diff --git a/proto/agynio/api/agents/v1/agents.proto b/proto/agynio/api/agents/v1/agents.proto
index b0d414e..3b7082c 100644
--- a/proto/agynio/api/agents/v1/agents.proto
+++ b/proto/agynio/api/agents/v1/agents.proto
@@ -45,6 +45,11 @@ service AgentsService {
   rpc UpdateSandboxRuntimeState(UpdateSandboxRuntimeStateRequest) returns (UpdateSandboxRuntimeStateResponse);
   rpc UpdateSandboxLastSession(UpdateSandboxLastSessionRequest) returns (UpdateSandboxLastSessionResponse);
 
+  // --- Sandbox Layouts ---
+  rpc GetSandboxLayout(GetSandboxLayoutRequest) returns (GetSandboxLayoutResponse);
+  rpc SetSandboxLayout(SetSandboxLayoutRequest) returns (SetSandboxLayoutResponse);
+  rpc SetSandboxLayoutDirectories(SetSandboxLayoutDirectoriesRequest) returns (SetSandboxLayoutDirectoriesResponse);
+
   // --- Agent Instances ---
   rpc CreateInstance(CreateInstanceRequest) returns (CreateInstanceResponse);
   rpc GetInstance(GetInstanceRequest) returns (GetInstanceResponse);
@@ -838,6 +843,81 @@ message UpdateSandboxLastSessionResponse {
   Sandbox sandbox = 1;
 }
 
+// ===========================================================================
+// Sandbox Layout
+// ===========================================================================
+
+// One identity's ordered set of shells in one sandbox.
+message SandboxLayout {
+  string sandbox_id = 1;
+
+  // Whose layout this is. Resolved from authenticated context on the external
+  // methods; not accepted as request input.
+  string identity_id = 2;
+
+  // Incremented on every write.
+  int64 version = 3;
+
+  // Ordered. Position is display order.
+  repeated SandboxTab tabs = 4;
+}
+
+message SandboxTab {
+  // Opaque, client-generated, ^[A-Za-z0-9_-]{1,64}$. Matches shell_id on a
+  // SHELL_ATTACH terminal session.
+  string shell_id = 1;
+
+  // Assigned when the tab is opened; not reused within a layout.
+  int32 number = 2;
+
+  // A caller-supplied name. Unset means the client derives one.
+  optional string name_override = 3;
+
+  // Working directory, absolute.
+  optional string cwd = 4;
+
+  // When a session last attached to this shell.
+  optional google.protobuf.Timestamp last_attached_at = 5;
+}
+
+message GetSandboxLayoutRequest {
+  string sandbox_id = 1;
+}
+
+message GetSandboxLayoutResponse {
+  // Empty at version 0 when no layout exists.
+  SandboxLayout layout = 1;
+}
+
+message SetSandboxLayoutRequest {
+  string sandbox_id = 1;
+
+  // The version the caller read. A mismatch returns FailedPrecondition.
+  int64 version = 2;
+
+  repeated SandboxTab tabs = 3;
+}
+
+message SetSandboxLayoutResponse {
+  SandboxLayout layout = 1;
+}
+
+// Internal only. Sets cwd on tabs of every layout of one sandbox, matched by
+// shell_id. Unmatched ids are ignored. Not version-checked.
+message SetSandboxLayoutDirectoriesRequest {
+  string sandbox_id = 1;
+  repeated ShellDirectory directories = 2;
+}
+
+message ShellDirectory {
+  string shell_id = 1;
+  string cwd = 2;
+}
+
+message SetSandboxLayoutDirectoriesResponse {
+  int32 tabs_updated = 1;
+}
+
 // ===========================================================================
 // Volume
 // ===========================================================================
diff --git a/proto/agynio/api/gateway/v1/agents.proto b/proto/agynio/api/gateway/v1/agents.proto
index adae111..564d00b 100644
--- a/proto/agynio/api/gateway/v1/agents.proto
+++ b/proto/agynio/api/gateway/v1/agents.proto
@@ -36,6 +36,12 @@ service AgentsGateway {
   rpc DeleteSandbox(agynio.api.agents.v1.DeleteSandboxRequest) returns (agynio.api.agents.v1.DeleteSandboxResponse);
   rpc EnsureSandboxRunning(agynio.api.agents.v1.EnsureSandboxRunningRequest) returns (agynio.api.agents.v1.EnsureSandboxRunningResponse);
 
