diff --git a/CHANGES.md b/CHANGES.md
index b9574435..93bfce2d 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,4 +1,12 @@
 
+## 0.13
+
+- feat: adapt to trace 0.11 (callbacks-based collector API, extensible span type, no more manual spans)
+- breaking: remove vendored `opentelemetry.ambient-context`; use the
+    `ambient-context` 0.2 package directly instead. To configure the
+    storage backend, call `Ambient_context.set_current_storage` (e.g.
+    `Ambient_context.set_current_storage Ambient_context_lwt.storage`).
+
 ## 0.12
 
 - breaking: change `Collector.cleanup` so it takes a callback
diff --git a/README.md b/README.md
index bd5b0550..0cd77482 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,5 @@
 
-# Opentelemetry [![build](https://github.com/imandra-ai/ocaml-opentelemetry/actions/workflows/main.yml/badge.svg)](https://github.com/imandra-ai/ocaml-opentelemetry/actions/workflows/main.yml)
+# Opentelemetry [![build](https://github.com/ocaml-tracing/ocaml-opentelemetry/actions/workflows/main.yml/badge.svg)](https://github.com/ocaml-tracing/ocaml-opentelemetry/actions/workflows/main.yml)
 
 This project provides an API for instrumenting server software
 using [opentelemetry](https://opentelemetry.io/docs), as well as
@@ -28,7 +28,7 @@ MIT
   * [x] batching, perf, etc.
 - [ ] async collector relying on ocurl-multi
 - [ ] interface with `logs` (carry context around)
-- [x] implicit scope (via vendored `ambient-context`, see `opentelemetry.ambient-context`)
+- [x] implicit scope (via [`ambient-context`](https://github.com/ocaml-tracing/ambient-context))
 
 ## Use
 
@@ -65,16 +65,17 @@ let main () =
   Otel.Globals.service_name := "my_service";
   Otel.GC_metrics.basic_setup();
 
-  Opentelemetry_ambient_context.set_storage_provider (Opentelemetry_ambient_context_lwt.storage ());
+  (* install Lwt's fiber-local storage as the ambient context backend *)
+  Ambient_context.set_current_storage Ambient_context_lwt.storage;
   Opentelemetry_client_ocurl.with_setup () @@ fun () ->
   (* … *)
   foo ();
   (* … *)
 ```
 
-  [`service_name`]: <https://v3.ocaml.org/p/opentelemetry/0.5/doc/Opentelemetry/Globals/index.html#val-service_name>
-  [`Collector`]: <https://v3.ocaml.org/p/opentelemetry/0.5/doc/Opentelemetry/Collector/index.html>
-  [ambient-context]: now vendored as `opentelemetry.ambient-context`, formerly <https://v3.ocaml.org/p/ambient-context>
+  [`service_name`]: <https://github.com/ocaml-tracing/ocaml-opentelemetry>
+  [`Collector`]: <https://github.com/ocaml-tracing/ocaml-opentelemetry>
+  [ambient-context]: <https://github.com/ocaml-tracing/ambient-context>
 
 ## Configuration
 
@@ -93,7 +94,7 @@ or the datadog agent).
 
 Do note that this backend uses a thread pool and is incompatible
 with uses of `fork` on some Unixy systems.
-See [#68](https://github.com/imandra-ai/ocaml-opentelemetry/issues/68) for a possible workaround.
+See [#68](https://github.com/ocaml-tracing/ocaml-opentelemetry/issues/68) for a possible workaround.
 
 ## Collector opentelemetry-client-cohttp-lwt
 
@@ -103,7 +104,7 @@ inside a `Lwt_main.run` scope.
 
 ## Opentelemetry-trace
 
-The optional library `opentelemetry.trace`, present if [trace](https://github.com/c-cube/trace) is
+The optional library `opentelemetry.trace`, present if [trace](https://github.com/ocaml-tracing/ocaml-trace) is
 installed, provides a collector for `trace`. This collector forwards and translates
 events from `trace` into `opentelemetry`. It's only useful if there also is also a OTEL collector.
 
diff --git a/dune-project b/dune-project
index 0dbc9c81..5c8b3d6f 100644
--- a/dune-project
+++ b/dune-project
@@ -40,6 +40,7 @@
     (>= 3.0)
     (< 4.0)))
   (ocaml-lsp-server :with-dev-setup)
+  (ambient-context (and (>= 0.2) (< 0.3)))
   (ocamlformat
    (and
     :with-dev-setup
@@ -48,7 +49,7 @@
  (depopts trace lwt eio)
  (conflicts
   (trace
-   (< 0.10)))
+   (< 0.11)))
  (tags
   (instrumentation tracing opentelemetry datadog jaeger)))
 
diff --git a/opentelemetry.opam b/opentelemetry.opam
index 76fd9499..54b6bfb0 100644
--- a/opentelemetry.opam
+++ b/opentelemetry.opam
@@ -23,11 +23,12 @@ depends: [
   "alcotest" {with-test}
   "pbrt" {>= "3.0" & < "4.0"}
   "ocaml-lsp-server" {with-dev-setup}
+  "ambient-context" {>= "0.2" & < "0.3"}
   "ocamlformat" {with-dev-setup & >= "0.27" & < "0.28"}
 ]
 depopts: ["trace" "lwt" "eio"]
 conflicts: [
-  "trace" {< "0.10"}
+  "trace" {< "0.11"}
 ]
 build: [
   ["dune" "subst"] {dev}
diff --git a/src/ambient-context/dune b/src/ambient-context/dune
deleted file mode 100644
index 68e7acf5..00000000
--- a/src/ambient-context/dune
+++ /dev/null
@@ -1,15 +0,0 @@
-(library
- (name opentelemetry_ambient_context)
- (public_name opentelemetry.ambient-context)
- (synopsis
-  "Abstraction over thread-local storage and fiber-local storage mechanisms")
- (private_modules hmap_key_)
- (libraries
-  thread-local-storage
-  threads
-  atomic
-  opentelemetry.ambient-context.types
-  (select
-   hmap_key_.ml
-   from
-   (-> hmap_key_.new.ml))))
diff --git a/src/ambient-context/eio/dune b/src/ambient-context/eio/dune
deleted file mode 100644
index f3f76be7..00000000
--- a/src/ambient-context/eio/dune
+++ /dev/null
@@ -1,7 +0,0 @@
-(library
- (name opentelemetry_ambient_context_eio)
- (public_name opentelemetry.ambient-context.eio)
- (synopsis
-  "Storage backend for ambient-context using Eio's fibre-local storage")
- (optional) ; eio
- (libraries eio hmap opentelemetry.ambient-context thread-local-storage))
diff --git a/src/ambient-context/eio/opentelemetry_ambient_context_eio.ml b/src/ambient-context/eio/opentelemetry_ambient_context_eio.ml
deleted file mode 100644
index 56451a1a..00000000
--- a/src/ambient-context/eio/opentelemetry_ambient_context_eio.ml
+++ /dev/null
@@ -1,39 +0,0 @@
-module Fiber = Eio.Fiber
-
-open struct
-  let _internal_key : Hmap.t Fiber.key = Fiber.create_key ()
-
-  let ( let* ) = Option.bind
-end
-
-module M = struct
-  let name = "Storage_eio"
-
-  let[@inline] get_map () = Fiber.get _internal_key
-
-  let[@inline] with_map m cb = Fiber.with_binding _internal_key m cb
-
-  let create_key = Hmap.Key.create
-
-  let get k =
-    let* context = get_map () in
-    Hmap.find k context
-
-  let with_binding k v cb =
-    let new_context =
-      match get_map () with
-      | None -> Hmap.singleton k v
-      | Some old_context -> Hmap.add k v old_context
-    in
-    with_map new_context cb
-
-  let without_binding k cb =
-    let new_context =
-      match get_map () with
-      | None -> Hmap.empty
-      | Some old_context -> Hmap.rem k old_context
-    in
-    with_map new_context cb
-end
-
-let storage () : Opentelemetry_ambient_context.storage = (module M)
