Reactive Agents — TypeScript AI Agent Framework

Run your first agent in 60 seconds. Scale up by composing layers — add reasoning loops, persistent 4-tier memory, production guardrails, cost routing, and a live local studio one .with() call at a time.

Works on local Ollama models (8B+) through frontier APIs — same code, same features. Built on Effect-TS for compile-time type safety at every boundary. No any.

31 composable packages	Enable exactly what you need, no hidden coupling
6 LLM providers	Anthropic, OpenAI, Gemini, Ollama (local), LiteLLM 40+, Test
5 reasoning strategies	ReAct · Reflexion · Plan-Execute · Tree-of-Thought · Adaptive
4,349 tests · 497 files	Production-grade confidence
Cortex Studio	Live agent canvas, entropy charts, debrief UI, agent builder
Effect-TS end to end	Compile-time type safety, zero any, explicit tagged errors

Documentation · Discord · Quick Start · Features · Comparison · Architecture · Packages

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Why Reactive Agents?

Most AI agent frameworks are dynamically typed, monolithic, and opaque. They assume you're using GPT-4, break when you try smaller models, and hide every decision behind abstractions you can't inspect. Reactive Agents takes a fundamentally different approach:

Problem	How We Solve It
No type safety	Effect-TS schemas validate every service boundary at compile time
Monolithic	13 independent layers -- enable only what you need
Opaque decisions	10-phase execution engine with before/after/error hooks on every phase
Model lock-in	Model-adaptive context profiles (4 tiers: local, mid, large, frontier) help smaller models punch above their weight
Single reasoning mode	5 strategies (ReAct, Reflexion, Plan-Execute, Tree-of-Thought, Adaptive)
Unsafe by default	Guardrails block injection/PII/toxicity before the LLM sees input
No cost control	Complexity router picks the cheapest capable model; budget enforcement at 4 levels
Poor DX	Builder API chains capabilities in one place

Cortex Studio

A full-featured local studio for live debugging — start it with .withCortex() or rax run --cortex:

Beacon view: live agent canvas — cognitive state, entropy signal, token usage per step

Run details: vitals strip, step-by-step execution trace, and AI-generated debrief summary

