DagPipe MCP server

DagPipe

The reliability layer that makes AI workflows safe to ship: crash recovery, schema validation, and cost routing

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NeurIPS 2025 research analyzing 1,642 real-world multi-agent execution traces found a 41–86.7% failure rate across 7 state-of-the-art open-source systems. The root cause: cascading error propagation, where one failed node corrupts all downstream nodes.

DagPipe makes cascade failure structurally impossible.

Every node's output is independently validated and checkpointed before the next node executes. A failure at node 4 cannot corrupt nodes 1, 2, or 3. Delete nothing. Just re-run. DagPipe resumes exactly where it stopped, automatically.

Pipeline: research → outline → draft → edit → publish
                                  ↑
                            crashed here

Re-run → research ✓ (restored) → outline ✓ (restored) → draft (re-runs) → ...

Zero infrastructure. Zero subscription. Runs entirely on free-tier APIs.

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Install

pip install dagpipe-core

Requirements: Python 3.12+ · pydantic >= 2.0 · pyyaml · A free Groq API key (no credit card)

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Three Ways to Use DagPipe

For developers: install the library and build crash-proof LLM pipelines in Python:

pip install dagpipe-core

For non-coders: describe your workflow in plain English, receive production-ready crash-proof pipeline code as a downloadable zip. No coding required: 👉 Pipeline Generator on Apify ($0.05/run)

For AI agents and IDE users: connect directly via MCP. Use DagPipe from Claude Desktop, Cursor, Windsurf, or any MCP-compatible client without writing any code: 👉 DagPipe Generator MCP on Smithery

The generator outputs DagPipe pipelines, as every generated zip already has crash recovery, schema validation, and cost routing built in by default. No other LLM pipeline framework ships this.

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Why DagPipe?

🔴 Without DagPipe	🟢 With DagPipe
Pipeline crashes = start over from zero	JSON checkpointing: resume from last successful node
Paying for large models on every task	Cognitive routing: route easy tasks to free-tier models
LLM returns malformed JSON	Guaranteed structured output: auto-retry with error feedback
Tight coupling to one provider	Provider-agnostic: any callable works as a model function
Fragile sequential scripts	Topological DAG execution: safe dependency resolution
Silent bad data passes through	Semantic assertions: catch structurally valid but wrong output

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What's New in v0.2.3

v0.2.3 adds the official MCP Registry metadata and identifier to the package repository, enabling one-click discovery on the official MCP Registry.

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What's New in v0.2.2

v0.2.2 improves PyPI discoverability with optimized metadata, a clearer project description, and enhanced AI agent categorization.

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What's New in v0.2.1

v0.2.1 brings crucial generator reliability fixes and a highly requested DX feature:

• verbose=True Output: Pass verbose=True to the PipelineOrchestrator to get real-time, per-node CLI progress updates with execution times, node descriptions, and running costs.
• Generator Core Fixes: The MCP and Apify generator prompts now strictly enforce the model=None positional argument, guarantee exact YAML topological dependency key lookups (DEPENDENCY_NODE_ID), and support native .csv, .xml, .html, and .md save nodes out of the box.

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What's New in v0.2.0

v0.2.0 was a significant architectural upgrade. All features are opt-in and fully backwards compatible, meaning existing v0.1.x pipelines run without changes.

Smart Model Router

The router automatically selects which AI model to use based on task complexity. Simple tasks go to fast, free models. Hard tasks escalate to more capable models. If a model fails or rate-limits, it tries the next one, automatically.

router = ModelRouter(
    low_complexity_fn=gemini_flash,   low_label="gemini_flash",
    high_complexity_fn=llama33_70b,   high_label="llama_70b",
    fallback_fn=gemini_flash,         fallback_label="fallback",
    complexity_threshold=0.6,
)

Live Model Registry

A self-maintaining database of free-tier model availability and pricing. Refreshes every 24 hours automatically. If a model goes offline, the registry marks it unavailable and the router stops routing to it, without any manual intervention.

Semantic Output Assertions

Beyond schema validation, nodes can declare semantic rules. If the LLM returns structurally valid but logically wrong data, the assertion catches it and forces self-correction:

DAGNode(
    id="revenue",
    fn_name="calculate_revenue",
    assert_fn=lambda out: 0 < out.get("revenue", 0) < 1e12,
    assert_message="Revenue must be a realistic positive number",
)

Context Isolation

Nodes only receive outputs from their declared dependencies. A node processing untrusted web data cannot access credentials or outputs from unrelated pipeline branches.

Dead Letter Queue

When a node exhausts all retries, DagPipe saves the complete failure context to .dagpipe/checkpoints/{node_id}.failed.json, including what was passed in, what error occurred, and instructions for manual correction. No failure context is ever lost.