diff --git a/src/ambient-context/eio/opentelemetry_ambient_context_eio.mli b/src/ambient-context/eio/opentelemetry_ambient_context_eio.mli
deleted file mode 100644
index ac5cf8ba..00000000
--- a/src/ambient-context/eio/opentelemetry_ambient_context_eio.mli
+++ /dev/null
@@ -1,2 +0,0 @@
-val storage : unit -> Opentelemetry_ambient_context.storage
-(** Storage using Eio's fibers local storage *)
diff --git a/src/ambient-context/hmap_key_.new.ml b/src/ambient-context/hmap_key_.new.ml
deleted file mode 100644
index 1925b70e..00000000
--- a/src/ambient-context/hmap_key_.new.ml
+++ /dev/null
@@ -1 +0,0 @@
-let key : Hmap.t Thread_local_storage.t = Thread_local_storage.create ()
diff --git a/src/ambient-context/lwt/dune b/src/ambient-context/lwt/dune
deleted file mode 100644
index 68a9de15..00000000
--- a/src/ambient-context/lwt/dune
+++ /dev/null
@@ -1,7 +0,0 @@
-(library
- (name opentelemetry_ambient_context_lwt)
- (public_name opentelemetry.ambient-context.lwt)
- (optional) ; lwt
- (synopsis
-  "Storage backend for ambient-context using Lwt's sequence-associated storage")
- (libraries lwt opentelemetry.ambient-context thread-local-storage))
diff --git a/src/ambient-context/lwt/opentelemetry_ambient_context_lwt.ml b/src/ambient-context/lwt/opentelemetry_ambient_context_lwt.ml
deleted file mode 100644
index b75105f2..00000000
--- a/src/ambient-context/lwt/opentelemetry_ambient_context_lwt.ml
+++ /dev/null
@@ -1,37 +0,0 @@
-open struct
-  let _internal_key : Hmap.t Lwt.key = Lwt.new_key ()
-
-  let ( let* ) = Option.bind
-end
-
-module M = struct
-  let name = "Storage_lwt"
-
-  let[@inline] get_map () = Lwt.get _internal_key
-
-  let[@inline] with_map m cb = Lwt.with_value _internal_key (Some m) cb
-
-  let create_key = Hmap.Key.create
-
-  let get k =
-    let* context = get_map () in
-    Hmap.find k context
-
-  let with_binding k v cb =
-    let new_context =
-      match get_map () with
-      | None -> Hmap.singleton k v
-      | Some old_context -> Hmap.add k v old_context
-    in
-    with_map new_context cb
-
-  let without_binding k cb =
-    let new_context =
-      match get_map () with
-      | None -> Hmap.empty
-      | Some old_context -> Hmap.rem k old_context
-    in
-    with_map new_context cb
-end
-
-let storage () : Opentelemetry_ambient_context.storage = (module M)
diff --git a/src/ambient-context/lwt/opentelemetry_ambient_context_lwt.mli b/src/ambient-context/lwt/opentelemetry_ambient_context_lwt.mli
deleted file mode 100644
index 3c462a8d..00000000
--- a/src/ambient-context/lwt/opentelemetry_ambient_context_lwt.mli
+++ /dev/null
@@ -1,2 +0,0 @@
-val storage : unit -> Opentelemetry_ambient_context.storage
-(** Storage using Lwt keys *)
diff --git a/src/ambient-context/opentelemetry_ambient_context.ml b/src/ambient-context/opentelemetry_ambient_context.ml
deleted file mode 100644
index 7c622eb7..00000000
--- a/src/ambient-context/opentelemetry_ambient_context.ml
+++ /dev/null
@@ -1,124 +0,0 @@
-module TLS = Thread_local_storage
-include Opentelemetry_ambient_context_types
-
-type 'a key = int * 'a Hmap.key
-
-let debug =
-  match Sys.getenv_opt "OCAML_AMBIENT_CONTEXT_DEBUG" with
-  | Some ("1" | "true") -> true
-  | _ -> false
-
-let _debug_id_ = Atomic.make 0
-
-let[@inline] generate_debug_id () = Atomic.fetch_and_add _debug_id_ 1
-
-let compare_key : int -> int -> int = Stdlib.compare
-
-module Storage_tls_hmap = struct
-  let[@inline] ( let* ) o f =
-    match o with
-    | None -> None
-    | Some x -> f x
-
-  let key : Hmap.t TLS.t = Hmap_key_.key
-
-  let name = "Storage_tls"
-
-  let[@inline] get_map () = TLS.get_opt key
-
-  let[@inline] with_map m cb =
-    let old = TLS.get_opt key |> Option.value ~default:Hmap.empty in
-    TLS.set key m;
-    Fun.protect ~finally:(fun () -> TLS.set key old) cb
-
-  let create_key = Hmap.Key.create
-
-  let get k =
-    let* context = get_map () in
-    Hmap.find k context
-
-  let with_binding k v cb =
-    let new_context =
-      match get_map () with
-      | None -> Hmap.singleton k v
-      | Some old_context -> Hmap.add k v old_context
-    in
-    with_map new_context @@ fun _context -> cb ()
-
-  let without_binding k cb =
-    match get_map () with
-    | None -> cb ()
-    | Some old_context ->
-      let new_context = Hmap.rem k old_context in
-      with_map new_context @@ fun _context -> cb ()
-end
-
-let default_storage : storage = (module Storage_tls_hmap)
-
-let k_current_storage : storage TLS.t = TLS.create ()
-
-let get_current_storage () =
-  match TLS.get_exn k_current_storage with
-  | v -> v
-  | exception TLS.Not_set ->
-    let v = default_storage in
-    TLS.set k_current_storage v;
-    v
-
-let create_key () =
-  let (module Store : STORAGE) = get_current_storage () in
-  if not debug then
-    0, Store.create_key ()
-  else (
-    let id = generate_debug_id () in
-    Printf.printf "%s: create_key %i\n%!" Store.name id;
-    id, Store.create_key ()
-  )
-
-let get (id, k) =
-  let (module Store : STORAGE) = get_current_storage () in
-  if not debug then
-    Store.get k
-  else (
-    let rv = Store.get k in
-    (match rv with
-    | Some _ -> Printf.printf "%s: get %i -> Some\n%!" Store.name id
-    | None -> Printf.printf "%s: get %i -> None\n%!" Store.name id);
-    rv
-  )
-
-let with_binding : 'a key -> 'a -> (unit -> 'r) -> 'r =
- fun (id, k) v cb ->
-  let (module Store : STORAGE) = get_current_storage () in
-  if not debug then
-    Store.with_binding k v cb
-  else (
-    Printf.printf "%s: with_binding %i enter\n%!" Store.name id;
-    let rv = Store.with_binding k v cb in
-    Printf.printf "%s: with_binding %i exit\n%!" Store.name id;
-    rv
-  )
-
-let without_binding (id, k) cb =
-  let (module Store : STORAGE) = get_current_storage () in
-  if not debug then
-    Store.without_binding k cb
-  else (
-    Printf.printf "%s: without_binding %i enter\n%!" Store.name id;
-    let rv = Store.without_binding k cb in
-    Printf.printf "%s: without_binding %i exit\n%!" Store.name id;
-    rv
-  )
-
-let set_storage_provider store_new =
-  let store_before = get_current_storage () in
-  if store_new == store_before then
-    ()
-  else
-    TLS.set k_current_storage store_new;
-  if debug then (
-    let (module Store_before : STORAGE) = store_before in
-    let (module Store_new : STORAGE) = store_new in
-    Printf.printf "set_storage_provider %s (previously %s)\n%!" Store_new.name
-      Store_before.name
-  )
diff --git a/src/ambient-context/opentelemetry_ambient_context.mli b/src/ambient-context/opentelemetry_ambient_context.mli
deleted file mode 100644
index 8f19ff0c..00000000
--- a/src/ambient-context/opentelemetry_ambient_context.mli
+++ /dev/null
@@ -1,55 +0,0 @@
-(** Ambient context.
