diff --git a/src/renderer/src/runtime/web-session-tabs-sync-editor-tabs.test.ts b/src/renderer/src/runtime/web-session-tabs-sync-editor-tabs.test.ts
index aa88fcd6d53..ccca65f73c8 100644
--- a/src/renderer/src/runtime/web-session-tabs-sync-editor-tabs.test.ts
+++ b/src/renderer/src/runtime/web-session-tabs-sync-editor-tabs.test.ts
@@ -1,3 +1,4 @@
+import type { RuntimeMobileSessionMarkdownTab } from '../../../shared/runtime-types'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 import { posix as pathPosix } from 'node:path'
 import type { BrowserPage, BrowserWorkspace } from '../../../shared/browser-workspace-types'
@@ -5,6 +6,9 @@ import type { Tab } from '../../../shared/tab-types'
 import type { OpenFile } from '../store/slices/editor'
 import { buildOwnedEditorFileId } from '../store/slices/editor/file-ids/editor-file-ids'
 import { applyWebSessionTabsSnapshot } from './web-session-tabs-sync/snapshot-api'
+import { recordWebSessionFocusIntent } from './web-session-focus-intent'
+import { buildMobileSessionTabSnapshots } from './sync-runtime-graph/mobile-session-snapshots'
+import { makeState as makePublisherState } from './sync-runtime-graph-test-harness'
 import type { WebSessionTabsSyncState } from './web-session-tabs-sync/state'
 import {
   ENV,
@@ -553,3 +557,299 @@ describe('applyWebSessionTabsSnapshot', () => {
     })
   })
 })
+
+describe('applyWebSessionTabsSnapshot host-invariant editor dedup', () => {
+  beforeEach(resetWebSessionTabsSyncTestState)
+
+  const variant = (id: string, isActive: boolean): RuntimeMobileSessionMarkdownTab => ({
+    type: 'markdown',
+    id,
+    title: 'README.md',
+    filePath: '/repo/README.md',
+    relativePath: 'README.md',
+    language: 'markdown',
+    mode: 'edit',
+    isDirty: false,
+    isActive,
+    sourceFileId: README_ID,
+    sourceFilePath: '/repo/README.md',
+    sourceRelativePath: 'README.md',
+    documentVersion: 'file:/repo/README.md'
+  })
+  const envVariantId = (env: string) => buildOwnedEditorFileId('/repo/README.md', WT, env)
+
+  function stateWithVariant(id: string, retained: OpenFile): WebSessionTabsSyncState {
+    return makeState({
+      activeFileId: retained.id,
+      activeFileIdByWorktree: { [WT]: retained.id },
+      activeTabType: 'editor',
+      activeTabTypeByWorktree: { [WT]: 'editor' },
+      activeGroupIdByWorktree: { [WT]: 'host-group-1' },
+      openFiles: [retained],
+      editorDrafts: { [retained.id]: '# unsaved client edit' },
+      unifiedTabsByWorktree: {
+        [WT]: [
+          {
+            id,
+            entityId: retained.id,
+            worktreeId: WT,
+            groupId: 'host-group-1',
+            contentType: 'editor',
+            label: 'README.md',
+            customLabel: null,
+            color: null,
+            sortOrder: 0,
+            createdAt: NOW - 1,
+            isPreview: false
+          }
+        ]
+      },
+      groupsByWorktree: {
+        [WT]: [
+          {
+            id: 'host-group-1',
+            worktreeId: WT,
+            activeTabId: id,
+            tabOrder: [id],
+            recentTabIds: [id]
+          }
+        ]
+      }
+    })
+  }
+
+  const ownedFile: OpenFile = {
+    id: README_ID,
+    filePath: '/repo/README.md',
+    relativePath: 'README.md',
+    worktreeId: WT,
+    language: 'markdown',
+    mode: 'edit',
+    isDirty: true,
+    runtimeEnvironmentId: ENV,
+    mirroredFromRuntimeSession: true
+  }
+
+  it('mirrors one tab when a snapshot lists the same file under several environment variants', () => {
+    const ids = [
+      envVariantId('env-a'),
