diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b86a691
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/ops
+/dist/
+*.tmp
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..df70935
--- /dev/null
+++ b/README.md
@@ -0,0 +1,486 @@
+# opencode-provider-switch (`ops`)
+
+`ops` 是一个给 OpenCode 使用的本地代理。
+
+它解决的问题很简单：
+
+- 你在 OpenCode 里只使用一个稳定的模型名，例如 `ops/gpt-5.4`
+- `ops` 在本地把这个别名映射到多个上游 `provider/model`
+- 按你配置的顺序依次尝试上游
+- 如果主上游在响应开始前失败，自动切到下一个上游
+
+当前实现只支持 OpenAI Responses 协议，也就是 `POST /v1/responses`，并且支持流式响应。
+
+## 适合什么场景
+
+- 你有多个 OpenAI 兼容上游
+- 你不想在 OpenCode 里频繁切换 provider
+- 你希望用一个固定别名承接多个备用上游
+- 你希望失败切换行为是确定的、可预期的
+
+## 当前能力
+
+- 本地维护 `ops` 配置文件：上游 provider、alias、监听地址
+- 支持手动添加 provider
+- 支持从 OpenCode 配置导入 `@ai-sdk/openai` 自定义 provider
+- 支持创建 alias，并按顺序绑定多个上游 target
+- 支持把 alias 同步到 OpenCode 的 `provider.ops.models`
+- 支持本地代理 `POST /v1/responses`
+- 支持流式透传
+- 支持首字节前失败切换
+- 返回调试响应头，便于确认这次请求实际落到了哪个上游
+
+## 不支持的内容
+
+- Anthropic 原生协议
+- 多协议路由
+- 自动按延迟、价格、提示词类型选路
+- 中途流式拼接切换
+- SQLite、管理后台、计费统计
+- 完整接管 OpenCode 所有配置层
+- 从 `auth.json` 自动导入 provider 定义
+
+## 安装
+
+```bash
+go build -o ops ./cmd/ops
+```
+
+如果你只想临时运行，也可以直接：
+
+```bash
+go run ./cmd/ops --help
+```
+
+## 5 分钟快速上手
+
+### 1. 添加上游 provider
+
+`ops` 要求上游是 OpenAI 兼容接口，并且 `--base-url` 需要带上 `/v1`。
+
+```bash
+ops provider add --id su8 --base-url https://cn2.su8.codes/v1 --api-key sk-xxx
+ops provider add --id codex --base-url https://api-vip.codex-for.me/v1 --api-key sk-yyy
+```
+
+如果某个上游还需要额外请求头，可以重复传 `--header`：
+
+```bash
+ops provider add \
+  --id relay \
+  --base-url https://example.com/v1 \
+  --api-key sk-zzz \
+  --header "X-Custom-Token=abc" \
+  --header "X-Workspace=my-team"
+```
+
+查看当前 provider：
+
+```bash
+ops provider list
+```
+
+### 2. 创建 alias，并绑定多个上游 target
+
+下面这个例子表示：当你使用 `ops/gpt-5.4` 时，优先走 `su8/gpt-5.4`，失败后再走 `codex/GPT-5.4`。
+
+```bash
+ops alias add --name gpt-5.4 --display-name "GPT 5.4"
+ops alias bind --alias gpt-5.4 --provider su8 --model gpt-5.4
+ops alias bind --alias gpt-5.4 --provider codex --model GPT-5.4
+```
+
+查看当前 alias：
+
+```bash
+ops alias list
+```
+
+注意：
+
+- target 的顺序就是失败切换顺序
+- enabled alias 必须至少有一个 enabled target
+- `ops alias bind` 在 alias 不存在时会自动创建一个 enabled alias
+
+### 3. 先做一次静态检查
+
+```bash
+ops doctor
+```
+
+`ops doctor` 只做静态校验，不会真的请求上游，不会消耗额度。
+
+它会检查：
+
+- 本地 `ops` 配置能不能正常加载
+- alias 是否引用了不存在的 provider
+- enabled alias 是否至少有一个 enabled target
+- 本地代理监听地址是否合理
+- 默认会同步到哪个 OpenCode 配置文件
+
+### 4. 把 alias 同步到 OpenCode
+
+```bash
+ops opencode sync
+```
+
+这个命令会做一件事：把当前 alias 列表同步进 OpenCode 的 `provider.ops.models`。
+
+默认行为：
+
+- 优先复用全局 OpenCode 配置文件：`opencode.jsonc` > `opencode.json` > `config.json`
+- 如果都不存在，就创建 `~/.config/opencode/opencode.jsonc`
+- 只更新 `provider.ops`
+- 不会修改顶层 `model`
+- 不会修改顶层 `small_model`
+
+如果你希望顺手把默认模型也切到 `ops`，需要显式指定：
+
+```bash
+ops opencode sync --set-model ops/gpt-5.4
+```
+
+如果你还有小模型 alias，也可以这样：
+
+```bash
+ops opencode sync \
+  --set-model ops/gpt-5.4 \
+  --set-small-model ops/gpt-5.4-mini
+```
+
+先预览不写入：
+
+```bash
+ops opencode sync --dry-run
+```
+
+写到指定 OpenCode 配置文件：
+
+```bash
+ops opencode sync --target /path/to/opencode.jsonc
+```
+
+### 5. 启动本地代理
+
+```bash
+ops serve
+```
+
+默认监听地址：
+
+- `127.0.0.1:9982`
+- 本地 API Key：`ops-local`
+
+启动后，本地代理地址是：
+
+```text
+http://127.0.0.1:9982/v1
+```
+
+### 6. 在 OpenCode 里使用
+
+完成 `ops opencode sync` 后，你应该能在 OpenCode 里看到 `ops/<alias>`。
+
+例如：
+
+- `ops/gpt-5.4`
+
+如果你执行了：
+
+```bash
+ops opencode sync --set-model ops/gpt-5.4
+```
+
+那么 OpenCode 默认模型也会直接切到这个 alias。
+
+## 直接验证本地代理
+
+如果你想先不走 OpenCode，直接验证 `ops` 是否能正常代理，可以自己发一个请求：
+
+```bash
+curl -sN -X POST http://127.0.0.1:9982/v1/responses \
+  -H "Authorization: Bearer ops-local" \
+  -H "Content-Type: application/json" \
+  -d '{"model":"gpt-5.4","stream":true,"input":"hello"}'
+```
+
+注意这里请求体里的 `model` 是 alias 本身，例如 `gpt-5.4`，不是 `ops/gpt-5.4`。
+
+因为 `ops/gpt-5.4` 是 OpenCode 侧的模型选择写法；真正发到本地 provider 的请求里，模型名会是 alias 自身。
+
+## 从现有 OpenCode 配置导入 provider
+
+如果你原来已经在 OpenCode 里配置过一些自定义 provider，可以直接导入：
+
+```bash
+ops provider import-opencode
+```
+
+或者指定导入源：
+
+```bash
+ops provider import-opencode --from ./examples/opencode.jsonc
+```
+
+支持范围只有这一类：
+
+- `npm: @ai-sdk/openai`
+- 有 `options.baseURL`
+- 有 `options.apiKey`
+
+注意：
+
+- 这不是完整迁移工具
+- 当前只导入 provider 的基本连接信息
+- 如果你的旧配置依赖额外自定义 header，需要导入后自己用 `ops provider add --header ...` 补齐
+- `ops` 自己不会被反向导入
+
+覆盖已存在的 provider：
+
+```bash
+ops provider import-opencode --overwrite
+```
+
+## 常用命令
+
+### provider
+
+添加或更新 provider：
+
+```bash
+ops provider add --id <id> --base-url <url-with-/v1> --api-key <key>
+```
+
+查看 provider：
+
+```bash
+ops provider list
+```
+
+删除 provider：
+
+```bash
+ops provider remove <id>
+```
+
+注意：删除 provider 不会自动帮你清理 alias 里的引用。引用还在的话，`ops doctor` 会报错。
+
+### alias
+
+创建或更新 alias：
+
+```bash
+ops alias add --name <alias>
+```
+
+给 alias 追加一个 target：
+
+```bash
+ops alias bind --alias <alias> --provider <provider-id> --model <upstream-model>
+```
+
+解绑 target：
+
+```bash
+ops alias unbind --alias <alias> --provider <provider-id> --model <upstream-model>
+```
+
+查看 alias：
+
+```bash
+ops alias list
+```
+
+删除 alias：
+
+```bash
+ops alias remove <alias>
+```
+
+### 其他
+
+静态检查：
+
+```bash
+ops doctor
+```
+
+启动代理：
+
+```bash
+ops serve
+```
+
+同步到 OpenCode：
+
+```bash
+ops opencode sync
+```
+
+全局帮助：
+
+```bash
+ops --help
+ops provider --help
+ops alias --help
+ops opencode sync --help
+```
+
+## 配置文件说明
+
+本地 `ops` 配置文件默认路径：
+
+- 如果设置了 `OPS_CONFIG`，优先使用它
+- 否则使用 `$XDG_CONFIG_HOME/ops/config.json`
+- 再否则使用 `~/.config/ops/config.json`
