fix(model-fallback): expose session fallback chains to background tasks

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/model-fallback/controller-accessor.ts

@@ -4,6 +4,7 @@ import type { ModelFallbackStateController } from "./fallback-state-controller"
 export type ModelFallbackControllerAccessor = {
   register: (controller: ModelFallbackStateController) => void
   setSessionFallbackChain: (sessionID: string, fallbackChain: FallbackEntry[] | undefined) => void
+  getSessionFallbackChain: (sessionID: string) => FallbackEntry[] | undefined
   clearSessionFallbackChain: (sessionID: string) => void
 }
 
@@ -18,6 +19,10 @@ export function createModelFallbackControllerAccessor(): ModelFallbackController
     controller?.setSessionFallbackChain(sessionID, fallbackChain)
   }
 
+  function getSessionFallbackChain(sessionID: string): FallbackEntry[] | undefined {
+    return controller?.getSessionFallbackChain(sessionID)
+  }
+
   function clearSessionFallbackChain(sessionID: string): void {
     controller?.clearSessionFallbackChain(sessionID)
   }
@@ -25,6 +30,7 @@ export function createModelFallbackControllerAccessor(): ModelFallbackController
   return {
     register,
     setSessionFallbackChain,
+    getSessionFallbackChain,
     clearSessionFallbackChain,
   }
 }

src/hooks/model-fallback/fallback-state-controller.ts

@@ -15,6 +15,7 @@ type ModelFallbackStateLike = {
 export type ModelFallbackStateController = {
   lastToastKey: Map<string, string>
   setSessionFallbackChain: (sessionID: string, fallbackChain: FallbackEntry[] | undefined) => void
+  getSessionFallbackChain: (sessionID: string) => FallbackEntry[] | undefined
   clearSessionFallbackChain: (sessionID: string) => void
   setPendingModelFallback: (
     sessionID: string,
@@ -45,6 +46,10 @@ export function createModelFallbackStateController(input: {
     sessionFallbackChains.delete(sessionID)
   }
 
+  function getSessionFallbackChain(sessionID: string): FallbackEntry[] | undefined {
+    return sessionFallbackChains.get(sessionID)
+  }
+
   function setPendingModelFallback(
     sessionID: string,
     agentName: string,
@@ -123,6 +128,7 @@ export function createModelFallbackStateController(input: {
   return {
     lastToastKey,
     setSessionFallbackChain,
+    getSessionFallbackChain,
     clearSessionFallbackChain,
     setPendingModelFallback,
     getNextFallback,

src/hooks/model-fallback/hook.ts

@@ -33,6 +33,7 @@ type ModelFallbackControllerWithState = Pick<
   ModelFallbackStateController,
   | "lastToastKey"
   | "setSessionFallbackChain"
+  | "getSessionFallbackChain"
   | "clearSessionFallbackChain"
   | "setPendingModelFallback"
   | "getNextFallback"
@@ -70,6 +71,13 @@ export function clearSessionFallbackChain(
   controller.clearSessionFallbackChain(sessionID)
 }
 
+export function getSessionFallbackChain(
+  controller: Pick<ModelFallbackStateController, "getSessionFallbackChain">,
+  sessionID: string,
+): FallbackEntry[] | undefined {
+  return controller.getSessionFallbackChain(sessionID)
+}
+
 /**
  * Sets a pending model fallback for a session.
  * Called when a model error is detected in session.error handler.
@@ -152,6 +160,7 @@ export function createModelFallbackHook(args?: ModelFallbackHookArgs): ModelFall
   return {
     lastToastKey: controller.lastToastKey,
     setSessionFallbackChain: controller.setSessionFallbackChain,
+    getSessionFallbackChain: controller.getSessionFallbackChain,
     clearSessionFallbackChain: controller.clearSessionFallbackChain,
     setPendingModelFallback: controller.setPendingModelFallback,
     getNextFallback: controller.getNextFallback,