diff --git a/src/lib/db/inspectorCustomHosts.ts b/src/lib/db/inspectorCustomHosts.ts
index 9874def829..a4b371eb60 100644
--- a/src/lib/db/inspectorCustomHosts.ts
+++ b/src/lib/db/inspectorCustomHosts.ts
@@ -75,3 +75,16 @@ export function touchLastSeen(host: string): void {
   const now = new Date().toISOString();
   db.prepare("UPDATE inspector_custom_hosts SET last_seen_at = ? WHERE host = ?").run(now, host);
 }
+
+/**
+ * Returns true when `host` is present in inspector_custom_hosts with enabled=1.
+ * Used by agentBridgeHook to distinguish custom-host intercepts from agent-bridge
+ * intercepts so that Mode 2 (Custom Hosts) entries appear in the "Custom" profile.
+ */
+export function isCustomHost(host: string): boolean {
+  const db = getDbInstance();
+  const row = db
+    .prepare("SELECT 1 AS found FROM inspector_custom_hosts WHERE host = ? AND enabled = 1")
+    .get(host) as { found: number } | undefined;
+  return row !== undefined;
+}
diff --git a/src/mitm/inspector/agentBridgeHook.ts b/src/mitm/inspector/agentBridgeHook.ts
index e247f38628..00d3e37243 100644
--- a/src/mitm/inspector/agentBridgeHook.ts
+++ b/src/mitm/inspector/agentBridgeHook.ts
@@ -14,6 +14,7 @@ import { sanitizeHeaders } from "../sanitizeHeaders.ts";
 import type { AgentId } from "../types.ts";
 import { globalTrafficBuffer } from "./buffer.ts";
 import type { InterceptedRequest } from "./types.ts";
+import { isCustomHost } from "@/lib/db/inspectorCustomHosts";
 
 export interface RecordRequestStartOpts {
   req: IncomingMessage;
@@ -42,13 +43,28 @@ export async function recordRequestStart(
   opts: RecordRequestStartOpts
 ): Promise<InterceptedRequest> {
   const requestBody = opts.body.length > 0 ? maskSecret(opts.body.toString("utf8")) : null;
+
+  // Determine whether this request originates from a custom-host intercept
+  // (Mode 2 / Custom Hosts) or a standard agent-bridge intercept (Mode 1).
+  //
+  // Both modes reach this hook via the same MITM server path: custom hosts are
+  // added to inspector_custom_hosts by the Mode 2 UI and are spoofed to
+  // 127.0.0.1 by /etc/hosts entries, so they arrive here just like agent
+  // targets. The DB lookup below is the cheapest reliable way to distinguish
+  // them without touching server.cjs — it costs one SQLite read per request.
+  //
+  // If the host resolves as a custom-host entry, source="custom-host" and
+  // agent is left undefined so the "Custom" profile filter matches correctly.
+  const host = opts.req.headers.host ?? "";
+  const customHost = isCustomHost(host);
+
   const intercepted: InterceptedRequest = {
     id: randomUUID(),
-    source: "agent-bridge",
-    agent: opts.agentId,
+    source: customHost ? "custom-host" : "agent-bridge",
+    agent: customHost ? undefined : opts.agentId,
     timestamp: new Date().toISOString(),
     method: opts.req.method ?? "GET",
-    host: opts.req.headers.host ?? "",
+    host,
     path: opts.req.url ?? "/",
     requestHeaders: sanitizeHeaders(opts.req.headers),
     requestBody,
diff --git a/tests/unit/inspector-agent-bridge-hook.test.ts b/tests/unit/inspector-agent-bridge-hook.test.ts
new file mode 100644
index 0000000000..a1a0c75b69
--- /dev/null
+++ b/tests/unit/inspector-agent-bridge-hook.test.ts
@@ -0,0 +1,98 @@
+/**
+ * Unit tests: agentBridgeHook — source and agent field assignment
+ *
+ * Verifies that recordRequestStart() sets:
+ *   - source="custom-host" + agent=undefined when the request host is in
+ *     inspector_custom_hosts with enabled=1 (R5-8)
+ *   - source="agent-bridge" + agent=agentId otherwise
+ */
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import type { IncomingMessage } from "node:http";
+
+const TEST_DATA_DIR = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-ab-hook-"));
+process.env.DATA_DIR = TEST_DATA_DIR;
+
+const { resetDbInstance, getDbInstance } = await import("../../src/lib/db/core.ts");
+const { addCustomHost, toggleCustomHost } = await import(
+  "../../src/lib/db/inspectorCustomHosts.ts"
+);
+const { recordRequestStart } = await import(
+  "../../src/mitm/inspector/agentBridgeHook.ts"
+);
+
+async function resetStorage() {
+  resetDbInstance();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+  fs.mkdirSync(TEST_DATA_DIR, { recursive: true });
+  getDbInstance();
+}
+
+function makeFakeReq(host: string): IncomingMessage {
+  return {
+    method: "POST",
+    url: "/v1/chat/completions",
+    headers: { host, "content-type": "application/json" },
+  } as unknown as IncomingMessage;
+}
+
+test.beforeEach(async () => {
+  await resetStorage();
+});
+
+test.after(() => {
+  resetDbInstance();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+});
+
+test("recordRequestStart: custom-host entry → source=custom-host, agent=undefined", async () => {
+  addCustomHost("my-app.example.com", "app", "My App");
+
+  const entry = await recordRequestStart({
+    req: makeFakeReq("my-app.example.com"),
+    body: Buffer.from("{}"),
+    agentId: "codex" as any,
+    mappedModel: "gpt-4o",
+  });
+
+  assert.equal(entry.source, "custom-host", "source should be custom-host");
+  assert.equal(entry.agent, undefined, "agent should be undefined for custom-host");
+  assert.equal(entry.host, "my-app.example.com");
+});
+
+test("recordRequestStart: non-custom host → source=agent-bridge, agent=agentId", async () => {
+  // Do NOT add the host to inspector_custom_hosts
+  const entry = await recordRequestStart({
+    req: makeFakeReq("api.openai.com"),
+    body: Buffer.from("{}"),
+    agentId: "codex" as any,
+    mappedModel: "gpt-4o",
+  });
+
+  assert.equal(entry.source, "agent-bridge", "source should be agent-bridge");
+  assert.equal(entry.agent, "codex", "agent should be the provided agentId");
+  assert.equal(entry.host, "api.openai.com");
+});
+
+test("recordRequestStart: disabled custom-host → source=agent-bridge (not matched)", async () => {
+  addCustomHost("disabled-app.example.com");
+  toggleCustomHost("disabled-app.example.com", false);
+
+  const entry = await recordRequestStart({
+    req: makeFakeReq("disabled-app.example.com"),
+    body: Buffer.from("{}"),
+    agentId: "codex" as any,
+    mappedModel: "gpt-4o",
+  });
+
+  assert.equal(
+    entry.source,
+    "agent-bridge",
+    "disabled custom-host should not be treated as custom-host source"
+  );
+  assert.equal(entry.agent, "codex");
+});