+
+也可以对每个命令显式指定：
+
+```bash
+ops --config /path/to/config.json doctor
+```
+
+一个最小配置示例：
+
+```json
+{
+  "server": {
+    "host": "127.0.0.1",
+    "port": 9982,
+    "api_key": "ops-local"
+  },
+  "providers": [
+    {
+      "id": "su8",
+      "name": "SU8",
+      "base_url": "https://cn2.su8.codes/v1",
+      "api_key": "sk-xxx"
+    },
+    {
+      "id": "codex",
+      "name": "Codex",
+      "base_url": "https://api-vip.codex-for.me/v1",
+      "api_key": "sk-yyy"
+    }
+  ],
+  "aliases": [
+    {
+      "alias": "gpt-5.4",
+      "display_name": "GPT 5.4",
+      "enabled": true,
+      "targets": [
+        {
+          "provider": "su8",
+          "model": "gpt-5.4",
+          "enabled": true
+        },
+        {
+          "provider": "codex",
+          "model": "GPT-5.4",
+          "enabled": true
+        }
+      ]
+    }
+  ]
+}
+```
+
+## 失败切换规则
+
+`ops` 的切换规则很保守，也很容易理解。
+
+会切换到下一个 target 的情况：
+
+- 连接失败
+- DNS / 网络错误
+- 上游在返回首字节前超时或断开
+- 上游返回 `429`
+- 上游返回 `5xx`
+
+不会切换的情况：
+
+- alias 不存在
+- alias 被禁用
+- alias 没有 enabled target
+- 上游返回 `400`
+- 上游返回 `401`
+- 上游返回 `403`
+- 上游返回 `404`
+- 响应已经开始向客户端写出后才出错
+
+重点是：
+
+- 只有在“还没向下游写出任何字节”之前，才允许切换
+- 一旦开始向客户端输出流，当前上游就锁定了
+- 不支持中途把一半流接到另一个 provider 上继续输出
+
+## 调试响应头
+
+每次成功代理或透传上游错误时，响应里都会附带这些头：
+
+- `X-OPS-Alias`
+- `X-OPS-Provider`
+- `X-OPS-Remote-Model`
+- `X-OPS-Attempt`
+- `X-OPS-Failover-Count`
+
+你可以用它们确认：
+
+- 本次请求命中了哪个 alias
+- 实际走了哪个 provider
+- 实际转发成了哪个上游 model
+- 这是第几次尝试
+- 前面已经失败切换过几次
+
+## 常见问题
+
+### 为什么 `opencode models` 里看不到 `ops/<alias>`？
+
+先检查这几件事：
+
+1. 你是否执行过 `ops opencode sync`
+2. 你的 alias 是否是 enabled 状态
+3. alias 是否至少绑定了一个 enabled target
+4. OpenCode 当前实际使用的配置文件，是否就是 `ops opencode sync` 写入的那个文件
+5. 执行一次 `ops doctor`，看输出里的 `opencode config target`
+
+### 为什么 `ops doctor` 报 alias 没有 enabled target？
+
+因为当前实现要求：只要 alias 是 enabled，就必须至少有一个 enabled target。
+
+你可以：
+
+- 给它绑定 target
+- 或者把这个 alias 改成 disabled 后再保存
+
+### 删除 provider 后为什么还有报错？
+
+因为 alias 里的 target 还是旧引用。需要继续执行：
+
+```bash
+ops alias unbind --alias <alias> --provider <provider-id> --model <model>
+```
+
+### 本地代理鉴权是什么？
+
+默认是静态 key：
+
+```text
+ops-local
+```
+
+OpenCode 在 `provider.ops.options.apiKey` 里会使用这个值。直接手工请求本地代理时，也要带上这个 key。
+
+## 安全说明
+
+- 默认只监听 `127.0.0.1`
+- 上游凭据保存在本地 `ops` 配置文件中
+- 本项目当前没有做多用户或远程网络安全保证
+
+所以请把本地配置文件当成敏感文件处理。
+
+## 英文版 README
+
+原英文版文档已保存在：
+
+- `README_EN.md`
diff --git a/README_EN.md b/README_EN.md
new file mode 100644
index 0000000..902c826
--- /dev/null
+++ b/README_EN.md
@@ -0,0 +1,87 @@
+# opencode-provider-switch (`ops`)
+
+A tiny local proxy for [OpenCode](https://opencode.ai) that gives you **one
+stable model alias** routed to **multiple upstream providers** with
+**deterministic failover**.
+
+- Expose one custom provider `ops` to OpenCode.
+- Configure logical aliases (`ops/gpt-5.4`, etc.).
+- Each alias has an ordered list of upstream `provider/model` targets.
+- When the primary upstream returns `5xx`/`429`/connect error *before* any
+  stream bytes are flushed, `ops` transparently retries the next target.
+- Once a stream has started, the upstream is locked for the rest of that
+  request — no mid-stream splicing.
+
+Protocol: OpenAI Responses (`POST /v1/responses`) only. Streaming supported.
+
+## Install
+
+```bash
+go build -o ops ./cmd/ops
+```
+
+## Quick start
+
+```bash
+# 1. add upstream providers
+ops provider add --id su8   --base-url https://cn2.su8.codes/v1 --api-key sk-...
+ops provider add --id codex --base-url https://api-vip.codex-for.me/v1 --api-key sk-...
+
+# 2. create alias and bind targets in priority order
+ops alias add --name gpt-5.4
+ops alias bind --alias gpt-5.4 --provider su8   --model gpt-5.4
+ops alias bind --alias gpt-5.4 --provider codex --model GPT-5.4
+
+# 3. push alias exposure into OpenCode global config
+ops opencode sync
+
+# 4. run the proxy
+ops serve
+```
+
+Inside OpenCode you can now pick `ops/gpt-5.4`.
+
+### Import providers from an existing OpenCode config
+
+```bash
+ops provider import-opencode             # reads global OpenCode config
+ops provider import-opencode --from ./examples/opencode.jsonc
+```
+
+Only `@ai-sdk/openai` custom providers with a `baseURL` and `apiKey` are
+imported. Everything else is out of MVP scope.
+
+### Doctor (static)
+
+```bash
+ops doctor
+```
+
+Runs structural checks only — never issues real upstream requests.
+
+## CLI reference
+
+- `ops serve` — run the proxy
+- `ops doctor` — validate config
+- `ops provider {add,list,remove,import-opencode}`
+- `ops alias {add,list,bind,unbind,remove}`
+- `ops opencode sync [--target FILE] [--set-model ALIAS] [--set-small-model ALIAS] [--dry-run]`
+
+Global flag: `--config PATH` (default `$XDG_CONFIG_HOME/ops/config.json`).
+
+## Debug headers
+
+Every proxied response includes:
+
+- `X-OPS-Alias`
+- `X-OPS-Provider`
+- `X-OPS-Remote-Model`
+- `X-OPS-Attempt`
+- `X-OPS-Failover-Count`
+
+## Scope
+
+Out of MVP: Anthropic native, multi-protocol routing, dashboard, billing,
+latency-based routing, `/v1/models` discovery, full OpenCode config takeover.
+See `.trellis/tasks/archive/2026-04/04-17-04-17-ops-mvp-design-review/prd.md`
+for the authoritative design notes.
diff --git a/cmd/ops/main.go b/cmd/ops/main.go
new file mode 100644
index 0000000..dc59085
--- /dev/null
+++ b/cmd/ops/main.go
@@ -0,0 +1,20 @@
+// Command ops: local alias + failover proxy for OpenCode.
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/anomalyco/opencode-provider-switch/internal/cli"
+)
+
+// version is overridden at build time via -ldflags "-X main.version=...".
