diff --git a/backend/openapi/v1.json b/backend/openapi/v1.json
index 878072d..5823ca4 100644
--- a/backend/openapi/v1.json
+++ b/backend/openapi/v1.json
@@ -3598,6 +3598,93 @@
         "x-moshiro-capability": "data.write"
       }
     },
+    "/api/admin/audit": {
+      "get": {
+        "tags": [
+          "admin-audit"
+        ],
+        "summary": "Audit log of admin actions, newest first",
+        "operationId": "audit_list",
+        "parameters": [
+          {
+            "name": "actor",
+            "in": "query",
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "action",
+            "in": "query",
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "limit",
+            "in": "query",
+            "schema": {
+              "pattern": "^-?(?:0|[1-9]\\d*)$",
+              "type": [
+                "integer",
+                "string"
+              ],
+              "format": "int32"
+            }
+          },
+          {
+            "name": "cursor",
+            "in": "query",
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/PageDtoOfAuditDto"
+                }
+              }
+            }
+          },
+          "400": {
+            "description": "Bad Request",
+            "content": {
+              "application/problem+json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ProblemDto"
+                }
+              }
+            }
+          },
+          "401": {
+            "description": "Unauthorized",
+            "content": {
+              "application/problem+json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ProblemDto"
+                }
+              }
+            }
+          },
+          "403": {
+            "description": "Forbidden",
+            "content": {
+              "application/problem+json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ProblemDto"
+                }
+              }
+            }
+          }
+        },
+        "x-moshiro-capability": "audit.read"
+      }
+    },
     "/api/admin/api-tokens": {
       "get": {
         "tags": [
@@ -4938,6 +5025,63 @@
           }
         }
       },
+      "AuditDto": {
+        "required": [
+          "id",
+          "at",
+          "actor",
+          "method",
+          "action",
+          "target",
+          "detail",
+          "remote",
+          "success"
+        ],
+        "type": "object",
+        "properties": {
+          "id": {
+            "pattern": "^-?(?:0|[1-9]\\d*)$",
+            "type": [
+              "integer",
+              "string"
+            ],
+            "format": "int64"
+          },
+          "at": {
+            "format": "date-time"
+          },
+          "actor": {
+            "type": "string"
+          },
+          "method": {
+            "type": "string"
+          },
+          "action": {
+            "type": "string"
+          },
+          "target": {
+            "type": [
+              "null",
+              "string"
+            ]
+          },
+          "detail": {
+            "type": [
+              "null",
+              "string"
+            ]
+          },
+          "remote": {
+            "type": [
+              "null",
+              "string"
+            ]
+          },
+          "success": {
+            "type": "boolean"
+          }
+        }
+      },
       "BackendUpdateDto": {
         "required": [
           "channel",
@@ -6982,6 +7126,27 @@
           }
         }
       },
+      "PageDtoOfAuditDto": {
+        "required": [
+          "items",
+          "next_cursor"
+        ],
+        "type": "object",
+        "properties": {
+          "items": {
+            "type": "array",
+            "items": {
+              "$ref": "#/components/schemas/AuditDto"
+            }
+          },
+          "next_cursor": {
+            "type": [
+              "null",
+              "string"
+            ]
+          }
+        }
+      },
       "PageDtoOfEventDto": {
         "required": [
           "items",
@@ -8623,6 +8788,9 @@
     {
       "name": "admin-data"
     },
+    {
+      "name": "admin-audit"
+    },
     {
       "name": "admin-api-tokens"
     },
diff --git a/backend/src/MoShiro.Backend.Api/Admin/AgentEndpoints.cs b/backend/src/MoShiro.Backend.Api/Admin/AgentEndpoints.cs
index b0c22b0..f80e267 100644
--- a/backend/src/MoShiro.Backend.Api/Admin/AgentEndpoints.cs
+++ b/backend/src/MoShiro.Backend.Api/Admin/AgentEndpoints.cs
@@ -132,6 +132,7 @@ public static class AgentEndpoints
     private static async Task<IResult> CreateTokenAsync(HttpContext http, JoinTokenService tokens, CreateJoinTokenRequest request, BackendOptions options)
     {
         string baseUrl = options.PublicUrl ?? $"{http.Request.Scheme}://{http.Request.Host}";
+        http.SetDetail($"{request.Role ?? JoinTokenService.AgentRole}: {request.Note}");
         Result<CreatedJoinToken> result = await tokens.CreateAsync(
             new Application.CreateJoinTokenRequest(request.Note, request.Labels, request.AutoApprove ?? true, request.MaxUses ?? 1, request.ExpiresInHours ?? 24, request.Role ?? JoinTokenService.AgentRole, http.GetPrincipal().Label), baseUrl, http.RequestAborted);
         if (!result.TryGet(out CreatedJoinToken? created, out FleetError? error))
diff --git a/backend/src/MoShiro.Backend.Api/Admin/AuditEndpoints.cs b/backend/src/MoShiro.Backend.Api/Admin/AuditEndpoints.cs
new file mode 100644
index 0000000..fc4180d
--- /dev/null
+++ b/backend/src/MoShiro.Backend.Api/Admin/AuditEndpoints.cs
@@ -0,0 +1,44 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Routing;
+using MoShiro.Backend.Application;
+using MoShiro.Protocol;
+
+namespace MoShiro.Backend.Api;
+
+/// <summary>审计日志：管理接口里每个写操作、登录和提权都会记一行，这里只读。</summary>
+public static class AuditEndpoints
+{
+    private const string Tag = "admin-audit";
+
+    /// <summary>handler 往这里放一句「这次具体做了什么」（例如新建令牌的名字），守卫记审计时一起写进去。</summary>
+    public const string DetailItem = "moshiro.audit.detail";
+
+    public static void Map(RouteGroupBuilder guarded) =>
+        guarded.MapGet("/audit", ListAsync)
+            .Api("audit_list", "Audit log of admin actions, newest first", Tag).Returns<PageDto<AuditDto>>().ProducesProblems(400, 401, 403)
+            .Requires(Capability.AuditRead);
+
+    public static void SetDetail(this HttpContext http, string detail) => http.Items[DetailItem] = detail;
+
+    private static async Task<IResult> ListAsync(HttpContext http, AuditService audit, string? actor, string? action, int? limit, string? cursor)
+    {
+        long? before = null;
+        if (cursor is not null)
+        {
+            if (!long.TryParse(cursor, out long parsed))
+            {
+                return Problems.From(http, ValidationError.Single("cursor", "is not a valid cursor"));
+            }
+
+            before = parsed;
+        }
+
+        int size = Math.Clamp(limit ?? 50, 1, 500);
+        IReadOnlyList<AuditRecord> rows = await audit.ListAsync(new AuditQuery(before, size + 1, string.IsNullOrEmpty(actor) ? null : actor, string.IsNullOrEmpty(action) ? null : action), http.RequestAborted);
+        bool more = rows.Count > size;
+        IReadOnlyList<AuditRecord> page = [.. rows.Take(size)];
+        string? next = more ? page[^1].Id.ToString(System.Globalization.CultureInfo.InvariantCulture) : null;
+        return TypedResults.Json(new PageDto<AuditDto>([.. page.Select(Mappers.ToDto)], next), ApiJsonContext.Default.PageDtoAuditDto);
+    }
+}
diff --git a/backend/src/MoShiro.Backend.Api/Admin/AuthEndpoints.cs b/backend/src/MoShiro.Backend.Api/Admin/AuthEndpoints.cs
index 85cc869..39e6f8a 100644
--- a/backend/src/MoShiro.Backend.Api/Admin/AuthEndpoints.cs
+++ b/backend/src/MoShiro.Backend.Api/Admin/AuthEndpoints.cs
@@ -57,7 +57,7 @@ public static class AuthEndpoints
             .Requires(Capability.Authenticated);
     }
 
