diff --git a/README.md b/README.md
index b457f7b..3095524 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,20 @@
 # lib-core.maps
 
-P.0.module.skeleton trivial-stub. Will be properly implemented in P.0.lib.maps slice.
+P.0 single-tile-grid-map implementation. Loads JSON map + tilemap files,
+provides tile-fetch + walkability queries.
 
 - Lib-ID: `lib-core.maps`
 - Version: `0.1.0`
+- Spec: `meta/docs/superpowers/specs/2026-05-09-p0-lib-maps-design.md`
+
+Forward-compat stubs (DEPRECATED-MVP) for multi-map graph, lifecycle states,
+walls, sprite-fields, generators, save-integration. See
+`meta/docs/architecture/map-topology.md` for the full target spec.
+
+## API
+- `maps.load(path)` — load + register a map from JSON
+- `maps.create(table)` — programmatic creation (tests, procedural)
+- `maps.tile_at(map_id, tx, ty)` / `maps.tile_at(tx, ty)` — current-map sugar
+- `maps.is_walkable(...)`, `maps.size(...)`, `maps.tile_size(...)`
+- `maps.current()`, `maps.set_current(id)`, `maps.list()`
+- Stubs (deferred): `maps.state()`, `maps.pin()`
diff --git a/init.lua b/init.lua
index 1326eed..8249604 100644
--- a/init.lua
+++ b/init.lua
@@ -1 +1,235 @@
-return { hello = function() return "maps loaded" end }
+-- =====================================================================
+-- lib-core.maps — Single Tile-Grid Map Lib (P.0)
+-- See: meta/docs/superpowers/specs/2026-05-09-p0-lib-maps-design.md
+--
+-- Forward-compat stubs (DEPRECATED-MVP) for: multi-map-graph,
+-- lifecycle-states, walls, sprite-fields, generators, save-integration,
+-- cross-lib tilemap resolution, override-field-merge, sub-require.
+-- =====================================================================
+
+-- Module-private state
+local map_registry      = {}    -- map_id -> Map
+local tilemap_registry  = {}    -- full_tilemap_id -> Tilemap
+local current_map_id    = nil
+
+-- =====================================================================
+-- Internal helpers
+-- =====================================================================
+
+-- Splits "lib-x.foo" -> "lib-x", "foo" (split at FIRST dot only).
+-- Returns (nil, full_id) if no dot present.
+local function split_namespaced_id(full_id)
+    local dot = string.find(full_id, ".", 1, true)
+    if not dot then return nil, full_id end
+    return string.sub(full_id, 1, dot-1), string.sub(full_id, dot+1)
+end
+
+-- "demo_tilemap"           -> "<current-module-id>.demo_tilemap"
+-- "lib-x.foo"              -> "lib-x.foo" (cross-lib path; checked at load)
+local function resolve_tilemap_id(ref)
+    if string.find(ref, ".", 1, true) then
+        return ref
+    end
+    return engine.module.id() .. "." .. ref
+end
+
+-- Schema-validation helper: reads required field with type-check.
+local function require_field(t, key, expected_type, source)
+    local v = t[key]
+    if v == nil then
+        error(string.format("maps.load: schema violation in %s: missing required field '%s'",
+            source, key))
+    end
+    if type(v) ~= expected_type then
+        error(string.format("maps.load: schema violation in %s: field '%s' must be %s, got %s",
+            source, key, expected_type, type(v)))
+    end
+    return v
+end
+
+local function validate_map_table(t, source)
+    require_field(t, "id", "string", source)
+    require_field(t, "tilemap", "string", source)
+    local size = require_field(t, "size", "table", source)
+    require_field(size, "w", "number", source .. ".size")
+    require_field(size, "h", "number", source .. ".size")
+    local tiles = require_field(t, "tiles", "table", source)
+    local expected = size.w * size.h
+    if #tiles ~= expected then
+        error(string.format("maps.load: schema violation in %s: tiles array length %d != size.w * size.h (%d)",
+            source, #tiles, expected))
+    end
+end
+
+local function validate_tilemap_table(t, source, expected_local_name)
+    require_field(t, "id", "string", source)
+    if t.id ~= expected_local_name then
+        error(string.format("maps.load: tilemap manifest id '%s' mismatches filename-stem '%s' in %s",
+            t.id, expected_local_name, source))
+    end
+    require_field(t, "tile_size", "number", source)
+    local tiles = require_field(t, "tiles", "table", source)
+    for i, entry in ipairs(tiles) do
+        if type(entry) ~= "table" then
+            error(string.format("maps.load: tilemap %s tiles[%d] must be table", source, i))
+        end
+        require_field(entry, "id", "string", source .. ".tiles[" .. i .. "]")
+        require_field(entry, "walkable", "boolean", source .. ".tiles[" .. i .. "]")
+    end
+end
+
+local function load_tilemap(full_id)
+    if tilemap_registry[full_id] then
+        return tilemap_registry[full_id]
+    end
+    local lib_id, local_name = split_namespaced_id(full_id)
+    local current_lib = engine.module.id()
+    if lib_id ~= current_lib then
+        -- DEPRECATED-MVP: cross-lib tilemap resolution deferred to render-slice
