lib/game/research.test.ts

@@ -6,9 +6,11 @@ import { eq } from 'drizzle-orm'
 import { openGameDb, type GameDb } from '@/lib/db/client'
 import * as schema from '@/lib/db/schema'
 import { BUILD_PART_COST, MAX_LEVEL, upgradeCost } from './ship-costs'
-import { buildSystem, getShipState, upgradeSystem, type ShipState } from './ship'
+import { buildSystem, getShipState, spendItems, upgradeSystem, type ShipState } from './ship'
 import { TECHS } from './tech'
-import { getTechState, researchTech } from './research'
+import { SCHEMA_VERSION } from './save'
+import { getTechState, researchTech, resolveResearchTask } from './research'
+import type { Task } from './tasks'
 
 const dirs: string[] = []
 
@@ -145,3 +147,74 @@ describe('gating of ship actions', () => {
     expect(systemOf(state, 'REACTOR').level).toBe(MAX_LEVEL + 1)
   })
 })
+
+// --- A/B: resolver vs the legacy immediate action (Task 4a) ---------------------------
+const T0 = '2026-10-01T00:00:00.000Z'
+
+// Stamped save (no backfill), the full tech tree, nothing researched yet. Identical build
+// per world → ids line up.
+async function buildResearchFixture(db: GameDb): Promise<void> {
+  const [save] = await db.db.insert(schema.saves).values({ seed: '42', turn: 0, createdAt: T0, schemaVersion: SCHEMA_VERSION }).returning()
+  for (const def of TECHS) {
+    await db.db.insert(schema.tech).values({ saveId: save.id, slug: def.slug, name: def.name, costKind: def.costKind, costQty: def.costQty, prerequisites: def.prereqs.join(','), effect: def.effect })
+  }
+}
+
+const task = (payload: object): Task =>
+  ({ id: 0, saveId: 0, type: 'RESEARCH', payload: JSON.stringify(payload), leadCrewId: 0, helpers: [], duration: 0, remaining: 0, status: 'ACTIVE', queuedAtTurn: 0 })
+
+async function snapshot(db: GameDb): Promise<string> {
+  const [saves, systems, routes, planets, inventory, crew, ship, tech, missions, events] = await Promise.all([
+    db.db.select({ id: schema.saves.id, seed: schema.saves.seed, turn: schema.saves.turn, schemaVersion: schema.saves.schemaVersion }).from(schema.saves),
+    db.db.select().from(schema.solarSystems),
+    db.db.select().from(schema.jumpRoutes),
+    db.db.select().from(schema.planets),
+    db.db.select().from(schema.inventoryItems),
+    db.db.select().from(schema.crew),
+    db.db.select().from(schema.shipSystems),
+    db.db.select().from(schema.tech),
+    db.db.select().from(schema.missions),
+    db.db.select({ id: schema.events.id, turn: schema.events.turn, type: schema.events.type, message: schema.events.message }).from(schema.events),
+  ])
+  return JSON.stringify({ saves, systems, routes, planets, inventory, crew, ship, tech, missions, events })
+}
+
+describe('resolveResearchTask (A/B against researchTech)', () => {
+  // A = legacy immediate action (validates, deducts the cost, +1 turn, marks researched,
+  // event). B = the queued shape: the cost was deducted at queue time (Task 3), the tick
+  // advanced the turn (Task 4b), then the resolver marks the tech. Same starting world →
+  // byte-identical end states.
+
+  it('lands exactly what researchTech lands', async () => {
+    const { db: a } = await freshFile()
+    const { db: b } = await freshFile()
+    await buildResearchFixture(a)
+    await buildResearchFixture(b)
+    await addItem(a, 'resource', 'IRON ORE', 2) // NAVIGATION AI costs 2 resources
+    await addItem(b, 'resource', 'IRON ORE', 2)
+
+    const [navA] = await a.db.select().from(schema.tech).where(eq(schema.tech.slug, 'NAV_AI'))
+    const [navB] = await b.db.select().from(schema.tech).where(eq(schema.tech.slug, 'NAV_AI'))
+    await researchTech(a, navA.id)
+    await spendItems(b, 1, 'resource', 2) // the queue-time deduction
+    await b.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+    await resolveResearchTask(b, task({ techId: navB.id }))
+
+    expect(await snapshot(b)).toEqual(await snapshot(a))
+    expect((await b.db.select().from(schema.tech)).find((t) => t.id === navB.id)?.researched).toBe(true)
+    const ev = (await b.db.select({ turn: schema.events.turn, type: schema.events.type, message: schema.events.message }).from(schema.events)).find((e) => e.type === 'research')!
+    expect(ev.turn).toBe(1)
+    expect(ev.message).toBe('Researched NAVIGATION AI (cost: 2× resources)')
+  })
+
+  it('guards: 404 unknown tech, 409 already researched (prereqs are monotone — no guard needed)', async () => {
+    const { db } = await freshFile()
+    await buildResearchFixture(db)
+    const [nav] = await db.db.select().from(schema.tech).where(eq(schema.tech.slug, 'NAV_AI'))
+    await db.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+
+    await expect(resolveResearchTask(db, task({ techId: 999 }))).rejects.toMatchObject({ status: 404, message: 'Unknown tech 999' })
+    await resolveResearchTask(db, task({ techId: nav.id }))
+    await expect(resolveResearchTask(db, task({ techId: nav.id }))).rejects.toMatchObject({ status: 409, message: 'NAVIGATION AI is already researched' })
+  })
+})

lib/game/research.ts

@@ -4,6 +4,7 @@ import { persist, type GameDb } from '@/lib/db/client'
 import { EFFECTS, TECHS, techStatus, type TechDto } from './tech'
 import { ensureSave } from './save'
 import { ShipError, spendItems } from './ship'
+import type { Task, TaskType } from './tasks'
 
 // Technology research: the SKILL TREE tab's read + action. Researching a tech costs inventory
 // items (oldest row first, like ship actions) plus a turn, and its unlock effect then gates or
@@ -46,8 +47,31 @@ export async function getTechState(db: GameDb): Promise<TechDto[]> {
   })
 }
 
