opencode-openai-residency

OpenCode plugin for OpenAI Codex API tweaks:

1. Data residency — adds x-openai-internal-codex-residency for OpenAI Enterprise workspaces with regional restrictions.
2. gpt-5.5 unlock (opt-in) — overrides the User-Agent / originator headers on outgoing codex requests so they pass OpenAI's codex_cli_rs client gate.
3. gpt-5.6-sol WebSocket transport (opt-in) — serves WS-only Codex models (e.g. gpt-5.6-sol) over the Codex WebSocket transport, which plain HTTP cannot reach.

This mirrors how the official Codex CLI talks to the Codex backend.

Note: If OpenCode merges built-in residency support (PR #15844), feature 1 becomes unnecessary.

Install

Add to your opencode.json:

{
  "plugin": ["opencode-openai-residency"],
  "provider": {
    "openai": {
      "options": {
        "enforce_residency": "us",          // feature 1 — residency header
        "ua_override": true,                // feature 2 — gpt-5.5/terra/luna unlock
        "ws_transport": true,               // feature 3 — gpt-5.6-sol WS transport (opt-in)
        "ua_version": "999.999.999",        // optional — codex_cli_rs version, defaults high
        "ws_models": ["gpt-5.6-sol"]        // optional — models forced over WS, defaults to this
      },
      "models": {
        "gpt-5.6-sol": {
          "name": "GPT-5.6-Sol",
          "reasoning": true,
          // service_tier:"priority" is injected automatically by the plugin's WS
          // transport for every model in ws_models — no model config needed for it.
          "variants": {
            "low":    { "reasoningEffort": "low" },
            "medium": { "reasoningEffort": "medium" },
            "high":   { "reasoningEffort": "high" },
            "xhigh":  { "reasoningEffort": "xhigh" },
            "max":    { "reasoningEffort": "max" }
          },
          "limit": { "context": 372000, "output": 128000 }
        }
      }
    }
  }
}

Restart OpenCode. The plugin is auto-loaded.

Feature 1 — Residency header

Without x-openai-internal-codex-residency, OpenAI Enterprise Codex API requests from non-US regions are rejected with 401 "Workspace is not authorized in this region". Set enforce_residency to the required region string (e.g. "us") and the plugin attaches the header on every OpenAI provider call.

If enforce_residency is unset, the hook does nothing.

Feature 2 — gpt-5.5 unlock (opt-in)

As of 2026-05-07, OpenAI gates gpt-5.5 (and other reasoning models on the codex pathway) by an AND-gate on two HTTP headers:

Header	Required value
User-Agent	must start with codex_cli_rs
originator	must be exactly codex_cli_rs

If either is wrong, the request enters reasoning and dies mid-stream with a silent server_error — looks like backend instability, isn't. Only the official Codex Rust CLI passes the check by default.

opencode's default UA (opencode/1.14.39 ...) and originator (opencode) both fail it. Why a chat.headers hook can't fix this: opencode 1.14.39's Vercel AI SDK constructs its own request and ignores hook overrides on default headers like User-Agent. The only effective injection point is patching globalThis.fetch at module load, which is what this plugin does when ua_override: true.

The patch is scoped to chatgpt.com/backend-api/codex and api.openai.com only; all other fetches pass through untouched.

Why opt-in (default off)

The override changes how opencode identifies itself to OpenAI's codex backend. Practical risk is low (just two headers, no payload tampering, no auth/payment bypass), but enabling it is the user's explicit choice. The config key is ua_override even though it overrides both User-Agent and originator — those two headers together form a single client-identity check from OpenAI's side.

Risks

• OpenAI may add deeper fingerprinting (TLS, timing, payload heuristics). If/when that happens, this stops working.
• opencode internals — if a future opencode version bypasses globalThis.fetch (e.g. uses Bun.fetch directly), the patch silently stops applying.

Debug / verification

Set OPENCODE_RESIDENCY_DEBUG=1 in the environment to log every codex/openai request the plugin intercepts. By default the log goes to stderr; set OPENCODE_RESIDENCY_DEBUG_FILE=/path/to/log to redirect to a file (useful inside the opencode TUI which swallows stderr).

Example output when ua_override is on:

[2026-05-07T13:03:34.362Z] fetch patch installed
[2026-05-07T13:03:36.972Z] intercepted https://chatgpt.com/backend-api/codex/responses | UA opencode/1.14.40 (...) ai-sdk/provider-utils/4.0.23 runtime/bun/1.3.13 -> codex_cli_rs/999.999.999 (...) | originator opencode -> codex_cli_rs

If you set ua_override: false (or omit it) the log file stays empty — the patch isn't installed, fetches pass through untouched.

Feature 3 — gpt-5.6-sol WebSocket transport (opt-in)

gpt-5.6-sol is not served over plain HTTP. A normal POST to /responses always returns a mid-stream server_error for sol, regardless of headers. It is served only over the Codex WebSocket transport, and the body must additionally carry service_tier: "priority" — the only accepted tier (there is no gpt-5.x-fast model name and no service_tier: "fast" value).

opencode has a built-in WebSocket path, but it is constructed from OPENCODE_EXPERIMENTAL_WEBSOCKETS before user plugins load, so a plugin cannot enable it. To avoid forcing an env var, this plugin performs the WS round-trip itself when ws_transport: true: it intercepts the streaming POST to the Codex /responses endpoint for any model in ws_models, replays it over wss://, injects service_tier: "priority" if absent, and translates the WebSocket frames back into the SSE stream opencode's Responses parser consumes.

Option	Default	Meaning
ws_transport	false	Master switch. When true, models listed in ws_models go over the plugin-owned WebSocket transport. Independent of ua_override.
ws_models	["gpt-5.6-sol"]	Which models to force over WebSocket.
ua_version	"999.999.999"	The codex_cli_rs/<version> version sent on both the HTTP and WS paths. The gate is >= minimum, so a high value never needs bumping.

The plugin injects service_tier: "priority" automatically for every model in ws_models, so you do not set it in config (opencode's model schema has no request-body field for it anyway). Define the reasoning gears with the variants object (keyed by id, using reasoningEffort) as shown above — low, medium, high, xhigh, max (default medium); ultra is rejected.

ws_transport is decoupled from ua_override by design: ua_override forges identity on the HTTP path (gpt-5.5 / terra / luna), while ws_transport switches the transport for WS-only models. Enable whichever you need — they do not depend on each other. The WebSocket handshake always carries the codex_cli_rs identity itself, so ws_transport works standalone.

Debug the same way as feature 2: set OPENCODE_RESIDENCY_DEBUG=1 and sol requests log WS transport for gpt-5.6-sol.

License

MIT