diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-attach.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-attach.ts
index 38595d4e6eb..2e42ffe9893 100644
--- a/src/main/native-chat/agent-session-wire/structured-agent-session-attach.ts
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-attach.ts
@@ -324,7 +324,6 @@ export function reserveRequestFor(input: {
       : {}),
     ...(authority.launchArgs ? { launchArgs: authority.launchArgs } : {}),
     ...(authority.launchEnv ? { launchEnv: authority.launchEnv } : {}),
-    runtimeKind: params.runtimeKind,
     ...(params.adopt
       ? {
           // Fence 1 is a new record's first, and the owner probe requires the head link to carry
diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-claude-root-exit.test.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-claude-root-exit.test.ts
index d83ca49a79c..c449711e745 100644
--- a/src/main/native-chat/agent-session-wire/structured-agent-session-claude-root-exit.test.ts
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-claude-root-exit.test.ts
@@ -43,7 +43,6 @@ describe('Claude root-exit eviction', () => {
       },
       provider: 'claude',
       accountHome: { variable: 'CLAUDE_CONFIG_DIR', path: root },
-      runtimeKind: 'native',
       expectedFence: null,
       spawnToken: 'spawn-1',
       claimKeyId: 'key-1',
diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-lease-renewer.test.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-lease-renewer.test.ts
index f8323d40fe1..f969e3c0bbf 100644
--- a/src/main/native-chat/agent-session-wire/structured-agent-session-lease-renewer.test.ts
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-lease-renewer.test.ts
@@ -26,7 +26,6 @@ async function liveStore(): Promise<AgentSessionRecordStore> {
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: root },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-renewal',
     claimKeyId: 'key-1',
diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-recovery-resolution.test.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-recovery-resolution.test.ts
index 105521bbf98..b647ed01883 100644
--- a/src/main/native-chat/agent-session-wire/structured-agent-session-recovery-resolution.test.ts
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-recovery-resolution.test.ts
@@ -48,7 +48,6 @@ async function reserve(store: AgentSessionRecordStore) {
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: '/tmp/codex' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-recovery',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-backup-recovery.test.ts b/src/main/runtime/agent-session-backup-recovery.test.ts
index 02866a49fb3..3c6ac2dcecf 100644
--- a/src/main/runtime/agent-session-backup-recovery.test.ts
+++ b/src/main/runtime/agent-session-backup-recovery.test.ts
@@ -27,7 +27,6 @@ async function seedLiveSession(sessionId: string): Promise<number> {
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: join(root, 'codex-home') },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'seed-live',
     claimKeyId: 'key-1',
@@ -101,7 +100,6 @@ async function seedSession(sessionId: string): Promise<number> {
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: join(root, 'codex-home') },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'seed',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-conversation-name-store.test.ts b/src/main/runtime/agent-session-conversation-name-store.test.ts
index ce5d3fd2621..7310c3fff89 100644
--- a/src/main/runtime/agent-session-conversation-name-store.test.ts
+++ b/src/main/runtime/agent-session-conversation-name-store.test.ts
@@ -30,7 +30,6 @@ const reserveRequest = (): AgentSessionReserveRequest => ({
   location: NATIVE,
   provider: 'claude',
   accountHome: { variable: 'CLAUDE_CONFIG_DIR', path: '/home/dev/.claude-work' },
-  runtimeKind: 'native',
   expectedFence: null,
   spawnToken: 'spawn-a',
   claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-launch-env-admission.test.ts b/src/main/runtime/agent-session-launch-env-admission.test.ts
index 97b0f95f2b6..51b2fe64daf 100644
--- a/src/main/runtime/agent-session-launch-env-admission.test.ts
+++ b/src/main/runtime/agent-session-launch-env-admission.test.ts
@@ -20,7 +20,6 @@ function request(overrides: Partial<AgentSessionReserveRequest> = {}): AgentSess
