diff --git a/install.sh b/install.sh
index 5d8f8c68cf..2d9a368555 100755
--- a/install.sh
+++ b/install.sh
@@ -949,6 +949,17 @@ if [ -x "$VENV_DIR/bin/python" ]; then
     substep "${VENV_DIR}"
 fi
 
+# Default torch constraint -- tightened for Python 3.13+ on arm64 macOS
+# (torch <2.6 has no cp313 macOS arm64 wheels)
+TORCH_CONSTRAINT="torch>=2.4,<2.11.0"
+if [ "$SKIP_TORCH" = false ] && [ "$OS" = "macos" ] && [ "$_ARCH" = "arm64" ]; then
+    _PY_MINOR=$("$VENV_DIR/bin/python" -c \
+        "import sys; print(sys.version_info.minor)" 2>/dev/null || echo "0")
+    if [ "$_PY_MINOR" -ge 13 ] 2>/dev/null; then
+        TORCH_CONSTRAINT="torch>=2.6,<2.11.0"
+    fi
+fi
+
 # ── Resolve repo root (for --local installs) ──
 _REPO_ROOT="$(cd "$(dirname "$0" 2>/dev/null || echo ".")" && pwd)"
 
@@ -1049,7 +1060,7 @@ elif [ -n "$TORCH_INDEX_URL" ]; then
         substep "skipping PyTorch (--no-torch or Intel Mac x86_64)." "$C_WARN"
     else
         substep "installing PyTorch ($TORCH_INDEX_URL)..."
-        run_install_cmd "install PyTorch" uv pip install --python "$_VENV_PY" "torch>=2.4,<2.11.0" torchvision torchaudio \
+        run_install_cmd "install PyTorch" uv pip install --python "$_VENV_PY" "$TORCH_CONSTRAINT" torchvision torchaudio \
             --index-url "$TORCH_INDEX_URL"
     fi
     # Fresh: Step 2 - install unsloth, preserving pre-installed torch
diff --git a/studio/backend/requirements/no-torch-runtime.txt b/studio/backend/requirements/no-torch-runtime.txt
index 7133fe8922..3b822ac2a4 100644
--- a/studio/backend/requirements/no-torch-runtime.txt
+++ b/studio/backend/requirements/no-torch-runtime.txt
@@ -28,6 +28,21 @@ peft>=0.18.0,!=0.11.0
 huggingface_hub>=0.34.0
 hf_transfer
 diffusers
+
+# Transitive deps required because this file is installed with --no-deps.
+# Without these, `from transformers import AutoConfig` fails at import time.
+regex
+typing_extensions
+filelock
+httpx
+httpcore
+certifi
+idna
+anyio
+sniffio
+h11
+
+tokenizers
 transformers>=4.51.3,!=4.52.0,!=4.52.1,!=4.52.2,!=4.52.3,!=4.53.0,!=4.54.0,!=4.55.0,!=4.55.1,!=4.57.0,!=4.57.4,!=4.57.5,!=5.0.0,!=5.1.0,<=5.3.0
 trl>=0.18.2,!=0.19.0,<=0.24.0
 sentence-transformers
diff --git a/tests/python/conftest.py b/tests/python/conftest.py
index 66542d2451..9129e384e5 100644
--- a/tests/python/conftest.py
+++ b/tests/python/conftest.py
@@ -5,3 +5,6 @@ def pytest_configure(config):
     config.addinivalue_line(
         "markers", "server: heavyweight tests requiring studio venv"
     )
+    config.addinivalue_line(
+        "markers", "e2e: end-to-end tests requiring network and venv creation"
+    )
diff --git a/tests/python/test_tokenizers_and_torch_constraint.py b/tests/python/test_tokenizers_and_torch_constraint.py
new file mode 100644
index 0000000000..4be53d2d03
--- /dev/null
+++ b/tests/python/test_tokenizers_and_torch_constraint.py
@@ -0,0 +1,572 @@
+"""
+Tests for two install fixes:
+  1. tokenizers added to no-torch-runtime.txt  (prevents AutoConfig crash)
+  2. TORCH_CONSTRAINT variable in install.sh    (arm64 macOS + py313+ -> torch>=2.6)
+"""
+
+from __future__ import annotations
+
+import pathlib
+import re
+import subprocess
+import textwrap
+
+import pytest
+
+# ── Locate source files relative to this test ──────────────────────────
+_TESTS_DIR = pathlib.Path(__file__).resolve().parent.parent  # tests/
+_REPO_ROOT = _TESTS_DIR.parent  # unsloth/
+_INSTALL_SH = _REPO_ROOT / "install.sh"
+_INSTALL_PS1 = _REPO_ROOT / "install.ps1"
+_NO_TORCH_RT = (
+    _REPO_ROOT / "studio" / "backend" / "requirements" / "no-torch-runtime.txt"
+)
+
+
+def _read(path: pathlib.Path) -> str:
+    return path.read_text(encoding = "utf-8")
+
+
+def _lines(path: pathlib.Path) -> list[str]:
+    """Return non-comment, non-blank lines stripped."""