+function syntheticTask(type: TaskType, payload: object): Task {
+  return { id: 0, saveId: 0, type, payload: JSON.stringify(payload), leadCrewId: 0, helpers: [], duration: 0, remaining: 0, status: 'ACTIVE', queuedAtTurn: 0 }
+}
+
+// RESEARCH — mark the payload's tech researched at the current turn. No cost here (deducted
+// at queue time — Task 3 — or by researchTech before delegating); no mission hooks (the
+// current action has none).
+export async function resolveResearchTask(db: GameDb, task: Task): Promise<void> {
+  await ensureSave(db)
+  const { techId } = JSON.parse(task.payload) as { techId: number }
+  const [save] = await db.db.select().from(schema.saves).limit(1)
+  const rows = await db.db.select().from(schema.tech)
+  const target = rows.find((t) => t.id === techId)
+  if (!target) throw new ResearchError(404, `Unknown tech ${techId}`)
+
+  const def = TECHS.find((t) => t.slug === target.slug)!
+  if (target.researched) throw new ResearchError(409, `${def.name} is already researched`)
+
+  await db.db.update(schema.tech).set({ researched: true }).where(eq(schema.tech.id, target.id))
+  await db.db.insert(schema.events).values({ saveId: save.id, turn: save.turn, type: 'research', message: `Researched ${def.name} (cost: ${def.costQty}× ${def.costKind === 'resource' ? 'resources' : 'parts'})`, createdAt: new Date().toISOString() })
+  await persist(db)
+}
+
 // Research one tech: validates prerequisites (409, naming what is missing) and the cost (422),
-// spends it from the cargo hold, marks it researched, costs a turn and writes an event.
+// spends it from the cargo hold, then delegates the unlock to the resolver at the new turn.
 export async function researchTech(db: GameDb, techId: number): Promise<TechDto[]> {
   await ensureSave(db)
   const [save] = await db.db.select().from(schema.saves).limit(1)
@@ -70,10 +94,8 @@ export async function researchTech(db: GameDb, techId: number): Promise<TechDto[
   }
 
   const turn = save.turn + 1
-  await db.db.update(schema.tech).set({ researched: true }).where(eq(schema.tech.id, target.id))
   await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, save.id))
-  await db.db.insert(schema.events).values({ saveId: save.id, turn, type: 'research', message: `Researched ${def.name} (cost: ${def.costQty}× ${def.costKind === 'resource' ? 'resources' : 'parts'})`, createdAt: new Date().toISOString() })
-  await persist(db)
+  await resolveResearchTask(db, syntheticTask('RESEARCH', { techId }))
 
   return getTechState(db)
 }

lib/game/save.test.ts

@@ -8,7 +8,8 @@ import * as schema from '@/lib/db/schema'
 import { generateStartingCrew, rollCrewMember, startingCrewRng } from './crew'
 import { BASE_CAPACITY, BASE_LEVEL, SHIP_TYPES } from './ship-costs'
 import { TECHS } from './tech'
-import { SCHEMA_VERSION, getCrewState, getSystemState, explorePlanet, getWorldState, jumpToSystem, type WorldState } from './save'
+import { SCHEMA_VERSION, getCrewState, getSystemState, explorePlanet, getWorldState, jumpToSystem, resolveJumpTask, resolveExploreTask, type WorldState } from './save'
+import type { Task } from './tasks'
 import { bodyRng, explorationRng, generatePlanets, rollExploration } from './world'
 
 const dirs: string[] = []
@@ -304,6 +305,140 @@ describe('explorePlanet crew finds', () => {
   })
 })
 
