set an agent's initial agents.md at create

hive-agent/src/main.rs

@@ -505,6 +505,8 @@ async fn serve_main<S: Surface>(socket: &Path, poll_ms: u64) -> Result<()> {
     swarm_agent_state::spawn(&bus, login_state.clone());
     // Once per start: a new icon only arrives with a new harness process.
     swarm_agent_icon::spawn();
+    // Before the mirror and before any turn reads the file.
+    swarm_agents_md::seed_initial().await;
     // At start and on every change, so the swarm can read it while the
     // agent is stopped.
     swarm_agents_md::spawn();

hive-agent/src/swarm_agents_md.rs

@@ -29,6 +29,7 @@ use std::time::Duration;
 use async_nats::jetstream::context::PublishErrorKind;
 use sha1::{Digest as _, Sha1};
 use swarm_queue_client::agents_md::{Apply, ApplyReply, Mirror};
+use swarm_queue_client::agents_md_initial::Initial;
 use tokio::sync::Notify;
 
 use crate::claude_md_watch::agents_md_path;
@@ -94,6 +95,103 @@ pub fn spawn() {
     });
 }
 
+/// How many times, and for how long each, the key is read at start before the
+/// agent starts without the text.
+const SEED_ATTEMPTS: u32 = 3;
+const SEED_READ_TIMEOUT: Duration = Duration::from_secs(5);
+const SEED_RETRY_WAIT: Duration = Duration::from_secs(1);
+
+/// Write the text the swarm stored for this agent at create to `AGENTS.md`,
+/// when the file does not exist. Done before anything reads the file, so the
+/// agent's first turn already has it, and before the mirror, so the swarm
+/// sees it from the first publish.
+///
+/// An existing file is never touched, so a restart or a re-created agent
+/// keeps its edits. The read of the key is bounded to about
+/// [`SEED_ATTEMPTS`] × [`SEED_READ_TIMEOUT`], so a queue that refuses it delays
+/// boot by seconds; the agent then starts without the text and a later start
+/// tries again.
+pub async fn seed_initial() {
+    let agent = crate::identity::label();
+    let dir = crate::paths::state_dir();
+    if agent.is_empty() || exists(&agents_md_path(&dir)) {
+        return;
+    }
+    let client = crate::swarm_queue::client().await;
+    let read = read_bounded(SEED_ATTEMPTS, SEED_READ_TIMEOUT, SEED_RETRY_WAIT, || {
+        swarm_queue_client::agents_md_initial::read_own(&client, &agent)
+    })
+    .await;
+    match read {
+        Ok(initial) => {
+            if let Err(e) = seed(&dir, initial.as_ref()) {
+                tracing::warn!(error = %e, "writing the initial AGENTS.md failed");
+            }
+        }
+        Err(e) => {
+            tracing::warn!(error = %e, "reading the initial AGENTS.md failed; starting without it");
+        }
+    }
+}
+
+/// `read`, tried up to `attempts` times with `wait` between, each cut off
+/// after `timeout`. The first answer wins; the last failure is the error.
+async fn read_bounded<T, E, F, Fut>(
+    attempts: u32,
+    timeout: Duration,
+    wait: Duration,
+    mut read: F,
+) -> Result<T, String>
+where
+    F: FnMut() -> Fut,
+    Fut: Future<Output = Result<T, E>>,
+    E: std::fmt::Display,
+{
+    let mut last = String::new();
+    for attempt in 0..attempts {
+        if attempt > 0 {
+            tokio::time::sleep(wait).await;
+        }
+        match tokio::time::timeout(timeout, read()).await {
+            Ok(Ok(value)) => return Ok(value),
+            Ok(Err(e)) => last = e.to_string(),
+            Err(_) => last = format!("no answer within {timeout:?}"),
+        }
+    }
+    Err(last)
+}
+
+/// Whether anything, a dangling link included, is at `path`.
+fn exists(path: &Path) -> bool {
+    std::fs::symlink_metadata(path).is_ok()
+}
+
+/// Create `AGENTS.md` in `state_dir` with `initial`'s text, unless a file is
+/// already there. The text goes to a temporary file in the same directory
+/// first and is linked into place without replacing anything
+/// (`persist_noclobber`), so a failed write leaves no file and a file written
+/// meanwhile is kept.
+fn seed(state_dir: &Path, initial: Option<&Initial>) -> std::io::Result<()> {
+    use std::os::unix::fs::PermissionsExt as _;
+
+    let Some(initial) = initial else {
+        return Ok(());
+    };
+    std::fs::create_dir_all(state_dir)?;
+    let mut temp = tempfile::NamedTempFile::new_in(state_dir)?;
+    temp.write_all(initial.content.as_bytes())?;
+    temp.as_file()
+        .set_permissions(std::fs::Permissions::from_mode(0o644))?;
+    match temp.persist_noclobber(agents_md_path(state_dir)) {
+        Ok(_) => {
+            tracing::info!(bytes = initial.content.len(), "wrote the initial AGENTS.md");
