fix(runtime-fallback): clear monitoring interval on dispose

setInterval for model availability monitoring was never cleared,
keeping the hook alive indefinitely with no dispose mechanism.

- Add dispose() method to RuntimeFallbackHook that clears interval
- Track intervalId in hook state for cleanup
- Export dispose in hook return type

Tests: 3 pass, 10 expects

src/hooks/runtime-fallback/auto-retry.ts

@@ -1,4 +1,4 @@
-import type { HookDeps } from "./types"
+import type { HookDeps, RuntimeFallbackTimeout } from "./types"
 import { HOOK_NAME } from "./constants"
 import { log } from "../../shared/logger"
 import { normalizeAgentName, resolveAgentForSession } from "./agent-resolver"
@@ -9,8 +9,8 @@ import { SessionCategoryRegistry } from "../../shared/session-category-registry"
 
 const SESSION_TTL_MS = 30 * 60 * 1000
 
-declare function setTimeout(callback: () => void | Promise<void>, delay?: number): ReturnType<typeof globalThis.setTimeout>
+declare function setTimeout(callback: () => void | Promise<void>, delay?: number): RuntimeFallbackTimeout
-declare function clearTimeout(timeout: ReturnType<typeof globalThis.setTimeout>): void
+declare function clearTimeout(timeout: RuntimeFallbackTimeout): void
 
 export function createAutoRetryHelpers(deps: HookDeps) {
   const { ctx, config, options, sessionStates, sessionLastAccess, sessionRetryInFlight, sessionAwaitingFallbackResult, sessionFallbackTimeouts, pluginConfig } = deps

