fix: enable runtime fallback for delegated child sessions (#2357)

src/hooks/runtime-fallback/fallback-bootstrap-model.ts

@@ -0,0 +1,49 @@
+import type { OhMyOpenCodeConfig } from "../../config"
+import { HOOK_NAME } from "./constants"
+import { log } from "../../shared/logger"
+import { SessionCategoryRegistry } from "../../shared/session-category-registry"
+
+type ResolveFallbackBootstrapModelOptions = {
+  sessionID: string
+  source: string
+  eventModel?: string
+  resolvedAgent?: string
+  pluginConfig?: OhMyOpenCodeConfig
+}
+
+export function resolveFallbackBootstrapModel(
+  options: ResolveFallbackBootstrapModelOptions,
+): string | undefined {
+  if (options.eventModel) {
+    return options.eventModel
+  }
+
+  const agentConfigs = options.pluginConfig?.agents
+  const agentConfig = options.resolvedAgent && agentConfigs
+    ? agentConfigs[options.resolvedAgent as keyof typeof agentConfigs]
+    : undefined
+  const agentModel = typeof agentConfig?.model === "string" ? agentConfig.model : undefined
+  if (agentModel) {
+    log(`[${HOOK_NAME}] Derived model from agent config for ${options.source}`, {
+      sessionID: options.sessionID,
+      agent: options.resolvedAgent,
+      model: agentModel,
+    })
+    return agentModel
+  }
+
+  const sessionCategory = SessionCategoryRegistry.get(options.sessionID)
+  const categoryModel = sessionCategory
+    ? options.pluginConfig?.categories?.[sessionCategory]?.model
+    : undefined
+  if (typeof categoryModel === "string" && categoryModel.length > 0) {
+    log(`[${HOOK_NAME}] Derived model from session category config for ${options.source}`, {
+      sessionID: options.sessionID,
+      category: sessionCategory,
+      model: categoryModel,
+    })
+    return categoryModel
+  }
+
+  return undefined
+}