diff --git a/src/Yavsc.Api.Test/EstimateAttachmentsApiTests.cs b/src/Yavsc.Api.Test/EstimateAttachmentsApiTests.cs
new file mode 100644
index 000000000..226b8e72a
--- /dev/null
+++ b/src/Yavsc.Api.Test/EstimateAttachmentsApiTests.cs
@@ -0,0 +1,303 @@
+using System.Net;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using System.Text.Json;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Yavsc.Api.Test.Fixtures;
+using Yavsc.Models;
+using Yavsc.Models.Billing;
+using Yavsc.Models.Blog;
+using Yavsc.Tests.Shared;
+
+namespace Yavsc.Api.Test;
+
+/// <summary>
+/// Integration tests for the estimate attachment endpoints
+/// (<c>GET/POST/DELETE api/v1/estimate/{id}/attachments</c>), which
+/// attach a file from the provider's personal storage to an estimate
+/// **by reference** (<see cref="EstimateAttachedFile"/>).
+///
+/// <para>Coverage mirrors the authorization contract documented on the
+/// controller: only the provider (<c>estimate.OwnerId</c>) may attach or
+/// detach, the file must belong to the caller, and listing is open to
+/// both parties (provider/client) plus admin. A third party is refused.
+/// The download of the bytes themselves is served by the Blogs host and
+/// exercised in <c>Yavsc.Blogs.Tests</c>; these tests cover only the
+/// metadata/relationship endpoints that live on the API host.</para>
+/// </summary>
+[Collection("Yavsc Api")]
+public sealed class EstimateAttachmentsApiTests : IClassFixture<ApiWebServerFixture>
+{
+    private readonly ApiWebServerFixture _fixture;
+
+    public EstimateAttachmentsApiTests(ApiWebServerFixture fixture)
+    {
+        _fixture = fixture;
+    }
+
+    private HttpClient NewClient(string subject = "alice", string scope = "api")
+    {
+        var handler = new HttpClientHandler
+        {
+            ServerCertificateCustomValidationCallback = (_, _, _, _) => true
+        };
+        var http = new HttpClient(handler)
+        {
+            BaseAddress = new Uri(_fixture.BaseAddress)
+        };
+        http.DefaultRequestHeaders.Authorization =
+            new AuthenticationHeaderValue("Bearer", TestTokenIssuer.Issue(subject, scope));
+        return http;
+    }
+
+    /// <summary>
+    /// Reset the graph (seeding alice the provider and bob the client),
+    /// create an estimate owned by alice for bob, and seed two personal
+    /// <see cref="UploadedFile"/> rows: one owned by alice (the provider's
+    /// own file) and one owned by bob (a file that does NOT belong to the
+    /// provider, used to assert the ownership guard on attach).
+    /// </summary>
+    private (long estimateId, long aliceFileId, long bobFileId) Seed()
+    {
+        _fixture.ResetAndSeedActivityGraph();
+
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+
+        var estimate = new Estimate
+        {
+            ClientId = "bob",
+            OwnerId = "alice",
+            CommandType = BillingCodes.Rdv,
+            Title = "Devis prestation",
+            Description = "Devis de test",
+            AttachedFiles = new List<string>(),
+            AttachedGraphics = new List<string>(),
+            Bill = new List<CommandLine>
+            {
+                new() { Name = "Prestation", Description = "Prestation de base", Count = 1, UnitaryCost = 120m, Currency = "EUR" },
+            },
+        };
+        db.Estimates.Add(estimate);
+        db.SaveChanges();
+
+        var aliceFile = new UploadedFile
+        {
+            OwnerId = "alice",
+            Path = "provider-doc.pdf",
+            ContentType = "application/pdf",
+            Length = 2048,
+        };
+        var bobFile = new UploadedFile
+        {
+            OwnerId = "bob",
+            Path = "client-note.txt",
+            ContentType = "text/plain",
+            Length = 64,
+        };
+        db.UploadedFiles.AddRange(aliceFile, bobFile);
+        db.SaveChanges();
+
+        return (estimate.Id, aliceFile.Id, bobFile.Id);
+    }
+
+    private int CountAttachments(long estimateId)
+    {
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+        return db.EstimateAttachedFiles.Count(a => a.EstimateId == estimateId);
+    }
+
+    [Fact]
+    public async Task Provider_attaching_own_file_creates_the_link()
+    {
+        var (estimateId, aliceFileId, _) = Seed();
+
+        using var http = NewClient("alice");
+        var response = await http.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+        var body = await response.Content.ReadAsStringAsync(TestContext.Current.CancellationToken);
+
