Support large target repos with with bind-mount option. (#577)

* fix: resolve pre-commit check failures

- Change RuntimeError to TypeError for type validation in report/writer.py
- Update pyupgrade to v3.21.2 for Python 3.14 compatibility

* chore: add pytest test infrastructure

Mirror the layout introduced on feature/438-token_budget: pytest +
pytest-asyncio dev deps, asyncio_mode auto, a tests.* mypy override, and
pytest in the mypy pre-commit hook deps so the tests/ package type-checks.

* feat: add --mount and large-target pre-flight for local repos (#492)

Large local targets were copied into the sandbox file-by-file via the SDK
LocalDir entry, which stalls on big repos and could leave /workspace empty.

- --mount <path> bind-mounts a host directory read-only at /workspace/<subdir>
  instead of copying it, bypassing the per-file stream.
- A size pre-flight (STRIX_MAX_LOCAL_COPY_MB, default 1024) fails fast with a
  clear message suggesting --mount when a non-mounted local target is too big.

* fix: reject empty --mount paths

An empty or whitespace-only --mount value resolves to the current working
directory and would silently bind-mount it into the sandbox. Reject it.

* fix: dedupe local targets so a dir is never both copied and mounted

If the same directory is passed via --target and --mount (or as duplicate
values), it previously produced two targets — copied AND bind-mounted, and
the copied one could trip the size pre-flight. Dedupe by resolved path,
preferring the bind mount.

* fix: treat non-positive STRIX_MAX_LOCAL_COPY_MB as disabled

Previously a value of 0 (or negative) made every local target count as
oversized, aborting all local scans. Now <= 0 disables the pre-flight.

* fix: log unreadable subtrees during size pre-flight

os.walk silently swallowed directory-listing errors, so a permission-denied
subtree could make a large repo under-count and slip past the pre-flight.
Surface such omissions via an onerror warning.

* docs: document --mount and STRIX_MAX_LOCAL_COPY_MB

Add CLI reference + example for --mount, document the size pre-flight env var,
note the read-only-is-not-a-hard-boundary caveat and that remote repos are not
size-checked, and clarify the backends docstring on when bind mounts apply.

* Update strix/interface/main.py


* Update strix/runtime/docker_client.py


---------

docs/advanced/configuration.mdx

@@ -79,6 +79,10 @@ When remote vars are set, Strix dual-writes telemetry to both local JSONL and th
   Runtime backend for the sandbox environment.
 </ParamField>
 
+<ParamField path="STRIX_MAX_LOCAL_COPY_MB" default="1024" type="integer">
+  Maximum size (in MB) of a local directory target that Strix will copy into the sandbox file-by-file. Larger targets exit early with a suggestion to use `--mount` instead. Set to `0` to disable the check.
+</ParamField>
+
 ## Sandbox Configuration
 
 <ParamField path="STRIX_SANDBOX_EXECUTION_TIMEOUT" default="120" type="integer">

docs/usage/cli.mdx

@@ -15,6 +15,20 @@ strix --target <target> [options]
   Target to test. Accepts URLs, repositories, local directories, domains, or IP addresses. Can be specified multiple times.
 </ParamField>
 
+<ParamField path="--mount" type="string">
+  Bind-mount a local directory into the sandbox (read-only) instead of copying it in file-by-file. Use this for large repositories that are too big to stream into the container. Can be specified multiple times.
+
+  Strix copies local `--target` directories into the sandbox one file at a time, which stalls on very large trees. When a local target exceeds the copy limit (see `STRIX_MAX_LOCAL_COPY_MB`, default 1024 MB) Strix exits early and asks you to re-run with `--mount`.
+
+  <Note>
+    The mount is read-only to protect your source from accidental modification. This is not a hard security boundary: a root process inside the container can remount it writable, so treat `--mount` as "scan my own code", not as isolation from untrusted code.
+  </Note>
+
+  <Note>
+    The size pre-flight only covers local directory targets. Remote repositories (cloned at scan time) are not size-checked.
+  </Note>
+</ParamField>
+
 <ParamField path="--instruction" type="string">
   Custom instructions for the scan. Use for credentials, focus areas, or specific testing approaches.
 </ParamField>
@@ -81,6 +95,9 @@ strix -n --target ./ --scan-mode quick --scope-mode diff --diff-base origin/main
 
