diff --git a/effectful/handlers/llm/langfuse.py b/effectful/handlers/llm/langfuse.py
new file mode 100644
index 00000000..5b687b45
--- /dev/null
+++ b/effectful/handlers/llm/langfuse.py
@@ -0,0 +1,104 @@
+import functools
+import typing
+
+import litellm
+from langfuse import get_client, observe
+
+from effectful.handlers.llm import Template, Tool
+from effectful.handlers.llm.completions import (
+    call_assistant,
+    call_system,
+    call_user,
+    completion,
+)
+from effectful.ops.semantics import fwd
+from effectful.ops.syntax import ObjectInterpretation, implements
+
+
+def _extract_generation_meta(result) -> dict[str, typing.Any]:
+    # helper function for populating usage metadata so they render
+    # more nicely on langfuse
+    usage = result.usage
+    if usage is None:
+        return {}
+    meta: dict[str, typing.Any] = {"model": getattr(result, "model", None)}
+    usage_details: dict[str, int] = {}
+    for k in ("prompt_tokens", "completion_tokens", "total_tokens"):
+        v = getattr(usage, k, None)
+        if v is not None:
+            usage_details[k] = v
+    if usage_details:
+        meta["usage_details"] = usage_details
+    try:
+        cost = litellm.completion_cost(completion_response=result)
+        meta["cost_details"] = {"total": cost}
+    except Exception:
+        pass
+    meta["metadata"] = {"response_id": getattr(result, "id", None)}
+    return meta
+
+
+def _make_instrumented(op, as_type):
+    @observe(as_type=as_type)
+    @functools.wraps(op)
+    def wrapper(*args, **kwargs):
+        return fwd(op, *args, **kwargs)
+
+    return wrapper
+
+
+class LangfuseProvider(ObjectInterpretation):
+    """Traces Tool, Template, and completion calls with Langfuse.
+
+    Compose with a provider via :func:`~effectful.ops.semantics.handler`
+    to add tracing::
+
+        with handler(provider), handler(LangfuseProvider()):
+            print(limerick(theme))
+    """
+
+    def __init__(self):
+        self.langfuse = get_client()
+        # cache each template instead of repeatedly instrumenting it
+        self._get_instrumented = functools.cache(_make_instrumented)
+
+    @implements(completion)
+    @observe(as_type="generation")
+    def completion(self, *args, **kwargs):
+        messages = kwargs.get("messages")
+        result = fwd(*args, **kwargs)
+        meta = _extract_generation_meta(result)
+
+        # populate messages as part of the langfuse metadata so we get
+        # the nice rendering of "Assistant", "User", and "System"
+        # messages
+        if messages is not None:
+            meta["input"] = messages
+        choice = result.choices[0] if result.choices else None
+        if choice is not None:
+            meta["output"] = choice.message.model_dump(mode="json", exclude_none=True)
+        self.langfuse.update_current_generation(**meta)
+        return result
+
+    @implements(call_user)
+    @observe()
+    def call_user(self, template, env):
+        return fwd(template, env)
+
+    @implements(call_system)
+    @observe()
+    def call_system(self, template):
+        return fwd(template)
+
+    @implements(call_assistant)
+    @observe()
+    def call_assistant(self, tools, response_format, model, **kwargs):
+        return fwd(tools, response_format, model, **kwargs)
+
+    @implements(Tool.__apply__)
+    def call_tool(self, tool, *args, **kwargs):
+        return self._get_instrumented(tool, "tool")(*args, **kwargs)
+
+    @implements(Template.__apply__)
+    def call_template(self, template, *args, **kwargs):
+        return self._get_instrumented(template, "generation")(*args, **kwargs)
diff --git a/effectful/handlers/llm/weave.py b/effectful/handlers/llm/weave.py
new file mode 100644
index 00000000..fe9e7dca
--- /dev/null
+++ b/effectful/handlers/llm/weave.py
@@ -0,0 +1,60 @@
+import functools
+
+import weave
+
+from effectful.handlers.llm import Template, Tool
+from effectful.handlers.llm.completions import (
+    call_assistant,
+    call_system,
+    call_user,
+)
+from effectful.ops.semantics import fwd
+from effectful.ops.syntax import ObjectInterpretation, implements
+
+
+def _make_instrumented(op):
+    @weave.op()
+    @functools.wraps(op)
+    def wrapper(*args, **kwargs):
+        return fwd(op, *args, **kwargs)
+
+    return wrapper
+
+
+class WeaveProvider(ObjectInterpretation):
+    """Traces Tool, Template, and message-level calls with Weights & Biases Weave.
+
+    Compose with a provider via :func:`~effectful.ops.semantics.handler`
+    to add tracing::
+
+        weave.init("my-project")
+        with handler(provider), handler(WeaveProvider()):
+            print(limerick(theme))
+    """
+
+    def __init__(self):
+        # cache each template instead of repeatedly instrumenting it
+        self._get_instrumented = functools.cache(_make_instrumented)
+
+    @implements(call_user)
+    @weave.op()
+    def call_user(self, template, env):
+        return fwd(template, env)
+
+    @implements(call_system)
+    @weave.op()
+    def call_system(self, template):
+        return fwd(template)
+
+    @implements(call_assistant)
+    @weave.op()
+    def call_assistant(self, tools, response_format, model, **kwargs):
+        return fwd(tools, response_format, model, **kwargs)
+
+    @implements(Tool.__apply__)
+    def call_tool(self, tool, *args, **kwargs):
+        return self._get_instrumented(tool)(*args, **kwargs)
+
+    @implements(Template.__apply__)
+    def call_template(self, template, *args, **kwargs):
+        return self._get_instrumented(template)(*args, **kwargs)
diff --git a/pyproject.toml b/pyproject.toml
index d6219f62..cb5adff7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -50,6 +50,8 @@ llm = [
   "typing_extensions",
   "restrictedpython>=8.1"
 ]
+llm-weave = ["effectful[llm]", "weave"]
+llm-langfuse = ["effectful[llm]", "langfuse"]
 prettyprinter = ["prettyprinter"]
 docs = [
     "effectful[torch,pyro,jax,numpyro,llm,prettyprinter]",
@@ -74,7 +76,7 @@ test = [
 ]
 
 [dependency-groups]
-dev = ["effectful[torch,pyro,jax,numpyro,llm,docs,test]"]
+dev = ["effectful[torch,pyro,jax,numpyro,llm,llm-weave,llm-langfuse,docs,test]"]
 
 [tool.ruff]
 target-version = "py312"