+        Assert.True(response.StatusCode == HttpStatusCode.OK,
+            $"Expected 200, got {(int)response.StatusCode} ({response.StatusCode}): {body}");
+
+        Assert.Equal(1, CountAttachments(estimateId));
+
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+        var link = Assert.Single(db.EstimateAttachedFiles.Where(a => a.EstimateId == estimateId));
+        Assert.Equal(aliceFileId, link.FileId);
+    }
+
+    [Fact]
+    public async Task Attaching_the_same_file_twice_is_idempotent()
+    {
+        var (estimateId, aliceFileId, _) = Seed();
+
+        using var http = NewClient("alice");
+        await http.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+        var second = await http.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.OK, second.StatusCode);
+        Assert.Equal(1, CountAttachments(estimateId));
+    }
+
+    [Fact]
+    public async Task Non_provider_cannot_attach_to_an_estimate()
+    {
+        var (estimateId, aliceFileId, _) = Seed();
+
+        // bob is the client of the estimate, not the provider.
+        using var http = NewClient("bob");
+        var response = await http.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+        Assert.Equal(0, CountAttachments(estimateId));
+    }
+
+    [Fact]
+    public async Task Provider_cannot_attach_a_file_they_do_not_own()
+    {
+        var (estimateId, _, bobFileId) = Seed();
+
+        // alice is the provider, but the file belongs to bob.
+        using var http = NewClient("alice");
+        var response = await http.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = bobFileId },
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+        Assert.Equal(0, CountAttachments(estimateId));
+    }
+
+    [Fact]
+    public async Task Provider_detaches_a_file()
+    {
+        var (estimateId, aliceFileId, _) = Seed();
+
+        using var http = NewClient("alice");
+        await http.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+        Assert.Equal(1, CountAttachments(estimateId));
+
+        var response = await http.DeleteAsync(
+            $"/api/v1/estimate/{estimateId}/attachments/{aliceFileId}",
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal(0, CountAttachments(estimateId));
+    }
+
+    [Fact]
+    public async Task Non_provider_cannot_detach()
+    {
+        var (estimateId, aliceFileId, _) = Seed();
+
+        using var http = NewClient("alice");
+        await http.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+
+        using var bob = NewClient("bob");
+        var response = await bob.DeleteAsync(
+            $"/api/v1/estimate/{estimateId}/attachments/{aliceFileId}",
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+        Assert.Equal(1, CountAttachments(estimateId));
+    }
+
+    [Fact]
+    public async Task Provider_lists_attachments()
+    {
+        var (estimateId, aliceFileId, _) = Seed();
+
+        using var http = NewClient("alice");
+        await http.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+
+        var response = await http.GetAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            TestContext.Current.CancellationToken);
+        var body = await response.Content.ReadAsStringAsync(TestContext.Current.CancellationToken);
+        Assert.True(response.StatusCode == HttpStatusCode.OK,
+            $"Expected 200, got {(int)response.StatusCode} ({response.StatusCode}): {body}");
+
+        using var doc = JsonDocument.Parse(body);
+        var item = Assert.Single(doc.RootElement.EnumerateArray());
+        Assert.Equal(aliceFileId, item.GetProperty("fileId").GetInt64());
+        Assert.Equal("provider-doc.pdf", item.GetProperty("path").GetString());
+        Assert.Equal("alice", item.GetProperty("ownerId").GetString());
+    }
+
+    [Fact]
+    public async Task Client_can_list_attachments_as_a_party()
+    {
+        var (estimateId, aliceFileId, _) = Seed();
+
+        using var alice = NewClient("alice");
+        await alice.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+
+        // bob is the client of the estimate: a party, may list.
+        using var bob = NewClient("bob");
+        var response = await bob.GetAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task Third_party_cannot_list_attachments()
+    {
+        var (estimateId, aliceFileId, _) = Seed();
+
+        using var alice = NewClient("alice");
+        await alice.PostAsJsonAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+
+        // carol is neither the provider nor the client.