→ Full Cortex documentation with more screenshots

Features

• 5 reasoning strategies + adaptive meta-strategy (ReAct, Reflexion, Plan-Execute, Tree-of-Thought, Adaptive) + Intelligent Context Synthesis — optional fast-template or deep-LLM transcript shaping each iteration (withReasoning({ synthesis, strategies: { … } }), ContextSynthesized on EventBus)
• 6 LLM providers -- Anthropic, OpenAI, Google Gemini, Ollama (local), LiteLLM (40+ models), Test (deterministic)
• Model-adaptive context profiles -- 4 tiers (local, mid, large, frontier) with tier-aware prompts, compaction, and truncation
• 4-layer memory -- working, episodic, semantic (vector + FTS5), procedural (bun:sqlite); ExperienceStore for cross-agent learning; background consolidation + decay
• Real-time token streaming + SSE via agent.runStream() with AbortSignal cancellation, IterationProgress + StreamCancelled events, and StreamCompleted.toolSummary
• Persistent autonomous gateway -- adaptive heartbeats, cron scheduling, webhook ingestion (GitHub adapter), composable policy engine
• Agent debrief + conversational chat -- agent.chat() and agent.session() (with optional SQLite persistence via SessionStoreService) for adaptive Q&A; post-run DebriefSynthesizer produces structured summaries persisted to SQLite
• A2A multi-agent protocol -- Agent Cards, JSON-RPC 2.0 server/client, SSE streaming, agent-as-tool composition
• Multi-agent orchestration -- sequential, parallel, pipeline, and map-reduce workflows with dynamic sub-agent spawning
• Production guardrails -- injection detection, PII filtering, toxicity blocking, kill switch, behavioral contracts
• Ed25519 identity -- real cryptographic agent certificates, RBAC, delegation, and audit trails
• Cost tracking -- complexity routing across 27 signals, semantic caching, budget enforcement with persistence across restarts, dynamic pricing fetching via .withDynamicPricing() (e.g. OpenRouter), cache-aware token discounts
• Professional metrics dashboard -- EventBus-driven execution timeline, tool call summary, smart alerts, and cost estimation (zero manual instrumentation)
• Native function-calling harness -- provider capability routing with robust fallback parsing for JSON tool calls embedded in model text (fenced or bare JSON) when native tool calls are missing
• Required tools guard -- ensure agents call critical tools before answering (static list or adaptive LLM inference), with relevant-tool pass-through, satisfied-required re-calls, and per-tool call budgets (maxCallsPerTool) to prevent research loops
• Builder hardening -- withStrictValidation(), withTimeout(), withRetryPolicy(), withCacheTimeout(), consolidated withGuardrails() thresholds, withErrorHandler(), withFallbacks(), withLogging(), withHealthCheck(), automatic strategy switching
• Harness quality controls -- withMinIterations(n) blocks early exit, withVerificationStep() adds LLM self-review, withOutputValidator(fn) retries on invalid output, withCustomTermination(fn) user-defined done predicate, withProgressCheckpoint(n) resumable agents, withTaskContext(record) background data injection
• ToolBuilder fluent API -- define tools without raw schema objects
• Provider fallback chains -- FallbackChain + withFallbacks() for graceful degradation across providers/models
• Cortex live reporting -- .withCortex(url?) streams runtime EventBus telemetry to Cortex over WebSocket (/ws/ingest) with best-effort delivery
• Structured logging -- makeLoggerService() with level filtering, JSON/text format, and file output with rotation via withLogging()
• Health checks -- withHealthCheck() + agent.health() returns { status, checks[] }
• Adaptive calibration -- three-tier live learning (shipped prior → community profile → local posterior); per-run observations stored at ~/.reactive-agents/observations/; parallelCallCapability and classifierReliability adapt empirically after 5 runs; classifier bypass saves an LLM round-trip when reliability is low; toolCallDialect probed per model (native-fc vs text-parse routing); auto-enabled when .withReasoning() is active, opt out with .withCalibration("skip")
• Adaptive tool calling -- toolCallDialect FC probe routes models to NativeFCDriver (native FC) or TextParseDriver (3-tier XML/JSON/pseudo-code cascade); HealingPipeline normalizes tool-name aliases, param aliases, paths, and types before every execution; ToolCallObservation closes the ExperienceStore feedback loop with N≥3 alias frequency gate
• Reactive intelligence -- 5-source entropy sensor, reactive controller (8 dispatched interventions: early-stop, context-compress, strategy-switch, temp-adjust, tool-inject, skill-activate, tool-failure-redirect, stall-detect; 4 advisory via pulse tool: prompt-switch, memory-boost, skill-reinject, human-escalate), local learning engine (conformal calibration, Thompson Sampling bandit, skill synthesis), telemetry client (api.reactiveagents.dev), .withReactiveIntelligence() builder method with hooks, constraints, and autonomy control
• Living Skills System -- agentskills.io SKILL.md compatibility, SkillStoreService (SQLite-backed), SkillEvolutionService (LLM refinement + version management), unified SkillResolverService (SQLite + filesystem), 5-stage compression pipeline, context-aware injection guard with model-tier budgets, activate_skill + get_skill_section meta-tools, .withSkills() builder, agent.skills() / exportSkill() / loadSkill() / refineSkills() runtime API
• Agent as Data -- AgentConfig JSON-serializable schema, builder.toConfig() reverse mapping, ReactiveAgents.fromConfig() / .fromJSON() reconstruction, roundtrip serialization
• Lightweight composition -- agentFn() lazy agent primitives, pipe() sequential chains, parallel() concurrent fan-out, race() first-to-complete — all composable
• Dynamic tool registration -- agent.registerTool() / agent.unregisterTool() for runtime tool management on live agents
• Web framework integration — @reactive-agents/react (useAgentStream, useAgent), @reactive-agents/vue composables, @reactive-agents/svelte stores — consume AgentStream.toSSE() from Next.js, SvelteKit, Nuxt, or any SSE-capable server
• 4,349 tests across 497 files

Quick Start

Install and run your first TypeScript AI agent in under 60 seconds.

