diff --git a/services/web/frontend/extracted-translations.json b/services/web/frontend/extracted-translations.json
index 4827f5208e..dbc74c8a56 100644
--- a/services/web/frontend/extracted-translations.json
+++ b/services/web/frontend/extracted-translations.json
@@ -1067,6 +1067,7 @@
   "join_x_managed_enterprise_group": "",
   "joined_team": "",
   "joining": "",
+  "jump_to_command_definition": "",
   "jump_to_line_x": "",
   "jump_to_line_x_column_y": "",
   "jump_to_location_in_pdf": "",
diff --git a/services/web/frontend/js/features/source-editor/hooks/use-command-definitions.ts b/services/web/frontend/js/features/source-editor/hooks/use-command-definitions.ts
new file mode 100644
index 0000000000..f43715af60
--- /dev/null
+++ b/services/web/frontend/js/features/source-editor/hooks/use-command-definitions.ts
@@ -0,0 +1,94 @@
+import { useEffect, useState } from 'react'
+import { EditorState } from '@codemirror/state'
+import { SyntaxNode } from '@lezer/common'
+import { syntaxTree } from '@codemirror/language'
+import { useProjectContext } from '@/shared/context/project-context'
+import { debugConsole } from '@/utils/debugging'
+import { CommandDefinition } from '../utils/command-definitions/command-definition'
+import { getCommandDefinitionIndexer } from '../utils/command-definitions/command-definition-indexer'
+import { useCodeMirrorStateContext } from '../components/codemirror-context'
+import { contextMenuStateField } from '../extensions/context-menu'
+
+/**
+ * Look up where `name` is defined in the project, by parsing the snapshot in a
+ * worker. Intended to be used while the editor context menu is open: the lookup
+ * runs off the main thread, so opening the menu is never blocked, and the item
+ * is disabled until the worker responds.
+ *
+ * Pass `name` null when the menu was not opened on a command, to avoid
+ * refreshing the snapshot (a project-history flush) and parsing on every
+ * right-click. `lookupKey` should change on each open (e.g. the tooltip object)
+ * so the lookup reruns even if the menu component stays mounted across reopens.
+ */
+function useCommandDefinition(name: string | null, lookupKey: unknown) {
+  const { projectSnapshot } = useProjectContext()
+
+  const [definition, setDefinition] = useState<CommandDefinition | null>(null)
+
+  useEffect(() => {
+    // Reset while the new lookup runs so a stale definition isn't shown.
+    setDefinition(null)
+    if (!name) {
+      return
+    }
+    let cancelled = false
+    ;(async () => {
+      try {
+        await projectSnapshot.refresh()
+        if (cancelled) {
+          return
+        }
+        const found = await getCommandDefinitionIndexer().findDefinition(
+          projectSnapshot,
+          name
+        )
+        if (!cancelled) {
+          setDefinition(found)
+        }
+      } catch (error) {
+        debugConsole.error('Failed to find command definition', error)
+      }
+    })()
+    return () => {
+      cancelled = true
+    }
+  }, [projectSnapshot, name, lookupKey])
+
+  return definition
+}
+
+/**
+ * Resolve the command the editor context menu was opened on and its project-wide
+ * definition (if any). Returns nulls when the menu was not opened on a command;
+ * the lookup only runs when the menu was opened on a command.
+ */
+export function useContextMenuCommandDefinition() {
+  const state = useCodeMirrorStateContext()
+  // The tooltip is a new object on each open, so use it as the lookup key.
+  const tooltip = state.field(contextMenuStateField, false)?.tooltip ?? null
+  const pos = tooltip?.pos ?? null
+  const commandName = pos != null ? commandNameAtPos(state, pos) : null
+  const commandDefinition = useCommandDefinition(commandName, tooltip)
+  return { commandName, commandDefinition }
+}
+
+/**
+ * Resolve the control sequence (e.g. `\mycmd`) at a document position, or null
+ * if the position is not on a command. Walks up from the innermost node to the
+ * nearest node carrying a control-sequence token, mirroring the command-usage
+ * logic in tree-operations/commands.ts.