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: '/home/dev/.codex' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-a',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-launch-env-backfill.test.ts b/src/main/runtime/agent-session-launch-env-backfill.test.ts
index c95705f2aa5..50cf9e6b35c 100644
--- a/src/main/runtime/agent-session-launch-env-backfill.test.ts
+++ b/src/main/runtime/agent-session-launch-env-backfill.test.ts
@@ -20,7 +20,6 @@ function request(overrides: Partial<AgentSessionReserveRequest> = {}): AgentSess
     },
     provider: 'claude',
     accountHome: { variable: 'CLAUDE_CONFIG_DIR', path: '/home/dev/.claude' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-a',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-lease-renewal.test.ts b/src/main/runtime/agent-session-lease-renewal.test.ts
index 0c1c88db003..b2788f81602 100644
--- a/src/main/runtime/agent-session-lease-renewal.test.ts
+++ b/src/main/runtime/agent-session-lease-renewal.test.ts
@@ -27,7 +27,6 @@ async function establishOwner(
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: directory },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken,
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-lease-transitions.ts b/src/main/runtime/agent-session-lease-transitions.ts
index 92c0ae27465..580fbeda255 100644
--- a/src/main/runtime/agent-session-lease-transitions.ts
+++ b/src/main/runtime/agent-session-lease-transitions.ts
@@ -19,13 +19,11 @@ import {
 import type {
   AgentSessionJournalCheckpoint,
   AgentSessionLease,
-  AgentSessionOwnerRuntimeKind,
   AgentSessionProcessIdentity,
   AgentSessionRecord
 } from '../../shared/agent-session-record'
 
 export type AgentSessionReservation = {
-  runtimeKind: AgentSessionOwnerRuntimeKind
   spawnToken: string
   claimKeyId: string
   handoffOperationId: string | null
@@ -76,7 +74,7 @@ export function reserveAgentSessionOwner(args: {
     disposition: 'reserved',
     record: withLease(record, {
       ...record.lease,
-      runtimeKind: reservation.runtimeKind,
+      runtimeKind: 'native',
       runtimeFence: decision.nextFence,
       // Why: a reserved owner is not yet a writer; it may only talk to the provider to prove resume.
       handoffStage: 'new-owner-proving',
diff --git a/src/main/runtime/agent-session-record-options.test.ts b/src/main/runtime/agent-session-record-options.test.ts
index 5795763d96c..5ba7c41cffc 100644
--- a/src/main/runtime/agent-session-record-options.test.ts
+++ b/src/main/runtime/agent-session-record-options.test.ts
@@ -57,7 +57,6 @@ it('persists resumed provider options atomically with owner proof', async () =>
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: '/accounts/codex' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-options',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-record-store-legacy-handoff-lease.test.ts b/src/main/runtime/agent-session-record-store-legacy-handoff-lease.test.ts
index 997e32fb7cb..77d94766212 100644
--- a/src/main/runtime/agent-session-record-store-legacy-handoff-lease.test.ts
+++ b/src/main/runtime/agent-session-record-store-legacy-handoff-lease.test.ts
@@ -44,7 +44,6 @@ async function persistLiveOwner(): Promise<void> {
     },
     provider: 'claude',
     accountHome: { variable: 'CLAUDE_CONFIG_DIR', path: '/home/dev/.claude-work' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-a',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-record-store-security.test.ts b/src/main/runtime/agent-session-record-store-security.test.ts
index f70145cf5a2..63ee368f873 100644
--- a/src/main/runtime/agent-session-record-store-security.test.ts
+++ b/src/main/runtime/agent-session-record-store-security.test.ts
@@ -20,7 +20,6 @@ function reserveRequest(): AgentSessionReserveRequest {
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: '/accounts/created' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-created',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-record-store-surface-tab-id.test.ts b/src/main/runtime/agent-session-record-store-surface-tab-id.test.ts
index 20ee4b402fd..f9603e7a86b 100644
--- a/src/main/runtime/agent-session-record-store-surface-tab-id.test.ts
+++ b/src/main/runtime/agent-session-record-store-surface-tab-id.test.ts
@@ -48,7 +48,6 @@ function reserveRequest(
     location: NATIVE,
     provider: 'claude',
