diff --git a/src/features/background-agent/manager.polling.session-status-unavailable.test.ts b/src/features/background-agent/manager.polling.session-status-unavailable.test.ts
new file mode 100644
index 000000000..ce6cc907c
--- /dev/null
+++ b/src/features/background-agent/manager.polling.session-status-unavailable.test.ts
@@ -0,0 +1,115 @@
+/// <reference types="bun-types" />
+
+import { describe, expect, test } from "bun:test"
+import { tmpdir } from "node:os"
+import type { PluginInput } from "@opencode-ai/plugin"
+import { BackgroundManager } from "./manager"
+import { MIN_SESSION_GONE_POLLS } from "./session-existence"
+import type { BackgroundTask } from "./types"
+
+type SessionStatus = { type: string }
+type SessionStatusResponse = { data: Record<string, SessionStatus> }
+type SessionOverrides = {
+  status?: (() => Promise<SessionStatusResponse>) | undefined
+  abort?: () => Promise<object>
+}
+
+function createRunningTask(sessionId: string): BackgroundTask {
+  return {
+    id: `bg_test_${sessionId}`,
+    sessionId,
+    parentSessionId: "parent-session",
+    parentMessageId: "parent-message",
+    description: "test task",
+    prompt: "test prompt",
+    agent: "explore",
+    status: "running",
+    startedAt: new Date(),
+    progress: { toolCalls: 0, lastUpdate: new Date() },
+  }
+}
+
+function createManager(overrides: SessionOverrides): BackgroundManager {
+  const session = {
+    ...(overrides.status === undefined ? {} : { status: overrides.status }),
+    get: async () => ({ data: { id: "session" } }),
+    prompt: async () => ({}),
+    promptAsync: async () => ({}),
+    abort: overrides.abort ?? (async () => ({})),
+    todo: async () => ({ data: [] }),
+    messages: async () => ({
+      data: [{
+        info: { role: "assistant", finish: "end_turn", id: "message-2" },
+        parts: [{ type: "text", text: "done" }],
+      }],
+    }),
+  }
+  const client = { session }
+
+  return new BackgroundManager({
+    pluginContext: { client, directory: tmpdir() } as PluginInput,
+    enableParentSessionNotifications: false,
+  })
+}
+
+async function poll(manager: BackgroundManager, cycles: number): Promise<void> {
+  for (let count = 0; count < cycles; count += 1) {
+    await manager["pollRunningTasks"]()
+  }
+}
+
+function injectTask(manager: BackgroundManager, task: BackgroundTask): void {
+  manager["tasks"].set(task.id, task)
+}
+
+describe("BackgroundManager pollRunningTasks when session status registry is unavailable", () => {
+  test("keeps running tasks active and does not increment missed polls when status is unavailable or throws", async () => {
+    const cases: Array<{ name: string; status?: () => Promise<SessionStatusResponse> }> = [
+      { name: "missing status method" },
+      { name: "throwing status method", status: async () => { throw new Error("status unavailable") } },
+    ]
+
+    for (const testCase of cases) {
+      // given
+      let abortCallCount = 0
+      const manager = createManager({
+        status: testCase.status,
+        abort: async () => {
+          abortCallCount += 1
+          return {}
+        },
+      })
+      const task = createRunningTask(`ses-${testCase.name.replaceAll(" ", "-")}`)
+      injectTask(manager, task)
+
+      // when
+      await poll(manager, MIN_SESSION_GONE_POLLS + 1)
+
+      // then
+      expect(task.status).toBe("running")
+      expect(task.completedAt).toBeUndefined()
+      expect(task.error).toBeUndefined()
+      expect(task.consecutiveMissedPolls ?? 0).toBe(0)
+      expect(abortCallCount).toBe(0)
+
+      await manager.shutdown()
+    }
+  })
+
+  test("completes a task when a reliable status response omits the session", async () => {
+    // given
+    const manager = createManager({
+      status: async () => ({ data: {} }),
+    })
+    const task = createRunningTask("ses-gone-after-reliable-status")
+    injectTask(manager, task)
+
+    // when
+    await poll(manager, MIN_SESSION_GONE_POLLS)
+    await manager.shutdown()
+
+    // then
+    expect(task.status).toBe("completed")
+    expect(task.completedAt).toBeDefined()
+  })
+})
diff --git a/src/features/background-agent/manager.polling.test.ts b/src/features/background-agent/manager.polling.test.ts
index 3bcceaf13..b436f62be 100644
--- a/src/features/background-agent/manager.polling.test.ts
+++ b/src/features/background-agent/manager.polling.test.ts
@@ -4,8 +4,25 @@ import { describe, test, expect, mock } from "bun:test"
 import { tmpdir } from "node:os"
 import type { PluginInput } from "@opencode-ai/plugin"
 import { BackgroundManager } from "./manager"
+import { MIN_SESSION_GONE_POLLS } from "./session-existence"
 import type { BackgroundTask } from "./types"
 
