diff --git a/docs/reference/omp-relay-session-roots.md b/docs/reference/omp-relay-session-roots.md
new file mode 100644
index 00000000000..cee4f1ef424
--- /dev/null
+++ b/docs/reference/omp-relay-session-roots.md
@@ -0,0 +1,36 @@
+# OMP relay history roots
+
+The relay's history sidecar now resolves OMP storage on the execution host using
+`resolveOmpSessionsDir`, the same resolver as the native reader and local history
+scanner. Its environment allowlist carries only OMP root/profile inputs alongside
+the existing runtime variables. Node loader flags and unrelated credentials remain
+excluded.
+
+The selected root replaces the legacy OMP source; it does not add a second scan.
+An invalid profile/root disables that source rather than selecting another store.
+The same bounded discovery, cancellation, child partition and parse cache remain.
+There are no new subprocesses, polls, recursive scan roots or wire fields.
+
+The optional scanner input is in-process only. A client performing the existing
+filesystem fallback against an older relay still uses that host's legacy root,
+without consulting the client's environment or disk. A new relay publishes the
+same session schema to old and new clients; relocated conversations become visible.
+No capability is needed to interpret those ordinary existing session rows.
+
+This covers the relay process's inherited environment. A profile or root set only
+inside an individual terminal is not automatically part of that environment. It
+does not prove resolution of the original iOS timing report #18663.
+
+Run the actual persistence-to-sidecar proof with a read-only OMP checkout:
+
+```sh
+ORCA_BACKGROUND_LAUNCH=1 bun tests/tools/omp-relay-root-smoke.mjs /path/to/oh-my-pi
+```
+
+It bundles the production service entry, launches it under native Node using the
+production environment filter, and sends the real init/list IPC messages. OMP's
+actual SessionManager writes default and named-profile XDG conversations in
+isolated home/config/data directories while a legacy directory coexists. Both are
+found by exact UUID and path. An invalid profile yields no OMP sessions. No model
+calls or visible app windows are used. This local sidecar proof is not a live SSH
+connection or Windows/Linux runtime validation.
diff --git a/src/main/ai-vault/remote-session-scanner-omp-roots.test.ts b/src/main/ai-vault/remote-session-scanner-omp-roots.test.ts
new file mode 100644
index 00000000000..ae218163540
--- /dev/null
+++ b/src/main/ai-vault/remote-session-scanner-omp-roots.test.ts
@@ -0,0 +1,106 @@
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { getRemoteHostPlatform } from '../ssh/ssh-remote-platform'
+import { scanRemoteAiVaultSessions } from './remote-session-scanner'
+import { MemoryRemoteProvider, jsonLines } from './remote-session-scanner-test-fixtures'
+
+const home = '/home/ada'
+const legacy = `${home}/.omp/agent/sessions`
+const relocated = '/data/omp/profiles/work/sessions'
+const platform = getRemoteHostPlatform('linux-x64')
+
+function fixture() {
+  const provider = new MemoryRemoteProvider()
+  for (const [root, id] of [
+    [legacy, 'legacy'],
+    [relocated, 'relocated']
+  ]) {
+    provider.addFile(
+      `${root}/folder/${id}.jsonl`,
+      jsonLines([
+        { type: 'session', id, cwd: '/folder workspace', timestamp: '2026-09-14T10:00:00Z' },
+        { type: 'message', message: { role: 'user', content: id } }
+      ]),
+      70
+    )
+  }
+  return provider
+}
+
+afterEach(() => vi.unstubAllEnvs())
+
+describe('host-resolved OMP remote scan roots', () => {
+  it('scans the host-selected root once instead of the coexisting legacy store', async () => {
+    const provider = fixture()
+    const result = await scanRemoteAiVaultSessions({
+      provider,
+      remoteHome: home,
+      hostPlatform: platform,
+      executionHostId: 'ssh:box',
+      ompSessionsDir: relocated
+    })
+    expect(result.sessions.map((row) => row.sessionId)).toEqual(['relocated'])
+    expect(result.sessions[0]?.executionHostId).toBe('ssh:box')
+    expect(provider.readDirPaths.filter((path) => path === relocated)).toHaveLength(1)
