diff --git a/hive-ag3nt/prompts/system.md b/hive-ag3nt/prompts/system.md
index 6514fca7..ba8f7dd5 100644
--- a/hive-ag3nt/prompts/system.md
+++ b/hive-ag3nt/prompts/system.md
@@ -38,7 +38,7 @@ Tools (hyperhive surface):
 - `mcp__hyperhive__cancel_loose_end(kind, id)` — cancel any question, reminder, or approval in the swarm. `kind` is `"question"` (bypasses the owner check used on sub-agents → hive-wide cleanup when an agent is offline / can't withdraw its own thread), `"reminder"` (same bypass), or `"approval"` (manager-only path → withdraws a pending approval YOU submitted that got superseded before the operator acted on it; the row resolves as `cancelled` and disappears from the operator's pending pane).
 <!-- /role:manager -->
 - `mcp__hyperhive__remind(message, delay_seconds? | at_unix_timestamp?, file_path?)` — schedule a message to land in your *own* inbox at a future time (sender shows as `reminder`). Set exactly one of `delay_seconds` (relative) or `at_unix_timestamp` (absolute). Use for self-paced follow-ups instead of blocking a whole turn on a long `recv` wait. A large `message` auto-spills to a file under `/agents/{label}/state/reminders/`; pass `file_path` to point at one yourself. Each agent's pending-reminder count is capped (default 50) — the tool will error if the cap is already reached.
-- `mcp__hyperhive__set_status(text)` — set a free-text status visible on the operator dashboard. **Call this at the start of every task** to say what you're working on (e.g. `"processing matrix messages"`, `"fixing #319 model priority"`, `"idle"`). Pass an empty string to clear. Persists across harness restarts.
+- `mcp__hyperhive__set_status(text)` — set a free-text status visible on the operator dashboard. **Call this at the start of every task** to say what you're working on (e.g. `"processing matrix messages"`, `"fixing #319 model priority"`, `"idle"`). Single line, ≤200 chars — the dashboard renders this as a short chip, so longer multi-line text is rejected. Pass an empty string to clear. Persists across harness restarts.
 - `mcp__hyperhive__get_agent_meta(name?)` — fetch identity + status metadata for an agent: canonical `name`, `role` (`agent` / `manager`), current `hyperhive_rev`, plus self-reported `status` text (set via `set_status`) and how long ago it was set. Pass `name` to query a peer (e.g. check whether iris is idle before pinging them). Omit `name` to get your own trustworthy identity stamp — useful for state files, commit messages, cross-agent attribution that won't drift across renames or session-continue boundaries where the system-prompt label could be stale.
 <!-- role:agent -->
 - `mcp__hyperhive__request_next_turn()` — ask the harness to start another turn immediately after this one ends, even if the inbox is empty. Use for multi-turn tasks (long builds, sequential steps) where you want to continue without waiting for an external message. The next turn starts with `from: "self"` and `body: "continue"`. No-op if new inbox messages arrive before this turn ends (the harness already loops immediately on pending messages). No args.
diff --git a/hive-c0re/src/agent_server.rs b/hive-c0re/src/agent_server.rs
index a46a456d..f0a419ad 100644
--- a/hive-c0re/src/agent_server.rs
+++ b/hive-c0re/src/agent_server.rs
@@ -230,6 +230,12 @@ async fn dispatch(req: &AgentRequest, agent: &str, coord: &Arc<Coordinator>) ->
             }
         }
         AgentRequest::SetStatus { text } => {
+            // #720: cap length + reject multi-line so a confused caller
+            // can't dump a multi-paragraph session report into the
+            // dashboard chip.
+            if let Err(message) = crate::limits::check_status_text(text) {
+                return AgentResponse::Err { message };
+            }
             let path = crate::coordinator::Coordinator::agent_notes_dir(agent)
                 .join("hyperhive-status");
             let result = if text.trim().is_empty() {
diff --git a/hive-c0re/src/limits.rs b/hive-c0re/src/limits.rs
index a1e3a173..e650971f 100644
--- a/hive-c0re/src/limits.rs
+++ b/hive-c0re/src/limits.rs
@@ -41,6 +41,56 @@ pub fn check_size(label: &str, body: &str) -> Result<(), String> {
     }
 }
 
+/// Per-status soft cap. `set_status` renders as a short chip on the
+/// dashboard agent card — the front-end truncates long strings to
+/// keep the row layout intact, so a multi-paragraph "session report"
+/// is wasted bytes that just bloat the rescan emit + container view
+/// payload. Cap at 200 chars to fit the chip plus a little
+/// descriptive padding without forcing the operator to read a
+/// scrolling chunk.
+pub const STATUS_MAX_CHARS: usize = 200;
+
+/// Validate a `set_status` payload (#720). Single-line + bounded so
+/// callers can't dump multi-paragraph session reports into the
+/// dashboard chip. Whitespace trim is done by the caller before the
+/// store-to-disk step — we run validation on the trimmed form so
+/// surrounding whitespace doesn't push a borderline-legal status
+/// past the cap.