-    private static async Task<IResult> LoginAsync(HttpContext http, LoginRequest request, AuthService auth, LoginRateLimiter limiter, BackendOptions options)
+    private static async Task<IResult> LoginAsync(HttpContext http, LoginRequest request, AuthService auth, AuditService audit, LoginRateLimiter limiter, BackendOptions options)
     {
         string source = http.Connection.RemoteIpAddress?.ToString() ?? "unknown";
         if (!limiter.TryAcquire(source, out int retryAfter))
@@ -66,11 +66,14 @@ public static class AuthEndpoints
         }
 
         Result<LoginResult> result = await auth.LoginAsync(request.Username ?? "", request.Password ?? "", http.RequestAborted);
+        string remote = source;
         if (!result.TryGet(out LoginResult? login, out FleetError? error))
         {
+            await audit.RecordAsync(null, request.Username ?? "", AuthMethods.Password, "auth.login", null, null, remote, false, http.RequestAborted);
             return Problems.From(http, error);
         }
 
+        await audit.RecordAsync(login.UserId, login.Username, AuthMethods.Password, "auth.login", null, null, remote, true, http.RequestAborted);
         return IssueSession(http, login, request.ReturnSession == true, options);
     }
 
@@ -132,7 +135,7 @@ public static class AuthEndpoints
         return TypedResults.Json(new PasskeyRequestOptionsDto(o.Challenge, o.RpId, o.TimeoutMs), ApiJsonContext.Default.PasskeyRequestOptionsDto);
     }
 
-    private static async Task<IResult> PasskeyLoginAsync(HttpContext http, PasskeyLoginRequest request, PasskeyService passkeys, LoginRateLimiter limiter, BackendOptions options)
+    private static async Task<IResult> PasskeyLoginAsync(HttpContext http, PasskeyLoginRequest request, PasskeyService passkeys, AuditService audit, LoginRateLimiter limiter, BackendOptions options)
     {
         IResult limit = Limited(http, limiter, out bool ok);
         if (!ok)
@@ -142,7 +145,15 @@ public static class AuthEndpoints
 
         Result<LoginResult> result = await passkeys.LoginAsync(
             new PasskeyAssertion(request.CredentialId ?? "", request.AuthenticatorData ?? "", request.ClientDataJson ?? "", request.Signature ?? ""), PasskeyContextOf(http, options), http.RequestAborted);
-        return result.TryGet(out LoginResult? login, out FleetError? error) ? IssueSession(http, login, request.ReturnSession == true, options) : Problems.From(http, error);
+        string? remote = http.Connection.RemoteIpAddress?.ToString();
+        if (!result.TryGet(out LoginResult? login, out FleetError? error))
+        {
+            await audit.RecordAsync(null, "?", AuthMethods.Passkey, "auth.login", null, null, remote, false, http.RequestAborted);
+            return Problems.From(http, error);
+        }
+
+        await audit.RecordAsync(login.UserId, login.Username, AuthMethods.Passkey, "auth.login", null, null, remote, true, http.RequestAborted);
+        return IssueSession(http, login, request.ReturnSession == true, options);
     }
 