+      envVariantId('env-b'),
+      envVariantId('env-c'),
+      buildOwnedEditorFileId('/repo/README.md', WT, null),
+      '/repo/README.md'
+    ]
+    const published = buildMobileSessionTabSnapshots(
+      makePublisherState({
+        openFiles: [ownedFile],
+        unifiedTabsByWorktree: {
+          [WT]: ids.flatMap((id) => stateWithVariant(id, ownedFile).unifiedTabsByWorktree[WT] ?? [])
+        }
+      })
+    )[0]
+    if (!published) {
+      throw new Error('Desktop did not publish its editor tabs')
+    }
+    expect(published.tabs).toHaveLength(5)
+    const tabs = published.tabs.filter((tab) => tab.type === 'markdown')
+    expect(tabs).toHaveLength(5)
+    const patch = applyWebSessionTabsSnapshot(
+      makeState(),
+      makeSnapshot(tabs, { activeTabId: null, activeTabType: null }),
+      ENV,
+      NOW
+    )
+
+    expect(patch.openFiles).toHaveLength(1)
+    expect(patch.unifiedTabsByWorktree?.[WT]).toHaveLength(1)
+    expect(patch.unifiedTabsByWorktree?.[WT]?.[0]?.id).toBe(envVariantId('env-a'))
+  })
+
+  it('keeps the variant a follow navigation targets over an active one', () => {
+    const patch = applyWebSessionTabsSnapshot(
+      makeState(),
+      makeSnapshot([variant(envVariantId('env-a'), true), variant(envVariantId('env-b'), false)], {
+        activeTabId: envVariantId('env-b'),
+        activeTabType: 'markdown',
+        navigationIntent: 'follow'
+      }),
+      ENV,
+      NOW
+    )
+
+    expect(patch.unifiedTabsByWorktree?.[WT]).toHaveLength(1)
+    expect(patch.unifiedTabsByWorktree?.[WT]?.[0]?.id).toBe(envVariantId('env-b'))
+  })
+
+  it('leaves split tabs with opaque ids alone', () => {
+    const patch = applyWebSessionTabsSnapshot(
+      makeState(),
+      makeSnapshot([variant(envVariantId('env-a'), false), variant('split-tab-7f3a', false)], {
+        activeTabId: null,
+        activeTabType: null
+      }),
+      ENV,
+      NOW
+    )
+
+    expect(patch.unifiedTabsByWorktree?.[WT]).toHaveLength(2)
+  })
+
+  it('keeps the visible local variant when a status snapshot marks another active', () => {
+    const visibleId = envVariantId('env-b')
+    const state = stateWithVariant(visibleId, ownedFile)
+    const patch = applyWebSessionTabsSnapshot(
+      state,
+      makeSnapshot([variant(envVariantId('env-a'), true), variant(visibleId, false)], {
+        activeTabId: envVariantId('env-a'),
+        activeTabType: 'markdown'
+      }),
+      ENV,
+      NOW
+    )
+
+    expect(patch.unifiedTabsByWorktree?.[WT]?.map((tab) => tab.id)).toEqual([visibleId])
+    expect((patch.groupsByWorktree ?? state.groupsByWorktree)[WT]?.[0]?.activeTabId).toBe(visibleId)
+    expect((patch.openFiles ?? state.openFiles)[0]).toMatchObject({
+      id: ownedFile.id,
+      isDirty: true
+    })
+    expect(patch.editorDrafts ?? state.editorDrafts).toEqual(state.editorDrafts)
+  })
+
+  it('retains a pending relay draft identity even when navigation selects another variant', () => {
+    const retained: OpenFile = {
+      ...ownedFile,
+      id: '/repo/README.md',
+      runtimeEnvironmentId: null,
+      pendingOwnerMigration: true
+    }
+    const state = stateWithVariant(envVariantId('env-b'), retained)
+    const selectedId = envVariantId('env-a')
+    const patch = applyWebSessionTabsSnapshot(
+      state,
+      makeSnapshot([variant(selectedId, true), variant(envVariantId('env-b'), false)], {
+        activeTabId: selectedId,
+        activeTabType: 'markdown',
+        navigationIntent: 'follow'
+      }),
+      ENV,
+      NOW
+    )
+
