fix: harden runtime config lease identity publication

backend/test/workspace-runtime-config-lease.test.ts

@@ -1,5 +1,5 @@
 import { test, expect } from "vitest";
-import { chmodSync, existsSync, lstatSync, mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { chmodSync, existsSync, lstatSync, mkdirSync, mkdtempSync, readFileSync, readdirSync, renameSync, rmSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { dirname, join } from "node:path";
 import { execFileSync } from "node:child_process";
@@ -32,7 +32,7 @@ llm_policy:
   allowed: [zai/glm-5.2]
 `;
 
-function fixture() {
+function fixture(extraEnv: Record<string, string> = {}) {
   const root = mkdtempSync(join(tmpdir(), "runtime-config-lease-"));
   const canonicalDescriptor = serializeWorkspaceYaml(parseWorkspaceYaml(descriptor));
   const snapshots = join(root, "snapshots");
@@ -73,13 +73,13 @@ function fixture() {
     env: {
       THT_WS_ABC_DWH_TRANSPORT: "postgres_direct", THT_WS_ABC_DWH_HOST: "dwh",
       THT_WS_ABC_DWH_PORT: "5432", THT_WS_ABC_DWH_USER: "reader",
-      THT_WS_ABC_DWH_PASSWORD_FILE: secret,
+      THT_WS_ABC_DWH_PASSWORD_FILE: secret, ...extraEnv,
     }, secretRoots: [root], semanticRuntime: {
       internalQdrantUrl: "http://qdrant:6333", internalEmbeddingUrl: "http://embedding:11434",
       internalEmbeddingModel: "qwen3-embedding:0.6b", internalEmbeddingDimensions: 1024,
     },
   });
-  return { root, snapshotPath, factory, canonicalDescriptor };
+  return { root, repo, snapshotPath, factory, canonicalDescriptor, snapshotManifest: join(snapshotsDir, "snapshot.json") };
 }
 
