Track Claude activity state via hook-based marker files

src/cli.ts

@@ -233,10 +233,9 @@ program
     }
 
     // Determine status for each session in parallel
-    const activeWorktrees = await vm.activeWorktrees()
     const statusEntries = await Promise.all(
       sessions.map(async (s): Promise<[string, string]> => {
-        if (activeWorktrees.includes(s.worktree)) return [s.branch, "active"]
+        if (await vm.isClaudeActive(s.worktree, s.branch)) return [s.branch, "active"]
         const dirty = await git.isDirty(s.worktree)
         if (dirty) return [s.branch, "dirty"]
         const commits = await git.hasNewCommits(s.worktree)
@@ -362,6 +361,8 @@ const closeAction = async (branch: string) => {
   const session = await state.getSession(root, branch)
   const worktreeAbs = session?.worktree ?? join(homedir(), '.sandlot', basename(root), branch)
 
+  await vm.clearActivity(worktreeAbs, branch)
+
   await git.removeWorktree(worktreeAbs, root)
     .catch((e) => console.warn(`⚠ Failed to remove worktree: ${e.message}`))
 

src/vm.ts

@@ -1,5 +1,6 @@
 import { $ } from "bun"
 import { homedir } from "os"
+import { dirname } from "path"
 
 const CONTAINER_NAME = "sandlot"
 const USER = "ubuntu"
@@ -73,9 +74,13 @@ export async function ensure(log?: (msg: string) => void): Promise<void> {
     log?.("Warning: ANTHROPIC_API_KEY not found in ~/.env — claude will require manual login")
   }
 
+  const hooks = {
+    UserPromptSubmit: [{ hooks: [{ type: "command", command: "sandlot-activity active" }] }],
+    Stop: [{ hooks: [{ type: "command", command: "sandlot-activity idle" }] }],
+  }
   const settingsJson = JSON.stringify(apiKey
-    ? { apiKeyHelper: "~/.claude/api-key-helper.sh", skipDangerousModePermissionPrompt: true }
+    ? { apiKeyHelper: "~/.claude/api-key-helper.sh", skipDangerousModePermissionPrompt: true, hooks }
-    : { skipDangerousModePermissionPrompt: true })
+    : { skipDangerousModePermissionPrompt: true, hooks })
   const claudeJson = JSON.stringify({ hasCompletedOnboarding: true, effortCalloutDismissed: true })
 
   // Write the helper script to a temp file and copy it in so the key
@@ -88,6 +93,19 @@ export async function ensure(log?: (msg: string) => void): Promise<void> {
     await Bun.file(tmp).unlink()
   }
 
+  // Install activity tracking hook script
+  const activityTmp = `${home}/.sandlot/.sandlot-activity.tmp`
+  await Bun.write(activityTmp, [
+    '#!/bin/bash',
+    'DIR=$(dirname "$CLAUDE_PROJECT_DIR")',
+    'BRANCH=$(basename "$CLAUDE_PROJECT_DIR")',
+    'echo "$1" > "$DIR/.activity-$BRANCH"',
+    '',
+  ].join('\n'))
+  await $`chmod +x ${activityTmp}`.quiet()
+  await $`container exec --user ${USER} ${CONTAINER_NAME} bash -c ${"cp /sandlot/.sandlot-activity.tmp ~/.local/bin/sandlot-activity"}`.quiet()
+  await Bun.file(activityTmp).unlink()
+
   await $`container exec --user ${USER} ${CONTAINER_NAME} bash -c ${`
 mkdir -p ~/.claude
 echo '${settingsJson}' > ~/.claude/settings.json
@@ -178,6 +196,23 @@ export async function activeWorktrees(): Promise<string[]> {
   })
 }
 
+/** Check if Claude is actively working in the given worktree (based on activity hook). */
+export async function isClaudeActive(worktree: string, branch: string): Promise<boolean> {
+  const file = `${dirname(worktree)}/.activity-${branch}`
+  try {
+    const content = await Bun.file(file).text()
+    return content.trim() === "active"
+  } catch {
+    return false
+  }
+}
+
+/** Remove the activity marker file for a worktree. */
+export async function clearActivity(worktree: string, branch: string): Promise<void> {
+  const file = `${dirname(worktree)}/.activity-${branch}`
+  await Bun.file(file).unlink().catch(() => {})
+}
+
 /** Stop the container. */
 export async function stop(): Promise<void> {
   await $`container stop ${CONTAINER_NAME}`.nothrow().quiet()