+    expect(provider.readDirPaths).not.toContain(legacy)
+  })
+
+  it('does not fall back when the host refuses an unsafe root', async () => {
+    const provider = fixture()
+    const result = await scanRemoteAiVaultSessions({
+      provider,
+      remoteHome: home,
+      hostPlatform: platform,
+      executionHostId: 'ssh:box',
+      ompSessionsDir: ''
+    })
+    expect(result.sessions).toEqual([])
+    expect(provider.readDirPaths).not.toContain(legacy)
+    expect(provider.readDirPaths).not.toContain('')
+  })
+
+  it('uses a Windows host root verbatim on a different client platform', async () => {
+    const provider = new MemoryRemoteProvider()
+    const root = 'D:\\OMP data\\profiles\\work\\sessions'
+    const file = `${root}\\folder\\session.jsonl`
+    provider.addFile(
+      file,
+      jsonLines([
+        {
+          type: 'session',
+          id: 'windows',
+          cwd: 'D:\\folder workspace',
+          timestamp: '2026-09-14T10:00:00Z'
+        },
+        { type: 'message', message: { role: 'user', content: 'Windows host' } }
+      ]),
+      80
+    )
+    const result = await scanRemoteAiVaultSessions({
+      provider,
+      remoteHome: 'C:\\Users\\ada',
+      hostPlatform: getRemoteHostPlatform('win32-x64'),
+      executionHostId: 'ssh:windows',
+      ompSessionsDir: root
+    })
+    expect(result.sessions).toHaveLength(1)
+    expect(result.sessions[0]).toMatchObject({
+      sessionId: 'windows',
+      executionHostId: 'ssh:windows',
+      executionHostPlatform: 'win32',
+      cwd: 'D:\\folder workspace'
+    })
+    expect(provider.readDirPaths).toContain(root.replaceAll('\\', '/'))
+  })
+
+  it('keeps legacy fallback scans independent of the client environment', async () => {
+    vi.stubEnv('OMP_CODING_AGENT_DIR', relocated)
+    vi.stubEnv('OMP_PROFILE', 'work')
+    const result = await scanRemoteAiVaultSessions({
+      provider: fixture(),
+      remoteHome: home,
+      hostPlatform: platform,
+      executionHostId: 'ssh:box'
+    })
+    expect(result.sessions.map((row) => row.sessionId)).toEqual(['legacy'])
+  })
+})
diff --git a/src/main/ai-vault/remote-session-scanner-sources.ts b/src/main/ai-vault/remote-session-scanner-sources.ts
index 92b9e9b4dc5..f99bf5f1ec1 100644
--- a/src/main/ai-vault/remote-session-scanner-sources.ts
+++ b/src/main/ai-vault/remote-session-scanner-sources.ts
@@ -17,7 +17,6 @@ import { parseHermesSessionContent } from './session-scanner-hermes-parser'
 import { partitionSubagentTranscriptPaths } from './session-scanner-subagent-transcripts'
 import { partitionOmpSubagentTranscriptPaths } from './session-scanner-omp-subagent-transcripts'
 import type { FileWithMtime } from './session-scanner-types'
-import { normalizeAgentSessionsDir } from './session-scanner-values'
 import { remoteCodexIndexedTitleReader } from './remote-session-scanner-codex-index'
 import { remoteClineSource } from './remote-session-scanner-cline-source'
 import type {
@@ -26,6 +25,9 @@ import type {
   RemoteSessionSource
 } from './remote-session-scanner-types'
 
+const PI_SESSIONS_SEGMENTS = ['.pi', 'agent', 'sessions']
+const OMP_SESSIONS_SEGMENTS = ['.omp', 'agent', 'sessions']
+
 type RemoteContentParser<T = string> = (
   file: FileWithMtime,
   content: T,
@@ -37,7 +39,8 @@ type RemoteContentParser<T = string> = (
 
 export function remoteSessionSources(
   remoteHome: string,
-  hostPlatform: RemoteHostPlatform
+  hostPlatform: RemoteHostPlatform,
+  ompSessionsDir?: string
 ): RemoteSessionSource[] {
   return [
     ...remoteCodexSources(remoteHome, hostPlatform),
@@ -97,14 +100,16 @@ export function remoteSessionSources(
       ['.json'],
       parseDevinSessionContent
     ),
-    jsonlSource('pi', remoteHome, hostPlatform, remotePiSessionsSegments(), piParser),
-    {
-      ...jsonlSource('omp', remoteHome, hostPlatform, remoteOmpSessionsSegments(), ompParser),
-      // Same posture as Claude above: OMP stores task-subagent transcripts in
-      // the session's same-named artifact dir; the walk supplies counts and the
-      // partition keeps the children out of the top-level list (#9330).
