diff --git a/tests/close_error.test.ts b/tests/close_error.test.ts
new file mode 100644
index 0000000..7601e85
--- /dev/null
+++ b/tests/close_error.test.ts
@@ -0,0 +1,53 @@
+import { expect, test, mock, beforeEach, afterEach, describe, spyOn } from "bun:test";
+import * as os from "node:os";
+import { closeMultiModel } from "../src/core/close";
+
+let originalBun$: typeof Bun.$ = (globalThis as any).Bun?.$;
+let mockCommandResponses: Record<string, { ok: boolean; stdout: string; stderr: string }> = {};
+let executedCommands: string[] = [];
+
+function setupMockBun$() {
+  const mockFn = mock((strings: TemplateStringsArray, ...values: any[]) => {
+    const parts = values[0] as string[];
+    const cmd = parts.join(" ");
+    executedCommands.push(cmd);
+    // Simulate throwing error for a specific command
+    if (cmd === "git worktree list --porcelain") {
+      throw new Error("unexpected error");
+    }
+    const response = mockCommandResponses[cmd] ?? { ok: true, stdout: "", stderr: "" };
+    return {
+      quiet: () => ({
+        nothrow: async () => ({
+          exitCode: response.ok ? 0 : 1,
+          stdout: { toString: () => response.stdout },
+          stderr: { toString: () => response.stderr },
+        }),
+      }),
+    };
+  });
+  (globalThis as any).Bun.$ = mockFn;
+  return mockFn;
+}
+
+function restoreOriginalBun$() {
+  (globalThis as any).Bun.$ = originalBun$;
+}
+
+describe("closeMultiModel unexpected error handling", () => {
+  beforeEach(() => {
+    spyOn(os, "homedir").mockReturnValue("/home/user");
+    mockCommandResponses = {};
+    executedCommands = [];
+    setupMockBun$();
+  });
+  afterEach(() => {
+    restoreOriginalBun$();
+  });
+
+  test("catches thrown error and returns failure", async () => {
+    const result = await closeMultiModel({ sessionName: "any-session", cleanupWorktrees: false, force: false });
+    expect(result.success).toBe(false);
+    expect(result.error).toContain("unexpected error");
+  });
+});
diff --git a/tests/open_error.test.ts b/tests/open_error.test.ts
new file mode 100644
index 0000000..89b6c7a
--- /dev/null
+++ b/tests/open_error.test.ts
@@ -0,0 +1,201 @@
+import { expect, test, mock, beforeEach, afterEach, describe, spyOn } from "bun:test";
+import * as os from "node:os";
+import { openMultiModel } from "../src/core/open";
+
+let originalBun$: typeof Bun.$ = (globalThis as any).Bun?.$;
+let mockCommandResponses: Record<string, { ok: boolean; stdout: string; stderr: string }> = {};
+let executedCommands: string[] = [];
+
+function setupMockBun$() {
+  const mockFn = mock((strings: TemplateStringsArray, ...values: any[]) => {
+    const parts = values[0] as string[];
+    const cmd = parts.join(" ");
+    executedCommands.push(cmd);
+    const response = mockCommandResponses[cmd] ?? { ok: true, stdout: "", stderr: "" };
+    return {
+      quiet: () => ({
+        nothrow: async () => ({
+          exitCode: response.ok ? 0 : 1,
+          stdout: { toString: () => response.stdout },
+          stderr: { toString: () => response.stderr },
+        }),
+      }),
+    };
+  });
+  (globalThis as any).Bun.$ = mockFn;
+  return mockFn;
+}
+
+function restoreOriginalBun$() {
+  (globalThis as any).Bun.$ = originalBun$;
+}
+
+describe("openMultiModel error paths", () => {
+  beforeEach(() => {
+    spyOn(os, "homedir").mockReturnValue("/mock/home");
+    mockCommandResponses = {};
+    executedCommands = [];
+    setupMockBun$();
+  });
+  afterEach(() => {
+    restoreOriginalBun$();
+  });
+
+  test("fails when model list command fails", async () => {
+    const session = "sess";
+    mockCommandResponses["git rev-parse --is-inside-work-tree"] = { ok: true, stdout: "true", stderr: "" };
+    mockCommandResponses["command -v tmux"] = { ok: true, stdout: "tmux", stderr: "" };
