Add optional Langfuse tracing to Cursor PR review action

agentic-pr-review/README.md

@@ -23,10 +23,14 @@ Artifacts: uploads `review-agent.json` from the workspace when present (for debu
 | `provider` | no | Review backend; the action resolves it via `scripts/providers/<provider>.sh` (default: `cursor`). |
 | `deepen-length` | no | Passed to `rmacklin/fetch-through-merge-base` as `deepen_length` (default: `30`). |
 | `additional-prompt` | no | Extra text appended to the review prompt after `prompts/review.md`. |
+| `langfuse-secret-key` | no | Langfuse secret key; set with `langfuse-public-key` to enable tracing. |
+| `langfuse-public-key` | no | Langfuse public key; required when tracing is enabled. |
+| `langfuse-base-url` | no | Langfuse base URL (defaults to `https://cloud.langfuse.com`). |
 
 ## Secrets and permissions
 
 - Store **`app-id`**, **`private-key`**, and **`provider-api-key`** as repository (or org) secrets; do not commit them.
+- If enabling Langfuse tracing, also store **`langfuse-secret-key`** and **`langfuse-public-key`** as secrets.
 - The calling workflow needs permission to **read** contents and **write** pull requests (for posting the review). The GitHub App installation must be allowed to clone the repo and create reviews on the target repository.
 
 ## Example Usage
@@ -98,3 +102,13 @@ If your workflow should avoid reviewing draft or closed pull requests, add a sma
 mkdir -p .cursor
 cp path/to/agentic-pr-review/config/cli-config.json .cursor/cli-config.json
 ```
+
+## Langfuse tracing (Cursor)
+
+Provide `langfuse-secret-key` and `langfuse-public-key` inputs to trace Cursor agent activity to Langfuse. When both are present, the action:
+
+- Copies the bundled Cursor hooks from `config/langfuse-hooks` into `.cursor/`
+- Installs hook dependencies with `npm ci` before invoking the Cursor CLI
+- Exports `LANGFUSE_*` variables (optional `langfuse-base-url` overrides the default `https://cloud.langfuse.com`)
+
+If the keys are omitted, Langfuse tracing is skipped and the review runs as before.

agentic-pr-review/action.yml

@@ -30,6 +30,18 @@ inputs:
     description: Extra instructions appended to the review prompt (e.g. full text of an @nitro-pr-review PR comment)
     required: false
     default: ""
+  langfuse-secret-key:
+    description: Langfuse secret key used to enable Cursor tracing
+    required: false
+    default: ""
+  langfuse-public-key:
+    description: Langfuse public key used to enable Cursor tracing
+    required: false
+    default: ""
+  langfuse-base-url:
+    description: Langfuse base URL (defaults to https://cloud.langfuse.com)
+    required: false
+    default: ""
 
 runs:
   using: composite
@@ -111,6 +123,9 @@ runs:
         REVIEW_JSON_PATH: ${{ github.workspace }}/review-agent.json
         REVIEW_PROMPT_PATH: ${{ github.action_path }}/prompts/review.md
         REVIEW_ADDITIONAL_INSTRUCTIONS: ${{ inputs.additional-prompt }}
+        LANGFUSE_SECRET_KEY: ${{ inputs.langfuse-secret-key }}
+        LANGFUSE_PUBLIC_KEY: ${{ inputs.langfuse-public-key }}
+        LANGFUSE_BASE_URL: ${{ inputs.langfuse-base-url }}
       run: |
         set -euo pipefail
 

agentic-pr-review/config/langfuse-hooks/hooks.json

@@ -0,0 +1,65 @@
+{
+  "version": 1,
+  "hooks": {
+    "beforeSubmitPrompt": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "afterAgentResponse": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "afterAgentThought": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "beforeShellExecution": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "afterShellExecution": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "beforeMCPExecution": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "afterMCPExecution": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "beforeReadFile": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "afterFileEdit": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "stop": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "beforeTabFileRead": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ],
+    "afterTabFileEdit": [
+      {
+        "command": "node .cursor/hooks/hook-handler.js"
+      }
+    ]
+  }
+}

agentic-pr-review/config/langfuse-hooks/hooks/hook-handler.js

@@ -0,0 +1,70 @@
+#!/usr/bin/env node
+
+/**
+ * Cursor Hooks Langfuse Integration
+ *
+ * Main entry point for Cursor hooks that sends traces to Langfuse.
+ *
+ * Features:
+ * - All 12 Cursor hooks supported (Agent + Tab)
+ * - Traces grouped by conversation_id
+ * - Sessions grouped by workspace
+ * - Dynamic tags based on activity
+ * - Completion scores and efficiency metrics
+ * - Rich metadata and edit statistics
+ *
+ * @version 1.1.0
+ * @see https://cursor.com/docs/agent/hooks
+ * @see https://langfuse.com/docs
+ */
+
+import { readStdin } from "./lib/utils.js";
+import {
+  getOrCreateTrace,
+  flushLangfuse,
+  HOOK_HANDLER_VERSION,
+} from "./lib/langfuse-client.js";
+import { routeHookHandler } from "./lib/handlers.js";
+
+/**
+ * Main handler function
+ * Reads hook data from stdin, creates Langfuse trace, and routes to handler
+ */
+async function main() {
+  try {
+    // Read JSON input from stdin
+    const input = await readStdin();
+
+    // Get or create a trace for this conversation
+    const trace = getOrCreateTrace(input);
+
+    // Route to the appropriate handler based on hook type
+    const hookName = input.hook_event_name;
+    const response = routeHookHandler(hookName, trace, input);
+
+    // Output response to Cursor if handler returned one
+    if (response !== null && response !== undefined) {
+      console.log(JSON.stringify(response));
+    }
+
+    // Flush all pending events to Langfuse before exiting
+    await flushLangfuse();
+  } catch (error) {
+    // Log error but don't crash - we don't want to block Cursor
+    console.error(`[Langfuse Hook v${HOOK_HANDLER_VERSION}] Error: ${error.message}`);
+
+    // Still output a permissive response so Cursor can continue
+    // This ensures the hook doesn't block operations if something goes wrong
+    console.log(
+      JSON.stringify({
+        continue: true,
+        permission: "allow",
+      }),
+    );
+
+    process.exit(1);
+  }
+}
+
+// Run the main function
+main();