+var version = "dev"
+
+func main() {
+	if err := cli.NewRootCmd(version).Execute(); err != nil {
+		// cobra already prints the error; ensure non-zero exit
+		fmt.Fprintln(os.Stderr)
+		os.Exit(1)
+	}
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..da80ada
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,13 @@
+module github.com/anomalyco/opencode-provider-switch
+
+go 1.22.2
+
+require (
+	github.com/spf13/cobra v1.8.1
+	github.com/tidwall/jsonc v0.3.2
+)
+
+require (
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..a230ae4
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,12 @@
+github.com/cpuguy83/go-md2man/v2 v2.0.4/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
+github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/spf13/cobra v1.8.1 h1:e5/vxKd/rZsfSJMUX1agtjeTDf+qv1/JdBF8gg5k9ZM=
+github.com/spf13/cobra v1.8.1/go.mod h1:wHxEcudfqmLYa8iTfL+OuZPbBZkmvliBWKIezN3kD9Y=
+github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/tidwall/jsonc v0.3.2 h1:ZTKrmejRlAJYdn0kcaFqRAKlxxFIC21pYq8vLa4p2Wc=
+github.com/tidwall/jsonc v0.3.2/go.mod h1:dw+3CIxqHi+t8eFSpzzMlcVYxKp08UP5CD8/uSFCyJE=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/internal/cli/alias.go b/internal/cli/alias.go
new file mode 100644
index 0000000..de04c4b
--- /dev/null
+++ b/internal/cli/alias.go
@@ -0,0 +1,179 @@
+package cli
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/spf13/cobra"
+
+	"github.com/anomalyco/opencode-provider-switch/internal/config"
+)
+
+func newAliasCmd() *cobra.Command {
+	c := &cobra.Command{
+		Use:   "alias",
+		Short: "Manage logical aliases routed by ops",
+	}
+	c.AddCommand(newAliasAddCmd(), newAliasListCmd(), newAliasBindCmd(), newAliasUnbindCmd(), newAliasRemoveCmd())
+	return c
+}
+
+func newAliasAddCmd() *cobra.Command {
+	var name, display string
+	var disabled bool
+	cmd := &cobra.Command{
+		Use:   "add",
+		Short: "Create or update an alias (without targets)",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if name == "" {
+				return fmt.Errorf("--name is required")
+			}
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			existing := cfg.FindAlias(name)
+			a := config.Alias{Alias: name, DisplayName: display, Enabled: !disabled}
+			if existing != nil {
+				a.Targets = existing.Targets
+			}
+			cfg.UpsertAlias(a)
+			if err := cfg.Save(); err != nil {
+				return err
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "saved alias %q (enabled=%v)\n", name, a.Enabled)
+			return nil
+		},
+	}
+	cmd.Flags().StringVar(&name, "name", "", "alias name exposed as ops/<name> in OpenCode (required)")
+	cmd.Flags().StringVar(&display, "display-name", "", "human-friendly display name")
+	cmd.Flags().BoolVar(&disabled, "disabled", false, "create in disabled state")
+	return cmd
+}
+
+func newAliasListCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "list",
+		Short: "List aliases and their target chains",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			aliases := append([]config.Alias(nil), cfg.Aliases...)
+			sort.Slice(aliases, func(i, j int) bool { return aliases[i].Alias < aliases[j].Alias })
+			if len(aliases) == 0 {
+				fmt.Fprintln(cmd.OutOrStdout(), "(no aliases)")
+				return nil
+			}
+			for _, a := range aliases {
+				state := "enabled"
+				if !a.Enabled {
+					state = "disabled"
+				}
+				fmt.Fprintf(cmd.OutOrStdout(), "%s  [%s]\n", a.Alias, state)
+				for i, t := range a.Targets {
+					mark := " "
+					if !t.Enabled {
+						mark = "x"
+					}
+					fmt.Fprintf(cmd.OutOrStdout(), "  [%s] %d. %s/%s\n", mark, i+1, t.Provider, t.Model)
+				}
+			}
+			return nil
+		},
+	}
+}
+
+func newAliasBindCmd() *cobra.Command {
+	var alias, provider, model string
+	var disabled bool
+	cmd := &cobra.Command{
+		Use:   "bind",
+		Short: "Append a target (provider/model) to an alias in failover order",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if alias == "" || provider == "" || model == "" {
+				return fmt.Errorf("--alias, --provider and --model are required")
+			}
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			if cfg.FindProvider(provider) == nil {
+				return fmt.Errorf("provider %q does not exist; add it first", provider)
+			}
+			if cfg.FindAlias(alias) == nil {
+				// auto-create enabled alias for ergonomics
+				cfg.UpsertAlias(config.Alias{Alias: alias, Enabled: true})
+			}
+			if err := cfg.AddTarget(alias, config.Target{Provider: provider, Model: model, Enabled: !disabled}); err != nil {
+				return err
+			}
+			if err := cfg.Save(); err != nil {
+				return err
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "bound %s → %s/%s\n", alias, provider, model)
+			return nil
+		},
+	}
+	cmd.Flags().StringVar(&alias, "alias", "", "alias name (required)")
+	cmd.Flags().StringVar(&provider, "provider", "", "upstream provider id (required)")
+	cmd.Flags().StringVar(&model, "model", "", "upstream model id (required)")
+	cmd.Flags().BoolVar(&disabled, "disabled", false, "add target in disabled state")
+	return cmd
+}
+
+func newAliasUnbindCmd() *cobra.Command {
+	var alias, provider, model string
+	cmd := &cobra.Command{
+		Use:   "unbind",
+		Short: "Remove a target from an alias",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if alias == "" || provider == "" || model == "" {
+				return fmt.Errorf("--alias, --provider and --model are required")
+			}
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			if err := cfg.RemoveTarget(alias, provider, model); err != nil {
+				return err
+			}
+			if err := cfg.Save(); err != nil {
+				return err
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "unbound %s → %s/%s\n", alias, provider, model)
+			return nil
+		},
+	}
+	cmd.Flags().StringVar(&alias, "alias", "", "alias name (required)")
+	cmd.Flags().StringVar(&provider, "provider", "", "upstream provider id (required)")
+	cmd.Flags().StringVar(&model, "model", "", "upstream model id (required)")
+	return cmd
+}
+
+func newAliasRemoveCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "remove <alias>",
+		Args:  cobra.ExactArgs(1),
+		Short: "Delete an alias entirely",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			if !cfg.RemoveAlias(args[0]) {
+				return fmt.Errorf("alias %q not found", args[0])
+			}
+			if err := cfg.Save(); err != nil {
+				return err
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "removed alias %q\n", args[0])
+			return nil
+		},
+	}
+}
+
+// unused helper kept for clarity if future commands want to normalize lists
+var _ = strings.TrimSpace
diff --git a/internal/cli/doctor.go b/internal/cli/doctor.go
new file mode 100644
index 0000000..9c736e5
--- /dev/null
+++ b/internal/cli/doctor.go
@@ -0,0 +1,48 @@
+package cli
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+
+	"github.com/anomalyco/opencode-provider-switch/internal/opencode"
+)
+
+func newDoctorCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "doctor",
+		Short: "Validate ops config (static checks, no upstream requests)",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			issues := cfg.Validate()
+			ok := len(issues) == 0
+			if ok {
+				fmt.Fprintf(cmd.OutOrStdout(), "✓ config loaded: %s\n", cfg.Path())
+			} else {
+				fmt.Fprintf(cmd.OutOrStdout(), "✗ config has %d issue(s):\n", len(issues))
+				for _, e := range issues {
+					fmt.Fprintf(cmd.OutOrStdout(), "  - %s\n", e)
+				}
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "  providers: %d\n", len(cfg.Providers))
+			fmt.Fprintf(cmd.OutOrStdout(), "  aliases:   %d\n", len(cfg.Aliases))
+
+			// Preview resolved opencode config target
+			path, existed := opencode.ResolveGlobalConfigPath()
+			marker := "(will be created)"
+			if existed {
+				marker = "(exists)"
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "  opencode config target: %s %s\n", path, marker)
+
+			fmt.Fprintf(cmd.OutOrStdout(), "  proxy bind: %s:%d\n", cfg.Server.Host, cfg.Server.Port)
+			if !ok {
+				return fmt.Errorf("%d config issue(s)", len(issues))
+			}
+			return nil
+		},
+	}
+}
diff --git a/internal/cli/opencode.go b/internal/cli/opencode.go
new file mode 100644
index 0000000..a16643c
--- /dev/null
+++ b/internal/cli/opencode.go
@@ -0,0 +1,101 @@
+package cli
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+
+	"github.com/anomalyco/opencode-provider-switch/internal/opencode"
+)
+
+func newOpencodeCmd() *cobra.Command {
+	c := &cobra.Command{
+		Use:   "opencode",
+		Short: "OpenCode integration commands",
+	}
+	c.AddCommand(newOpencodeSyncCmd())
+	return c
+}
+
+func newOpencodeSyncCmd() *cobra.Command {
+	var target string
+	var setModel string
+	var setSmallModel string
+	var dryRun bool
+	cmd := &cobra.Command{
+		Use:   "sync",
+		Short: "Update provider.ops in the global OpenCode config to match current aliases",
+		Long: `ops opencode sync writes provider.ops into the target OpenCode config.
