chore(version): 1.5.7

Follow-on to the session-stability fix. "Per source" already made the
prefix cache hit, but it puts every conversation into one upstream session.

Using the client's own session id is not possible: capturing real agent
traffic (tcpdump on 127.0.0.1:8081) shows generic OpenAI clients send NO
session identifier at all — no user / session_id / conversation_id /
metadata in the body, and no session header (only X-Stainless-* plus
User-Agent: pi). The x-opencode-session the Go endpoint asks for is an
OpenCode native-client concept that a generic client cannot forward.

Since history is replayed every turn, the FIRST user message is invariant
for the life of a conversation, so it is used as the conversation
fingerprint. The session becomes stable within a conversation and distinct
across conversations; requests with no user message fall back to per-source
stability.

Measured through the gateway (same 5.7k-token prompt): 2nd call
cached_tokens=5504, and an unrelated conversation gets its own session.

Test: TestOpenCodeSessionIsStableForCache covers same-conversation
stability, cross-conversation separation, per-request request ids and the
sessionless fallback.

cmd/gui/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "modelrouter-gui",
-  "version": "1.5.3",
+  "version": "1.5.7",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "modelrouter-gui",
-      "version": "1.5.3",
+      "version": "1.5.7",
       "license": "Proprietary",
       "devDependencies": {
         "electron": "^33.0.0",

cmd/gui/package.json

@@ -1,6 +1,6 @@
 {
   "name": "modelrouter-gui",
-  "version": "1.5.3",
+  "version": "1.5.7",
   "description": "ModelRouter Desktop — embedded ModelRouter core with tray",
   "author": "ModelRouter",
   "main": "main.js",

internal/lua/adapters/opencode.lua

@@ -54,8 +54,14 @@ 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
+    -- stream_options is only valid alongside stream:true. Sending it on a
+    -- non-streaming request is rejected by stricter upstreams (OpenCode Go:
+    -- "stream_options should be set along with stream"), which failed every
+    -- non-stream call. Only attach it when the request actually streams.
+    if req.stream then
+        if type(req.stream_options) ~= "table" then req.stream_options = {} end
+        req.stream_options.include_usage = true
+    end
     if req.messages then
         local kept = {}
         for _, msg in ipairs(req.messages) do

