diff --git a/.agents/scripts/issue-sync-helper.sh b/.agents/scripts/issue-sync-helper.sh
index 5052be77db..74cfdcda7d 100755
--- a/.agents/scripts/issue-sync-helper.sh
+++ b/.agents/scripts/issue-sync-helper.sh
@@ -18,7 +18,13 @@
 
 set -euo pipefail
 
-SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)" || exit
+# Defensive PATH export — ensures coreutils (sed, grep, awk, jq, gh) are available
+# in headless/MCP environments where PATH may be minimal.
+export PATH="/usr/local/bin:/usr/bin:/bin:${PATH:-}"
+
+# Use pure-bash parameter expansion instead of dirname (which is an external binary
+# and may not be in PATH in headless/MCP environments). See issue #2602.
+SCRIPT_DIR="$(cd "${BASH_SOURCE[0]%/*}" && pwd)" || exit
 source "${SCRIPT_DIR}/shared-constants.sh"
 # shellcheck source=issue-sync-lib.sh
 source "${SCRIPT_DIR}/issue-sync-lib.sh"
diff --git a/.agents/scripts/issue-sync-lib.sh b/.agents/scripts/issue-sync-lib.sh
index 09fe44b292..f092e9bb8a 100755
--- a/.agents/scripts/issue-sync-lib.sh
+++ b/.agents/scripts/issue-sync-lib.sh
@@ -28,7 +28,9 @@ _ISSUE_SYNC_LIB_LOADED=1
 # Source shared-constants.sh to make the library self-contained.
 # Resolves SCRIPT_DIR from BASH_SOURCE so it works when sourced from any location.
 if [[ -z "${SCRIPT_DIR:-}" ]]; then
-	SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+	# Use pure-bash parameter expansion instead of dirname (external binary).
+	# See issue #2602 — dirname may not be in PATH in headless/MCP environments.
+	SCRIPT_DIR="$(cd "${BASH_SOURCE[0]%/*}" && pwd)"
 fi
 source "${SCRIPT_DIR}/shared-constants.sh"