diff --git a/.agents/scripts/commands/pulse.md b/.agents/scripts/commands/pulse.md
index abad0107ea..7ef7056100 100644
--- a/.agents/scripts/commands/pulse.md
+++ b/.agents/scripts/commands/pulse.md
@@ -60,13 +60,20 @@ Check external contributor gate before ANY merge (see Pre-merge checks below).
 For each unassigned, non-blocked issue with no open PR and no active worker:
 
 ```bash
-# Dedup guard (MANDATORY)
+# Dedup guard (MANDATORY — all three checks required)
 source ~/.aidevops/agents/scripts/pulse-wrapper.sh
+RUNNER_USER=$(gh api user --jq '.login' 2>/dev/null || whoami)
+
+# 1. Local process dedup (same machine only)
 if has_worker_for_repo_issue NUMBER SLUG; then continue; fi
 if ~/.aidevops/agents/scripts/dispatch-dedup-helper.sh is-duplicate "Issue #NUMBER: TITLE"; then continue; fi
 
+# 2. Cross-machine assignee dedup (checks GitHub — visible to ALL runners)
+# This is the primary guard against duplicate dispatch across machines.
+# If another runner already assigned themselves, skip this issue.
+if ~/.aidevops/agents/scripts/dispatch-dedup-helper.sh is-assigned NUMBER SLUG "$RUNNER_USER"; then continue; fi
+
 # Assign and dispatch
-RUNNER_USER=$(gh api user --jq '.login' 2>/dev/null || whoami)
 gh issue edit NUMBER --repo SLUG --add-assignee "$RUNNER_USER" --add-label "status:queued" 2>/dev/null || true
 
 ~/.aidevops/agents/scripts/headless-runtime-helper.sh run \
diff --git a/.agents/scripts/dispatch-dedup-helper.sh b/.agents/scripts/dispatch-dedup-helper.sh
index 210f7bb33f..f65ec0a73e 100755
--- a/.agents/scripts/dispatch-dedup-helper.sh
+++ b/.agents/scripts/dispatch-dedup-helper.sh
@@ -278,6 +278,72 @@ is_duplicate() {
 	return 1
 }
 
+#######################################
+# Check if a GitHub issue is already assigned to someone else.
+#
+# This is the primary cross-machine dedup guard. Process-based checks
+# (is_duplicate, has_worker_for_repo_issue) only see local processes —
+# they miss workers running on other machines. The GitHub assignee is
+# the single source of truth visible to all runners.
+#
+# Args:
+#   $1 = issue number
+#   $2 = repo slug (owner/repo)
+#   $3 = (optional) current runner login — if assigned to self, not a dup
+# Returns:
+#   exit 0 if assigned to someone else (do NOT dispatch)
+#   exit 1 if unassigned or assigned to self (safe to dispatch)
+# Outputs: assignee info on stdout if assigned
+#######################################
+is_assigned() {
+	local issue_number="$1"
+	local repo_slug="$2"
+	local self_login="${3:-}"
+
+	if [[ -z "$issue_number" || -z "$repo_slug" ]]; then
+		# Missing args — cannot check, allow dispatch
+		return 1
+	fi
+
+	# Validate issue number is numeric
+	if [[ ! "$issue_number" =~ ^[0-9]+$ ]]; then
+		return 1
+	fi
+
+	# Query GitHub for current assignees
+	local assignees
+	assignees=$(gh issue view "$issue_number" --repo "$repo_slug" \
+		--json assignees --jq '[.assignees[].login] | join(",")' 2>/dev/null) || assignees=""
+
+	if [[ -z "$assignees" ]]; then
+		# No assignees — safe to dispatch
+		return 1
+	fi
+
+	# If assigned to self, not a duplicate
+	if [[ -n "$self_login" ]]; then
+		# Check if ALL assignees are self (could be multiple)
+		local dominated_by_self=true
+		local -a assignee_array=()
+		local saved_ifs="${IFS:-}"
+		IFS=',' read -ra assignee_array <<<"$assignees"
+		IFS="$saved_ifs"
+		local assignee
+		for assignee in "${assignee_array[@]}"; do
