diff --git a/src/features/chat/chat-view-controller-assembly.ts b/src/features/chat/chat-view-controller-assembly.ts
index 8f91af29..64dae139 100644
--- a/src/features/chat/chat-view-controller-assembly.ts
+++ b/src/features/chat/chat-view-controller-assembly.ts
@@ -362,6 +362,7 @@ export function createChatViewControllerAssembly(host: ChatViewControllerAssembl
     resetThreadTurnPresence: host.effects.thread.resetTurnPresence,
     setStatus: host.effects.status.set,
     addSystemMessage: host.effects.status.addSystemMessage,
+    configuredCommand: () => host.plugin.settings.codexPath,
     refreshLiveState: host.effects.liveState.refresh,
     render: host.effects.render.now,
     scheduleRender: host.effects.render.schedule,
diff --git a/src/features/chat/controllers/connection/connection-controller.ts b/src/features/chat/controllers/connection/connection-controller.ts
index 84816787..ffaea04c 100644
--- a/src/features/chat/controllers/connection/connection-controller.ts
+++ b/src/features/chat/controllers/connection/connection-controller.ts
@@ -25,6 +25,7 @@ export interface ChatConnectionControllerHost {
   resetThreadTurnPresence: (hadTurns: boolean) => void;
   setStatus: (status: string) => void;
   addSystemMessage: (text: string) => void;
+  configuredCommand: () => string;
   refreshLiveState: () => void;
   render: () => void;
   scheduleRender: () => void;
@@ -125,7 +126,7 @@ export class ChatConnectionController {
       if (this.host.connectionWork.isStale(connection)) return;
       if (error instanceof StaleConnectionError) return;
       this.host.setStatus("Connection failed.");
-      this.host.addSystemMessage(error instanceof Error ? error.message : String(error));
+      this.host.addSystemMessage(connectionErrorMessage(error, this.host.configuredCommand()));
       this.host.notifyConnectionFailed();
     }
     if (!this.host.connectionWork.isStale(connection)) {
@@ -137,3 +138,15 @@ export class ChatConnectionController {
     this.host.stateStore.dispatch(action);
   }
 }
+
+function connectionErrorMessage(error: unknown, configuredCommand: string): string {
+  const message = error instanceof Error ? error.message : String(error);
+  if (!isMissingCommandError(error)) return message;
+  return `Could not start Codex app-server because the configured command was not found: ${configuredCommand}. Check the Codex command path in settings. (${message})`;
+}
+
+function isMissingCommandError(error: unknown): boolean {
+  if (!(error instanceof Error)) return false;
+  const candidate = error as { code?: unknown; syscall?: unknown };
+  return candidate.code === "ENOENT" && candidate.syscall === "spawn";
+}
diff --git a/src/features/chat/view-model.ts b/src/features/chat/view-model.ts
index 02b8b991..94d3bce1 100644
--- a/src/features/chat/view-model.ts
+++ b/src/features/chat/view-model.ts
@@ -50,6 +50,7 @@ export interface StatusDotStateInput {
   connected: boolean;
   turnBusy: boolean;
   diagnostics: AppServerDiagnostics;
+  connectionFailed?: boolean;
   turnStartBlocked?: boolean;
 }
 
@@ -156,6 +157,7 @@ export function toolbarViewModel(input: ToolbarViewModelInput): ToolbarViewModel
     connected: input.connected,
     turnBusy: input.turnBusy,
     diagnostics: state.appServerDiagnostics,
+    connectionFailed: state.status === "Connection failed.",
   });
   const model = currentModel(snapshot, config);
   const effort = currentReasoningEffort(snapshot, config);
@@ -197,6 +199,7 @@ export function toolbarViewModel(input: ToolbarViewModelInput): ToolbarViewModel
 
 export function statusDotState(input: StatusDotStateInput): ToolbarStatusState {
   if (input.turnBusy) return "running";
+  if (input.connectionFailed) return "blocked";
   if (!input.connected) return "offline";
   if (input.turnStartBlocked) return "blocked";
   return hasDiagnosticIssue(input.diagnostics) ? "degraded" : "ready";
diff --git a/tests/features/chat/controllers/connection/connection-controller.test.ts b/tests/features/chat/controllers/connection/connection-controller.test.ts
index ccb667ad..fd9ce432 100644
--- a/tests/features/chat/controllers/connection/connection-controller.test.ts
+++ b/tests/features/chat/controllers/connection/connection-controller.test.ts
@@ -46,6 +46,7 @@ function createController({ connected = false, client = {} as AppServerClient }
     resetThreadTurnPresence: vi.fn(),
     setStatus: vi.fn(),
     addSystemMessage: vi.fn(),
+    configuredCommand: () => "codex",
     refreshLiveState: vi.fn(),
     render: vi.fn(),
     scheduleRender: vi.fn(),
@@ -117,4 +118,18 @@ describe("ChatConnectionController", () => {
       runtimePicker: null,
     });
   });
+
+  it("explains missing configured command failures", async () => {
+    const { controller, connect, host } = createController();
+    const error = Object.assign(new Error("spawn codex ENOENT"), { code: "ENOENT", syscall: "spawn" });
+    connect.mockRejectedValueOnce(error);
+
+    await controller.ensureConnected();
+
+    expect(host.setStatus).toHaveBeenCalledWith("Connection failed.");
+    expect(host.addSystemMessage).toHaveBeenCalledWith(
+      "Could not start Codex app-server because the configured command was not found: codex. Check the Codex command path in settings. (spawn codex ENOENT)",
+    );
+    expect(host.notifyConnectionFailed).toHaveBeenCalledOnce();
+  });
 });
diff --git a/tests/features/chat/view-model.test.ts b/tests/features/chat/view-model.test.ts
index 6d70688e..5775fed6 100644
--- a/tests/features/chat/view-model.test.ts
+++ b/tests/features/chat/view-model.test.ts
@@ -81,6 +81,7 @@ describe("chat view model", () => {
 
     expect(statusDotState({ connected: true, turnBusy: true, diagnostics })).toBe("running");
     expect(statusDotState({ connected: false, turnBusy: false, diagnostics })).toBe("offline");
+    expect(statusDotState({ connected: false, turnBusy: false, diagnostics, connectionFailed: true })).toBe("blocked");
     expect(statusDotState({ connected: true, turnBusy: false, diagnostics })).toBe("ready");
     expect(statusDotState({ connected: true, turnBusy: false, diagnostics, turnStartBlocked: true })).toBe("blocked");
   });
@@ -138,6 +139,27 @@ describe("chat view model", () => {
     expect(runningModel.statusState).toBe("running");
   });
 
+  it("marks connection failure status as blocked in the toolbar model", () => {
+    const state = createChatState();
+    state.status = "Connection failed.";
+
+    const model = toolbarViewModel({
+      state,
+      snapshot: runtimeSnapshotForChatState({ state }),
+      connected: false,
+      turnBusy: false,
+      vaultPath: "/vault",
+      configuredCommand: "codex",
+      archiveConfirmThreadId: null,
+      archiveExportEnabled: true,
+      modelChoices: [],
+      effortChoices: [],
+      renameState: () => null,
+    });
+
+    expect(model.statusState).toBe("blocked");
+  });
+
   it("builds slash-command status lines from chat state", () => {
     const state = createChatState();
     state.activeThreadId = "thread-1";