diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1048446..96953b4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,32 @@
 
 All notable changes to Chat Switchboard.
 
+## [0.21.5] — 2026-03-01
+
+### Added
+- **Editor Surface (Development Mode).** IDE-like experience built as a v0.21.3 surface consuming workspace primitives. Activates automatically when a channel or project has a bound workspace. Three-pane layout: file tree (sidebar), code editor (CM6), and AI chat panel with resizable split.
+- **`editor-mode.js`** — Full editor surface module. File tree backed by `workspace_ls` API with nested directory expansion, file icons by extension, and context menus. Tab bar with modified indicators, close buttons, and multi-file editing. CM6 integration with language auto-detection (20+ languages) and textarea fallback when CM6 bundle unavailable.
+- **Split pane layout** with draggable resize handle. Editor (left) and AI chat (right) share the main region. Chat DOM borrowed from Surfaces saved fragments — real conversation history and input preserved across mode switches.
+- **Quick Open** (`Ctrl/Cmd+P`): Fuzzy file finder overlay using workspace file index. `Ctrl/Cmd+S` save, `Ctrl/Cmd+W` close tab.
+- **Live editor updates**: When AI tool calls modify workspace files (`workspace_write`, `workspace_patch`), the server emits `workspace.file.changed` via WebSocket. If the file is open and unmodified in the editor, content refreshes automatically.
+- **Status bar**: Current file path, language mode, git branch display.
+- **`editor-mode.css`**: Complete styling for all editor components with dark theme support, mobile responsive (stacked layout at ≤768px).
+- **Workspace API methods** on frontend `API` module: `getWorkspace`, `listWorkspaceFiles`, `readWorkspaceFile`, `writeWorkspaceFile`, `deleteWorkspaceFile`, `mkdirWorkspace`, `getWorkspaceGitStatus`, `getWorkspaceGitBranches`.
+- **`Surfaces.getSavedFragment()` / `putSavedFragment()`** — Cross-surface DOM sharing. Allows the editor surface to borrow chat DOM into its split pane without cloning.
+- **`workspace.file.` event routing** added to server event route table (`DirToClient`).
+- **Workspace management UI**: Create, list, and bind workspaces from the frontend. Project settings panel gains a Workspace section with dropdown picker and "New" button. Chat context menu gains "Set workspace…" option for per-channel override. Both paths support creating new workspaces inline.
+- **`GET /workspaces`** — List all workspaces accessible to the current user (user-owned + team-owned).
+- **`workspace_id` in channel API**: `updateChannelRequest` accepts `workspace_id` for binding/unbinding. `channelResponse` and both list/get queries now include `workspace_id`.
+
+### Changed
+- `stream_loop.go`: Emits `workspace.file.changed` event after successful `workspace_write`/`workspace_patch` tool calls.
+- `index.html`: Added `editor-mode.css` stylesheet and `editor-mode.js` script.
+- `channels.go`: `channelResponse` includes `workspace_id`, list/get queries select it, update accepts it.
+- `workspaces.go`: Added `List` handler for `GET /workspaces`.
+- `main.go`: Added `GET /workspaces` route.
+- `projects-ui.js`: Workspace section in project panel, workspace picker in chat context menu.
+- `styles.css`: Workspace row layout in project panel.
+
 ## [0.21.4] — 2026-03-01
 
 ### Added
diff --git a/VERSION b/VERSION
index b166f00..c9532c6 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.21.4
\ No newline at end of file
+0.21.5
\ No newline at end of file
diff --git a/docs/ROADMAP.md b/docs/ROADMAP.md
index 2d66f6e..e58af8e 100644
--- a/docs/ROADMAP.md
+++ b/docs/ROADMAP.md
@@ -85,7 +85,7 @@ v0.21.0 Workspace Storage Primitive                      ✅
 v0.21.1 Workspace ✅   v0.21.3 Surface Infra ✅
   Tools + Bindings       + REPL (parallel)
   │                      │
-v0.21.2 Workspace ✅   v0.21.5 Editor Surface
+v0.21.2 Workspace ✅   v0.21.5 Editor Surface ✅
   Indexing + Search      (Development Mode)
   │                      │
 v0.21.4 Git ✅         v0.21.6 Article Surface
@@ -772,15 +772,29 @@ Layer git operations onto workspaces.
 - [ ] Integration tests: clone, commit, push/pull cycle (requires git binary in CI)
 - [ ] `.gitignore` respect in workspace indexing (deferred to v0.21.5+)
 
-### v0.21.5 — Editor Surface (Development Mode)
+### v0.21.5 — Editor Surface (Development Mode) ✅
 
-IDE-like experience. Browser-tier extension consuming workspace primitives.
+IDE-like experience. Browser-tier surface consuming workspace primitives.
 
-- [ ] Layout: file tree (sidebar), code editor (CM6, main), AI chat panel (resizable split), status bar
-- [ ] File tree: workspace_ls backed, git status indicators, context menu, drag-drop
-- [ ] Code editor: CM6 codeEditor() factory, language auto-detection, tab bar, Ctrl+S save
-- [ ] AI chat panel: same channel context, workspace tools auto-injected, live update via EventBus
-- [ ] Keyboard shortcuts: Ctrl+P quick open, Ctrl+Shift+F workspace search
+- [x] Layout: file tree (sidebar), code editor (CM6, main), AI chat panel (resizable split), status bar
+- [x] File tree: workspace_ls backed, context menu (open, delete), nested directory expansion, file icons
+- [x] Code editor: CM6 codeEditor() factory with textarea fallback, language auto-detection (20+ languages), tab bar, Ctrl+S save
+- [x] AI chat panel: same channel context via Surfaces DOM borrowing, live update via workspace.file.changed event
+- [x] Keyboard shortcuts: Ctrl+P quick open, Ctrl+S save, Ctrl+W close tab
+- [x] Split pane layout with draggable resize handle
+- [x] Status bar: file path, language mode, git branch
+- [x] Workspace API methods on frontend (8 methods)
+- [x] Surfaces.getSavedFragment/putSavedFragment for cross-surface DOM sharing
+- [x] workspace.file.changed event emission from stream_loop.go after tool calls
+- [x] Event route table: workspace.file. → DirToClient
+- [x] editor-mode.css: dark theme, mobile responsive (stacked at ≤768px)
+- [x] Auto-registration: surface registers when channel/project has workspace binding
+- [x] Workspace management UI: create, list, bind from project settings + chat context menu
+- [x] GET /workspaces list endpoint, workspace_id in channel API (update, get, list)
+- [ ] Git status indicators in file tree (visual indicators per-file) — deferred
+- [ ] Drag-drop file reorder — deferred
+- [ ] Ctrl+Shift+F workspace search — deferred
+- [ ] Auto-save on tab/mode switch — deferred
 
 ### v0.21.6 — Article Surface + Document Output Pipeline
 
diff --git a/server/events/types.go b/server/events/types.go
index b1e010d..0deaceb 100644
--- a/server/events/types.go
+++ b/server/events/types.go
@@ -60,6 +60,9 @@ var routeTable = map[string]Direction{
 	"notification.new":  DirToClient, // targeted via Hub.SendToUser, not room-based
 	"notification.read": DirToClient, // badge sync across tabs
 
+	// Workspace (v0.21.5)
+	"workspace.file.": DirToClient, // file changed events for live editor updates
+
 	// Plugin hooks — never cross the wire
 	"plugin.hook.":      DirLocal,
 	"internal.":         DirLocal,
diff --git a/server/handlers/channels.go b/server/handlers/channels.go
index 12324e9..818487f 100644
--- a/server/handlers/channels.go
+++ b/server/handlers/channels.go
@@ -38,7 +38,8 @@ type updateChannelRequest struct {
 	IsPinned     *bool            `json:"is_pinned,omitempty"`
 	Folder       *string          `json:"folder,omitempty"`
 	Tags         []string         `json:"tags,omitempty"`
-	Settings     *json.RawMessage `json:"settings,omitempty"` // JSONB merge into existing settings
+	Settings     *json.RawMessage `json:"settings,omitempty"`     // JSONB merge into existing settings
+	WorkspaceID  *string          `json:"workspace_id,omitempty"` // bind workspace (v0.21.5)
 }
 