Requires Bun ≥1.0.0 — the framework uses Bun's native SQLite, subprocess, and HTTP APIs. Node.js support is planned for a future release. Install Bun in one command: curl -fsSL https://bun.sh/install | bash

bun add reactive-agents

Note: effect is included as a dependency of reactive-agents and installed automatically. If you import from effect directly in your own code (e.g. import { Effect } from "effect"), add it to your project explicitly: bun add effect.

import { ReactiveAgents } from 'reactive-agents'

const agent = await ReactiveAgents.create()
    .withName('assistant')
    .withProvider('anthropic')
    .withModel('claude-sonnet-4-20250514')
    .build()

const result = await agent.run('Explain quantum entanglement')
console.log(result.output)
console.log(result.metadata) // { duration, cost, tokensUsed, stepsCount }

Add Capabilities

Every capability is opt-in. Chain what you need:

const agent = await ReactiveAgents.create()
    .withName('research-agent')
    .withProvider('anthropic')
    .withReasoning() // ReAct reasoning loop
    .withTools() // Built-in tools + MCP support
    .withMemory('1') // Persistent memory (FTS5 search)
    .withGuardrails() // Block injection, PII, toxicity
    .withKillSwitch() // Per-agent + global emergency halt
    .withBehavioralContracts({
        // Enforce tool whitelist + iteration cap
        deniedTools: ['file-write'],
        maxIterations: 10,
    })
    .withVerification() // Fact-check outputs
    .withCostTracking() // Budget enforcement + model routing
    .withObservability({ verbosity: 'verbose', live: true }) // Live log streaming + tracing
    .withContextProfile({ tier: 'local' }) // Adaptive context for model tier
    .withIdentity() // RBAC + agent certificates (Ed25519)
    .withInteraction() // 5 autonomy modes
    .withOrchestration() // Multi-agent workflows
    .withSelfImprovement() // Cross-task strategy outcome learning
    .withRequiredTools({
        // Ensure critical tools are called
        tools: ['web-search'],
        maxRetries: 2,
    })
    .withStrictValidation() // Throw at build time if required config is missing
    .withTimeout(60_000) // Execution timeout (ms)
    .withRetryPolicy({ maxRetries: 3, backoffMs: 1_000 }) // Retry on transient LLM failures
    .withCacheTimeout(3_600_000) // Semantic cache TTL (ms)
    .withErrorHandler((err, ctx) => {
        // Global error callback
        console.error('Agent error:', err.message)
    })
    .withFallbacks({
        // Provider/model fallback chain
        providers: ['anthropic', 'openai'],
        errorThreshold: 3,
    })
    .withLogging({ level: 'info', format: 'json', filePath: './agent.log' }) // Structured logging
    .withHealthCheck() // Enable agent.health() probe
    .withMinIterations(3) // Require at least 3 iterations before exit
    .withVerificationStep({ mode: 'reflect' }) // LLM self-review pass after initial answer
    .withOutputValidator((output) => ({
        // Structural validation with retry
        valid: output.includes('COMPLETE'),
        feedback: 'Response must include COMPLETE marker',
    }))
    .withTaskContext({ project: 'acme', env: 'prod' }) // Background data → reasoning context
    .withSkills({
        // Living Skills System
        paths: ['./my-skills/'],
        evolution: { mode: 'suggest' },
    })
    .withGateway({
        // Persistent autonomous harness
        heartbeat: { intervalMs: 1_800_000, policy: 'adaptive' },
        crons: [{ schedule: '0 9 * * MON', instruction: 'Weekly review' }],
        policies: { dailyTokenBudget: 50_000 },
    })
    .build()

Conversational Chat

Use agent.chat() for single-turn Q&A or agent.session() for multi-turn conversations with adaptive routing -- direct LLM for simple questions, full ReAct loop for tool-capable queries:

// Single-turn chat
const answer = await agent.chat("What's the status of the deployment?")