+    mockCommandResponses["command -v opencode"] = { ok: true, stdout: "opencode", stderr: "" };
+    mockCommandResponses["opencode models"] = { ok: false, stdout: "", stderr: "model error" };
+
+    const result = await openMultiModel({ sessionName: session, models: ["openai/gpt-5.2"], binaryName: "opencode", mode: "cli" });
+    expect(result.success).toBe(false);
+    expect(result.error).toContain("Failed to load valid models");
+  });
+
+  test("fails when duplicate models provided", async () => {
+    const session = "dup";
+    mockCommandResponses["git rev-parse --is-inside-work-tree"] = { ok: true, stdout: "true", stderr: "" };
+    mockCommandResponses["command -v tmux"] = { ok: true, stdout: "tmux", stderr: "" };
+    mockCommandResponses["command -v opencode"] = { ok: true, stdout: "opencode", stderr: "" };
+    mockCommandResponses["opencode models"] = { ok: true, stdout: "openai/gpt-5.2", stderr: "" };
+
+    const result = await openMultiModel({ sessionName: session, models: ["openai/gpt-5.2", "openai/gpt-5.2"], binaryName: "opencode", mode: "cli" });
+    expect(result.success).toBe(false);
+    expect(result.error).toContain("Duplicate model names are not allowed");
+  });
+
+  test("fails when session already exists", async () => {
+    const session = "existing";
+    mockCommandResponses["git rev-parse --is-inside-work-tree"] = { ok: true, stdout: "true", stderr: "" };
+    mockCommandResponses["command -v tmux"] = { ok: true, stdout: "tmux", stderr: "" };
+    mockCommandResponses["command -v opencode"] = { ok: true, stdout: "opencode", stderr: "" };
+    mockCommandResponses["opencode models"] = { ok: true, stdout: "openai/gpt-5.2", stderr: "" };
+    mockCommandResponses[`tmux has-session -t ${session}`] = { ok: true, stdout: "", stderr: "" };
+
+    const result = await openMultiModel({ sessionName: session, models: ["openai/gpt-5.2"], binaryName: "opencode", mode: "cli" });
+    expect(result.success).toBe(false);
+    expect(result.error).toContain("Session already exists");
+  });
+
+    test("second model fails because branch already exists", async () => {
+      const session = "sess-add";
+      const binary = "opencode";
+      const models = ["openai/gpt-5.2", "anthropic/gpt-5-2"];
+      // common mocks
+      mockCommandResponses["git rev-parse --is-inside-work-tree"] = { ok: true, stdout: "true", stderr: "" };
+      mockCommandResponses["command -v tmux"] = { ok: true, stdout: "tmux", stderr: "" };
+      mockCommandResponses["command -v opencode"] = { ok: true, stdout: "opencode", stderr: "" };
+      mockCommandResponses["opencode models"] = { ok: true, stdout: models.join("\n"), stderr: "" };
+      mockCommandResponses[`tmux has-session -t ${session}`] = { ok: false, stdout: "", stderr: "" };
+      // first model success
+      const firstBranch = `opencode/${session}/gpt-5-2`;
+      const firstPath = `/home/user/.local/share/opencode/multi-model/${session}/gpt-5-2`;
+      mockCommandResponses[`git show-ref --verify --quiet refs/heads/${firstBranch}`] = { ok: false, stdout: "", stderr: "" };
+      mockCommandResponses[`git worktree add -b ${firstBranch} ${firstPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux new-session -d -s ${session} -n gpt-5-2 -c ${firstPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux send-keys -t ${session}:gpt-5-2 ${binary} --model 'openai/gpt-5.2' C-m`] = { ok: true, stdout: "", stderr: "" };
+      // second model branch exists
+      const secondBranch = `opencode/${session}/gpt-5-2-2`;
+      mockCommandResponses[`git show-ref --verify --quiet refs/heads/${secondBranch}`] = { ok: true, stdout: "", stderr: "" };
+      const result = await openMultiModel({ sessionName: session, models, binaryName: binary, mode: "cli" });
+      expect(result.success).toBe(true);
+      expect(result.instructions).toContain("Failed: anthropic/gpt-5-2 (Branch");
