windhover 0.32.2

Self-hosted, mobile-friendly observability for LangGraph — traces, run history, cost, and a living graph view.

Windhover

Windhover: the old poetic name for the kestrel, the falcon that hangs motionless in the wind, watching everything below. This tool does the same for your agent graphs.

Self-hosted, mobile-friendly observability for LangGraph. Trace depth like LangSmith (LLM prompts, tokens, cost, latency - plus retrievers and human-in-the-loop interrupts), run history, a timing waterfall, per-node stats, error forensics down to the throwing source line - and a living graph view that auto-updates when your code's topology changes. Point it at any compiled graph, or trace runs in from your own app. No LangSmith account, no cloud tunnel, no fragile websocket. HTTP + SSE, MIT.

Nothing about your graph's domain is baked in. Topology, the input form, and run outputs all come from the graph itself. Windhover observes - it never edits your graph.

Living graph (parallel fan-out)	Trace drawer - retrievers, LLM calls, cost, state

Runs - search, tags, sessions, interrupts	Dashboards - per-day, per-model

Quick start

pip install windhover langgraph
WINDHOVER_GRAPH=windhover.demo_graph:graph windhover   # -> :8090

Open http://<host>:8090. New run (input pre-filled from the graph's schema) → watch it execute → Runs for history, span trees, and replay → Stats for cost/latency. Edit the graph file while it runs and the canvas updates itself.

Your own graph: WINDHOVER_GRAPH="myapp.graphs:g" WINDHOVER_GRAPH_DIR=/path python -m windhover.server

Several graphs behind one URL: WINDHOVER_GRAPH="checkout=app.flows:checkout,support=app.flows:support" (a selector appears in the top bar; langgraph.json projects serve all their graphs automatically).

Trace runs from any app

from windhover import WindhoverTracer
graph.invoke(input, config={"callbacks": [WindhoverTracer("http://HOST:8090")]})

Node spans, LLM calls (model/prompt/response/tokens/cost), and tools show up in Runs - wherever your app runs. Non-blocking, best-effort; never raises into your graph.

Sessions and tags use standard LangChain config - no Windhover imports needed beyond the tracer:

graph.invoke(input, config={
    "callbacks": [WindhoverTracer("http://HOST:8090")],
    "metadata": {"windhover_session": "chat-42", "windhover_tags": ["prod"]},
    "tags": ["also-captured"],          # langgraph-internal tags are filtered out
})

Features

• Any graph: topology from graph.get_graph(); input form from its state schema.
• Full trace tree: nodes → nested LLM / tool / retriever spans: prompts, responses, tokens, cost, latency, retrieved documents with their metadata.
• Clickable graph: tap a node for health, latency, wiring, its source code, and recent executions with payloads.
• Error forensics: failed runs show the full traceback; the failing node turns red on the graph, and the node's source renders with the throwing line highlighted.
• Human-in-the-loop console: a paused graph shows an amber interrupted status with the question it's asking; answer it (Command(resume=…)), redirect it (Command(goto=…)), set static breakpoints per run (interrupt_before), edit state at any checkpoint (update_state), or fork a thread from any historical checkpoint - all from the UI, all pure LangGraph primitives.
• State evolution: every trace shows which state keys each node wrote, in order.
• X-ray: graphs with subgraphs get a canvas toggle that expands composite nodes (get_graph(xray=True)).
• Search & filters: full-text over prompts/payloads/errors (FTS5, LIKE fallback), status/tag/session filters, bookmarks, pagination, CSV/JSON export.
• Sessions: group runs into threads/batches; roll-up tokens, cost, errors.
• Scores: attach numeric evals to runs (API or UI): eval harnesses, LLM-as-judge, human review.
• Live tail: open a running run and watch spans arrive - including the model typing (streamed tokens flush into the span twice a second); nodes push progress via get_stream_writer().
• Call configs: every LLM span records temperature/max-tokens/stream and the tools the model was offered; conditional-edge branch labels and add_node(metadata=…) render on the graph and node pane; graphs with a context schema get a runtime-context box on New run.
• Custom events: dispatch_custom_event("name", {...}) anywhere in your app lands as an event marker in the trace, parented to the node that fired it.
• Retries + TTFT: tenacity retries badge the span (↻2); streaming LLM calls record time-to-first-token; cache-read / reasoning token details show on the model line.
• Memory browser: graphs compiled with a LangGraph Store get a Memory view: browse namespaces and search long-term memory items.
• Time-travel: checkpointed graphs get a per-thread checkpoint browser: state, writes, and next-nodes at every superstep (get_state_history).
• Run diff: compare any two runs node-by-node: identical vs differing outputs, duration and token deltas.
• Datasets / batch eval: store golden input sets, run the graph over them, and get an expected_match score per item (see Datasets on the Stats page).
• Run history + replay: SQLite; runs persist even if the browser closes (worker thread).
• Living graph: file watcher re-extracts topology in a subprocess and pushes it to the UI.
• Dashboards: runs/tokens per day, per-model usage and latency, per-node latency, error rate.
• Multi-graph: serve every graph in your project behind one URL; a top-bar selector scopes all views (runs, sessions, stats included - metrics never mix graphs). The selector also offers All graphs: Stats shows deployment-wide totals with per-node rows grouped per graph (same-named nodes never merge), Sessions shows every graph a session spanned - a journey that crosses graphs stays one session - and Runs lists everything. The graph canvas and Memory keep showing your last concrete graph (a small note says which), since a topology and a store are per-graph by nature.
• Artifacts: when a node's output records a file path (a report it wrote, a chart, an export), the run drawer and the node pane both surface it with inline preview and one-click download. Previews: HTML/PDF/images/text/CSV/code, rendered Markdown, audio/video, and Office - Word/Excel/PowerPoint rendered in-browser (vendored mammoth/SheetJS/jszip, lazy-loaded, shown in a sandboxed frame). Only paths recorded by that run's own outputs are servable - never arbitrary files - behind the same /api token gate.
• Fleet view: with multiple graphs, a cross-graph overview becomes the landing page: a Needs attention list of every run paused on an interrupt (question shown inline, resume right from the row) or still running, plus per-graph health cards (last run, 7-day run/error counts with a daily sparkline - errors in red - and recent runs). Interrupts that were already resumed on their thread don't linger as false positives. Also available as GET /api/overview.
• Alerts: WINDHOVER_WEBHOOK posts a JSON summary when a run errors or pauses; set VAPID keys and installed browsers can also subscribe to Web Push notifications (a 🔔 in the top bar; works as an installed PWA, iOS 16.4+ included).
• Never slows your app: the remote tracer is non-blocking (bounded queue; drops rather than delays when the collector is down).
• Mobile-first PWA, light/dark. Fully local (FastAPI + Cytoscape.js).