// Multi-turn session
const session = agent.session()
await session.chat("Summarize yesterday's logs")
await session.chat('Which errors were most frequent?')

Agent Config (Agent as Data)

Define agents as JSON-serializable config objects. Save, share, and reconstruct agents without code:

import {
    agentConfigToJSON,
    agentConfigFromJSON,
    ReactiveAgents,
} from 'reactive-agents'

// Builder → Config → JSON
const builder = ReactiveAgents.create()
    .withName('researcher')
    .withProvider('anthropic')
    .withReasoning({ defaultStrategy: 'plan-execute-reflect' })
    .withTools({ adaptive: true })
    .withMemory('2')

const config = builder.toConfig()
const json = agentConfigToJSON(config)
// Save to file, database, or send over the wire

// JSON → Builder → Agent
const restored = await ReactiveAgents.fromJSON(json)
const agent = await restored.build()
const result = await agent.run('Research quantum computing advances')

Composition API

Build agent pipelines with functional combinators:

import { agentFn, pipe, parallel, race } from 'reactive-agents'

// Create lazy agent functions
const researcher = agentFn({ name: 'researcher', provider: 'anthropic' }, (b) =>
    b.withReasoning().withTools()
)
const summarizer = agentFn({ name: 'summarizer', provider: 'anthropic' })

// Sequential pipeline: research → summarize
const pipeline = pipe(researcher, summarizer)
const result = await pipeline('What are the latest AI breakthroughs?')

// Parallel fan-out: run multiple analyses concurrently
const multiAnalysis = parallel(
    agentFn({ name: 'sentiment', provider: 'anthropic' }),
    agentFn({ name: 'keywords', provider: 'anthropic' }),
    agentFn({ name: 'summary', provider: 'anthropic' })
)
const combined = await multiAnalysis('Article text here...')
// combined.output contains labeled results from all 3 agents

// Race: fastest agent wins
const fastest = race(
    agentFn({ name: 'claude', provider: 'anthropic' }),
    agentFn({ name: 'gpt4', provider: 'openai' })
)
const winner = await fastest('Quick answer needed')

// Clean up
await pipeline.dispose()
await multiAnalysis.dispose()
await fastest.dispose()

Streaming

Tokens arrive as they're generated via AsyncGenerator. Pass an AbortSignal to cancel mid-stream:

const controller = new AbortController()

for await (const event of agent.runStream('Analyze this dataset', {
    signal: controller.signal,
})) {
    if (event._tag === 'TextDelta') process.stdout.write(event.text)
    if (event._tag === 'IterationProgress')
        console.log(`Step ${event.iteration}/${event.maxIterations}`)
    if (event._tag === 'StreamCancelled') console.log('Stream cancelled')
    if (event._tag === 'StreamCompleted') {
        console.log('\nDone!')
        // event.toolSummary: Array<{ toolName, calls, successRate }>
    }
}

// Cancel from elsewhere (e.g., HTTP request abort)
controller.abort()

Lifecycle Hooks

Intercept any of the 10 execution phases with before, after, or error hooks:

import { Effect } from 'effect'
import { ReactiveAgents } from 'reactive-agents'

const agent = await ReactiveAgents.create()
    .withProvider('anthropic')
    .withReasoning()
    .withTools()
    .withHook({
        phase: 'think',
        timing: 'after',
        handler: (ctx) => {
            console.log(
                `Step ${ctx.metadata.stepsCount}: ${ctx.metadata.strategyUsed}`
            )
            return Effect.succeed(ctx)
        },
    })
    .withHook({
        phase: 'act',
        timing: 'after',
        handler: (ctx) => {
            const last = ctx.toolResults.at(-1) as
                | { toolName?: string }
                | undefined
            if (last?.toolName) console.log(`Tool called: ${last.toolName}`)
            return Effect.succeed(ctx)
        },
    })
    .build()

Available phases: bootstrap, guardrail, cost-route, strategy, think, act, observe, verify, memory-flush, complete. Each supports before, after, and on-error timing.