+			if [[ "$assignee" != "$self_login" ]]; then
+				dominated_by_self=false
+				break
+			fi
+		done
+		if [[ "$dominated_by_self" == "true" ]]; then
+			return 1
+		fi
+	fi
+
+	printf 'ASSIGNED: issue #%s in %s is assigned to %s\n' "$issue_number" "$repo_slug" "$assignees"
+	return 0
+}
+
 #######################################
 # Show help
 #######################################
@@ -288,6 +354,8 @@ dispatch-dedup-helper.sh - Normalize and deduplicate worker dispatch titles (t23
 Usage:
   dispatch-dedup-helper.sh extract-keys <title>    Extract dedup keys from a title
   dispatch-dedup-helper.sh is-duplicate <title>     Check if already running (exit 0=dup, 1=safe)
+  dispatch-dedup-helper.sh is-assigned <issue> <slug> [self-login]
+                                                    Check if issue is assigned (exit 0=assigned, 1=free)
   dispatch-dedup-helper.sh list-running-keys        List keys for all running workers
   dispatch-dedup-helper.sh normalize <title>        Normalize a title for comparison
   dispatch-dedup-helper.sh help                     Show this help
@@ -298,12 +366,19 @@ Examples:
   # Output: issue-2300
   #         task-t1337
 
-  # Check before dispatching
+  # Check before dispatching (local process dedup)
   if dispatch-dedup-helper.sh is-duplicate "Issue #2300: Fix auth"; then
     echo "Already running — skip dispatch"
   else
     echo "Safe to dispatch"
   fi
+
+  # Check before dispatching (cross-machine assignee dedup)
+  if dispatch-dedup-helper.sh is-assigned 2300 owner/repo mylogin; then
+    echo "Assigned to someone else — skip dispatch"
+  else
+    echo "Unassigned or assigned to self — safe to dispatch"
+  fi
 HELP
 	return 0
 }
@@ -330,6 +405,13 @@ main() {
 		}
 		is_duplicate "$1"
 		;;
+	is-assigned)
+		[[ $# -lt 2 ]] && {
+			echo "Error: is-assigned requires <issue-number> <repo-slug> [self-login]" >&2
+			return 1
+		}
+		is_assigned "$1" "$2" "${3:-}"
+		;;
 	list-running-keys)
 		list_running_keys
 		;;
diff --git a/.agents/scripts/pulse-wrapper.sh b/.agents/scripts/pulse-wrapper.sh
index 3fe7641d65..d40a703430 100755
--- a/.agents/scripts/pulse-wrapper.sh
+++ b/.agents/scripts/pulse-wrapper.sh
@@ -63,6 +63,26 @@ set -euo pipefail
 #######################################
 export PATH="/bin:/usr/bin:/usr/local/bin:/opt/homebrew/bin:${PATH}"
 
+#######################################
+# Startup jitter — desynchronise concurrent pulse instances
+#
+# When multiple runners share the same launchd interval (120s), their
+# pulses fire simultaneously, creating a race window where both evaluate
+# the same issue before either can self-assign. A random 0-30s delay at
+# startup staggers the pulses so the first runner to wake assigns the
+# issue before the second runner evaluates it.
+#
+# PULSE_JITTER_MAX: max jitter in seconds (default 30, set to 0 to disable)
+#######################################
+PULSE_JITTER_MAX="${PULSE_JITTER_MAX:-30}"
+if [[ "$PULSE_JITTER_MAX" =~ ^[0-9]+$ && "$PULSE_JITTER_MAX" -gt 0 ]]; then
+	# $RANDOM is 0-32767; modulo gives 0 to PULSE_JITTER_MAX
+	jitter_seconds=$((RANDOM % (PULSE_JITTER_MAX + 1)))
+	if [[ "$jitter_seconds" -gt 0 ]]; then
+		sleep "$jitter_seconds"
+	fi
+fi
+
 # Use ${BASH_SOURCE[0]:-$0} for shell portability — BASH_SOURCE is undefined
 # in zsh, which is the MCP shell environment. This fallback ensures SCRIPT_DIR
 # resolves correctly whether the script is executed directly (bash) or sourced