diff --git a/include/haproxy/applet-t.h b/include/haproxy/applet-t.h
index 8b31e02bc..da6dc5024 100644
--- a/include/haproxy/applet-t.h
+++ b/include/haproxy/applet-t.h
@@ -47,7 +47,7 @@
 #define APPCTX_FL_ERROR          0x00000080
 #define APPCTX_FL_SHUTDOWN       0x00000100  /* applet was shut down (->release() called if any). No more data exchange with SCs */
 #define APPCTX_FL_WANT_DIE       0x00000200  /* applet was running and requested to die */
-#define APPCTX_FL_INOUT_BUFS     0x00000400  /* applet uses its own buffers */
+/* unused: 0x00000400 */
 #define APPCTX_FL_FASTFWD        0x00000800  /* zero-copy forwarding is in-use, don't fill the outbuf */
 #define APPCTX_FL_IN_MAYALLOC    0x00001000  /* applet may try again to allocate its inbuf */
 #define APPCTX_FL_OUT_MAYALLOC   0x00002000  /* applet may try again to allocate its outbuf */
@@ -73,8 +73,8 @@ static forceinline char *appctx_show_flags(char *buf, size_t len, const char *de
 	_(APPCTX_FL_OUTBLK_ALLOC, _(APPCTX_FL_OUTBLK_FULL,
 	_(APPCTX_FL_EOI, _(APPCTX_FL_EOS,
 	_(APPCTX_FL_ERR_PENDING, _(APPCTX_FL_ERROR,
-	_(APPCTX_FL_SHUTDOWN, _(APPCTX_FL_WANT_DIE, _(APPCTX_FL_INOUT_BUFS,
-	_(APPCTX_FL_FASTFWD, _(APPCTX_FL_IN_MAYALLOC, _(APPCTX_FL_OUT_MAYALLOC))))))))))))));
+	_(APPCTX_FL_SHUTDOWN, _(APPCTX_FL_WANT_DIE,
+	_(APPCTX_FL_FASTFWD, _(APPCTX_FL_IN_MAYALLOC, _(APPCTX_FL_OUT_MAYALLOC)))))))))))));
 	/* epilogue */
 	_(~0U);
 	return buf;
diff --git a/include/haproxy/applet.h b/include/haproxy/applet.h
index 6856a3b28..0df52d854 100644
--- a/include/haproxy/applet.h
+++ b/include/haproxy/applet.h
@@ -288,7 +288,7 @@ static inline void applet_expect_data(struct appctx *appctx)
  */
 static inline struct buffer *applet_get_inbuf(struct appctx *appctx)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		if (applet_fl_test(appctx, APPCTX_FL_INBLK_ALLOC) || !appctx_get_buf(appctx, &appctx->inbuf))
 			return NULL;
 		return &appctx->inbuf;
@@ -303,7 +303,7 @@ static inline struct buffer *applet_get_inbuf(struct appctx *appctx)
  */
 static inline struct buffer *applet_get_outbuf(struct appctx *appctx)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		if (applet_fl_test(appctx, APPCTX_FL_OUTBLK_ALLOC|APPCTX_FL_OUTBLK_FULL) ||
 		    !appctx_get_buf(appctx, &appctx->outbuf))
 			return NULL;
@@ -316,7 +316,7 @@ static inline struct buffer *applet_get_outbuf(struct appctx *appctx)
 /* Returns the amount of data in the input buffer (see applet_get_inbuf) */
 static inline size_t applet_input_data(const struct appctx *appctx)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS)
+	if (appctx->applet->flags & APPLET_FL_NEW_API)
 		return b_data(&appctx->inbuf);
 	else
 		return co_data(sc_oc(appctx_sc(appctx)));
@@ -325,7 +325,7 @@ static inline size_t applet_input_data(const struct appctx *appctx)
 /* Returns the amount of HTX data in the input buffer (see applet_get_inbuf) */
 static inline size_t applet_htx_input_data(const struct appctx *appctx)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS)
+	if (appctx->applet->flags & APPLET_FL_NEW_API)
 		return htx_used_space(htxbuf(&appctx->inbuf));
 	else
 		return co_data(sc_oc(appctx_sc(appctx)));
@@ -340,7 +340,7 @@ static inline size_t applet_htx_input_data(const struct appctx *appctx)
  */
 static inline void applet_skip_input(struct appctx *appctx, size_t len)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		b_del(&appctx->inbuf, len);
 		applet_fl_clr(appctx, APPCTX_FL_INBLK_FULL);
 	}
@@ -352,7 +352,7 @@ static inline void applet_skip_input(struct appctx *appctx, size_t len)
  */
 static inline void applet_reset_input(struct appctx *appctx)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		b_reset(&appctx->inbuf);
 		applet_fl_clr(appctx, APPCTX_FL_INBLK_FULL);
 	}
@@ -364,7 +364,7 @@ static inline void applet_reset_input(struct appctx *appctx)
  */
 static inline size_t applet_output_room(const struct appctx *appctx)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS)
+	if (appctx->applet->flags & APPLET_FL_NEW_API)
 		return b_room(&appctx->outbuf);
 	else
 		return channel_recv_max(sc_ic(appctx_sc(appctx)));
@@ -374,7 +374,7 @@ static inline size_t applet_output_room(const struct appctx *appctx)
  */
 static inline size_t applet_htx_output_room(const struct appctx *appctx)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS)
+	if (appctx->applet->flags & APPLET_FL_NEW_API)
 		return htx_free_data_space(htxbuf(&appctx->outbuf));
 	else
 		return channel_recv_max(sc_ic(appctx_sc(appctx)));
@@ -390,7 +390,7 @@ static inline size_t applet_htx_output_room(const struct appctx *appctx)
  */
 static inline void applet_need_room(struct appctx *appctx, size_t room_needed)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS)
+	if (appctx->applet->flags & APPLET_FL_NEW_API)
 		applet_have_more_data(appctx);
 	else
 		sc_need_room(appctx_sc(appctx), room_needed);
@@ -402,7 +402,7 @@ static inline int _applet_putchk(struct appctx *appctx, struct buffer *chunk,
 {
 	int ret;
 