-      partitionSubagentTranscripts: partitionOmpSubagentTranscriptPaths
-    },
+    jsonlSource('pi', remoteHome, hostPlatform, PI_SESSIONS_SEGMENTS, piParser),
+    ...(ompSessionsDir === ''
+      ? []
+      : [
+          {
+            ...jsonlSource('omp', remoteHome, hostPlatform, OMP_SESSIONS_SEGMENTS, ompParser),
+            ...(ompSessionsDir === undefined ? {} : { rootDir: ompSessionsDir }),
+            partitionSubagentTranscripts: partitionOmpSubagentTranscriptPaths
+          }
+        ]),
     jsonlSource(
       'prime-agent',
       remoteHome,
@@ -311,14 +316,6 @@ function remotePathSegments(path: string): string[] {
   return path.replace(/\\/g, '/').split('/').filter(Boolean)
 }
 
-function remotePiSessionsSegments(): string[] {
-  return normalizeAgentSessionsDir('/.pi/agent/sessions', '.pi').split('/').filter(Boolean)
-}
-
-function remoteOmpSessionsSegments(): string[] {
-  return normalizeAgentSessionsDir('/.omp/agent/sessions', '.omp').split('/').filter(Boolean)
-}
-
 // Why: remote roots are posix regardless of the client platform, so these stay literal
 // rather than round-tripping through a local-platform path join that would emit
 // backslashes on a Windows client and collapse into a single bogus segment.
diff --git a/src/main/ai-vault/remote-session-scanner.ts b/src/main/ai-vault/remote-session-scanner.ts
index 971bc20f70e..635e76f3e0a 100644
--- a/src/main/ai-vault/remote-session-scanner.ts
+++ b/src/main/ai-vault/remote-session-scanner.ts
@@ -50,6 +50,8 @@ export async function scanRemoteAiVaultSessions(args: {
   provider: RemoteSessionFilesystemProvider
   executionHostId: ExecutionHostId
   remoteHome: string
+  // Host-resolved only; omission preserves legacy client-side fallback discovery.
+  ompSessionsDir?: string
   hostPlatform: RemoteHostPlatform
   limit?: number
   unlimited?: boolean
@@ -85,7 +87,7 @@ export async function scanRemoteAiVaultSessions(args: {
   const candidates = dedupeCodexRolloutFileAliases(
     (
       await mapRemoteScanBatches(
-        remoteSessionSources(args.remoteHome, args.hostPlatform),
+        remoteSessionSources(args.remoteHome, args.hostPlatform, args.ompSessionsDir),
         REMOTE_SCAN_CONCURRENCY,
         (source) => discoverRemoteSourceCandidates({ source, context, issues }),
         args.signal
diff --git a/src/main/ai-vault/session-scanner-service-env.test.ts b/src/main/ai-vault/session-scanner-service-env.test.ts
index 88d393fcced..3b68d0d50df 100644
--- a/src/main/ai-vault/session-scanner-service-env.test.ts
+++ b/src/main/ai-vault/session-scanner-service-env.test.ts
@@ -118,9 +118,7 @@ describe('buildRelayAiVaultServiceEnv', () => {
     expect(env.HOME).toBe('/home/ada')
   })
 
-  // The sidecar takes remoteHome and hostPlatform from its init message, so an
-  // agent-home override on the remote host is not part of how it finds roots.
