError(null);
-  }, [state]);
 
   // Market picker selections — same "effective selection" pattern as LoadControls: the
   // user's pick while it stays valid, else a sensible default (first catalog entry / first plane).
@@ -119,33 +119,31 @@ export default function RightPane({ state, loading, applySnapshot, onHover }: Ri
   const [sellPlaneId, setSellPlaneId] = useState<string | null>(null);
   const [refuelPlaneId, setRefuelPlaneId] = useState<string | null>(null);
 
-  // POST an action endpoint. Every success returns the FULL post-action snapshot (v0.8.0
+  // ISS-010 (v0.18.0): Relocate row selections — same "effective selection" pattern as the rows above:
-  // convention) — pushed into the shared state immediately; a 4xx {error} body becomes the
+  // the user's pick while it stays valid, else a sensible default (first grounded plane / first airport).
-  // inline pane error and the stale UI stays until the next poll. Buttons are disabled while
+  const [relocatePlaneId, setRelocatePlaneId] = useState<string | null>(null);
-  // a request is in flight, so at most one action runs at a time.
+  const [relocateDestIcao, setRelocateDestIcao] = useState<string | null>(null);
-  const runAction = useCallback(
+
-    async (path: string, body?: unknown) => {
+  // ISS-010 (v0.18.0): one-time /api/airports fetch per page life — destination options for the
-      if (busy) return;
+  // Relocate row, sorted by name so e2e selection is stable. Same promise-ref pattern as Map.tsx;
-      setBusy(true);
+  // on failure airportOptions stays null and the Relocate button simply remains disabled.
-      try {
+  const [airportOptions, setAirportOptions] = useState<Array<{ name: string; icao: string }> | null>(null);
-        const res = await fetch(path, {
+  const airportsPromiseRef = useRef<Promise<Array<{ name: string; icao: string }>> | null>(null);
-          method: 'POST',
+  useEffect(() => {
-          headers: { 'Content-Type': 'application/json' },
+    if (!airportsPromiseRef.current) {
-          body: body === undefined ? undefined : JSON.stringify(body),
+      airportsPromiseRef.current = fetch('/api/airports', { cache: 'no-store' })
-          cache: 'no-store',
+        .then((res) => {
-        });
+          if (!res.ok) throw new Error(`GET /api/airports → HTTP ${res.status}`);
-        const data = (await res.json()) as StateSnapshot & { error?: string };
+          return res.json() as Promise<GeoJsonFeatureCollection>;
-        if (!res.ok) throw new Error(data.error ?? `HTTP ${res.status}`);
+        })
-        setActionError(null);
+        .then((fc) =>
-        applySnapshot(data);
+          fc.features
-      } catch (err) {
+            .map((f) => ({ name: f.properties.name, icao: f.properties.icao }))
-        setActionError(err instanceof Error ? err.message : String(err));
+            .sort((a, b) => a.name.localeCompare(b.name, 'en')),
-      } finally {
-        setBusy(false);
-      }
-    },
-    [applySnapshot, busy],
         );
+    }
+    void airportsPromiseRef.current.then(setAirportOptions).catch(() => {});
+  }, []);
 
   if (loading && !state) {
     return (
@@ -160,13 +158,6 @@ export default function RightPane({ state, loading, applySnapshot, onHover }: Ri
   const clockMs = state.simState.clockMs;
   const open = state.packages.filter((p) => p.status === 'open');
 
-  // On board (v0.12.0): every plane that carries cargo or is mid-flight gets a block —
-  // its loaded/expired packages with fly-to-destination + abandon controls, and flying
-  // planes show their current leg.
-  const onboard = state.planes.filter(
-    (p) => p.status === 'flying' || slotsUsedFor(state, p.id) > 0,
-  );
-
   const catalog = state.catalog;
   const buyEntry = catalog.find((e) => e.model === buyModelId) ?? catalog[0] ?? null;
 
@@ -177,6 +168,11 @@ export default function RightPane({ state, loading, applySnapshot, onHover }: Ri
     state.planes.find((p) => p.id === refuelPlaneId && p.status === 'available' && p.fuel < p.maxFuel) ??
     refuelable[0] ??
     null;
+  // ISS-010 (v0.18.0): Relocate — any GROUNDED plane can be repositioned to any airport via the
+  // existing fly endpoint (pure repositioning, no package needed since v0.12.0).
+  const relocatePlane = grounded.find((p) => p.id === relocatePlaneId) ?? grounded[0] ?? null;
+  const relocateDest =
+    airportOptions === null ? null : airportOptions.find((a) => a.icao === relocateDestIcao) ?? airportOptions[0] ?? null;
 
   // Previews computed client-side from the snapshot's catalog + economy constants (v0.10.0).
   const sellEntry = sellPlane ? catalog.find((e) => e.model === sellPlane.model) : undefined;
@@ -233,83 +229,7 @@ export default function RightPane({ state, loading, applySnapshot, onHover }: Ri
         )}
       </section>
 
-      <section className="pane-section">
+      {/* ISS-021 (v0.20.0): the On board section moved to the left pane (between Fleet and Time). */}
-        <h3 className="pane-heading">On board</h3>
-        {onboard.length === 0 ? (
-          <p className="pane-muted">Nothing on board.</p>
-        ) : (
-          onboard.map((plane) => {
-            const cargo = state.packages.filter(
-              (pkg) => pkg.planeId === plane.id && (pkg.status === 'loaded' || pkg.status === 'expired'),
-            );
-            return (
-              // ISS-002: hovering the on-board block (including its cargo rows) highlights the plane.
-              // Handlers live only on the outer div — React's enter/leave don't fire when moving to a
-              // child, so this covers the whole block without flicker between sub-elements.
-              <div
-                key={plane.id}
-                data-testid={`onboard-${plane.id}`}
-                className="onboard-block"
-                onMouseEnter={() => onHover({ kind: 'plane', id: plane.id })}
-                onMouseLeave={() => onHover(null)}
-              >
-                <div className="contract-main">
-                  <span className="plane-model">{planeName(plane)}</span>
-                  {plane.status === 'flying' ? (
-                    <>
-                      <span className="plane-status status-flying">in flight</span>
-                      {plane.destName && (
-                        <span data-testid={`plane-leg-${plane.id}`} className="contract-route">
-                          {plane.locationName} → {plane.destName}
-                        </span>
-                      )}
-                    </>
-                  ) : (
-                    <span className="plane-status status-available">{plane.locationIcao}</span>
-                  )}
-                </div>
-                {cargo.map((pkg) => {
-                  const penalty = abandonPenalty(pkg, clockMs);
-                  return (
-                    <div key={pkg.id} data-testid={`onboard-package-${pkg.id}`} className="contract-row">
-                      <div className="contract-main">
-                        <button
-                          type="button"
-                          data-testid={`fly-to-${pkg.id}`}
-                          className="pane-btn"
-                          disabled={busy || plane.status !== 'available'}
-                          onClick={() => void runAction(`/api/planes/${plane.id}/fly`, { destIcao: pkg.destIcao })}
-                        >
-                          Fly to {pkg.destName}
-                        </button>
-                        <button
-                          type="button"
-                          data-testid={`abandon-${pkg.id}`}
-                          className="pane-btn"
-                          disabled={busy || plane.status !== 'available'}
-                          onClick={() => void runAction(`/api/packages/${pkg.id}/abandon`)}
-                        >
-                          Abandon{' '}
-                          <span data-testid={`abandon-penalty-${pkg.id}`}>−{formatCash(penalty)}</span>
-                        </button>
-                      </div>
-                      <div className="contract-sub">
-                        <span>{pkg.originName} → {pkg.destName}</span>
-                        <span>{formatCash(pkg.reward)}</span>
-                        {pkg.status === 'expired' ? (
-                          <span data-testid={`onboard-expired-${pkg.id}`}>expired</span>
-                        ) : (
-                          <span>{formatDeadlineRelative(pkg.deadlineSimTime, clockMs)}</span>
-                        )}
-                      </div>
-                    </div>
-                  );
-                })}
-              </div>
-            );
-          })
-        )}
-      </section>
 
       <section className="pane-section">
         <h3 className="pane-heading">Market</h3>
@@ -405,7 +325,49 @@ export default function RightPane({ state, loading, applySnapshot, onHover }: Ri
               if (refuelPlane) void runAction(`/api/planes/${refuelPlane.id}/refuel`);
             }}
           >
-            Refuel
+            Refuel to full
+          </button>
+        </div>
+
+        {/* ISS-010 (v0.18.0): relocate a grounded plane — the fly endpoint already allows pure
+            repositioning, this row just exposes it for planes with nothing on board. */}
+        <div className="market-row market-row-relocate">
+          <select
+            data-testid="relocate-plane"
+            aria-label="Plane to relocate"
+            value={relocatePlane?.id ?? ''}
+            onChange={(e) => setRelocatePlaneId(e.target.value || null)}
+          >
+            {grounded.map((p) => (
+              <option key={p.id} value={p.id}>
+                {planeName(p)} — {p.locationIcao}
+              </option>
+            ))}
+          </select>
+          <select
+            data-testid="relocate-dest"
+            aria-label="Relocation destination airport"
+            value={relocateDest?.icao ?? ''}
+            onChange={(e) => setRelocateDestIcao(e.target.value || null)}
+          >
+            {airportOptions?.map((a) => (
+              <option key={a.icao} value={a.icao}>
+                {a.name}
+              </option>
+            ))}
+          </select>
+          <button
+            type="button"
+            data-testid="relocate-go"
+            className="pane-btn"
+            disabled={busy || relocatePlane === null || relocateDest === null}
+            onClick={() => {
+              if (relocatePlane && relocateDest) {
+                void runAction(`/api/planes/${relocatePlane.id}/fly`, { destIcao: relocateDest.icao });
+              }
+            }}
+          >
+            Relocate
           </button>
         </div>
       </section>

components/Toasts.tsx

@@ -0,0 +1,24 @@
+'use client';
+
+import type { Toast } from '@/lib/useToasts';
+
+// ISS-008 (v0.17.0): the bottom-right toast stack — action errors and game events derived
+// from snapshot diffs. Fixed-position overlay above the map; each item auto-dismisses via
+// the hook's TTL or its × button.
+export default function ToastStack({ toasts, onDismiss }: { toasts: Toast[]; onDismiss?: (id: number) => void }) {
+  if (toasts.length === 0) return null;
+  return (
+    <div className="toasts" role="status">
+      {toasts.map((t) => (
+        <div key={t.id} data-testid="toast" className={`toast toast-${t.kind}`}>
+          <span>{t.message}</span>
+          {onDismiss && (
+            <button type="button" data-testid={`toast-dismiss-${t.id}`} className="toast-close" onClick={() => onDismiss(t.id)}>
+              ×
+            </button>
+          )}
+        </div>
+      ))}
+    </div>
+  );
+}

components/left-pane.test.ts

@@ -1,5 +1,5 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it, vi } from 'vitest';
-import { pendingScaleConfirmed } from './LeftPane';
+import { pendingScaleConfirmed, retrySimPost, SIM_POST_MAX_ATTEMPTS, SIM_POST_RETRY_DELAY_MS } from './LeftPane';
 
 // ISS-001 — the optimistic slider value is cleared exactly when a rendered snapshot confirms
 // it (server scale === pending), never earlier. Clearing at commit time would snap the pointer
@@ -22,3 +22,70 @@ describe('pendingScaleConfirmed', () => {
     expect(pendingScaleConfirmed(1, 1)).toBe(true); // committing the current value confirms immediately
   });
 });
+
+// ISS-008 fix (CI runs #44/#47): a dropped POST /api/sim must be retried before surfacing the
+// error — up to SIM_POST_MAX_ATTEMPTS tries with SIM_POST_RETRY_DELAY_MS between them, and a newer
+// intent supersedes the in-flight body instead of waiting out its retries.
+
+describe('retrySimPost', () => {
+  it('pins the retry budget: 3 attempts total, ~500 ms backoff', () => {
+    expect(SIM_POST_MAX_ATTEMPTS).toBe(3);
+    expect(SIM_POST_RETRY_DELAY_MS).toBe(500);
+  });
+
+  it('succeeds on the first attempt without sleeping or retrying', async () => {
+    const post = vi.fn(async () => {});
+    const sleep = vi.fn(async () => {});
+    await expect(retrySimPost(post, () => false, sleep)).resolves.toEqual({ ok: true });
+    expect(post).toHaveBeenCalledTimes(1);
+    expect(sleep).not.toHaveBeenCalled();
+  });
+
+  it('retries with the backoff delay and succeeds on a later attempt', async () => {
+    let calls = 0;
+    const post = vi.fn(async () => {
+      if (++calls < 3) throw new Error('dropped');
+    });
+    const sleep = vi.fn(async () => {});
+    await expect(retrySimPost(post, () => false, sleep)).resolves.toEqual({ ok: true });
+    expect(post).toHaveBeenCalledTimes(3);
+    expect(sleep).toHaveBeenCalledTimes(2); // one backoff between each pair of attempts
+    expect(sleep).toHaveBeenCalledWith(SIM_POST_RETRY_DELAY_MS);
+  });
+
+  it('gives up after the final attempt with the last error (no trailing sleep)', async () => {
+    const err = new Error('down');
+    const post = vi.fn(async () => {
+      throw err;
+    });
+    const sleep = vi.fn(async () => {});
+    const result = await retrySimPost(post, () => false, sleep);
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.reason).toBe('exhausted');
+      if (result.reason === 'exhausted') expect(result.error).toBe(err); // the LAST attempt's error
+    }
+    expect(post).toHaveBeenCalledTimes(SIM_POST_MAX_ATTEMPTS);
+    expect(sleep).toHaveBeenCalledTimes(SIM_POST_MAX_ATTEMPTS - 1);
+  });
+
+  it('stops retrying once a newer intent supersedes the in-flight body (no further attempts or sleeps)', async () => {
+    let calls = 0;
+    const post = vi.fn(async () => {
+      calls++; // flip "superseded" right after the first failure, like a queued commitNow would
+      throw new Error('dropped');
+    });
+    const sleep = vi.fn(async () => {});
+    await expect(retrySimPost(post, () => calls >= 1, sleep)).resolves.toEqual({ ok: false, reason: 'superseded' });
+    expect(post).toHaveBeenCalledTimes(1); // the caller's loop sends the newer body instead
+    expect(sleep).not.toHaveBeenCalled(); // supersede is checked before the backoff sleep
+  });
+
+  it('never even sends a body that is already superseded', async () => {
+    const post = vi.fn(async () => {});
+    const sleep = vi.fn(async () => {});
+    await expect(retrySimPost(post, () => true, sleep)).resolves.toEqual({ ok: false, reason: 'superseded' });
+    expect(post).not.toHaveBeenCalled();
+    expect(sleep).not.toHaveBeenCalled();
+  });
+});

components/right-pane.test.ts

@@ -8,7 +8,7 @@ import type { PackageState, PlaneState, StateSnapshot } from '@/lib/game/state';
 // directly on the single eligible plane, or shows a picker when several qualify.
 
 const CATALOG = [
-  { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, speedKmh: 510, capacity: 6 },
+  { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, emptyWeightKg: 9_300, speedKmh: 510, capacity: 6 },
 ];
 
 function plane(over: Partial<PlaneState> & Pick<PlaneState, 'id'>): PlaneState {

e2e/actions.spec.ts

@@ -3,21 +3,31 @@ import { expect, test } from '@playwright/test';
 
 // v0.12.0 package model against the live origin (https://flight.dev.kkhost.pl):
 // the full core loop through the UI — hook creates a short package at EDDF → Load
-// via the right pane → click its destination in the on-board list → fly at 1000× →
+// via the right pane → click its destination in the on-board list (left pane since
+// v0.20.0, ISS-021) → fly at 1000× →
 // arrival delivers EXACTLY the reward + rep; abandon deducts exactly the formula
 // penalty while grounded; expired packages deliver/abandon with no reward and no
 // penalty. Mirrors lib/game/penalty.ts for exact-value assertions.
 
 const SCALE = 1000; // fastest sim speed (v0.14.0 ladder top) — keeps flights to seconds of real time
 const HUB = 'EDDF'; // Frankfurt Main — the seeded starter plane's home base (lib/game/seed.ts)
-const FAR = 'LEZL'; // Seville — one-way burn 3174 L > half tank, so the return leg is unfuelable
+const FAR = 'LEZL'; // Seville — a long leg: under the v0.16.0 weighted model a full tank covers the
+                    // round trip, but the return leaves too little for another outbound
 