     private static async Task<IResult> ListPasskeysAsync(HttpContext http, PasskeyService passkeys)
diff --git a/backend/src/MoShiro.Backend.Api/Admin/SystemEndpoints.cs b/backend/src/MoShiro.Backend.Api/Admin/SystemEndpoints.cs
index f52f95a..3c3b1dc 100644
--- a/backend/src/MoShiro.Backend.Api/Admin/SystemEndpoints.cs
+++ b/backend/src/MoShiro.Backend.Api/Admin/SystemEndpoints.cs
@@ -64,6 +64,7 @@ public static class SystemEndpoints
 
     private static async Task<IResult> CreateTokenAsync(HttpContext http, AuthService auth, CreateApiTokenRequest request)
     {
+        http.SetDetail($"{request.Name}: {string.Join(',', request.Capabilities ?? [])}");
         Result<CreatedApiToken> result = await auth.CreateApiTokenAsync(request.Name ?? "", request.Capabilities ?? [], request.ExpiresInDays, http.GetPrincipal(), http.RequestAborted);
         if (!result.TryGet(out CreatedApiToken? created, out FleetError? error))
         {
diff --git a/backend/src/MoShiro.Backend.Api/ApiModule.cs b/backend/src/MoShiro.Backend.Api/ApiModule.cs
index 74300f3..95d72f0 100644
--- a/backend/src/MoShiro.Backend.Api/ApiModule.cs
+++ b/backend/src/MoShiro.Backend.Api/ApiModule.cs
@@ -110,6 +110,7 @@ public static class ApiModule
         AgentEndpoints.Map(guarded);
         TaskEndpoints.Map(guarded);
         DataEndpoints.Map(guarded);
+        AuditEndpoints.Map(guarded);
         SystemEndpoints.Map(guarded);
         BuildEndpoints.Map(guarded);
         LinkEndpoints.Map(guarded);
diff --git a/backend/src/MoShiro.Backend.Api/Common/Guards.cs b/backend/src/MoShiro.Backend.Api/Common/Guards.cs
index 431c4d3..92ec7dc 100644
--- a/backend/src/MoShiro.Backend.Api/Common/Guards.cs
+++ b/backend/src/MoShiro.Backend.Api/Common/Guards.cs
@@ -1,4 +1,5 @@
 using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Routing;
 using Microsoft.Extensions.DependencyInjection;
 using MoShiro.Backend.Application;
 using MoShiro.Protocol;
@@ -88,6 +89,19 @@ public static class CapabilityGuard
             }
         }
 
+        if (principal.Kind != PrincipalKind.Anonymous && !HttpMethods.IsGet(http.Request.Method) && !HttpMethods.IsHead(http.Request.Method) && !HttpMethods.IsOptions(http.Request.Method))
+        {
+            // 写操作都记审计：响应发完之后才知道结果，所以放在 OnCompleted 里
+            string action = http.GetEndpoint()?.Metadata.GetMetadata<IEndpointNameMetadata>()?.EndpointName ?? http.Request.Path.Value ?? "";
+            string? target = http.Request.RouteValues.Count == 0 ? null : string.Join(' ', http.Request.RouteValues.Where(v => v.Value is not null).Select(v => v.Key + "=" + v.Value));
+            http.Response.OnCompleted(() =>
+            {
+                http.Items.TryGetValue(AuditEndpoints.DetailItem, out object? detail);
+                return http.RequestServices.GetRequiredService<AuditService>()
+                    .RecordAsync(principal, action, target, detail as string, http.Connection.RemoteIpAddress?.ToString(), http.Response.StatusCode < 400).AsTask();
+            });
+        }
+
         return await next(context);
     }
 }
diff --git a/backend/src/MoShiro.Backend.Api/Common/Mappers.cs b/backend/src/MoShiro.Backend.Api/Common/Mappers.cs
index 131affe..cf56e6c 100644
--- a/backend/src/MoShiro.Backend.Api/Common/Mappers.cs
+++ b/backend/src/MoShiro.Backend.Api/Common/Mappers.cs
@@ -156,6 +156,8 @@ public static class Mappers
     public static JoinTokenDto ToDto(JoinTokenInfo t) =>
         new(t.Id, t.Note, t.Labels, t.AutoApprove, t.MaxUses, t.Uses, Time(t.ExpiresAtMs), Time(t.RevokedAtMs), Time(t.CreatedAtMs), JoinTokenService.RoleOf(t.Kind), t.CreatedBy);
 
+    public static AuditDto ToDto(AuditRecord a) => new(a.Id, Time(a.AtMs), a.Actor, a.Method, a.Action, a.Target, a.Detail, a.Remote, a.Success);
+
     public static PasskeyDto ToDto(PasskeyRecord p) => new(p.Id, p.Name, Time(p.CreatedAtMs), Time(p.LastUsedAtMs), p.Transports);
 
