diff --git a/src/client/Sidebar.tsx b/src/client/Sidebar.tsx
index 1f824a2..39b0356 100644
--- a/src/client/Sidebar.tsx
+++ b/src/client/Sidebar.tsx
@@ -15,7 +15,7 @@ import clsx from 'clsx'
 import { IconChevronRightOutline14, IconFullscreenOutline16, IconPanelLeftOutline16, Tooltip } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { Context, SidebarConversation, SidebarSessionList } from '../context-types.ts'
 import {
-  agentUuidOf, allLeaves, closeTab, isAgentTabId, leafWithTab, mapLeaf, moveTab, moveTabToEdge, openDiffTab, openTab,
+  agentUuidOf, allLeaves, closeTab, isAgentTabId, leafWithTab, mapLeaf, moveTab, moveTabToEdge, openDiffTab,
   reconcileAgentTerminals,
   resizeSplit, setWidth, toggleExpanded, togglePanel,
   TERMINAL_LIMIT, type DropZone, type SidebarState, type SidebarStore, type SidebarTab, type SplitNode,
@@ -185,12 +185,9 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
     if (sessionId === undefined || prev === undefined) return
     if (!detectNewDirectSubagent(prev, sessionList, sessionId)) return
     if (!store.getPrefs().autoOpenSubagent) return
-    store.reduce(s => openTab(s.panelOpen ? s : togglePanel(s), {
-      id: 'subagent',
-      type: 'subagent',
-      title: t('subagent'),
-    }))
-  }, [sessionList, sessionId, store])
+    store.reduce(s => s.panelOpen ? s : togglePanel(s))
+    ctx.betterSidebar?.openTab({ type: 'subagent', title: t('subagent') })
+  }, [sessionList, sessionId, store, ctx])
 
   /**
    * Topology jump-back: clicking a subagent node on the Subagent page calls
@@ -208,12 +205,9 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
     const pending = subagentJumpRef.current
     if (pending === undefined || sessionId !== pending) return
     subagentJumpRef.current = undefined
-    store.reduce(s => openTab(s.panelOpen ? s : togglePanel(s), {
-      id: 'subagent',
-      type: 'subagent',
-      title: t('subagent'),
-    }))
-  }, [sessionId, store])
+    store.reduce(s => s.panelOpen ? s : togglePanel(s))
+    ctx.betterSidebar?.openTab({ type: 'subagent', title: t('subagent') })
+  }, [sessionId, store, ctx])
 
   // Panel width drag (left edge strip).
   const widthDrag = useRef({ startX: 0, startWidth: 0 })
@@ -443,6 +437,11 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
             actions={actions}
             onNewTab={onNewTab}
             renderTab={renderTab}
+            getTabIcon={(tab) => {
+              const descriptor = ctx.betterSidebar?.getTab(tab.type)
+              if (descriptor === undefined) return null
+              return typeof descriptor.icon === 'function' ? descriptor.icon(14) : descriptor.icon
+            }}
           />
         </div>
       </div>
diff --git a/src/client/TabBar.tsx b/src/client/TabBar.tsx
index 493f99b..116c9af 100644
--- a/src/client/TabBar.tsx
+++ b/src/client/TabBar.tsx
@@ -11,7 +11,6 @@ import {
   IconCloseFill14, IconPlusOutline16, Menu,
 } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { SidebarTab } from './state.ts'
-import { tabTypeIcon } from './icons.tsx'
 import { t } from './locales.ts'
 import css from './sidebar.module.css'
 
