diff --git a/apps/cli/src/main.ts b/apps/cli/src/main.ts
index 0192820eb..0c786464e 100644
--- a/apps/cli/src/main.ts
+++ b/apps/cli/src/main.ts
@@ -394,6 +394,7 @@ const executeCode = (input: {
       payload: {
         code: input.code,
       },
+      headers: { "x-executor-trigger": "cli" },
     });
 
     if (response.status === "paused") {
diff --git a/packages/core/api/src/executions/api.ts b/packages/core/api/src/executions/api.ts
index 12b557919..d92332435 100644
--- a/packages/core/api/src/executions/api.ts
+++ b/packages/core/api/src/executions/api.ts
@@ -11,6 +11,16 @@ const ExecuteRequest = Schema.Struct({
   code: Schema.String,
 });
 
+/**
+ * Optional header naming the surface that triggered this execution —
+ * `"cli"`, `"http"`, `"mcp"`, etc. Persisted on the execution row so
+ * the runs UI can facet by trigger kind. Defaults to `"http"` when
+ * absent.
+ */
+const ExecuteHeaders = Schema.Struct({
+  "x-executor-trigger": Schema.optional(Schema.String),
+});
+
 const CompletedResult = Schema.Struct({
   status: Schema.Literal("completed"),
   text: Schema.String,
@@ -55,6 +65,7 @@ export class ExecutionsApi extends HttpApiGroup.make("executions")
   .add(
     HttpApiEndpoint.post("execute")`/executions`
       .setPayload(ExecuteRequest)
+      .setHeaders(ExecuteHeaders)
       .addSuccess(ExecuteResponse),
   )
   .add(
diff --git a/packages/core/api/src/handlers/executions.ts b/packages/core/api/src/handlers/executions.ts
index 3eedd3e65..82fc2ea39 100644
--- a/packages/core/api/src/handlers/executions.ts
+++ b/packages/core/api/src/handlers/executions.ts
@@ -8,10 +8,15 @@ import { capture, captureEngineError } from "@executor/api";
 
 export const ExecutionsHandlers = HttpApiBuilder.group(ExecutorApi, "executions", (handlers) =>
   handlers
-    .handle("execute", ({ payload }) =>
+    .handle("execute", ({ payload, headers }) =>
       capture(Effect.gen(function* () {
         const engine = yield* ExecutionEngineService;
-        const outcome = yield* captureEngineError(engine.executeWithPause(payload.code));
+        const triggerKind = headers["x-executor-trigger"] ?? "http";
+        const outcome = yield* captureEngineError(
+          engine.executeWithPause(payload.code, {
+            trigger: { kind: triggerKind },
+          }),
+        );
 
         if (outcome.status === "completed") {
           const formatted = formatExecuteResult(outcome.result);
diff --git a/packages/hosts/mcp/src/server.ts b/packages/hosts/mcp/src/server.ts
index 4c30abbb5..894ec9cc0 100644
--- a/packages/hosts/mcp/src/server.ts
+++ b/packages/hosts/mcp/src/server.ts
@@ -297,10 +297,13 @@ export const createExecutorMcpServer = <E extends Cause.YieldableError>(
         if (supportsManagedElicitation(server)) {
           const result = yield* engine.execute(code, {
             onElicitation: makeMcpElicitationHandler(server, debugLog),
+            trigger: { kind: "mcp" },
           });
           return toMcpResult(formatExecuteResult(result));
         }
-        const outcome = yield* engine.executeWithPause(code);
+        const outcome = yield* engine.executeWithPause(code, {
+          trigger: { kind: "mcp" },
+        });
         debugLog("execute.paused_flow_result", {
           status: outcome.status,
           executionId: outcome.status === "paused" ? outcome.execution.id : undefined,