Pluggable Checkpoint Backends

Swap out filesystem storage for Redis, S3, or any custom backend by implementing the CheckpointStorage protocol.

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Quickstart

from pathlib import Path
from dagpipe.dag import PipelineOrchestrator, DAGNode, FilesystemCheckpoint
from dagpipe.router import ModelRouter
from dagpipe.constrained import constrained_generate

# 1. Define your node functions
def research(context, model):
    prompt = [{"role": "user", "content": f"Research: {context['topic']}"}]
    return {"summary": model(prompt)}

def write_draft(context, model):
    summary = context["research"]["summary"]
    prompt = [{"role": "user", "content": f"Write an article based on: {summary}"}]
    return {"draft": model(prompt)}

def publish(context, model):
    print(f"Publishing: {context['write_draft']['draft'][:100]}...")
    return {"status": "published"}


# 2. Wire your LLM providers (any Python callable works)
import groq
from google.genai import Client

groq_client = groq.Groq()
def llama33_70b(messages):
    return groq_client.chat.completions.create(
        model="llama-3.3-70b-versatile", messages=messages
    ).choices[0].message.content

gemini_client = Client()
def gemini_flash(messages):
    return gemini_client.models.generate_content(
        model="gemini-2.5-flash", contents=messages[0]["content"]
    ).text


# 3. Build the router
router = ModelRouter(
    low_complexity_fn=gemini_flash,  low_label="gemini_flash",
    high_complexity_fn=llama33_70b,  high_label="llama_70b",
    fallback_fn=gemini_flash,        fallback_label="fallback",
    complexity_threshold=0.6,
)


# 4. Define the DAG
nodes = [
    DAGNode(id="research",    fn_name="research",    complexity=0.4),
    DAGNode(id="write_draft", fn_name="write_draft", complexity=0.7,
            depends_on=["research"]),
    DAGNode(id="publish",     fn_name="publish",
            depends_on=["write_draft"], is_deterministic=True),
]


# 5. Run it
orchestrator = PipelineOrchestrator(
    nodes=nodes,
    node_registry={
        "research":    research,
        "write_draft": write_draft,
        "publish":     publish,
    },
    router=router,
    checkpoint_backend=FilesystemCheckpoint(Path(".dagpipe/checkpoints")),
    max_retries=3,
    on_node_complete=lambda node_id, result, duration:
        print(f"  ✓ {node_id} ({duration:.1f}s)"),
)

result = orchestrator.run(initial_state={"topic": "AI in African fintech"})

Crash mid-run? Delete nothing. Just re-run. DagPipe reads the checkpoints and skips completed nodes automatically.

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How It Works

Your Tasks (YAML or Python list of DAGNodes)
                    │
                    ▼
         ┌──────────────────┐
         │  Topological     │  resolves execution order,
         │  Sort            │  detects cycles before running
         └────────┬─────────┘
                  │
        ┌─────────▼──────────┐
        │  Checkpoint        │  restores any completed nodes
        │  Restore           │  from previous runs
        └─────────┬──────────┘
                  │
          ┌───────▼────────┐
          │  For each node │◄─────────────────────────┐
          └───────┬────────┘                          │
                  │                                   │
        ┌─────────▼──────────┐    ┌────────────────┐  │
        │  ModelRouter       │───▶│ low / high /   │  │
        │  (complexity score)│    │ fallback fn    │  │
        └─────────┬──────────┘    └────────────────┘  │
                  │                                   │
        ┌─────────▼──────────┐                        │
        │  Constrained       │  forces valid output   │
        │  Generator         │  retries on failure    │
        └─────────┬──────────┘                        │
                  │                                   │
        ┌─────────▼──────────┐                        │
        │  Checkpoint Save   │  writes result to disk │
        └─────────┬──────────┘                        │
                  │                                   │
          crash here = resume from ✓            next node

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📦 Core Modules

dagpipe.dag: The Orchestrator

The central engine. Loads a DAG from a Python list or YAML file, sorts nodes by dependency, and executes them with checkpointing and retry.

from dagpipe.dag import PipelineOrchestrator, DAGNode, load_dag

# Load from YAML
nodes = load_dag(Path("my_pipeline.yaml"))

# Or define in Python
nodes = [DAGNode(id="step_a", fn_name="fn_a", complexity=0.3)]

dagpipe.checkpoints: Crash Recovery

Saves node output to disk after every successful execution. On resume, completed nodes are skipped entirely.

