diff --git a/script/run-ci-tests.ts b/script/run-ci-tests.ts
index 5466885ce..10cf80b21 100644
--- a/script/run-ci-tests.ts
+++ b/script/run-ci-tests.ts
@@ -29,13 +29,7 @@ async function usesModuleMock(rootDirectory: string, testFile: string): Promise<
 }
 
 function toIsolatedTarget(testFile: string): string {
-  const pathSegments = testFile.split("/")
-
-  if (pathSegments.length <= 3) {
-    return testFile
-  }
-
-  return pathSegments.slice(0, -1).join("/")
+  return testFile
 }
 
 function isCoveredByTarget(testFile: string, isolatedTarget: string): boolean {
diff --git a/src/features/background-agent/manager.test.ts b/src/features/background-agent/manager.test.ts
index 9e10e3c57..5a3a430e6 100644
--- a/src/features/background-agent/manager.test.ts
+++ b/src/features/background-agent/manager.test.ts
@@ -218,6 +218,10 @@ function getRootDescendantCounts(manager: BackgroundManager): Map<string, number
   return (manager as unknown as { rootDescendantCounts: Map<string, number> }).rootDescendantCounts
 }
 
+function getPreStartDescendantReservations(manager: BackgroundManager): Set<string> {
+  return (manager as unknown as { preStartDescendantReservations: Set<string> }).preStartDescendantReservations
+}
+
 function getQueuesByKey(
   manager: BackgroundManager
 ): Map<string, Array<{ task: BackgroundTask; input: import("./types").LaunchInput }>> {
@@ -1144,7 +1148,18 @@ describe("BackgroundManager.notifyParentSession - notifications toggle", () => {
         prompt: promptMock,
         promptAsync: promptMock,
         abort: async () => ({}),
-        messages: async () => ({ data: [] }),
+        messages: async () => ({
+          data: [{
+            info: {
+              agent: "explore",
+              model: {
+                providerID: "anthropic",
+                modelID: "claude-opus-4-6",
+                variant: "high",
+              },
+            },
+          }],
+        }),
       },
     }
     const manager = new BackgroundManager(
@@ -1178,7 +1193,7 @@ describe("BackgroundManager.notifyParentSession - notifications toggle", () => {
 })
 
 describe("BackgroundManager.notifyParentSession - variant propagation", () => {
-  test("should propagate variant in parent notification promptAsync body", async () => {
+  test("should prefer parent session variant over child task variant in parent notification promptAsync body", async () => {
     //#given
     const promptCalls: Array<{ body: Record<string, unknown> }> = []
     const client = {
@@ -1189,16 +1204,27 @@ describe("BackgroundManager.notifyParentSession - variant propagation", () => {
           return {}
         },
         abort: async () => ({}),
-        messages: async () => ({ data: [] }),
+        messages: async () => ({
+          data: [{
+            info: {
+              agent: "explore",
+              model: {
+                providerID: "anthropic",
+                modelID: "claude-opus-4-6",
+                variant: "max",
+              },
+            },
+          }],
+        }),
       },
     }
     const manager = new BackgroundManager({ client, directory: tmpdir() } as unknown as PluginInput)
     const task: BackgroundTask = {
-      id: "task-variant-test",
+      id: "task-parent-variant-wins",
       sessionID: "session-child",
       parentSessionID: "session-parent",
       parentMessageID: "msg-parent",
-      description: "task with variant",
+      description: "task with mismatched variant",
       prompt: "test",
       agent: "explore",
       status: "completed",
@@ -1214,7 +1240,7 @@ describe("BackgroundManager.notifyParentSession - variant propagation", () => {
 