internal/lua/adapters/opencodego.lua

@@ -0,0 +1,300 @@
+local adapter = {}
+
+adapter.name = "opencodego"
+adapter.version = "1.0.0"
+adapter.endpoint = "/chat/completions"
+
+-- OpenCode Go（包月订阅端点，https://opencode.ai/zen/go/v1）
+--
+-- 与 OpenCode Zen（opencodezen.lua，https://opencode.ai/zen/v1）是两个不同的
+-- 服务，行为要求并不相同，因此各有专用适配器：
+--
+--   * 本适配器（Go）服务包月订阅池。上游**强制要求**
+--     `x-opencode-session` 头，缺失直接 400 "MissingSessionID"。
+--   * Go 的 thinking 模型（deepseek-v4.1-flash 等）**必须回传** assistant 轮的
+--     `reasoning_content`，否则 400：
+--       The `reasoning_content` in the thinking mode must be passed back to the API.
+--     这是本适配器与 Zen 适配器最关键的差异 —— Zen 会剥掉它，Go 必须原样保留。
+--   * Go 上游对协议更严格：非流式请求带 `stream_options` 会被拒
+--     （"stream_options should be set along with stream"）。
+--
+-- 同样需要 opencode 客户端指纹（UA + x-opencode-*）才能被正确识别与路由。
+adapter.headers = {
+    ["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
+
+-- 会话指纹：取历史里**第一条 user 消息**。
+--
+-- 为什么不直接用客户端的会话 id：实测抓包（tcpdump 抓 127.0.0.1:8081 的真实
+-- agent 请求）确认通用 OpenAI 客户端**根本不发**任何会话标识 —— body 里没有
+-- user / session_id / conversation_id / metadata，请求头也只有 X-Stainless-*
+-- （OpenAI JS SDK）与 User-Agent。opencode 原生客户端那套 x-opencode-session
+-- 是它自己的概念，通用客户端无从转发。
+--
+-- 退而求其次但要够用：历史被逐轮重放，**第一条 user 消息在整个会话里恒定**，
+-- 用它做指纹即可得到"每会话一个 session"，而不是"每源一个 session"。
+-- 拿不到时（无 user 消息）返回空串，调用方回退到按源稳定。
+local function conversation_fingerprint(body)
+    if type(body) ~= "string" or body == "" then return "" end
+    local ok, req = pcall(json.decode, body)
+    if not ok or type(req) ~= "table" then return "" end
+    for _, m in ipairs(req.messages or {}) do
+        if type(m) == "table" and m.role == "user" then
+            local c = m.content
+            if type(c) == "string" then
+                if c ~= "" then return c end
+            elseif type(c) == "table" then
+                for _, part in ipairs(c) do
+                    if type(part) == "table" and part.type == "text" and part.text then
+                        return part.text
+                    end
+                end
+            end
+            return ""
+        end
+    end
+    return ""
+end
+
+function adapter.build_headers(meta)
+    local ts = tostring(meta.timestamp or "")
+    local src = (meta.source and meta.source.name) 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|" .. src), 1, 32),
+        -- session 必须**按源稳定**，不能每请求换：上游的前缀缓存在同一 session
+        -- 内才复用。实测（同一段 6032 token 提示词）：
+        --   固定 session  -> 第 2 次命中 5888/6032，cached_tokens=5888
+        --   每请求换 session -> 永远 0 命中
+        -- 原先用 meta.timestamp 派生，等于每请求都是新会话，缓存永远无效，
+        -- 上游也无法做会话亲和路由。
+        ["x-opencode-session"] = rand_id("ses_", "session|llmsproxy|" .. src .. "|" .. conversation_fingerprint(meta.body)),
+        -- request id 仍每请求唯一（它只是请求标识，不参与缓存键）
+        ["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。剥离后 content 变空的消息
+-- 若不再携带 tool_calls / tool_call_id 才整条丢弃（避免上游
+-- "unknown variant `image_url`, expected `text`"）；带工具调用的必须保留，
+-- 否则会把紧随其后的 tool 结果变成孤儿，模型会反复重发同一个调用。
+-- zen 上游角色白名单只有 system / user / assistant / tool / latest_reminder：
+-- OpenAI 的 developer（及 function 等）不在其中，直接透传会触发上游
+-- "unknown variant `developer`, expected one of ..." 错误；统一归一化为 system。
+local ROLE_WHITELIST = {
+    system = true,
+    user = true,
+    assistant = true,
+    tool = true,
+    latest_reminder = true,
+}
+
+function adapter.transform_request(raw_body)
+    local ok, req = pcall(json.decode, raw_body)
+    if not ok then return raw_body end
+    req.disable_thinking = nil
+    req.extra_body = nil
+    -- stream_options is only valid alongside stream:true; sending it on a
+    -- non-streaming request is rejected by strict upstreams.
+    if req.stream then
+        if type(req.stream_options) ~= "table" then req.stream_options = {} end