 type channelResponse struct {
@@ -54,6 +55,7 @@ type channelResponse struct {
 	IsPinned     bool            `json:"is_pinned"`
 	Folder       *string         `json:"folder"`
 	ProjectID    *string         `json:"project_id,omitempty"`
+	WorkspaceID  *string         `json:"workspace_id,omitempty"`
 	Tags         []string        `json:"tags"`
 	Settings     json.RawMessage `json:"settings,omitempty"`
 	MessageCount int             `json:"message_count"`
@@ -178,7 +180,7 @@ func (h *ChannelHandler) ListChannels(c *gin.Context) {
 	// Fetch channels with message count
 	query := `
 		SELECT c.id, c.user_id, c.title, c.type, c.description, c.model, c.provider_config_id,
-		       c.system_prompt, c.is_archived, c.is_pinned, c.folder, c.project_id,
+		       c.system_prompt, c.is_archived, c.is_pinned, c.folder, c.project_id, c.workspace_id,
 		       c.tags, c.settings,
 		       COALESCE(mc.cnt, 0) AS message_count,
 		       c.created_at, c.updated_at
@@ -230,7 +232,7 @@ func (h *ChannelHandler) ListChannels(c *gin.Context) {
 		var tags []string
 		err := rows.Scan(
 			&ch.ID, &ch.UserID, &ch.Title, &ch.Type, &ch.Description, &ch.Model, &ch.APIConfigID,
-			&ch.SystemPrompt, &ch.IsArchived, &ch.IsPinned, &ch.Folder, &ch.ProjectID,
+			&ch.SystemPrompt, &ch.IsArchived, &ch.IsPinned, &ch.Folder, &ch.ProjectID, &ch.WorkspaceID,
 			scanTags(&tags), scanJSON(&ch.Settings),
 			&ch.MessageCount, &ch.CreatedAt, &ch.UpdatedAt,
 		)
@@ -377,7 +379,7 @@ func (h *ChannelHandler) GetChannel(c *gin.Context) {
 	var tags []string
 	err := database.DB.QueryRow(database.Q(`
 		SELECT c.id, c.user_id, c.title, c.type, c.description, c.model, c.provider_config_id,
-		       c.system_prompt, c.is_archived, c.is_pinned, c.folder, c.project_id,
+		       c.system_prompt, c.is_archived, c.is_pinned, c.folder, c.project_id, c.workspace_id,
 		       c.tags, c.settings,
 		       COALESCE(mc.cnt, 0) AS message_count,
 		       c.created_at, c.updated_at
@@ -388,7 +390,7 @@ func (h *ChannelHandler) GetChannel(c *gin.Context) {
 		WHERE c.id = $1 AND c.user_id = $2
 	`), channelID, userID).Scan(
 		&ch.ID, &ch.UserID, &ch.Title, &ch.Type, &ch.Description, &ch.Model, &ch.APIConfigID,
-		&ch.SystemPrompt, &ch.IsArchived, &ch.IsPinned, &ch.Folder, &ch.ProjectID,
+		&ch.SystemPrompt, &ch.IsArchived, &ch.IsPinned, &ch.Folder, &ch.ProjectID, &ch.WorkspaceID,
 		scanTags(&tags), scanJSON(&ch.Settings),
 		&ch.MessageCount, &ch.CreatedAt, &ch.UpdatedAt,
 	)
@@ -484,6 +486,13 @@ func (h *ChannelHandler) UpdateChannel(c *gin.Context) {
 		}
 		args = append(args, []byte(*req.Settings))
 	}
+	if req.WorkspaceID != nil {
+		if *req.WorkspaceID == "" {
+			addClause("workspace_id", nil) // unbind
+		} else {
+			addClause("workspace_id", *req.WorkspaceID)
+		}
+	}
 
 	if len(setClauses) == 0 {
 		c.JSON(http.StatusBadRequest, gin.H{"error": "no fields to update"})
diff --git a/server/handlers/stream_loop.go b/server/handlers/stream_loop.go
index ad78e4b..4548a42 100644
--- a/server/handlers/stream_loop.go
+++ b/server/handlers/stream_loop.go
@@ -207,6 +207,22 @@ func streamWithToolLoop(
 			})
 			sendEvent("tool_result", string(resultJSON))
 
+			// Emit workspace.file.changed for live editor updates (v0.21.5)
+			if hub != nil && !toolResult.IsError && workspaceID != "" {
+				if call.Name == "workspace_write" || call.Name == "workspace_patch" {
+					var toolArgs struct{ Path string `json:"path"` }
+					if json.Unmarshal([]byte(call.Arguments), &toolArgs) == nil && toolArgs.Path != "" {
+						hub.SendToUser(userID, events.Event{
+							Label: "workspace.file.changed",
+							Payload: events.MustJSON(map[string]string{
+								"workspace_id": workspaceID,
+								"path":         toolArgs.Path,
+							}),
+						})
+					}
+				}
+			}
+
 			// Collect for persistence
 			result.ToolActivity = append(result.ToolActivity, map[string]interface{}{
 				"id":        tc.ID,
diff --git a/server/handlers/workspaces.go b/server/handlers/workspaces.go
index 7ad36ac..76e866c 100644
--- a/server/handlers/workspaces.go
+++ b/server/handlers/workspaces.go
@@ -101,6 +101,34 @@ func (h *WorkspaceHandler) Get(c *gin.Context) {
 	c.JSON(http.StatusOK, w)
 }
 