     //#then
     expect(promptCalls).toHaveLength(1)
-    expect(promptCalls[0].body.variant).toBe("high")
+    expect(promptCalls[0].body.variant).toBe("max")
 
     manager.shutdown()
   })
@@ -1521,6 +1547,7 @@ describe("BackgroundManager.tryCompleteTask", () => {
 
     const task = createMockTask({
       id: "task-zombie-session",
+      sessionID: "session-zombie-placeholder",
       parentSessionID: "parent-zombie",
       status: "pending",
       agent: "explore",
@@ -1863,10 +1890,10 @@ describe("BackgroundManager.resume model persistence", () => {
     expect(getSessionPromptParams("session-advanced")).toEqual({
       temperature: 0.25,
       topP: 0.55,
+      maxOutputTokens: 8192,
       options: {
         reasoningEffort: "high",
         thinking: { type: "disabled" },
-        maxTokens: 8192,
       },
     })
   })
@@ -2463,6 +2490,46 @@ describe("BackgroundManager - Non-blocking Queue Integration", () => {
       expect(retryTask.status).toBe("pending")
     })
 
+    test("should only roll back the failed task reservation once when siblings still exist", async () => {
+      // given
+      const concurrencyKey = "test-agent"
+      const task = createMockTask({
+        id: "task-single-reservation-rollback",
+        sessionID: "session-single-reservation-rollback",
+        parentSessionID: "session-root",
+        status: "pending",
+        agent: "test-agent",
+        rootSessionID: "session-root",
+      })
+      delete (task as Partial<BackgroundTask>).sessionID
+
+      const input = {
+        description: task.description,
+        prompt: task.prompt,
+        agent: task.agent,
+        parentSessionID: task.parentSessionID,
+        parentMessageID: task.parentMessageID,
+      }
+
+      getTaskMap(manager).set(task.id, task)
+      getQueuesByKey(manager).set(concurrencyKey, [{ task, input }])
+      getRootDescendantCounts(manager).set("session-root", 2)
+      getPreStartDescendantReservations(manager).add(task.id)
+      stubNotifyParentSession(manager)
+
+      ;(manager as unknown as {
+        startTask: (item: { task: BackgroundTask; input: typeof input }) => Promise<void>
+      }).startTask = async () => {
+        throw new Error("session create failed")
+      }
+
+      // when
+      await processKeyForTest(manager, concurrencyKey)
+
+      // then
+      expect(getRootDescendantCounts(manager).get("session-root")).toBe(1)
+    })
+
     test("should keep the next queued task when the first task is cancelled during session creation", async () => {
       // given
       const firstSessionID = "ses-first-cancelled-during-create"
diff --git a/src/features/background-agent/manager.ts b/src/features/background-agent/manager.ts
index 1a23c3569..bd8ff2477 100644
--- a/src/features/background-agent/manager.ts
+++ b/src/features/background-agent/manager.ts
@@ -422,10 +422,6 @@ export class BackgroundManager {
             this.concurrencyManager.release(key)
           }
 
-          if (item.task.rootSessionID) {
-            this.unregisterRootDescendant(item.task.rootSessionID)
-          }
-
           removeTaskToastTracking(item.task.id)
 
           // Abort the orphaned session if one was created before the error
@@ -1783,6 +1779,7 @@ export class BackgroundManager {
       let agent: string | undefined = task.parentAgent
       let model: { providerID: string; modelID: string } | undefined
       let tools: Record<string, boolean> | undefined = task.parentTools
+      let promptContext: ReturnType<typeof resolvePromptContextFromSessionMessages> = null
 
       if (this.enableParentSessionNotifications) {
         try {
@@ -1796,7 +1793,7 @@ export class BackgroundManager {
               tools?: Record<string, boolean | "allow" | "deny" | "ask">
             }
           }>)
-          const promptContext = resolvePromptContextFromSessionMessages(
+          promptContext = resolvePromptContextFromSessionMessages(
             messages,
             task.parentSessionID,
           )
@@ -1840,7 +1837,7 @@ export class BackgroundManager {
         const isTaskFailure = task.status === "error" || task.status === "cancelled" || task.status === "interrupt"
         const shouldReply = allComplete || isTaskFailure
 
