diff --git a/Cargo.lock b/Cargo.lock
index c2077db5b..74755ac4c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -168,6 +168,14 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f7144d30dcf0fafbce74250a3963025d8d52177934239851c917d29f1df280c2"
 
+[[package]]
+name = "context-checks"
+version = "0.1.0"
+dependencies = [
+ "log",
+ "proxy-wasm 0.2.1",
+]
+
 [[package]]
 name = "core-foundation-sys"
 version = "0.8.4"
@@ -589,6 +597,15 @@ version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c08c74e62047bb2de4ff487b251e4a92e24f48745648451635cec7d591162d9f"
 
+[[package]]
+name = "root-context-checks"
+version = "0.1.0"
+dependencies = [
+ "context-checks",
+ "log",
+ "proxy-wasm 0.2.1",
+]
+
 [[package]]
 name = "rust-sdk-ver-zero-one"
 version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index 0aa52f776..82b36c1f7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,6 +11,8 @@ members = [
     "t/lib/proxy-wasm-tests/rust-sdk-ver-zero-one",
     "t/lib/proxy-wasm-tests/benchmarks",
     "t/lib/proxy-wasm-tests/instance-lifecycle",
+    "t/lib/proxy-wasm-tests/contexts",
+    "t/lib/proxy-wasm-tests/contexts/crates/root",
 ]
 exclude = [
     "lib/ngx-wasm-rs",
diff --git a/src/common/proxy_wasm/ngx_proxy_wasm.c b/src/common/proxy_wasm/ngx_proxy_wasm.c
index f3c1d9e81..5d49f3462 100644
--- a/src/common/proxy_wasm/ngx_proxy_wasm.c
+++ b/src/common/proxy_wasm/ngx_proxy_wasm.c
@@ -501,6 +501,7 @@ action2rc(ngx_proxy_wasm_ctx_t *pwctx,
         case NGX_HTTP_REWRITE_PHASE:
         case NGX_HTTP_ACCESS_PHASE:
         case NGX_HTTP_CONTENT_PHASE:
+        case NGX_WASM_BACKGROUND_PHASE:
             ngx_log_debug6(NGX_LOG_DEBUG_WASM, pwctx->log, 0,
                            "proxy_wasm pausing in \"%V\" phase "
                            "(filter: %l/%l, step: %d, action: %d, "
@@ -683,6 +684,7 @@ ngx_proxy_wasm_run_step(ngx_proxy_wasm_exec_t *pwexec,
     ngx_int_t                 rc;
     ngx_proxy_wasm_err_e      ecode;
     ngx_proxy_wasm_action_e   action = NGX_PROXY_WASM_ACTION_CONTINUE;
+    ngx_proxy_wasm_exec_t    *out;
     ngx_proxy_wasm_ctx_t     *pwctx = pwexec->parent;
     ngx_proxy_wasm_filter_t  *filter = pwexec->filter;
 #if (NGX_DEBUG)
@@ -700,10 +702,12 @@ ngx_proxy_wasm_run_step(ngx_proxy_wasm_exec_t *pwexec,
     if (pwexec->ictx == NULL || pwexec->ictx->instance->trapped) {
 #endif
         ecode = ngx_proxy_wasm_create_context(filter, pwctx, pwexec->id,
-                                              pwexec, NULL);
+                                              pwexec, &out);
         if (ecode != NGX_PROXY_WASM_ERR_NONE) {
             return ecode;
         }
+
+        pwexec = out;
 #if 1
     }
 #endif
@@ -842,6 +846,9 @@ get_instance(ngx_proxy_wasm_filter_t *filter,
 
     dd("get instance in store: %p", store);
 
+    /* store initialized */
+    ngx_wasm_assert(store->pool);
+
     for (q = ngx_queue_head(&store->busy);
          q != ngx_queue_sentinel(&store->busy);
          q = ngx_queue_next(q))
@@ -988,9 +995,6 @@ ngx_proxy_wasm_create_context(ngx_proxy_wasm_filter_t *filter,
         ictx = in->ictx;
 
     } else {
-        /* store initialized */
-        ngx_wasm_assert(store->pool);
-
         ictx = get_instance(filter, store, log);
         if (ictx == NULL) {
             goto error;
@@ -1187,10 +1191,15 @@ ngx_proxy_wasm_create_context(ngx_proxy_wasm_filter_t *filter,
 
             pwexec->started = 1;
         }
-    }
 
-    if (out) {
-        *out = pwexec;
+        if (out) {
+            *out = pwexec;
+        }
+
+    } else {
+        if (out) {
+            *out = rexec;
+        }
     }
 
     return NGX_PROXY_WASM_ERR_NONE;
@@ -1232,10 +1241,8 @@ ngx_proxy_wasm_on_done(ngx_proxy_wasm_exec_t *pwexec)
 {
     ngx_wavm_instance_t             *instance;
     ngx_proxy_wasm_filter_t         *filter = pwexec->filter;
-#if 0
 #ifdef NGX_WASM_HTTP
     ngx_http_proxy_wasm_dispatch_t  *call;
-#endif
 #endif
 
     instance = ngx_proxy_wasm_pwexec2instance(pwexec);
@@ -1244,25 +1251,13 @@ ngx_proxy_wasm_on_done(ngx_proxy_wasm_exec_t *pwexec)
                              "filter %l/%l finalizing context",
                              pwexec->index + 1, pwexec->parent->nfilters);
 