 # Multi-target white-box testing
 strix -t https://github.com/org/app -t https://staging.example.com
+
+# Large local repository — bind-mount instead of copying it in
+strix --mount ./huge-monorepo
 ```
 
 ## Exit Codes

strix/config/settings.py

@@ -47,6 +47,11 @@ class RuntimeSettings(BaseSettings):
         alias="STRIX_IMAGE",
     )
     backend: str = Field(default="docker", alias="STRIX_RUNTIME_BACKEND")
+    # Hard cap on a local target's size before we refuse to stream it into the
+    # sandbox file-by-file (the SDK copies every file individually, which stalls
+    # on large repos). Above this, the user must bind-mount via ``--mount``.
+    # Set to 0 (or less) to disable the pre-flight check entirely.
+    max_local_copy_mb: int = Field(default=1024, alias="STRIX_MAX_LOCAL_COPY_MB")
 
 
 class TelemetrySettings(BaseSettings):

strix/core/inputs.py

@@ -44,7 +44,8 @@ def build_root_task(scan_config: dict[str, Any]) -> str:
             )
         elif ttype == "local_code":
             path = details.get("target_path", "unknown")
-            sections["Local Codebases"].append(f"- {path} (available at: {workspace_path})")
+            suffix = ", read-only mount" if details.get("mount") else ""
+            sections["Local Codebases"].append(f"- {path} (available at: {workspace_path}{suffix})")
         elif ttype == "web_application":
             sections["URLs"].append(f"- {details.get('target_url', '')}")
         elif ttype == "ip_address":

strix/core/runner.py

@@ -55,7 +55,7 @@ async def run_strix_scan(
     scan_config: dict[str, Any],
     scan_id: str | None = None,
     image: str,
-    local_sources: list[dict[str, str]] | None = None,
+    local_sources: list[dict[str, Any]] | None = None,
     coordinator: AgentCoordinator | None = None,
     interactive: bool = False,
     max_turns: int = DEFAULT_MAX_TURNS,

strix/interface/main.py

@@ -33,9 +33,12 @@ from strix.interface.tui import run_tui
 from strix.interface.utils import (
     assign_workspace_subdirs,
     build_final_stats_text,
+    build_mount_targets_info,
     check_docker_connection,
     clone_repository,
     collect_local_sources,
+    dedupe_local_targets,
+    find_oversized_local_targets,
     generate_run_name,
     image_exists,
     infer_target_type,
@@ -328,6 +331,9 @@ Examples:
   # Local code analysis
   strix --target ./my-project
 
+  # Large local repository (bind-mounted read-only instead of copied)
+  strix --mount ./huge-monorepo
+
   # Domain penetration test
   strix --target example.com
 
@@ -363,6 +369,15 @@ Examples:
         "Can be specified multiple times for multi-target scans. "
         "Required for fresh runs; loaded from disk when ``--resume`` is set.",
     )
+    parser.add_argument(
+        "--mount",
+        type=str,
+        action="append",
+        metavar="PATH",
+        help="Bind-mount a local directory into the sandbox (read-only) instead of "
+        "copying it file-by-file. Use this for large repositories that are too big to "
+        "stream into the container. Can be specified multiple times.",
+    )
     parser.add_argument(
         "--instruction",
         type=str,
@@ -473,9 +488,9 @@ Examples:
     args.user_explicit_instruction = args.instruction if args.resume else None
 
     if args.resume:
-        if args.target:
+        if args.target or args.mount:
             parser.error(
-                "Cannot combine --resume with --target. --resume picks up where "
+                "Cannot combine --resume with --target/--mount. --resume picks up where "
                 "the prior run left off, including the original target list."
             )
         _load_resume_state(args, parser)
@@ -488,13 +503,13 @@ Examples:
                 f"or remove --resume to start over with the same targets."
             )
     else:
-        if not args.target:
+        if not args.target and not args.mount:
             parser.error(
