fix(tests): resolve 6 test isolation failures in full suite

3 failures in fallback.cliproxyapi-matrix.test.ts:
- Root cause: leaked spyOn(getMainSessionID) in
  tool-execute-before-session-notification.test.ts was never restored,
  poisoning module state for subsequent tests in the same worker
- Added mockRestore() call and _resetModelFallbackForTesting in afterEach

3 failures in background-agent/manager.test.ts:
- Root cause: connected-providers-cache memConnected/memProviderModels
  persisted across test files, making isReachable() skip fallback
  candidates in retry tests
- Added mock.module for connected-providers-cache at file level
- Added _resetMemCacheForTesting export and global beforeEach cleanup

Full suite: 4638/4638 pass, 0 fail

src/features/background-agent/manager.test.ts

@@ -1,5 +1,15 @@
 declare const require: (name: string) => any
-const { describe, test, expect, beforeEach, afterEach, spyOn } = require("bun:test")
+const { describe, test, expect, beforeEach, afterEach, spyOn, mock } = require("bun:test")
+
+mock.module("../../shared/connected-providers-cache", () => ({
+  readConnectedProvidersCache: () => null,
+  readProviderModelsCache: () => null,
+  hasConnectedProvidersCache: () => false,
+  hasProviderModelsCache: () => false,
+  writeProviderModelsCache: () => {},
+  updateConnectedProvidersCache: () => {},
+}))
+
 import { getSessionPromptParams, clearSessionPromptParams } from "../../shared/session-prompt-params-state"
 import { tmpdir } from "node:os"
 import type { PluginInput } from "@opencode-ai/plugin"

src/plugin/fallback.cliproxyapi-matrix.test.ts

@@ -15,6 +15,7 @@ import { createChatMessageHandler } from "./chat-message"
 import { createModelFallbackHook } from "../hooks/model-fallback/hook"
 import { createRuntimeFallbackHook } from "../hooks/runtime-fallback"
 import { _resetForTesting } from "../features/claude-code-session-state"
+import { _resetForTesting as _resetModelFallbackForTesting } from "../hooks/model-fallback/hook"
 import { SessionCategoryRegistry } from "../shared/session-category-registry"
 
 const PRIMARY_MODEL = {
@@ -311,6 +312,7 @@ async function triggerAssistantMessageError(
 
 afterEach(() => {
   _resetForTesting()
+  _resetModelFallbackForTesting()
   SessionCategoryRegistry.clear()
 })
 

src/plugin/tool-execute-before-session-notification.test.ts

@@ -27,6 +27,8 @@ describe("createToolExecuteBeforeHandler session notification sessionID", () =>
 
     expect(getMainSessionIDSpy).toHaveBeenCalled()
     expect(capturedSessionID).toBe(mainSessionID)
+
+    getMainSessionIDSpy.mockRestore()
   })
 })
 

src/shared/connected-providers-cache.ts

@@ -222,6 +222,11 @@ export function createConnectedProvidersCacheStore(
 		}
 	}
 
+	function _resetMemCacheForTesting(): void {
+		memConnected = undefined
+		memProviderModels = undefined
+	}
+
 	return {
 		readConnectedProvidersCache,
 		hasConnectedProvidersCache,
@@ -229,6 +234,7 @@ export function createConnectedProvidersCacheStore(
 		hasProviderModelsCache,
 		writeProviderModelsCache,
 		updateConnectedProvidersCache,
+		_resetMemCacheForTesting,
 	}
 }
 
@@ -269,4 +275,5 @@ export const {
 	hasProviderModelsCache,
 	writeProviderModelsCache,
 	updateConnectedProvidersCache,
+	_resetMemCacheForTesting,
 } = defaultConnectedProvidersCacheStore

test-setup.ts

@@ -1,8 +1,10 @@
 import { beforeEach } from "bun:test"
 import { _resetForTesting as resetClaudeSessionState } from "./src/features/claude-code-session-state/state"
 import { _resetForTesting as resetModelFallbackState } from "./src/hooks/model-fallback/hook"
+import { _resetMemCacheForTesting as resetConnectedProvidersCache } from "./src/shared/connected-providers-cache"
 
 beforeEach(() => {
   resetClaudeSessionState()
   resetModelFallbackState()
+  resetConnectedProvidersCache()
 })