-// Mirrors lib/sim/movement.ts + lib/game/catalog.ts (atr72).
+// Mirrors lib/sim/movement.ts (v0.16.0 weight-proportional burn) + lib/game/catalog.ts (atr72).
-const BURN_PER_KM = 1.75;
+const FUEL_DENSITY_KG_PER_L = 0.8; // Jet-A1 density — must match FUEL_DENSITY_KG_PER_L in movement.ts
-const FUEL_PRICE_PER_L = 0.8;
+const FUEL_PRICE_PER_L = 0.8; // must match catalog.ts
 const REP_BASE = 1; // lib/sim/engine.ts
 const REP_PER_KM = 0.0005;
 
+// Fuel remaining after distanceKm from startFuel — closed form of dF/dx = −k(We + ρF),
+// k calibrated so a full tank burns exactly burnPerKm (mirrors fuelAtWeighted).
+function fuelAfter(startFuel: number, burnPerKm: number, emptyWeightKg: number, maxFuel: number, distanceKm: number): number {
+  const k = burnPerKm / (emptyWeightKg + FUEL_DENSITY_KG_PER_L * maxFuel);
+  const rho = FUEL_DENSITY_KG_PER_L;
+  return Math.max(0, (startFuel + emptyWeightKg / rho) * Math.exp(-k * rho * distanceKm) - emptyWeightKg / rho);
+}
+
 // Mirrors lib/game/penalty.ts — the exact abandon penalty at a given game clock.
 function penaltyFor(reward: number, createdSimTime: number, deadlineSimTime: number, clockMs: number): number {
   const span = deadlineSimTime - createdSimTime;
@@ -33,6 +43,7 @@ interface StateBody {
     id: string; originIcao: string; destIcao: string; reward: number; cargoType: string; cargoCount: number;
     deadlineSimTime: number; status: 'open' | 'loaded' | 'delivered' | 'expired' | 'abandoned'; planeId: string | null; createdSimTime: number;
   }>;
+  catalog: Array<{ model: string; burnPerKm: number; emptyWeightKg: number; maxFuel: number }>; // v0.16.0 weighted burn inputs
 }
 
 async function getState(page: Page): Promise<StateBody> {
@@ -90,17 +101,26 @@ test.describe.configure({ mode: 'serial' }); // shared live DB — order matters
 // (repositioning needs no package — v0.12.0 manual flight), and abandon any leftover cargo so
 // exact cash/rep assertions start from a clean baseline even after an interrupted previous run.
 async function flyHomeViaApi(page: Page): Promise<void> {
-  const s0 = await getState(page);
+  let s = await getState(page);
-  const plane = s0.planes.find((p) => p.id === 'plane-starter')!;
+  let plane = s.planes.find((p) => p.id === 'plane-starter')!;
   if (plane.status === 'flying' || plane.locationIcao !== HUB) {
     // Fast-forward any leftover leg / repositioning flight (~20 s real time worst case at 1000×).
     await setScale(page, SCALE);
   }
   if (plane.status === 'flying') {
-    // Let the in-flight leg finish before repositioning.
+    // Let the in-flight leg finish before repositioning. While flying, locationIcao stays at the
+    // DEPARTURE airport, so the pre-landing snapshot can't tell us where the plane ends up — re-read
+    // state after landing before deciding whether a repositioning flight is needed (run #41 retry: a
+    // leftover EDDF→EDFH leg landed away from home but the helper still believed it was home and
+    // skipped the fly-home).
     await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === 'plane-starter')!.status), { timeout: 240_000 }).toBe('available');
+    s = await getState(page);
+    plane = s.planes.find((p) => p.id === 'plane-starter')!;
   }
   if (plane.locationIcao !== HUB) {
+    // ISS-011: the landing above auto-slown the sim to 1× — re-set SCALE so the return leg
+    // fast-forwards instead of taking real-time hours.
+    await setScale(page, SCALE);
     const res = await page.request.post(`/api/planes/${plane.id}/fly`, { data: { destIcao: HUB } });
     expect(res.ok()).toBeTruthy(); // repositioning needs no package (v0.12.0 manual flight)
     await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === 'plane-starter')!.locationIcao), { timeout: 240_000 }).toBe(HUB);
@@ -133,6 +153,14 @@ test('full core loop via UI: load → fly to destination → exact reward + rep
   expect(pkg.originIcao).toBe(HUB);
   expect(pkg.destIcao).toBe(nearest.icao);
 
+  // Precondition (server truth) before clicking Load: the starter must be grounded at the package's
+  // origin — that is exactly what makes it load-eligible, and a stale pane snapshot can't prove it.
+  await expect.poll(async () => {
+    const b = await getState(page);
+    const p = b.planes.find((x) => x.id === 'plane-starter')!;
+    return p.status === 'available' && p.locationIcao === pkg.originIcao;
+  }, { timeout: 30_000, message: 'waiting for plane-starter to be grounded at the package origin (self-heal incomplete?)' }).toBe(true);
+
   // LOAD via the UI: exactly one eligible plane (the starter at EDDF) → direct button.
   await page.goto('/');
   const loadBtn = page.getByTestId(`load-${pkg.id}`);
@@ -149,10 +177,17 @@ test('full core loop via UI: load → fly to destination → exact reward + rep
   await expect(flyBtn).toBeEnabled();
   await flyBtn.click();
 
-  let s = await getState(page);
   const planeId = 'plane-starter';
-  expect(s.planes.find((p) => p.id === planeId)!.status).toBe('flying');
+  // The click fires the fly POST asynchronously (runAction is fire-and-forget from the test's view),
-  expect(s.planes.find((p) => p.id === planeId)!.destIcao).toBe(nearest.icao);
+  // so a getState issued immediately can race ahead of it and still see 'available' — poll until the
+  // fly actually took effect on the server (the run #36/#41 flake).
+  await expect.poll(async () => {
+    const b = await getState(page);
+    const p = b.planes.find((x) => x.id === planeId)!;
+    return p.status === 'flying' && p.destIcao === nearest.icao;
+  }, { timeout: 15_000, message: 'waiting for the fly click to take effect (status "flying" + dest set)' }).toBe(true);
+
+  let s = await getState(page);
 
   // Fast-forward to arrival (a few seconds of real time at 1000×).
   await setScale(page, SCALE);
@@ -174,8 +209,12 @@ test('full core loop via UI: load → fly to destination → exact reward + rep
   const repGain = Math.round((REP_BASE + REP_PER_KM * exactKm) * 100) / 100;
   expect(s.account.reputation).toBeCloseTo(Math.round((before.account.reputation + repGain) * 100) / 100, 9);
 
-  // Fuel burned exactly burnPerKm × km (analytic movement — no rounding drift).
+  // Fuel burned per the v0.16.0 weight-proportional model (closed form — no rounding drift).
-  expect(landed.fuel).toBeCloseTo(Math.max(0, before.planes.find((p) => p.id === planeId)!.fuel - BURN_PER_KM * exactKm), 6);
+  const entry = before.catalog.find((e) => e.model === 'atr72')!;
+  expect(landed.fuel).toBeCloseTo(
+    fuelAfter(before.planes.find((p) => p.id === planeId)!.fuel, entry.burnPerKm, entry.emptyWeightKg, entry.maxFuel, exactKm),
+    6,
+  );
 
   // Refuel via the API: cost = (maxFuel − fuel) × FUEL_PRICE_PER_L, deducted exactly.
   const refuelRes = await page.request.post(`/api/planes/${planeId}/refuel`);
@@ -186,7 +225,9 @@ test('full core loop via UI: load → fly to destination → exact reward + rep
   const refuelCost = Math.round((afterRefuel.maxFuel - landed.fuel) * FUEL_PRICE_PER_L * 100) / 100;
   expect(s.account.cash).toBeCloseTo(before.account.cash + pkg.reward - refuelCost, 6);
 
-  // Restore: fly home (repositioning — no package needed in the v0.12.0 model).
+  // Restore: fly home (repositioning — no package needed in the v0.12.0 model). ISS-011: the
+  // arrival above auto-slown the sim to 1×, so re-set SCALE for the return leg.
+  await setScale(page, SCALE);
   const homeRes = await page.request.post(`/api/planes/${planeId}/fly`, { data: { destIcao: HUB } });
   expect(homeRes.ok()).toBeTruthy();
   await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === planeId)!.locationIcao), { timeout: 120_000 }).toBe(HUB);
@@ -273,8 +314,10 @@ test('expired packages deliver and abandon with no reward and no penalty', async
   expect(s.packages.find((p) => p.id === pkgB.id)!.status).toBe('abandoned');
   expect(s.account.cash).toBe(cashBeforeAbandon); // free — expired abandons cost nothing
 
-  // Restore: refuel + fly home (scale is still SCALE from the expiry wait above).
+  // Restore: refuel + fly home. ISS-011: the LEMD arrival above auto-slown the sim to 1×, so
+  // re-set SCALE for the return leg (the expiry wait's scale no longer persists past a landing).
   await page.request.post('/api/planes/plane-starter/refuel');
+  await setScale(page, SCALE);
   const homeRes = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: HUB } });
   expect(homeRes.ok()).toBeTruthy();
   await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === 'plane-starter')!.locationIcao), { timeout: 240_000 }).toBe(HUB);
@@ -312,17 +355,21 @@ test('load and fly validation paths (404 / 409 / 400)', async ({ page }) => {
   res = await page.request.post(`/api/packages/${pkg.id}/abandon`);
   expect(res.status()).toBe(409);
 
-  // Fly home from the hop so the fuel section starts at the hub.
+  // Fly home from the hop so the fuel section starts at the hub. ISS-011: the hop arrival above
+  // auto-slown the sim to 1×, so re-set SCALE for this leg.
+  await setScale(page, SCALE);
   res = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: HUB } });
   expect(res.ok()).toBeTruthy();
   await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === 'plane-starter')!.locationIcao), { timeout: 120_000 }).toBe(HUB);
 
-  // Insufficient fuel: a full-tank one-way burn of > half the tank makes the return leg unfuelable.
+  // Insufficient fuel (v0.16.0 weighted burn): a full tank covers the FAR round trip —
+  // the plane gets lighter as fuel burns off, so both legs fit — but landing back at the
+  // hub leaves too little for ANOTHER long leg: the second outbound must 409.
   const s0 = await getState(page);
   const starter = s0.planes.find((p) => p.id === 'plane-starter')!;
   expect(starter.locationIcao).toBe(HUB); // landed back at the hub from the hop above
   if (starter.fuel < starter.maxFuel) {
-    await page.request.post('/api/planes/plane-starter/refuel'); // ensure a full tank for the long leg
+    await page.request.post('/api/planes/plane-starter/refuel'); // ensure a full tank for the long legs
   }
   const farRes = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: FAR } });
   expect(farRes.ok()).toBeTruthy();
@@ -332,16 +379,20 @@ test('load and fly validation paths (404 / 409 / 400)', async ({ page }) => {
   const sFar = await getState(page);
   const atFar = sFar.planes.find((p) => p.id === 'plane-starter')!;
   expect(atFar.locationIcao).toBe(FAR);
-  // The return leg needs the same burn as the outbound — more than what's left.
+  // The return leg fits: the weighted burn over it is less than what's left in the tank.
+  // ISS-011: the FAR arrival above auto-slown the sim to 1×, so re-set SCALE for this leg.
+  await setScale(page, SCALE);
   const backRes = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: HUB } });
-  expect(backRes.status()).toBe(409);
+  expect(backRes.ok()).toBeTruthy();
-  expect(((await backRes.json()) as { error: string }).error).toMatch(/insufficient fuel/i);
-
-  // Restore: refuel + fly home.
-  await page.request.post('/api/planes/plane-starter/refuel');
-  const homeRes = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: HUB } });
-  expect(homeRes.ok()).toBeTruthy();
   await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === 'plane-starter')!.locationIcao), { timeout: 240_000 }).toBe(HUB);
+
+  // …but the tank is now too light for another FAR leg.
+  const againFar = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: FAR } });
+  expect(againFar.status()).toBe(409);
+  expect(((await againFar.json()) as { error: string }).error).toMatch(/insufficient fuel/i);
+
+  // Restore: refuel (the plane is already home).
+  await page.request.post('/api/planes/plane-starter/refuel');
 });
 
 // Great-circle distance in km — mirrors lib/geo.ts (same formula, same R).

e2e/auto-slow.spec.ts

@@ -0,0 +1,130 @@
+import type { Page } from '@playwright/test';
+import { expect, test } from '@playwright/test';
+
+// v0.19.0 — ISS-011: when the LAST plane lands (no plane remains in flight) the sim auto-slows
+// to 1×, server-side and persisted on the sim_state row so the UI slider reflects it on the next
+// snapshot. Arrival-triggered by design: a grounded fleet at high scale is left alone, there is no
+// auto-restore — the player speeds up manually again (asserted below).
+
+const SCALE = 1000; // fastest sim speed — top of the v0.14.0 ladder (same convention as e2e/sim.spec.ts)
+const HUB = 'EDDF'; // Frankfurt Main — the seeded starter plane's home base (lib/game/seed.ts)
+
+interface SimState {
+  clockMs: number;
+  timeScale: number;
+  paused: boolean;
+}
+
+interface StateBody {
+  simState: SimState;
+  planes: Array<{ id: string; status: string; locationIcao: string; destIcao: string | null }>;
+}
+
+async function getState(page: Page): Promise<StateBody> {
+  const res = await page.request.get('/api/state');
+  expect(res.ok()).toBeTruthy();
+  return (await res.json()) as StateBody;
+}
+
+async function postSim(page: Page, body: Record<string, unknown>): Promise<void> {
+  const res = await page.request.post('/api/sim', { data: body });
+  expect(res.status()).toBe(200);
+}
+
+// Set the time scale and VERIFY from the response that it stuck — if something external ever
+// resets the live instance's controls mid-test, fail loudly here instead of timing out later.
+async function setScale(page: Page, scale: number): Promise<void> {
+  const res = await page.request.post('/api/sim', { data: { timeScale: scale } });
+  expect(res.status()).toBe(200);
+  const body = (await res.json()) as SimState;
+  expect(body.timeScale, `timeScale should be ${scale} after POST /api/sim`).toBe(scale);
+}
+
+// Closest airport to the hub from /api/airports → shortest possible leg (fastest e2e flight).
+async function nearestToHub(page: Page): Promise<{ icao: string }> {
+  const res = await page.request.get('/api/airports');
+  expect(res.ok()).toBeTruthy();
+  const fc = (await res.json()) as { features: Array<{ properties: { icao: string; lat: number; lon: number } }> };
+  const hub = fc.features.find((f) => f.properties.icao === HUB)!.properties;
+  let nearest = fc.features.filter((f) => f.properties.icao !== HUB)[0].properties;
+  for (const f of fc.features) {
+    if (f.properties.icao === HUB) continue;
+    const d = Math.hypot(f.properties.lat - hub.lat, f.properties.lon - hub.lon);
+    const dn = Math.hypot(nearest.lat - hub.lat, nearest.lon - hub.lon);
+    if (d < dn) nearest = f.properties;
+  }
+  return { icao: nearest.icao };
+}
+
+// Self-heal helper (same pattern as e2e/relocation.spec.ts): let any in-flight leg finish and
+// reposition plane-starter home via the API so every test starts from the canonical state even
+// after an interrupted previous run.
+async function flyHomeViaApi(page: Page): Promise<void> {
+  let s = await getState(page);
+  let plane = s.planes.find((p) => p.id === 'plane-starter')!;
+  if (plane.status === 'flying' || plane.locationIcao !== HUB) {
+    // Fast-forward any leftover leg / repositioning flight (~20 s real time worst case at 1000×).
+    await setScale(page, SCALE);
+  }
+  if (plane.status === 'flying') {
+    // Let the in-flight leg finish before repositioning. While flying, locationIcao stays at the
+    // DEPARTURE airport — re-read state after landing before deciding whether a repositioning
+    // flight is needed.
+    await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === 'plane-starter')!.status), { timeout: 240_000 }).toBe('available');
+    s = await getState(page);
+    plane = s.planes.find((p) => p.id === 'plane-starter')!;
+  }
+  if (plane.locationIcao !== HUB) {
+    // ISS-011: the landing above auto-slown the sim to 1× — re-set SCALE so the return leg
+    // fast-forwards instead of taking real-time hours.
+    await setScale(page, SCALE);
+    const res = await page.request.post(`/api/planes/${plane.id}/fly`, { data: { destIcao: HUB } });
+    expect(res.ok()).toBeTruthy(); // repositioning needs no package (v0.12.0 manual flight)
+    await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === 'plane-starter')!.locationIcao), { timeout: 240_000 }).toBe(HUB);
+  }
+}
+
+// Self-heal in CLEANUP (afterEach): the test deliberately leaves plane-starter at the far end, so
+// fast-forward + reposition home here; then restore scale=1 / unpaused for later specs.
+test.afterEach(async ({ page }) => {
+  await flyHomeViaApi(page);
+  await postSim(page, { timeScale: 1, paused: false });
+});
+
+test.describe.configure({ mode: 'serial' }); // shared live DB — order matters within this file
+
+test('auto-slow to 1× when the last plane lands; manual speed-up still works (ISS-011)', async ({ page }) => {
+  test.setTimeout(300_000); // self-heal (worst case ~20 s at 1000×) + one short leg
+  await flyHomeViaApi(page); // deterministic: the starter sits grounded at EDDF
+
+  const nearest = await nearestToHub(page);
+
+  // Set 1000× via the API and verify it stuck.
+  await setScale(page, SCALE);
+
+  // Dispatch plane-starter on the shortest leg from its hub (repositioning — no package needed).
+  const flyRes = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: nearest.icao } });
+  expect(flyRes.status()).toBe(200);
+
+  // Wait for the landing…
+  let landedBody: StateBody | undefined;
+  await expect
+    .poll(async () => {
+      const b = await getState(page);
+      const p = b.planes.find((x) => x.id === 'plane-starter')!;
+      if (p.status === 'available' && p.locationIcao === nearest.icao) landedBody = b;
+      return !!landedBody;
+    }, { timeout: 120_000, message: `waiting for plane-starter to land at ${nearest.icao}` })
+    .toBe(true);
+
+  // …and the server has auto-slown to 1× — persisted on sim_state, so this very snapshot shows it.
+  expect(landedBody!.simState.timeScale).toBe(1);
+
+  // Manual override still works: POST /api/sim {timeScale: 1000} → confirmed by the response…
+  const post = await page.request.post('/api/sim', { data: { timeScale: SCALE } });
+  expect(post.status()).toBe(200);
+  expect(((await post.json()) as SimState).timeScale).toBe(SCALE);
+  // …and by a fresh snapshot (no auto-restore of the previous scale — and no re-slow either,
+  // since nothing is in flight: the trigger is arrival-based, not idle-enforcement).
+  expect((await getState(page)).simState.timeScale).toBe(SCALE);
+});

