plexus-agent-plugins

Exposes models from a self-hosted Plexus AI proxy as a first-class provider inside AI coding agents. Models appear in the agent's model picker with correct wire-protocol behavior, as if they were natively supported providers.

Supported agents

Package	Agent	npm
plexus-pi	pi	@mcowger/pi-plexus
plexus-oh-my-pi	Oh My Pi	@mcowger/oh-my-pi-plexus

Prerequisites

• A running Plexus instance
• pi 0.85.1 or later (for plexus-pi)

Installation

The built dist artifact is committed to the repo, so no build step is needed for any install method.

---

pi

Option 1 — npm (recommended)

cd ~/.pi/agent/extensions
npm install @mcowger/pi-plexus

Option 2 — git clone into the extensions directory

git clone https://github.com/mcowger/plexus-agent-plugins ~/.pi/agent/extensions/plexus-agent-plugins

Option 3 — git clone anywhere + settings.json

git clone https://github.com/mcowger/plexus-agent-plugins ~/code/plexus-agent-plugins

Then register the path in ~/.pi/agent/settings.json:

{
  "extensions": [
    "~/code/plexus-agent-plugins/packages/plexus-pi"
  ]
}

---

Oh My Pi

Oh My Pi is a fork of pi and is not wire-compatible with plexus-pi in every respect (different runtime packages, extension manifest field, and built-in model registry — see AGENTS.md), so it has its own adapter package.

Option 1 — npm (recommended)

cd ~/.omp/agent/extensions
npm install @mcowger/oh-my-pi-plexus

Option 2 — git clone into the extensions directory

git clone https://github.com/mcowger/plexus-agent-plugins ~/.omp/agent/extensions/plexus-agent-plugins

Option 3 — git clone anywhere + settings.json

git clone https://github.com/mcowger/plexus-agent-plugins ~/code/plexus-agent-plugins

Then register the path in ~/.omp/agent/settings.json:

{
  "extensions": [
    "~/code/plexus-agent-plugins/packages/plexus-oh-my-pi"
  ]
}

---

First-time setup

pi

Run inside pi using the native login flow:

/login plexus

You will be prompted for:

• Plexus base URL — e.g. https://plexus.example.com
• Plexus API key

To force a model refresh:

/plexus refresh

Inspect the effective URL, authentication availability, and catalog source without exposing a credential:

/plexus status

Select a Plexus model in /model. Save its startup default with the host's normal model-picker action; Plexus does not maintain a separate default-model setting.

Use /login plexus for setup and /logout plexus to remove stored credentials.

Oh My Pi

Run inside Oh My Pi using the native login flow:

/login plexus

Same prompts and /plexus refresh / /plexus status commands as pi (see above). Save the selected startup model through OMP's normal /model or /models flow.

Configuration files

Connection state

Each adapter stores only non-secret Plexus settings in its own config.json:

<agent-dir>/extensions/plexus/config.json  # base URL and optional model suppression

Credentials stay in the host credential store (auth.json for Pi, agent.db for OMP). Model catalogs stay in the host model registry/store. The extension no longer writes a second model cache, ETag file, raw API response, or default-model preference.

At runtime, configuration resolves as follows:

base URL: PLEXUS_API_URL → PLEXUS_BASE_URL → saved Plexus base URL
API key: host credential store → PLEXUS_API_KEY process fallback
catalog: host model store → live Plexus refresh
startup model: host model-picker preference

PLEXUS_API_URL and PLEXUS_BASE_URL are process-only URL overrides; PLEXUS_API_KEY is a process-only credential fallback. None are persisted. /plexus status reports the effective URL source, whether auth is available, and catalog state without exposing credentials.

Plexus accepts a root URL or a /v1 API URL. The adapter normalizes that only for the Plexus discovery request. Each model then receives its own API-specific base URL: OpenAI stays on /v1, Anthropic uses the root, and Google uses /v1beta.

---

Model suppression

All plugin packages support suppressing models by name or pattern so undesired models do not appear in model selectors or cache restored lists.

Pattern matching syntax

• Exact match (case-insensitive): Matches model id, name, or short ID (suffix after / or :). Example: "gpt-4o", "Claude 3.5 Sonnet".
• Glob wildcards: Supports * (0+ characters) and ? (1 character). Example: "gpt-3.5*", "*deprecated*", "anthropic/*".
• Regex patterns: Prefix with regex:. Example: "regex:^gpt-[34]".

Configuration methods

• Environment variables:

  export PLEXUS_SUPPRESS_MODELS="gpt-3.5*, *deprecated*, whisper"

  PLEXUS_EXCLUDE_MODELS is also accepted. Values can be comma-, semicolon-, or newline-separated.

• pi / Oh My Pi config: Add suppressModels (or suppress) to config.json:

  {
    "baseUrl": "https://plexus.example.com",
    "suppressModels": ["gpt-3.5*", "*deprecated*"]
  }

---

Package layout

packages/
  plexus-models/        # host-agnostic data layer
    src/
      types.ts          # wire types (PlexusApiModel, PlexusModelDescriptor, etc.)
      convert.ts        # model fetching, conversion, compat detection
      suppress.ts       # model pattern suppression / exclusion matching
      index.ts          # barrel export
  plexus-pi/            # pi host adapter
    src/
      extension.ts      # entry point: commands, session refresh, auth flow
      mapper.ts         # PlexusModelDescriptor → pi ProviderModelConfig
      config.ts         # base URL / suppression config I/O
      cache.ts          # Pi native model-store restore
      log.ts            # append-only log
    package.json        # declares pi.extensions entry point
  plexus-oh-my-pi/      # Oh My Pi host adapter (fork of pi; own runtime packages + catalog)
    src/
      extension.ts      # entry point: commands, session refresh, auth flow
      mapper.ts         # PlexusModelDescriptor → Oh My Pi ProviderModelConfig
      config.ts         # base URL / suppression config I/O
      log.ts            # append-only log
    package.json        # declares omp.extensions entry point

plexus-models has zero imports from any agent framework. Each host adapter imports it via a relative path.

Plexus model metadata

The /v1/models endpoint returns an OpenRouter-style list. These fields drive host behavior:

Field	Effect
preferred_api	String or array. First recognized value selects the host API dialect.
supported_parameters	reasoning, include_reasoning, or reasoning_effort enables reasoning support.
architecture.input_modalities	Enables text/image/audio/video/pdf support where the host supports it.
pricing	Converted into host per-million-token cost metadata. Plexus returns per-token prices.
pricing.tiers	Alternate rates above input_tokens_above; mapped to native pi context pricing tiers.
top_provider	Supplies context and output token limits when present.
pi_provider / pi_model	Lets the pi adapter reuse built-in pi compat, headers, and thinking-level metadata.
pi_options	pi compat overrides. These win over heuristic and built-in metadata.

Models with a falsy id are skipped. Missing metadata falls back to safe defaults.

Adapter behavior

• pi refreshes on session start and through /plexus refresh, without changing the model selected for the session. It accepts either root URLs or URLs ending in /v1 and normalizes them before calling Plexus.
• The active adapters convert Plexus's per-token base and tier rates to the per-million-token units expected by their host.

Development

After cloning, install dependencies to set up the pre-commit hook:

bun install

The pre-commit hook (via lefthook) rebuilds the active dist artifacts automatically whenever source files change. After committing, reload/restart your agent.

Archived adapters

packages/deprecated/plexus-opencode is preserved for reference but is archived. It is private and excluded from builds, tests, hooks, version sync, and publishing. In my testing, OpenCode was notably slower and less token-efficient than pi and Oh My Pi.

To add support for a new host agent, see AGENTS.md.