+        error(string.format("maps.load: cross-lib tilemap resolution deferred [DEPRECATED-MVP]; tilemap '%s' not from current module '%s'",
+            full_id, current_lib))
+    end
+    local path = "assets/tiles/" .. local_name .. ".tilemap.json"
+    local raw = engine.asset.load_json(path)
+    validate_tilemap_table(raw, path, local_name)
+    local tilemap = {
+        id        = full_id,
+        tile_size = raw.tile_size,
+        tiles     = raw.tiles,
+    }
+    tilemap_registry[full_id] = tilemap
+    return tilemap
+end
+
+local function build_map(t_map, tilemap)
+    -- Verify each tile-id is in palette range
+    for i, tid in ipairs(t_map.tiles) do
+        if type(tid) ~= "number" or tid < 1 or tid > #tilemap.tiles then
+            error(string.format("maps.load: tile-id %s at index %d exceeds palette size %d (in map '%s')",
+                tostring(tid), i, #tilemap.tiles, t_map.id))
+        end
+    end
+    return {
+        id        = t_map.id,
+        size      = t_map.size,
+        tile_size = t_map.tile_size or tilemap.tile_size,
+        tiles     = t_map.tiles,        -- shallow-ref
+        tilemap   = tilemap,             -- shallow-ref
+        -- DEPRECATED-MVP: forward-compat stubs (multi-map slice fills)
+        walls     = {},
+        regions   = {},
+        edges     = {},
+        state     = "Active",
+        pinned    = false,
+    }
+end
+
+-- =====================================================================
+-- Public API
+-- =====================================================================
+
+local M = {}
+
+function M.load(path)
+    local raw = engine.asset.load_json(path)
+    validate_map_table(raw, path)
+    local full_id = resolve_tilemap_id(raw.tilemap)
+    local tilemap = load_tilemap(full_id)
+    local map = build_map(raw, tilemap)
+    if map_registry[map.id] then
+        error(string.format("maps.load: map-id '%s' already registered", map.id))
+    end
+    map_registry[map.id] = map
+    return map.id
+end
+
+-- Programmatic creation (tests, future procedural-map generators).
+-- Caller must provide a fully-built tilemap-table (not a path/id ref).
+function M.create(t)
+    if type(t.tilemap_table) ~= "table" then
+        error("maps.create: tilemap_table required (use maps.load for JSON path)")
+    end
+    local map = build_map(t, t.tilemap_table)
+    if map_registry[map.id] then
+        error(string.format("maps.create: map-id '%s' already registered", map.id))
+    end
+    map_registry[map.id] = map
+    return map.id
+end
+
+function M.size(map_id)
+    local id = map_id or current_map_id
+    if not id then error("maps.size: no current map") end
+    return map_registry[id].size
+end
+
+function M.tile_size(map_id)
+    local id = map_id or current_map_id
+    if not id then error("maps.tile_size: no current map") end
+    return map_registry[id].tile_size
+end
+
+-- Arity-flex sugar: tile_at(tx, ty) uses current_map_id; tile_at(map_id, tx, ty) is explicit.
+function M.tile_at(a, b, c)
+    local map_id, tx, ty
+    if c == nil then
+        map_id, tx, ty = current_map_id, a, b
+        if not map_id then
+            error("maps.tile_at: no current map; call set_current() first or pass map_id")
+        end
+    else
+        map_id, tx, ty = a, b, c
+    end
+    local m = map_registry[map_id]
+    if not m then
+        error(string.format("maps.tile_at: unknown map-id '%s'", tostring(map_id)))
+    end
+    if tx < 0 or tx >= m.size.w or ty < 0 or ty >= m.size.h then
+        return nil
+    end
+    local palette_id = m.tiles[ty * m.size.w + tx + 1]
+    return m.tilemap.tiles[palette_id]
+end
+
+function M.is_walkable(a, b, c)
+    local t = M.tile_at(a, b, c)
+    if t == nil then return false end
+    return t.walkable == true
+end
+
+function M.tilemap_id(map_id)
+    local id = map_id or current_map_id
+    return map_registry[id].tilemap.id
+end
+
+function M.current()
+    return current_map_id
+end
+
+function M.set_current(map_id)
+    if not map_registry[map_id] then
+        error(string.format("maps.set_current: unknown map-id '%s'", tostring(map_id)))
+    end
+    current_map_id = map_id
+end
+
+function M.list()
+    local out = {}
+    for id, _ in pairs(map_registry) do
+        out[#out+1] = id
+    end
+    return out
+end
+
+-- Forward-compat stubs (DEPRECATED-MVP — implemented in later slices)
+function M.state(map_id)
+    -- DEPRECATED-MVP: lifecycle states (Virgin/Inert/Passive/Active/Pinned) — multi-map slice
+    return "Active"
+end
+
+function M.pin(map_id, reason)
+    -- DEPRECATED-MVP: world.pin_map mechanic — multi-map slice
+    engine.warn("maps.pin: deferred to map-topology lifecycle slice")
+end
+
+return M
diff --git a/manifest.lib b/manifest.lib
index d4330ea..fb2d819 100644
--- a/manifest.lib
+++ b/manifest.lib
@@ -1 +1 @@
-{"id":"lib-core.maps","version":"0.1.0"}
+{"id":"lib-core.maps","version":"0.1.0","api_min":"0.1"}