diff --git a/src/main/runtime/orca-runtime-get-pty-record-for-pane-key.ts b/src/main/runtime/orca-runtime-get-pty-record-for-pane-key.ts
index 65e57bd5f08..c408451a028 100644
--- a/src/main/runtime/orca-runtime-get-pty-record-for-pane-key.ts
+++ b/src/main/runtime/orca-runtime-get-pty-record-for-pane-key.ts
@@ -10,9 +10,7 @@ import type { StructuredPointerTarget } from './orchestration/structured-mailbox
 import { releaseRestoredStructuredPointerClaims } from './orchestration/structured-pointer-claim-restore'
 import {
   handleLessCoordinatorSessionId,
-  findConnectedPtyBoundToSession,
   structuredSessionAddressTarget,
-  structuredSessionMailDestination,
   structuredSessionMailTarget,
   structuredSessionIdleEdgeMailboxes
 } from './orchestration/structured-session-mail-target'
@@ -198,8 +196,8 @@ export class OrcaRuntimeWithGetPtyRecordForPaneKey extends OrcaRuntimeWithPruneM
 
   /**
    * Every structured session's status change reaches here. At its idle edge, retry what is parked
-   * on it and re-derive the mailboxes it owns, so mail it could not take earlier (evicted, closed,
-   * in its terminal view) is pointed again. Workers and chats alike: this is not per-dispatch.
+   * on it and re-derive the mailboxes it owns, so mail it could not take earlier (evicted, closed)
+   * is pointed again. Workers and chats alike: this is not per-dispatch.
    */
   onStructuredSessionStatusForMail(summary: {
     sessionId: string
@@ -214,16 +212,6 @@ export class OrcaRuntimeWithGetPtyRecordForPaneKey extends OrcaRuntimeWithPruneM
     structuredSessionIdleEdgeMailboxes(summary.sessionId, openDb).forEach(deliver)
   }
 
-  /** The terminal of a session's terminal view, while a TUI owns it; the PTY lane types there. */
-  getTerminalViewHandleForSession(sessionId: string): string | null {
-    const destination = structuredSessionMailDestination(sessionId, this._orchestrationDb)
-    const pty =
-      destination?.view === 'terminal-view'
-        ? findConnectedPtyBoundToSession(this.ptysById.values(), destination.sessionId)
-        : undefined
-    return pty?.paneKey ? this.getTerminalHandleForPaneKey(pty.paneKey) : null
-  }
-
   /** Settlement drops anything parked for the session; nothing will ever redrive it again. */
   forgetStructuredSessionMail(sessionId: string): void {
     this.orchestrationStructuredMailboxPointerDelivery.forgetSession(sessionId)
diff --git a/src/main/runtime/orca-runtime-stop-requested-pty-ids.ts b/src/main/runtime/orca-runtime-stop-requested-pty-ids.ts
index 46dad7b17b4..4989245fdf6 100644
--- a/src/main/runtime/orca-runtime-stop-requested-pty-ids.ts
+++ b/src/main/runtime/orca-runtime-stop-requested-pty-ids.ts
@@ -2,7 +2,6 @@
 import { OrchestrationStructuredMailboxPointerDelivery } from './orchestration/structured-mailbox-pointer-delivery'
 import { createStructuredMailboxPointerHost } from './orchestration/structured-mailbox-pointer-host'
 import { isStructuredWorkerHandle } from './structured-worker-identity'
-import { agentSessionPtyWriteGate } from './agent-session-pty-write-gate'
 import { resolveStructuredWorkerAuthority } from './structured-worker-authority'
 import { OrcaRuntimeWithRuntimeId } from './orca-runtime-runtime-id'
 import { RuntimeTerminalAgentPresence } from './runtime-terminal-agent-presence'
@@ -184,8 +183,7 @@ export class OrcaRuntimeWithStopRequestedPtyIds extends OrcaRuntimeWithRuntimeId
     onRoutedMessageTypes: (mailboxHandle, types) =>
       this.messageWaiters.notifyRouted(mailboxHandle, types),
     onForeignMailboxRouted: (mailboxHandle, messageType) =>
-      this.notifyMessageArrived(mailboxHandle, messageType),
-    getBoundSessionIdForPty: (ptyId) => agentSessionPtyWriteGate.boundSessionId(ptyId)
+      this.notifyMessageArrived(mailboxHandle, messageType)
   })
 
   protected readonly orchestrationMailboxDeliveryTarget = new OrchestrationMailboxDeliveryTarget({
@@ -195,8 +193,7 @@ export class OrcaRuntimeWithStopRequestedPtyIds extends OrcaRuntimeWithRuntimeId
     isStructuredWorkerHandle: (handle) => isStructuredWorkerHandle(handle),
     canProbePtyLiveness: () => Boolean(this.ptyController?.probePtyLiveness),
     controllerKnowsPtyIsLive: (ptyId) => this.controllerKnowsPtyIsLive(ptyId),
-    isLeafPtyProvenAbsent: (ptyId) => this.isLeafPtyProvenAbsent(ptyId),
-    getTerminalViewHandleForSession: (sessionId) => this.getTerminalViewHandleForSession(sessionId)
+    isLeafPtyProvenAbsent: (ptyId) => this.isLeafPtyProvenAbsent(ptyId)
   })
 
   protected readonly orchestrationMailboxPointerDelivery = new OrchestrationMailboxPointerDelivery({
diff --git a/src/main/runtime/orchestration/canonical-orca-session-id.ts b/src/main/runtime/orchestration/canonical-orca-session-id.ts
index 7889e257f48..4aee8cbea15 100644
--- a/src/main/runtime/orchestration/canonical-orca-session-id.ts
+++ b/src/main/runtime/orchestration/canonical-orca-session-id.ts
@@ -1,7 +1,38 @@
-import type { OrcaSessionId } from '../../../shared/orca-session-address'
+import { isOrcaSessionId, type OrcaSessionId } from '../../../shared/orca-session-address'
+import {
+  clearedInto,
+  readAgentSessionRecordStore,
+  type AgentSessionRecordReader
+} from './structured-session-lineage'
 
-/** The Orca session id orchestration addresses a session by; every session-to-party step calls this. */
-export function canonicalOrcaSessionId(orcaSessionId: OrcaSessionId): OrcaSessionId {
-  // Later lineage canonicalization (a `/clear`ed session to its lineage root) plugs in here.
-  return orcaSessionId
+/**
+ * The Orca session id orchestration addresses a session by: the first session of its `/clear`
+ * lineage, so a cleared chat keeps the address, Runs and mail it had. Every session-to-party step
+ * calls this. Without a record store there is no lineage to read, and the id stands for itself.
+ */
+export function canonicalOrcaSessionId(
+  orcaSessionId: OrcaSessionId,
+  store: AgentSessionRecordReader | null = readAgentSessionRecordStore()
+): OrcaSessionId {
+  if (!store) {
+    return orcaSessionId
+  }
+  const clearedFrom = new Map<string, string>()
+  for (const record of store.listRecords()) {
+    const next = clearedInto(record)
+    if (next) {
+      clearedFrom.set(next, record.sessionId)
+    }
+  }
+  // A clear chain is acyclic by construction; the visited set only bounds a corrupt store.
+  let root: string = orcaSessionId
+  const earlier = new Set([root])
+  let prior = clearedFrom.get(root)
+  while (prior && !earlier.has(prior)) {
+    earlier.add(prior)
+    root = prior
+    prior = clearedFrom.get(root)
+  }
+  // Record ids are minted as Orca session ids; one that is not cannot name the conversation.
+  return isOrcaSessionId(root) ? root : orcaSessionId
 }
diff --git a/src/main/runtime/orchestration/db/dispatch-context/dispatch-context-store.ts b/src/main/runtime/orchestration/db/dispatch-context/dispatch-context-store.ts
index 67be16e6cf2..b51e5b4a8aa 100644
--- a/src/main/runtime/orchestration/db/dispatch-context/dispatch-context-store.ts
+++ b/src/main/runtime/orchestration/db/dispatch-context/dispatch-context-store.ts
@@ -9,7 +9,7 @@ import { recordedCreatorIdentity, type DispatchCreator } from '../dispatch-depth
 import type { OrchestrationDb } from '../orchestration-db'
 import { transitionLifecycleWithDb } from '../lifecycle-transition'
 import { taskNotFoundError, taskNotStartableError } from '../../task-dispatch-refusal'
-import { structuredWorkerOrcaSessionIdForIncarnation } from '../../../structured-worker-identity'
+import { dispatchAssigneeOrcaSessionId } from '../../dispatch-assignee-orca-session-id'
 
