diff --git a/registry/coder/modules/filebrowser/README.md b/registry/coder/modules/filebrowser/README.md
index 80ab3e853..ab668537a 100644
--- a/registry/coder/modules/filebrowser/README.md
+++ b/registry/coder/modules/filebrowser/README.md
@@ -14,7 +14,7 @@ A file browser for your workspace.
 module "filebrowser" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/filebrowser/coder"
-  version  = "1.1.4"
+  version  = "1.1.5"
   agent_id = coder_agent.main.id
 }
 ```
@@ -29,7 +29,7 @@ module "filebrowser" {
 module "filebrowser" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/filebrowser/coder"
-  version  = "1.1.4"
+  version  = "1.1.5"
   agent_id = coder_agent.main.id
   folder   = "/home/coder/project"
 }
@@ -41,7 +41,7 @@ module "filebrowser" {
 module "filebrowser" {
   count         = data.coder_workspace.me.start_count
   source        = "registry.coder.com/coder/filebrowser/coder"
-  version       = "1.1.4"
+  version       = "1.1.5"
   agent_id      = coder_agent.main.id
   database_path = ".config/filebrowser.db"
 }
@@ -49,11 +49,13 @@ module "filebrowser" {
 
 ### Serve from the same domain (no subdomain)
 
+When `subdomain = false`, you must also set `agent_name` to the name of your `coder_agent` resource. Coder serves path-based apps at `/@<owner>/<workspace>.<agent>/apps/<slug>/`, so the agent name is required to build a base URL that matches the URL the user is actually browsing. If `agent_name` is omitted in this mode, `terraform apply` will fail with an explanatory error.
+
 ```tf
 module "filebrowser" {
   count      = data.coder_workspace.me.start_count
   source     = "registry.coder.com/coder/filebrowser/coder"
-  version    = "1.1.4"
+  version    = "1.1.5"
   agent_id   = coder_agent.main.id
   agent_name = "main"
   subdomain  = false
diff --git a/registry/coder/modules/filebrowser/main.test.ts b/registry/coder/modules/filebrowser/main.test.ts
index 1d925c35a..56beb998e 100644
--- a/registry/coder/modules/filebrowser/main.test.ts
+++ b/registry/coder/modules/filebrowser/main.test.ts
@@ -102,4 +102,19 @@ describe("filebrowser", async () => {
 
     testBaseLine(output);
   }, 15000);
+
+  it("fails when subdomain=false and agent_name is not provided", async () => {
+    let caught: Error | undefined;
+    try {
+      await runTerraformApply(import.meta.dir, {
+        agent_id: "foo",
+        subdomain: false,
+      });
+    } catch (e) {
+      caught = e as Error;
+    }
+    expect(caught).toBeDefined();
+    expect(caught!.message).toContain("agent_name");
+    expect(caught!.message).toContain("subdomain");
+  }, 15000);
 });
diff --git a/registry/coder/modules/filebrowser/main.tf b/registry/coder/modules/filebrowser/main.tf
index 498682dd8..e5285d0af 100644
--- a/registry/coder/modules/filebrowser/main.tf
+++ b/registry/coder/modules/filebrowser/main.tf
@@ -20,7 +20,7 @@ data "coder_workspace_owner" "me" {}
 
 variable "agent_name" {
   type        = string
-  description = "The name of the coder_agent resource. (Only required if subdomain is false and the template uses multiple agents.)"
+  description = "The name of the coder_agent resource. Required when `subdomain` is `false` so the path-based base URL matches the URL Coder serves."
   default     = null
 }
 
@@ -102,6 +102,13 @@ resource "coder_script" "filebrowser" {
     SERVER_BASE_PATH : local.server_base_path
   })
   run_on_start = true
+
+  lifecycle {
+    precondition {
+      condition     = var.subdomain || var.agent_name != null
+      error_message = "`agent_name` is required when `subdomain` is `false`. Coder always builds path-based app URLs as `/@<owner>/<workspace>.<agent>/apps/<slug>/`, so the filebrowser base URL must include the agent name to match. Set `agent_name = \"<your coder_agent name>\"` (e.g. `\"main\"`)."
+    }
+  }
 }
 
 resource "coder_app" "filebrowser" {