-  it('withholds the agent-home variables the desktop child needs', () => {
+  it('withholds unrelated agent-home variables', () => {
     const env = buildRelayAiVaultServiceEnv(
       { CODEX_HOME: '/remote/.codex', PATH: '/usr/bin' },
       'linux'
@@ -135,7 +133,7 @@ describe('buildRelayAiVaultServiceEnv', () => {
   })
 })
 
-it('carries OMP root/profile inputs only to the desktop service, retaining empty canonical profile', () => {
+it('carries OMP root/profile inputs to both services, retaining empty canonical profile', () => {
   const roots = {
     OMP_PROFILE: '',
     PI_PROFILE: 'work',
@@ -144,5 +142,30 @@ it('carries OMP root/profile inputs only to the desktop service, retaining empty
     XDG_DATA_HOME: '/home/dev/data'
   }
   expect(buildAiVaultServiceEnv(roots, 'linux')).toEqual({ ...roots, ELECTRON_RUN_AS_NODE: '1' })
-  expect(buildRelayAiVaultServiceEnv(roots, 'linux')).toEqual({})
+  expect(buildRelayAiVaultServiceEnv(roots, 'linux')).toEqual(roots)
+})
+
+it('carries Windows OMP roots case-insensitively without forwarding other agent roots', () => {
+  expect(
+    buildRelayAiVaultServiceEnv(
+      {
+        omp_profile: 'work',
+        omp_coding_agent_dir: 'D:\\omp',
+        pi_profile: 'old',
+        pi_config_dir: '.custom',
+        pi_coding_agent_dir: 'D:\\inherited',
+        xdg_data_home: 'D:\\data',
+        codex_home: 'D:\\codex',
+        AWS_SECRET_ACCESS_KEY: 'secret'
+      },
+      'win32'
+    )
+  ).toEqual({
+    OMP_PROFILE: 'work',
+    OMP_CODING_AGENT_DIR: 'D:\\omp',
+    PI_PROFILE: 'old',
+    PI_CONFIG_DIR: '.custom',
+    PI_CODING_AGENT_DIR: 'D:\\inherited',
+    XDG_DATA_HOME: 'D:\\data'
+  })
 })
diff --git a/src/main/ai-vault/session-scanner-service-env.ts b/src/main/ai-vault/session-scanner-service-env.ts
index c6513434c8d..40f78c6ea01 100644
--- a/src/main/ai-vault/session-scanner-service-env.ts
+++ b/src/main/ai-vault/session-scanner-service-env.ts
@@ -30,6 +30,15 @@ export const RUNTIME_ENV_ALLOWLIST = [
   'NUMBER_OF_PROCESSORS'
 ] as const
 
+const OMP_ROOT_ENV_ALLOWLIST = [
+  'OMP_CODING_AGENT_DIR',
+  'OMP_PROFILE',
+  'PI_CODING_AGENT_DIR',
+  'PI_CONFIG_DIR',
+  'PI_PROFILE',
+  'XDG_DATA_HOME'
+] as const
+
 // Why: the desktop child resolves agent roots from its own environment, so
 // dropping one hides every session of a user who relocated that agent's home.
 const AGENT_ROOT_ENV_ALLOWLIST = [
@@ -39,19 +48,12 @@ const AGENT_ROOT_ENV_ALLOWLIST = [
   'DEVIN_HOME',
   'GROK_HOME',
   'KIMI_CODE_HOME',
-  'OMP_CODING_AGENT_DIR',
-  'OMP_PROFILE',
   'OPENCLAW_STATE_DIR',
   'OPENCODE_DB',
-  'PI_CODING_AGENT_DIR',
-  'PI_CONFIG_DIR',
-  'PI_PROFILE',
   'PRIME_AGENT_CODING_AGENT_DIR',
   'PRIME_AGENT_CODING_AGENT_SESSION_DIR',
   'PRIME_AGENT_SESSION_DIR',
-  // Why: OpenCode and migrated OMP session stores use the XDG data dir,
-  // so this one is an agent root here rather than generic runtime state.
