fix(cursor): return valid responses from trace hooks

bt-daemon/src/hook.rs

@@ -90,14 +90,31 @@ pub(crate) fn should_flush_ingress_event(env: &wire::Envelope) -> bool {
 /// Returns `Ok` once the daemon has durably journaled the event. Delivery
 /// happens later; an `Err` means capture failed before acknowledgement.
 pub async fn run_hook(args: HookArgs, route: SessionRoute, host: HostInfo) -> anyhow::Result<()> {
-    if suppress_inherited_hook(&args) {
-        return Ok(());
+    let response =
+        (args.source == "cursor").then(|| cursor_hook_response_for_event(args.event.as_deref()));
+    let result = async move {
+        if suppress_inherited_hook(&args) {
+            return Ok(());
+        }
+        let settings = settings::AgentSettings::load_for_hook(&args.source)?;
+        if !settings.tracing_enabled() {
+            return Ok(());
+        }
+        run_hook_with_route(args, settings.route.unwrap_or(route), host).await
+    }
+    .await;
+    if let Some(response) = response {
+        println!("{response}");
     }
-    let settings = settings::AgentSettings::load_for_hook(&args.source)?;
-    if !settings.tracing_enabled() {
-        return Ok(());
+    result
+}
+
+fn cursor_hook_response_for_event(event: Option<&str>) -> &'static str {
+    if event == Some("beforeSubmitPrompt") {
+        r#"{"continue":true}"#
+    } else {
+        "{}"
     }
-    run_hook_with_route(args, settings.route.unwrap_or(route), host).await
 }
 
 /// A managed run injects its own hook definitions. Suppress an inherited

bt-daemon/tests/cursor_pipeline.rs

@@ -16,9 +16,9 @@ use std::path::{Path, PathBuf};
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
-/// Smoke-test Cursor's proposed direct Windows command through the native
-/// command shell. This checks executable lookup and stdin forwarding, which
-/// the POSIX-only launcher cannot exercise on a Windows runner.
+/// Smoke-test Cursor's portable direct command through the native Windows
+/// shell. This checks executable lookup, stdin forwarding, and its JSON
+/// response without relying on a POSIX-only launcher.
 #[cfg(windows)]
 #[allow(
     clippy::disallowed_methods,
@@ -35,14 +35,14 @@ fn cursor_direct_hook_command_receives_native_stdin_on_windows() {
     let shim = tmp.path().join("bt.cmd");
     std::fs::write(
         &shim,
-        "@echo off\r\nif /I not \"%~1 %~2\"==\"trace hook\" exit /b 13\r\n> \"%CURSOR_HOOK_ARGS_FILE%\" echo %*\r\nset /p BT_EVENT=\r\n> \"%CURSOR_HOOK_INPUT_FILE%\" echo %BT_EVENT%\r\nexit /b 0\r\n",
+        "@echo off\r\nif /I not \"%~1 %~2\"==\"trace hook\" exit /b 13\r\n> \"%CURSOR_HOOK_ARGS_FILE%\" echo %*\r\nset /p BT_EVENT=\r\n> \"%CURSOR_HOOK_INPUT_FILE%\" echo %BT_EVENT%\r\necho {}\r\nexit /b 0\r\n",
     )
     .unwrap();
     let path = std::env::join_paths(std::iter::once(tmp.path().to_owned()).chain(
         std::env::split_paths(&std::env::var_os("PATH").expect("Windows PATH is present")),
     ))
     .unwrap();
-    let command = "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000";
+    let command = "bt trace hook --source cursor --event afterAgentResponse --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000";
     let payload = r#"{"conversation_id":"windows-smoke","hook_event_name":"afterAgentResponse","transcript_path":null}"#;
     let mut child = Command::new("cmd.exe")
         .args(["/d", "/s", "/c", command])
@@ -67,8 +67,8 @@ fn cursor_direct_hook_command_receives_native_stdin_on_windows() {
         String::from_utf8_lossy(&output.stderr)
     );
     assert!(
-        output.stdout.is_empty(),
-        "direct tracing command must not write a policy response"
+        String::from_utf8_lossy(&output.stdout).trim() == "{}",
+        "Cursor CLI hook response must be valid JSON"
     );
     let args = std::fs::read_to_string(args_path).unwrap();
     assert!(args.starts_with("trace hook --source cursor "), "{args}");