+// List returns all workspaces accessible to the current user.
+// Includes user-owned workspaces and those owned by the user's teams.
+func (h *WorkspaceHandler) List(c *gin.Context) {
+	userID := getUserID(c)
+	ctx := c.Request.Context()
+
+	// Fetch user-owned workspaces
+	userWs, err := h.stores.Workspaces.ListByOwner(ctx, "user", userID)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
+	all := make([]models.Workspace, 0, len(userWs))
+	all = append(all, userWs...)
+
+	// Also include team-owned workspaces
+	teamIDs, _ := h.stores.Teams.GetUserTeamIDs(ctx, userID)
+	for _, tid := range teamIDs {
+		teamWs, err := h.stores.Workspaces.ListByOwner(ctx, "team", tid)
+		if err == nil {
+			all = append(all, teamWs...)
+		}
+	}
+
+	c.JSON(http.StatusOK, all)
+}
+
 func (h *WorkspaceHandler) Update(c *gin.Context) {
 	w, ok := h.loadAndAuthorize(c)
 	if !ok {
diff --git a/server/main.go b/server/main.go
index 589c866..0711dd6 100644
--- a/server/main.go
+++ b/server/main.go
@@ -454,6 +454,7 @@ func main() {
 			if wfs != nil {
 				wsH := handlers.NewWorkspaceHandler(stores, wfs)
 				protected.POST("/workspaces", wsH.Create)
+				protected.GET("/workspaces", wsH.List)
 				protected.GET("/workspaces/:id", wsH.Get)
 				protected.PATCH("/workspaces/:id", wsH.Update)
 				protected.DELETE("/workspaces/:id", wsH.Delete)
diff --git a/src/css/editor-mode.css b/src/css/editor-mode.css
new file mode 100644
index 0000000..80578c2
--- /dev/null
+++ b/src/css/editor-mode.css
@@ -0,0 +1,229 @@
+/* ==========================================
+   Editor Surface (v0.21.5)
+   IDE-like layout: file tree | code + chat
+   ========================================== */
+
+/* ── Header ──────────────────────────────── */
+
+.editor-header {
+    display: flex; align-items: center; justify-content: space-between;
+    padding: 6px 12px; gap: 8px;
+    font-size: 13px; color: var(--text-secondary);
+    border-bottom: 1px solid var(--border);
+    min-height: 36px; box-sizing: border-box;
+}
+.editor-header-left { display: flex; align-items: center; gap: 8px; min-width: 0; }
+.editor-ws-name { font-weight: 600; color: var(--text-primary); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
+.editor-branch { font-size: 12px; color: var(--text-tertiary); white-space: nowrap; }
+.editor-header-right { display: flex; align-items: center; gap: 4px; }
+.editor-hdr-btn {
+    background: none; border: none; color: var(--text-secondary);
+    cursor: pointer; padding: 4px; border-radius: 4px;
+    display: flex; align-items: center;
+}
+.editor-hdr-btn:hover { background: var(--hover); color: var(--text-primary); }
+
+/* ── File Tree (sidebar-content region) ──── */
+
+.editor-file-tree {
+    flex: 1; overflow-y: auto; overflow-x: hidden;
+    padding: 4px 0; font-size: 13px;
+    user-select: none;
+}
+.editor-tree-row {
+    display: flex; align-items: center; gap: 4px;
+    padding: 3px 8px; cursor: pointer;
+    white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
+    border-radius: 4px; margin: 0 4px;
+}
+.editor-tree-row:hover { background: var(--hover); }
+.editor-tree-row.active { background: var(--active-bg, rgba(59,130,246,0.12)); color: var(--accent); }
+.editor-tree-arrow { width: 14px; text-align: center; font-size: 10px; color: var(--text-tertiary); flex-shrink: 0; }
+.editor-tree-arrow.expanded { /* already rotated via character */ }
+.editor-tree-icon { flex-shrink: 0; font-size: 14px; line-height: 1; }
+.editor-tree-name { overflow: hidden; text-overflow: ellipsis; }
+
+.editor-tree-loading, .editor-tree-empty, .editor-tree-error {
+    padding: 16px; text-align: center; color: var(--text-tertiary); font-size: 12px;
+}
+
+/* ── Main Split Layout ───────────────────── */
+
+.editor-main {
+    display: flex; flex: 1; min-height: 0; overflow: hidden;
+}
+.editor-left-pane {
+    display: flex; flex-direction: column; min-width: 200px; overflow: hidden;
+}
+.editor-right-pane {
+    display: flex; flex-direction: column; min-width: 200px; overflow: hidden;
+    border-left: 1px solid var(--border);
+}
+
+/* Resize handle */
+.editor-split-handle {
+    width: 5px; cursor: col-resize; flex-shrink: 0;
+    background: transparent; position: relative; z-index: 5;
+}
+.editor-split-handle:hover,
+.editor-split-handle:active {
+    background: var(--accent);
+    opacity: 0.3;
+}
+
+/* ── Tab Bar ─────────────────────────────── */
+
+.editor-tab-bar {
+    display: flex; overflow-x: auto; overflow-y: hidden;
+    border-bottom: 1px solid var(--border);
+    min-height: 32px; flex-shrink: 0;
+    scrollbar-width: none;
+}
+.editor-tab-bar::-webkit-scrollbar { height: 0; }
+
+.editor-tab {
+    display: flex; align-items: center; gap: 4px;
+    padding: 4px 10px; font-size: 12px;
+    cursor: pointer; white-space: nowrap;
+    border-right: 1px solid var(--border);
+    color: var(--text-secondary);
+    flex-shrink: 0; max-width: 180px;
+    position: relative;
+}
+.editor-tab:hover { background: var(--hover); }
+.editor-tab.active {
+    background: var(--bg-primary);
+    color: var(--text-primary);
+    border-bottom: 2px solid var(--accent);
+}
+.editor-tab.modified .editor-tab-name { font-style: italic; }
+.editor-tab-icon { font-size: 13px; flex-shrink: 0; }
+.editor-tab-name { overflow: hidden; text-overflow: ellipsis; }
+.editor-tab-modified { color: var(--accent); font-size: 10px; margin-left: 2px; }
+.editor-tab-close {
+    background: none; border: none; color: var(--text-tertiary);
+    cursor: pointer; font-size: 11px; padding: 0 2px;
+    border-radius: 3px; opacity: 0; transition: opacity 0.1s;
+    margin-left: 4px;
+}
+.editor-tab:hover .editor-tab-close { opacity: 1; }
+.editor-tab-close:hover { background: var(--hover); color: var(--text-primary); }
+
+/* ── Code Editor Area ────────────────────── */
+
+.editor-code-area {
+    flex: 1; min-height: 0; position: relative; overflow: hidden;
+}
+.editor-cm-wrap {
+    position: absolute; inset: 0; overflow: hidden;
+}
+.editor-cm-wrap .cm-editor { height: 100%; }
+.editor-cm-wrap .cm-scroller { overflow: auto; }
+
+/* Textarea fallback */
+.editor-textarea-fallback {
+    width: 100%; height: 100%; resize: none; border: none; outline: none;
+    background: var(--bg-primary); color: var(--text-primary);
+    font-family: 'SF Mono', 'Fira Code', 'Cascadia Code', monospace;
+    font-size: 13px; line-height: 1.5;
+    padding: 8px 12px; box-sizing: border-box;
+    tab-size: 4;
+}
+
+/* Welcome screen */
+.editor-welcome {
+    position: absolute; inset: 0;
+    display: flex; align-items: center; justify-content: center;
+}
+.editor-welcome-inner { text-align: center; color: var(--text-tertiary); }
+.editor-welcome-inner p { margin: 8px 0; font-size: 14px; }
+.editor-welcome-hint { font-size: 12px; opacity: 0.6; }
+.editor-welcome-hint kbd {
+    background: var(--hover); border: 1px solid var(--border);
+    border-radius: 3px; padding: 1px 5px; font-size: 11px;
+    font-family: inherit;
+}
+
+/* ── Chat Panel (right pane) ─────────────── */
+
+.editor-chat-header {
+    padding: 6px 12px; font-size: 12px; font-weight: 600;
+    color: var(--text-secondary); border-bottom: 1px solid var(--border);
+    flex-shrink: 0;
+}
+.editor-chat-messages {
+    flex: 1; overflow-y: auto; min-height: 0;
+}
+/* Inherit chat message styles when embedded */
+.editor-chat-messages .messages { height: auto; overflow: visible; }
+.editor-chat-input { flex-shrink: 0; }
+/* Inherit input-area styles */
+.editor-chat-input .input-area { border-top: 1px solid var(--border); }
+
+/* ── Status Bar (footer) ─────────────────── */
+
+.editor-status-bar {
+    display: flex; align-items: center; gap: 8px;
+    padding: 2px 12px; font-size: 11px;
+    color: var(--text-tertiary);
+    border-top: 1px solid var(--border);
+    min-height: 22px; flex-shrink: 0;
+    background: var(--bg-secondary);
+}
+.editor-status-sep { opacity: 0.3; }
+.editor-status-right { margin-left: auto; }
+.editor-status-branch { font-size: 11px; }
+.editor-status-file { max-width: 300px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+
+/* ── Context Menu ────────────────────────── */
+
+.editor-ctx-menu {
+    position: fixed; z-index: 1000;
+    background: var(--bg-primary); border: 1px solid var(--border);
+    border-radius: 6px; padding: 4px 0;
+    box-shadow: 0 4px 16px rgba(0,0,0,0.2);
+    min-width: 120px; font-size: 13px;
+}
+.editor-ctx-item {
+    padding: 6px 12px; cursor: pointer;
+    color: var(--text-primary);
+}
+.editor-ctx-item:hover { background: var(--hover); }
+
+/* ── Quick Open Overlay ──────────────────── */
+
+.editor-quick-open {
+    position: fixed; inset: 0; z-index: 2000;
+    background: rgba(0,0,0,0.4);
+    display: flex; align-items: flex-start; justify-content: center;
+    padding-top: 15vh;
+}
+.editor-qo-dialog {
+    background: var(--bg-primary); border: 1px solid var(--border);
+    border-radius: 8px; width: 460px; max-width: 90vw;
+    box-shadow: 0 8px 32px rgba(0,0,0,0.3);
+    overflow: hidden;
+}
+.editor-qo-input {
+    width: 100%; padding: 10px 14px; font-size: 14px;
+    border: none; outline: none; box-sizing: border-box;
+    background: var(--bg-primary); color: var(--text-primary);
+    border-bottom: 1px solid var(--border);
+}
+.editor-qo-results { max-height: 300px; overflow-y: auto; }
+.editor-qo-row {
+    padding: 6px 14px; cursor: pointer; font-size: 13px;
+    display: flex; align-items: center; gap: 6px;
+    color: var(--text-primary);
+}
+.editor-qo-row:hover { background: var(--hover); }
+.editor-qo-icon { font-size: 14px; flex-shrink: 0; }
+
+/* ── Mobile: single pane ─────────────────── */
+
+@media (max-width: 768px) {
+    .editor-main { flex-direction: column; }
+    .editor-left-pane { flex: 1 !important; min-width: 0; }
+    .editor-right-pane { min-width: 0; border-left: none; border-top: 1px solid var(--border); max-height: 40vh; }
+    .editor-split-handle { display: none; }
+}
diff --git a/src/css/styles.css b/src/css/styles.css
index 49ee9fd..2cd730d 100644
--- a/src/css/styles.css
+++ b/src/css/styles.css
@@ -2583,6 +2583,8 @@ select option { background: var(--bg-surface); color: var(--text); }
 }
 .project-panel-select:focus { outline: none; border-color: var(--accent); }
 .project-panel-hint { font-size: 11px; color: var(--text-3); margin-top: 2px; }
+.project-panel-ws-row { display: flex; gap: 6px; align-items: center; }
+.project-panel-ws-row select { flex: 1; }
 .project-panel-checkbox {
     display: flex; align-items: center; gap: 8px; font-size: 13px;
     cursor: pointer; color: var(--text-2);
diff --git a/src/index.html b/src/index.html
index abfba80..eab587e 100644
--- a/src/index.html
+++ b/src/index.html
@@ -19,6 +19,7 @@
     <meta name="apple-mobile-web-app-capable" content="yes">
     <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
     <link rel="stylesheet" href="css/styles.css?v=%%APP_VERSION%%">
+    <link rel="stylesheet" href="css/editor-mode.css?v=%%APP_VERSION%%">
     <link rel="stylesheet" href="css/persona-kb.css?v=%%APP_VERSION%%">
     <link rel="stylesheet" href="css/memory.css?v=%%APP_VERSION%%">
     <link rel="stylesheet" href="css/notifications.css?v=%%APP_VERSION%%">
@@ -1201,6 +1202,7 @@
 <script src="js/chat.js?v=%%APP_VERSION%%"></script>
 <script src="js/settings-handlers.js?v=%%APP_VERSION%%"></script>
 <script src="js/admin-handlers.js?v=%%APP_VERSION%%"></script>
+<script src="js/editor-mode.js?v=%%APP_VERSION%%"></script>
 <script src="js/app.js?v=%%APP_VERSION%%"></script>
 <script>
 // ── Service Worker Registration ─────────
diff --git a/src/js/api.js b/src/js/api.js
index 2e312a8..d36f695 100644
--- a/src/js/api.js
+++ b/src/js/api.js
@@ -207,6 +207,43 @@ const API = {
     },
     listProjectNotes(projectId) { return this._get(`/api/v1/projects/${projectId}/notes`); },
 
