diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7003a85..4c7be35 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 - Splitted the `download` command into `new`, `open`, and `download`. ([#3](https://github.com/qryxip/cargo-compete/pull/3))
 - Changed the format of `workspace-metadata.toml`.
     - Now `cargo-compete.test-suite`s are [Liquid](https://shopify.github.io/liquid/) templates.  ([#4](https://github.com/qryxip/cargo-compete/pull/4))
+    - Now `cargo-compete.open`s are [jq](https://github.com/stedolan/jq) commands. ([#5](https://github.com/qryxip/cargo-compete/pull/5))
 
 ### Fixed
 
diff --git a/README-ja.md b/README-ja.md
index dab5f56..cebfba9 100644
--- a/README-ja.md
+++ b/README-ja.md
@@ -100,7 +100,7 @@ AtCoderを選択に入れる場合、
 
 ## 設定
 
-**v0.2.0で`workspace-metadata.toml`のフォーマットを変更する予定です。** ([#4](https://github.com/qryxip/cargo-compete/pull/4))
+**v0.2.0で`workspace-metadata.toml`のフォーマットを変更する予定です。** ([#4](https://github.com/qryxip/cargo-compete/pull/4), [#5](https://github.com/qryxip/cargo-compete/pull/5))
 
 設定は各ワークスペース下にある`workspace-metadata.toml`にあります。
 バイナリ提出関連の設定もこちらです。
diff --git a/src/commands/init.rs b/src/commands/init.rs
index c08e6b3..1c6ee31 100644
--- a/src/commands/init.rs
+++ b/src/commands/init.rs
@@ -219,9 +219,16 @@ fn write_workspace_metadata_toml(
 ) -> anyhow::Result<()> {
     let content = format!(
         r#"[cargo-compete]
-new-workspace-member = "include" # "include", "focus"
+# How to manage new workspace members ("include", "focus")
+new-workspace-member = "include"
+# Path to the test file (Liquid template)
 test-suite = "./testcases/{{{{ contest }}}}/{{{{ problem | kebabcase }}}}.yml"
-#open = "vscode" # "vscode", "emacsclient"
+# Open files with the command (`jq` command)
+#
+# VSCode:
+#open = '["code"] + (.paths | map([.src, .test_suite]) | flatten) + ["-a", .manifest_dir]'
+# Emacs:
+#open = '["emacsclient", "-n"] + (.paths | map([.src, .test_suite]) | flatten)'
 
 [cargo-compete.template]
 code = "./cargo-compete-template/src/main.rs"
diff --git a/src/open.rs b/src/open.rs
index ee0a86b..0dbf913 100644
--- a/src/open.rs
+++ b/src/open.rs
@@ -1,10 +1,12 @@
-use crate::{project::Open, shell::Shell};
+use crate::shell::Shell;
+use anyhow::{ensure, Context as _};
+use serde_json::json;
 use std::{borrow::Borrow, path::Path};
 use url::Url;
 
 pub(crate) fn open(
     urls: &[impl Borrow<Url>],
-    open: Option<Open>,
+    open: Option<impl AsRef<str>>,
     paths: &[(impl AsRef<Path>, impl AsRef<Path>)],
     pkg_manifest_dir: &Path,
     cwd: &Path,
@@ -17,26 +19,44 @@ pub(crate) fn open(
     }
 
     if let Some(open) = open {
-        let mut cmd = match open {
-            Open::Vscode => crate::process::with_which("code", cwd)?,
-            Open::Emacsclient => {
-                let mut cmd = crate::process::with_which("emacsclient", cwd)?;
-                cmd.arg("-n");
-                cmd
-            }
-        };
-
-        for (src_path, test_suite_path) in paths {
-            cmd.arg(src_path.as_ref());
-            cmd.arg(test_suite_path.as_ref());
+        fn ensure_utf8(path: &Path) -> anyhow::Result<&str> {
+            path.to_str()
+                .with_context(|| format!("must be UTF-8: {:?}", path.display()))
         }
 
-        if open == Open::Vscode {
-            cmd.arg("-a");
-            cmd.arg(pkg_manifest_dir);
-        }
+        let input = json!({
+            "manifest_dir": ensure_utf8(pkg_manifest_dir)?,
+            "paths": paths
+                .iter()
+                .map(|(src_path, test_suite_path)| {
+                    let src_path = ensure_utf8(src_path.as_ref())?;
+                    let test_suite_path = ensure_utf8(test_suite_path.as_ref())?;
+                    Ok(json!({
+                        "src": src_path,
+                        "test_suite": test_suite_path
+                    }))
+                })
+                .collect::<anyhow::Result<Vec<_>>>()?
+        })
+        .to_string();
+
+        let jq = crate::process::which("jq", cwd).with_context(|| {
+            "`jq` not found. install `jq` from https://github.com/stedolan/jq/releases"
+        })?;
+
+        let output = crate::process::process(jq, &cwd)
+            .args(&["-c", open.as_ref()])
+            .pipe_input(Some(input))
+            .read_with_shell_status(shell)?;
+
+        let args = serde_json::from_str::<Vec<String>>(&output)
+            .with_context(|| "expected string array")?;
+
+        ensure!(!args.is_empty(), "empty command");
 