+        using var carol = NewClient("carol");
+        var response = await carol.GetAsync(
+            $"/api/v1/estimate/{estimateId}/attachments",
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task Listing_an_unknown_estimate_returns_404()
+    {
+        _fixture.ResetAndSeedActivityGraph();
+        using var http = NewClient("alice");
+
+        var response = await http.GetAsync(
+            "/api/v1/estimate/999999/attachments",
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+}
\ No newline at end of file
diff --git a/src/Yavsc.Api.Test/FrontOfficeQueryAttachmentsApiTests.cs b/src/Yavsc.Api.Test/FrontOfficeQueryAttachmentsApiTests.cs
new file mode 100644
index 000000000..d4438ef4e
--- /dev/null
+++ b/src/Yavsc.Api.Test/FrontOfficeQueryAttachmentsApiTests.cs
@@ -0,0 +1,256 @@
+using System.Net;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using System.Text.Json;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Yavsc.Api.Test.Fixtures;
+using Yavsc.Helpers;
+using Yavsc.Models;
+using Yavsc.Models.Billing;
+using Yavsc.Models.Blog;
+using Yavsc.Models.Workflow;
+using Yavsc.Tests.Shared;
+
+namespace Yavsc.Api.Test;
+
+/// <summary>
+/// Integration tests for the query (demande) attachment endpoints
+/// (<c>GET/POST/DELETE api/v1/front/query/{queryId}/attachments</c>),
+/// which attach a file from the client's personal storage to their
+/// <c>NominativeServiceCommand</c> **by reference**
+/// (<see cref="QueryAttachedFile"/>).
+///
+/// <para>Coverage mirrors the controller contract: only the client
+/// (the demande's <c>ClientId</c>) may attach or detach, the file must
+/// belong to the caller, and listing is open to both parties
+/// (client/provider) plus admin. A third party is refused.</para>
+/// </summary>
+[Collection("Yavsc Api")]
+public sealed class FrontOfficeQueryAttachmentsApiTests : IClassFixture<ApiWebServerFixture>
+{
+    private readonly ApiWebServerFixture _fixture;
+
+    public FrontOfficeQueryAttachmentsApiTests(ApiWebServerFixture fixture)
+    {
+        _fixture = fixture;
+    }
+
+    private HttpClient NewClient(string subject = "bob", string scope = "api")
+    {
+        var handler = new HttpClientHandler
+        {
+            ServerCertificateCustomValidationCallback = (_, _, _, _) => true
+        };
+        var http = new HttpClient(handler)
+        {
+            BaseAddress = new Uri(_fixture.BaseAddress)
+        };
+        http.DefaultRequestHeaders.Authorization =
+            new AuthenticationHeaderValue("Bearer", TestTokenIssuer.Issue(subject, scope));
+        return http;
+    }
+
+    /// <summary>
+    /// Seed an Rdv query from bob (client) to alice (provider) and two
+    /// personal <see cref="UploadedFile"/> rows: one owned by bob (the
+    /// client's own file) and one owned by alice (a file that does NOT
+    /// belong to the client, used to assert the ownership guard).