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		if (unlikely(stress) ?
 		    b_data(&appctx->outbuf) :
 		    b_data(chunk) > b_room(&appctx->outbuf)) {
@@ -457,7 +457,7 @@ static inline int applet_putblk(struct appctx *appctx, const char *blk, int len)
 {
 	int ret;
 
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		if (len > b_room(&appctx->outbuf)) {
 			applet_fl_set(appctx, APPCTX_FL_OUTBLK_FULL);
 			ret = -1;
@@ -493,7 +493,7 @@ static inline int applet_putstr(struct appctx *appctx, const char *str)
 {
 	int ret;
 
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		int len = strlen(str);
 
 		if (len > b_room(&appctx->outbuf)) {
@@ -529,7 +529,7 @@ static inline int applet_putchr(struct appctx *appctx, char chr)
 {
 	int ret;
 
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		if (b_full(&appctx->outbuf)) {
 			applet_fl_set(appctx, APPCTX_FL_OUTBLK_FULL);
 			ret = -1;
@@ -558,7 +558,7 @@ static inline int applet_putchr(struct appctx *appctx, char chr)
 
 static inline int applet_may_get(const struct appctx *appctx, size_t len)
 {
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		if (len > b_data(&appctx->inbuf)) {
 			if (se_fl_test(appctx->sedesc, SE_FL_SHW))
 				return -1;
@@ -593,7 +593,7 @@ static inline int applet_getchar(const struct appctx *appctx, char *c)
 	ret = applet_may_get(appctx, 1);
 	if (ret <= 0)
 		return ret;
-	*c = ((appctx->flags & APPCTX_FL_INOUT_BUFS)
+	*c = ((appctx->applet->flags & APPLET_FL_NEW_API)
 	      ? *(b_head(&appctx->inbuf))
 	      : *(co_head(sc_oc(appctx_sc(appctx)))));
 
@@ -622,7 +622,7 @@ static inline int applet_getblk(const struct appctx *appctx, char *blk, int len,
 	if (ret <= 0)
 		return ret;
 
-	buf = ((appctx->flags & APPCTX_FL_INOUT_BUFS)
+	buf = ((appctx->applet->flags & APPLET_FL_NEW_API)
 	       ? &appctx->inbuf
 	       : sc_ob(appctx_sc(appctx)));
 	return b_getblk(buf, blk, len, offset);
@@ -654,7 +654,7 @@ static inline int applet_getword(const struct appctx *appctx, char *str, int len
 	if (ret <= 0)
 		goto out;
 
