fix(adapter): send x-opencode-* identity headers so zen stops returning empty tool-call replies

zen fingerprints clients via UA + x-opencode-client/session/request/project
headers; requests without them are routed as anonymous and fail with a
single-chunk network_error stream (tools+stream) or 503 Endpoint is
unavailable (non-stream), which the adapter laundered into empty-but-valid
replies. Derive per-request session/request ids from build_headers meta
(sandbox has no os/math), bump UA to the real client format, map zen
reasoning field to reasoning_content, and set stream_options.include_usage.

internal/lua/adapters/opencode.lua

@@ -4,14 +4,34 @@ adapter.name = "opencode"
 adapter.version = "1.0.0"
 adapter.endpoint = "/chat/completions"
 
--- opencode.ai zen 网关按 User-Agent 指纹识别官方客户端并把请求分到免费额度池；
--- 非官方 UA（curl/Go 默认等）会被分到匿名池并触发 FreeUsageLimitError。
--- 因此固定发送 opencode 客户端的 UA；配合源配置 api_key: "public"（官方无 key
--- 客户端实际发送 Bearer public）即可走免费池。
+-- opencode.ai zen 网关按客户端指纹（UA + x-opencode-* 头）路由请求池：
+-- 缺少 x-opencode-client/session/request/project 身份头的请求会被判为匿名
+-- 客户端，x-preview-f-free 等模型在带 tools 时上游直接失败——流式返回单
+-- chunk "finish_reason":"network_error" 空 content，非流式返回 503
+-- "Endpoint is unavailable"，表现为"空回复"。因此除 UA 外必须附带
+-- x-opencode-* 身份头；session/request 每请求派生唯一值（见 build_headers）。
 adapter.headers = {
-    ["User-Agent"] = "opencode/0.1.0",
+    ["User-Agent"] = "opencode/1.18.21 ai-sdk/provider-utils/4.0.23 runtime/bun/1.3.14",
 }
 
+-- 每请求生成身份头。沙箱无 os/math，用 meta.timestamp + 请求体哈希派生：
+-- 同秒内重复请求 id 相同可接受（zen 只校验存在性，不校验格式）。
+local function rand_id(prefix, seed)
+    return prefix .. string.sub(sha256_hex(seed), 1, 24)
+end
+
+function adapter.build_headers(meta)
+    local ts = tostring(meta.timestamp or "")
+    return {
+        ["User-Agent"] = adapter.headers["User-Agent"],
+        ["x-opencode-client"] = "cli",
+        -- project 固定：同网关实例共享一个工作区身份
+        ["x-opencode-project"] = string.sub(sha256_hex("llmsproxy|" .. (meta.source and meta.source.name or "")), 1, 32),
+        ["x-opencode-session"] = rand_id("ses_", "session|" .. ts),
+        ["x-opencode-request"] = rand_id("msg_", "request|" .. ts .. "|" .. tostring(meta.body or "")),
+    }
+end
+
 -- OpenAI /chat/completions format (pass-through, strip provider-specific fields)
 -- zen 上游 schema 只接受 text content part（无视觉/音频能力）：多模态 part
 -- （image_url / input_audio / file 等）一律剥离；因此失去全部 content 的
@@ -32,6 +52,8 @@ function adapter.transform_request(raw_body)
     if not ok then return raw_body end
     req.disable_thinking = nil
     req.extra_body = nil
+    if type(req.stream_options) ~= "table" then req.stream_options = {} end
+    req.stream_options.include_usage = true
     if req.messages then
         local kept = {}
         for _, msg in ipairs(req.messages) do
@@ -84,8 +106,9 @@ function adapter.transform_response(raw_body)
         local ch = resp.choices[1]
         if type(ch.message) == "table" then
             unified.content = ch.message.content or ""
-            if ch.message.reasoning_content then
-                unified.reasoning_content = ch.message.reasoning_content
+            local reasoning = ch.message.reasoning_content or ch.message.reasoning
+            if reasoning then
+                unified.reasoning_content = reasoning
             end
             if type(ch.message.tool_calls) == "table" then
                 local tcs = {}
@@ -143,8 +166,10 @@ function adapter.transform_stream_chunk(raw_chunk)
     if uses ~= nil then
         unified.usage = uses
     end
-    if delta.reasoning_content then
-        unified.reasoning_content = delta.reasoning_content
+    -- zen 用 reasoning 字段承载推理文本（OpenAI 惯例是 reasoning_content）
+    local reasoning = delta.reasoning_content or delta.reasoning
+    if reasoning then
+        unified.reasoning_content = reasoning
     end
     if delta.tool_calls then
         -- pass raw streaming fragments through; OpenAI clients accumulate index+id+name+arguments

internal/lua/vm_test.go

@@ -115,12 +115,31 @@ func TestOpenCodeAdapterFingerprint(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer vm.Stop()
-	hdrs, err := vm.BuildHeaders("opencode", map[string]interface{}{"api_key": "public"})
+	hdrs, err := vm.BuildHeaders("opencode", map[string]interface{}{
+		"api_key":   "public",
+		"timestamp": 1700000000,
+		"body":      `{"model":"x"}`,
+		"url":       "https://opencode.ai/zen/v1/chat/completions",
+		"method":    "POST",
+	})
 	if err != nil {
 		t.Fatalf("build headers: %v", err)
 	}
-	if ua := hdrs["User-Agent"]; ua != "opencode/0.1.0" {
-		t.Fatalf("opencode adapter must send the opencode client UA, got %q", ua)
+	// zen 按客户端指纹路由请求池：UA 必须是 opencode 真实格式，
+	// 且必须携带 x-opencode-* 身份头，否则带 tools 的请求会被上游
+	// 判为匿名客户端并返回 network_error 空流（表现为空回复）。
+	if ua := hdrs["User-Agent"]; !strings.HasPrefix(ua, "opencode/") ||
+		!strings.Contains(ua, "ai-sdk/provider-utils/") {
+		t.Fatalf("opencode adapter must send the real opencode client UA, got %q", ua)
+	}
+	for _, h := range []string{"x-opencode-client", "x-opencode-project", "x-opencode-session", "x-opencode-request"} {
+		if hdrs[h] == "" {
+			t.Fatalf("opencode adapter must send %q (zen client fingerprint), got %v", h, hdrs)
+		}
+	}
+	hdrs2, _ := vm.BuildHeaders("opencode", map[string]interface{}{"api_key": "public", "timestamp": 1700000001, "body": `{"model":"y"}`, "method": "POST"})
+	if hdrs["x-opencode-request"] == hdrs2["x-opencode-request"] {
+		t.Fatalf("x-opencode-request must vary per request, got %q twice", hdrs["x-opencode-request"])
 	}
 	if hdrs["Authorization"] != "" {
 		t.Fatalf("opencode adapter must not hardcode Authorization (config api_key supplies it), got %q", hdrs["Authorization"])