+ */
+function commandNameAtPos(state: EditorState, pos: number): string | null {
+  const tree = syntaxTree(state)
+  // Bias right (as resolveCommandNode does) so a click on the command's first
+  // character resolves into it rather than the preceding token.
+  let node: SyntaxNode | null = tree.resolveInner(pos, 1)
+  for (; node; node = node.parent) {
+    const ctrlSeq = node.getChild('$CtrlSeq')
+    if (ctrlSeq && !ctrlSeq.type.is('$CtrlSym')) {
+      const name = state.sliceDoc(ctrlSeq.from, ctrlSeq.to)
+      return name.length > 0 ? name : null
+    }
+  }
+  return null
+}
diff --git a/services/web/frontend/js/features/source-editor/hooks/use-context-menu-items.tsx b/services/web/frontend/js/features/source-editor/hooks/use-context-menu-items.tsx
index c1a3bf56d5..612f283965 100644
--- a/services/web/frontend/js/features/source-editor/hooks/use-context-menu-items.tsx
+++ b/services/web/frontend/js/features/source-editor/hooks/use-context-menu-items.tsx
@@ -16,6 +16,9 @@ import {
   useCommandRegistry,
 } from '@/features/ide-react/context/command-registry-context'
 import { closeContextMenuEffect } from '../extensions/context-menu'
+import { useEditorManagerContext } from '@/features/ide-react/context/editor-manager-context'
+import { useFileTreePathContext } from '@/features/file-tree/contexts/file-tree-path'
+import { useContextMenuCommandDefinition } from './use-command-definitions'
 import * as commands from '../extensions/toolbar/commands'
 import {
   cutSelection,
@@ -58,6 +61,9 @@ export const useContextMenuItems = () => {
   const isReview = trackingChangesMode === 'review'
   const { changesInSelection, acceptChangesHandler, rejectChangesHandler } =
     useTrackedChangesActions()
+  const { openDocWithId } = useEditorManagerContext()
+  const { findEntityByPath } = useFileTreePathContext()
+  const { commandName, commandDefinition } = useContextMenuCommandDefinition()
 
   const closeMenu = useCallback(() => {
     view.dispatch({ effects: closeContextMenuEffect.of(null) })
@@ -186,6 +192,20 @@ export const useContextMenuItems = () => {
     return true
   })
 
+  const handleJumpToDefinition = wrapForContextMenu(
+    'jump-to-definition',
+    () => {
+      if (!commandDefinition) {
+        return true
+      }
+      const result = findEntityByPath(commandDefinition.path)
+      if (result?.type === 'doc') {
+        openDocWithId(result.entity._id, { gotoOffset: commandDefinition.pos })
+      }
+      return true
+    }
+  )
+
   // Sync-to-PDF is special: it needs to wait for async completion before closing
   const handleSyncToPdf = useCallback(() => {
     // Switch to split view only when in editor-only mode with non-detached PDF
@@ -262,6 +282,14 @@ export const useContextMenuItems = () => {
         show: jumpToLocationInPdfEnabled,
         shortcut: undefined,
       },
+      {
+        label: t('jump_to_command_definition'),
+        handler: handleJumpToDefinition,
+        disabled: !commandDefinition,
+        separatorAbove: !jumpToLocationInPdfEnabled,
+        show: Boolean(commandName),
+        shortcut: undefined,
+      },
       {
         label: wantTrackChanges ? t('back_to_editing') : t('suggest_edits'),
         handler: handleToggleTrackChanges,
diff --git a/services/web/frontend/js/features/source-editor/utils/command-definitions/command-definition-indexer.ts b/services/web/frontend/js/features/source-editor/utils/command-definitions/command-definition-indexer.ts
new file mode 100644
index 0000000000..fe8c655f50
--- /dev/null
+++ b/services/web/frontend/js/features/source-editor/utils/command-definitions/command-definition-indexer.ts
@@ -0,0 +1,78 @@
+import type { ProjectSnapshot } from '@/infrastructure/project-snapshot'
+import { CommandDefinition, isIndexablePath } from './command-definition'
+import type {
+  CommandDefinitionWorkerRequest,
+  CommandDefinitionWorkerResponse,
+} from './command-definition.worker'
+
+type SnapshotLike = Pick<ProjectSnapshot, 'getDocPaths' | 'getDocContents'>
+
+/**
+ * Locates the definition of a single command in the project by parsing the
+ * snapshot in a worker, off the main thread, so opening the context menu is
+ * never blocked. A single worker is reused across lookups so opening the menu
+ * never spawns one.