+        req.stream_options.include_usage = true
+    end
+    if req.messages then
+        local kept = {}
+        for _, msg in ipairs(req.messages) do
+            if type(msg.role) == "string" and not ROLE_WHITELIST[msg.role] then
+                msg.role = "system"
+            end
+            -- Go 的 thinking 模式**必须**回传 reasoning_content：剥掉它会让
+            -- 上游直接 400（"The `reasoning_content` in the thinking mode must
+            -- be passed back to the API"），agent 的每一轮都会失败。
+            -- 注意：与 opencodezen.lua 的行为**相反**，不要在这里剥。
+            --
+            -- 但绝大多数客户端（pi 等）根本不保存也不回传 reasoning，只保留
+            -- 工具调用本身。上游只在“带 tool_calls 的助手轮”上校验这个字段，
+            -- 实测**空串即可通过校验**，所以缺省时补空串：既满足上游的
+            -- 一致性要求，又不伪造任何推理内容（用户看到的 reasoning 仍然是
+            -- 上游本轮真实返回的）。
+            if msg.role == "assistant"
+                and type(msg.tool_calls) == "table" and #msg.tool_calls > 0
+                and msg.reasoning_content == nil then
+                msg.reasoning_content = ""
+            end
+            local drop = false
+            if type(msg.content) == "table" then
+                local parts = {}
+                for _, part in ipairs(msg.content) do
+                    if type(part) == "table" and part.type ~= nil and part.type ~= "text" then
+                        -- multimodal part not supported by zen
+                    else
+                        table.insert(parts, part)
+                    end
+                end
+                if #parts == 0 then
+                    -- Content collapsed to nothing after stripping unsupported
+                    -- parts. A message that still carries a tool call must
+                    -- NEVER be dropped: the very next message is its tool
+                    -- result, and dropping the call orphans that result. The
+                    -- model then sees a result for a call it never made and
+                    -- re-issues the same tool call on every turn (observed as
+                    -- an infinite "repeated tool call" loop).
+                    if (type(msg.tool_calls) == "table" and #msg.tool_calls > 0)
+                        or msg.tool_call_id ~= nil then
+                        msg.content = ""
+                    else
+                        drop = true
+                    end
+                else
+                    msg.content = parts
+                end
+            end
+            if not drop then
+                table.insert(kept, msg)
+            end
+        end
+        req.messages = kept
+    end
+    return json.encode(req)
+end
+
+function adapter.transform_response(raw_body)
+    local ok, resp = pcall(json.decode, raw_body)
+    if not ok or resp == nil then return raw_body end
+
+    local unified = {
+        content = "",
+        finish_reason = "",
+        token_usage = { prompt = 0, completion = 0, total = 0 }
+    }
+
+    if type(resp.usage) == "table" then
+        unified.token_usage.prompt = resp.usage.prompt_tokens or 0
+        unified.token_usage.completion = resp.usage.completion_tokens or 0
+        unified.token_usage.total = resp.usage.total_tokens or 0
+        local hit = 0
+        if type(resp.usage.prompt_tokens_details) == "table" and resp.usage.prompt_tokens_details.cached_tokens ~= nil then
+            hit = resp.usage.prompt_tokens_details.cached_tokens
+            unified.token_usage.prompt_tokens_details = { cached_tokens = hit }
+        end
+        if (resp.usage.prompt_cache_hit_tokens or 0) > 0 then
+            unified.token_usage.prompt_cache_hit_tokens = resp.usage.prompt_cache_hit_tokens
+            unified.token_usage.prompt_cache_miss_tokens = resp.usage.prompt_cache_miss_tokens or 0
+            if hit == 0 then