 export function createDispatchContext(
   this: OrchestrationDb,
@@ -66,7 +66,7 @@ export function createDispatchContext(
       launchTokenHash: launchTokenHash ?? null,
       assigneeHandle,
       assigneePaneKey: assigneePaneKey ?? null,
-      assigneeOrcaSessionId: structuredWorkerOrcaSessionIdForIncarnation(processIncarnation),
+      assigneeOrcaSessionId: dispatchAssigneeOrcaSessionId(processIncarnation),
       processIncarnation: processIncarnation ?? null,
       creatorDispatchId,
       ...recordedCreatorIdentity(params.creator),
diff --git a/src/main/runtime/orchestration/db/worker-dispatch/worker-dispatch-authority.ts b/src/main/runtime/orchestration/db/worker-dispatch/worker-dispatch-authority.ts
index bc7b2c0cc0c..733833c9aca 100644
--- a/src/main/runtime/orchestration/db/worker-dispatch/worker-dispatch-authority.ts
+++ b/src/main/runtime/orchestration/db/worker-dispatch/worker-dispatch-authority.ts
@@ -2,7 +2,7 @@ import { randomBytes } from 'node:crypto'
 import { OrchestrationError } from '../../orchestration-error'
 import { hashDispatchCapability } from '../dispatch-capability-hash'
 import type { OrchestrationDb } from '../orchestration-db'
-import { structuredWorkerOrcaSessionIdForIncarnation } from '../../../structured-worker-identity'
+import { dispatchAssigneeOrcaSessionId } from '../../dispatch-assignee-orca-session-id'
 
 export function prepareStartingWorkerAuthority(
   this: OrchestrationDb,
@@ -64,7 +64,7 @@ export function prepareStartingWorkerAuthority(
       .run(
         params.handle,
         params.paneKey,
-        structuredWorkerOrcaSessionIdForIncarnation(params.processIncarnation),
+        dispatchAssigneeOrcaSessionId(params.processIncarnation),
         params.processIncarnation,
         params.hostScope ?? null,
         hashDispatchCapability(capability),
diff --git a/src/main/runtime/orchestration/db/worker-terminal/failed-start-dispatch-identity.ts b/src/main/runtime/orchestration/db/worker-terminal/failed-start-dispatch-identity.ts
index 490cfbb1138..3d45c9a8630 100644
--- a/src/main/runtime/orchestration/db/worker-terminal/failed-start-dispatch-identity.ts
+++ b/src/main/runtime/orchestration/db/worker-terminal/failed-start-dispatch-identity.ts
@@ -1,6 +1,6 @@
 import type { WorkerDispatchRow } from '../../types'
 import type { OrchestrationDb } from '../orchestration-db'
-import { structuredWorkerOrcaSessionIdForIncarnation } from '../../../structured-worker-identity'
+import { dispatchAssigneeOrcaSessionId } from '../../dispatch-assignee-orca-session-id'
 
 /**
  * A start that dies before `prepareStartingWorkerAuthority` never filled the Dispatch context in,
@@ -29,7 +29,7 @@ export function recordFailedStartDispatchIdentity(
     .run(
       resource.terminal_handle,
       resource.pane_key,
-      structuredWorkerOrcaSessionIdForIncarnation(resource.process_incarnation),
+      dispatchAssigneeOrcaSessionId(resource.process_incarnation),
       resource.process_incarnation,
       resource.host_scope,
       worker.dispatch_id
diff --git a/src/main/runtime/orchestration/dispatch-assignee-orca-session-id.ts b/src/main/runtime/orchestration/dispatch-assignee-orca-session-id.ts
new file mode 100644
index 00000000000..52c75ece732
--- /dev/null
+++ b/src/main/runtime/orchestration/dispatch-assignee-orca-session-id.ts
@@ -0,0 +1,11 @@
+import type { OrcaSessionId } from '../../../shared/orca-session-address'
+import { structuredWorkerOrcaSessionIdForIncarnation } from '../structured-worker-identity'
+import { canonicalOrcaSessionId } from './canonical-orca-session-id'
+
+/** The Orca session id a Dispatch row stores for the structured worker a process incarnation names. */
+export function dispatchAssigneeOrcaSessionId(
+  processIncarnation: string | null | undefined
+): OrcaSessionId | null {
+  const orcaSessionId = structuredWorkerOrcaSessionIdForIncarnation(processIncarnation)
+  return orcaSessionId === null ? null : canonicalOrcaSessionId(orcaSessionId)
+}
diff --git a/src/main/runtime/orchestration/mailbox-delivery-target.ts b/src/main/runtime/orchestration/mailbox-delivery-target.ts
index eb2282def0b..5d412bb12e8 100644
--- a/src/main/runtime/orchestration/mailbox-delivery-target.ts
+++ b/src/main/runtime/orchestration/mailbox-delivery-target.ts
@@ -1,6 +1,5 @@
 import type { OrchestrationDb } from './db'
 import type { OrchestrationMailboxLeaf } from './mailbox-owner'
-import { handleLessCoordinatorSessionId } from './structured-session-mail-target'
 
 type OrchestrationMailboxDeliveryTargetDependencies = {
   getDb: () => OrchestrationDb | null
@@ -11,8 +10,6 @@ type OrchestrationMailboxDeliveryTargetDependencies = {
   canProbePtyLiveness: () => boolean
   controllerKnowsPtyIsLive: (ptyId: string) => boolean
   isLeafPtyProvenAbsent: (ptyId: string) => Promise<boolean>
-  /** The terminal of a structured session's terminal view, while a TUI owns that session. */
-  getTerminalViewHandleForSession?: (sessionId: string) => string | null
 }
 