+    // ── Workspaces (v0.21.0) ────────────────
+    getWorkspace(id) { return this._get(`/api/v1/workspaces/${id}`); },
+    listWorkspaceFiles(wsId, path = '', recursive = false) {
+        let url = `/api/v1/workspaces/${wsId}/files?path=${encodeURIComponent(path)}`;
+        if (recursive) url += '&recursive=true';
+        return this._get(url);
+    },
+    async readWorkspaceFile(wsId, path) {
+        // Returns raw text, not JSON
+        const resp = await fetch(BASE + `/api/v1/workspaces/${wsId}/files/read?path=${encodeURIComponent(path)}`, {
+            headers: this._authHeaders(),
+        });
+        if (!resp.ok) {
+            const data = await resp.json().catch(() => ({}));
+            throw Object.assign(new Error(data.error || `HTTP ${resp.status}`), { status: resp.status });
+        }
+        const ct = resp.headers.get('content-type') || '';
+        if (ct.includes('application/json')) {
+            const data = await resp.json();
+            return data.content || '';
+        }
+        return resp.text();
+    },
+    writeWorkspaceFile(wsId, path, content) {
+        return this._put(`/api/v1/workspaces/${wsId}/files/write`, { path, content });
+    },
+    deleteWorkspaceFile(wsId, path) {
+        return this._del(`/api/v1/workspaces/${wsId}/files/delete?path=${encodeURIComponent(path)}`);
+    },
+    mkdirWorkspace(wsId, path) {
+        return this._post(`/api/v1/workspaces/${wsId}/files/mkdir`, { path });
+    },
+    getWorkspaceGitStatus(wsId) { return this._get(`/api/v1/workspaces/${wsId}/git/status`); },
+    getWorkspaceGitBranches(wsId) { return this._get(`/api/v1/workspaces/${wsId}/git/branches`); },
+    listWorkspaces() { return this._get('/api/v1/workspaces'); },
+    createWorkspace(data) { return this._post('/api/v1/workspaces', data); },
+
     // ── Messages ─────────────────────────────
 
