fix(claude): record why a native passthrough failed in its request-log row

src/server/claude-messages.ts

@@ -15,6 +15,7 @@ import {
 } from "./admission-model-scope";
 import { jsonUtf8Bytes } from "../lib/json-byte-size";
 import { redactSecretString } from "../lib/redact";
+import { formatAnthropicErrorBody } from "../adapters/anthropic";
 import { sseFieldValue } from "../lib/sse-decoder";
 import { enforceAnthropicImageLimits, sniffImageDimensions } from "../adapters/anthropic-image-guard";
 import { normalizeAnthropicImages } from "../adapters/anthropic-image-normalize";
@@ -555,6 +556,15 @@ async function anthropicNativePassthrough(
   logCtx.provider = "anthropic-native";
   logCtx.requestedModel = model;
   const finalize = createFinalRequestLog(logIds, logCtx).finish;
+  // Every local answer carries its reason into the row, as the managed native lane's
+  // finishLog does; without it a failed passthrough row has no upstreamError at all. Like
+  // that lane's fail(), the client and the log both get the redacted message.
+  const fail = (status: number, closeReason: PassthroughCloseReason | "non_stream", message: string, type: string) => {
+    const safeMessage = redactSecretString(message);
+    logCtx.upstreamError = safeMessage.slice(0, 500);
+    finalize(status, { closeReason });
+    return anthropicErrorResponse(status, safeMessage, type);
+  };
 
   const base = (config.claudeCode?.anthropicBaseUrl ?? "https://api.anthropic.com").replace(/\/$/, "");
   const search = new URL(req.url).search;
@@ -581,13 +591,11 @@ async function anthropicNativePassthrough(
     req.signal,
   );
   if (result.kind === "timeout") {
-    finalize(504, { closeReason: "non_stream" });
-    return anthropicErrorResponse(504, "anthropic passthrough timed out waiting for response headers", "timeout_error");
+    return fail(504, "non_stream", "anthropic passthrough timed out waiting for response headers", "timeout_error");
   }
   if (result.kind === "error") {
     const err = result.error;
-    finalize(502, { closeReason: "non_stream" });
-    return anthropicErrorResponse(502, `anthropic passthrough failed: ${err instanceof Error ? err.message : String(err)}`, "api_error");
+    return fail(502, "non_stream", `anthropic passthrough failed: ${err instanceof Error ? err.message : String(err)}`, "api_error");
   }
   const upstream = result.upstream;
 
@@ -607,23 +615,30 @@ async function anthropicNativePassthrough(
   // idle/size bounds — headers are NOT yet sent here, so real statuses are available.
   const bodyResult = await readBoundedPassthroughBody(upstream, bodyGuard);
   if (bodyResult.kind === "client_cancel") {
-    finalize(499, { closeReason: "client_cancel" });
-    return anthropicErrorResponse(499, "client closed request during anthropic passthrough", "api_error");
+    return fail(499, "client_cancel", "client closed request during anthropic passthrough", "api_error");
   }
   if (bodyResult.kind === "stall") {
-    finalize(504, { closeReason: "body_stall" });
-    return anthropicErrorResponse(504, `anthropic passthrough body stalled: no upstream bytes for ${Math.round(bodyGuard.stallMs / 1000)}s`, "timeout_error");
+    return fail(504, "body_stall", `anthropic passthrough body stalled: no upstream bytes for ${Math.round(bodyGuard.stallMs / 1000)}s`, "timeout_error");
   }
   if (bodyResult.kind === "overflow") {
-    finalize(502, { closeReason: "body_overflow" });
-    return anthropicErrorResponse(502, `anthropic passthrough body exceeded ${bodyGuard.maxBytes} bytes`, "api_error");
+    return fail(502, "body_overflow", `anthropic passthrough body exceeded ${bodyGuard.maxBytes} bytes`, "api_error");
   }
   const text = bodyResult.text;
   if (upstream.ok) {
     try {
       const parsed = JSON.parse(text) as { usage?: Rec };
       if (isRec(parsed?.usage)) logCtx.usage = anthropicUsageToOcx(parsed.usage);
     } catch { /* count_tokens etc. */ }
+  } else if (upstream.status >= 400) {
+    // The body is relayed verbatim; the row gets a "Provider error" reason from the same
+    // redacting formatAnthropicErrorBody the managed lane falls back to. Only a body of at
+    // most 64 Ki characters (the order of that lane's 64 KiB error read bound) is parsed for
+    // it: the body cap here is far larger, and JSON.parse plus redaction over a huge body
+    // would block the event loop. Characters, not bytes, are what that cost scales with.
+    const detail = text.length <= PASSTHROUGH_ERROR_DETAIL_MAX_CHARS
+      ? formatAnthropicErrorBody(upstream.status, upstream.headers, text)
+      : "";
+    logCtx.upstreamError = detail ? `Provider error ${upstream.status}: ${detail}` : `Provider error ${upstream.status}`;
   }
   finalize(upstream.status, { closeReason: "non_stream" });
   const retryAfter = upstream.headers.get("retry-after");
@@ -633,6 +648,7 @@ async function anthropicNativePassthrough(
   });
 }
 
