dsh-opencode-session

A DeepSeek Harness (dsh) plugin that fixes the 400 MissingSessionID error returned by opencode.ai's gateway (Console Go) — it sends the x-opencode-session header on every opencode / opencode-go request.

Search terms: dsh plugin · DeepSeek Harness · opencode · opencode-go · x-opencode-session · MissingSessionID · Console Go · 400 · cannot be routed efficiently · pi-ai · dsh-plugin

The problem

Since the Console Go gateway started requiring a session header, every opencode / opencode-go model call started from dsh fails with:

400: {"type":"MissingSessionID","message":"Error from provider (Console Go):
Request is missing x-opencode-session and cannot be routed efficiently. Please
see https://opencode.ai/docs/go/#where-can-i-use-it"}

The header names the conversation so the gateway can route the request to the node holding that conversation's cache. The pi coding agent sends it from its provider-attribution layer; the shared library dsh uses for these routes (@earendil-works/pi-ai 0.85.1) does not implement it yet, so the error is specific to dsh.

This plugin restores parity.

Install

# from GitHub (works today)
dsh plugin --profile web add github:BrackRat/dsh-opencode-session

# from npm (once published)
dsh plugin --profile web add dsh-opencode-session

# from a local checkout or tarball
dsh plugin --profile web add /path/to/dsh-opencode
dsh plugin --profile web add ./dsh-opencode-session-0.1.0.tgz

Because the package declares dsh.bundle, dsh plugin add adds it to dsh.profile.bundles automatically — no manual profile edit. Restart dsh web afterwards.

FAQ

Does this fix 400 MissingSessionID from dsh web?

Yes. Install the plugin and restart the dsh process that serves your UI; every following opencode / opencode-go request carries the header and the gateway routes it normally.

Why does the pi coding agent work while dsh fails?

pi adds x-opencode-session (plus x-opencode-client: pi) in its own provider-attribution layer for opencode / opencode-go. dsh reaches the same gateway through @earendil-works/pi-ai, which does not implement that header yet. This plugin supplies the missing piece inside dsh.

Does it patch files, credentials, or settings?

No. It is a normal dsh plugin bundle: it installs into the profile, registers one llm/stream middleware, and wraps the live pi-ai Models prototype in memory. Nothing outside the dsh process is modified, and the wrapper re-installs itself on every boot, so dsh upgrades need no action. Uninstalling removes every trace.

Which routes and models does it cover?

opencode, opencode-go, and any model whose base URL is hosted on opencode.ai — the same predicate the pi coding agent uses. Other providers (DeepSeek official, Anthropic, OpenAI, …) are untouched.

Will it conflict with a header I configured myself?

No: an x-opencode-session you set on the provider or the model wins; the plugin only fills the gap when the header is absent. Once pi-ai implements the header itself, this plugin becomes a no-op and can be removed.

Is it tested?

9 unit tests (node --test, zero dependencies) cover the predicate, the header precedence rules, the prototype wrapper, and the fail-safe path, plus an end-to-end check against a live opencode-go model during development.

Verify

dsh --profile web --dump-config | grep -A 2 opencode-session-header

The composed tree should show the plugin entry, and a chat on an opencode-go model should answer instead of returning MissingSessionID.

Uninstall

dsh plugin --profile web remove dsh-opencode-session

How it works

• The plugin registers on dsh's llm/stream waterfall, the documented interception point for model calls.
• On every request it resolves the live pi-ai Models instance from the adapter about to serve that request — so it patches the exact module instance in play — and installs one wrapper per prototype (idempotent, process-lifetime).
• The wrapper injects x-opencode-session: <session id> and x-opencode-client: dsh into the request options for the opencode routes.
• pi-ai merges options.headers last in every wire protocol (openai-completions, anthropic-messages, openai-responses), so a header you configure explicitly always wins.
• Fail-safe: if a future dsh or pi-ai build changes the internals, the plugin logs a warning and steps aside; it never fails a request.

Compatibility

Validated on dsh 0.1.5-rc.1 with @earendil-works/pi-ai 0.85.1 (DeepSeek V4 Pro / V4 Flash on opencode-go, openai-completions protocol).

Development

npm test        # node:test, no dependencies
npm pack        # inspect the published file set

License

MIT