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src/Graph/StellaOps.Graph.Api/Services/IGraphSearchService.cs

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+using StellaOps.Graph.Api.Contracts;
+
+namespace StellaOps.Graph.Api.Services;
+
+public interface IGraphSearchService
+{
+    IAsyncEnumerable<string> SearchAsync(string tenant, GraphSearchRequest request, CancellationToken ct = default);
+}

src/Graph/StellaOps.Graph.Api/Services/InMemoryGraphRepository.cs

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+using StellaOps.Graph.Api.Contracts;
+
+namespace StellaOps.Graph.Api.Services;
+
+public sealed class InMemoryGraphRepository
+{
+    private readonly List<NodeTile> _nodes;
+
+    public InMemoryGraphRepository()
+    {
+        _nodes = new List<NodeTile>
+        {
+            new() { Id = "gn:acme:component:example",    Kind = "component", Tenant = "acme", Attributes = new() { ["purl"] = "pkg:npm/example@1.0.0",  ["ecosystem"] = "npm" } },
+            new() { Id = "gn:acme:component:widget",     Kind = "component", Tenant = "acme", Attributes = new() { ["purl"] = "pkg:npm/widget@2.0.0",   ["ecosystem"] = "npm" } },
+            new() { Id = "gn:acme:artifact:sha256:abc",  Kind = "artifact",  Tenant = "acme", Attributes = new() { ["digest"] = "sha256:abc",           ["ecosystem"] = "container" } },
+            new() { Id = "gn:acme:component:gamma",      Kind = "component", Tenant = "acme", Attributes = new() { ["purl"] = "pkg:nuget/Gamma@3.1.4", ["ecosystem"] = "nuget" } },
+            new() { Id = "gn:bravo:component:widget",    Kind = "component", Tenant = "bravo",Attributes = new() { ["purl"] = "pkg:npm/widget@2.0.0",   ["ecosystem"] = "npm" } },
+            new() { Id = "gn:bravo:artifact:sha256:def", Kind = "artifact",  Tenant = "bravo",Attributes = new() { ["digest"] = "sha256:def",           ["ecosystem"] = "container" } },
+        };
+    }
+
+    public IEnumerable<NodeTile> Query(string tenant, GraphSearchRequest request)
+    {
+        var limit = Math.Clamp(request.Limit ?? 50, 1, 500);
+        var cursorOffset = CursorCodec.Decode(request.Cursor);
+
+        var queryable = _nodes
+            .Where(n => n.Tenant.Equals(tenant, StringComparison.Ordinal))
+            .Where(n => request.Kinds.Contains(n.Kind, StringComparer.OrdinalIgnoreCase));
+
+        if (!string.IsNullOrWhiteSpace(request.Query))
+        {
+            queryable = queryable.Where(n => MatchesQuery(n, request.Query!));
+        }
+
+        if (request.Filters is not null)
+        {
+            queryable = queryable.Where(n => FiltersMatch(n, request.Filters!));
+        }
+
+        queryable = request.Ordering switch
+        {
+            "id" => queryable.OrderBy(n => n.Id, StringComparer.Ordinal),
+            _ => queryable.OrderBy(n => n.Id.Length).ThenBy(n => n.Id, StringComparer.Ordinal)
+        };
+
+        return queryable.Skip(cursorOffset).Take(limit + 1).ToArray();
+    }
+
+    private static bool MatchesQuery(NodeTile node, string query)
+    {
+        var q = query.ToLowerInvariant();
+        return node.Id.ToLowerInvariant().Contains(q)
+            || node.Attributes.Values.OfType<string>().Any(v => v.Contains(q, StringComparison.OrdinalIgnoreCase));
+    }
+
+    private static bool FiltersMatch(NodeTile node, IReadOnlyDictionary<string, object> filters)
+    {
+        foreach (var kvp in filters)
+        {
+            if (!node.Attributes.TryGetValue(kvp.Key, out var value))
+            {
+                return false;
+            }
+            if (kvp.Value is null)
+            {
+                continue;
+            }
+            if (!kvp.Value.ToString()!.Equals(value?.ToString(), StringComparison.OrdinalIgnoreCase))
+            {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+
+internal static class CursorCodec
+{
+    public static string Encode(int offset) => Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(offset.ToString()));
+
+    public static int Decode(string? token)
+    {
+        if (string.IsNullOrWhiteSpace(token)) return 0;
+        try
+        {
+            var text = System.Text.Encoding.UTF8.GetString(Convert.FromBase64String(token));
+            return int.TryParse(text, out var value) ? value : 0;
+        }
+        catch
+        {
+            return 0;
+        }
+    }
+}

src/Graph/StellaOps.Graph.Api/Services/InMemoryGraphSearchService.cs

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+using System.Runtime.CompilerServices;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using StellaOps.Graph.Api.Contracts;
+
+namespace StellaOps.Graph.Api.Services;
+
+public sealed class InMemoryGraphSearchService : IGraphSearchService
+{
+    private readonly InMemoryGraphRepository _repository;
+    private static readonly JsonSerializerOptions Options = new(JsonSerializerDefaults.Web)
+    {
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
+    };
+
+    public InMemoryGraphSearchService(InMemoryGraphRepository repository)
+    {
+        _repository = repository;
+    }
+
+    public async IAsyncEnumerable<string> SearchAsync(string tenant, GraphSearchRequest request, [EnumeratorCancellation] CancellationToken ct = default)
+    {
+        var limit = Math.Clamp(request.Limit ?? 50, 1, 500);
+        var results = _repository.Query(tenant, request).ToArray();
+
+        var items = results.Take(limit).ToArray();
+        var remaining = results.Length > limit ? results.Length - limit : 0;
+        var cost = new CostBudget(limit, Math.Max(0, limit - items.Length), items.Length);
+
+        var seq = 0;
+        foreach (var item in items)
+        {
+            var envelope = new TileEnvelope("node", seq++, item, cost);
+            yield return JsonSerializer.Serialize(envelope, Options);
+        }
+
+        if (remaining > 0)
+        {
+            var nextCursor = CursorCodec.Encode(CursorCodec.Decode(request.Cursor) + items.Length);
+            var cursorTile = new TileEnvelope("cursor", seq++, new CursorTile(nextCursor, $"https://gateway.local/api/graph/search?cursor={nextCursor}"));
+            yield return JsonSerializer.Serialize(cursorTile, Options);
+        }
+
+        await Task.CompletedTask;
+    }
+}