+// --- A/B: resolvers vs the legacy immediate actions (Task 4a) -------------------------
+//
+// Each test builds the identical deterministic fixture in two fresh files (seed '42',
+// stamped save → no backfill; ids line up across worlds) and compares their full state:
+// A = the legacy immediate action (validates, costs a turn, applies the effect);
+// B = the queued shape — the tick has advanced the turn (Task 4b) and the resolver
+// applies the effect (ship/research rows deduct the cost up front, as queueTask did at
+// queue time — Task 3). snapshot() normalizes every game table (wall-clock columns
+// excluded), so the two end states must be byte-identical.
+const T0 = '2026-10-01T00:00:00.000Z'
+
+async function buildWorldFixture(db: GameDb, outpostDiscovered = false): Promise<{ sys1: number; p0: number; p1: number }> {
+  const [save] = await db.db.insert(schema.saves).values({ seed: '42', turn: 0, createdAt: T0, schemaVersion: SCHEMA_VERSION }).returning()
+  const [s0] = await db.db.insert(schema.solarSystems).values({ saveId: save.id, name: 'Origin', x: 50, y: 50, discovered: true, isCurrent: true }).returning({ id: schema.solarSystems.id })
+  const [s1] = await db.db.insert(schema.solarSystems).values({ saveId: save.id, name: 'Outpost', x: 55, y: 50, discovered: outpostDiscovered }).returning({ id: schema.solarSystems.id })
+  await db.db.insert(schema.jumpRoutes).values({ fromSystem: s0.id, toSystem: s1.id })
+  await db.db.insert(schema.jumpRoutes).values({ fromSystem: s1.id, toSystem: s0.id })
+  const [p0] = await db.db.insert(schema.planets).values({ systemId: s0.id, parentId: null, name: 'Alder', type: 'ROCKY', hazard: false }).returning({ id: schema.planets.id })
+  const [p1] = await db.db.insert(schema.planets).values({ systemId: s1.id, parentId: null, name: 'Basalt', type: 'GAS', hazard: false }).returning({ id: schema.planets.id })
+  return { sys1: s1.id, p0: p0.id, p1: p1.id }
+}
+
+// The resolvers only read `type` + `payload` — tests mint stand-in rows with zeroed
+// identity fields, the same way the public functions' delegation does.
+const task = (type: 'JUMP' | 'EXPLORE', payload: object): Task =>
+  ({ id: 0, saveId: 0, type, payload: JSON.stringify(payload), leadCrewId: 0, helpers: [], duration: 0, remaining: 0, status: 'ACTIVE', queuedAtTurn: 0 })
+
+async function snapshot(db: GameDb): Promise<string> {
+  const [saves, systems, routes, planets, inventory, crew, ship, tech, missions, events] = await Promise.all([
+    db.db.select({ id: schema.saves.id, seed: schema.saves.seed, turn: schema.saves.turn, schemaVersion: schema.saves.schemaVersion }).from(schema.saves),
+    db.db.select().from(schema.solarSystems),
+    db.db.select().from(schema.jumpRoutes),
+    db.db.select().from(schema.planets),
+    db.db.select().from(schema.inventoryItems),
+    db.db.select().from(schema.crew),
+    db.db.select().from(schema.shipSystems),
+    db.db.select().from(schema.tech),
+    db.db.select().from(schema.missions),
+    db.db.select({ id: schema.events.id, turn: schema.events.turn, type: schema.events.type, message: schema.events.message }).from(schema.events),
+  ])
+  return JSON.stringify({ saves, systems, routes, planets, inventory, crew, ship, tech, missions, events })
+}
+
+describe('resolveJumpTask (A/B against jumpToSystem)', () => {
+  it('undiscovered target: lands exactly what jumpToSystem lands — move, discover, ring, event', async () => {
+    const { db: a } = await freshFile()
+    const { db: b } = await freshFile()
+    const fa = await buildWorldFixture(a)
+    const fb = await buildWorldFixture(b)
+
+    await jumpToSystem(a, fa.sys1) // legacy: validates, +1 turn, effect, event at turn 1
+    await b.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1)) // the tick's job (Task 4b)
+    await resolveJumpTask(b, task('JUMP', { systemId: fb.sys1, hops: 1 }))
+
+    expect(await snapshot(b)).toEqual(await snapshot(a))
+  })
+
+  it('discovered target: no ring — still byte-identical to jumpToSystem', async () => {
+    const { db: a } = await freshFile()
+    const { db: b } = await freshFile()
+    const fa = await buildWorldFixture(a, true)
+    const fb = await buildWorldFixture(b, true)
+
+    await jumpToSystem(a, fa.sys1)
+    await b.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+    await resolveJumpTask(b, task('JUMP', { systemId: fb.sys1, hops: 1 }))
+
+    expect(await snapshot(b)).toEqual(await snapshot(a))
+    expect(await b.db.select().from(schema.solarSystems)).toHaveLength(2) // no ring added
+  })
+
+  it('guards: 404 unknown system, 409 already-current', async () => {
+    const { db } = await freshFile()
+    const f = await buildWorldFixture(db)
+    await db.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+
+    await expect(resolveJumpTask(db, task('JUMP', { systemId: 999, hops: 1 }))).rejects.toMatchObject({ status: 404, message: 'Unknown system 999' })
+    await db.db.update(schema.solarSystems).set({ isCurrent: false }).where(eq(schema.solarSystems.id, 1))
+    await db.db.update(schema.solarSystems).set({ isCurrent: true }).where(eq(schema.solarSystems.id, f.sys1))
+    await expect(resolveJumpTask(db, task('JUMP', { systemId: f.sys1, hops: 1 }))).rejects.toMatchObject({ status: 409, message: 'Already at this system' })
+  })
+})
+
+describe('resolveExploreTask (A/B against explorePlanet)', () => {
+  it('planet in the current system: lands exactly what explorePlanet lands — haul, explored, event', async () => {
+    const { db: a } = await freshFile()
+    const { db: b } = await freshFile()
+    const fa = await buildWorldFixture(a)
+    const fb = await buildWorldFixture(b)
+
+    await explorePlanet(a, fa.p0)
+    await b.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+    await resolveExploreTask(b, task('EXPLORE', { planetId: fb.p0 }))
+
+    expect(await snapshot(b)).toEqual(await snapshot(a))
+  })
+
+  it('payload planet wins over the current system — the ship stays put (elsewhere semantics)', async () => {
+    const { db: a } = await freshFile()
+    const { db: b } = await freshFile()
+    const fa = await buildWorldFixture(a)
+    const fb = await buildWorldFixture(b)
+
+    await explorePlanet(a, fa.p1) // the current function already scans any planet, not just the current system's
+    await b.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+    await resolveExploreTask(b, task('EXPLORE', { planetId: fb.p1 }))
+
+    expect(await snapshot(b)).toEqual(await snapshot(a))
+
+    const sysB = await b.db.select().from(schema.solarSystems)
+    expect(sysB.filter((s) => s.isCurrent).map((s) => s.name)).toEqual(['Origin']) // the ship never moved
+    expect(sysB.find((s) => s.name === 'Outpost')!.discovered).toBe(false) // a scan never discovers a system
+
+    const ev = (await b.db.select({ turn: schema.events.turn, type: schema.events.type, message: schema.events.message }).from(schema.events)).find((e) => e.type === 'explore')!
+    expect(ev.turn).toBe(1)
+    // Exact existing format, recomputed the way save.ts computes it: haul first, crew roll on the same stream.
+    const rng = explorationRng('42', fb.p1)
+    const haul = rollExploration(rng)
+    const member = rollCrewMember(rng, new Set<string>())
+    const foundText = haul.length > 0 ? haul.map((i) => `${i.qty}× ${i.name}`).join(', ') : 'nothing'
+    expect(ev.message).toBe(`Explored Basalt — found ${foundText}${member ? ` — ${member.name} joined the crew` : ''}`)
+  })
+
+  it('guards: 404 unknown planet, 409 already explored (double-resolution safe)', async () => {
+    const { db } = await freshFile()
+    const f = await buildWorldFixture(db)
+    await db.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+
+    await expect(resolveExploreTask(db, task('EXPLORE', { planetId: 999 }))).rejects.toMatchObject({ status: 404, message: 'Unknown planet 999' })
+    await resolveExploreTask(db, task('EXPLORE', { planetId: f.p1 }))
+    await expect(resolveExploreTask(db, task('EXPLORE', { planetId: f.p1 }))).rejects.toMatchObject({ status: 409, message: 'Basalt was already explored' })
+  })
+})
+
 describe('backfill (old saves)', () => {
   // Planets/moons of one system in insertion order, nested by parent — ids are excluded so a
   // regenerated set compares equal to the original even though autoincrement moved on.

