dsh-opencode-session-fallback
A small DeepSeek Harness (DSH) plugin that gives
session-less LLM requests on OpenCode routes a fallback sessionId, so auto permission presets stop
failing every tool call with 400 MissingSessionID.
No global fetch patching, no provider config changes, no official package overrides.
The problem
OpenCode / OpenCode Go reject inference requests that do not carry an x-opencode-session header:
400 {"type":"error","error":{"type":"MissingSessionID","message":"Request is missing x-opencode-session ..."}}
DSH's @deepseek-ai/dsh-llm-pi-ai adapter only lets pi-ai add that header when the request carries a
sessionId. Main conversation calls do carry one — but
@deepseek-ai/dsh-experimental-auto-review builds its reviewer request by hand without a sessionId.
So with the auto permission preset on an opencode-go route:
- every tool call is first sent to the reviewer model,
- that request has no session header → gateway 400,
- the review fails → DSH fails closed → the tool body never runs:
Auto review of tool "pwsh" failed; its body was not executed:
auto-review: reviewer ended with error INVALID_REQUEST: 400: {"type":"MissingSessionID", ...}
The fix
Wrap ctx.llm.stream once at startup. Requests that already carry a sessionId, or that target a
provider outside the configured list, pass through untouched. Only session-less requests on OpenCode
routes (in practice: the auto-review reviewer call) get the configured fallback id; pi-ai then adds
x-opencode-session on its own.
ctx.llm.stream(options)
├─ options.sessionId present .......... pass through (main chat, subagents, compaction, titles)
├─ provider not opencode/opencode-go .. pass through (official DeepSeek etc. untouched)
└─ session-less + OpenCode route ...... { ...options, sessionId: <fallback> }
Why not patch globalThis.fetch (what some other plugins do)? Because replacing the global fetch wraps
every outbound call of the host — including the app's own networking — and can take the whole UI down
with connection errors. This plugin only touches the LLM service method.
Behavior guarantees
- Existing
sessionIds are never replaced → per-conversation routing / prompt-cache affinity is preserved.
- Other providers (for example the official
deepseek provider) are not affected at all.
- Options objects passed by callers are never mutated (a copy is used, so frozen options are fine).
- Uninstalling restores the original
ctx.llm.stream automatically.
- If the service shape changes in a future DSH release, the plugin logs a warning and stays inert instead of
breaking the boot.
Install
Plugins are assembled at DSH startup — restart DSH after installing.
From npm
dsh plugin --profile web add dsh-opencode-session-fallback
Or use the GUI: Settings → Plugins → install, package name dsh-opencode-session-fallback.
From this Git repository
dsh plugin --profile web add git+https://github.com/zlxlsy666/dsh-opencode-session-fallback.git
From a local checkout
dsh plugin --profile web add "file:C:\path\to\dsh-opencode-session-fallback"
The desktop application manages its own desktop profile: use its Plugin Manager UI for that profile
instead of the CLI.
After a successful start the log shows:
[opencode-session-fallback] active for providers [opencode, opencode-go], fallback session id "dsh-opencode-session-fallback"
Configuration (optional)
Override with the same entry id in the profile's cordis.patch.yml:
- id: opencode-session-fallback
name: dsh-opencode-session-fallback
config:
providers: [opencode, opencode-go] # routes that need a session id
fallbackSessionId: my-stable-id # value used when the request has none
debug: false # log every injection
Uninstall
dsh plugin --profile web remove dsh-opencode-session-fallback
Restart DSH afterwards.
Compatibility
- Built and verified against DSH
0.2.1-rc.2 (desktop) with opencode-go + deepseek-v4.1-flash,
where it fixed the failure end-to-end (auto preset, tools execute, reviewer returns normal allow/deny
decisions).
- Requires
ctx.llm.stream to exist (inject: ['llm']); otherwise the plugin logs a warning and does nothing.
- Pairs well with any DSH version that ships the pi-ai OpenCode providers.
Development
node --check lib/index.js
node test/smoke.mjs # 5 assertions, no DSH runtime required
License
MIT
中文说明
解决的问题
OpenCode / OpenCode Go 要求每个推理请求都带 x-opencode-session 头，缺失会返回
400 MissingSessionID。DSH 的 dsh-llm-pi-ai 只在请求带 sessionId 时才让 pi-ai 补这个头，而
@deepseek-ai/dsh-experimental-auto-review 的 reviewer 请求是手工拼的、没有 sessionId。
结果：在 opencode-go 路由 + auto 权限预设下，每次工具调用先过 reviewer → reviewer 请求 400 →
审查失败 → fail-closed → 工具全部无法执行。
修复方式
启动时包一层 ctx.llm.stream：
- 已有
sessionId 的请求（主对话、子代理、压缩、会话标题）原样透传；
- 其他 provider（例如官方
deepseek）完全不受影响；
- 只有「缺 sessionId 且命中 OpenCode 路由」的请求（实际就是 reviewer）补一个兜底 id，
pi-ai 随后自动加上
x-opencode-session。
不接管全局 fetch（那会把宿主自身的出网调用一起包住，可能直接让 UI 报 connection error），
也不修改 provider 配置、不覆盖任何官方包。
安装
插件在 DSH 启动时装配，装完必须重启 DSH。
- npm：
dsh plugin --profile web add dsh-opencode-session-fallback
- GUI：设置 → 插件 → 安装，填包名
- Git：
dsh plugin --profile web add git+https://github.com/zlxlsy666/dsh-opencode-session-fallback.git
- 本地目录：
dsh plugin --profile web add "file:C:\path\to\dsh-opencode-session-fallback"
桌面版的 desktop profile 由应用自己管理，请在应用的插件管理器里安装。
启动日志应出现：
[opencode-session-fallback] active for providers [opencode, opencode-go], fallback session id "dsh-opencode-session-fallback"
可选配置
在 profile 的 cordis.patch.yml 用同 id 覆盖：
- id: opencode-session-fallback
name: dsh-opencode-session-fallback
config:
providers: [opencode, opencode-go]
fallbackSessionId: my-stable-id
debug: false
卸载
从插件管理器卸载（或 dsh plugin --profile web remove dsh-opencode-session-fallback）后重启 DSH，
ctx.llm.stream 会自动恢复。
已验证环境
DSH 0.2.1-rc.2 桌面版 + opencode-go 路由 + deepseek-v4.1-flash：修复后 auto 预设下工具正常执行，
reviewer 能正常返回 allow/deny 决策。
许可
MIT
