#Diagnostics (Checks panel)

The Checks tab is the unified view of every problem the parser and analyzer found in the current model. In the VS Code build the same items also appear in the Problems panel with line numbers.

Each diagnostic has a severity (error / warning / info), a stable code, an optional file/line, and a human message.

#XML / xacro

Code	Severity	Triggered by
`xml.parse`	error	The XML is malformed at the byte level. The URDF cannot be loaded.
`xacro.expand`	error	Xacro expansion failed and no recovery was possible. The pre-expansion text is shown instead.
`xacro.expressionSkipped`	warning	An expression failed to evaluate; URDF Studio retried with the offending expression elided so the rest of the file could still be expanded.
`xacro.packageMissing`	warning	`$(find pkg)` was called with a package name not in the discovered map. The substitution returns `/unknown-package` so expansion can continue.

#Tree structure

Code	Severity	Triggered by
`link.missingName`	error	A `<link>` element without a `name` attribute.
`link.duplicate`	error	Two `<link>` elements share the same name.
`joint.missingName`	error	A `<joint>` element without a `name` attribute.
`joint.duplicate`	error	Two `<joint>` elements share the same name.
`joint.parentMissing`	error	Joint references a parent link that does not exist.
`joint.childMissing`	error	Joint references a child link that does not exist.
`tree.multipleParents`	error	A link is named as the child of more than one joint.
`tree.cycle`	error	A cycle was detected in the link tree (DFS).
`tree.rootCount`	warning	Expected one root link; found zero or many.

#Joints

Code	Severity	Triggered by
`joint.limitMissing`	warning	A `revolute` or `prismatic` joint has no `<limit lower>` / `<limit upper>`.
`joint.limitInvalid`	error	`lower > upper` on a `<limit>` element.
`joint.mimicMissing`	warning	`<mimic joint="other">` references a joint that does not exist.

#Meshes

Code	Severity	Triggered by
`mesh.packageMalformed`	error	A `package://` URI without a package name.
`mesh.packageMissing`	error	A `package://` URI references a package not found in the workspace / folder.
`mesh.missing`	error	The resolved mesh path does not exist on disk. The link still shows; just without that particular mesh.

#Inertial

Code	Severity	Triggered by
`inertial.massInvalid`	warning	`<mass value>` is missing, zero, or negative.
`inertial.tensorMissing`	warning	`<inertial>` block without an `<inertia>` tensor.
`inertial.notPositiveDefinite`	warning	Eigenvalues of the inertia tensor are not all strictly positive. Either the link can't physically rotate that way, or the URDF is wrong.

#Semantic (SRDF)

Code	Severity	Triggered by
`srdf.parse`	error	The SRDF file is malformed XML.
`srdf.groupMissingName`	warning	A `<group>` element without `name`. Skipped.
`srdf.groupMissing`	warning	A `<group>` references a subgroup that does not exist.
`srdf.groupCycle`	warning	Cycle in group inheritance. The branch is ignored.
`srdf.stateInvalid`	warning	A `<group_state>` without `name` or `group`.
`semantic.readFailed`	warning	Configured semantic file could not be read.
`semantic.yamlParse`	warning	YAML semantic file did not parse.

#Preview

Code	Severity	Triggered by
`preview.loadFailed`	error	The preview pipeline threw an exception not classified above.

#What to do with them

Errors typically prevent something visible from working (a link won't render, a mesh won't load). Fix the URDF.
Warnings are usually fine but worth a second look — they often catch copy-paste mistakes in xacro macros or mesh paths.
The xacro.expressionSkipped category in particular is forgiving: the rest of the file expands fine, you just get a noticeable hole where the bad expression was. Search the file for the expression text to find it.