e2e/hover.spec.ts

@@ -89,6 +89,9 @@ async function flyHomeViaApi(page: Page): Promise<void> {
       .toBe(true);
   }
   if (starter.locationIcao !== HUB) {
+    // ISS-011: the landing above auto-slown the sim to 1× — re-set SCALE so the return leg
+    // fast-forwards instead of taking real-time hours.
+    await setScale(page, SCALE);
     const res = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: HUB } });
     expect(res.status()).toBe(200); // repositioning needs no package (v0.12.0 manual flight)
     await expect
@@ -291,6 +294,8 @@ test('hovering an on-board block of a flying plane highlights its route', async
     }, { timeout: 120_000, message: `waiting for plane-starter to land at ${DEST}` })
     .toBe(true);
 
+  // ISS-011: the arrival above auto-slown the sim to 1×, so re-set SCALE for this leg.
+  await setScale(page, SCALE);
   const home = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: HUB } });
   expect(home.status()).toBe(200);
   await expect

e2e/map-interactions.spec.ts

@@ -266,20 +266,35 @@ test('plane markers move while flying and the plane popup shows status + route',
     }, { timeout: 15_000, message: 'waiting for the paused clock to freeze the plane position' })
     .toBe(true);
 
-  // Fetch + project in one evaluate — with the sim paused above, the server's analytic
+  // Click the RENDERED marker position, not a fresh /api/state fetch. With the sim paused
-  // position is static, so the projected point matches what the map renders.
+  // above the server's analytic position is static — but the map renders from its own ~1 s
+  // poll, so right after the freeze confirmation the last rendered frame can still be up to
+  // one poll interval stale (tens of px at scale 1000 on this leg) and a click projected
+  // from a fresh fetch misses the small circle layer (CI run #37). Poll for the plane's
+  // rendered feature instead and project ITS coordinates — exactly what the map draws.
+  // Find + project in one evaluate so nothing can change between the two steps.
   const pt = await page.evaluate(async () => {
     const m = (window as any).__flightMap;
     if (!m) return null;
-    const res = await fetch('/api/state', { cache: 'no-store' });
+    const deadline = Date.now() + 5_000;
-    const body = (await res.json()) as StateBody;
+    for (;;) {
-    const p = body.planes.find((x) => x.id === 'plane-starter');
+      let feats: Array<{ properties?: Record<string, unknown>; geometry?: { coordinates: number[] } }> = [];
-    if (!p || p.status !== 'flying') return null;
+      try {
-    const projected = m.project([p.lon, p.lat]);
+        feats = m.queryRenderedFeatures(undefined, { layers: ['planes-flying', 'planes-grounded'] });
+      } catch {
+        // map not ready yet — keep polling
+      }
+      const f = feats.find((x) => x.properties?.id === 'plane-starter');
+      if (f && f.geometry) {
+        const projected = m.project(f.geometry.coordinates);
         const rect = m.getContainer().getBoundingClientRect();
         return { x: rect.left + projected.x, y: rect.top + projected.y };
+      }
+      if (Date.now() >= deadline) return null;
+      await new Promise((r) => setTimeout(r, 100));
+    }
   });
-  expect(pt).not.toBeNull(); // the ~10 s window at scale 1000 is still open this early after departure
+  expect(pt, 'plane marker not rendered after pause').not.toBeNull();
 
   await page.mouse.click(pt!.x, pt!.y);
   const popup = page.getByTestId('plane-popup');

e2e/panes.spec.ts

@@ -4,6 +4,8 @@ import { test, expect, type Page } from '@playwright/test';
 // The panes render from the shell's single /api/state poll (lib/useGameState.ts); time
 // controls POST to /api/sim and refetch immediately, so UI assertions settle within a tick.
 
+const SCALE = 1000; // fastest sim speed — top of the v0.14.0 ladder (same convention as e2e/sim.spec.ts)
+
 interface SimState {
   clockMs: number;
   timeScale: number;
@@ -67,6 +69,12 @@ test('left pane renders wallet, reputation and the starter fleet at Frankfurt',
 
   // Sim clock renders (UTC wall-clock of the game time).
   await expect(page.getByTestId('sim-clock')).toContainText(/UTC/);
+
+  // ISS-021 (v0.20.0): the On board section moved to the left pane (between Fleet and Time) —
+  // its heading renders here…
+  await expect(page.getByTestId('left-pane').getByRole('heading', { name: 'On board', exact: true })).toBeVisible();
+  // …and no longer in the right pane.
+  await expect(page.getByTestId('right-pane').getByRole('heading', { name: 'On board', exact: true })).toHaveCount(0);
 });
 
 test('time controls: pause freezes the sim and the ladder slider sets timeScale', async ({ page }) => {
@@ -104,6 +112,40 @@ test('time controls: pause freezes the sim and the ladder slider sets timeScale'
   expect(after.simState.paused).toBe(false);
 });
 
+test('sim clock ticks smoothly between polls — seconds advance without waiting for a snapshot (ISS-007)', async ({ page }) => {
+  await page.goto('/');
+  const clock = page.getByTestId('sim-clock');
+  await expect(clock).toBeVisible({ timeout: 15_000 });
+
+  // Fastest scale so game seconds move visibly inside the sampling window.
+  const post = await page.request.post('/api/sim', { data: { timeScale: SCALE, paused: false } });
+  expect(post.status()).toBe(200);
+
+  // "YYYY-MM-DD HH:MM:SS UTC" → epoch ms (UTC). While running there is no "(paused)" suffix.
+  const sample = async () => {
+    const text = ((await clock.textContent()) ?? '').trim();
+    expect(text, `clock format: ${text}`).toMatch(/^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2} UTC$/);
+    return Date.parse(text.replace(' ', 'T').replace(' UTC', 'Z'));
+  };
+
+  // Three samples ~1.3 s apart real time: at scale 1000 each gap is ≈1300 game seconds, so the
+  // displayed clock must strictly advance between CONSECUTIVE samples — with the old poll-only
+  // rendering a sample pair could straddle zero snapshot updates and show no change at all.
+  const t0 = await sample();
+  await new Promise((r) => setTimeout(r, 1_300));
+  const t1 = await sample();
+  await new Promise((r) => setTimeout(r, 1_300));
+  const t2 = await sample();
+
+  expect(t1).toBeGreaterThan(t0);
+  expect(t2).toBeGreaterThan(t1);
+  // Sanity: ~2.6 s real × 1000 ≈ 2.6 M game ms — generous bounds keep slow CI boxes safe while
+  // still catching a frozen or wildly mis-scaled clock.
+  const total = t2 - t0;
+  expect(total).toBeGreaterThanOrEqual(1_000_000);
+  expect(total).toBeLessThanOrEqual(6_000_000);
+});
+
 test('slider commit keeps the chosen scale on screen until confirmed — no snap-back (ISS-001)', async ({ page }) => {
   test.setTimeout(60_000);
   await page.goto('/');

e2e/relocation.spec.ts

@@ -0,0 +1,189 @@
+import type { Page } from '@playwright/test';
+import { expect, test } from '@playwright/test';
+
+// v0.18.0 — ISS-010: relocating a GROUNDED (empty) plane to any airport against the live origin.
+// Two UI surfaces drive the EXISTING POST /api/planes/{id}/fly endpoint (pure repositioning has
+// been allowed since v0.12.0 — no API change): the right-pane market row
+// (relocate-plane / relocate-dest / relocate-go) and the Relocate row inside the airport popup on
+// the map (airport-popup-plane / airport-popup-relocate). Marker-size regression is covered by
+// the existing e2e/map.spec.ts click tests, not here.
+
+const SCALE = 1000; // fastest sim speed (v0.14.0 ladder top) — keeps cleanup flights to seconds of real time
+const HUB = 'EDDF'; // Frankfurt Main — the seeded starter plane's home base (lib/game/seed.ts)
+// LFRS Nantes Atlantique — same isolated marker as e2e/map.spec.ts: its nearest neighbour is ~78 px
+// away at the initial zoom, so a click on its projected center cannot hit another circle.
+const POPUP_AIRPORT = { icao: 'LFRS', lon: -1.61073, lat: 47.153198 };
+
+interface StateBody {
+  planes: Array<{ id: string; status: string; locationIcao: string; destIcao: string | null }>;
+}
+
+async function getState(page: Page): Promise<StateBody> {
+  const res = await page.request.get('/api/state');
+  expect(res.ok()).toBeTruthy();
+  return (await res.json()) as StateBody;
+}
+
+async function postSim(page: Page, body: Record<string, unknown>): Promise<void> {
+  const res = await page.request.post('/api/sim', { data: body });
+  expect(res.ok()).toBeTruthy();
+}
+
+// Set the time scale and VERIFY from the response that it stuck — if something external ever
+// resets the live instance's controls mid-test, fail loudly here instead of timing out later.
+async function setScale(page: Page, scale: number): Promise<void> {
+  const res = await page.request.post('/api/sim', { data: { timeScale: scale } });
+  expect(res.status()).toBe(200);
+  const body = (await res.json()) as { timeScale: number };
+  expect(body.timeScale, `timeScale should be ${scale} after POST /api/sim`).toBe(scale);
+}
+
+// Closest airport to the hub from /api/airports → shortest possible leg (fuel trivial).
+async function nearestToHub(page: Page): Promise<{ icao: string }> {
+  const res = await page.request.get('/api/airports');
+  expect(res.ok()).toBeTruthy();
+  const fc = (await res.json()) as { features: Array<{ properties: { icao: string; lat: number; lon: number } }> };
+  const hub = fc.features.find((f) => f.properties.icao === HUB)!.properties;
+  let nearest = fc.features.filter((f) => f.properties.icao !== HUB)[0].properties;
+  for (const f of fc.features) {
+    if (f.properties.icao === HUB) continue;
+    const d = Math.hypot(f.properties.lat - hub.lat, f.properties.lon - hub.lon);
+    const dn = Math.hypot(nearest.lat - hub.lat, nearest.lon - hub.lon);
+    if (d < dn) nearest = f.properties;
+  }
+  return { icao: nearest.icao };
+}
+
+// Self-heal helper (same pattern as e2e/actions.spec.ts): let any in-flight leg finish and
+// reposition plane-starter home via the API — repositioning needs no package (v0.12.0 manual
+// flight) — so every test starts from the canonical state even after an interrupted previous run.
+async function flyHomeViaApi(page: Page): Promise<void> {
+  let s = await getState(page);
+  let plane = s.planes.find((p) => p.id === 'plane-starter')!;
+  if (plane.status === 'flying' || plane.locationIcao !== HUB) {
+    // Fast-forward any leftover leg / repositioning flight (~20 s real time worst case at 1000×).
+    await setScale(page, SCALE);
+  }
+  if (plane.status === 'flying') {
+    // While flying, locationIcao stays at the DEPARTURE airport — re-read state after landing
+    // before deciding whether a repositioning flight is needed.
+    await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === 'plane-starter')!.status), { timeout: 240_000 }).toBe('available');
+    s = await getState(page);
+    plane = s.planes.find((p) => p.id === 'plane-starter')!;
+  }
+  if (plane.locationIcao !== HUB) {
+    // ISS-011: the landing above auto-slown the sim to 1× — re-set SCALE so the return leg
+    // fast-forwards instead of taking real-time hours.
+    await setScale(page, SCALE);
+    const res = await page.request.post(`/api/planes/${plane.id}/fly`, { data: { destIcao: HUB } });
+    expect(res.ok()).toBeTruthy(); // repositioning needs no package (v0.12.0 manual flight)
+    await expect.poll(async () => ((await getState(page)).planes.find((p) => p.id === 'plane-starter')!.locationIcao), { timeout: 240_000 }).toBe(HUB);
+  }
+}
+
+// Self-heal in CLEANUP (afterEach): the tests deliberately leave plane-starter mid-flight, so
+// fast-forward + reposition home here; then restore scale=1 / unpaused for later specs.
+test.afterEach(async ({ page }) => {
+  await flyHomeViaApi(page);
+  await postSim(page, { timeScale: 1, paused: false });
+});
+
+test.describe.configure({ mode: 'serial' }); // shared live DB — order matters within this file
+
+test('market row relocates a grounded plane via the right pane', async ({ page }) => {
+  test.setTimeout(300_000); // self-heal (worst case ~20 s at 1000×) + one short leg
+  await flyHomeViaApi(page);
+
+  // Full tank before departure — a partially drained plane left by an earlier spec could not
+  // afford the cleanup round trip.
+  const refuel = await page.request.post('/api/planes/plane-starter/refuel');
+  expect(refuel.ok()).toBeTruthy();
+
+  const nearest = await nearestToHub(page);
+
+  await page.goto('/');
+  const planeSel = page.getByTestId('relocate-plane');
+  await expect(planeSel).toBeVisible({ timeout: 15_000 }); // pane renders once the first snapshot lands
+  await planeSel.selectOption('plane-starter');
+
+  // Destination options come from the one-time /api/airports fetch (sorted by name) — selectOption
+  // waits until the matching option exists, so this doubles as the load wait.
+  const destSel = page.getByTestId('relocate-dest');
+  await destSel.selectOption(nearest.icao);
+
+  const goBtn = page.getByTestId('relocate-go');
+  await expect(goBtn).toBeEnabled();
+  await goBtn.click();
+
+  // The click fires the fly POST asynchronously (runAction is fire-and-forget from the test's view),
+  // so poll until it took effect on the server.
+  await expect.poll(async () => {
+    const b = await getState(page);
+    const p = b.planes.find((x) => x.id === 'plane-starter')!;
+    return p.status === 'flying' && p.destIcao === nearest.icao;
+  }, { timeout: 15_000, message: 'waiting for the relocate click to take effect (status "flying" + dest set)' }).toBe(true);
+});
+
+test('airport popup offers Relocate options for grounded planes', async ({ page }) => {
+  test.setTimeout(300_000); // self-heal (worst case ~20 s at 1000×) + one leg to LFRS
+  await flyHomeViaApi(page);
+
+  const refuel = await page.request.post('/api/planes/plane-starter/refuel');
+  expect(refuel.ok()).toBeTruthy();
+
+  await page.goto('/');
+
+  // Wait until the airport count renders (airports loaded) and the map has a snapshot containing
+  // the plane — the popup's Relocate row is built from that same latest snapshot.
+  const countEl = page.getByTestId('airport-count');
+  await expect.poll(async () => {
+    const text = (await countEl.textContent()) ?? '';
+    const m = text.match(/(\d+)/);
+    return m ? parseInt(m[1], 10) : -1;
+  }, { timeout: 15_000 }).toBeGreaterThan(0);
+  await expect.poll(async () =>
+    page.evaluate(() => {
+      const m = (window as any).__flightMap;
+      if (!m || !m.getSource('planes')) return false;
+      try {
+        return m.querySourceFeatures('planes').some((f: { properties?: Record<string, unknown> }) => f.properties?.id === 'plane-starter');
+      } catch {
+        return false; // source not ready yet — keep polling
+      }
+    }),
+    { timeout: 15_000 },
+  ).toBe(true);
+
+  // Click the LFRS marker (projected center — same pattern as e2e/map.spec.ts). The constant is
+  // passed AS AN ARGUMENT: the evaluate callback runs in the browser, where Node-scope values don't exist.
+  const pt = await page.evaluate(({ lon, lat }) => {
+    const map = (window as any).__flightMap;
+    const p = map.project([lon, lat]);
+    const rect = map.getContainer().getBoundingClientRect();
+    return { x: rect.left + p.x, y: rect.top + p.y };
+  }, POPUP_AIRPORT);
+  await page.mouse.click(pt.x, pt.y);
+
+  const popup = page.getByTestId('airport-popup');
+  await expect(popup).toBeVisible();
+  await expect(popup).toContainText(POPUP_AIRPORT.icao);
+
+  // The Relocate row: a select of grounded planes + the button (disabled until one is picked).
+  const planeSel = page.getByTestId('airport-popup-plane');
+  await expect(planeSel).toBeVisible();
+  // Target THE PLANE OPTION specifically — locator('option') also matches the placeholder and
+  // trips strict mode (CI run #51).
+  await expect(planeSel.locator('option[value="plane-starter"]')).toHaveText(/ATR 72-600 — EDDF/);
+  const goBtn = page.getByTestId('airport-popup-relocate');
+  await expect(goBtn).toBeDisabled(); // placeholder selected
+
+  await planeSel.selectOption('plane-starter');
+  await expect(goBtn).toBeEnabled();
+  await goBtn.click();
+
+  await expect.poll(async () => {
+    const b = await getState(page);
+    const p = b.planes.find((x) => x.id === 'plane-starter')!;
+    return p.status === 'flying' && p.destIcao === POPUP_AIRPORT.icao;
+  }, { timeout: 15_000, message: 'waiting for the popup relocate click to take effect (status "flying" + dest set)' }).toBe(true);
+});