@@ -62,9 +61,11 @@ export function TabBar(props: {
   newTabOptions: NewTabOption[]
   /** Drop of a tab from any pane: (payload, insertBeforeTabId | null). */
   onDropTab: (payload: TabDragPayload, before: string | null) => void
+  /** Icon resolver for tab labels (reads from the tab descriptor registry). */
+  getTabIcon?: (tab: SidebarTab) => ReactNode
 }) {
   const {
-    paneId, tabs, active, onActivate, onClose, onNewTab, newTabOptions, onDropTab,
+    paneId, tabs, active, onActivate, onClose, onNewTab, newTabOptions, onDropTab, getTabIcon,
   } = props
   const [menuOpen, setMenuOpen] = useState(false)
   const [dragOver, setDragOver] = useState(false)
@@ -134,7 +135,7 @@ export function TabBar(props: {
               }
             }}
           >
-            {tabTypeIcon(tab.type, 14)}
+            {getTabIcon?.(tab) ?? null}
             <span className={css.tabTitle}>{tab.title}</span>
             <button
               type="button"
diff --git a/src/client/intercept.tsx b/src/client/intercept.tsx
index 1a62fd3..94ca887 100644
--- a/src/client/intercept.tsx
+++ b/src/client/intercept.tsx
@@ -8,7 +8,7 @@
  */
 import { IconCodeOutline16 } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { Context } from '../context-types.ts'
-import { openTab, type SidebarStore } from './state.ts'
+import type { SidebarStore } from './state.ts'
 import { t } from './locales.ts'
 import { resolveSidebarPath, selectProducedFiles } from './produced-files.ts'
 import css from './sidebar.module.css'
@@ -19,12 +19,9 @@ export function openSidebarFile(ctx: Context, store: SidebarStore, sessionId: st
   const absolute = resolveSidebarPath(summary?.cwd, path)
   const at = Math.max(absolute.lastIndexOf('/'), absolute.lastIndexOf('\\'))
   const title = at === -1 ? absolute : absolute.slice(at + 1)
-  store.reduce(state => openTab(state, {
-    id: `editor:${absolute}`,
-    type: 'editor',
-    title,
-    path: absolute,
-  }))
+  // Route through the sidebar service so the editor descriptor's dedupeKey
+  // (per-path) applies; the id is path-derived so multiple editors coexist.
+  ctx.betterSidebar?.openTab({ type: 'editor', title, path: absolute, id: `editor:${absolute}` })
 }
 
 /** The intercepted produced-files row (visual twin of the deliverables chips). */
diff --git a/src/client/service.ts b/src/client/service.ts
index b9fe077..cf0401e 100644
--- a/src/client/service.ts
+++ b/src/client/service.ts
@@ -126,7 +126,7 @@ export interface BetterSidebarService {
   /** Find a file viewer for a path (priority desc → detect → exts). */
   matchFileViewer(path: string, head?: Uint8Array): FileViewerDescriptor | undefined
   /** Open a tab (used by external tabs and the + menu). */
-  openTab(seed: { type: string; title: string; path?: string; diff?: SidebarTab['diff'] }): void
+  openTab(seed: { type: string; title: string; path?: string; diff?: SidebarTab['diff']; id?: string }): void
   /** Close a tab by id. */
   closeTab(tabId: string): void
   /** Subscribe to registry changes (register/dispose). */
@@ -216,7 +216,7 @@ export function createBetterSidebarService(store: SidebarStore): BetterSidebarSe
     return undefined
   }
 
-  const openTab = (seed: { type: string; title: string; path?: string; diff?: SidebarTab['diff'] }): void => {
+  const openTab = (seed: { type: string; title: string; path?: string; diff?: SidebarTab['diff']; id?: string }): void => {
     store.reduce((state) => {
       const descriptor = tabs.get(seed.type)
       if (descriptor === undefined) return state
@@ -228,7 +228,7 @@ export function createBetterSidebarService(store: SidebarStore): BetterSidebarSe
         return result.patch !== undefined ? { ...next, ...result.patch } : next
       }
       const tab: SidebarTab = {
-        id: seed.type,
+        id: seed.id ?? seed.type,
         type: seed.type,
         title: typeof descriptor.title === 'function' ? descriptor.title() : descriptor.title,
         ...(seed.path !== undefined ? { path: seed.path } : {}),
diff --git a/src/client/split-pane.tsx b/src/client/split-pane.tsx
index bdd20fd..a6048c6 100644
--- a/src/client/split-pane.tsx
+++ b/src/client/split-pane.tsx
@@ -15,7 +15,6 @@ import clsx from 'clsx'
 import type { SidebarState, SidebarTab, SplitNode } from './state.ts'
 import type { DropZone } from './state.ts'
 import { TabBar, type NewTabOption, parseDrag, type TabDragPayload } from './TabBar.tsx'
-import { tabTypeIcon } from './icons.tsx'
 import css from './sidebar.module.css'
 
