diff --git a/sync/sync-agent.ps1 b/sync/sync-agent.ps1
index 5299dd0..b4cc09f 100644
--- a/sync/sync-agent.ps1
+++ b/sync/sync-agent.ps1
@@ -1,13 +1,16 @@
 param(
     [int]$IntervalSeconds = 30,
+    [int]$HeartbeatEverySeconds = 60,
     [switch]$Once
 )
 
 $ErrorActionPreference = "Stop"
 
 $RepoRoot = (Resolve-Path (Join-Path $PSScriptRoot "..")).Path
-$StateDir = Join-Path $RepoRoot ".sync-state"
-$ErrorFile = Join-Path $StateDir "sync-error-pc.md"
+$LocalStateDir = Join-Path $RepoRoot ".sync-state"
+$PublicStateDir = Join-Path $RepoRoot "sync-state"
+$HeartbeatFile = Join-Path $PublicStateDir "heartbeat-pc.json"
+$ErrorFile = Join-Path $PublicStateDir "error-pc.md"
 $AllowedPaths = @(
     "AGENT_BOARD.md",
     "README.md",
@@ -17,12 +20,16 @@ $AllowedPaths = @(
     "rollback",
     "tasks",
     "sync",
+    "sync-state",
+    ".gitattributes",
     ".gitignore"
 )
 
 function Ensure-StateDir {
-    if (-not (Test-Path $StateDir)) {
-        New-Item -ItemType Directory -Path $StateDir | Out-Null
+    foreach ($path in @($LocalStateDir, $PublicStateDir)) {
+        if (-not (Test-Path $path)) {
+            New-Item -ItemType Directory -Path $path | Out-Null
+        }
     }
 }
 
@@ -42,6 +49,15 @@ Manual action required. Do not continue automatic sync until the repository is c
 "@ | Set-Content -Path $ErrorFile -Encoding UTF8
 }
 
+function Get-GitOutput {
+    param([string[]]$GitArgs)
+    $output = & git @GitArgs
+    if ($LASTEXITCODE -ne 0) {
+        throw "git $($GitArgs -join ' ') failed with exit code $LASTEXITCODE"
+    }
+    return $output
+}
+
 function Invoke-Git {
     param([string[]]$GitArgs)
     & git @GitArgs
@@ -79,6 +95,48 @@ function Test-ConflictMarkers {
     return -not [string]::IsNullOrWhiteSpace(($conflicts -join ""))
 }
 
+function Get-RepoCleanStatus {
+    $changes = & git -C $RepoRoot status --porcelain
+    if ($LASTEXITCODE -ne 0) {
+        throw "git status failed with exit code $LASTEXITCODE"
+    }
+    if ([string]::IsNullOrWhiteSpace(($changes -join ""))) {
+        return "clean"
+    }
+    return "dirty"
+}
+
+function Test-HeartbeatDue {
+    if ($Once -or -not (Test-Path $HeartbeatFile)) {
+        return $true
+    }
+
+    $age = (Get-Date) - (Get-Item $HeartbeatFile).LastWriteTime
+    return $age.TotalSeconds -ge $HeartbeatEverySeconds
+}
+
+function Write-Heartbeat {
+    Ensure-StateDir
+    if (-not (Test-HeartbeatDue)) {
+        return
+    }
+
+    $head = (Get-GitOutput @("-C", $RepoRoot, "rev-parse", "--short", "HEAD")) -join ""
+    $branch = (Get-GitOutput @("-C", $RepoRoot, "branch", "--show-current")) -join ""
+    $status = Get-RepoCleanStatus
+    $timestamp = Get-Date -Format "yyyy-MM-ddTHH:mm:sszzz"
+
+    [ordered]@{
+        host = "pc"
+        time = $timestamp
+        branch = $branch
+        head = $head
+        status = $status
+        intervalSeconds = $IntervalSeconds
+        heartbeatEverySeconds = $HeartbeatEverySeconds
+    } | ConvertTo-Json | Set-Content -Path $HeartbeatFile -Encoding UTF8
+}
+
 function Sync-Once {
     Set-Location $RepoRoot
     Ensure-StateDir
@@ -89,6 +147,8 @@ function Sync-Once {
         throw "merge or rebase conflicts detected"
     }
 
+    Write-Heartbeat
+
     $allowedChanges = @(Get-AllowedChanges)
     if ($allowedChanges.Count -eq 0) {
         return
diff --git a/sync/sync-agent.sh b/sync/sync-agent.sh
index ea36d34..a0e8877 100644
--- a/sync/sync-agent.sh
+++ b/sync/sync-agent.sh
@@ -2,12 +2,15 @@
 set -euo pipefail
 
 INTERVAL_SECONDS="${INTERVAL_SECONDS:-30}"
+HEARTBEAT_EVERY_SECONDS="${HEARTBEAT_EVERY_SECONDS:-60}"
 ONCE="${1:-}"
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
-STATE_DIR="$REPO_ROOT/.sync-state"
-ERROR_FILE="$STATE_DIR/sync-error-vps.md"
+LOCAL_STATE_DIR="$REPO_ROOT/.sync-state"
+PUBLIC_STATE_DIR="$REPO_ROOT/sync-state"
+HEARTBEAT_FILE="$PUBLIC_STATE_DIR/heartbeat-vps.json"
+ERROR_FILE="$PUBLIC_STATE_DIR/error-vps.md"
 
 ALLOWED_PATHS=(
   "AGENT_BOARD.md"
@@ -18,11 +21,13 @@ ALLOWED_PATHS=(
   "rollback"
   "tasks"
   "sync"
+  "sync-state"
+  ".gitattributes"
   ".gitignore"
 )
 
 ensure_state_dir() {
-  mkdir -p "$STATE_DIR"
+  mkdir -p "$LOCAL_STATE_DIR" "$PUBLIC_STATE_DIR"
 }
 
 write_sync_error() {
@@ -41,6 +46,51 @@ Manual action required. Do not continue automatic sync until the repository is c
 EOF
 }
 
+repo_clean_status() {
+  if [[ -z "$(git status --porcelain)" ]]; then
+    echo "clean"
+  else
+    echo "dirty"
+  fi
+}
+
+heartbeat_due() {
+  if [[ "$ONCE" == "--once" || ! -f "$HEARTBEAT_FILE" ]]; then
+    return 0
+  fi
+
+  local now last age
+  now="$(date +%s)"
+  last="$(stat -c %Y "$HEARTBEAT_FILE")"
+  age=$((now - last))
+  [[ "$age" -ge "$HEARTBEAT_EVERY_SECONDS" ]]
+}
+
+write_heartbeat() {
+  ensure_state_dir
+  if ! heartbeat_due; then
+    return 0
+  fi
+
+  local head branch status timestamp
+  head="$(git rev-parse --short HEAD)"
+  branch="$(git branch --show-current)"
+  status="$(repo_clean_status)"
+  timestamp="$(date '+%Y-%m-%dT%H:%M:%S%z')"
+
+  cat > "$HEARTBEAT_FILE" <<EOF
+{
+  "host": "vps",
+  "time": "$timestamp",
+  "branch": "$branch",
+  "head": "$head",
+  "status": "$status",
+  "intervalSeconds": $INTERVAL_SECONDS,
+  "heartbeatEverySeconds": $HEARTBEAT_EVERY_SECONDS
+}
+EOF
+}
+
 has_allowed_changes() {
   local line path allowed
   while IFS= read -r line; do
@@ -69,6 +119,8 @@ sync_once() {
     return 20
   fi
 
+  write_heartbeat
+
   if ! has_allowed_changes; then
     return 0
   fi