 export class OrchestrationMailboxDeliveryTarget {
@@ -34,12 +31,8 @@ export class OrchestrationMailboxDeliveryTarget {
     const remote =
       dispatchId && !dispatch ? db?.getRemoteDispatchAttachment?.(dispatchId) : undefined
     const paneKey = dispatch?.assignee_pane_key ?? remote?.pane_key
-    const run = runId ? db?.getRun(runId) : undefined
-    const coordinatorSessionId = run ? handleLessCoordinatorSessionId(run) : null
     const ownerHandle = runId
-      ? coordinatorSessionId
-        ? this.deps.getTerminalViewHandleForSession?.(coordinatorSessionId)
-        : run?.coordinator_handle
+      ? db?.getRun(runId)?.coordinator_handle
       : ((paneKey ? this.deps.getTerminalHandleForPaneKey(paneKey) : null) ??
         dispatch?.assignee_handle ??
         remote?.terminal_handle)
diff --git a/src/main/runtime/orchestration/mailbox-owner.ts b/src/main/runtime/orchestration/mailbox-owner.ts
index 60ac5b9e52d..ae315511b15 100644
--- a/src/main/runtime/orchestration/mailbox-owner.ts
+++ b/src/main/runtime/orchestration/mailbox-owner.ts
@@ -1,8 +1,5 @@
 import type { AgentStatus } from '../../../shared/agent-detection'
-import { isOrcaSessionId } from '../../../shared/orca-session-address'
 import type { OrchestrationDb } from './db'
-import type { OrchestrationCallerIdentity } from './orchestration-caller-identity'
-import { sessionOrchestrationIdentity } from './structured-session-mail-address'
 
 export type OrchestrationMailboxLeaf = {
   tabId: string
@@ -33,8 +30,6 @@ type OrchestrationMailboxOwnerDependencies = {
   getTerminalProcessIncarnation: (terminalHandle: string) => string | null
   onRoutedMessageTypes: (mailboxHandle: string, types: readonly string[]) => void
   onForeignMailboxRouted: (mailboxHandle: string, messageType: string) => void
-  /** The structured session a PTY is the terminal view of, if any. */
-  getBoundSessionIdForPty?: (ptyId: string) => string | null
 }
 
 export class OrchestrationMailboxOwner {
@@ -62,23 +57,17 @@ export class OrchestrationMailboxOwner {
       return null
     }
     const paneKey = `${leaf.tabId}:${leaf.leafId}`
-    const session = this.sessionMailOwner(db, leaf)
-    const sessionRun = session ? db.getCurrentRunForCoordinator?.(session) : null
-    const run = sessionRun ?? db.getCurrentRunForPane?.(paneKey)
+    const run = db.getCurrentRunForPane?.(paneKey)
     if (run) {
-      const address = sessionRun && session ? session.address : terminalHandle
-      return this.resolveRunMailbox(db, leaf, address, run.id, requestedMailbox, options)
+      return this.resolveRunMailbox(db, leaf, terminalHandle, run.id, requestedMailbox, options)
     }
 
-    const sessionDispatch = session
-      ? db.getActiveDispatchForIdentity?.(session.address, session.paneKey ?? undefined)
-      : null
-    const dispatch = sessionDispatch ?? db.getActiveDispatchForIdentity?.(terminalHandle, paneKey)
+    const dispatch = db.getActiveDispatchForIdentity?.(terminalHandle, paneKey)
     if (dispatch) {
       return this.resolveDispatchMailbox(
         db,
         leaf,
-        sessionDispatch && session ? session.address : terminalHandle,
+        terminalHandle,
         dispatch.id,
         dispatch.run_id,
         requestedMailbox,
@@ -103,21 +92,6 @@ export class OrchestrationMailboxOwner {
     return !requestedMailbox || requestedMailbox === terminalHandle ? terminalHandle : null
   }
 
-  /**
-   * A terminal view speaks for its session (the CLI there acts as the session), so its Run and
-   * Dispatch are the session's. A PTY-born worker adopted into a session still owns its mail by
-   * terminal, which is why callers fall back to the pane when the session owns nothing.
-   */
-  private sessionMailOwner(
-    db: OrchestrationDb,
-    leaf: OrchestrationMailboxLeaf
-  ): OrchestrationCallerIdentity | null {
-    const sessionId = leaf.ptyId ? this.deps.getBoundSessionIdForPty?.(leaf.ptyId) : null
-    return sessionId && isOrcaSessionId(sessionId)
-      ? sessionOrchestrationIdentity(sessionId, db)
-      : null
-  }
-
   routeForeignDirectMessages(leaf: OrchestrationMailboxLeaf): RoutedOrchestrationMailbox[] {
     const db = this.deps.getDb()
     if (!db) {
@@ -138,13 +112,10 @@ export class OrchestrationMailboxOwner {
     if (!ownerRunId) {
       return []
     }
-    const session = this.sessionMailOwner(db, leaf)
-    const sessionOwnsRun =
-      session !== null && db.getCurrentRunForCoordinator?.(session)?.id === ownerRunId
     const routed = db.routeForeignDirectMessagesToOwnedMailboxes?.(
-      sessionOwnsRun ? session.address : terminalHandle,
+      terminalHandle,
       ownerRunId,
-      sessionOwnsRun ? (session.paneKey ?? undefined) : paneKey
+      paneKey
     )
     if (routed?.hasMore) {
       this.scheduleDirectReconciliation(leaf)
diff --git a/src/main/runtime/orchestration/structured-session-lineage.ts b/src/main/runtime/orchestration/structured-session-lineage.ts
new file mode 100644
index 00000000000..8cf6e94f12d
--- /dev/null
+++ b/src/main/runtime/orchestration/structured-session-lineage.ts
@@ -0,0 +1,44 @@
+/**
+ * A structured session's `/clear` lineage, read off the durable session records. `/clear` continues
+ * a chat in a new session; the committed clear on the old record names the session that replaced it.
+ * Derived from the records every time; nothing is rewritten at a clear.
+ */
+
+import type { AgentSessionRecord } from '../../../shared/agent-session-record'
+import { getStructuredAgentSessionHost } from '../../native-chat/agent-session-wire/structured-agent-session-registry'
+
+export type AgentSessionRecordReader = {
+  getRecord: (sessionId: string) => AgentSessionRecord | null
+  listRecords: () => AgentSessionRecord[]
+  /** Absent on a store that predates tab visibility; every session then counts as open. */
+  getVisibleSessionTabIndex?: () => { present: boolean; sessionIds: string[] }
+}
+
+/** Null until the agent-session host is installed; callers that must see records ensure it first. */
+export function readAgentSessionRecordStore(): AgentSessionRecordReader | null {
+  return getStructuredAgentSessionHost()?.deps.store ?? null
+}
+
+/** The session a committed `/clear` continued this one in, if any. */
+export function clearedInto(record: AgentSessionRecord): string | null {
+  const command = record.conversationCommand
+  return command?.command === 'clear' && command.phase === 'committed'
+    ? (command.replacementSessionId ?? null)
+    : null
+}
+
+/** The session running the lineage now; null when the chain names a session with no record. */
+export function lineageLiveSession(
+  store: AgentSessionRecordReader,
+  sessionId: string
+): AgentSessionRecord | null {
+  let live = store.getRecord(sessionId)
+  const later = new Set([sessionId])
+  let next = live ? clearedInto(live) : null
+  while (live && next && !later.has(next)) {
+    later.add(next)
+    live = store.getRecord(next)
+    next = live ? clearedInto(live) : null
+  }
+  return live
+}
diff --git a/src/main/runtime/orchestration/structured-session-mail-address.ts b/src/main/runtime/orchestration/structured-session-mail-address.ts
index 4a987d77512..4352cdb17b1 100644
--- a/src/main/runtime/orchestration/structured-session-mail-address.ts
+++ b/src/main/runtime/orchestration/structured-session-mail-address.ts
@@ -3,10 +3,8 @@
  * told is its public address. Recipient routing and pointer delivery both read these rules off the
  * durable session record, so the two can never disagree about which sessions mail can reach.
  *
- * The address names a conversation, not one session of it. `/clear` continues a chat in a new
- * session, and the conversation keeps the address of its first session (its lineage root): a Run it
- * coordinates, mail sent to it, and what it sends all stay under that one spelling, and any session
- * of the lineage names it. Derived from the records every time; nothing is rewritten at a clear.
+ * The address names a conversation, not one session of it: any session of a `/clear` lineage names
+ * the lineage root's address (`canonicalOrcaSessionId`), and mail reaches the lineage's live session.
  *
  * A released lease does not end a session. The host evicts a chat nobody is looking at 15s after
  * its last turn and hands its lease back, and mail must wake it again (resume on demand). For mail,
@@ -14,77 +12,13 @@
  */
 