Comparison

How Reactive Agents compares to other TypeScript agent frameworks on shipped, working features:

Capability	Reactive Agents	LangChain JS	Vercel AI SDK	Mastra
Full type safety (Effect-TS)	Yes	--	Partial	Partial
Composable layer architecture	13 layers	--	--	--
Reasoning strategies	5 + adaptive	1 (ReAct)	--	1
Model-adaptive context	4 tiers	--	--	--
Local model optimization	Yes	--	--	--
Execution lifecycle hooks	10 phases	Callbacks	Middleware	--
Multi-agent orchestration	A2A + workflows	Yes	--	Yes
Token streaming	Yes	Yes	Yes	Yes
Production guardrails	Yes	--	--	--
Cost tracking + budgets	Yes	--	--	--
Persistent gateway	Yes	--	--	--
Agent debrief + chat	Yes	--	--	--
Metrics dashboard	Yes	LangSmith	--	--
Agent-as-data config	Yes	--	--	--
Functional composition	Yes	Yes	--	--
Dynamic tool registration	Yes	Yes	--	--
Test suite	4,349 tests	--	--	--

Use Cases

• Autonomous engineering agents with tool execution and code generation
• Research and reporting workflows with verifiable reasoning steps
• Scheduled background agents using heartbeats, cron jobs, and webhooks
• Secure enterprise copilots with RBAC, audit trails, and policy controls
• Hybrid local/cloud AI deployments with adaptive context profiles
• Multi-agent teams with A2A protocol and dynamic sub-agent delegation

Architecture

ReactiveAgentBuilder
  -> createRuntime()
    -> Core Services     EventBus, AgentService, TaskService
    -> LLM Provider      Anthropic, OpenAI, Gemini, Ollama, LiteLLM, Test
    -> Memory            Working, Semantic, Episodic, Procedural
    -> Reasoning         ReAct, Reflexion, Plan-Execute, ToT, Adaptive
    -> Tools             Registry, Sandbox, MCP Client
    -> Guardrails        Injection, PII, Toxicity, Kill Switch, Behavioral Contracts
    -> Verification      Semantic Entropy, Fact Decomposition, NLI
    -> Cost              Complexity Router, Budget Enforcer, Cache
    -> Identity          Certificates, RBAC, Delegation, Audit
    -> Observability     Tracing, Metrics, Structured Logging
    -> Interaction       5 Modes, Checkpoints, Preference Learning
    -> Orchestration     Sequential, Parallel, Pipeline, Map-Reduce
    -> Prompts           Template Engine, Version Control
    -> Gateway           Heartbeats, Crons, Webhooks, Policy Engine
    -> ExecutionEngine   10-phase lifecycle with hooks

Every layer is an Effect Layer -- composable, independently testable, and tree-shakeable.

10-Phase Execution Engine

Every task flows through a deterministic lifecycle. Each phase calls its corresponding service when enabled:

Bootstrap --> Guardrail --> Cost Route --> Strategy Select
                                              |
                                    +--------------------+
                                    | Think -> Act -> Observe | <-- loop
                                    +--------------------+
                                              |
Verify --> Memory Flush --> Cost Track --> Audit --> Complete

Phase	Service Called	What It Does
Bootstrap	MemoryService	Load context from semantic/episodic memory
Guardrail	GuardrailService	Block unsafe input before LLM sees it
Cost Route	CostService	Select optimal model tier by complexity
Strategy Select	ReasoningService	Pick reasoning strategy (or direct LLM)
Think/Act/Observe	LLMService + ToolService	Reasoning loop with real tool execution
Verify	VerificationService	Fact-check output (entropy, decomposition, NLI)
Memory Flush	MemoryService	Persist session + episodic memories
Cost Track	CostService	Record spend against budget
Audit	ObservabilityService	Log audit trail (tokens, cost, strategy, duration)
Complete	--	Build final result with metadata

Every phase supports before, after, and on-error lifecycle hooks. When observability is enabled, every phase emits trace spans and metrics.

