fix(stockbit): tell a polling agent when Stockbit refuses the sign-in

A refused cookie in idx's browser was only a stderr warning, which nobody
reads under idx-mcp: stockbit_status showed `waiting` until the timeout, and
the timeout message did not mention the refusal.

- runtime::on_warning sends a thread's warnings to a sink as well as
  stderr, until its guard drops.
- The background sign-in puts its warnings in `sign_in.warning`, cleared
  once it signs in.
- The errors that end a browser wait (timeout, window closed, browser
  exited) name a refusal it hit.

Claude-Session: https://claude.ai/code/session_01RqPPVeVDrnLoP7NUZmLRxY

crates/idx-core/src/api/stockbit/browser.rs

@@ -234,6 +234,9 @@ fn wait_for_session(
 ) -> Result<(), IdxError> {
     let deadline = Instant::now() + timeout;
     let mut rejected: Option<String> = None;
+    // Why Stockbit refused that cookie, so the error that ends the wait says
+    // so: a polling frontend never saw the warning.
+    let mut refusal: Option<String> = None;
     // After a check fails for a passing reason, the next is held back.
     let mut retry_at: Option<Instant> = None;
     let mut last_error: Option<String> = None;
@@ -273,6 +276,7 @@ fn wait_for_session(
                             "Stockbit refused the session in idx's browser ({err}); sign in \
                              again in that window"
                         ));
+                        refusal = Some(err.to_string());
                         rejected = Some(cookie.value);
                         retry_at = None;
                     }
@@ -283,12 +287,18 @@ fn wait_for_session(
             Ok(_) => last_error = None,
             Err(err) => last_error = Some(err.to_string()),
         }
+        let refused = || {
+            refusal
+                .as_ref()
+                .map(|err| format!("; Stockbit refused the session signed in there ({err})"))
+                .unwrap_or_default()
+        };
         if !alive() {
             devtools.close();
-            return Err(IdxError::Io(
-                "the browser exited before idx got a session; run `idx stockbit login` again"
-                    .to_string(),
-            ));
+            return Err(IdxError::Io(format!(
+                "the browser exited before idx got a session{}; run `idx stockbit login` again",
+                refused()
+            )));
         }
         match devtools.has_page() {
             Ok(true) => {
@@ -299,11 +309,11 @@ fn wait_for_session(
                 misses += 1;
                 if saw_window && misses >= 2 {
                     devtools.close();
-                    return Err(IdxError::Io(
-                        "the Stockbit sign-in window was closed before the session arrived; \
-                         run `idx stockbit login` again"
-                            .to_string(),
-                    ));
+                    return Err(IdxError::Io(format!(
+                        "the Stockbit sign-in window was closed before the session arrived{}; \
+                         run `idx stockbit login` again",
+                        refused()
+                    )));
                 }
             }
             Err(err) => last_error = Some(err.to_string()),
@@ -311,9 +321,10 @@ fn wait_for_session(
         if Instant::now() >= deadline {
             devtools.close();
             let mut message = format!(
-                "the Stockbit sign-in timed out after {}s and idx closed its browser window; \
+                "the Stockbit sign-in timed out after {}s and idx closed its browser window{}; \
                  re-run `idx stockbit login`, or add --no-browser for the local page",
-                timeout.as_secs()
+                timeout.as_secs(),
+                refused()
             );
             if let Some(err) = last_error {
                 message.push_str(&format!(" (last DevTools error: {err})"));
@@ -993,6 +1004,11 @@ mod tests {
         )
         .unwrap_err();
         assert!(err.to_string().contains("timed out"), "{err}");
+        assert!(
+            err.to_string()
+                .contains("Stockbit refused the session signed in there (auth error: expired)"),
+            "{err}"
+        );
         assert_eq!(checks.get(), 1, "one refusal per distinct cookie");
         browser.finish();
         let _ = std::fs::remove_dir_all(&profile);

crates/idx-core/src/api/stockbit/signin.rs

@@ -242,6 +242,10 @@ pub struct Progress {
     /// Why it failed: the error's code and message.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub error: Option<ProgressError>,
+    /// The latest warning while it waits, such as Stockbit refusing the
+    /// session signed in so far; gone once it signs in.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub warning: Option<String>,
 }
 
