internal/app/app.go

@@ -8,6 +8,7 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log"
 	"net"
@@ -627,6 +628,9 @@ func Run(opt Options) error {
 		if req.Actor == "" || req.Actor != req.Owner || req.ConversationID == "" || req.AnchorMessageID == "" || req.HostProjectID == "" {
 			return fmt.Errorf("formal project command requires an authenticated conversation source")
 		}
+		if err := rejectScratchCommandHost(st, req); err != nil {
+			return err
+		}
 		conv, err := st.GetConversation(req.Owner, req.ConversationID)
 		if err != nil || string(conv.ProjectID) != req.HostProjectID {
 			return fmt.Errorf("formal project command conversation binding changed")
@@ -1123,6 +1127,27 @@ func splitKeyPool(s string) []string {
 	return out
 }
 
+// ErrScratchCommandHost 是命令分发的临时会话门禁：临时会话没有 RDM 项目域，
+// 任何以基座项目为前提的命令（rdm.* 与正式项目命令）在里面一律不可用。
+var ErrScratchCommandHost = errors.New("not available in scratch sessions")
+
+// rejectScratchCommandHost 在命令总线内部分发（宿主与插件处理器共用的分发面）
+// 上执行同一个门禁。基座项目是临时会话时拒绝；不是临时会话（包括项目读不到）
+// 时交回原路径，不改变任何现有判定。
+func rejectScratchCommandHost(st *store.Store, req cmdbus.Request) error {
+	if st == nil || req.HostProjectID == "" {
+		return nil
+	}
+	handled, err := st.ScratchProjectDecision(req.HostProjectID, req.Owner)
+	if err != nil {
+		return err
+	}
+	if handled {
+		return ErrScratchCommandHost
+	}
+	return nil
+}
+
 // busAdapter EXT-14：cmdbus.Bus 适配 runmgr.CommandSource。视图类型转换在此收口
 // （runmgr 不依赖 cmdbus，边不进架构基线）；Entrance 由 runmgr 固定为 agent。
 type busAdapter struct{ bus *cmdbus.Bus }

internal/app/scratch_gates_test.go

@@ -0,0 +1,117 @@
+package app
+
+// 临时会话的内部命令分发门禁（U2）：组合根在命令总线的项目预检入口上拒绝
+// “基座项目是临时会话”的正式项目命令，宿主与插件处理器共用这一条分发面。
+
+import (
+	"context"
+	"errors"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	agentcommand "agent-command"
+	"agent-system-backend/internal/cmdbus"
+	"agent-system-backend/internal/store"
+	core "agent-system-core"
+)
+
+func newScratchGateStore(t *testing.T) (*store.Store, core.Project, core.Conversation) {
+	t.Helper()
+	st, err := store.OpenSQLite(filepath.Join(t.TempDir(), "scratch-gate.db"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { st.Close() })
+	if err := st.CreateAccount("alice", "Alice", "", false); err != nil {
+		t.Fatal(err)
+	}
+	project, conversation, err := st.CreateScratchSessionAccountChecked("alice", "临时会话", "临时会话", "", false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return st, project, conversation
+}
+
+// TestScratchCommandHostGateDecidesOwnership 门禁本身：属主的临时会话拒绝，
+// 普通项目与无基座项目的分发不受影响；非属主按存储判定（NotFound）。
+func TestScratchCommandHostGateDecidesOwnership(t *testing.T) {
+	st, project, _ := newScratchGateStore(t)
+
+	if err := rejectScratchCommandHost(st, cmdbus.Request{
+		ID: "rdm.reqs.add", Owner: "alice", HostProjectID: string(project.ID),
+	}); !errors.Is(err, ErrScratchCommandHost) {
+		t.Fatalf("scratch host project accepted a formal command: %v", err)
+	}
+	normal, err := st.CreateProject("alice", "普通项目")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := rejectScratchCommandHost(st, cmdbus.Request{
+		ID: "rdm.reqs.add", Owner: "alice", HostProjectID: string(normal.ID),
+	}); err != nil {
+		t.Fatalf("normal host project refused: %v", err)
+	}
+	if err := rejectScratchCommandHost(st, cmdbus.Request{ID: "rdm.reqs.add", Owner: "alice"}); err != nil {
+		t.Fatalf("hostless dispatch refused: %v", err)
+	}
+	// 非属主不能把自己的“属主身份”带进临时会话。
+	if err := rejectScratchCommandHost(st, cmdbus.Request{
+		ID: "rdm.reqs.add", Owner: "bob", HostProjectID: string(project.ID),
+	}); !errors.Is(err, store.ErrNotFound) {
+		t.Fatalf("non-owner scratch dispatch = %v", err)
+	}
+}
+
+// TestScratchCommandHostGateOnBusPreflight 门禁在真实分发面上生效：正式项目命令
+// 在临时会话宿主上被拒，普通项目宿主不受影响（失败原因来自后续的会话来源校验，
+// 不是临时会话门禁）。
+func TestScratchCommandHostGateOnBusPreflight(t *testing.T) {
+	st, project, conversation := newScratchGateStore(t)
+	normal, err := st.CreateProject("alice", "普通项目")
+	if err != nil {
+		t.Fatal(err)
+	}
+	normalConv, err := st.CreateConversation("alice", string(normal.ID), "会话", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	bus := cmdbus.New(st, nil, func() time.Time { return time.Unix(1700000000, 0).UTC() })
+	bus.SetProjectWorkPreflight(func(ctx context.Context, req cmdbus.Request) error {
+		if req.Actor == "" || req.Actor != req.Owner || req.ConversationID == "" || req.AnchorMessageID == "" || req.HostProjectID == "" {
+			return errors.New("formal project command requires an authenticated conversation source")
+		}
+		if err := rejectScratchCommandHost(st, req); err != nil {
+			return err
+		}
+		conv, err := st.GetConversation(req.Owner, req.ConversationID)
+		if err != nil || string(conv.ProjectID) != req.HostProjectID {
+			return errors.New("formal project command conversation binding changed")
+		}
+		return errors.New("source analysis did not commit a proceed decision")
+	})
+	if err := bus.RegisterPluginCommand(agentcommand.CommandSpec{ID: "rdm.reqs.add", Title: "登记需求"},
+		func(context.Context, cmdbus.Request) (any, error) { return map[string]any{"ok": true}, nil }); err != nil {
+		t.Fatal(err)
+	}
+
+	scratchResp := bus.Dispatch(context.Background(), cmdbus.Request{
+		ID: "rdm.reqs.add", Entrance: "api", Actor: "alice", Owner: "alice",
+		ConversationID: string(conversation.ID), AnchorMessageID: "msg-1", HostProjectID: string(project.ID),
+	})
+	if scratchResp.Receipt.State != agentcommand.StateRejected ||
+		!strings.Contains(scratchResp.Receipt.Reason, ErrScratchCommandHost.Error()) {
+		t.Fatalf("scratch host dispatch = %+v (want %s)", scratchResp.Receipt, ErrScratchCommandHost)
+	}
+
+	normalResp := bus.Dispatch(context.Background(), cmdbus.Request{
+		ID: "rdm.reqs.add", Entrance: "api", Actor: "alice", Owner: "alice",
+		ConversationID: string(normalConv.ID), AnchorMessageID: "msg-1", HostProjectID: string(normal.ID),
+	})
+	if normalResp.Receipt.State != agentcommand.StateRejected ||
+		strings.Contains(normalResp.Receipt.Reason, ErrScratchCommandHost.Error()) {
+		t.Fatalf("normal host dispatch was blocked by the scratch gate: %+v", normalResp.Receipt)
+	}
+}

internal/runmgr/memory.go

@@ -2,6 +2,7 @@ package runmgr
 
 import (
 	"context"
+	"errors"
 	"time"
 
 	"agent-native/runtime/memory"
@@ -17,23 +18,38 @@ type storeMemory struct {
 	projectID            string
 	checked              bool
 	allowImplicitDefault bool
+	// scratch 为真时端口对 user/project 记忆完全关闭：临时会话不读也不写
+	// 跨会话记忆（U2 隔离）。会话内状态不受影响。
+	scratch bool
 }
 
+// ErrScratchMemory 临时会话不写记忆：记忆是跨会话的共享层。
+var ErrScratchMemory = errors.New("memory is not available in scratch sessions")
+
 // NewStoreMemory 构建端口实现（owner 为空时用默认租户）。
 func NewStoreMemory(st *store.Store, owner, projectID string) memory.Store {
+	return newStoreMemory(st, owner, projectID, false)
+}
+
+func newStoreMemory(st *store.Store, owner, projectID string, checked bool) *storeMemory {
 	if owner == "" {
 		owner = store.OwnerDefault
 	}
-	return &storeMemory{st: st, owner: owner, projectID: projectID}
+	return &storeMemory{st: st, owner: owner, projectID: projectID, checked: checked}
 }
 
-func newAccountCheckedStoreMemory(st *store.Store, owner, projectID string, allowImplicitDefault bool) memory.Store {
-	return &storeMemory{st: st, owner: owner, projectID: projectID, checked: true, allowImplicitDefault: allowImplicitDefault}
+func newAccountCheckedStoreMemory(st *store.Store, owner, projectID string, allowImplicitDefault bool) *storeMemory {
+	port := newStoreMemory(st, owner, projectID, true)
+	port.allowImplicitDefault = allowImplicitDefault
+	return port
 }
 