+    return [
+        ln.strip()
+        for ln in _read(path).splitlines()
+        if ln.strip() and not ln.strip().startswith("#")
+    ]
+
+
+# ======================================================================
+# Group 1 -- Structural checks (no network, instant)
+# ======================================================================
+class TestStructuralTokenizers:
+    """Verify tokenizers presence and ordering in no-torch-runtime.txt."""
+
+    def test_tokenizers_present(self):
+        """tokenizers must be a standalone package line."""
+        pkgs = _lines(_NO_TORCH_RT)
+        bare_names = [
+            p.split(">")[0].split("<")[0].split("!")[0].split("=")[0] for p in pkgs
+        ]
+        assert "tokenizers" in bare_names
+
+    def test_tokenizers_before_transformers(self):
+        """tokenizers should appear before transformers (install order intent)."""
+        pkgs = _lines(_NO_TORCH_RT)
+        bare_names = [
+            p.split(">")[0].split("<")[0].split("!")[0].split("=")[0] for p in pkgs
+        ]
+        idx_tok = bare_names.index("tokenizers")
+        idx_tf = bare_names.index("transformers")
+        assert idx_tok < idx_tf, (
+            f"tokenizers at index {idx_tok} should appear before "
+            f"transformers at index {idx_tf}"
+        )
+
+    def test_torch_not_in_no_torch_file(self):
+        """torch itself must NOT be listed in the no-torch requirements."""
+        pkgs = _lines(_NO_TORCH_RT)
+        bare_names = [
+            p.split(">")[0].split("<")[0].split("!")[0].split("=")[0] for p in pkgs
+        ]
+        assert "torch" not in bare_names
+
+
+class TestStructuralTorchConstraint:
+    """Verify TORCH_CONSTRAINT wiring in install.sh."""
+
+    _sh = _read(_INSTALL_SH)
+
+    def test_default_assignment_exists(self):
+        assert 'TORCH_CONSTRAINT="torch>=2.4,<2.11.0"' in self._sh
+
+    def test_tightened_assignment_exists(self):
+        assert 'TORCH_CONSTRAINT="torch>=2.6,<2.11.0"' in self._sh
+
+    def test_variable_used_in_pip_install(self):
+        """$TORCH_CONSTRAINT must appear in a uv pip install line."""
+        assert '"$TORCH_CONSTRAINT"' in self._sh
+
+    def test_hardcoded_torch_constraint_only_once(self):
+        """The hard-coded torch>=2.4,<2.11.0 string should appear exactly once
+        in install.sh (the default assignment), not in pip install lines."""
+        count = self._sh.count('"torch>=2.4,<2.11.0"')
+        assert count == 1, f"Expected 1, found {count}"
+
+    def test_tightening_guarded_by_skip_torch(self):
+        """The block must check SKIP_TORCH=false."""
+        # Find the tightening if-block
+        m = re.search(
+            r"if\s.*SKIP_TORCH.*=\s*false.*&&.*OS.*=.*macos.*&&.*_ARCH.*=.*arm64",
+            self._sh,
+        )
+        assert m is not None, "Guard not found: SKIP_TORCH + macos + arm64"
+
+    def test_tightening_guarded_by_arch(self):
+        m = re.search(r"_ARCH.*=.*arm64", self._sh)
+        assert m is not None
+
+    def test_tightening_guarded_by_os(self):
+        m = re.search(r"OS.*=.*macos", self._sh)
+        assert m is not None
+
+
+class TestStructuralInstallPs1Unchanged:
+    """install.ps1 should NOT have TORCH_CONSTRAINT variable."""
