fix(hooks): use API instead of filesystem to resolve model info for session.prompt

Previously, continuation hooks (todo-continuation, boulder-continuation, ralph-loop)
and background tasks resolved model info from filesystem cache, which could be stale
or missing. This caused session.prompt to fallback to default model (Sonnet) instead
of using the originally configured model (e.g., Opus).

Now all session.prompt calls first try API (session.messages) to get current model
info, with filesystem as fallback if API fails.

Affected files:
- todo-continuation-enforcer.ts
- sisyphus-orchestrator/index.ts
- ralph-loop/index.ts
- background-agent/manager.ts
- sisyphus-task/tools.ts
- hook-message-injector/index.ts (export ToolPermission type)

src/hooks/todo-continuation-enforcer.ts

@@ -6,6 +6,7 @@ import { getMainSessionID, subagentSessions } from "../features/claude-code-sess
 import {
     findNearestMessageWithFields,
     MESSAGE_STORAGE,
+    type ToolPermission,
 } from "../features/hook-message-injector"
 import { log } from "../shared/logger"
 
@@ -151,7 +152,18 @@ export function createTodoContinuationEnforcer(
     }).catch(() => {})
   }
 
-  async function injectContinuation(sessionID: string, incompleteCount: number, total: number): Promise<void> {
+  interface ResolvedMessageInfo {
+    agent?: string
+    model?: { providerID: string; modelID: string }
+    tools?: Record<string, ToolPermission>
+  }
+
+  async function injectContinuation(
+    sessionID: string,
+    incompleteCount: number,
+    total: number,
+    resolvedInfo?: ResolvedMessageInfo
+  ): Promise<void> {
     const state = sessions.get(sessionID)
 
     if (state?.isRecovering) {
@@ -159,8 +171,6 @@ export function createTodoContinuationEnforcer(
       return
     }
 
-
-
     const hasRunningBgTasks = backgroundManager
       ? backgroundManager.getTasksByParentSession(sessionID).some(t => t.status === "running")
       : false
@@ -185,38 +195,44 @@ export function createTodoContinuationEnforcer(
       return
     }
 
-    const messageDir = getMessageDir(sessionID)
-    const prevMessage = messageDir ? findNearestMessageWithFields(messageDir) : null
+    let agentName = resolvedInfo?.agent
+    let model = resolvedInfo?.model
+    let tools = resolvedInfo?.tools
+
+    if (!agentName || !model) {
+      const messageDir = getMessageDir(sessionID)
+      const prevMessage = messageDir ? findNearestMessageWithFields(messageDir) : null
+      agentName = agentName ?? prevMessage?.agent
+      model = model ?? (prevMessage?.model?.providerID && prevMessage?.model?.modelID
+        ? { providerID: prevMessage.model.providerID, modelID: prevMessage.model.modelID }
+        : undefined)
+      tools = tools ?? prevMessage?.tools
+    }
 
-    const agentName = prevMessage?.agent
     if (agentName && skipAgents.includes(agentName)) {
       log(`[${HOOK_NAME}] Skipped: agent in skipAgents list`, { sessionID, agent: agentName })
       return
     }
 
-    const editPermission = prevMessage?.tools?.edit
-    const writePermission = prevMessage?.tools?.write
-    const hasWritePermission = !prevMessage?.tools ||
+    const editPermission = tools?.edit
+    const writePermission = tools?.write
+    const hasWritePermission = !tools ||
       ((editPermission !== false && editPermission !== "deny") &&
        (writePermission !== false && writePermission !== "deny"))
     if (!hasWritePermission) {
-      log(`[${HOOK_NAME}] Skipped: agent lacks write permission`, { sessionID, agent: prevMessage?.agent })
+      log(`[${HOOK_NAME}] Skipped: agent lacks write permission`, { sessionID, agent: agentName })
       return
     }
 
     const prompt = `${CONTINUATION_PROMPT}\n\n[Status: ${todos.length - freshIncompleteCount}/${todos.length} completed, ${freshIncompleteCount} remaining]`
 