 #[derive(Debug, Clone, Serialize)]
@@ -257,6 +261,7 @@ struct Slot {
     timeout: Duration,
     state: State,
     error: Option<ProgressError>,
+    warning: Option<String>,
     cancel: Arc<AtomicBool>,
     thread: Option<JoinHandle<()>>,
 }
@@ -273,6 +278,7 @@ impl Slot {
             expires_in_secs,
             already_open,
             error: self.error.clone(),
+            warning: self.warning.clone(),
         }
     }
 
@@ -303,6 +309,7 @@ pub fn start_background(options: &Options) -> Result<Progress, IdxError> {
             expires_in_secs: 0,
             already_open: false,
             error: None,
+            warning: None,
         });
     }
     let sign_in = SignIn::start(options)?;
@@ -315,16 +322,29 @@ pub fn start_background(options: &Options) -> Result<Progress, IdxError> {
         timeout: sign_in.timeout(),
         state: State::Waiting,
         error: None,
+        warning: None,
         cancel: cancel.clone(),
         thread: None,
     };
     let progress = open.progress(false);
     open.thread = Some(std::thread::spawn(move || {
+        // Nobody reads a polling frontend's stderr, so what the wait warns
+        // about (a refused session) goes into the progress it polls.
+        let sink = crate::runtime::on_warning(move |message| {
+            let mut slot = SLOT.lock().unwrap_or_else(PoisonError::into_inner);
+            if let Some(open) = slot.as_mut().filter(|open| open.id == id) {
+                open.warning = Some(message.to_string());
+            }
+        });
         let result = sign_in.wait_until(&cancel);
+        drop(sink);
         let mut slot = SLOT.lock().unwrap_or_else(PoisonError::into_inner);
         if let Some(open) = slot.as_mut().filter(|open| open.id == id) {
             match result {
-                Ok(_) => open.state = State::SignedIn,
+                Ok(_) => {
+                    open.state = State::SignedIn;
+                    open.warning = None;
+                }
                 Err(err) => {
                     open.state = State::Failed;
                     open.error = Some(ProgressError {
@@ -398,12 +418,17 @@ mod tests {
             expires_in_secs: 300,
             already_open: false,
             error: None,
+            warning: None,
         };
         let value = serde_json::to_value(&page).unwrap();
         assert_eq!(value["state"], "waiting");
         assert_eq!(value["method"], "page");
         assert_eq!(value["port"], 7878);
-        assert!(value.get("reason").is_none() && value.get("error").is_none());
+        assert!(
+            ["reason", "error", "warning"]
+                .iter()
+                .all(|key| value.get(key).is_none())
+        );
 
         let failed = Progress {
             state: State::Failed,
@@ -416,10 +441,12 @@ mod tests {
                 code: "IO".to_string(),
                 message: "the window was closed".to_string(),
             }),
+            warning: Some("Stockbit refused the session".to_string()),
         };
         let value = serde_json::to_value(&failed).unwrap();
         assert_eq!(value["method"], "browser");
         assert_eq!(value["browser"], "Helium");
         assert_eq!(value["error"]["code"], "IO");
+        assert_eq!(value["warning"], "Stockbit refused the session");
     }
 }

crates/idx-core/src/lib.rs

@@ -22,12 +22,40 @@ pub mod text;
 pub use client::{CachePolicy, Fetched, Idx};
 
 pub mod runtime {
+    use std::cell::RefCell;
     use std::fmt::Display;
     use std::sync::atomic::{AtomicBool, Ordering};
 
     static QUIET: AtomicBool = AtomicBool::new(false);
     static JSON: AtomicBool = AtomicBool::new(false);
 
