fix(runtime-fallback): per-model cooldown and stricter retry patterns

src/hooks/runtime-fallback/constants.ts

@@ -29,9 +29,9 @@ export const RETRYABLE_ERROR_PATTERNS = [
   /overloaded/i,
   /temporarily.?unavailable/i,
   /try.?again/i,
-  /429/,
+  /\b429\b/,
-  /503/,
+  /\b503\b/,
-  /529/,
+  /\b529\b/,
 ]
 
 /**

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

@@ -1,7 +1,8 @@
 import { describe, expect, test, beforeEach, afterEach, spyOn } from "bun:test"
 import { createRuntimeFallbackHook, type RuntimeFallbackHook } from "./index"
-import type { RuntimeFallbackConfig } from "../../config"
+import type { RuntimeFallbackConfig, OhMyOpenCodeConfig } from "../../config"
 import * as sharedModule from "../../shared"
+import { SessionCategoryRegistry } from "../../shared/session-category-registry"
 
 describe("runtime-fallback", () => {
   let logCalls: Array<{ msg: string; data?: unknown }>
@@ -11,12 +12,14 @@ describe("runtime-fallback", () => {
   beforeEach(() => {
     logCalls = []
     toastCalls = []
+    SessionCategoryRegistry.clear()
     logSpy = spyOn(sharedModule, "log").mockImplementation((msg: string, data?: unknown) => {
       logCalls.push({ msg, data })
     })
   })
 
   afterEach(() => {
+    SessionCategoryRegistry.clear()
     logSpy?.mockRestore()
   })
 
@@ -48,6 +51,16 @@ describe("runtime-fallback", () => {
     }
   }
 
+  function createMockPluginConfigWithCategoryFallback(fallbackModels: string[]): OhMyOpenCodeConfig {
+    return {
+      categories: {
+        test: {
+          fallback_models: fallbackModels,
+        },
+      },
+    }
+  }
+
   describe("session.error handling", () => {
     test("should detect retryable error with status code 429", async () => {
       const hook = createRuntimeFallbackHook(createMockPluginInput(), { config: createMockConfig() })
@@ -448,11 +461,15 @@ describe("runtime-fallback", () => {
   })
 
   describe("model switching via chat.message", () => {
-    test("should set pending fallback model after error", async () => {
+    test("should apply fallback model on next chat.message after error", async () => {
-      const hook = createRuntimeFallbackHook(createMockPluginInput(), { config: createMockConfig() })
+      const hook = createRuntimeFallbackHook(createMockPluginInput(), {
+        config: createMockConfig({ notify_on_fallback: false }),
+        pluginConfig: createMockPluginConfigWithCategoryFallback(["openai/gpt-5.2", "google/gemini-3-pro"]),
+      })
       const sessionID = "test-session-switch"
+      SessionCategoryRegistry.register(sessionID, "test")
 
-      //#given - session with fallback models configured
+      //#given
       await hook.event({
         event: {
           type: "session.created",
@@ -460,25 +477,30 @@ describe("runtime-fallback", () => {
         },
       })
 
-      //#when - retryable error occurs
+      //#when
       await hook.event({
         event: {
           type: "session.error",
-          properties: {
+          properties: { sessionID, error: { statusCode: 429, message: "Rate limit" } },
-            sessionID,
-            error: { statusCode: 429, message: "Rate limit" },
-          },
         },
       })
 
-      //#then - fallback preparation should be logged
+      const output = { message: {}, parts: [] }
-      const fallbackPrepLog = logCalls.find((c) => c.msg.includes("Preparing fallback") || c.msg.includes("fallback"))
+      await hook["chat.message"]?.(
-      expect(fallbackPrepLog !== undefined || logCalls.some(c => c.msg.includes("No fallback"))).toBe(true)
+        { sessionID, model: { providerID: "anthropic", modelID: "claude-opus-4-5" } },
+        output
+      )
+
+      expect(output.message.model).toEqual({ providerID: "openai", modelID: "gpt-5.2" })
     })
 