New in v0.2.0: the CheckpointStorage Protocol, allowing you to swap the default filesystem backend for Redis, S3, or any custom store:

from dagpipe.dag import CheckpointStorage

class RedisCheckpoint(CheckpointStorage):
    def save(self, id: str, data: dict): redis_client.set(id, json.dumps(data))
    def load(self, id: str): return json.loads(redis_client.get(id) or "null")
    def exists(self, id: str): return redis_client.exists(id) > 0
    def clear(self): redis_client.flushdb()

(Note: passing checkpoint_dir directly to the Orchestrator is deprecated in v0.2.0. Use checkpoint_backend=FilesystemCheckpoint(path) instead.)

dagpipe.router: Intelligent Model Selection

Routes tasks to the cheapest model that can handle them. Tracks rate limit budgets and escalates on retry.

from dagpipe.router import ModelRouter, classify_complexity

score = classify_complexity("implement OAuth authentication", token_count=1200)
# → 0.8 (high complexity, triggers high_complexity_fn)

router = ModelRouter(
    low_complexity_fn=cheap_model,   low_label="7b",
    high_complexity_fn=smart_model,  high_label="70b",
    fallback_fn=backup_model,        fallback_label="backup",
)
fn, label = router.route(complexity=0.8)

dagpipe.constrained: Guaranteed Structured Output

Wraps any LLM call with Pydantic schema validation. On failure, injects the error back into the prompt and retries automatically.

from pydantic import BaseModel
from dagpipe.constrained import constrained_generate

class ArticleOutput(BaseModel):
    title: str
    body: str
    word_count: int

result = constrained_generate(
    messages=[{"role": "user", "content": "Write a short article about AI."}],
    schema=ArticleOutput,
    llm_call_fn=my_llm,
    max_retries=3,
)
# result is a validated ArticleOutput instance, every time

dagpipe.registry: Live Model Registry (New in v0.2.0)

Self-maintaining database of model availability and pricing. Refreshes every 24 hours. If a model goes offline, the registry marks it unavailable automatically.

from dagpipe.registry import ModelRegistry

registry = ModelRegistry()
available = registry.list_available()   # live model list
cost = registry.get_cost("llama-3.3-70b-versatile")  # per-token pricing

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📝 YAML Pipeline Definition

# my_pipeline.yaml
nodes:
  - id: research
    fn: research_fn
    complexity: 0.4
  - id: summarize
    fn: summarize_fn
    depends_on: [research]
    complexity: 0.5
  - id: publish
    fn: publish_fn
    depends_on: [summarize]
    is_deterministic: true

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The Zero-Cost Stack

DagPipe is designed to run entirely on free tiers:

Provider	Model	Free Tier
Groq	Llama 3.3 70B	30 req/min
Groq	Llama 3.1 8B	30 req/min
Google	Gemini 2.5 Flash	10 req/min
Google	Gemini 2.5 Flash-Lite	15 req/min
Modal	Any 7B model	$30/month free credits
Ollama	Any model	Local, unlimited

⚠️ Gemini 2.0 Flash was retired March 3, 2026. Update any old model references to gemini-2.5-flash.

Wire any of these as your low_complexity_fn, high_complexity_fn, or fallback_fn. DagPipe is provider-agnostic, and any Python callable works.

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🔌 MCP Server

DagPipe exposes a live MCP server that lets any MCP-compatible AI client generate crash-proof pipelines through natural language.

Live endpoint:

https://gastronomic-desk--dagpipe-generator-mcp.apify.actor/mcp

Listed on Smithery: https://smithery.ai/server/gastronomic-desk/dagpipe-generator

Connect via Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "dagpipe-generator": {
      "url": "https://gastronomic-desk--dagpipe-generator-mcp.apify.actor/mcp?groqApiKey=YOUR_GROQ_KEY",
      "transport": "streamable-http"
    }
  }
}

Connect via Cursor / Windsurf

{
  "dagpipe-generator": {
    "url": "https://gastronomic-desk--dagpipe-generator-mcp.apify.actor/mcp?groqApiKey=YOUR_GROQ_KEY",
    "transport": "streamable-http"
  }
}

Get your free Groq API key at console.groq.com/keys. Takes 2 minutes, no credit card required.

Run Locally (stdio transport)

git clone https://github.com/devilsfave/dagpipe
cd dagpipe
pip install -r servers/dagpipe-generator/requirements.txt
export GROQ_API_KEY=your_key_here
python servers/dagpipe-generator/server.py

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🔒 Security Architecture

Static Execution Graph

DagPipe pipelines cannot self-modify. The graph is declared in YAML before runtime. No LLM call can add, remove, or reorder nodes. This makes DagPipe safe to run on sensitive data, unlike agent frameworks where the LLM decides what executes next.

Semantic Output Contracts (v0.2.0+)

Beyond schema validation, nodes can declare semantic assertions. Structurally valid but logically wrong data is caught, injected back into the retry prompt, and forced to self-correct:

DAGNode(
    id="revenue",
    fn_name="calculate_revenue",
    assert_fn=lambda out: 0 < out.get("revenue", 0) < 1e12,
    assert_message="Revenue must be a realistic positive number",
)

Context Isolation (v0.2.0+)

Nodes only receive outputs from their declared dependencies. A node processing untrusted web data cannot access API keys, credentials, or outputs from unrelated pipeline branches.

