feat(llm_analytics): support Anthropic responses

.sampo/changesets/roguish-windweaver-tuonetar.md

@@ -0,0 +1,5 @@
+---
+hex/posthog: minor
+---
+
+Add support for Anthropic messages in the LLM analytis module

lib/posthog/integrations/llm_analytics/req.ex

@@ -9,6 +9,8 @@ defmodule PostHog.Integrations.LLMAnalytics.Req do
   responses. Currently, it works best with the following APIs:
   * OpenAI (Responses)
   * OpenAI (Chat Completions)
+  * Anthropic (Create Message)
+  * Gemini (generateContent)
 
   ## Usage
 
@@ -204,6 +206,16 @@ defmodule PostHog.Integrations.LLMAnalytics.Req do
     }
   end
 
+  defp request_url_properties(
+         %Req.Request{url: %URI{host: "api.anthropic.com", path: "/v1/messages" <> _}} = request
+       ) do
+    %{
+      "$ai_base_url": "https://api.anthropic.com/v1/messages",
+      "$ai_request_url": URI.to_string(request.url),
+      "$ai_provider": "anthropic"
+    }
+  end
+
   defp request_url_properties(%Req.Request{} = request) do
     %{
       "$ai_base_url": URI.to_string(%{request.url | path: nil}),
@@ -233,6 +245,7 @@ defmodule PostHog.Integrations.LLMAnalytics.Req do
     # OpenAI Responses
     # OpenAI Chat Completions
     # Gemini generateContent
+    # Anthropic
     get_in(body, [atom_or_string_key(:input)]) ||
       get_in(body, [atom_or_string_key(:messages)]) ||
       get_in(body, [atom_or_string_key(:contents)])
@@ -241,6 +254,7 @@ defmodule PostHog.Integrations.LLMAnalytics.Req do
   defp request_optional_property(:"$ai_temperature", body) do
     # OpenAI Responses
     # OpenAI Chat Completions
+    # Anthropic
     get_in(body, [atom_or_string_key(:temperature)]) ||
       get_in(body, [atom_or_string_key(:generationConfig), atom_or_string_key(:temperature)])
   end
@@ -254,15 +268,18 @@ defmodule PostHog.Integrations.LLMAnalytics.Req do
   defp request_optional_property(:"$ai_max_tokens", body) do
     # OpenAI Responses
     # OpenAI Chat Completions
+    # Anthropic
     get_in(body, [atom_or_string_key(:max_output_tokens)]) ||
       get_in(body, [atom_or_string_key(:max_completion_tokens)]) ||
-      get_in(body, [atom_or_string_key(:generationConfig), atom_or_string_key(:maxOutputTokens)])
+      get_in(body, [atom_or_string_key(:generationConfig), atom_or_string_key(:maxOutputTokens)]) ||
+      get_in(body, [atom_or_string_key(:max_tokens)])
   end
 
   defp request_optional_property(:"$ai_tools", body) do
     # OpenAI Responses
     # OpenAI Chat Completions
     # Gemini
+    # Anthropic
     get_in(body, [atom_or_string_key(:tools)])
   end
 
@@ -324,6 +341,21 @@ defmodule PostHog.Integrations.LLMAnalytics.Req do
     }
   end
 
+  # Anthropic Create Message
+  defp response_properties(%{
+         "model" => model,
+         "content" => output,
+         "usage" => %{"output_tokens" => output_tokens, "input_tokens" => input_tokens}
+       }) do
+    %{
+      "$ai_output_choices": output,
+      "$ai_input_tokens": input_tokens,
+      "$ai_output_tokens": output_tokens,
+      "$ai_model": model,
+      "$ai_is_error": false
+    }
+  end
+
   defp response_properties(%{"error" => error}) do
     %{
       "$ai_is_error": true,

lib/posthog/llm_analytics.ex

@@ -101,7 +101,7 @@ defmodule PostHog.LLMAnalytics do
   def generate_response(user_message) do
     LLMAnalytics.start_span(%{"$ai_span_name": "LLM call", "$ai_input_state": user_message})
 
-    Req.post!("https://api.openai.com/v1/responses, json: %{input: user_message})
+    Req.post!("https://api.openai.com/v1/responses", json: %{input: user_message})
     |> handle_response()
   end
 