 import type { AgentSessionRecord } from '../../../shared/agent-session-record'
-import {
-  formatOrcaSessionAddress,
-  isOrcaSessionId,
-  type OrcaSessionId
-} from '../../../shared/orca-session-address'
-import { getStructuredAgentSessionHost } from '../../native-chat/agent-session-wire/structured-agent-session-registry'
-import {
-  isRecordedStructuredWorkerSession,
-  resolveStructuredWorkerIdentityForSession
-} from '../structured-worker-authority'
+import { isOrcaSessionId, type OrcaSessionId } from '../../../shared/orca-session-address'
+import { ORCHESTRATION_SESSION_CALLER_ERROR_CODES as CODES } from '../../../shared/orchestration-session-caller-codes'
 import { structuredWorkerHostScope } from '../structured-worker-identity'
 import type { OrchestrationDb } from './db'
-import type { OrchestrationCallerIdentity } from './orchestration-caller-identity'
-
-export type AgentSessionRecordReader = {
-  getRecord: (sessionId: string) => AgentSessionRecord | null
-  listRecords: () => AgentSessionRecord[]
-  /** Absent on a store that predates tab visibility; every session then counts as open. */
-  getVisibleSessionTabIndex?: () => { present: boolean; sessionIds: string[] }
-}
-
-export function readAgentSessionRecordStore(): AgentSessionRecordReader | null {
-  return getStructuredAgentSessionHost()?.deps.store ?? null
-}
-
-/** The session a committed `/clear` continued this one in, if any. */
-function clearedInto(record: AgentSessionRecord): string | null {
-  const command = record.conversationCommand
-  return command?.command === 'clear' && command.phase === 'committed'
-    ? (command.replacementSessionId ?? null)
-    : null
-}
-
-export type StructuredSessionLineage = {
-  /** The conversation's first session: its address for as long as the conversation lasts. */
-  rootSessionId: string
-  /** The session running the conversation now; null when the chain names a session with no record. */
-  live: AgentSessionRecord | null
-}
-
-/** Any session of a `/clear` lineage, resolved to the lineage's root and its live end. */
-export function structuredSessionLineage(
-  store: AgentSessionRecordReader,
-  sessionId: string
-): StructuredSessionLineage {
-  const clearedFrom = new Map<string, string>()
-  for (const record of store.listRecords()) {
-    const next = clearedInto(record)
-    if (next) {
-      clearedFrom.set(next, record.sessionId)
-    }
-  }
-  // A clear chain is acyclic by construction; the visited sets only bound a corrupt store.
-  let rootSessionId = sessionId
-  const earlier = new Set([sessionId])
-  let prior = clearedFrom.get(rootSessionId)
-  while (prior && !earlier.has(prior)) {
-    earlier.add(prior)
-    rootSessionId = prior
-    prior = clearedFrom.get(rootSessionId)
-  }
-  let live = store.getRecord(sessionId)
-  const later = new Set([sessionId])
-  let next = live ? clearedInto(live) : null
-  while (live && next && !later.has(next)) {
-    later.add(next)
-    live = store.getRecord(next)
-    next = live ? clearedInto(live) : null
-  }
-  return { rootSessionId, live }
-}
+import { OrchestrationError } from './orchestration-error'
+import { resolveOrcaSessionParty, type OrchestrationSessionParty } from './orchestration-party'
+import { lineageLiveSession, type AgentSessionRecordReader } from './structured-session-lineage'
 
 export type OrcaAgentSessionLookup =
   | { kind: 'found'; record: AgentSessionRecord }
@@ -122,17 +56,14 @@ export function structuredSessionMailReach(
   record: AgentSessionRecord,
   db: OrchestrationDb | null | undefined
 ): StructuredSessionMailReach {
-  const live = structuredSessionLineage(store, record.sessionId).live
+  const live = lineageLiveSession(store, record.sessionId)
   if (!live) {
     return { kind: 'ended', reason: 'continuation-missing' }
   }
   if (!structuredWorkerHostScope(live.location)) {
     return { kind: 'other-host' }
   }
-  const identity = isOrcaSessionId(live.sessionId)
-    ? sessionOrchestrationIdentity(live.sessionId, db, store)
-    : null
-  if (db && identity && hasLostStructuredWorkerIdentity(identity, db)) {
+  if (isOrcaSessionId(live.sessionId) && !addressableSessionParty(live.sessionId, db)) {
     // Why: it can no longer act (the caller resolver refuses it), so mail to it could never be read.
     return { kind: 'ended', reason: 'worker-identity-lost' }
   }
@@ -145,58 +76,19 @@ export function structuredSessionMailReach(
 }
 
