Ask for a new signature in the request-deadline 503 body

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## [Unreleased]
 
+- The 503 body of a request that reached its deadline reads "request_timeout: no change was applied; retry the request with a new signature". Details: TC-1997.
+
 ## [1.25.2] - 2026-10-26
 
 - No code changes since 1.25.1. Prepared so that named keys can be turned off with the deploy input `named_keys_v1` without a rebuild.

tinycloud-core/src/sql/types.rs

@@ -327,7 +327,7 @@ pub enum SqlError {
     Busy(SqlBusyStage),
     /// The request deadline was reached before the request's write began, so
     /// nothing was applied (TC-1274).
-    #[error("request_timeout: no change was applied; retry the request")]
+    #[error("request_timeout: no change was applied; retry the request with a new signature")]
     RequestTimeout,
 }
 

tinycloud-node-server/src/routes/mod.rs

@@ -142,7 +142,8 @@ pub const SQL_BUSY_RETRY_AFTER_SECS: u32 = 5;
 /// write began (TC-1274).
 pub const REQUEST_TIMEOUT: &str = "request_timeout";
 /// The whole body of a [`REQUEST_TIMEOUT`] response.
-pub const REQUEST_TIMEOUT_BODY: &str = "request_timeout: no change was applied; retry the request";
+pub const REQUEST_TIMEOUT_BODY: &str =
+    "request_timeout: no change was applied; retry the request with a new signature";
 /// Body prefix of a `503` whose read's audit record was not committed within
 /// the read-audit wait bound (TC-1317); `Retry-After` is
 /// [`SQL_BUSY_RETRY_AFTER_SECS`], since the audit queue is backlogged.