+                unified.token_usage.prompt_tokens_details = { cached_tokens = resp.usage.prompt_cache_hit_tokens }
+            end
+        end
+    end
+
+    if type(resp.choices) == "table" and #resp.choices > 0 then
+        local ch = resp.choices[1]
+        if type(ch.message) == "table" then
+            unified.content = ch.message.content or ""
+            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 = {}
+                for _, tc in ipairs(ch.message.tool_calls) do
+                    local args_ok, args = pcall(json.decode, tc["function"].arguments)
+                    if not args_ok then args = {} end
+                    table.insert(tcs, {
+                        id = tc.id,
+                        type = tc.type or "function",
+                        name = tc["function"].name,
+                        arguments = args
+                    })
+                end
+                unified.tool_calls = tcs
+            end
+        end
+        unified.finish_reason = ch.finish_reason or ""
+    end
+
+    return json.encode(unified)
+end
+
+function adapter.transform_stream_chunk(raw_chunk)
+    local ok, chunk = pcall(json.decode, raw_chunk)
+    if not ok then return "" end
+
+    -- OpenAI-style streams may attach usage to a chunk with empty choices
+    -- (the final usage chunk). Preserve it; the gateway emits it as the
+    -- terminal usage chunk. Note: keys must match Go's TokenUsage json tags
+    -- (prompt/completion/total); the gateway re-emits standard *_tokens.
+    local uses = nil
+    if type(chunk.usage) == "table" then
+        uses = {
+            prompt = chunk.usage.prompt_tokens or chunk.usage.prompt or 0,
+            completion = chunk.usage.completion_tokens or chunk.usage.completion or 0,
+            total = chunk.usage.total_tokens or chunk.usage.total or 0,
+        }
+        if type(chunk.usage.prompt_tokens_details) == "table" and chunk.usage.prompt_tokens_details.cached_tokens ~= nil then
+            uses.prompt_tokens_details = { cached_tokens = chunk.usage.prompt_tokens_details.cached_tokens }
+        elseif (chunk.usage.prompt_cache_hit_tokens or 0) > 0 then
+            uses.prompt_cache_hit_tokens = chunk.usage.prompt_cache_hit_tokens
+            uses.prompt_cache_miss_tokens = chunk.usage.prompt_cache_miss_tokens or 0
+            uses.prompt_tokens_details = { cached_tokens = chunk.usage.prompt_cache_hit_tokens }
+        end
+    end
+
+    if not chunk.choices or #chunk.choices == 0 then
+        if uses ~= nil then
+            -- usage-only chunk is not a content/finish signal; the gateway
+            -- emits its own terminal stop chunk and merges this usage.
+            return json.encode({ usage = uses, done = false })
+        end
+        return ""
+    end
+    local delta = chunk.choices[1].delta or {}
+    local fr = chunk.choices[1].finish_reason
+
+    local finish = (type(fr) == "string" and fr ~= "") and fr or nil
+
+    local unified = {
+        content = delta.content or "",
+        done = (finish ~= nil)
+    }
+    if finish then
+        unified.finish_reason = finish
+    end
+    if uses ~= nil then
+        unified.usage = uses
+    end
+    -- 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
+        unified.tool_calls = delta.tool_calls
+    end
+    return json.encode(unified)
+end
+
+-- 错误收敛（可选钩子）：zen 错误信封固定为 {error={type,message}}；
+-- 免费池限流 FreeUsageLimitError 单独标注。返回 nil 走通用兜底。
+function adapter.transform_error(status, body)
+    local ok, resp = pcall(json.decode, body)
+    if not ok or type(resp) ~= "table" then return nil end
+    local e = resp.error
+    if type(e) ~= "table" then return nil end
+    if e.type == "FreeUsageLimitError" then
+        return "zen free pool quota exhausted"
+    end
+    return e.message
+end
+
+return adapter