lib/game/save.ts

@@ -5,6 +5,7 @@ import * as schema from '@/lib/db/schema'
 import { generateStartingCrew, rollCrewMember, startingCrewRng, type CrewMember } from './crew'
 import { BASE_CAPACITY, BASE_LEVEL, SHIP_TYPES } from './ship-costs'
 import { checkMissionCompletion, topUpMissionBoard } from './missions'
+import type { Task, TaskType } from './tasks'
 import { TECHS } from './tech'
 import { bodyRng, explorationRng, generatePlanets, generateRing, generateStartRegion, mulberry32, reachableWithin, rollExploration, type FoundItem } from './world'
 
@@ -211,6 +212,58 @@ export async function getWorldState(db: GameDb): Promise<WorldState> {
   }
 }
 
+// --- Per-type resolvers (PR A, spec §3) -------------------------------------------
+//
+// The effect bodies of the instant actions, extracted so the turn tick (Task 4b) can
+// resolve a completed task row against whatever the world looks like at resolution time.
+// Contract (all six resolvers across save.ts / ship.ts / research.ts — see the Interfaces
+// block of this plan): effects land on the PAYLOAD target, never on the current location;
+// no turn advance (the caller owns the turn); no cost deduction (queueTask deducted at
+// queue time — Task 3; the immediate public functions deduct before delegating); a minimal
+// guard against a stale or double-resolved target (existing error class + exact message —
+// a throw is the signal for the 4b tick's re-validation); the existing event text formats
+// at the current turn; persist at the end.
+
+// A stand-in task row for the immediate public functions delegating to a resolver: the
+// resolvers only read `type` + `payload`, so the identity fields are zeroed.
+function syntheticTask(type: TaskType, payload: object): Task {
+  return { id: 0, saveId: 0, type, payload: JSON.stringify(payload), leadCrewId: 0, helpers: [], duration: 0, remaining: 0, status: 'ACTIVE', queuedAtTurn: 0 }
+}
+
+// JUMP — move the ship to the payload's system: flip isCurrent, discover the target, and
+// when it was undiscovered grow the chart ring off the same (seed, turn) stream as before.
+export async function resolveJumpTask(db: GameDb, task: Task): Promise<void> {
+  await ensureSave(db)
+  const { systemId } = JSON.parse(task.payload) as { systemId: number }
+  const [save] = await db.db.select().from(schema.saves).limit(1)
+  const systems = await db.db.select().from(schema.solarSystems)
+
+  const target = systems.find((s) => s.id === systemId)
+  if (!target) throw new JumpError(404, `Unknown system ${systemId}`)
+  if (target.isCurrent) throw new JumpError(409, 'Already at this system')
+  const current = systems.find((s) => s.isCurrent)!
+
+  await db.db.update(schema.solarSystems).set({ isCurrent: false }).where(eq(schema.solarSystems.id, current.id))
+  await db.db.update(schema.solarSystems).set({ isCurrent: true, discovered: true }).where(eq(schema.solarSystems.id, target.id))
+
+  if (!target.discovered) {
+    // Growing the chart: a ring of new (undiscovered) neighbours around the newly reached
+    // system, so there is always somewhere to jump next and a route back.
+    const rng = expansionRng(save.seed, save.turn)
+    const takenNames = new Set(systems.map((s) => s.name))
+    const ring = generateRing(rng, target.x, target.y, takenNames, systems)
+    const ringIds: number[] = []
+    for (const s of ring.systems) ringIds.push(await insertSystemWithBodies(db, save.id, s, save.seed))
+    const resolve = (index: number) => (index === 0 ? target.id : ringIds[index - 1])
+    await insertRoutes(db, ring.edges, resolve)
+  }
+
+  await db.db.insert(schema.events).values({ saveId: save.id, turn: save.turn, type: 'jump', message: `Jumped to ${target.name}`, createdAt: new Date().toISOString() })
+  await checkMissionCompletion(db, save.id, save.turn, { jumpedTo: target.id }) // an ACTIVE DELIVER may have arrived at its destination
+  await topUpMissionBoard(db)
+  await persist(db)
+}
+
 export async function jumpToSystem(db: GameDb, systemId: number): Promise<WorldState> {
   await ensureSave(db)
   const [save] = await db.db.select().from(schema.saves).limit(1)
@@ -222,33 +275,18 @@ export async function jumpToSystem(db: GameDb, systemId: number): Promise<WorldS
   if (current.id === target.id) throw new JumpError(409, 'Already at this system')
 
   const routes = await db.db.select().from(schema.jumpRoutes)
-  // #35 — NAVIGATION AI extends the jump range from adjacent (1 hop) to 2 hops; a multi-hop jump
-  // costs one turn per hop, so single-hop jumps keep their existing cost.
+  // #35 — NAVIGATION AI extends the jump range from adjacent (1 hop) to 2 hops; a multi-hop
+  // jump costs one turn per hop, so single-hop jumps keep their existing cost.
   const navAi = (await db.db.select().from(schema.tech)).some((t) => t.slug === 'NAV_AI' && t.researched)
   const hopCount = reachableWithin(routes.map((r) => [r.fromSystem, r.toSystem]), current.id, navAi ? 2 : 1).get(target.id)
   if (hopCount === undefined) throw new JumpError(409, `${target.name} is not reachable from ${current.name}`)
 