     public static ApiTokenDto ToDto(ApiTokenRecord t) => new(t.Id, t.Name, t.Capabilities, Time(t.CreatedAtMs), Time(t.LastUsedAtMs), Time(t.ExpiresAtMs), Time(t.RevokedAtMs));
diff --git a/backend/src/MoShiro.Backend.Api/Contracts/ApiJsonContext.cs b/backend/src/MoShiro.Backend.Api/Contracts/ApiJsonContext.cs
index cbb44f7..ce5b95d 100644
--- a/backend/src/MoShiro.Backend.Api/Contracts/ApiJsonContext.cs
+++ b/backend/src/MoShiro.Backend.Api/Contracts/ApiJsonContext.cs
@@ -70,6 +70,7 @@ namespace MoShiro.Backend.Api;
 [JsonSerializable(typeof(RawChunkMetaDto))]
 [JsonSerializable(typeof(PageDto<RawChunkMetaDto>))]
 [JsonSerializable(typeof(PageDto<EventDto>))]
+[JsonSerializable(typeof(PageDto<AuditDto>))]
 [JsonSerializable(typeof(ApiTokenDto))]
 [JsonSerializable(typeof(PageDto<ApiTokenDto>))]
 [JsonSerializable(typeof(CreateApiTokenRequest))]
diff --git a/backend/src/MoShiro.Backend.Api/Contracts/PublicDtos.cs b/backend/src/MoShiro.Backend.Api/Contracts/PublicDtos.cs
index 7698bb5..5033e40 100644
--- a/backend/src/MoShiro.Backend.Api/Contracts/PublicDtos.cs
+++ b/backend/src/MoShiro.Backend.Api/Contracts/PublicDtos.cs
@@ -10,6 +10,8 @@ public sealed record EdgePartialDto(bool First, bool Last);
 
 public sealed record GapDto(DateTimeOffset From, DateTimeOffset To, string Reason);
 
+public sealed record AuditDto(long Id, DateTimeOffset At, string Actor, string Method, string Action, string? Target, string? Detail, string? Remote, bool Success);
+
 public sealed record EventDto(long Id, string? AgentId, string Kind, DateTimeOffset At, string? Detail);
 
 public sealed record TestSummaryDto(string Id, string Plan, string Status, DateTimeOffset RequestedAt, DateTimeOffset? FinishedAt);
diff --git a/backend/src/MoShiro.Backend.Application/ApplicationServiceCollectionExtensions.cs b/backend/src/MoShiro.Backend.Application/ApplicationServiceCollectionExtensions.cs
index d8a1c19..cfb3ad2 100644
--- a/backend/src/MoShiro.Backend.Application/ApplicationServiceCollectionExtensions.cs
+++ b/backend/src/MoShiro.Backend.Application/ApplicationServiceCollectionExtensions.cs
@@ -36,6 +36,7 @@ public static class ApplicationServiceCollectionExtensions
         services.AddSingleton<WindowComputer>();
         services.AddSingleton<AuthService>();
         services.AddSingleton<PasskeyService>();
+        services.AddSingleton<AuditService>();
         services.AddSingleton<SettingsService>();
         services.AddSingleton<ReleaseService>();
         services.AddSingleton<ScheduleService>();
diff --git a/backend/src/MoShiro.Backend.Application/Audit/AuditService.cs b/backend/src/MoShiro.Backend.Application/Audit/AuditService.cs
new file mode 100644
index 0000000..36c9b47
--- /dev/null
+++ b/backend/src/MoShiro.Backend.Application/Audit/AuditService.cs
@@ -0,0 +1,60 @@
+using Microsoft.Extensions.Logging;
+
+namespace MoShiro.Backend.Application;
+
+/// <summary>
+/// 审计日志里的一行：谁（<see cref="Actor"/>，用户名或 <c>key:令牌名</c>）、怎么登录的（<see cref="Method"/>）、做了什么（<see cref="Action"/>，
+/// 管理接口的 operationId，或 <c>auth.login</c> 这类登录事件）、对谁（<see cref="Target"/>）、结果如何。
+/// </summary>
+public sealed record AuditRecord(long Id, long AtMs, string? UserId, string Actor, string Method, string Action, string? Target, string? Detail, string? Remote, bool Success);
+
+public sealed record AuditQuery(long? BeforeId, int Limit, string? Actor, string? Action);
+
+/// <summary>审计日志只追加：没有修改和单条删除，只按保留期整体清理。</summary>
+public sealed partial class AuditService
+{
+    /// <summary>保留一年。审计记录的是谁动过信任相关的东西，比监测数据留得久。</summary>
+    public const int RetentionDays = 365;
+
+    private readonly IAuditStore _store;
+    private readonly TimeProvider _time;
+    private readonly ILogger<AuditService> _logger;
+
+    public AuditService(IAuditStore store, TimeProvider time, ILogger<AuditService> logger)
+    {
+        _store = store;
+        _time = time;
+        _logger = logger;
+    }
+
+    /// <summary>记一条。写不进去只记日志，不能因为审计失败而让已经完成的操作报错。</summary>
+    public async ValueTask RecordAsync(Principal principal, string action, string? target, string? detail, string? remote, bool success, CancellationToken ct = default) =>
+        await RecordAsync(principal.UserId, principal.Label, MethodOf(principal), action, target, detail, remote, success, ct);
+
+    public async ValueTask RecordAsync(string? userId, string actor, string method, string action, string? target, string? detail, string? remote, bool success, CancellationToken ct = default)
+    {
+        try
+        {
+            await _store.AddAsync(new AuditRecord(0, _time.GetUtcNow().ToUnixTimeMilliseconds(), userId, actor, method, action, Clip(target, 200), Clip(detail, 500), remote, success), ct);
+        }
+        catch (Exception ex) when (ex is not OperationCanceledException)
+        {
+            LogFailed(ex, action);
+        }
+    }
+
+    public ValueTask<IReadOnlyList<AuditRecord>> ListAsync(AuditQuery query, CancellationToken ct) => _store.ListAsync(query, ct);
+
+    public ValueTask<int> PruneAsync(long nowMs, CancellationToken ct) => _store.DeleteOlderThanAsync(nowMs - (RetentionDays * 86_400_000L), ct);
+
+    /// <summary>登录方式：密码、passkey，或 API key。</summary>
+    public static string MethodOf(Principal principal) =>
+        principal.Kind == PrincipalKind.Anonymous ? "anonymous"
+        : principal.Kind == PrincipalKind.Token && principal.UserId is null ? "key"
+        : principal.AuthMethod.Length > 0 ? principal.AuthMethod : AuthMethods.Password;
+
+    private static string? Clip(string? text, int max) => text is { } t && t.Length > max ? t[..max] : text;
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "could not write the audit record for {Action}")]
+    private partial void LogFailed(Exception exception, string action);
+}
diff --git a/backend/src/MoShiro.Backend.Application/Ports/StorePorts.cs b/backend/src/MoShiro.Backend.Application/Ports/StorePorts.cs
index ba1c7ef..15d72ee 100644
--- a/backend/src/MoShiro.Backend.Application/Ports/StorePorts.cs
+++ b/backend/src/MoShiro.Backend.Application/Ports/StorePorts.cs
@@ -144,6 +144,15 @@ public interface IEventStore
     ValueTask<int> DeleteOlderThanAsync(long cutoffMs, CancellationToken ct);
 }
 