-        cmd.exec_with_shell_status(shell)?;
+        crate::process::with_which(&args[0], cwd)?
+            .args(&args[1..])
+            .exec_with_shell_status(shell)?;
     }
     Ok(())
 }
diff --git a/src/process.rs b/src/process.rs
index 87dab85..d609b03 100644
--- a/src/process.rs
+++ b/src/process.rs
@@ -5,7 +5,9 @@ use std::{
     env,
     ffi::{OsStr, OsString},
     fmt,
+    io::Write as _,
     path::{Path, PathBuf},
+    process::Stdio,
 };
 
 #[derive(Debug)]
@@ -13,6 +15,7 @@ pub(crate) struct ProcessBuilder {
     program: OsString,
     args: Vec<OsString>,
     cwd: PathBuf,
+    pipe_input: Option<Vec<u8>>,
 }
 
 impl ProcessBuilder {
@@ -26,12 +29,13 @@ impl ProcessBuilder {
         self
     }
 
-    pub(crate) fn exec(&self) -> anyhow::Result<()> {
-        let status = std::process::Command::new(&self.program)
-            .args(&self.args)
-            .current_dir(&self.cwd)
-            .status()?;
+    pub(crate) fn pipe_input(&mut self, pipe_input: Option<impl Into<Vec<u8>>>) -> &mut Self {
+        self.pipe_input = pipe_input.map(Into::into);
+        self
+    }
 
+    pub(crate) fn exec(&self) -> anyhow::Result<()> {
+        let status = self.spawn(Stdio::inherit())?.wait()?;
         if !status.success() {
             bail!("{} didn't exit successfully: {}", self, status);
         }
@@ -42,6 +46,41 @@ impl ProcessBuilder {
         shell.status("Running", self)?;
         self.exec()
     }
+
+    fn read(&self) -> anyhow::Result<String> {
+        let std::process::Output { status, stdout, .. } =
+            self.spawn(Stdio::piped())?.wait_with_output()?;
+        if !status.success() {
+            bail!("{} didn't exit successfully: {}", self, status);
+        }
+        String::from_utf8(stdout).with_context(|| "non UTF-8 output")
+    }
+
+    pub(crate) fn read_with_shell_status(&self, shell: &mut Shell) -> anyhow::Result<String> {
+        shell.status("Running", self)?;
+        self.read()
+    }
+
+    fn spawn(&self, stdout: Stdio) -> anyhow::Result<std::process::Child> {
+        let mut child = std::process::Command::new(&self.program)
+            .args(&self.args)
+            .current_dir(&self.cwd)
+            .stdin(if self.pipe_input.is_some() {
+                Stdio::piped()
+            } else {
+                Stdio::inherit()
+            })
+            .stdout(stdout)
+            .spawn()?;
+
+        if let (Some(mut stdin), Some(pipe_input)) = (child.stdin.take(), self.pipe_input.as_ref())
+        {
+            stdin.write_all(pipe_input)?;
+            stdin.flush()?;
+        }
+
+        Ok(child)
+    }
 }
 
 impl fmt::Display for ProcessBuilder {
@@ -64,6 +103,7 @@ pub(crate) fn process(program: impl AsRef<Path>, cwd: impl AsRef<Path>) -> Proce
         program: program.as_ref().into(),
         args: vec![],
         cwd: cwd.as_ref().into(),
+        pipe_input: None,
     }
 }
 
diff --git a/src/project.rs b/src/project.rs
index 34b05be..b1affc0 100644
--- a/src/project.rs
+++ b/src/project.rs
@@ -29,7 +29,7 @@ pub(crate) struct WorkspaceMetadataCargoCompete {
     #[derivative(Debug = "ignore")]
     #[serde(deserialize_with = "deserialize_liquid_template_with_custom_filter")]
     pub(crate) test_suite: liquid::Template,
-    pub(crate) open: Option<Open>,
+    pub(crate) open: Option<String>,
     pub(crate) template: WorkspaceMetadataCargoCompeteTemplate,
     pub(crate) platform: WorkspaceMetadataCargoCompetePlatform,
 }
@@ -75,13 +75,6 @@ fn liquid_template_with_custom_filter(text: &str) -> Result<liquid::Template, St
     }
 }
 
-#[derive(Deserialize, Clone, Copy, PartialEq, Debug)]
-#[serde(rename_all = "kebab-case")]
-pub(crate) enum Open {
-    Vscode,
-    Emacsclient,
-}
-
 #[derive(Deserialize, Clone, Copy, Debug)]
 #[serde(rename_all = "kebab-case")]
 pub(crate) enum NewWorkspaceMember {