e2e/right-pane.spec.ts

@@ -2,8 +2,9 @@ import type { Page } from '@playwright/test';
 import { expect, test } from '@playwright/test';
 
 // v0.12.0 — right Jobs & Market pane against the live origin: open packages render with
-// names/reward/deadline and Load (UI click) binds one to the starter; the on-board list shows
+// names/reward/deadline and Load (UI click) binds one to the starter; the on-board list
-// loaded packages with fly-to-destination + abandon buttons (penalty preview from the same
+// (moved to the left pane in v0.20.0, ISS-021) shows loaded packages with fly-to-destination +
+// abandon buttons (penalty preview from the same
 // formula as the server); flying planes show their current leg; market buy/sell/refuel previews
 // match the catalog + economy constants exposed in /api/state. Packages are created via
 // POST /api/test/create-package (FLIGHT_TEST_HOOKS=1), same pattern as e2e/actions.spec.ts.
@@ -38,6 +39,7 @@ interface CatalogEntry {
   price: number;
   maxFuel: number;
   burnPerKm: number;
+  emptyWeightKg: number; // v0.16.0 weighted burn input
   speedKmh: number;
   capacity: number;
 }
@@ -114,6 +116,39 @@ async function nearestToHub(page: Page): Promise<{ icao: string; lat: number; lo
   return nearest;
 }
 
+// Farthest airport from EDDF whose leg still FITS A FULL TANK — the longest flyable leg (v0.16.0
+// refuel-for-flight test). The dataset's absolute farthest can exceed the aircraft's range (UNNT is
+// ~4803 km out and needs ~6955 L > the 6300 L tank), so a full-tank fly there would rightly 409;
+// this test wants a long-but-flyable leg instead.
+async function farthestFlyableToHub(
+  page: Page,
+  entry: CatalogEntry,
+): Promise<{ icao: string; lat: number; lon: number; hubLat: number; hubLon: number }> {
+  const fc = (await (await page.request.get('/api/airports')).json()) as {
+    features: Array<{ properties: { icao: string; lat: number; lon: number } }>;
+  };
+  const hub = fc.features.find((f) => f.properties.icao === HUB)!.properties;
+  let farthest: { icao: string; lat: number; lon: number; d: number } | null = null;
+  for (const f of fc.features) {
+    if (f.properties.icao === HUB) continue;
+    const d = haversineKm(hub.lat, hub.lon, f.properties.lat, f.properties.lon);
+    if (requiredFuelFor(entry.burnPerKm, entry.emptyWeightKg, entry.maxFuel, d) > entry.maxFuel) continue; // beyond range
+    if (!farthest || d > farthest.d) {
+      farthest = { icao: f.properties.icao, lat: f.properties.lat, lon: f.properties.lon, d };
+    }
+  }
+  if (!farthest) throw new Error('no full-tank-flyable airport found in the dataset');
+  return { ...farthest, hubLat: hub.lat, hubLon: hub.lon };
+}
+
+// Mirrors lib/sim/movement.ts (v0.16.0): fuel required to cover distanceKm arriving empty —
+// closed form of the weight-proportional burn model, k calibrated so a full tank burns burnPerKm.
+const FUEL_DENSITY_KG_PER_L = 0.8; // must match FUEL_DENSITY_KG_PER_L in lib/sim/movement.ts
+function requiredFuelFor(burnPerKm: number, emptyWeightKg: number, maxFuel: number, distanceKm: number): number {
+  const k = burnPerKm / (emptyWeightKg + FUEL_DENSITY_KG_PER_L * maxFuel);
+  return (emptyWeightKg / FUEL_DENSITY_KG_PER_L) * (Math.exp(k * FUEL_DENSITY_KG_PER_L * distanceKm) - 1);
+}
+
 // Test hook (FLIGHT_TEST_HOOKS=1): create an open package on a known route.
 async function createPackage(page: Page, fromIcao: string, toIcao: string, deadlineOffsetMs?: number): Promise<PackageState> {
   const created = await page.request.post('/api/test/create-package', {
@@ -140,6 +175,9 @@ async function flyHomeViaApi(page: Page): Promise<void> {
       .toBe(true);
   }
   if (starter.locationIcao !== HUB) {
+    // ISS-011: the landing above auto-slown the sim to 1× — re-set SCALE so the return leg
+    // fast-forwards instead of taking real-time hours.
+    await setScale(page, SCALE);
     const res = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: HUB } });
     expect(res.status()).toBe(200); // repositioning needs no package (v0.12.0 manual flight)
     await expect
@@ -250,6 +288,8 @@ test('on-board list: fly-to-destination + abandon with penalty preview; flying p
   await expect(onboardRow).not.toBeVisible({ timeout: 15_000 });
 
   // Restore: fly home so the live instance stays in its onboarding state for the next run.
+  // ISS-011: the arrival above auto-slown the sim to 1×, so re-set SCALE for this leg.
+  await setScale(page, SCALE);
   const homeRes = await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: HUB } });
   expect(homeRes.status()).toBe(200);
   await expect
@@ -307,3 +347,76 @@ test('market buy/sell/refuel render with previews from the catalog in /api/state
     expect(after.planes.find((p) => p.id === 'plane-starter')!.fuel).toBe(starter.maxFuel);
   }
 });
+
+test('on-board row Refuel tops up just enough for the package leg; market button says "Refuel to full"', async ({ page }) => {
+  test.setTimeout(300_000); // self-heal + one long flight each way at scale 1000
+  await flyHomeViaApi(page);
+
+  const body = await getState(page);
+  const entry = body.catalog.find((e) => e.model === 'atr72')!;
+
+  // Deterministic baseline: a full tank.
+  expect((await page.request.post('/api/planes/plane-starter/refuel')).status()).toBe(200);
+
+  // Longest FLYABLE leg from the hub (fits a full tank) — long enough that "just enough" for it
+  // exceeds what's left on arrival.
+  const farthest = await farthestFlyableToHub(page, entry);
+  const pkg1 = await createPackage(page, HUB, farthest.icao, 24 * 3_600_000);
+  expect((await page.request.post(`/api/packages/${pkg1.id}/load`, { data: { planeId: 'plane-starter' } })).status()).toBe(200);
+
+  // Fly there (delivers pkg1 on arrival) — the tank is now partial.
+  expect((await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: farthest.icao } })).status()).toBe(200);
+  await setScale(page, SCALE);
+  await expect
+    .poll(async () => {
+      const b = await getState(page);
+      const p = b.planes.find((x) => x.id === 'plane-starter');
+      return !!p && p.status === 'available' && p.locationIcao === farthest.icao;
+    }, { timeout: 240_000, message: `waiting for arrival at ${farthest.icao} (scale 1000)` })
+    .toBe(true);
+
+  // New work at the far end: a package back to the hub — its leg is exactly what we refuel for.
+  const pkg2 = await createPackage(page, farthest.icao, HUB, 24 * 3_600_000);
+  expect((await page.request.post(`/api/packages/${pkg2.id}/load`, { data: { planeId: 'plane-starter' } })).status()).toBe(200);
+
+  // Expected "just enough" from the snapshot constants (mirrors requiredFuelFor in lib/sim/movement.ts).
+  const pre = await getState(page);
+  const fuelBefore = pre.planes.find((p) => p.id === 'plane-starter')!.fuel;
+  const cashBefore = pre.account.cash;
+  const km = haversineKm(farthest.hubLat, farthest.hubLon, farthest.lat, farthest.lon); // symmetric: hub ↔ far end
+  const liters = Math.max(0, requiredFuelFor(entry.burnPerKm, entry.emptyWeightKg, entry.maxFuel, km) - fuelBefore);
+  expect(liters).toBeGreaterThan(0); // the long leg genuinely needs more than what's left
+  const expectedCost = Math.round(liters * pre.fuelPricePerL * 100) / 100;
+
+  await page.goto('/');
+  const refuelBtn = page.getByTestId(`refuel-for-${pkg2.id}`);
+  await expect(refuelBtn, 'row Refuel button appears for the loaded package').toBeVisible({ timeout: 15_000 });
+  // Capture the endpoint's OWN response — the full post-action snapshot at the action's clock.
+  const [res] = await Promise.all([
+    page.waitForResponse((r) => r.url().includes(`/api/planes/plane-starter/refuel`), { timeout: 15_000 }),
+    refuelBtn.click(),
+  ]);
+  expect(res.status()).toBe(200);
+  const post = (await res.json()) as StateBody;
+
+  // Cash dropped by exactly L × price and fuel rose by exactly L.
+  expect(post.account.cash).toBeCloseTo(cashBefore - expectedCost, 6);
+  expect(post.planes.find((p) => p.id === 'plane-starter')!.fuel).toBeCloseTo(fuelBefore + liters, 6);
+
+  // Market row: the fill-up button is labeled "Refuel to full" (testid unchanged).
+  await expect(page.getByTestId('market-refuel')).toHaveText('Refuel to full');
+
+  // Restore: fly home — pkg2's destination IS the hub, so it delivers on arrival. The tank holds
+  // exactly the leg requirement, so this also proves "just enough" is enough. ISS-011: the far-end
+  // arrival above auto-slown the sim to 1×, so re-set SCALE for this leg.
+  await setScale(page, SCALE);
+  expect((await page.request.post('/api/planes/plane-starter/fly', { data: { destIcao: HUB } })).status()).toBe(200);
+  await expect
+    .poll(async () => (await getState(page)).planes.find((p) => p.id === 'plane-starter')?.locationIcao === HUB, {
+      timeout: 240_000,
+      message: 'waiting for plane-starter to land back at the hub',
+    })
+    .toBe(true);
+  // Top the tank back up so later specs start with a full tank.
+  expect((await page.request.post('/api/planes/plane-starter/refuel')).status()).toBe(200);
+});

e2e/toasts.spec.ts

@@ -0,0 +1,76 @@
+import type { Page } from '@playwright/test';
+import { expect, test } from '@playwright/test';
+
+// v0.17.0 — ISS-008: action errors surface as bottom-right toasts (in addition to the inline
+// pane error) and game events appear as info toasts via snapshot diffing; the left-pane Time
+// section offers an explicit "Enable notifications" opt-in for browser notifications.
+
+interface CatalogEntry {
+  model: string;
+  label: string;
+  price: number;
+}
+
+interface StateBody {
+  account: { cash: number };
+  catalog: CatalogEntry[];
+}
+
+async function getState(page: Page): Promise<StateBody> {
+  const res = await page.request.get('/api/state');
+  expect(res.status()).toBe(200);
+  return (await res.json()) as StateBody;
+}
+
+test('failed actions toast bottom-right (inline error stays) and the Time section offers a notifications opt-in', async ({ page }) => {
+  await page.goto('/');
+  const buyModel = page.getByTestId('market-buy-model');
+  await expect(buyModel, 'the market section renders once the first snapshot lands').toBeVisible({ timeout: 15_000 });
+
+  // Part A — deterministic error path: the most expensive catalog model (ATR 72-600, €200k) is
+  // unaffordable with starting cash (€20k). On a long-lived local instance cash may have grown
+  // past it — then this part is skipped in place; CI's isolated stack always starts fresh.
+  const body = await getState(page);
+  const priciest = [...body.catalog].sort((a, b) => b.price - a.price)[0];
+  if (body.account.cash < priciest.price) {
+    await buyModel.selectOption(priciest.model);
+    await page.getByTestId('market-buy').click();
+
+    // The toast appears with the server's error message and the error variant class…
+    const toast = page.locator('[data-testid="toast"]').filter({ hasText: /insufficient funds/i });
+    await expect(toast, 'the error toast appears bottom-right').toBeVisible({ timeout: 10_000 });
+    await expect(toast).toHaveClass(/toast-error/);
+
+    // …and the inline pane error still shows (both surfaces by design). It auto-clears on the
+    // next poll (~1 s), so assert right after the toast — both are set in the same commit.
+    await expect(page.getByTestId('right-error')).toContainText(/insufficient funds/);
+  }
+
+  // Part B — notifications opt-in in the Time section.
+  const btn = page.getByTestId('enable-notifications');
+  await expect(btn, 'the notifications button renders in the Time section').toBeVisible({ timeout: 15_000 });
+
+  // Browsers without the Notification API: disabled with a tooltip-ish title.
+  const supported = await page.evaluate(() => 'Notification' in window);
+  if (!supported) {
+    await expect(btn).toBeDisabled();
+    await expect(btn).toHaveAttribute('title', /does not support/i);
+    return;
+  }
+
+  // Branch on the ACTUAL permission state — headless CI reports 'denied' (not 'default'), so a
+  // fresh context is not guaranteed to show the opt-in prompt (CI run #47).
+  const permission = await page.evaluate(() => Notification.permission);
+  if (permission === 'denied') {
+    // LeftPane renders the blocked-state label without any click.
+    await expect(btn, 'denied context shows the blocked-state label').toHaveText('Notifications blocked', { timeout: 10_000 });
+  } else if (permission === 'granted') {
+    await expect(btn, 'pre-granted context shows the enabled label').toHaveText('Notifications enabled', { timeout: 10_000 });
+  } else {
+    // 'default' — the opt-in prompt. Clicking requests it; headless may deny, so accept either
+    // outcome, but the label must CHANGE from the prompt to reflect the result.
+    await expect(btn, 'non-denied context shows the opt-in prompt').toHaveText('Enable notifications', { timeout: 10_000 });
+    await btn.click();
+    await expect(btn).not.toHaveText('Enable notifications', { timeout: 10_000 });
+  }
+});

