Visor — AI workflow engine for code review, assistants & automation

Orchestrate checks, MCP tools, and AI providers with YAML-driven pipelines.
Runs as GitHub Action, CLI, Slack bot, Telegram bot, or HTTP API.

Visor is an open-source workflow engine that lets you define multi-step AI pipelines in YAML. Wire up shell commands, AI providers, MCP tools, HTTP calls, and custom scripts into dependency-aware DAGs — then run them from your terminal, CI, Slack, Telegram, Email, WhatsApp, Teams, or an HTTP endpoint.

What you get out of the box:

• YAML-driven pipelines — define checks, transforms, routing, and AI prompts in a single config file.
• 8 runtime modes — CLI, GitHub Action, Slack bot, Telegram bot, Email, WhatsApp, Teams, HTTP server — same config, any surface.
• 17 provider types — ai, command, script, mcp, utcp, http, claude-code, a2a, github, memory, workflow, and more.
• AI orchestration — multi-provider (Gemini, Claude, OpenAI, Bedrock), session reuse, MCP/UTCP tool calling, retry & fallback.
• Execution engine — dependency DAGs, parallel waves, forEach fan-out, conditional routing, failure auto-remediation.
• Built-in testing — YAML-native integration tests with fixtures, mocks, and assertions.

What do you want to build?

First time? Run npx visor init to scaffold a working config, then npx visor to run it.

Table of Contents

• Quick Start
• AI Assistant Framework
• Runtime Modes
• PR Comment Commands
• Core Concepts
• Provider Types
• Orchestration
• AI & MCP
• GitHub Provider
• Templating & Transforms
• Suppressing Warnings
• Testing Framework
• SDK
• Configuration
• Observability
• Security
• Enterprise Policy Engine
• Further Reading
• Contributing
• License

Requirements: Node.js 18+ (CI runs Node 20).

🚀 Quick Start

Install & Run

# Install
npm i -D @probelabs/visor

# Scaffold a starter config (pick a template)
npx visor init                  # interactive picker
npx visor init code-review      # PR review pipeline
npx visor init agent            # AI agent with tools
npx visor init automation       # multi-step pipeline
npx visor init assistant        # chat assistant / Slack bot

# Run
npx visor                       # run all steps
npx visor --tags fast           # run steps tagged "fast"
npx visor validate              # check config for errors

Or one-off without installing: npx -y @probelabs/visor@latest --check all --output table

Minimal Config (.visor.yaml)

version: "1.0"
steps:
  security:
    type: ai
    prompt: "Identify security issues in changed files"
    tags: ["fast", "security"]

  run-tests:
    type: command
    exec: npm test
    depends_on: [security]

  notify:
    type: http
    method: POST
    url: https://hooks.slack.com/...
    body: '{ "text": "Tests {{ outputs[''run-tests''].status }}" }'
    depends_on: [run-tests]

As a GitHub Action

# .github/workflows/visor.yml
name: Visor
on:
  pull_request: { types: [opened, synchronize] }
  issues: { types: [opened] }
  issue_comment: { types: [created] }
permissions:
  contents: read
  pull-requests: write
  issues: write
  checks: write
jobs:
  visor:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: probelabs/visor@v1
        env:
          GOOGLE_API_KEY: ${{ secrets.GOOGLE_API_KEY }}

Tip: Pin releases for stability with @v1. For bleeding-edge, use @nightly.

🤖 AI Assistant Framework

Visor ships with a built-in assistant framework — three composable workflows for building AI-powered assistants with skills, tools, and multi-repo code exploration. Import them with a single line:

version: "1.0"

imports:
  - visor://assistant.yaml

checks:
  chat:
    type: workflow
    workflow: assistant
    assume: ["true"]
    args:
      question: "{{ conversation.current.text }}"
      system_prompt: "You are a helpful engineering assistant."
      intents:
        - id: chat
          description: general Q&A or small talk
        - id: code_help
          description: questions about code or architecture
          default_skills: [code-explorer]
      skills:
        - id: code-explorer
          description: needs codebase exploration or code search
          tools:
            code-talk:
              workflow: code-talk
              inputs:
                projects:
                  - id: backend
                    repo: my-org/backend
                    description: Backend API service
          allowed_commands: ['git:log:*', 'git:diff:*']
    on_success:
      goto: chat

The visor:// protocol resolves to bundled workflows shipped with the package — no network fetch needed.

