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/features/background-agent/manager.ts

@@ -675,21 +675,33 @@ Use \`background_output(task_id="${task.id}")\` to retrieve this result when rea
 </system-reminder>`
     }
 
-    // Dynamically lookup the parent session's current message context
+    let agent: string | undefined = task.parentAgent
-    // This ensures we use the CURRENT model/agent, not the stale one from task creation time
+    let model: { providerID: string; modelID: string } | undefined
+
+    try {
+      const messagesResp = await this.client.session.messages({ path: { id: task.parentSessionID } })
+      const messages = (messagesResp.data ?? []) as Array<{
+        info?: { agent?: string; model?: { providerID: string; modelID: string } }
+      }>
+      for (let i = messages.length - 1; i >= 0; i--) {
+        const info = messages[i].info
+        if (info?.agent || info?.model) {
+          agent = info.agent ?? task.parentAgent
+          model = info.model
+          break
+        }
+      }
+    } catch {
       const messageDir = getMessageDir(task.parentSessionID)
       const currentMessage = messageDir ? findNearestMessageWithFields(messageDir) : null
-
+      agent = currentMessage?.agent ?? task.parentAgent
-    const agent = currentMessage?.agent ?? task.parentAgent
+      model = currentMessage?.model?.providerID && currentMessage?.model?.modelID
-    const model = currentMessage?.model?.providerID && currentMessage?.model?.modelID
         ? { providerID: currentMessage.model.providerID, modelID: currentMessage.model.modelID }
         : undefined
+    }
 
     log("[background-agent] notifyParentSession context:", {
       taskId: task.id,
-      messageDir: !!messageDir,
-      currentAgent: currentMessage?.agent,
-      currentModel: currentMessage?.model,
       resolvedAgent: agent,
       resolvedModel: model,
     })

src/features/hook-message-injector/index.ts

@@ -1,4 +1,4 @@
 export { injectHookMessage, findNearestMessageWithFields, findFirstMessageWithAgent } from "./injector"
 export type { StoredMessage } from "./injector"
-export type { MessageMeta, OriginalMessageContext, TextPart } from "./types"
+export type { MessageMeta, OriginalMessageContext, TextPart, ToolPermission } from "./types"
 export { MESSAGE_STORAGE } from "./constants"

src/hooks/ralph-loop/index.ts

@@ -315,12 +315,30 @@ export function createRalphLoopHook(
         .catch(() => {})
 
       try {
+        let agent: string | undefined
+        let model: { providerID: string; modelID: string } | undefined
+
+        try {
+          const messagesResp = await ctx.client.session.messages({ path: { id: sessionID } })
+          const messages = (messagesResp.data ?? []) as Array<{
+            info?: { agent?: string; model?: { providerID: string; modelID: string } }
+          }>
+          for (let i = messages.length - 1; i >= 0; i--) {
+            const info = messages[i].info
+            if (info?.agent || info?.model) {
+              agent = info.agent
+              model = info.model
+              break
+            }
+          }
+        } catch {
           const messageDir = getMessageDir(sessionID)
           const currentMessage = messageDir ? findNearestMessageWithFields(messageDir) : null
-        const agent = currentMessage?.agent
+          agent = currentMessage?.agent
-        const model = currentMessage?.model?.providerID && currentMessage?.model?.modelID
+          model = currentMessage?.model?.providerID && currentMessage?.model?.modelID
             ? { providerID: currentMessage.model.providerID, modelID: currentMessage.model.modelID }
             : undefined
+        }
 
         await ctx.client.session.prompt({
           path: { id: sessionID },

src/hooks/sisyphus-orchestrator/index.ts

@@ -436,11 +436,26 @@ export function createSisyphusOrchestratorHook(
     try {
       log(`[${HOOK_NAME}] Injecting boulder continuation`, { sessionID, planName, remaining })
 
+      let model: { providerID: string; modelID: string } | undefined
+      try {
+        const messagesResp = await ctx.client.session.messages({ path: { id: sessionID } })
+        const messages = (messagesResp.data ?? []) as Array<{
+          info?: { model?: { providerID: string; modelID: string } }
+        }>
+        for (let i = messages.length - 1; i >= 0; i--) {
+          const msgModel = messages[i].info?.model
+          if (msgModel?.providerID && msgModel?.modelID) {
+            model = { providerID: msgModel.providerID, modelID: msgModel.modelID }
+            break
+          }
+        }
+      } catch {
         const messageDir = getMessageDir(sessionID)
         const currentMessage = messageDir ? findNearestMessageWithFields(messageDir) : null
-      const model = currentMessage?.model?.providerID && currentMessage?.model?.modelID
+        model = currentMessage?.model?.providerID && currentMessage?.model?.modelID
           ? { providerID: currentMessage.model.providerID, modelID: currentMessage.model.modelID }
           : undefined
+      }
 
       await ctx.client.session.prompt({
         path: { id: sessionID },

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
     }
 
+    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 editPermission = tools?.edit
-    const writePermission = prevMessage?.tools?.write
+    const writePermission = tools?.write
-    const hasWritePermission = !prevMessage?.tools ||
+    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) {
+          const info = messages[i].info
-            agentName = messages[i].info?.agent
+          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(`[${HOOK_NAME}] Agent check`, { sessionID, agentName, skipAgents })
+      log(`[${HOOK_NAME}] Agent check`, { sessionID, agentName: resolvedInfo?.agent, skipAgents })
-      if (agentName && skipAgents.includes(agentName)) {
+      if (resolvedInfo?.agent && skipAgents.includes(resolvedInfo.agent)) {
-        log(`[${HOOK_NAME}] Skipped: agent in skipAgents list`, { sessionID, agent: agentName })
+        log(`[${HOOK_NAME}] Skipped: agent in skipAgents list`, { sessionID, agent: resolvedInfo.agent })
         return
       }
 
-      startCountdown(sessionID, incompleteCount, todos.length)
+      startCountdown(sessionID, incompleteCount, todos.length, resolvedInfo)
       return
     }
 

src/tools/sisyphus-task/tools.ts

@@ -279,12 +279,30 @@ Use \`background_output\` with task_id="${task.id}" to check progress.`
         })
 
         try {
+          let resumeAgent: string | undefined
+          let resumeModel: { providerID: string; modelID: string } | undefined
+
+          try {
+            const messagesResp = await client.session.messages({ path: { id: args.resume } })
+            const messages = (messagesResp.data ?? []) as Array<{
+              info?: { agent?: string; model?: { providerID: string; modelID: string } }
+            }>
+            for (let i = messages.length - 1; i >= 0; i--) {
+              const info = messages[i].info
+              if (info?.agent || info?.model) {
+                resumeAgent = info.agent
+                resumeModel = info.model
+                break
+              }
+            }
+          } catch {
             const resumeMessageDir = getMessageDir(args.resume)
             const resumeMessage = resumeMessageDir ? findNearestMessageWithFields(resumeMessageDir) : null
-          const resumeAgent = resumeMessage?.agent
+            resumeAgent = resumeMessage?.agent
-          const resumeModel = resumeMessage?.model?.providerID && resumeMessage?.model?.modelID
+            resumeModel = resumeMessage?.model?.providerID && resumeMessage?.model?.modelID
               ? { providerID: resumeMessage.model.providerID, modelID: resumeMessage.model.modelID }
               : undefined
+          }
 
           await client.session.prompt({
             path: { id: args.resume },