feat(opencode-go): add muse-spark-1.3-contributor and fix parallel tool calls on Responses paths (#3819)

- Add muse-spark-1.3-contributor as responses-only model on OpenCode Go with dedicated executor
- Key Responses→chat streaming tool calls by item_id to prevent parallel tool calls merging into index 0
- Standardize tool coercions and call_id clamping in Responses API translation

open-sse/translator/formats/responsesApi.js

@@ -23,6 +23,46 @@ export function normalizeResponsesInput(input) {
   return null;
 }
 
+// Strict Responses upstreams reject overlong call_ids with InputValidationError (#393).
+export const MAX_RESPONSES_CALL_ID_LEN = 64;
+
+export function clampResponsesCallId(id) {
+  if (typeof id !== "string" || !id) return `call_${Date.now()}`;
+  return id.length > MAX_RESPONSES_CALL_ID_LEN ? id.substring(0, MAX_RESPONSES_CALL_ID_LEN) : id;
+}
+
+// Single-stringify: objects → JSON once; valid JSON strings pass through untouched;
+// anything else (partial fragments, empty) falls back to "{}" instead of
+// double-encoding and tripping upstream InputValidationError.
+export function coerceResponsesArguments(value) {
+  if (value === undefined || value === null || value === "") return "{}";
+  if (typeof value !== "string") {
+    try {
+      return JSON.stringify(value);
+    } catch {
+      return "{}";
+    }
+  }
+  try {
+    JSON.parse(value);
+    return value;
+  } catch {
+    return "{}";
+  }
+}
+
+// function_call_output.output must be a string — never null/object.
+export function coerceResponsesOutput(value) {
+  if (typeof value === "string") return value;
+  if (value === undefined || value === null) return "";
+  if (Array.isArray(value)) return value.map((c) => c?.text ?? JSON.stringify(c)).join("");
+  try {
+    return JSON.stringify(value);
+  } catch {
+    return String(value);
+  }
+}
+
 /**
  * Convert OpenAI Responses API format to standard chat completions format
  * Responses API uses: { input: [...], instructions: "..." }

open-sse/translator/request/openai-responses.js

@@ -6,12 +6,15 @@
  */
 import { register } from "../index.js";
 import { FORMATS } from "../formats.js";
-import { normalizeResponsesInput } from "../formats/responsesApi.js";
+import {
+  normalizeResponsesInput,
+  clampResponsesCallId,
+  coerceResponsesArguments,
+  coerceResponsesOutput,
+} from "../formats/responsesApi.js";
 import { ROLE, OPENAI_BLOCK, RESPONSES_ITEM } from "../schema/index.js";
 
-// Responses API enforces max 64 chars on call_id (#393)
-const MAX_CALL_ID_LEN = 64;
-const clampCallId = (id) => (typeof id === "string" && id.length > MAX_CALL_ID_LEN ? id.substring(0, MAX_CALL_ID_LEN) : id);
+const MAX_TOOL_NAME_LEN = 128;
 
 /**
  * Convert OpenAI Responses API request to OpenAI Chat Completions format
@@ -249,6 +252,23 @@ export function openaiResponsesToOpenAIRequest(model, body, stream, credentials)
   return result;
 }
 
+/**
+ * Extract plain text from a system/developer message for Responses instructions.
+ * Array content (text parts) is joined; anything else falls back to "" rather
+ * than leaking "[object Object]" upstream.
+ */
+function extractInstructionsText(content) {
+  if (typeof content === "string") return content;
+  if (Array.isArray(content)) {
+    return content.map((c) => {
+      if (typeof c?.text === "string") return c.text;
+      if (typeof c?.content === "string") return c.content;
+      return "";
+    }).filter(Boolean).join("\n");
+  }
+  return "";
+}
+
 /**
  * Ensure object schema always has properties field (required by Codex Responses API)
  */
@@ -327,7 +347,7 @@ export function openaiToOpenAIResponsesRequest(model, body, stream, credentials)
       // Use the first instruction-bearing message as instructions.
       // OpenAI recommends role="developer" for GPT-5/Codex as the system-level prompt.
       if (!hasSystemMessage) {
-        result.instructions = typeof msg.content === "string" ? msg.content : "";
+        result.instructions = extractInstructionsText(msg.content);
         hasSystemMessage = true;
       }
       continue; // Skip instruction messages in input
@@ -378,26 +398,24 @@ export function openaiToOpenAIResponsesRequest(model, body, stream, credentials)
     // Convert tool calls
     if (msg.role === ROLE.ASSISTANT && msg.tool_calls) {
       for (const tc of msg.tool_calls) {
+        // Skip nameless calls — strict Responses upstreams reject them (#444)
+        const name = typeof tc.function?.name === "string" ? tc.function.name.trim() : "";
+        if (!name) continue;
         result.input.push({
           type: RESPONSES_ITEM.FUNCTION_CALL,
-          call_id: clampCallId(tc.id),
-          name: tc.function?.name || "_unknown",
-          arguments: tc.function?.arguments || "{}"
+          call_id: clampResponsesCallId(tc.id),
+          name: name.slice(0, MAX_TOOL_NAME_LEN),
+          arguments: coerceResponsesArguments(tc.function?.arguments)
         });
       }
     }
 