 test("session and maintenance share deterministic bytes and path", () => {
@@ -141,3 +141,113 @@ test("same-byte replacement of the registry descriptor is refused", () => {
     first.release();
   } finally { rmSync(f.root, { recursive: true, force: true }); }
 });
+
+
+test("manifest binds the complete canonical destination directory chain", () => {
+  const f = fixture();
+  try {
+    const lease = f.factory.acquireSession(f.snapshotPath);
+    const manifest = JSON.parse(readFileSync(lease.manifestPath, "utf8"));
+    expect(manifest.directory_identities.length).toBeGreaterThan(5);
+    expect(manifest.directory_identities.map((entry: { path: string }) => entry.path)).toContain(
+      `${process.platform === "darwin" ? "/private" : ""}${join(f.root, "data", "sessions", workspace, "preprocessing")}`,
+    );
+    expect(manifest.directory_identities.every((entry: Record<string, string>) =>
+      ["path", "dev", "ino", "mode", "uid"].every((key) => typeof entry[key] === "string"),
+    )).toBe(true);
+  } finally { rmSync(f.root, { recursive: true, force: true }); }
+});
+
+test("raw Git identity ignores replacement refs", () => {
+  const f = fixture();
+  try {
+    const evil = f.canonicalDescriptor.replace("database: analytics", "database: evil");
+    chmodSync(join(f.repo, "workspaces", `${workspace}.yaml`), 0o600);
+    writeFileSync(join(f.repo, "workspaces", `${workspace}.yaml`), evil);
+    execFileSync("git", ["add", "."], { cwd: f.repo });
+    execFileSync("git", ["commit", "-m", "evil"], { cwd: f.repo });
+    const evilCommit = execFileSync("git", ["rev-parse", "HEAD"], { cwd: f.repo, encoding: "utf8" }).trim();
+    const oldCommit = JSON.parse(readFileSync(f.snapshotManifest, "utf8")).head;
+    execFileSync("git", ["replace", oldCommit, evilCommit], { cwd: f.repo });
+    chmodSync(f.snapshotPath, 0o600);
+    writeFileSync(f.snapshotPath, evil);
+    chmodSync(f.snapshotPath, 0o400);
+    const snapshot = JSON.parse(readFileSync(f.snapshotManifest, "utf8"));
+    snapshot.files[`${workspace}.yaml`] = createHash("sha256").update(evil).digest("hex");
+    chmodSync(f.snapshotManifest, 0o600);
+    writeFileSync(f.snapshotManifest, JSON.stringify(snapshot));
+    chmodSync(f.snapshotManifest, 0o400);
+    expect(() => f.factory.acquireSession(f.snapshotPath)).toThrow(/Git descriptor|integrity|identity/i);
+  } finally { rmSync(f.root, { recursive: true, force: true }); }
+});
+
+test("replacement of canonical destination directories is refused", () => {
+  const f = fixture();
+  try {
+    const lease = f.factory.acquireSession(f.snapshotPath);
+    const original = join(f.root, "data", "sessions", workspace);
+    const moved = `${original}.moved`;
+    renameSync(original, moved);
+    mkdirSync(join(original, "preprocessing", "runtime-config"), { recursive: true, mode: 0o700 });
+    mkdirSync(join(original, "preprocessing", "runtime-config-manifests"), { recursive: true, mode: 0o700 });
+    renameSync(join(moved, "preprocessing", "runtime-config", `${lease.workspaceRevision}.yaml`), join(original, "preprocessing", "runtime-config", `${lease.workspaceRevision}.yaml`));