-#if 0
-    /**
-     * Currently, dispatches are synchronous hence will always
-     * have been executed when on_done is invoked.
-     */
 #ifdef NGX_WASM_HTTP
     call = pwexec->call;
     if (call) {
-        ngx_log_debug3(NGX_LOG_DEBUG_WASM, pwexec->log, 0,
-                       "proxy_wasm \"%V\" filter (%l/%l) "
-                       "cancelling HTTP dispatch",
-                       pwexec->filter->name, pwexec->index + 1,
-                       pwexec->parent->nfilters);
-
         ngx_http_proxy_wasm_dispatch_destroy(call);
 
         pwexec->call = NULL;
     }
-#endif
 #endif
 
     (void) ngx_wavm_instance_call_funcref(instance,
diff --git a/src/common/proxy_wasm/ngx_proxy_wasm_host.c b/src/common/proxy_wasm/ngx_proxy_wasm_host.c
index a5be0a1a3..a3b53ceef 100644
--- a/src/common/proxy_wasm/ngx_proxy_wasm_host.c
+++ b/src/common/proxy_wasm/ngx_proxy_wasm_host.c
@@ -26,21 +26,44 @@ static ngx_int_t ngx_proxy_wasm_hfuncs_no_http(ngx_wavm_instance_t *instance,
 
 static ngx_chain_t *
 ngx_proxy_wasm_get_buffer_helper(ngx_wavm_instance_t *instance,
-    ngx_proxy_wasm_buffer_type_e buf_type, unsigned *none)
+    ngx_proxy_wasm_buffer_type_e buf_type, unsigned *none, char **trapmsg)
 {
 #ifdef NGX_WASM_HTTP
     ngx_chain_t              *cl;
     ngx_http_wasm_req_ctx_t  *rctx;
     ngx_http_request_t       *r;
+    ngx_proxy_wasm_ctx_t     *pwctx;
+#endif
+    ngx_proxy_wasm_exec_t    *pwexec;
 
-    rctx = ngx_http_proxy_wasm_get_rctx(instance);
-    r = rctx->r;
+    pwexec = ngx_proxy_wasm_instance2pwexec(instance);
+#ifdef NGX_WASM_HTTP
+    pwctx = pwexec->parent;
 #endif
 
     switch (buf_type) {
 
 #ifdef NGX_WASM_HTTP
     case NGX_PROXY_WASM_BUFFER_HTTP_REQUEST_BODY:
+
+        /* check context */
+
+        switch (pwctx->step) {
+        case NGX_PROXY_WASM_STEP_REQ_HEADERS:
+        case NGX_PROXY_WASM_STEP_REQ_BODY:
+        case NGX_PROXY_WASM_STEP_LOG:
+            break;
+        default:
+            *trapmsg = "can only get request body during "
+                       "\"on_request_body\", \"on_log\"";
+            return NULL;
+        }
+
+        /* get */
+
+        rctx = ngx_http_proxy_wasm_get_rctx(instance);
+        r = rctx->r;
+
         if (r->request_body == NULL
             || r->request_body->bufs == NULL)
         {
@@ -61,6 +84,23 @@ ngx_proxy_wasm_get_buffer_helper(ngx_wavm_instance_t *instance,
         return r->request_body->bufs;
 
     case NGX_PROXY_WASM_BUFFER_HTTP_RESPONSE_BODY:
+
+        /* check context */
+
+        switch (pwctx->step) {
+        case NGX_PROXY_WASM_STEP_RESP_BODY:
+        case NGX_PROXY_WASM_STEP_LOG:
+            break;
+        default:
+            *trapmsg = "can only get response body during "
+                       "\"on_response_body\", \"on_log\"";
+            return NULL;
+        }
+
+        /* get */
+
+        rctx = ngx_http_proxy_wasm_get_rctx(instance);
+
         cl = rctx->resp_chunk;
         if (cl == NULL) {
             /* no body */
@@ -74,9 +114,21 @@ ngx_proxy_wasm_get_buffer_helper(ngx_wavm_instance_t *instance,
         {
             ngx_wasm_http_reader_ctx_t      *reader;
             ngx_http_proxy_wasm_dispatch_t  *call;
-            ngx_proxy_wasm_exec_t           *pwexec;
 
-            pwexec = ngx_proxy_wasm_instance2pwexec(instance);
+            /* check context */
+
+            switch (pwctx->step) {
+            case NGX_PROXY_WASM_STEP_DISPATCH_RESPONSE:
+            case NGX_PROXY_WASM_STEP_LOG:
+                break;
+            default:
+                *trapmsg = "can only get dispatch response body during "
+                           "\"on_http_dispatch_response\"";
+                return NULL;
+            }
+
+            /* get */
+
             call = pwexec->call;
             if (call == NULL) {
                 return NULL;
@@ -210,8 +262,9 @@ ngx_proxy_wasm_hfuncs_set_tick_period(ngx_wavm_instance_t *instance,
     ngx_wasm_assert(rexec->root_id == NGX_PROXY_WASM_ROOT_CTX_ID);
 
     if (rexec->root_id != NGX_PROXY_WASM_ROOT_CTX_ID) {
-        /* ignore */
-        return ngx_proxy_wasm_result_ok(rets);
+        return ngx_proxy_wasm_result_trap(rexec,
+                                          "can only set tick_period in "
+                                          "root context", rets, NGX_WAVM_OK);
     }
 
     if (ngx_exiting) {
@@ -254,6 +307,7 @@ ngx_proxy_wasm_hfuncs_get_buffer(ngx_wavm_instance_t *instance,
 {
     size_t                         offset, max_len, len, chunk_len;
     unsigned                       none = 0;
+    char                          *trapmsg = NULL;
     u_char                        *start = NULL;
     ngx_chain_t                   *cl = NULL;
     ngx_buf_t                     *buf;
@@ -282,8 +336,14 @@ ngx_proxy_wasm_hfuncs_get_buffer(ngx_wavm_instance_t *instance,
         break;
 
     default:
-        cl = ngx_proxy_wasm_get_buffer_helper(instance, buf_type, &none);
+        cl = ngx_proxy_wasm_get_buffer_helper(instance, buf_type, &none,
+                                              &trapmsg);
         if (cl == NULL) {
+            if (trapmsg) {
+                return ngx_proxy_wasm_result_trap(pwexec, trapmsg,
+                                                  rets, NGX_WAVM_BAD_USAGE);
+            }
+
             if (none) {
                 return ngx_proxy_wasm_result_notfound(rets);
             }
@@ -376,9 +436,10 @@ ngx_proxy_wasm_hfuncs_set_buffer(ngx_wavm_instance_t *instance,
     ngx_wavm_ptr_t                *buf_data;
     ngx_http_wasm_req_ctx_t       *rctx;
     ngx_proxy_wasm_exec_t         *pwexec;
+    ngx_proxy_wasm_ctx_t          *pwctx;
 
