Let the machine's own CLI refresh an expired token, and retry once

A 401 from the usage endpoint means the stored access token has expired.
Refreshing it here is not an option: Anthropic's OAuth rotates the refresh
token, so a second refresher invalidates the CLI's copy and forces a
re-login on a machine that usually has a live session on it. So run the CLI
there instead and re-read what it wrote.

`doctor` rather than `auth status`: probed against 2.1.258 with an invalid
token, `auth status` answers loggedIn:true from the file alone and never
reaches the network. The same probe showed a failed refresh blanks both
tokens, which is why this stays on the 401 path.

Also gives ProviderConfig one program() so the CLI's default path is not
written down twice.

server/src/usage.rs

@@ -141,6 +141,10 @@ pub struct ClaudeUsage {
     pub setup_name: String,
     /// How to reach that machine. `Here` for the backend's own.
     pub transport: Transport,
+    /// The CLI to run there, for the one thing this asks of it: refreshing its
+    /// own expired token. The provider's, so a machine with the CLI somewhere
+    /// odd is asked at the same path its sessions run.
+    pub program: String,
 }
 
 /// Where Claude Code keeps its credentials, as a shell word rather than a path:
@@ -198,46 +202,109 @@ impl UsageProvider for ClaudeUsage {
             Ok(token) => token,
             Err(state) => return self.snapshot(state, Vec::new()),
         };
-        let text = match ureq::get(USAGE_URL)
+        let body = match self.call(&token) {
+            Ok(body) => body,
+            Err(Refused::Other(detail)) => {
+                return self.snapshot(UsageState::Failed { detail }, Vec::new());
+            }
+            Err(Refused::Unauthorized) => match self.after_cli_refresh(&token) {
+                Ok(body) => body,
+                Err(state) => return self.snapshot(state, Vec::new()),
+            },
+        };
+        self.snapshot(UsageState::Ok, parse_windows(&body))
+    }
+}
+
+/// Why one call to the usage endpoint did not produce numbers.
+///
+/// 401 is apart from the rest because it is the only one with a way out: the
+/// endpoint answered, and it means the access token has expired rather than
+/// that anything is broken.
+enum Refused {
+    Unauthorized,
+    Other(String),
+}
+
+impl ClaudeUsage {
+    /// One call to the endpoint with one token.
+    fn call(&self, token: &str) -> Result<Value, Refused> {
+        let text = ureq::get(USAGE_URL)
             .header("Authorization", &format!("Bearer {token}"))
             .header("anthropic-beta", "oauth-2025-04-20")
             .header("User-Agent", USER_AGENT)
             .call()
             .and_then(|mut response| response.body_mut().read_to_string())
-        {
-            Ok(text) => text,
             // The error string can embed the URL but never the token.
-            Err(err) => return self.snapshot(UsageState::Failed { detail: why(&err) }, Vec::new()),
-        };
-        let body: Value = match serde_json::from_str(&text) {
-            Ok(body) => body,
-            Err(err) => {
-                return self.snapshot(
-                    UsageState::Failed {
-                        detail: format!("usage endpoint sent non-JSON: {err}"),
-                    },
-                    Vec::new(),
-                );
-            }
-        };
-        self.snapshot(UsageState::Ok, parse_windows(&body))
+            .map_err(|err| match err {
+                ureq::Error::StatusCode(401) => Refused::Unauthorized,
+                other => Refused::Other(why(&other)),
+            })?;
+        serde_json::from_str(&text)
+            .map_err(|err| Refused::Other(format!("usage endpoint sent non-JSON: {err}")))
+    }
+
+    /// Have the machine's own CLI refresh its token, then ask once more.
+    ///
+    /// **The CLI does the refresh, never this.** Anthropic's OAuth rotates the
+    /// refresh token, so whoever refreshes second presents a dead one and the
+    /// machine is logged out until somebody runs `/login` on it -- and the
+    /// machine we would be refreshing on is usually one with a live session of
+    /// its own. Running the CLI keeps it the only writer of
+    /// `.credentials.json`.
+    ///
+    /// `doctor` rather than the `auth status` it reads like, measured against
+    /// this CLI (2.1.258) on 2026-09-05 with a deliberately invalid token:
+    /// `auth status` reports `loggedIn: true` off the file alone and never
+    /// touches the network, so it would have refreshed nothing while looking
+    /// like it had. `doctor` resolves the account, which is what makes it
+    /// refresh, and it spends no quota. The same probe showed what a *failed*
+    /// refresh does -- the CLI blanks both tokens -- so this must stay on the
+    /// 401 path, where the access token is already dead, and never be used to
+    /// refresh speculatively.
+    ///
+    /// Only a token that actually changed is retried, so a CLI that refreshed
+    /// nothing costs one call rather than two, and this cannot become a loop.
+    fn after_cli_refresh(&self, stale: &str) -> Result<Value, UsageState> {
+        let launch = Launch::new(&self.program, vec!["doctor".to_string()], None);
+        if let Err(err) = self.transport.capture_blocking(&launch) {
+            return Err(UsageState::Failed {
+                detail: format!(
+                    "the Claude login on {} has expired, and `{} doctor` couldn't be run there to refresh it: {err:#}",
+                    self.setup_name, self.program
+                ),
+            });
+        }
+        let fresh = self.access_token()?;
+        if fresh == stale {
+            return Err(self.still_expired());
+        }
+        self.call(&fresh).map_err(|err| match err {
+            Refused::Unauthorized => self.still_expired(),
+            Refused::Other(detail) => UsageState::Failed { detail },
+        })
+    }
+
+    /// A login the CLI could not renew: the one state here somebody has to act
+    /// on, so it says where and what to run.
+    fn still_expired(&self) -> UsageState {
+        UsageState::Failed {
+            detail: format!(
+                "the Claude login on {} has expired and could not be refreshed; run `{} /login` there",
+                self.setup_name, self.program
+            ),
+        }
     }
 }
 