+    renameSync(join(moved, "preprocessing", "runtime-config-manifests", `${lease.workspaceRevision}.json`), join(original, "preprocessing", "runtime-config-manifests", `${lease.workspaceRevision}.json`));
+    expect(() => f.factory.acquireSession(f.snapshotPath)).toThrow(/changed|mismatch|same-revision|identity|trusted/i);
+  } finally { rmSync(f.root, { recursive: true, force: true }); }
+});
+
+test("rename faults fail closed and remove staging files", () => {
+  const f = fixture({ THT_RUNTIME_CONFIG_RENAME_FAIL: "1" });
+  try {
+    expect(() => f.factory.acquireSession(f.snapshotPath)).toThrow(/rename|failed/i);
+    const runtime = join(f.root, "data", "sessions", workspace, "preprocessing");
+    for (const dir of ["runtime-config", "runtime-config-manifests"]) {
+      if (existsSync(join(runtime, dir))) expect(readdirSync(join(runtime, dir)).filter((name) => name.includes("staging")).length).toBe(0);
+    }
+  } finally { rmSync(f.root, { recursive: true, force: true }); }
+});
+
+
+test("session and operator outputs retain normalized private-host policy and binding", () => {
+  const f = fixture({ THT_HTTP_PRIVATE_HOST_ALLOWLIST: "internal.example,warehouse.example" });
+  try {
+    const session = f.factory.acquireSession(f.snapshotPath);
+    const maintenance = f.factory.acquireMaintenance({ snapshotPath: f.snapshotPath });
+    const output = readFileSync(session.path, "utf8");
+    expect(output).toContain("http_private_host_allowlist");
+    expect(output).toContain("- internal.example");
+    expect(output).toContain("- warehouse.example");
+    expect(output).toBe(readFileSync(maintenance.path, "utf8"));
+    const manifest = JSON.parse(readFileSync(session.manifestPath, "utf8"));
+    expect(manifest.config_dwh_binding).toEqual({
+      workspace_id: expect.any(String), config_fingerprint: expect.any(String), input_fingerprint: expect.any(String),
+    });
+  } finally { rmSync(f.root, { recursive: true, force: true }); }
+});
+
+
+test("unexpected manifest fields are refused before handoff", () => {
+  const f = fixture();
+  try {
+    const lease = f.factory.acquireSession(f.snapshotPath);
+    const manifest = JSON.parse(readFileSync(lease.manifestPath, "utf8"));
+    manifest.unexpected = true;
+    chmodSync(lease.manifestPath, 0o600);
+    writeFileSync(lease.manifestPath, JSON.stringify(manifest));
+    expect(() => f.factory.acquireSession(f.snapshotPath)).toThrow(/manifest|invalid|changed/i);
+  } finally { rmSync(f.root, { recursive: true, force: true }); }
+});
+
+test("runtime config symlink replacement is refused", () => {
+  const f = fixture();
+  try {
+    const lease = f.factory.acquireSession(f.snapshotPath);
+    const replacement = `${lease.path}.real`;
+    writeFileSync(replacement, readFileSync(lease.path), { mode: 0o400 });
+    chmodSync(lease.path, 0o600);
+    rmSync(lease.path);
+    // A no-follow handoff must never consume this pathname.
+    execFileSync("ln", ["-s", replacement, lease.path]);
+    expect(() => f.factory.acquireSession(f.snapshotPath)).toThrow(/trusted|changed|configuration|symbolic/i);
+  } finally { rmSync(f.root, { recursive: true, force: true }); }
+});