+const PASSTHROUGH_ERROR_DETAIL_MAX_CHARS = 64 * 1024;
 const DEFAULT_BODY_STALL_SEC = 90;
 const DEFAULT_BODY_MAX_BYTES = 64 * 1024 * 1024;
 

structure/clients/claude-desktop.md

@@ -466,4 +466,6 @@ Native Anthropic passthrough in `src/server/claude-messages.ts` forwards the cal
 
 `tapAnthropicSseForLog` in `src/server/claude-messages.ts` relays the streamed body of both the native passthrough and the managed native Messages lane (`src/server/messages-native.ts`). The response headers are already sent, so a stall, a byte-cap overflow, or an upstream read failure ends the body with an Anthropic `event: error` frame after a blank-line boundary and a clean close: `timeout_error` for an idle stall, `api_error` for the byte cap, and `api_error` when an upstream read fails mid-stream (a socket reset). The mid-stream reset is logged like the Responses relay's read error: status 502, `terminalStatus: "failed"`, `closeReason: "terminal"`, `transportPhase: "mid_stream"`, a synthetic terminal source, the attempt marked `streamAborted`, the redacted reason in `upstreamError`, and the usage seen before the reset. The non-streaming fold in the managed lane closes its row with the tap's meta for a reset, a stall or the byte cap, so its row matches the streaming lane's. The request is not replayed. The logged status is not uniform across these frames: a stall and the byte cap keep status 200 with `closeReason` `body_stall` or `body_overflow`, which classify as `incomplete`, while a reset is a 502 that classifies as `failed`. Some read failures are not upstream failures. When the cancel signal is already aborted, the rejection is a `499` client cancel, because Bun can reject the read before it dispatches the abort listener. The managed lane passes its upstream controller's signal, so shutdown and turn release count as cancels too. When `message_stop` or an upstream `error` event has been seen, including one still in the buffer without its blank-line delimiter, the turn is complete: it logs 200 and closes with no error frame. A terminal found only in that unterminated tail gets its blank line restored, because an SSE parser drops an event that EOF cuts off. A translator budget overflow is a local cap, so it still errors the stream, and the non-streaming fold answers it with 413. `tests/claude-integration/claude-native-passthrough.test.ts` and `tests/claude-integration/messages-native.test.ts` cover both lanes against an upstream that resets after a partial or a complete body, plus both cancel paths.
 
+A native passthrough answered without a stream records its reason in `upstreamError` as well, so the row and the failure diagnostics in usage.jsonl name the cause. An upstream error response (status 400 or above) is relayed verbatim and logged as `Provider error <status>: <type>: <message>`, built by the same redacting, bounded `formatAnthropicErrorBody` in `src/adapters/anthropic.ts` that the managed lane falls back to. A body without an Anthropic error, or one over 64 Ki characters (the order of the managed lane's 64 KiB error read bound), logs `Provider error <status>`. A header timeout, fetch failure, body stall, byte-cap overflow or client cancel logs the message the client receives; both are redacted, as in the managed lane. With a reason present, `requestLogErrorCode` classifies the row the way it does for the other lanes; for example, an authentication-shaped 403 becomes `invalid_api_key` instead of `permission_denied`. `tests/claude-integration/claude-native-passthrough.test.ts` covers each case.
+
 Linked-machine data uses the [connection-bound relay contract](../remote-link.md#connection-bound-relay-authentication); client-local credentials and routing policy remain unchanged.