+public interface IAuditStore
+{
+    ValueTask AddAsync(AuditRecord record, CancellationToken ct);
+
+    ValueTask<IReadOnlyList<AuditRecord>> ListAsync(AuditQuery query, CancellationToken ct);
+
+    ValueTask<int> DeleteOlderThanAsync(long cutoffMs, CancellationToken ct);
+}
+
 /// <summary>主机资源占用的历史：每个 Agent 每分钟一个样本。</summary>
 public interface IHostStore
 {
diff --git a/backend/src/MoShiro.Backend.Application/Retention/RetentionService.cs b/backend/src/MoShiro.Backend.Application/Retention/RetentionService.cs
index 85448fb..81966b3 100644
--- a/backend/src/MoShiro.Backend.Application/Retention/RetentionService.cs
+++ b/backend/src/MoShiro.Backend.Application/Retention/RetentionService.cs
@@ -12,19 +12,21 @@ public sealed partial class RetentionService : BackgroundService
     private readonly IMetricStore _metrics;
     private readonly IEventStore _events;
     private readonly IAuthStore _auth;
+    private readonly AuditService _audit;
     private readonly IHostStore _hosts;
     private readonly SettingsService _settings;
     private readonly LoginRateLimiter _limiter;
     private readonly TimeProvider _time;
     private readonly ILogger<RetentionService> _logger;
 
-    public RetentionService(IRawStore raw, IMetricStore metrics, IEventStore events, IHostStore hosts, IAuthStore auth, SettingsService settings, LoginRateLimiter limiter, TimeProvider time, ILogger<RetentionService> logger)
+    public RetentionService(IRawStore raw, IMetricStore metrics, IEventStore events, IHostStore hosts, IAuthStore auth, AuditService audit, SettingsService settings, LoginRateLimiter limiter, TimeProvider time, ILogger<RetentionService> logger)
     {
         _raw = raw;
         _metrics = metrics;
         _events = events;
         _hosts = hosts;
         _auth = auth;
+        _audit = audit;
         _settings = settings;
         _limiter = limiter;
         _time = time;
@@ -69,6 +71,7 @@ public sealed partial class RetentionService : BackgroundService
         await _events.DeleteOlderThanAsync(nowMs - (await _settings.GetIntAsync(SettingsService.EventDays, ct) * Steps.Day), ct);
         await _hosts.DeleteOlderThanAsync(nowMs - (await _settings.GetIntAsync(SettingsService.HostDays, ct) * Steps.Day), ct);
         await _auth.DeleteExpiredSessionsAsync(nowMs, ct);
+        await _audit.PruneAsync(nowMs, ct);
         _limiter.Prune();
     }
 
