Split two files back under the line cap after the merge

Merging main put both one effective line over 300, and the cap forbids a
disable or a shave. The wire module's refusal vocabulary moves to its own file
and is re-exported, so its consumers are untouched; the host's four thin
mutation delegates move next to the functions they call.

src/main/native-chat/agent-session-wire/structured-agent-session-host-mutations.ts

@@ -193,3 +193,25 @@ export async function settleStructuredAgentSessionLateDispatch(
   })
   context.publish(input.sessionId, session.journal)
 }
+
+/** The host's thin mutation surface. Each call re-reads the context, so a session
+ *  map or fence that moves between calls is never captured by a stale closure. */
+export function structuredAgentSessionMutationDelegates(
+  context: () => StructuredAgentSessionMutationContext
+) {
+  return {
+    cancel: (
+      caller: StructuredAgentSessionCaller,
+      params: Parameters<typeof cancelStructuredAgentSessionTurn>[2]
+    ) => cancelStructuredAgentSessionTurn(context(), caller, params),
+    respondToPrompt: (
+      caller: StructuredAgentSessionCaller,
+      params: Parameters<typeof respondToStructuredAgentSessionPrompt>[2]
+    ) => respondToStructuredAgentSessionPrompt(context(), caller, params),
+    setOption: (
+      caller: StructuredAgentSessionCaller,
+      params: Parameters<typeof setStructuredAgentSessionOption>[2]
+    ) => setStructuredAgentSessionOption(context(), caller, params),
+    readOptions: (sessionId: string) => readStructuredAgentSessionOptions(context(), sessionId)
+  }
+}

src/main/native-chat/agent-session-wire/structured-agent-session-host.ts

@@ -36,10 +36,7 @@ import type {
 import type { StructuredAgentSessionAttachContext } from './structured-agent-session-attach-context'
 import { listStructuredAgentSessionTabs } from './structured-agent-session-host-tabs'
 import {
-  cancelStructuredAgentSessionTurn,
-  readStructuredAgentSessionOptions,
-  respondToStructuredAgentSessionPrompt,
-  setStructuredAgentSessionOption,
+  structuredAgentSessionMutationDelegates,
   settleStructuredAgentSessionLateDispatch,
   type StructuredAgentSessionMutationContext
 } from './structured-agent-session-host-mutations'
@@ -283,23 +280,11 @@ export class StructuredAgentSessionHost {
   send = (...args: Parameters<StructuredConversationCommandController['send']>) =>
     this.conversationCommands.send(...args)
 
-  cancel = (
-    caller: StructuredAgentSessionCaller,
-    params: Parameters<typeof cancelStructuredAgentSessionTurn>[2]
-  ): ReturnType<typeof cancelStructuredAgentSessionTurn> =>
-    cancelStructuredAgentSessionTurn(this.mutationContext(), caller, params)
-
-  respondToPrompt = (
-    caller: StructuredAgentSessionCaller,
-    params: Parameters<typeof respondToStructuredAgentSessionPrompt>[2]
-  ): ReturnType<typeof respondToStructuredAgentSessionPrompt> =>
-    respondToStructuredAgentSessionPrompt(this.mutationContext(), caller, params)
-
-  setOption = (
-    caller: StructuredAgentSessionCaller,
-    params: Parameters<typeof setStructuredAgentSessionOption>[2]
-  ): ReturnType<typeof setStructuredAgentSessionOption> =>
-    setStructuredAgentSessionOption(this.mutationContext(), caller, params)
+  private mutations = structuredAgentSessionMutationDelegates(() => this.mutationContext())
+  cancel = this.mutations.cancel
+  respondToPrompt = this.mutations.respondToPrompt
+  setOption = this.mutations.setOption
+  readOptions = this.mutations.readOptions
 
   requestHandoff = (
     caller: StructuredAgentSessionCaller,
@@ -307,9 +292,6 @@ export class StructuredAgentSessionHost {
   ): Promise<SessionWire.AgentSessionMutationResult<SessionWire.AgentSessionHandoffResult>> =>
     this.handoffs.request(caller.callerKey, params)
 