-                "the following arguments are required: -t/--target "
+                "the following arguments are required: -t/--target or --mount "
                 "(or use --resume <run_name> to continue a prior scan)"
             )
         args.targets_info = []
-        for target in args.target:
+        for target in args.target or []:
             try:
                 target_type, target_dict = infer_target_type(target)
 
@@ -509,9 +524,30 @@ Examples:
             except ValueError:
                 parser.error(f"Invalid target '{target}'")
 
+        try:
+            args.targets_info.extend(build_mount_targets_info(args.mount or []))
+        except ValueError as e:
+            parser.error(str(e))
+
+        args.targets_info = dedupe_local_targets(args.targets_info)
+
         assign_workspace_subdirs(args.targets_info)
         rewrite_localhost_targets(args.targets_info, HOST_GATEWAY_HOSTNAME)
 
+        max_local_copy_mb = load_settings().runtime.max_local_copy_mb
+        max_copy_bytes = max_local_copy_mb * 1024 * 1024
+        oversized = find_oversized_local_targets(args.targets_info, max_copy_bytes)
+        if oversized:
+            details = "; ".join(
+                f"{path} ({size / (1024 * 1024):.0f} MB)" for path, size in oversized
+            )
+            parser.error(
+                f"Local target too large to stream into the sandbox: {details}. "
+                f"The limit is {max_local_copy_mb} MB "
+                "(set STRIX_MAX_LOCAL_COPY_MB to change it). Re-run with "
+                "--mount <path> to bind-mount the directory instead of copying it."
+            )
+
     return args
 
 

strix/interface/utils.py

@@ -1,5 +1,6 @@
 import ipaddress
 import json
+import logging
 import os
 import re
 import secrets
@@ -23,6 +24,9 @@ from rich.text import Text
 from strix.config import load_settings
 
 
+logger = logging.getLogger(__name__)
+
+
 def get_severity_color(severity: str) -> str:
     severity_colors = {
         "critical": "#dc2626",
@@ -1185,8 +1189,8 @@ def is_whitebox_scan(targets_info: list[dict[str, Any]]) -> bool:
     return any(t.get("type") == "local_code" for t in targets_info or [])
 
 
-def collect_local_sources(targets_info: list[dict[str, Any]]) -> list[dict[str, str]]:
-    local_sources: list[dict[str, str]] = []
+def collect_local_sources(targets_info: list[dict[str, Any]]) -> list[dict[str, Any]]:
+    local_sources: list[dict[str, Any]] = []
 
     for target_info in targets_info:
         details = target_info["details"]
@@ -1197,6 +1201,7 @@ def collect_local_sources(targets_info: list[dict[str, Any]]) -> list[dict[str,
                 {
                     "source_path": details["target_path"],
                     "workspace_subdir": workspace_subdir,
+                    "mount": bool(details.get("mount", False)),
                 }
             )
 
@@ -1205,12 +1210,126 @@ def collect_local_sources(targets_info: list[dict[str, Any]]) -> list[dict[str,
                 {
                     "source_path": details["cloned_repo_path"],
                     "workspace_subdir": workspace_subdir,
+                    "mount": False,
                 }
             )
 
     return local_sources
 
 
+def directory_size_bytes(path: Path) -> int:
+    """Total size in bytes of regular files under ``path`` (symlinks not followed).
+
+    Best-effort: files that disappear or can't be stat'd mid-walk are skipped.
+    Used as a cheap (stat-only) pre-flight to estimate the cost of streaming a
+    local target into the sandbox before we actually try to copy it.
+
+    Directories that can't be listed (e.g. permission denied) are logged and
+    skipped rather than silently dropped — so an under-count is at least
+    visible — but the returned total then excludes their contents.
+    """
+
+    def _on_walk_error(error: OSError) -> None:
+        logger.warning("Could not read %s while measuring size: %s", error.filename, error)