+      expect(result.windows).toContain("gpt-5-2");
+      expect(result.windows).toContain("gpt-5-2-2");
+    });
+
+    test("second model worktree creation fails", async () => {
+      const session = "sess-wt";
+      const binary = "opencode";
+      const models = ["openai/gpt-5.2", "anthropic/gpt-5-2"];
+      mockCommandResponses["git rev-parse --is-inside-work-tree"] = { ok: true, stdout: "true", stderr: "" };
+      mockCommandResponses["command -v tmux"] = { ok: true, stdout: "tmux", stderr: "" };
+      mockCommandResponses["command -v opencode"] = { ok: true, stdout: "opencode", stderr: "" };
+      mockCommandResponses["opencode models"] = { ok: true, stdout: models.join("\n"), stderr: "" };
+      mockCommandResponses[`tmux has-session -t ${session}`] = { ok: false, stdout: "", stderr: "" };
+      // first model success
+      const firstBranch = `opencode/${session}/gpt-5-2`;
+      const firstPath = `/home/user/.local/share/opencode/multi-model/${session}/gpt-5-2`;
+      mockCommandResponses[`git show-ref --verify --quiet refs/heads/${firstBranch}`] = { ok: false, stdout: "", stderr: "" };
+      mockCommandResponses[`git worktree add -b ${firstBranch} ${firstPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux new-session -d -s ${session} -n gpt-5-2 -c ${firstPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux send-keys -t ${session}:gpt-5-2 ${binary} --model 'openai/gpt-5.2' C-m`] = { ok: true, stdout: "", stderr: "" };
+      // second model fails worktree
+      const secondBranch = `opencode/${session}/gpt-5-2-2`;
+      const secondPath = `/home/user/.local/share/opencode/multi-model/${session}/gpt-5-2-2`;
+      mockCommandResponses[`git show-ref --verify --quiet refs/heads/${secondBranch}`] = { ok: false, stdout: "", stderr: "" };
+      mockCommandResponses[`git worktree add -b ${secondBranch} ${secondPath}`] = { ok: false, stdout: "", stderr: "wt error" };
+      mockCommandResponses[`git worktree remove -f ${secondPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`git branch -D ${secondBranch}`] = { ok: true, stdout: "", stderr: "" };
+      const result = await openMultiModel({ sessionName: session, models, binaryName: binary, mode: "cli" });
+      expect(result.success).toBe(true);
+      expect(result.instructions).toContain("Error: Created tmux session"); expect(result.instructions).toContain("Failed: anthropic/gpt-5-2");
+      expect(result.windows).toContain("gpt-5-2");
+      expect(result.windows).toContain("gpt-5-2-2");
+    });
+
+    test("second model window creation fails", async () => {
+      const session = "sess-win";
+      const binary = "opencode";
+      const models = ["openai/gpt-5.2", "anthropic/gpt-5-2"];
+      mockCommandResponses["git rev-parse --is-inside-work-tree"] = { ok: true, stdout: "true", stderr: "" };
+      mockCommandResponses["command -v tmux"] = { ok: true, stdout: "tmux", stderr: "" };
+      mockCommandResponses["command -v opencode"] = { ok: true, stdout: "opencode", stderr: "" };
+      mockCommandResponses["opencode models"] = { ok: true, stdout: models.join("\n"), stderr: "" };
+      mockCommandResponses[`tmux has-session -t ${session}`] = { ok: false, stdout: "", stderr: "" };
+      // first model success
+      const firstBranch = `opencode/${session}/gpt-5-2`;
+      const firstPath = `/home/user/.local/share/opencode/multi-model/${session}/gpt-5-2`;
+      mockCommandResponses[`git show-ref --verify --quiet refs/heads/${firstBranch}`] = { ok: false, stdout: "", stderr: "" };
+      mockCommandResponses[`git worktree add -b ${firstBranch} ${firstPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux new-session -d -s ${session} -n gpt-5-2 -c ${firstPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux send-keys -t ${session}:gpt-5-2 ${binary} --model 'openai/gpt-5.2' C-m`] = { ok: true, stdout: "", stderr: "" };