-    rctx = ngx_http_proxy_wasm_get_rctx(instance);
     pwexec = ngx_proxy_wasm_instance2pwexec(instance);
+    pwctx = pwexec->parent;
 
     offset = args[1].of.i32;
     max = args[2].of.i32;
@@ -400,6 +461,26 @@ ngx_proxy_wasm_hfuncs_set_buffer(ngx_wavm_instance_t *instance,
 
 #ifdef NGX_WASM_HTTP
     case NGX_PROXY_WASM_BUFFER_HTTP_REQUEST_BODY:
+
+        /* check context */
+
+        switch (pwctx->step) {
+        case NGX_PROXY_WASM_STEP_REQ_HEADERS:
+        case NGX_PROXY_WASM_STEP_REQ_BODY:
+            break;
+        default:
+            return ngx_proxy_wasm_result_trap(pwexec,
+                                              "can only set request body "
+                                              "during \"on_request_body\"",
+                                              rets, NGX_WAVM_BAD_USAGE);
+        }
+
+        /* set */
+
+        rctx = ngx_http_proxy_wasm_get_rctx(instance);
+
+        ngx_wasm_assert(rctx);
+
         if (offset == 0 && max == 0 && buf_len > 0) {
             rc = ngx_http_wasm_prepend_req_body(rctx, &s);
 
@@ -407,15 +488,29 @@ ngx_proxy_wasm_hfuncs_set_buffer(ngx_wavm_instance_t *instance,
             rc = ngx_http_wasm_set_req_body(rctx, &s, offset, max);
         }
 
-        if (rc == NGX_ABORT) {
+        ngx_wasm_assert(rc != NGX_ABORT);
+        break;
+
+    case NGX_PROXY_WASM_BUFFER_HTTP_RESPONSE_BODY:
+
+        /* check context */
+
+        switch (pwctx->step) {
+        case NGX_PROXY_WASM_STEP_RESP_BODY:
+            break;
+        default:
             return ngx_proxy_wasm_result_trap(pwexec,
-                                              "cannot set request body",
+                                              "can only set response body "
+                                              "during \"on_response_body\"",
                                               rets, NGX_WAVM_BAD_USAGE);
         }
 
-        break;
+        /* set */
+
+        rctx = ngx_http_proxy_wasm_get_rctx(instance);
+
+        ngx_wasm_assert(rctx);
 
-    case NGX_PROXY_WASM_BUFFER_HTTP_RESPONSE_BODY:
         if (offset == 0 && max == 0 && buf_len > 0) {
             rc = ngx_http_wasm_prepend_resp_body(rctx, &s);
 
@@ -423,12 +518,7 @@ ngx_proxy_wasm_hfuncs_set_buffer(ngx_wavm_instance_t *instance,
             rc = ngx_http_wasm_set_resp_body(rctx, &s, offset, max);
         }
 
-        if (rc == NGX_ABORT) {
-            return ngx_proxy_wasm_result_trap(pwexec,
-                                              "cannot set response body",
-                                              rets, NGX_WAVM_BAD_USAGE);
-        }
-
+        ngx_wasm_assert(rc != NGX_ABORT);
         break;
 #endif
 
diff --git a/src/http/proxy_wasm/ngx_http_proxy_wasm_dispatch.c b/src/http/proxy_wasm/ngx_http_proxy_wasm_dispatch.c
index 6b5c37243..41d967a87 100644
--- a/src/http/proxy_wasm/ngx_http_proxy_wasm_dispatch.c
+++ b/src/http/proxy_wasm/ngx_http_proxy_wasm_dispatch.c
@@ -155,7 +155,6 @@ ngx_http_proxy_wasm_dispatch(ngx_proxy_wasm_exec_t *pwexec,
     /* rctx or fake request */
 
     if (rctx == NULL) {
-        ngx_wasm_assert(pwexec->in_tick);
         ngx_wasm_assert(pwexec->root_id == NGX_PROXY_WASM_ROOT_CTX_ID);
         ngx_wasm_assert(pwexec->parent->id == NGX_PROXY_WASM_ROOT_CTX_ID);
 
@@ -825,6 +824,11 @@ ngx_http_proxy_wasm_dispatch_resume_handler(ngx_wasm_socket_tcp_t *sock)
         /* save step */
         step = pwexec->parent->step;
 
+#ifdef NGX_WASM_HTTP
+        pwexec->parent->phase = ngx_wasm_phase_lookup(&ngx_http_wasm_subsystem,
+                                    NGX_WASM_BACKGROUND_PHASE);
+#endif
+
         ecode = ngx_proxy_wasm_run_step(pwexec,
                                         NGX_PROXY_WASM_STEP_DISPATCH_RESPONSE);
         if (ecode != NGX_PROXY_WASM_ERR_NONE) {
@@ -838,6 +842,12 @@ ngx_http_proxy_wasm_dispatch_resume_handler(ngx_wasm_socket_tcp_t *sock)
             /* resume current step if unfinished */
             rc = ngx_proxy_wasm_resume(pwexec->parent, pwexec->parent->phase,
                                        step);
+            if (rc == NGX_AGAIN) {
+                goto done;
+
+            } else if (rc != NGX_OK) {
+                goto error;
+            }
 
