OpenPrism

Many diverse model voices, split and recombined into one judged answer.

OpenPrism sends your prompt to a panel of different models in parallel, then a judge model reconciles their answers. The judge runs an explicit pass over them (consensus, contradictions, gaps, blind spots) and writes one response that beats any single model's. It's the OpenRouter "Fusion" pattern as a small, self-hostable tool.

Works with Claude Code, opencode, Cursor, Windsurf, Gemini CLI, and Codex, or anything that speaks MCP. It runs on models you already have: any model configured in opencode (75+ providers, recommended, no extra keys), or your own OpenAI-compatible provider keys.

Why it works

• Diversity beats raw strength. Independent models from different houses catch different things, and a judge that reconciles them does better than any single model on open-ended problems.
• Parallel panel. Wall-clock is about the slowest panelist, not the sum, so a fourth model adds almost no latency.
• Use it deliberately. A call costs roughly the slowest model plus the judge. Point it at hard questions (research, architecture, ambiguous trade-offs), not routine work.
• Diversity is counted by model family, not by raw count. OpenPrism picks default panels by family (Anthropic, OpenAI, Google, Qwen, GLM, Kimi, MiniMax, and so on), so two models from the same maker don't count as two voices. Every run is graded: full (all panelists answered, at least OPENPRISM_MIN_FAMILIES distinct families), degraded (a panelist failed but the family floor still holds), or stop (fewer than the floor answered, i.e. a single-family monoculture). The grade always prints, and OPENPRISM_STRICT=1 refuses a stop outright.

How it works

            ┌──────────── panel (parallel) ────────────┐
prompt ───▶ │  model A    model B    model C    model D │ ──▶  judge ──▶ answer
            └───────────────────────────────────────────┘   (reconcile +
                  (different providers / houses)               synthesize)

Two backends decide where panel calls go (set with OPENPRISM_BACKEND):

Two modes:

• research (default). Fusion-style synthesis. This is the mode with measured benchmark benefit.
• code. Code is verifiable, so blending prose is wrong. Each model produces a candidate, then the judge picks the strongest one and repairs it (best-of-N) and adds a Verify by: line. v1 does not auto-run the tests yet.

Install

Pick whichever fits. All of them work on Linux, macOS, Windows, and WSL.

A. Claude Code marketplace (simplest):

/plugin marketplace add ba1lly/OpenPrism
/plugin install openprism@openprism

B. Any MCP host via uvx (needs uv; no clone, no venv). Generate the config for your host with the built-in wizard:

uvx openprism init --host opencode
#   ...or --host cursor | windsurf | gemini | codex | claude-code

It prints (or --writes) the MCP config block, launching the server via uvx --from openprism openprism-mcp (the published PyPI package). For the latest GitHub branch use --git; to pin a tag use --ref v0.1.0.

C. From source (for development):

git clone https://github.com/ba1lly/OpenPrism && cd OpenPrism
./install.sh          # Linux / macOS / WSL   (Windows: ./install.ps1)

The installer creates a venv, installs OpenPrism, seeds .env, and prints host config. To point a host at this checkout, run openprism init --host <h> --local.

Then add a provider key to .env (direct backend), or set OPENPRISM_BACKEND=opencode to use opencode's providers with no keys here.

Judge options

Usage (CLI)

openprism "Best architecture for X, and the trade-offs?"          # research
openprism "Implement a token-bucket rate limiter" --mode code
openprism "..." --panel "google/gemini-2.5-flash,anthropic/claude-haiku-4-5"
openprism --bakeoff modelA modelB "a hard prompt"                 # which model wins?
openprism --list                                                  # presets + known models
openprism doctor                                                  # check your setup

With OPENPRISM_BACKEND=opencode, panels are provider/model refs. With no --panel, OpenPrism picks a diverse default across your connected providers.

Use as a plugin

OpenPrism is one MCP server with four tools (research, code, bakeoff, models), so every host calls the same core. openprism init --host <host> generates the right config for each:

openprism init --host cursor            # print the block
openprism init --host opencode --write  # merge it into the config file (makes a .bak)

For opencode, also copy the command files for slash commands:

cp integrations/opencode/commands/*.md ~/.config/opencode/commands/

Run /openprism-models (or the models tool) to see which provider/model refs are connected.

Panelist tools (opencode backend)

Like Fusion, panelists can use live web tools. On the opencode backend the panel runs according to OPENPRISM_PANEL_TOOLS:

The direct backend is plain completions and ignores tools.

Adding models & providers

opencode backend (recommended): you don't add anything to OpenPrism. Add the provider in opencode and it shows up automatically:

opencode auth login          # pick a provider, paste its key / OAuth

Then run /openprism-models (or the models tool) in any host to see every provider/model ref now available, and use them:

openprism "..." --panel "anthropic/claude-opus-4-7,google/gemini-3-pro,openai/gpt-5.2"

With no --panel, OpenPrism picks a diverse default across your connected providers, or set OPENPRISM_PANEL to pin a fixed default panel.

direct backend: add providers to OpenPrism. The default provider comes from .env (ALIBABA_API_KEY + ALIBABA_BASE_URL). Add more OpenAI-compatible providers in providers.json (copy providers.json.example):

{ "openrouter": { "base_url": "https://openrouter.ai/api/v1",
                  "api_key": "env:OPENROUTER_API_KEY",
                  "models": ["anthropic/claude-opus-4", "google/gemini-2.5-pro"] } }

Reference them as provider/model in --panel.

The judge model is independent of the panel. Set OPENPRISM_JUDGE_BACKEND and OPENPRISM_JUDGE_MODEL (see the judge table).

Health check & uninstall

openprism doctor      # checks backend, opencode server, judge, keys; prints no secrets
./uninstall.sh        # or ./uninstall.ps1; removes venv/build, leaves your .env

Configuration

Everything is set through env vars (.env in the repo root; see .env.example): OPENPRISM_BACKEND, OPENPRISM_JUDGE_BACKEND, OPENPRISM_JUDGE_MODEL, ANTHROPIC_API_KEY (for the anthropic-api judge), OPENPRISM_DEFAULT_PROVIDER (which direct provider a bare model id uses), OPENPRISM_PANEL (pin the default panel: a preset name or comma-separated model refs; a per-call panel overrides it), OPENPRISM_PANEL_TOOLS (research/none/all), OPENPRISM_MIN_FAMILIES (diversity floor, default 2), OPENPRISM_STRICT (refuse below the floor), OPENPRISM_MAX_PANEL (size cap), OPENPRISM_PANEL_TIMEOUT, OPENPRISM_MAX_TOKENS, and the opencode-backend OPENPRISM_OPENCODE_* settings. Extra direct-backend providers go in providers.json (see providers.json.example).

Security notes

• OpenPrism never logs provider keys. The opencode backend queries only the keyless /provider endpoint (never /config/providers, which would return keys), and the judge always runs without tools. Even so, bind the opencode server to localhost and set OPENCODE_SERVER_PASSWORD if you expose it. See SECURITY.md.
• Keep .env and providers.json out of git (both are already in .gitignore).

Roadmap

• code mode: optional sandboxed test execution (--verify "<cmd>").
• Panelist tools on the direct backend (a tool-call loop, so non-opencode panels can browse too).
• Smarter default-panel selection that accounts for model capability, not just family.

License

MIT