 /**
- * Which view carries a pointer to the session right now. A terminal view owns the session while a
- * TUI holds its lease, and its PTY takes the pointer; otherwise the host sends a session turn,
- * resuming an evicted session for it.
+ * The party a session resolves to, or null for a worker whose identity this host lost: the party
+ * resolver refuses it in every role, so it can never read mail and none is owed to it.
  */
-export function structuredSessionDeliveryView(
-  record: AgentSessionRecord
-): 'session-turn' | 'terminal-view' {
-  return record.lease.runtimeKind === 'tui' && record.lease.claimStatus !== 'released'
-    ? 'terminal-view'
-    : 'session-turn'
-}
-
-/**
- * Who a session is to orchestration: its conversation's Orca session id (the lineage root's), plus
- * the handle and pane a structured worker was minted. The caller resolver and mail delivery both take
- * it from here, so a session is matched the same way whether it is sending, checking, or being
- * delivered to. Without a record store there is no lineage to read, and the id stands for itself.
- */
-export function sessionOrchestrationIdentity(
+export function addressableSessionParty(
   sessionId: OrcaSessionId,
-  db: OrchestrationDb | null | undefined,
-  store: AgentSessionRecordReader | null = readAgentSessionRecordStore()
-): OrchestrationCallerIdentity & { orcaSessionId: OrcaSessionId } {
-  const lineage = store ? structuredSessionLineage(store, sessionId) : null
-  const root = lineage?.rootSessionId ?? sessionId
-  // Record ids are minted as Orca session ids; one that is not cannot name the conversation.
-  const orcaSessionId = isOrcaSessionId(root) ? root : sessionId
-  // A worker identity is minted for one session, so it is looked up on the one running now.
-  const worker = resolveStructuredWorkerIdentityForSession(
-    lineage?.live?.sessionId ?? sessionId,
-    db
-  )
-  return {
-    orcaSessionId,
-    address: worker?.handle ?? formatOrcaSessionAddress(orcaSessionId),
-    terminalHandle: worker?.handle ?? null,
-    paneKey: worker?.paneKey ?? null
+  db: OrchestrationDb | null | undefined
+): OrchestrationSessionParty | null {
+  try {
+    return resolveOrcaSessionParty(sessionId, db)
+  } catch (error) {
+    if (error instanceof OrchestrationError && error.code === CODES.notLive) {
+      return null
+    }
+    throw error
   }
 }
-
-/**
- * A structured worker whose worker identity this host no longer has. It may not act handle-less (that
- * would split one worker into two identities), so mail to it could never be read either. Checked on
- * the conversation, whose root session is the one a Dispatch assigned.
- */
-export function hasLostStructuredWorkerIdentity(
-  identity: OrchestrationCallerIdentity,
-  db: OrchestrationDb
-): boolean {
-  return (
-    identity.terminalHandle === null &&
-    identity.orcaSessionId !== null &&
-    isRecordedStructuredWorkerSession(identity.orcaSessionId, db)
-  )
-}
diff --git a/src/main/runtime/orchestration/structured-session-mail-target.test.ts b/src/main/runtime/orchestration/structured-session-mail-target.test.ts
index 7ceca93908b..743b729d987 100644
--- a/src/main/runtime/orchestration/structured-session-mail-target.test.ts
+++ b/src/main/runtime/orchestration/structured-session-mail-target.test.ts
@@ -25,12 +25,15 @@ vi.mock('../../native-chat/agent-session-wire/structured-agent-session-registry'
 const { OrcaRuntimeWithGetPtyRecordForPaneKey } =
   await import('../orca-runtime-get-pty-record-for-pane-key')
 const { OrchestrationDb } = await import('./db')
-const { agentSessionPtyWriteGate } = await import('../agent-session-pty-write-gate')
-const { sessionOrchestrationIdentity } = await import('./structured-session-mail-address')
+const { resolveOrcaSessionParty } = await import('./orchestration-party')
+const {
+  mintStructuredWorkerHandle,
+  mintStructuredWorkerPaneKey,
+  structuredWorkerProcessIncarnation
+} = await import('../structured-worker-identity')
 
 const CHAT = testOrcaSessionId('4a1f6c2e-8b3d-4e7a-9c15-0d2b6e8f1a37')
 const CHAT_ADDRESS = formatOrcaSessionAddress(CHAT)
-const TERMINAL_VIEW_PANE = 'tab_view:77777777-7777-4777-8777-777777777777'
 
 /** The real methods through the real prototype chain; a re-declared copy would pin nothing. */
 class MailTargetProbe extends OrcaRuntimeWithGetPtyRecordForPaneKey {
@@ -99,7 +102,6 @@ beforeEach(() => {
 })
 
 afterEach(() => {
-  agentSessionPtyWriteGate.detachRecordLookup()
   db.close()
 })
 
@@ -118,12 +120,6 @@ describe('a Run whose coordinator is a chat (an Orca session id, no handle)', ()
     expect(probe().target(`run:${runId}`)).toEqual({ sessionId: CHAT, dispatchId: null })
   })
 
-  it('leaves the mailbox to the PTY lane while the chat is in its terminal view', () => {
-    installStore(chatRecord({ runtimeKind: 'tui' }))
-    const runId = chatCoordinatedRun()
-    expect(probe().target(`run:${runId}`)).toBeNull()
-  })
-
   it('does not deliver to a chat that was closed, cleared into no known session, or runs on another host', () => {
     const runId = chatCoordinatedRun()
     installStore(chatRecord(), false)
@@ -185,25 +181,6 @@ describe('a session addressed directly', () => {
   })
 })
 
-describe('a chat in its terminal view', () => {
-  it('is reached through the PTY bound to it', () => {
-    installStore(chatRecord({ runtimeKind: 'tui' }))
-    agentSessionPtyWriteGate.attachRecordLookup(() => null)
-    agentSessionPtyWriteGate.bindPty('pty-view', CHAT)
-    const runtime = probe({
-      ptysById: new Map([
-        ['pty-view', { ptyId: 'pty-view', connected: true, paneKey: TERMINAL_VIEW_PANE }]
-      ]),
-      getTerminalHandleForPaneKey: (paneKey: string) =>
-        paneKey === TERMINAL_VIEW_PANE ? 'term_view' : null
-    })
-    expect(runtime.getTerminalViewHandleForSession(CHAT)).toBe('term_view')
-    // Its native view does not answer at the same time.
-    installStore(chatRecord())
-    expect(runtime.getTerminalViewHandleForSession(CHAT)).toBeNull()
-  })
-})
-
 describe('the idle edge of a structured session', () => {
   it('re-derives and delivers the mailboxes the session owns, and nothing while it works', () => {
     installStore(chatRecord())
@@ -382,10 +359,23 @@ describe('a coordinator chat continued by /clear', () => {
       objective: 'o',
       coordinatorHandle: null,
       coordinatorPaneKey: null,
-      coordinatorOrcaSessionId: sessionOrchestrationIdentity(sessionId, db).orcaSessionId
+      coordinatorOrcaSessionId: resolveOrcaSessionParty(sessionId, db).orcaSessionId
     }).id
   }
 
+  it('stores a Dispatch assignee by the lineage root of the session its incarnation names', () => {
+    installLineage(SUCCESSOR)
+    const dispatch = db.createDispatchContext({
+      taskId: db.createTask({ runId: chatCoordinatedRun(), spec: 'work' }).id,
+      assigneeHandle: mintStructuredWorkerHandle(),
+      assigneePaneKey: mintStructuredWorkerPaneKey(SUCCESSOR),
+      processIncarnation: structuredWorkerProcessIncarnation(SUCCESSOR),
+      creator: { kind: 'system' },
+      maxDepth: Number.MAX_SAFE_INTEGER
+    })
+    expect(db.getDispatchContextById(dispatch.id)?.assignee_orca_session_id).toBe(CHAT)
+  })
+
   it("never unbinds the successor's own Run", () => {
     // The strand this pins: the successor's own run-create, then its idle edge rebinding the
     // predecessor's Run through an exclusive bind, which unbound the Run the successor created.
@@ -397,7 +387,7 @@ describe('a coordinator chat continued by /clear', () => {
     expect(idleEdge(SUCCESSOR)).toContain(`run:${ownRun}`)
     idleEdge(SUCCESSOR)
 
-    const successor = sessionOrchestrationIdentity(SUCCESSOR, db)
+    const successor = resolveOrcaSessionParty(SUCCESSOR, db)
     expect(db.getRunRaw(ownRun)).toMatchObject({
       coordinator_orca_session_id: successor.orcaSessionId,
       consumer_generation: generation
@@ -418,9 +408,7 @@ describe('a coordinator chat continued by /clear', () => {
       consumer_generation: generation
     })
     for (const member of [CHAT, MIDDLE, SUCCESSOR]) {
-      expect(db.getCurrentRunForCoordinator(sessionOrchestrationIdentity(member, db))?.id).toBe(
-        runId
-      )
+      expect(db.getCurrentRunForCoordinator(resolveOrcaSessionParty(member, db))?.id).toBe(runId)
     }
     expect(probe().target(`run:${runId}`)).toEqual({ sessionId: SUCCESSOR, dispatchId: null })
   })
@@ -434,7 +422,7 @@ describe('a coordinator chat continued by /clear', () => {
     installLineage(MIDDLE, SUCCESSOR)
     idleEdge(SUCCESSOR)
 