+ */
+class CommandDefinitionIndexer {
+  private worker: Worker
+  private nextId = 0
+  private resolvers = new Map<
+    number,
+    (definition: CommandDefinition | null) => void
+  >()
+
+  constructor() {
+    this.worker = new Worker(
+      /* webpackChunkName: "command-definition-worker" */
+      new URL('./command-definition.worker.ts', import.meta.url),
+      { type: 'module' }
+    )
+    this.worker.addEventListener('message', event => {
+      const data = event.data as CommandDefinitionWorkerResponse
+      if (data.type === 'definition') {
+        this.resolvers.get(data.id)?.(data.definition)
+        this.resolvers.delete(data.id)
+      }
+    })
+  }
+
+  findDefinition(
+    snapshot: SnapshotLike,
+    name: string
+  ): Promise<CommandDefinition | null> {
+    // Only send documents that mention the command (its defined name always
+    // appears literally in its definition), to avoid cloning the whole project
+    // to the worker.
+    const docs: { path: string; content: string }[] = []
+    for (const path of snapshot.getDocPaths()) {
+      if (!isIndexablePath(path)) {
+        continue
+      }
+      const content = snapshot.getDocContents(path)
+      if (content != null && content.includes(name)) {
+        docs.push({ path, content })
+      }
+    }
+
+    const id = this.nextId++
+    const request: CommandDefinitionWorkerRequest = {
+      id,
+      type: 'find',
+      name,
+      docs,
+    }
+    this.worker.postMessage(request)
+    return new Promise(resolve => {
+      this.resolvers.set(id, resolve)
+    })
+  }
+}
+
+let indexer: CommandDefinitionIndexer | undefined
+
+export function getCommandDefinitionIndexer(): CommandDefinitionIndexer {
+  if (!indexer) {
+    indexer = new CommandDefinitionIndexer()
+  }
+  return indexer
+}
diff --git a/services/web/frontend/js/features/source-editor/utils/command-definitions/command-definition.ts b/services/web/frontend/js/features/source-editor/utils/command-definitions/command-definition.ts
new file mode 100644
index 0000000000..10818f88a1
--- /dev/null
+++ b/services/web/frontend/js/features/source-editor/utils/command-definitions/command-definition.ts
@@ -0,0 +1,108 @@
+import { SyntaxNode } from '@lezer/common'
+import { parser } from '../../lezer-latex/latex.mjs'
+import { childOfNodeWithType } from '../tree-operations/common'
+
+/**
+ * Parsing helpers for locating where a custom command is defined across the
+ * project. These are pure and worker-safe: the parsing runs in
+ * command-definition.worker.ts, off the main thread, so opening the context menu
+ * is never blocked.
+ *
+ * Definitions are parsed with the same lezer-latex grammar the editor uses, so
+ * commented-out or verbatim definitions are ignored, and are named by their
+ * control sequence, e.g. `\mycmd`.
+ */
+
+export type CommandDefinition = {
+  name: string
+  path: string
+  // Document offset of the definition, resolved to a line/cursor position when
+  // the defining file is opened.
+  pos: number
+}
+
+// File extensions worth scanning for command definitions.