 /** Actions the workbench needs (bound to the store by the sidebar shell). */
@@ -108,7 +107,7 @@ function PaneEmptyCards(props: {
           title={option.label}
           onClick={() => { onNewTab(option.id) }}
         >
-          {option.icon ?? tabTypeIcon(option.id as SidebarTab['type'], 16)}
+          {option.icon ?? null}
           <span>{option.label}</span>
         </button>
       ))}
@@ -123,8 +122,9 @@ function LeafView(props: {
   actions: WorkbenchActions
   onNewTab: (optionId: string) => void
   renderTab: (tab: SidebarTab, active: boolean, paneId: string) => ReactNode
+  getTabIcon?: (tab: SidebarTab) => ReactNode
 }) {
-  const { leaf, newTabOptions, actions, onNewTab, renderTab } = props
+  const { leaf, newTabOptions, actions, onNewTab, renderTab, getTabIcon } = props
   const [dropZone, setDropZone] = useState<DropZone | null>(null)
   const activeTab = leaf.tabs.find(tab => tab.id === leaf.active) ?? leaf.tabs[leaf.tabs.length - 1]
 
@@ -177,6 +177,7 @@ function LeafView(props: {
         onClose={(tabId) => { actions.closeTab(leaf.id, tabId) }}
         onNewTab={onNewTab}
         newTabOptions={newTabOptions}
+        getTabIcon={getTabIcon}
         onDropTab={(payload, before) => {
           if (before === null) actions.moveTabToEdge(payload, leaf.id, 'center')
           else actions.moveTabBefore(payload, leaf.id, before)
@@ -215,8 +216,9 @@ function NodeView(props: {
   actions: WorkbenchActions
   onNewTab: (optionId: string) => void
   renderTab: (tab: SidebarTab, active: boolean, paneId: string) => ReactNode
+  getTabIcon?: (tab: SidebarTab) => ReactNode
 }) {
-  const { node, state, newTabOptions, actions, onNewTab, renderTab } = props
+  const { node, state, newTabOptions, actions, onNewTab, renderTab, getTabIcon } = props
   if (node.kind === 'leaf') {
     return (
       <LeafView
@@ -225,6 +227,7 @@ function NodeView(props: {
         actions={actions}
         onNewTab={onNewTab}
         renderTab={renderTab}
+        getTabIcon={getTabIcon}
       />
     )
   }
@@ -250,6 +253,7 @@ function NodeView(props: {
               actions={actions}
               onNewTab={onNewTab}
               renderTab={renderTab}
+              getTabIcon={getTabIcon}
             />
           </div>
         </Fragment>
@@ -265,8 +269,9 @@ export function Workbench(props: {
   actions: WorkbenchActions
   onNewTab: (optionId: string) => void
   renderTab: (tab: SidebarTab, active: boolean, paneId: string) => ReactNode
+  getTabIcon?: (tab: SidebarTab) => ReactNode
 }) {
-  const { state, newTabOptions, actions, onNewTab, renderTab } = props
+  const { state, newTabOptions, actions, onNewTab, renderTab, getTabIcon } = props
   return (
     <div className={css.workbench}>
       <NodeView
@@ -276,6 +281,7 @@ export function Workbench(props: {
         actions={actions}
         onNewTab={onNewTab}
         renderTab={renderTab}
+        getTabIcon={getTabIcon}
       />
     </div>
   )
diff --git a/src/client/state.ts b/src/client/state.ts
index 82eb64a..c6ce084 100644
--- a/src/client/state.ts
+++ b/src/client/state.ts
@@ -309,15 +309,13 @@ export function activateTab(state: SidebarState, paneId: string, tabId: string):
   }
 }
 
