diff --git a/src/features/background-agent/session-existence.test.ts b/src/features/background-agent/session-existence.test.ts
index f0cdbed52..44b978b36 100644
--- a/src/features/background-agent/session-existence.test.ts
+++ b/src/features/background-agent/session-existence.test.ts
@@ -1,7 +1,7 @@
 import { describe, expect, mock, test } from "bun:test"
 
 import type { OpencodeClient } from "./opencode-client"
-import { verifySessionExists } from "./session-existence"
+import { checkSessionExistence, verifySessionExists } from "./session-existence"
 import { unsafeTestValue } from "../../../test-support/unsafe-test-value"
 
 describe("verifySessionExists", () => {
@@ -24,4 +24,20 @@ describe("verifySessionExists", () => {
       query: { directory: "/project/root" },
     })
   })
+
+  test("classifies transient lookup errors as unknown", async () => {
+    const get = mock(async () => ({
+      error: { message: "Network timeout", status: 500 },
+      data: undefined,
+    }))
+    const client = unsafeTestValue<OpencodeClient>({
+      session: {
+        get,
+      },
+    })
+
+    const result = await checkSessionExistence(client, "session-123")
+
+    expect(result).toBe("unknown")
+  })
 })
diff --git a/src/features/background-agent/session-existence.ts b/src/features/background-agent/session-existence.ts
index 789b01899..d61544f9f 100644
--- a/src/features/background-agent/session-existence.ts
+++ b/src/features/background-agent/session-existence.ts
@@ -1,6 +1,7 @@
 import type { OpencodeClient } from "./opencode-client"
 
 export const MIN_SESSION_GONE_POLLS = 3
+export type SessionExistenceStatus = "exists" | "missing" | "unknown"
 
 function extractErrorMessage(error: unknown): string | undefined {
   if (typeof error === "string") {
@@ -35,11 +36,11 @@ function isSessionNotFoundError(error: unknown): boolean {
   return message.includes("not found") || message.includes("missing")
 }
 
-export async function verifySessionExists(
+export async function checkSessionExistence(
   client: OpencodeClient,
   sessionID: string,
   directory?: string
-): Promise<boolean> {
+): Promise<SessionExistenceStatus> {
   try {
     const response = await client.session.get({
       path: { id: sessionID },
@@ -47,11 +48,19 @@ export async function verifySessionExists(
     })
 
     if (response.error !== undefined && response.error !== null) {
-      return !isSessionNotFoundError(response.error)
+      return isSessionNotFoundError(response.error) ? "missing" : "unknown"
     }
 
-    return response.data != null
+    return response.data != null ? "exists" : "missing"
   } catch (error) {
-    return !isSessionNotFoundError(error)
+    return isSessionNotFoundError(error) ? "missing" : "unknown"
   }
 }
+
+export async function verifySessionExists(
+  client: OpencodeClient,
+  sessionID: string,
+  directory?: string
+): Promise<boolean> {
+  return await checkSessionExistence(client, sessionID, directory) !== "missing"
+}
diff --git a/src/features/background-agent/task-poller.test.ts b/src/features/background-agent/task-poller.test.ts
index b08f78c59..da4d2da1e 100644
--- a/src/features/background-agent/task-poller.test.ts
+++ b/src/features/background-agent/task-poller.test.ts
@@ -472,7 +472,7 @@ describe("checkAndInterruptStaleTasks", () => {
     expect(mockClient.session.get).toHaveBeenCalledWith({ path: { id: "ses-1" } })
   })
 
-  it("should NOT cancel task when session.get returns a transient error response", async () => {
+  it("should NOT cancel or reset missed polls when session.get returns a transient error response", async () => {
     //#given - repeated missing polls but lookup failed with a retryable transport error
     const task = createRunningTask({
       startedAt: new Date(Date.now() - 300_000),
@@ -500,7 +500,7 @@ describe("checkAndInterruptStaleTasks", () => {
 
     //#then
     expect(task.status).toBe("running")
-    expect(task.consecutiveMissedPolls).toBe(0)
+    expect(task.consecutiveMissedPolls).toBe(3)
     expect(mockClient.session.get).toHaveBeenCalledWith({ path: { id: "ses-1" } })
   })
 
diff --git a/src/features/background-agent/task-poller.ts b/src/features/background-agent/task-poller.ts
index 9f0e0362a..d80a16cfa 100644
--- a/src/features/background-agent/task-poller.ts
+++ b/src/features/background-agent/task-poller.ts
@@ -16,7 +16,7 @@ import {
 } from "./constants"
 import { abortWithTimeout } from "./abort-with-timeout"
 import { removeTaskToastTracking } from "./remove-task-toast-tracking"
-import { MIN_SESSION_GONE_POLLS, verifySessionExists } from "./session-existence"
+import { checkSessionExistence, MIN_SESSION_GONE_POLLS } from "./session-existence"
 
 import { isActiveSessionStatus } from "./session-status-classifier"
 import { getSessionActivityFromClient, type SessionActivityResolver } from "./session-activity"
@@ -178,9 +178,13 @@ export async function checkAndInterruptStaleTasks(args: {
         if (activityRefresh.type === "activity" && now - activityRefresh.activityTime <= effectiveTimeout) continue
       }
 
-      if (sessionGone && await verifySessionExists(client, sessionID, directory)) {
-        task.consecutiveMissedPolls = 0
-        continue
+      if (sessionGone) {
+        const existence = await checkSessionExistence(client, sessionID, directory)
+        if (existence === "exists") {
+          task.consecutiveMissedPolls = 0
+          continue
+        }
+        if (existence === "unknown") continue
       }
 
       const staleMinutes = Math.round(runtime / 60000)
@@ -228,9 +232,13 @@ export async function checkAndInterruptStaleTasks(args: {
 
     if (task.status !== "running") continue
 
-    if (sessionGone && await verifySessionExists(client, sessionID, directory)) {
-      task.consecutiveMissedPolls = 0
-      continue
+    if (sessionGone) {
+      const existence = await checkSessionExistence(client, sessionID, directory)
+      if (existence === "exists") {
+        task.consecutiveMissedPolls = 0
+        continue
+      }
+      if (existence === "unknown") continue
     }
 
     const staleMinutes = Math.round(timeSinceLastUpdate / 60000)
diff --git a/src/plugin-handlers/agent-key-remapper.test.ts b/src/plugin-handlers/agent-key-remapper.test.ts
index a39c73566..8e62bf64d 100644
--- a/src/plugin-handlers/agent-key-remapper.test.ts
+++ b/src/plugin-handlers/agent-key-remapper.test.ts
@@ -231,7 +231,7 @@ describe("remapAgentKeysToDisplayNames", () => {
       const result = remapAgentKeysToDisplayNames(agents, overrides)
 
       // then the legacy AGENT_DISPLAY_NAMES value is used
-      expect(result["Sisyphus - Ultraworker"]).toBeDefined()
+      expect(result[getAgentListDisplayName("sisyphus")]).toBeDefined()
       expect(result["总指挥"]).toBeUndefined()
     })
 
@@ -245,7 +245,7 @@ describe("remapAgentKeysToDisplayNames", () => {
       const result = remapAgentKeysToDisplayNames(agents)
 
       // then the legacy AGENT_DISPLAY_NAMES value is used
-      expect(result["Sisyphus - Ultraworker"]).toBeDefined()
+      expect(result[getAgentListDisplayName("sisyphus")]).toBeDefined()
     })
   })
 })