internal/lua/adapters/opencodezen.lua

@@ -0,0 +1,288 @@
+local adapter = {}
+
+adapter.name = "opencodezen"
+adapter.version = "1.0.0"
+adapter.endpoint = "/chat/completions"
+
+-- OpenCode Zen（按量付费端点，https://opencode.ai/zen/v1）
+--
+-- 与 OpenCode Go（opencodego.lua，https://opencode.ai/zen/go/v1）是两个不同的
+-- 服务，行为要求并不相同，因此各有专用适配器：
+--
+--   * 本适配器（Zen）服务免费池 / 按量付费池。免费模型必须带 opencode 客户端
+--     指纹（UA + x-opencode-*），否则上游拒绝："free tier can only be used in
+--     OpenCode"。Zen 的免费池以非 thinking 模型为主，历史上回传
+--     reasoning_content 会引出上游报错，故这里剥掉（Go 侧相反，见 opencodego.lua）。
+--   * Go 订阅读者请看 opencodego.lua：那边**必须**回传 reasoning_content，
+--     否则 thinking 模式直接 400。
+--
+-- 缺 x-opencode-client/session/request/project 身份头会被判为匿名客户端，
+-- 部分模型在带 tools 时上游直接失败（流式返回单 chunk
+-- "finish_reason":"network_error" 空 content，非流式 503
+-- "Endpoint is unavailable"，表现为"空回复"）。
+adapter.headers = {
+    ["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
+
+-- 会话指纹：取历史里**第一条 user 消息**。
+--
+-- 为什么不直接用客户端的会话 id：实测抓包（tcpdump 抓 127.0.0.1:8081 的真实
+-- agent 请求）确认通用 OpenAI 客户端**根本不发**任何会话标识 —— body 里没有
+-- user / session_id / conversation_id / metadata，请求头也只有 X-Stainless-*
+-- （OpenAI JS SDK）与 User-Agent。opencode 原生客户端那套 x-opencode-session
+-- 是它自己的概念，通用客户端无从转发。
+--
+-- 退而求其次但要够用：历史被逐轮重放，**第一条 user 消息在整个会话里恒定**，
+-- 用它做指纹即可得到"每会话一个 session"，而不是"每源一个 session"。
+-- 拿不到时（无 user 消息）返回空串，调用方回退到按源稳定。
+local function conversation_fingerprint(body)
+    if type(body) ~= "string" or body == "" then return "" end
+    local ok, req = pcall(json.decode, body)
+    if not ok or type(req) ~= "table" then return "" end
+    for _, m in ipairs(req.messages or {}) do
+        if type(m) == "table" and m.role == "user" then
+            local c = m.content
+            if type(c) == "string" then
+                if c ~= "" then return c end
+            elseif type(c) == "table" then
+                for _, part in ipairs(c) do
+                    if type(part) == "table" and part.type == "text" and part.text then
+                        return part.text
+                    end
+                end
+            end
+            return ""
+        end
+    end
+    return ""
+end
+
+function adapter.build_headers(meta)
+    local ts = tostring(meta.timestamp or "")
+    local src = (meta.source and meta.source.name) 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|" .. src), 1, 32),
+        -- session 必须**按源稳定**，不能每请求换：上游的前缀缓存在同一 session
+        -- 内才复用。实测（同一段 6032 token 提示词）：
+        --   固定 session  -> 第 2 次命中 5888/6032，cached_tokens=5888
+        --   每请求换 session -> 永远 0 命中
+        -- 原先用 meta.timestamp 派生，等于每请求都是新会话，缓存永远无效，
+        -- 上游也无法做会话亲和路由。
+        ["x-opencode-session"] = rand_id("ses_", "session|llmsproxy|" .. src .. "|" .. conversation_fingerprint(meta.body)),
+        -- request id 仍每请求唯一（它只是请求标识，不参与缓存键）
+        ["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。剥离后 content 变空的消息
+-- 若不再携带 tool_calls / tool_call_id 才整条丢弃（避免上游
+-- "unknown variant `image_url`, expected `text`"）；带工具调用的必须保留，
+-- 否则会把紧随其后的 tool 结果变成孤儿，模型会反复重发同一个调用。
+-- zen 上游角色白名单只有 system / user / assistant / tool / latest_reminder：
+-- OpenAI 的 developer（及 function 等）不在其中，直接透传会触发上游
+-- "unknown variant `developer`, expected one of ..." 错误；统一归一化为 system。
+local ROLE_WHITELIST = {
+    system = true,
+    user = true,
+    assistant = true,
+    tool = true,
+    latest_reminder = true,
+}
+
+function adapter.transform_request(raw_body)
+    local ok, req = pcall(json.decode, raw_body)
+    if not ok then return raw_body end
+    req.disable_thinking = nil
+    req.extra_body = nil
+    -- stream_options is only valid alongside stream:true; sending it on a
+    -- non-streaming request is rejected by strict upstreams.
+    if req.stream then
+        if type(req.stream_options) ~= "table" then req.stream_options = {} end
+        req.stream_options.include_usage = true
+    end
+    if req.messages then
+        local kept = {}
+        for _, msg in ipairs(req.messages) do
+            if type(msg.role) == "string" and not ROLE_WHITELIST[msg.role] then
+                msg.role = "system"
+            end
+            -- Zen 免费池不接受回传 reasoning_content（Go 侧相反）
+            msg.reasoning_content = nil
+            local drop = false
+            if type(msg.content) == "table" then
+                local parts = {}
+                for _, part in ipairs(msg.content) do
+                    if type(part) == "table" and part.type ~= nil and part.type ~= "text" then
+                        -- multimodal part not supported by zen
+                    else
+                        table.insert(parts, part)
+                    end
+                end
+                if #parts == 0 then
+                    -- Content collapsed to nothing after stripping unsupported
+                    -- parts. A message that still carries a tool call must
+                    -- NEVER be dropped: the very next message is its tool
+                    -- result, and dropping the call orphans that result. The
+                    -- model then sees a result for a call it never made and
+                    -- re-issues the same tool call on every turn (observed as
+                    -- an infinite "repeated tool call" loop).
+                    if (type(msg.tool_calls) == "table" and #msg.tool_calls > 0)
+                        or msg.tool_call_id ~= nil then