-
-    The ambient context, like the Matrix, is everywhere around you.
-
-    It is responsible for keeping track of that context in a manner that's
-    consistent with the program's choice of control flow paradigm:
-
-    - for synchronous/threaded/direct style code, {b TLS} ("thread local
-      storage") keeps track of a global variable per thread. Each thread has its
-      own copy of the variable and updates it independently of other threads.
-
-    - for Lwt, any ['a Lwt.t] created inside the [with_binding k v (fun _ -> …)]
-      will inherit the [k := v] assignment.
-
-    - for Eio, fibers created inside [with_binding k v (fun () -> …)] will
-      inherit the [k := v] assignment. This is consistent with the structured
-      concurrency approach of Eio.
-
-    The only data stored by this storage is a {!Hmap.t}, ie a heterogeneous map.
-    Various users (libraries, user code, etc.) can create their own {!key} to
-    store what they are interested in, without affecting other parts of the
-    storage. *)
-
-module Types := Opentelemetry_ambient_context_types
-
-module type STORAGE = Types.STORAGE
-
-type storage = (module STORAGE)
-
-val default_storage : storage
-
-val get_current_storage : unit -> storage
-
-val set_storage_provider : storage -> unit
-
-type 'a key
-(** A key that can be mapped to values of type ['a] in the ambient context. *)
-
-val compare_key : int -> int -> int
-(** Total order on keys *)
-
-val create_key : unit -> 'a key
-(** Create a new fresh key, distinct from any previously created key. *)
-
-val get : 'a key -> 'a option
-(** Get the current value for a given key, or [None] if no value was associated
-    with the key in the ambient context. *)
-
-val with_binding : 'a key -> 'a -> (unit -> 'r) -> 'r
-(** [with_binding k v cb] calls [cb()] in a context in which [k] is bound to
-    [v]. This does not affect storage outside of [cb()]. *)
-
-val without_binding : 'a key -> (unit -> 'b) -> 'b
-(** [without_binding k cb] calls [cb()] in a context where [k] has no binding
-    (possibly shadowing the current ambient binding of [k] if it exists). *)
diff --git a/src/ambient-context/types/dune b/src/ambient-context/types/dune
deleted file mode 100644
index b9e4146c..00000000
--- a/src/ambient-context/types/dune
+++ /dev/null
@@ -1,4 +0,0 @@
-(library
- (name opentelemetry_ambient_context_types)
- (public_name opentelemetry.ambient-context.types)
- (libraries hmap thread-local-storage))
diff --git a/src/ambient-context/types/opentelemetry_ambient_context_types.ml b/src/ambient-context/types/opentelemetry_ambient_context_types.ml
deleted file mode 100644
index 829f7789..00000000
--- a/src/ambient-context/types/opentelemetry_ambient_context_types.ml
+++ /dev/null
@@ -1,19 +0,0 @@
-type 'a key = 'a Hmap.key
-
-module type STORAGE = sig
-  val name : string
-
-  val get_map : unit -> Hmap.t option
-
-  val with_map : Hmap.t -> (unit -> 'b) -> 'b
-
-  val create_key : unit -> 'a key
-
-  val get : 'a key -> 'a option
-
-  val with_binding : 'a key -> 'a -> (unit -> 'b) -> 'b
-
-  val without_binding : 'a key -> (unit -> 'b) -> 'b
-end
-
-type storage = (module STORAGE)
diff --git a/src/ambient-context/types/opentelemetry_ambient_context_types.mli b/src/ambient-context/types/opentelemetry_ambient_context_types.mli
deleted file mode 100644
index 738b7520..00000000
--- a/src/ambient-context/types/opentelemetry_ambient_context_types.mli
+++ /dev/null
@@ -1,32 +0,0 @@
-(** Storage implementation.
-
-    There is a singleton storage for a given program, responsible for providing
-    ambient context to the rest of the program. *)
-
-type 'a key = 'a Hmap.key
-
-module type STORAGE = sig
-  val name : string
-  (** Name of the storage implementation. *)
-
-  val get_map : unit -> Hmap.t option
-  (** Get the hmap from the current ambient context, or [None] if there is no
-      ambient context. *)
-
-  val with_map : Hmap.t -> (unit -> 'b) -> 'b
-  (** [with_hmap h cb] calls [cb()] in an ambient context in which [get_map()]
-      will return [h]. Once [cb()] returns, the storage is reset to its previous
-      value. *)
-
-  val create_key : unit -> 'a key
-  (** Create a new storage key, guaranteed to be distinct from any previously
-      created key. *)
-
-  val get : 'a key -> 'a option
-
-  val with_binding : 'a key -> 'a -> (unit -> 'b) -> 'b
-
-  val without_binding : 'a key -> (unit -> 'b) -> 'b
-end
-
-type storage = (module STORAGE)
diff --git a/src/client/batch.mli b/src/client/batch.mli
index 8bd410fd..a7ed2aa9 100644
--- a/src/client/batch.mli
+++ b/src/client/batch.mli
@@ -47,6 +47,6 @@ val pop_if_ready : ?force:bool -> now:Mtime.t -> 'a t -> 'a list option
       batches before exit or because the user asks for it *)
 
 val push : 'a t -> 'a list -> [ `Dropped | `Ok ]
-(** [push b xs] is [`Ok] if it succeeds in pushing the values in [xs] into the batch
-    [b], or [`Dropped] if the current size of the batch has exceeded the high water
-    mark determined by the [batch] argument to [{!make}]. ) *)
+(** [push b xs] is [`Ok] if it succeeds in pushing the values in [xs] into the
+    batch [b], or [`Dropped] if the current size of the batch has exceeded the
+    high water mark determined by the [batch] argument to [{!make}]. ) *)
diff --git a/src/core/dune b/src/core/dune
index 248e3aff..18c6f260 100644
--- a/src/core/dune
+++ b/src/core/dune
@@ -4,7 +4,8 @@
  (flags :standard -warn-error -a+8)
  (libraries
   opentelemetry.proto
-  opentelemetry.ambient-context
+  ambient-context.core
+  ambient-context
   ptime
   ptime.clock.os
   pbrt
diff --git a/src/core/opentelemetry.ml b/src/core/opentelemetry.ml
index 69a8325c..63d52a91 100644
--- a/src/core/opentelemetry.ml
+++ b/src/core/opentelemetry.ml
@@ -4,7 +4,7 @@ open struct
   let spf = Printf.sprintf
 
   module Atomic = Opentelemetry_atomic.Atomic
-  module Ambient_context = Opentelemetry_ambient_context
+  module Ambient_context = Ambient_context
 end
 
 module Lock = Lock
@@ -961,7 +961,7 @@ module Scope : sig
   (** Set the span's kind.