         } else {
             /* another call was setup during the callback */
diff --git a/t/03-proxy_wasm/hfuncs/114-proxy_set_http_request_body.t b/t/03-proxy_wasm/hfuncs/114-proxy_set_http_request_body.t
index 1c31f21b1..8d63af23a 100644
--- a/t/03-proxy_wasm/hfuncs/114-proxy_set_http_request_body.t
+++ b/t/03-proxy_wasm/hfuncs/114-proxy_set_http_request_body.t
@@ -254,10 +254,11 @@ HelloWorld
 qr/from_request_headers
 from_request_body
 [\s\S]+500 Internal Server Error/
---- grep_error_log eval: qr/(.*?cannot set|\[.*?failed resuming).*/
+--- grep_error_log eval: qr/(.*?can only set|\[.*?failed resuming).*/
 --- grep_error_log_out eval
-qr/.*?host trap \(bad usage\): cannot set request body.*
+qr/.*?host trap \(bad usage\): can only set request body during.*
 \[info\] .*? \*\d+ .*? filter chain failed resuming: previous error \(instance trapped\).*? subrequest: "\/response_headers".*
+\[info\] .*? \*\d+ .*? filter chain failed resuming: previous error \(instance trapped\).*? request: "GET \/t.*
 \z/
 --- no_error_log
 [alert]
diff --git a/t/03-proxy_wasm/hfuncs/116-proxy_set_http_response_body.t b/t/03-proxy_wasm/hfuncs/116-proxy_set_http_response_body.t
index 15ce88076..a49616de1 100644
--- a/t/03-proxy_wasm/hfuncs/116-proxy_set_http_response_body.t
+++ b/t/03-proxy_wasm/hfuncs/116-proxy_set_http_response_body.t
@@ -133,7 +133,7 @@ on_response_body, 0 bytes, eof: true.*/
 
