diff --git a/src/common/libidset/Makefile.am b/src/common/libidset/Makefile.am
index 5825b8e14a35..984fbce398f5 100644
--- a/src/common/libidset/Makefile.am
+++ b/src/common/libidset/Makefile.am
@@ -16,7 +16,8 @@ fluxinclude_HEADERS = idset.h
 libidset_la_SOURCES = idset.c \
 		      idset_private.h \
 		      idset_decode.c \
-		      idset_encode.c
+		      idset_encode.c \
+		      idset_format.c
 
 libidset_la_CPPFLAGS = \
 	$(AM_CPPFLAGS)
diff --git a/src/common/libidset/idset.h b/src/common/libidset/idset.h
index 83993f02836b..2eecc9bc5147 100644
--- a/src/common/libidset/idset.h
+++ b/src/common/libidset/idset.h
@@ -100,6 +100,17 @@ size_t idset_count (const struct idset *idset);
  */
 bool idset_equal (const struct idset *set1, const struct idset *set2);
 
+/* Substitute a numerical 'id' for bracketed text (e.g. an embedded idset)
+ * in 'fmt', placing result in 'buf'. Returns 0 on success, -1 on failure
+ * with errno set.
+ */
+int idset_format (char *buf, size_t bufsz, const char *fmt, unsigned int id);
+
+/* Decode the first bracketed idset embedded in a string.
+ * Returns idset on success, or NULL on failure with errno set.
+ */
+struct idset *idset_decode_embedded (const char *s);
+
 #endif /* !FLUX_IDSET_H */
 
 /*
diff --git a/src/common/libidset/idset_format.c b/src/common/libidset/idset_format.c
new file mode 100644
index 000000000000..a3f1e7d2ae39
--- /dev/null
+++ b/src/common/libidset/idset_format.c
@@ -0,0 +1,63 @@
+/************************************************************\
+ * Copyright 2014 Lawrence Livermore National Security, LLC
+ * (c.f. AUTHORS, NOTICE.LLNS, COPYING)
+ *
+ * This file is part of the Flux resource manager framework.
+ * For details, see https://github.com/flux-framework.
+ *
+ * SPDX-License-Identifier: LGPL-3.0
+\************************************************************/
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+#include <sys/param.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdbool.h>
+
+#include "idset.h"
+#include "idset_private.h"
+
+int idset_format (char *buf, size_t bufsz, const char *fmt, unsigned int id)
+{
+    char *p, *q;
+
+    if (!buf || !fmt) {
+        errno = EINVAL;
+        return -1;
+    }
+    if (!(p = strchr (fmt, '[')) || !(q = strchr (p + 1, ']'))) {
+        errno = EINVAL;
+        return -1;
+    }
+    if (snprintf (buf,
+                  bufsz,
+                  "%.*s%u%s",
+                  (int)(p - fmt),
+                  fmt,
+                  id,
+                  q + 1) >= bufsz) {
+        errno = EOVERFLOW;
+        return -1;
+    }
+    return 0;
+}
+
+struct idset *idset_decode_embedded (const char *s)
+{
+    char *p, *q;
+
+    if (!s || !(p = strchr (s, '[')) || !(q = strchr (p + 1, ']'))) {
+        errno = EINVAL;
+        return NULL;
+    }
+    return idset_ndecode (p, q - p + 1);
+}
+
+/*
+ * vi:tabstop=4 shiftwidth=4 expandtab
+ */