       @since 0.11 *)
 
-  val ambient_scope_key : t Ambient_context.key
+  val ambient_scope_key : t Ambient_context.Context.key
   (** The opaque key necessary to access/set the ambient scope with
       {!Ambient_context}. *)
 
@@ -1097,7 +1097,8 @@ end = struct
   let set_kind (scope : t) (k : Span_kind.t) : unit =
     if Collector.has_backend () then scope.items <- Span_kind (k, scope.items)
 
-  let ambient_scope_key : t Ambient_context.key = Ambient_context.create_key ()
+  let ambient_scope_key : t Ambient_context.Context.key =
+    Ambient_context.new_key ()
 
   let get_ambient_scope ?scope () : t option =
     match scope with
@@ -1105,7 +1106,7 @@ end = struct
     | None -> Ambient_context.get ambient_scope_key
 
   let[@inline] with_ambient_scope (sc : t) (f : unit -> 'a) : 'a =
-    Ambient_context.with_binding ambient_scope_key sc (fun _ -> f ())
+    Ambient_context.with_key_bound_to ambient_scope_key sc f
 end
 
 (** {2 Traces} *)
diff --git a/src/integrations/cohttp/opentelemetry_cohttp_lwt.ml b/src/integrations/cohttp/opentelemetry_cohttp_lwt.ml
index 67272d36..ad670b5c 100644
--- a/src/integrations/cohttp/opentelemetry_cohttp_lwt.ml
+++ b/src/integrations/cohttp/opentelemetry_cohttp_lwt.ml
@@ -145,14 +145,21 @@ let client ?(scope : Otel.Scope.t option) (module C : Cohttp_lwt.S.Client) =
 
     (*   These types and values are not customized by our client, but are required to satisfy
          [Cohttp_lwt.S.Client]. *)
-    include (C : sig
-               type ctx = C.ctx
-               type 'a io = 'a C.io
-               type 'a with_context = 'a C.with_context
-               type body = C.body
-               val map_context : 'a with_context -> ('a -> 'b) -> 'b with_context
-               val set_cache : Cohttp_lwt.S.call -> unit
-             end)
+    include (
+      C :
+        sig
+          type ctx = C.ctx
+
+          type 'a io = 'a C.io
+
+          type 'a with_context = 'a C.with_context
+
+          type body = C.body
+
+          val map_context : 'a with_context -> ('a -> 'b) -> 'b with_context
+
+          val set_cache : Cohttp_lwt.S.call -> unit
+        end)
 
     let attrs_for ~uri ~meth:_ () =
       [
diff --git a/src/trace/dune b/src/trace/dune
index 9606e2a5..b8e3926e 100644
--- a/src/trace/dune
+++ b/src/trace/dune
@@ -3,4 +3,4 @@
  (public_name opentelemetry.trace)
  (synopsis "Use opentelemetry as a collector for trace")
  (optional)
- (libraries opentelemetry.ambient-context trace.core opentelemetry))
+ (libraries ambient-context.core ambient-context trace.core opentelemetry))
diff --git a/src/trace/opentelemetry_trace.ml b/src/trace/opentelemetry_trace.ml
index 0126257b..d8e966a1 100644
--- a/src/trace/opentelemetry_trace.ml
+++ b/src/trace/opentelemetry_trace.ml
@@ -6,149 +6,32 @@ open struct
   let spf = Printf.sprintf
 end
 
-module Conv = struct
-  let[@inline] trace_id_of_otel (id : Otel.Trace_id.t) : Otrace.trace_id =
-    if id == Otel.Trace_id.dummy then
-      Otrace.Collector.dummy_trace_id
-    else
-      Bytes.unsafe_to_string (Otel.Trace_id.to_bytes id)
-
-  let[@inline] trace_id_to_otel (id : Otrace.trace_id) : Otel.Trace_id.t =
-    if id == Otrace.Collector.dummy_trace_id then
-      Otel.Trace_id.dummy
-    else
-      Otel.Trace_id.of_bytes @@ Bytes.unsafe_of_string id
-
-  let[@inline] span_id_of_otel (id : Otel.Span_id.t) : Otrace.span =
-    if id == Otel.Span_id.dummy then
-      Otrace.Collector.dummy_span
-    else
-      Bytes.get_int64_le (Otel.Span_id.to_bytes id) 0
-
-  let[@inline] span_id_to_otel (id : Otrace.span) : Otel.Span_id.t =
-    if id == Otrace.Collector.dummy_span then
-      Otel.Span_id.dummy
-    else (
-      let b = Bytes.create 8 in
-      Bytes.set_int64_le b 0 id;
-      Otel.Span_id.of_bytes b
-    )
-
-  let[@inline] ctx_to_otel (self : Otrace.explicit_span_ctx) : Otel.Span_ctx.t =
-    Otel.Span_ctx.make
-      ~trace_id:(trace_id_to_otel self.trace_id)
-      ~parent_id:(span_id_to_otel self.span)
-      ()
-
-  let[@inline] ctx_of_otel (ctx : Otel.Span_ctx.t) : Otrace.explicit_span_ctx =
-    {
-      trace_id = trace_id_of_otel (Otel.Span_ctx.trace_id ctx);
-      span = span_id_of_otel (Otel.Span_ctx.parent_id ctx);
-    }
-end
-
-open Conv
-
-module Well_known = struct
-  let spankind_key = "otrace.spankind"
-
-  let internal = `String "INTERNAL"
-
-  let server = `String "SERVER"
-
-  let client = `String "CLIENT"
-
-  let producer = `String "PRODUCER"
-
-  let consumer = `String "CONSUMER"
-
-  let spankind_of_string =
-    let open Otel.Span in
-    function
-    | "INTERNAL" -> Span_kind_internal
-    | "SERVER" -> Span_kind_server
-    | "CLIENT" -> Span_kind_client
-    | "PRODUCER" -> Span_kind_producer
-    | "CONSUMER" -> Span_kind_consumer
-    | _ -> Span_kind_unspecified
-
-  let otel_attrs_of_otrace_data data =
-    let kind : Otel.Span.kind ref = ref Otel.Span.Span_kind_unspecified in
-    let data =
-      List.filter_map
-        (function
-          | name, `String v when name = "otrace.spankind" ->
-            kind := spankind_of_string v;
-            None
-          | x -> Some x)
-        data
-    in
-    !kind, data
-
-  (** Key to store an error [Otel.Span.status] with the message. Set
-      ["otrace.error" = "mymsg"] in a span data to set the span's status to
-      [{message="mymsg"; code=Error}]. *)
-  let status_error_key = "otrace.error"
-end
-
-open Well_known
+module Well_known = struct end
 
 let on_internal_error =
   ref (fun msg -> Printf.eprintf "error in Opentelemetry_trace: %s\n%!" msg)
 
-type Otrace.extension_event +=
-  | Ev_link_span of Otrace.explicit_span * Otrace.explicit_span
-  | Ev_set_span_kind of Otrace.explicit_span * Otel.Span_kind.t
-  | Ev_record_exn of Otrace.explicit_span * exn * Printexc.raw_backtrace
-
-module Internal = struct
-  type span_begin = {
+module Span_info = struct
+  type t = {
     start_time: int64;