+///
+/// Empty / all-whitespace input is accepted: the call site treats
+/// that as "clear the status" and removes the on-disk sentinel. Tests
+/// + caller cover both directions.
+///
+/// Returns a caller-ready error string suitable for surfacing in the
+/// `*Response::Err` shape.
+pub fn check_status_text(text: &str) -> Result<(), String> {
+    let trimmed = text.trim();
+    if trimmed.is_empty() {
+        // Empty = clear-status sentinel; nothing to validate.
+        return Ok(());
+    }
+    // Newline / carriage-return: status is a single-line chip on the
+    // dashboard. A multi-line argus session report is the canonical
+    // failure mode from #720.
+    if trimmed.contains('\n') || trimmed.contains('\r') {
+        return Err(
+            "set_status text must be a single line — write multi-line context to \
+             a file under your `/agents/<you>/state/` dir and reference that path \
+             from the chip instead"
+                .to_owned(),
+        );
+    }
+    let len = trimmed.chars().count();
+    if len > STATUS_MAX_CHARS {
+        return Err(format!(
+            "set_status text too long ({len} chars, max {STATUS_MAX_CHARS}); the \
+             dashboard chip truncates anything longer, so trim to a short summary \
+             and write the detail to `/agents/<you>/state/<file>` instead"
+        ));
+    }
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -63,4 +113,62 @@ mod tests {
         let err = check_size("question", &"x".repeat(MESSAGE_MAX_BYTES + 1)).unwrap_err();
         assert!(err.starts_with("question body too long"));
     }
+
+    #[test]
+    fn check_status_accepts_short_single_line() {
+        assert!(check_status_text("idle").is_ok());
+        assert!(check_status_text("processing matrix messages").is_ok());
+        // Boundary: exactly STATUS_MAX_CHARS chars trimmed is still
+        // accepted; one more rejects.
+        let max = "a".repeat(STATUS_MAX_CHARS);
+        assert!(check_status_text(&max).is_ok());
+    }
+
+    #[test]
+    fn check_status_accepts_empty_and_whitespace() {
+        // Empty + whitespace-only are the "clear status" sentinel and
+        // bypass the rest of the checks.
+        assert!(check_status_text("").is_ok());
+        assert!(check_status_text("   ").is_ok());
+        assert!(check_status_text("\n\t  ").is_ok());
+    }
+
+    #[test]
+    fn check_status_rejects_multi_line() {
+        let err = check_status_text("line one\nline two").unwrap_err();
+        assert!(err.contains("single line"), "err = {err}");
+        // Carriage return alone also rejects (windows linebreak / CR-only).
+        assert!(check_status_text("a\rb").is_err());
+    }
+
+    #[test]
+    fn check_status_rejects_oversize() {
+        let too_long = "a".repeat(STATUS_MAX_CHARS + 1);
+        let err = check_status_text(&too_long).unwrap_err();
+        assert!(err.contains("too long"), "err = {err}");
+        assert!(err.contains(&format!("max {STATUS_MAX_CHARS}")));
+    }
+
+    #[test]
+    fn check_status_counts_chars_not_bytes() {
+        // Multi-byte chars (emoji, accented letters) count once each
+        // per char — chars().count() not byte len. STATUS_MAX_CHARS
+        // worth of 4-byte chars is still legal.
+        let emoji = "💜".repeat(STATUS_MAX_CHARS);
+        assert!(
+            check_status_text(&emoji).is_ok(),
+            "{STATUS_MAX_CHARS} emoji should fit"
+        );
+        let too_many = "💜".repeat(STATUS_MAX_CHARS + 1);
+        assert!(check_status_text(&too_many).is_err());
+    }
+
+    #[test]
+    fn check_status_validates_post_trim() {
+        // Leading/trailing whitespace is trimmed before the length
+        // check — a borderline-legal payload with spaces around it
+        // still passes.
+        let padded = format!("  {}  ", "a".repeat(STATUS_MAX_CHARS));
+        assert!(check_status_text(&padded).is_ok());
+    }
 }
diff --git a/hive-c0re/src/manager_server.rs b/hive-c0re/src/manager_server.rs
index d867740d..9843ca63 100644
--- a/hive-c0re/src/manager_server.rs
+++ b/hive-c0re/src/manager_server.rs
@@ -502,6 +502,12 @@ async fn dispatch(req: &ManagerRequest, coord: &Arc<Coordinator>) -> ManagerResp
             }
         }
         ManagerRequest::SetStatus { text } => {
+            // #720: cap length + reject multi-line so a confused caller
+            // can't dump a multi-paragraph session report into the
+            // dashboard chip.
+            if let Err(message) = crate::limits::check_status_text(text) {
+                return ManagerResponse::Err { message };
+            }
             let path = Coordinator::agent_notes_dir(MANAGER_AGENT).join("hyperhive-status");
             let result = if text.trim().is_empty() {
                 std::fs::remove_file(&path).or_else(|e| {