Learn more: docs/assistant-workflows.md | Examples: code-talk-workflow · code-talk-as-tool · intent-router

🖥️ Runtime Modes

Visor runs the same YAML config across multiple surfaces:

See Bot Integrations for a comparison of all bot transports.

Additional modes:

• TUI — interactive chat-style terminal UI: visor --tui
• SDK — programmatic Node.js API: import { runChecks } from '@probelabs/visor/sdk'
• Scheduler — cron-based execution with database-backed persistence

# CLI examples
visor --check all --output table
visor --tags fast,local --max-parallelism 5
visor --analyze-branch-diff                   # PR-style diff analysis
visor --event pr_updated                      # Simulate GitHub events
visor --tui --config ./workflow.yaml          # Interactive TUI
visor --debug-server --debug-port 3456        # Live web debugger
visor config snapshots                        # Config version history
visor validate                                # Validate config
visor test --progress compact                 # Run integration tests

Run modes: Default is CLI mode everywhere. For GitHub-specific behavior (comments, checks, annotations), run with --mode github-actions or set mode: github-actions in the Action. Force CLI mode inside Actions with VISOR_MODE=cli.

See docs/commands.md for the full CLI reference.

💬 PR Comment Commands

Trigger reviews and assistant actions via comments on PRs or issues:

/review                        # Re-run all checks
/review --check security       # Re-run specific check
/visor how does caching work?  # Ask the built-in assistant

Learn more: docs/commands.md

🧩 Core Concepts

🔌 Provider Types

See docs/pluggable.md for building custom providers.

⚙️ Orchestration

Dependencies & Parallel Execution

Steps without dependencies run in parallel waves. depends_on enforces ordering:

steps:
  fetch-data:
    type: command
    exec: curl -s https://api.example.com/data

  analyze:
    type: ai
    prompt: "Analyze: {{ outputs['fetch-data'] }}"
    depends_on: [fetch-data]

  report:
    type: command
    exec: 'echo "Done: {{ outputs[''analyze''] | truncate: 100 }}"'
    depends_on: [analyze]

forEach Fan-Out

Transform output into an array, run dependents once per item:

steps:
  list-services:
    type: command
    exec: 'echo ''["auth","payments","notifications"]'''
    forEach: true

  check-service:
    type: command
    exec: 'curl -s https://{{ outputs["list-services"] }}/health'
    depends_on: [list-services]

Use outputs_raw in downstream steps to access the aggregated array of all forEach results:

  summarize:
    type: script
    depends_on: [list-services]
    content: |
      const arr = outputs_raw['list-services'] || [];
      return { total: arr.length };

Learn more: docs/foreach-dependency-propagation.md

Failure Routing & Auto-Remediation

Steps can retry, run remediation, or jump to other steps on failure:

version: "2.0"
routing:
  max_loops: 5
steps:
  build:
    type: command
    exec: make build
    on_fail:
      retry: { max: 2, backoff: { mode: exponential, delay_ms: 500 } }
      goto: setup            # Jump back on exhausted retries

  deploy:
    type: command
    exec: make deploy
    depends_on: [build]
    on_success:
      run: [notify]          # Run extra steps on success
    on_fail:
      goto_js: |
        return attempt <= 2 ? 'build' : null;  # Dynamic routing

Learn more: docs/failure-routing.md

Conditional Execution & Author Permissions

steps:
  security-scan:
    type: command
    exec: npm audit
    if: "!hasMinPermission('MEMBER')"    # Only for external contributors

  auto-approve:
    type: github
    op: labels.add
    values: ["approved"]
    if: "hasMinPermission('COLLABORATOR') && totalIssues === 0"

  protect-secrets:
    type: command
    exec: echo "Checking permissions..."
    fail_if: "!isMember() && files.some(f => f.filename.startsWith('secrets/'))"

Available permission functions: hasMinPermission(level), isOwner(), isMember(), isCollaborator(), isContributor(), isFirstTimer().