+
+    _ps1 = _read(_INSTALL_PS1)
+
+    def test_no_torch_constraint_variable(self):
+        assert "TORCH_CONSTRAINT" not in self._ps1
+        assert "$TorchConstraint" not in self._ps1
+
+    def test_hardcoded_torch_constraint_present(self):
+        assert '"torch>=2.4,<2.11.0"' in self._ps1
+
+
+# ======================================================================
+# Group 2 -- Shell snippet tests (bash subprocess, mocked python)
+# ======================================================================
+class TestTorchConstraintShell:
+    """Test the TORCH_CONSTRAINT block using bash subprocesses with
+    mocked python binaries that return controlled minor versions."""
+
+    # The extracted snippet we test in isolation.  We override OS, _ARCH,
+    # SKIP_TORCH, and provide a mock python at $VENV_DIR/bin/python.
+    _SNIPPET_TEMPLATE = textwrap.dedent(r"""
+        #!/bin/bash
+        set -e
+        SKIP_TORCH={skip_torch}
+        OS="{os}"
+        _ARCH="{arch}"
+        VENV_DIR="{venv_dir}"
+
+        TORCH_CONSTRAINT="torch>=2.4,<2.11.0"
+        if [ "$SKIP_TORCH" = false ] && [ "$OS" = "macos" ] && [ "$_ARCH" = "arm64" ]; then
+            _PY_MINOR=$("$VENV_DIR/bin/python" -c \
+                "import sys; print(sys.version_info.minor)" 2>/dev/null || echo "0")
+            if [ "$_PY_MINOR" -ge 13 ] 2>/dev/null; then
+                TORCH_CONSTRAINT="torch>=2.6,<2.11.0"
+            fi
+        fi
+        echo "$TORCH_CONSTRAINT"
+    """).strip()
+
+    @staticmethod
+    def _make_mock_python(tmp_path: pathlib.Path, minor: int) -> pathlib.Path:
+        """Create a mock python that prints a controlled minor version."""
+        venv = tmp_path / "venv"
+        bin_dir = venv / "bin"
+        bin_dir.mkdir(parents = True, exist_ok = True)
+        mock_py = bin_dir / "python"
+        mock_py.write_text(
+            textwrap.dedent(f"""\
+            #!/bin/bash
+            # Mock python: always report minor={minor}
+            if echo "$@" | grep -q "sys.version_info.minor"; then
+                echo "{minor}"
+            else
+                echo "0"
+            fi
+        """)
+        )
+        mock_py.chmod(0o755)
+        return venv
+
+    def _run(
+        self,
+        tmp_path: pathlib.Path,
+        *,
+        py_minor: int = 12,
+        os_val: str = "macos",
+        arch: str = "arm64",
+        skip_torch: str = "false",
+    ) -> str:
+        venv = self._make_mock_python(tmp_path, py_minor)
+        script = self._SNIPPET_TEMPLATE.format(
+            skip_torch = skip_torch,
+            os = os_val,
+            arch = arch,
+            venv_dir = str(venv),
+        )
+        script_file = tmp_path / "test_snippet.sh"
+        script_file.write_text(script)
+        script_file.chmod(0o755)
+        result = subprocess.run(
+            ["bash", str(script_file)],
+            capture_output = True,
+            text = True,
+            timeout = 10,
+        )
+        assert result.returncode == 0, f"Script failed: {result.stderr}"
+        return result.stdout.strip()
+
+    # -- arm64 macOS tightening cases --
+
+    def test_arm64_macos_py313_tightened(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 13, os_val = "macos", arch = "arm64")
+        assert out == "torch>=2.6,<2.11.0"
+
+    def test_arm64_macos_py314_tightened(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 14, os_val = "macos", arch = "arm64")
+        assert out == "torch>=2.6,<2.11.0"
+
+    # -- arm64 macOS default (older python) --
+
+    def test_arm64_macos_py312_default(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 12, os_val = "macos", arch = "arm64")
+        assert out == "torch>=2.4,<2.11.0"
+
+    def test_arm64_macos_py311_default(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 11, os_val = "macos", arch = "arm64")
