diff --git a/lib/spec/openapi/index.js b/lib/spec/openapi/index.js
index a309822b..a145b4bb 100644
--- a/lib/spec/openapi/index.js
+++ b/lib/spec/openapi/index.js
@@ -72,6 +72,11 @@ module.exports = function (opts, cache, routes, Ref) {
       openapiObject.paths[url] = openapiRoute
     }
 
+    // the schemas with an `$id` nested in the route schemas (eg. TypeBox
+    // recursive types) are referenced as `#/components/schemas/def-N`:
+    // they must be emitted as well
+    Object.assign(openapiObject.components.schemas, prepareOpenapiSchemas(defOpts, ref.inlineDefinitions, ref, hoisted))
+
     rewriteHoistedRefs(openapiObject, '#/components/schemas/', hoisted)
 
     const transformObjectResult = defOpts.transformObject
diff --git a/lib/spec/openapi/utils.js b/lib/spec/openapi/utils.js
index 8845a55c..8d330ad7 100644
--- a/lib/spec/openapi/utils.js
+++ b/lib/spec/openapi/utils.js
@@ -724,7 +724,7 @@ function prepareOpenapiSchemas (opts, jsonSchemas, ref, hoisted = new Map()) {
     const resolvedJsonSchema = ref.resolve(jsonSchema, { externalSchemas })
     // OpenAPI does not support the `definitions` keyword: before it gets
     // dropped by the conversion, the definitions are moved to the top-level
-    const hoistedSchemas = hoistDefinitions(schemaName, resolvedJsonSchema, jsonSchemas, hoisted)
+    const hoistedSchemas = hoistDefinitions(schemaName, resolvedJsonSchema, { ...ref.definitions().definitions, ...jsonSchemas }, hoisted)
 
     for (const [name, schema] of [[schemaName, resolvedJsonSchema], ...hoistedSchemas]) {
       const openapiSchema = convertJsonSchemaToOpenapi3(opts, schema)
diff --git a/lib/spec/swagger/index.js b/lib/spec/swagger/index.js
index cdf722f4..fdbc8503 100644
--- a/lib/spec/swagger/index.js
+++ b/lib/spec/swagger/index.js
@@ -64,6 +64,11 @@ module.exports = function (opts, cache, routes, Ref) {
       swaggerObject.paths[url] = swaggerRoute
     }
 
+    // the schemas with an `$id` nested in the route schemas (eg. TypeBox
+    // recursive types) are referenced as `#/definitions/def-N`:
+    // they must be emitted as well
+    Object.assign(swaggerObject.definitions, prepareSwaggerDefinitions(ref.inlineDefinitions, ref, hoisted))
+
     rewriteHoistedRefs(swaggerObject, '#/definitions/', hoisted)
 
     const transformObjectResult = defOpts.transformObject
diff --git a/lib/spec/swagger/utils.js b/lib/spec/swagger/utils.js
index af9db7ad..96ea2f68 100644
--- a/lib/spec/swagger/utils.js
+++ b/lib/spec/swagger/utils.js
@@ -345,7 +345,7 @@ function prepareSwaggerDefinitions (definitions, ref, hoisted = new Map()) {
       // Swagger doesn't accept the `definitions` keyword either:
       // the nested definitions are moved to the top-level ones
       res[name] = resolved
-      for (const [hoistedName, schema] of hoistDefinitions(name, resolved, definitions, hoisted)) {
+      for (const [hoistedName, schema] of hoistDefinitions(name, resolved, { ...ref.definitions().definitions, ...definitions }, hoisted)) {
         delete schema.$id
         res[hoistedName] = schema
       }
diff --git a/lib/util/add-hook.js b/lib/util/add-hook.js
index 6410df0a..0e5d4cc4 100644
--- a/lib/util/add-hook.js
+++ b/lib/util/add-hook.js
@@ -2,7 +2,7 @@
 
 const Ref = require('json-schema-resolver')
 const cloner = require('rfdc')({ proto: true, circles: false })
-const { prepareSharedSchemas, rewriteAnchorRefs } = require('./definitions')
+const { prepareSharedSchemas, referenceInlineDefinitions, rewriteAnchorRefs } = require('./definitions')
 
 function addHook (fastify, pluginOptions) {
   const routes = []
@@ -77,14 +77,39 @@ function addHook (fastify, pluginOptions) {
         pluginOptions.refResolver,
         { clone: true, externalSchemas })
       )
-      if (anchors.size === 0) return ref
 