     listMessages(channelId, page = 1, perPage = 200) {
diff --git a/src/js/editor-mode.js b/src/js/editor-mode.js
new file mode 100644
index 0000000..54438e1
--- /dev/null
+++ b/src/js/editor-mode.js
@@ -0,0 +1,936 @@
+// ==========================================
+// Chat Switchboard – Editor Surface (v0.21.5)
+// ==========================================
+// IDE-like experience built as a surface consuming workspace
+// primitives (v0.21.0) and surface infrastructure (v0.21.3).
+//
+// Layout: file tree (sidebar) | code editor (CM6) + chat panel (split)
+// Load order: surfaces.js → editor-mode.js (after app init)
+// ==========================================
+
+const EditorMode = {
+
+    // ── State ────────────────────────────────
+    _wsId: null,            // workspace ID
+    _wsName: '',            // workspace display name
+    _gitBranch: null,       // current git branch (nullable)
+    _registered: false,     // surface registered?
+    _active: false,         // currently active?
+
+    // DOM (built once, reused across activations)
+    _els: null,             // { header, fileTree, main, footer }
+    _built: false,
+
+    // File tree
+    _treeData: [],          // flat file list from API
+    _expandedDirs: new Set(['']), // expanded directory paths
+
+    // Tabs + editors
+    _openFiles: new Map(),  // path → { tab, editorWrap, editor(CM6), content, modified, language }
+    _activeFile: null,      // path of currently active tab
+    _tabBarEl: null,
+    _editorAreaEl: null,
+    _welcomeEl: null,
+
+    // Split
+    _splitRatio: 0.6,       // editor pane width ratio (0.0-1.0)
+
+    // ── Initialization ───────────────────────
+
+    /**
+     * Check if the current channel/project has a workspace.
+     * Called on channel switch and app init.
+     */
+    async check() {
+        const channelId = App.currentChatId;
+        if (!channelId) {
+            this._unregister();
+            return;
+        }
+
+        try {
+            const ch = await API.getChannel(channelId);
+            const wsId = ch.workspace_id || null;
+
+            // Also check project workspace if channel doesn't have one
+            if (!wsId && ch.project_id) {
+                try {
+                    const proj = await API.getProject(ch.project_id);
+                    if (proj.workspace_id) {
+                        this._register(proj.workspace_id, proj.name || 'Workspace');
+                        return;
+                    }
+                } catch (_) { /* no project workspace */ }
+            }
+
+            if (wsId) {
+                // Fetch workspace details
+                try {
+                    const ws = await API.getWorkspace(wsId);
+                    this._register(wsId, ws.name || 'Workspace');
+                } catch (_) {
+                    this._register(wsId, 'Workspace');
+                }
+            } else {
+                this._unregister();
+            }
+        } catch (e) {
+            console.warn('[EditorMode] check failed:', e);
+        }
+    },
+
+    _register(wsId, name) {
+        this._wsId = wsId;
+        this._wsName = name;
+
+        if (this._registered) return;
+        this._registered = true;
+
+        Surfaces.register('editor', {
+            label: 'Editor',
+            icon: 'code',
+            regions: ['surface-header', 'surface-main', 'surface-footer', 'sidebar-content'],
+            activate: () => this._activate(),
+            deactivate: () => this._deactivate(),
+        });
+
+        console.log(`[EditorMode] Registered for workspace ${wsId}`);
+    },
+
+    _unregister() {
+        if (!this._registered) return;
+        if (this._active) {
+            Surfaces.activate('chat');
+        }
+        Surfaces.unregister('editor');
+        this._registered = false;
+        this._wsId = null;
+        this._built = false;
+        this._els = null;
+        this._openFiles.clear();
+        this._activeFile = null;
+        console.log('[EditorMode] Unregistered');
+    },
+
+    // ── Surface Callbacks ────────────────────
+
+    _activate() {
+        this._active = true;
+
+        if (!this._built) {
+            this._build();
+        }
+
+        // Populate regions
+        const regions = Surfaces._regionEls;
+
+        // Header
+        const headerEl = regions.get('surface-header');
+        if (headerEl) headerEl.appendChild(this._els.header);
+
+        // Sidebar → file tree
+        const sidebarEl = regions.get('sidebar-content');
+        if (sidebarEl) sidebarEl.appendChild(this._els.fileTree);
+
+        // Main → split pane (editor + chat)
+        const mainEl = regions.get('surface-main');
+        if (mainEl) mainEl.appendChild(this._els.main);
+
+        // Footer → status bar
+        const footerEl = regions.get('surface-footer');
+        if (footerEl) footerEl.appendChild(this._els.footer);
+
+        // Embed saved chat DOM into our chat pane
+        this._embedChat();
+
+        // Refresh file tree
+        this._refreshFileTree();
+        this._refreshGitBranch();
+
+        // Focus active editor
+        if (this._activeFile) {
+            const f = this._openFiles.get(this._activeFile);
+            if (f?.editor?.focus) setTimeout(() => f.editor.focus(), 50);
+        }
+    },
+
+    _deactivate() {
+        this._active = false;
+
+        // Return chat DOM to Surfaces saved store before regions are saved
+        this._returnChat();
+    },
+
+    // ── Chat Panel Embedding ─────────────────
+    // Borrow chat DOM from the saved fragments so the chat panel
+    // shows real messages and the user can interact with AI.
+
+    _chatPane: null,
+    _chatMessagesSlot: null,
+    _chatInputSlot: null,
+
+    _embedChat() {
+        if (!this._chatPane) return;
+
+        // Grab saved chat fragments
+        const msgFrag = Surfaces.getSavedFragment('chat', 'surface-main');
+        const inputFrag = Surfaces.getSavedFragment('chat', 'surface-footer');
+
+        if (msgFrag) {
+            this._chatMessagesSlot.appendChild(msgFrag);
+            // Scroll to bottom
+            this._chatMessagesSlot.scrollTop = this._chatMessagesSlot.scrollHeight;
+        }
+        if (inputFrag) {
+            this._chatInputSlot.appendChild(inputFrag);
+        }
+    },
+
+    _returnChat() {
+        if (!this._chatPane) return;
+
+        // Collect chat DOM back into fragments and return to Surfaces store
+        const msgFrag = document.createDocumentFragment();
+        while (this._chatMessagesSlot.firstChild) {
+            msgFrag.appendChild(this._chatMessagesSlot.firstChild);
+        }
+        Surfaces.putSavedFragment('chat', 'surface-main', msgFrag);
+
+        const inputFrag = document.createDocumentFragment();
+        while (this._chatInputSlot.firstChild) {
+            inputFrag.appendChild(this._chatInputSlot.firstChild);
+        }
+        Surfaces.putSavedFragment('chat', 'surface-footer', inputFrag);
+    },
+
+    // ── DOM Construction ─────────────────────
+
+    _build() {
+        this._els = {
+            header: this._buildHeader(),
+            fileTree: this._buildFileTreeContainer(),
+            main: this._buildMain(),
+            footer: this._buildFooter(),
+        };
+        this._built = true;
+    },
+
+    _buildHeader() {
+        const el = document.createElement('div');
+        el.className = 'editor-header';
+        el.innerHTML = `
+            <div class="editor-header-left">
+                <span class="editor-ws-name" id="editorWsName">${this._esc(this._wsName)}</span>
+                <span class="editor-branch" id="editorBranch"></span>
+            </div>
+            <div class="editor-header-right">
+                <button class="editor-hdr-btn" id="editorRefreshBtn" title="Refresh file tree">
+                    <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polyline points="23 4 23 10 17 10"/><polyline points="1 20 1 14 7 14"/><path d="M3.51 9a9 9 0 0 1 14.85-3.36L23 10M1 14l4.64 4.36A9 9 0 0 0 20.49 15"/></svg>
+                </button>
+            </div>`;
+        el.querySelector('#editorRefreshBtn').addEventListener('click', () => this._refreshFileTree());
+        return el;
+    },
+
+    _buildFileTreeContainer() {
+        const el = document.createElement('div');
+        el.className = 'editor-file-tree';
+        el.innerHTML = '<div class="editor-tree-loading">Loading files…</div>';
+        return el;
+    },
+
+    _buildMain() {
+        const el = document.createElement('div');
+        el.className = 'editor-main';
+
+        // Left: editor area (tabs + code)
+        const leftPane = document.createElement('div');
+        leftPane.className = 'editor-left-pane';
+
+        this._tabBarEl = document.createElement('div');
+        this._tabBarEl.className = 'editor-tab-bar';
+        leftPane.appendChild(this._tabBarEl);
+
+        this._editorAreaEl = document.createElement('div');
+        this._editorAreaEl.className = 'editor-code-area';
+        leftPane.appendChild(this._editorAreaEl);
+
+        // Welcome screen
+        this._welcomeEl = document.createElement('div');
+        this._welcomeEl.className = 'editor-welcome';
+        this._welcomeEl.innerHTML = `
+            <div class="editor-welcome-inner">
+                <svg width="48" height="48" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round" opacity="0.3"><polyline points="16 18 22 12 16 6"/><polyline points="8 6 2 12 8 18"/></svg>
+                <p>Select a file to start editing</p>
+                <p class="editor-welcome-hint"><kbd>Ctrl+P</kbd> Quick Open</p>
+            </div>`;
+        this._editorAreaEl.appendChild(this._welcomeEl);
+
+        // Resize handle
+        const handle = document.createElement('div');
+        handle.className = 'editor-split-handle';
+        this._initResize(handle, leftPane);
+
+        // Right: chat panel
+        const rightPane = document.createElement('div');
+        rightPane.className = 'editor-right-pane';
+
+        const chatHeader = document.createElement('div');
+        chatHeader.className = 'editor-chat-header';
+        chatHeader.innerHTML = '<span>AI Chat</span>';
+        rightPane.appendChild(chatHeader);
+
+        this._chatMessagesSlot = document.createElement('div');
+        this._chatMessagesSlot.className = 'editor-chat-messages';
+        rightPane.appendChild(this._chatMessagesSlot);
+
+        this._chatInputSlot = document.createElement('div');
+        this._chatInputSlot.className = 'editor-chat-input';
+        rightPane.appendChild(this._chatInputSlot);
+
+        this._chatPane = rightPane;
+
+        el.appendChild(leftPane);
+        el.appendChild(handle);
+        el.appendChild(rightPane);
+
+        // Apply initial split ratio
+        leftPane.style.flex = `0 0 ${this._splitRatio * 100}%`;
+        rightPane.style.flex = '1';
+
+        return el;
+    },
+
+    _buildFooter() {
+        const el = document.createElement('div');
+        el.className = 'editor-status-bar';
+        el.innerHTML = `
+            <span class="editor-status-file" id="editorStatusFile">No file open</span>
+            <span class="editor-status-sep">│</span>
+            <span class="editor-status-cursor" id="editorStatusCursor"></span>
+            <span class="editor-status-sep">│</span>
+            <span class="editor-status-lang" id="editorStatusLang"></span>
+            <span class="editor-status-right">
+                <span class="editor-status-branch" id="editorStatusBranch"></span>
+            </span>`;
+        return el;
+    },
+
+    // ── Resize Handle ────────────────────────
+
+    _initResize(handle, leftPane) {
+        let startX = 0, startWidth = 0;
+
+        const onMove = (e) => {
+            const dx = (e.clientX || e.touches?.[0]?.clientX || 0) - startX;
+            const parentWidth = handle.parentElement.clientWidth;
+            const newWidth = Math.max(200, Math.min(parentWidth - 200, startWidth + dx));
+            leftPane.style.flex = `0 0 ${newWidth}px`;
+            this._splitRatio = newWidth / parentWidth;
+        };
+
+        const onUp = () => {
+            document.removeEventListener('mousemove', onMove);
+            document.removeEventListener('mouseup', onUp);
+            document.removeEventListener('touchmove', onMove);
+            document.removeEventListener('touchend', onUp);
+            document.body.style.userSelect = '';
+            document.body.style.cursor = '';
+        };
+
+        handle.addEventListener('mousedown', (e) => {
+            e.preventDefault();
+            startX = e.clientX;
+            startWidth = leftPane.clientWidth;
+            document.body.style.userSelect = 'none';
+            document.body.style.cursor = 'col-resize';
+            document.addEventListener('mousemove', onMove);
+            document.addEventListener('mouseup', onUp);
+        });
+
+        handle.addEventListener('touchstart', (e) => {
+            startX = e.touches[0].clientX;
+            startWidth = leftPane.clientWidth;
+            document.addEventListener('touchmove', onMove, { passive: false });
+            document.addEventListener('touchend', onUp);
+        });
+    },
+
+    // ── File Tree ────────────────────────────
+
+    async _refreshFileTree() {
+        if (!this._wsId) return;
+        try {
+            const resp = await API.listWorkspaceFiles(this._wsId, '', true);
+            this._treeData = resp.files || resp.data || resp || [];
+            this._renderFileTree();
+        } catch (e) {
+            console.error('[EditorMode] Failed to load file tree:', e);
+            this._els.fileTree.innerHTML = '<div class="editor-tree-error">Failed to load files</div>';
+        }
+    },
+
+    _renderFileTree() {
+        const container = this._els.fileTree;
+        container.innerHTML = '';
+
+        if (!this._treeData.length) {
+            container.innerHTML = '<div class="editor-tree-empty">No files</div>';
+            return;
+        }
+
+        // Build tree structure from flat list
+        const tree = this._buildTreeStructure(this._treeData);
+        this._renderTreeNodes(tree, container, 0);
+    },
+
+    _buildTreeStructure(files) {
+        // files: [{path, is_directory, size_bytes, content_type}, ...]
+        // Build nested tree: { name, path, isDir, children[], file }
+        const root = { name: '', path: '', isDir: true, children: [], file: null };
+        const dirs = new Map();
+        dirs.set('', root);
+
+        // Sort: directories first, then alphabetical
+        const sorted = [...files].sort((a, b) => {
+            if (a.is_directory !== b.is_directory) return a.is_directory ? -1 : 1;
+            return a.path.localeCompare(b.path);
+        });
+
+        for (const f of sorted) {
+            const parts = f.path.split('/');
+            const name = parts[parts.length - 1];
+            const parentPath = parts.slice(0, -1).join('/');
+
+            // Ensure parent directories exist
+            let parent = dirs.get(parentPath);
+            if (!parent) {
+                // Create implicit parent dirs
+                let accumulated = '';
+                for (let i = 0; i < parts.length - 1; i++) {
+                    const prev = accumulated;
+                    accumulated = accumulated ? accumulated + '/' + parts[i] : parts[i];
+                    if (!dirs.has(accumulated)) {
+                        const dirNode = { name: parts[i], path: accumulated, isDir: true, children: [], file: null };
+                        dirs.set(accumulated, dirNode);
+                        const p = dirs.get(prev);
+                        if (p) p.children.push(dirNode);
+                    }
+                }
+                parent = dirs.get(parentPath);
+            }
+
+            if (f.is_directory) {
+                let existing = dirs.get(f.path);
+                if (!existing) {
+                    existing = { name, path: f.path, isDir: true, children: [], file: f };
+                    dirs.set(f.path, existing);
+                    if (parent) parent.children.push(existing);
+                } else {
+                    existing.file = f;
+                }
+            } else {
+                const node = { name, path: f.path, isDir: false, children: [], file: f };
+                if (parent) parent.children.push(node);
+            }
+        }
+
+        return root.children;
+    },
+
+    _renderTreeNodes(nodes, container, depth) {
+        for (const node of nodes) {
+            const row = document.createElement('div');
+            row.className = 'editor-tree-row' + (node.path === this._activeFile ? ' active' : '');
+            row.style.paddingLeft = (12 + depth * 16) + 'px';
+            row.dataset.path = node.path;
+
+            if (node.isDir) {
+                const expanded = this._expandedDirs.has(node.path);
+                row.innerHTML = `
+                    <span class="editor-tree-arrow ${expanded ? 'expanded' : ''}">${expanded ? '▾' : '▸'}</span>
+                    <span class="editor-tree-icon">📁</span>
+                    <span class="editor-tree-name">${this._esc(node.name)}</span>`;
+                row.addEventListener('click', () => {
+                    if (this._expandedDirs.has(node.path)) {
+                        this._expandedDirs.delete(node.path);
+                    } else {