     test("should notify when fallback occurs", async () => {
-      const hook = createRuntimeFallbackHook(createMockPluginInput(), { config: createMockConfig() })
+      const hook = createRuntimeFallbackHook(createMockPluginInput(), {
+        config: createMockConfig({ notify_on_fallback: true }),
+        pluginConfig: createMockPluginConfigWithCategoryFallback(["openai/gpt-5.2"]),
+      })
       const sessionID = "test-session-notify"
+      SessionCategoryRegistry.register(sessionID, "test")
 
       await hook.event({
         event: {
@@ -490,13 +512,12 @@ describe("runtime-fallback", () => {
       await hook.event({
         event: {
           type: "session.error",
-          properties: { sessionID, error: { statusCode: 429 }, agent: "sisyphus" },
+          properties: { sessionID, error: { statusCode: 429 } },
         },
       })
 
-      //#then - should show notification toast or prepare fallback
+      expect(toastCalls.length).toBe(1)
-      const notifyLog = logCalls.find((c) => c.msg.includes("Preparing fallback") || c.msg.includes("No fallback models"))
+      expect(toastCalls[0]?.message.includes("gpt-5.2")).toBe(true)
-      expect(notifyLog).toBeDefined()
     })
   })
 
@@ -553,9 +574,14 @@ describe("runtime-fallback", () => {
   describe("cooldown mechanism", () => {
     test("should respect cooldown period before retrying failed model", async () => {
       const hook = createRuntimeFallbackHook(createMockPluginInput(), {
-        config: createMockConfig({ cooldown_seconds: 1 }),
+        config: createMockConfig({ cooldown_seconds: 60, notify_on_fallback: false }),
+        pluginConfig: createMockPluginConfigWithCategoryFallback([
+          "openai/gpt-5.2",
+          "anthropic/claude-opus-4-5",
+        ]),
       })
       const sessionID = "test-session-cooldown"
+      SessionCategoryRegistry.register(sessionID, "test")
 
       await hook.event({
         event: {
@@ -564,7 +590,7 @@ describe("runtime-fallback", () => {
         },
       })
 
-      //#when - first error occurs
+      //#when - first error occurs, switches to openai
       await hook.event({
         event: {
           type: "session.error",
@@ -572,11 +598,7 @@ describe("runtime-fallback", () => {
         },
       })
 
-      const firstFallback = logCalls.find((c) => c.msg.includes("Preparing fallback") || c.msg.includes("No fallback models"))
+      //#when - second error occurs immediately; tries to switch back to original model but should be in cooldown
-      expect(firstFallback).toBeDefined()
-
-      //#when - second error occurs immediately (within cooldown)
-      logCalls = []
       await hook.event({
         event: {
           type: "session.error",
@@ -584,11 +606,8 @@ describe("runtime-fallback", () => {
         },
       })
 
-      //#then - should skip due to cooldown (no new logs or cooldown message)
+      const cooldownSkipLog = logCalls.find((c) => c.msg.includes("Skipping fallback model in cooldown"))
-      const hasCooldownSkip = logCalls.some((c) => 
+      expect(cooldownSkipLog).toBeDefined()
-        c.msg.includes("cooldown") || c.msg.includes("Skipping")
-      )
-      expect(hasCooldownSkip || logCalls.length <= 2).toBe(true)
     })
   })
 

src/hooks/runtime-fallback/index.ts

@@ -1,6 +1,6 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import type { RuntimeFallbackConfig, OhMyOpenCodeConfig } from "../../config"
-import type { FallbackState, FallbackResult, RuntimeFallbackHook } from "./types"
+import type { FallbackState, FallbackResult, RuntimeFallbackHook, RuntimeFallbackOptions } from "./types"
 import { DEFAULT_CONFIG, RETRYABLE_ERROR_PATTERNS, HOOK_NAME } from "./constants"
 import { log } from "../../shared/logger"
 import { SessionCategoryRegistry } from "../../shared/session-category-registry"
@@ -10,8 +10,7 @@ function createFallbackState(originalModel: string): FallbackState {
     originalModel,
     currentModel: originalModel,
     fallbackIndex: -1,
-    lastFallbackTime: 0,
+    failedModels: new Map<string, number>(),
-    failedModels: new Set<string>(),
     attemptCount: 0,
     pendingFallbackModel: undefined,
   }
@@ -132,12 +131,10 @@ function getFallbackModelsForSession(
 }
 