     name: string;
-    __FILE__: string;
-    __LINE__: int;
-    __FUNCTION__: string option;
     scope: Otel.Scope.t;
     parent: Otel.Span_ctx.t option;
   }
+end
 
-  module Active_span_tbl = Hashtbl.Make (struct
-    include Int64
+type Otrace.span += Span_otel of Span_info.t
 
-    let hash : t -> int = Hashtbl.hash
-  end)
+type Otrace.extension_event +=
+  | Ev_link_span of Otrace.span * Otrace.span
+  | Ev_set_span_kind of Otrace.span * Otel.Span_kind.t
+  | Ev_record_exn of Otrace.span * exn * Printexc.raw_backtrace
 
-  (** key to access a OTEL scope from an explicit span *)
-  let k_explicit_scope : Otel.Scope.t Otrace.Meta_map.key =
-    Otrace.Meta_map.Key.create ()
-
-  (** Per-thread set of active spans. *)
-  module Active_spans = struct
-    type t = { tbl: span_begin Active_span_tbl.t } [@@unboxed]
-
-    let create () : t = { tbl = Active_span_tbl.create 32 }
-
-    let k_tls : t TLS.t = TLS.create ()
-
-    let[@inline] get () : t =
-      try TLS.get_exn k_tls
-      with TLS.Not_set ->
-        let self = create () in
-        TLS.set k_tls self;
-        self
-  end
-
-  let otrace_of_otel (id : Otel.Span_id.t) : int64 =
-    let bs = Otel.Span_id.to_bytes id in
-    (* lucky that it coincides! *)
-    assert (Bytes.length bs = 8);
-    Bytes.get_int64_le bs 0
-
-  let enter_span' ?(explicit_parent : Otrace.explicit_span_ctx option)
-      ~__FUNCTION__ ~__FILE__ ~__LINE__ ~data name =
+module Internal = struct
+  let enter_span' ?(parent_span : Otrace.span option) ~__FUNCTION__ ~__FILE__
+      ~__LINE__ ~data name : Span_info.t =
     let open Otel in
-    let otel_id = Span_id.create () in
-    let otrace_id = otrace_of_otel otel_id in
+    let span_id = Span_id.create () in
 
     let parent_scope = Scope.get_ambient_scope () in
     let trace_id =
@@ -157,215 +40,121 @@ module Internal = struct
       | None -> Trace_id.create ()
     in
     let parent =
-      match explicit_parent, parent_scope with
-      | Some p, _ ->
-        Some
-          (Otel.Span_ctx.make ~trace_id ~parent_id:(span_id_to_otel p.span) ())
-      | None, Some parent -> Some (Otel.Scope.to_span_ctx parent)
-      | None, None -> None
+      match parent_span, parent_scope with
+      | Some (Span_otel parent_span), _ ->
+        Some (Otel.Scope.to_span_ctx parent_span.scope)
+      | _, Some sc -> Some (Otel.Scope.to_span_ctx sc)
+      | _, None -> None
     in
 
-    let new_scope = Otel.Scope.make ~trace_id ~span_id:otel_id ~attrs:data () in
-
+    let new_scope = Otel.Scope.make ~trace_id ~span_id ~attrs:data () in
     let start_time = Timestamp_ns.now_unix_ns () in
-    let sb =
-      {
-        start_time;
-        name;
-        __FILE__;
-        __LINE__;
-        __FUNCTION__;
-        scope = new_scope;
-        parent;
-      }
+
+    let attrs_function =
+      match __FUNCTION__ with
+      | None -> []
+      | Some __FUNCTION__ ->
+        (try
+           let last_dot = String.rindex __FUNCTION__ '.' in
+           let module_path = String.sub __FUNCTION__ 0 last_dot in
+           let function_name =
+             String.sub __FUNCTION__ (last_dot + 1)
+               (String.length __FUNCTION__ - last_dot - 1)
+           in
+           [
+             "code.function", `String function_name;
+             "code.namespace", `String module_path;
+           ]
+         with Not_found -> [])
     in
 
-    let active_spans = Active_spans.get () in
-    Active_span_tbl.add active_spans.tbl otrace_id sb;
+    (* directly store file, line, etc in scope *)
+    Otel.Scope.add_attrs new_scope (fun () ->
+        ("code.filepath", `String __FILE__)
+        :: ("code.lineno", `Int __LINE__)
+        :: attrs_function);
 
-    otrace_id, sb
+    { Span_info.start_time; name; scope = new_scope; parent }
 
-  let exit_span_
-      { start_time; name; __FILE__; __LINE__; __FUNCTION__; scope; parent } =
+  let exit_span_ ({ name; start_time; scope; parent } : Span_info.t) :
+      Otel.Span.t =
     let open Otel in
     let end_time = Timestamp_ns.now_unix_ns () in
-    let kind, attrs = otel_attrs_of_otrace_data (Scope.attrs scope) in
+    let attrs = Scope.attrs scope in
+    let parent_id = Option.map Span_ctx.parent_id parent in
+    let kind = Scope.kind scope in
+    let status = Scope.status scope in
 
-    let status : Span_status.t =
-      match List.assoc_opt Well_known.status_error_key attrs with
-      | Some (`String message) -> { message; code = Status_code_error }
-      | _ -> { message = ""; code = Status_code_ok }
-    in
-
-    let attrs =
-      match __FUNCTION__ with
-      | None ->
-        [ "code.filepath", `String __FILE__; "code.lineno", `Int __LINE__ ]
-        @ attrs
-      | Some __FUNCTION__ ->
-        let last_dot = String.rindex __FUNCTION__ '.' in
-        let module_path = String.sub __FUNCTION__ 0 last_dot in
-        let function_name =
-          String.sub __FUNCTION__ (last_dot + 1)
-            (String.length __FUNCTION__ - last_dot - 1)
-        in
-        [
-          "code.filepath", `String __FILE__;
-          "code.lineno", `Int __LINE__;
-          "code.function", `String function_name;
-          "code.namespace", `String module_path;
-        ]
-        @ attrs
-    in
-
-    let parent_id = Option.map Otel.Span_ctx.parent_id parent in
-    Span.create ~kind ~trace_id:scope.trace_id ?parent:parent_id ~status
+    Span.create ?kind ~trace_id:scope.trace_id ?parent:parent_id ?status
       ~id:scope.span_id ~start_time ~end_time ~attrs
-      ~events:(Scope.events scope) name
+      ~events:(Scope.events scope) ~links:(Scope.links scope) name
     |> fst
 
-  let exit_span' otrace_id otel_span_begin =
-    let active_spans = Active_spans.get () in
-    Active_span_tbl.remove active_spans.tbl otrace_id;
-    exit_span_ otel_span_begin
+  let enter_span _st ~__FUNCTION__ ~__FILE__ ~__LINE__ ~level:_ ~params:_ ~data