diff --git a/backend/src/MoShiro.Backend.Storage.Sqlite/Schema.cs b/backend/src/MoShiro.Backend.Storage.Sqlite/Schema.cs
index 2745ce7..1f03d07 100644
--- a/backend/src/MoShiro.Backend.Storage.Sqlite/Schema.cs
+++ b/backend/src/MoShiro.Backend.Storage.Sqlite/Schema.cs
@@ -191,6 +191,21 @@ internal static class Schema
             connection.Exec("ALTER TABLE join_tokens ADD COLUMN created_by TEXT");
             connection.Exec("ALTER TABLE agents ADD COLUMN added_by TEXT");
             connection.Exec("ALTER TABLE probes ADD COLUMN added_by TEXT");
+            connection.Exec("""
+                CREATE TABLE audit_log (
+                  id INTEGER PRIMARY KEY,
+                  at INTEGER NOT NULL,
+                  user_id TEXT,
+                  actor TEXT NOT NULL,
+                  method TEXT NOT NULL,
+                  action TEXT NOT NULL,
+                  target TEXT,
+                  detail TEXT,
+                  remote TEXT,
+                  success INTEGER NOT NULL
+                )
+                """);
+            connection.Exec("CREATE INDEX ix_audit_time ON audit_log (at)");
             connection.Exec("PRAGMA user_version = 13");
             transaction.Commit();
         }
diff --git a/backend/src/MoShiro.Backend.Storage.Sqlite/SqliteAuditStore.cs b/backend/src/MoShiro.Backend.Storage.Sqlite/SqliteAuditStore.cs
new file mode 100644
index 0000000..cbeb7d7
--- /dev/null
+++ b/backend/src/MoShiro.Backend.Storage.Sqlite/SqliteAuditStore.cs
@@ -0,0 +1,33 @@
+using MoShiro.Backend.Application;
+
+namespace MoShiro.Backend.Storage.Sqlite;
+
+public sealed class SqliteAuditStore : IAuditStore
+{
+    private readonly SqliteDatabase _db;
+
+    public SqliteAuditStore(SqliteDatabase db)
+    {
+        _db = db;
+    }
+
+    public ValueTask AddAsync(AuditRecord record, CancellationToken ct) =>
+        _db.ExecuteAsync(
+            c => c.Exec(
+                "INSERT INTO audit_log (at, user_id, actor, method, action, target, detail, remote, success) VALUES (@at, @uid, @actor, @method, @action, @target, @detail, @remote, @ok)",
+                ("@at", record.AtMs), ("@uid", record.UserId), ("@actor", record.Actor), ("@method", record.Method), ("@action", record.Action),
+                ("@target", record.Target), ("@detail", record.Detail), ("@remote", record.Remote), ("@ok", record.Success ? 1 : 0)),
+            ct);
+
+    public ValueTask<IReadOnlyList<AuditRecord>> ListAsync(AuditQuery query, CancellationToken ct) =>
+        _db.ReadAsync<IReadOnlyList<AuditRecord>>(
+            c => c.Query(
+                "SELECT id, at, user_id, actor, method, action, target, detail, remote, success FROM audit_log " +
+                "WHERE (@before IS NULL OR id < @before) AND (@actor IS NULL OR actor = @actor) AND (@action IS NULL OR action = @action) ORDER BY id DESC LIMIT @limit",
+                r => new AuditRecord(r.GetInt64(0), r.GetInt64(1), r.NullableString(2), r.GetString(3), r.GetString(4), r.GetString(5), r.NullableString(6), r.NullableString(7), r.NullableString(8), r.GetInt64(9) != 0),
+                ("@before", query.BeforeId), ("@actor", query.Actor), ("@action", query.Action), ("@limit", query.Limit)),
+            ct);
+
+    public ValueTask<int> DeleteOlderThanAsync(long cutoffMs, CancellationToken ct) =>
+        _db.WriteAsync(c => c.Exec("DELETE FROM audit_log WHERE at < @cutoff", ("@cutoff", cutoffMs)), ct);
+}
diff --git a/backend/src/MoShiro.Backend.Storage.Sqlite/StorageServiceCollectionExtensions.cs b/backend/src/MoShiro.Backend.Storage.Sqlite/StorageServiceCollectionExtensions.cs
index bf05c7f..63b4f1a 100644
--- a/backend/src/MoShiro.Backend.Storage.Sqlite/StorageServiceCollectionExtensions.cs
+++ b/backend/src/MoShiro.Backend.Storage.Sqlite/StorageServiceCollectionExtensions.cs
@@ -22,6 +22,7 @@ public static class StorageServiceCollectionExtensions
         services.AddSingleton<IHostStore, SqliteHostStore>();
         services.AddSingleton<INodeMetaStore, SqliteNodeMetaStore>();
         services.AddSingleton<IAuthStore, SqliteAuthStore>();
+        services.AddSingleton<IAuditStore, SqliteAuditStore>();
         services.AddSingleton<IRawStore, SqliteRawStore>();
         services.AddSingleton<IMetricStore, SqliteMetricStore>();
         services.AddSingleton<IStorageHealth, SqliteStorageHealth>();