 // Recall 按 scope 过滤（空 = 不限，保持迁移前 Memories() 的全量语义），
 // 过期与空内容条目的剔除与文案渲染在 memory.Block（同一形态）。
 func (m *storeMemory) Recall(ctx context.Context, q memory.RecallQuery) ([]memory.Entry, error) {
+	if m.scratch {
+		return nil, nil
+	}
 	projectID := ""
 	if q.Scope == "project" {
 		projectID = m.projectID
@@ -65,14 +81,21 @@ func (c *runCtx) StoreMemory() memory.Store {
 	if c.mgr == nil || c.mgr.st == nil {
 		return nil
 	}
+	var port *storeMemory
 	if c.mgr.accountEffectiveAuthorization != nil {
-		return newAccountCheckedStoreMemory(c.mgr.st, c.run.Owner, c.run.ProjectID, c.mgr.accountAllowImplicitLocal)
+		port = newAccountCheckedStoreMemory(c.mgr.st, c.run.Owner, c.run.ProjectID, c.mgr.accountAllowImplicitLocal)
+	} else {
+		port = newStoreMemory(c.mgr.st, c.run.Owner, c.run.ProjectID, false)
 	}
-	return NewStoreMemory(c.mgr.st, c.run.Owner, c.run.ProjectID)
+	port.scratch = c.scratchProject()
+	return port
 }
 
 // Append 写回一条（project scope 用适配器的项目上下文）。
 func (m *storeMemory) Append(ctx context.Context, e memory.Entry) error {
+	if m.scratch {
+		return ErrScratchMemory
+	}
 	projectID := e.ProjectID
 	if e.Scope == "project" && projectID == "" {
 		projectID = m.projectID

internal/runmgr/project_context.go

@@ -31,8 +31,10 @@ func (m *Manager) SetProjectContextSourceRechecker(fn func(context.Context, exte
 	m.projectSourceRechecker = fn
 }
 
+// ProjectContextEnabled 报告本回合是否组装项目上下文。临时会话没有 RDM 项目
+// 上下文（它就是一个通用代理会话），所以即使 provider 已注册也不启用。
 func (c *runCtx) ProjectContextEnabled() bool {
-	return c.run.ProjectID != "" && c.mgr.projectContextResolver != nil
+	return c.run.ProjectID != "" && c.mgr.projectContextResolver != nil && !c.scratchProject()
 }
 
 // ValidateProjectCrossGuard links separate model streams in one persisted run.

internal/runmgr/runmgr.go

@@ -344,7 +344,7 @@ func (m *Manager) SetProjectWorkGate(preflight projectWorkPreflight, respond pro
 }
 
 func (c *runCtx) requireProjectWorkDecision(action string) error {
-	if !c.mgr.projectWorkObservationEnabled || c.run.ProjectID == "" {
+	if !c.projectWorkObservationApplies() {
 		return nil
 	}
 	for {
@@ -408,7 +408,38 @@ func (m *Manager) cancelActiveOwnerRuns(owner string) {
 		cancel()
 	}
 }
+
+// scratchProject 报告本次 run 的基座项目是否是临时会话。判据是存储里的 host
+// 标记（store.IsScratchProject），run 生命周期内项目不变，所以判定一次缓存。
+// 读不到项目时按“非临时会话”处理：临时与否只放宽自己的门禁，不收紧别人的。
+func (c *runCtx) scratchProject() bool {
+	if c == nil || c.mgr == nil || c.mgr.st == nil || c.run.ProjectID == "" {
+		return false
+	}
+	c.scratchOnce.Do(func() {
+		c.scratchHost, _ = c.mgr.st.IsScratchProjectID(string(c.run.ProjectID))
+	})
+	return c.scratchHost
+}
+
+// projectWorkObservationApplies 报告本回合是否走 RDM 观察/预检通道。临时会话
+// 没有 RDM（provider 从未见过它），观察与预检门都不适用：它就是一次普通聊天。
+func (c *runCtx) projectWorkObservationApplies() bool {
+	return c.mgr.projectWorkObservationEnabled && c.run.ProjectID != "" && !c.scratchProject()
+}
+
+// authorizeProjectWork is the run-side project work gate. A scratch project is
+// never known to the domain provider (RDM would always report false), so the
+// stored ownership decides: its owner works without the provider, everyone else
+// is NotFound. Ordinary projects keep the provider decision unchanged.
 func (m *Manager) authorizeProjectWork(ctx context.Context, owner string, id core.ID) error {
+	if m.st != nil {
+		if handled, err := m.st.ScratchProjectDecision(string(id), owner); err != nil {
+			return err
+		} else if handled {
+			return nil
+		}
+	}
 	if m.projectWorkAuthorization == nil {
 		return nil
 	}
@@ -531,6 +562,9 @@ type runCtx struct {
 	launch              *workflow.Launch
 	files               *filestate.Tracker
 	permissionMode      string
+	// scratchHost 缓存本次 run 的基座项目是否为临时会话（U2 隔离门禁）。
+	scratchHost bool
+	scratchOnce sync.Once
 	// 材料整理（附件即保证）：预启动说明注入第 0 回合；ensureMaterial 兜底幂等。
 	materialNote    string
 	workContext     string
@@ -807,11 +841,17 @@ func (c *runCtx) Injections() []runtime.ContextInjection {
 	if err != nil {
 		return nil
 	}
+	// 临时会话只带本会话自己的上下文条目：owner 级/项目级条目会把别的会话的
+	// 材料带进来，与“私有会话”相反。
+	scratch := c.scratchProject()
 	out := make([]runtime.ContextInjection, 0, len(list))
 	for _, e := range list {
 		if !e.Enabled {
 			continue
 		}
+		if scratch && e.ConversationID != c.run.ConversationID {
+			continue
+		}
 		out = append(out, runtime.ContextInjection{
 			Keys: e.Keys, Secondary: e.Secondary, Logic: e.Logic, Content: e.Content,
 			Constant: e.Constant, ScanDepth: e.ScanDepth, BudgetChars: e.BudgetChars,
@@ -824,6 +864,11 @@ func (c *runCtx) Memories() []core.MemoryEntry {
 	if c.mgr == nil || c.mgr.st == nil {
 		return nil
 	}
+	// 临时会话不读 user/project 级记忆：记忆是跨会话的，正好是被隔离的那一层。
+	// 会话内状态（SessionNote）不受影响。
+	if c.scratchProject() {
+		return nil
+	}
 	list, err := c.mgr.st.ListMemory(c.run.Owner, "", "")
 	if err != nil {
 		return nil
@@ -843,7 +888,7 @@ func (c *runCtx) Emit(typ core.StreamEventType, payload any) error {
 	if err := c.mgr.authorizeRunWork(c.ctx, c.run.Owner, c.run.ProjectID); err != nil {
 		return err
 	}
-	if c.mgr.projectWorkObservationEnabled && c.run.ProjectID != "" && (typ == core.EvMessageDelta || typ == core.EvThinkingDelta) {
+	if c.projectWorkObservationApplies() && (typ == core.EvMessageDelta || typ == core.EvThinkingDelta) {
 		// Project reply text is released only through the committed message after
 		// the complete run-source manifest receives a domain risk decision.
 		return nil
@@ -1237,8 +1282,13 @@ func indexTextOf(name, mime string, content []byte) string {
 }
 
 func (c *runCtx) Retrieve(q core.RetrievalQuery) ([]core.RetrievalHit, error) {
+	// 临时会话没有可检索的共享知识：@knowledge 与 knowledge_search 一律空手
+	// 而非报错（会话里的附件仍以材料形式进入本回合）。
+	if c.scratchProject() {
+		return []core.RetrievalHit{}, nil
+	}
 	hits, err := c.retrieveRaw(q)
-	if err != nil || !c.mgr.projectWorkObservationEnabled || c.run.ProjectID == "" {
+	if err != nil || !c.projectWorkObservationApplies() {
 		return hits, err
 	}
 	for _, hit := range hits {
@@ -1364,7 +1414,7 @@ func (c *runCtx) ExecuteTool(call core.ToolCallRequest) core.ToolCallResult {
 			if ct.ID != call.Name {
 				continue
 			}
-			if c.mgr.projectWorkObservationEnabled && c.run.ProjectID != "" {
+			if c.projectWorkObservationApplies() {
 				return core.ToolCallResult{CallID: call.CallID, Status: "error", Output: "project command tool awaits trusted source preflight"}
 			}
 			var params map[string]any
@@ -1403,7 +1453,7 @@ func (c *runCtx) ExecuteTool(call core.ToolCallRequest) core.ToolCallResult {
 		last := tc.arts[len(tc.arts)-1]
 		res.Artifact = &last
 	}
-	if c.mgr.projectWorkObservationEnabled && c.run.ProjectID != "" {
+	if c.projectWorkObservationApplies() {
 		if call.CallID == "" {
 			return core.ToolCallResult{CallID: call.CallID, Status: "error", Output: "project tool result lacks a stable call ID"}
 		}
@@ -1494,7 +1544,11 @@ var (
 )
 
 // crossReadSelf 加载当前会话并校验项目闸门；出站检查由调用方按目标是否为自身决定。
+// 临时会话直接关闭出站读取：它的材料不流向任何其他会话（U2）。
 func (t *toolCtx) crossReadSelf() (core.Conversation, error) {
+	if t.rc.scratchProject() {
+		return core.Conversation{}, ErrCrossReadDisabled
+	}
 	if !t.rc.eff.GetBool("crossSession.read", false) {
 		return core.Conversation{}, ErrCrossReadDisabled
 	}
@@ -1505,6 +1559,20 @@ func (t *toolCtx) crossReadSelf() (core.Conversation, error) {
 	return self, nil
 }
 