+                        this._expandedDirs.add(node.path);
+                    }
+                    this._renderFileTree();
+                });
+                container.appendChild(row);
+
+                if (expanded && node.children.length) {
+                    this._renderTreeNodes(node.children, container, depth + 1);
+                }
+            } else {
+                row.innerHTML = `
+                    <span class="editor-tree-icon">${this._fileIcon(node.name)}</span>
+                    <span class="editor-tree-name">${this._esc(node.name)}</span>`;
+                row.addEventListener('click', () => this._openFile(node.path));
+
+                // Context menu
+                row.addEventListener('contextmenu', (e) => {
+                    e.preventDefault();
+                    this._showFileContextMenu(e, node);
+                });
+
+                container.appendChild(row);
+            }
+        }
+    },
+
+    _fileIcon(name) {
+        const ext = name.split('.').pop()?.toLowerCase();
+        const icons = {
+            js: '📜', ts: '📜', jsx: '⚛', tsx: '⚛',
+            go: '🔵', py: '🐍', rs: '🦀', rb: '💎',
+            html: '🌐', css: '🎨', scss: '🎨', less: '🎨',
+            json: '📋', yaml: '📋', yml: '📋', toml: '📋',
+            md: '📝', txt: '📄', svg: '🖼',
+            sql: '🗃', sh: '⚙', bash: '⚙', zsh: '⚙',
+            dockerfile: '🐳', makefile: '🔧',
+            mod: '📦', sum: '📦', lock: '🔒',
+        };
+        return icons[ext] || '📄';
+    },
+
+    _showFileContextMenu(e, node) {
+        // Simple context menu using CSS positioned div
+        const existing = document.querySelector('.editor-ctx-menu');
+        if (existing) existing.remove();
+
+        const menu = document.createElement('div');
+        menu.className = 'editor-ctx-menu';
+        menu.style.left = e.clientX + 'px';
+        menu.style.top = e.clientY + 'px';
+
+        const items = [
+            { label: 'Open', action: () => this._openFile(node.path) },
+            { label: 'Delete', action: () => this._deleteFile(node.path) },
+        ];
+        for (const item of items) {
+            const row = document.createElement('div');
+            row.className = 'editor-ctx-item';
+            row.textContent = item.label;
+            row.addEventListener('click', () => { menu.remove(); item.action(); });
+            menu.appendChild(row);
+        }
+
+        document.body.appendChild(menu);
+
+        const dismiss = (ev) => {
+            if (!menu.contains(ev.target)) { menu.remove(); document.removeEventListener('click', dismiss); }
+        };
+        setTimeout(() => document.addEventListener('click', dismiss), 0);
+    },
+
+    // ── Tab Management ───────────────────────
+
+    async _openFile(path) {
+        if (this._openFiles.has(path)) {
+            this._activateTab(path);
+            return;
+        }
+
+        // Fetch file content
+        let content = '';
+        try {
+            content = await API.readWorkspaceFile(this._wsId, path);
+        } catch (e) {
+            console.error('[EditorMode] Failed to read file:', e);
+            if (typeof UI !== 'undefined') UI.toast(`Failed to open ${path}`, 'error');
+            return;
+        }
+
+        const lang = this._detectLanguage(path);
+
+        // Create tab
+        const tab = document.createElement('div');
+        tab.className = 'editor-tab';
+        tab.dataset.path = path;
+        tab.innerHTML = `
+            <span class="editor-tab-icon">${this._fileIcon(path.split('/').pop())}</span>
+            <span class="editor-tab-name">${this._esc(path.split('/').pop())}</span>
+            <span class="editor-tab-modified" style="display:none">●</span>
+            <button class="editor-tab-close" title="Close">✕</button>`;
+        tab.addEventListener('click', (e) => {
+            if (!e.target.closest('.editor-tab-close')) this._activateTab(path);
+        });
+        tab.querySelector('.editor-tab-close').addEventListener('click', (e) => {
+            e.stopPropagation();
+            this._closeFile(path);
+        });
+        this._tabBarEl.appendChild(tab);
+
+        // Create editor wrapper
+        const editorWrap = document.createElement('div');
+        editorWrap.className = 'editor-cm-wrap';
+        editorWrap.style.display = 'none';
+        this._editorAreaEl.appendChild(editorWrap);
+
+        // Create CM6 editor or textarea fallback
+        let editor = null;
+        if (window.CM?.codeEditor) {
+            editor = CM.codeEditor(editorWrap, {
+                language: lang,
+                value: content,
+                lineNumbers: true,
+            });
+            // Listen for changes to mark modified
+            if (editor.onUpdate) {
+                editor.onUpdate(() => this._markModified(path));
+            }
+        } else {
+            // Textarea fallback
+            const ta = document.createElement('textarea');
+            ta.className = 'editor-textarea-fallback';
+            ta.value = content;
+            ta.addEventListener('input', () => this._markModified(path));
+            editorWrap.appendChild(ta);
+            editor = {
+                getValue: () => ta.value,
+                setValue: (v) => { ta.value = v; },
+                focus: () => ta.focus(),
+                destroy: () => {},
+                _textarea: true,
+            };
+        }
+
+        this._openFiles.set(path, {
+            tab, editorWrap, editor, content, modified: false, language: lang,
+        });
+
+        this._activateTab(path);
+    },
+
+    _activateTab(path) {
+        if (this._activeFile === path) return;
+
+        // Deactivate previous
+        if (this._activeFile && this._openFiles.has(this._activeFile)) {
+            const prev = this._openFiles.get(this._activeFile);
+            prev.tab.classList.remove('active');
+            prev.editorWrap.style.display = 'none';
+        }
+
+        this._activeFile = path;
+        const f = this._openFiles.get(path);
+        if (!f) return;
+
+        f.tab.classList.add('active');
+        f.editorWrap.style.display = '';
+        this._welcomeEl.style.display = 'none';
+
+        // Update status bar
+        this._updateStatusBar();
+
+        // Update file tree active state
+        this._els.fileTree.querySelectorAll('.editor-tree-row').forEach(row => {
+            row.classList.toggle('active', row.dataset.path === path);
+        });
+
+        // Focus editor
+        if (f.editor?.focus) setTimeout(() => f.editor.focus(), 10);
+    },
+
+    async _closeFile(path) {
+        const f = this._openFiles.get(path);
+        if (!f) return;
+
+        // Confirm if modified
+        if (f.modified) {
+            const save = await this._confirmClose(path);
+            if (save === null) return; // cancelled
+            if (save) await this._saveFile(path);
+        }
+
+        // Clean up
+        f.tab.remove();
+        f.editorWrap.remove();
+        if (f.editor?.destroy) f.editor.destroy();
+        this._openFiles.delete(path);
+
+        // Activate next tab
+        if (this._activeFile === path) {
+            this._activeFile = null;
+            const remaining = Array.from(this._openFiles.keys());
+            if (remaining.length) {
+                this._activateTab(remaining[remaining.length - 1]);
+            } else {
+                this._welcomeEl.style.display = '';
+                this._updateStatusBar();
+            }
+        }
+    },
+
+    async _confirmClose(path) {
+        if (typeof showConfirm === 'function') {
+            const r = await showConfirm(`Save changes to ${path.split('/').pop()}?`, {
+                confirmLabel: 'Save', cancelLabel: 'Discard', showCancel: true
+            });
+            return r; // true = save, false = discard
+        }
+        return window.confirm(`Save changes to ${path.split('/').pop()}?`);
+    },
+
+    _markModified(path) {
+        const f = this._openFiles.get(path);
+        if (!f || f.modified) return;
+        const currentVal = f.editor?.getValue?.() ?? '';
+        if (currentVal === f.content) return;
+        f.modified = true;
+        f.tab.querySelector('.editor-tab-modified').style.display = '';
+        f.tab.classList.add('modified');
+    },
+
+    // ── Save ─────────────────────────────────
+
+    async _saveFile(path) {
+        const f = this._openFiles.get(path);
+        if (!f) return;
+
+        const content = f.editor?.getValue?.() ?? '';
+        try {
+            await API.writeWorkspaceFile(this._wsId, path, content);
+            f.content = content;
+            f.modified = false;
+            f.tab.querySelector('.editor-tab-modified').style.display = 'none';
+            f.tab.classList.remove('modified');
+            if (typeof UI !== 'undefined') UI.toast(`Saved ${path.split('/').pop()}`, 'success');
+        } catch (e) {
+            console.error('[EditorMode] Save failed:', e);
+            if (typeof UI !== 'undefined') UI.toast(`Failed to save: ${e.message}`, 'error');
+        }
+    },
+
+    async _saveActiveFile() {
+        if (this._activeFile) await this._saveFile(this._activeFile);
+    },
+
+    async _deleteFile(path) {
+        const ok = typeof showConfirm === 'function'
+            ? await showConfirm(`Delete ${path}?`)
+            : window.confirm(`Delete ${path}?`);
+        if (!ok) return;
+
+        try {
+            await API.deleteWorkspaceFile(this._wsId, path);
+            // Close tab if open
+            if (this._openFiles.has(path)) {
+                const f = this._openFiles.get(path);
+                f.modified = false; // skip save prompt
+                await this._closeFile(path);
+            }
+            this._refreshFileTree();
+        } catch (e) {
+            if (typeof UI !== 'undefined') UI.toast(`Delete failed: ${e.message}`, 'error');
+        }
+    },
+
+    // ── Language Detection ────────────────────
+
+    _detectLanguage(path) {
+        const ext = path.split('.').pop()?.toLowerCase();
+        const map = {
+            js: 'javascript', mjs: 'javascript', cjs: 'javascript',
+            ts: 'typescript', tsx: 'typescript', jsx: 'javascript',
+            go: 'go', py: 'python', rs: 'rust', rb: 'ruby',
+            html: 'html', htm: 'html', css: 'css', scss: 'css', less: 'css',
+            json: 'json', yaml: 'yaml', yml: 'yaml', toml: 'toml',
+            md: 'markdown', mdx: 'markdown',
+            sql: 'sql', sh: 'shell', bash: 'shell', zsh: 'shell',
+            xml: 'xml', svg: 'xml',
+            c: 'cpp', cpp: 'cpp', h: 'cpp', hpp: 'cpp',
+            java: 'java', kt: 'java',
+            php: 'php', pl: 'perl',
+            dockerfile: 'dockerfile',
+        };
+        return map[ext] || 'text';
+    },
+
+    // ── Git ──────────────────────────────────
+
+    async _refreshGitBranch() {
+        if (!this._wsId) return;
+        try {
+            const resp = await API.getWorkspaceGitBranches(this._wsId);
+            this._gitBranch = resp.current || null;
+            this._updateBranchDisplay();
+        } catch (_) {
+            this._gitBranch = null;
+            this._updateBranchDisplay();
+        }
+    },
+
+    _updateBranchDisplay() {
+        const headerEl = this._els?.header?.querySelector('#editorBranch');
+        const statusEl = this._els?.footer?.querySelector('#editorStatusBranch');
+        const branchText = this._gitBranch ? `⎇ ${this._gitBranch}` : '';
+
+        if (headerEl) headerEl.textContent = branchText;
+        if (statusEl) statusEl.textContent = branchText;
+    },
+
+    // ── Status Bar ───────────────────────────
+
+    _updateStatusBar() {
+        if (!this._els?.footer) return;
+        const fileEl = this._els.footer.querySelector('#editorStatusFile');
+        const langEl = this._els.footer.querySelector('#editorStatusLang');
+        const cursorEl = this._els.footer.querySelector('#editorStatusCursor');
+
+        if (this._activeFile) {
+            const f = this._openFiles.get(this._activeFile);
+            if (fileEl) fileEl.textContent = this._activeFile;
+            if (langEl) langEl.textContent = f?.language || '';
+            if (cursorEl) cursorEl.textContent = '';
+        } else {
+            if (fileEl) fileEl.textContent = 'No file open';
+            if (langEl) langEl.textContent = '';
+            if (cursorEl) cursorEl.textContent = '';
+        }
+    },
+
+    // ── Quick Open (Ctrl+P) ──────────────────
+
+    _quickOpenEl: null,
+
+    _showQuickOpen() {
+        if (this._quickOpenEl) { this._quickOpenEl.remove(); this._quickOpenEl = null; return; }
+
+        const overlay = document.createElement('div');
+        overlay.className = 'editor-quick-open';
+        overlay.innerHTML = `
+            <div class="editor-qo-dialog">
+                <input class="editor-qo-input" type="text" placeholder="Open file…" autocomplete="off">
+                <div class="editor-qo-results"></div>
+            </div>`;
+
+        const input = overlay.querySelector('.editor-qo-input');
+        const results = overlay.querySelector('.editor-qo-results');
+
+        const allFiles = this._treeData.filter(f => !f.is_directory);
+
+        const render = (query) => {
+            results.innerHTML = '';
+            const q = query.toLowerCase();
+            const matches = q
+                ? allFiles.filter(f => f.path.toLowerCase().includes(q)).slice(0, 20)
+                : allFiles.slice(0, 20);
+
+            for (const f of matches) {
+                const row = document.createElement('div');
+                row.className = 'editor-qo-row';
+                row.innerHTML = `<span class="editor-qo-icon">${this._fileIcon(f.path.split('/').pop())}</span> ${this._esc(f.path)}`;
+                row.addEventListener('click', () => {
+                    overlay.remove();
+                    this._quickOpenEl = null;
+                    this._openFile(f.path);
+                });
+                results.appendChild(row);
+            }
+        };
+
+        input.addEventListener('input', () => render(input.value));
+        input.addEventListener('keydown', (e) => {
+            if (e.key === 'Escape') { overlay.remove(); this._quickOpenEl = null; }
+            if (e.key === 'Enter') {
+                const first = results.querySelector('.editor-qo-row');
+                if (first) first.click();
+            }
+        });
+
+        overlay.addEventListener('click', (e) => {
+            if (e.target === overlay) { overlay.remove(); this._quickOpenEl = null; }
+        });
+
+        document.body.appendChild(overlay);
+        this._quickOpenEl = overlay;
+        render('');
+        input.focus();
+    },
+
+    // ── Keyboard Shortcuts ───────────────────
+
+    _onKeyDown(e) {
+        if (!EditorMode._active) return;
+
+        // Ctrl/Cmd+S — save
+        if ((e.ctrlKey || e.metaKey) && e.key === 's') {
+            e.preventDefault();
+            EditorMode._saveActiveFile();
+            return;
+        }
+
+        // Ctrl/Cmd+P — quick open
+        if ((e.ctrlKey || e.metaKey) && e.key === 'p') {
+            e.preventDefault();
+            EditorMode._showQuickOpen();
+            return;
+        }
+
+        // Ctrl/Cmd+W — close tab
+        if ((e.ctrlKey || e.metaKey) && e.key === 'w') {
+            if (EditorMode._activeFile) {
+                e.preventDefault();
+                EditorMode._closeFile(EditorMode._activeFile);
+            }
+        }
+    },
+
+    // ── Live Update on workspace.file.changed ─
+
+    _onFileChanged(ev) {
+        if (!EditorMode._active) return;
+        const { path } = ev || {};
+        if (!path) return;
+
+        // If the file is open, refresh its content
+        const f = EditorMode._openFiles.get(path);
+        if (f && !f.modified) {
+            API.readWorkspaceFile(EditorMode._wsId, path).then(content => {
+                if (f.editor?.setValue) f.editor.setValue(content);
+                f.content = content;
+            }).catch(() => {});
+        }
+
+        // Also refresh file tree
+        EditorMode._refreshFileTree();
+    },
+
+    // ── Helpers ──────────────────────────────
+
+    _esc(s) {
+        const d = document.createElement('div');
+        d.textContent = s || '';
+        return d.innerHTML;
+    },
+
+    // ── Global Init ──────────────────────────
+
+    init() {
+        // Keyboard shortcuts
+        document.addEventListener('keydown', this._onKeyDown);
+
+        // Listen for channel switches to check workspace availability
+        Events.on('chat.switched', () => this.check());
+        Events.on('chat.created', () => this.check());
+
+        // Listen for workspace file changes (from AI tool calls)
+        Events.on('workspace.file.changed', this._onFileChanged);
+
+        // Initial check
+        setTimeout(() => this.check(), 500);
+
+        console.log('[EditorMode] Initialized');
+    },
+};
+
+// Auto-init after DOM ready
+if (document.readyState === 'loading') {
+    document.addEventListener('DOMContentLoaded', () => EditorMode.init());
+} else {
+    EditorMode.init();
+}
diff --git a/src/js/projects-ui.js b/src/js/projects-ui.js
index 40e2f58..28378cc 100644
--- a/src/js/projects-ui.js
+++ b/src/js/projects-ui.js
@@ -240,6 +240,12 @@ function showChatContextMenu(e, chatId) {
         <span class="ctx-icon">+</span> New project…
     </button>`;
 