+    /// </summary>
+    private (long queryId, long bobFileId, long aliceFileId) Seed()
+    {
+        WorkflowHelpers.ConfigureBillingService();
+        _fixture.ResetAndSeedActivityGraph();
+
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+        var location = db.Locations.Single(l => l.Address == "1 rue du Test");
+
+        var query = new RdvQuery
+        {
+            ActivityCode = "dev",
+            ClientId = "bob",
+            PerformerId = "alice",
+            Consent = true,
+            UserCreated = "bob",
+            UserModified = "bob",
+            DateCreated = DateTime.UtcNow,
+            DateModified = DateTime.UtcNow,
+            EventDate = DateTime.UtcNow.AddDays(1),
+            Location = location,
+            Reason = "Demande de devis",
+            Status = QueryStatus.InProgress,
+            Description = "Demande en attente",
+        };
+        db.RdvQueries.Add(query);
+        db.SaveChanges();
+
+        var bobFile = new UploadedFile
+        {
+            OwnerId = "bob",
+            Path = "demande-photo.jpg",
+            ContentType = "image/jpeg",
+            Length = 4096,
+        };
+        var aliceFile = new UploadedFile
+        {
+            OwnerId = "alice",
+            Path = "provider-spec.pdf",
+            ContentType = "application/pdf",
+            Length = 1024,
+        };
+        db.UploadedFiles.AddRange(bobFile, aliceFile);
+        db.SaveChanges();
+
+        return (query.Id, bobFile.Id, aliceFile.Id);
+    }
+
+    private int CountAttachments(long queryId)
+    {
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+        return db.QueryAttachedFiles.Count(a => a.CommandId == queryId);
+    }
+
+    private string AttachUrl(long queryId) =>
+        $"/api/v1/front/query/{queryId}/attachments?billingCode=Rdv";
+
+    private string DetachUrl(long queryId, long fileId) =>
+        $"/api/v1/front/query/{queryId}/attachments/{fileId}?billingCode=Rdv";
+
+    [Fact]
+    public async Task Client_attaching_own_file_creates_the_link()
+    {
+        var (queryId, bobFileId, _) = Seed();
+
+        using var http = NewClient("bob");
+        var response = await http.PostAsJsonAsync(
+            AttachUrl(queryId),
+            new { fileId = bobFileId },
+            TestContext.Current.CancellationToken);
+        var body = await response.Content.ReadAsStringAsync(TestContext.Current.CancellationToken);
+
+        Assert.True(response.StatusCode == HttpStatusCode.OK,
+            $"Expected 200, got {(int)response.StatusCode} ({response.StatusCode}): {body}");
+
+        Assert.Equal(1, CountAttachments(queryId));
+
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+        var link = Assert.Single(db.QueryAttachedFiles.Where(a => a.CommandId == queryId));
+        Assert.Equal(bobFileId, link.FileId);
+    }
+
+    [Fact]
+    public async Task Provider_cannot_attach_to_a_query()
+    {
+        var (queryId, bobFileId, _) = Seed();
+
+        // alice is the provider of the query; only the client attaches.
+        using var http = NewClient("alice");
+        var response = await http.PostAsJsonAsync(
+            AttachUrl(queryId),
+            new { fileId = bobFileId },
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+        Assert.Equal(0, CountAttachments(queryId));
+    }
+
+    [Fact]
+    public async Task Client_cannot_attach_a_file_they_do_not_own()
+    {
+        var (queryId, _, aliceFileId) = Seed();
+
+        // bob is the client, but the file belongs to alice.
+        using var http = NewClient("bob");
+        var response = await http.PostAsJsonAsync(
+            AttachUrl(queryId),
+            new { fileId = aliceFileId },
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+        Assert.Equal(0, CountAttachments(queryId));
+    }
+
+    [Fact]
+    public async Task Client_detaches_a_file()
+    {
+        var (queryId, bobFileId, _) = Seed();
+
+        using var http = NewClient("bob");
+        await http.PostAsJsonAsync(
+            AttachUrl(queryId),
+            new { fileId = bobFileId },
+            TestContext.Current.CancellationToken);
+        Assert.Equal(1, CountAttachments(queryId));
+
+        var response = await http.DeleteAsync(
+            DetachUrl(queryId, bobFileId),
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal(0, CountAttachments(queryId));
+    }
+
+    [Fact]
+    public async Task Provider_cannot_detach()
+    {
+        var (queryId, bobFileId, _) = Seed();
+
+        using var bob = NewClient("bob");
+        await bob.PostAsJsonAsync(
+            AttachUrl(queryId),
+            new { fileId = bobFileId },
+            TestContext.Current.CancellationToken);
+
+        using var alice = NewClient("alice");
+        var response = await alice.DeleteAsync(
+            DetachUrl(queryId, bobFileId),
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+        Assert.Equal(1, CountAttachments(queryId));
+    }
+
+    [Fact]
+    public async Task Provider_lists_attachments_as_a_party()
+    {
+        var (queryId, bobFileId, _) = Seed();
+
+        using var bob = NewClient("bob");
+        await bob.PostAsJsonAsync(
+            AttachUrl(queryId),
+            new { fileId = bobFileId },
+            TestContext.Current.CancellationToken);
+
+        // alice is the provider: a party, may list.