+        assert out == "torch>=2.4,<2.11.0"
+
+    # -- Linux (unaffected) --
+
+    def test_linux_x86_py313_default(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 13, os_val = "linux", arch = "x86_64")
+        assert out == "torch>=2.4,<2.11.0"
+
+    def test_linux_aarch64_py313_default(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 13, os_val = "linux", arch = "aarch64")
+        assert out == "torch>=2.4,<2.11.0"
+
+    # -- Intel Mac (arch mismatch) --
+
+    def test_intel_mac_x86_py313_default(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 13, os_val = "macos", arch = "x86_64")
+        assert out == "torch>=2.4,<2.11.0"
+
+    # -- SKIP_TORCH bypass --
+
+    def test_skip_torch_arm64_macos_py313_default(self, tmp_path):
+        out = self._run(
+            tmp_path,
+            py_minor = 13,
+            os_val = "macos",
+            arch = "arm64",
+            skip_torch = "true",
+        )
+        assert out == "torch>=2.4,<2.11.0"
+
+    # -- WSL --
+
+    def test_wsl_py313_default(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 13, os_val = "wsl", arch = "x86_64")
+        assert out == "torch>=2.4,<2.11.0"
+
+    # -- Edge cases --
+
+    def test_py_minor_0_fallback_default(self, tmp_path):
+        """If python query fails (returns 0), should stay at default."""
+        out = self._run(tmp_path, py_minor = 0, os_val = "macos", arch = "arm64")
+        assert out == "torch>=2.4,<2.11.0"
+
+    def test_boundary_py_minor_12_not_tightened(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 12, os_val = "macos", arch = "arm64")
+        assert out == "torch>=2.4,<2.11.0"
+
+    def test_boundary_py_minor_13_tightened(self, tmp_path):
+        out = self._run(tmp_path, py_minor = 13, os_val = "macos", arch = "arm64")
+        assert out == "torch>=2.6,<2.11.0"
+
+    def test_mock_uv_receives_correct_constraint(self, tmp_path):
+        """Verify a mock uv would receive the correct constraint string."""
+        venv = self._make_mock_python(tmp_path, minor = 13)
+
+        # Create a mock uv that logs its arguments
+        mock_uv = tmp_path / "mock_uv"
+        log_file = tmp_path / "uv_log.txt"
+        mock_uv.write_text(
+            textwrap.dedent(f"""\
+            #!/bin/bash
+            echo "$@" >> {log_file}
+        """)
+        )
+        mock_uv.chmod(0o755)
+
+        script = textwrap.dedent(f"""\
+            #!/bin/bash
+            set -e
+            SKIP_TORCH=false
+            OS="macos"
+            _ARCH="arm64"
+            VENV_DIR="{venv}"
+
+            TORCH_CONSTRAINT="torch>=2.4,<2.11.0"
+            if [ "$SKIP_TORCH" = false ] && [ "$OS" = "macos" ] && [ "$_ARCH" = "arm64" ]; then
+                _PY_MINOR=$("$VENV_DIR/bin/python" -c \\
+                    "import sys; print(sys.version_info.minor)" 2>/dev/null || echo "0")
+                if [ "$_PY_MINOR" -ge 13 ] 2>/dev/null; then
+                    TORCH_CONSTRAINT="torch>=2.6,<2.11.0"
+                fi
+            fi
+            # Simulate the uv pip install line
+            {mock_uv} pip install --python "$VENV_DIR/bin/python" "$TORCH_CONSTRAINT" torchvision torchaudio
+        """)
+        script_file = tmp_path / "test_uv.sh"
+        script_file.write_text(script)
+        script_file.chmod(0o755)
+
+        result = subprocess.run(
+            ["bash", str(script_file)],
+            capture_output = True,
+            text = True,
+            timeout = 10,
+        )
+        assert result.returncode == 0, f"Script failed: {result.stderr}"
+        logged = log_file.read_text()
+        assert "torch>=2.6,<2.11.0" in logged, f"uv log: {logged}"
+
+    def test_mock_uv_receives_default_constraint(self, tmp_path):
+        """On py3.12 arm64 macOS, uv should receive the default constraint."""