     accountHome: { variable: 'CLAUDE_CONFIG_DIR', path: '/home/dev/.claude-work' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-a',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-record-store.test.ts b/src/main/runtime/agent-session-record-store.test.ts
index d3525de2de9..65d689503c2 100644
--- a/src/main/runtime/agent-session-record-store.test.ts
+++ b/src/main/runtime/agent-session-record-store.test.ts
@@ -57,7 +57,6 @@ function reserveRequest(
     location: NATIVE,
     provider: 'claude',
     accountHome: { variable: 'CLAUDE_CONFIG_DIR', path: '/home/dev/.claude-work' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-a',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-record-unsupported-schema.test.ts b/src/main/runtime/agent-session-record-unsupported-schema.test.ts
index 1f807870682..dd0a9dcd28d 100644
--- a/src/main/runtime/agent-session-record-unsupported-schema.test.ts
+++ b/src/main/runtime/agent-session-record-unsupported-schema.test.ts
@@ -25,7 +25,6 @@ function reserveRequest(): AgentSessionReserveRequest {
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: '/home/user/.codex' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-new',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-reservation-admission.test.ts b/src/main/runtime/agent-session-reservation-admission.test.ts
index 30d54a108c9..83e9c610056 100644
--- a/src/main/runtime/agent-session-reservation-admission.test.ts
+++ b/src/main/runtime/agent-session-reservation-admission.test.ts
@@ -50,7 +50,6 @@ function reserveRequest(
     location: LOCATION,
     provider: 'claude',
     accountHome: { variable: 'CLAUDE_CONFIG_DIR', path: '/home/dev/.claude' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-a',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-reservation-admission.ts b/src/main/runtime/agent-session-reservation-admission.ts
index d7a84f6ef69..4bd3bf9b4db 100644
--- a/src/main/runtime/agent-session-reservation-admission.ts
+++ b/src/main/runtime/agent-session-reservation-admission.ts
@@ -62,7 +62,6 @@ export type AgentSessionReserveRequest = {
   /** Set only when this create adopts an existing provider conversation. Seeds the handle chain so
    *  the adapter resumes; without it a new record has never proved a thread and starts a fresh one. */
   adoptedHandleLink?: AgentSessionProviderHandleLink
-  runtimeKind: AgentSessionReservation['runtimeKind']
   /** Null when the session does not exist yet; otherwise the fence the caller last observed. */
   expectedFence: number | null
   /** A supplier is invoked only when this operation wins a new reservation. */
@@ -154,7 +153,6 @@ export function applyAgentSessionReservation(
     throw new Error('agent_session_options_invalid')
   }
   const reservation: AgentSessionReservation = {
-    runtimeKind: request.runtimeKind,
     spawnToken:
       typeof request.spawnToken === 'function' ? request.spawnToken() : request.spawnToken,
     claimKeyId: request.claimKeyId,
@@ -283,7 +281,7 @@ function createAgentSessionRecord(
     updatedAt: request.now,
     lease: {
       sessionId: request.sessionId,
-      runtimeKind: reservation.runtimeKind,
+      runtimeKind: 'native',
       // Why: fence 1 is the first reservation; 0 is reserved for "no owner has ever existed".
       runtimeFence: 1,
       handoffStage: 'new-owner-proving',
diff --git a/src/main/runtime/agent-session-unreadable-record-salvage.test.ts b/src/main/runtime/agent-session-unreadable-record-salvage.test.ts
index 0d44d88d82b..cde4091d7eb 100644
--- a/src/main/runtime/agent-session-unreadable-record-salvage.test.ts
+++ b/src/main/runtime/agent-session-unreadable-record-salvage.test.ts
@@ -34,7 +34,6 @@ function reserveRequest(
     },
     provider: 'claude',
     accountHome: { variable: 'CLAUDE_CONFIG_DIR', path: '/home/dev/.claude-work' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: 'spawn-a',
     claimKeyId: 'key-1',
diff --git a/src/main/runtime/agent-session-unsaved-creation-supersession.test.ts b/src/main/runtime/agent-session-unsaved-creation-supersession.test.ts
index ec2a1e82e92..50d27baa57a 100644
--- a/src/main/runtime/agent-session-unsaved-creation-supersession.test.ts
+++ b/src/main/runtime/agent-session-unsaved-creation-supersession.test.ts
@@ -26,7 +26,6 @@ function reserveRequest(
     },
     provider: 'codex',
     accountHome: { variable: 'CODEX_HOME', path: '/home/dev/.codex' },
-    runtimeKind: 'native',
     expectedFence: null,
     spawnToken: `spawn-${operations}`,
     claimKeyId: 'key-1',