Learn more: docs/author-permissions.md

🤖 AI & MCP

Multi-Provider AI

steps:
  review:
    type: ai
    prompt: "Review this code for security issues"
    ai:
      provider: anthropic          # or: google, openai, bedrock
      model: claude-sonnet-4-20250514
      fallback:
        strategy: any              # Try other providers on failure

Supported providers: Google Gemini, Anthropic Claude, OpenAI GPT, AWS Bedrock.

Set one key via environment: GOOGLE_API_KEY, ANTHROPIC_API_KEY, OPENAI_API_KEY, or AWS credentials.

MCP Tool Integration

Give AI steps access to MCP tools, or call MCP tools directly:

# AI step with MCP tools
steps:
  analyze:
    type: ai
    prompt: "Use the search tool to find security patterns"
    ai:
      mcp_servers:
        - name: code-search
          command: npx
          args: ["-y", "@probe/search"]

# Direct MCP tool execution
  search:
    type: mcp
    transport: stdio
    command: npx
    args: ["-y", "@probe/search"]
    method: search
    arguments:
      query: "{{ outputs['setup'].pattern }}"

AI Session Reuse

Chain AI conversations across steps:

steps:
  security:
    type: ai
    prompt: "Find security issues"

  remediation:
    type: ai
    prompt: "Suggest fixes for the issues you found"
    depends_on: [security]
    reuse_ai_session: true          # Carries conversation history
    session_mode: append            # Or: clone (default)

Claude Code Provider

Full Claude Code SDK integration with MCP tools and subagents:

steps:
  deep-review:
    type: claude-code
    prompt: "Analyze code complexity and suggest refactoring"
    max_turns: 10
    mcp_servers:
      - name: filesystem
        command: npx
        args: ["-y", "@modelcontextprotocol/server-filesystem", "."]

Learn more: docs/claude-code.md · docs/mcp-provider.md · docs/advanced-ai.md

🧰 GitHub Provider

Native GitHub operations (labels, comments, checks) without shelling out to gh:

steps:
  apply-labels:
    type: github
    op: labels.add
    values:
      - "{{ outputs.overview.tags.label | default: '' | safe_label }}"
    value_js: |
      return values.filter(v => typeof v === 'string' && v.trim().length > 0);

Learn more: docs/github-ops.md

🧬 Templating & Transforms

Liquid Templates

Steps can use Liquid templates in prompts, exec commands, HTTP bodies, and more:

steps:
  greet:
    type: command
    exec: 'echo "Files changed: {{ files | size }}, branch: {{ branch }}"'

  post-results:
    type: http
    url: https://api.example.com/results
    body: |
      { "issues": {{ outputs["review"] | json }},
        "pr": {{ pr.number }} }

Available context: outputs, outputs_raw, inputs, pr, files, env, memory, branch, event, conversation.

JavaScript Transforms

Transform step output before passing to dependents:

steps:
  fetch:
    type: command
    exec: 'node -e "console.log(JSON.stringify({items:[1,2,3]}))"'
    transform_js: |
      return output.items.filter(i => i > 1);

Dynamic Routing with JavaScript

steps:
  check:
    type: command
    exec: npm test
    on_fail:
      goto_js: |
        if (attempt > 3) return null;   // Give up
        return 'fix-and-retry';         // Jump to remediation

Prompts can live in external files with full Liquid variable access:

steps:
  overview:
    type: ai
    schema: code-review
    prompt: ./prompts/overview.liquid