+            Ok(())
+        }
+        Err(e) if e.error.kind() == std::io::ErrorKind::AlreadyExists => Ok(()),
+        Err(e) => Err(e.error),
+    }
+}
+
 /// What became of one mirror write.
 #[derive(Debug)]
 enum Published {
@@ -503,4 +601,95 @@ mod tests {
         assert_eq!(second.revision, revision(AFTER.as_bytes()));
         task.abort();
     }
+
+    fn initial(text: &str) -> swarm_queue_client::agents_md_initial::Initial {
+        swarm_queue_client::agents_md_initial::Initial {
+            content: text.to_owned(),
+        }
+    }
+
+    /// The stored text becomes the file when there is none, and the mirror's
+    /// revision then covers it.
+    #[test]
+    fn the_initial_text_is_written_when_there_is_no_file() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        super::seed(dir.path(), Some(&initial(BEFORE))).expect("seed");
+        assert_eq!(file(&dir), BEFORE);
+        // Presence control for the next two: nothing stored writes nothing.
+        let empty = tempfile::tempdir().expect("tempdir");
+        super::seed(empty.path(), None).expect("seed");
+        assert!(!empty.path().join("AGENTS.md").exists());
+    }
+
+    /// A file the agent already has, edited or not, is never replaced.
+    #[test]
+    fn an_existing_file_is_not_overwritten_by_the_initial_text() {
+        let dir = state(AFTER);
+        super::seed(dir.path(), Some(&initial(BEFORE))).expect("seed");
+        assert_eq!(file(&dir), AFTER);
+        let empty = state("");
+        super::seed(empty.path(), Some(&initial(BEFORE))).expect("seed");
+        assert_eq!(file(&empty), "", "an emptied file is still the agent's");
+    }
+
+    /// A second start, with the key still stored, keeps the agent's edits.
+    #[test]
+    fn a_second_seed_keeps_what_the_agent_did_with_the_file() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        super::seed(dir.path(), Some(&initial(BEFORE))).expect("seed");
+        std::fs::write(dir.path().join("AGENTS.md"), AFTER).expect("edit");
+        super::seed(dir.path(), Some(&initial(BEFORE))).expect("seed again");
+        assert_eq!(file(&dir), AFTER);
+    }
+
+    /// A seed that cannot finish leaves no `AGENTS.md`, so the next start
+    /// tries again. The state dir's parent is a file, so no temp file can be
+    /// made; the leftover directory listing is empty either way.
+    #[test]
+    fn a_seed_that_fails_leaves_no_file_and_no_temp_file() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let blocker = dir.path().join("blocker");
+        std::fs::write(&blocker, "x").expect("write");
+        super::seed(&blocker.join("state"), Some(&initial(BEFORE))).expect_err("no dir");
+        assert!(!blocker.join("state").exists());
+        // Control: a good dir leaves exactly AGENTS.md, no temp file.
+        let ok = tempfile::tempdir().expect("tempdir");
+        super::seed(ok.path(), Some(&initial(BEFORE))).expect("seed");
+        let names: Vec<_> = std::fs::read_dir(ok.path())
+            .expect("ls")
+            .map(|e| e.expect("entry").file_name())
+            .collect();
+        assert_eq!(names, ["AGENTS.md"]);
+    }
+
+    /// A read that never answers costs `attempts` × `timeout` plus the waits,
+    /// not a startup retry schedule, and the last failure is reported.
+    #[tokio::test(start_paused = true)]
+    async fn a_read_that_never_answers_is_given_up_after_the_bound() {
+        let started = tokio::time::Instant::now();
+        let out = super::read_bounded(3, Duration::from_secs(5), Duration::from_secs(1), || {
+            std::future::pending::<Result<(), String>>()
+        })
+        .await;
+        assert!(out.unwrap_err().contains("no answer within"));
+        assert_eq!(started.elapsed(), Duration::from_secs(17));
+    }
+
+    /// A later attempt that answers wins over an earlier failure.
+    #[tokio::test(start_paused = true)]
+    async fn a_read_that_fails_once_and_then_answers_returns_the_answer() {
+        let calls = std::sync::atomic::AtomicU32::new(0);
+        let out = super::read_bounded(3, Duration::from_secs(5), Duration::from_secs(1), || {
+            let n = calls.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+            async move {
+                if n == 0 {
+                    Err("down".to_owned())
+                } else {
+                    Ok(7)
+                }
+            }
+        })
+        .await;
+        assert_eq!(out, Ok(7));
+    }
 }