+const INDEXABLE_EXTENSIONS = ['.tex', '.sty', '.cls', '.def', '.ltx']
+
+export function isIndexablePath(path: string): boolean {
+  const lower = path.toLowerCase()
+  return INDEXABLE_EXTENSIONS.some(ext => lower.endsWith(ext))
+}
+
+function sliceChild(
+  content: string,
+  node: SyntaxNode,
+  ...childTypes: string[]
+): string | null {
+  const child = childOfNodeWithType(node, ...childTypes)
+  if (!child) {
+    return null
+  }
+  const text = content.slice(child.from, child.to)
+  return text.length > 0 ? text : null
+}
+
+/**
+ * Parse a document and return the command definitions it contains.
+ */
+export function parseDefinitionsFromDoc(
+  path: string,
+  content: string
+): CommandDefinition[] {
+  const definitions: CommandDefinition[] = []
+  const tree = parser.parse(content)
+
+  const push = (name: string | null, pos: number) => {
+    if (!name) {
+      return
+    }
+    definitions.push({ name, path, pos })
+  }
+
+  tree.iterate({
+    enter(nodeRef) {
+      const node = nodeRef.node
+      switch (nodeRef.type.name) {
+        case 'NewCommand':
+        case 'RenewCommand':
+          push(
+            sliceChild(content, node, 'LiteralArgContent', 'Csname'),
+            node.from
+          )
+          break
+        case 'Def':
+          push(sliceChild(content, node, 'Csname', 'CtrlSym'), node.from)
+          break
+        case 'Let':
+          push(sliceChild(content, node, 'Csname'), node.from)
+          break
+      }
+    },
+  })
+
+  return definitions
+}
+
+/**
+ * Find the first definition of `name` across the given documents. Documents that
+ * don't mention the control sequence at all are skipped without parsing (the
+ * defined name always appears literally in its definition), and the search stops
+ * at the first match.
+ */
+export function findDefinition(
+  docs: { path: string; content: string }[],
+  name: string
+): CommandDefinition | null {
+  for (const { path, content } of docs) {
+    if (!content.includes(name)) {
+      continue
+    }
+    const match = parseDefinitionsFromDoc(path, content).find(
+      definition => definition.name === name
+    )
+    if (match) {
+      return match
+    }
+  }
+  return null
+}
diff --git a/services/web/frontend/js/features/source-editor/utils/command-definitions/command-definition.worker.ts b/services/web/frontend/js/features/source-editor/utils/command-definitions/command-definition.worker.ts
new file mode 100644
index 0000000000..8f13aaa1af
--- /dev/null
+++ b/services/web/frontend/js/features/source-editor/utils/command-definitions/command-definition.worker.ts
@@ -0,0 +1,28 @@
+import { CommandDefinition, findDefinition } from './command-definition'
+
+export type CommandDefinitionWorkerRequest = {
+  id: number
+  type: 'find'
+  name: string
+  docs: { path: string; content: string }[]
+}
+
+export type CommandDefinitionWorkerResponse = {
+  id: number
+  type: 'definition'
+  definition: CommandDefinition | null
+}
+
+self.addEventListener('message', (event: MessageEvent) => {
+  const message = event.data as CommandDefinitionWorkerRequest
+  if (message.type !== 'find') {
+    return
+  }
+
+  const response: CommandDefinitionWorkerResponse = {
+    id: message.id,
+    type: 'definition',
+    definition: findDefinition(message.docs, message.name),
+  }
+  self.postMessage(response)
+})
diff --git a/services/web/frontend/js/features/source-editor/utils/context-menu-analytics.ts b/services/web/frontend/js/features/source-editor/utils/context-menu-analytics.ts
index 22504601b5..4d31a88951 100644
--- a/services/web/frontend/js/features/source-editor/utils/context-menu-analytics.ts