-  readOptions = (sessionId: string): Promise<SessionWire.AgentSessionOptionsResult> =>
-    readStructuredAgentSessionOptions(this.mutationContext(), sessionId)
-
   rewind = (caller: StructuredAgentSessionCaller, params: AgentSessionRewindParams) =>
     rewindStructuredAgentSession(this.mutationContext(), this.attachContext(), caller, params)
 

src/shared/agent-session-wire-refusals.ts

@@ -0,0 +1,46 @@
+// How the host declines an `agentSession.*` mutation: the closed code list, its
+// narrowing guard, and the refusal body a client reads.
+
+import type { AgentJournalResolution } from './agent-session-journal-types'
+import type { AgentSessionRewindReason } from './agent-session-rewind'
+
+export const AGENT_SESSION_WIRE_REFUSAL_CODES = [
+  'structured_agent_session_unsupported',
+  'agent_session_checkpoint_stale',
+  'agent_session_conflict',
+  'agent_session_ownership_unknown',
+  'agent_session_operation_conflict',
+  'agent_session_operation_expired',
+  'agent_session_operation_capacity',
+  'agent_session_operation_invalid',
+  'agent_session_operation_unknown',
+  'agent_session_item_revision_stale',
+  'agent_session_already_resolved',
+  'agent_session_identity_required',
+  'agent_session_journal_unreadable',
+  'execution_owner_reconciling'
+] as const
+export type AgentSessionWireRefusalCode = (typeof AGENT_SESSION_WIRE_REFUSAL_CODES)[number]
+
+/** For a host path that raises its refusal as the thrown code. Narrowing through this keeps an
+ *  unrelated fault from being reported to the client as a tidy, wrong refusal. */
+export function isAgentSessionWireRefusalCode(
+  value: unknown
+): value is AgentSessionWireRefusalCode {
+  return (
+    typeof value === 'string' &&
+    (AGENT_SESSION_WIRE_REFUSAL_CODES as readonly string[]).includes(value)
+  )
+}
+
+export type AgentSessionWireRefusal = {
+  rewindReason?: AgentSessionRewindReason
+  code: AgentSessionWireRefusalCode
+  message: string
+  /** On a stale fence, so the client can retry without another round trip. */
+  currentFence?: number
+  /** On a lost compare-and-set: the winning answer and who gave it. */
+  resolution?: AgentJournalResolution
+  /** On a lost compare-and-set: the revision the host actually holds. */
+  currentRevision?: number
+}

src/shared/agent-session-wire.ts

@@ -1,4 +1,7 @@
 import type { AgentSessionRewindReason, AgentSessionRewindSupport } from './agent-session-rewind'
+import type { AgentSessionWireRefusal } from './agent-session-wire-refusals'
+
+export * from './agent-session-wire-refusals'
 import type { AgentSessionConversationCommand } from './agent-session-conversation-command'
 // ─── Structured agent-session wire contract ─────────────────────────────────
 // The shapes `agentSession.*` accepts and publishes. Phase 2 builds provider
@@ -302,47 +305,6 @@ export type AgentSessionMutationEnvelope = {
   payloadFingerprint: string
 }
 
-export const AGENT_SESSION_WIRE_REFUSAL_CODES = [
-  'structured_agent_session_unsupported',
-  'agent_session_checkpoint_stale',
-  'agent_session_conflict',
-  'agent_session_ownership_unknown',
-  'agent_session_operation_conflict',
-  'agent_session_operation_expired',
-  'agent_session_operation_capacity',
-  'agent_session_operation_invalid',
-  'agent_session_operation_unknown',
-  'agent_session_item_revision_stale',
-  'agent_session_already_resolved',
-  'agent_session_identity_required',
-  'agent_session_journal_unreadable',
-  'execution_owner_reconciling'
-] as const
-export type AgentSessionWireRefusalCode = (typeof AGENT_SESSION_WIRE_REFUSAL_CODES)[number]
-
-/** For a host path that raises its refusal as the thrown code. Narrowing through this keeps an
- *  unrelated fault from being reported to the client as a tidy, wrong refusal. */
-export function isAgentSessionWireRefusalCode(
-  value: unknown
-): value is AgentSessionWireRefusalCode {
-  return (
-    typeof value === 'string' &&
-    (AGENT_SESSION_WIRE_REFUSAL_CODES as readonly string[]).includes(value)
-  )
-}
-
-export type AgentSessionWireRefusal = {
-  rewindReason?: AgentSessionRewindReason
-  code: AgentSessionWireRefusalCode
-  message: string
-  /** On a stale fence, so the client can retry without another round trip. */
-  currentFence?: number
-  /** On a lost compare-and-set: the winning answer and who gave it. */
-  resolution?: AgentJournalResolution
-  /** On a lost compare-and-set: the revision the host actually holds. */
-  currentRevision?: number
-}
-
 export type AgentSessionMutationResult<TValue> =
   | {
       ok: true