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		buf = &appctx->inbuf;
 		input = b_data(buf);
 	}
@@ -681,7 +681,7 @@ static inline int applet_getword(const struct appctx *appctx, char *str, int len
 		p = b_next(buf, p);
 	}
 
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		if (ret < len && (ret < input || b_room(buf)) &&
 		    !se_fl_test(appctx->sedesc, SE_FL_SHW))
 			ret = 0;
@@ -741,7 +741,7 @@ static inline int applet_getblk_nc(const struct appctx *appctx, const char **blk
 	if (ret <= 0)
 		return ret;
 
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		buf = &appctx->inbuf;
 		max = b_data(buf);
 	}
@@ -797,7 +797,7 @@ static inline int applet_getword_nc(const struct appctx *appctx, const char **bl
 	 * the resulting string is made of the concatenation of the pending
 	 * blocks (1 or 2).
 	 */
-	if (appctx->flags & APPCTX_FL_INOUT_BUFS) {
+	if (appctx->applet->flags & APPLET_FL_NEW_API) {
 		if (b_full(&appctx->inbuf) || se_fl_test(appctx->sedesc, SE_FL_SHW))
 			return ret;
 	}
diff --git a/include/haproxy/sc_strm.h b/include/haproxy/sc_strm.h
index 996b7ea88..61b72a9fd 100644
--- a/include/haproxy/sc_strm.h
+++ b/include/haproxy/sc_strm.h
@@ -386,7 +386,7 @@ static inline int sc_is_send_allowed(const struct stconn *sc)
 	if (sc->flags & SC_FL_SHUT_DONE)
 		return 0;
 
-	if (!sc_appctx(sc) || !(__sc_appctx(sc)->flags & APPCTX_FL_INOUT_BUFS))
+	if (!sc_appctx(sc) || !(__sc_appctx(sc)->applet->flags & APPLET_FL_NEW_API))
 		return !sc_ep_test(sc, SE_FL_WAIT_DATA | SE_FL_WONT_CONSUME);
 
 	if (sc_ep_test(sc, SE_FL_WONT_CONSUME))
diff --git a/src/applet.c b/src/applet.c
index 584d2b9f0..e60ff8b18 100644
--- a/src/applet.c
+++ b/src/applet.c
@@ -274,12 +274,9 @@ struct appctx *appctx_new_on(struct applet *applet, struct sedesc *sedesc, int t
 	appctx->outbuf = BUF_NULL;
 	appctx->to_forward = 0;
 
-	if (applet->rcv_buf != NULL && applet->snd_buf != NULL) {
-		appctx->t->process = task_process_applet;
-		applet_fl_set(appctx, APPCTX_FL_INOUT_BUFS);
-	}
-	else
-		appctx->t->process = task_run_applet;
+	appctx->t->process = ((applet->flags & APPLET_FL_NEW_API)
+			      ? task_process_applet
+			      : task_run_applet);
 	appctx->t->context = appctx;
 
 	LIST_INIT(&appctx->buffer_wait.list);
diff --git a/src/stconn.c b/src/stconn.c
index a9ce03d4d..646c4ca6e 100644
--- a/src/stconn.c
+++ b/src/stconn.c
@@ -2194,7 +2194,7 @@ int sc_applet_recv(struct stconn *sc)
  */
 int sc_applet_sync_recv(struct stconn *sc)
 {
-	if (!(__sc_appctx(sc)->flags & APPCTX_FL_INOUT_BUFS))
+	if (!(__sc_appctx(sc)->applet->flags & APPLET_FL_NEW_API))
 		return 0;
 
 	if (!sc_state_in(sc->state, SC_SB_RDY|SC_SB_EST))
@@ -2295,7 +2295,7 @@ void sc_applet_sync_send(struct stconn *sc)
 
 	oc->flags &= ~CF_WRITE_EVENT;
 
-	if (!(__sc_appctx(sc)->flags & APPCTX_FL_INOUT_BUFS))
+	if (!(__sc_appctx(sc)->applet->flags & APPLET_FL_NEW_API))
 		return;
 
 	if (sc->flags & SC_FL_SHUT_DONE)