diff --git a/backend/tests/MoShiro.Backend.Tests/AuditTests.cs b/backend/tests/MoShiro.Backend.Tests/AuditTests.cs
new file mode 100644
index 0000000..9d1f5ec
--- /dev/null
+++ b/backend/tests/MoShiro.Backend.Tests/AuditTests.cs
@@ -0,0 +1,68 @@
+using System.Net;
+using System.Text.Json.Nodes;
+
+namespace MoShiro.Backend.Tests;
+
+/// <summary>审计日志：写操作、登录成败都会记一行；谁做的（用户名或 key:令牌名）、结果、细节。</summary>
+[Collection("probe-e2e")]
+public sealed class AuditTests
+{
+    private readonly BackendFixture _backend;
+
+    public AuditTests(BackendFixture backend)
+    {
+        _backend = backend;
+    }
+
+    /// <summary>审计在响应发完之后才写，轮询一下。</summary>
+    private async Task<JsonNode?> FindAsync(string query, Func<JsonNode, bool> match)
+    {
+        for (int i = 0; i < 50; i++)
+        {
+            JsonNode page = JsonNode.Parse(await _backend.Admin.GetStringAsync("/api/admin/audit?" + query))!;
+            if (page["items"]!.AsArray().FirstOrDefault(x => x is not null && match(x)) is { } found)
+            {
+                return found;
+            }
+
+            await Task.Delay(100);
+        }
+
+        return null;
+    }
+
+    [Fact]
+    public async Task WriteActions_AreRecorded_WithWhoAndTheDetail()
+    {
+        string note = "audit-" + Guid.NewGuid().ToString("N")[..8];
+        using HttpResponseMessage created = await _backend.Admin.PostAsync("/api/admin/join-tokens", BackendFixture.Json(new JsonObject { ["role"] = "probe", ["note"] = note }));
+        Assert.Equal(HttpStatusCode.Created, created.StatusCode);
+
+        JsonNode? row = await FindAsync("limit=100", x => x["detail"]?.GetValue<string>().Contains(note, StringComparison.Ordinal) == true);
+        Assert.NotNull(row);
+        Assert.StartsWith("key:", row["actor"]!.GetValue<string>(), StringComparison.Ordinal);
+        Assert.Equal("key", row["method"]!.GetValue<string>());
+        Assert.True(row["success"]!.GetValue<bool>());
+        Assert.False(string.IsNullOrEmpty(row["action"]!.GetValue<string>()));
+    }
+
+    [Fact]
+    public async Task FailedSignIn_IsRecorded_WithTheAttemptedName_AndWithoutThePassword()
+    {
+        string name = "nobody-" + Guid.NewGuid().ToString("N")[..8];
+        using HttpResponseMessage denied = await _backend.Anonymous.PostAsync("/api/admin/auth/login", BackendFixture.Json(new JsonObject { ["username"] = name, ["password"] = "secret-pw-123" }));
+        Assert.Equal(HttpStatusCode.Unauthorized, denied.StatusCode);
+
+        JsonNode? row = await FindAsync("action=auth.login&limit=100", x => x["actor"]!.GetValue<string>() == name);
+        Assert.NotNull(row);
+        Assert.False(row["success"]!.GetValue<bool>());
+        Assert.DoesNotContain("secret-pw-123", row.ToJsonString(), StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public async Task Audit_NeedsItsOwnCapability()
+    {
+        using HttpResponseMessage response = await _backend.Anonymous.GetAsync("/api/admin/audit");
+        Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
+    }
+}
diff --git a/web/admin/src/pages/System.tsx b/web/admin/src/pages/System.tsx
index ef7651f..1cc6d72 100644
--- a/web/admin/src/pages/System.tsx
+++ b/web/admin/src/pages/System.tsx
@@ -1,7 +1,7 @@
 import { Download, KeyRound, Plus, Trash2 } from 'lucide-react'
 import { useEffect, useMemo, useState, type ReactNode } from 'react'
 import { api } from '@shared/api/client'
-import type { AgentDto, ApiTokenDto, BuildInfoDto, CapabilityCatalogDto, MeDto, PasskeyDto, NodeUpdateDto, ReleaseDto, CreatedApiTokenDto, EventDto, Page, ProbeDto, RawChunkMetaDto, RecomputeDto, SettingDto, UserDto } from '@shared/api/types'
+import type { AgentDto, ApiTokenDto, BuildInfoDto, CapabilityCatalogDto, MeDto, PasskeyDto, NodeUpdateDto, ReleaseDto, CreatedApiTokenDto, AuditDto, EventDto, Page, ProbeDto, RawChunkMetaDto, RecomputeDto, SettingDto, UserDto } from '@shared/api/types'
 import { fmtBuiltAt, frontendBuild } from '@shared/buildInfo'
 import { fmtNum, fmtTime } from '@shared/format'
 import { translateSetting } from '@shared/i18n'
@@ -10,7 +10,7 @@ import { Chip, Confirm, CopyButton, Dialog, Empty, ErrorNotice, Field, Segmented
 import { CapabilityPicker, capabilityName } from './CapabilityPicker'
 import { PasskeyAddForm } from './PasskeyAdd'
 