 function isModelInCooldown(model: string, state: FallbackState, cooldownSeconds: number): boolean {
-  if (!state.failedModels.has(model)) return false
+  const failedAt = state.failedModels.get(model)
-
+  if (failedAt === undefined) return false
   const cooldownMs = cooldownSeconds * 1000
-  const timeSinceLastFallback = Date.now() - state.lastFallbackTime
+  return Date.now() - failedAt < cooldownMs
-
-  return timeSinceLastFallback < cooldownMs
 }
 
 function findNextAvailableFallback(
@@ -180,9 +177,11 @@ function prepareFallback(
     attempt: state.attemptCount + 1,
   })
 
+  const failedModel = state.currentModel
+  const now = Date.now()
+
   state.fallbackIndex = fallbackModels.indexOf(nextModel)
-  state.failedModels.add(state.currentModel)
+  state.failedModels.set(failedModel, now)
-  state.lastFallbackTime = Date.now()
   state.attemptCount++
   state.currentModel = nextModel
   state.pendingFallbackModel = nextModel
@@ -194,7 +193,7 @@ export type { RuntimeFallbackHook, RuntimeFallbackOptions } from "./types"
 
 export function createRuntimeFallbackHook(
   ctx: PluginInput,
-  options?: { config?: RuntimeFallbackConfig }
+  options?: RuntimeFallbackOptions
 ): RuntimeFallbackHook {
   const config: Required<RuntimeFallbackConfig> = {
     enabled: options?.config?.enabled ?? DEFAULT_CONFIG.enabled,
@@ -207,11 +206,15 @@ export function createRuntimeFallbackHook(
   const sessionStates = new Map<string, FallbackState>()
 
   let pluginConfig: OhMyOpenCodeConfig | undefined
-  try {
+  if (options?.pluginConfig) {
-    const { loadPluginConfig } = require("../../plugin-config")
+    pluginConfig = options.pluginConfig
-    pluginConfig = loadPluginConfig(ctx.directory, ctx)
+  } else {
-  } catch {
+    try {
-    log(`[${HOOK_NAME}] Plugin config not available`)
+      const { loadPluginConfig } = require("../../plugin-config")
+      pluginConfig = loadPluginConfig(ctx.directory, ctx)
+    } catch {
+      log(`[${HOOK_NAME}] Plugin config not available`)
+    }
   }
 
   const eventHandler = async ({ event }: { event: { type: string; properties?: unknown } }) => {
@@ -238,6 +241,7 @@ export function createRuntimeFallbackHook(
       if (sessionID) {
         log(`[${HOOK_NAME}] Cleaning up session state`, { sessionID })
         sessionStates.delete(sessionID)
+        SessionCategoryRegistry.remove(sessionID)
       }
       return
     }

src/hooks/runtime-fallback/types.ts

@@ -4,7 +4,7 @@
  * Types for managing runtime model fallback when API errors occur.
  */
 
-import type { RuntimeFallbackConfig } from "../../config"
+import type { RuntimeFallbackConfig, OhMyOpenCodeConfig } from "../../config"
 
 /**
  * Tracks the state of fallback attempts for a session
@@ -13,8 +13,7 @@ export interface FallbackState {
   originalModel: string
   currentModel: string
   fallbackIndex: number
-  lastFallbackTime: number
+  failedModels: Map<string, number>
-  failedModels: Set<string>
   attemptCount: number
   pendingFallbackModel?: string
 }
@@ -57,6 +56,8 @@ export interface FallbackResult {
 export interface RuntimeFallbackOptions {
   /** Runtime fallback configuration */
   config?: RuntimeFallbackConfig
+  /** Optional plugin config override (primarily for testing) */
+  pluginConfig?: OhMyOpenCodeConfig
 }
 
 export interface RuntimeFallbackHook {