diff --git a/src/dvsim/job/deploy.py b/src/dvsim/job/deploy.py
index 6cdac479..cdf258ff 100644
--- a/src/dvsim/job/deploy.py
+++ b/src/dvsim/job/deploy.py
@@ -431,6 +431,7 @@ def __init__(self, build_mode: "BuildMode", sim_cfg: "SimCfg") -> None:
         self.build_cmd: str = ""
         self.build_dir: str = ""
         self.build_opts: list[str] = []
+        self.build_opts_file: str = ""
         self.post_build_cmds: list[str] = []
         self.build_fail_patterns: list[str] = []
         self.build_pass_patterns: list[str] = []
@@ -485,6 +486,7 @@ def _define_attrs(self) -> None:
         self.mandatory_misc_attrs.update(
             {
                 "build_fail_patterns": False,
+                "build_opts_file": False,
                 "build_pass_patterns": False,
                 "build_timeout_mins": False,
                 "cov_db_dir": False,
@@ -509,6 +511,25 @@ def _set_attrs(self) -> None:
         if self.sim_cfg.args.build_timeout_mins is not None:
             self.build_timeout_mins = self.sim_cfg.args.build_timeout_mins
 
+    def _write_build_opts_file(self) -> None:
+        """Record the options this build used, in the build directory.
+
+        A run step may compile and elaborate for itself instead of loading the snapshot the build
+        produced. Such a run has to compile the way the build did. Build modes and individual cfgs
+        each contribute their own defines, include paths and libraries, and a run compiled with a
+        different set would simulate a differently configured design.
+
+        The merged option list exists only here, so write it out as a file the tools accept in
+        place of command line options. The run step names that file with {build_opts_file}, which
+        SimCfg sets and the HJson may override.
+        """
+        opts_file = Path(self.build_opts_file)
+        opts_file.parent.mkdir(parents=True, exist_ok=True)
+        opts_file.write_text(
+            "".join(f"{opt.strip()}\n" for opt in self.build_opts if opt.strip()),
+            encoding="UTF-8",
+        )
+
     def pre_launch(self) -> Callable[[], None]:
         """Get pre-launch callback."""
 
@@ -518,6 +539,8 @@ def callback() -> None:
             # need to do this because the build directory is not 'renewed'.
             rm_path(Path(self.cov_db_dir))
 
+            self._write_build_opts_file()
+
         return callback
 
     def get_timeout_mins(self) -> float:
diff --git a/src/dvsim/sim/flow.py b/src/dvsim/sim/flow.py
index 1ebeea32..a800979d 100644
--- a/src/dvsim/sim/flow.py
+++ b/src/dvsim/sim/flow.py
@@ -134,6 +134,7 @@ def __init__(self, flow_cfg_file, hjson_data, args, mk_config) -> None:
         self.post_build_cmds = []
         self.post_build_opts = []
         self.build_dir = ""
+        self.build_opts_file = ""
         self.pre_run_cmds = []
         self.post_run_cmds = []
         self.run_dir = ""
@@ -200,6 +201,13 @@ def _expand(self) -> None:
         if self.args.verbosity is not None:
             self.verbosity = self.args.verbosity
 
+        # Where each build records the options it compiled with, for a run step that compiles for
+        # itself rather than loading the snapshot the build produced, see
+        # CompileSim._write_build_opts_file(). The HJSON can name this path as {build_opts_file},
+        # and can also set it, to move the file or to share one between cfgs.
+        if not self.build_opts_file:
+            self.build_opts_file = "{build_dir}/build_opts.f"
+
         super()._expand()
 
         if self.variant:
diff --git a/tests/job/test_deploy.py b/tests/job/test_deploy.py
index b19f055b..7ac1d5e0 100644
--- a/tests/job/test_deploy.py
+++ b/tests/job/test_deploy.py
@@ -5,6 +5,7 @@
 """Test Job deployment models."""
 
 from collections.abc import Mapping
+from pathlib import Path
 
 import pytest
 from hamcrest import assert_that, equal_to
@@ -48,6 +49,7 @@ def __init__(self) -> None:
         self.pre_build_cmds = ["A", "B"]
         self.post_build_cmds = ["C", "D"]
         self.build_dir = "build/dir"
+        self.build_opts_file = "{build_dir}/build_opts.f"
         self.build_pass_patterns = None
         self.build_fail_patterns = None
         self.build_seed = 123
@@ -202,6 +204,49 @@ def test_seed(
 
         assert_that(job.seed, equal_to(seed))
 
+    @staticmethod
+    def test_build_opts_file(tmp_path: Path) -> None:
+        """Test that a CompileSim records the options it built with, for the run step."""
+        build_dir = tmp_path / "build" / "dir"
+        job = _build_compile_sim(
+            sim_overrides={"build_dir": str(build_dir), "cov_db_dir": str(tmp_path / "cov")},
+        )
+
+        assert_that(job.build_opts_file, equal_to(str(build_dir / "build_opts.f")))
+
+        # The build directory does not exist until the build job launches.
+        job.pre_launch()()
+
+        assert_that(
+            Path(job.build_opts_file).read_text(encoding="UTF-8"),
+            equal_to('-b path/here\n-a "Quoted"\n'),
+        )
+
+    @staticmethod
+    def test_build_opts_file_from_cfg(tmp_path: Path) -> None:
+        """Test that a cfg-supplied build_opts_file is used as given.
+
+        SimCfg only fills in a default, so an HJson that sets build_opts_file itself can put the
+        file outside the build directory.
+        """
+        opts_file = tmp_path / "elsewhere" / "opts.f"
+        job = _build_compile_sim(
+            sim_overrides={
+                "build_dir": str(tmp_path / "build" / "dir"),
+                "build_opts_file": str(opts_file),
+                "cov_db_dir": str(tmp_path / "cov"),
+            },
+        )
+
+        assert_that(job.build_opts_file, equal_to(str(opts_file)))
+
+        job.pre_launch()()
+
+        assert_that(
+            opts_file.read_text(encoding="UTF-8"),
+            equal_to('-b path/here\n-a "Quoted"\n'),
+        )
+
     @staticmethod
     @pytest.mark.parametrize(
         ("cli_args_overrides", "build_overrides", "timeout"),