+        venv = self._make_mock_python(tmp_path, minor = 12)
+        mock_uv = tmp_path / "mock_uv"
+        log_file = tmp_path / "uv_log.txt"
+        mock_uv.write_text(
+            textwrap.dedent(f"""\
+            #!/bin/bash
+            echo "$@" >> {log_file}
+        """)
+        )
+        mock_uv.chmod(0o755)
+
+        script = textwrap.dedent(f"""\
+            #!/bin/bash
+            set -e
+            SKIP_TORCH=false
+            OS="macos"
+            _ARCH="arm64"
+            VENV_DIR="{venv}"
+
+            TORCH_CONSTRAINT="torch>=2.4,<2.11.0"
+            if [ "$SKIP_TORCH" = false ] && [ "$OS" = "macos" ] && [ "$_ARCH" = "arm64" ]; then
+                _PY_MINOR=$("$VENV_DIR/bin/python" -c \\
+                    "import sys; print(sys.version_info.minor)" 2>/dev/null || echo "0")
+                if [ "$_PY_MINOR" -ge 13 ] 2>/dev/null; then
+                    TORCH_CONSTRAINT="torch>=2.6,<2.11.0"
+                fi
+            fi
+            {mock_uv} pip install --python "$VENV_DIR/bin/python" "$TORCH_CONSTRAINT" torchvision torchaudio
+        """)
+        script_file = tmp_path / "test_uv.sh"
+        script_file.write_text(script)
+        script_file.chmod(0o755)
+
+        result = subprocess.run(
+            ["bash", str(script_file)],
+            capture_output = True,
+            text = True,
+            timeout = 10,
+        )
+        assert result.returncode == 0, f"Script failed: {result.stderr}"
+        logged = log_file.read_text()
+        assert "torch>=2.4,<2.11.0" in logged, f"uv log: {logged}"
+
+
+# ======================================================================
+# Group 3 -- E2E tokenizers fix (requires network, ~2-5 min)
+# ======================================================================
+@pytest.mark.e2e
+class TestE2ETokenizersFix:
+    """Creates real uv venvs to verify tokenizers + transformers work
+    without torch installed."""
+
+    @staticmethod
+    def _create_venv(tmp_path: pathlib.Path, name: str, py: str) -> pathlib.Path:
+        venv = tmp_path / name
+        result = subprocess.run(
+            ["uv", "venv", str(venv), "--python", py],
+            capture_output = True,
+            text = True,
+            timeout = 120,
+        )
+        if result.returncode != 0:
+            pytest.skip(f"uv venv creation failed for {py}: {result.stderr}")
+        return venv
+
+    @staticmethod
+    def _pip_install(venv: pathlib.Path, *args: str) -> subprocess.CompletedProcess:
+        py = str(venv / "bin" / "python")
+        cmd = ["uv", "pip", "install", "--python", py, *args]
+        return subprocess.run(cmd, capture_output = True, text = True, timeout = 300)
+
+    @staticmethod
+    def _run_python(venv: pathlib.Path, code: str) -> subprocess.CompletedProcess:
+        py = str(venv / "bin" / "python")
+        return subprocess.run(
+            [py, "-c", code],
+            capture_output = True,
+            text = True,
+            timeout = 60,
+        )
+
+    @pytest.mark.parametrize("py_version", ["3.12", "3.13"])
+    def test_autoconfig_works_with_no_torch_runtime(self, tmp_path, py_version):
+        """Install from no-torch-runtime.txt with --no-deps (matching the
+        real install.sh path), then verify AutoConfig imports successfully."""