Learn more: docs/liquid-templates.md · docs/schema-templates.md

🔇 Suppressing Warnings

Suppress a specific issue by adding a nearby visor-disable comment:

const testPassword = "demo123"; // visor-disable

Learn more: docs/suppressions.md

🧪 Testing Framework

Write and run integration tests for your Visor config in YAML:

# .visor.tests.yaml
tests:
  - name: "Security check finds issues"
    config: .visor.yaml
    steps:
      security:
        mock_output: '{"issues": [{"severity": "high"}]}'
    assertions:
      - step: security
        called: { exactly: 1 }
      - step: security
        output_contains: "high"

visor test --progress compact          # Run tests
visor test --list                      # List test cases
visor test --only "Security*"          # Filter tests
visor test --bail                      # Stop on first failure

Docs: Getting started · DSL reference · Fixtures & mocks · Assertions · Cookbook

📦 SDK (Programmatic Usage)

Run Visor programmatically from Node.js:

import { loadConfig, runChecks } from '@probelabs/visor/sdk';

const config = await loadConfig('.visor.yaml');
const result = await runChecks({
  config,
  checks: Object.keys(config.checks || {}),
  output: { format: 'json' },
});
console.log('Issues:', result.reviewSummary.issues?.length ?? 0);

Learn more: docs/sdk.md

🔧 Configuration

Config Loading Order

1. CLI --config flag
2. .visor.yaml in project root
3. Built-in defaults

Extending Configs

extends:
  - default
  - ./team-standards.yaml
  - https://raw.githubusercontent.com/org/policies/main/base.yaml

Dynamic Config Reloading

Long-running modes (Slack, Telegram, Email, HTTP) support live config reload:

visor --slack --config .visor.yaml --watch       # Auto-reload on file change
visor --telegram --config .visor.yaml --watch    # Telegram with hot reload
visor --email --config .visor.yaml --watch       # Email with hot reload
visor config snapshots                        # List config versions
visor config diff 1 2                         # Diff two snapshots

Key Config Options

version: "1.0"
max_parallelism: 3            # Concurrent steps
max_ai_concurrency: 3         # Concurrent AI API calls
routing:
  max_loops: 10               # Loop safety limit

http_server:
  enabled: true
  port: 8080
  auth: { bearer_token: "${WEBHOOK_SECRET}" }

telemetry:
  enabled: true
  sink: otlp                  # or: file, console

steps:
  # ... your pipeline

Where Things Go (Quick Reference)

A common source of confusion is where to put AI settings. Here's the map:

version: "1.0"

# ── Global defaults (top level) ──────────────────────
ai_provider: google              # default AI provider for all steps
ai_model: gemini-2.5-flash       # default model for all steps

steps:
  my-step:
    type: ai
    prompt: "Analyze the code"

    # ── Per-step overrides (step level) ──────────────
    ai_provider: anthropic       # override provider for this step
    ai_model: claude-sonnet-4-20250514    # override model for this step
    ai_system_prompt: "You are..." # system prompt shorthand

    # ── OR use the ai: block for full config ─────────
    ai:
      provider: anthropic
      model: claude-sonnet-4-20250514
      system_prompt: "You are a senior engineer."
      retry:
        maxRetries: 3
      fallback:
        providers: [{ provider: google, model: gemini-2.5-flash }]

Common mistakes: system_prompt at step level (ignored — use ai_system_prompt or put it inside ai:). Top-level ai: block (not supported — use ai_provider/ai_model). parseJson on command steps (commands auto-parse JSON). Run visor validate to catch these.