lib/deriveEvents.test.ts

@@ -0,0 +1,162 @@
+import { describe, expect, it } from 'vitest';
+import type { PackageState, PlaneState, StateSnapshot } from './game/state';
+import { diffSnapshots } from './deriveEvents';
+
+// ISS-008 (v0.17.0): snapshot-diffing event derivation — pure core of the toast/notification
+// feature, unit-tested in node like advanceSimClock/fetchState.
+
+const CATALOG = [
+  { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, emptyWeightKg: 9300, speedKmh: 510, capacity: 6 },
+];
+
+const basePlane = (id: string): PlaneState => ({
+  id,
+  model: 'atr72',
+  status: 'available',
+  fuel: 6300,
+  maxFuel: 6300,
+  locationIcao: 'EDDF',
+  locationName: 'Frankfurt',
+  destIcao: null,
+  destName: null,
+  departureSimTime: null,
+  lat: 50.03,
+  lon: 8.56,
+});
+
+const basePackage = (id: string): PackageState => ({
+  id,
+  originIcao: 'EDDF',
+  originName: 'Frankfurt',
+  destIcao: 'LEMD',
+  destName: 'Madrid–Barajas',
+  reward: 1234.5,
+  cargoType: 'mail',
+  cargoCount: 2,
+  deadlineSimTime: 0,
+  status: 'open',
+  planeId: null,
+  createdSimTime: 0,
+});
+
+const snapshot = (over: Partial<StateSnapshot> = {}): StateSnapshot => ({
+  account: { cash: 20_000, reputation: 10 },
+  simState: { clockMs: 0, timeScale: 1, paused: false },
+  planes: [basePlane('plane-starter')],
+  packages: [],
+  catalog: CATALOG,
+  fuelPricePerL: 0.8,
+  sellFraction: 0.5,
+  ...over,
+});
+
+describe('diffSnapshots', () => {
+  it('returns [] for identical snapshots (only clock/cash drift)', () => {
+    const prev = snapshot();
+    const next = snapshot({ account: { cash: 21_000, reputation: 11 }, simState: { clockMs: 60_000, timeScale: 1, paused: false } });
+    expect(diffSnapshots(prev, next)).toEqual([]);
+  });
+
+  it('returns [] for the first snapshot (no baseline — no "new package" spam on page load)', () => {
+    const next = snapshot({ packages: [basePackage('pkg-1'), basePackage('pkg-2')] });
+    expect(diffSnapshots(null, next)).toEqual([]);
+  });
+
+  it('emits a landing event when a plane goes flying → available (new locationName is the arrival)', () => {
+    const prev = snapshot({
+      planes: [
+        {
+          ...basePlane('plane-starter'),
+          status: 'flying',
+          destIcao: 'LEMD',
+          destName: 'Madrid–Barajas',
+          departureSimTime: 0,
+        },
+      ],
+    });
+    const next = snapshot({
+      planes: [
+        { ...basePlane('plane-starter'), locationIcao: 'LEMD', locationName: 'Madrid–Barajas' },
+      ],
+    });
+    expect(diffSnapshots(prev, next)).toEqual([
+      { kind: 'info', message: 'ATR 72-600 landed at Madrid–Barajas' },
+    ]);
+  });
+
+  it('emits a delivery event with the reward when a loaded package is delivered on arrival', () => {
+    const prev = snapshot({ packages: [{ ...basePackage('pkg-1'), status: 'loaded', planeId: 'plane-starter' }] });
+    const next = snapshot({ packages: [{ ...basePackage('pkg-1'), status: 'delivered', planeId: 'plane-starter' }] });
+    expect(diffSnapshots(prev, next)).toEqual([
+      { kind: 'info', message: 'Package delivered: +€1,234.50' },
+    ]);
+  });
+
+  it('emits an expiry event for open → expired and loaded → expired', () => {
+    const fromOpen = diffSnapshots(
+      snapshot({ packages: [basePackage('pkg-1')] }),
+      snapshot({ packages: [{ ...basePackage('pkg-1'), status: 'expired' }] }),
+    );
+    expect(fromOpen).toEqual([{ kind: 'info', message: 'Package expired: Frankfurt → Madrid–Barajas' }]);
+
+    const fromLoaded = diffSnapshots(
+      snapshot({ packages: [{ ...basePackage('pkg-2'), status: 'loaded', planeId: 'plane-starter' }] }),
+      snapshot({ packages: [{ ...basePackage('pkg-2'), status: 'expired', planeId: 'plane-starter' }] }),
+    );
+    expect(fromLoaded).toEqual([{ kind: 'info', message: 'Package expired: Frankfurt → Madrid–Barajas' }]);
+  });
+
+  it('emits a new-package event for ids only in the next snapshot', () => {
+    const prev = snapshot({ packages: [basePackage('pkg-1')] });
+    const next = snapshot({ packages: [basePackage('pkg-1'), basePackage('pkg-2')] });
+    expect(diffSnapshots(prev, next)).toEqual([
+      { kind: 'info', message: 'New package available: Frankfurt → Madrid–Barajas' },
+    ]);
+  });
+
+  it('emits bought/sold events when the plane id set changes (with the model name)', () => {
+    const bought = diffSnapshots(
+      snapshot(),
+      snapshot({ planes: [basePlane('plane-starter'), basePlane('plane-2')] }),
+    );
+    expect(bought).toEqual([{ kind: 'info', message: 'Bought ATR 72-600' }]);
+
+    const sold = diffSnapshots(
+      snapshot({ planes: [basePlane('plane-starter'), basePlane('plane-2')] }),
+      snapshot(),
+    );
+    expect(sold).toEqual([{ kind: 'info', message: 'Sold ATR 72-600' }]);
+  });
+
+  it('reports every transition in one diff (planes first, then packages)', () => {
+    const prev = snapshot({
+      planes: [
+        { ...basePlane('plane-starter'), status: 'flying', destIcao: 'LEMD', destName: 'Madrid–Barajas' },
+        basePlane('plane-2'),
+      ],
+      packages: [{ ...basePackage('pkg-1'), status: 'loaded', planeId: 'plane-starter' }],
+    });
+    const next = snapshot({
+      planes: [
+        { ...basePlane('plane-starter'), locationIcao: 'LEMD', locationName: 'Madrid–Barajas' },
+        basePlane('plane-3'),
+      ],
+      packages: [{ ...basePackage('pkg-1'), status: 'delivered', planeId: 'plane-starter' }],
+    });
+    expect(diffSnapshots(prev, next)).toEqual([
+      { kind: 'info', message: 'ATR 72-600 landed at Madrid–Barajas' },
+      { kind: 'info', message: 'Bought ATR 72-600' },
+      { kind: 'info', message: 'Sold ATR 72-600' },
+      { kind: 'info', message: 'Package delivered: +€1,234.50' },
+    ]);
+  });
+
+  it('ignores transitions that are not events (open → loaded, available → flying)', () => {
+    const prev = snapshot({ packages: [basePackage('pkg-1')] });
+    const next = snapshot({
+      planes: [{ ...basePlane('plane-starter'), status: 'flying', destIcao: 'LEMD', destName: 'Madrid–Barajas' }],
+      packages: [{ ...basePackage('pkg-1'), status: 'loaded', planeId: 'plane-starter' }],
+    });
+    expect(diffSnapshots(prev, next)).toEqual([]);
+  });
+});

lib/deriveEvents.ts

@@ -0,0 +1,61 @@
+import type { StateSnapshot } from './game/state';
+import { PLANE_TYPES } from './game/catalog';
+import { formatCash } from './format';
+
+// ISS-008 (v0.17.0): derive human-readable game events by diffing two consecutive /api/state
+// snapshots — there is no server event feed, so the client watches for transitions in the
+// fields it already receives. Pure and unit-tested; the shell calls it once per new snapshot
+// and turns each result into an info toast (plus a browser notification when hidden).
+
+export interface GameEvent {
+  kind: 'info';
+  message: string;
+}
+
+const planeName = (model: string): string => PLANE_TYPES[model]?.name ?? model;
+
+export function diffSnapshots(prev: StateSnapshot | null, next: StateSnapshot): GameEvent[] {
+  // No baseline yet (first snapshot after load) — nothing to compare against. Emitting a
+  // "new package" event for every existing row would spam the stack on page load.
+  if (prev === null) return [];
+
+  const events: GameEvent[] = [];
+
+  // Planes: landed (flying → available, new locationName is the arrival airport), bought or
+  // sold (id set changed — ids are stable for a plane's whole life).
+  const prevPlanes = new Map(prev.planes.map((p) => [p.id, p]));
+  for (const plane of next.planes) {
+    const before = prevPlanes.get(plane.id);
+    if (!before) {
+      events.push({ kind: 'info', message: `Bought ${planeName(plane.model)}` });
+      continue;
+    }
+    if (before.status === 'flying' && plane.status === 'available') {
+      events.push({ kind: 'info', message: `${planeName(plane.model)} landed at ${plane.locationName}` });
+    }
+  }
+  for (const [id, before] of prevPlanes) {
+    if (!next.planes.some((p) => p.id === id)) {
+      events.push({ kind: 'info', message: `Sold ${planeName(before.model)}` });
+    }
+  }
+
+  // Packages: delivered (loaded → delivered, reward paid out in the same tick), expired
+  // (open|loaded → expired), newly appeared (id only in next — terminal packages are never
+  // deleted, so an id appearing is always a genuinely new one).
+  const prevPackages = new Map(prev.packages.map((p) => [p.id, p]));
+  for (const pkg of next.packages) {
+    const before = prevPackages.get(pkg.id);
+    if (!before) {
+      events.push({ kind: 'info', message: `New package available: ${pkg.originName} → ${pkg.destName}` });
+      continue;
+    }
+    if (before.status === 'loaded' && pkg.status === 'delivered') {
+      events.push({ kind: 'info', message: `Package delivered: +${formatCash(pkg.reward)}` });
+    } else if ((before.status === 'open' || before.status === 'loaded') && pkg.status === 'expired') {
+      events.push({ kind: 'info', message: `Package expired: ${pkg.originName} → ${pkg.destName}` });
+    }
+  }
+
+  return events;
+}

lib/game/actions.test.ts

@@ -6,6 +6,8 @@ import { afterAll, beforeAll, describe, expect, it, vi } from 'vitest';
 import { openGameDb, type GameDb } from '@/lib/db/client';
 import * as schema from '@/lib/db/schema';
 import { loadAirportsGeoJson } from '@/lib/airports';
+import { haversineKm } from '@/lib/geo';
+import { requiredFuelFor } from '@/lib/sim/movement';
 import { FUEL_PRICE_PER_L, PLANE_TYPES, SELL_FRACTION } from './catalog';
 import { HUB_ICAO } from './seed';
 import {
@@ -412,4 +414,110 @@ describe('refuelPlane', () => {
     const inst = await freshDb('refuel-unknown.db');
     await expectActionError(refuelPlane(inst, 'ghost'), 404);
   });
+
+  // --- forFlight mode (v0.16.0) ---
+
+  it('forFlight adds exactly the liters needed for the package leg and deducts L × price', async () => {
+    const inst = await freshDb('refuel-forflight-ok.db');
+    await insertOpenPackage(inst, 'p-ff', { destIcao: 'LEMD' }); // EDDF → LEMD
+    await loadPackage(inst, 'p-ff', 'plane-starter');
+
+    const fc = await loadAirportsGeoJson();
+    const from = fc.features.find((f) => f.properties.icao === HUB_ICAO)!.properties;
+    const to = fc.features.find((f) => f.properties.icao === 'LEMD')!.properties;
+    const km = haversineKm(from.lat, from.lon, to.lat, to.lon);
+    const type = PLANE_TYPES.atr72;
+    const required = requiredFuelFor(type.burnPerKm, type.emptyWeightKg, type.maxFuel, km);
+
+    // Partial tank below the requirement so L > 0.
+    const startFuel = Math.round(required / 2);
+    await inst.db.update(schema.planes).set({ fuel: startFuel }).where(eq(schema.planes.id, 'plane-starter'));
+    const cashBefore = (await inst.db.select().from(schema.account))[0].cash;
+
+    const { cost } = await refuelPlane(inst, 'plane-starter', { mode: 'forFlight', packageId: 'p-ff' });
+
+    expect(cost).toBe(Math.round((required - startFuel) * FUEL_PRICE_PER_L * 100) / 100);
+    const plane = (await inst.db.select().from(schema.planes))[0];
+    expect(plane.fuel).toBeCloseTo(required, 6); // topped up to exactly the leg requirement
+    const account = (await inst.db.select().from(schema.account))[0];
+    expect(account.cash).toBeCloseTo(cashBefore - cost, 6);
+  });
+
+  it('forFlight leaves an exactly-feasible tank — flyPlane to the package dest succeeds right after', async () => {
+    const inst = await freshDb('refuel-ff-flyafter.db');
+    await insertOpenPackage(inst, 'p-fa', { destIcao: 'LEMD' }); // EDDF → LEMD
+    await loadPackage(inst, 'p-fa', 'plane-starter');
+
+    const fc = await loadAirportsGeoJson();
+    const from = fc.features.find((f) => f.properties.icao === HUB_ICAO)!.properties;
+    const to = fc.features.find((f) => f.properties.icao === 'LEMD')!.properties;
+    const km = haversineKm(from.lat, from.lon, to.lat, to.lon);
+    const type = PLANE_TYPES.atr72;
+    const required = requiredFuelFor(type.burnPerKm, type.emptyWeightKg, type.maxFuel, km);
+
+    // Empty-ish tank: well below the leg requirement.
+    await inst.db.update(schema.planes).set({ fuel: Math.round(required / 4) }).where(eq(schema.planes.id, 'plane-starter'));
+
+    await refuelPlane(inst, 'plane-starter', { mode: 'forFlight', packageId: 'p-fa' });
+
+    // The leg must now be flyable — no epsilon-short 409 (regression guard for the float-exact target).
+    await flyPlane(inst, 'plane-starter', 'LEMD');
+    const plane = (await inst.db.select().from(schema.planes))[0];
+    expect(plane.status).toBe('flying');
+    expect(plane.destIcao).toBe('LEMD');
+  });
+
+  it('forFlight is a free no-op when the tank already covers the leg', async () => {
+    const inst = await freshDb('refuel-forflight-enough.db'); // seeded starter is full at EDDF
+    await insertOpenPackage(inst, 'p-ff2', { destIcao: 'LEMD' });
+    await loadPackage(inst, 'p-ff2', 'plane-starter');
+    const cashBefore = (await inst.db.select().from(schema.account))[0].cash;
+
+    const { cost } = await refuelPlane(inst, 'plane-starter', { mode: 'forFlight', packageId: 'p-ff2' });
+
+    expect(cost).toBe(0);
+    const plane = (await inst.db.select().from(schema.planes))[0];
+    expect(plane.fuel).toBe(PLANE_TYPES.atr72.maxFuel); // untouched
+    expect((await inst.db.select().from(schema.account))[0].cash).toBe(cashBefore);
+  });
+
+  it('forFlight rejects a package that is not loaded on this plane with 409', async () => {
+    const inst = await freshDb('refuel-ff-open.db'); // open — never loaded
+    await insertOpenPackage(inst, 'p-x');
+    await expectActionError(refuelPlane(inst, 'plane-starter', { mode: 'forFlight', packageId: 'p-x' }), 409);
+
+    const inst2 = await freshDb('refuel-ff-other.db'); // loaded on ANOTHER plane
+    await insertOpenPackage(inst2, 'p-y', { status: 'loaded', planeId: 'plane-someone-else' });
+    await expectActionError(refuelPlane(inst2, 'plane-starter', { mode: 'forFlight', packageId: 'p-y' }), 409);
+  });
+
+  it('forFlight rejects an expired package with 409', async () => {
+    const inst = await freshDb('refuel-ff-expired.db');
+    await insertOpenPackage(inst, 'p-z', { status: 'expired', planeId: 'plane-starter' });
+    await expectActionError(refuelPlane(inst, 'plane-starter', { mode: 'forFlight', packageId: 'p-z' }), 409);
+  });
+
+  it('forFlight rejects an unknown package id with 404', async () => {
+    const inst = await freshDb('refuel-ff-unknown.db');
+    await expectActionError(refuelPlane(inst, 'plane-starter', { mode: 'forFlight', packageId: 'nope' }), 404);
+  });
+
+  it('forFlight rejects a missing packageId with 400', async () => {
+    const inst = await freshDb('refuel-ff-nopkg.db');
+    await expectActionError(refuelPlane(inst, 'plane-starter', { mode: 'forFlight' }), 400);
+  });
+
+  it('forFlight rejects a leg that does not fit even a full tank with 409', async () => {
+    const inst = await freshDb('refuel-ff-nofit.db');
+    // UNNT (Narsarsuaq, Greenland) ↔ LPPD are ~7670 km apart — far beyond the ATR's range.
+    await insertOpenPackage(inst, 'p-far', { destIcao: 'LPPD' });
+    await loadPackage(inst, 'p-far', 'plane-starter');
+    await inst.db.update(schema.planes).set({ locationIcao: 'UNNT' }).where(eq(schema.planes.id, 'plane-starter'));
+
+    await expectActionError(
+      refuelPlane(inst, 'plane-starter', { mode: 'forFlight', packageId: 'p-far' }),
+      409,
+      /does not fit/i,
+    );
+  });
 });

lib/game/actions.ts

@@ -4,6 +4,7 @@ import * as schema from '@/lib/db/schema';
 import { persist, type GameDb } from '@/lib/db/client';
 import { loadAirportsGeoJson } from '@/lib/airports';
 import { haversineKm } from '@/lib/geo';
+import { requiredFuelFor } from '@/lib/sim/movement';
 import { runAction } from '@/lib/sim/engine';
 import { getStateSnapshot } from './state';
 import { FUEL_PRICE_PER_L, PLANE_TYPES, SELL_FRACTION } from './catalog';
@@ -105,9 +106,10 @@ export async function flyPlane(inst: GameDb, planeId: string, destIcao: string):
   const type = PLANE_TYPES[plane.model];
   if (!type) throw new Error(`unknown plane model ${plane.model}`); // → 500, cannot happen for seeded data
   const distanceKm = haversineKm(origin.lat, origin.lon, destFeature.properties.lat, destFeature.properties.lon);
-  const burnL = type.burnPerKm * distanceKm;
+  // Weighted burn model (v0.16.0): the leg needs enough fuel to cover it arriving empty.
-  if (burnL > plane.fuel) {
+  const requiredL = requiredFuelFor(type.burnPerKm, type.emptyWeightKg, type.maxFuel, distanceKm);
-    throw new GameActionError(409, `insufficient fuel: the leg needs ${Math.round(burnL)} L but the plane has ${Math.round(plane.fuel)} L`);
+  if (requiredL > plane.fuel) {
+    throw new GameActionError(409, `insufficient fuel: the leg needs ${Math.round(requiredL)} L but the plane has ${Math.round(plane.fuel)} L`);
   }
 