+    expect(patch.openFiles ?? state.openFiles).toEqual([retained])
+    expect((patch.openFiles ?? state.openFiles)[0]).toBe(retained)
+    expect(patch.unifiedTabsByWorktree?.[WT]).toMatchObject([
+      { id: selectedId, entityId: retained.id }
+    ])
+    expect(patch.unifiedTabsByWorktree?.[WT]).toHaveLength(1)
+    expect(patch.editorDrafts ?? state.editorDrafts).toEqual(state.editorDrafts)
+  })
+
+  it('honors a pending caller focus intent over the visible and host-active variants', () => {
+    const visibleId = envVariantId('env-b')
+    const requestedId = envVariantId('env-c')
+    const state = stateWithVariant(visibleId, ownedFile)
+    recordWebSessionFocusIntent({ environmentId: ENV }, WT, requestedId)
+    const patch = applyWebSessionTabsSnapshot(
+      state,
+      makeSnapshot([
+        variant(envVariantId('env-a'), true),
+        variant(visibleId, false),
+        variant(requestedId, false)
+      ]),
+      ENV,
+      NOW
+    )
+
+    expect(patch.unifiedTabsByWorktree?.[WT]?.map((tab) => tab.id)).toEqual([requestedId])
+    expect((patch.groupsByWorktree ?? state.groupsByWorktree)[WT]?.[0]?.activeTabId).toBe(
+      requestedId
+    )
+  })
+
+  it.each([
+    { filePath: '/workspace/notes/Read me #1%.md', worktree: 'folder:/workspace' },
+    { filePath: 'C:\\workspace\\docs\\Read me.md', worktree: 'folder:C:\\workspace' },
+    { filePath: '\\\\server\\share\\Read me.md', worktree: 'folder:\\\\server\\share' }
+  ])('collapses encoded variants for the host path $filePath', ({ filePath, worktree }) => {
+    const tabs = ['host:a', 'host:b'].map((environment) => ({
+      ...variant(buildOwnedEditorFileId(filePath, worktree, environment), false),
+      filePath,
+      sourceFilePath: filePath
+    }))
+    const state = makeState({ activeWorktreeId: worktree })
+    const snapshot = makeSnapshot(tabs, { worktree, activeTabId: null, activeTabType: null })
+    const patch = applyWebSessionTabsSnapshot(state, snapshot, ENV, NOW)
+    const nextState = { ...state, ...patch }
+    const replay = applyWebSessionTabsSnapshot(nextState, snapshot, ENV, NOW + 1)
+
+    expect(patch.openFiles).toMatchObject([{ filePath, worktreeId: worktree }])
+    expect(patch.openFiles).toHaveLength(1)
+    expect(patch.unifiedTabsByWorktree?.[worktree]).toHaveLength(1)
+    expect((replay.openFiles ?? nextState.openFiles)[0]?.id).toBe(patch.openFiles?.[0]?.id)
+    expect(
+      (replay.unifiedTabsByWorktree ?? nextState.unifiedTabsByWorktree)[worktree]
+    ).toHaveLength(1)
+  })
+
+  it('keeps edit and preview views distinct while collapsing edit aliases', () => {
+    const preview = { ...variant(envVariantId('env-c'), false), mode: 'markdown-preview' as const }
+    const patch = applyWebSessionTabsSnapshot(
+      makeState(),
+      makeSnapshot([
+        variant(envVariantId('env-a'), false),
+        variant(envVariantId('env-b'), false),
+        preview
+      ]),
+      ENV,
+      NOW
+    )
+
+    expect(patch.unifiedTabsByWorktree?.[WT]).toHaveLength(2)
+    expect(patch.openFiles).toMatchObject([
+      { id: README_ID, mode: 'edit' },
+      { mode: 'markdown-preview', markdownPreviewSourceFileId: README_ID }
+    ])
+  })
+
+  it('leaves a malformed environment segment opaque', () => {
+    const malformedId = `editor:${encodeURIComponent(WT)}:%:${encodeURIComponent('/repo/README.md')}`
+    const patch = applyWebSessionTabsSnapshot(
+      makeState(),
+      makeSnapshot([variant(envVariantId('env-a'), false), variant(malformedId, false)]),
+      ENV,
+      NOW
+    )
+
+    expect(patch.unifiedTabsByWorktree?.[WT]?.map((tab) => tab.id)).toEqual([