+  // The immediate jump keeps its own turn cost (the tick owns turn advances for queued
+  // tasks): advance it before delegating so the resolver's event lands at exactly the
+  // turn the old code wrote.
   const turn = save.turn + hopCount
-  await db.db.update(schema.solarSystems).set({ isCurrent: false }).where(eq(schema.solarSystems.id, current.id))
-  await db.db.update(schema.solarSystems).set({ isCurrent: true, discovered: true }).where(eq(schema.solarSystems.id, target.id))
-
-  if (!target.discovered) {
-    // Growing the chart: a ring of new (undiscovered) neighbours around the newly reached
-    // system, so there is always somewhere to jump next and a route back.
-    const rng = expansionRng(save.seed, turn)
-    const takenNames = new Set(systems.map((s) => s.name))
-    const ring = generateRing(rng, target.x, target.y, takenNames, systems)
-    const ringIds: number[] = []
-    for (const s of ring.systems) ringIds.push(await insertSystemWithBodies(db, save.id, s, save.seed))
-    const resolve = (index: number) => (index === 0 ? target.id : ringIds[index - 1])
-    await insertRoutes(db, ring.edges, resolve)
-  }
-
   await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, save.id))
-  await db.db.insert(schema.events).values({ saveId: save.id, turn, type: 'jump', message: `Jumped to ${target.name}`, createdAt: new Date().toISOString() })
-  await checkMissionCompletion(db, save.id, turn, { jumpedTo: target.id }) // an ACTIVE DELIVER may have arrived at its destination
-  await topUpMissionBoard(db)
-  await persist(db)
+  await resolveJumpTask(db, syntheticTask('JUMP', { systemId, hops: hopCount }))
 
   return getWorldState(db)
 }
@@ -331,12 +369,13 @@ export interface ExploreResult extends SystemState {
   crewFound: CrewDto | null // a member who joined the ship on this scan (null when none)
 }
 
-// Scan one body of the save: deterministic haul from (seed, planet id), marks it explored,
-// costs a turn, accumulates finds into inventory and writes an event. The same per-planet
-// rng stream also rolls for a crew member (~18% of scans) who joins the roster. Any existing
-// planet may be scanned (the UI only offers the current system's rows).
-export async function explorePlanet(db: GameDb, planetId: number): Promise<ExploreResult> {
+// EXPLORE — scan the payload's planet (any system — the UI only offered the current
+// system's rows; a queued scan may resolve while the ship is elsewhere): deterministic
+// haul into the inventory, planet marked explored, crew-join roll on the same
+// (seed, planet) stream.
+export async function resolveExploreTask(db: GameDb, task: Task): Promise<{ outcome: FoundItem[]; crewFound: CrewDto | null }> {
   await ensureSave(db)
+  const { planetId } = JSON.parse(task.payload) as { planetId: number }
   const [save] = await db.db.select().from(schema.saves).limit(1)
   const planets = await db.db.select().from(schema.planets)
   const target = planets.find((p) => p.id === planetId)
@@ -347,7 +386,6 @@ export async function explorePlanet(db: GameDb, planetId: number): Promise<Explo
   const outcome = rollExploration(rng) // resource/part haul first…
   const takenNames = new Set((await db.db.select().from(schema.crew)).map((c) => c.name))
   const foundMember = rollCrewMember(rng, takenNames) // …then the crew roll on the same stream
-  const turn = save.turn + 1
 
   await db.db.update(schema.planets).set({ explored: true }).where(eq(schema.planets.id, target.id))
   for (const item of outcome) {
@@ -370,11 +408,30 @@ export async function explorePlanet(db: GameDb, planetId: number): Promise<Explo
 
   const foundText = outcome.length > 0 ? outcome.map((i) => `${i.qty}× ${i.name}`).join(', ') : 'nothing'
   const crewText = crewFound ? ` — ${crewFound.name} joined the crew` : ''
-  await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, save.id))
-  await db.db.insert(schema.events).values({ saveId: save.id, turn, type: 'explore', message: `Explored ${target.name} — found ${foundText}${crewText}`, createdAt: new Date().toISOString() })
-  await checkMissionCompletion(db, save.id, turn, { outcome }) // an ACTIVE EXPLORE/FIND may have advanced or completed
+  await db.db.insert(schema.events).values({ saveId: save.id, turn: save.turn, type: 'explore', message: `Explored ${target.name} — found ${foundText}${crewText}`, createdAt: new Date().toISOString() })
+  await checkMissionCompletion(db, save.id, save.turn, { outcome }) // an ACTIVE EXPLORE/FIND may have advanced or completed
   await topUpMissionBoard(db)
   await persist(db)
 
+  return { outcome, crewFound }
+}
+
+// Scan one body of the save: deterministic haul from (seed, planet id), marks it explored,
+// costs a turn, accumulates finds into inventory and writes an event. The same per-planet
+// rng stream also rolls for a crew member (~18% of scans) who joins the roster. Any existing
+// planet may be scanned (the UI only offers the current system's rows).
+export async function explorePlanet(db: GameDb, planetId: number): Promise<ExploreResult> {
+  await ensureSave(db)
+  const [save] = await db.db.select().from(schema.saves).limit(1)
+  const planets = await db.db.select().from(schema.planets)
+  const target = planets.find((p) => p.id === planetId)
+  if (!target) throw new ExploreError(404, `Unknown planet ${planetId}`)
+  if (target.explored) throw new ExploreError(409, `${target.name} was already explored`)
+
+  // The immediate scan keeps its one-turn cost; the resolver applies everything else at that turn.
+  const turn = save.turn + 1
+  await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, save.id))
+  const { outcome, crewFound } = await resolveExploreTask(db, syntheticTask('EXPLORE', { planetId }))
+
   return { ...(await readSystemState(db)), outcome, crewFound }
 }

lib/game/ship.test.ts

@@ -6,7 +6,10 @@ import { eq } from 'drizzle-orm'
 import { openGameDb, type GameDb } from '@/lib/db/client'
 import * as schema from '@/lib/db/schema'
 import { BASE_CAPACITY, BASE_LEVEL, BUILD_PART_COST, MAX_CAPACITY, MAX_LEVEL, SHIP_TYPES } from './ship-costs'
-import { buildSystem, expandSystem, getShipState, upgradeSystem, type ShipState } from './ship'
+import { buildSystem, expandSystem, getShipState, resolveShipBuildTask, resolveShipExpandTask, resolveShipUpgradeTask, spendItems, upgradeSystem, type ShipState } from './ship'
+import { SCHEMA_VERSION } from './save'
+import { TECHS } from './tech'
+import type { Task } from './tasks'
 
 const dirs: string[] = []
 