   // runAction() ticked first, so this is current game time.
@@ -225,8 +227,19 @@ export async function sellPlane(inst: GameDb, planeId: string): Promise<{ payout
 
 // --- Refuel (POST /api/planes/:planeId/refuel) ---
 
-// Fill a grounded plane to maxFuel at FUEL_PRICE_PER_L per missing liter.
+// Refuel modes (v0.16.0): 'full' fills the tank to maxFuel; 'forFlight' adds just
-export async function refuelPlane(inst: GameDb, planeId: string): Promise<{ cost: number }> {
+// enough fuel for one loaded package's destination leg — required liters per the
+// weighted burn model, independent of how much is already in the tank.
+export interface RefuelOptions {
+  mode?: 'full' | 'forFlight';
+  packageId?: string;
+}
+
+// Fill a grounded plane to maxFuel at FUEL_PRICE_PER_L per missing liter — or, with
+// {mode:'forFlight', packageId}, top it up just enough to fly the loaded package's
+// destination leg (409 if the package isn't loaded on this plane, is expired, or the
+// leg doesn't fit a full tank).
+export async function refuelPlane(inst: GameDb, planeId: string, opts: RefuelOptions = {}): Promise<{ cost: number }> {
   const rows = await inst.db.select().from(schema.planes).where(eq(schema.planes.id, planeId));
   const plane = rows[0];
   if (!plane) throw new GameActionError(404, `plane ${planeId} not found`);
@@ -234,14 +247,47 @@ export async function refuelPlane(inst: GameDb, planeId: string): Promise<{ cost
     throw new GameActionError(409, `plane is ${plane.status}, only grounded planes can be refueled`);
   }
 
-  const cost = Math.round((plane.maxFuel - plane.fuel) * FUEL_PRICE_PER_L * 100) / 100;
+  const mode = opts.mode ?? 'full';
+  let targetFuel: number; // tank level after the refuel
+  if (mode === 'forFlight') {
+    if (!opts.packageId) throw new GameActionError(400, 'packageId is required when mode is "forFlight"');
+
+    const pkgRows = await inst.db.select().from(schema.packages).where(eq(schema.packages.id, opts.packageId));
+    const pkg = pkgRows[0];
+    if (!pkg) throw new GameActionError(404, `package ${opts.packageId} not found`);
+    if (pkg.status !== 'loaded' || pkg.planeId !== plane.id) {
+      const where = pkg.planeId === plane.id ? '' : ', and it is bound to another plane';
+      throw new GameActionError(409, `only a package loaded on this plane can be refueled for (it is ${pkg.status}${where})`);
+    }
+
+    const type = PLANE_TYPES[plane.model];
+    if (!type) throw new Error(`unknown plane model ${plane.model}`); // → 500, cannot happen for seeded data
+    const origin = await airportByIcao(plane.locationIcao);
+    const dest = await airportByIcao(pkg.destIcao);
+    const distanceKm = haversineKm(origin.lat, origin.lon, dest.lat, dest.lon);
+    const requiredL = requiredFuelFor(type.burnPerKm, type.emptyWeightKg, type.maxFuel, distanceKm);
+    if (requiredL > plane.maxFuel) {
+      throw new GameActionError(409, `the leg to ${pkg.destIcao} needs ${Math.round(requiredL)} L even starting empty — it does not fit a full ${plane.maxFuel} L tank`);
+    }
+    // Land EXACTLY on the leg requirement when topping up: flyPlane re-computes this same value and
+    // compares with strict `>`, so fuel := requiredL guarantees the leg is feasible. The alternative
+    // (fuel + liters) can round a hair BELOW R in IEEE754 — f + fl(R − f) is not guaranteed ≥ R — and
+    // would 409 on an otherwise-feasible leg. Already enough → free no-op, tank untouched.
+    targetFuel = Math.max(plane.fuel, requiredL);
+  } else {
+    // Exactly maxFuel (as before v0.16.0) — clients/tests compare against it with strict equality.
+    targetFuel = plane.maxFuel;
+  }
+
+  const liters = Math.max(0, targetFuel - plane.fuel);
+  const cost = Math.round(liters * FUEL_PRICE_PER_L * 100) / 100;
   const account = (await inst.db.select().from(schema.account))[0];
   if (!account) throw new Error('account row missing');
   if (cost > 0 && account.cash < cost) {
     throw new GameActionError(409, `insufficient funds: refueling costs ${cost}, you have ${Math.round(account.cash)}`);
   }
 
-  await inst.db.update(schema.planes).set({ fuel: plane.maxFuel }).where(eq(schema.planes.id, planeId));
+  await inst.db.update(schema.planes).set({ fuel: targetFuel }).where(eq(schema.planes.id, planeId));
   if (cost > 0) {
     await inst.db.update(schema.account).set({ cash: Math.round((account.cash - cost) * 100) / 100 });
   }

lib/game/catalog.ts

@@ -6,8 +6,11 @@ export interface PlaneType {
   name: string;
   // Fuel capacity, liters.
   maxFuel: number;
-  // Fuel burn per km of flight, liters/km (cruise).
+  // Fuel burn per km of flight at a FULL tank, liters/km (cruise) — the weighted burn
+  // model (v0.16.0) calibrates its rate constant to this value at F = maxFuel.
   burnPerKm: number;
+  // Operating empty weight in kg (v0.16.0) — feeds the weight-proportional burn model.
+  emptyWeightKg: number;
   // Cruise speed, km/h — used by the sim tick to advance planes along routes.
   speedKmh: number;
   // Market price in € (v0.8.0): buying costs `price`, selling pays out
@@ -22,7 +25,8 @@ export const PLANE_TYPES: Record<string, PlaneType> = {
     id: 'atr72',
     name: 'ATR 72-600',
     maxFuel: 6300,
-    burnPerKm: 1.75, // ~900 kg/h at 510 km/h cruise (Jet-A1 ≈ 0.8 kg/L)
+    burnPerKm: 1.75, // full-tank rate: ~893 L/h ≈ 714 kg/h at 510 km/h cruise (Jet-A1 ≈ 0.8 kg/L); the weighted model burns less as fuel drops off
+    emptyWeightKg: 9_300, // ATR 72-600 operating empty weight
     speedKmh: 510,
     // €200k — with the starting cash of €20k and typical hop rewards (~€1–3k),
     // a second ATR takes sustained play to afford, as intended for the MVP sink.
@@ -49,6 +53,9 @@ export interface CatalogEntry {
   price: number;
   maxFuel: number;
   burnPerKm: number;
+  // Weighted burn model inputs (v0.16.0) — clients can mirror the closed forms in
+  // lib/sim/movement.ts with these + FUEL_DENSITY_KG_PER_L.
+  emptyWeightKg: number;
   speedKmh: number;
   capacity: number;
 }
@@ -62,6 +69,7 @@ export function catalogEntries(): CatalogEntry[] {
     price: t.price,
     maxFuel: t.maxFuel,
     burnPerKm: t.burnPerKm,
+    emptyWeightKg: t.emptyWeightKg,
     speedKmh: t.speedKmh,
     capacity: t.capacity,
   }));

lib/game/state.ts

@@ -3,7 +3,7 @@ import { haversineKm } from '@/lib/geo';
 import { getGameDb } from '@/lib/db/client';
 import * as schema from '@/lib/db/schema';
 import { catalogEntries, FUEL_PRICE_PER_L, PLANE_TYPES, SELL_FRACTION, type CatalogEntry } from './catalog';
-import { fuelAt, progressAt, positionAt } from '@/lib/sim/movement';
+import { fuelAtWeighted, progressAt, positionAt } from '@/lib/sim/movement';
 
 // Read-only game-state snapshot for client polling (GET /api/state).
 
@@ -84,7 +84,7 @@ export async function getStateSnapshot(): Promise<StateSnapshot> {
     const distanceKm = haversineKm(from.lat, from.lon, to.lat, to.lon);
     const progress = progressAt(p.departureSimTime, distanceKm, type.speedKmh, simRow.clockMs);
     const pos = positionAt(from.lat, from.lon, to.lat, to.lon, progress);
-    return { ...pos, fuel: fuelAt(p.fuel, type.burnPerKm, distanceKm, progress) };
+    return { ...pos, fuel: fuelAtWeighted(p.fuel, type.burnPerKm, type.emptyWeightKg, type.maxFuel, distanceKm, progress) };
   };
 
   return {

lib/mapData.test.ts

@@ -17,7 +17,7 @@ function snapshot(overrides: Partial<StateSnapshot> = {}): StateSnapshot {
     planes: [],
     packages: [],
     catalog: [
-      { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, speedKmh: 510, capacity: 6 },
+      { model: 'atr72', label: 'ATR 72-600', price: 200_000, maxFuel: 6300, burnPerKm: 1.75, emptyWeightKg: 9_300, speedKmh: 510, capacity: 6 },
     ],
     fuelPricePerL: 0.8,
     sellFraction: 0.5,

lib/openapi.test.ts

@@ -90,8 +90,17 @@ describe('OpenAPI spec', () => {
     expect(snap.sellFraction.type).toBe('number');
 
     const catalog = openApiSpec.components.schemas.CatalogEntry.properties;
-    expect(Object.keys(catalog).sort()).toEqual(['burnPerKm', 'capacity', 'label', 'maxFuel', 'model', 'price', 'speedKmh']);
+    expect(Object.keys(catalog).sort()).toEqual([
-    for (const key of ['burnPerKm', 'maxFuel', 'price', 'speedKmh'] as const) {
+      'burnPerKm',
+      'capacity',
+      'emptyWeightKg', // v0.16.0 weighted burn model input
+      'label',
+      'maxFuel',
+      'model',
+      'price',
+      'speedKmh',
+    ]);
+    for (const key of ['burnPerKm', 'emptyWeightKg', 'maxFuel', 'price', 'speedKmh'] as const) {
       expect(catalog[key].type, `CatalogEntry.${key}`).toBe('number');
     }
     expect(catalog.capacity.type).toBe('integer'); // v0.12.0 slot capacity
@@ -165,7 +174,7 @@ describe('OpenAPI spec', () => {
     const post = (p: string) =>
       ((openApiSpec.paths as Record<string, { post?: unknown }>)[p]?.post ?? {}) as {
         responses: Record<string, unknown>;
-        requestBody?: { content: Record<string, { schema: { $ref: string } }> };
+        requestBody?: { required?: boolean; content: Record<string, { schema: { $ref: string } }> };
         parameters?: Array<{ name: string }>;
       };
 
@@ -189,9 +198,10 @@ describe('OpenAPI spec', () => {
     expect(errorCodes('/api/planes/{planeId}/fly')).toEqual(['400', '404', '409']);
     expect(errorCodes('/api/market/buy-plane')).toEqual(['400', '409']);
     expect(errorCodes('/api/market/sell-plane')).toEqual(['400', '404', '409']);
-    expect(errorCodes('/api/planes/{planeId}/refuel')).toEqual(['404', '409']);
+    expect(errorCodes('/api/planes/{planeId}/refuel')).toEqual(['400', '404', '409']); // v0.16.0 optional body
 
-    // Request bodies: load/fly/buy/sell take their dedicated schemas; abandon/refuel take none.
+    // Request bodies: load/fly/buy/sell take their dedicated schemas; abandon takes none;
+    // refuel's is OPTIONAL (v0.16.0) — no body still means "fill to full".
     expect(post('/api/packages/{id}/load').requestBody?.content['application/json'].schema.$ref).toBe(
       '#/components/schemas/LoadPackageRequest',
     );
@@ -205,7 +215,9 @@ describe('OpenAPI spec', () => {
       '#/components/schemas/SellPlaneRequest',
     );
     expect(post('/api/packages/{id}/abandon').requestBody).toBeUndefined();
-    expect(post('/api/planes/{planeId}/refuel').requestBody).toBeUndefined();
+    const refuelBody = post('/api/planes/{planeId}/refuel').requestBody;
+    expect(refuelBody?.content['application/json'].schema.$ref).toBe('#/components/schemas/RefuelRequest');
+    expect(refuelBody?.required).toBe(false); // optional — no body still means "fill to full"
 