-    const successor = sessionOrchestrationIdentity(SUCCESSOR, db)
+    const successor = resolveOrcaSessionParty(SUCCESSOR, db)
     expect(db.getRunRaw(middleRun)).toMatchObject({
       coordinator_orca_session_id: successor.orcaSessionId,
       consumer_generation: generation
@@ -445,7 +433,7 @@ describe('a coordinator chat continued by /clear', () => {
   it('reaches the live session through any spelling of the conversation, and stores one', () => {
     installLineage(MIDDLE, SUCCESSOR)
     for (const member of [CHAT, MIDDLE, SUCCESSOR]) {
-      expect(sessionOrchestrationIdentity(member, db)).toMatchObject({
+      expect(resolveOrcaSessionParty(member, db)).toMatchObject({
         orcaSessionId: CHAT,
         address: CHAT_ADDRESS
       })
diff --git a/src/main/runtime/orchestration/structured-session-mail-target.ts b/src/main/runtime/orchestration/structured-session-mail-target.ts
index 2e538717fa6..23a0d1e5555 100644
--- a/src/main/runtime/orchestration/structured-session-mail-target.ts
+++ b/src/main/runtime/orchestration/structured-session-mail-target.ts
@@ -1,11 +1,8 @@
 /**
  * Where a mailbox owned by a structured session is delivered, for sessions that are not structured
  * workers: a chat that coordinates a Run (`run:<id>` with no coordinator handle) and a session
- * addressed directly at `session:<id>`.
- *
- * The session is resolved here, never a pane: its native view takes the pointer as a session turn
- * (the structured lane), its terminal view as bytes typed into the PTY that owns it (the PTY lane).
- * Exactly one view answers for a session at a time, so the two lanes never both claim a mailbox.
+ * addressed directly at `session:<id>`. The session is resolved here, never a pane, and takes the
+ * pointer as a session turn.
  */
 
 import {
@@ -14,32 +11,19 @@ import {
   parseOrcaSessionAddress,
   type OrcaSessionId
 } from '../../../shared/orca-session-address'
-import { agentSessionPtyWriteGate } from '../agent-session-pty-write-gate'
 import type { OrchestrationDb } from './db'
 import { currentRunCoordinatorOrcaSessionId } from './db/runs/run-coordinator-orca-session'
 import type { StructuredPointerTarget } from './structured-mailbox-pointer-delivery'
 import {
-  readAgentSessionRecordStore,
-  sessionOrchestrationIdentity,
-  structuredSessionDeliveryView,
-  structuredSessionMailReach,
-  type AgentSessionRecordReader
+  addressableSessionParty,
+  structuredSessionMailReach
 } from './structured-session-mail-address'
+import {
+  readAgentSessionRecordStore,
+  type AgentSessionRecordReader
+} from './structured-session-lineage'
 import type { RunRow } from './types'
 
-/** The live PTY the write gate binds to a session: its terminal view, when a TUI owns it. */
-export function findConnectedPtyBoundToSession<T extends { ptyId: string; connected: boolean }>(
-  ptys: Iterable<T>,
-  sessionId: string
-): T | undefined {
-  for (const pty of ptys) {
-    if (pty.connected && agentSessionPtyWriteGate.boundSessionId(pty.ptyId) === sessionId) {
-      return pty
-    }
-  }
-  return undefined
-}
-
 /**
  * The session a Run's coordinator binding names when that binding has no handle. A structured
  * worker coordinates by its own handle and resolves through it, so only a handle-less binding names
@@ -62,29 +46,18 @@ export function handleLessCoordinatorSessionId(
 }
 
 /**
- * The session that takes a pointer for `sessionId`'s conversation now (its live session, whichever
- * session of the lineage was named) and through which view; null when mail cannot reach it here.
+ * The structured-lane target for `sessionId`'s conversation: its live session, whichever session of
+ * the lineage was named; null when mail cannot reach it here.
  */
-export function structuredSessionMailDestination(
+export function structuredSessionMailTarget(
   sessionId: string,
   db: OrchestrationDb | null | undefined,
   store: AgentSessionRecordReader | null = readAgentSessionRecordStore()
-): { sessionId: string; view: 'session-turn' | 'terminal-view' } | null {
+): StructuredPointerTarget | null {
   const record = store?.getRecord(sessionId)
   const reach = store && record ? structuredSessionMailReach(store, record, db) : null
   return reach?.kind === 'reachable'
-    ? { sessionId: reach.session.sessionId, view: structuredSessionDeliveryView(reach.session) }
-    : null
-}
-
-/** The structured-lane target for a session whose native view takes the pointer. */
-export function structuredSessionMailTarget(
-  sessionId: string,
-  db: OrchestrationDb | null | undefined
-): StructuredPointerTarget | null {
-  const destination = structuredSessionMailDestination(sessionId, db)
-  return destination?.view === 'session-turn'
-    ? { sessionId: destination.sessionId, dispatchId: null }
+    ? { sessionId: reach.session.sessionId, dispatchId: null }
     : null
 }
 