harness/tht/config.py

@@ -599,10 +599,14 @@ def _strict_runtime_manifest(raw: object) -> dict[str, object]:
         "version", "workspace_id", "workspace_revision", "descriptor_git_blob",
         "descriptor_sha256", "descriptor_dev", "descriptor_ino", "config_sha256",
         "config_dwh_binding", "config_dev", "config_ino", "config_size", "config_mode",
-        "config_uid", "config_nlink",
+        "config_uid", "config_nlink", "directory_identities",
     }
     if not isinstance(raw, dict) or set(raw) != required or raw.get("version") != 1:
         raise ConfigError("Manifest runtime non valido")
+    if (not isinstance(raw.get("workspace_id"), str) or not re.fullmatch(r"[a-z][a-z0-9-]{2,62}", raw["workspace_id"])
+            or not isinstance(raw.get("workspace_revision"), str) or not re.fullmatch(r"[0-9a-f]{40}", raw["workspace_revision"])
+            or not isinstance(raw.get("descriptor_git_blob"), str) or not re.fullmatch(r"[0-9a-f]{40}", raw["descriptor_git_blob"])):
+        raise ConfigError("Manifest runtime non valido")
     if not isinstance(raw.get("config_dwh_binding"), dict):
         raise ConfigError("Manifest runtime non valido")
     binding = raw["config_dwh_binding"]
@@ -614,12 +618,88 @@ def _strict_runtime_manifest(raw: object) -> dict[str, object]:
     for key in ("descriptor_dev", "descriptor_ino", "config_dev", "config_ino", "config_size", "config_uid", "config_nlink"):
         if not isinstance(raw[key], str) or not raw[key].isdigit():
             raise ConfigError("Manifest runtime non valido")
+    identities = raw.get("directory_identities")
+    if (not isinstance(identities, list) or not identities or
+            any(not isinstance(item, dict) or set(item) != {"path", "dev", "ino", "mode", "uid"}
+                or not isinstance(item["path"], str) or not item["path"].startswith("/")
+                or any(not isinstance(item[key], str) or not item[key].isdigit()
+                       for key in ("dev", "ino", "mode", "uid"))
+                or item["mode"] == "0"
+                for item in identities)):
+        raise ConfigError("Manifest runtime non valido")
+    if len({item["path"] for item in identities}) != len(identities):
+        raise ConfigError("Manifest runtime non valido")
     if raw["config_mode"] != "400":
         raise ConfigError("Manifest runtime non valido")
     return raw
 
 
 
