diff --git a/app/api/jump/route.ts b/app/api/jump/route.ts
new file mode 100644
index 0000000..68bfd59
--- /dev/null
+++ b/app/api/jump/route.ts
@@ -0,0 +1,27 @@
+import { getGameDb } from '@/lib/db/client'
+import { JumpError, jumpToSystem } from '@/lib/game/save'
+
+// Jump to an adjacent solar system. Body: { "systemId": number }. Returns the fresh world state.
+export async function POST(req: Request) {
+  let body: unknown
+  try {
+    body = await req.json()
+  } catch {
+    return Response.json({ error: 'Invalid JSON body' }, { status: 400 })
+  }
+
+  const systemId = (body as { systemId?: unknown }).systemId
+  if (typeof systemId !== 'number' || !Number.isInteger(systemId)) {
+    return Response.json({ error: 'systemId must be an integer' }, { status: 400 })
+  }
+
+  try {
+    const db = await getGameDb()
+    return Response.json(await jumpToSystem(db, systemId))
+  } catch (err) {
+    if (err instanceof JumpError) {
+      return Response.json({ error: err.message }, { status: err.status })
+    }
+    throw err
+  }
+}
diff --git a/app/api/world/route.ts b/app/api/world/route.ts
new file mode 100644
index 0000000..d395736
--- /dev/null
+++ b/app/api/world/route.ts
@@ -0,0 +1,8 @@
+import { getGameDb } from '@/lib/db/client'
+import { getWorldState } from '@/lib/game/save'
+
+// The full world state for the single active save; auto-initializes on first hit.
+export async function GET() {
+  const db = await getGameDb()
+  return Response.json(await getWorldState(db))
+}
diff --git a/lib/openapi.ts b/lib/openapi.ts
index e2e9262..3c7450e 100644
--- a/lib/openapi.ts
+++ b/lib/openapi.ts
@@ -8,7 +8,7 @@ export const openApiSpec = {
   info: {
     title: 'SpaceWanderer API',
     description:
-      'JSON API for SpaceWanderer — a single-player turn-based space adventure. Scaffold stage: app metadata only; game endpoints (turn actions, state snapshots) land with the first game systems.',
+      'JSON API for SpaceWanderer — a single-player turn-based space adventure (one save, no accounts). World endpoints: read the generated world state and jump between adjacent solar systems.',
     // Sourced from package.json so it stays in sync with every version bump.
     version: pkg.version,
   },
@@ -32,6 +32,74 @@ export const openApiSpec = {
         },
       },
     },
+    '/api/world': {
+      get: {
+        summary: 'World state',
+        description:
+          'The full world of the single active save — every known solar system, jump routes and the turn counter. Auto-initializes a new game (seeded world generation) when no save exists yet.',
+        operationId: 'getWorld',
+        responses: {
+          200: {
+            description: 'Current world state',
+            content: {
+              'application/json': {
+                schema: { $ref: '#/components/schemas/WorldState' },
+              },
+            },
+          },
+        },
+      },
+    },
+    '/api/jump': {
+      post: {
+        summary: 'Jump to an adjacent solar system',
+        description:
+          'Validates that the target is a jump route away from the current system, sets it as current (discovering it if new and generating its neighbours), increments the turn counter and writes a jump event. Returns the fresh world state.',
+        operationId: 'jumpToSystem',
+        requestBody: {
+          required: true,
+          content: {
+            'application/json': {
+              schema: { $ref: '#/components/schemas/JumpRequest' },
+            },
+          },
+        },
+        responses: {
+          200: {
+            description: 'Fresh world state after the jump',
+            content: {
+              'application/json': {
+                schema: { $ref: '#/components/schemas/WorldState' },
+              },
+            },
+          },
+          400: {
+            description: 'Malformed body or non-integer systemId',
+            content: {
+              'application/json': {
+                schema: { $ref: '#/components/schemas/Error' },
+              },
+            },
+          },
+          404: {
+            description: 'Unknown system id',
+            content: {
+              'application/json': {
+                schema: { $ref: '#/components/schemas/Error' },
+              },
+            },
+          },
+          409: {
+            description: 'Target is not adjacent to the current system (or is the current system itself)',
+            content: {
+              'application/json': {
+                schema: { $ref: '#/components/schemas/Error' },
+              },
+            },
+          },
+        },
+      },
+    },
   },
   components: {
     schemas: {
@@ -42,6 +110,50 @@ export const openApiSpec = {
         },
         required: ['version'],
       },
+      WorldSystem: {
+        type: 'object',
+        properties: {
+          id: { type: 'integer' },
+          name: { type: 'string' },
+          x: { type: 'number', description: '0–100 chart coordinate' },
+          y: { type: 'number', description: '0–100 chart coordinate' },
+          discovered: { type: 'boolean' },
+          current: { type: 'boolean', description: 'True for the system the ship is in now' },
+        },
+        required: ['id', 'name', 'x', 'y', 'discovered', 'current'],
+      },
+      WorldState: {
+        type: 'object',
+        properties: {
+          systems: { type: 'array', items: { $ref: '#/components/schemas/WorldSystem' } },
+          edges: {
+            type: 'array',
+            description: 'Undirected jump routes as [fromId, toId] pairs (sorted, deduped)',
+            items: {
+              type: 'array',
+              items: { type: 'integer' },
+              minItems: 2,
+              maxItems: 2,
+            },
+          },
+          turn: { type: 'integer', description: 'Turn counter — one per jump' },
+        },
+        required: ['systems', 'edges', 'turn'],
+      },
+      JumpRequest: {
+        type: 'object',
+        properties: {
+          systemId: { type: 'integer', description: 'solar_systems.id of the jump target' },
+        },
+        required: ['systemId'],
+      },
+      Error: {
+        type: 'object',
+        properties: {
+          error: { type: 'string' },
+        },
+        required: ['error'],
+      },
     },
   },
 };