+      // second model window failure
+      const secondBranch = `opencode/${session}/gpt-5-2-2`;
+      const secondPath = `/home/user/.local/share/opencode/multi-model/${session}/gpt-5-2-2`;
+      mockCommandResponses[`git show-ref --verify --quiet refs/heads/${secondBranch}`] = { ok: false, stdout: "", stderr: "" };
+      mockCommandResponses[`git worktree add -b ${secondBranch} ${secondPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux new-window -d -t ${session} -n gpt-5-2-2 -c ${secondPath}`] = { ok: false, stdout: "", stderr: "win err" };
+      mockCommandResponses[`git worktree remove -f ${secondPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`git branch -D ${secondBranch}`] = { ok: true, stdout: "", stderr: "" };
+      const result = await openMultiModel({ sessionName: session, models, binaryName: binary, mode: "cli" });
+      expect(result.success).toBe(true);
+      expect(result.instructions).toContain("Error: Created tmux session"); expect(result.instructions).toContain("Failed: anthropic/gpt-5-2");
+      expect(result.windows).toContain("gpt-5-2");
+      expect(result.windows).toContain("gpt-5-2-2");
+    });
+
+    test("second model launch command fails", async () => {
+      const session = "sess-launch";
+      const binary = "opencode";
+      const models = ["openai/gpt-5.2", "anthropic/gpt-5-2"];
+      mockCommandResponses["git rev-parse --is-inside-work-tree"] = { ok: true, stdout: "true", stderr: "" };
+      mockCommandResponses["command -v tmux"] = { ok: true, stdout: "tmux", stderr: "" };
+      mockCommandResponses["command -v opencode"] = { ok: true, stdout: "opencode", stderr: "" };
+      mockCommandResponses["opencode models"] = { ok: true, stdout: models.join("\n"), stderr: "" };
+      mockCommandResponses[`tmux has-session -t ${session}`] = { ok: false, stdout: "", stderr: "" };
+      // first model success
+      const firstBranch = `opencode/${session}/gpt-5-2`;
+      const firstPath = `/home/user/.local/share/opencode/multi-model/${session}/gpt-5-2`;
+      mockCommandResponses[`git show-ref --verify --quiet refs/heads/${firstBranch}`] = { ok: false, stdout: "", stderr: "" };
+      mockCommandResponses[`git worktree add -b ${firstBranch} ${firstPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux new-session -d -s ${session} -n gpt-5-2 -c ${firstPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux send-keys -t ${session}:gpt-5-2 ${binary} --model 'openai/gpt-5.2' C-m`] = { ok: true, stdout: "", stderr: "" };
+      // second model launch fails
+      const secondBranch = `opencode/${session}/gpt-5-2-2`;
+      const secondPath = `/home/user/.local/share/opencode/multi-model/${session}/gpt-5-2-2`;
+      mockCommandResponses[`git show-ref --verify --quiet refs/heads/${secondBranch}`] = { ok: false, stdout: "", stderr: "" };
+      mockCommandResponses[`git worktree add -b ${secondBranch} ${secondPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux new-window -d -t ${session} -n gpt-5-2-2 -c ${secondPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`tmux send-keys -t ${session}:gpt-5-2-2 ${binary} --model 'anthropic/gpt-5-2' C-m`] = { ok: false, stdout: "", stderr: "launch err" };
+      mockCommandResponses[`git worktree remove -f ${secondPath}`] = { ok: true, stdout: "", stderr: "" };
+      mockCommandResponses[`git branch -D ${secondBranch}`] = { ok: true, stdout: "", stderr: "" };
+      const result = await openMultiModel({ sessionName: session, models, binaryName: binary, mode: "cli" });
+      expect(result.success).toBe(true);
+      expect(result.instructions).toContain("Failed: anthropic/gpt-5-2 (launch err");
+      expect(result.windows).toContain("gpt-5-2");
+      expect(result.windows).toContain("gpt-5-2-2");
+    });
+
+    });