+        venv = self._create_venv(tmp_path, f"tok-{py_version}", py_version)
+        r = self._pip_install(venv, "--no-deps", "-r", str(_NO_TORCH_RT))
+        assert r.returncode == 0, f"Install failed: {r.stderr}"
+
+        result = self._run_python(
+            venv, "from transformers import AutoConfig; print('OK')"
+        )
+        assert (
+            result.returncode == 0
+        ), f"AutoConfig import failed:\nstdout: {result.stdout}\nstderr: {result.stderr}"
+        assert "OK" in result.stdout
+
+    @pytest.mark.parametrize("py_version", ["3.12", "3.13"])
+    def test_tokenizers_directly_importable(self, tmp_path, py_version):
+        venv = self._create_venv(tmp_path, f"tok-imp-{py_version}", py_version)
+        r = self._pip_install(venv, "--no-deps", "-r", str(_NO_TORCH_RT))
+        assert r.returncode == 0, f"Install failed: {r.stderr}"
+        result = self._run_python(venv, "import tokenizers; print('OK')")
+        assert result.returncode == 0, f"Failed: {result.stderr}"
+
+    @pytest.mark.parametrize("py_version", ["3.12", "3.13"])
+    def test_torch_not_importable(self, tmp_path, py_version):
+        """In the no-torch scenario, torch should not be available."""
+        venv = self._create_venv(tmp_path, f"no-torch-{py_version}", py_version)
+        r = self._pip_install(venv, "--no-deps", "-r", str(_NO_TORCH_RT))
+        assert r.returncode == 0, f"Install failed: {r.stderr}"
+        result = self._run_python(venv, "import torch")
+        assert result.returncode != 0, "torch should NOT be importable"
+
+    def test_negative_control_no_tokenizers(self, tmp_path):
+        """Without tokenizers, AutoConfig should fail. We create a copy of
+        no-torch-runtime.txt with the tokenizers line removed."""
+        venv = self._create_venv(tmp_path, "neg-ctrl", "3.12")
+        req_no_tokenizers = tmp_path / "no-tokenizers.txt"
+        req_no_tokenizers.write_text(
+            "\n".join(
+                line
+                for line in _read(_NO_TORCH_RT).splitlines()
+                if line.strip() != "tokenizers"
+            ),
+            encoding = "utf-8",
+        )
+        r = self._pip_install(venv, "--no-deps", "-r", str(req_no_tokenizers))
+        assert r.returncode == 0, f"Install failed: {r.stderr}"
+        result = self._run_python(venv, "from transformers import AutoConfig")
+        assert (
+            result.returncode != 0
+        ), "AutoConfig should fail without tokenizers installed"
+        assert (
+            "tokenizers" in result.stderr.lower()
+            or "ModuleNotFoundError" in result.stderr
+        )
+
+
+# ======================================================================
+# Group 4 -- Integration: install.sh reads no-torch-runtime.txt correctly
+# ======================================================================
+class TestInstallShNoTorchIntegration:
+    """Verify install.sh has the correct no-torch-runtime.txt wiring."""
+
+    _sh = _read(_INSTALL_SH)
+
+    def test_find_no_torch_runtime_exists(self):
+        assert "_find_no_torch_runtime()" in self._sh
+
+    def test_no_deps_invocation_for_migrated(self):
+        """Migrated path should use --no-deps -r."""
+        assert '--no-deps -r "$_NO_TORCH_RT"' in self._sh
+
+    def test_no_deps_invocation_for_fresh(self):
+        """Fresh install path should also use --no-deps -r."""
+        # Count occurrences of the no-deps -r pattern
+        count = self._sh.count('--no-deps -r "$_NO_TORCH_RT"')
+        assert count >= 2, f"Expected >=2 no-deps -r invocations, found {count}"
+
+    def test_mock_uv_skip_torch_reads_requirements(self, tmp_path):
+        """When SKIP_TORCH=true, the _find_no_torch_runtime path should be used."""
+        # We test this structurally: verify the SKIP_TORCH=true blocks contain
+        # _find_no_torch_runtime calls
+        skip_blocks = re.findall(
+            r'if \[ "\$SKIP_TORCH" = true \].*?(?=\n    (?:else|elif|fi))',
+            self._sh,
+            re.DOTALL,
+        )
+        found = any("_find_no_torch_runtime" in block for block in skip_blocks)
+        assert found, "SKIP_TORCH=true block should call _find_no_torch_runtime"
+
+
+# ======================================================================
+# Group 5 -- Full no-torch sandbox (requires network, ~5 min)
+# ======================================================================
+@pytest.mark.e2e
+class TestE2EFullNoTorchSandbox:
+    """Creates venvs and installs the actual no-torch-runtime.txt."""
