feat(config): add runtime_fallback and fallback_models schema

Add configuration schemas for runtime model fallback feature:
- RuntimeFallbackConfigSchema with enabled, retry_on_errors,
  max_fallback_attempts, cooldown_seconds, notify_on_fallback
- FallbackModelsSchema for init-time fallback model selection
- Add fallback_models to AgentOverrideConfigSchema and CategoryConfigSchema
- Export types and schemas from config/index.ts

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/config/index.ts

@@ -11,6 +11,8 @@ export {
   RalphLoopConfigSchema,
   TmuxConfigSchema,
   TmuxLayoutSchema,
+  RuntimeFallbackConfigSchema,
+  FallbackModelsSchema,
 } from "./schema"
 
 export type {
@@ -29,4 +31,5 @@ export type {
   TmuxLayout,
   SisyphusConfig,
   SisyphusTasksConfig,
+  RuntimeFallbackConfig,
 } from "./schema"

src/config/schema.ts

@@ -9,11 +9,13 @@ export * from "./schema/comment-checker"
 export * from "./schema/commands"
 export * from "./schema/dynamic-context-pruning"
 export * from "./schema/experimental"
+export * from "./schema/fallback-models"
 export * from "./schema/git-master"
 export * from "./schema/hooks"
 export * from "./schema/notification"
 export * from "./schema/oh-my-opencode-config"
 export * from "./schema/ralph-loop"
+export * from "./schema/runtime-fallback"
 export * from "./schema/skills"
 export * from "./schema/sisyphus"
 export * from "./schema/sisyphus-agent"

src/config/schema/agent-overrides.ts

@@ -1,9 +1,11 @@
 import { z } from "zod"
+import { FallbackModelsSchema } from "./fallback-models"
 import { AgentPermissionSchema } from "./internal/permission"
 
 export const AgentOverrideConfigSchema = z.object({
   /** @deprecated Use `category` instead. Model is inherited from category defaults. */
   model: z.string().optional(),
+  fallback_models: FallbackModelsSchema.optional(),
   variant: z.string().optional(),
   /** Category name to inherit model and other settings from CategoryConfig */
   category: z.string().optional(),

src/config/schema/categories.ts

@@ -1,9 +1,11 @@
 import { z } from "zod"
+import { FallbackModelsSchema } from "./fallback-models"
 
 export const CategoryConfigSchema = z.object({
   /** Human-readable description of the category's purpose. Shown in task prompt. */
   description: z.string().optional(),
   model: z.string().optional(),
+  fallback_models: FallbackModelsSchema.optional(),
   variant: z.string().optional(),
   temperature: z.number().min(0).max(2).optional(),
   top_p: z.number().min(0).max(1).optional(),

src/config/schema/fallback-models.ts

@@ -0,0 +1,5 @@
+import { z } from "zod"
+
+export const FallbackModelsSchema = z.union([z.string(), z.array(z.string())])
+
+export type FallbackModels = z.infer<typeof FallbackModelsSchema>

src/config/schema/hooks.ts

@@ -46,6 +46,7 @@ export const HookNameSchema = z.enum([
   "task-resume-info",
   "stop-continuation-guard",
   "tasks-todowrite-disabler",
+  "runtime-fallback",
   "write-existing-file-guard",
   "anthropic-effort",
   "hashline-read-enhancer",

src/config/schema/oh-my-opencode-config.ts

@@ -14,6 +14,7 @@ import { GitMasterConfigSchema } from "./git-master"
 import { HookNameSchema } from "./hooks"
 import { NotificationConfigSchema } from "./notification"
 import { RalphLoopConfigSchema } from "./ralph-loop"
+import { RuntimeFallbackConfigSchema } from "./runtime-fallback"
 import { SkillsConfigSchema } from "./skills"
 import { SisyphusConfigSchema } from "./sisyphus"
 import { SisyphusAgentConfigSchema } from "./sisyphus-agent"
@@ -52,6 +53,7 @@ export const OhMyOpenCodeConfigSchema = z.object({
   websearch: WebsearchConfigSchema.optional(),
   tmux: TmuxConfigSchema.optional(),
   sisyphus: SisyphusConfigSchema.optional(),
+  runtime_fallback: RuntimeFallbackConfigSchema.optional(),
   /** Migration history to prevent re-applying migrations (e.g., model version upgrades) */
   _migrations: z.array(z.string()).optional(),
 })

src/config/schema/runtime-fallback.ts

@@ -0,0 +1,11 @@
+import { z } from "zod"
+
+export const RuntimeFallbackConfigSchema = z.object({
+  enabled: z.boolean().default(true),
+  retry_on_errors: z.array(z.number()).default([429, 503, 529]),
+  max_fallback_attempts: z.number().min(1).max(10).default(3),
+  cooldown_seconds: z.number().min(0).default(60),
+  notify_on_fallback: z.boolean().default(true),
+})
+
+export type RuntimeFallbackConfig = z.infer<typeof RuntimeFallbackConfigSchema>