diff --git a/crates/cli/src/plugin_install/host.rs b/crates/cli/src/plugin_install/host.rs
index a6f5a87e9..3bc2355fe 100644
--- a/crates/cli/src/plugin_install/host.rs
+++ b/crates/cli/src/plugin_install/host.rs
@@ -220,17 +220,23 @@ fn codex_plugin_registered(
     options: &PluginInstallOptions,
     runner: &dyn CommandRunner,
 ) -> Result<bool, String> {
-    let output = run_capture_command(
-        "codex",
-        &["plugin".into(), "list".into(), "--json".into()],
-        options,
-        runner,
-    )?;
-    let plugins = parse_json_command_output("codex plugin list --json", output)?;
-    Ok(plugins
-        .get("installed")
-        .and_then(Value::as_array)
-        .is_some_and(|plugins| plugins.iter().any(plugin_entry_matches)))
+    // Codex `plugin list` has no `--json` flag (unlike Claude Code).
+    let output = run_capture_command("codex", &["plugin".into(), "list".into()], options, runner)?;
+    let plugin_id = format!("{PLUGIN_NAME}@{MARKETPLACE_NAME}");
+    Ok(output
+        .stdout
+        .lines()
+        .any(|line| codex_plugin_line_installed(line, &plugin_id)))
+}
+
+fn codex_plugin_line_installed(line: &str, plugin_id: &str) -> bool {
+    let mut columns = line.split_whitespace();
+    if columns.next() != Some(plugin_id) {
+        return false;
+    }
+    columns
+        .next()
+        .is_some_and(|status| status.starts_with("installed"))
 }
 
 fn codex_marketplace_registered(
diff --git a/crates/cli/tests/coverage/plugin_install_tests.rs b/crates/cli/tests/coverage/plugin_install_tests.rs
index 4d6535190..dc8b706d3 100644
--- a/crates/cli/tests/coverage/plugin_install_tests.rs
+++ b/crates/cli/tests/coverage/plugin_install_tests.rs
@@ -560,20 +560,7 @@ fn host_command_helpers_cover_dry_run_missing_failure_and_reporting() {
 
     let runner = MockRunner::default()
         .with_executable("codex", "/bin/codex")
-        .with_capture_output("/bin/codex plugin list --json", "not json")
-        .with_capture_output("/bin/codex plugin marketplace list", "");
-    assert!(
-        host_registration_report(PluginHost::Codex, &normal, &runner)
-            .unwrap_err()
-            .contains("failed to parse")
-    );
-
-    let runner = MockRunner::default()
-        .with_executable("codex", "/bin/codex")
-        .with_capture_output(
-            "/bin/codex plugin list --json",
-            json!({"installed": []}).to_string(),
-        )
+        .with_capture_output("/bin/codex plugin list", "PLUGIN  STATUS  VERSION  PATH\n")
         .with_capture_output("/bin/codex plugin marketplace list", "MARKETPLACE ROOT\n");
     let error = validate_host_registration(PluginHost::Codex, &normal, &runner).unwrap_err();
     assert!(
@@ -618,30 +605,38 @@ fn host_registration_report_accepts_claude_and_codex_shape_variants() {
         assert!(report.host_marketplace_registered);
     }
 
-    for plugin_entry in [
-        json!({"id": plugin_id.clone()}),
-        json!({"pluginId": plugin_id.clone()}),
-        json!({"name": PLUGIN_NAME, "marketplaceName": MARKETPLACE_NAME}),
-    ] {
-        let runner = MockRunner::default()
-            .with_executable("codex", "/bin/codex")
-            .with_capture_output(
-                "/bin/codex plugin list --json",
-                json!({"installed": [plugin_entry]}).to_string(),
-            )
-            .with_capture_output(
-                "/bin/codex plugin marketplace list",
-                format!("{MARKETPLACE_NAME} /tmp/nemo-relay-local\n"),
-            );
-        let report = host_registration_report(PluginHost::Codex, &normal, &runner).unwrap();
-        assert!(report.ok());
-    }
+    let runner = MockRunner::default()
+        .with_executable("codex", "/bin/codex")
+        .with_capture_output(
+            "/bin/codex plugin list",
+            format!("{plugin_id}  installed, enabled  0.4.0  /tmp/nemo-relay-plugin\n"),
+        )
+        .with_capture_output(
+            "/bin/codex plugin marketplace list",
+            format!("{MARKETPLACE_NAME} /tmp/nemo-relay-local\n"),
+        );
+    let report = host_registration_report(PluginHost::Codex, &normal, &runner).unwrap();
+    assert!(report.ok());
+
+    let runner = MockRunner::default()
+        .with_executable("codex", "/bin/codex")
+        .with_capture_output(
+            "/bin/codex plugin list",
+            format!("{plugin_id}  not installed\n"),
+        )
+        .with_capture_output(
+            "/bin/codex plugin marketplace list",
+            format!("{MARKETPLACE_NAME} /tmp/nemo-relay-local\n"),
+        );
+    let report = host_registration_report(PluginHost::Codex, &normal, &runner).unwrap();
+    assert!(!report.host_plugin_registered);
+    assert!(report.host_marketplace_registered);
 
     let runner = MockRunner::default()
         .with_executable("codex", "/bin/codex")
         .with_capture_output(
-            "/bin/codex plugin list --json",
-            json!({"installed": [{"name": PLUGIN_NAME, "marketplaceName": "other"}]}).to_string(),
+            "/bin/codex plugin list",
+            format!("{PLUGIN_NAME}@other  installed, enabled  0.4.0  /tmp/other\n"),
         )
         .with_capture_output("/bin/codex plugin marketplace list", "other /tmp/other\n");
     let report = host_registration_report(PluginHost::Codex, &normal, &runner).unwrap();
@@ -655,6 +650,15 @@ fn host_registration_report_surfaces_capture_status_and_stderr_variants() {
     let dir = tempdir().unwrap();
     let normal = options(dir.path());
 
+    let runner = MockRunner::default()
+        .with_executable("claude", "/bin/claude")
+        .with_capture_output("/bin/claude plugin list --json", "not json");
+    assert!(
+        host_registration_report(PluginHost::ClaudeCode, &normal, &runner)
+            .unwrap_err()
+            .contains("failed to parse")
+    );
+
     let runner = MockRunner::default()
         .with_executable("claude", "/bin/claude")
         .with_capture_status(
@@ -1328,13 +1332,9 @@ fn doctor_json_uses_quiet_plugin_report() {
         .with_executable("nemo-relay", "/bin/nemo-relay")
         .with_executable("codex", "/bin/codex")
         .with_capture_output(
-            "/bin/codex plugin list --json",
-            json!({
-                "installed": [
-                    { "pluginId": "nemo-relay-plugin@nemo-relay-local" }
-                ]
-            })
-            .to_string(),
+            "/bin/codex plugin list",
+            "PLUGIN                              STATUS              VERSION  PATH\n\
+             nemo-relay-plugin@nemo-relay-local  installed, enabled  0.4.0    /tmp/nemo-relay-plugin\n",
         )
         .with_capture_output(
             "/bin/codex plugin marketplace list",
@@ -1357,7 +1357,7 @@ fn doctor_json_uses_quiet_plugin_report() {
     assert_eq!(
         runner.capture_commands(),
         vec![
-            "/bin/codex plugin list --json",
+            "/bin/codex plugin list",
             "/bin/codex plugin marketplace list"
         ]
     );