-    const model = prevMessage?.model?.providerID && prevMessage?.model?.modelID
-      ? { providerID: prevMessage.model.providerID, modelID: prevMessage.model.modelID }
-      : undefined
-
     try {
-      log(`[${HOOK_NAME}] Injecting continuation`, { sessionID, agent: prevMessage?.agent, model, incompleteCount: freshIncompleteCount })
+      log(`[${HOOK_NAME}] Injecting continuation`, { sessionID, agent: agentName, model, incompleteCount: freshIncompleteCount })
 
       await ctx.client.session.prompt({
         path: { id: sessionID },
         body: {
-          agent: prevMessage?.agent,
+          agent: agentName,
           ...(model !== undefined ? { model } : {}),
           parts: [{ type: "text", text: prompt }],
         },
@@ -229,7 +245,12 @@ export function createTodoContinuationEnforcer(
     }
   }
 
-  function startCountdown(sessionID: string, incompleteCount: number, total: number): void {
+  function startCountdown(
+    sessionID: string,
+    incompleteCount: number,
+    total: number,
+    resolvedInfo?: ResolvedMessageInfo
+  ): void {
     const state = getState(sessionID)
     cancelCountdown(sessionID)
 
@@ -246,7 +267,7 @@ export function createTodoContinuationEnforcer(
 
     state.countdownTimer = setTimeout(() => {
       cancelCountdown(sessionID)
-      injectContinuation(sessionID, incompleteCount, total)
+      injectContinuation(sessionID, incompleteCount, total, resolvedInfo)
     }, COUNTDOWN_SECONDS * 1000)
 
     log(`[${HOOK_NAME}] Countdown started`, { sessionID, seconds: COUNTDOWN_SECONDS, incompleteCount })
@@ -350,15 +371,26 @@ export function createTodoContinuationEnforcer(
         return
       }
 
-      let agentName: string | undefined
+      let resolvedInfo: ResolvedMessageInfo | undefined
       try {
         const messagesResp = await ctx.client.session.messages({
           path: { id: sessionID },
         })
-        const messages = (messagesResp.data ?? []) as Array<{ info?: { agent?: string } }>
+        const messages = (messagesResp.data ?? []) as Array<{
+          info?: {
+            agent?: string
+            model?: { providerID: string; modelID: string }
+            tools?: Record<string, ToolPermission>
+          }
+        }>
         for (let i = messages.length - 1; i >= 0; i--) {
-          if (messages[i].info?.agent) {
-            agentName = messages[i].info?.agent
+          const info = messages[i].info
+          if (info?.agent || info?.model) {
+            resolvedInfo = {
+              agent: info.agent,
+              model: info.model,
+              tools: info.tools,
+            }
             break
           }
         }
@@ -366,13 +398,13 @@ export function createTodoContinuationEnforcer(
         log(`[${HOOK_NAME}] Failed to fetch messages for agent check`, { sessionID, error: String(err) })
       }
 
-      log(`[${HOOK_NAME}] Agent check`, { sessionID, agentName, skipAgents })
-      if (agentName && skipAgents.includes(agentName)) {
-        log(`[${HOOK_NAME}] Skipped: agent in skipAgents list`, { sessionID, agent: agentName })
+      log(`[${HOOK_NAME}] Agent check`, { sessionID, agentName: resolvedInfo?.agent, skipAgents })
+      if (resolvedInfo?.agent && skipAgents.includes(resolvedInfo.agent)) {
+        log(`[${HOOK_NAME}] Skipped: agent in skipAgents list`, { sessionID, agent: resolvedInfo.agent })
         return
       }
 
-      startCountdown(sessionID, incompleteCount, todos.length)
+      startCountdown(sessionID, incompleteCount, todos.length, resolvedInfo)
       return
     }