+
+    total = 0
+    for root, _dirs, files in os.walk(path, followlinks=False, onerror=_on_walk_error):
+        for name in files:
+            file_path = os.path.join(root, name)  # noqa: PTH118
+            try:
+                if os.path.islink(file_path):  # noqa: PTH114
+                    continue
+                total += os.path.getsize(file_path)  # noqa: PTH202
+            except OSError:
+                continue
+    return total
+
+
+def find_oversized_local_targets(
+    targets_info: list[dict[str, Any]], max_bytes: int
+) -> list[tuple[str, int]]:
+    """Return ``(path, size_bytes)`` for non-mounted local targets over ``max_bytes``.
+
+    Mounted targets are bind-mounted rather than copied, so their size is
+    irrelevant and they are excluded. A ``max_bytes`` of zero or less disables
+    the check entirely (returns no targets).
+    """
+    if max_bytes <= 0:
+        return []
+    oversized: list[tuple[str, int]] = []
+    for target in targets_info:
+        if target.get("type") != "local_code":
+            continue
+        details = target.get("details") or {}
+        if details.get("mount"):
+            continue
+        target_path = details.get("target_path")
+        if not target_path:
+            continue
+        size = directory_size_bytes(Path(target_path))
+        if size > max_bytes:
+            oversized.append((target_path, size))
+    return oversized
+
+
+def build_mount_targets_info(mount_paths: list[str]) -> list[dict[str, Any]]:
+    """Build ``targets_info`` entries for ``--mount`` directories.
+
+    Each path must be an existing local directory; it is bind-mounted into the
+    sandbox (read-only) instead of being copied file-by-file. Raises
+    ``ValueError`` for an empty path, or one that does not exist or is not a
+    directory.
+    """
+    targets_info: list[dict[str, Any]] = []
+    for raw in mount_paths:
+        if not raw or not raw.strip():
+            raise ValueError("--mount path must not be empty.")
+        path = Path(raw).expanduser()
+        try:
+            resolved = path.resolve()
+            is_dir = resolved.is_dir()
+        except (OSError, RuntimeError) as e:
+            raise ValueError(f"Invalid mount path '{raw}': {e!s}") from e
+        if not is_dir:
+            raise ValueError(
+                f"Mount path '{raw}' is not an existing directory. "
+                "--mount requires a path to a local directory."
+            )
+        targets_info.append(
+            {
+                "type": "local_code",
+                "details": {"target_path": str(resolved), "mount": True},
+                "original": str(resolved),
+            }
+        )
+    return targets_info
+
+
+def dedupe_local_targets(targets_info: list[dict[str, Any]]) -> list[dict[str, Any]]:
+    """Collapse local_code targets that resolve to the same path.
+
+    When a directory is supplied both as a copied ``--target`` and via
+    ``--mount`` (or as duplicate values of either), keep one entry and prefer
+    the bind-mounted one — so the same tree is never both streamed in and
+    mounted. Order is preserved; non-local targets pass through untouched.
+    """
+    result: list[dict[str, Any]] = []
+    index_by_path: dict[str, int] = {}
+    for target in targets_info:
+        details = target.get("details") or {}
+        path = details.get("target_path")
+        if target.get("type") != "local_code" or not path:
+            result.append(target)
+            continue
+        existing = index_by_path.get(path)
+        if existing is None:
+            index_by_path[path] = len(result)
+            result.append(target)
+        elif details.get("mount") and not (result[existing].get("details") or {}).get("mount"):
+            result[existing] = target  # bind mount supersedes the copied entry
+    return result
+
+
 def _is_localhost_host(host: str) -> bool:
     host_lower = host.lower().strip("[]")
 