+      ~parent name : Otrace.span =
+    let parent_span =
+      match parent with
+      | Otrace.P_some sp -> Some sp
+      | _ -> None
+    in
+    let span_info =
+      enter_span' ?parent_span ~__FUNCTION__ ~__FILE__ ~__LINE__ ~data name
+    in
+    Span_otel span_info
 
-  let exit_span_from_id otrace_id =
-    let active_spans = Active_spans.get () in
-    match Active_span_tbl.find_opt active_spans.tbl otrace_id with
-    | None -> None
-    | Some otel_span_begin ->
-      Active_span_tbl.remove active_spans.tbl otrace_id;
-      Some (exit_span_ otel_span_begin)
+  let exit_span _st (span : Otrace.span) =
+    match span with
+    | Span_otel span_info ->
+      let otel_span = exit_span_ span_info in
+      Otel.Trace.emit [ otel_span ]
+    | _ -> ()
 
-  let[@inline] get_scope (span : Otrace.explicit_span) : Otel.Scope.t option =
-    Otrace.Meta_map.find k_explicit_scope span.meta
+  let add_data_to_span _st (span : Otrace.span) data =
+    match span with
+    | Span_otel span_info ->
+      Otel.Scope.add_attrs span_info.scope (fun () -> data)
+    | _ -> ()
 
-  module M = struct
-    let with_span ~__FUNCTION__ ~__FILE__ ~__LINE__ ~data name cb =
-      let otrace_id, sb =
-        enter_span' ~__FUNCTION__ ~__FILE__ ~__LINE__ ~data name
-      in
+  let message _st ~level:_ ~params:_ ~data:_ ~span msg : unit =
+    let trace_id, span_id =
+      match span with
+      | Some (Span_otel si) -> Some si.scope.trace_id, Some si.scope.span_id
+      | _ ->
+        (match Otel.Scope.get_ambient_scope () with
+        | None -> None, None
+        | Some scope -> Some scope.trace_id, Some scope.span_id)
+    in
 
-      Otel.Scope.with_ambient_scope sb.scope @@ fun () ->
-      match cb otrace_id with
-      | res ->
-        let otel_span = exit_span' otrace_id sb in
-        Otel.Trace.emit [ otel_span ];
-        res
-      | exception e ->
-        let bt = Printexc.get_raw_backtrace () in
+    let log = Otel.Logs.make_str ?trace_id ?span_id msg in
+    Otel.Logs.emit [ log ]
 
-        Otel.Scope.record_exception sb.scope e bt;
-        let otel_span = exit_span' otrace_id sb in
-        Otel.Trace.emit [ otel_span ];
-
-        Printexc.raise_with_backtrace e bt
-
-    let enter_span ~__FUNCTION__ ~__FILE__ ~__LINE__ ~data name :
-        Trace_core.span =
-      let otrace_id, _sb =
-        enter_span' ~__FUNCTION__ ~__FILE__ ~__LINE__ ~data name
-      in
-      (* NOTE: we cannot enter ambient scope in a disjoint way
-         with the exit, because we only have [Ambient_context.with_binding],
-         no [set_binding] *)
-      otrace_id
-
-    let exit_span otrace_id =
-      match exit_span_from_id otrace_id with
-      | None -> ()
-      | Some otel_span -> Otel.Trace.emit [ otel_span ]
-
-    let enter_manual_span ~(parent : Otrace.explicit_span_ctx option) ~flavor:_
-        ~__FUNCTION__ ~__FILE__ ~__LINE__ ~data name : Otrace.explicit_span =
-      let otrace_id, sb =
-        match parent with
-        | None -> enter_span' ~__FUNCTION__ ~__FILE__ ~__LINE__ ~data name
-        | Some parent ->
-          enter_span' ~explicit_parent:parent ~__FUNCTION__ ~__FILE__ ~__LINE__
-            ~data name
-      in
-
-      let active_spans = Active_spans.get () in
-      Active_span_tbl.add active_spans.tbl otrace_id sb;
-
-      Otrace.
-        {
-          span = otrace_id;
-          trace_id = trace_id_of_otel sb.scope.trace_id;
-          meta = Meta_map.(empty |> add k_explicit_scope sb.scope);
-        }
-
-    let exit_manual_span Otrace.{ span = otrace_id; _ } =
-      let active_spans = Active_spans.get () in
-      match Active_span_tbl.find_opt active_spans.tbl otrace_id with
-      | None -> !on_internal_error (spf "no active span with ID %Ld" otrace_id)
-      | Some sb ->
-        let otel_span = exit_span' otrace_id sb in
-        Otel.Trace.emit [ otel_span ]
-
-    let add_data_to_span otrace_id data =
-      let active_spans = Active_spans.get () in
-      match Active_span_tbl.find_opt active_spans.tbl otrace_id with
-      | None -> !on_internal_error (spf "no active span with ID %Ld" otrace_id)
-      | Some sb -> Otel.Scope.add_attrs sb.scope (fun () -> data)
-
-    let add_data_to_manual_span (span : Otrace.explicit_span) data : unit =
-      match get_scope span with
-      | None ->
-        !on_internal_error (spf "manual span does not a contain an OTEL scope")
-      | Some scope -> Otel.Scope.add_attrs scope (fun () -> data)
-
-    let message ?span ~data:_ msg : unit =
-      (* gather information from context *)
-      let old_scope = Otel.Scope.get_ambient_scope () in
-      let trace_id = Option.map (fun sc -> sc.Otel.Scope.trace_id) old_scope in
-
-      let span_id =
-        match span with
-        | Some id -> Some (span_id_to_otel id)
-        | None -> Option.map (fun sc -> sc.Otel.Scope.span_id) old_scope
-      in
-
-      let log = Otel.Logs.make_str ?trace_id ?span_id msg in
-      Otel.Logs.emit [ log ]
-
-    let shutdown () = ()
-
-    let name_process _name = ()
-
-    let name_thread _name = ()
-
-    let counter_int ~data name cur_val : unit =
-      let _kind, attrs = otel_attrs_of_otrace_data data in
-      let m = Otel.Metrics.(gauge ~name [ int ~attrs cur_val ]) in
+  let metric _st ~level:_ ~params:_ ~data:attrs name v =
+    let open Otrace.Core_ext in
+    match v with
+    | Metric_int i ->
+      let m = Otel.Metrics.(gauge ~name [ int ~attrs i ]) in
       Otel.Metrics.emit [ m ]
-
-    let counter_float ~data name cur_val : unit =
-      let _kind, attrs = otel_attrs_of_otrace_data data in
-      let m = Otel.Metrics.(gauge ~name [ float ~attrs cur_val ]) in
+    | Metric_float f ->
+      let m = Otel.Metrics.(gauge ~name [ float ~attrs f ]) in
       Otel.Metrics.emit [ m ]
+    | _ -> ()
 
-    let extension_event = function
-      | Ev_link_span (sp1, sp2) ->