     location /t {
         echo_subrequest GET /subrequest;
-        proxy_wasm hostcalls 'on=response_headers \
+        proxy_wasm hostcalls 'on=log \
                               test=/t/log/response_body';
     }
 --- response_headers
@@ -344,13 +344,13 @@ Transfer-Encoding: chunked
 Content-Length:
 --- response_body eval
 qr/500 Internal Server Error/
---- grep_error_log eval: qr/(.*?cannot set|\[.*?failed resuming).*/
+--- grep_error_log eval: qr/(.*?can only set|\[.*?failed resuming).*/
 --- grep_error_log_out eval
-qr/.*?host trap \(bad usage\): cannot set response body.*
+qr/.*?host trap \(bad usage\): can only set response body during.*
 \[info\] .*? \*\d+ .*? filter chain failed resuming: previous error \(instance trapped\).*? subrequest: "\/request_headers".*
-.*?host trap \(bad usage\): cannot set response body.*
+.*?host trap \(bad usage\): can only set response body during.*
 \[info\] .*? \*\d+ .*? filter chain failed resuming: previous error \(instance trapped\).*? subrequest: "\/response_headers".*
-.*?host trap \(bad usage\): cannot set response body.*/
+.*?host trap \(bad usage\): can only set response body during.*/
 --- no_error_log
 [alert]
 [stderr]
diff --git a/t/03-proxy_wasm/hfuncs/root-context/001-set_tick_period.t b/t/03-proxy_wasm/hfuncs/root-context/001-set_tick_period.t
new file mode 100644
index 000000000..2bee4dc7e
--- /dev/null
+++ b/t/03-proxy_wasm/hfuncs/root-context/001-set_tick_period.t
@@ -0,0 +1,85 @@
+# vim:set ft= ts=4 sts=4 sw=4 et fdm=marker:
+
+use strict;
+use lib '.';
+use t::TestWasm;
+
+skip_hup();
+skip_no_debug();
+skip_valgrind();
+
+plan tests => repeat_each() * (blocks() * 4);
+
+run_tests();
+
+__DATA__
+
+=== TEST 1: proxy_wasm contexts - set_tick_period on_vm_start
+--- main_config
+    wasm {
+        module root_context_checks $TEST_NGINX_CRATES_DIR/root_context_checks.wasm 'set_tick_period';
+    }
+--- config
+    location /t {
+        proxy_wasm root_context_checks;
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+set_tick_period status: 0
+--- no_error_log
+[error]
+[crit]
+
+
+
+=== TEST 2: proxy_wasm contexts - set_tick_period on_configure
+--- wasm_modules: root_context_checks
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_configure=set_tick_period';
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+set_tick_period status: 0
+--- no_error_log
+[error]
+[crit]
+
+
+
+=== TEST 3: proxy_wasm contexts - set_tick_period on_tick
+--- wasm_modules: root_context_checks
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_tick=set_tick_period';
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+tick_period already set
+--- no_error_log
+[crit]
+
+
+
+=== TEST 4: proxy_wasm contexts - set_tick_period on_http_dispatch_response
+--- wasm_modules: root_context_checks
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_http_dispatch_response=set_tick_period \
+                                        host=127.0.0.1:$TEST_NGINX_SERVER_PORT';
+        return 200;
+    }
+
+    location /dispatch {
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+set_tick_period status: 0
+--- no_error_log
+[error]
+[crit]
diff --git a/t/03-proxy_wasm/hfuncs/root-context/002-get_buffer_bytes.t b/t/03-proxy_wasm/hfuncs/root-context/002-get_buffer_bytes.t
new file mode 100644
index 000000000..4153fbb86
--- /dev/null
+++ b/t/03-proxy_wasm/hfuncs/root-context/002-get_buffer_bytes.t
@@ -0,0 +1,175 @@
+# vim:set ft= ts=4 sts=4 sw=4 et fdm=marker:
+
+use strict;
+use lib '.';
+use t::TestWasm;
+
+skip_hup();
+skip_no_debug();
+skip_valgrind();
+
+plan tests => repeat_each() * (blocks() * 4);
+
+run_tests();
+
+__DATA__
+
+=== TEST 1: proxy_wasm contexts - get_buffer_bytes on_vm_start (request_body_buffer)
+'daemon off' must be set to check exit_code is 2
+Valgrind mode already writes 'daemon off'
+HUP mode does not catch the worker exit_code
+--- skip_eval: 4: $ENV{TEST_NGINX_USE_HUP} == 1
+--- main_config eval
+qq{
+    wasm {
+        module root_context_checks $ENV{TEST_NGINX_CRATES_DIR}/root_context_checks.wasm 'get_request_body_buffer';
+    }
+}.($ENV{TEST_NGINX_USE_VALGRIND} ? '' : 'daemon off;')
+--- config
+    location /t {
+        proxy_wasm root_context_checks;
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+[emerg]
+can only get request body during "on_request_body", "on_log"
+--- no_error_log
+--- must_die: 2
+
+
+
+=== TEST 2: proxy_wasm contexts - get_buffer_bytes on_vm_start (response_body_buffer)
+'daemon off' must be set to check exit_code is 2
+Valgrind mode already writes 'daemon off'
+HUP mode does not catch the worker exit_code
+--- skip_eval: 4: $ENV{TEST_NGINX_USE_HUP} == 1
+--- main_config eval
+qq{
+    wasm {
+        module root_context_checks $ENV{TEST_NGINX_CRATES_DIR}/root_context_checks.wasm 'get_response_body_buffer';
+    }
+}.($ENV{TEST_NGINX_USE_VALGRIND} ? '' : 'daemon off;')
+--- config
+    location /t {
+        proxy_wasm root_context_checks;
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+[emerg]
+can only get response body during "on_response_body", "on_log"
+--- no_error_log
+--- must_die: 2
+
+
+
+=== TEST 3: proxy_wasm contexts - get_buffer_bytes on_configure (request_body_buffer)
+'daemon off' must be set to check exit_code is 2
+Valgrind mode already writes 'daemon off'
+HUP mode does not catch the worker exit_code
+--- skip_eval: 4: $ENV{TEST_NGINX_USE_HUP} == 1
+--- main_config eval
+qq{
+    wasm {
+        module root_context_checks $ENV{TEST_NGINX_CRATES_DIR}/root_context_checks.wasm;
+    }
+}.($ENV{TEST_NGINX_USE_VALGRIND} ? '' : 'daemon off;')
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_configure=get_request_body_buffer';
+        return 200;
+    }
+
+--- ignore_response_body
+--- error_log
+[error]
+[emerg]
+can only get request body during "on_request_body", "on_log"
+--- must_die: 2
+
+
+
+=== TEST 4: proxy_wasm contexts - get_buffer_bytes on_configure (response_body_buffer)
+'daemon off' must be set to check exit_code is 2
+Valgrind mode already writes 'daemon off'
+HUP mode does not catch the worker exit_code
+--- skip_eval: 4: $ENV{TEST_NGINX_USE_HUP} == 1
+--- main_config eval
+qq{
+    wasm {
+        module root_context_checks $ENV{TEST_NGINX_CRATES_DIR}/root_context_checks.wasm;
+    }
+}.($ENV{TEST_NGINX_USE_VALGRIND} ? '' : 'daemon off;')
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_configure=get_response_body_buffer';
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+[emerg]
+can only get response body during "on_response_body", "on_log"
+--- must_die: 2
+
+
+
+=== TEST 5: proxy_wasm contexts - get_buffer_bytes on_tick
+--- wasm_modules: root_context_checks
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_tick=get_request_body_buffer';
+        proxy_wasm root_context_checks 'on_tick=get_response_body_buffer';
+        proxy_wasm root_context_checks 'on_tick=get_dispatch_response_body_buffer';
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+can only get request body during "on_request_body", "on_log"
+can only get response body during "on_response_body", "on_log"
+can only get dispatch response body during "on_http_dispatch_response"
+
+
+
+=== TEST 6: proxy_wasm contexts - get_buffer_bytes on_http_dispatch_response (request_body_buffer)
+--- wasm_modules: root_context_checks
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_http_dispatch_response=get_request_body_buffer \
+                                        host=127.0.0.1:$TEST_NGINX_SERVER_PORT';
+        return 200;
+    }
+
+    location /dispatch {
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+can only get request body during "on_request_body", "on_log"
+--- no_error_log
+[crit]
+
+
+