+    // Workspace override (v0.21.5)
+    items += '<div class="ctx-divider"></div>';
+    items += `<button class="ctx-item" onclick="showWorkspacePicker('${chatId}');dismissChatContextMenu()">
+        <span class="ctx-icon">📁</span> Set workspace…
+    </button>`;
+
     menu.innerHTML = items;
 
     // Position near cursor
@@ -392,6 +398,16 @@ function _registerProjectPanel() {
                 <label class="project-panel-label">Notes</label>
                 <div id="projectNoteList" class="project-panel-list"></div>
             </div>
+            <div class="project-panel-section">
+                <label class="project-panel-label">Workspace</label>
+                <div class="project-panel-ws-row" id="projectWsRow">
+                    <select id="projectWsSelect" class="project-panel-select">
+                        <option value="">None</option>
+                    </select>
+                    <button class="btn-small" id="projectWsCreate" title="Create workspace">+ New</button>
+                </div>
+                <div class="project-panel-hint">Workspace files are available to AI in all project chats. Enables the Editor surface.</div>
+            </div>
             <div class="project-panel-section project-panel-footer">
                 <label class="project-panel-checkbox">
                     <input type="checkbox" id="projectArchiveToggle">
@@ -413,6 +429,10 @@ function _registerProjectPanel() {
     // Wire archive toggle (v0.19.2)
     el.querySelector('#projectArchiveToggle').addEventListener('change', _toggleProjectArchive);
 