+  // --- Sandbox Layouts ---
+  // Operate on the caller's own layout; identity comes from authenticated
+  // context and is not a request field.
+  rpc GetSandboxLayout(agynio.api.agents.v1.GetSandboxLayoutRequest) returns (agynio.api.agents.v1.GetSandboxLayoutResponse);
+  rpc SetSandboxLayout(agynio.api.agents.v1.SetSandboxLayoutRequest) returns (agynio.api.agents.v1.SetSandboxLayoutResponse);
+
   // --- Agent Instances ---
   rpc CreateInstance(agynio.api.agents.v1.CreateInstanceRequest) returns (agynio.api.agents.v1.CreateInstanceResponse);
   rpc GetInstance(agynio.api.agents.v1.GetInstanceRequest) returns (agynio.api.agents.v1.GetInstanceResponse);
diff --git a/proto/agynio/api/gateway/v1/terminal.proto b/proto/agynio/api/gateway/v1/terminal.proto
index f35127a..9da0088 100644
--- a/proto/agynio/api/gateway/v1/terminal.proto
+++ b/proto/agynio/api/gateway/v1/terminal.proto
@@ -24,6 +24,14 @@ message CreateTerminalSessionRequest {
   // The directory to serve. Meaningful only when kind is SYNC. Must be
   // absolute.
   string sync_root = 5;
+
+  // Names the shell. Required when kind is SHELL_ATTACH, ignored otherwise.
+  // Opaque, ^[A-Za-z0-9_-]{1,64}$.
+  string shell_id = 6;
+
+  // Working directory for the shell. Optional; applied when the shell is
+  // created. Must be absolute when set.
+  string shell_cwd = 7;
 }
 
 message CreateTerminalSessionResponse {
diff --git a/proto/agynio/api/terminal_proxy/v1/terminal_proxy.proto b/proto/agynio/api/terminal_proxy/v1/terminal_proxy.proto
index 1c1b2c8..bfab652 100644
--- a/proto/agynio/api/terminal_proxy/v1/terminal_proxy.proto
+++ b/proto/agynio/api/terminal_proxy/v1/terminal_proxy.proto
@@ -18,7 +18,7 @@ enum SessionKind {
   // ends up in a ticket.
   SESSION_KIND_UNSPECIFIED = 0;
 
-  // A login shell on a PTY, with the platform binaries on PATH.
+  // A login shell on a PTY. The PTY closes with the connection.
   SESSION_KIND_SHELL = 1;
 
   // A caller-supplied command on a PTY. Carries no more privilege than SHELL —
@@ -28,6 +28,11 @@ enum SessionKind {
   // The workspace sync endpoint. Non-TTY: no PTY, no resize, and stdout kept
   // separate from stderr so diagnostics cannot corrupt protocol frames.
   SESSION_KIND_SYNC = 3;
+
+  // A PTY on a named shell that outlives the session. Attaches to shell_id,
+  // creating it when it does not exist. A second session on the same shell
+  // displaces the first.
+  SESSION_KIND_SHELL_ATTACH = 4;
 }
 
 message IssueTicketRequest {
@@ -48,6 +53,15 @@ message IssueTicketRequest {
   // absolute; it is normalized before being bound into the ticket, and
   // resolved against the real filesystem inside the container.
   string sync_root = 6;
+
+  // Names the shell. Required when kind is SHELL_ATTACH, ignored otherwise.
+  // Client-generated and opaque, matching ^[A-Za-z0-9_-]{1,64}$.
+  string shell_id = 7;
+
+  // Working directory for the shell. Optional; meaningful only when kind is
+  // SHELL_ATTACH. Applied when the shell is created and ignored when it
+  // already exists. Must be absolute.
+  string shell_cwd = 8;
 }
 
 message IssueTicketResponse {