5 Reasoning Strategies

Strategy	How It Works	Best For
ReAct	Think -> Act -> Observe loop	Tool use, step-by-step tasks
Reflexion	Generate -> Critique -> Improve	Quality-critical output
Plan-Execute	Plan steps -> Execute -> Reflect -> Refine	Structured multi-step work
Tree-of-Thought	Branch -> Score -> Prune -> Synthesize	Creative, open-ended problems
Adaptive	Analyze task -> Auto-select best strategy	Mixed workloads

// Auto-select the best strategy per task
const agent = await ReactiveAgents.create()
    .withProvider('anthropic')
    .withReasoning({ defaultStrategy: 'adaptive' })
    .build()

// Automatic strategy switching on loop detection
const agent2 = await ReactiveAgents.create()
    .withProvider('anthropic')
    .withReasoning({
        enableStrategySwitching: true,
        maxStrategySwitches: 1,
        fallbackStrategy: 'plan-execute-reflect',
    })
    .build()

Multi-Provider Support

Provider	Models	Tool Calling	Streaming
Anthropic	Claude Haiku, Sonnet, Opus	Yes	Yes
OpenAI	GPT-4o, GPT-4o-mini	Yes	Yes
Google Gemini	Gemini Flash, Pro	Yes	Yes
Ollama	Any local model	Yes	Yes
LiteLLM	40+ models via LiteLLM proxy	Yes	Yes
Test	Mock (deterministic)	--	--

Switch providers with one line -- agent code stays the same.

Model-Adaptive Context

Optimize prompt construction and context compaction for your model tier:

const agent = await ReactiveAgents.create()
    .withProvider('ollama')
    .withModel('qwen3:4b')
    .withReasoning()
    .withTools()
    .withContextProfile({ tier: 'local' }) // Lean prompts, aggressive compaction
    .build()

Tier	Models	Context Strategy
"local"	Ollama small models (<=14b)	Lean prompts, aggressive compaction after 6 steps, 800-char truncation
"mid"	Mid-range models	Balanced prompts, moderate compaction
"large"	Anthropic, OpenAI, Gemini	Full context, standard compaction
"frontier"	Flagship models	Maximum context, minimal compaction

Packages

Package	Description
@reactive-agents/core	EventBus pub/sub, AgentService lifecycle, TaskService state machine, canonical types
@reactive-agents/runtime	10-phase ExecutionEngine, ReactiveAgentBuilder, createRuntime() layer composer
@reactive-agents/llm-provider	Unified LLM interface for Anthropic, OpenAI, Gemini, Ollama, LiteLLM, and Test providers
@reactive-agents/memory	4-layer memory (working, semantic, episodic, procedural) on bun:sqlite; ExperienceStore cross-agent learning; background consolidation + decay
@reactive-agents/reasoning	5 strategies (ReAct, Reflexion, Plan-Execute, ToT, Adaptive) with composable kernel architecture
@reactive-agents/tools	Tool registry with sandboxed execution, MCP client, agent-as-tool adapter, dynamic sub-agent spawning
@reactive-agents/guardrails	Pre-LLM safety: injection detection, PII filtering, toxicity blocking
@reactive-agents/verification	Post-LLM quality: semantic entropy, fact decomposition, NLI hallucination detection
@reactive-agents/cost	27-signal complexity routing, per-execution budget enforcement, semantic cache
@reactive-agents/identity	Ed25519 agent certificates, RBAC policies, delegation chains, audit logging
@reactive-agents/observability	Distributed tracing (OTLP), MetricsCollector, structured logging, console + JSON exporters
@reactive-agents/interaction	5 autonomy modes, checkpoint/resume, approval gates, preference learning
@reactive-agents/orchestration	Multi-agent workflows: sequential, parallel, pipeline, map-reduce with A2A support
@reactive-agents/prompts	Version-controlled template engine with variable interpolation and prompt library
@reactive-agents/eval	Evaluation framework: LLM-as-judge scoring, EvalStore persistence, comparison reports
@reactive-agents/a2a	A2A protocol: Agent Cards, JSON-RPC 2.0 server/client, SSE streaming
@reactive-agents/gateway	Persistent autonomous harness: adaptive heartbeats, cron scheduling, webhook ingestion, composable policy engine
@reactive-agents/testing	Mock services (LLM, tools, EventBus), assertion helpers, deterministic test fixtures
@reactive-agents/benchmarks	Benchmark suite: 20 tasks x 5 tiers, overhead measurement, report generation
@reactive-agents/health	Health checks and readiness probes for production deployments
@reactive-agents/reactive-intelligence	Metacognitive layer: entropy sensor (5 sources), reactive controller (early-stop, compression, strategy switch), learning engine (calibration, bandit, skill synthesis), telemetry client
@reactive-agents/react	React 18+ hooks: useAgentStream (token streaming), useAgent (one-shot) — consume AgentStream.toSSE() endpoints
@reactive-agents/vue	Vue 3 composables: useAgentStream, useAgent with reactive refs
@reactive-agents/svelte	Svelte 4/5 stores: createAgentStream, createAgent writable stores