+=== TEST 7: proxy_wasm contexts - get_buffer_bytes on_http_dispatch_response (response_body_buffer)
+--- wasm_modules: root_context_checks
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_http_dispatch_response=get_response_body_buffer \
+                                        host=127.0.0.1:$TEST_NGINX_SERVER_PORT';
+        return 200;
+    }
+
+    location /dispatch {
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+can only get response body during "on_response_body", "on_log"
+--- no_error_log
+[crit]
diff --git a/t/03-proxy_wasm/hfuncs/root-context/003-set_buffer_bytes.t b/t/03-proxy_wasm/hfuncs/root-context/003-set_buffer_bytes.t
new file mode 100644
index 000000000..564206e90
--- /dev/null
+++ b/t/03-proxy_wasm/hfuncs/root-context/003-set_buffer_bytes.t
@@ -0,0 +1,174 @@
+# vim:set ft= ts=4 sts=4 sw=4 et fdm=marker:
+
+use strict;
+use lib '.';
+use t::TestWasm;
+
+skip_hup();
+skip_no_debug();
+skip_valgrind();
+
+plan tests => repeat_each() * (blocks() * 4);
+
+run_tests();
+
+__DATA__
+
+=== TEST 1: proxy_wasm contexts - set_buffer_bytes on_vm_start (request_body_buffer)
+'daemon off' must be set to check exit_code is 2
+Valgrind mode already writes 'daemon off'
+HUP mode does not catch the worker exit_code
+--- skip_eval: 4: $ENV{TEST_NGINX_USE_HUP} == 1
+--- main_config eval
+qq{
+    wasm {
+        module root_context_checks $ENV{TEST_NGINX_CRATES_DIR}/root_context_checks.wasm 'set_request_body_buffer';
+    }
+}.($ENV{TEST_NGINX_USE_VALGRIND} ? '' : 'daemon off;')
+--- config
+    location /t {
+        proxy_wasm root_context_checks;
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+[emerg]
+can only set request body during "on_request_body"
+--- no_error_log
+--- must_die: 2
+
+
+
+=== TEST 2: proxy_wasm contexts - set_buffer_bytes on_vm_start (response_body_buffer)
+'daemon off' must be set to check exit_code is 2
+Valgrind mode already writes 'daemon off'
+HUP mode does not catch the worker exit_code
+--- skip_eval: 4: $ENV{TEST_NGINX_USE_HUP} == 1
+--- main_config eval
+qq{
+    wasm {
+        module root_context_checks $ENV{TEST_NGINX_CRATES_DIR}/root_context_checks.wasm 'set_response_body_buffer';
+    }
+}.($ENV{TEST_NGINX_USE_VALGRIND} ? '' : 'daemon off;')
+--- config
+    location /t {
+        proxy_wasm root_context_checks;
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+[emerg]
+can only set response body during "on_response_body"
+--- no_error_log
+--- must_die: 2
+
+
+
+=== TEST 3: proxy_wasm contexts - set_buffer_bytes on_configure (request_body_buffer)
+'daemon off' must be set to check exit_code is 2
+Valgrind mode already writes 'daemon off'
+HUP mode does not catch the worker exit_code
+--- skip_eval: 4: $ENV{TEST_NGINX_USE_HUP} == 1
+--- main_config eval
+qq{
+    wasm {
+        module root_context_checks $ENV{TEST_NGINX_CRATES_DIR}/root_context_checks.wasm;
+    }
+}.($ENV{TEST_NGINX_USE_VALGRIND} ? '' : 'daemon off;')
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_configure=set_request_body_buffer';
+        return 200;
+    }
+
+--- ignore_response_body
+--- error_log
+[error]
+[emerg]
+can only set request body during "on_request_body"
+--- must_die: 2
+
+
+
+=== TEST 4: proxy_wasm contexts - set_buffer_bytes on_configure (response_body_buffer)
+'daemon off' must be set to check exit_code is 2
+Valgrind mode already writes 'daemon off'
+HUP mode does not catch the worker exit_code
+--- skip_eval: 4: $ENV{TEST_NGINX_USE_HUP} == 1
+--- main_config eval
+qq{
+    wasm {
+        module root_context_checks $ENV{TEST_NGINX_CRATES_DIR}/root_context_checks.wasm;
+    }
+}.($ENV{TEST_NGINX_USE_VALGRIND} ? '' : 'daemon off;')
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_configure=set_response_body_buffer';
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+[emerg]
+can only set response body during "on_response_body"
+--- must_die: 2
+
+
+
+=== TEST 5: proxy_wasm contexts - set_buffer_bytes on_tick
+--- wasm_modules: root_context_checks
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_tick=set_request_body_buffer';
+        proxy_wasm root_context_checks 'on_tick=set_response_body_buffer';
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+can only set request body during "on_request_body"
+can only set response body during "on_response_body"
+
+
+
+=== TEST 6: proxy_wasm contexts - set_buffer_bytes on_http_dispatch_response (request_body_buffer)
+--- wasm_modules: root_context_checks
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_http_dispatch_response=set_request_body_buffer \
+                                        host=127.0.0.1:$TEST_NGINX_SERVER_PORT';
+        return 200;
+    }
+
+    location /dispatch {
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+can only set request body during "on_request_body"
+--- no_error_log
+[crit]
+
+
+
+=== TEST 7: proxy_wasm contexts - set_buffer_bytes on_http_dispatch_response (response_body_buffer)
+--- wasm_modules: root_context_checks
+--- config
+    location /t {
+        proxy_wasm root_context_checks 'on_http_dispatch_response=set_response_body_buffer \
+                                        host=127.0.0.1:$TEST_NGINX_SERVER_PORT';
+        return 200;
+    }
+
+    location /dispatch {
+        return 200;
+    }
+--- ignore_response_body
+--- error_log
+[error]
+can only set response body during "on_response_body"
+--- no_error_log
+[crit]
diff --git a/t/04-openresty/ffi/200-proxy_wasm_and_lua_sanity.t b/t/04-openresty/ffi/200-proxy_wasm_and_lua_sanity.t
index 161bbed3c..60a18aaf4 100644
--- a/t/04-openresty/ffi/200-proxy_wasm_and_lua_sanity.t
+++ b/t/04-openresty/ffi/200-proxy_wasm_and_lua_sanity.t
@@ -245,7 +245,7 @@ qr/on_http_call_response \(id: \d+, status: 200, headers: 5, body_bytes: \d+, tr
 --- grep_error_log eval: qr/\*\d+.*?\[proxy-wasm\].*?(resuming|freeing).*/
 --- grep_error_log_out eval
 qr/\A\*\d+ .*? filter 1\/1 resuming "on_request_headers" step in "rewrite" phase[^#*]*
-\*\d+ .*? filter 1\/1 resuming "on_dispatch_response" step in "access" phase[^#*]*
+\*\d+ .*? filter 1\/1 resuming "on_dispatch_response" step in "background" phase[^#*]*
 \*\d+ .*? filter 1\/1 resuming "on_response_headers" step in "header_filter" phase[^#*]*
 \*\d+ .*? filter 1\/1 resuming "on_response_body" step in "body_filter" phase[^#*]*
 \*\d+ .*? filter 1\/1 resuming "on_log" step in "log" phase[^#*]*
@@ -308,7 +308,7 @@ qr/on_http_call_response \(id: \d+, status: 200, headers: 5, body_bytes: \d+, tr
 --- grep_error_log eval: qr/\*\d+.*?\[proxy-wasm\].*?(resuming|freeing).*/
 --- grep_error_log_out eval
 qr/\A\*\d+ .*? filter 1\/1 resuming "on_request_headers" step in "rewrite" phase[^#*]*
-\*\d+ .*? filter 1\/1 resuming "on_dispatch_response" step in "access" phase[^#*]*
+\*\d+ .*? filter 1\/1 resuming "on_dispatch_response" step in "background" phase[^#*]*
 \*\d+ .*? filter 1\/1 resuming "on_response_headers" step in "header_filter" phase[^#*]*
 \*\d+ .*? filter 1\/1 resuming "on_response_body" step in "body_filter" phase[^#*]*
 \*\d+ .*? filter 1\/1 resuming "on_response_body" step in "body_filter" phase[^#*]*
@@ -377,7 +377,7 @@ qr/\A\*\d+ .*? filter 1\/1 resuming "on_request_headers" step in "rewrite" phase
 --- grep_error_log eval: qr/\*\d+.*?\[proxy-wasm\].*?(resuming|freeing).*/
 --- grep_error_log_out eval
 qr/\A\*\d+ .*? filter 1\/1 resuming "on_request_headers" step in "rewrite" phase[^#*]*
-\*\d+ .*? filter 1\/1 resuming "on_dispatch_response" step in "access" phase[^#*]*
+\*\d+ .*? filter 1\/1 resuming "on_dispatch_response" step in "background" phase[^#*]*
 \*\d+ .*? filter chain failed resuming: previous error \(dispatch failure\)[^#*]*
 \*\d+ .*? filter freeing context #\d+ \(1\/1\)[^#*]*\Z/
 