+        using var alice = NewClient("alice");
+        var response = await alice.GetAsync(AttachUrl(queryId), TestContext.Current.CancellationToken);
+        var body = await response.Content.ReadAsStringAsync(TestContext.Current.CancellationToken);
+        Assert.True(response.StatusCode == HttpStatusCode.OK,
+            $"Expected 200, got {(int)response.StatusCode} ({response.StatusCode}): {body}");
+
+        using var doc = JsonDocument.Parse(body);
+        var item = Assert.Single(doc.RootElement.EnumerateArray());
+        Assert.Equal(bobFileId, item.GetProperty("fileId").GetInt64());
+        Assert.Equal("bob", item.GetProperty("ownerId").GetString());
+    }
+
+    [Fact]
+    public async Task Third_party_cannot_list_attachments()
+    {
+        var (queryId, bobFileId, _) = Seed();
+
+        using var bob = NewClient("bob");
+        await bob.PostAsJsonAsync(
+            AttachUrl(queryId),
+            new { fileId = bobFileId },
+            TestContext.Current.CancellationToken);
+
+        using var carol = NewClient("carol");
+        var response = await carol.GetAsync(AttachUrl(queryId), TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+    }
+}
\ No newline at end of file
diff --git a/src/Yavsc.Blogs.Tests/FileSystemApiTests.cs b/src/Yavsc.Blogs.Tests/FileSystemApiTests.cs
new file mode 100644
index 000000000..b5eeb8e00
--- /dev/null
+++ b/src/Yavsc.Blogs.Tests/FileSystemApiTests.cs
@@ -0,0 +1,294 @@
+using System.Net;
+using System.Net.Http.Headers;
+using System.Text.Json;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Yavsc.Blogs.Tests.Fixtures;
+using Yavsc.Models;
+using Yavsc.Models.Billing;
+using Yavsc.Models.Blog;
+using Yavsc.Models.Relationship;
+using Yavsc.Models.Workflow;
+using Yavsc.Tests.Shared;
+
+namespace Yavsc.Blogs.Tests;
+
+/// <summary>
+/// Integration tests for the personal-storage file endpoints
+/// (<c>api/v1/fs</c>) served by <c>FileSystemApiController</c> on the
+/// Blogs host.
+///
+/// <para>Two concerns:</para>
+/// <list type="number">
+///   <item><description><b>Upload records metadata</b>: a multipart
+///   <c>POST api/v1/fs</c> persists an <see cref="UploadedFile"/> row
+///   owned by the caller and returns its <c>fileId</c>, so the client
+///   can later attach that file to an estimate/query by
+///   reference.</description></item>
+///   <item><description><b>Download authorization</b>:
+///   <c>GET api/v1/fs/file/{fileId}</c> serves the bytes from the
+///   owner's personal space. The owner may always read; a party
+///   (client or provider) of an estimate/query the file is attached
+///   to may read; a third party is refused. The bytes live on the
+///   Blogs host's disk — this is the cross-container reason the
+///   download endpoint lives here and not on the API host.</description></item>
+/// </list>
+/// </summary>
+[Collection("Yavsc Blogs")]
+public sealed class FileSystemApiTests : IClassFixture<BlogsWebServerFixture>
+{
+    private readonly BlogsWebServerFixture _fixture;
+
+    public FileSystemApiTests(BlogsWebServerFixture fixture)
+    {
+        _fixture = fixture;
+    }
+
+    private HttpClient NewClient(string subject = "alice")
+    {
+        var handler = new HttpClientHandler
+        {
+            ServerCertificateCustomValidationCallback = (_, _, _, _) => true
+        };
+        var http = new HttpClient(handler)
+        {
+            BaseAddress = new Uri(_fixture.Addresses.First(a => a.StartsWith("https://")))
+        };
+        http.DefaultRequestHeaders.Authorization =
+            new AuthenticationHeaderValue("Bearer", TestTokenIssuer.Issue(subject));
+        return http;
+    }
+
+    private static string PhysicalFile(BlogsWebServerFixture fixture, string owner, string fileName) =>
+        Path.Combine(fixture.BlogFilesRoot, owner, fileName);
+
+    /// <summary>Write a physical file into the owner's personal space,
+    /// so <c>GetFile</c> can stream it back. Creates the directory if
+    /// needed.</summary>
+    private static void WritePhysicalFile(BlogsWebServerFixture fixture, string owner, string fileName, byte[] content)
+    {
+        var path = PhysicalFile(fixture, owner, fileName);
+        Directory.CreateDirectory(Path.GetDirectoryName(path)!);
+        File.WriteAllBytes(path, content);
+    }
+
+    private long SeedUploadedFile(string ownerId, string path, string contentType, long length)
+    {
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+        var file = new UploadedFile
+        {
+            OwnerId = ownerId,
+            Path = path,
+            ContentType = contentType,
+            Length = length,
+        };
+        db.UploadedFiles.Add(file);
+        db.SaveChanges();
+        return file.Id;
+    }
+
+    [Fact]
+    public async Task Post_fs_creates_an_UploadedFile_row_owned_by_the_caller()
+    {
+        _fixture.ResetDatabase();
+        // DiskQuota must be non-zero: ReceiveUserFile flags QuotaOffense
+        // once usage >= DiskQuota, and the controller skips the metadata
+        // row when QuotaOffense is set. A fresh user has quota 0.