+    type Sink = Box<dyn Fn(&str)>;
+
+    thread_local! {
+        static SINK: RefCell<Option<Sink>> = const { RefCell::new(None) };
+    }
+
+    /// Sends this thread's warnings to `sink` too, until the guard drops: a
+    /// frontend whose stderr nobody reads (idx-mcp) hands them on this way.
+    /// Warnings still go to stderr, and `set_quiet` does not silence `sink`.
+    pub fn on_warning(sink: impl Fn(&str) + 'static) -> WarningSink {
+        let previous = SINK.with(|slot| slot.replace(Some(Box::new(sink))));
+        WarningSink { previous }
+    }
+
+    /// Restores the thread's previous sink when dropped.
+    #[must_use = "warnings reach the sink only while this guard lives"]
+    pub struct WarningSink {
+        previous: Option<Sink>,
+    }
+
+    impl Drop for WarningSink {
+        fn drop(&mut self) {
+            let previous = self.previous.take();
+            SINK.with(|slot| *slot.borrow_mut() = previous);
+        }
+    }
+
     pub fn set_quiet(quiet: bool) {
         QUIET.store(quiet, Ordering::Relaxed);
     }
@@ -62,6 +90,40 @@ pub mod runtime {
     }
 
     pub fn warn(message: impl Display) {
+        let message = message.to_string();
+        SINK.with(|slot| {
+            if let Some(sink) = slot.borrow().as_ref() {
+                sink(&message);
+            }
+        });
         emit("warning", message);
     }
+
+    #[cfg(test)]
+    mod tests {
+        use super::*;
+        use std::rc::Rc;
+
+        /// A sink sees this thread's warnings while its guard lives, and an
+        /// inner one hands back to the outer when it drops.
+        #[test]
+        fn warnings_reach_the_sink_while_its_guard_lives() {
+            let seen = Rc::new(RefCell::new(Vec::new()));
+            let outer = {
+                let seen = seen.clone();
+                on_warning(move |m| seen.borrow_mut().push(format!("outer {m}")))
+            };
+            warn("one");
+            {
+                let seen = seen.clone();
+                let _inner = on_warning(move |m| seen.borrow_mut().push(format!("inner {m}")));
+                warn("two");
+            }
+            warn("three");
+            drop(outer);
+            warn("four");
+            info("not a warning");
+            assert_eq!(*seen.borrow(), ["outer one", "inner two", "outer three"]);
+        }
+    }
 }

crates/idx-mcp/src/server.rs

@@ -189,7 +189,9 @@ IDX_STOCKBIT_REFRESH_TOKEN) and when its tokens expire; never the tokens. Withou
 get_orderbook fails and stockbit-provider quotes use Stockbit's delayed public page; the \
 user adds one with stockbit_login, or `idx stockbit login` in a terminal. After \
 stockbit_login, `sign_in.state` says whether that sign-in is waiting, signed_in or failed \
-(with `sign_in.error`).")]
+(with `sign_in.error`). While it waits, `sign_in.warning` is the latest problem it hit, such \
+as Stockbit refusing the session the user signed in with: pass it on, since the user may need \
+to sign in again.")]
     async fn stockbit_status(&self) -> ToolResult {
         blocking(login_status).await
     }

crates/idx-mcp/tests/golden/tools.json

@@ -604,7 +604,7 @@
     "name": "stockbit_login"
   },
   {
-    "description": "Whether a Stockbit session is stored (or seeded by IDX_STOCKBIT_REFRESH_TOKEN) and when its tokens expire; never the tokens. Without one, get_orderbook fails and stockbit-provider quotes use Stockbit's delayed public page; the user adds one with stockbit_login, or `idx stockbit login` in a terminal. After stockbit_login, `sign_in.state` says whether that sign-in is waiting, signed_in or failed (with `sign_in.error`).",
+    "description": "Whether a Stockbit session is stored (or seeded by IDX_STOCKBIT_REFRESH_TOKEN) and when its tokens expire; never the tokens. Without one, get_orderbook fails and stockbit-provider quotes use Stockbit's delayed public page; the user adds one with stockbit_login, or `idx stockbit login` in a terminal. After stockbit_login, `sign_in.state` says whether that sign-in is waiting, signed_in or failed (with `sign_in.error`). While it waits, `sign_in.warning` is the latest problem it hit, such as Stockbit refusing the session the user signed in with: pass it on, since the user may need to sign in again.",
     "inputSchema": {
       "properties": {},
       "type": "object"