+def _canonical_runtime_path(path: Path) -> Path:
+    value = str(path)
+    if value == "/tmp" or value.startswith("/tmp/"):
+        return Path("/private" + value)
+    if value == "/var" or value.startswith("/var/"):
+        return Path("/private" + value)
+    return path
+
+
+def _runtime_directory_identities(paths: list[Path]) -> list[dict[str, str]]:
+    """Open/stat every directory component and return its current identity chain."""
+    out: list[dict[str, str]] = []
+    seen: set[str] = set()
+    for path in paths:
+        canonical = _canonical_runtime_path(path)
+        parts = list(canonical.parts)
+        if not parts or parts[0] != "/":
+            raise OSError("runtime config path is invalid")
+        current = "/"
+        components = ["/"] + parts[1:]
+        for component in components:
+            if component != "/":
+                current = current.rstrip("/") + "/" + component
+            # Re-open shared prefixes for each destination branch too: a
+            # replacement between config-parent and manifest-parent traversal
+            # must not be hidden by de-duplication.
+            # lstat before and fstat after open closes the stat/open replacement
+            # window for each component, including canonical destination parents.
+            parent = os.open("/", os.O_RDONLY | getattr(os, "O_DIRECTORY", 0))
+            try:
+                for name in [part for part in Path(current).parts[1:-1]]:
+                    nxt = _open_runtime_component(parent, name)
+                    os.close(parent); parent = nxt
+                if current == "/":
+                    fd = os.dup(parent)
+                else:
+                    name = Path(current).name
+                    fd = _open_runtime_component(parent, name)
+                try:
+                    info = os.fstat(fd)
+                    if not stat.S_ISDIR(info.st_mode) or info.st_nlink < 1:
+                        raise OSError("unsafe runtime directory")
+                    identity = {"path": current, "dev": str(info.st_dev), "ino": str(info.st_ino),
+                                "mode": format(stat.S_IMODE(info.st_mode), "o"),
+                                "uid": str(info.st_uid)}
+                    if current in seen:
+                        previous = next(item for item in out if item["path"] == current)
+                        if identity != previous:
+                            raise OSError("runtime config directory changed")
+                    else:
+                        out.append(identity)
+                        seen.add(current)
+                finally:
+                    os.close(fd)
+            finally:
+                os.close(parent)
+    return out
+
+
+def _verify_runtime_directory_identities(config_path: Path, manifest_path: Path, expected: object) -> None:
+    current = _runtime_directory_identities([config_path.parent, manifest_path.parent])
+    if current != expected:
+        raise ConfigError("Destinazione config runtime modificata")
+
+
 def _open_runtime_component(parent: int, name: str) -> int:
     before = os.stat(name, dir_fd=parent, follow_symlinks=False)
     if stat.S_ISLNK(before.st_mode):
@@ -687,6 +767,7 @@ def load_config(path: Path) -> Config:
             if hashlib.sha256(manifest_bytes).hexdigest() != expected_manifest:
                 raise ConfigError("Manifest runtime modificato")
             runtime_manifest = _strict_runtime_manifest(json.loads(manifest_bytes.decode("utf-8")))
+            _verify_runtime_directory_identities(path, _runtime_manifest_path(path), runtime_manifest["directory_identities"])
             if (runtime_manifest["config_sha256"] != hashlib.sha256(config_bytes).hexdigest()
                     or int(runtime_manifest["config_dev"]) != config_info.st_dev
                     or int(runtime_manifest["config_ino"]) != config_info.st_ino
@@ -715,6 +796,7 @@ def load_config(path: Path) -> Config:
             if hashlib.sha256(manifest_bytes).hexdigest() != legacy_expected:
                 raise ConfigError("Manifest runtime modificato")
             runtime_manifest = _strict_runtime_manifest(json.loads(manifest_bytes.decode("utf-8")))
+            _verify_runtime_directory_identities(path, _runtime_manifest_path(path), runtime_manifest["directory_identities"])
             if (runtime_manifest["config_sha256"] != hashlib.sha256(config_bytes).hexdigest()
                     or int(runtime_manifest["config_dev"]) != config_info.st_dev
                     or int(runtime_manifest["config_ino"]) != config_info.st_ino

harness/tht/runtime_config_lease_io.py

@@ -2,10 +2,12 @@
 
 from __future__ import annotations
 
+import ctypes
 import fcntl
 import hashlib
 import json
 import os
+import platform
 import stat
 import subprocess
 import sys
@@ -17,6 +19,99 @@ def fail(msg: str) -> None:
     raise RuntimeError(msg)
 