-        (match get_scope sp1, get_scope sp2 with
-        | Some sc1, Some sc2 ->
-          Otel.Scope.add_links sc1 (fun () -> [ Otel.Scope.to_span_link sc2 ])
-        | _ -> !on_internal_error "could not find scope for OTEL span")
-      | Ev_set_span_kind (sp, k) ->
-        (match get_scope sp with
-        | None -> !on_internal_error "could not find scope for OTEL span"
-        | Some sc -> Otel.Scope.set_kind sc k)
-      | Ev_record_exn (sp, exn, bt) ->
-        (match get_scope sp with
-        | None -> !on_internal_error "could not find scope for OTEL span"
-        | Some sc -> Otel.Scope.record_exception sc exn bt)
-      | _ -> ()
-  end
+  let extension _st ~level:_ ev =
+    match ev with
+    | Ev_link_span (Span_otel sb1, Span_otel sb2) ->
+      Otel.Scope.add_links sb1.scope (fun () ->
+          [ Otel.Scope.to_span_link sb2.scope ])
+    | Ev_set_span_kind (Span_otel sb, k) -> Otel.Scope.set_kind sb.scope k
+    | Ev_record_exn (Span_otel sb, exn, bt) ->
+      Otel.Scope.record_exception sb.scope exn bt
+    | _ -> ()
+
+  let callbacks : unit Otrace.Collector.Callbacks.t =
+    Otrace.Collector.Callbacks.make ~enter_span ~exit_span ~add_data_to_span
+      ~message ~metric ~extension ()
 end
 
-let link_spans (sp1 : Otrace.explicit_span) (sp2 : Otrace.explicit_span) : unit
-    =
+let link_spans (sp1 : Otrace.span) (sp2 : Otrace.span) : unit =
   if Otrace.enabled () then Otrace.extension_event @@ Ev_link_span (sp1, sp2)
 
 let set_span_kind sp k : unit =
@@ -374,7 +163,13 @@ let set_span_kind sp k : unit =
 let record_exception sp exn bt : unit =
   if Otrace.enabled () then Otrace.extension_event @@ Ev_record_exn (sp, exn, bt)
 
-let collector () : Otrace.collector = (module Internal.M)
+let with_ambient_span (sp : Otrace.span) f =
+  match sp with
+  | Span_otel sb -> Otel.Scope.with_ambient_scope sb.scope f
+  | _ -> f ()
+
+let collector () : Otrace.collector =
+  Trace_core.Collector.C_some ((), Internal.callbacks)
 
 let setup () = Otrace.setup_collector @@ collector ()
 
diff --git a/src/trace/opentelemetry_trace.mli b/src/trace/opentelemetry_trace.mli
index 060f4f13..1e7e145e 100644
--- a/src/trace/opentelemetry_trace.mli
+++ b/src/trace/opentelemetry_trace.mli
@@ -1,21 +1,3 @@
-module Otel := Opentelemetry
-module Otrace := Trace_core
-module TLS := Thread_local_storage
-
-module Conv : sig
-  val trace_id_of_otel : Otel.Trace_id.t -> string
-
-  val trace_id_to_otel : string -> Otel.Trace_id.t
-
-  val span_id_of_otel : Otel.Span_id.t -> int64
-
-  val span_id_to_otel : int64 -> Otel.Span_id.t
-
-  val ctx_to_otel : Otrace.explicit_span_ctx -> Otel.Span_ctx.t
-
-  val ctx_of_otel : Otel.Span_ctx.t -> Otrace.explicit_span_ctx
-end
-
 (** [opentelemetry.trace] implements a {!Trace_core.Collector} for
     {{:https://v3.ocaml.org/p/trace} ocaml-trace}.
 
@@ -23,33 +5,27 @@ end
     that use [ocaml-trace], and they will automatically emit OpenTelemetry spans
     and logs.
 
-    Both explicit scope (in the [_manual] functions such as [enter_manual_span])
-    and implicit scope (in {!Internal.M.with_span}, via {!Ambient_context}) are
-    supported; see the detailed notes on {!Internal.M.enter_manual_span}.
+    [Ambient_context] is used to propagate the current span to child spans.
 
-    {1:wellknown Well-known identifiers}
-
-    Because [ocaml-trace]'s API is a subset of OpenTelemetry functionality, this
-    interface allows for a few 'well-known' identifiers to be used in
-    [Trace]-instrumented libraries that wish to further support OpenTelemetry
-    usage.
-
-    (These strings will not change in subsequent versions of this library, so
-    you do not need to depend on [opentelemetry.trace] to use them.)
-
-    - If a key of exactly ["otrace.spankind"] is included in the
-      {!Trace_core.user_data} passed to [with_span] et al., it will be used as
-      the {!Opentelemetry.Span.kind} of the emitted span. (See
-      {!Internal.spankind_of_string} for the list of supported values.)
+    [Trace_core.extension_event] is used to expose OTEL-specific features on top
+    of the common tracing interface, e.g. to set the span kind:
 
     {[
-      ocaml
-      let describe () = [ Opentelemetry_trace.(spankind_key, client) ] in
-      Trace_core.with_span ~__FILE__ ~__LINE__ ~data:describe "my-span"
-      @@ fun _ ->
-        (* ... *)
+      let@ span = Trace_core.with_span ~__FILE__ ~__LINE__ "my-span" in
+      Opentelemetry_trace.set_span_kind span Span_kind_client
+      (* ... *)
     ]} *)
 
+module Otel := Opentelemetry
+module Otrace := Trace_core
+
+type Otrace.extension_event +=
+  | Ev_link_span of Otrace.span * Otrace.span
+        (** Link the two spans together. Both must be currently active spans. *)
+  | Ev_set_span_kind of Otrace.span * Otel.Span_kind.t
+  | Ev_record_exn of Otrace.span * exn * Printexc.raw_backtrace
+        (** Record exception and potentially turn span to an error *)
+
 val on_internal_error : (string -> unit) ref
 (** Callback to print errors in the library itself (ie bugs) *)
 
@@ -62,166 +38,23 @@ val setup_with_otel_backend : Opentelemetry.Collector.backend -> unit
 val collector : unit -> Trace_core.collector
 (** Make a Trace collector that uses the OTEL backend to send spans and logs *)
 
-val link_spans : Otrace.explicit_span -> Otrace.explicit_span -> unit
+val link_spans : Otrace.span -> Otrace.span -> unit
 (** [link_spans sp1 sp2] modifies [sp1] by adding a span link to [sp2].
     @since 0.11 *)
 
-val set_span_kind : Otrace.explicit_span -> Otel.Span.kind -> unit
+val set_span_kind : Otrace.span -> Otel.Span_kind.t -> unit
 (** [set_span_kind sp k] sets the span's kind.
     @since 0.11 *)
 
-val record_exception :
-  Otrace.explicit_span -> exn -> Printexc.raw_backtrace -> unit
+val record_exception : Otrace.span -> exn -> Printexc.raw_backtrace -> unit
 (** Record exception in the current span.