@@ -106,16 +79,16 @@ export function structuredSessionAddressTarget(
 /**
  * Every mailbox a session reads for itself: the Runs it coordinates and its own direct mail.
  * Re-derived from the database on each idle edge rather than remembered, so mail that arrived
- * while the session could not take it (closed, evicted, in the other view) is found again.
+ * while the session could not take it (closed, evicted) is found again.
  */
 export function structuredSessionOwnedMailboxes(sessionId: string, db: OrchestrationDb): string[] {
-  if (!isOrcaSessionId(sessionId)) {
+  const party = isOrcaSessionId(sessionId) ? addressableSessionParty(sessionId, db) : null
+  if (!party) {
     return []
   }
-  const identity = sessionOrchestrationIdentity(sessionId, db)
-  const mailboxes = db.runsBoundToCoordinator(identity).map((run) => `run:${run.id}`)
-  if (db.getUnreadDirectMessageTypes(identity.address).length > 0) {
-    mailboxes.push(identity.address)
+  const mailboxes = db.runsBoundToCoordinator(party).map((run) => `run:${run.id}`)
+  if (db.getUnreadDirectMessageTypes(party.address).length > 0) {
+    mailboxes.push(party.address)
   }
   return mailboxes
 }
diff --git a/src/main/runtime/orchestration/structured-session-terminal-view-mail.test.ts b/src/main/runtime/orchestration/structured-session-terminal-view-mail.test.ts
deleted file mode 100644
index 16a9f4f4f40..00000000000
--- a/src/main/runtime/orchestration/structured-session-terminal-view-mail.test.ts
+++ /dev/null
@@ -1,86 +0,0 @@
-import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
-import { OrchestrationDb } from './db'
-import { OrchestrationMailboxDeliveryTarget } from './mailbox-delivery-target'
-import { OrchestrationMailboxOwner, type OrchestrationMailboxLeaf } from './mailbox-owner'
-import { testOrcaSessionId } from '../../../shared/orca-session-address-test-fixture'
-
-const CHAT = testOrcaSessionId('4a1f6c2e-8b3d-4e7a-9c15-0d2b6e8f1a37')
-const VIEW_TAB = 'tab_view'
-const VIEW_LEAF = '77777777-7777-4777-8777-777777777777'
-
-let db: OrchestrationDb
-
-beforeEach(() => {
-  db = new OrchestrationDb(':memory:')
-})
-
-afterEach(() => {
-  db.close()
-})
-
-const viewLeaf: OrchestrationMailboxLeaf = {
-  tabId: VIEW_TAB,
-  leafId: VIEW_LEAF,
-  ptyId: 'pty-view',
-  writable: true,
-  lastAgentStatus: 'idle',
-  lastAgentStatusObservedLive: true,
-  lastOscTitle: null
-}
-
-function owner(boundSessionId: string | null): OrchestrationMailboxOwner {
-  return new OrchestrationMailboxOwner({
-    getDb: () => db,
-    getLeaf: () => viewLeaf,
-    getLeafKey: (tabId, leafId) => `${tabId}::${leafId}`,
-    getTerminalHandleForLeafKey: () => 'term_view',
-    getTerminalProcessIncarnation: () => null,
-    onRoutedMessageTypes: vi.fn(),
-    onForeignMailboxRouted: vi.fn(),
-    getBoundSessionIdForPty: (ptyId) => (ptyId === 'pty-view' ? boundSessionId : null)
-  })
-}
-
-function chatRun(): string {
-  return db.createRun({
-    objective: 'o',
-    coordinatorHandle: null,
-    coordinatorPaneKey: null,
-    coordinatorOrcaSessionId: CHAT
-  }).id
-}
-
-describe("a chat's terminal view reads the chat's mail", () => {
-  it('owns the Run the chat coordinates, which no pane binding names', () => {
-    // The CLI in a terminal view acts as the session, so the Run is bound by Orca session id and the pane
-    // path finds nothing: without this the idle edge of the view never pointed coordinator mail.
-    const runId = chatRun()
-    expect(owner(CHAT).resolve(viewLeaf)).toBe(`run:${runId}`)
-    expect(owner(CHAT).resolve(viewLeaf, `run:${runId}`)).toBe(`run:${runId}`)
-    expect(owner(null).resolve(viewLeaf)).toBe('term_view')
-  })
-
-  it('falls back to the pane for a terminal whose session owns nothing', () => {
-    const runId = db.createRun({
-      objective: 'o',
-      coordinatorHandle: 'term_view',
-      coordinatorPaneKey: `${VIEW_TAB}:${VIEW_LEAF}`
-    }).id
-    expect(owner(CHAT).resolve(viewLeaf)).toBe(`run:${runId}`)
-  })
-
-  it("resolves a chat-coordinated Run's mailbox to the terminal view's handle", () => {
-    const runId = chatRun()
-    const target = new OrchestrationMailboxDeliveryTarget({
-      getDb: () => db,
-      getTerminalHandleForPaneKey: () => null,
-      hasTerminalHandle: (handle) => handle === 'term_view',
-      isStructuredWorkerHandle: () => false,
-      canProbePtyLiveness: () => false,
-      controllerKnowsPtyIsLive: () => true,
-      isLeafPtyProvenAbsent: async () => false,
-      getTerminalViewHandleForSession: (sessionId) => (sessionId === CHAT ? 'term_view' : null)
-    })
-    expect(target.resolveTerminalHandle(`run:${runId}`)).toBe('term_view')
-  })
-})
diff --git a/src/main/runtime/orchestration/structured-worker-group-addressing.test.ts b/src/main/runtime/orchestration/structured-worker-group-addressing.test.ts
index 2f7b0a49eaf..1c5dc4d6435 100644
--- a/src/main/runtime/orchestration/structured-worker-group-addressing.test.ts
+++ b/src/main/runtime/orchestration/structured-worker-group-addressing.test.ts
@@ -56,6 +56,8 @@ function installHost(options: {
   hostRef.current = {
     deps: {
       store: {
+        // No committed /clear: each session is its own lineage's root.
+        listRecords: () => [],
         getRecord: (sessionId: string) =>
           ({
             sessionId,
diff --git a/src/main/runtime/rpc/methods/orchestration-worker-mode-opacity.test.ts b/src/main/runtime/rpc/methods/orchestration-worker-mode-opacity.test.ts
index 199e43fae7b..9531e0f468b 100644
--- a/src/main/runtime/rpc/methods/orchestration-worker-mode-opacity.test.ts
+++ b/src/main/runtime/rpc/methods/orchestration-worker-mode-opacity.test.ts
@@ -12,7 +12,6 @@
  */
 
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
-import { setStructuredAgentSessionHost } from '../../../native-chat/agent-session-wire/structured-agent-session-registry'
 import { OrcaRuntimeService } from '../../orca-runtime'
 import { OrchestrationDb } from '../../orchestration/db'
 import {
@@ -29,6 +28,12 @@ const STRUCTURED_HANDLE = 'structworker_worker'
 const TERMINAL_HANDLE = 'term_worker'
 
 const structuredPreambles: string[] = []
+// The session host the code under test reads; a structural fake, so no host type is claimed.
+const hostRef = vi.hoisted((): { current: unknown } => ({ current: null }))
+
+vi.mock('../../../native-chat/agent-session-wire/structured-agent-session-registry', () => ({
+  getStructuredAgentSessionHost: () => hostRef.current
+}))
 
 vi.mock('./orchestration/worker/worker-topology', async (importOriginal) => ({
   ...(await importOriginal<Record<string, unknown>>()),
@@ -70,7 +75,7 @@ function installStructuredCoordinator(handle: string, sessionId: string): string
     worktreeId: WORKTREE,
     hostScope: { kind: 'local', hostId: 'local' }
   })
-  setStructuredAgentSessionHost({
+  hostRef.current = {
     hasSession: () => true,
     deps: {
       store: {
@@ -83,10 +88,12 @@ function installStructuredCoordinator(handle: string, sessionId: string): string
             deathEvidence: null,
             runtimeFence: 1
           }
-        })
+        }),
+        // No committed /clear: each session is its own lineage's root.
+        listRecords: () => []
       }
     }
-  } as never)
+  }
   return paneKey
 }
 
@@ -150,7 +157,7 @@ describe('a worker cannot tell which mode it is running in', () => {
 
   afterEach(() => {
     db.close()
-    setStructuredAgentSessionHost(null)
+    hostRef.current = null
     structuredWorkerIdentities.clear()
     vi.restoreAllMocks()
   })
diff --git a/src/main/runtime/rpc/methods/orchestration/messaging/recipient-routing.ts b/src/main/runtime/rpc/methods/orchestration/messaging/recipient-routing.ts
index f4e304f3b0c..8828c771876 100644
--- a/src/main/runtime/rpc/methods/orchestration/messaging/recipient-routing.ts
+++ b/src/main/runtime/rpc/methods/orchestration/messaging/recipient-routing.ts
@@ -5,7 +5,7 @@ import type { OrcaRuntimeService } from '../../../../orca-runtime'
 import { resolveOrchestrationParty } from '../../../../orchestration/orchestration-party'
 import { isEquivalentPaneKey } from '../../../../orchestration/db/pane-key-match'
 import { CURRENT_CONTRACT_VERSION } from '../../../../orchestration/db/contract-constants'
-import { readAgentSessionRecordStore } from '../../../../orchestration/structured-session-mail-address'
+import { readAgentSessionRecordStore } from '../../../../orchestration/structured-session-lineage'
 import {
   readSessionRecipient,
   refuseUndeliverableSessionRecipient,
diff --git a/src/main/runtime/rpc/methods/orchestration/messaging/session-recipient.ts b/src/main/runtime/rpc/methods/orchestration/messaging/session-recipient.ts
index 483d388955f..b7e17523689 100644
--- a/src/main/runtime/rpc/methods/orchestration/messaging/session-recipient.ts
+++ b/src/main/runtime/rpc/methods/orchestration/messaging/session-recipient.ts
@@ -21,9 +21,9 @@ import {
 import { ORCHESTRATION_SESSION_CALLER_ERROR_CODES as CODES } from '../../../../../../shared/orchestration-session-caller-codes'
 import {
   lookupOrcaAgentSession,
-  structuredSessionMailReach,
-  type AgentSessionRecordReader
+  structuredSessionMailReach
 } from '../../../../orchestration/structured-session-mail-address'
+import type { AgentSessionRecordReader } from '../../../../orchestration/structured-session-lineage'
 import type { OrchestrationDb } from '../../../../orchestration/db'
 
