How do I enable query execution tracing in the playground?

Add the X-WG-TRACE header to your request in the playground headers panel. The Cosmo Router captures and returns Advanced Request Tracing (ART) data alongside the response.

What is the difference between tree view and waterfall view?

Tree view shows the hierarchical structure of query execution — which subgraph handles which fields. Waterfall view shows a timeline, making it clear which calls run in parallel and where time is spent.

Does tracing affect production performance?

The X-WG-TRACE header must be included in the request for tracing to activate. Production requests without the header are not traced.

Can I see which fields came from which subgraph?

Yes. Both tree and waterfall views show subgraph assignments for each portion of the execution.

Can I see the data flowing between subgraphs?

Yes. Each step in the visualization includes the input sent to the subgraph and the output it returned.

Where is the ART feature documented?

The Advanced Request Tracing documentation is at cosmo-docs.wundergraph.com/router/advanced-request-tracing-art. The playground overview is at cosmo-docs.wundergraph.com/studio/playground.

GraphiQL Playground++ for Federated GraphQL | Cosmo by WunderGraph

The problem

Standard IDEs hide federation

The final merged response tells you nothing about which subgraph handled which field, how long each took, or whether calls ran in parallel.

Generic IDEs only show the final response

A standard GraphQL client returns the merged result. Which subgraph contributed which field, and how long each call took, is never visible.

Parallel execution is invisible without tracing

A query dispatching to four subgraphs looks identical to one making four serial calls. Without timing data, you cannot tell which calls overlap and which wait.

Debugging slow queries requires guesswork

Without per-subgraph timing, any service in the chain could be the bottleneck. Optimization becomes trial and error across multiple teams.

Our solution

Visual query execution tracing

The Cosmo Playground extends GraphiQL with Advanced Request Tracing (ART). One header activates it. The playground renders the execution data in two visualization modes.

From request to visualization

Include the X-WG-TRACE header in a playground request.
The Cosmo Router executes the query and captures Advanced Request Tracing (ART) data alongside the response.
The Playground parses the trace payload and renders it in two modes: tree view and waterfall view.
Tree view shows the hierarchical execution structure — which subgraph handles which portion of the query.
Waterfall view shows the execution timeline — which calls run in parallel and which are sequential.
Each step includes the subgraph name, duration, inputs sent, and outputs received.

One header. Two views. Full execution visibility.

GraphiQL Playground++

Before & After

Before Cosmo	With Cosmo
Final merged response with no execution breakdown	Tree view of execution with subgraph assignments per field
No visibility into parallel vs sequential calls	Waterfall view showing which calls overlap and which are serial
Guessing which subgraph is causing latency	Per-subgraph timing in milliseconds for every call
No insight into data flowing between subgraphs	Inputs and outputs visible for each step in the execution chain

Visualization modes

Two views of the same execution

Tree view: Shows the hierarchical execution structure. Navigate through nested subgraph calls and see which fields come from which service.
Waterfall view: Shows the execution timeline. Parallel calls appear side by side. Sequential calls stack vertically. Duration is visible for each call.

How tracing works in Cosmo Playground

01

One header enables tracing.

Add the header

Include X-WG-TRACE in the playground request headers. No router configuration change is required.

02

ART data captured per subgraph.

Execute

Run the query. The Cosmo Router executes it across subgraphs and captures timing, inputs, and outputs for every step.

03

Hierarchical subgraph breakdown.

Inspect — tree view

Switch to the tree view tab. See which fields come from which subgraphs, nested by the query structure.

04

Timeline of parallel and serial calls.

Inspect — waterfall view

Switch to the waterfall view tab. See the full execution timeline — which calls run in parallel and where latency is concentrated.

Capabilities

What you get with Playground++

Tree view

Hierarchical breakdown of query execution. See which subgraph handles each field, nested by the query structure.

Waterfall view

Timeline visualization of the full execution. Parallel calls appear side by side. Sequential calls stack vertically with total duration per subgraph.

Per-subgraph timing

Duration in milliseconds for every subgraph call in the execution chain. Identify slow services without instrumenting each one separately.

Inputs and outputs

View the data sent to each subgraph and the response returned at every step in the execution chain.

Debug your federated queries visually

Add X-WG-TRACE to any playground request. See the full execution tree and waterfall in seconds.

Start Free Read the Docs

See exactly how your federated query executes across subgraphs