+    // Wire workspace select + create (v0.21.5)
+    el.querySelector('#projectWsSelect').addEventListener('change', _saveProjectWorkspace);
+    el.querySelector('#projectWsCreate').addEventListener('click', _createProjectWorkspace);
+
     PanelRegistry.register('project', {
         element: el,
         label: 'Project',
@@ -457,6 +477,9 @@ async function _loadProjectPanel(projectId) {
 
     // Load notes
     await _renderProjectNotes(projectId);
+
+    // Load workspace picker (v0.21.5)
+    await _renderProjectWorkspace(projectId);
 }
 
 async function _saveProjectPrompt() {
@@ -643,6 +666,143 @@ async function _toggleProjectArchive() {
     }
 }
 
+// ── Workspace picker (v0.21.5) ───────────────
+
+async function _renderProjectWorkspace(projectId) {
+    const sel = document.getElementById('projectWsSelect');
+    if (!sel) return;
+
+    // Fetch current project state + available workspaces in parallel
+    const [proj, workspaces] = await Promise.all([
+        API.getProject(projectId).catch(() => null),
+        API.listWorkspaces().catch(() => []),
+    ]);
+
+    const currentWsId = proj?.workspace_id || '';
+    const wsList = Array.isArray(workspaces) ? workspaces : (workspaces?.data || []);
+
+    sel.innerHTML = '<option value="">None</option>';
+    for (const ws of wsList) {
+        const opt = document.createElement('option');
+        opt.value = ws.id;
+        opt.textContent = ws.name || ws.id.slice(0, 8);
+        if (ws.id === currentWsId) opt.selected = true;
+        sel.appendChild(opt);
+    }
+}
+
+async function _saveProjectWorkspace() {
+    if (!_projectPanelId) return;
+    const wsId = document.getElementById('projectWsSelect').value;
+    try {
+        await API.updateProject(_projectPanelId, { workspace_id: wsId || null });
+        UI.toast(wsId ? 'Workspace linked' : 'Workspace unlinked', 'success');
+        // Trigger editor surface check
+        if (typeof EditorMode !== 'undefined') EditorMode.check();
+    } catch (e) {
+        UI.toast('Failed to update workspace', 'error');
+    }
+}
+
+async function _createProjectWorkspace() {
+    if (!_projectPanelId) return;
+    const proj = App.projects.find(p => p.id === _projectPanelId);
+    const name = prompt('Workspace name:', (proj?.name || 'Project') + ' Workspace');
+    if (!name || !name.trim()) return;
+
+    try {
+        const ws = await API.createWorkspace({
+            name: name.trim(),
+            owner_type: 'user',
+            owner_id: API.user?.id || '',
+        });
+        // Auto-bind to project
+        await API.updateProject(_projectPanelId, { workspace_id: ws.id });
+        UI.toast('Workspace created and linked', 'success');
+        // Refresh the picker
+        await _renderProjectWorkspace(_projectPanelId);
+        // Trigger editor surface check
+        if (typeof EditorMode !== 'undefined') EditorMode.check();
+    } catch (e) {
+        UI.toast('Failed to create workspace: ' + (e.message || e), 'error');
+    }
+}
+
+// ── Channel workspace picker (v0.21.5) ───────
+
+async function showWorkspacePicker(chatId) {
+    let workspaces = [];
+    try {
+        const resp = await API.listWorkspaces();
+        workspaces = Array.isArray(resp) ? resp : (resp?.data || []);
+    } catch (_) {}
+
+    // Get current channel workspace
+    let currentWsId = '';
+    try {
+        const ch = await API.getChannel(chatId);
+        currentWsId = ch.workspace_id || '';
+    } catch (_) {}
+
+    // Build options
+    const options = [{ value: '', label: 'None (inherit from project)' }];
+    for (const ws of workspaces) {
+        options.push({ value: ws.id, label: ws.name || ws.id.slice(0, 8) });
+    }
+    options.push({ value: '__new__', label: '+ Create new workspace…' });
+
+    // Use simple select via popup
+    const overlay = document.createElement('div');
+    overlay.className = 'editor-quick-open'; // reuse overlay style
+    overlay.innerHTML = `
+        <div class="editor-qo-dialog" style="width:340px">
+            <div style="padding:10px 14px; font-weight:600; border-bottom:1px solid var(--border)">Set Workspace</div>
+            <div class="editor-qo-results" id="wsPickerList"></div>
+        </div>`;
+
+    const list = overlay.querySelector('#wsPickerList');
+    for (const opt of options) {
+        const row = document.createElement('div');
+        row.className = 'editor-qo-row' + (opt.value === currentWsId ? ' active' : '');
+        row.style.fontWeight = opt.value === currentWsId ? '600' : '';
+        row.textContent = opt.label;
+        row.addEventListener('click', async () => {
+            overlay.remove();
+            if (opt.value === '__new__') {
+                const name = prompt('Workspace name:');
+                if (!name || !name.trim()) return;
+                try {
+                    const ws = await API.createWorkspace({
+                        name: name.trim(),
+                        owner_type: 'user',
+                        owner_id: API.user?.id || '',
+                    });
+                    await API.updateChannel(chatId, { workspace_id: ws.id });
+                    UI.toast('Workspace created and linked', 'success');
+                    if (typeof EditorMode !== 'undefined') EditorMode.check();
+                } catch (e) {
+                    UI.toast('Failed: ' + (e.message || e), 'error');
+                }
+            } else {
+                try {
+                    await API.updateChannel(chatId, { workspace_id: opt.value || '' });
+                    UI.toast(opt.value ? 'Workspace linked' : 'Workspace unlinked', 'success');
+                    if (typeof EditorMode !== 'undefined') EditorMode.check();
+                } catch (e) {
+                    UI.toast('Failed: ' + (e.message || e), 'error');
+                }
+            }
+        });
+        list.appendChild(row);
+    }
+
+    overlay.addEventListener('click', (e) => {
+        if (e.target === overlay) overlay.remove();
+    });
+
+    document.body.appendChild(overlay);
+}
+
 // ═══════════════════════════════════════════
 // CHANNEL REORDER WITHIN PROJECT (v0.19.2)
 // ═══════════════════════════════════════════
diff --git a/src/js/surfaces.js b/src/js/surfaces.js
index 35f0697..5bba8ad 100644
--- a/src/js/surfaces.js
+++ b/src/js/surfaces.js
@@ -167,6 +167,28 @@ const Surfaces = {
         return this._registry.size > 1;
     },
 
+    /**
+     * Get a saved DocumentFragment for a specific surface + region.
+     * Used by surfaces like editor-mode that want to embed chat DOM
+     * inside their own layout.
+     * @param {string} surfaceId — the surface that owns the saved DOM
+     * @param {string} regionId — the region name
+     * @returns {DocumentFragment|null}
+     */
+    getSavedFragment(surfaceId, regionId) {
+        const key = `${surfaceId}::${regionId}`;
+        return this._saved.get(key) || null;
+    },
+
+    /**
+     * Put a DocumentFragment back into the saved store.
+     * Used during deactivation to return borrowed DOM.
+     */
+    putSavedFragment(surfaceId, regionId, frag) {
+        const key = `${surfaceId}::${regionId}`;
+        this._saved.set(key, frag);
+    },
+
     // ── Region Management ────────────────────
 
     /**