diff --git a/lib/structured-output.mjs b/lib/structured-output.mjs
index a444bd9..238e7fb 100644
--- a/lib/structured-output.mjs
+++ b/lib/structured-output.mjs
@@ -221,7 +221,12 @@ export function validateJsonSchemaSafe(value, schema, path = "$", strict = false
   try {
     return validateJsonSchema(value, schema, path, strict, root);
   } catch (e) {
-    return [`${path}: schema validation aborted (${e instanceof RangeError ? "value nesting too deep" : "internal error"})`];
+    // Catch ONLY the deep-nesting stack overflow (the #181 vector) and turn it into a validation
+    // miss → retry → refusal, never a 500. Any OTHER throw is a genuine bug: re-throw it so it
+    // surfaces at error level instead of being silently masked as "did not validate" (reviewer
+    // finding — a catch-all would hide a future TypeError behind a warn-level structured_retry).
+    if (e instanceof RangeError) return [`${path}: schema validation aborted (value nesting too deep)`];
+    throw e;
   }
 }
 
diff --git a/server.mjs b/server.mjs
index 71c8995..7da098d 100644
--- a/server.mjs
+++ b/server.mjs
@@ -42,7 +42,7 @@ import { dirname, join } from "node:path";
 import { homedir } from "node:os";
 import { validateKey, recordUsage, getUsageByKey, getUsageTimeline, getRecentUsage, createKey, listKeys, revokeKey, closeDb, checkQuota, updateKeyQuota, getKeyQuota, findKey, cacheHash, getCachedResponse, setCachedResponse, clearCache, getCacheStats, hasCacheControl, singleflight, getInflightStats } from "./keys.mjs";
 import { DEFAULT_PORT } from "./lib/constants.mjs";
-import { StructuredOutputError, detectStructuredOutput, validateJsonSchema, validateJsonSchemaSafe, extractJsonPayload, structuredSystemInstruction, resolveMaxAttempts } from "./lib/structured-output.mjs";
+import { StructuredOutputError, detectStructuredOutput, validateJsonSchemaSafe, extractJsonPayload, structuredSystemInstruction, resolveMaxAttempts } from "./lib/structured-output.mjs";
 import { isLoopbackBind } from "./lib/net.mjs";
 import { runTuiTurn, reapStaleTuiSessions, resolveTuiHome, bootTuiPane, tuiPaneHealthy, poolPaneName, POOL_BOOT_MS } from "./lib/tui/session.mjs";
 import { detectTuiUpstreamError } from "./lib/tui/transcript.mjs";
diff --git a/test-features.mjs b/test-features.mjs
index f847512..3042157 100644
--- a/test-features.mjs
+++ b/test-features.mjs
@@ -4405,6 +4405,12 @@ test("validateJsonSchemaSafe: well-formed value passes through unchanged (byte-i
   assert.deepEqual(validateJsonSchemaSafe({ name: "a" }, schema), validateJsonSchema({ name: "a" }, schema)); // error case matches too
 });
 
+test("validateJsonSchemaSafe: re-throws a non-RangeError so genuine bugs aren't masked as a validation miss", () => {
+  // A schema whose `required` is a non-iterable makes the inner validator throw a TypeError — that's
+  // a real bug, not a deep-value overflow, and must surface (not be swallowed as "did not validate").
+  assert.throws(() => validateJsonSchemaSafe({ x: 1 }, { type: "object", required: 42 }), (e) => !(e instanceof RangeError));
+});
+
 test("validateJsonSchema: valid object passes", () => {
   assert.deepEqual(validateJsonSchema({ name: "a", age: 3 }, { type: "object", required: ["name", "age"], properties: { name: { type: "string" }, age: { type: "integer" } } }), []);
 });