diff --git a/src/adapters/codex-launch.test.ts b/src/adapters/codex-launch.test.ts
new file mode 100644
index 0000000..a816714
--- /dev/null
+++ b/src/adapters/codex-launch.test.ts
@@ -0,0 +1,101 @@
+import { EventEmitter } from "node:events";
+import * as fs from "node:fs/promises";
+import * as os from "node:os";
+import * as path from "node:path";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+// Track spawn calls
+const spawnCalls: { cmd: string; args: string[] }[] = [];
+
+vi.mock("node:child_process", async (importOriginal) => {
+  const orig = await importOriginal<typeof import("node:child_process")>();
+  return {
+    ...orig,
+    spawn: (cmd: string, args: string[], _opts: unknown) => {
+      spawnCalls.push({ cmd, args: [...args] });
+      const child = new EventEmitter();
+      Object.assign(child, {
+        pid: 77777,
+        unref: () => {},
+        stdout: new EventEmitter(),
+        stderr: new EventEmitter(),
+      });
+      return child;
+    },
+  };
+});
+
+vi.mock("../utils/resolve-binary.js", () => ({
+  resolveBinaryPath: async () => "/usr/local/bin/codex",
+}));
+
+// Import after mocks are declared (vitest hoists vi.mock)
+const { CodexAdapter } = await import("./codex.js");
+
+let tmpDir: string;
+let adapter: InstanceType<typeof CodexAdapter>;
+
+beforeEach(async () => {
+  spawnCalls.length = 0;
+  tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "agentctl-codex-launch-"));
+  const codexDir = path.join(tmpDir, "codex");
+  const sessionsMetaDir = path.join(tmpDir, "codex-sessions");
+  await fs.mkdir(path.join(codexDir, "sessions"), { recursive: true });
+  await fs.mkdir(sessionsMetaDir, { recursive: true });
+
+  adapter = new CodexAdapter({
+    codexDir,
+    sessionsMetaDir,
+    getPids: async () => new Map(),
+    isProcessAlive: () => false,
+  });
+});
+
+afterEach(async () => {
+  await fs.rm(tmpDir, { recursive: true, force: true });
+});
+
+describe("CodexAdapter launch", () => {
+  it("uses -- separator so dash-prefixed prompts are not parsed as options", async () => {
+    const dashPrompt = "---\ntitle: spec\n---\nFix the bug";
+    await adapter.launch({
+      adapter: "codex",
+      prompt: dashPrompt,
+      cwd: tmpDir,
+    });
+
+    expect(spawnCalls).toHaveLength(1);
+    const args = spawnCalls[0].args;
+    // -- must appear before the prompt
+    const sepIdx = args.indexOf("--");
+    const promptIdx = args.indexOf(dashPrompt);
+    expect(sepIdx).toBeGreaterThanOrEqual(0);
+    expect(promptIdx).toBe(sepIdx + 1);
+    expect(args).toEqual([
+      "exec",
+      "--dangerously-bypass-approvals-and-sandbox",
+      "--json",
+      "--cd",
+      tmpDir,
+      "--",
+      dashPrompt,
+    ]);
+  });
+
+  it("places -- separator after --model flag", async () => {
+    await adapter.launch({
+      adapter: "codex",
+      prompt: "fix the bug",
+      model: "gpt-4o",
+      cwd: tmpDir,
+    });
+
+    expect(spawnCalls).toHaveLength(1);
+    const args = spawnCalls[0].args;
+    const sepIdx = args.indexOf("--");
+    const modelIdx = args.indexOf("--model");
+    expect(modelIdx).toBeLessThan(sepIdx);
+    expect(args[args.length - 1]).toBe("fix the bug");
+    expect(args[args.length - 2]).toBe("--");
+  });
+});
diff --git a/src/adapters/codex.ts b/src/adapters/codex.ts
index fcde699..1255c1d 100644
--- a/src/adapters/codex.ts
+++ b/src/adapters/codex.ts
@@ -252,7 +252,9 @@ export class CodexAdapter implements AgentAdapter {
 
     const cwd = opts.cwd || process.cwd();
     args.push("--cd", cwd);
-    args.push(opts.prompt);
+    // Use -- separator to prevent prompts starting with dashes from being
+    // interpreted as CLI options by the downstream arg parser.
+    args.push("--", opts.prompt);
 
     const env = buildSpawnEnv(undefined, opts.env);
 