+function createPluginContext(client: object): PluginInput {
+  const directory = tmpdir()
+  return {
+    project: {
+      id: "test-project",
+      worktree: directory,
+      time: { created: Date.now() },
+    },
+    directory,
+    worktree: directory,
+    serverUrl: new URL("http://localhost:4096"),
+    $: {} as PluginInput["$"],
+    client: client as PluginInput["client"],
+  }
+}
+
 function createManagerWithStatus(statusImpl: () => Promise<{ data: Record<string, { type: string }> }>): BackgroundManager {
   const client = {
     session: {
@@ -18,7 +35,7 @@ function createManagerWithStatus(statusImpl: () => Promise<{ data: Record<string
     },
   }
 
-  return new BackgroundManager({ pluginContext: { client, directory: tmpdir() } as unknown as PluginInput })
+  return new BackgroundManager({ pluginContext: createPluginContext(client) })
 }
 
 describe("BackgroundManager polling overlap", () => {
@@ -42,9 +59,9 @@ describe("BackgroundManager polling overlap", () => {
     })
 
     //#when
-    const firstPoll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks()
+    const firstPoll = manager["pollRunningTasks"]()
     await Promise.resolve()
-    const secondPoll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks()
+    const secondPoll = manager["pollRunningTasks"]()
     releaseStatus?.()
     await Promise.all([firstPoll, secondPoll])
     manager.shutdown()
@@ -72,8 +89,7 @@ function createRunningTask(sessionId: string): BackgroundTask {
 }
 
 function injectTask(manager: BackgroundManager, task: BackgroundTask): void {
-  const tasks = (manager as unknown as { tasks: Map<string, BackgroundTask> }).tasks
-  tasks.set(task.id, task)
+  manager["tasks"].set(task.id, task)
 }
 
 function createManagerWithClient(clientOverrides: Record<string, unknown> = {}): BackgroundManager {
@@ -98,7 +114,7 @@ function createManagerWithClient(clientOverrides: Record<string, unknown> = {}):
     },
   }
   return new BackgroundManager(
-    { pluginContext: { client, directory: tmpdir() } as unknown as PluginInput, config: undefined, enableParentSessionNotifications: false },
+    { pluginContext: createPluginContext(client), config: undefined, enableParentSessionNotifications: false },
   )
 }
 
@@ -151,7 +167,7 @@ describe("BackgroundManager pollRunningTasks", () => {
       injectTask(manager, task)
 
       //#when
-      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      const poll = manager["pollRunningTasks"]
       await poll.call(manager)
       manager.shutdown()
 
@@ -184,6 +200,62 @@ describe("BackgroundManager pollRunningTasks", () => {
       expect(task.consecutiveMissedPolls).toBe(1)
       expect(getSession).not.toHaveBeenCalled()
     })
+
+    test("#when status polling is unavailable #then it does not complete or increment missed polls", async () => {
+      const cases: Array<{ name: string; status?: (() => Promise<{ data: Record<string, { type: string }> }>) | undefined }> = [
+        { name: "missing status method", status: undefined },
+        { name: "throwing status method", status: async () => { throw new Error("status unavailable") } },
+      ]
+
+      for (const testCase of cases) {
+        //#given
+        let abortCallCount = 0
+        const manager = createManagerWithClient({
+          status: testCase.status,
+          abort: async () => {
+            abortCallCount += 1
+            return {}
+          },
+        })
+        const task = createRunningTask(`ses-${testCase.name.replace(/ /g, "-")}`)
+        injectTask(manager, task)
+
+        //#when
+        const poll = manager["pollRunningTasks"]
+        for (let count = 0; count < MIN_SESSION_GONE_POLLS + 1; count += 1) {
+          await poll.call(manager)
+        }
+
+        //#then
+        expect(task.status).toBe("running")
+        expect(task.completedAt).toBeUndefined()
+        expect(task.error).toBeUndefined()
+        expect(task.consecutiveMissedPolls ?? 0).toBe(0)
+        expect(abortCallCount).toBe(0)
+
+        await manager.shutdown()
+      }
+    })
+
+    test("#when reliable status polling omits the session #then it completes through the session-gone path", async () => {
+      //#given
+      const manager = createManagerWithClient({
+        status: async () => ({ data: {} }),
+      })
+      const task = createRunningTask("ses-reliably-gone")
+      injectTask(manager, task)
+
+      //#when
+      const poll = manager["pollRunningTasks"]
+      for (let count = 0; count < MIN_SESSION_GONE_POLLS; count += 1) {
+        await poll.call(manager)
+      }
+      await manager.shutdown()
+
+      //#then
+      expect(task.status).toBe("completed")
+      expect(task.completedAt).toBeDefined()
+    })
   })
 