-type Tab = 'settings' | 'versions' | 'tokens' | 'users' | 'events' | 'raw' | 'analysis'
+type Tab = 'settings' | 'versions' | 'tokens' | 'users' | 'audit' | 'events' | 'raw' | 'analysis'
 
 const RESTART_KEYS = ['fleet.restart_enabled', 'fleet.restart_hour', 'fleet.restart_minute', 'fleet.restart_utc_offset_minutes']
 
@@ -636,6 +636,55 @@ function Users() {
   )
 }
 
+/** 审计：谁在什么时候做了什么。写操作、登录成败都在里面，保留一年。 */
+function Audit() {
+  const [actor, setActor] = useState('')
+  const [action, setAction] = useState('')
+  const audit = useQuery(() => api.get<Page<AuditDto>>('/api/admin/audit', { actor: actor || undefined, action: action || undefined, limit: 100 }), [actor, action], 10_000)
+  return (
+    <div className="card">
+      <div className="row wrap" style={{ marginBottom: 12 }}>
+        <input className="input" style={{ width: 200 }} placeholder="按操作者筛选，例如 admin" value={actor} onChange={(e) => setActor(e.target.value)} />
+        <input className="input" style={{ width: 240 }} placeholder="按操作筛选，例如 auth.login" value={action} onChange={(e) => setAction(e.target.value)} />
+        <span className="right">{audit.loading && !audit.data ? <Spinner /> : null}</span>
+      </div>
+      <ErrorNotice error={audit.error} />
+      {(audit.data?.items ?? []).length === 0 ? (
+        <Empty>没有记录</Empty>
+      ) : (
+        <table className="table">
+          <thead>
+            <tr>
+              <th>时间</th>
+              <th>操作者</th>
+              <th>方式</th>
+              <th>操作</th>
+              <th>对象 / 细节</th>
+              <th>来源</th>
+              <th>结果</th>
+            </tr>
+          </thead>
+          <tbody>
+            {audit.data?.items.map((a) => (
+              <tr key={a.id}>
+                <td className="muted num">{fmtTime(a.at)}</td>
+                <td>{a.actor}</td>
+                <td className="muted">{a.method === 'key' ? 'API 令牌' : a.method === 'passkey' ? 'Passkey' : '密码'}</td>
+                <td className="mono">{a.action}</td>
+                <td className="mono muted">{[a.target, a.detail].filter(Boolean).join(' · ')}</td>
+                <td className="mono faint">{a.remote ?? ''}</td>
+                <td>
+                  <Chip tone={a.success ? 'ok' : 'bad'}>{a.success ? '成功' : '失败'}</Chip>
+                </td>
+              </tr>
+            ))}
+          </tbody>
+        </table>
+      )}
+    </div>
+  )
+}
+
 function Events() {
   const [kind, setKind] = useState('')
   const events = useQuery(() => api.get<Page<EventDto>>('/api/admin/events', { kind: kind || undefined, limit: 100 }), [kind], 10_000)
@@ -783,6 +832,7 @@ export function System() {
             { value: 'versions' as const, label: '版本' },
             { value: 'tokens' as const, label: 'API 令牌' },
             { value: 'users' as const, label: '用户' },
+            { value: 'audit' as const, label: '审计' },
             { value: 'events' as const, label: '事件' },
             { value: 'raw' as const, label: '原始数据' },
             { value: 'analysis' as const, label: '分析' },
@@ -790,7 +840,7 @@ export function System() {
           value={tab}
           onChange={setTab}
         />
-        {tab === 'settings' ? <Settings /> : tab === 'versions' ? <Versions /> : tab === 'tokens' ? <Tokens /> : tab === 'users' ? <Users /> : tab === 'events' ? <Events /> : tab === 'raw' ? <Raw /> : <Analysis />}
+        {tab === 'settings' ? <Settings /> : tab === 'versions' ? <Versions /> : tab === 'tokens' ? <Tokens /> : tab === 'users' ? <Users /> : tab === 'audit' ? <Audit /> : tab === 'events' ? <Events /> : tab === 'raw' ? <Raw /> : <Analysis />}
       </div>
     </>
   )
diff --git a/web/shared/api/schema.ts b/web/shared/api/schema.ts
index dec44f8..f02fce8 100644
--- a/web/shared/api/schema.ts
+++ b/web/shared/api/schema.ts
@@ -814,6 +814,23 @@ export interface paths {
         patch?: never;
         trace?: never;
     };
+    "/api/admin/audit": {
+        parameters: {
+            query?: never;
+            header?: never;
+            path?: never;
+            cookie?: never;
+        };
+        /** Audit log of admin actions, newest first */
+        get: operations["audit_list"];
+        put?: never;
+        post?: never;
+        delete?: never;
+        options?: never;
+        head?: never;
+        patch?: never;
+        trace?: never;
+    };
     "/api/admin/api-tokens": {
         parameters: {
             query?: never;
@@ -1183,6 +1200,19 @@ export interface components {
             /** Format: date-time */
             revoked_at: unknown;
         };
+        AuditDto: {
+            /** Format: int64 */
+            id: number | string;
+            /** Format: date-time */
+            at: unknown;
+            actor: string;
+            method: string;
+            action: string;
+            target: null | string;
+            detail: null | string;
+            remote: null | string;
+            success: boolean;
+        };
         BackendUpdateDto: {
             channel: string;
             enabled: boolean;
@@ -1634,6 +1664,10 @@ export interface components {
             items: components["schemas"]["ApiTokenDto"][];
             next_cursor: null | string;
         };
+        PageDtoOfAuditDto: {
+            items: components["schemas"]["AuditDto"][];
+            next_cursor: null | string;
+        };
         PageDtoOfEventDto: {
             items: components["schemas"]["EventDto"][];
             next_cursor: null | string;
@@ -4783,6 +4817,58 @@ export interface operations {
             };
         };
     };
+    audit_list: {
+        parameters: {
+            query?: {
+                actor?: string;
+                action?: string;
+                limit?: number | string;
+                cursor?: string;
+            };
+            header?: never;
+            path?: never;
+            cookie?: never;
+        };
+        requestBody?: never;
+        responses: {
+            /** @description OK */
+            200: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/json": components["schemas"]["PageDtoOfAuditDto"];
+                };
+            };
+            /** @description Bad Request */
+            400: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/problem+json": components["schemas"]["ProblemDto"];
+                };
+            };
+            /** @description Unauthorized */
+            401: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/problem+json": components["schemas"]["ProblemDto"];
+                };
+            };
+            /** @description Forbidden */
+            403: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/problem+json": components["schemas"]["ProblemDto"];
+                };
+            };
+        };
+    };
     api_tokens_list: {
         parameters: {
             query?: never;
diff --git a/web/shared/api/types.ts b/web/shared/api/types.ts
index 0833115..8d1cf71 100644
--- a/web/shared/api/types.ts
+++ b/web/shared/api/types.ts
@@ -47,6 +47,7 @@ export type MeDto = Narrow<S['MeDto']>
 export type SettingDto = Narrow<S['SettingDto']>
 export type UserDto = Narrow<S['UserDto']>
 export type EventDto = Narrow<S['EventDto']>
+export type AuditDto = Narrow<S['AuditDto']>
 export type GapDto = Narrow<S['GapDto']>
 export type RecomputeDto = Narrow<S['RecomputeDto']>
 export type RawChunkMetaDto = Narrow<S['RawChunkMetaDto']>