Dead Letter Queue (v0.2.0+)

When a node fails after all retries, DagPipe saves the full failure context to .dagpipe/checkpoints/{node_id}.failed.json, including the context passed in, the last error, and instructions for manual correction. No failure context is ever lost.

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🛒 Templates & Ecosystem

Ready-to-run pipeline packages built on DagPipe. Download, drop in your API key, and run.

Template	Description	Link
DagPipe Generator MCP	🔌 Connect from any AI IDE	Smithery →
Content Pipeline	Research, draft, edit, SEO-optimize blog posts on Groq's free tier	Get it →

🎭 Apify Actors

Actor	Purpose	Link
Pipeline Generator	🌟 The flagship workflow architect	Apify Store →
Structured Extract	Multi-model (Groq/Gemini/Ollama) data extractor	Apify Store →
E-Commerce Extractor	Specialized price and product data extraction	Apify Store →

More templates coming. Have a use case? Open an issue.

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📊 Project Status

Phase 1: Core Library + Checkpointing   ████████████████████  COMPLETE (v0.1.0)
Phase 2: PyPI + Templates + Actors      ████████████████████  COMPLETE (v0.1.0)
Phase 3: V2 - Router + Registry + MCP   ████████████████████  COMPLETE (v0.2.3)
Phase 4: Parallel Execution (asyncio)   ░░░░░░░░░░░░░░░░░░░░  ROADMAP  (v0.3.0)

Test coverage: 132 tests · 5 modules · 0 regressions · Python 3.12 + 3.13

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❓ FAQ

Why not just use LangChain or LangGraph?

LangGraph has checkpointing, but it is tightly coupled to their TypedDict state system and graph compilation model. You adopt the full framework to get it. DagPipe's checkpoints are plain JSON files on disk, readable with any text editor, and requiring no framework lock-in. DagPipe also ships a built-in generator that produces entire crash-proof pipelines from a plain English description. LangGraph does not have this.

Why not just wrap my pipeline in a try/except and restart manually?

A try/except tells you something failed. It does not save the work that succeeded before the crash. DagPipe checkpoints the output of every completed node before moving to the next one. When you restart, completed nodes are skipped automatically. You only pay to re-run the node that actually failed.

How is DagPipe's checkpointing different from LangGraph's?

LangGraph's checkpointing requires a StateGraph, TypedDict schemas, and a compiled checkpointer object. You are adopting their full framework architecture to access it. DagPipe's checkpoints are just JSON files. You can open them in a text editor, copy them, inspect them, or move them without any framework code.

Can I use this with OpenAI, Anthropic, or any other provider?

Yes. Any Python function that takes a list of messages and returns a string works as a model function. OpenAI, Anthropic, Cohere, a local Ollama call, or a mock function for testing: if it is callable, DagPipe can route to it.

Does DagPipe store my checkpoint data anywhere online?

No. Checkpoints are plain JSON files written to a local directory on your machine (default: .dagpipe/checkpoints/). Nothing leaves your environment unless you build a custom CheckpointStorage backend pointing to Redis, S3, or wherever you choose.

How does the router work without using an LLM?

Using an LLM to route an LLM is too expensive. The router uses pure Python heuristics, such as keyword matching and token count thresholds, to estimate cognitive complexity. If the task scores below your threshold, it routes to your low_complexity_fn. Above it, it routes to your high_complexity_fn.

What happens if the schema validator keeps failing?

The PipelineOrchestrator respects the max_retries parameter. If a node exhausts its retry budget, DagPipe halts and raises a RuntimeError. Because of checkpointing, you can adjust the prompt or schema and restart without losing any previously completed work.

Does this support parallel or async execution?

Not yet. v0.2.x executes nodes sequentially. Full asyncio support for concurrent execution of independent nodes is on the roadmap for v0.3.0. The focus of v0.2.0 is crash resilience, smart routing, and state persistence.

How do I use DagPipe from Claude Desktop or Cursor?

Install the MCP server from Smithery at smithery.ai/server/gastronomic-desk/dagpipe-generator. You will need a free Groq API key from console.groq.com/keys. Once connected, type "Generate a pipeline that does X" in your AI chat and receive a deployable ZIP in seconds.

Does this work if my pipeline was built with an AI coding tool?

Yes. DagPipe does not care how your node functions were written. Whether you wrote them by hand, with GitHub Copilot, or with a vibe coding tool, the checkpointing, validation, and routing work the same way. If the pipeline crashes, DagPipe picks up from the last successful node regardless of how the code was produced.

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🤝 Contributing

Issues and PRs are welcome. If you find a bug, open an issue with the error output and your Python version. If you want to add a feature, open an issue first so we can agree on the design before any code is written.

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