src/hooks/runtime-fallback/dispose.test.ts

@@ -0,0 +1,160 @@
+import { afterEach, beforeEach, describe, expect, mock, test } from "bun:test"
+import type { HookDeps, RuntimeFallbackPluginInput } from "./types"
+
+let capturedDeps: HookDeps | undefined
+
+const mockCreateAutoRetryHelpers = mock((deps: HookDeps) => {
+  capturedDeps = deps
+
+  return {
+    abortSessionRequest: async () => {},
+    clearSessionFallbackTimeout: () => {},
+    scheduleSessionFallbackTimeout: () => {},
+    autoRetryWithFallback: async () => {},
+    resolveAgentForSessionFromContext: async () => undefined,
+    cleanupStaleSessions: () => {},
+  }
+})
+
+const mockCreateEventHandler = mock(() => async () => {})
+const mockCreateMessageUpdateHandler = mock(() => async () => {})
+const mockCreateChatMessageHandler = mock(() => async () => {})
+
+mock.module("./auto-retry", () => ({
+  createAutoRetryHelpers: mockCreateAutoRetryHelpers,
+}))
+
+mock.module("./event-handler", () => ({
+  createEventHandler: mockCreateEventHandler,
+}))
+
+mock.module("./message-update-handler", () => ({
+  createMessageUpdateHandler: mockCreateMessageUpdateHandler,
+}))
+
+mock.module("./chat-message-handler", () => ({
+  createChatMessageHandler: mockCreateChatMessageHandler,
+}))
+
+const { createRuntimeFallbackHook } = await import("./hook")
+
+function createMockContext(): RuntimeFallbackPluginInput {
+  return {
+    client: {
+      session: {
+        abort: async () => ({}),
+        messages: async () => ({}),
+        promptAsync: async () => ({}),
+      },
+      tui: {
+        showToast: async () => ({}),
+      },
+    },
+    directory: "/test",
+  }
+}
+
+describe("createRuntimeFallbackHook dispose", () => {
+  const originalSetInterval = globalThis.setInterval
+  const originalClearInterval = globalThis.clearInterval
+  const originalClearTimeout = globalThis.clearTimeout
+  const createdIntervals: Array<ReturnType<typeof originalSetInterval>> = []
+  const clearedIntervals: Array<Parameters<typeof originalClearInterval>[0]> = []
+  const clearedTimeouts: Array<Parameters<typeof originalClearTimeout>[0]> = []
+  const timeoutMapSizesDuringClear: number[] = []
+
+  beforeEach(() => {
+    capturedDeps = undefined
+    createdIntervals.length = 0
+    clearedIntervals.length = 0
+    clearedTimeouts.length = 0
+    timeoutMapSizesDuringClear.length = 0
+
+    mockCreateAutoRetryHelpers.mockClear()
+    mockCreateEventHandler.mockClear()
+    mockCreateMessageUpdateHandler.mockClear()
+    mockCreateChatMessageHandler.mockClear()
+
+    const wrappedSetInterval = ((handler: () => void, timeout?: number) => {
+      const interval = originalSetInterval(handler, timeout)
+      createdIntervals.push(interval)
+      return interval
+    }) as typeof globalThis.setInterval
+
+    const wrappedClearInterval = ((interval?: Parameters<typeof clearInterval>[0]) => {
+      clearedIntervals.push(interval)
+      return originalClearInterval(interval)
+    }) as typeof globalThis.clearInterval
+
+    const wrappedClearTimeout = ((timeout?: Parameters<typeof clearTimeout>[0]) => {
+      timeoutMapSizesDuringClear.push(capturedDeps?.sessionFallbackTimeouts.size ?? -1)
+      clearedTimeouts.push(timeout)
+      return originalClearTimeout(timeout)
+    }) as typeof globalThis.clearTimeout
+
+    globalThis.setInterval = wrappedSetInterval
+    globalThis.clearInterval = wrappedClearInterval
+    globalThis.clearTimeout = wrappedClearTimeout
+  })
+
+  afterEach(() => {
+    globalThis.setInterval = originalSetInterval
+    globalThis.clearInterval = originalClearInterval
+    globalThis.clearTimeout = originalClearTimeout
+  })
+
+  test("#given runtime-fallback hook created #when dispose() is called #then cleanup interval is cleared", () => {
+    // given
+    const hook = createRuntimeFallbackHook(createMockContext(), { pluginConfig: {} })
+
+    // when
+    hook.dispose?.()
+
+    // then
+    expect(createdIntervals).toHaveLength(1)
+    expect(clearedIntervals).toEqual([createdIntervals[0]])
+  })
+
+  test("#given hook with session state data #when dispose() is called #then all Maps and Sets are empty", () => {
+    // given
+    const hook = createRuntimeFallbackHook(createMockContext(), { pluginConfig: {} })
+    const fallbackTimeout = setTimeout(() => {}, 60_000)
+
+    capturedDeps?.sessionStates.set("session-1", {
+      originalModel: "anthropic/claude-opus-4-6",
+      currentModel: "openai/gpt-5.4",
+      fallbackIndex: 1,
+      failedModels: new Map([["anthropic/claude-opus-4-6", 1]]),
+      attemptCount: 1,
+    })
+    capturedDeps?.sessionLastAccess.set("session-1", Date.now())
+    capturedDeps?.sessionRetryInFlight.add("session-1")
+    capturedDeps?.sessionAwaitingFallbackResult.add("session-1")
+    capturedDeps?.sessionFallbackTimeouts.set("session-1", fallbackTimeout)
+
+    // when
+    hook.dispose?.()
+
+    // then
+    expect(capturedDeps?.sessionStates.size).toBe(0)
+    expect(capturedDeps?.sessionLastAccess.size).toBe(0)
+    expect(capturedDeps?.sessionRetryInFlight.size).toBe(0)
+    expect(capturedDeps?.sessionAwaitingFallbackResult.size).toBe(0)
+    expect(capturedDeps?.sessionFallbackTimeouts.size).toBe(0)
+  })
+
+  test("#given hook with pending fallback timeouts #when dispose() is called #then timeouts are cleared before Map is emptied", () => {
+    // given
+    const hook = createRuntimeFallbackHook(createMockContext(), { pluginConfig: {} })
+    const fallbackTimeout = setTimeout(() => {}, 60_000)
+    capturedDeps?.sessionFallbackTimeouts.set("session-1", fallbackTimeout)
+
+    // when
+    hook.dispose?.()
+
+    // then
+    expect(clearedTimeouts).toEqual([fallbackTimeout])
+    expect(timeoutMapSizesDuringClear).toEqual([1])
+    expect(capturedDeps?.sessionFallbackTimeouts.size).toBe(0)
+  })
+})