+                        msg.content = ""
+                    else
+                        drop = true
+                    end
+                else
+                    msg.content = parts
+                end
+            end
+            if not drop then
+                table.insert(kept, msg)
+            end
+        end
+        req.messages = kept
+    end
+    return json.encode(req)
+end
+
+function adapter.transform_response(raw_body)
+    local ok, resp = pcall(json.decode, raw_body)
+    if not ok or resp == nil then return raw_body end
+
+    local unified = {
+        content = "",
+        finish_reason = "",
+        token_usage = { prompt = 0, completion = 0, total = 0 }
+    }
+
+    if type(resp.usage) == "table" then
+        unified.token_usage.prompt = resp.usage.prompt_tokens or 0
+        unified.token_usage.completion = resp.usage.completion_tokens or 0
+        unified.token_usage.total = resp.usage.total_tokens or 0
+        local hit = 0
+        if type(resp.usage.prompt_tokens_details) == "table" and resp.usage.prompt_tokens_details.cached_tokens ~= nil then
+            hit = resp.usage.prompt_tokens_details.cached_tokens
+            unified.token_usage.prompt_tokens_details = { cached_tokens = hit }
+        end
+        if (resp.usage.prompt_cache_hit_tokens or 0) > 0 then
+            unified.token_usage.prompt_cache_hit_tokens = resp.usage.prompt_cache_hit_tokens
+            unified.token_usage.prompt_cache_miss_tokens = resp.usage.prompt_cache_miss_tokens or 0
+            if hit == 0 then
+                unified.token_usage.prompt_tokens_details = { cached_tokens = resp.usage.prompt_cache_hit_tokens }
+            end
+        end
+    end
+
+    if type(resp.choices) == "table" and #resp.choices > 0 then
+        local ch = resp.choices[1]
+        if type(ch.message) == "table" then
+            unified.content = ch.message.content or ""
+            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 = {}
+                for _, tc in ipairs(ch.message.tool_calls) do
+                    local args_ok, args = pcall(json.decode, tc["function"].arguments)
+                    if not args_ok then args = {} end
+                    table.insert(tcs, {
+                        id = tc.id,
+                        type = tc.type or "function",
+                        name = tc["function"].name,
+                        arguments = args
+                    })
+                end
+                unified.tool_calls = tcs
+            end
+        end
+        unified.finish_reason = ch.finish_reason or ""
+    end
+
+    return json.encode(unified)
+end
+
+function adapter.transform_stream_chunk(raw_chunk)
+    local ok, chunk = pcall(json.decode, raw_chunk)
+    if not ok then return "" end
+
+    -- OpenAI-style streams may attach usage to a chunk with empty choices
+    -- (the final usage chunk). Preserve it; the gateway emits it as the
+    -- terminal usage chunk. Note: keys must match Go's TokenUsage json tags
+    -- (prompt/completion/total); the gateway re-emits standard *_tokens.
+    local uses = nil
+    if type(chunk.usage) == "table" then
+        uses = {
+            prompt = chunk.usage.prompt_tokens or chunk.usage.prompt or 0,
+            completion = chunk.usage.completion_tokens or chunk.usage.completion or 0,
+            total = chunk.usage.total_tokens or chunk.usage.total or 0,
+        }
+        if type(chunk.usage.prompt_tokens_details) == "table" and chunk.usage.prompt_tokens_details.cached_tokens ~= nil then
+            uses.prompt_tokens_details = { cached_tokens = chunk.usage.prompt_tokens_details.cached_tokens }
+        elseif (chunk.usage.prompt_cache_hit_tokens or 0) > 0 then
+            uses.prompt_cache_hit_tokens = chunk.usage.prompt_cache_hit_tokens
+            uses.prompt_cache_miss_tokens = chunk.usage.prompt_cache_miss_tokens or 0
+            uses.prompt_tokens_details = { cached_tokens = chunk.usage.prompt_cache_hit_tokens }
+        end
+    end
+
+    if not chunk.choices or #chunk.choices == 0 then
+        if uses ~= nil then
+            -- usage-only chunk is not a content/finish signal; the gateway
+            -- emits its own terminal stop chunk and merges this usage.
+            return json.encode({ usage = uses, done = false })
+        end
+        return ""
+    end
+    local delta = chunk.choices[1].delta or {}
+    local fr = chunk.choices[1].finish_reason
+
+    local finish = (type(fr) == "string" and fr ~= "") and fr or nil
+
+    local unified = {
+        content = delta.content or "",
+        done = (finish ~= nil)
+    }
+    if finish then
+        unified.finish_reason = finish
+    end
+    if uses ~= nil then
+        unified.usage = uses
+    end
+    -- 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
+        unified.tool_calls = delta.tool_calls
+    end
+    return json.encode(unified)
+end
+
+-- 错误收敛（可选钩子）：zen 错误信封固定为 {error={type,message}}；
+-- 免费池限流 FreeUsageLimitError 单独标注。返回 nil 走通用兜底。
+function adapter.transform_error(status, body)
+    local ok, resp = pcall(json.decode, body)
+    if not ok or type(resp) ~= "table" then return nil end
+    local e = resp.error
+    if type(e) ~= "table" then return nil end
+    if e.type == "FreeUsageLimitError" then
+        return "zen free pool quota exhausted"
+    end
+    return e.message
+end
+
+return adapter

