diff --git a/src/specify_cli/integrations/forge/__init__.py b/src/specify_cli/integrations/forge/__init__.py
index f455556e36..520e417523 100644
--- a/src/specify_cli/integrations/forge/__init__.py
+++ b/src/specify_cli/integrations/forge/__init__.py
@@ -9,6 +9,7 @@
 
 from __future__ import annotations
 
+from collections.abc import Mapping, Sequence
 from pathlib import Path
 from typing import Any
 
@@ -91,6 +92,35 @@ class ForgeIntegration(MarkdownIntegration):
     }
     invoke_separator = "-"
 
+    def build_exec_args(
+        self,
+        prompt: str,
+        *,
+        model: str | None = None,
+        output_json: bool = True,
+        integration_args: Sequence[str] | None = None,
+        integration_options: Mapping[str, Any] | None = None,
+        project_root: Path | None = None,
+    ) -> list[str] | None:
+        """Build CLI arguments for non-interactive ``forge`` execution.
+
+        ``MarkdownIntegration``'s default appends ``--model`` and
+        ``--output-format``, neither of which exists in the Forge CLI (see
+        issue #4666) — a dispatched step exits 2 at argument parsing
+        whenever either flag ends up appended (a configured ``model``, or
+        ``output_json=True``). Forge only accepts ``-p/--prompt``; ``model``
+        is deliberately dropped rather than remapped, since Forge selects it
+        out of band via ``forge config set model`` and its ``--agent`` flag
+        selects an agent ID, not a model.
+        """
+        self.validate_runtime_config(integration_args, integration_options)
+        args = [self._resolve_executable()]
+        # Forge's global flags parse before -p, so extra args go first
+        # (matches opencode / goose / codex / cursor-agent ordering).
+        self._apply_extra_args_env_var(args)
+        args.extend(["-p", prompt])
+        return args
+
     def build_command_invocation(self, command_name: str, args: str = "") -> str:
         """Forge installs hyphenated slash-commands (``/speckit-<name>``), so the
         dispatch invocation must match. The inherited MarkdownIntegration default
diff --git a/tests/integrations/test_integration_forge.py b/tests/integrations/test_integration_forge.py
index 0559e9be98..96b7fd0e5a 100644
--- a/tests/integrations/test_integration_forge.py
+++ b/tests/integrations/test_integration_forge.py
@@ -282,6 +282,51 @@ def test_name_field_uses_hyphenated_format(self, tmp_path):
             )
 
 
+class TestForgeExecArgs:
+    """Forge only accepts `-p/--prompt`; `--model` and `--output-format` do
+    not exist in the Forge CLI and abort dispatch with exit code 2 (#4666)."""
+
+    def test_build_exec_args_uses_prompt_flag_only(self):
+        forge = get_integration("forge")
+
+        args = forge.build_exec_args("/speckit-plan add OAuth", output_json=False)
+
+        assert args == ["forge", "-p", "/speckit-plan add OAuth"]
+
+    def test_build_exec_args_omits_output_format_flag(self):
+        """`--output-format` is not a Forge flag; requesting JSON output must
+        not append it."""
+        forge = get_integration("forge")
+
+        args = forge.build_exec_args("hello", output_json=True)
+
+        assert args == ["forge", "-p", "hello"]
+        assert "--output-format" not in args
+
+    def test_build_exec_args_omits_model_flag(self):
+        """Forge has no model-selection flag; `model` is set out of band via
+        `forge config set model`, so it must not be forwarded onto `--model`
+        or `--agent` (the latter selects an agent ID, not a model)."""
+        forge = get_integration("forge")
+
+        args = forge.build_exec_args("hello", model="gpt-4o", output_json=True)
+
+        assert args == ["forge", "-p", "hello"]
+        assert "--model" not in args
+        assert "--agent" not in args
+        assert "gpt-4o" not in args
+
+    def test_build_exec_args_applies_extra_args_before_prompt(self, monkeypatch):
+        """Forge's global flags parse before -p, so operator-injected extra
+        args go first (matches opencode / goose / codex / cursor-agent)."""
+        monkeypatch.setenv("SPECKIT_INTEGRATION_FORGE_EXTRA_ARGS", "--verbose")
+        forge = get_integration("forge")
+
+        args = forge.build_exec_args("check the build", output_json=False)
+
+        assert args == ["forge", "--verbose", "-p", "check the build"]
+
+
 class TestForgeCommandRegistrar:
     """Test CommandRegistrar's Forge-specific name formatting."""