test/integration_test.exs

@@ -273,5 +273,68 @@ defmodule PostHog.IntegrationTest do
 
       wait.()
     end
+
+    test "Anthropic", %{wait_fun: wait} do
+      Req.new()
+      |> LLMReq.attach()
+      |> Req.post!(
+        url: "https://api.anthropic.com/v1/messages",
+        headers: [
+          {"x-api-key", Application.get_env(:posthog, :anthropic_key)},
+          {"anthropic-version", "2023-06-01"}
+        ],
+        json: %{
+          messages: [
+            %{
+              role: :user,
+              content: "Cite me the greatest opening line in the history of cyberpunk."
+            }
+          ],
+          max_tokens: 1024,
+          model: "claude-haiku-4-5"
+        }
+      )
+
+      wait.()
+    end
+
+    test "Anthropic with tool", %{wait_fun: wait} do
+      Req.new()
+      |> LLMReq.attach()
+      |> Req.post!(
+        url: "https://api.anthropic.com/v1/messages",
+        headers: [
+          {"x-api-key", Application.get_env(:posthog, :anthropic_key)},
+          {"anthropic-version", "2023-06-01"}
+        ],
+        json: %{
+          messages: [%{role: :user, content: "Tell me weather in Vancouver, BC. Celsius."}],
+          max_tokens: 1024,
+          model: "claude-haiku-4-5",
+          tools: [
+            %{
+              name: "get_current_weather",
+              description: "Get the current weather in a given location",
+              input_schema: %{
+                type: "object",
+                properties: %{
+                  location: %{
+                    type: "string",
+                    description: "The city and state, e.g. San Francisco, CA"
+                  },
+                  unit: %{
+                    type: "string",
+                    enum: ["celsius", "fahrenheit"]
+                  }
+                },
+                required: ["location", "unit"]
+              }
+            }
+          ]
+        }
+      )
+
+      wait.()
+    end
   end
 end