diff --git a/t/05-others/010-client_connection_abort.t b/t/05-others/010-client_connection_abort.t
index d49637f5a..71111b674 100644
--- a/t/05-others/010-client_connection_abort.t
+++ b/t/05-others/010-client_connection_abort.t
@@ -4,12 +4,9 @@ use strict;
 use lib '.';
 use t::TestWasm;
 
-if ($ENV{TEST_NGINX_USE_HUP}) {
-    plan(skip_all => "unavailable in HUP mode");
+skip_hup();
 
-} else {
-    plan tests => repeat_each() * (blocks() * 4);
-}
+plan tests => repeat_each() * (blocks() * 4);
 
 run_tests();
 
diff --git a/t/05-others/011-upstream_connection_abort.t b/t/05-others/011-upstream_connection_abort.t
index 86703b0c7..1a17fd98a 100644
--- a/t/05-others/011-upstream_connection_abort.t
+++ b/t/05-others/011-upstream_connection_abort.t
@@ -4,14 +4,10 @@ use strict;
 use lib '.';
 use t::TestWasm;
 
+skip_hup();
 skip_valgrind();
 
-if ($ENV{TEST_NGINX_USE_HUP}) {
-    plan(skip_all => "unavailable in HUP mode");
-
-} else {
-    plan tests => repeat_each() * (blocks() * 4);
-}
+plan tests => repeat_each() * (blocks() * 4);
 
 run_tests();
 
diff --git a/t/TestWasm.pm b/t/TestWasm.pm
index 14638bec4..9493a58e2 100644
--- a/t/TestWasm.pm
+++ b/t/TestWasm.pm
@@ -31,6 +31,7 @@ our @EXPORT = qw(
     skip_no_debug
     skip_no_tinygo
     skip_valgrind
+    skip_hup
 );
 
 $ENV{TEST_NGINX_USE_HUP} ||= 0;
@@ -64,6 +65,12 @@ sub skip_valgrind (@) {
     }
 }
 