Datasets API

curl -X POST :8090/api/datasets -H 'Content-Type: application/json' -d '{
  "name": "golden", "items": [
    {"input": {"n": 2},  "expected": 6},
    {"input": {"n": 40}, "expected": "big"}]}'
curl -X POST :8090/api/datasets/golden/run   # -> runs land in an eval:golden:<ts> session

Scores API

curl -X POST :8090/api/runs/RUN_ID/scores -H 'Content-Type: application/json' \
     -d '{"name": "accuracy", "value": 0.92, "comment": "vs golden set"}'

Config (env)

WINDHOVER_GRAPH (module:attr, or a comma list name=module:attr,…; unset = langgraph.json discovery, else ingest-only) · WINDHOVER_GRAPH_DIR · WINDHOVER_DB · WINDHOVER_HOST/WINDHOVER_PORT (0.0.0.0/8090) · WINDHOVER_WATCH (1) · WINDHOVER_PRICING · WINDHOVER_RETENTION_DAYS (0 = keep forever; else prune older runs on startup + every 6h) · WINDHOVER_TOKEN (set to require Authorization: Bearer <token> - or ?token= - on all /api routes; the UI prompts once and remembers it) · WINDHOVER_WEBHOOK (POST a JSON alert whenever a run errors or pauses on an interrupt; accepts a single URL, or a comma list mixing a default with per-graph name=url overrides - e.g. https://hooks.example/all,billing=https://hooks.example/billing) · WINDHOVER_VAPID_PUBLIC/WINDHOVER_VAPID_PRIVATE (base64url VAPID keypair - set both to enable browser Web Push; unset = feature hidden) · WINDHOVER_VAPID_SUBJECT (a mailto: or https: contact URL sent to the push service; use a real domain - some services reject .local) · WINDHOVER_DIGEST (HH:MM local time for one daily summary push - runs/errors/awaiting across all graphs, linking to the fleet; quiet days send nothing; requires Web Push keys). When several runs await approval, interrupt pushes link to the fleet queue instead of a single run. Edit windhover/pricing.json for your models' $/1M rates (unknown model → cost null).

Web Push setup: generate a VAPID keypair (e.g. openssl/py-vapid), set the three env vars above (over HTTPS: browsers only allow push from a secure origin), install the app to your home screen, and tap the 🔔. Alerts fire on the same errors/interrupts as the webhook.

Docs

The guide covers every feature with how-tos and the fine print - including the most important nuance: panels light up based on what your graph supports (Memory needs a store=, time-travel/HITL need a checkpointer=, X-ray needs subgraphs, live typing needs streaming=True). An absent tab isn't a bug - it's a graph without that capability. SPEC.md has the architecture.

Notes

Runs use the imported graph (restart to run new code); the view always reflects current-on-disk topology. All frontend assets are vendored - no CDN, works fully offline. Deep links: #runs, #sessions, #stats, #run=<id>.

License

MIT.