+
+By default it targets the global user config (~/.config/opencode), picking the
+existing file in precedence order opencode.jsonc > opencode.json > config.json,
+or creating opencode.jsonc if none exists. It does NOT touch the top-level
+"model" or "small_model" unless --set-model / --set-small-model are given.`,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			if errs := cfg.Validate(); len(errs) > 0 {
+				for _, e := range errs {
+					cmd.PrintErrln("config error:", e)
+				}
+				return errs[0]
+			}
+			path := target
+			if path == "" {
+				p, _ := opencode.ResolveGlobalConfigPath()
+				path = p
+			}
+			raw, err := opencode.Load(path)
+			if err != nil {
+				return err
+			}
+			aliasNames := []string{}
+			for _, a := range cfg.Aliases {
+				if !a.Enabled {
+					continue
+				}
+				aliasNames = append(aliasNames, a.Alias)
+			}
+			baseURL := fmt.Sprintf("http://%s:%d/v1", cfg.Server.Host, cfg.Server.Port)
+			changed := opencode.EnsureOpsProvider(raw, baseURL, cfg.Server.APIKey, aliasNames)
+			if setModel != "" {
+				if raw["model"] != setModel {
+					raw["model"] = setModel
+					changed = true
+				}
+			}
+			if setSmallModel != "" {
+				if raw["small_model"] != setSmallModel {
+					raw["small_model"] = setSmallModel
+					changed = true
+				}
+			}
+			if !changed {
+				fmt.Fprintf(cmd.OutOrStdout(), "✓ no changes required at %s\n", path)
+				return nil
+			}
+			if dryRun {
+				fmt.Fprintf(cmd.OutOrStdout(), "would write %s (dry-run)\n", path)
+				return nil
+			}
+			if err := opencode.Save(path, raw); err != nil {
+				return err
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "synced provider.ops into %s (%d alias(es))\n", path, len(aliasNames))
+			if setModel != "" {
+				fmt.Fprintf(cmd.OutOrStdout(), "  model = %s\n", setModel)
+			}
+			if setSmallModel != "" {
+				fmt.Fprintf(cmd.OutOrStdout(), "  small_model = %s\n", setSmallModel)
+			}
+			return nil
+		},
+	}
+	cmd.Flags().StringVar(&target, "target", "", "explicit opencode config file to write (default: global)")
+	cmd.Flags().StringVar(&setModel, "set-model", "", "also set top-level model (opt-in only)")
+	cmd.Flags().StringVar(&setSmallModel, "set-small-model", "", "also set top-level small_model (opt-in only)")
+	cmd.Flags().BoolVar(&dryRun, "dry-run", false, "do not write, just report intent")
+	return cmd
+}
diff --git a/internal/cli/provider.go b/internal/cli/provider.go
new file mode 100644
index 0000000..71adc62
--- /dev/null
+++ b/internal/cli/provider.go
@@ -0,0 +1,180 @@
+package cli
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/spf13/cobra"
+
+	"github.com/anomalyco/opencode-provider-switch/internal/config"
+	"github.com/anomalyco/opencode-provider-switch/internal/opencode"
+)
+
+func newProviderCmd() *cobra.Command {
+	c := &cobra.Command{
+		Use:   "provider",
+		Short: "Manage upstream providers",
+	}
+	c.AddCommand(newProviderAddCmd(), newProviderListCmd(), newProviderRemoveCmd(), newProviderImportCmd())
+	return c
+}
+
+func newProviderAddCmd() *cobra.Command {
+	var id, name, baseURL, apiKey string
+	var headers []string
+	cmd := &cobra.Command{
+		Use:   "add",
+		Short: "Add or update an upstream provider",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if id == "" || baseURL == "" {
+				return fmt.Errorf("--id and --base-url are required")
+			}
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			hdrs := map[string]string{}
+			for _, h := range headers {
+				k, v, ok := strings.Cut(h, "=")
+				if !ok {
+					return fmt.Errorf("invalid --header %q (want KEY=VALUE)", h)
+				}
+				hdrs[strings.TrimSpace(k)] = strings.TrimSpace(v)
+			}
+			cfg.UpsertProvider(config.Provider{
+				ID:      id,
+				Name:    name,
+				BaseURL: baseURL,
+				APIKey:  apiKey,
+				Headers: hdrs,
+			})
+			if err := cfg.Save(); err != nil {
+				return err
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "saved provider %q → %s\n", id, baseURL)
+			return nil
+		},
+	}
+	cmd.Flags().StringVar(&id, "id", "", "provider id (required)")
+	cmd.Flags().StringVar(&name, "name", "", "display name")
+	cmd.Flags().StringVar(&baseURL, "base-url", "", "OpenAI-compatible base URL, including /v1 (required)")
+	cmd.Flags().StringVar(&apiKey, "api-key", "", "upstream API key")
+	cmd.Flags().StringArrayVar(&headers, "header", nil, "extra header KEY=VALUE (repeatable)")
+	return cmd
+}
+
+func newProviderListCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "list",
+		Short: "List configured providers",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			providers := append([]config.Provider(nil), cfg.Providers...)
+			sort.Slice(providers, func(i, j int) bool { return providers[i].ID < providers[j].ID })
+			if len(providers) == 0 {
+				fmt.Fprintln(cmd.OutOrStdout(), "(no providers)")
+				return nil
+			}
+			for _, p := range providers {
+				key := "(none)"
+				if p.APIKey != "" {
+					key = maskKey(p.APIKey)
+				}
+				fmt.Fprintf(cmd.OutOrStdout(), "%-20s %s  apiKey=%s\n", p.ID, p.BaseURL, key)
+			}
+			return nil
+		},
+	}
+}
+
+func newProviderRemoveCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "remove <id>",
+		Args:  cobra.ExactArgs(1),
+		Short: "Remove a provider (targets referencing it must be removed first or will fail doctor)",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			if !cfg.RemoveProvider(args[0]) {
+				return fmt.Errorf("provider %q not found", args[0])
+			}
+			if err := cfg.Save(); err != nil {
+				return err
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "removed provider %q\n", args[0])
+			return nil
+		},
+	}
+}
+
+func newProviderImportCmd() *cobra.Command {
+	var srcPath string
+	var overwrite bool
+	cmd := &cobra.Command{
+		Use:   "import-opencode",
+		Short: "Import @ai-sdk/openai custom providers from an OpenCode config file",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if srcPath == "" {
+				p, existed := opencode.ResolveGlobalConfigPath()
+				if !existed {
+					return fmt.Errorf("no OpenCode config found at %s; use --from to specify", p)
+				}
+				srcPath = p
+			}
+			raw, err := opencode.Load(srcPath)
+			if err != nil {
+				return err
+			}
+			imports := opencode.ImportCustomProviders(raw)
+			if len(imports) == 0 {
+				fmt.Fprintf(cmd.OutOrStdout(), "no importable @ai-sdk/openai providers found in %s\n", srcPath)
+				return nil
+			}
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			imported := 0
+			skipped := 0
+			for _, ip := range imports {
+				if !overwrite && cfg.FindProvider(ip.ID) != nil {
+					skipped++
+					fmt.Fprintf(cmd.OutOrStdout(), "skip %q (already exists, use --overwrite)\n", ip.ID)
+					continue
+				}
+				cfg.UpsertProvider(config.Provider{
+					ID:      ip.ID,
+					Name:    ip.Name,
+					BaseURL: ip.BaseURL,
+					APIKey:  ip.APIKey,
+				})
+				imported++
+				fmt.Fprintf(cmd.OutOrStdout(), "import %q → %s (models: %s)\n", ip.ID, ip.BaseURL, strings.Join(ip.Models, ","))
+			}
+			if imported > 0 {
+				if err := cfg.Save(); err != nil {
+					return err
+				}
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "imported=%d skipped=%d\n", imported, skipped)
+			return nil
+		},
+	}
+	cmd.Flags().StringVar(&srcPath, "from", "", "OpenCode config to read (default: global user config)")
+	cmd.Flags().BoolVar(&overwrite, "overwrite", false, "overwrite existing provider entries")
+	return cmd
+}
+
+// maskKey redacts middle characters of an API key for display.