Learn more: docs/ai-configuration.md · docs/configuration.md

👀 Observability

Output Formats

visor --output table                          # Terminal-friendly (default)
visor --output json --output-file results.json
visor --output sarif --output-file results.sarif
visor --output markdown

OpenTelemetry Tracing

telemetry:
  enabled: true
  sink: otlp

OTEL_EXPORTER_OTLP_TRACES_ENDPOINT=http://localhost:4318/v1/traces visor --check all

Span hierarchy: visor.run → engine.state.* → visor.check.* → visor.foreach.item

Debug Tools

visor --debug                                 # Verbose logging
visor --debug-server --debug-port 3456        # Live web visualizer

Quick debugging tips:

Use log() in JavaScript expressions (if, fail_if, transform_js):

if: |
  log("Outputs:", outputs);
  outputs["fetch-data"]?.status === "ready"

Use the json filter in Liquid to inspect objects:

type: logger
message: "Outputs: {{ outputs | json }}"

TUI mode (visor --tui): Press Tab to switch between Chat and Logs tabs, q to exit.

Learn more: docs/observability.md · docs/debugging.md · docs/debug-visualizer.md

🔐 Security

• GitHub App support for scoped, auditable access
• Remote extends allowlist to control external config sources
• MCP method filtering — allow/deny lists with wildcards
• Bash allow/deny patterns for AI-driven command execution
• Docker & process sandboxes for isolated step execution
• Author permissions — hasMinPermission(), isMember(), etc. for role-based logic
• Environment filtering — control which env vars steps can access

visor --no-remote-extends
visor --allowed-remote-patterns "https://raw.githubusercontent.com/myorg/"

Learn more: docs/security.md · docs/author-permissions.md

🏢 Enterprise Policy Engine (EE)

Enterprise Edition. Requires a Visor EE license. Contact [email protected].

OPA-based policy enforcement for gating checks, MCP tools, and AI capabilities:

policy:
  engine: local
  rules: ./policies/
  fallback: deny
  roles:
    admin: { author_association: [OWNER] }
    developer: { author_association: [MEMBER, COLLABORATOR] }

Learn more: docs/enterprise-policy.md

📚 Further Reading

Getting started:
Configuration · AI config · CLI commands · GitHub Auth · CI/CLI mode · GitHub Action reference · Migration · FAQ · Glossary

Guides:
Tools & Toolkits · Assistant workflows · TDD for assistant workflows · Workflow creation · Workflow style guide · Dependencies · forEach propagation · Failure routing · Router patterns · Lifecycle hooks · Liquid templates · Schema-template system · Fail conditions · Failure conditions schema · Failure conditions impl · Timeouts · Execution limits · Event triggers · Output formats · Output formatting · Default output schema · Output history · Reusable workflows · Criticality modes · Fault management

Providers:
A2A · Command · Script · MCP · UTCP · MCP tools for AI · Claude Code · AI custom tools · AI custom tools usage · Custom tools · GitHub ops · Git checkout · HTTP integration · Memory · Human input · Custom providers

Operations:
Security · Performance · Observability · Debugging · Debug visualizer · Telemetry setup · Dashboards · Troubleshooting · Suppressions · GitHub checks · Bot integrations · Slack · Telegram · Email · WhatsApp · Teams · Scheduler · Sandbox engines

Testing:
Getting started · DSL reference · Flows · Fixtures & mocks · Assertions · Cookbook · TDD for assistants · CLI & reporters · CI integration · Troubleshooting

Enterprise:
Licensing · Enterprise policy · Scheduler storage · Database operations · Capacity planning · Production deployment · Deployment

Architecture & RFCs:
Architecture · Contributing · Failure routing RFC · Bot transports RFC · Debug visualizer RFC · Debug visualizer progress · Engine state machine plan · Engine pause/resume RFC · Event-driven GitHub RFC · Execution statistics RFC · Telemetry tracing RFC · Test framework RFC · SDK RFC · Goto/forward run plan · Loop routing refactor · Schema next PR · Fact validator gap analysis · Fact validator plan

Recipes & examples:
Recipes · Dev playbook · Tag filtering · Author permissions · Session reuse · SDK

🤝 Contributing

Learn more: CONTRIBUTING.md

📄 License

MIT License — see LICENSE