+        _fixture.SeedUser("alice", u => u.DiskQuota = 10_000_000);
+
+        var payload = System.Text.Encoding.UTF8.GetBytes("hello personal storage");
+
+        using var form = new MultipartFormDataContent();
+        var fileContent = new ByteArrayContent(payload);
+        fileContent.Headers.ContentType = new MediaTypeHeaderValue("text/plain");
+        form.Add(fileContent, "file", "note.txt");
+
+        using var http = NewClient("alice");
+        var response = await http.PostAsync("/api/v1/fs", form, TestContext.Current.CancellationToken);
+        var body = await response.Content.ReadAsStringAsync(TestContext.Current.CancellationToken);
+        Assert.True(response.StatusCode == HttpStatusCode.OK,
+            $"Expected 200, got {(int)response.StatusCode} ({response.StatusCode}): {body}");
+
+        using var doc = JsonDocument.Parse(body);
+        var item = Assert.Single(doc.RootElement.EnumerateArray());
+        var fileId = item.GetProperty("fileId").GetInt64();
+        Assert.True(fileId > 0, $"Expected a positive fileId, got {fileId}. Body: {body}");
+        Assert.Equal("note.txt", item.GetProperty("fileName").GetString());
+        Assert.False(item.GetProperty("quotaOffense").GetBoolean());
+
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+        var row = Assert.Single(db.UploadedFiles.Where(u => u.OwnerId == "alice"));
+        Assert.Equal("note.txt", row.Path);
+        Assert.Equal("text/plain", row.ContentType);
+        Assert.Equal(payload.Length, row.Length);
+
+        // The file physically landed under {BlogFilesRoot}/alice/note.txt.
+        Assert.True(File.Exists(PhysicalFile(_fixture, "alice", "note.txt")),
+            "Expected the uploaded file on disk under the owner's personal root");
+    }
+
+    [Fact]
+    public async Task GetFile_owner_can_download_their_own_file()
+    {
+        _fixture.ResetDatabase();
+        _fixture.SeedUser("alice");
+
+        var bytes = System.Text.Encoding.UTF8.GetBytes("owner payload");
+        WritePhysicalFile(_fixture, "alice", "owner-note.txt", bytes);
+        var fileId = SeedUploadedFile("alice", "owner-note.txt", "text/plain", bytes.Length);
+
+        using var http = NewClient("alice");
+        var response = await http.GetAsync(
+            $"/api/v1/fs/file/{fileId}", TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var downloaded = await response.Content.ReadAsByteArrayAsync(TestContext.Current.CancellationToken);
+        Assert.Equal(bytes, downloaded);
+    }
+
+    [Fact]
+    public async Task GetFile_refuses_a_third_party()
+    {
+        _fixture.ResetDatabase();
+        _fixture.SeedUser("alice");
+        _fixture.SeedUser("carol");
+
+        var bytes = System.Text.Encoding.UTF8.GetBytes("private to alice");
+        WritePhysicalFile(_fixture, "alice", "secret.txt", bytes);
+        var fileId = SeedUploadedFile("alice", "secret.txt", "text/plain", bytes.Length);
+
+        // carol is neither the owner nor a party to any estimate/query
+        // this file is attached to.
+        using var http = NewClient("carol");
+        var response = await http.GetAsync(
+            $"/api/v1/fs/file/{fileId}", TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Forbidden, response.StatusCode);
+    }
+
+    /// <summary>
+    /// Seed the graph needed to prove a party (the client of an
+    /// estimate the file is attached to) can download a file they do
+    /// not own: alice owns the file and is the provider; bob is the
+    /// client; the file is attached to the estimate by reference.