src/plugins/cursor/content/hooks/hooks.json

@@ -3,84 +3,84 @@
   "hooks": {
     "sessionStart": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event sessionStart --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "sessionEnd": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event sessionEnd --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "beforeSubmitPrompt": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event beforeSubmitPrompt --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "postToolUse": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event postToolUse --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "postToolUseFailure": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event postToolUseFailure --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "subagentStop": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event subagentStop --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "afterShellExecution": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event afterShellExecution --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "afterMCPExecution": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event afterMCPExecution --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "afterFileEdit": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event afterFileEdit --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "preCompact": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event preCompact --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "stop": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event stop --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }
     ],
     "afterAgentResponse": [
       {
-        "command": "bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
+        "command": "bt trace hook --source cursor --event afterAgentResponse --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000",
         "timeout": 10,
         "failClosed": false
       }

src/plugins/cursor/test/test_capture.sh

@@ -20,13 +20,17 @@ with tempfile.TemporaryDirectory(prefix="cursor-capture-") as temporary:
     fake_bt.write_text('''#!/bin/sh
 printf '%s\\n' "$*" >> "$CAPTURE_DIR/args"
 /bin/cat > "$CAPTURE_DIR/payload"
+case " $* " in
+  *" --event beforeSubmitPrompt "*) printf '%s\\n' '{"continue":true}' ;;
+  *) printf '%s\\n' '{}' ;;
+esac
 exit "${BT_EXIT_CODE:-0}"
 ''')
     fake_bt.chmod(0o755)
     environment = dict(os.environ, CAPTURE_DIR=str(root), PATH=str(fake_bin))
     payload = b'{"conversation_id":"session-a","hook_event_name":"postToolUse","transcript_path":null,"tool_input":{"command":"echo $HOME; `pwd`"},"additive_field":42}\n'
-    # One successful and one failed invocation exercise direct executable
-    # forwarding; Cursor's failClosed=false setting keeps capture fail-open.
+    # Cursor hook responses come from the CLI after capture. The protocol
+    # response must still be present when capture itself fails.
     for exit_code in ('0', '1'):
         environment['BT_EXIT_CODE'] = exit_code
         for event, registrations in config['hooks'].items():
@@ -35,10 +39,13 @@ exit "${BT_EXIT_CODE:-0}"
                                     input=payload, env=environment,
                                     capture_output=True, executable='/bin/sh')
             assert result.returncode == int(exit_code), (event, result.returncode)
-            assert result.stdout == b'', (event, result.stdout)
+            expected_output = (b'{"continue":true}\n' if event == 'beforeSubmitPrompt'
+                               else b'{}\n')
+            assert result.stdout == expected_output, (event, result.stdout)
             assert (root / 'payload').read_bytes() == payload
             args = (root / 'args').read_text().splitlines()[-1]
             assert args == ('trace hook --source cursor '
+                            f'--event {event} '
                             '--session-id-field conversation_id --event-field hook_event_name '
                             '--transcript-path-field transcript_path --flush-on-turn-end '
                             '--capture-timeout-ms 8000'), args
@@ -51,5 +58,5 @@ exit "${BT_EXIT_CODE:-0}"
                                 capture_output=True, executable='/bin/sh')
         assert result.returncode != 0, (event, result.returncode)
         assert registrations[0]['failClosed'] is False
-print('cursor capture: direct command forwarding and fail-open configuration OK')
+print('cursor capture: portable command forwarding OK')
 PY

src/plugins/cursor/validate.sh

@@ -51,7 +51,10 @@ expected = {
 assert set(config['hooks']) == expected
 for event, registrations in config['hooks'].items():
     assert registrations == [{
-        'command': 'bt trace hook --source cursor --session-id-field conversation_id --event-field hook_event_name --transcript-path-field transcript_path --flush-on-turn-end --capture-timeout-ms 8000',
+        'command': ('bt trace hook --source cursor '
+                    f'--event {event} --session-id-field conversation_id '
+                    '--event-field hook_event_name --transcript-path-field transcript_path '
+                    '--flush-on-turn-end --capture-timeout-ms 8000'),
         'timeout': 10,
         'failClosed': False,
     }]