diff --git a/backend/app/api/routes/compile.py b/backend/app/api/routes/compile.py
index 9fca1efd..cd75430e 100644
--- a/backend/app/api/routes/compile.py
+++ b/backend/app/api/routes/compile.py
@@ -181,6 +181,10 @@ class CompileRequest(BaseModel):
     # the arduino-esp32 component is left out of the build entirely. None /
     # 'arduino' = classic Arduino sketch compile. ESP32 boards only.
     language: str | None = None
+    # Who triggered this compile: None/'user' = manual UI action,
+    # 'agent' = the AI assistant's compile_sketch tool. Metrics overlays
+    # use it to keep agent activity distinguishable from the user's own.
+    initiated_by: str | None = None
 
 
 class CompileResponse(BaseModel):
@@ -509,6 +513,7 @@ async def _compile_job(
                 "file_count": len(files),
                 "has_wifi": response.has_wifi,
                 "async": True,
+                "initiated_by": request.initiated_by,
                 "partition_scheme": (request.board_options or {}).get("partitionScheme"),
                 "spiffs_file_count": len(request.spiffs_files or []),
             },
@@ -530,7 +535,7 @@ async def _compile_job(
             success=False,
             duration_ms=int((time.monotonic() - started) * 1000),
             error_kind="exception",
-            extra={"file_count": len(files), "exception": str(exc)[:200], "async": True},
+            extra={"file_count": len(files), "exception": str(exc)[:200], "async": True, "initiated_by": request.initiated_by},
         )
 
 
@@ -563,7 +568,7 @@ async def compile_sketch(
             success=False,
             duration_ms=int((time.monotonic() - started) * 1000),
             error_kind="exception",
-            extra={"file_count": len(files), "exception": str(e)[:200]},
+            extra={"file_count": len(files), "exception": str(e)[:200], "initiated_by": request.initiated_by},
             request=http_request,
         )
         raise HTTPException(status_code=500, detail=str(e))
@@ -579,6 +584,7 @@ async def compile_sketch(
         extra={
             "file_count": len(files),
             "has_wifi": response.has_wifi,
+            "initiated_by": request.initiated_by,
             "partition_scheme": (request.board_options or {}).get("partitionScheme"),
             "spiffs_file_count": len(request.spiffs_files or []),
         },
diff --git a/frontend/src/services/compilation.ts b/frontend/src/services/compilation.ts
index e4458403..989d8daf 100644
--- a/frontend/src/services/compilation.ts
+++ b/frontend/src/services/compilation.ts
@@ -24,6 +24,9 @@ export interface CompileExtras {
   // ESP-IDF project (user app_main, no arduino-esp32 component). Omitted /
   // undefined = classic Arduino sketch compile. ESP32 boards only.
   language?: 'espidf';
+  // Who triggered the compile — 'agent' when the AI assistant's tool did.
+  // Threads through to backend metrics; omitted = manual user action.
+  initiatedBy?: 'agent';
 }
 
 export interface CompileResult {
@@ -118,6 +121,7 @@ export async function compileCode(
         spiffs_files,
         libraries,
         language: extras?.language ?? null,
+        initiated_by: extras?.initiatedBy ?? null,
       },
       { withCredentials: true, timeout: 30000 },
     );