-  'XDG_DATA_HOME'
+  ...OMP_ROOT_ENV_ALLOWLIST
 ] as const
 
 export function pickAllowedEnv(
@@ -94,10 +96,10 @@ export function buildAiVaultServiceEnv(
   return env
 }
 
-/** Relay: the sidecar takes every root from its init message, not the environment. */
+/** Relay: resolve OMP storage from the execution host, never the client. */
 export function buildRelayAiVaultServiceEnv(
   baseEnv: NodeJS.ProcessEnv = process.env,
   platform: NodeJS.Platform = process.platform
 ): NodeJS.ProcessEnv {
-  return pickAllowedEnv(RUNTIME_ENV_ALLOWLIST, baseEnv, platform)
+  return pickAllowedEnv([...RUNTIME_ENV_ALLOWLIST, ...OMP_ROOT_ENV_ALLOWLIST], baseEnv, platform)
 }
diff --git a/src/relay/ai-vault-service-entry.ts b/src/relay/ai-vault-service-entry.ts
index 9bd3ea35786..2c268106ff0 100644
--- a/src/relay/ai-vault-service-entry.ts
+++ b/src/relay/ai-vault-service-entry.ts
@@ -1,3 +1,4 @@
+import { resolveOmpSessionsDir } from '../main/ai-vault/omp-session-root'
 import { LOCAL_EXECUTION_HOST_ID } from '../shared/execution-host'
 import { scanRemoteAiVaultSessions } from '../main/ai-vault/remote-session-scanner'
 import { readAiVaultSessionTitlesFromFiles } from '../main/ai-vault/session-title-file-reader'
@@ -50,6 +51,10 @@ async function execute(request: RelayAiVaultServiceRequest): Promise<void> {
       provider,
       executionHostId: LOCAL_EXECUTION_HOST_ID,
       remoteHome: init.remoteHome,
+      ompSessionsDir: resolveOmpSessionsDir({
+        homeDir: init.remoteHome,
+        platform: init.hostPlatform.os
+      }),
       hostPlatform: init.hostPlatform,
       limit: request.params.limit,
       unlimited: request.params.unlimited,
diff --git a/tests/tools/omp-relay-root-smoke.mjs b/tests/tools/omp-relay-root-smoke.mjs
new file mode 100644
index 00000000000..0a82db3f980
--- /dev/null
+++ b/tests/tools/omp-relay-root-smoke.mjs
@@ -0,0 +1,145 @@
+import assert from 'node:assert/strict'
+import { mkdtemp, mkdir, rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join, resolve } from 'node:path'
+import { fileURLToPath, pathToFileURL } from 'node:url'
+import { build } from 'esbuild'
+import { spawnProcess } from '../../src/shared/child-process/run-process.ts'
+import { buildRelayAiVaultServiceEnv } from '../../src/main/ai-vault/session-scanner-service-env.ts'
+import { getRemoteHostPlatform } from '../../src/main/ssh/ssh-remote-platform.ts'
+
+assert.ok(process.argv[2], 'Pass a read-only OMP checkout')
+const node = Bun.which('node')
+assert.ok(node, 'A native Node executable is required')
+const root = fileURLToPath(new URL('../../', import.meta.url))
+const scratch = await mkdtemp(join(tmpdir(), 'orca-omp-relay-root-'))
+const home = join(scratch, 'home')
+const xdg = join(scratch, 'data')
+Object.assign(process.env, {
+  HOME: home,
+  USERPROFILE: home,
+  XDG_CONFIG_HOME: join(scratch, 'config'),
+  XDG_DATA_HOME: xdg,
+  XDG_STATE_HOME: join(scratch, 'state'),
+  XDG_CACHE_HOME: join(scratch, 'cache')
+})
+for (const key of [
+  'OMP_CODING_AGENT_DIR',
+  'PI_CODING_AGENT_DIR',
+  'OMP_PROFILE',
+  'PI_PROFILE',
+  'PI_CONFIG_DIR',
+  'PI_CONFIG_FILES'
+]) {
+  delete process.env[key]
+}
+const source = (path) => pathToFileURL(join(resolve(process.argv[2]), path)).href
+const managers = []
+const entry = join(scratch, 'relay-ai-vault-service.cjs')
+
+async function scan(profile, env = process.env) {
+  const child = spawnProcess({
+    program: node,
+    args: [entry],
+    cwd: scratch,
+    env: { ...buildRelayAiVaultServiceEnv(env), ORCA_BACKGROUND_LAUNCH: '1' },