@@ -155,3 +158,127 @@ describe('buildSystem', () => {
     await expect(buildSystem(db, 'SHIELDS')).rejects.toMatchObject({ status: 404 }) // not a known type
   })
 })
+
+// --- A/B: resolvers vs the legacy immediate ship actions (Task 4a) ---------------------
+const T0 = '2026-10-01T00:00:00.000Z'
+
+// Stamped save (no backfill), the full ship per SHIP_TYPES, the full tech tree with
+// WEAPONS_SYSTEMS researched (unlocks the BUILD row). Identical build per world → ids line up.
+async function buildShipFixture(db: GameDb): Promise<void> {
+  const [save] = await db.db.insert(schema.saves).values({ seed: '42', turn: 0, createdAt: T0, schemaVersion: SCHEMA_VERSION }).returning()
+  for (const def of SHIP_TYPES) {
+    await db.db.insert(schema.shipSystems).values({ saveId: save.id, type: def.type, level: def.builtAtStart ? BASE_LEVEL : 0, capacity: def.builtAtStart ? BASE_CAPACITY : 0 })
+  }
+  for (const def of TECHS) {
+    await db.db.insert(schema.tech).values({ saveId: save.id, slug: def.slug, name: def.name, costKind: def.costKind, costQty: def.costQty, prerequisites: def.prereqs.join(','), effect: def.effect, researched: def.slug === 'WEAPONS_SYSTEMS' })
+  }
+}
+
+const task = (type: 'SHIP_UPGRADE' | 'SHIP_EXPAND' | 'SHIP_BUILD', payload: object): Task =>
+  ({ id: 0, saveId: 0, type, payload: JSON.stringify(payload), leadCrewId: 0, helpers: [], duration: 0, remaining: 0, status: 'ACTIVE', queuedAtTurn: 0 })
+
+async function snapshot(db: GameDb): Promise<string> {
+  const [saves, systems, routes, planets, inventory, crew, ship, tech, missions, events] = await Promise.all([
+    db.db.select({ id: schema.saves.id, seed: schema.saves.seed, turn: schema.saves.turn, schemaVersion: schema.saves.schemaVersion }).from(schema.saves),
+    db.db.select().from(schema.solarSystems),
+    db.db.select().from(schema.jumpRoutes),
+    db.db.select().from(schema.planets),
+    db.db.select().from(schema.inventoryItems),
+    db.db.select().from(schema.crew),
+    db.db.select().from(schema.shipSystems),
+    db.db.select().from(schema.tech),
+    db.db.select().from(schema.missions),
+    db.db.select({ id: schema.events.id, turn: schema.events.turn, type: schema.events.type, message: schema.events.message }).from(schema.events),
+  ])
+  return JSON.stringify({ saves, systems, routes, planets, inventory, crew, ship, tech, missions, events })
+}
+
+describe('resolveShip* (A/B against the immediate actions)', () => {
+  // A = legacy immediate action (validates, deducts the cost, +1 turn, effect, event).
+  // B = the queued shape: the cost is deducted up front (queueTask did it at queue time —
+  // Task 3), the tick advanced the turn (Task 4b), then the resolver applies the effect.
+  // Same starting world → byte-identical end states.
+
+  it('UPGRADE: lands exactly what upgradeSystem lands', async () => {
+    const { db: a } = await freshFile()
+    const { db: b } = await freshFile()
+    await buildShipFixture(a)
+    await buildShipFixture(b)
+    await addItem(a, 'resource', 'IRON ORE', 1) // level 1 → cost 1
+    await addItem(b, 'resource', 'IRON ORE', 1)
+
+    const reactorId = systemOf(await getShipState(a), 'REACTOR').id
+    await upgradeSystem(a, reactorId)
+    await spendItems(b, 1, 'resource', 1) // the queue-time deduction
+    await b.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+    await resolveShipUpgradeTask(b, task('SHIP_UPGRADE', { systemId: reactorId }))
+
+    expect(await snapshot(b)).toEqual(await snapshot(a))
+    const ev = (await b.db.select({ turn: schema.events.turn, type: schema.events.type, message: schema.events.message }).from(schema.events)).find((e) => e.type === 'upgrade')!
+    expect(ev.turn).toBe(1)
+    expect(ev.message).toBe('Upgraded REACTOR to level 2 (cost: 1× resources)')
+  })
+
+  it('EXPAND: lands exactly what expandSystem lands', async () => {
+    const { db: a } = await freshFile()
+    const { db: b } = await freshFile()
+    await buildShipFixture(a)
+    await buildShipFixture(b)
+    await addItem(a, 'resource', 'CRYSTAL DUST', 2) // capacity 2 → cost 2
+    await addItem(b, 'resource', 'CRYSTAL DUST', 2)
+
+    const hullId = systemOf(await getShipState(a), 'HULL').id
+    await expandSystem(a, hullId)
+    await spendItems(b, 1, 'resource', 2)
+    await b.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+    await resolveShipExpandTask(b, task('SHIP_EXPAND', { systemId: hullId }))
+
+    expect(await snapshot(b)).toEqual(await snapshot(a))
+    const ev = (await b.db.select({ turn: schema.events.turn, type: schema.events.type, message: schema.events.message }).from(schema.events)).find((e) => e.type === 'expand')!
+    expect(ev.turn).toBe(1)
+    expect(ev.message).toBe('Expanded HULL capacity to 3 (cost: 2× resources)')
+  })
+
+  it('BUILD: lands exactly what buildSystem lands', async () => {
+    const { db: a } = await freshFile()
+    const { db: b } = await freshFile()
+    await buildShipFixture(a)
+    await buildShipFixture(b)
+    await addItem(a, 'part', 'SERVO ACTUATOR', 3)
+    await addItem(b, 'part', 'SERVO ACTUATOR', 3)
+
+    await buildSystem(a, 'WEAPONS')
+    await spendItems(b, 1, 'part', 3)
+    await b.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+    await resolveShipBuildTask(b, task('SHIP_BUILD', { type: 'WEAPONS' }))
+
+    expect(await snapshot(b)).toEqual(await snapshot(a))
+    const ev = (await b.db.select({ turn: schema.events.turn, type: schema.events.type, message: schema.events.message }).from(schema.events)).find((e) => e.type === 'build')!
+    expect(ev.turn).toBe(1)
+    expect(ev.message).toBe('Built WEAPONS at base values (cost: 3× parts)')
+  })
+
+  it('guards: 404 unknown, 409 unbuilt / max level / max capacity / gate / already built', async () => {
+    const { db } = await freshFile()
+    await buildShipFixture(db)
+    const state = await getShipState(db)
+    const reactorId = systemOf(state, 'REACTOR').id
+    const hullId = systemOf(state, 'HULL').id
+    const weaponsId = systemOf(state, 'WEAPONS').id
+    await db.db.update(schema.saves).set({ turn: 1 }).where(eq(schema.saves.id, 1))
+
+    await expect(resolveShipUpgradeTask(db, task('SHIP_UPGRADE', { systemId: 999 }))).rejects.toMatchObject({ status: 404, message: 'Unknown ship system 999' })
+    await expect(resolveShipUpgradeTask(db, task('SHIP_UPGRADE', { systemId: weaponsId }))).rejects.toMatchObject({ status: 409, message: 'WEAPONS is not built' })
+    await db.db.update(schema.shipSystems).set({ level: MAX_LEVEL }).where(eq(schema.shipSystems.id, reactorId))
+    await expect(resolveShipUpgradeTask(db, task('SHIP_UPGRADE', { systemId: reactorId }))).rejects.toMatchObject({ status: 409, message: `REACTOR is at max level (${MAX_LEVEL})` })
+
+    await expect(resolveShipExpandTask(db, task('SHIP_EXPAND', { systemId: 999 }))).rejects.toMatchObject({ status: 404, message: 'Unknown ship system 999' })
+    await db.db.update(schema.shipSystems).set({ capacity: MAX_CAPACITY }).where(eq(schema.shipSystems.id, hullId))
+    await expect(resolveShipExpandTask(db, task('SHIP_EXPAND', { systemId: hullId }))).rejects.toMatchObject({ status: 409, message: `HULL is at max capacity (${MAX_CAPACITY})` })
+
+    await expect(resolveShipBuildTask(db, task('SHIP_BUILD', { type: 'SHIELDS' }))).rejects.toMatchObject({ status: 404, message: 'Unknown ship system type SHIELDS' })
+    await db.db.update(schema.tech).set({ researched: false }).where(eq(schema.tech.slug, 'WEAPONS_SYSTEMS'))
+    await expect(resolveShipBuildTask(db, task('SHIP_BUILD', { type: 'WEAPONS' }))).rejects.toMatchObject({ status: 409, message: 'Building WEAPONS requires the WEAPONS SYSTEMS tech' })
+    await expect(resolveShipBuildTask(db, task('SHIP_BUILD', { type: 'HULL' }))).rejects.toMatchObject({ status: 409, message: 'HULL is already built' })
+  })
+})

