fix(error-classifier): widen STREAM_RE to cover all 7 V8 JSON parse error variants (#2916) (#3243)

Stream-truncation JSON parse errors like "Expected ',' or '}' after
property value in JSON" were falling through to kind: "unknown", causing
permanent auto-mode pause instead of transient 15s backoff.

- Broaden STREAM_RE: replace narrow "Expected double-quoted property name"
  with "Expected.*in JSON" and add "Unterminated.*in JSON" to catch all 7
  V8 JSON parse error message variants
- Move stream check before server/connection checks to prevent false
  matches (e.g. "position 500" matching SERVER_RE, "Unterminated" matching
  CONNECTION_RE's "terminated" pattern)
- Add 4 test cases for the previously uncovered V8 error variants

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/resources/extensions/gsd/error-classifier.ts

@@ -48,7 +48,7 @@ const NETWORK_RE = /network|ECONNRESET|ETIMEDOUT|ECONNREFUSED|socket hang up|fet
 const SERVER_RE = /internal server error|500|502|503|overloaded|server_error|api_error|service.?unavailable/i;
 // ECONNRESET/ECONNREFUSED are in NETWORK_RE (same-model retry first).
 const CONNECTION_RE = /terminated|connection.?refused|other side closed|EPIPE|network.?(?:is\s+)?unavailable|stream_exhausted(?:_without_result)?/i;
-const STREAM_RE = /Unexpected end of JSON|Unexpected token.*JSON|Expected double-quoted property name|SyntaxError.*JSON/i;
+const STREAM_RE = /Unexpected end of JSON|Unexpected token.*JSON|Expected.*in JSON|Unterminated.*in JSON|SyntaxError.*JSON/i;
 const RESET_DELAY_RE = /reset in (\d+)s/i;
 
 /**
@@ -58,9 +58,9 @@ const RESET_DELAY_RE = /reset in (\d+)s/i;
  *  1. Permanent (auth/billing/quota) — unless also rate-limited
  *  2. Rate limit (429, rate.?limit, too many requests)
  *  3. Network (ECONNRESET, ETIMEDOUT, socket hang up, fetch failed, dns)
- *  4. Server (500/502/503, overloaded, server_error)
- *  5. Connection (terminated, ECONNREFUSED, EPIPE, other side closed)
- *  6. Stream truncation (malformed JSON from mid-stream cut)
+ *  4. Stream truncation (malformed JSON from mid-stream cut)
+ *  5. Server (500/502/503, overloaded, server_error)
+ *  6. Connection (terminated, ECONNREFUSED, EPIPE, other side closed)
  *  7. Unknown
  */
 export function classifyError(errorMsg: string, retryAfterMs?: number): ErrorClass {
@@ -90,21 +90,24 @@ export function classifyError(errorMsg: string, retryAfterMs?: number): ErrorCla
     return { kind: "network", retryAfterMs: retryAfterMs ?? 3_000 };
   }
 
-  // 4. Server errors — try fallback model
+  // 4. Stream truncation — downstream symptom of connection drop
+  //    Checked before server/connection because JSON parse errors can contain
+  //    substrings like "position 500" (matches SERVER_RE) or "Unterminated"
+  //    (matches CONNECTION_RE's "terminated" pattern).
+  if (STREAM_RE.test(errorMsg)) {
+    return { kind: "stream", retryAfterMs: retryAfterMs ?? 15_000 };
+  }
+
+  // 5. Server errors — try fallback model
   if (SERVER_RE.test(errorMsg)) {
     return { kind: "server", retryAfterMs: retryAfterMs ?? 30_000 };
   }
 
-  // 5. Connection errors — try fallback model
+  // 6. Connection errors — try fallback model
   if (CONNECTION_RE.test(errorMsg)) {
     return { kind: "connection", retryAfterMs: retryAfterMs ?? 15_000 };
   }
 
-  // 6. Stream truncation — downstream symptom of connection drop
-  if (STREAM_RE.test(errorMsg)) {
-    return { kind: "stream", retryAfterMs: retryAfterMs ?? 15_000 };
-  }
-
   // 7. Unknown
   return { kind: "unknown" };
 }

src/resources/extensions/gsd/tests/provider-errors.test.ts

@@ -118,6 +118,44 @@ test("classifyError: rate limit takes precedence over auth keywords", () => {
   assert.ok(isTransient(result));
 });
 
+// ── STREAM_RE: V8 JSON parse error variants (#2916) ────────────────────────
+
+test("classifyError: 'Expected comma/brace after property value in JSON' is transient stream", () => {
+  const result = classifyError(
+    "Expected ',' or '}' after property value in JSON at position 2056 (line 1 column 2057)"
+  );
+  assert.equal(result.kind, "stream");
+  assert.ok(isTransient(result));
+  assert.ok("retryAfterMs" in result && result.retryAfterMs === 15_000);
+});
+
+test("classifyError: 'Expected colon after property name in JSON' is transient stream", () => {
+  const result = classifyError(
+    "Expected ':' after property name in JSON at position 500 (line 1 column 501)"
+  );
+  assert.equal(result.kind, "stream");
+  assert.ok(isTransient(result));
+  assert.ok("retryAfterMs" in result && result.retryAfterMs === 15_000);
+});
+
+test("classifyError: 'Expected property name or brace in JSON' is transient stream", () => {
+  const result = classifyError(
+    "Expected property name or '}' in JSON at position 42 (line 1 column 43)"
+  );
+  assert.equal(result.kind, "stream");
+  assert.ok(isTransient(result));
+  assert.ok("retryAfterMs" in result && result.retryAfterMs === 15_000);
+});
+
+test("classifyError: 'Unterminated string in JSON' is transient stream", () => {
+  const result = classifyError(
+    "Unterminated string in JSON at position 100 (line 1 column 101)"
+  );
+  assert.equal(result.kind, "stream");
+  assert.ok(isTransient(result));
+  assert.ok("retryAfterMs" in result && result.retryAfterMs === 15_000);
+});
+
 // ── isTransientNetworkError ──────────────────────────────────────────────────
 
 test("isTransientNetworkError detects ECONNRESET", () => {