+    stdio: ['ignore', 'pipe', 'pipe', 'ipc']
+  })
+  let stderr = ''
+  child.stderr.on('data', (data) => {
+    stderr = (stderr + data).slice(-16000)
+  })
+  const exited = new Promise((resolveExit) => child.once('exit', resolveExit))
+  let timer
+  try {
+    const result = new Promise((resolveResult, reject) => {
+      timer = setTimeout(() => reject(new Error(`Relay scan timed out: ${stderr}`)), 15000)
+      child.once('error', reject)
+      child.once('exit', (code) => reject(new Error(`Relay exited ${code}: ${stderr}`)))
+      child.on('message', (message) => {
+        if (message.type === 'ready') {
+          child.send({ type: 'request', id: 1, operation: 'list', params: { limit: 20 } })
+        } else if (message.type === 'error') {
+          reject(new Error(message.message))
+        } else if (message.type === 'result') {
+          resolveResult(message.value)
+        }
+      })
+    })
+    child.send({
+      type: 'init',
+      protocol: 1,
+      remoteHome: home,
+      hostPlatform: getRemoteHostPlatform(`${process.platform}-${process.arch}`)
+    })
+    const value = await result
+    assert.equal(value.issues.length, 0, JSON.stringify(value.issues))
+    const sessions = value.sessions.filter((session) => session.agent === 'omp')
+    if (profile === 'invalid') {
+      assert.deepEqual(sessions, [])
+    } else {
+      const manager = managers.at(-1)
+      assert.equal(sessions.length, 1)
+      assert.equal(sessions[0].sessionId, manager.getSessionId())
+      assert.equal(sessions[0].filePath, manager.getSessionFile())
+      assert.equal(sessions[0].cwd, join(scratch, 'folder workspace'))
+    }
+    return { profile: profile || 'default', sessions: sessions.length, actualNodeSidecar: true }
+  } finally {
+    clearTimeout(timer)
+    child.kill()
+    await exited
+  }
+}
+
+try {
+  await mkdir(join(home, '.omp', 'agent', 'sessions'), { recursive: true })
+  await mkdir(join(xdg, 'omp', 'profiles', 'work'), { recursive: true })
+  await build({
+    entryPoints: [join(root, 'src/relay/ai-vault-service-entry.ts')],
+    bundle: true,
+    platform: 'node',
+    target: 'node18',
+    format: 'cjs',
+    outfile: entry,
+    external: ['electron'],
+    define: { 'process.env.NODE_ENV': '"production"' }
+  })
+  const upstream = await import(source('packages/utils/src/dirs.ts'))
+  const { SessionManager } = await import(
+    source('packages/coding-agent/src/session/session-manager.ts')
+  )
+  const results = []
+  for (const profile of ['', 'work']) {
+    process.env.OMP_PROFILE = profile
+    upstream.__resetDirsFromEnvForTests()
+    const cwd = join(scratch, 'folder workspace')
+    await mkdir(cwd, { recursive: true })
+    const manager = SessionManager.create(cwd)
+    managers.push(manager)
+    manager.appendMessage({
+      role: 'user',
+      content: 'OMP relay history proof',
+      timestamp: Date.now()
+    })
+    await manager.ensureOnDisk()
+    await manager.flush()
+    const expected = join(xdg, 'omp', ...(profile ? ['profiles', profile] : []), 'sessions')
+    assert.ok(manager.getSessionFile().startsWith(expected))
+    results.push(await scan(profile))
+  }
+  results.push(await scan('invalid', { ...process.env, OMP_PROFILE: '../invalid' }))
+  console.log(
+    JSON.stringify({
+      results,
+      actualOmpPersistence: true,
+      legacyDirectoryCoexists: true,
+      modelCalls: 0
+    })
+  )
+} finally {
+  for (const manager of managers) {
+    await manager.close()
+  }
+  await rm(scratch, { recursive: true, force: true })
+}