Observability & Metrics Dashboard

When observability is enabled, the agent displays a professional metrics dashboard after each execution:

+-------------------------------------------------------------+
| Agent Execution Summary                                      |
+-------------------------------------------------------------+
| Status:    Success      Duration: 13.9s   Steps: 7          |
| Tokens:    1,963        Cost: ~$0.003     Model: claude-3.5 |
+-------------------------------------------------------------+

Execution Timeline
|- [bootstrap]       100ms    ok
|- [think]        10,001ms    warn  (7 iter, 72% of time)
|- [act]           1,000ms    ok    (2 tools)
|- [complete]         28ms    ok

Tool Execution (2 called)
|- file-write    ok  3 calls, 450ms avg
|- web-search    ok  2 calls, 280ms avg

• Per-phase execution timing and bottleneck identification
• Tool call summary (success/error counts, average duration)
• Smart alerts and optimization tips
• Cost estimation in USD
• EventBus-driven collection (no manual instrumentation)

Enable with:

.withObservability({ verbosity: "normal", live: true })

CLI (rax)

rax init my-project --template full              # Scaffold a project
rax create agent researcher --recipe researcher   # Generate an agent from recipe
rax create agent my-agent --interactive           # Interactive scaffolding (readline prompts)
rax run "Explain quantum computing" --provider anthropic  # Run an agent
rax cortex --dev                                         # Cortex API + Vite UI (like apps/cortex bun start)
rax cortex                                               # Cortex API only (or bundled static UI)
rax run "Task" --cortex --provider anthropic             # Stream events to Cortex (.withCortex())

Register Custom Tools

Tools are registered at build time, via agent.registerTool() after build(), or through MCP. Built-in task tools include web search, file I/O, HTTP, and code execution; dynamic sub-agents add spawn-agent. With .withTools(), the Conductor's Suite also injects recall, find, brief, and pulse (override with .withMetaTools(false)).

Use the ToolBuilder fluent API to define tools without raw schema objects:

import { ReactiveAgents } from 'reactive-agents'
import { ToolBuilder } from '@reactive-agents/tools'
import { Effect } from 'effect'

const webSearchTool = ToolBuilder.create('web_search')
    .description('Search the web for current information')
    .param('query', 'string', 'Search query', { required: true })
    .riskLevel('low')
    .timeout(10_000)
    .handler((args) => Effect.succeed(`Results for: ${args.query}`))
    .build()

const agent = await ReactiveAgents.create()
    .withProvider('anthropic')
    .withReasoning()
    .withTools({ tools: [webSearchTool] })
    .build()

