diff --git a/open-sse/utils/errorPathRedaction.ts b/open-sse/utils/errorPathRedaction.ts
index 2b372af583..cdf33fc4dc 100644
--- a/open-sse/utils/errorPathRedaction.ts
+++ b/open-sse/utils/errorPathRedaction.ts
@@ -464,8 +464,8 @@ function findUnquotedPathEnd(
   let hasFilesystemEvidence = false;
   let hasUnresolvedFragments = false;
 
-  const resolveEndpoint = (): number => {
-    if (hasUnresolvedFragments) {
+  const resolveEndpoint = (ignoreAmbiguity = false): number => {
+    if (hasUnresolvedFragments && !ignoreAmbiguity) {
       return failClosedAmbiguity || hasFilesystemEvidence ? value.length : -1;
     }
     if (resolvedExtensionEnd >= 0) return resolvedExtensionEnd;
@@ -530,7 +530,12 @@ function findUnquotedPathEnd(
     while (nextTokenStart < value.length && isWhitespace(value[nextTokenStart])) nextTokenStart++;
     if (nextTokenStart >= value.length) return resolveEndpoint();
     if (isSyntacticallyAbsolutePathAt(value, nextTokenStart)) {
-      const endpoint = resolveEndpoint();
+      // A route-shielded upcoming span (e.g. "POST /v1/foo") is never
+      // filesystem-sensitive by design — see hasRouteContextBefore. Its mere
+      // presence must not force ambiguous prose in between (like "Use POST")
+      // to fail closed and swallow past it into the shielded route and
+      // beyond; resolve with whatever evidence was already gathered instead.
+      const endpoint = resolveEndpoint(hasRouteContextBefore(value, nextTokenStart));
       if (endpoint >= 0) return endpoint;
       return acceptEndpointBeforeAnotherAbsolute ? lastPathTokenEnd : -1;
     }
diff --git a/tests/unit/error-message-sanitization.test.ts b/tests/unit/error-message-sanitization.test.ts
index 8813e7ac71..21f989ef9e 100644
--- a/tests/unit/error-message-sanitization.test.ts
+++ b/tests/unit/error-message-sanitization.test.ts
@@ -239,6 +239,21 @@ test("sanitizeErrorMessage replaces absolute paths with <path>", async () => {
   assert.ok(out2.includes("<path>"));
 });
 
+test("sanitizeErrorMessage does not swallow a shielded route hint that follows an earlier redacted path (#6457)", async () => {
+  // Regression: an unshielded route-looking span ("on /v1/chat/completions")
+  // followed by ambiguous prose ("Use POST") used to make the unquoted-path
+  // scanner fail closed all the way to the end of the string, deleting a
+  // second, legitimately-shielded route reference ("POST /v1/images/...")
+  // and everything after it instead of just redacting the first span.
+  const { sanitizeErrorMessage } = await import("../../open-sse/utils/error.ts");
+  const input =
+    "Model 'x' is an image-generation model and cannot be used on /v1/chat/completions. Use POST /v1/images/generations instead.";
+  const out = sanitizeErrorMessage(input);
+  assert.match(out, /\/v1\/images\/generations/, "shielded route hint must survive");
+  assert.match(out, /instead\.$/, "text after the shielded route hint must not be dropped");
+  assert.ok(out.includes("<path>"), "the earlier unshielded route span is still redacted");
+});
+
 test("sanitizeErrorMessage handles non-string inputs safely", async () => {
   const { sanitizeErrorMessage } = await import("../../open-sse/utils/error.ts");
   assert.equal(sanitizeErrorMessage(undefined), "");