feat: inject LETTA_AGENT_ID into hook environment context (#731)

Co-authored-by: letta-code <248085862+letta-code@users.noreply.github.com>
Co-authored-by: Cameron <cpfiffer@users.noreply.github.com>

src/hooks/executor.ts

@@ -29,13 +29,21 @@ function trySpawnWithLauncher(
     throw new Error("Empty launcher");
   }
 
+  // Extract agent_id if present (available on many hook input types)
+  const agentId = "agent_id" in input ? input.agent_id : undefined;
+
+  // Build environment: start with parent env but exclude LETTA_AGENT_ID to prevent inheritance
+  // We only want to pass the agent ID that's explicitly provided in the hook input
+  const { LETTA_AGENT_ID: _, ...parentEnv } = process.env;
+
   return spawn(executable, args, {
     cwd: workingDirectory,
     env: {
-      ...process.env,
+      ...parentEnv,
       // Add hook-specific environment variables
       LETTA_HOOK_EVENT: input.event_type,
       LETTA_WORKING_DIR: workingDirectory,
+      ...(agentId && { LETTA_AGENT_ID: agentId }),
     },
     stdio: ["pipe", "pipe", "pipe"],
   });