+      envVariantId('env-a'),
+      malformedId
+    ])
+  })
+
+  it('keeps distinct backing source identities at the same path', () => {
+    const first = { ...variant(envVariantId('env-a'), true), sourceFileId: 'local-file-owner' }
+    const second = { ...variant(envVariantId('env-b'), false), sourceFileId: 'remote-file-owner' }
+    const patch = applyWebSessionTabsSnapshot(makeState(), makeSnapshot([first, second]), ENV, NOW)
+
+    expect(patch.unifiedTabsByWorktree?.[WT]?.map((tab) => tab.id)).toEqual([first.id, second.id])
+  })
+
+  it('keeps legacy file views without a backing source identity', () => {
+    const tabs = ['env-a', 'env-b'].map((environment) => ({
+      type: 'file' as const,
+      id: envVariantId(environment),
+      title: 'README.md',
+      filePath: '/repo/README.md',
+      relativePath: 'README.md',
+      language: 'plaintext',
+      isDirty: false,
+      isActive: false
+    }))
+    const patch = applyWebSessionTabsSnapshot(makeState(), makeSnapshot(tabs), ENV, NOW)
+
+    expect(patch.unifiedTabsByWorktree?.[WT]?.map((tab) => tab.id)).toEqual(
+      tabs.map((tab) => tab.id)
+    )
+  })
+})
diff --git a/src/renderer/src/runtime/web-session-tabs-sync/apply-preparation-browser.ts b/src/renderer/src/runtime/web-session-tabs-sync/apply-preparation-browser.ts
index 2d63988f600..914edaa3259 100644
--- a/src/renderer/src/runtime/web-session-tabs-sync/apply-preparation-browser.ts
+++ b/src/renderer/src/runtime/web-session-tabs-sync/apply-preparation-browser.ts
@@ -1,4 +1,5 @@
 import { buildWebSessionExistingTabIndex } from '../web-session-existing-tab-index'
+import { resolveWebSessionVisibleTabId } from '../web-session-focus-intent'
 import { chooseTargetGroupId, buildHostGroupIdByTabId } from './tab-group-layout-tree'
 import {
   buildMirroredBrowserTabs,
@@ -35,7 +36,8 @@ export function prepareWebSessionTabsSnapshotBrowser(
     mirroredTerminalIds,
     removedTerminalIds,
     reconcilesNonAgentTabs,
-    batchContext
+    batchContext,
+    navigationIntentTab
   } = base
   const targetGroupId = chooseTargetGroupId(state, snapshot)
   const hostGroupIdByTabId = buildHostGroupIdByTabId(snapshot.tabGroups)
@@ -123,7 +125,8 @@ export function prepareWebSessionTabsSnapshotBrowser(
     targetGroupId,
     mirroredTerminalTabEntries.length + mirroredBrowserTabs.length,
     now,
-    (fileId) => state.editorDrafts?.[fileId] !== undefined
+    (fileId) => state.editorDrafts?.[fileId] !== undefined,
+    navigationIntentTab?.id ?? resolveWebSessionVisibleTabId(state, worktreeId)
   )
   const mirroredAgentTabs = buildMirroredAgentTabs(
     snapshot,
diff --git a/src/renderer/src/runtime/web-session-tabs-sync/tab-builders.ts b/src/renderer/src/runtime/web-session-tabs-sync/tab-builders.ts
index a04fe7cf787..8c4fb5ac595 100644
--- a/src/renderer/src/runtime/web-session-tabs-sync/tab-builders.ts
+++ b/src/renderer/src/runtime/web-session-tabs-sync/tab-builders.ts
@@ -11,6 +11,7 @@ import type { ReadyEditorSurface, MirroredEditorTab } from './state'
 import type { WebSessionExistingTabIndex } from '../web-session-existing-tab-index'
 import { isReadyEditorTab } from './terminal-surfaces'
 import { createMirroredEditorFileResolver } from './mirrored-editor-file-identity'
+import { buildOwnedEditorFileId } from '../../store/slices/editor/file-ids/editor-file-ids'
 
 export function buildTerminalUnifiedTab(
   tab: TerminalTab,
@@ -100,6 +101,71 @@ export function buildEditorUnifiedTab(
   }
 }
 
+// Older peers can echo one file under IDs minted by several environments.