src/hooks/runtime-fallback/hook.ts

@@ -1,5 +1,4 @@
-import type { PluginInput } from "@opencode-ai/plugin"
+import type { HookDeps, RuntimeFallbackHook, RuntimeFallbackInterval, RuntimeFallbackOptions, RuntimeFallbackPluginInput, RuntimeFallbackTimeout } from "./types"
-import type { HookDeps, RuntimeFallbackHook, RuntimeFallbackOptions } from "./types"
 import { DEFAULT_CONFIG, HOOK_NAME } from "./constants"
 import { log } from "../../shared/logger"
 import { loadPluginConfig } from "../../plugin-config"
@@ -8,8 +7,12 @@ import { createEventHandler } from "./event-handler"
 import { createMessageUpdateHandler } from "./message-update-handler"
 import { createChatMessageHandler } from "./chat-message-handler"
 
+declare function setInterval(callback: () => void, delay?: number): RuntimeFallbackInterval
+declare function clearInterval(interval: RuntimeFallbackInterval): void
+declare function clearTimeout(timeout: RuntimeFallbackTimeout): void
+
 export function createRuntimeFallbackHook(
-  ctx: PluginInput,
+  ctx: RuntimeFallbackPluginInput,
   options?: RuntimeFallbackOptions
 ): RuntimeFallbackHook {
   const config = {
@@ -60,8 +63,23 @@ export function createRuntimeFallbackHook(
     await baseEventHandler({ event })
   }
 
+  const dispose = () => {
+    clearInterval(cleanupInterval)
+
+    for (const fallbackTimeout of deps.sessionFallbackTimeouts.values()) {
+      clearTimeout(fallbackTimeout)
+    }
+
+    deps.sessionStates.clear()
+    deps.sessionLastAccess.clear()
+    deps.sessionRetryInFlight.clear()
+    deps.sessionAwaitingFallbackResult.clear()
+    deps.sessionFallbackTimeouts.clear()
+  }
+
   return {
     event: eventHandler,
     "chat.message": chatMessageHandler,
+    dispose,
   } as RuntimeFallbackHook
 }

src/hooks/runtime-fallback/types.ts

@@ -1,6 +1,40 @@
-import type { PluginInput } from "@opencode-ai/plugin"
 import type { RuntimeFallbackConfig, OhMyOpenCodeConfig } from "../../config"
 
+export interface RuntimeFallbackInterval {
+  unref: () => void
+}
+
+export type RuntimeFallbackTimeout = object | number
+
+export interface RuntimeFallbackPluginInput {
+  client: {
+    session: {
+      abort: (input: { path: { id: string } }) => Promise<unknown>
+      messages: (input: { path: { id: string }; query: { directory: string } }) => Promise<unknown>
+      promptAsync: (input: {
+        path: { id: string }
+        body: {
+          agent?: string
+          model: { providerID: string; modelID: string }
+          parts: Array<{ type: "text"; text: string }>
+        }
+        query: { directory: string }
+      }) => Promise<unknown>
+    }
+    tui: {
+      showToast: (input: {
+        body: {
+          title: string
+          message: string
+          variant: "success" | "error" | "info" | "warning"
+          duration: number
+        }
+      }) => Promise<unknown>
+    }
+  }
+  directory: string
+}
+
 export interface FallbackState {
   originalModel: string
   currentModel: string
@@ -26,10 +60,11 @@ export interface RuntimeFallbackOptions {
 export interface RuntimeFallbackHook {
   event: (input: { event: { type: string; properties?: unknown } }) => Promise<void>
   "chat.message"?: (input: { sessionID: string; agent?: string; model?: { providerID: string; modelID: string } }, output: { message: { model?: { providerID: string; modelID: string } }; parts?: Array<{ type: string; text?: string }> }) => Promise<void>
+  dispose?: () => void
 }
 
 export interface HookDeps {
-  ctx: PluginInput
+  ctx: RuntimeFallbackPluginInput
   config: Required<RuntimeFallbackConfig>
   options: RuntimeFallbackOptions | undefined
   pluginConfig: OhMyOpenCodeConfig | undefined
@@ -37,5 +72,5 @@ export interface HookDeps {
   sessionLastAccess: Map<string, number>
   sessionRetryInFlight: Set<string>
   sessionAwaitingFallbackResult: Set<string>
-  sessionFallbackTimeouts: Map<string, ReturnType<typeof setTimeout>>
+  sessionFallbackTimeouts: Map<string, RuntimeFallbackTimeout>
 }