     // Convert tool results - output must be a string for Responses API
     if (msg.role === ROLE.TOOL) {
-      const output = typeof msg.content === "string"
-        ? msg.content
-        : Array.isArray(msg.content)
-          ? msg.content.map(c => c.text || JSON.stringify(c)).join("")
-          : JSON.stringify(msg.content);
       result.input.push({
         type: RESPONSES_ITEM.FUNCTION_CALL_OUTPUT,
-        call_id: clampCallId(msg.tool_call_id),
-        output
+        call_id: clampResponsesCallId(msg.tool_call_id),
+        output: coerceResponsesOutput(msg.content)
       });
     }
   }
@@ -411,16 +429,19 @@ export function openaiToOpenAIResponsesRequest(model, body, stream, credentials)
   if (body.tools && Array.isArray(body.tools)) {
     result.tools = body.tools.map(tool => {
       if (tool.type === OPENAI_BLOCK.FUNCTION) {
+        // Strict upstreams reject nameless/overlong tool declarations
+        const name = typeof tool.function?.name === "string" ? tool.function.name.trim() : "";
+        if (!name) return null;
         return {
           type: OPENAI_BLOCK.FUNCTION,
-          name: tool.function.name,
+          name: name.slice(0, MAX_TOOL_NAME_LEN),
           description: String(tool.function.description || ""),
           parameters: normalizeToolParameters(tool.function.parameters),
           strict: tool.function.strict
         };
       }
       return tool;
-    });
+    }).filter(Boolean);
   }
 
   // Pass through other relevant fields

open-sse/translator/response/openai-responses.js

@@ -446,6 +446,13 @@ export function openaiResponsesToOpenAIResponse(chunk, state) {
     state.created = Math.floor(Date.now() / 1000);
     state.toolCallIndex = 0;
     state.currentToolCallId = null;
+    // item_id → chat tool_calls index. Deltas carry item_id; keying on it (not
+    // stream position) keeps parallel calls separate when upstream emits all
+    // output_item.added events before any done/delta. Lazily created so callers
+    // that build their own state object (stream.js) need no changes.
+    state.respToolChatIndex ??= new Map();
+    // Indices that already received argument deltas (guards done-with-args).
+    state.respToolArgsEmitted ??= new Set();
   }
 
   // Text content delta
@@ -464,16 +471,29 @@ export function openaiResponsesToOpenAIResponse(chunk, state) {
     return null;
   }
 
-  // Function call started (standard function_call or custom_tool_call)
+  // Function call started (standard function_call or custom_tool_call).
+  // Index is assigned here (not on done): attributing deltas by stream position
+  // merges parallel calls into index 0 whenever upstream emits all addeds
+  // before dones — the client then concatenates N JSON payloads into one
+  // tool input and fails validation. The server item id is the correlator.
   if (eventType === "response.output_item.added" && (data.item?.type === RESPONSES_ITEM.FUNCTION_CALL || data.item?.type === "custom_tool_call")) {
     const item = data.item;
     state.currentToolCallId = item.call_id || fallbackToolCallId();
+    state.respToolChatIndex ??= new Map();
+    const key = item.id || data.item_id || state.currentToolCallId;
+    let idx;
+    if (key && state.respToolChatIndex.has(key)) {
+      idx = state.respToolChatIndex.get(key); // duplicate added (retry) — reuse
+    } else {
+      idx = state.toolCallIndex++;
+      if (key) state.respToolChatIndex.set(key, idx);
+    }
 
     return buildChunk(
       { id: state.chatId, created: state.created, model: state.model || MODEL_FALLBACK },
       {
         tool_calls: [{
-          index: state.toolCallIndex,
+          index: idx,
           id: state.currentToolCallId,
           type: OPENAI_BLOCK.FUNCTION,
           function: { name: item.name || "", arguments: "" }
@@ -482,20 +502,39 @@ export function openaiResponsesToOpenAIResponse(chunk, state) {
     );
   }
 
-  // Function call arguments delta (standard or custom_tool_call variant)
+  // Function call arguments delta (standard or custom_tool_call variant).
+  // Routed by item_id so interleaved parallel fragments stay on their own call.
   if (eventType === "response.function_call_arguments.delta" || eventType === "response.custom_tool_call_input.delta") {
     const argsDelta = data.delta || "";
     if (!argsDelta) return null;
 
+    const known = data.item_id ? state.respToolChatIndex?.get(data.item_id) : undefined;
+    const idx = known ?? Math.max(0, (state.toolCallIndex || 1) - 1);
+    state.respToolArgsEmitted ??= new Set();
+    state.respToolArgsEmitted.add(idx);
     return buildChunk(
       { id: state.chatId, created: state.created, model: state.model || MODEL_FALLBACK },
-      { tool_calls: [{ index: state.toolCallIndex, function: { arguments: argsDelta } }] }
+      { tool_calls: [{ index: idx, function: { arguments: argsDelta } }] }
     );
   }
 
-  // Function call done (standard or custom_tool_call variant)
+  // Function call done (standard or custom_tool_call variant).
+  // Index was assigned at added-time; nothing to advance. Some upstreams send
+  // complete arguments only here (no deltas) — emit them once in that case.
   if (eventType === "response.output_item.done" && (data.item?.type === RESPONSES_ITEM.FUNCTION_CALL || data.item?.type === "custom_tool_call")) {
-    state.toolCallIndex++;
+    const key = data.item?.id || data.item_id;
+    const idx = (key && state.respToolChatIndex?.get(key)) ?? Math.max(0, (state.toolCallIndex || 1) - 1);
+    const fullArgs = data.item?.arguments;
+    if (typeof fullArgs === "string" && fullArgs) {
+      state.respToolArgsEmitted ??= new Set();
+      if (!state.respToolArgsEmitted.has(idx)) {
+        state.respToolArgsEmitted.add(idx);
+        return buildChunk(
+          { id: state.chatId, created: state.created, model: state.model || MODEL_FALLBACK },
+          { tool_calls: [{ index: idx, function: { arguments: fullArgs } }] }
+        );
+      }
+    }
     return null;
   }