       // The ref resolver does not support the references to an anchor
       // (`http://foo/common.json#address`): they are converted to JSON pointers
       // before the resolution. The clone avoids touching the route schemas.
+      const resolve = anchors.size === 0
+        ? ref.resolve
+        : (schema, opts) => ref.resolve(rewriteAnchorRefs(cloner(schema), anchors), opts)
+
+      // The ref resolver collects the subschemas having an `$id` (eg. TypeBox
+      // recursive types) and rewrites the references to them, but it does not
+      // emit them: they are replaced by a reference and collected here, to be
+      // added to the top-level definitions of the document.
+      const sharedNames = new Set(Object.keys(ref.definitions().definitions))
+      const inlineDefinitions = {}
+
       return {
         definitions: ref.definitions,
-        resolve: (schema, opts) => ref.resolve(rewriteAnchorRefs(cloner(schema), anchors), opts)
+        resolve (schema, opts) {
+          const resolved = resolve(schema, opts)
+          // the schemas nested in a collected one are collected as well
+          const queue = [resolved]
+          while (queue.length > 0) {
+            const found = referenceInlineDefinitions(queue.shift(), ref, sharedNames)
+            for (const name of Object.keys(found)) {
+              if (Object.hasOwn(inlineDefinitions, name)) continue
+              inlineDefinitions[name] = found[name]
+              queue.push(found[name])
+            }
+          }
+          return resolved
+        },
+        // the definitions collected from the route schemas, by name
+        inlineDefinitions
       }
     }
   }
diff --git a/lib/util/definitions.js b/lib/util/definitions.js
index 860d239c..33bf3ab2 100644
--- a/lib/util/definitions.js
+++ b/lib/util/definitions.js
@@ -284,8 +284,58 @@ function rewriteHoistedRefs (node, prefix, hoisted) {
   }
 }
 
