huskies: merge 601_story_project_local_agent_prompt_layer_for_huskies

server/src/agents/local_prompt.rs

@@ -0,0 +1,118 @@
+//! Project-local agent prompt layer.
+//!
+//! Reads `.huskies/AGENT.md` from the project root and appends its content to
+//! the baked-in agent prompt at spawn time.  This lets projects record
+//! non-obvious facts (directory conventions, known traps, etc.) that every
+//! agent should know without modifying the shared agent configuration.
+//!
+//! Behaviour contract:
+//! - If the file is missing or empty the caller receives `None`; agents spawn
+//!   normally with no warnings or errors.
+//! - If the file exists and is non-empty, the content is returned and an
+//!   INFO-level log line is emitted with the file path and byte count.
+//! - The file is read fresh on every agent spawn — no caching.
+
+use std::path::Path;
+
+/// Attempt to load the project-local agent prompt from `.huskies/AGENT.md`.
+///
+/// Returns `Some(content)` when the file exists and is non-empty, or `None`
+/// when the file is absent or empty.  Never returns an error; any I/O problem
+/// is silently treated as "no local prompt".
+pub fn read_project_local_prompt(project_root: &Path) -> Option<String> {
+    let path = project_root.join(".huskies/AGENT.md");
+    let content = std::fs::read_to_string(&path).ok()?;
+    let trimmed = content.trim();
+    if trimmed.is_empty() {
+        return None;
+    }
+    crate::slog!(
+        "[agents] project-local prompt loaded: {} ({} bytes)",
+        path.display(),
+        trimmed.len()
+    );
+    Some(trimmed.to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn returns_none_when_file_absent() {
+        let tmp = tempfile::tempdir().unwrap();
+        let result = read_project_local_prompt(tmp.path());
+        assert!(result.is_none(), "missing file must return None");
+    }
+
+    #[test]
+    fn returns_none_when_file_empty() {
+        let tmp = tempfile::tempdir().unwrap();
+        let huskies_dir = tmp.path().join(".huskies");
+        std::fs::create_dir_all(&huskies_dir).unwrap();
+        std::fs::write(huskies_dir.join("AGENT.md"), "").unwrap();
+        let result = read_project_local_prompt(tmp.path());
+        assert!(result.is_none(), "empty file must return None");
+    }
+
+    #[test]
+    fn returns_none_when_file_whitespace_only() {
+        let tmp = tempfile::tempdir().unwrap();
+        let huskies_dir = tmp.path().join(".huskies");
+        std::fs::create_dir_all(&huskies_dir).unwrap();
+        std::fs::write(huskies_dir.join("AGENT.md"), "   \n\n  ").unwrap();
+        let result = read_project_local_prompt(tmp.path());
+        assert!(result.is_none(), "whitespace-only file must return None");
+    }
+
+    #[test]
+    fn returns_content_when_file_non_empty() {
+        let tmp = tempfile::tempdir().unwrap();
+        let huskies_dir = tmp.path().join(".huskies");
+        std::fs::create_dir_all(&huskies_dir).unwrap();
+        let marker = "DISTINCTIVE_MARKER_XYZ42";
+        std::fs::write(huskies_dir.join("AGENT.md"), format!("# Hints\n{marker}\n")).unwrap();
+        let result = read_project_local_prompt(tmp.path());
+        assert!(result.is_some(), "non-empty file must return Some");
+        let content = result.unwrap();
+        assert!(
+            content.contains(marker),
+            "returned content must include the marker: {content}"
+        );
+    }
+
+    #[test]
+    fn appended_to_prompt_integration() {
+        // Simulates the start.rs usage: marker appears in the constructed
+        // system prompt when the file is present, absent when it is not.
+        let tmp_with = tempfile::tempdir().unwrap();
+        let huskies_dir = tmp_with.path().join(".huskies");
+        std::fs::create_dir_all(&huskies_dir).unwrap();
+        let marker = "INTEGRATION_MARKER_601";
+        std::fs::write(huskies_dir.join("AGENT.md"), marker).unwrap();
+
+        let base_prompt = "You are a coder agent.".to_string();
+        let local = read_project_local_prompt(tmp_with.path());
+        let effective = match local {
+            Some(ref extra) => format!("{base_prompt}\n\n{extra}"),
+            None => base_prompt.clone(),
+        };
+        assert!(
+            effective.contains(marker),
+            "marker must appear in effective prompt when file present: {effective}"
+        );
+
+        // Without the file
+        let tmp_without = tempfile::tempdir().unwrap();
+        let local2 = read_project_local_prompt(tmp_without.path());
+        assert!(local2.is_none(), "no marker when file absent");
+        let effective2 = match local2 {
+            Some(ref extra) => format!("{base_prompt}\n\n{extra}"),
+            None => base_prompt.clone(),
+        };
+        assert!(
+            !effective2.contains(marker),
+            "marker must NOT appear in effective prompt when file absent: {effective2}"
+        );
+    }
+}