Share SSE null-delta patch between openai-compatible and opencode adapters

Author: Gustav-Simonsson

src/provider/openai-compatible-adapter.ts

@@ -1,5 +1,6 @@
 import { type BuiltRequest, type ProviderAdapter } from "@intx/inference";
 import { createOpenAIAdapter } from "@intx/inference/providers";
+import { normalizeNullDeltaFields } from "./sse-delta-patch.js";
 
 // The stock OpenAI adapter builds the request body from a fixed set of fields
 // (max_tokens, temperature, tools, messages, response_format) and ignores
@@ -58,37 +59,9 @@ export function createOpenAICompatibleAdapter(
     return ensureAccept(merged);
   };
 
-  // DeepSeek via NVIDIA NIM sends null for delta fields the upstream schema
-  // requires to be non-null (role: string, tool_calls: array). Fields that
-  // legitimately accept null (content, reasoning_content, etc.) are left alone.
-  const NULL_REJECTED_DELTA_FIELDS = new Set(["role", "tool_calls"]);
   const parseResponse: ProviderAdapter["parseResponse"] = (sseData: string) => {
     if (!needsDeepSeekPatch) return base.parseResponse(sseData);
-    let data = sseData;
-    try {
-      const parsed = JSON.parse(sseData) as Record<string, unknown>;
-      const choices = parsed["choices"];
-      if (Array.isArray(choices)) {
-        let patched = false;
-        for (const choice of choices) {
-          if (choice !== null && typeof choice === "object") {
-            const delta = (choice as Record<string, unknown>)["delta"];
-            if (delta !== null && typeof delta === "object") {
-              for (const key of NULL_REJECTED_DELTA_FIELDS) {
-                if ((delta as Record<string, unknown>)[key] === null) {
-                  Reflect.deleteProperty(delta as object, key);
-                  patched = true;
-                }
-              }
-            }
-          }
-        }
-        if (patched) data = JSON.stringify(parsed);
-      }
-    } catch {
-      /* not JSON — pass through */
-    }
-    return base.parseResponse(data);
+    return base.parseResponse(normalizeNullDeltaFields(sseData));
   };
 
   return { ...base, buildRequest, parseResponse };

src/provider/opencode-go-adapter.ts

@@ -1,39 +1,10 @@
 import type { BuiltRequest, ProviderAdapter } from "@intx/inference";
 import { createOpenAICompatibleAdapter } from "./openai-compatible-adapter.js";
 import { OPENCODE_SESSION_ID_OPTION, optionString } from "./responses-adapters.js";
+import { normalizeNullDeltaFields } from "./sse-delta-patch.js";
 
 type AdapterSource = Parameters<typeof createOpenAICompatibleAdapter>[0];
 
-const NULL_DELTA_FIELDS = ["role", "tool_calls"] as const;
-
-function normalizeNullDeltaFields(sseData: string): string {
-  let parsed: unknown;
-  try {
-    parsed = JSON.parse(sseData);
-  } catch {
-    return sseData;
-  }
-  if (parsed === null || typeof parsed !== "object") return sseData;
-
-  const choices = (parsed as Record<string, unknown>)["choices"];
-  if (!Array.isArray(choices)) return sseData;
-
-  let normalized = false;
-  for (const choice of choices) {
-    if (choice === null || typeof choice !== "object") continue;
-    const delta = (choice as Record<string, unknown>)["delta"];
-    if (delta === null || typeof delta !== "object") continue;
-    for (const field of NULL_DELTA_FIELDS) {
-      if ((delta as Record<string, unknown>)[field] === null) {
-        Reflect.deleteProperty(delta, field);
-        normalized = true;
-      }
-    }
-  }
-
-  return normalized ? JSON.stringify(parsed) : sseData;
-}
-
 export function createOpenCodeGoAdapter(source: AdapterSource, quirks?: unknown): ProviderAdapter {
   const base = createOpenAICompatibleAdapter(source, quirks);
   const buildRequest: ProviderAdapter["buildRequest"] = (messages, model, options) => {

src/provider/sse-delta-patch.ts

@@ -0,0 +1,44 @@
+// Chat Completions SSE frames from some backends send `null` for delta fields
+// the upstream schema requires to be non-null (`role: string`, `tool_calls:
+// array`): DeepSeek via NVIDIA NIM and OpenCode Go both do this. Deleting the
+// null fields lets the stock OpenAI adapter parse the frame; fields that
+// legitimately accept null (content, reasoning_content, etc.) are left alone.
+//
+// Shared by the openai-compatible and OpenCode Go adapters so the patch stays
+// in one place.
+
+/** Delta fields that must never be null in a valid Chat Completions frame. */
+export const NULL_REJECTED_DELTA_FIELDS = ["role", "tool_calls"] as const;
+
+/**
+ * Delete null-valued non-nullable delta fields from a Chat Completions SSE
+ * frame. Returns the input unchanged when the payload is not JSON, has no
+ * `choices[].delta` objects, or contains no null fields to remove.
+ */
+export function normalizeNullDeltaFields(sseData: string): string {
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(sseData);
+  } catch {
+    return sseData;
+  }
+  if (parsed === null || typeof parsed !== "object") return sseData;
+
+  const choices = (parsed as Record<string, unknown>)["choices"];
+  if (!Array.isArray(choices)) return sseData;
+
+  let normalized = false;
+  for (const choice of choices) {
+    if (choice === null || typeof choice !== "object") continue;
+    const delta = (choice as Record<string, unknown>)["delta"];
+    if (delta === null || typeof delta !== "object") continue;
+    for (const field of NULL_REJECTED_DELTA_FIELDS) {
+      if ((delta as Record<string, unknown>)[field] === null) {
+        Reflect.deleteProperty(delta, field);
+        normalized = true;
+      }
+    }
+  }
+
+  return normalized ? JSON.stringify(parsed) : sseData;
+}