+function mintedEnvironmentSegment(tab: ReadyEditorSurface, worktreeId: string): string | null {
+  if (
+    tab.type !== 'markdown' ||
+    typeof tab.sourceFileId !== 'string' ||
+    !tab.sourceFileId ||
+    tab.sourceFileId === tab.sourceFilePath
+  ) {
+    return null
+  }
+  if (tab.id === tab.filePath) {
+    return ''
+  }
+  const prefix = `editor:${encodeURIComponent(worktreeId)}:`
+  const suffix = `:${encodeURIComponent(tab.filePath)}`
+  if (
+    !tab.id.startsWith(prefix) ||
+    !tab.id.endsWith(suffix) ||
+    tab.id.length <= prefix.length + suffix.length
+  ) {
+    return null
+  }
+  const segment = tab.id.slice(prefix.length, tab.id.length - suffix.length)
+  let runtimeKey: string
+  try {
+    runtimeKey = decodeURIComponent(segment)
+  } catch {
+    return null
+  }
+  return buildOwnedEditorFileId(tab.filePath, worktreeId, runtimeKey) === tab.id ? segment : null
+}
+
+function dedupeReadyEditorTabsBySource(
+  tabs: readonly ReadyEditorSurface[],
+  worktreeId: string,
+  preferredHostTabId: string | null
+): ReadyEditorSurface[] {
+  const bucketOf = (tab: ReadyEditorSurface): string =>
+    JSON.stringify([
+      worktreeId,
+      tab.type === 'markdown' ? tab.mode : 'edit',
+      tab.filePath,
+      tab.type === 'markdown' ? tab.sourceFileId : null
+    ])
+  const rank = (tab: ReadyEditorSurface): number =>
+    tab.id === preferredHostTabId ? 2 : tab.isActive ? 1 : 0
+  const winnerByBucket = new Map<string, { segment: string; rank: number }>()
+  for (const tab of tabs) {
+    const segment = mintedEnvironmentSegment(tab, worktreeId)
+    if (segment === null) {
+      continue
+    }
+    const bucket = bucketOf(tab)
+    const current = winnerByBucket.get(bucket)
+    const tabRank = rank(tab)
+    if (!current || tabRank > current.rank) {
+      winnerByBucket.set(bucket, { segment, rank: tabRank })
+    }
+  }
+  return tabs.filter((tab) => {
+    const segment = mintedEnvironmentSegment(tab, worktreeId)
+    return segment === null || segment === winnerByBucket.get(bucketOf(tab))?.segment
+  })
+}
+
 export function buildMirroredEditorTabs(
   snapshot: RuntimeMobileSessionTabsResult,
   environmentId: string,
@@ -109,7 +175,8 @@ export function buildMirroredEditorTabs(
   fallbackGroupId: string,
   sortOffset: number,
   now: number,
-  hasLocalDraft: (fileId: string) => boolean
+  hasLocalDraft: (fileId: string) => boolean,
+  preferredHostTabId: string | null = null
 ): MirroredEditorTab[] {
   const readyTabs = snapshot.tabs.filter(isReadyEditorTab)
   if (readyTabs.length === 0) {
@@ -120,7 +187,12 @@ export function buildMirroredEditorTabs(
   for (const tab of readyTabs) {
     resolveFile(tab, existingTabIndex.getEditorUnifiedTabByHostId(tab.id))
   }
-  return readyTabs.map((tab, index) => {
+  const distinctTabs = dedupeReadyEditorTabsBySource(
+    readyTabs,
+    snapshot.worktree,
+    preferredHostTabId
+  )
+  return distinctTabs.map((tab, index) => {
     const identity = resolveFile(tab, existingTabIndex.getEditorUnifiedTabByHostId(tab.id))