+// scratchPeer reports whether a conversation lives in a scratch project. Peers are
+// grouped by project so the trusted lookup runs once per distinct project.
+func (t *toolCtx) scratchPeer(c core.Conversation, cache map[core.ID]bool) bool {
+	if seen, ok := cache[c.ProjectID]; ok {
+		return seen
+	}
+	scratch, err := t.rc.mgr.st.IsScratchProjectID(string(c.ProjectID))
+	if err != nil {
+		scratch = false
+	}
+	cache[c.ProjectID] = scratch
+	return scratch
+}
+
 func (t *toolCtx) PeerConversations() ([]core.Conversation, error) {
 	self, err := t.crossReadSelf()
 	if err != nil {
@@ -1517,12 +1585,17 @@ func (t *toolCtx) PeerConversations() ([]core.Conversation, error) {
 	if err != nil {
 		return nil, err
 	}
+	scratchProjects := map[core.ID]bool{}
 	out := make([]core.Conversation, 0, len(convs))
 	for _, c := range convs {
 		// 只读他人：排除自身；私有会话不出现（存在性本身是信息）。
 		if c.ID == self.ID || c.CrossPrivate {
 			continue
 		}
+		// 临时会话永不作为同伴出现：它不是共享材料，而是别人的私有会话。
+		if t.scratchPeer(c, scratchProjects) {
+			continue
+		}
 		out = append(out, c)
 	}
 	return out, nil
@@ -1548,6 +1621,10 @@ func (t *toolCtx) PeerConversationMessages(conversationID string, limit int) ([]
 	if !isSelf && !self.AllowCrossRead {
 		return nil, ErrCrossReadDisabled
 	}
+	// 临时会话的材料不出会话：即使同租户、即使未标私有也拒（自读除外）。
+	if !isSelf && t.scratchPeer(target, map[core.ID]bool{}) {
+		return nil, ErrCrossReadForbidden
+	}
 	if !isSelf && (target.CrossPrivate || target.ProjectID != t.rc.run.ProjectID) {
 		return nil, ErrCrossReadForbidden
 	}

internal/runmgr/scratch_gates_test.go

@@ -0,0 +1,311 @@
+package runmgr
+
+import (
+	"context"
+	"errors"
+	"path/filepath"
+	"testing"
+
+	"agent-native/runtime/memory"
+	"agent-system-backend/internal/settings"
+	"agent-system-backend/internal/store"
+	"agent-system-backend/pkg/extension"
+	core "agent-system-core"
+)
+
+// 临时会话隔离门禁（U2，runmgr 侧）。产品规则：临时会话是“只属于自己的通用代理
+// 会话”——属主的回合像普通聊天一样跑，但它不读检索、不带 owner/项目级上下文、
+// 不读不写跨会话记忆、也不与任何会话互相读。
+
+type scratchRunEnv struct {
+	mgr      *Manager
+	st       *store.Store
+	svc      *settings.Service
+	project  core.Project // scratch 宿主项目
+	scratch  core.Conversation
+	normal   core.Project
+	normalAt core.Conversation // 普通项目的调用方会话
+	peer     core.Conversation // 普通项目的同伴会话
+}
+
+func newScratchRunEnv(t *testing.T) *scratchRunEnv {
+	t.Helper()
+	st, err := store.OpenSQLite(filepath.Join(t.TempDir(), "scratch.db"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { st.Close() })
+	if err := st.CreateAccount("alice", "Alice", "", false); err != nil {
+		t.Fatal(err)
+	}
+	if err := st.CreateAccount("bob", "Bob", "", false); err != nil {
+		t.Fatal(err)
+	}
+	env := &scratchRunEnv{st: st, mgr: &Manager{st: st}, svc: settings.NewService(st)}
+	project, conversation, err := st.CreateScratchSessionAccountChecked("alice", "临时会话", "临时会话", "", false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	env.project, env.scratch = project, conversation
+	normal, err := st.CreateProject("alice", "普通项目")
+	if err != nil {
+		t.Fatal(err)
+	}
+	env.normal = normal
+	if env.normalAt, err = st.CreateConversation("alice", normal.ID, "调用方", ""); err != nil {
+		t.Fatal(err)
+	}
+	if env.peer, err = st.CreateConversation("alice", normal.ID, "同伴", ""); err != nil {
+		t.Fatal(err)
+	}
+	msg := core.Message{ConversationID: env.peer.ID, Role: core.RoleUser, Parts: []core.Part{{Type: core.PartText, Text: "同伴内容"}}}
+	if err := st.AppendMessage(&msg); err != nil {
+		t.Fatal(err)
+	}
+	return env
+}
+
+// runCtx 造一次“回合视角”：项目 + 会话 + 属主。
+func (e *scratchRunEnv) runCtx(projectID, conversationID, owner string) *runCtx {
+	return &runCtx{mgr: e.mgr, eff: e.svc.Effective(owner, projectID),
+		run: core.Run{ID: "run-1", Owner: core.ID(owner), ProjectID: core.ID(projectID), ConversationID: core.ID(conversationID)}}
+}
+
+func (e *scratchRunEnv) scratchCtx() *runCtx {
+	return e.runCtx(string(e.project.ID), e.scratch.ID, "alice")
+}
+
+func (e *scratchRunEnv) normalCtx() *runCtx {
+	return e.runCtx(string(e.normal.ID), e.normalAt.ID, "alice")
+}
+
+// 门禁①：runmgr.authorizeRunWork —— 领域 provider 恒 false 时，scratch 属主照常
+// 工作（provider 从未见过这个项目），其他人 NotFound；普通项目仍由 provider 决定。
+func TestScratchRunWorkUsesOwnerInsteadOfDomainProvider(t *testing.T) {
+	env := newScratchRunEnv(t)
+	asked := 0
+	env.mgr.SetProjectWorkAuthorization(func(context.Context, string, core.ID) (bool, error) {
+		asked++
+		return false, nil // RDM 视角：永远没有这个项目
+	})
+	scratchID := core.ID(env.project.ID)
+
+	if err := env.mgr.authorizeRunWork(context.Background(), "alice", scratchID); err != nil {
+		t.Fatalf("scratch owner blocked by the domain provider: %v", err)
+	}
+	if asked != 0 {
+		t.Fatalf("scratch owner work consulted the provider %d times", asked)
+	}
+	if err := env.mgr.authorizeRunWork(context.Background(), "bob", scratchID); !errors.Is(err, store.ErrNotFound) {
+		t.Fatalf("non-owner reached a scratch run: %v", err)
+	}
+	// 负面：普通项目没有被这条门禁放宽。
+	if err := env.mgr.authorizeRunWork(context.Background(), "alice", core.ID(env.normal.ID)); !errors.Is(err, store.ErrNotFound) {
+		t.Fatalf("normal project bypassed the provider decision: %v", err)
+	}
+	// 正面：provider 放行的普通项目照旧放行。
+	env.mgr.SetProjectWorkAuthorization(func(context.Context, string, core.ID) (bool, error) { return true, nil })
+	if err := env.mgr.authorizeRunWork(context.Background(), "alice", core.ID(env.normal.ID)); err != nil {
+		t.Fatalf("provider-approved normal project blocked: %v", err)
+	}
+	// 无 provider 注册时，非属主仍然进不去 scratch。
+	env.mgr.projectWorkAuthorization = nil
+	if err := env.mgr.authorizeRunWork(context.Background(), "bob", scratchID); !errors.Is(err, store.ErrNotFound) {
+		t.Fatalf("unregistered host opened a scratch run for a non-owner: %v", err)
+	}
+}
+
+// 门禁②：RDM 预检/观察通道不适用于临时会话。
+func TestScratchRunSkipsDomainPreflightGate(t *testing.T) {
+	env := newScratchRunEnv(t)
+	preflights := 0
+	env.mgr.SetProjectWorkGate(
+		func(context.Context, string, string) (extension.ProjectWorkDecision, error) {
+			preflights++
+			return extension.ProjectWorkDecision{State: extension.ProjectWorkProceed, DecisionID: "d1"}, nil
+		},
+		func(context.Context, extension.ProjectRiskAnswer) (extension.ProjectWorkDecision, error) {
+			return extension.ProjectWorkDecision{State: extension.ProjectWorkProceed, DecisionID: "d1"}, nil
+		},
+	)
+	rc := env.scratchCtx()
+	rc.h = &runHandle{}
+	if err := rc.requireProjectWorkDecision("conversation.run"); err != nil {
+		t.Fatalf("scratch run hit the domain preflight: %v", err)
+	}
+	if preflights != 0 {
+		t.Fatalf("scratch run called the domain preflight %d times", preflights)
+	}
+	if rc.projectWorkObservationApplies() {
+		t.Fatal("scratch run must not enter the RDM observation channel")
+	}
+}
+
+// 门禁③：项目上下文（X1）即使 provider 已注册也不装配。
+func TestScratchProjectContextDisabled(t *testing.T) {
+	env := newScratchRunEnv(t)
+	resolved := 0
+	env.mgr.SetProjectContextResolver(func(context.Context, extension.ProjectContextRequest) (extension.ProjectContextBundle, error) {
+		resolved++
+		return extension.ProjectContextBundle{ProjectID: env.project.ID}, nil
+	})
+	if env.scratchCtx().ProjectContextEnabled() {
+		t.Fatal("scratch run assembled project context")
+	}
+	if resolved != 0 {
+		t.Fatalf("scratch run resolved project context %d times", resolved)
+	}
+	// 正面：普通项目照旧启用。
+	if !env.normalCtx().ProjectContextEnabled() {
+		t.Fatal("normal project lost project context")
+	}
+}
+
+// 门禁④：检索为空 —— @knowledge / knowledge_search 在临时会话里拿不到任何东西。
+func TestScratchRunRetrievalReturnsNoHits(t *testing.T) {
+	env := newScratchRunEnv(t)
+	docs := []core.KnowledgeDoc{
+		{Owner: "alice", ProjectID: core.ID(env.project.ID), Source: "manual", Title: "临时项目文档", Chunk: "临时会话项目内的文档"},
+		{Owner: "alice", Source: "manual", Title: "属主文档", Chunk: "属主全局文档"},
+	}
+	if err := env.st.AddKnowledge(docs...); err != nil {
+		t.Fatal(err)
+	}
+	query := core.RetrievalQuery{Text: "文档", TopK: 10}
+
+	hits, err := env.scratchCtx().Retrieve(query)
+	if err != nil || len(hits) != 0 {
+		t.Fatalf("scratch retrieval must return no hits: %+v %v", hits, err)
+	}
+	// 工具面（toolCtx.Retrieve）同样空手。
+	tc := &toolCtx{rc: env.scratchCtx(), callID: "call-1"}
+	if hits, err := tc.Retrieve(query); err != nil || len(hits) != 0 {
+		t.Fatalf("scratch tool retrieval must return no hits: %+v %v", hits, err)
+	}
+	// 正面：普通项目照旧检索得到（这里是项目文档 + 属主文档）。
+	hits, err = env.normalCtx().Retrieve(query)
+	if err != nil || len(hits) == 0 {
+		t.Fatalf("normal project retrieval lost hits: %+v %v", hits, err)
+	}
+}
+
+// 门禁⑤：上下文注入只留本会话条目；记忆不读不写。
+func TestScratchRunKeepsNoSharedContextAndNoMemory(t *testing.T) {
+	env := newScratchRunEnv(t)
+	// 三种作用域各一条：属主级、项目级（本临时会话项目）、本会话级。
+	for _, entry := range []store.ContextEntry{
+		{Keys: []string{"owner"}, Content: "属主级上下文", Enabled: true},
+		{Keys: []string{"project"}, ProjectID: env.project.ID, Content: "项目级上下文", Enabled: true},
+		{Keys: []string{"conversation"}, ProjectID: env.project.ID, ConversationID: env.scratch.ID, Content: "本会话上下文", Enabled: true},
+	} {
+		if _, err := env.st.SaveContextEntry("alice", entry); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	got := map[string]string{}
+	for _, inj := range env.scratchCtx().Injections() {
+		for _, key := range inj.Keys {
+			got[key] = inj.Content
+		}
+	}
+	if got["conversation"] != "本会话上下文" {
+		t.Fatalf("scratch run lost its own context entry: %+v", got)
+	}
+	if _, ok := got["owner"]; ok {
+		t.Fatalf("owner-wide context entry leaked into a scratch run: %+v", got)
+	}
+	if _, ok := got["project"]; ok {
+		t.Fatalf("project-wide context entry leaked into a scratch run: %+v", got)
+	}
+	// 正面：普通项目的回合仍然带属主级上下文。
+	normalInj := map[string]bool{}
+	for _, inj := range env.normalCtx().Injections() {
+		for _, key := range inj.Keys {
+			normalInj[key] = true
+		}
+	}
+	if !normalInj["owner"] {
+		t.Fatalf("normal run lost owner-wide context: %+v", normalInj)
+	}
+
+	// 记忆：临时会话既不读也不写 user/project 记忆。
+	if _, err := env.st.PutMemory("alice", core.MemoryEntry{Scope: "user", Type: "note", Content: "属主记忆", Confidence: 0.9}); err != nil {
+		t.Fatal(err)
+	}
+	if entries := env.scratchCtx().Memories(); len(entries) != 0 {
+		t.Fatalf("scratch run read user memory: %+v", entries)
+	}
+	if entries := env.normalCtx().Memories(); len(entries) != 1 || entries[0].Content != "属主记忆" {
+		t.Fatalf("normal run lost user memory: %+v", entries)
+	}
+
+	scratchPort := env.scratchCtx().StoreMemory()
+	if entries, err := scratchPort.Recall(context.Background(), memory.RecallQuery{Scope: "user"}); err != nil || len(entries) != 0 {
+		t.Fatalf("scratch memory port recalled: %+v %v", entries, err)
+	}
+	if err := scratchPort.Append(context.Background(), memory.Entry{Scope: "user", Type: "note", Content: "临时记忆"}); !errors.Is(err, ErrScratchMemory) {
+		t.Fatalf("scratch memory port accepted a user-scope write: %v", err)
+	}
+	if err := scratchPort.Append(context.Background(), memory.Entry{Scope: "project", Type: "note", Content: "临时项目记忆"}); !errors.Is(err, ErrScratchMemory) {
+		t.Fatalf("scratch memory port accepted a project-scope write: %v", err)
+	}
+	if entries, err := env.st.ListMemory("alice", "", ""); err != nil || len(entries) != 1 {
+		t.Fatalf("refused writes reached the store: %+v %v", entries, err)
+	}
+	// 正面：普通项目的记忆端口照常读写。
+	normalPort := env.normalCtx().StoreMemory()
+	if err := normalPort.Append(context.Background(), memory.Entry{Scope: "user", Type: "note", Content: "普通记忆"}); err != nil {
+		t.Fatalf("normal memory port write: %v", err)
+	}
+	if entries, err := normalPort.Recall(context.Background(), memory.RecallQuery{Scope: "user"}); err != nil || len(entries) < 2 {
+		t.Fatalf("normal memory port recall: %+v %v", entries, err)
+	}
+}
+
+// 门禁⑥：跨会话读取 —— 临时会话读不到别人；别人的列表里也没有临时会话。
+func TestScratchCrossSessionReadIsIsolated(t *testing.T) {
+	env := newScratchRunEnv(t)
+	// 临时会话自己的项目开关：即使显式开闸也不放行。
+	if err := env.svc.MergeProject("alice", string(env.project.ID), map[string]any{"crossSession": map[string]any{"read": true}}); err != nil {
+		t.Fatal(err)
+	}
+	if err := env.svc.MergeProject("alice", string(env.normal.ID), map[string]any{"crossSession": map[string]any{"read": true}}); err != nil {
+		t.Fatal(err)
+	}
+
+	scratchTool := &toolCtx{rc: env.scratchCtx(), callID: "call-1"}
+	if _, err := scratchTool.PeerConversations(); !errors.Is(err, ErrCrossReadDisabled) {
+		t.Fatalf("scratch run listed peers: %v", err)
+	}
+	if _, err := scratchTool.PeerConversationMessages(env.peer.ID, 0); !errors.Is(err, ErrCrossReadDisabled) {
+		t.Fatalf("scratch run read a peer: %v", err)
+	}
+
+	normalTool := &toolCtx{rc: env.normalCtx(), callID: "call-2"}
+	convs, err := normalTool.PeerConversations()
+	if err != nil {
+		t.Fatalf("normal peer listing: %v", err)
+	}
+	for _, c := range convs {
+		if c.ID == env.scratch.ID {
+			t.Fatalf("scratch conversation showed up in a normal peer list: %+v", convs)
+		}
+	}
+	found := false
+	for _, c := range convs {
+		if c.ID == env.peer.ID {
+			found = true
+		}
+	}
+	if !found {
+		t.Fatalf("normal peer listing lost the real peer: %+v", convs)
+	}
+	if _, err := normalTool.PeerConversationMessages(env.scratch.ID, 0); !errors.Is(err, ErrCrossReadForbidden) {
+		t.Fatalf("normal run read a scratch conversation: %v", err)
+	}
+	// 正面：普通项目的同伴会话照旧可读。
+	if msgs, err := normalTool.PeerConversationMessages(env.peer.ID, 0); err != nil || len(msgs) != 1 {
+		t.Fatalf("normal peer read: %+v %v", msgs, err)
+	}
+}