test/posthog/integrations/llm_analytics/req_test.exs

@@ -845,4 +845,195 @@ defmodule PostHog.Integrations.LLMAnalytics.ReqTest do
              }
            ] = all_captured(@supervisor_name)
   end
+
+  test "captures Anthropic create message properties", %{req: req} do
+    Req.Test.expect(@mock_module, fn conn ->
+      Req.Test.json(conn, %{
+        "content" => [
+          %{
+            "text" =>
+              "I'd argue for this one from **William Gibson's \"Neuromancer\" (1984)**:\n\n\"The sky above the port was the color of television, tuned to a dead channel.\"\n\nIt's often cited as one of the greatest opening lines in science fiction period. It's evocative, immediately establishes a gritty aesthetic, and perfectly captures that cyberpunk blend of high-tech futurity meeting urban decay. The image is both poetic and oddly mundane—comparing something vast to the banal experience of dead air on a TV screen.\n\nThat said, honorable mentions go to:\n- **Bruce Sterling's \"Schismatrix\"** for its ambitious far-future worldbuilding\n- **Pat Cadigan's work** for her psychological approach to cyberspace\n\nBut Gibson's opening has become almost archetypal—it defined what cyberpunk *feels* like for generations of readers and writers who followed.",
+            "type" => "text"
+          }
+        ],
+        "id" => "msg_01USjdBRtDVTcZCcVQMdtAnW",
+        "model" => "claude-haiku-4-5-20251001",
+        "role" => "assistant",
+        "stop_reason" => "end_turn",
+        "stop_sequence" => nil,
+        "type" => "message",
+        "usage" => %{
+          "cache_creation" => %{
+            "ephemeral_1h_input_tokens" => 0,
+            "ephemeral_5m_input_tokens" => 0
+          },
+          "cache_creation_input_tokens" => 0,
+          "cache_read_input_tokens" => 0,
+          "inference_geo" => "not_available",
+          "input_tokens" => 22,
+          "output_tokens" => 205,
+          "service_tier" => "standard"
+        }
+      })
+    end)
+
+    assert %{status: 200, body: %{}} =
+             Req.post!(req,
+               url: "https://api.anthropic.com/v1/messages",
+               headers: [
+                 {"x-api-key", Application.get_env(:posthog, :anthropic_key)},
+                 {"anthropic-version", "2023-06-01"}
+               ],
+               json: %{
+                 messages: [
+                   %{
+                     role: :user,
+                     content: "Cite me the greatest opening line in the history of cyberpunk."
+                   }
+                 ],
+                 max_tokens: 1024,
+                 model: "claude-haiku-4-5"
+               }
+             )
+
+    assert [
+             %{
+               event: "$ai_generation",
+               properties: %{
+                 "$ai_base_url": "https://api.anthropic.com/v1/messages",
+                 "$ai_http_status": 200,
+                 "$ai_input": [
+                   %{
+                     role: :user,
+                     content: "Cite me the greatest opening line in the history of cyberpunk."
+                   }
+                 ],
+                 "$ai_input_tokens": 22,
+                 "$ai_model": "claude-haiku-4-5-20251001",
+                 "$ai_output_choices": [
+                   %{
+                     "text" =>
+                       "I'd argue for this one from **William Gibson's \"Neuromancer\" (1984)**:\n\n\"The sky above the port was the color of television, tuned to a dead channel.\"\n\nIt's often cited as one of the greatest opening lines in science fiction period. It's evocative, immediately establishes a gritty aesthetic, and perfectly captures that cyberpunk blend of high-tech futurity meeting urban decay. The image is both poetic and oddly mundane—comparing something vast to the banal experience of dead air on a TV screen.\n\nThat said, honorable mentions go to:\n- **Bruce Sterling's \"Schismatrix\"** for its ambitious far-future worldbuilding\n- **Pat Cadigan's work** for her psychological approach to cyberspace\n\nBut Gibson's opening has become almost archetypal—it defined what cyberpunk *feels* like for generations of readers and writers who followed.",
+                     "type" => "text"
+                   }
+                 ],
+                 "$ai_output_tokens": 205,
+                 "$ai_provider": "anthropic",
+                 "$ai_request_url": "https://api.anthropic.com/v1/messages",
+                 "$ai_is_error": false
+               }
+             }
+           ] = all_captured(@supervisor_name)
+  end
+
+  test "captures Anthropic with tools", %{req: req} do
+    Req.Test.expect(@mock_module, fn conn ->
+      Req.Test.json(conn, %{
+        "content" => [
+          %{
+            "id" => "toolu_01TB42J8UvzAYvRwaQC4xT2R",
+            "input" => %{"location" => "Vancouver, BC", "unit" => "celsius"},
+            "name" => "get_current_weather",
+            "type" => "tool_use"
+          }
+        ],
+        "id" => "msg_012zLWPheFNRzjaGeMSr35u9",
+        "model" => "claude-haiku-4-5-20251001",
+        "role" => "assistant",
+        "stop_reason" => "tool_use",
+        "stop_sequence" => nil,
+        "type" => "message",
+        "usage" => %{
+          "cache_creation" => %{
+            "ephemeral_1h_input_tokens" => 0,
+            "ephemeral_5m_input_tokens" => 0
+          },
+          "cache_creation_input_tokens" => 0,
+          "cache_read_input_tokens" => 0,
+          "inference_geo" => "not_available",
+          "input_tokens" => 613,
+          "output_tokens" => 75,
+          "service_tier" => "standard"
+        }
+      })
+    end)
+
+    assert %{status: 200, body: %{}} =
+             Req.post!(req,
+               url: "https://api.anthropic.com/v1/messages",
+               headers: [
+                 {"x-api-key", Application.get_env(:posthog, :anthropic_key)},
+                 {"anthropic-version", "2023-06-01"}
+               ],
+               json: %{
+                 messages: [%{role: :user, content: "Tell me weather in Vancouver, BC. Celsius."}],
+                 max_tokens: 1024,
+                 model: "claude-haiku-4-5",
+                 tools: [
+                   %{
+                     name: "get_current_weather",
+                     description: "Get the current weather in a given location",
+                     input_schema: %{
+                       type: "object",
+                       properties: %{
+                         location: %{
+                           type: "string",
+                           description: "The city and state, e.g. San Francisco, CA"
+                         },
+                         unit: %{
+                           type: "string",
+                           enum: ["celsius", "fahrenheit"]
+                         }
+                       },
+                       required: ["location", "unit"]
+                     }
+                   }
+                 ]
+               }
+             )
+
+    assert [
+             %{
+               event: "$ai_generation",
+               properties: %{
+                 "$ai_base_url": "https://api.anthropic.com/v1/messages",
+                 "$ai_http_status": 200,
+                 "$ai_input": [
+                   %{role: :user, content: "Tell me weather in Vancouver, BC. Celsius."}
+                 ],
+                 "$ai_input_tokens": 613,
+                 "$ai_model": "claude-haiku-4-5-20251001",
+                 "$ai_output_choices": [
+                   %{
+                     "type" => "tool_use",
+                     "id" => "toolu_01TB42J8UvzAYvRwaQC4xT2R",
+                     "input" => %{"location" => "Vancouver, BC", "unit" => "celsius"},
+                     "name" => "get_current_weather"
+                   }
+                 ],
+                 "$ai_output_tokens": 75,
+                 "$ai_provider": "anthropic",
+                 "$ai_request_url": "https://api.anthropic.com/v1/messages",
+                 "$ai_is_error": false,
+                 "$ai_tools": [
+                   %{
+                     name: "get_current_weather",
+                     description: "Get the current weather in a given location",
+                     input_schema: %{
+                       type: "object",
+                       required: ["location", "unit"],
+                       properties: %{
+                         unit: %{type: "string", enum: ["celsius", "fahrenheit"]},
+                         location: %{
+                           type: "string",
+                           description: "The city and state, e.g. San Francisco, CA"
+                         }
+                       }
+                     }
+                   }
+                 ]
+               }
+             }
+           ] = all_captured(@supervisor_name)
+  end
 end