+    /// </summary>
+    private long SeedPartyDownloadGraph(out long estimateId, out string fileName)
+    {
+        _fixture.ResetDatabase();
+        _fixture.SeedUser("alice");
+        _fixture.SeedUser("bob");
+
+        fileName = "party-spec.pdf";
+        var bytes = System.Text.Encoding.UTF8.GetBytes("party payload");
+
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+
+        // Location + PerformerProfile(alice): Estimate.OwnerId is a FK
+        // to PerformerProfile.PerformerId, so the provider profile must
+        // exist before the estimate can be inserted.
+        var location = new Location { Address = "1 rue du Test", Latitude = 48.8, Longitude = 2.3 };
+        db.Locations.Add(location);
+        db.SaveChanges();
+
+        db.Performers.Add(new PerformerProfile
+        {
+            PerformerId = "alice",
+            SIREN = "12345678901234",
+            OrganizationAddressId = location.Id,
+            ExerciseCountryCode = "fr",
+            AcceptNotifications = true,
+            AcceptPublicContact = true,
+            Active = true,
+            Rate = 5,
+            WebSite = "https://alice.dev",
+        });
+        db.SaveChanges();
+
+        var estimate = new Estimate
+        {
+            OwnerId = "alice",
+            ClientId = "bob",
+            CommandType = "Rdv",
+            Title = "Devis party test",
+            Description = "Devis",
+            AttachedFiles = new List<string>(),
+            AttachedGraphics = new List<string>(),
+            Bill = new List<CommandLine>
+            {
+                new() { Name = "Prestation", Description = "Prestation", Count = 1, UnitaryCost = 10m, Currency = "EUR" },
+            },
+        };
+        db.Estimates.Add(estimate);
+        db.SaveChanges();
+        estimateId = estimate.Id;
+
+        var file = new UploadedFile
+        {
+            OwnerId = "alice",
+            Path = fileName,
+            ContentType = "application/pdf",
+            Length = bytes.Length,
+        };
+        db.UploadedFiles.Add(file);
+        db.SaveChanges();
+
+        db.EstimateAttachedFiles.Add(new EstimateAttachedFile
+        {
+            FileId = file.Id,
+            EstimateId = estimate.Id,
+        });
+        db.SaveChanges();
+
+        // The bytes must exist on disk for GetFile to stream them.
+        WritePhysicalFile(_fixture, "alice", fileName, bytes);
+        return file.Id;
+    }
+
+    [Fact]
+    public async Task GetFile_party_client_of_an_attached_estimate_can_download()
+    {
+        var fileId = SeedPartyDownloadGraph(out _, out _);
+
+        // bob is the client of the estimate the file is attached to:
+        // a party, authorized to read even though alice owns the file.
+        using var http = NewClient("bob");
+        var response = await http.GetAsync(
+            $"/api/v1/fs/file/{fileId}", TestContext.Current.CancellationToken);
+        var body = await response.Content.ReadAsStringAsync(TestContext.Current.CancellationToken);
+
+        Assert.True(response.StatusCode == HttpStatusCode.OK,
+            $"Expected 200, got {(int)response.StatusCode} ({response.StatusCode}): {body}");
+        var downloaded = await response.Content.ReadAsByteArrayAsync(TestContext.Current.CancellationToken);
+        Assert.Equal(System.Text.Encoding.UTF8.GetBytes("party payload"), downloaded);
+    }
+
+    [Fact]
+    public async Task GetFile_party_provider_of_an_attached_estimate_can_download()
+    {
+        var fileId = SeedPartyDownloadGraph(out _, out _);
+
+        // alice is the owner too, so this also exercises the owner path;
+        // the provider of an attached estimate is authorized regardless.
+        using var http = NewClient("alice");
+        var response = await http.GetAsync(
+            $"/api/v1/fs/file/{fileId}", TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task GetFile_unknown_id_returns_404()
+    {
+        _fixture.ResetDatabase();
+        _fixture.SeedUser("alice");
+
+        using var http = NewClient("alice");
+        var response = await http.GetAsync(
+            "/api/v1/fs/file/999999", TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+}
\ No newline at end of file