diff --git a/src/adapters/opencode-launch.test.ts b/src/adapters/opencode-launch.test.ts
index d917eaa..e9cb4f1 100644
--- a/src/adapters/opencode-launch.test.ts
+++ b/src/adapters/opencode-launch.test.ts
@@ -74,7 +74,13 @@ describe("OpenCodeAdapter launch", () => {
     const modelIdx = args.indexOf("--model");
     const promptIdx = args.indexOf("fix the bug");
     expect(modelIdx).toBeLessThan(promptIdx);
-    expect(args).toEqual(["run", "--model", "deepseek-r1", "fix the bug"]);
+    expect(args).toEqual([
+      "run",
+      "--model",
+      "deepseek-r1",
+      "--",
+      "fix the bug",
+    ]);
   });
 
   it("omits --model flag when opts.model is not set", async () => {
@@ -87,6 +93,24 @@ describe("OpenCodeAdapter launch", () => {
     expect(spawnCalls).toHaveLength(1);
     const args = spawnCalls[0].args;
     expect(args).not.toContain("--model");
-    expect(args).toEqual(["run", "fix the bug"]);
+    expect(args).toEqual(["run", "--", "fix the bug"]);
+  });
+
+  it("uses -- separator so dash-prefixed prompts are not parsed as options", async () => {
+    const dashPrompt = "---\ntitle: spec\n---\nFix the bug";
+    await adapter.launch({
+      adapter: "opencode",
+      prompt: dashPrompt,
+      cwd: tmpDir,
+    });
+
+    expect(spawnCalls).toHaveLength(1);
+    const args = spawnCalls[0].args;
+    // -- must appear before the prompt
+    const sepIdx = args.indexOf("--");
+    const promptIdx = args.indexOf(dashPrompt);
+    expect(sepIdx).toBeGreaterThanOrEqual(0);
+    expect(promptIdx).toBe(sepIdx + 1);
+    expect(args).toEqual(["run", "--", dashPrompt]);
   });
 });
diff --git a/src/adapters/opencode.ts b/src/adapters/opencode.ts
index dcc70d9..850613d 100644
--- a/src/adapters/opencode.ts
+++ b/src/adapters/opencode.ts
@@ -301,7 +301,9 @@ export class OpenCodeAdapter implements AgentAdapter {
     if (opts.model) {
       args.push("--model", opts.model);
     }
-    args.push(opts.prompt);
+    // Use -- separator to prevent prompts starting with dashes from being
+    // interpreted as CLI options by the downstream arg parser.
+    args.push("--", opts.prompt);
 
     const env = buildSpawnEnv(undefined, opts.env);
     const cwd = opts.cwd || process.cwd();
diff --git a/src/adapters/pi-rust-launch.test.ts b/src/adapters/pi-rust-launch.test.ts
index a114443..a909243 100644
--- a/src/adapters/pi-rust-launch.test.ts
+++ b/src/adapters/pi-rust-launch.test.ts
@@ -179,4 +179,24 @@ describe("PiRustAdapter launch", () => {
     expect(args).toContain("--provider");
     expect(args).toContain("openrouter");
   });
+
+  it("uses -- separator so dash-prefixed prompts are not parsed as options", async () => {
+    const dashPrompt = "---\ntitle: spec\n---\nFix the bug";
+    await adapter.launch({
+      adapter: "pi-rust",
+      prompt: dashPrompt,
+      cwd: tmpDir,
+    });
+
+    expect(spawnCalls).toHaveLength(1);
+    const args = spawnCalls[0].args;
+    // -- must appear before the prompt
+    const sepIdx = args.indexOf("--");
+    const promptIdx = args.indexOf(dashPrompt);
+    expect(sepIdx).toBeGreaterThanOrEqual(0);
+    expect(promptIdx).toBe(sepIdx + 1);
+    // prompt should be the last arg, after --
+    expect(args[args.length - 1]).toBe(dashPrompt);
+    expect(args[args.length - 2]).toBe("--");
+  });
 });
diff --git a/src/adapters/pi-rust.ts b/src/adapters/pi-rust.ts
index 27974c2..ac454f3 100644
--- a/src/adapters/pi-rust.ts
+++ b/src/adapters/pi-rust.ts
@@ -328,7 +328,9 @@ export class PiRustAdapter implements AgentAdapter {
   }
 
   async launch(opts: LaunchOpts): Promise<AgentSession> {
-    const args = ["--print", "--mode", "json", opts.prompt];
+    // Use -- separator to prevent prompts starting with dashes from being
+    // interpreted as CLI options by the downstream arg parser.
+    const args = ["--print", "--mode", "json", "--", opts.prompt];
 
     if (opts.model) {
       const { provider, model } = parseProviderModel(