lib/game/ship.ts

@@ -4,6 +4,7 @@ import { persist, type GameDb } from '@/lib/db/client'
 import { BUILD_PART_COST, BASE_CAPACITY, BASE_LEVEL, SHIP_TYPES, expandCost, upgradeCost } from './ship-costs'
 import { buildGate, effectiveCapacityCap, effectiveLevelCap } from './tech'
 import { ensureSave, type InventoryItemDto } from './save'
+import type { Task, TaskType } from './tasks'
 
 export interface ShipSystemDto {
   id: number
@@ -68,17 +69,69 @@ export async function spendItems(db: GameDb, saveId: number, kind: 'resource' |
   }
 }
 
-async function bumpTurnAndEvent(db: GameDb, saveId: number, turn: number, type: string, message: string): Promise<void> {
-  await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, saveId))
-  await db.db.insert(schema.events).values({ saveId, turn, type, message, createdAt: new Date().toISOString() })
-}
-
 // Slugs of the researched techs on this save — drives the effective caps and build gates below.
 async function researchedTechSlugs(db: GameDb): Promise<Set<string>> {
   return new Set((await db.db.select().from(schema.tech)).filter((t) => t.researched).map((t) => t.slug))
 }
 
-// UPGRADE — level up a built system by one (capped at the effective max level, raised by techs). Cost: `level` units of any resource.
+function syntheticTask(type: TaskType, payload: object): Task {
+  return { id: 0, saveId: 0, type, payload: JSON.stringify(payload), leadCrewId: 0, helpers: [], duration: 0, remaining: 0, status: 'ACTIVE', queuedAtTurn: 0 }
+}
+
+// SHIP_UPGRADE — level a built system by one, at whatever level it sits at resolution
+// time. No cost here (deducted at queue time — Task 3 — or by upgradeSystem before
+// delegating); no mission hooks (the current action has none).
+export async function resolveShipUpgradeTask(db: GameDb, task: Task): Promise<void> {
+  await ensureSave(db)
+  const { systemId } = JSON.parse(task.payload) as { systemId: number }
+  const [save] = await db.db.select().from(schema.saves).limit(1)
+  const target = (await db.db.select().from(schema.shipSystems)).find((s) => s.id === systemId)
+  if (!target) throw new ShipError(404, `Unknown ship system ${systemId}`)
+  if (target.level <= 0) throw new ShipError(409, `${target.type} is not built`)
+  const maxLevel = effectiveLevelCap(target.type, await researchedTechSlugs(db))
+  if (target.level >= maxLevel) throw new ShipError(409, `${target.type} is at max level (${maxLevel})`)
+
+  const cost = upgradeCost(target.level)
+  await db.db.update(schema.shipSystems).set({ level: target.level + 1 }).where(eq(schema.shipSystems.id, target.id))
+  await db.db.insert(schema.events).values({ saveId: save.id, turn: save.turn, type: 'upgrade', message: `Upgraded ${target.type} to level ${target.level + 1} (cost: ${cost}× resources)`, createdAt: new Date().toISOString() })
+  await persist(db)
+}
+
+// SHIP_EXPAND — same shape for capacity (cost: `capacity` units of any resource, deducted).
+export async function resolveShipExpandTask(db: GameDb, task: Task): Promise<void> {
+  await ensureSave(db)
+  const { systemId } = JSON.parse(task.payload) as { systemId: number }
+  const [save] = await db.db.select().from(schema.saves).limit(1)
+  const target = (await db.db.select().from(schema.shipSystems)).find((s) => s.id === systemId)
+  if (!target) throw new ShipError(404, `Unknown ship system ${systemId}`)
+  if (target.level <= 0) throw new ShipError(409, `${target.type} is not built`)
+  const maxCapacity = effectiveCapacityCap(target.type, await researchedTechSlugs(db))
+  if (target.capacity >= maxCapacity) throw new ShipError(409, `${target.type} is at max capacity (${maxCapacity})`)
+
+  const cost = expandCost(target.capacity)
+  await db.db.update(schema.shipSystems).set({ capacity: target.capacity + 1 }).where(eq(schema.shipSystems.id, target.id))
+  await db.db.insert(schema.events).values({ saveId: save.id, turn: save.turn, type: 'expand', message: `Expanded ${target.type} capacity to ${target.capacity + 1} (cost: ${cost}× resources)`, createdAt: new Date().toISOString() })
+  await persist(db)
+}
+
+// SHIP_BUILD — build an unbuilt type at base values. The flat parts cost is already
+// deducted; some types are gated behind a researched tech (see EFFECTS in lib/game/tech.ts).
+export async function resolveShipBuildTask(db: GameDb, task: Task): Promise<void> {
+  await ensureSave(db)
+  const { type } = JSON.parse(task.payload) as { type: string }
+  const [save] = await db.db.select().from(schema.saves).limit(1)