+func maskKey(k string) string {
+	if len(k) <= 8 {
+		return "***"
+	}
+	return k[:4] + "…" + k[len(k)-4:]
+}
diff --git a/internal/cli/root.go b/internal/cli/root.go
new file mode 100644
index 0000000..9b765e9
--- /dev/null
+++ b/internal/cli/root.go
@@ -0,0 +1,44 @@
+// Package cli wires the ops cobra command tree.
+package cli
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+
+	"github.com/anomalyco/opencode-provider-switch/internal/config"
+)
+
+// configPath is populated from the global --config flag.
+var configPath string
+
+// loadCfg opens the active ops config, with the selected path.
+func loadCfg() (*config.Config, error) {
+	return config.Load(configPath)
+}
+
+// NewRootCmd builds the root ops command.
+func NewRootCmd(version string) *cobra.Command {
+	root := &cobra.Command{
+		Use:           "ops",
+		Short:         "opencode-provider-switch: local alias + failover proxy for OpenCode",
+		SilenceUsage:  true,
+		SilenceErrors: false,
+		Version:       version,
+	}
+	root.PersistentFlags().StringVar(&configPath, "config", "", "path to ops config.json (default: $XDG_CONFIG_HOME/ops/config.json)")
+
+	root.AddCommand(newServeCmd())
+	root.AddCommand(newDoctorCmd())
+	root.AddCommand(newProviderCmd())
+	root.AddCommand(newAliasCmd())
+	root.AddCommand(newOpencodeCmd())
+	return root
+}
+
+// fail prints to stderr and exits 1.
+func fail(format string, args ...any) {
+	fmt.Fprintf(os.Stderr, "error: "+format+"\n", args...)
+	os.Exit(1)
+}
diff --git a/internal/cli/serve.go b/internal/cli/serve.go
new file mode 100644
index 0000000..fea1cd7
--- /dev/null
+++ b/internal/cli/serve.go
@@ -0,0 +1,33 @@
+package cli
+
+import (
+	"os/signal"
+	"syscall"
+
+	"github.com/spf13/cobra"
+
+	"github.com/anomalyco/opencode-provider-switch/internal/proxy"
+)
+
+func newServeCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "serve",
+		Short: "Run the local ops proxy (alias → failover upstream)",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			cfg, err := loadCfg()
+			if err != nil {
+				return err
+			}
+			if errs := cfg.Validate(); len(errs) > 0 {
+				for _, e := range errs {
+					cmd.PrintErrln("config error:", e)
+				}
+				return errs[0]
+			}
+			srv := proxy.New(cfg)
+			ctx, stop := signal.NotifyContext(cmd.Context(), syscall.SIGINT, syscall.SIGTERM)
+			defer stop()
+			return srv.ListenAndServe(ctx)
+		},
+	}
+}
diff --git a/internal/config/config.go b/internal/config/config.go
new file mode 100644
index 0000000..4db04b1
--- /dev/null
+++ b/internal/config/config.go
@@ -0,0 +1,322 @@
+// Package config manages the local ops JSON config file.
+package config
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"sync"
+)
+
+// Target is one concrete upstream candidate for an alias.
+type Target struct {
+	Provider string `json:"provider"`
+	Model    string `json:"model"`
+	Enabled  bool   `json:"enabled"`
+}
+
+// Alias maps a logical model name to ordered upstream targets.
+type Alias struct {
+	Alias       string   `json:"alias"`
+	DisplayName string   `json:"display_name,omitempty"`
+	Enabled     bool     `json:"enabled"`
+	Targets     []Target `json:"targets"`
+}
+
+// Provider is one upstream OpenAI-compatible endpoint.
+type Provider struct {
+	ID      string            `json:"id"`
+	Name    string            `json:"name,omitempty"`
+	BaseURL string            `json:"base_url"`
+	APIKey  string            `json:"api_key"`
+	Headers map[string]string `json:"headers,omitempty"`
+}
+
+// Server holds proxy listen settings.
+type Server struct {
+	Host   string `json:"host"`
+	Port   int    `json:"port"`
+	APIKey string `json:"api_key"`
+}
+
+// Config is the on-disk ops config.
+type Config struct {
+	Server    Server     `json:"server"`
+	Providers []Provider `json:"providers"`
+	Aliases   []Alias    `json:"aliases"`
+
+	path string
+	mu   sync.RWMutex
+}
+
+// Default returns an empty config with sane defaults.
+func Default() *Config {
+	return &Config{
+		Server: Server{
+			Host:   "127.0.0.1",
+			Port:   9982,
+			APIKey: "ops-local",
+		},
+		Providers: []Provider{},
+		Aliases:   []Alias{},
+	}
+}
+
+// DefaultPath returns ~/.config/ops/config.json (XDG aware).
+func DefaultPath() string {
+	if p := os.Getenv("OPS_CONFIG"); p != "" {
+		return p
+	}
+	if xdg := os.Getenv("XDG_CONFIG_HOME"); xdg != "" {
+		return filepath.Join(xdg, "ops", "config.json")
+	}
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "ops-config.json"
+	}
+	return filepath.Join(home, ".config", "ops", "config.json")
+}
+
+// Load reads the config at path. Missing file returns a default config anchored to path.
+func Load(path string) (*Config, error) {
+	if path == "" {
+		path = DefaultPath()
+	}
+	c := Default()
+	c.path = path
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return c, nil
+		}
+		return nil, fmt.Errorf("read config: %w", err)
+	}
+	if len(data) == 0 {
+		return c, nil
+	}
+	if err := json.Unmarshal(data, c); err != nil {
+		return nil, fmt.Errorf("parse config: %w", err)
+	}
+	if c.Server.Host == "" {
+		c.Server.Host = "127.0.0.1"
+	}
+	if c.Server.Port == 0 {
+		c.Server.Port = 9982
+	}
+	if c.Server.APIKey == "" {
+		c.Server.APIKey = "ops-local"
+	}
+	c.path = path
+	return c, nil
+}
+
+// Path returns the on-disk path of this config.
+func (c *Config) Path() string { return c.path }
+
+// Save writes config atomically.
+func (c *Config) Save() error {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	if c.path == "" {
+		c.path = DefaultPath()
+	}
+	if err := os.MkdirAll(filepath.Dir(c.path), 0o755); err != nil {
+		return fmt.Errorf("mkdir: %w", err)
+	}
+	// sort for stability
+	providers := append([]Provider(nil), c.Providers...)
+	sort.Slice(providers, func(i, j int) bool { return providers[i].ID < providers[j].ID })
+	aliases := append([]Alias(nil), c.Aliases...)
+	sort.Slice(aliases, func(i, j int) bool { return aliases[i].Alias < aliases[j].Alias })
+	snap := struct {
+		Server    Server     `json:"server"`
+		Providers []Provider `json:"providers"`
+		Aliases   []Alias    `json:"aliases"`
+	}{c.Server, providers, aliases}
+	data, err := json.MarshalIndent(snap, "", "  ")
+	if err != nil {
+		return fmt.Errorf("marshal: %w", err)
+	}
+	data = append(data, '\n')
+	tmp := c.path + ".tmp"
+	if err := os.WriteFile(tmp, data, 0o600); err != nil {
+		return fmt.Errorf("write tmp: %w", err)
+	}
+	return os.Rename(tmp, c.path)
+}
+
+// FindProvider returns the provider with matching id or nil.
+func (c *Config) FindProvider(id string) *Provider {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	for i := range c.Providers {
+		if c.Providers[i].ID == id {
+			return &c.Providers[i]
+		}
+	}
+	return nil
+}
+
+// UpsertProvider adds or replaces a provider by id.
