Inspect deterministic boundary execution over probabilistic systems.
boundary-inspector is an open source UI for exploring how boundary runtimes execute, fail, repair, and succeed.
It turns raw boundary event streams into an interactive view of:
- runs — top-level contract executions
- attempts — retry cycles within a run
- events — verification, repair, retry, and terminal outcomes
The goal is simple: make probabilistic systems understandable when they are embedded inside deterministic software.
Systems built on probabilistic components (LLMs, agents, automation systems) behave differently from traditional software.
They don't fail once.
They iterate, repair, retry, and converge.
Raw logs make this behavior difficult to understand:
- Where exactly did the failure occur?
- What triggered a repair?
- How did the system evolve between attempts?
- Why did the run ultimately succeed or fail?
boundary-inspector exists to make these execution boundaries visible.
Boundary runtimes enforce deterministic guarantees around probabilistic outputs.
Execution typically follows a pattern like:
input
↓
probabilistic system (LLM, agent, automation)
↓
verification
↓
repair
↓
retry
↓
terminal outcome
boundary-inspector visualizes this lifecycle as structured execution traces.
The inspector is designed to sit on top of boundary event streams.
Producer (llm-contract or other boundary runtime)
↓
BoundaryEvent stream
↓
boundary-inspector
The UI itself is runtime-agnostic. Any system that emits compatible boundary events can be inspected.
Currently supported:
- import or paste JSON event arrays
- live WebSocket event stream
Future versions will support additional transport adapters.
npm install
npm run dev
The inspector expects events shaped like:
type BoundaryEvent = {
system: string
runId: string
ts: string
type: string
level?: "info" | "warn" | "error"
attempt?: number
data: Record<string, unknown>
}Events are grouped into runs and attempts automatically by the UI.
The UI is organized into three main views.
Top-level executions.
Shows:
- run id
- terminal status
- attempt count
- duration
Visualizes the retry lifecycle for a selected run.
Each attempt contains a sequence of events such as:
- attempt started
- output observed
- verification failed
- repair generated
- retry scheduled
- verification passed
Displays the raw payload for the selected event, including failure explanations and reproduction payloads.
This allows developers to inspect exactly how a boundary execution evolved.
Stable DOM anchors are included to support documentation screenshots and automated capture.
Available targets:
- header:
#shot-header - controls:
#shot-controls - runs list:
#shot-runs-list - run inspector:
#shot-run-inspector - event details:
#shot-event-details - full layout:
#shot-layout
Planned improvements include:
- richer attempt timeline visualization
- event filtering and search
- attempt-to-attempt diffing
- replay debugger mode
- OTEL and JSONL adapters
- multi-run comparison
boundary-inspector is an early stage project.
Event schemas and UI behavior may evolve as boundary runtimes mature.
Issues and PRs are welcome.
If proposing schema changes, please include:
- sample events
- migration guidance
- expected UI behavior impact
MIT