fix(cli): improve exec eval observability

src/apps/cli/src/diagnostics.rs

@@ -0,0 +1,96 @@
+//! Exec-mode exit diagnostics for automated runners.
+
+use std::path::Path;
+
+pub const EXIT_LINE_PREFIX: &str = "BITFUN_EXIT: ";
+pub const DETAIL_MAX_LEN: usize = 500;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ExitKind {
+    SessionCreateFailed,
+    SendMessageFailed,
+    DialogTurnFailed,
+    SystemError,
+    ExecError,
+    PatchWriteFailed,
+}
+
+impl ExitKind {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            Self::SessionCreateFailed => "session_create_failed",
+            Self::SendMessageFailed => "send_message_failed",
+            Self::DialogTurnFailed => "dialog_turn_failed",
+            Self::SystemError => "system_error",
+            Self::ExecError => "exec_error",
+            Self::PatchWriteFailed => "patch_write_failed",
+        }
+    }
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct ExitContext<'a> {
+    pub session_id: Option<&'a str>,
+    pub turn_id: Option<&'a str>,
+    pub agent_type: Option<&'a str>,
+    pub workspace: Option<&'a Path>,
+}
+
+pub fn sanitize_exit_detail(detail: &str) -> String {
+    let collapsed = detail.split_whitespace().collect::<Vec<_>>().join(" ");
+    if collapsed.chars().count() <= DETAIL_MAX_LEN {
+        return collapsed;
+    }
+    let truncated: String = collapsed.chars().take(DETAIL_MAX_LEN).collect();
+    format!("{truncated}...")
+}
+
+pub fn format_exit_line(kind: ExitKind, detail: &str) -> String {
+    format!(
+        "{}{}: {}",
+        EXIT_LINE_PREFIX,
+        kind.as_str(),
+        sanitize_exit_detail(detail)
+    )
+}
+
+pub fn emit_exit_diagnostic(kind: ExitKind, detail: &str, ctx: &ExitContext<'_>) {
+    eprintln!("{}", format_exit_line(kind, detail));
+    tracing::error!(
+        kind = kind.as_str(),
+        session_id = ctx.session_id.unwrap_or("-"),
+        turn_id = ctx.turn_id.unwrap_or("-"),
+        agent_type = ctx.agent_type.unwrap_or("-"),
+        workspace = ?ctx.workspace,
+        detail = %detail,
+        "exec exit diagnostic"
+    );
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn format_exit_line_uses_stable_prefix_and_kind() {
+        let line = format_exit_line(ExitKind::DialogTurnFailed, "429 Too Many Requests");
+        assert_eq!(
+            line,
+            "BITFUN_EXIT: dialog_turn_failed: 429 Too Many Requests"
+        );
+    }
+
+    #[test]
+    fn sanitize_exit_detail_collapses_whitespace_and_newlines() {
+        let detail = "line one\nline two\t\tline three";
+        assert_eq!(sanitize_exit_detail(detail), "line one line two line three");
+    }
+
+    #[test]
+    fn sanitize_exit_detail_truncates_long_messages() {
+        let detail = "x".repeat(DETAIL_MAX_LEN + 10);
+        let sanitized = sanitize_exit_detail(&detail);
+        assert!(sanitized.ends_with("..."));
+        assert!(sanitized.chars().count() <= DETAIL_MAX_LEN + 3);
+    }
+}

src/apps/cli/src/main.rs

@@ -10,6 +10,7 @@ mod agent;
 mod chat_state;
 mod commands;
 mod config;
+mod diagnostics;
 mod logging;
 mod management;
 mod modes;