   describe("#given a running task whose session status is idle", () => {
@@ -196,7 +268,7 @@ describe("BackgroundManager pollRunningTasks", () => {
       injectTask(manager, task)
 
       //#when
-      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      const poll = manager["pollRunningTasks"]
       await poll.call(manager)
       manager.shutdown()
 
@@ -228,7 +300,7 @@ describe("BackgroundManager pollRunningTasks", () => {
       })
 
       //#when
-      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      const poll = manager["pollRunningTasks"]
       await poll.call(manager)
       manager.shutdown()
 
@@ -265,7 +337,7 @@ describe("BackgroundManager pollRunningTasks", () => {
       })
 
       //#when
-      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      const poll = manager["pollRunningTasks"]
       await poll.call(manager)
       manager.shutdown()
 
@@ -285,7 +357,7 @@ describe("BackgroundManager pollRunningTasks", () => {
       injectTask(manager, task)
 
       //#when
-      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      const poll = manager["pollRunningTasks"]
       await poll.call(manager)
       manager.shutdown()
 
@@ -304,7 +376,7 @@ describe("BackgroundManager pollRunningTasks", () => {
       injectTask(manager, task)
 
       //#when
-      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      const poll = manager["pollRunningTasks"]
       await poll.call(manager)
       manager.shutdown()
 
@@ -322,7 +394,7 @@ describe("BackgroundManager pollRunningTasks", () => {
       injectTask(manager, task)
 
       //#when
-      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      const poll = manager["pollRunningTasks"]
       await poll.call(manager)
       manager.shutdown()
 
diff --git a/src/features/background-agent/manager.ts b/src/features/background-agent/manager.ts
index 9442c23d9..8221e7f78 100644
--- a/src/features/background-agent/manager.ts
+++ b/src/features/background-agent/manager.ts
@@ -66,7 +66,7 @@ import {
 import { handleSessionIdleBackgroundEvent } from "./session-idle-event-handler"
 import { MESSAGE_STORAGE } from "../hook-message-injector"
 import { join } from "node:path"
-import { pruneStaleTasksAndNotifications } from "./task-poller"
+import { pruneStaleTasksAndNotifications, type SessionStatusMap } from "./task-poller"
 import { checkAndInterruptStaleTasks } from "./task-poller"
 import { removeTaskToastTracking } from "./remove-task-toast-tracking"
 import { abortWithTimeout } from "./abort-with-timeout"
@@ -214,6 +214,7 @@ export class BackgroundManager {
   private preStartDescendantReservations: Set<string>
   private enableParentSessionNotifications: boolean
   private modelFallbackControllerAccessor?: ModelFallbackControllerAccessor
+  private loggedSessionStatusUnavailable = false
   readonly taskHistory = new TaskHistory()
   private cachedCircuitBreakerSettings?: CircuitBreakerSettings
 
@@ -2186,7 +2187,7 @@ The task was re-queued on a fallback model after a retryable failure.
   }
 
   private async checkAndInterruptStaleTasks(
-    allStatuses: Record<string, { type: string }> = {},
+    allStatuses: SessionStatusMap | undefined,
   ): Promise<void> {
     await checkAndInterruptStaleTasks({
       tasks: this.tasks.values(),
@@ -2251,8 +2252,26 @@ The task was re-queued on a fallback model after a retryable failure.
     try {
       this.pruneStaleTasksAndNotifications()
 