-        const variant = task.model?.variant
+        const variant = promptContext?.model?.variant
 
         try {
           await this.client.session.promptAsync({
diff --git a/src/features/background-agent/spawner.test.ts b/src/features/background-agent/spawner.test.ts
index d3896e55f..4c5ddeaf2 100644
--- a/src/features/background-agent/spawner.test.ts
+++ b/src/features/background-agent/spawner.test.ts
@@ -400,10 +400,10 @@ describe("background-agent spawner fallback model promotion", () => {
     expect(getSessionPromptParams("session-123")).toEqual({
       temperature: 0.4,
       topP: 0.7,
+      maxOutputTokens: 4096,
       options: {
         reasoningEffort: "high",
         thinking: { type: "disabled" },
-        maxTokens: 4096,
       },
     })
   })
diff --git a/src/features/tmux-subagent/zombie-pane.test.ts b/src/features/tmux-subagent/zombie-pane.test.ts
index 42fcfb760..267c03cb3 100644
--- a/src/features/tmux-subagent/zombie-pane.test.ts
+++ b/src/features/tmux-subagent/zombie-pane.test.ts
@@ -40,10 +40,22 @@ mock.module("./action-executor", () => ({
 mock.module("../../shared/tmux", () => ({
   isInsideTmux: mockIsInsideTmux,
   getCurrentPaneId: mockGetCurrentPaneId,
+  isServerRunning: mock(async () => true),
+  resetServerCheck: mock(() => {}),
+  markServerRunningInProcess: mock(() => {}),
+  getPaneDimensions: mock(async () => ({ width: 220, height: 44 })),
+  spawnTmuxPane: mock(async () => ({ success: true, paneId: "%1" })),
+  closeTmuxPane: mock(async () => ({ success: true })),
+  replaceTmuxPane: mock(async () => ({ success: true, paneId: "%1" })),
+  spawnTmuxWindow: mock(async () => ({ success: true, windowId: "@1" })),
+  spawnTmuxSession: mock(async () => ({ success: true, sessionId: "mock" })),
+  applyLayout: mock(async () => ({ success: true })),
+  enforceMainPaneWidth: mock(async () => ({ success: true })),
   POLL_INTERVAL_BACKGROUND_MS: 10,
   SESSION_READY_POLL_INTERVAL_MS: 10,
   SESSION_READY_TIMEOUT_MS: 50,
   SESSION_MISSING_GRACE_MS: 1_000,
+  SESSION_TIMEOUT_MS: 600_000,
 }))
 
 afterAll(() => { mock.restore() })
diff --git a/src/shared/session-prompt-params-helpers.ts b/src/shared/session-prompt-params-helpers.ts
index 7ce24c826..f50707956 100644
--- a/src/shared/session-prompt-params-helpers.ts
+++ b/src/shared/session-prompt-params-helpers.ts
@@ -20,12 +20,12 @@ export function applySessionPromptParams(
   const promptOptions: Record<string, unknown> = {
     ...(model.reasoningEffort ? { reasoningEffort: model.reasoningEffort } : {}),
     ...(model.thinking ? { thinking: model.thinking } : {}),
-    ...(model.maxTokens !== undefined ? { maxTokens: model.maxTokens } : {}),
   }
 
   setSessionPromptParams(sessionID, {
     ...(model.temperature !== undefined ? { temperature: model.temperature } : {}),
     ...(model.top_p !== undefined ? { topP: model.top_p } : {}),
+    ...(model.maxTokens !== undefined ? { maxOutputTokens: model.maxTokens } : {}),
     ...(Object.keys(promptOptions).length > 0 ? { options: promptOptions } : {}),
   })
 }
diff --git a/src/shared/session-prompt-params-state.test.ts b/src/shared/session-prompt-params-state.test.ts
index b97a80565..d52670be6 100644
--- a/src/shared/session-prompt-params-state.test.ts
+++ b/src/shared/session-prompt-params-state.test.ts
@@ -18,9 +18,9 @@ describe("session-prompt-params-state", () => {
     const params = {
       temperature: 0.4,
       topP: 0.7,
+      maxOutputTokens: 4096,
       options: {
         reasoningEffort: "high",
-        maxTokens: 4096,
       },
     }
 