internal/server/project_lifecycle.go

@@ -21,7 +21,24 @@ func (s *Server) lifecycleHost(owner string) extension.Host {
 	}
 	return s.projectHost(owner)
 }
+
+// scratchProjectWork 让临时会话的属主在没有 RDM provider 时也能工作。scratch 项目
+// 从不进入 RDM：provider 只会报 Work=false，属主会被自己的临时会话挡住（U2 核心）。
+// 所以门禁先走存储侧归属：属主放行且不再问 provider，非属主一律 NotFound（与
+// 项目工作同一错误面）。handled=false 表示这不是临时会话，调用点照旧。
+func (s *Server) scratchProjectWork(owner, projectID string) (handled bool, err error) {
+	if s.st == nil {
+		return false, nil
+	}
+	return s.st.ScratchProjectDecision(projectID, owner)
+}
+
 func (s *Server) projectWork(ctx context.Context, owner, projectID string) error {
+	if handled, err := s.scratchProjectWork(owner, projectID); err != nil {
+		return err
+	} else if handled {
+		return nil
+	}
 	if s.projectLifecycle == nil {
 		return nil
 	}
@@ -48,6 +65,12 @@ func (s *Server) projectWork(ctx context.Context, owner, projectID string) error
 // With no resource authorizer registered (EXT-8b V2 absent) this is exactly
 // projectWork, so un-extended hosts keep their current denial unchanged.
 func (s *Server) projectRead(ctx context.Context, owner, projectID string) error {
+	if handled, err := s.scratchProjectWork(owner, projectID); err != nil {
+		return err
+	} else if handled {
+		// 临时会话只对属主可读：共享域回落永远不参与（它不是共享资源）。
+		return nil
+	}
 	if s.projectLifecycle == nil {
 		return nil
 	}
@@ -73,7 +96,7 @@ func (s *Server) projectRead(ctx context.Context, owner, projectID string) error
 // A scratch project already holds its one private conversation, so this shared
 // path refuses a second one instead of handing out a normal session under it.
 func (s *Server) createPrivateConversation(ctx context.Context, owner, projectID, title, profile string) (core.Conversation, error) {
-	if err := s.rejectScratchProjectConversation(projectID); err != nil {
+	if err := s.rejectScratchProjectConversation(projectID, owner); err != nil {
 		return core.Conversation{}, err
 	}
 	if s.projectLifecycle != nil {
@@ -91,19 +114,19 @@ func (s *Server) createPrivateConversation(ctx context.Context, owner, projectID
 