 /** `address` is the named session's own spelling; the mailbox mail lands in is its identity address. */
diff --git a/src/main/runtime/rpc/orchestration-session-caller.ts b/src/main/runtime/rpc/orchestration-session-caller.ts
index 507fa1ac8c4..0d2253481b4 100644
--- a/src/main/runtime/rpc/orchestration-session-caller.ts
+++ b/src/main/runtime/rpc/orchestration-session-caller.ts
@@ -29,10 +29,8 @@ import {
   resolveOrcaSessionParty,
   resolveOrchestrationParty
 } from '../orchestration/orchestration-party'
-import {
-  lookupOrcaAgentSession,
-  type AgentSessionRecordReader
-} from '../orchestration/structured-session-mail-address'
+import { lookupOrcaAgentSession } from '../orchestration/structured-session-mail-address'
+import { readAgentSessionRecordStore } from '../orchestration/structured-session-lineage'
 import { structuredWorkerHostScope } from '../structured-worker-identity'
 import type { RpcRequest } from './core'
 
diff --git a/src/main/runtime/rpc/orchestration-session-recipient.test.ts b/src/main/runtime/rpc/orchestration-session-recipient.test.ts
index e21d31556d5..f8f2de266d4 100644
--- a/src/main/runtime/rpc/orchestration-session-recipient.test.ts
+++ b/src/main/runtime/rpc/orchestration-session-recipient.test.ts
@@ -7,6 +7,7 @@ import {
 } from '../structured-worker-identity'
 import {
   ADDRESS_X,
+  ADDRESS_Y,
   createSessionCallerHarness,
   idOf,
   isRecord,
@@ -16,6 +17,7 @@ import {
   SESSION_X,
   SESSION_Y,
   sessionRecord,
+  WORKER_HANDLE,
   type SessionCallerHarness
 } from './orchestration-session-caller-test-fixture'
 
@@ -217,3 +219,114 @@ describe('a live structured worker addressed by its session id', () => {
     expect(await flaglessCheck()).toMatchObject({ messages: [{ subject: 'hello' }] })
   })
 })
+
+describe('mail sent to a session address reaches the mailbox that session reads', () => {
+  let h: SessionCallerHarness
+
+  beforeEach(() => {
+    h = createSessionCallerHarness(hostRef)
+  })
+
+  afterEach(() => {
+    h.close()
+    vi.restoreAllMocks()
+  })
+
+  async function as(sessionId: string | undefined, method: string, params: Row): Promise<Row> {
+    return resultOf(await h.dispatch(orchestrationRequest(method, params, { sessionId })))
+  }
+
+  function sendFromTerminal(to: string): Promise<Row> {
+    return as(undefined, 'orchestration.send', { from: WORKER_HANDLE, to, subject: 'hello' })
+  }
+
+  it("files it under the chat's current Run, as a terminal coordinator's pane does", async () => {
+    await as(SESSION_X, 'orchestration.runCreate', { objective: 'first' })
+    const current = idOf(
+      (await as(SESSION_X, 'orchestration.runCreate', { objective: 'next' })).run
+    )
+
+    const { message } = await sendFromTerminal(ADDRESS_X)
+
+    expect(message).toMatchObject({ to_handle: `run:${current}`, run_id: current })
+    expect(await as(SESSION_X, 'orchestration.check', {})).toMatchObject({
+      runId: current,
+      messages: [{ subject: 'hello' }]
+    })
+  })
+
+  it('delivers it to a chat with no Run, which reads its direct mailbox', async () => {
+    const { message } = await sendFromTerminal(ADDRESS_X)
+
+    expect(message).toMatchObject({ to_handle: ADDRESS_X })
+    expect(await as(SESSION_X, 'orchestration.check', {})).toMatchObject({
+      messages: [{ subject: 'hello' }]
+    })
+  })
+
+  it('reaches a chat with no Run after a restart, once the send has started the session host', async () => {
+    // After an app restart the agent-session host starts lazily; routing reads the session record
+    // synchronously, so the send must start the host before it resolves the recipient.
+    const store = hostRef.current
+    hostRef.current = null
+    vi.mocked(h.runtime.ensureStructuredAgentSessionHost).mockImplementation(async () => {
+      hostRef.current = store
+    })
+
+    const { message } = await sendFromTerminal(ADDRESS_X)
+
+    expect(message).toMatchObject({ to_handle: ADDRESS_X })
+  })
+
+  it('refuses an Orca session this host does not run, or has no record of', async () => {
+    h.records.set(
+      SESSION_X,
+      sessionRecord(SESSION_X, { location: { executionHostId: 'ssh:devbox' } })
+    )
+    h.records.delete(SESSION_Y)
+
+    for (const [to, code] of [
+      [ADDRESS_X, 'session_caller_host_boundary'],
+      [ADDRESS_Y, 'session_caller_unknown']
+    ]) {
+      const response = await h.dispatch(
+        orchestrationRequest('orchestration.send', { from: WORKER_HANDLE, to, subject: 's' })
+      )
+      expect(response).toMatchObject({ ok: false, error: { code } })
+    }
+  })
+
+  it("routes a structured worker's session address to the Dispatch it is working", async () => {
+    const handle = mintStructuredWorkerHandle()
+    const paneKey = mintStructuredWorkerPaneKey(SESSION_Y)
+    structuredWorkerIdentities.register({
+      handle,
+      sessionId: SESSION_Y,
+      agent: 'claude',
+      paneKey,
+      processIncarnation: structuredWorkerProcessIncarnation(SESSION_Y),
+      worktreeId: 'wt_1',
+      hostScope: { kind: 'local', hostId: 'local' }
+    })
+    const runId = idOf((await as(SESSION_X, 'orchestration.runCreate', { objective: 'o' })).run)
+    const dispatch = h.db.createDispatchContext({
+      taskId: h.db.createTask({ runId, spec: 'work' }).id,
+      assigneeHandle: handle,
+      assigneePaneKey: paneKey,
+      processIncarnation: structuredWorkerProcessIncarnation(SESSION_Y),
+      creator: { kind: 'session', orcaSessionId: SESSION_X },
+      maxDepth: Number.MAX_SAFE_INTEGER
+    })
+
+    const { message } = await as(SESSION_X, 'orchestration.send', {
+      to: ADDRESS_Y,
+      subject: 'to the worker'
+    })
+
+    expect(message).toMatchObject({ to_handle: `dispatch:${dispatch.id}`, run_id: runId })
+    expect(await as(SESSION_Y, 'orchestration.check', { peek: true })).toMatchObject({
+      dispatchId: dispatch.id,
+      messages: [{ subject: 'to the worker' }]
+    })
+  })
+})