diff --git a/script/check-infra-if-index-changed b/script/check-infra-if-index-changed
index 51f7ce2fc..18712bd0d 100755
--- a/script/check-infra-if-index-changed
+++ b/script/check-infra-if-index-changed
@@ -112,7 +112,7 @@ do_check()
     RADIO_NCP_PATH="$PWD/build/simulation/examples/apps/ncp/ot-rcp"
     RADIO_URL="spinel+hdlc+forkpty://${RADIO_NCP_PATH}?forkpty-arg=2"
 
-    sudo -E "$PWD/build/posix/src/posix/ot-daemon" -d7 -v -I wpan0 -B veth-a "${RADIO_URL}" &
+    sudo -E "$PWD/build/posix/src/posix/ot-daemon" -d5 -v -I wpan0 -B veth-a "${RADIO_URL}" &
     wait_for "state" "Done" || die "failed to start daemon"
 
     # verify this reset and factoryreset end immediately
diff --git a/script/check-posix-pty b/script/check-posix-pty
index f166a6b16..1480f8176 100755
--- a/script/check-posix-pty
+++ b/script/check-posix-pty
@@ -211,7 +211,7 @@ do_check()
     if [[ ${OT_DAEMON} == 'on' ]]; then
         # The log file is in our own tmp directory, so the redirect does not need sudo.
         # shellcheck disable=SC2024
-        sudo -E "$PWD/build/posix/src/posix/ot-daemon" -d7 -v -I "${VALID_NETIF_NAME}" "${RADIO_URL}" >"${OT_DAEMON_OUTPUT}" 2>&1 &
+        sudo -E "$PWD/build/posix/src/posix/ot-daemon" -d5 -v -I "${VALID_NETIF_NAME}" "${RADIO_URL}" >"${OT_DAEMON_OUTPUT}" 2>&1 &
         OT_DAEMON_JOB=$!
         sleep 3
         # macOS cannot explicitly set network interface name
@@ -222,6 +222,9 @@ do_check()
         else
             OT_CTL=(sudo "${OT_CTL_PATH}")
         fi
+        # -d5 asks for debug logging; the daemon's output must carry OpenThread's own log lines, not only the
+        # syslog() lines of its startup.
+        timeout_run 10 grep -qE '\[(D|I)\] ' "${OT_DAEMON_OUTPUT}" || die 'the daemon does not log at the level -d asked for'
         "${OT_CTL[@]}" -I "${NETIF_NAME}" panid 0xface | grep 'Done' || die 'failed to set panid with ot-ctl'
 
         # verify supports options in OpenThread commands without separator --
@@ -250,8 +253,8 @@ do_check()
             die
         fi
 
-        # check_daemon_multicast_group reads INFO lines of the netif; `-d7` does not take
-        # effect, as main.c sets the level before the instance exists.
+        # check_daemon_multicast_group reads INFO lines of the netif; -d5 above gives them along
+        # with everything at DEBG, so settle on INFO for the rest of the run.
         "${OT_CTL[@]}" -I "${NETIF_NAME}" log level 4 | grep 'Done' || die 'failed to set log level'
         OT_CLI_CMD="${OT_CTL[*]} -I ${NETIF_NAME}"
     else
diff --git a/src/posix/main.c b/src/posix/main.c
index d4f8bf51e..e671b85b9 100644
--- a/src/posix/main.c
+++ b/src/posix/main.c
@@ -323,10 +323,11 @@ static otInstance *InitInstance(PosixConfig *aConfig)
 
     syslog(LOG_INFO, "Running %s", otGetVersionString());
     syslog(LOG_INFO, "Thread version: %hu", otThreadGetVersion());
-    IgnoreError(otLoggingSetLevel(aConfig->mLogLevel));
 
     instance = otSysInit(&aConfig->mPlatformConfig);
     VerifyOrDie(instance != NULL, OT_EXIT_FAILURE);
+    // The instance starts at OPENTHREAD_CONFIG_LOG_LEVEL_INIT; a level set before it exists is lost.
+    IgnoreError(otLoggingSetLevel(aConfig->mLogLevel));
     syslog(LOG_INFO, "Thread interface: %s", otSysGetThreadNetifName());
 
     if (aConfig->mPlatformConfig.mCoprocessorType != OT_COPROCESSOR_RCP)