+  const target = (await db.db.select().from(schema.shipSystems)).find((s) => s.type === type)
+  if (!target) throw new ShipError(404, `Unknown ship system type ${type}`)
+  if (target.level > 0) throw new ShipError(409, `${target.type} is already built`)
+  const gate = buildGate(type, await researchedTechSlugs(db))
+  if (gate) throw new ShipError(409, `Building ${type} requires the ${gate} tech`)
+
+  await db.db.update(schema.shipSystems).set({ level: BASE_LEVEL, capacity: BASE_CAPACITY }).where(eq(schema.shipSystems.id, target.id))
+  await db.db.insert(schema.events).values({ saveId: save.id, turn: save.turn, type: 'build', message: `Built ${target.type} at base values (cost: ${BUILD_PART_COST}× parts)`, createdAt: new Date().toISOString() })
+  await persist(db)
+}
+
+// UPGRADE — level up a built system by one (capped at the effective max level, raised by techs).
 export async function upgradeSystem(db: GameDb, systemId: number): Promise<ShipState> {
   await ensureSave(db)
   const [save] = await db.db.select().from(schema.saves).limit(1)
@@ -88,16 +141,14 @@ export async function upgradeSystem(db: GameDb, systemId: number): Promise<ShipS
   const maxLevel = effectiveLevelCap(target.type, await researchedTechSlugs(db))
   if (target.level >= maxLevel) throw new ShipError(409, `${target.type} is at max level (${maxLevel})`)
 
-  const cost = upgradeCost(target.level)
-  await spendItems(db, save.id, 'resource', cost)
+  await spendItems(db, save.id, 'resource', upgradeCost(target.level))
   const turn = save.turn + 1
-  await db.db.update(schema.shipSystems).set({ level: target.level + 1 }).where(eq(schema.shipSystems.id, target.id))
-  await bumpTurnAndEvent(db, save.id, turn, 'upgrade', `Upgraded ${target.type} to level ${target.level + 1} (cost: ${cost}× resources)`)
-  await persist(db)
+  await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, save.id))
+  await resolveShipUpgradeTask(db, syntheticTask('SHIP_UPGRADE', { systemId }))
   return readShipState(db)
 }
 
-// EXPAND — raise a built system's capacity by one (capped at the effective max capacity, raised by techs). Cost: `capacity` units of any resource.
+// EXPAND — raise a built system's capacity by one (capped at the effective max capacity, raised by techs).
 export async function expandSystem(db: GameDb, systemId: number): Promise<ShipState> {
   await ensureSave(db)
   const [save] = await db.db.select().from(schema.saves).limit(1)
@@ -107,17 +158,14 @@ export async function expandSystem(db: GameDb, systemId: number): Promise<ShipSt
   const maxCapacity = effectiveCapacityCap(target.type, await researchedTechSlugs(db))
   if (target.capacity >= maxCapacity) throw new ShipError(409, `${target.type} is at max capacity (${maxCapacity})`)
 
-  const cost = expandCost(target.capacity)
-  await spendItems(db, save.id, 'resource', cost)
+  await spendItems(db, save.id, 'resource', expandCost(target.capacity))
   const turn = save.turn + 1
-  await db.db.update(schema.shipSystems).set({ capacity: target.capacity + 1 }).where(eq(schema.shipSystems.id, target.id))
-  await bumpTurnAndEvent(db, save.id, turn, 'expand', `Expanded ${target.type} capacity to ${target.capacity + 1} (cost: ${cost}× resources)`)
-  await persist(db)
+  await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, save.id))
+  await resolveShipExpandTask(db, syntheticTask('SHIP_EXPAND', { systemId }))
   return readShipState(db)
 }
 
-// BUILD — build an unbuilt type at base values. Cost: a flat amount of parts. Some types are
-// gated behind a researched tech (see EFFECTS in lib/game/tech.ts).
+// BUILD — build an unbuilt type at base values. Cost: a flat amount of parts.
 export async function buildSystem(db: GameDb, type: string): Promise<ShipState> {
   await ensureSave(db)
   const [save] = await db.db.select().from(schema.saves).limit(1)
@@ -129,8 +177,7 @@ export async function buildSystem(db: GameDb, type: string): Promise<ShipState>
 
   await spendItems(db, save.id, 'part', BUILD_PART_COST)
   const turn = save.turn + 1
-  await db.db.update(schema.shipSystems).set({ level: BASE_LEVEL, capacity: BASE_CAPACITY }).where(eq(schema.shipSystems.id, target.id))
-  await bumpTurnAndEvent(db, save.id, turn, 'build', `Built ${target.type} at base values (cost: ${BUILD_PART_COST}× parts)`)
-  await persist(db)
+  await db.db.update(schema.saves).set({ turn }).where(eq(schema.saves.id, save.id))
+  await resolveShipBuildTask(db, syntheticTask('SHIP_BUILD', { type }))
   return readShipState(db)
 }