+/**
+ * The ref resolver collects the subschemas having an `$id` (eg. the ones
+ * produced by TypeBox `Type.Recursive()`) as definitions, and rewrites the
+ * references to them as `#/definitions/def-N`, but it leaves them inline.
+ * Replaces each of them with a reference, so that the schema is emitted once,
+ * as a top-level definition.
+ * @param {object} schema - Resolved and cloned schema; mutated in place.
+ * @param {object} ref - Ref resolver instance.
+ * @param {Set<string>} [ignore] - Names of the definitions to leave as they are.
+ * @returns {Record<string, object>} The `name -> schema` inline definitions found.
+ */
+function referenceInlineDefinitions (schema, ref, ignore = new Set()) {
+  const names = new Map()
+  const definitions = ref.definitions().definitions
+  for (const name of Object.keys(definitions)) {
+    const { $id } = definitions[name]
+    if (typeof $id === 'string' && !ignore.has(name)) names.set($id, name)
+  }
+
+  const found = {}
+  const replacements = []
+  walkSchema(schema, (subschema, pointer) => {
+    if (pointer.length === 0) return
+    // the ref resolver adds the consumed definitions to the root `definitions`:
+    // those are moved to the top-level by `hoistDefinitions`
+    if (pointer.length === 2 && DEFINITIONS_KEYWORDS.includes(pointer[0])) return
+    // a fragment-only $id is an anchor, not a schema resource
+    if (typeof subschema.$id !== 'string' || subschema.$id[0] === '#') return
+    // the resolver ignores the duplicates of an `$id` (eg. the same schema
+    // used by two routes): they are matched by `$id`, not by identity
+    const name = names.get(subschema.$id)
+    if (name === undefined) return
+    found[name] = definitions[name]
+    replacements.push([pointer.slice(), name])
+  })
+
+  // A nested match is inside a definition (replaced as a whole): skip it
+  const replaced = []
+  for (const [pointer, name] of replacements) {
+    if (replaced.some((prefix) => prefix.every((token, i) => pointer[i] === token))) continue
+    replaced.push(pointer)
+    let parent = schema
+    for (let i = 0; i < pointer.length - 1; i++) parent = parent[pointer[i]]
+    parent[pointer[pointer.length - 1]] = { $ref: `#/definitions/${name}` }
+  }
+
+  return found
+}
+
 module.exports = {
   prepareSharedSchemas,
+  referenceInlineDefinitions,
   rewriteAnchorRefs,
   hoistDefinitions,
   unknownSchemas,
diff --git a/test/spec/openapi/refs.test.js b/test/spec/openapi/refs.test.js
index f0ac5314..dae4409c 100644
--- a/test/spec/openapi/refs.test.js
+++ b/test/spec/openapi/refs.test.js
@@ -788,3 +788,54 @@ for (const [name, option, getSchemas, prefix] of definitionsCases) {
     t.assert.match(JSON.stringify(document.paths['/'].post), new RegExp(`"\\$ref":"${prefix}def-0/properties/shipping"`))
   })
 }
+
+// https://github.com/fastify/fastify-swagger/issues/865
+test('openapi: support recursive schemas with an `$id` nested in a route schema', async (t) => {
+  const fastify = Fastify()
+  await fastify.register(fastifySwagger, { openapi: {} })
+
+  // what TypeBox `Type.Recursive(..., { $id: 'Node' })` produces
+  const node = {
+    $id: 'Node',
+    type: 'object',
+    properties: {
+      name: { type: 'string' },
+      children: { type: 'array', items: { $ref: 'Node' } }
+    }
+  }
+  const body = { type: 'object', properties: { treeNodes: { type: 'array', items: node } } }
+  fastify.post('/', { schema: { body } }, () => {})
+  fastify.put('/', { schema: { body } }, () => {})
+
+  await fastify.ready()
+
+  const document = fastify.swagger()
+  await Swagger.validate(JSON.parse(JSON.stringify(document)))
+
+  const schemas = document.components.schemas
+  t.assert.deepStrictEqual(Object.keys(schemas), ['def-0'])
+  t.assert.deepStrictEqual(schemas['def-0'].properties.children.items, { $ref: '#/components/schemas/def-0' })
+  t.assert.deepStrictEqual(document.paths['/'].post.requestBody.content['application/json'].schema.properties.treeNodes.items, { $ref: '#/components/schemas/def-0' })
+  t.assert.deepStrictEqual(document.paths['/'].put, document.paths['/'].post)
+})
+
+test('openapi: support schemas with an `$id` nested in another one', async (t) => {
+  const fastify = Fastify()
+  await fastify.register(fastifySwagger, { openapi: {} })
+
+  fastify.addSchema({ $id: 'Shared', type: 'object', properties: { name: { type: 'string' } } })
+  const leaf = { $id: 'Leaf', type: 'object', properties: { shared: { $ref: 'Shared#' } } }
+  const tree = { $id: 'Tree', type: 'object', properties: { leaf, leaves: { type: 'array', items: { $ref: 'Leaf' } } } }
+  fastify.post('/', { schema: { body: { type: 'object', properties: { tree } } } }, () => {})
+
+  await fastify.ready()
+
+  const document = fastify.swagger()
+  await Swagger.validate(JSON.parse(JSON.stringify(document)))
+
+  const schemas = document.components.schemas
+  t.assert.deepStrictEqual(Object.keys(schemas).sort(), ['def-0', 'def-1', 'def-2'])