 
+def _canonical_root(root: str) -> str:
+    # Darwin exposes /tmp and /var as symlink aliases.  The trusted path boundary
+    # records the real OS-owned prefix so a manifest never contains a symlink.
+    if root == "/tmp" or root.startswith("/tmp/"):
+        return "/private" + root
+    if root == "/var" or root.startswith("/var/"):
+        return "/private" + root
+    return root
+
+
+def _identity(st: os.stat_result, path: str) -> dict[str, str]:
+    return {"path": path, "dev": str(st.st_dev), "ino": str(st.st_ino),
+            "mode": format(stat.S_IMODE(st.st_mode), "o"), "uid": str(st.st_uid)}
+
+
+def _rename_noreplace(src: str, dst: str, directory_fd: int, kind: str) -> None:
+    """Atomically rename *src* to *dst* without replacing an existing entry.
+
+    ``link`` is deliberately not used here: the state-file protocol requires a
+    rename, and a hard-link publication leaves a second name visible during a
+    crash.  Unsupported platforms fail closed rather than silently weakening the
+    protocol.  The env seam is intentionally narrow so fault tests can exercise
+    every publication rename without monkey-patching the privileged process.
+    """
+    if os.environ.get("THT_RUNTIME_CONFIG_RENAME_FAIL") in {"1", kind}:
+        fail("runtime config rename failed")
+    libc = ctypes.CDLL(None, use_errno=True)
+    src_b = os.fsencode(src)
+    dst_b = os.fsencode(dst)
+    if sys.platform == "darwin":
+        fn = getattr(libc, "renameatx_np", None)
+        if fn is None:
+            fail("runtime config no-replace rename is unavailable")
+        fn.argtypes = [ctypes.c_int, ctypes.c_char_p, ctypes.c_int, ctypes.c_char_p, ctypes.c_uint]
+        fn.restype = ctypes.c_int
+        # RENAME_EXCL is the Darwin no-overwrite operation.
+        rc = fn(directory_fd, src_b, directory_fd, dst_b, 0x00000004)
+    elif sys.platform.startswith("linux"):
+        # renameat2(2), RENAME_NOREPLACE.  syscall numbers are stable for the
+        # supported Linux architectures; an unavailable syscall fails closed.
+        number = {"x86_64": 316, "aarch64": 276, "arm64": 276}.get(platform.machine())
+        if number is None or not hasattr(libc, "syscall"):
+            fail("runtime config no-replace rename is unavailable")
+        libc.syscall.argtypes = [ctypes.c_long, ctypes.c_int, ctypes.c_char_p,
+                                 ctypes.c_int, ctypes.c_char_p, ctypes.c_uint]
+        libc.syscall.restype = ctypes.c_long
+        rc = libc.syscall(number, directory_fd, src_b, directory_fd, dst_b, 1)
+    else:
+        fail("runtime config no-replace rename is unavailable")
+    if rc != 0:
+        err = ctypes.get_errno()
+        if err == 17:
+            raise FileExistsError(err, os.strerror(err), dst)
+        raise OSError(err, os.strerror(err), dst)
+
+
+def directory_identities(root: str, paths: list[tuple[str, int]]) -> list[dict[str, str]]:
+    """Return the ordered, no-follow identity chain bound by a publication.
+
+    ``paths`` contains canonical absolute directory paths paired with already-open
+    descriptors.  Prefix components are stat'ed without following symlinks; the
+    terminal workspace-owned components are additionally represented by fstat on
+    the descriptors opened by ``walk``.
+    """
+    canonical = _canonical_root(root)
+    root_parts = [part for part in Path(canonical).parts if part not in ("", "/")]
+    entries: list[dict[str, str]] = []
+    current = "/"
+    st = os.stat("/", follow_symlinks=False)
+    entries.append(_identity(st, current))
+    for part in root_parts:
+        current = (current.rstrip("/") + "/" + part) if current != "/" else "/" + part
+        st = os.stat(current, follow_symlinks=False)
+        if stat.S_ISLNK(st.st_mode) or not stat.S_ISDIR(st.st_mode):
+            fail("runtime config directory is not trusted")
+        entries.append(_identity(st, current))
+    for path, fd in paths:
+        cpath = _canonical_root(path)
+        st = os.fstat(fd)
+        if not stat.S_ISDIR(st.st_mode) or stat.S_IMODE(st.st_mode) != 0o700 or st.st_uid != os.getuid():
+            fail("runtime config directory is not trusted")
+        # Keep one ordered entry per path.  Existing prefixes are left in place.
+        if not any(item["path"] == cpath for item in entries):
+            entries.append(_identity(st, cpath))
+        else:
+            for item in entries:
+                if item["path"] == cpath:
+                    if item["dev"] != str(st.st_dev) or item["ino"] != str(st.st_ino):
+                        fail("runtime config directory changed")
+                    break
+    return entries
+
+
 def safe_id(v: str) -> bool:
     return bool(__import__("re").fullmatch(r"[a-z][a-z0-9-]{2,62}", v))
 