     // Path parameters are declared on the parameterized routes.
     const paramNames = (p: string) => post(p).parameters?.map((x) => x.name);
@@ -227,5 +239,11 @@ describe('OpenAPI spec', () => {
     const sell = openApiSpec.components.schemas.SellPlaneRequest;
     expect(sell.required).toEqual(['planeId']);
     expect(sell.properties.planeId.type).toBe('string');
+
+    // RefuelRequest (v0.16.0): both fields optional — no body / {} means "full".
+    const refuel = openApiSpec.components.schemas.RefuelRequest;
+    expect((refuel as { required?: string[] }).required ?? []).toEqual([]);
+    expect(((refuel.properties.mode) as { enum: string[] }).enum.sort()).toEqual(['forFlight', 'full']);
+    expect(refuel.properties.packageId.type).toBe('string');
   });
 });

lib/openapi.ts

@@ -197,7 +197,8 @@ export const openApiSpec = {
             content: { 'application/json': { schema: { $ref: '#/components/schemas/Error' } } },
           },
           409: {
-            description: 'Plane not grounded, or insufficient fuel for the leg (burnPerKm × great-circle km)',
+            description:
+              'Plane not grounded, or insufficient fuel for the leg (v0.16.0 weight-proportional burn — the fuel required to cover the great-circle distance arriving empty)',
             content: { 'application/json': { schema: { $ref: '#/components/schemas/Error' } } },
           },
         },
@@ -271,22 +272,35 @@ export const openApiSpec = {
       post: {
         summary: 'Refuel a grounded plane',
         description:
-          'Fill a grounded plane to maxFuel (v0.8.0). Cost = (maxFuel − fuel) × fuel price per liter, deducted from cash; no body.',
+          'Refuel a grounded plane at the fuel price per added liter, deducted from cash (v0.8.0). The body is optional (v0.16.0): no body or mode "full" fills to maxFuel; mode "forFlight" with packageId adds just enough for that loaded package\'s destination leg — liters = required fuel for the great-circle distance (weight-proportional burn model) minus what is already in the tank.',
         operationId: 'refuelPlane',
         parameters: [
           { name: 'planeId', in: 'path', required: true, schema: { type: 'string' } },
         ],
+        requestBody: {
+          required: false,
+          content: {
+            'application/json': {
+              schema: { $ref: '#/components/schemas/RefuelRequest' },
+            },
+          },
+        },
         responses: {
           200: {
-            description: 'Refueled — full state snapshot (fuel at max, cash reduced by the cost)',
+            description: 'Refueled — full state snapshot (fuel raised by exactly the added liters, cash reduced by the cost)',
             content: { 'application/json': { schema: { $ref: '#/components/schemas/StateSnapshot' } } },
           },
+          400: {
+            description: 'Invalid body (not an object, unknown field, unknown mode, or forFlight without packageId)',
+            content: { 'application/json': { schema: { $ref: '#/components/schemas/Error' } } },
+          },
           404: {
-            description: 'Unknown plane id',
+            description: 'Unknown plane id (or unknown package id in forFlight mode)',
             content: { 'application/json': { schema: { $ref: '#/components/schemas/Error' } } },
           },
           409: {
-            description: 'Plane is flying, or cash is insufficient for the fill-up',
+            description:
+              'Plane is flying, the package is not loaded on this plane (or is expired), the leg does not fit a full tank, or cash is insufficient for the refuel',
             content: { 'application/json': { schema: { $ref: '#/components/schemas/Error' } } },
           },
         },
@@ -376,11 +390,12 @@ export const openApiSpec = {
           label: { type: 'string', description: 'Display name (e.g. "ATR 72-600").' },
           price: { type: 'number', description: 'Market price in € (buy cost; sell pays out sellFraction × this).' },
           maxFuel: { type: 'number', description: 'Fuel capacity, liters.' },
-          burnPerKm: { type: 'number', description: 'Cruise fuel burn, liters/km.' },
+          burnPerKm: { type: 'number', description: 'Cruise fuel burn at a full tank, liters/km (v0.16.0 weighted model calibrates to this).' },
+          emptyWeightKg: { type: 'number', description: 'Operating empty weight, kg — with burnPerKm and maxFuel it drives the v0.16.0 weight-proportional burn model.' },
           speedKmh: { type: 'number', description: 'Cruise speed, km/h.' },
           capacity: { type: 'integer', description: 'Cargo slot capacity — packages that can be loaded on one plane (v0.12.0).' },
         },
-        required: ['model', 'label', 'price', 'maxFuel', 'burnPerKm', 'speedKmh', 'capacity'],
+        required: ['model', 'label', 'price', 'maxFuel', 'burnPerKm', 'emptyWeightKg', 'speedKmh', 'capacity'],
       },
       AccountState: {
         type: 'object',
@@ -440,6 +455,22 @@ export const openApiSpec = {
         },
         required: ['planeId'],
       },
+      RefuelRequest: {
+        type: 'object',
+        description:
+          'Optional refuel body (v0.16.0) — omit it entirely or send {} to fill the tank; both fields are optional.',
+        properties: {
+          mode: {
+            enum: ['full', 'forFlight'],
+            description:
+              '"full" (default) fills the tank to maxFuel; "forFlight" adds just enough fuel for one loaded package\'s destination leg.',
+          },
+          packageId: {
+            type: 'string',
+            description: 'Required with mode "forFlight": a package LOADED on this plane — its destIcao is the refuel target.',
+          },
+        },
+      },
       Error: {
         type: 'object',
         properties: {

lib/sim/engine.test.ts

@@ -9,7 +9,7 @@ import { loadAirportsGeoJson } from '@/lib/airports';
 import { haversineKm } from '@/lib/geo';
 import { PLANE_TYPES } from '@/lib/game/catalog';
 import { MARKET_TARGET_OPEN_PACKAGES, mulberry32 } from '@/lib/game/seed';
-import { arrivalTimeFor } from './movement';
+import { arrivalTimeFor, fuelAtWeighted } from './movement';
 import {
   clampTimeScale,
   deliverPackages,
@@ -182,7 +182,8 @@ describe('deliverPackages (v0.12.0 arrival delivery)', () => {
     expect(plane.locationIcao).toBe(TO);
     expect(plane.lat).toBe(to.lat);
     expect(plane.lon).toBe(to.lon);
-    expect(plane.fuel).toBeCloseTo(Math.max(0, type.maxFuel - type.burnPerKm * km), 6); // remaining fuel
+    // Remaining fuel per the v0.16.0 weight-proportional burn model (closed form).
+    expect(plane.fuel).toBeCloseTo(fuelAtWeighted(type.maxFuel, type.burnPerKm, type.emptyWeightKg, type.maxFuel, km, 1), 6);
     expect(plane.departureSimTime).toBeNull();
     expect(plane.destIcao).toBeNull(); // flight context cleared on landing
 
@@ -236,6 +237,80 @@ describe('deliverPackages (v0.12.0 arrival delivery)', () => {
   });
 });
 
+describe('auto-slow to 1× when the last plane lands (ISS-011)', () => {
+  const FROM = 'EDDF';
+  const TO = 'LEMD';
+
+  // Starter flying EDDF→LEMD with departureSimTime set so its arrival is EXACTLY T0 —
+  // any advancing tick past T0 finalizes it. timeScale is the value under test.
+  async function setupLanding(name: string, timeScale: number) {
+    const inst = await freshDb(name);
+    const fc = await loadAirportsGeoJson();
+    const from = fc.features.find((f) => f.properties.icao === FROM)!.properties;
+    const to = fc.features.find((f) => f.properties.icao === TO)!.properties;
+    const km = haversineKm(from.lat, from.lon, to.lat, to.lon);
+    const type = PLANE_TYPES.atr72;
+
+    await inst.db.update(schema.simState).set({ timeScale });
+    await inst.db.update(schema.planes)
+      .set({ status: 'flying', destIcao: TO, departureSimTime: T0 - travelMs(km, type.speedKmh), fuel: type.maxFuel })
+      .where(eq(schema.planes.id, 'plane-starter'));
+
+    return { inst, from, km, type };
+  }
+
+  it('last plane lands → stored timeScale becomes 1', async () => {
+    const { inst } = await setupLanding('autoslow-last.db', 1000);
+    vi.setSystemTime(T0 + 2_000); // one full clamped tick at scale 1000 → clock T0+2e6 ≥ arrival (T0)
+
+    const sim = await tickOnce(inst);
+
+    expect(sim.timeScale).toBe(1); // persisted on the sim_state row…
+    expect((await inst.db.select().from(schema.simState))[0].timeScale).toBe(1); // …and visible to the next snapshot
+    expect((await inst.db.select().from(schema.planes))[0].status).toBe('available'); // landing itself unchanged
+  });
+
+  it('a landing while another plane is still flying → no change', async () => {
+    const { inst, from, type } = await setupLanding('autoslow-other.db', 1000);
+    // A second plane on the same route departing at T0 — arrives far after this tick's clock.
+    await inst.db.insert(schema.planes).values({
+      id: 'p-b', model: 'atr72', status: 'flying', fuel: type.maxFuel, maxFuel: type.maxFuel,
+      locationIcao: FROM, destIcao: TO, lat: from.lat, lon: from.lon, departureSimTime: T0,
+    });
+
+    vi.setSystemTime(T0 + 2_000);
+    const sim = await tickOnce(inst);
+
+    expect(sim.timeScale).toBe(1000); // p-b still in flight — no auto-slow
+    const byId = new Map((await inst.db.select().from(schema.planes)).map((p) => [p.id, p.status]));
+    expect(byId.get('plane-starter')).toBe('available'); // the starter did land…
+    expect(byId.get('p-b')).toBe('flying'); // …but the fleet is not idle
+  });
+
+  it('already at 1× → stays 1', async () => {
+    const { inst } = await setupLanding('autoslow-one.db', 1);
+    vi.setSystemTime(T0 + 2_000); // one tick at scale 1 advances 2e3 game ms — past the T0 arrival
+
+    const sim = await tickOnce(inst);
+
+    expect(sim.timeScale).toBe(1);
+    expect((await inst.db.select().from(schema.planes))[0].status).toBe('available');
+  });
+
+  it('paused sim with all planes landed → no change', async () => {
+    const inst = await freshDb('autoslow-paused.db');
+    // The fleet is fully grounded (the seeded starter) — a paused tick must not touch the
+    // scale even though "no plane in flight" holds: the trigger requires a landing this tick.
+    await inst.db.update(schema.simState).set({ timeScale: 1000, paused: true });
+
+    vi.setSystemTime(T0 + 5_000);
+    const sim = await tickOnce(inst);
+
+    expect(sim.timeScale).toBe(1000); // no landing processed while paused → trigger never fires
+    expect((await inst.db.select().from(schema.planes))[0].status).toBe('available');
+  });
+});
+
 describe('spawnOpenPackages', () => {
   it('tops the market up to MARKET_TARGET_OPEN_PACKAGES using the shared seed builder', async () => {
     const inst = await freshDb('spawn.db');

lib/sim/engine.ts

@@ -12,7 +12,7 @@ import {
   type Rng,
   type SeedAirport,
 } from '@/lib/game/seed';
-import { arrivalTimeFor, fuelAt } from './movement';
+import { arrivalTimeFor, fuelAtWeighted } from './movement';
 
 // Server-authoritative sim engine (v0.7.0) — tick-on-read: there is NO background
 // timer. Every read/action endpoint calls tickNow() first; the clock advances by
@@ -71,17 +71,33 @@ export async function tickOnce(inst: GameDb): Promise<schema.SimStateRow> {
   const advanceMs = sim.paused ? 0 : Math.min(elapsed, MAX_TICK_ELAPSED_MS) * sim.timeScale;
   const clockMs = Math.round(sim.clockMs + advanceMs);
 
+  let landedThisTick = 0;
   if (advanceMs > 0) {
     await expirePackages(inst, clockMs);
-    await deliverPackages(inst, clockMs);
+    // ISS-011: remember the landings so the tick can auto-slow to 1× when this was
+    // the last plane in flight.
+    landedThisTick = await deliverPackages(inst, clockMs);
     await spawnOpenPackages(inst, clockMs);
     // AFTER delivery on purpose: a plane that just landed gets work spawned
     // at its new location within the same tick.
     await spawnCoveragePackages(inst, clockMs);
   }
 
+  const sets: Partial<Pick<schema.SimStateRow, 'clockMs' | 'lastRealTickMs' | 'timeScale'>> = {
+    clockMs,
+    lastRealTickMs: nowMs,
+  };
+  // Auto-slow (ISS-011): when ≥1 plane landed this tick and NO plane remains in flight,
+  // drop the stored timeScale to 1× — persisted here so the UI slider reflects it on the
+  // next snapshot. Arrival-triggered by design: a grounded fleet at high scale is left
+  // alone (the player speeds up manually again; there is no auto-restore).
+  if (landedThisTick > 0 && !sim.paused) {
+    const flying = await inst.db.select().from(schema.planes).where(eq(schema.planes.status, 'flying'));
+    if (flying.length === 0) sets.timeScale = MIN_TIME_SCALE;
+  }
+
   // Persist lastRealTickMs even when nothing advanced — it is the tick anchor.
-  await inst.db.update(schema.simState).set({ clockMs, lastRealTickMs: nowMs });
+  await inst.db.update(schema.simState).set(sets);
   await persist(inst);
   const updated = (await inst.db.select().from(schema.simState))[0];
   if (!updated) throw new Error('sim_state row missing after tick');
@@ -131,14 +147,14 @@ export async function deliverPackages(inst: GameDb, clockMs: number): Promise<nu
     const distanceKm = haversineKm(from.lat, from.lon, to.lat, to.lon);
     if (clockMs < arrivalTimeFor(p.departureSimTime, distanceKm, type.speedKmh)) continue;
 
-    // Arrived: progress is exactly 1 here, so remaining fuel is the full-leg burn.
+    // Arrived: progress is exactly 1 here, so remaining fuel is the full-leg weighted burn.
     await inst.db.update(schema.planes)
       .set({
         status: 'available',
         locationIcao: to.icao,
         lat: to.lat,
         lon: to.lon,
-        fuel: fuelAt(p.fuel, type.burnPerKm, distanceKm, 1),
+        fuel: fuelAtWeighted(p.fuel, type.burnPerKm, type.emptyWeightKg, type.maxFuel, distanceKm, 1),
         departureSimTime: null,
         destIcao: null,
       })

lib/sim/movement.test.ts

@@ -1,12 +1,23 @@
 import { describe, expect, it } from 'vitest';
 import { haversineKm } from '@/lib/geo';
-import { arrivalTimeFor, fuelAt, positionAt, progressAt, travelDurationMs } from './movement';
+import {
+  arrivalTimeFor,
+  burnRateConstant,
+  FUEL_DENSITY_KG_PER_L,
+  fuelAtWeighted,
+  positionAt,
+  progressAt,
+  requiredFuelFor,
+  travelDurationMs,
+} from './movement';
 
 // Synthetic in-flight fixtures — no DB needed: everything is a pure function of
 // the sim clock. ATR 72-600 numbers from lib/game/catalog.ts.
 const DEP = 1_750_000_000_000; // departure sim time (ms)
 const SPEED = 510; // km/h
-const BURN = 1.75; // L/km
+const BURN = 1.75; // L/km at a full tank
+const WE = 9_300; // kg, operating empty weight
+const TANK = 6_300; // liters, full tank
 
 // Frankfurt → Madrid, real coordinates from the CSV dataset.
 const FROM = { lat: 50.0333, lon: 8.5706 };
@@ -96,17 +107,53 @@ describe('positionAt (great-circle slerp)', () => {
   });
 });
 
-describe('fuelAt', () => {
+describe('weighted burn model (v0.16.0)', () => {
-  it('burns fuel proportionally to distance flown', () => {
+  it('calibrates so a full tank burns exactly the old constant rate', () => {
-    const start = 6_300; // full ATR tank
+    const k = burnRateConstant(BURN, WE, TANK);
-    expect(fuelAt(start, BURN, KM, 0)).toBe(start);
+    expect(k * (WE + FUEL_DENSITY_KG_PER_L * TANK)).toBeCloseTo(BURN, 12);
-    expect(fuelAt(start, BURN, KM, 0.5)).toBeCloseTo(start - BURN * KM / 2, 9);
+
-    expect(fuelAt(start, BURN, KM, 1)).toBeCloseTo(start - BURN * KM, 9);
+    // Over a short hop from full, weighted ≈ constant — divergence only grows as fuel drops off.
+    const d = 100;
+    const consumed = TANK - fuelAtWeighted(TANK, BURN, WE, TANK, d, 1);
+    expect(Math.abs(consumed - BURN * d)).toBeLessThan(1); // < 1 L over 100 km from full
+  });
+
+  it('consumption matches numeric integration of r(F) = k·(We + ρF)', () => {
+    const k = burnRateConstant(BURN, WE, TANK);
+    const rho = FUEL_DENSITY_KG_PER_L;
+    // Euler-integrate dF/dx = −k(We + ρF) from a full tank over the whole leg.
+    const steps = 200_000;
+    const h = KM / steps;
+    let f = TANK;
+    for (let i = 0; i < steps; i++) f -= k * (WE + rho * f) * h;
+    expect(Math.abs(fuelAtWeighted(TANK, BURN, WE, TANK, KM, 1) - f)).toBeLessThan(0.001); // Euler drift is sub-milliliter here
+  });
+
+  it('requiredFuelFor is zero for a zero leg and strictly increasing in distance', () => {
+    expect(requiredFuelFor(BURN, WE, TANK, 0)).toBe(0);
+    let prev = requiredFuelFor(BURN, WE, TANK, 100);
+    for (const d of [500, 1_000, 2_000, 3_000, 4_000]) {
+      const cur = requiredFuelFor(BURN, WE, TANK, d);
+      expect(cur).toBeGreaterThan(prev);
+      prev = cur;
+    }
+  });
+
+  it('a lighter start burns less over the same distance', () => {
+    const burnFromFull = TANK - fuelAtWeighted(TANK, BURN, WE, TANK, KM, 1);
+    const burnFromHalf = TANK / 2 - fuelAtWeighted(TANK / 2, BURN, WE, TANK, KM, 1);
+    expect(burnFromFull).toBeGreaterThan(burnFromHalf);
+  });
+
+  it('starting with exactly the required fuel arrives on empty', () => {
+    const req = requiredFuelFor(BURN, WE, TANK, KM);
+    expect(fuelAtWeighted(req, BURN, WE, TANK, KM, 1)).toBeCloseTo(0, 6);
   });
 