+func (c *Config) UpsertProvider(p Provider) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for i := range c.Providers {
+		if c.Providers[i].ID == p.ID {
+			c.Providers[i] = p
+			return
+		}
+	}
+	c.Providers = append(c.Providers, p)
+}
+
+// RemoveProvider deletes a provider and returns true if removed.
+func (c *Config) RemoveProvider(id string) bool {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for i := range c.Providers {
+		if c.Providers[i].ID == id {
+			c.Providers = append(c.Providers[:i], c.Providers[i+1:]...)
+			return true
+		}
+	}
+	return false
+}
+
+// FindAlias returns the alias record with matching name or nil.
+func (c *Config) FindAlias(name string) *Alias {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	for i := range c.Aliases {
+		if c.Aliases[i].Alias == name {
+			return &c.Aliases[i]
+		}
+	}
+	return nil
+}
+
+// UpsertAlias adds or replaces an alias.
+func (c *Config) UpsertAlias(a Alias) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for i := range c.Aliases {
+		if c.Aliases[i].Alias == a.Alias {
+			c.Aliases[i] = a
+			return
+		}
+	}
+	c.Aliases = append(c.Aliases, a)
+}
+
+// RemoveAlias deletes an alias.
+func (c *Config) RemoveAlias(name string) bool {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for i := range c.Aliases {
+		if c.Aliases[i].Alias == name {
+			c.Aliases = append(c.Aliases[:i], c.Aliases[i+1:]...)
+			return true
+		}
+	}
+	return false
+}
+
+// AddTarget appends a target to an alias; creates alias if missing.
+func (c *Config) AddTarget(alias string, t Target) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for i := range c.Aliases {
+		if c.Aliases[i].Alias == alias {
+			// prevent exact duplicate
+			for _, x := range c.Aliases[i].Targets {
+				if x.Provider == t.Provider && x.Model == t.Model {
+					return fmt.Errorf("target %s/%s already bound to alias %s", t.Provider, t.Model, alias)
+				}
+			}
+			c.Aliases[i].Targets = append(c.Aliases[i].Targets, t)
+			return nil
+		}
+	}
+	return fmt.Errorf("alias %q not found", alias)
+}
+
+// RemoveTarget removes a target by provider+model.
+func (c *Config) RemoveTarget(alias, provider, model string) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for i := range c.Aliases {
+		if c.Aliases[i].Alias != alias {
+			continue
+		}
+		out := c.Aliases[i].Targets[:0]
+		found := false
+		for _, t := range c.Aliases[i].Targets {
+			if t.Provider == provider && t.Model == model {
+				found = true
+				continue
+			}
+			out = append(out, t)
+		}
+		if !found {
+			return fmt.Errorf("target %s/%s not found on alias %s", provider, model, alias)
+		}
+		c.Aliases[i].Targets = out
+		return nil
+	}
+	return fmt.Errorf("alias %q not found", alias)
+}
+
+// Validate returns a non-nil error slice for every structural issue found.
+func (c *Config) Validate() []error {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	var errs []error
+	ids := map[string]bool{}
+	for _, p := range c.Providers {
+		if p.ID == "" {
+			errs = append(errs, fmt.Errorf("provider with empty id"))
+			continue
+		}
+		if ids[p.ID] {
+			errs = append(errs, fmt.Errorf("duplicate provider id %q", p.ID))
+		}
+		ids[p.ID] = true
+		if p.BaseURL == "" {
+			errs = append(errs, fmt.Errorf("provider %q missing base_url", p.ID))
+		}
+	}
+	seen := map[string]bool{}
+	for _, a := range c.Aliases {
+		if a.Alias == "" {
+			errs = append(errs, fmt.Errorf("alias with empty name"))
+			continue
+		}
+		if seen[a.Alias] {
+			errs = append(errs, fmt.Errorf("duplicate alias %q", a.Alias))
+		}
+		seen[a.Alias] = true
+		enabled := 0
+		for _, t := range a.Targets {
+			if t.Provider == "" || t.Model == "" {
+				errs = append(errs, fmt.Errorf("alias %q has malformed target", a.Alias))
+				continue
+			}
+			if !ids[t.Provider] {
+				errs = append(errs, fmt.Errorf("alias %q references unknown provider %q", a.Alias, t.Provider))
+			}
+			if t.Enabled {
+				enabled++
+			}
+		}
+		if a.Enabled && enabled == 0 {
+			errs = append(errs, fmt.Errorf("alias %q has no enabled targets", a.Alias))
+		}
+	}
+	if c.Server.Port <= 0 || c.Server.Port > 65535 {
+		errs = append(errs, fmt.Errorf("invalid server port %d", c.Server.Port))
+	}
+	return errs
+}
diff --git a/internal/opencode/opencode.go b/internal/opencode/opencode.go
new file mode 100644
index 0000000..f5844b0
--- /dev/null
+++ b/internal/opencode/opencode.go
@@ -0,0 +1,248 @@
+// Package opencode reads and writes OpenCode config files, including the
+// `provider.ops` sync path. Files may be JSON or JSONC; we preserve the
+// detected extension on write.
+package opencode
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/tidwall/jsonc"
+)
+
+// ConfigFileCandidates is the precedence order inside the global config dir.
+var ConfigFileCandidates = []string{"opencode.jsonc", "opencode.json", "config.json"}
+
+// GlobalConfigDir returns the default user-global OpenCode config directory.
+func GlobalConfigDir() string {
+	if dir := os.Getenv("OPENCODE_CONFIG_DIR"); dir != "" {
+		return dir
+	}
+	if xdg := os.Getenv("XDG_CONFIG_HOME"); xdg != "" {
+		return filepath.Join(xdg, "opencode")
+	}
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "."
+	}
+	return filepath.Join(home, ".config", "opencode")
+}
+
+// ResolveGlobalConfigPath returns the existing global config file if any,
+// otherwise the default target path (opencode.jsonc).
+func ResolveGlobalConfigPath() (path string, existed bool) {
+	dir := GlobalConfigDir()
+	for _, name := range ConfigFileCandidates {
+		p := filepath.Join(dir, name)
+		if _, err := os.Stat(p); err == nil {
+			return p, true
+		}
+	}
+	return filepath.Join(dir, "opencode.jsonc"), false
+}
+
+// Raw is the JSON object form of an OpenCode config. We treat it as a generic
+// map so unknown fields pass through untouched on write.
+type Raw map[string]any
+
+// Load reads an OpenCode config file. Missing files yield an empty Raw.
+// JSONC (line/block comments, trailing commas) is supported on read, but the
+// write side always emits plain JSON (comments are not preserved).
+func Load(path string) (Raw, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return Raw{}, nil
+		}
+		return nil, fmt.Errorf("read %s: %w", path, err)
+	}
+	if len(data) == 0 {
+		return Raw{}, nil
+	}
+	stripped := jsonc.ToJSON(data)
+	out := Raw{}
+	if err := json.Unmarshal(stripped, &out); err != nil {
+		return nil, fmt.Errorf("parse %s: %w", path, err)
+	}
+	return out, nil
+}
+
+// Save writes Raw back to path. Parent dirs are created. Writes are atomic.
+func Save(path string, raw Raw) error {
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return fmt.Errorf("mkdir: %w", err)
+	}
+	// ensure $schema first; tidwall/jsonc indent not needed — plain JSON is fine.
+	data, err := json.MarshalIndent(raw, "", "  ")
+	if err != nil {
+		return fmt.Errorf("marshal: %w", err)
+	}
+	data = append(data, '\n')
+	tmp := path + ".tmp"
+	if err := os.WriteFile(tmp, data, 0o600); err != nil {
+		return fmt.Errorf("write tmp: %w", err)
+	}
+	return os.Rename(tmp, path)
+}
+
+// EnsureOpsProvider updates (or creates) the provider.ops entry with the given
+// local base URL, local api key and alias set. Existing keys on provider.ops
+// are preserved unless they conflict with the sync intent. Returns true if the
+// file would actually change.