 /// What a failed call to the usage endpoint should say.
 ///
 /// A status is not a network fault and must not be reported as one: the
-/// endpoint answered, and 401 in particular says the stored token has expired
-/// -- Claude Code refreshes it as it runs, so a machine whose CLI has been
-/// idle long enough hands us a stale one. That is fixable, and the message is
-/// the only place anybody finds out how.
+/// endpoint answered. 401 never reaches here -- it has its own way out in
+/// [`ClaudeUsage::after_cli_refresh`] -- so what is left is a refusal nobody
+/// on this side can fix.
 fn why(err: &ureq::Error) -> String {
     match err {
-        ureq::Error::StatusCode(401) => {
-            format!(
-                "the Claude login on this machine has expired (401); run `claude` there, or re-run `/login`, to refresh {CREDENTIALS}"
-            )
-        }
         ureq::Error::StatusCode(code) => format!("usage endpoint refused the request: HTTP {code}"),
         other => format!("usage endpoint unreachable: {other}"),
     }
@@ -552,6 +619,7 @@ fn providers_for(setup: &SetupConfig, fixture: &Fixture) -> Vec<Box<dyn UsagePro
                 setup: setup.id.clone(),
                 setup_name: setup.name.clone(),
                 transport: Transport::for_setup(setup),
+                program: provider.program().to_string(),
             })),
             // Nothing at all until a test has asked for something: an
             // echo session costs nothing, so the honest answer is no row
@@ -644,14 +712,42 @@ mod tests {
     use crate::config::DriverKind;
 
     #[test]
-    fn an_expired_login_is_not_reported_as_an_unreachable_endpoint() {
-        let stale = why(&ureq::Error::StatusCode(401));
-        assert!(stale.contains("expired"), "{stale}");
-        assert!(!stale.contains("unreachable"), "{stale}");
+    fn a_refusal_the_endpoint_answered_is_not_reported_as_an_unreachable_one() {
         assert!(why(&ureq::Error::StatusCode(500)).contains("HTTP 500"));
         assert!(why(&ureq::Error::HostNotFound).contains("unreachable"));
     }
 
+    #[test]
+    fn an_expired_login_says_where_to_log_in_rather_than_naming_the_network() {
+        let provider = ClaudeUsage {
+            setup: "far".to_string(),
+            setup_name: "somewhere else".to_string(),
+            transport: Transport::for_setup(&unreachable_setup()),
+            program: "/opt/claude".to_string(),
+        };
+        // The machine cannot be reached, so the refresh attempt fails there
+        // rather than at the endpoint -- and the message still has to name the
+        // machine and the command, since that is all anybody gets to act on.
+        let UsageState::Failed { detail } = provider
+            .after_cli_refresh("stale")
+            .expect_err("an unreachable machine cannot refresh anything")
+        else {
+            panic!("an expired login is a fault to report, not a logged-out machine");
+        };
+        assert!(detail.contains("somewhere else"), "{detail}");
+        assert!(detail.contains("/opt/claude doctor"), "{detail}");
+        assert!(
+            !detail.contains("stale"),
+            "the token must never be quoted back"
+        );
+
+        let UsageState::Failed { detail } = provider.still_expired() else {
+            panic!("still expired is a fault");
+        };
+        assert!(detail.contains("/opt/claude /login"), "{detail}");
+        assert!(!detail.contains("unreachable"), "{detail}");
+    }
+
     #[test]
     fn parses_the_limits_array_defensively() {
         // Trimmed from a live 2026-08-24 response.
@@ -706,6 +802,7 @@ mod tests {
             setup: "far".to_string(),
             setup_name: "somewhere else".to_string(),
             transport: Transport::for_setup(&unreachable_setup()),
+            program: "claude".to_string(),
         };
         let snapshot = provider.fetch();
         // The distinction the old single `error` string could not make: this