   it('clamps at zero instead of going negative', () => {
-    expect(fuelAt(100, BURN, 1_000, 1)).toBe(0); // needs 1750 L, has 100
+    expect(fuelAtWeighted(100, BURN, WE, TANK, KM, 1)).toBe(0); // needs ~2800 L from full, has 100
-    expect(fuelAt(100, BURN, 1_000, 0.01)).toBeCloseTo(100 - 17.5, 9);
+    expect(fuelAtWeighted(TANK, BURN, WE, TANK, KM, 0)).toBe(TANK);
+    expect(fuelAtWeighted(TANK, BURN, WE, TANK, 0, 1)).toBe(TANK);
   });
 
   it('composes with progressAt for a just-before-arrival snapshot', () => {
@@ -114,9 +161,6 @@ describe('fuelAt', () => {
     const clock = DEP + duration - 1; // one ms before arrival
     const p = positionAt(FROM.lat, FROM.lon, TO.lat, TO.lon, progressAt(DEP, KM, SPEED, clock));
     expect(haversineKm(p.lat, p.lon, TO.lat, TO.lon)).toBeGreaterThan(0); // not yet at the gate
-    expect(fuelAt(6_300, BURN, KM, progressAt(DEP, KM, SPEED, clock))).toBeCloseTo(
+    expect(fuelAtWeighted(TANK, BURN, WE, TANK, KM, progressAt(DEP, KM, SPEED, clock))).toBeGreaterThan(0);
-      6_300 - BURN * KM * (1 - 1 / duration),
-      6,
-    );
   });
 });

lib/sim/movement.ts

@@ -65,8 +65,56 @@ export function positionAt(
   };
 }
 
-// Fuel remaining after flying `progress` of a leg of distanceKm. Clamped at 0 —
+// --- Weight-proportional fuel burn (v0.16.0) ---
-// range exhaustion is not modeled yet (fuel management/refueling comes later).
+//
-export function fuelAt(startFuel: number, burnPerKm: number, distanceKm: number, progress: number): number {
+// The instantaneous burn rate is proportional to total weight: r(F) = k·(We + ρF) L/km,
-  return Math.max(0, startFuel - burnPerKm * distanceKm * progress);
+// where We is the empty weight in kg, ρ the fuel density and F the current load in
+// liters — a heavier plane burns more per km. k is calibrated so that a FULL tank
+// burns exactly the catalog's constant burnPerKm: k = burnPerKm / (We + ρ·maxFuel),
+// so full-tank legs match the old model at departure and only diverge as fuel (and
+// weight) drops off in flight. Closed forms of dF/dx = −k(We + ρF):
+//   fuel after distance D from F₀:        (F₀ + We/ρ)·e^{−kρD} − We/ρ
+//   consumption over D:                   (F₀ + We/ρ)·(1 − e^{−kρD})
+//   fuel required to cover D arriving with 0, independent of F₀: (We/ρ)(e^{kρD} − 1)
+
+// Jet-A1 density in kg/L — converts a liter load into its weight contribution.
+export const FUEL_DENSITY_KG_PER_L = 0.8;
+
+// Calibration constant k for one plane type (see the model note above).
+export function burnRateConstant(burnPerKm: number, emptyWeightKg: number, maxFuel: number): number {
+  return burnPerKm / (emptyWeightKg + FUEL_DENSITY_KG_PER_L * maxFuel);
+}
+
+// Fuel remaining after flying `progress` of a leg of distanceKm from startFuel under the
+// weighted model. Clamped at 0 — range exhaustion is not modeled (a plane that runs dry
+// limps to the gate on fumes, same as before).
+export function fuelAtWeighted(
+  startFuel: number,
+  burnPerKm: number,
+  emptyWeightKg: number,
+  maxFuel: number,
+  distanceKm: number,
+  progress: number,
+): number {
+  const d = distanceKm * progress;
+  if (d <= 0) return startFuel;
+  const k = burnRateConstant(burnPerKm, emptyWeightKg, maxFuel);
+  const rho = FUEL_DENSITY_KG_PER_L;
+  const f = (startFuel + emptyWeightKg / rho) * Math.exp(-k * rho * d) - emptyWeightKg / rho;
+  return Math.max(0, f);
+}
+
+// Total fuel required to cover distanceKm arriving with an empty tank — independent of the
+// starting load. A leg is flyable from a plane iff its current fuel covers this amount; it
+// fits in the aircraft at all iff this does not exceed the tank capacity.
+export function requiredFuelFor(
+  burnPerKm: number,
+  emptyWeightKg: number,
+  maxFuel: number,
+  distanceKm: number,
+): number {
+  if (distanceKm <= 0) return 0;
+  const k = burnRateConstant(burnPerKm, emptyWeightKg, maxFuel);
+  const rho = FUEL_DENSITY_KG_PER_L;
+  return (emptyWeightKg / rho) * (Math.exp(k * rho * distanceKm) - 1);
 }

lib/useGameAction.ts

@@ -0,0 +1,53 @@
+'use client';
+
+import { useCallback, useEffect, useState } from 'react';
+import type { StateSnapshot } from '@/lib/game/state';
+
+// ISS-021 (v0.20.0) — shared action runner for the side panes (extracted verbatim from
+// RightPane.runAction when the On board section moved to LeftPane). POSTs an action endpoint;
+// every success returns the FULL post-action snapshot (v0.8.0 convention), pushed into the
+// shared shell state immediately via applySnapshot so the UI updates without waiting for the
+// next poll tick. A non-2xx {error} body becomes the pane's inline error AND is mirrored to
+// the shell as a bottom-right toast via onError (ISS-008 — both surfaces by design). Buttons
+// are disabled while a request is in flight, so at most one action runs per pane at a time.
+export function useGameAction(
+  state: StateSnapshot | null,
+  applySnapshot: (snapshot: StateSnapshot) => void,
+  onError?: (message: string) => void,
+): { runAction: (path: string, body?: unknown) => Promise<void>; busy: boolean; actionError: string | null } {
+  const [busy, setBusy] = useState(false);
+  // Inline error from a failed action — auto-clears on the next successful poll (the shell's
+  // snapshot prop changes every tick) or the next successful action.
+  const [actionError, setActionError] = useState<string | null>(null);
+  useEffect(() => {
+    if (state !== null) setActionError(null);
+  }, [state]);
+
+  const runAction = useCallback(
+    async (path: string, body?: unknown) => {
+      if (busy) return;
+      setBusy(true);
+      try {
+        const res = await fetch(path, {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: body === undefined ? undefined : JSON.stringify(body),
+          cache: 'no-store',
+        });
+        const data = (await res.json()) as StateSnapshot & { error?: string };
+        if (!res.ok) throw new Error(data.error ?? `HTTP ${res.status}`);
+        setActionError(null);
+        applySnapshot(data);
+      } catch (err) {
+        const message = err instanceof Error ? err.message : String(err);
+        setActionError(message); // inline pane error stays…
+        onError?.(message); // …and the shell mirrors it as a bottom-right toast (ISS-008)
+      } finally {
+        setBusy(false);
+      }
+    },
+    [applySnapshot, busy, onError],
+  );
+
+  return { runAction, busy, actionError };
+}

lib/useSimClock.test.ts

@@ -0,0 +1,49 @@
+import { describe, expect, it } from 'vitest';
+import { advanceSimClock, type SimClockAnchor } from './useSimClock';
+
+// ISS-007 (v0.16.1) — the pure extrapolation core of lib/useSimClock.ts. The hook itself is a
+// thin setInterval + re-sync wrapper covered by e2e (panes.spec.ts "ticks smoothly between polls");
+// this suite pins the math: game time advances real-time × timeScale, frozen while paused.
+
+const anchor = (over: Partial<SimClockAnchor> = {}): SimClockAnchor => ({
+  clockMs: 1_750_000_000_000,
+  at: 1_000_000,
+  timeScale: 1,
+  paused: false,
+  ...over,
+});
+
+describe('advanceSimClock', () => {
+  it('advances by exactly elapsed real-time × timeScale while running', () => {
+    expect(advanceSimClock(anchor(), 1_001_000)).toBe(1_750_000_000_000 + 1_000); // scale 1: 1 s real = 1 s game
+    expect(advanceSimClock(anchor({ timeScale: 25 }), 1_002_500)).toBe(1_750_000_000_000 + 62_500);
+    // The e2e scenario: scale 1000, 2.5 s real → 2 500 game seconds.
+    expect(advanceSimClock(anchor({ timeScale: 1000 }), 1_002_500)).toBe(1_750_000_000_000 + 2_500_000);
+  });
+
+  it('returns the anchor value exactly at zero elapsed', () => {
+    expect(advanceSimClock(anchor({ timeScale: 1000 }), 1_000_000)).toBe(1_750_000_000_000);
+  });
+
+  it('is frozen while paused regardless of elapsed or scale', () => {
+    const a = anchor({ timeScale: 1000, paused: true });
+    expect(advanceSimClock(a, 1_000_000)).toBe(1_750_000_000_000);
+    expect(advanceSimClock(a, 2_000_000)).toBe(1_750_000_000_000); // a full second later — still frozen
+  });
+
+  it('clamps to the anchor value when nowMs is before the anchor (clock skew), never backwards', () => {
+    expect(advanceSimClock(anchor({ timeScale: 1000 }), 999_999)).toBe(1_750_000_000_000);
+    expect(advanceSimClock(anchor({ paused: true }), 999_999)).toBe(1_750_000_000_000);
+  });
+
+  it('mirrors the server tick model (tickOnce): advance = elapsed × timeScale while actively polled', () => {
+    // lib/sim/engine.ts: clockMs += min(now − lastRealTickMs, MAX_TICK_ELAPSED_MS) × timeScale.
+    // For gaps under the 2 s clamp the client extrapolation is exactly the server's own formula.
+    const scale = 50;
+    for (const gap of [1, 250, 999, 1_999]) {
+      expect(advanceSimClock(anchor({ timeScale: scale }), 1_000_000 + gap)).toBe(
+        1_750_000_000_000 + gap * scale,
+      );
+    }
+  });
+});

lib/useSimClock.ts

@@ -0,0 +1,68 @@
+'use client';
+
+import { useEffect, useRef, useState } from 'react';
+import type { StateSnapshot } from './game/state';
+
+// ISS-007 (v0.16.1): the sim clock ticks smoothly on the CLIENT between polls instead of
+// jumping once per snapshot. The server's authoritative rate is exactly real-time × timeScale
+// (tickOnce in lib/sim/engine.ts: advance = min(elapsed, MAX_TICK_ELAPSED_MS) × timeScale), so
+// client-side extrapolation mirrors the server's own model. Every new snapshot re-anchors to
+// server truth, bounding any drift by network latency only.
+
+export interface SimClockAnchor {
+  // Server truth at anchor time — the snapshot's simState.clockMs.
+  clockMs: number;
+  // Date.now() when that snapshot was received.
+  at: number;
+  timeScale: number;
+  paused: boolean;
+}
+
+// Pure core of the extrapolation — mirrors tickOnce: while running, game time advances by
+// real-time × timeScale; while paused it is frozen (advance 0). nowMs before `at` clamps to
+// the anchor value instead of going backwards. Unit-testable in node.
+export function advanceSimClock(anchor: SimClockAnchor, nowMs: number): number {
+  if (anchor.paused) return anchor.clockMs;
+  return anchor.clockMs + Math.max(0, nowMs - anchor.at) * anchor.timeScale;
+}
+
+// ~10 fps display refresh — smooth for a seconds-precision wall clock without busy re-renders.
+const DISPLAY_TICK_MS = 100;
+
+export interface SimClockControls {
+  // EFFECTIVE controls (optimistic pending scale / current pause), not the snapshot's:
+  // UI changes take effect on click/drag without waiting for a confirming snapshot.
+  timeScale: number;
+  paused: boolean;
+}
+
+// Returns the display clockMs to render, or null until the first snapshot arrives.
+export function useSimClock(snapshot: StateSnapshot | null, controls: SimClockControls): number | null {
+  const anchorRef = useRef<SimClockAnchor | null>(null);
+  const [displayMs, setDisplayMs] = useState<number | null>(null);
+
+  // Re-sync on every snapshot AND effective-control change: snap to server truth. The snapshot
+  // object is fresh per poll (useGameState), so this runs once per poll cycle as well.
+  useEffect(() => {
+    if (!snapshot) return;
+    anchorRef.current = {
+      clockMs: snapshot.simState.clockMs,
+      at: Date.now(),
+      timeScale: controls.timeScale,
+      paused: controls.paused,
+    };
+    setDisplayMs(advanceSimClock(anchorRef.current, Date.now()));
+  }, [snapshot, controls.timeScale, controls.paused]);
+
+  useEffect(() => {
+    const id = setInterval(() => {
+      const anchor = anchorRef.current;
+      if (anchor) setDisplayMs(advanceSimClock(anchor, Date.now()));
+    }, DISPLAY_TICK_MS);
+    return () => clearInterval(id);
+  }, []);
+
+  // First paint after a snapshot arrives happens before the re-sync effect runs — show the
+  // snapshot value directly so the clock never blanks for a frame.
+  return displayMs ?? (snapshot ? snapshot.simState.clockMs : null);
+}

lib/useToasts.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, it } from 'vitest';
+import { MAX_TOASTS, pushToast, type Toast } from './useToasts';
+
+// ISS-008 (v0.17.0): the toast queue's pure core — append + cap at MAX_TOASTS dropping the
+// oldest. The hook itself is a thin useState wrapper around this (auto-dismiss timers are
+// plain setTimeout, covered by e2e via the visible toasts).
+
+const toast = (id: number, message: string): Toast => ({ id, kind: 'info', message });
+
+describe('pushToast', () => {
+  it('appends to an empty queue and preserves order', () => {
+    expect(pushToast([], toast(1, 'a'))).toEqual([toast(1, 'a')]);
+    expect(pushToast([toast(1, 'a')], toast(2, 'b'))).toEqual([toast(1, 'a'), toast(2, 'b')]);
+  });
+
+  it('keeps the newest MAX_TOASTS entries, dropping the oldest beyond the cap', () => {
+    let queue: Toast[] = [];
+    for (let id = 1; id <= MAX_TOASTS + 2; id++) queue = pushToast(queue, toast(id, `m${id}`));
+    expect(queue).toEqual([toast(MAX_TOASTS - 1, 'm3'), toast(MAX_TOASTS, 'm4'), toast(MAX_TOASTS + 1, 'm5'), toast(MAX_TOASTS + 2, 'm6')]);
+  });
+
+  it('does not mutate the input queue', () => {
+    const before = [toast(1, 'a')];
+    pushToast(before, toast(2, 'b'));
+    expect(before).toEqual([toast(1, 'a')]);
+  });
+});

lib/useToasts.ts

@@ -0,0 +1,50 @@
+'use client';
+
+import { useCallback, useRef, useState } from 'react';
+
+// ISS-008 (v0.17.0): transient toast notifications — a bottom-right stack for action errors
+// and game events derived from snapshot diffs. Each toast auto-dismisses after TOAST_TTL_MS;
+// the queue is capped at MAX_TOASTS (oldest dropped) so an event burst can't fill the corner.
+
+export type ToastKind = 'error' | 'info';
+
+export interface Toast {
+  id: number;
+  kind: ToastKind;
+  message: string;
+}
+
+export const TOAST_TTL_MS = 5_000;
+export const MAX_TOASTS = 4;
+
+// Pure core (unit-tested): append a toast, dropping the oldest beyond the cap.
+export function pushToast(toasts: Toast[], toast: Toast): Toast[] {
+  return [...toasts, toast].slice(-MAX_TOASTS);
+}
+
+export interface UseToastsResult {
+  toasts: Toast[];
+  push: (kind: ToastKind, message: string) => void;
+  dismiss: (id: number) => void;
+}
+
+export function useToasts(): UseToastsResult {
+  const [toasts, setToasts] = useState<Toast[]>([]);
+  const nextIdRef = useRef(1);
+
+  // Functional update — a late timer for an already-dismissed/dropped id is a no-op.
+  const dismiss = useCallback((id: number) => {
+    setToasts((current) => current.filter((t) => t.id !== id));
+  }, []);
+
+  const push = useCallback(
+    (kind: ToastKind, message: string) => {
+      const toast: Toast = { id: nextIdRef.current++, kind, message };
+      setToasts((current) => pushToast(current, toast));
+      setTimeout(() => dismiss(toast.id), TOAST_TTL_MS);
+    },
+    [dismiss],
+  );
+
+  return { toasts, push, dismiss };
+}

package.json

@@ -1,6 +1,6 @@
 {
   "name": "flight-ops",
-  "version": "0.15.0",
+  "version": "0.20.0",
   "private": true,
   "scripts": {
     "dev": "next dev -p 3000",