 // rejectScratchProjectConversation keeps the scratch 1:1 rule on the shared
 // conversation-create path (POST /api/projects/{id}/conversations and /new).
-// The lookup is the internal trusted one, so a scratch project cannot slip
-// through the shared-project retry branch; nothing here is returned to the
-// caller, and an unreadable project is left to the store path, which decides
-// not-found and shared access as before.
-func (s *Server) rejectScratchProjectConversation(projectID string) error {
-	project, err := s.st.ProjectMetadata(projectID)
-	if err != nil {
+// The lookup is the internal trusted one, and it is ownership-aware: a non-owner
+// is not told anything about the session (projectWork answers NotFound), while
+// the owner still gets the 1:1 refusal. Nothing here is returned to the caller
+// for an unreadable project, which the store path decides as before.
+func (s *Server) rejectScratchProjectConversation(projectID, owner string) error {
+	if s.st == nil {
 		return nil
 	}
-	if store.IsScratchProject(project.Settings) {
-		return store.ErrScratchSessionSingle
+	handled, err := s.st.ScratchProjectDecision(projectID, owner)
+	if !handled || err != nil {
+		return nil
 	}
-	return nil
+	return store.ErrScratchSessionSingle
 }
 
 func writeProjectErr(w http.ResponseWriter, err error) {

internal/server/scratch_gates_test.go

@@ -0,0 +1,311 @@
+package server
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"mime/multipart"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	agentcommand "agent-command"
+	"agent-system-backend/internal/cmdbus"
+	"agent-system-backend/internal/store"
+	"agent-system-backend/pkg/extension"
+	core "agent-system-core"
+)
+
+// 临时会话隔离门禁（U2）。产品规则：scratch 会话是“只属于自己的通用代理会话”——
+// 属主能像普通聊天一样用它，但它不共享任何文档/上下文，也不触达项目域能力。
+// 每个门禁都成对验证：owner 放行、其他人/其它项目照旧。
+
+// scratchGateFixture 建一个已登录的属主账号并落下一个临时会话。
+func scratchGateFixture(t *testing.T, srv *Server, st *store.Store, owner string) (key, projectID, conversationID string) {
+	t.Helper()
+	key = scratchAccountKey(t, st, owner)
+	rec := bearerRequest(srv.Handler(), "POST", "/api/scratch-sessions", `{}`, key)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("create scratch session: %d %s", rec.Code, rec.Body.String())
+	}
+	view := decodeScratchSessionHTTP(t, rec)
+	return key, view.Project.ID, view.Conversation.ID
+}
+
+// TestScratchOwnerWorksWithoutRDMProvider 是 U2 的核心：注册一个 Work 恒为 false
+// 的 projectLifecycle（RDM 从未听说过 scratch 项目）后，属主仍能在自己的临时
+// 会话里发消息，而别的账号读不到这个临时会话——即使共享授权适配器对所有人放行。
+func TestScratchOwnerWorksWithoutRDMProvider(t *testing.T) {
+	srv, st := newAuthTestServer(t)
+	h := srv.Handler()
+	aliceKey, projectID, conversationID := scratchGateFixture(t, srv, st, "alice")
+	bobKey := scratchAccountKey(t, st, "bob")
+
+	providerCalls := 0
+	srv.SetProjectLifecycle(extension.ProjectLifecycle{
+		Work: func(context.Context, string, core.ID) (bool, error) {
+			providerCalls++
+			return false, nil // RDM 视角：没有这个项目
+		},
+	}, nil)
+	// 共享域适配器对任何人都放行（最宽松的现网配置），临时会话仍不可共享。
+	srv.SetProjectAuthorizer(func(string, core.ID) (bool, error) { return true, nil })
+	srv.SetResourceAuthorizerV2(func(extension.ResourceAuthzQuery) (bool, error) { return true, nil })
+
+	rec := bearerRequest(h, "POST", "/api/conversations/"+conversationID+"/messages", `{"text":"帮我总结这段话"}`, aliceKey)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("scratch owner could not chat without the provider: %d %s", rec.Code, rec.Body.String())
+	}
+	msgs, err := st.ListMessages(conversationID)
+	if err != nil || len(msgs) == 0 {
+		t.Fatalf("owner message not persisted: %+v %v", msgs, err)
+	}
+	if providerCalls != 0 {
+		t.Fatalf("scratch owner work asked the domain provider %d times", providerCalls)
+	}
+
+	// 负面：别的账号读不到这个临时会话（共享授权适配器一律放行也不作数）。
+	if rec := bearerRequest(h, "GET", "/api/projects/"+projectID+"/conversations", "", bobKey); rec.Code != http.StatusNotFound {
+		t.Fatalf("non-owner listed a scratch project: %d %s", rec.Code, rec.Body.String())
+	}
+	if rec := bearerRequest(h, "POST", "/api/projects/"+projectID+"/conversations", `{"title":"混入"}`, bobKey); rec.Code != http.StatusNotFound {
+		t.Fatalf("non-owner created a conversation under scratch: %d %s", rec.Code, rec.Body.String())
+	}
+	if err := srv.projectRead(context.Background(), "bob", projectID); !errors.Is(err, store.ErrNotFound) {
+		t.Fatalf("projectRead opened a scratch project for a non-owner: %v", err)
+	}
+	if err := srv.projectWork(context.Background(), "bob", projectID); !errors.Is(err, store.ErrNotFound) {
+		t.Fatalf("projectWork opened a scratch project for a non-owner: %v", err)
+	}
+	// 属主的读面不受共享适配器影响（存储归属即可）。
+	if err := srv.projectRead(context.Background(), "alice", projectID); err != nil {
+		t.Fatalf("scratch owner projectRead: %v", err)
+	}
+	// 普通项目不受影响：provider 说 false 就是 false。
+	normal, err := st.CreateProject("alice", "普通项目")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := srv.projectWork(context.Background(), "alice", string(normal.ID)); !errors.Is(err, store.ErrNotFound) {
+		t.Fatalf("normal project bypassed the provider decision: %v", err)
+	}
+}
+
+// TestScratchHasNoKnowledgeBase 知识库是项目域能力：入库与检索两个面都 400。
+func TestScratchHasNoKnowledgeBase(t *testing.T) {
+	srv, st := newAuthTestServer(t)
+	h := srv.Handler()
+	key, projectID, _ := scratchGateFixture(t, srv, st, "alice")
+	grantProjectCreateFixture(t, st, "alice")
+	normal := createdProjectID(t, bearerRequest(h, "POST", "/api/projects", `{"name":"普通项目"}`, key))
+	doc := `[{"title":"手动文档","chunk":"知识库内容"}]`
+
+	for name, path := range map[string]string{"scratch": projectID, "normal": normal} {
+		rec := bearerRequest(h, "POST", "/api/projects/"+path+"/knowledge", doc, key)
+		switch name {
+		case "scratch":
+			if rec.Code != http.StatusBadRequest || !strings.Contains(rec.Body.String(), "scratch sessions have no knowledge base") {
+				t.Fatalf("addKnowledge on scratch = %d %s", rec.Code, rec.Body.String())
+			}
+		case "normal":
+			if rec.Code != http.StatusOK {
+				t.Fatalf("addKnowledge on a normal project = %d %s", rec.Code, rec.Body.String())
+			}
+		}
+	}
+	// 被拒的写入没有落库。
+	if docs, err := st.SearchKnowledge("alice", core.RetrievalQuery{ProjectID: projectID, Text: "手动文档", TopK: 10}); err != nil || len(docs) != 0 {
+		t.Fatalf("scratch project kept knowledge rows: %+v %v", docs, err)
+	}
+
+	rec := bearerRequest(h, "GET", "/api/knowledge/search?q=知识库&project="+projectID, "", key)
+	if rec.Code != http.StatusBadRequest || !strings.Contains(rec.Body.String(), "scratch sessions have no knowledge base") {
+		t.Fatalf("searchKnowledge on scratch = %d %s", rec.Code, rec.Body.String())
+	}
+	// 正面：普通项目仍然检索得到自己刚入库的文档。
+	if rec := bearerRequest(h, "GET", "/api/knowledge/search?q=知识库&project="+normal, "", key); rec.Code != http.StatusOK {
+		t.Fatalf("searchKnowledge on a normal project = %d %s", rec.Code, rec.Body.String())
+	}
+	// 无 project 参数的全局检索不受门禁影响（它本来就不落在临时会话上）。
+	if rec := bearerRequest(h, "GET", "/api/knowledge/search?q=知识库", "", key); rec.Code != http.StatusOK {
+		t.Fatalf("global search = %d %s", rec.Code, rec.Body.String())
+	}
+}
+
+// TestScratchUploadStaysOutOfKnowledgeIndex 上传仍可用（对话附件），但临时会话的
+// 附件不进任何知识索引；普通项目的上传照旧入库。
+func TestScratchUploadStaysOutOfKnowledgeIndex(t *testing.T) {
+	srv, st := newAuthTestServer(t)
+	h := srv.Handler()
+	key, projectID, _ := scratchGateFixture(t, srv, st, "alice")
+	grantProjectCreateFixture(t, st, "alice")
+	normal := createdProjectID(t, bearerRequest(h, "POST", "/api/projects", `{"name":"普通项目"}`, key))
+
+	upload := func(projectID, name, text string) string {
+		var buf bytes.Buffer
+		mw := multipart.NewWriter(&buf)