+func EnsureOpsProvider(raw Raw, baseURL, apiKey string, aliases []string) bool {
+	changed := false
+	if _, ok := raw["$schema"]; !ok {
+		raw["$schema"] = "https://opencode.ai/config.json"
+		changed = true
+	}
+	provRaw, _ := raw["provider"].(map[string]any)
+	if provRaw == nil {
+		provRaw = map[string]any{}
+		raw["provider"] = provRaw
+		changed = true
+	}
+	opsRaw, _ := provRaw["ops"].(map[string]any)
+	if opsRaw == nil {
+		opsRaw = map[string]any{}
+		provRaw["ops"] = opsRaw
+		changed = true
+	}
+	if setIfDiff(opsRaw, "npm", "@ai-sdk/openai") {
+		changed = true
+	}
+	if setIfDiff(opsRaw, "name", "OPS") {
+		changed = true
+	}
+	opts, _ := opsRaw["options"].(map[string]any)
+	if opts == nil {
+		opts = map[string]any{}
+		opsRaw["options"] = opts
+		changed = true
+	}
+	if setIfDiff(opts, "baseURL", baseURL) {
+		changed = true
+	}
+	if setIfDiff(opts, "apiKey", apiKey) {
+		changed = true
+	}
+	// Build models map from alias list. Preserve any existing per-model extras
+	// if the alias key matches; drop aliases removed locally.
+	existingModels, _ := opsRaw["models"].(map[string]any)
+	newModels := map[string]any{}
+	aliasSet := map[string]bool{}
+	for _, a := range aliases {
+		aliasSet[a] = true
+		if existing, ok := existingModels[a].(map[string]any); ok {
+			// make sure "name" stays consistent with alias key
+			if setIfDiff(existing, "name", a) {
+				changed = true
+			}
+			newModels[a] = existing
+		} else {
+			newModels[a] = map[string]any{"name": a}
+			changed = true
+		}
+	}
+	// removed entries?
+	for k := range existingModels {
+		if !aliasSet[k] {
+			changed = true
+		}
+	}
+	if !mapsEqualShallow(existingModels, newModels) {
+		opsRaw["models"] = newModels
+	}
+	return changed
+}
+
+// setIfDiff assigns key=val and returns true if the value actually changed.
+func setIfDiff(m map[string]any, key string, val any) bool {
+	cur, ok := m[key]
+	if ok && cur == val {
+		return false
+	}
+	m[key] = val
+	return true
+}
+
+// ImportableProvider is a subset extracted from an OpenCode custom provider.
+type ImportableProvider struct {
+	ID      string
+	Name    string
+	BaseURL string
+	APIKey  string
+	Models  []string
+}
+
+// ImportCustomProviders scans raw for @ai-sdk/openai custom providers that
+// declare baseURL and an apiKey-compatible setting. The `ops` id itself is
+// skipped so sync output is not re-imported.
+func ImportCustomProviders(raw Raw) []ImportableProvider {
+	out := []ImportableProvider{}
+	provRaw, _ := raw["provider"].(map[string]any)
+	for id, v := range provRaw {
+		if id == "ops" {
+			continue
+		}
+		m, ok := v.(map[string]any)
+		if !ok {
+			continue
+		}
+		npm, _ := m["npm"].(string)
+		if npm != "@ai-sdk/openai" {
+			continue
+		}
+		opts, _ := m["options"].(map[string]any)
+		if opts == nil {
+			continue
+		}
+		baseURL, _ := opts["baseURL"].(string)
+		apiKey, _ := opts["apiKey"].(string)
+		if baseURL == "" {
+			continue
+		}
+		ip := ImportableProvider{
+			ID:      id,
+			BaseURL: baseURL,
+			APIKey:  apiKey,
+		}
+		if n, ok := m["name"].(string); ok {
+			ip.Name = n
+		}
+		if models, ok := m["models"].(map[string]any); ok {
+			for k := range models {
+				ip.Models = append(ip.Models, k)
+			}
+		}
+		out = append(out, ip)
+	}
+	return out
+}
+
+// mapsEqualShallow compares two string-keyed maps for structural equality.
+func mapsEqualShallow(a, b map[string]any) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for k, v := range a {
+		bv, ok := b[k]
+		if !ok {
+			return false
+		}
+		am, amOk := v.(map[string]any)
+		bm, bmOk := bv.(map[string]any)
+		if amOk && bmOk {
+			if !mapsEqualShallow(am, bm) {
+				return false
+			}
+			continue
+		}
+		if v != bv {
+			return false
+		}
+	}
+	return true
+}
diff --git a/internal/proxy/server.go b/internal/proxy/server.go
new file mode 100644
index 0000000..30ece2a
--- /dev/null
+++ b/internal/proxy/server.go
@@ -0,0 +1,357 @@
+// Package proxy implements the local `/v1/responses` HTTP server that resolves
+// ops aliases and forwards requests to upstream providers with deterministic
+// pre-first-byte failover.
+package proxy
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"strings"
+	"sync/atomic"
+	"time"
+
+	"github.com/anomalyco/opencode-provider-switch/internal/config"
+)
+
+// Server is the local ops HTTP proxy.
+type Server struct {
+	cfg    *config.Config
+	client *http.Client
+	logger *log.Logger
+}
+
+// New constructs a Server from cfg.
+func New(cfg *config.Config) *Server {
+	transport := &http.Transport{
+		Proxy: http.ProxyFromEnvironment,
+		DialContext: (&net.Dialer{
+			Timeout:   10 * time.Second,
+			KeepAlive: 30 * time.Second,
+		}).DialContext,
+		MaxIdleConns:          100,
+		IdleConnTimeout:       90 * time.Second,
+		TLSHandshakeTimeout:   10 * time.Second,
+		ExpectContinueTimeout: 1 * time.Second,
+		// no response buffering so streams flow through immediately
+		DisableCompression: false,
+		ForceAttemptHTTP2:  true,
+	}
+	return &Server{
+		cfg: cfg,
+		client: &http.Client{
+			Transport: transport,
+			Timeout:   0, // streaming, no overall timeout
+		},
+		logger: log.New(log.Writer(), "[ops] ", log.LstdFlags|log.Lmicroseconds),
+	}
+}
+
+// ListenAndServe starts the HTTP listener until ctx is cancelled.
+func (s *Server) ListenAndServe(ctx context.Context) error {
+	addr := fmt.Sprintf("%s:%d", s.cfg.Server.Host, s.cfg.Server.Port)
+	mux := http.NewServeMux()
+	mux.HandleFunc("/v1/responses", s.handleResponses)
+	mux.HandleFunc("/v1/models", s.handleModels)
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"status":"ok"}`))
+	})
+	srv := &http.Server{
+		Addr:              addr,
+		Handler:           mux,
+		ReadHeaderTimeout: 10 * time.Second,
+	}
+	errCh := make(chan error, 1)
+	go func() { errCh <- srv.ListenAndServe() }()
+	s.logger.Printf("listening on http://%s", addr)
+	select {
+	case <-ctx.Done():
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		return srv.Shutdown(shutdownCtx)
+	case err := <-errCh:
+		if errors.Is(err, http.ErrServerClosed) {
+			return nil
+		}
+		return err
+	}
+}
+
+// handleModels exposes a minimal /v1/models listing of alias names. OpenCode
+// does not rely on this, but clients sometimes probe it for connectivity.
+func (s *Server) handleModels(w http.ResponseWriter, r *http.Request) {
+	if !s.authorize(r) {
+		http.Error(w, "unauthorized", http.StatusUnauthorized)
+		return
+	}
+	data := []map[string]any{}
+	for _, a := range s.cfg.Aliases {
+		if !a.Enabled {
+			continue
+		}
+		data = append(data, map[string]any{
+			"id":       a.Alias,
+			"object":   "model",
+			"owned_by": "ops",
+		})
+	}
+	w.Header().Set("Content-Type", "application/json")
+	_ = json.NewEncoder(w).Encode(map[string]any{"object": "list", "data": data})
+}
+
+// authorize enforces the static local api key when one is configured.
+func (s *Server) authorize(r *http.Request) bool {
+	expected := s.cfg.Server.APIKey
+	if expected == "" {
+		return true
+	}
+	h := r.Header.Get("Authorization")
+	if strings.HasPrefix(h, "Bearer ") {
+		return strings.TrimPrefix(h, "Bearer ") == expected
+	}
+	if k := r.Header.Get("X-Api-Key"); k != "" {
+		return k == expected
+	}
+	return false
+}
+
+var reqCounter uint64
+
+// handleResponses is the main alias→failover proxy entry.