+++ b/services/web/frontend/js/features/source-editor/utils/context-menu-analytics.ts
@@ -10,6 +10,7 @@ export type ContextMenuItemSegmentation =
   | 'give-feedback'
   | 'delete'
   | 'jump-to-location-in-pdf'
+  | 'jump-to-definition'
   | 'suggest-edits'
   | 'back-to-editing'
   | 'comment'
diff --git a/services/web/locales/en.json b/services/web/locales/en.json
index 897271f4c7..5770f27cc2 100644
--- a/services/web/locales/en.json
+++ b/services/web/locales/en.json
@@ -1370,6 +1370,7 @@
   "joined_team": "You have joined the group subscription managed by __inviterName__",
   "joining": "Joining",
   "july": "July",
+  "jump_to_command_definition": "Jump to command definition",
   "jump_to_line_x": "Jump to line __line__",
   "jump_to_line_x_column_y": "Jump to line __line__, column __column__",
   "jump_to_location_in_pdf": "Jump to location in PDF",
diff --git a/services/web/test/frontend/features/source-editor/utils/command-definitions/command-definition.test.ts b/services/web/test/frontend/features/source-editor/utils/command-definitions/command-definition.test.ts
new file mode 100644
index 0000000000..feebc935a9
--- /dev/null
+++ b/services/web/test/frontend/features/source-editor/utils/command-definitions/command-definition.test.ts
@@ -0,0 +1,63 @@
+import { expect } from 'chai'
+import {
+  findDefinition,
+  parseDefinitionsFromDoc,
+} from '../../../../../../frontend/js/features/source-editor/utils/command-definitions/command-definition'
+
+describe('command-definition', function () {
+  describe('parseDefinitionsFromDoc', function () {
+    it('indexes \\newcommand definitions at their offset', function () {
+      const content = 'line one\n\\newcommand{\\foo}{bar}\n'
+      const defs = parseDefinitionsFromDoc('macros.tex', content)
+      expect(defs).to.have.length(1)
+      expect(defs[0]).to.include({
+        name: '\\foo',
+        path: 'macros.tex',
+        pos: content.indexOf('\\newcommand'),
+      })
+    })
+
+    it('indexes \\def and \\let definitions', function () {
+      const content = '\\def\\bar#1{#1}\n\\let\\baz\\bar\n'
+      const names = parseDefinitionsFromDoc('defs.tex', content).map(
+        d => d.name
+      )
+      expect(names).to.include('\\bar')
+      expect(names).to.include('\\baz')
+    })
+
+    it('ignores commented-out definitions', function () {
+      const content =
+        '% \\newcommand{\\ignored}{nope}\n\\newcommand{\\real}{x}\n'
+      const names = parseDefinitionsFromDoc('main.tex', content).map(
+        d => d.name
+      )
+      expect(names).to.include('\\real')
+      expect(names).not.to.include('\\ignored')
+    })
+  })
+
+  describe('findDefinition', function () {
+    it('finds the defining document for a command', function () {
+      const docs = [
+        { path: 'macros.tex', content: '\\newcommand{\\foo}{x}\n' },
+        { path: 'chapters/intro.tex', content: '\\def\\bar{y}\n' },
+      ]
+      expect(findDefinition(docs, '\\foo')?.path).to.equal('macros.tex')
+      expect(findDefinition(docs, '\\bar')?.path).to.equal('chapters/intro.tex')
+    })
+
+    it('returns null when the command is not defined', function () {
+      const docs = [{ path: 'macros.tex', content: '\\newcommand{\\foo}{x}\n' }]
+      expect(findDefinition(docs, '\\missing')).to.equal(null)
+    })
+
+    it('returns the first definition across documents', function () {
+      const docs = [
+        { path: 'a.tex', content: '\\newcommand{\\dup}{1}\n' },
+        { path: 'b.tex', content: '\\renewcommand{\\dup}{2}\n' },
+      ]
+      expect(findDefinition(docs, '\\dup')?.path).to.equal('a.tex')
+    })
+  })
+})