-      const statusResult = await this.client.session.status()
-      const allStatuses = normalizeSDKResponse(statusResult, {} as Record<string, { type: string }>)
+      let allStatuses: SessionStatusMap | undefined
+      const sessionStatusMethod = this.client?.session?.status
+      if (typeof sessionStatusMethod !== "function") {
+        if (!this.loggedSessionStatusUnavailable) {
+          log("[background-agent] Unable to poll session statuses:", {
+            reason: "session.status unavailable",
+          })
+          this.loggedSessionStatusUnavailable = true
+        }
+      } else {
+        try {
+          const statusResult = await this.client.session.status()
+          allStatuses = normalizeSDKResponse(statusResult, {})
+        } catch (error) {
+          if (!this.loggedSessionStatusUnavailable) {
+            log("[background-agent] Error polling session statuses:", { error })
+            this.loggedSessionStatusUnavailable = true
+          }
+        }
+      }
 
       await this.checkAndInterruptStaleTasks(allStatuses)
 
@@ -2263,7 +2282,7 @@ The task was re-queued on a fallback model after a retryable failure.
         if (!sessionID) continue
 
         try {
-          const sessionStatus = allStatuses[sessionID]
+          const sessionStatus = allStatuses?.[sessionID]
           // Handle retry before checking running state
           if (sessionStatus?.type === "retry") {
             const retryMessage = typeof (sessionStatus as { message?: string }).message === "string"
@@ -2300,8 +2319,12 @@ The task was re-queued on a fallback model after a retryable failure.
             })
           }
 