strix/runtime/backends.py

@@ -22,6 +22,7 @@ async def _docker_backend(
     image: str,
     manifest: Manifest,
     exposed_ports: tuple[int, ...],
+    bind_mounts: list[dict[str, Any]] | None = None,
 ) -> tuple[Any, Any]:
     """Bring up a session backed by the local Docker daemon.
 
@@ -31,11 +32,15 @@ async def _docker_backend(
     backend don't need the docker-py library installed.
 
     ``session.start()`` is what materializes the manifest entries
-    (LocalDir copies, mount setup, etc.) into the running container —
-    the SDK's ``client.create()`` only builds the inner session object
-    without applying the manifest. ``async with session:`` would call it
-    too, but Strix manages session lifetime explicitly via
+    (LocalDir copies and manifest-declared volume/FUSE mounts) into the
+    running container — the SDK's ``client.create()`` only builds the inner
+    session object without applying the manifest. ``async with session:``
+    would call it too, but Strix manages session lifetime explicitly via
     ``client.delete()`` so we trigger ``start()`` ourselves.
+
+    ``bind_mounts`` are host directories (e.g. large repos passed via
+    ``--mount``) bind-mounted read-only; unlike manifest entries they are
+    applied by Docker at container-create time, not by ``start()``.
     """
     import docker
     from agents.sandbox.sandboxes.docker import DockerSandboxClientOptions
@@ -43,6 +48,7 @@ async def _docker_backend(
     from strix.runtime.docker_client import StrixDockerSandboxClient
 
     client = StrixDockerSandboxClient(docker.from_env())
+    client.strix_bind_mounts = bind_mounts or []
     options = DockerSandboxClientOptions(image=image, exposed_ports=exposed_ports)
     session = await client.create(options=options, manifest=manifest)
     await session.start()

strix/runtime/docker_client.py

@@ -38,6 +38,7 @@ from agents.sandbox.sandboxes.docker import (
 from agents.sandbox.session.sandbox_session import SandboxSession
 from docker import errors as docker_errors  # type: ignore[import-untyped, unused-ignore]
 from docker.models.containers import Container  # type: ignore[import-untyped, unused-ignore]
+from docker.types import Mount as DockerSDKMount  # type: ignore[import-untyped, unused-ignore]
 from docker.utils import parse_repository_tag  # type: ignore[import-untyped, unused-ignore]
 
 
@@ -45,6 +46,10 @@ logger = logging.getLogger(__name__)
 
 
 class StrixDockerSandboxClient(DockerSandboxClient):
+    # Host directories to bind-mount into the container, set by the docker
+    # backend before ``create()``. Each item is ``{source, target, read_only}``.
+    strix_bind_mounts: list[dict[str, Any]] = []  # overridden per-instance in backends.py
+
     async def _create_container(
         self,
         image: str,
@@ -111,6 +116,21 @@ class StrixDockerSandboxClient(DockerSandboxClient):
         extra_hosts = create_kwargs.setdefault("extra_hosts", {})
         extra_hosts["host.docker.internal"] = "host-gateway"
 
+        # Strix injection: host bind mounts (e.g. large repos passed via --mount)
+        # that bypass the SDK's file-by-file LocalDir copy.
+        bind_mounts = getattr(self, "strix_bind_mounts", ())
+        if bind_mounts:
+            mounts = create_kwargs.setdefault("mounts", [])
+            for spec in bind_mounts:
+                mounts.append(
+                    DockerSDKMount(
+                        target=spec["target"],
+                        source=spec["source"],
+                        type="bind",
+                        read_only=spec.get("read_only", True),
+                    )
+                )
+
         logger.debug(
             "Creating sandbox container: image=%s caps=%s exposed_ports=%s",
             image,

strix/runtime/session_manager.py

@@ -23,30 +23,59 @@ _CONTAINER_CAIDO_PORT = 48080
 
 _SESSION_CACHE: dict[str, dict[str, Any]] = {}
 
+# Manifest root inside the container; entry keys hang off this path.