+sub skip_hup {
+    if ($ENV{TEST_NGINX_USE_HUP} == 1) {
+        plan(skip_all => "skipped in HUP mode");
+    }
+}
+
 sub skip_no_debug {
     if ($nginxV !~ m/--with-debug/) {
         plan(skip_all => "--with-debug required (NGX_BUILD_DEBUG=1)");
diff --git a/t/lib/proxy-wasm-tests/contexts/Cargo.toml b/t/lib/proxy-wasm-tests/contexts/Cargo.toml
new file mode 100644
index 000000000..a1f3f5c7a
--- /dev/null
+++ b/t/lib/proxy-wasm-tests/contexts/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "context-checks"
+version = "0.1.0"
+authors = ["Thibault Charbonnier <thibaultcha@me.com>"]
+edition = "2018"
+
+[dependencies]
+proxy-wasm = "0.2"
+log = "0.4"
diff --git a/t/lib/proxy-wasm-tests/contexts/crates/root/Cargo.toml b/t/lib/proxy-wasm-tests/contexts/crates/root/Cargo.toml
new file mode 100644
index 000000000..beed79e32
--- /dev/null
+++ b/t/lib/proxy-wasm-tests/contexts/crates/root/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "root-context-checks"
+version = "0.1.0"
+authors = ["Thibault Charbonnier <thibaultcha@me.com>"]
+edition = "2018"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+proxy-wasm = "0.2"
+log = "0.4"
+context-checks = { path = "../.." }
diff --git a/t/lib/proxy-wasm-tests/contexts/crates/root/src/lib.rs b/t/lib/proxy-wasm-tests/contexts/crates/root/src/lib.rs
new file mode 100644
index 000000000..f905b1214
--- /dev/null
+++ b/t/lib/proxy-wasm-tests/contexts/crates/root/src/lib.rs
@@ -0,0 +1,136 @@
+use context_checks::*;
+use log::*;
+use proxy_wasm::{traits::*, types::*};
+use std::collections::HashMap;
+use std::time::Duration;
+
+pub struct TestRoot {
+    pub config: HashMap<String, String>,
+}
+
+pub trait TestContext {
+    fn get_config(&self, name: &str) -> Option<&str>;
+    fn check_host_function(&self, name: &str);
+}
+
+impl Context for dyn TestContext {}
+impl TestContext for TestRoot {
+    fn get_config(&self, name: &str) -> Option<&str> {
+        self.config.get(name).map(|s| s.as_str())
+    }
+
+    fn check_host_function(&self, name: &str) {
+        match name {
+            "set_tick_period" => set_tick_period(),
+            "set_request_body_buffer" => set_request_body_buffer(),
+            "set_response_body_buffer" => set_response_body_buffer(),
+            "get_request_body_buffer" => get_request_body_buffer(),
+            "get_response_body_buffer" => get_response_body_buffer(),
+            "get_dispatch_response_body_buffer" => get_dispatch_response_body_buffer(),
+            _ => (),
+        }
+    }
+}
+
+struct TestContextHttp;
+impl Context for TestContextHttp {}
+impl HttpContext for TestContextHttp {}
+
+proxy_wasm::main! {{
+    proxy_wasm::set_log_level(LogLevel::Trace);
+    proxy_wasm::set_root_context(|_| -> Box<dyn RootContext> {
+        Box::new(TestRoot {
+            config: HashMap::new(),
+        })
+    });
+}}
+
+impl RootContext for TestRoot {
+    fn on_vm_start(&mut self, _: usize) -> bool {
+        info!("on_vm_start");
+
+        if let Some(config) = self.get_vm_configuration() {
+            match std::str::from_utf8(&config) {
+                Ok(text) => {
+                    info!("vm config: {}", text);
+                    self.check_host_function(text);
+                }
+                _ => info!("cannot parse vm config"),
+            }
+        }
+
+        true
+    }
+
+    fn on_configure(&mut self, _: usize) -> bool {
+        info!("on_configure");
+
+        if let Some(config_bytes) = self.get_plugin_configuration() {
+            let config_str = String::from_utf8(config_bytes).unwrap();
+            self.config = config_str
+                .split_whitespace()
+                .filter_map(|s| s.split_once('='))
+                .map(|(k, v)| (k.to_string(), v.to_string()))
+                .collect();
+        } else {
+            self.config = HashMap::new();
+        }
+
+        if self.get_config("on_tick").is_some() {
+            self.set_tick_period(Duration::from_millis(100));
+        }
+
+        if let Some(name) = self.get_config("on_configure") {
+            self.check_host_function(name)
+        }
+
+        if self.get_config("on_http_dispatch_response").is_some() {
+            let _ = self.dispatch_http_call(
+                self.get_config("host").unwrap_or(""),
+                vec![(":path", "/dispatch"), (":method", "GET")],
+                None,
+                vec![],
+                Duration::from_secs(0),
+            );
+        }
+
+        true
+    }
+
+    fn on_tick(&mut self) {
+        info!("on_tick",);
+
+        if let Some(name) = self.get_config("on_tick") {
+            self.check_host_function(name)
+        }
+    }
+
+    fn get_type(&self) -> Option<ContextType> {
+        Some(ContextType::HttpContext)
+    }
+
+    fn create_http_context(&self, _: u32) -> Option<Box<dyn HttpContext>> {
+        Some(Box::new(TestContextHttp {}))
+    }
+}
+
+impl Context for TestRoot {
+    fn on_http_call_response(
+        &mut self,
+        token_id: u32,
+        nheaders: usize,
+        body_size: usize,
+        ntrailers: usize,
+    ) {
+        let status = self.get_http_call_response_header(":status");
+
+        info!(
+            "on_root_http_call_response (id: {}, status: {}, headers: {}, body_bytes: {}, trailers: {})",
+            token_id, status.unwrap_or("".to_string()), nheaders, body_size, ntrailers
+        );
+
+        if let Some(name) = self.get_config("on_http_dispatch_response") {
+            self.check_host_function(name)
+        }
+    }
+}
diff --git a/t/lib/proxy-wasm-tests/contexts/src/lib.rs b/t/lib/proxy-wasm-tests/contexts/src/lib.rs
new file mode 100644
index 000000000..08e061cda
--- /dev/null
+++ b/t/lib/proxy-wasm-tests/contexts/src/lib.rs
@@ -0,0 +1,123 @@
+use log::*;
+use proxy_wasm::types::*;
+use std::ptr::null_mut;
+
+#[allow(improper_ctypes)]
+extern "C" {
+    fn proxy_set_tick_period_milliseconds(period: u32) -> Status;
+}
+
+pub fn set_tick_period() {
+    unsafe {
+        let status = proxy_set_tick_period_milliseconds(10000);
+        info!("set_tick_period status: {}", status as u32);
+    }
+}
+
+#[allow(improper_ctypes)]
+extern "C" {
+    fn proxy_set_buffer_bytes(
+        buffer_type: u32,
+        start: usize,
+        size: usize,
+        buffer_data: *const u8,
+        buffer_size: usize,
+    ) -> Status;
+}
+
+pub fn set_request_body_buffer() {
+    let v = String::default();
+
+    unsafe {
+        let status = proxy_set_buffer_bytes(
+            BufferType::HttpRequestBody as u32,
+            0,
+            0,
+            v.as_ptr(),
+            v.len(),
+        );
+
+        info!("set_request_body_buffer status: {}", status as u32);
+    }
+}
+
+pub fn set_response_body_buffer() {
+    let v = String::default();
+
+    unsafe {
+        let status = proxy_set_buffer_bytes(
+            BufferType::HttpResponseBody as u32,
+            0,
+            0,
+            v.as_ptr(),
+            v.len(),
+        );
+
+        info!("set_response_body_buffer status: {}", status as u32);
+    }
+}
+
+#[allow(improper_ctypes)]
+extern "C" {
+    fn proxy_get_buffer_bytes(
+        buffer_type: u32,
+        start: usize,
+        max_size: usize,
+        return_buffer_data: *mut *mut u8,
+        return_buffer_size: *mut usize,
+    ) -> Status;
+}
+
+pub fn get_request_body_buffer() {
+    let mut return_data: *mut u8 = null_mut();
+    let mut return_size: usize = 0;
+
+    unsafe {
+        let status = proxy_get_buffer_bytes(
+            BufferType::HttpRequestBody as u32,
+            0,
+            0,
+            &mut return_data,
+            &mut return_size,
+        );
+
+        info!("get_request_body_buffer status: {}", status as u32);
+    }
+}
+
+pub fn get_response_body_buffer() {
+    let mut return_data: *mut u8 = null_mut();
+    let mut return_size: usize = 0;
+
+    unsafe {
+        let status = proxy_get_buffer_bytes(
+            BufferType::HttpResponseBody as u32,
+            0,
+            0,
+            &mut return_data,
+            &mut return_size,
+        );
+
+        info!("get_response_body_buffer status: {}", status as u32);
+    }
+}
+
+pub fn get_dispatch_response_body_buffer() {
+    let mut return_data: *mut u8 = null_mut();
+    let mut return_size: usize = 0;
+
+    unsafe {
+        let status = proxy_get_buffer_bytes(
+            BufferType::HttpCallResponseBody as u32,
+            0,
+            0,
+            &mut return_data,
+            &mut return_size,
+        );
+
+        info!(
+            "get_dispatch_response_body_buffer status: {}",
+            status as u32
+        );
+    }
+}