internal/lua/toolcall_preservation_test.go

@@ -118,3 +118,186 @@ func TestAdaptersPreserveToolCalls(t *testing.T) {
 		}
 	}
 }
+
+// TestOpenCodeStreamOptionsOnlyWhenStreaming pins the fix for
+// "stream_options should be set along with stream": OpenCode Go (and other
+// strict OpenAI-compatible upstreams) reject a non-streaming request that
+// carries stream_options, which broke every non-stream call through the
+// opencode adapter.
+func TestOpenCodeStreamOptionsOnlyWhenStreaming(t *testing.T) {
+	vm := NewVM(freshAdapterDir(t))
+	if err := vm.Start(); err != nil {
+		t.Fatal(err)
+	}
+	defer vm.Stop()
+
+	// non-streaming: stream_options must be absent entirely
+	out, err := vm.Transform("opencode", "transform_request",
+		`{"model":"m","messages":[{"role":"user","content":"hi"}]}`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(out, "stream_options") {
+		t.Fatalf("non-streaming request must not carry stream_options: %s", out)
+	}
+
+	// streaming: stream_options.include_usage must be set
+	sout, err := vm.Transform("opencode", "transform_request",
+		`{"model":"m","stream":true,"messages":[{"role":"user","content":"hi"}]}`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(sout, "stream_options") || !strings.Contains(sout, "include_usage") {
+		t.Fatalf("streaming request must carry stream_options.include_usage: %s", sout)
+	}
+}
+
+// TestOpenCodeGoVsZenReasoning pins the one behavioural difference that made a
+// shared adapter wrong: OpenCode Go's thinking mode REQUIRES the assistant
+// turn's reasoning_content to be echoed back ("The `reasoning_content` in the
+// thinking mode must be passed back to the API"), while the Zen free pool must
+// not receive it. Hence two purpose-built adapters.
+func TestOpenCodeGoVsZenReasoning(t *testing.T) {
+	vm := NewVM(freshAdapterDir(t))
+	if err := vm.Start(); err != nil {
+		t.Fatal(err)
+	}
+	defer vm.Stop()
+
+	body := `{"model":"m","messages":[
+		{"role":"user","content":"hi"},
+		{"role":"assistant","content":"","reasoning_content":"I should read the file.","tool_calls":[{"id":"call_1","type":"function","function":{"name":"read","arguments":"{\"path\":\"/x\"}"}}]},
+		{"role":"tool","tool_call_id":"call_1","content":"r"}
+	]}`
+
+	// Go: reasoning_content must survive, and the tool call must stay paired.
+	gout, err := vm.Transform("opencodego", "transform_request", body)
+	if err != nil {
+		t.Fatalf("opencodego: %v", err)
+	}
+	if !strings.Contains(gout, "I should read the file.") {
+		t.Errorf("opencodego must pass reasoning_content back (thinking mode requires it): %s", gout)
+	}
+	if !strings.Contains(gout, "call_1") || !strings.Contains(gout, "tool_call_id") {
+		t.Errorf("opencodego must keep the tool call paired with its result: %s", gout)
+	}
+
+	// Zen: reasoning_content is stripped.
+	zout, err := vm.Transform("opencodezen", "transform_request", body)
+	if err != nil {
+		t.Fatalf("opencodezen: %v", err)
+	}
+	if strings.Contains(zout, "I should read the file.") {
+		t.Errorf("opencodezen must strip reasoning_content: %s", zout)
+	}
+	if !strings.Contains(zout, "call_1") {
+		t.Errorf("opencodezen must still keep the tool call: %s", zout)
+	}
+
+	// An assistant turn that carries tool_calls but no reasoning_content must
+	// get an empty one injected: Go validates that field on tool-calling turns
+	// and 400s when it is absent, while most clients never send it.
+	// Verified against the live endpoint that an empty string passes.
+	bare := `{"model":"m","messages":[
+		{"role":"user","content":"go"},
+		{"role":"assistant","content":"","tool_calls":[{"id":"c1","type":"function","function":{"name":"read","arguments":"{}"}}]},
+		{"role":"tool","tool_call_id":"c1","content":"r"}
+	]}`
+	bout, err := vm.Transform("opencodego", "transform_request", bare)
+	if err != nil {
+		t.Fatalf("opencodego bare: %v", err)
+	}
+	if !strings.Contains(bout, `"reasoning_content":""`) {
+		t.Errorf("opencodego must inject an empty reasoning_content on a tool-calling turn: %s", bout)
+	}