+  t.assert.deepStrictEqual(document.paths['/'].post.requestBody.content['application/json'].schema.properties.tree, { $ref: '#/components/schemas/def-1' })
+  t.assert.deepStrictEqual(schemas['def-1'].properties, { leaf: { $ref: '#/components/schemas/def-2' }, leaves: { type: 'array', items: { $ref: '#/components/schemas/def-2' } } })
+  t.assert.deepStrictEqual(schemas['def-2'].properties, { shared: { $ref: '#/components/schemas/def-0' } })
+})
diff --git a/test/spec/swagger/refs.test.js b/test/spec/swagger/refs.test.js
index 5bf645ab..fe02c786 100644
--- a/test/spec/swagger/refs.test.js
+++ b/test/spec/swagger/refs.test.js
@@ -345,3 +345,54 @@ for (const [name, option, getSchemas, prefix] of definitionsCases) {
     t.assert.match(JSON.stringify(document.paths['/'].post), new RegExp(`"\\$ref":"${prefix}def-0/properties/shipping"`))
   })
 }
+
+// https://github.com/fastify/fastify-swagger/issues/865
+test('swagger: support recursive schemas with an `$id` nested in a route schema', async (t) => {
+  const fastify = Fastify()
+  await fastify.register(fastifySwagger, { swagger: {} })
+
+  // what TypeBox `Type.Recursive(..., { $id: 'Node' })` produces
+  const node = {
+    $id: 'Node',
+    type: 'object',
+    properties: {
+      name: { type: 'string' },
+      children: { type: 'array', items: { $ref: 'Node' } }
+    }
+  }
+  const body = { type: 'object', properties: { treeNodes: { type: 'array', items: node } } }
+  fastify.post('/', { schema: { body } }, () => {})
+  fastify.put('/', { schema: { body } }, () => {})
+
+  await fastify.ready()
+
+  const document = fastify.swagger()
+  await Swagger.validate(JSON.parse(JSON.stringify(document)))
+
+  const schemas = document.definitions
+  t.assert.deepStrictEqual(Object.keys(schemas), ['def-0'])
+  t.assert.deepStrictEqual(schemas['def-0'].properties.children.items, { $ref: '#/definitions/def-0' })
+  t.assert.deepStrictEqual(document.paths['/'].post.parameters[0].schema.properties.treeNodes.items, { $ref: '#/definitions/def-0' })
+  t.assert.deepStrictEqual(document.paths['/'].put, document.paths['/'].post)
+})
+
+test('swagger: support schemas with an `$id` nested in another one', async (t) => {
+  const fastify = Fastify()
+  await fastify.register(fastifySwagger, { swagger: {} })
+
+  fastify.addSchema({ $id: 'Shared', type: 'object', properties: { name: { type: 'string' } } })
+  const leaf = { $id: 'Leaf', type: 'object', properties: { shared: { $ref: 'Shared#' } } }
+  const tree = { $id: 'Tree', type: 'object', properties: { leaf, leaves: { type: 'array', items: { $ref: 'Leaf' } } } }
+  fastify.post('/', { schema: { body: { type: 'object', properties: { tree } } } }, () => {})
+
+  await fastify.ready()
+
+  const document = fastify.swagger()
+  await Swagger.validate(JSON.parse(JSON.stringify(document)))
+
+  const schemas = document.definitions
+  t.assert.deepStrictEqual(Object.keys(schemas).sort(), ['def-0', 'def-1', 'def-2'])
+  t.assert.deepStrictEqual(document.paths['/'].post.parameters[0].schema.properties.tree, { $ref: '#/definitions/def-1' })
+  t.assert.deepStrictEqual(schemas['def-1'].properties, { leaf: { $ref: '#/definitions/def-2' }, leaves: { type: 'array', items: { $ref: '#/definitions/def-2' } } })
+  t.assert.deepStrictEqual(schemas['def-2'].properties, { shared: { $ref: '#/definitions/def-0' } })
+})
diff --git a/test/util.test.js b/test/util.test.js
index 047c5423..16998a22 100644
--- a/test/util.test.js
+++ b/test/util.test.js
@@ -166,6 +166,7 @@ describe('definitions', () => {
   const {
     prepareSharedSchemas,
     hoistDefinitions,
+    referenceInlineDefinitions,
     rewriteAnchorRefs,
     rewriteHoistedRefs
   } = require('../lib/util/definitions')
@@ -310,4 +311,35 @@ describe('definitions', () => {
     })
     t.assert.strictEqual(rewriteAnchorRefs(true, anchors), true)
   })
+
+  test('referenceInlineDefinitions only replaces the known schema resources', (t) => {
+    const node = { $id: 'Node', type: 'object' }
+    const shared = { $id: 'Shared', type: 'object' }
+    const ref = { definitions: () => ({ definitions: { 'def-0': shared, 'def-1': node } }) }
+    const schema = {
+      $id: 'Root',
+      definitions: { 'def-0': shared },
+      properties: {
+        node: { $id: 'Node', type: 'object', properties: { child: { $id: 'Node', type: 'object' } } },
+        shared: { $id: 'Shared', type: 'object' },
+        anchor: { $id: '#anchor', type: 'object' },
+        unknown: { $id: 'Unknown', type: 'object' },
+        plain: { type: 'object' }
+      }
+    }
+
+    const found = referenceInlineDefinitions(schema, ref, new Set(['def-0']))
+    t.assert.deepStrictEqual(found, { 'def-1': node })
+    t.assert.deepStrictEqual(schema, {
+      $id: 'Root',
+      definitions: { 'def-0': shared },
+      properties: {
+        node: { $ref: '#/definitions/def-1' },
+        shared: { $id: 'Shared', type: 'object' },
+        anchor: { $id: '#anchor', type: 'object' },
+        unknown: { $id: 'Unknown', type: 'object' },
+        plain: { type: 'object' }
+      }
+    })
+  })
 })