+		fw, err := mw.CreateFormFile("file", name)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, err := fw.Write([]byte(text)); err != nil {
+			t.Fatal(err)
+		}
+		mw.Close()
+		req := httptest.NewRequest(http.MethodPost, "/api/projects/"+projectID+"/uploads", &buf)
+		req.Header.Set("Authorization", "Bearer "+key)
+		req.Header.Set("Content-Type", mw.FormDataContentType())
+		rec := httptest.NewRecorder()
+		h.ServeHTTP(rec, req)
+		if rec.Code != http.StatusOK {
+			t.Fatalf("upload to %s: %d %s", projectID, rec.Code, rec.Body.String())
+		}
+		var up struct {
+			ArtifactID string `json:"artifactId"`
+		}
+		if err := json.Unmarshal(rec.Body.Bytes(), &up); err != nil {
+			t.Fatal(err)
+		}
+		return up.ArtifactID
+	}
+
+	scratchArtifact := upload(projectID, "临时附件.txt", "临时会话的附件正文")
+	if scratchArtifact == "" {
+		t.Fatal("scratch upload returned no artifact")
+	}
+	upload(normal, "普通附件.txt", "普通项目的附件正文")
+
+	scratchHits, err := st.SearchKnowledge("alice", core.RetrievalQuery{ProjectID: projectID, Text: "附件", TopK: 10})
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, hit := range scratchHits {
+		if string(hit.Doc.ProjectID) == projectID || hit.Doc.Ref == scratchArtifact {
+			t.Fatalf("scratch upload was indexed: %+v", hit.Doc)
+		}
+	}
+	normalHits, err := st.SearchKnowledge("alice", core.RetrievalQuery{ProjectID: normal, Text: "附件", TopK: 10})
+	if err != nil || len(normalHits) == 0 {
+		t.Fatalf("normal project upload lost indexing: %+v %v", normalHits, err)
+	}
+}
+
+// TestScratchRejectsDomainCommands 临时会话里 rdm.* 命令 403；不碰项目域的内置
+// 命令照旧可用（它就是普通聊天能力）。
+func TestScratchRejectsDomainCommands(t *testing.T) {
+	srv, st := newAuthTestServer(t)
+	h := srv.Handler()
+	key, projectID, conversationID := scratchGateFixture(t, srv, st, "alice")
+	grantProjectCreateFixture(t, st, "alice")
+	normal := createdProjectID(t, bearerRequest(h, "POST", "/api/projects", `{"name":"普通项目"}`, key))
+	normalConv := createdProjectID(t, bearerRequest(h, "POST", "/api/projects/"+normal+"/conversations", `{"title":"会话"}`, key))
+
+	srv.Bus = cmdbus.New(st, nil, func() time.Time { return time.Now() })
+	srv.WireBuiltinCommands()
+	if err := srv.Bus.RegisterPluginCommand(agentcommand.CommandSpec{ID: "rdm.reqs.add", Title: "登记需求"}, func(ctx context.Context, req cmdbus.Request) (any, error) {
+		return map[string]any{"ok": true}, nil
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if err := srv.Bus.RegisterPluginCommand(agentcommand.CommandSpec{ID: "rdm.reqs.list", Title: "需求列表"}, func(ctx context.Context, req cmdbus.Request) (any, error) {
+		return map[string]any{"ok": true}, nil
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	// API 入口（POST /api/commands/{id}）：临时会话宿主一律 403。
+	for _, id := range []string{"rdm.reqs.add", "rdm.reqs.list"} {
+		rec := bearerRequest(h, "POST", "/api/commands/"+id, `{"conversationId":"`+conversationID+`"}`, key)
+		if rec.Code != http.StatusForbidden || !strings.Contains(rec.Body.String(), "not available in scratch sessions") {
+			t.Fatalf("%s on a scratch host = %d %s", id, rec.Code, rec.Body.String())
+		}
+	}
+	// 正面：读侧命令在普通项目宿主上照旧分发。
+	if rec := bearerRequest(h, "POST", "/api/commands/rdm.reqs.list", `{"conversationId":"`+normalConv+`"}`, key); rec.Code != http.StatusOK {
+		t.Fatalf("rdm.reqs.list on a normal host = %d %s", rec.Code, rec.Body.String())
+	}
+	// 没有会话就没有基座项目：门禁不适用，命令走原路径（正式项目命令仍由总线预检拒绝）。
+	if rec := bearerRequest(h, "POST", "/api/commands/rdm.reqs.list", `{}`, key); rec.Code != http.StatusOK {
+		t.Fatalf("command without a host project = %d %s", rec.Code, rec.Body.String())
+	}
+	if rec := bearerRequest(h, "POST", "/api/commands/rdm.reqs.add", `{}`, key); rec.Code != http.StatusBadRequest {
+		t.Fatalf("hostless formal command must keep the bus preflight answer: %d %s", rec.Code, rec.Body.String())
+	}
+	// 内置会话命令在临时会话里照旧可用（它不碰项目域）。
+	rec := bearerRequest(h, "POST", "/api/conversations/"+conversationID+"/messages", `{"text":"/help"}`, key)
+	if rec.Code != http.StatusOK || !strings.Contains(rec.Body.String(), "command") {
+		t.Fatalf("builtin host command in a scratch session = %d %s", rec.Code, rec.Body.String())
+	}
+	if !store.IsScratchProject(mustScratchSettings(t, st, projectID)) {
+		t.Fatalf("scratch marker lost during command gating: %s", projectID)
+	}
+}
+
+func mustScratchSettings(t *testing.T, st *store.Store, projectID string) map[string]any {
+	t.Helper()
+	p, err := st.ProjectMetadata(projectID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return p.Settings
+}
+
+// TestScratchProjectPatchAllowsNameOnly 临时会话只允许改名；任何设置写入 400。
+func TestScratchProjectPatchAllowsNameOnly(t *testing.T) {
+	srv, st := newAuthTestServer(t)
+	h := srv.Handler()
+	key, projectID, _ := scratchGateFixture(t, srv, st, "alice")
+	grantProjectCreateFixture(t, st, "alice")
+
+	if rec := bearerRequest(h, "PATCH", "/api/projects/"+projectID, `{"name":"改个名字"}`, key); rec.Code != http.StatusOK {
+		t.Fatalf("rename scratch project = %d %s", rec.Code, rec.Body.String())
+	}
+	if p, err := st.ProjectMetadata(projectID); err != nil || p.Name != "改个名字" {
+		t.Fatalf("scratch project not renamed: %+v %v", p, err)
+	}
+	for _, body := range []string{`{"settings":{"note":"任何设置"}}`, `{"settings":{"crossSession":{"read":true}}}`, `{"settings":{"host":{"kind":"normal"}}}`} {
+		rec := bearerRequest(h, "PATCH", "/api/projects/"+projectID, body, key)
+		if rec.Code != http.StatusBadRequest || !strings.Contains(rec.Body.String(), "scratch sessions have no project settings") {
+			t.Fatalf("scratch settings patch %s = %d %s", body, rec.Code, rec.Body.String())
+		}
+	}
+	if !store.IsScratchProject(mustScratchSettings(t, st, projectID)) {
+		t.Fatal("refused patch changed the scratch marker")
+	}
+	// 正面：普通项目的设置写入照旧放行。
+	normal := createdProjectID(t, bearerRequest(h, "POST", "/api/projects", `{"name":"普通项目"}`, key))
+	if rec := bearerRequest(h, "PATCH", "/api/projects/"+normal, `{"settings":{"note":"普通"}}`, key); rec.Code != http.StatusOK {
+		t.Fatalf("normal settings patch = %d %s", rec.Code, rec.Body.String())
+	}
+}
+
+// TestDeletingScratchConversationRemovesScratchProject 删会话即删临时会话外壳；
+// 普通项目删会话仍保留项目。
+func TestDeletingScratchConversationRemovesScratchProject(t *testing.T) {
+	srv, st := newAuthTestServer(t)
+	h := srv.Handler()
+	key, projectID, conversationID := scratchGateFixture(t, srv, st, "alice")
+	grantProjectCreateFixture(t, st, "alice")
+	normal := createdProjectID(t, bearerRequest(h, "POST", "/api/projects", `{"name":"普通项目"}`, key))
+	normalConv := createdProjectID(t, bearerRequest(h, "POST", "/api/projects/"+normal+"/conversations", `{"title":"会话"}`, key))
+
+	bobKey := scratchAccountKey(t, st, "bob")
+	if rec := bearerRequest(h, "DELETE", "/api/conversations/"+conversationID, "", bobKey); rec.Code == http.StatusOK {
+		t.Fatalf("non-owner deleted a scratch conversation: %d %s", rec.Code, rec.Body.String())
+	}
+	if rec := bearerRequest(h, "DELETE", "/api/conversations/"+conversationID, "", key); rec.Code != http.StatusOK {
+		t.Fatalf("delete scratch conversation = %d %s", rec.Code, rec.Body.String())
+	}
+	if _, err := st.ProjectMetadata(projectID); !errors.Is(err, store.ErrNotFound) {
+		t.Fatalf("scratch project survived its conversation: %v", err)
+	}
+	if rec := bearerRequest(h, "DELETE", "/api/conversations/"+normalConv, "", key); rec.Code != http.StatusOK {
+		t.Fatalf("delete normal conversation = %d %s", rec.Code, rec.Body.String())
+	}
+	if _, err := st.ProjectMetadata(normal); err != nil {
+		t.Fatalf("normal project removed with its conversation: %v", err)
+	}
+}

internal/server/scratch_session.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"strings"
 