     @since 0.11 *)
 
-(** Static references for well-known identifiers; see {!label-wellknown}. *)
-module Well_known : sig
-  val spankind_key : string
+val with_ambient_span : Otrace.span -> (unit -> 'a) -> 'a
+(** [with_ambient_span sp f] calls [f()] in an ambient context where [sp] is the
+    current span. *)
 
-  val internal : Otrace.user_data
-
-  val server : Otrace.user_data
-
-  val client : Otrace.user_data
-
-  val producer : Otrace.user_data
-
-  val consumer : Otrace.user_data
-
-  val spankind_of_string : string -> Otel.Span.kind
-
-  val otel_attrs_of_otrace_data :
-    (string * Otrace.user_data) list ->
-    Otel.Span.kind * Otel.Span.key_value list
-end
-[@@deprecated "use the regular functions for this"]
-
-(**/**)
-
-(** Internal implementation details; do not consider these stable. *)
-module Internal : sig
-  module M : sig
-    val with_span :
-      __FUNCTION__:string option ->
-      __FILE__:string ->
-      __LINE__:int ->
-      data:(string * Otrace.user_data) list ->
-      string (* span name *) ->
-      (Otrace.span -> 'a) ->
-      'a
-    (** Implements {!Trace_core.Collector.S.with_span}, with the OpenTelemetry
-        collector as the backend. Invoked via {!Trace_core.with_span}.
-
-        Notably, this has the same implicit-scope semantics as
-        {!Opentelemetry.Trace.with_}, and requires configuration of
-        {!Ambient_context}.
-
-        @see <https://github.com/ELLIOTTCABLE/ocaml-ambient-context>
-          ambient-context docs *)
-
-    val enter_manual_span :
-      parent:Otrace.explicit_span_ctx option ->
-      flavor:'a ->
-      __FUNCTION__:string option ->
-      __FILE__:string ->
-      __LINE__:int ->
-      data:(string * Otrace.user_data) list ->
-      string (* span name *) ->
-      Otrace.explicit_span
-    (** Implements {!Trace_core.Collector.S.enter_manual_span}, with the
-        OpenTelemetry collector as the backend. Invoked at
-        {!Trace_core.enter_manual_toplevel_span} and
-        {!Trace_core.enter_manual_sub_span}; requires an eventual call to
-        {!Trace_core.exit_manual_span}.
-
-        These 'manual span' functions {e do not} implement the same implicit-
-        scope semantics of {!with_span}; and thus don't need to wrap a single
-        stack-frame / callback; you can freely enter a span at any point, store
-        the returned {!Trace_core.explicit_span}, and exit it at any later point
-        with {!Trace_core.exit_manual_span}.
-
-        However, for that same reason, they also cannot update the
-        {!Ambient_context} — that is, when you invoke the various [manual]
-        functions, if you then invoke other functions that use
-        {!Trace_core.with_span}, those callees {e will not} see the span you
-        entered manually as their [parent].
-
-        Generally, the best practice is to only use these [manual] functions at
-        the 'leaves' of your callstack: that is, don't invoke user callbacks
-        from within them; or if you do, make sure to pass the [explicit_span]
-        you recieve from this function onwards to the user callback, so they can
-        create further child-spans. *)
-
-    val exit_manual_span : Otrace.explicit_span -> unit
-    (** Implements {!Trace_core.Collector.S.exit_manual_span}, with the
-        OpenTelemetry collector as the backend. Invoked at
-        {!Trace_core.exit_manual_span}. Expects the [explicit_span] returned
-        from an earlier call to {!Trace_core.enter_manual_toplevel_span} or
-        {!Trace_core.enter_manual_sub_span}.
-
-        (See the notes at {!enter_manual_span} about {!Ambient_context}.) *)
-
-    val add_data_to_span :
-      Otrace.span -> (string * Otrace.user_data) list -> unit
-
-    val add_data_to_manual_span :
-      Otrace.explicit_span -> (string * Otrace.user_data) list -> unit
-
-    val message :
-      ?span:Otrace.span ->
-      data:(string * Otrace.user_data) list ->
-      string ->
-      unit
-
-    val shutdown : unit -> unit
-
-    val name_process : string -> unit
-
-    val name_thread : string -> unit
-
-    val counter_int :
-      data:(string * Otrace.user_data) list -> string -> int -> unit
-
-    val counter_float :
-      data:(string * Otrace.user_data) list -> string -> float -> unit
-  end
-
-  type span_begin = {
-    start_time: int64;
-    name: string;
-    __FILE__: string;
-    __LINE__: int;
-    __FUNCTION__: string option;
-    scope: Otel.Scope.t;
-    parent: Otel.Span_ctx.t option;
-  }
-
-  module Active_span_tbl : Hashtbl.S with type key = Otrace.span
-
-  (** Table indexed by ocaml-trace spans. *)
-  module Active_spans : sig
-    type t = private { tbl: span_begin Active_span_tbl.t } [@@unboxed]
-
-    val create : unit -> t
-
-    val k_tls : t TLS.t
-
-    val get : unit -> t
-  end
-
-  val otrace_of_otel : Otel.Span_id.t -> Otrace.span
-
-  val enter_span' :
-    ?explicit_parent:Otrace.explicit_span_ctx ->
-    __FUNCTION__:string option ->
-    __FILE__:string ->
-    __LINE__:int ->
-    data:(string * Otrace.user_data) list ->
-    string ->
-    Otrace.span * span_begin
-
-  val exit_span' : Otrace.span -> span_begin -> Otel.Span.t
-end
-
-(**/**)
+module Well_known : sig end
+[@@deprecated
+  "use the regular functions such as `link_spans` or `set_span_kind` for this"]
+(** Static references for well-known identifiers *)
diff --git a/tests/bin/dune b/tests/bin/dune
index 7787eece..c5b31ee9 100644
--- a/tests/bin/dune
+++ b/tests/bin/dune
@@ -48,8 +48,7 @@
   opentelemetry-client-cohttp-lwt
   opentelemetry-cohttp-lwt
   opentelemetry-logs
-  logs
-))
+  logs))
 
 (executable
  (name cohttp_client)
@@ -59,5 +58,3 @@
   opentelemetry
   opentelemetry-client-cohttp-lwt
   opentelemetry-cohttp-lwt))
-
-
diff --git a/tests/logs/dune b/tests/logs/dune
index 5702037c..d41d8040 100644
--- a/tests/logs/dune
+++ b/tests/logs/dune
@@ -3,16 +3,10 @@
   ; Make the binaries for the test emitters available on the path for the components defined in this dir.
   ; See https://dune.readthedocs.io/en/stable/reference/dune/env.html
   (binaries
-   (../bin/emit_logs_cohttp.exe as emit_logs_cohttp)
-   )))
+   (../bin/emit_logs_cohttp.exe as emit_logs_cohttp))))
 
 (tests
  (names test_logs_e2e)
  (package opentelemetry-logs)
- (libraries
-   opentelemetry
-   opentelemetry-logs
-   signal_gatherer
-   alcotest)
-  (deps %{bin:emit_logs_cohttp})
-)
+ (libraries opentelemetry opentelemetry-logs signal_gatherer alcotest)
+ (deps %{bin:emit_logs_cohttp}))