Debugger for multi-agent systems

Find the decisive step.

See what broke. Replay the fix.

Start using 404 AI See how it works

What changes

From a long trace to one defensible next move.

3framework starting pointsLangGraph · CrewAI · AutoGen
1decisive error stepearliest causal break
4moves from failure to fixingest · graph · traverse · replay

The diagnosis

A failed run is not the diagnosis.

Observability can show what happened. 404 AI follows the causal chain to the earliest step whose correction could change the outcome.

TRACE / 8F3A2D

Make the signal legible.

See the agent, tool call, memory state, deviation, and downstream impact that support a suspected decisive step. The graph is the explanation, not another log view.

Inspect the workflow
Abstract trace evidence converging on one highlighted point
SIGNAL / EARLIEST BREAK

How it works

Trace the cause. Test the fix.

A debugging workflow built for systems where one small reasoning step can shape everything downstream.

01

Ingest the run

Bring in OpenTelemetry spans from LangGraph, CrewAI, or AutoGen without changing the workflow you are debugging.

span / tool_call / memory
02

See the causal graph

Agent steps, tool calls, memory operations, and downstream effects become one Multi-Agent Cognitive Execution Graph.

MACEG / structure
03

Traverse the failure

Counterfactual Causal Traversal backtracks to the earliest Decisive Error Step, then tests whether a correction changes the outcome.

CCT / DES
04

Replay the branch

Snapshot state at span boundaries and replay with controlled seeds, temperatures, and mocked tool outputs.

replay / controlled

Deterministic control

When the fix matters, replay it.

Snapshot state at span boundaries. Reinject the same context. Change one variable. See whether the branch recovers.

Deterministic replay paths with one branch selected
REPLAY / CONTROLLED BRANCH

State snapshots
at span boundaries

Controlled variables
seeds · temperatures · tool outputs

Counterfactual check
did the outcome change?

Evidence first

Stop rerunning the whole system.

Move from broad inspection to a precise question: which step first put the run on the path to failure?

Confidence and uncertainty stay visible.

TRACE SUMMARY

run_8F3A2D

failed
Agents6
Steps142
Tools27
Duration02:14

DECISIVE ERROR STEP

span_42·Agent: Planner
Downstream impact high
View graph Replay branch

Start with the trace you already have

Make the next failure explainable.

Instrument a workflow. Inspect the causal graph. Replay the branch that matters.

Start using 404 AI