+          if (allStatuses === undefined) {
+            continue
+          }
+
           // Session is idle or no longer in status response (completed/disappeared)
-          const sessionGoneFromStatus = !sessionStatus
+          const sessionGoneFromStatus = allStatuses !== undefined && !sessionStatus
           const sessionGoneThresholdReached = sessionGoneFromStatus
             && (task.consecutiveMissedPolls ?? 0) >= MIN_SESSION_GONE_POLLS
           const completionSource = sessionStatus?.type === "idle"
diff --git a/src/shared/agent-runtime-name-sort.test.ts b/src/shared/agent-runtime-name-sort.test.ts
deleted file mode 100644
index c39b4a545..000000000
--- a/src/shared/agent-runtime-name-sort.test.ts
+++ /dev/null
@@ -1,152 +0,0 @@
-/// <reference types="bun-types" />
-
-import { describe, expect, it, test } from "bun:test"
-
-import {
-  AGENT_DISPLAY_NAMES,
-  getAgentRuntimeName,
-  normalizeAgentForPromptKey,
-} from "./agent-display-names"
-
-// OpenCode Agent.list() sorts via remeda sortBy: default_agent desc, then name asc localeCompare.
-// Reference: ../opencode/packages/opencode/src/agent/agent.ts:284-293.
-// Earlier ZWSP prefixes silently failed: Unicode collation treats zero-width chars as ignorable.
-function simulateOpencodeSort(agentNames: string[], defaultName: string): string[] {
-  return [...agentNames].sort((a, b) => {
-    const aIsDefault = a === defaultName ? 1 : 0
-    const bIsDefault = b === defaultName ? 1 : 0
-    if (aIsDefault !== bIsDefault) return bIsDefault - aIsDefault
-    return a.localeCompare(b)
-  })
-}
-
-describe("OpenCode Agent.list() sort with runtime-name prefixes", () => {
-  describe("#given the four core agents and a mix of non-core agents", () => {
-    test("#when sorted using opencode-style sortBy #then core agents come first in canonical order", () => {
-      const sisyphus = getAgentRuntimeName("sisyphus")
-      const hephaestus = getAgentRuntimeName("hephaestus")
-      const prometheus = getAgentRuntimeName("prometheus")
-      const atlas = getAgentRuntimeName("atlas")
-
-      const allAgents = [
-        sisyphus,
-        hephaestus,
-        prometheus,
-        atlas,
-        "athena",
-        "explore",
-        "metis",
-        "oracle",
-      ]
-
-      const sorted = simulateOpencodeSort(allAgents, sisyphus)
-      const orderedConfigKeys = sorted.map((name) => normalizeAgentForPromptKey(name))
-
-      expect(orderedConfigKeys).toEqual([
-        "sisyphus",
-        "hephaestus",
-        "prometheus",
-        "atlas",
-        "athena",
-        "explore",
-        "metis",
-        "oracle",
-      ])
-    })
-
-    test("#when default_agent is unset #then canonical core order still holds via prefix alone", () => {
-      const sisyphus = getAgentRuntimeName("sisyphus")
-      const hephaestus = getAgentRuntimeName("hephaestus")
-      const prometheus = getAgentRuntimeName("prometheus")
-      const atlas = getAgentRuntimeName("atlas")
-
-      const allAgents = [hephaestus, prometheus, atlas, sisyphus, "athena", "oracle"]
-
-      const sorted = simulateOpencodeSort(allAgents, "no-such-default-agent")
-      const orderedConfigKeys = sorted.map((name) => normalizeAgentForPromptKey(name))
-
-      expect(orderedConfigKeys.slice(0, 4)).toEqual([
-        "sisyphus",
-        "hephaestus",
-        "prometheus",
-        "atlas",
-      ])
-    })
-  })
-
-  describe("#given input array in random order", () => {
-    test("#when sorted with opencode comparator #then result is always canonical", () => {
-      const sisyphus = getAgentRuntimeName("sisyphus")
-      const hephaestus = getAgentRuntimeName("hephaestus")
-      const prometheus = getAgentRuntimeName("prometheus")
-      const atlas = getAgentRuntimeName("atlas")
-      const nonCore = ["athena", "explore", "librarian", "metis", "oracle"]
-      const allAgents = [...nonCore, atlas, prometheus, hephaestus, sisyphus]
-
-      for (let attempt = 0; attempt < 25; attempt += 1) {
-        const shuffled = [...allAgents]
-        for (let i = shuffled.length - 1; i > 0; i -= 1) {
-          const j = Math.floor(Math.random() * (i + 1))
-          ;[shuffled[i], shuffled[j]] = [shuffled[j], shuffled[i]]
-        }
-        const sorted = simulateOpencodeSort(shuffled, sisyphus)
-        const orderedConfigKeys = sorted.map((name) => normalizeAgentForPromptKey(name))
-
-        expect(orderedConfigKeys).toEqual([
-          "sisyphus",
-          "hephaestus",
-          "prometheus",
-          "atlas",
-          "athena",
-          "explore",
-          "librarian",
-          "metis",
-          "oracle",
-        ])
-      }
-    })
-  })
-
-  describe("#given runtime names containing only core agents", () => {
-    test("#when sorted #then sisyphus, hephaestus, prometheus, atlas in that order", () => {
-      const sisyphus = getAgentRuntimeName("sisyphus")
-      const hephaestus = getAgentRuntimeName("hephaestus")
-      const prometheus = getAgentRuntimeName("prometheus")
-      const atlas = getAgentRuntimeName("atlas")
-
-      const sorted = simulateOpencodeSort([atlas, prometheus, hephaestus, sisyphus], sisyphus)
-      const orderedConfigKeys = sorted.map((name) => normalizeAgentForPromptKey(name))
-
-      expect(orderedConfigKeys).toEqual([
-        "sisyphus",
-        "hephaestus",
-        "prometheus",
-        "atlas",
-      ])
-    })
-  })
-
-  describe("#given the prefix is meant to render in OpenCode TUI", () => {
-    it("uses ASCII whitespace so terminals render the prefix without character corruption", () => {
-      const runtimeNames = Object.keys(AGENT_DISPLAY_NAMES).map(getAgentRuntimeName)
-      const invisibleCharsRegex = /[\u200B\u200C\u200D\uFEFF]/
-
-      for (const name of runtimeNames) {
-        expect(invisibleCharsRegex.test(name)).toBe(false)
-      }
-    })
-
-    it("only adds leading whitespace, never trailing or interior whitespace beyond the display name", () => {
-      const sisyphus = getAgentRuntimeName("sisyphus")
-      const hephaestus = getAgentRuntimeName("hephaestus")
-      const prometheus = getAgentRuntimeName("prometheus")
-      const atlas = getAgentRuntimeName("atlas")
-
-      for (const name of [sisyphus, hephaestus, prometheus, atlas]) {
-        const trimmed = name.trimStart()
-        expect(name.length).toBeGreaterThanOrEqual(trimmed.length)
-        expect(trimmed.endsWith(" ")).toBe(false)
-      }
-    })
-  })
-})