+_WORKSPACE_ROOT = "/workspace"
+
+
+def build_session_entries(
+    local_sources: list[dict[str, Any]],
+) -> tuple[dict[str | Path, BaseEntry], list[dict[str, Any]]]:
+    """Split local sources into copied manifest entries and host bind mounts.
+
+    Sources flagged ``mount`` are bind-mounted read-only at
+    ``/workspace/<workspace_subdir>`` (not added to the manifest, so the SDK
+    does not stream them in file-by-file). Every other source becomes a
+    ``LocalDir`` entry copied into the container as before.
+    """
+    entries: dict[str | Path, BaseEntry] = {}
+    bind_mounts: list[dict[str, Any]] = []
+    for src in local_sources:
+        ws_subdir = src.get("workspace_subdir") or ""
+        host_path = src.get("source_path") or ""
+        if not ws_subdir or not host_path:
+            continue
+        resolved = Path(host_path).expanduser().resolve()
+        if src.get("mount"):
+            bind_mounts.append(
+                {
+                    "source": str(resolved),
+                    "target": f"{_WORKSPACE_ROOT}/{ws_subdir}",
+                    "read_only": True,
+                }
+            )
+        else:
+            entries[ws_subdir] = LocalDir(src=resolved)
+    return entries, bind_mounts
+
 
 async def create_or_reuse(
     scan_id: str,
     *,
     image: str,
-    local_sources: list[dict[str, str]],
+    local_sources: list[dict[str, Any]],
 ) -> dict[str, Any]:
     """Return the existing session bundle for ``scan_id`` or create a new one.
 
-    Each ``local_sources`` entry mounts its host ``source_path`` at
-    ``/workspace/<workspace_subdir>`` inside the container.
+    Each ``local_sources`` entry exposes its host ``source_path`` at
+    ``/workspace/<workspace_subdir>`` inside the container — copied in, or
+    bind-mounted read-only when the entry is flagged ``mount``.
     """
     cached = _SESSION_CACHE.get(scan_id)
     if cached is not None:
         logger.info("Reusing existing sandbox session for scan %s", scan_id)
         return cached
 
-    entries: dict[str | Path, BaseEntry] = {}
-    for src in local_sources:
-        ws_subdir = src.get("workspace_subdir") or ""
-        host_path = src.get("source_path") or ""
-        if not ws_subdir or not host_path:
-            continue
-        entries[ws_subdir] = LocalDir(src=Path(host_path).expanduser().resolve())
+    entries, bind_mounts = build_session_entries(local_sources)
 
     # Caido runs as an in-container sidecar; HTTP(S) traffic from any
     # process started via ``session.exec`` (the SDK's Shell tool, etc.)
@@ -81,6 +110,7 @@ async def create_or_reuse(
         image=image,
         manifest=manifest,
         exposed_ports=(_CONTAINER_CAIDO_PORT,),
+        bind_mounts=bind_mounts,
     )
 
     caido_endpoint = await session.resolve_exposed_port(_CONTAINER_CAIDO_PORT)

tests/test_local_sources.py

@@ -0,0 +1,188 @@
+"""Tests for local-source sizing and ``--mount`` target helpers in interface.utils."""
+
+from __future__ import annotations
+
+import logging
+import os
+import sys
+from typing import TYPE_CHECKING, Any
+
+import pytest
+
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+from strix.interface.utils import (
+    build_mount_targets_info,
+    collect_local_sources,
+    dedupe_local_targets,
+    directory_size_bytes,
+    find_oversized_local_targets,
+)
+
+
+def _write_file(path: Path, size: int) -> None:
+    path.write_bytes(b"x" * size)
+
+
+def _local_target(target_path: str, *, mount: bool = False) -> dict[str, Any]:
+    details: dict[str, Any] = {"target_path": target_path, "workspace_subdir": "repo"}
+    if mount:
+        details["mount"] = True
+    return {"type": "local_code", "details": details, "original": target_path}
+
+
+def test_directory_size_empty_dir_is_zero(tmp_path: Path) -> None:
+    assert directory_size_bytes(tmp_path) == 0
+
+
+def test_directory_size_sums_flat_and_nested_files(tmp_path: Path) -> None:
+    _write_file(tmp_path / "a.txt", 100)
+    nested = tmp_path / "sub" / "deep"
+    nested.mkdir(parents=True)
+    _write_file(nested / "b.txt", 250)
+    assert directory_size_bytes(tmp_path) == 350
+
+
+def test_directory_size_skips_symlinks(tmp_path: Path) -> None:
+    _write_file(tmp_path / "real.txt", 100)
+    (tmp_path / "link.txt").symlink_to(tmp_path / "real.txt")
+    # The symlink target is counted once via the real file, not doubled.
+    assert directory_size_bytes(tmp_path) == 100
+
+
+@pytest.mark.skipif(sys.platform == "win32", reason="relies on POSIX permissions")
+def test_directory_size_logs_and_skips_unreadable_subdir(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    if hasattr(os, "geteuid") and os.geteuid() == 0:
+        pytest.skip("root bypasses directory permissions")
+    _write_file(tmp_path / "top.txt", 100)
+    locked = tmp_path / "locked"
+    locked.mkdir()
+    _write_file(locked / "secret.bin", 9999)
+    locked.chmod(0o000)
+    try:
+        with caplog.at_level(logging.WARNING):
+            size = directory_size_bytes(tmp_path)
+    finally:
+        locked.chmod(0o755)
+    # The unreadable subtree is excluded (not silently treated as readable) and
+    # the omission is logged rather than vanishing without a trace.
+    assert size == 100
+    assert any("Could not read" in record.message for record in caplog.records)
+
+
+def test_find_oversized_returns_nothing_under_limit(tmp_path: Path) -> None:
+    _write_file(tmp_path / "a.txt", 100)
+    targets = [_local_target(str(tmp_path))]
+    assert find_oversized_local_targets(targets, max_bytes=1000) == []
+
+
+def test_find_oversized_returns_target_over_limit(tmp_path: Path) -> None:
+    _write_file(tmp_path / "big.bin", 500)
+    targets = [_local_target(str(tmp_path))]
+    result = find_oversized_local_targets(targets, max_bytes=100)
+    assert result == [(str(tmp_path), 500)]
+
+
+def test_find_oversized_ignores_mounted_targets(tmp_path: Path) -> None:
+    _write_file(tmp_path / "big.bin", 500)
+    targets = [_local_target(str(tmp_path), mount=True)]
+    assert find_oversized_local_targets(targets, max_bytes=100) == []
+
+
+def test_find_oversized_ignores_non_local_targets() -> None:
+    targets = [{"type": "web_application", "details": {"target_url": "https://x"}}]
+    assert find_oversized_local_targets(targets, max_bytes=1) == []
+
+
+@pytest.mark.parametrize("disabled", [0, -1])
+def test_find_oversized_disabled_for_non_positive_limit(tmp_path: Path, disabled: int) -> None:
+    _write_file(tmp_path / "big.bin", 500)
+    targets = [_local_target(str(tmp_path))]
+    assert find_oversized_local_targets(targets, max_bytes=disabled) == []
+
+
+def test_collect_local_sources_propagates_mount_flag() -> None:
+    copied = _local_target("/copied")
+    copied["details"]["workspace_subdir"] = "copied"
+    mounted = _local_target("/mounted", mount=True)
+    mounted["details"]["workspace_subdir"] = "mounted"
+
+    sources = collect_local_sources([copied, mounted])
+
+    by_path = {s["source_path"]: s for s in sources}
+    assert by_path["/copied"]["mount"] is False
+    assert by_path["/mounted"]["mount"] is True
+
+
+def test_collect_local_sources_repository_is_never_mounted() -> None:
+    repo = {
+        "type": "repository",
+        "details": {"cloned_repo_path": "/clone", "workspace_subdir": "clone"},
+    }
+    sources = collect_local_sources([repo])
+    assert sources == [{"source_path": "/clone", "workspace_subdir": "clone", "mount": False}]
+
+
+def test_build_mount_targets_info_for_valid_dir(tmp_path: Path) -> None:
+    result = build_mount_targets_info([str(tmp_path)])
+    assert len(result) == 1
+    entry = result[0]
+    assert entry["type"] == "local_code"
+    assert entry["details"]["mount"] is True
+    assert entry["details"]["target_path"] == str(tmp_path.resolve())
+
+
+def test_build_mount_targets_info_rejects_missing_path(tmp_path: Path) -> None:
+    missing = tmp_path / "does-not-exist"
+    with pytest.raises(ValueError, match="not an existing directory"):
+        build_mount_targets_info([str(missing)])
+
+
+def test_build_mount_targets_info_rejects_file(tmp_path: Path) -> None:
+    file_path = tmp_path / "a-file.txt"
+    _write_file(file_path, 10)
+    with pytest.raises(ValueError, match="not an existing directory"):
+        build_mount_targets_info([str(file_path)])
+
+
+@pytest.mark.parametrize("empty", ["", "   "])
+def test_build_mount_targets_info_rejects_empty_path(empty: str) -> None:
+    # An empty path would otherwise resolve to the current working directory
+    # and silently bind-mount it into the sandbox.
+    with pytest.raises(ValueError, match="must not be empty"):
+        build_mount_targets_info([empty])
+
+
+def test_dedupe_keeps_distinct_targets_in_order() -> None:
+    targets = [
+        _local_target("/a"),
+        {"type": "web_application", "details": {"target_url": "https://x"}},
+        _local_target("/b", mount=True),
+    ]
+    assert dedupe_local_targets(targets) == targets
+
+
+def test_dedupe_mount_supersedes_copied_same_path() -> None:
+    copied = _local_target("/repo")
+    mounted = _local_target("/repo", mount=True)
+
+    # Copied first, then mounted: the single surviving entry is the mount.
+    result = dedupe_local_targets([copied, mounted])
+    assert len(result) == 1
+    assert result[0]["details"]["mount"] is True
+
+    # Order-independent: mounted first, copied second also yields the mount.
+    result_rev = dedupe_local_targets([mounted, copied])
+    assert len(result_rev) == 1
+    assert result_rev[0]["details"]["mount"] is True
+
+
+def test_dedupe_collapses_duplicate_mounts() -> None:
+    result = dedupe_local_targets(
+        [_local_target("/repo", mount=True), _local_target("/repo", mount=True)]
+    )
+    assert len(result) == 1

tests/test_session_entries.py

@@ -0,0 +1,67 @@
+"""Tests for build_session_entries: splitting copied vs bind-mounted sources."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any
+
+from agents.sandbox.entries import LocalDir
+
+from strix.runtime.session_manager import build_session_entries
+
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
+def _source(subdir: str, path: str, *, mount: bool = False) -> dict[str, Any]:
+    return {"source_path": path, "workspace_subdir": subdir, "mount": mount}
+
+
+def test_copied_source_becomes_localdir_entry(tmp_path: Path) -> None:
+    entries, bind_mounts = build_session_entries([_source("repo", str(tmp_path))])
+
+    assert bind_mounts == []
+    assert isinstance(entries["repo"], LocalDir)
+    assert entries["repo"].src == tmp_path.resolve()
+
+
+def test_mounted_source_becomes_bind_mount(tmp_path: Path) -> None:
+    entries, bind_mounts = build_session_entries([_source("repo", str(tmp_path), mount=True)])
+
+    assert entries == {}
+    assert bind_mounts == [
+        {
+            "source": str(tmp_path.resolve()),
+            "target": "/workspace/repo",
+            "read_only": True,
+        }
+    ]
+
+
+def test_mixed_sources_split_correctly(tmp_path: Path) -> None:
+    copied = tmp_path / "copied"
+    mounted = tmp_path / "mounted"
+    copied.mkdir()
+    mounted.mkdir()
+
+    entries, bind_mounts = build_session_entries(
+        [
+            _source("copied", str(copied)),
+            _source("mounted", str(mounted), mount=True),
+        ]
+    )
+
+    assert list(entries) == ["copied"]
+    assert isinstance(entries["copied"], LocalDir)
+    assert [m["target"] for m in bind_mounts] == ["/workspace/mounted"]
+
+
+def test_incomplete_sources_are_skipped() -> None:
+    entries, bind_mounts = build_session_entries(
+        [
+            {"source_path": "", "workspace_subdir": "x"},
+            {"source_path": "/p", "workspace_subdir": ""},
+        ]
+    )
+    assert entries == {}
+    assert bind_mounts == []