+	"agent-system-backend/internal/cmdbus"
 	"agent-system-backend/internal/store"
 	core "agent-system-core"
 )
@@ -61,3 +62,52 @@ func (s *Server) createScratchSession(w http.ResponseWriter, r *http.Request) {
 	// 200 配 writeJSON，而不是 201。
 	writeJSON(w, http.StatusOK, scratchSessionView{Project: project, Conversation: conversation})
 }
+
+// ---- U2：隔离门禁 ----
+//
+// 临时会话是“只属于自己的通用代理会话”：没有知识库、没有项目上下文、不与任何
+// 会话共享材料。这些门禁只认存储里的 host 标记（store.IsScratchProject），调用点
+// 不自己比对标记字符串。
+
+const (
+	// scratchNoKnowledge 知识库是项目域能力，临时会话一律没有。
+	scratchNoKnowledge = "scratch sessions have no knowledge base"
+	// scratchNoSettings 临时会话只有会话，没有可写的项目设置。
+	scratchNoSettings = "scratch sessions have no project settings"
+	// scratchNoCommand 项目域命令（RDM 及其它需要基座项目的命令）在临时会话不可用。
+	scratchNoCommand = "not available in scratch sessions"
+)
+
+// scratchProjectOf reports whether projectID is the caller's own scratch project.
+// Other owners' projects (and unknown ids) fall through to the normal decision
+// path, so the gate never leaks the existence of someone else's scratch session.
+func (s *Server) scratchProjectOf(projectID, owner string) bool {
+	if s.st == nil {
+		return false
+	}
+	handled, err := s.st.ScratchProjectDecision(projectID, owner)
+	return handled && err == nil
+}
+
+// refuseScratchProjectCapability 门禁拒绝：只对调用者自己的临时会话生效。
+func (s *Server) refuseScratchProjectCapability(w http.ResponseWriter, projectID, owner, message string) bool {
+	if !s.scratchProjectOf(projectID, owner) {
+		return false
+	}
+	http.Error(w, message, http.StatusBadRequest)
+	return true
+}
+
+// refuseScratchCommandHost 命令门禁（403）：临时会话里不得分发需要基座项目的命令。
+// rdm.* 全族与正式项目命令（cmdbus.RequiresProjectWorkDecision）都不行；内置的
+// 会话类命令照旧可用。
+func (s *Server) refuseScratchCommandHost(w http.ResponseWriter, hostProjectID, owner, commandID string) bool {
+	if !s.scratchProjectOf(hostProjectID, owner) {
+		return false
+	}
+	if !strings.HasPrefix(commandID, "rdm.") && !cmdbus.RequiresProjectWorkDecision(commandID) {
+		return false
+	}
+	http.Error(w, scratchNoCommand, http.StatusForbidden)
+	return true
+}

internal/server/server.go

@@ -140,6 +140,9 @@ func (s *Server) authorizeProjectAction(owner string, projectID core.ID, action
 // Owner/ProjectID 从受信存储元数据解析；出错/字段缺失一律 false，fail-closed
 // 且不泄露存在性）；V2 未注册回落 authorizeSharedProject（现行兼容）。
 func (s *Server) authorizeSharedResource(actor, action, resourceType string, resourceID, owner, projectID core.ID) bool {
+	if s.sharedScratchDenied(actor, projectID) {
+		return false
+	}
 	if s.ProjectAuthzV2 == nil {
 		return s.authorizeSharedProject(actor, projectID)
 	}
@@ -164,10 +167,24 @@ func (s *Server) authorizeSharedProject(owner string, projectID core.ID) bool {
 	if s.ProjectAuthz == nil {
 		return false
 	}
+	if s.sharedScratchDenied(owner, projectID) {
+		return false
+	}
 	ok, err := s.ProjectAuthz(owner, projectID)
 	return err == nil && ok
 }
 
+// sharedScratchDenied 保证共享域授权永远打不开临时会话：临时会话是私有的
+// 1:1 会话外壳，不是共享资源，EXT-8/EXT-8b 适配器不得为他人授予它。属主
+// 不受影响（属主的读写按存储归属判定）。
+func (s *Server) sharedScratchDenied(actor string, projectID core.ID) bool {
+	if s.st == nil || projectID == "" {
+		return false
+	}
+	handled, err := s.st.ScratchProjectDecision(string(projectID), actor)
+	return handled && err != nil
+}
+
 func New(st *store.Store, mgr *runmgr.Manager, reg *tools.Registry, p *profiles.Service, s *settings.Service, ph *plugins.Host) *Server {
 	sub, err := web.Dist()
 	if err != nil {
@@ -780,6 +797,7 @@ func (s *Server) createProject(w http.ResponseWriter, r *http.Request) {
 
 func (s *Server) patchProject(w http.ResponseWriter, r *http.Request) {
 	id := r.PathValue("id")
+	owner := s.owner(r)
 	var req struct {
 		Name     *string        `json:"name"`
 		Settings map[string]any `json:"settings"`
@@ -788,6 +806,11 @@ func (s *Server) patchProject(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
+	// 临时会话只有会话：除了改名没有任何项目设置可写（标记保护之外再加一道）。
+	if req.Settings != nil && s.scratchProjectOf(id, owner) {
+		http.Error(w, scratchNoSettings, http.StatusBadRequest)
+		return
+	}
 	if req.Settings != nil {
 		values, err := s.set.PrepareProjectMetadataWrite(req.Settings)
 		if err != nil {
@@ -1291,6 +1314,10 @@ func (s *Server) handleCommand(w http.ResponseWriter, r *http.Request, conv core
 		http.Error(w, "未知命令 "+slash+"（/help 查看）", http.StatusBadRequest)
 		return
 	}
+	// 临时会话里没有项目域：rdm.* 与正式项目命令一律 403。
+	if s.refuseScratchCommandHost(w, string(conv.ProjectID), s.owner(r), id) {
+		return
+	}
 	params, err := parseSlashParams(id, fields[1:])
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusBadRequest)
@@ -1374,6 +1401,10 @@ func (s *Server) execCommand(w http.ResponseWriter, r *http.Request) {
 			}
 		}
 	}
+	// 基座项目是临时会话时，项目域命令一律 403（无会话上下文的命令不在此门）。
+	if s.refuseScratchCommandHost(w, hostProject, s.owner(r), commandID) {
+		return
+	}
 
 	dispatch := cmdbus.Request{
 		ID: commandID, Params: body.Params, Entrance: body.Entrance, Actor: s.owner(r),
@@ -1714,7 +1745,9 @@ func (s *Server) upload(w http.ResponseWriter, r *http.Request) {
 	}
 	// 文本可解析的进检索索引（管线分块+全文+可选向量）。
 	// EXT-9：宿主关闭自动索引时跳过（发布决定移交下游命令层；原件与摄取卡不变）。
-	if !s.DisableUploadIndexing {
+	// 临时会话只有会话：附件进入对话，但不进任何知识索引（否则会话材料会
+	// 漏进别的会话的检索结果）。
+	if !s.DisableUploadIndexing && !s.scratchProjectOf(projectID, owner) {
 		if plain := doc.PlainText(); plain != "" && len(plain) < 200000 {
 			var indexErr error
 			if s.Indexer != nil {
@@ -2294,6 +2327,10 @@ func (s *Server) addKnowledge(w http.ResponseWriter, r *http.Request) {
 		writeStoreErr(w, err)
 		return
 	}
+	// 知识库是项目域能力：临时会话不接收任何文档入库。
+	if s.refuseScratchProjectCapability(w, r.PathValue("id"), owner, scratchNoKnowledge) {
+		return
+	}
 	for i := range docs {
 		docs[i].Owner = owner
 		docs[i].ProjectID = r.PathValue("id")
@@ -2313,6 +2350,10 @@ func (s *Server) searchKnowledge(w http.ResponseWriter, r *http.Request) {
 	topK, _ := strconv.Atoi(r.URL.Query().Get("topK"))
 	query := core.RetrievalQuery{ProjectID: r.URL.Query().Get("project"), Text: q, TopK: topK}
 	owner := s.owner(r)
+	// 检索面同样先问门禁：临时会话没有知识库（而不是“搜出来是空的”）。
+	if s.refuseScratchProjectCapability(w, query.ProjectID, owner, scratchNoKnowledge) {
+		return
+	}
 	if s.projectLifecycle != nil && query.ProjectID != "" {
 		id, err := projectscope.Resolve(r.Context(), s.lifecycleHost(owner), *s.projectLifecycle, query.ProjectID)
 		if err != nil {

internal/store/projects.go

@@ -464,8 +464,13 @@ func (s *Store) SetPermissionMode(owner, id, mode string) error {
 	return nil
 }
 
+// DeleteConversation deletes one conversation; deleting the sole conversation of
+// a scratch project also removes that scratch project, so a scratch session is
+// never left as an empty shell project.
 func (s *Store) DeleteConversation(owner, id string) error {
-	return s.updateProjectRow(owner, id, `DELETE FROM conversations WHERE id=? AND owner=?`, id, owner)
+	return s.deleteConversationCascade(s.db, owner, id, func() error {
+		return s.updateProjectRow(owner, id, `DELETE FROM conversations WHERE id=? AND owner=?`, id, owner)
+	})
 }
 
 // withOwnedConversationWrite locks the actor before the conversation and
@@ -521,10 +526,14 @@ func (s *Store) UpdateConversationAccountChecked(actor, id, title, profileID str
 	})
 }
 
-// DeleteConversationAccountChecked retains the legacy owner-only delete rule.
+// DeleteConversationAccountChecked deletes the conversation; when it was the
+// sole conversation of a scratch project, that scratch project goes with it in
+// the same write transaction, so a scratch session cannot be left half-deleted.
 func (s *Store) DeleteConversationAccountChecked(actor, id string, allowImplicitDefault bool) error {
 	return s.withOwnedConversationWrite(actor, id, allowImplicitDefault, func(tx *sql.Tx) error {
-		return s.execOwnedConversationWrite(tx, `DELETE FROM conversations WHERE id=? AND owner=?`, id, actor)
+		return s.deleteConversationCascade(tx, actor, id, func() error {
+			return s.execOwnedConversationWrite(tx, `DELETE FROM conversations WHERE id=? AND owner=?`, id, actor)
+		})
 	})
 }
 

internal/store/scratch.go

@@ -43,6 +43,108 @@ func IsScratchProject(settings map[string]any) bool {
 	return kind == ScratchHostKind
 }
 