@@ -162,7 +257,7 @@ def strict_manifest(value: object) -> dict:
         "version", "workspace_id", "workspace_revision", "descriptor_git_blob",
         "descriptor_sha256", "descriptor_dev", "descriptor_ino", "config_sha256",
         "config_dwh_binding", "config_dev", "config_ino", "config_size", "config_mode",
-        "config_uid", "config_nlink",
+        "config_uid", "config_nlink", "directory_identities",
     }
     if set(value) != required or value.get("version") != 1:
         fail("runtime config manifest is invalid")
@@ -179,6 +274,17 @@ def strict_manifest(value: object) -> dict:
     for key in ("descriptor_dev", "descriptor_ino", "config_dev", "config_ino", "config_size", "config_uid", "config_nlink"):
         if not isinstance(value[key], str) or not value[key].isdigit():
             fail("runtime config manifest is invalid")
+    identities = value.get("directory_identities")
+    if (not isinstance(identities, list) or not identities or
+            any(not isinstance(item, dict) or set(item) != {"path", "dev", "ino", "mode", "uid"}
+                or not isinstance(item["path"], str) or not os.path.isabs(item["path"])
+                or any(not isinstance(item[key], str) or not item[key].isdigit()
+                       for key in ("dev", "ino", "mode", "uid"))
+                or item["mode"] == "0"
+                for item in identities)):
+        fail("runtime config manifest is invalid")
+    if len({item["path"] for item in identities}) != len(identities):
+        fail("runtime config manifest is invalid")
     if value["config_mode"] != "400":
         fail("runtime config manifest is invalid")
     return value
@@ -213,6 +319,14 @@ def publish(inp: dict) -> dict:
     checked_dir(cfgdir)
     mandir = open_dir(prep, "runtime-config-manifests", True)
     checked_dir(mandir)
+    canonical = _canonical_root(root)
+    directory_manifest = directory_identities(root, [
+        (f"{canonical}/sessions", sessions),
+        (f"{canonical}/sessions/{wid}", ws),
+        (f"{canonical}/sessions/{wid}/preprocessing", prep),
+        (f"{canonical}/sessions/{wid}/preprocessing/runtime-config", cfgdir),
+        (f"{canonical}/sessions/{wid}/preprocessing/runtime-config-manifests", mandir),
+    ])
     # The retained preprocessing directory is the single cross-process lock seam.
     # No pathname lock file is created in the workspace layout.
     fcntl.flock(prep, fcntl.LOCK_EX)
@@ -249,15 +363,11 @@ def publish(inp: dict) -> dict:
                 os.fchmod(fd, 0o400)
                 os.fsync(fd)
                 try:
-                    os.link(
-                        stage, name, src_dir_fd=cfgdir, dst_dir_fd=cfgdir, follow_symlinks=False
-                    )
+                    _rename_noreplace(stage, name, cfgdir, "config")
                 except FileExistsError:
+                    # A concurrent equal publisher may already have won.  It is
+                    # accepted only after reopening and comparing its bytes below.
                     pass
-                # Keep metadata ordering explicit even on filesystems where a
-                # hardlink publication does not retain fchmod as expected.
-                os.fchmod(fd, 0o400)
-                os.fsync(fd)
             finally:
                 os.close(fd)
                 try:
@@ -290,6 +400,7 @@ def publish(inp: dict) -> dict:
                 "config_mode": format(stat.S_IMODE(s.st_mode), "o"),
                 "config_uid": str(s.st_uid),
                 "config_nlink": str(s.st_nlink),
+                "directory_identities": directory_manifest,
             }
         )
         strict_manifest(manifest)
@@ -314,7 +425,7 @@ def publish(inp: dict) -> dict:
                 os.fchmod(fd, 0o600)
                 os.fsync(fd)
                 try:
-                    os.link(stage, mname, src_dir_fd=mandir, dst_dir_fd=mandir, follow_symlinks=False)
+                    _rename_noreplace(stage, mname, mandir, "manifest")
                 except FileExistsError:
                     # A no-replace loser is successful only after validating the
                     # durable winner byte-for-byte and against the strict schema.
@@ -438,14 +549,22 @@ def verified_snapshot(inp: dict) -> dict:
     repo = inp.get("repository_root")
     if not isinstance(repo, str) or not os.path.isabs(repo):
         fail("invalid repository root")
+    # Git replacement refs and ambient repository/config variables are attacker
+    # controlled process state.  Snapshot identity must be the raw object named by
+    # the commit, with fixed Git configuration and repository boundaries.
+    # Keep no inherited GIT_* controls at all (including GIT_CONFIG_PARAMETERS,
+    # alternates, and repository path overrides), then add only fixed semantics.
+    git_env = {key: value for key, value in os.environ.items() if not key.startswith("GIT_")}
+    git_env.update({"GIT_NO_REPLACE_OBJECTS": "1", "GIT_CONFIG_NOSYSTEM": "1",
+                    "GIT_CONFIG_GLOBAL": os.devnull, "GIT_CONFIG_SYSTEM": os.devnull})
     try:
         blob = subprocess.check_output(
-            ["git", "-C", repo, "rev-parse", f"{rev}:workspaces/{wid}.yaml"],
-            stderr=subprocess.DEVNULL, text=True, timeout=5,
+            ["git", "--no-replace-objects", "-C", repo, "rev-parse", f"{rev}:workspaces/{wid}.yaml"],
+            stderr=subprocess.DEVNULL, text=True, timeout=5, env=git_env,
         ).strip()
         git_source = subprocess.check_output(
-            ["git", "-C", repo, "show", f"{rev}:workspaces/{wid}.yaml"],
-            stderr=subprocess.DEVNULL, timeout=5,
+            ["git", "--no-replace-objects", "-C", repo, "show", f"{rev}:workspaces/{wid}.yaml"],
+            stderr=subprocess.DEVNULL, timeout=5, env=git_env,
         )
     except (OSError, subprocess.SubprocessError):
         fail("workspace Git revision is unavailable")