diff --git a/src/tools/call-omo-agent/sync-executor.test.ts b/src/tools/call-omo-agent/sync-executor.test.ts
index baa59fb78..404e3fee0 100644
--- a/src/tools/call-omo-agent/sync-executor.test.ts
+++ b/src/tools/call-omo-agent/sync-executor.test.ts
@@ -190,10 +190,10 @@ describe("executeSync", () => {
     expect(promptInput?.body.temperature).toBe(0.12)
     expect(promptInput?.body.topP).toBe(0.34)
     expect(promptInput?.body.options).toEqual({
-      maxTokens: 5678,
       reasoningEffort: "medium",
       thinking: { type: "disabled" },
     })
+    expect(promptInput?.body.maxOutputTokens).toBe(5678)
   })
 
   test("records metadata with description and created session id", async () => {
diff --git a/src/tools/call-omo-agent/sync-executor.ts b/src/tools/call-omo-agent/sync-executor.ts
index 096a80216..f0f65d7e1 100644
--- a/src/tools/call-omo-agent/sync-executor.ts
+++ b/src/tools/call-omo-agent/sync-executor.ts
@@ -43,12 +43,12 @@ function buildPromptGenerationParams(model: DelegatedModelConfig | undefined): R
   const promptOptions: Record<string, unknown> = {
     ...(model.reasoningEffort ? { reasoningEffort: model.reasoningEffort } : {}),
     ...(model.thinking ? { thinking: model.thinking } : {}),
-    ...(model.maxTokens !== undefined ? { maxTokens: model.maxTokens } : {}),
   }
 
   return {
     ...(model.temperature !== undefined ? { temperature: model.temperature } : {}),
     ...(model.top_p !== undefined ? { topP: model.top_p } : {}),
+    ...(model.maxTokens !== undefined ? { maxOutputTokens: model.maxTokens } : {}),
     ...(Object.keys(promptOptions).length > 0 ? { options: promptOptions } : {}),
   }
 }
diff --git a/src/tools/delegate-task/sync-prompt-sender.test.ts b/src/tools/delegate-task/sync-prompt-sender.test.ts
index 32970e72a..f86e87997 100644
--- a/src/tools/delegate-task/sync-prompt-sender.test.ts
+++ b/src/tools/delegate-task/sync-prompt-sender.test.ts
@@ -277,15 +277,15 @@ bunDescribe("sendSyncPrompt", () => {
     bunExpect(promptArgs.body.options).toEqual({
       reasoningEffort: "high",
       thinking: { type: "disabled" },
-      maxTokens: 4096,
     })
+    bunExpect(promptArgs.body.maxOutputTokens).toBe(4096)
     bunExpect(getSessionPromptParams("test-session")).toEqual({
       temperature: 0.4,
       topP: 0.7,
+      maxOutputTokens: 4096,
       options: {
         reasoningEffort: "high",
         thinking: { type: "disabled" },
-        maxTokens: 4096,
       },
     })
   })
diff --git a/src/tools/delegate-task/sync-prompt-sender.ts b/src/tools/delegate-task/sync-prompt-sender.ts
index 882258d98..bd38830e5 100644
--- a/src/tools/delegate-task/sync-prompt-sender.ts
+++ b/src/tools/delegate-task/sync-prompt-sender.ts
@@ -30,12 +30,12 @@ function buildPromptGenerationParams(model: DelegatedModelConfig | undefined): R
   const promptOptions: Record<string, unknown> = {
     ...(model.reasoningEffort ? { reasoningEffort: model.reasoningEffort } : {}),
     ...(model.thinking ? { thinking: model.thinking } : {}),
-    ...(model.maxTokens !== undefined ? { maxTokens: model.maxTokens } : {}),
   }
 
   return {
     ...(model.temperature !== undefined ? { temperature: model.temperature } : {}),
     ...(model.top_p !== undefined ? { topP: model.top_p } : {}),
+    ...(model.maxTokens !== undefined ? { maxOutputTokens: model.maxTokens } : {}),
     ...(Object.keys(promptOptions).length > 0 ? { options: promptOptions } : {}),
   }
 }