diff --git a/src/main/pi/agent-status-extension-source.test.ts b/src/main/pi/agent-status-extension-source.test.ts
index 3bae53f6cf6..e5b610a34c5 100644
--- a/src/main/pi/agent-status-extension-source.test.ts
+++ b/src/main/pi/agent-status-extension-source.test.ts
@@ -6,7 +6,13 @@ describe('getPiAgentStatusExtensionSource', () => {
   it('registers Prime hooks only in the event-emitting daemon worker', () => {
     const frontend = createHarness({
       kind: 'prime-agent',
-      env: { PRIME_AGENT_INTERNAL_DAEMON_WORKER: undefined }
+      env: {
+        PRIME_AGENT_INTERNAL_DAEMON_WORKER: undefined,
+        ORCA_PRIME_AGENT_STATUS_OWNED: String(SELF_PID - 1)
+      },
+      killImpl: () => {
+        throw Object.assign(new Error('ESRCH'), { code: 'ESRCH' })
+      }
     })
     const worker = createHarness({
       kind: 'prime-agent',
@@ -14,7 +20,8 @@ describe('getPiAgentStatusExtensionSource', () => {
     })
 
     expect(frontend.handlers).toEqual({})
-    expect(frontend.processEnv.ORCA_PI_STATUS_OWNED).toBeUndefined()
+    expect(frontend.killMock).not.toHaveBeenCalled()
+    expect(frontend.processEnv.ORCA_PRIME_AGENT_STATUS_OWNED).toBe(String(SELF_PID - 1))
     expect(worker.handlers.agent_start).toBeTypeOf('function')
     expect(worker.processEnv.ORCA_PRIME_AGENT_STATUS_OWNED).toBe(String(SELF_PID))
   })
@@ -322,6 +329,30 @@ describe('getPiAgentStatusExtensionSource', () => {
     expect(harness.processEnv.ORCA_PI_STATUS_OWNED).toBe(String(SELF_PID))
   })
 
+  it('claims the pane when the inherited owner PID exceeds safe integer precision', () => {
+    const harness = createHarness({
+      kind: 'pi',
+      pid: SELF_PID,
+      env: { ORCA_PI_STATUS_OWNED: '99999999999999999999999' }
+    })
+
+    expect(harness.killMock).not.toHaveBeenCalled()
+    expect(harness.handlers.agent_end).toBeTypeOf('function')
+    expect(harness.processEnv.ORCA_PI_STATUS_OWNED).toBe(String(SELF_PID))
+  })
+
+  it('claims the pane when the inherited owner PID exceeds the process API range', () => {
+    const harness = createHarness({
+      kind: 'pi',
+      pid: SELF_PID,
+      env: { ORCA_PI_STATUS_OWNED: String(2 ** 31) }
+    })
+
+    expect(harness.killMock).not.toHaveBeenCalled()
+    expect(harness.handlers.agent_end).toBeTypeOf('function')
+    expect(harness.processEnv.ORCA_PI_STATUS_OWNED).toBe(String(SELF_PID))
+  })
+
   it.each(['pi', 'omp', 'prime-agent'] as const)(
     'registers no status handlers for a nested %s subagent process',
     (kind) => {
diff --git a/src/main/pi/agent-status-handler-source.ts b/src/main/pi/agent-status-handler-source.ts
index b9c4b7583ae..f4b417d4d01 100644
--- a/src/main/pi/agent-status-handler-source.ts
+++ b/src/main/pi/agent-status-handler-source.ts
@@ -66,7 +66,7 @@ export function getPiAgentStatusHandlerSourceLines(kind: PiAgentKind): string[]
     '// import (the extension loads inside pi/omp with no Orca deps).',
     'function isStatusOwnerAlive(pid: string): boolean {',
     '  const parsed = Number(pid)',
-    '  if (!Number.isInteger(parsed) || parsed < 1) return false',
+    '  if (!Number.isSafeInteger(parsed) || parsed < 1 || parsed > 0x7fffffff) return false',
     "  if (typeof process.kill !== 'function') return true",
     '  try {',
     '    process.kill(parsed, 0)',