     const { fileId, existingFile, sourceFileId } = identity
     const existingUnifiedTab = existingTabIndex.getEditorUnifiedTab(fileId, tab.id)
diff --git a/tests/e2e/headless-editor-mirror-identities.unit.test.ts b/tests/e2e/headless-editor-mirror-identities.unit.test.ts
new file mode 100644
index 00000000000..b362575d752
--- /dev/null
+++ b/tests/e2e/headless-editor-mirror-identities.unit.test.ts
@@ -0,0 +1,71 @@
+import { describe, expect, it, vi } from 'vitest'
+import { buildHeadlessMobileSessionEditorTabs } from '../../src/main/runtime/mobile-session-editor-projection'
+import type { WorkspaceSessionState } from '../../src/shared/workspace-session-state-types'
+import { buildOwnedEditorFileId } from '../../src/renderer/src/store/slices/editor/file-ids/editor-file-ids'
+import { applyWebSessionTabsSnapshot } from '../../src/renderer/src/runtime/web-session-tabs-sync/snapshot-api'
+import {
+  ENV,
+  NOW,
+  WT,
+  makeSnapshot,
+  makeState
+} from '../../src/renderer/src/runtime/web-session-tabs-sync-test-harness'
+
+const host = vi.hoisted(() => ({ layoutOwnerIsMain: true }))
+vi.mock('../../src/shared/layout-owner-switch', () => ({
+  get ORCA_LAYOUT_OWNER_IS_MAIN() {
+    return host.layoutOwnerIsMain
+  }
+}))
+
+describe('headless editor identity in an older desktop mirror', () => {
+  it('keeps two owners when the producer represents both source identities by the path', () => {
+    const filePath = '/repo/README.md'
+    const owners = [null, 'other-host']
+    const session: WorkspaceSessionState = {
+      activeRepoId: null,
+      activeWorktreeId: WT,
+      activeTabId: null,
+      tabsByWorktree: {},
+      terminalLayoutsByTabId: {},
+      openFilesByWorktree: {
+        [WT]: owners.map((owner) => ({
+          filePath,
+          relativePath: 'README.md',
+          worktreeId: WT,
+          language: 'markdown',
+          runtimeEnvironmentId: owner,
+          ...(owner ? { dirtyDraftContent: 'remote draft' } : {})
+        }))
+      },
+      unifiedTabs: {
+        [WT]: owners.map((owner, index) => ({
+          id: buildOwnedEditorFileId(filePath, WT, owner),
+          entityId: buildOwnedEditorFileId(filePath, WT, owner),
+          groupId: 'host-group-1',
+          worktreeId: WT,
+          contentType: 'editor',
+          label: 'README.md',
+          customLabel: null,
+          color: null,
+          sortOrder: index,
+          createdAt: NOW,
+          isPreview: false
+        }))
+      }
+    }
+    const tabs = buildHeadlessMobileSessionEditorTabs(WT, session)
+    expect(tabs).toHaveLength(2)
+    expect(tabs.map((tab) => tab.id)).toEqual(
+      owners.map((owner) => buildOwnedEditorFileId(filePath, WT, owner))
+    )
+    expect(tabs.map((tab) => tab.isDirty)).toEqual([false, true])
+
+    host.layoutOwnerIsMain = false
+    const patch = applyWebSessionTabsSnapshot(makeState(), makeSnapshot(tabs), ENV, NOW)
+
+    expect(patch.unifiedTabsByWorktree?.[WT]?.map((tab) => tab.id)).toEqual(
+      tabs.map((tab) => tab.id)
+    )
+  })
+})