+func (s *Server) handleResponses(w http.ResponseWriter, r *http.Request) {
+	reqID := atomic.AddUint64(&reqCounter, 1)
+	if r.Method != http.MethodPost {
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	if !s.authorize(r) {
+		http.Error(w, "unauthorized", http.StatusUnauthorized)
+		return
+	}
+	body, err := io.ReadAll(http.MaxBytesReader(w, r.Body, 50<<20))
+	if err != nil {
+		http.Error(w, "read body: "+err.Error(), http.StatusBadRequest)
+		return
+	}
+	var payload map[string]any
+	if err := json.Unmarshal(body, &payload); err != nil {
+		http.Error(w, "invalid json: "+err.Error(), http.StatusBadRequest)
+		return
+	}
+	aliasName, _ := payload["model"].(string)
+	if aliasName == "" {
+		http.Error(w, "missing model field", http.StatusBadRequest)
+		return
+	}
+	alias := s.cfg.FindAlias(aliasName)
+	if alias == nil {
+		http.Error(w, fmt.Sprintf("alias %q not found", aliasName), http.StatusNotFound)
+		return
+	}
+	if !alias.Enabled {
+		http.Error(w, fmt.Sprintf("alias %q is disabled", aliasName), http.StatusNotFound)
+		return
+	}
+	var targets []config.Target
+	for _, t := range alias.Targets {
+		if t.Enabled {
+			targets = append(targets, t)
+		}
+	}
+	if len(targets) == 0 {
+		http.Error(w, fmt.Sprintf("alias %q has no enabled targets", aliasName), http.StatusFailedDependency)
+		return
+	}
+
+	failoverCount := 0
+	for attempt, t := range targets {
+		p := s.cfg.FindProvider(t.Provider)
+		if p == nil {
+			s.logger.Printf("req=%d alias=%s attempt=%d target provider %q missing, skipping", reqID, aliasName, attempt+1, t.Provider)
+			failoverCount++
+			continue
+		}
+		// rewrite payload.model for this upstream
+		cloned := cloneMap(payload)
+		cloned["model"] = t.Model
+		newBody, err := json.Marshal(cloned)
+		if err != nil {
+			s.logger.Printf("req=%d marshal error: %v", reqID, err)
+			http.Error(w, "marshal error", http.StatusInternalServerError)
+			return
+		}
+
+		ok, retryable, upstreamErr := s.tryOnce(r.Context(), w, r, p, t, newBody, aliasName, attempt+1, failoverCount)
+		if ok {
+			return
+		}
+		if !retryable {
+			// final — response was either already committed or unrecoverable
+			s.logger.Printf("req=%d alias=%s attempt=%d final failure: %v", reqID, aliasName, attempt+1, upstreamErr)
+			return
+		}
+		s.logger.Printf("req=%d alias=%s attempt=%d retryable: %v", reqID, aliasName, attempt+1, upstreamErr)
+		failoverCount++
+	}
+
+	// exhausted all targets with retryable failures
+	http.Error(w, fmt.Sprintf("all upstream targets failed for alias %q", aliasName), http.StatusBadGateway)
+}
+
+// tryOnce proxies one attempt. Returns (ok, retryable, err).
+// ok=true means successful response fully/partially written to client.
+// retryable=true means failure happened before any bytes flushed downstream.
+func (s *Server) tryOnce(
+	ctx context.Context,
+	w http.ResponseWriter,
+	clientReq *http.Request,
+	provider *config.Provider,
+	target config.Target,
+	body []byte,
+	aliasName string,
+	attempt int,
+	failoverCount int,
+) (ok bool, retryable bool, err error) {
+	upstreamURL := strings.TrimRight(provider.BaseURL, "/") + "/responses"
+	upReq, err := http.NewRequestWithContext(ctx, http.MethodPost, upstreamURL, bytes.NewReader(body))
+	if err != nil {
+		return false, false, fmt.Errorf("build request: %w", err)
+	}
+	copyForwardHeaders(upReq.Header, clientReq.Header)
+	upReq.Header.Set("Content-Type", "application/json")
+	upReq.Header.Set("Accept", clientReq.Header.Get("Accept"))
+	if provider.APIKey != "" {
+		upReq.Header.Set("Authorization", "Bearer "+provider.APIKey)
+	}
+	for k, v := range provider.Headers {
+		upReq.Header.Set(k, v)
+	}
+	upReq.ContentLength = int64(len(body))
+
+	resp, err := s.client.Do(upReq)
+	if err != nil {
+		return false, true, fmt.Errorf("upstream dial/transport: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode >= 500 || resp.StatusCode == 429 {
+		// drain up to small cap for logging context
+		peek, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
+		return false, true, fmt.Errorf("upstream %d: %s", resp.StatusCode, truncate(string(peek), 200))
+	}
+	if resp.StatusCode >= 400 {
+		// non-retryable: forward status + body to client
+		s.writeDebugHeaders(w, aliasName, provider.ID, target.Model, attempt, failoverCount)
+		copyResponseHeaders(w.Header(), resp.Header)
+		w.WriteHeader(resp.StatusCode)
+		_, _ = io.Copy(w, resp.Body)
+		return true, false, fmt.Errorf("upstream %d", resp.StatusCode)
+	}
+
+	// 2xx: start streaming pass-through. From this point no failover is allowed.
+	s.writeDebugHeaders(w, aliasName, provider.ID, target.Model, attempt, failoverCount)
+	copyResponseHeaders(w.Header(), resp.Header)
+	w.WriteHeader(resp.StatusCode)
+	flusher, _ := w.(http.Flusher)
+	buf := make([]byte, 16<<10)
+	for {
+		n, rerr := resp.Body.Read(buf)
+		if n > 0 {
+			if _, werr := w.Write(buf[:n]); werr != nil {
+				return true, false, werr
+			}
+			if flusher != nil {
+				flusher.Flush()
+			}
+		}
+		if rerr != nil {
+			if errors.Is(rerr, io.EOF) {
+				return true, false, nil
+			}
+			// mid-stream error — already committed, cannot failover
+			return true, false, rerr
+		}
+	}
+}
+
+// writeDebugHeaders sets the X-OPS-* debug headers before WriteHeader.
+func (s *Server) writeDebugHeaders(w http.ResponseWriter, alias, provider, remoteModel string, attempt, failoverCount int) {
+	h := w.Header()
+	h.Set("X-OPS-Alias", alias)
+	h.Set("X-OPS-Provider", provider)
+	h.Set("X-OPS-Remote-Model", remoteModel)
+	h.Set("X-OPS-Attempt", fmt.Sprintf("%d", attempt))
+	h.Set("X-OPS-Failover-Count", fmt.Sprintf("%d", failoverCount))
+}
+
+// hopByHopHeaders lists headers that must not be forwarded per RFC 7230.
+var hopByHopHeaders = map[string]bool{
+	"Connection":          true,
+	"Proxy-Connection":    true,
+	"Keep-Alive":          true,
+	"Proxy-Authenticate":  true,
+	"Proxy-Authorization": true,
+	"Te":                  true,
+	"Trailer":             true,
+	"Transfer-Encoding":   true,
+	"Upgrade":             true,
+}
+
+// copyForwardHeaders copies safe request headers from client to upstream,
+// dropping Authorization (the upstream key replaces it) and hop-by-hop headers.
+func copyForwardHeaders(dst, src http.Header) {
+	for k, vs := range src {
+		ck := http.CanonicalHeaderKey(k)
+		if hopByHopHeaders[ck] {
+			continue
+		}
+		switch ck {
+		case "Authorization", "X-Api-Key", "Host", "Content-Length":
+			continue
+		}
+		for _, v := range vs {
+			dst.Add(ck, v)
+		}
+	}
+}
+
+// copyResponseHeaders copies upstream response headers into client response.
+func copyResponseHeaders(dst, src http.Header) {
+	for k, vs := range src {
+		ck := http.CanonicalHeaderKey(k)
+		if hopByHopHeaders[ck] {
+			continue
+		}
+		if ck == "Content-Length" {
+			// We may transform nothing, but streaming responses often omit this.
+			continue
+		}
+		for _, v := range vs {
+			dst.Add(ck, v)
+		}
+	}
+}
+
+// cloneMap performs a shallow copy of a top-level map.
+func cloneMap(m map[string]any) map[string]any {
+	out := make(map[string]any, len(m))
+	for k, v := range m {
+		out[k] = v
+	}
+	return out
+}
+
+// truncate returns s truncated to at most n bytes (best-effort).
+func truncate(s string, n int) string {
+	if len(s) <= n {
+		return s
+	}
+	return s[:n] + "…"
+}