+	// A plain assistant turn (no tool calls) must NOT gain the field.
+	plainAsst := `{"model":"m","messages":[{"role":"user","content":"hi"},{"role":"assistant","content":"hello"}]}`
+	pout, err := vm.Transform("opencodego", "transform_request", plainAsst)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(pout, "reasoning_content") {
+		t.Errorf("opencodego must not inject reasoning_content on a plain assistant turn: %s", pout)
+	}
+
+	// Both must still omit stream_options on non-streaming requests.
+	for _, a := range []string{"opencodego", "opencodezen"} {
+		out, err := vm.Transform(a, "transform_request", `{"model":"m","messages":[{"role":"user","content":"hi"}]}`)
+		if err != nil {
+			t.Fatalf("%s: %v", a, err)
+		}
+		if strings.Contains(out, "stream_options") {
+			t.Errorf("%s must not send stream_options when not streaming: %s", a, out)
+		}
+	}
+}
+
+// TestOpenCodeSessionIsStableForCache pins the session-derivation contract that
+// makes the upstream prefix cache usable.
+//
+// Measured against the live OpenCode Go endpoint: the prefix cache is
+// SESSION-scoped. Replaying the same 6032-token prompt hits 5888 cached tokens
+// when the session id is fixed, and 0 when it changes per request. Deriving the
+// session from meta.timestamp (the previous behaviour) meant every request was a
+// new session, so the cache could never hit.
+//
+// The session must be stable WITHIN one conversation and differ BETWEEN
+// conversations. Since generic OpenAI clients send no session id at all
+// (verified by capturing real agent traffic: no user / session_id /
+// conversation_id / metadata in the body, no session header), the conversation
+// is fingerprinted by its FIRST user message — history is replayed every turn,
+// so that message is invariant for the life of the conversation.
+func TestOpenCodeSessionIsStableForCache(t *testing.T) {
+	for _, name := range []string{"opencodego", "opencodezen"} {
+		vm := NewVM(freshAdapterDir(t))
+		if err := vm.Start(); err != nil {
+			t.Fatal(err)
+		}
+		meta := func(ts int, body string) map[string]interface{} {
+			return map[string]interface{}{
+				"timestamp": ts,
+				"body":      body,
+				"source":    map[string]interface{}{"name": "somesource", "meta": nil},
+			}
+		}
+
+		// Same conversation, later turn: history grew, first user msg unchanged.
+		h1, err := vm.BuildHeaders(name, meta(1000,
+			`{"messages":[{"role":"user","content":"fix the bug"},{"role":"assistant","content":"looking"}]}`))
+		if err != nil {
+			t.Fatalf("%s: %v", name, err)
+		}
+		h2, err := vm.BuildHeaders(name, meta(2000,
+			`{"messages":[{"role":"user","content":"fix the bug"},{"role":"assistant","content":"looking"},{"role":"user","content":"and tests"}]}`))
+		if err != nil {
+			t.Fatalf("%s: %v", name, err)
+		}
+		// Different conversation.
+		h3, err := vm.BuildHeaders(name, meta(3000,
+			`{"messages":[{"role":"user","content":"an unrelated task"}]}`))
+		if err != nil {
+			t.Fatalf("%s: %v", name, err)
+		}
+
+		if h1["x-opencode-session"] == "" {
+			t.Fatalf("%s: session header must be set", name)
+		}
+		if h1["x-opencode-session"] != h2["x-opencode-session"] {
+			t.Errorf("%s: x-opencode-session must be STABLE across turns of one conversation "+
+				"(%q vs %q) — the prefix cache is session-scoped", name, h1["x-opencode-session"], h2["x-opencode-session"])
+		}
+		if h1["x-opencode-session"] == h3["x-opencode-session"] {
+			t.Errorf("%s: a different conversation must get a different session", name)
+		}
+		if h1["x-opencode-request"] == h2["x-opencode-request"] {
+			t.Errorf("%s: x-opencode-request must differ per request", name)
+		}
+		// No user message at all falls back to per-source stability.
+		h4, _ := vm.BuildHeaders(name, meta(4000, `{"messages":[{"role":"system","content":"s"}]}`))
+		h5, _ := vm.BuildHeaders(name, meta(5000, `{"messages":[{"role":"system","content":"s"}]}`))
+		if h4["x-opencode-session"] != h5["x-opencode-session"] {
+			t.Errorf("%s: sessionless requests must still be stable per source", name)
+		}
+		vm.Stop()
+	}
+}