+// IsScratchProjectID 是内部可信判定：按 id 读 projects.settings 的 host 标记。
+// 调用点（HTTP 门禁、回合门禁、命令分发）一律走它，不自己比对标记字符串。
+func (s *Store) IsScratchProjectID(projectID string) (bool, error) {
+	if projectID == "" {
+		return false, nil
+	}
+	p, err := s.ProjectMetadata(projectID)
+	if err != nil {
+		return false, err
+	}
+	return IsScratchProject(p.Settings), nil
+}
+
+// ScratchProjectDecision 是临时会话的归属判定，回答“这个调用是否发生在某个
+// 临时会话里”：
+//   - handled=false：不是临时会话（或项目读不到），调用点继续走原来的判定面；
+//   - handled=true, err=nil：调用者是该临时会话的属主，放行且不必再问 RDM；
+//   - handled=true, err=ErrNotFound：临时会话不是共享资源，其他人一律不可见。
+//
+// 判据只来自存储里的属主列与 host 标记，不接受调用方自称的身份。
+func (s *Store) ScratchProjectDecision(projectID, actor string) (bool, error) {
+	if projectID == "" {
+		return false, nil
+	}
+	p, err := s.ProjectMetadata(projectID)
+	if err != nil {
+		// 读不到项目（不存在或存储异常）：存在性与共享判定留给原路径，
+		// 这里不把“读不到”当成临时会话，也就不会放宽任何门禁。
+		return false, nil
+	}
+	if !IsScratchProject(p.Settings) {
+		return false, nil
+	}
+	if p.Owner != core.ID(actor) {
+		return true, ErrNotFound
+	}
+	return true, nil
+}
+
+// scratchQuerier 是本文件里临时会话判定可用的两种执行面（*sql.DB 与 *sql.Tx），
+// 于是同一个事务内的级联删除与 store 级删除共用一份语义。
+type scratchQuerier interface {
+	QueryRow(string, ...any) *sql.Row
+	Exec(string, ...any) (sql.Result, error)
+}
+
+// scratchProjectOfConversation 返回会话所属的 scratch 项目 id；普通项目返回空串。
+func (s *Store) scratchProjectOfConversation(q scratchQuerier, owner, conversationID string) (string, error) {
+	var projectID, settings string
+	err := q.QueryRow(s.q(`SELECT c.project_id, COALESCE(p.settings,'') FROM conversations c LEFT JOIN projects p ON p.id=c.project_id WHERE c.id=? AND c.owner=?`),
+		conversationID, owner).Scan(&projectID, &settings)
+	if errors.Is(err, sql.ErrNoRows) {
+		return "", ErrNotFound
+	}
+	if err != nil {
+		return "", err
+	}
+	if !IsScratchProject(decodeProjectSettings(settings)) {
+		return "", nil
+	}
+	return projectID, nil
+}
+
+// deleteScratchProjectIfEmpty 在会话已被删掉之后连带删掉它的临时会话项目：
+// 临时会话项目只承载这一个会话，删会话即删临时会话（同一个执行面、同一个门禁）。
+// 仍有会话时不动（1:1 由创建面保证，删除面不依赖该不变量做正确性）；普通项目
+// id 传进来也不会被删。
+func (s *Store) deleteScratchProjectIfEmpty(q scratchQuerier, owner, projectID string) error {
+	if projectID == "" {
+		return nil
+	}
+	var remaining int
+	if err := q.QueryRow(s.q(`SELECT COUNT(1) FROM conversations WHERE project_id=?`), projectID).Scan(&remaining); err != nil {
+		return err
+	}
+	if remaining > 0 {
+		return nil
+	}
+	res, err := q.Exec(s.q(`DELETE FROM projects WHERE id=? AND owner=?`), projectID, owner)
+	if err != nil {
+		return err
+	}
+	if n, _ := res.RowsAffected(); n == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+// deleteConversationCascade 删除一个会话，并在它是临时会话唯一会话时连带删掉
+// 临时会话项目。account-checked 路径在最终写事务内调用，legacy 路径在同一执行
+// 面上调用：语义只有一份。
+func (s *Store) deleteConversationCascade(q scratchQuerier, owner, id string, del func() error) error {
+	scratchProject, err := s.scratchProjectOfConversation(q, owner, id)
+	if err != nil {
+		return err
+	}
+	if err := del(); err != nil {
+		return err
+	}
+	return s.deleteScratchProjectIfEmpty(q, owner, scratchProject)
+}
+
 // decodeProjectSettings 把存储的 settings JSON 读成 map；缺省或损坏都是空表。
 func decodeProjectSettings(raw string) map[string]any {
 	if raw == "" || raw == "{}" {

internal/store/scratch_test.go

@@ -215,3 +215,121 @@ func TestScratchSessionTransactionLeavesNothingOnFailure(t *testing.T) {
 		t.Fatalf("rolled back create left rows: %+v %v", all, err)
 	}
 }
+
+// ---- U2：隔离门禁的 store 契约 ----
+
+// IsScratchProjectID / ScratchProjectDecision 是所有门禁唯一的判定来源：
+// 属主放行，其他人 NotFound，普通项目不接管（交回原判定面）。
+func TestScratchProjectLookupAndOwnershipDecision(t *testing.T) {
+	st := openTestStore(t)
+	scratchAccountFixture(t, st, "alice", false)
+	scratchAccountFixture(t, st, "bob", false)
+	project, conversation, err := st.CreateScratchSessionAccountChecked("alice", "临时会话", "临时会话", "", false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	normal, err := st.CreateProjectAccountChecked("alice", "普通项目", false)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, tc := range []struct {
+		name      string
+		projectID string
+		scratch   bool
+		err       error
+	}{
+		{"scratch", string(project.ID), true, nil},
+		{"normal", string(normal.ID), false, nil},
+		{"empty", "", false, nil},
+		{"missing", "prj_missing", false, ErrNotFound},
+	} {
+		got, err := st.IsScratchProjectID(tc.projectID)
+		if got != tc.scratch || !errors.Is(err, tc.err) {
+			t.Fatalf("%s: IsScratchProjectID = %v, %v (want %v, %v)", tc.name, got, err, tc.scratch, tc.err)
+		}
+	}
+
+	// 属主：门禁接管并放行（不查 RDM）。
+	handled, err := st.ScratchProjectDecision(string(project.ID), "alice")
+	if !handled || err != nil {
+		t.Fatalf("scratch owner decision = %v, %v", handled, err)
+	}
+	// 其他人：NotFound——临时会话不是共享资源。
+	if handled, err := st.ScratchProjectDecision(string(project.ID), "bob"); !handled || !errors.Is(err, ErrNotFound) {
+		t.Fatalf("scratch non-owner decision = %v, %v", handled, err)
+	}
+	// 普通项目与空项目 id 都不接管，原路径继续。
+	if handled, err := st.ScratchProjectDecision(string(normal.ID), "bob"); handled || err != nil {
+		t.Fatalf("normal project decision = %v, %v", handled, err)
+	}
+	if handled, err := st.ScratchProjectDecision("", "bob"); handled || err != nil {
+		t.Fatalf("empty project decision = %v, %v", handled, err)
+	}
+	// 读不到的项目不按临时会话处理（不因此放宽任何门禁）。
+	if handled, err := st.ScratchProjectDecision("prj_missing", "alice"); handled || err != nil {
+		t.Fatalf("missing project decision = %v, %v", handled, err)
+	}
+	_ = conversation
+}
+
+// 删掉临时会话的唯一会话即删掉它的 scratch 项目（不留空壳）；普通项目照旧。
+func TestDeletingScratchConversationDeletesScratchProject(t *testing.T) {
+	st := openTestStore(t)
+	scratchAccountFixture(t, st, "alice", false)
+	scratchAccountFixture(t, st, "bob", false)
+	project, conversation, err := st.CreateScratchSessionAccountChecked("alice", "临时会话", "临时会话", "", false)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// 他人删除：仍然 NotFound，且临时会话原样存在。
+	if err := st.DeleteConversationAccountChecked("bob", string(conversation.ID), false); !errors.Is(err, ErrNotFound) {
+		t.Fatalf("non-owner delete = %v", err)
+	}
+	if _, err := st.ProjectMetadata(string(project.ID)); err != nil {
+		t.Fatalf("non-owner delete removed the scratch project: %v", err)
+	}
+
+	if err := st.DeleteConversationAccountChecked("alice", string(conversation.ID), false); err != nil {
+		t.Fatalf("owner delete: %v", err)
+	}
+	if _, err := st.ProjectMetadata(string(project.ID)); !errors.Is(err, ErrNotFound) {
+		t.Fatalf("scratch project survived its only conversation: %v", err)
+	}
+	if scratch, err := st.IsScratchProjectID(string(project.ID)); scratch || !errors.Is(err, ErrNotFound) {
+		t.Fatalf("deleted scratch project still answers as scratch: %v %v", scratch, err)
+	}
+
+	// 普通项目的会话删除不动项目。
+	normal, err := st.CreateProjectAccountChecked("alice", "普通项目", false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	conv, err := st.CreateConversationAccountChecked("alice", string(normal.ID), "会话", "", false, true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := st.DeleteConversationAccountChecked("alice", string(conv.ID), false); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := st.ProjectMetadata(string(normal.ID)); err != nil {
+		t.Fatalf("normal project removed with its conversation: %v", err)
+	}
+}
+
+// legacy DeleteConversation 是同一条语义：删会话即删临时会话外壳。
+func TestLegacyDeleteConversationCascadesScratchProject(t *testing.T) {
+	st := openTestStore(t)
+	scratchAccountFixture(t, st, "alice", false)
+	project, conversation, err := st.CreateScratchSessionAccountChecked("alice", "临时会话", "临时会话", "", false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := st.DeleteConversation("alice", string(conversation.ID)); err != nil {
+		t.Fatalf("legacy delete: %v", err)
+	}
+	if _, err := st.ProjectMetadata(string(project.ID)); !errors.Is(err, ErrNotFound) {
+		t.Fatalf("legacy delete left the scratch shell: %v", err)
+	}
+}