-/** Whether a tab type is single-instance per session (explorer/git/subagent). */
-function isSingle(type: TabType): boolean {
-  return type === 'explorer' || type === 'git' || type === 'subagent'
-}
-
 /**
- * Open a tab (or focus its existing instance). Single-instance types focus
- * the existing tab wherever it lives; editors dedupe by path. The tab lands
- * in the active pane (or the first pane when the active one is gone).
+ * Open a tab (or focus its existing instance by id). Dedup strategies
+ * (single-instance, per-path, per-change) are owned by the tab descriptor
+ * through {@link BetterSidebarService.openTab} / `dedupeKey`; this reducer
+ * only handles the id-based safety net (reconcile/openDiffTab already
+ * check existence before calling) and lands the tab in the active pane
+ * (or the first pane when the active one is gone).
  */
 export function openTab(state: SidebarState, tab: SidebarTab): SidebarState {
   let targetId = state.activePane ?? firstLeaf(state.splits).id
@@ -326,24 +324,10 @@ export function openTab(state: SidebarState, tab: SidebarTab): SidebarState {
   if (!allLeaves(state.splits).some(leaf => leaf.id === targetId)) {
     targetId = firstLeaf(state.splits).id
   }
-  if (isSingle(tab.type)) {
-    for (const leaf of allLeaves(state.splits)) {
-      const existing = leaf.tabs.find(candidate => candidate.type === tab.type)
-      if (existing !== undefined) return activateTab(state, leaf.id, existing.id)
-    }
-  }
-  if (tab.type === 'editor' && tab.path !== undefined) {
-    for (const leaf of allLeaves(state.splits)) {
-      const existing = leaf.tabs.find(candidate => candidate.type === 'editor' && candidate.path === tab.path)
-      if (existing !== undefined) return activateTab(state, leaf.id, existing.id)
-    }
-  }
-  if (tab.type === 'diff') {
-    // One tab per change: the same path+side (or commit) focuses its instance.
-    for (const leaf of allLeaves(state.splits)) {
-      const existing = leaf.tabs.find(candidate => candidate.type === 'diff' && candidate.id === tab.id)
-      if (existing !== undefined) return activateTab(state, leaf.id, existing.id)
-    }
+  // Id-based safety net: if a tab with the same id exists, focus it.
+  for (const leaf of allLeaves(state.splits)) {
+    const existing = leaf.tabs.find(candidate => candidate.id === tab.id)
+    if (existing !== undefined) return activateTab(state, leaf.id, existing.id)
   }
   return {
     ...state,
diff --git a/tests/unit.spec.ts b/tests/unit.spec.ts
index 2a36ba1..c16fdc2 100644
--- a/tests/unit.spec.ts
+++ b/tests/unit.spec.ts
@@ -214,23 +214,26 @@ describe('git parsing', () => {
 describe('sidebar state', () => {
   const state = (): SidebarState => makeDefaultState()
 
-  it('opens tabs into the active pane and dedupes single-instance types', () => {
+  it('opens tabs into the active pane and dedupes by id (safety net)', () => {
     let s = state()
     const gitTab = { id: 'git', type: 'git' as const, title: 'Git' }
     s = openTab(s, gitTab)
     expect(s.splits.kind).toBe('leaf')
     expect((s.splits as { tabs: unknown[] }).tabs).toHaveLength(2)
-    // Reopening git focuses the existing tab instead of duplicating.
-    const after = openTab(s, { id: 'git2', type: 'git' as const, title: 'Git' })
+    // Reopening with the SAME id focuses the existing tab instead of duplicating.
+    const after = openTab(s, { id: 'git', type: 'git' as const, title: 'Git' })
     expect((after.splits as { tabs: unknown[] }).tabs).toHaveLength(2)
+    // A different id opens a new tab (type-level dedupe is the service's job).
+    const after2 = openTab(s, { id: 'git2', type: 'git' as const, title: 'Git' })
+    expect((after2.splits as { tabs: unknown[] }).tabs).toHaveLength(3)
   })
 
-  it('dedupes editors by path', () => {
+  it('opens multiple editors with distinct ids (path-level dedupe is the service descriptor\'s job)', () => {
     let s = state()
     const firstId = (s.splits as { tabs: { id: string }[] }).tabs[0]!.id
     s = openTab(s, { id: 'e1', type: 'editor', title: 'a.ts', path: '/p/a.ts' })
     const after = openTab(s, { id: 'e2', type: 'editor', title: 'a.ts', path: '/p/a.ts' })
-    expect((after.splits as { tabs: { id: string }[] }).tabs.map(t => t.id)).toEqual([firstId, 'e1'])
+    expect((after.splits as { tabs: { id: string }[] }).tabs.map(t => t.id)).toEqual([firstId, 'e1', 'e2'])
   })
 
   const diffTab = (id: string): SidebarTab => ({