Or use raw schema objects directly:

const agent = await ReactiveAgents.create()
    .withProvider('anthropic')
    .withReasoning()
    .withTools({
        tools: [
            {
                definition: {
                    name: 'web_search',
                    description: 'Search the web for current information',
                    parameters: [
                        {
                            name: 'query',
                            type: 'string',
                            description: 'Search query',
                            required: true,
                        },
                    ],
                    riskLevel: 'low',
                    timeoutMs: 10_000,
                    requiresApproval: false,
                    source: 'function',
                },
                handler: (args) => Effect.succeed(`Results for: ${args.query}`),
            },
        ],
    })
    .build()

Dynamic Tool Registration

Add or remove tools from a running agent at runtime:

import { Effect } from 'effect'

const agent = await ReactiveAgents.create()
    .withName('adaptive-agent')
    .withProvider('anthropic')
    .withReasoning()
    .withTools()
    .build()

// Register a new tool at runtime
await agent.registerTool(
    {
        name: 'custom_api',
        description: 'Call the custom API',
        parameters: [
            {
                name: 'endpoint',
                type: 'string',
                description: 'API endpoint',
                required: true,
            },
        ],
        riskLevel: 'low',
        source: 'function',
    },
    (args) => Effect.succeed(`Response from ${args.endpoint}`)
)

// Later, remove it when no longer needed
await agent.unregisterTool('custom_api')

Dynamic Sub-Agent Spawning

Use .withDynamicSubAgents() to let the model spawn ad-hoc sub-agents at runtime without pre-configuring named agent tools. This registers the built-in spawn-agent tool, which the model can invoke freely:

const agent = await ReactiveAgents.create()
    .withProvider('anthropic')
    .withModel('claude-sonnet-4-6')
    .withTools()
    .withDynamicSubAgents({ maxIterations: 5 })
    .build()

Sub-agents receive a clean context window, inherit the parent's provider and model by default, and are depth-limited to MAX_RECURSION_DEPTH = 3.

Approach	When to use
.withAgentTool("name", config)	Named, purpose-built sub-agent with a specific role
.withDynamicSubAgents()	Ad-hoc delegation at model's discretion, unknown tasks

Testing

Built-in test scenario support for deterministic, offline tests:

const agent = await ReactiveAgents.create()
    .withTestScenario([
        { match: 'capital of France', text: 'Paris is the capital of France.' },
    ])
    .build()

const result = await agent.run('What is the capital of France?')
// result.output -> "Paris is the capital of France."

The @reactive-agents/testing package includes streaming assertions and pre-built scenario fixtures:

import {
    expectStream,
    createGuardrailBlockScenario,
    createBudgetExhaustedScenario,
} from '@reactive-agents/testing'

// Stream assertions
const stream = agent.runStream('Write a haiku')
await expectStream(stream)
    .toEmitTextDeltas()
    .toComplete()
    .toEmitEvents(['TextDelta', 'StreamCompleted'])

// Pre-built scenario fixtures
const scenario = createGuardrailBlockScenario() // agent + prompt that triggers guardrail
const budget = createBudgetExhaustedScenario() // agent + prompt that exhausts budget
const maxIter = createMaxIterationsScenario() // agent + prompt that hits max iterations

Development

bun install              # Install dependencies
bun test                 # Run full test suite (4,349 tests, 497 files)
bun run build            # Build all packages (31 packages, ESM + DTS)

Environment Variables

ANTHROPIC_API_KEY=sk-ant-...          # Anthropic Claude
OPENAI_API_KEY=sk-...                 # OpenAI GPT-4o
GOOGLE_API_KEY=...                    # Google Gemini
EMBEDDING_PROVIDER=openai             # For vector memory
EMBEDDING_MODEL=text-embedding-3-small
LLM_DEFAULT_MODEL=claude-sonnet-4-20250514

Documentation

Full documentation at docs.reactiveagents.dev

• Getting Started -- Build an agent in 5 minutes
• Reasoning Strategies -- All 5 strategies explained
• Architecture -- Layer system deep dive
• Cookbook -- Testing, multi-agent patterns, production deployment

Getting Help

• Discord -- Join the community for questions, discussions, and support
• GitHub Issues -- Report bugs or request features
• GitHub Discussions -- Ask questions and share ideas

License

MIT