+
+    @staticmethod
+    def _create_venv(tmp_path: pathlib.Path, name: str) -> pathlib.Path:
+        venv = tmp_path / name
+        result = subprocess.run(
+            ["uv", "venv", str(venv), "--python", "3.12"],
+            capture_output = True,
+            text = True,
+            timeout = 120,
+        )
+        if result.returncode != 0:
+            pytest.skip(f"uv venv creation failed: {result.stderr}")
+        return venv
+
+    @staticmethod
+    def _pip_install(venv: pathlib.Path, *args: str) -> subprocess.CompletedProcess:
+        py = str(venv / "bin" / "python")
+        cmd = ["uv", "pip", "install", "--python", py, *args]
+        return subprocess.run(cmd, capture_output = True, text = True, timeout = 600)
+
+    @staticmethod
+    def _run_python(venv: pathlib.Path, code: str) -> subprocess.CompletedProcess:
+        py = str(venv / "bin" / "python")
+        return subprocess.run(
+            [py, "-c", code],
+            capture_output = True,
+            text = True,
+            timeout = 60,
+        )
+
+    def test_autoconfig_succeeds(self, tmp_path):
+        """The real bug fix: install with --no-deps (matching install.sh)
+        and verify from transformers import AutoConfig works."""
+        venv = self._create_venv(tmp_path, "full-no-torch")
+        r = self._pip_install(venv, "--no-deps", "-r", str(_NO_TORCH_RT))
+        assert r.returncode == 0, f"Install failed: {r.stderr}"
+        result = self._run_python(
+            venv, "from transformers import AutoConfig; print('OK')"
+        )
+        assert (
+            result.returncode == 0
+        ), f"AutoConfig failed:\nstdout: {result.stdout}\nstderr: {result.stderr}"
+
+    def test_torch_not_importable(self, tmp_path):
+        """With --no-deps (as install.sh uses), torch must not be pulled in."""
+        venv = self._create_venv(tmp_path, "no-torch-check")
+        r = self._pip_install(venv, "--no-deps", "-r", str(_NO_TORCH_RT))
+        assert r.returncode == 0, f"Install failed: {r.stderr}"
+        result = self._run_python(venv, "import torch")
+        assert result.returncode != 0, "torch should NOT be importable"
+
+    def test_tokenizers_importable(self, tmp_path):
+        venv = self._create_venv(tmp_path, "tok-check")
+        r = self._pip_install(venv, "--no-deps", "-r", str(_NO_TORCH_RT))
+        assert r.returncode == 0, f"Install failed: {r.stderr}"
+        result = self._run_python(venv, "import tokenizers; print('OK')")
+        assert result.returncode == 0, f"tokenizers import failed: {result.stderr}"
+
+    def test_safetensors_importable(self, tmp_path):
+        venv = self._create_venv(tmp_path, "st-check")
+        r = self._pip_install(venv, "--no-deps", "-r", str(_NO_TORCH_RT))
+        assert r.returncode == 0, f"Install failed: {r.stderr}"
+        result = self._run_python(venv, "import safetensors; print('OK')")
+        assert result.returncode == 0, f"safetensors import failed: {result.stderr}"
+
+    def test_huggingface_hub_importable(self, tmp_path):
+        venv = self._create_venv(tmp_path, "hfhub-check")
+        r = self._pip_install(venv, "--no-deps", "-r", str(_NO_TORCH_RT))
+        assert r.returncode == 0, f"Install failed: {r.stderr}"
+        result = self._run_python(venv, "import huggingface_hub; print('OK')")
+        assert result.returncode == 0, f"huggingface_hub import failed: {result.stderr}"
diff --git a/tests/run_all.sh b/tests/run_all.sh
index a1516aa6c8..6525263d8f 100755
--- a/tests/run_all.sh
+++ b/tests/run_all.sh
@@ -7,6 +7,7 @@ TESTS_DIR="$(cd "$(dirname "$0")" && pwd)"
 echo "=== Bash tests ==="
 sh "$TESTS_DIR/sh/test_get_torch_index_url.sh"
 sh "$TESTS_DIR/sh/test_mac_intel_compat.sh"
+sh "$TESTS_DIR/sh/test_torch_constraint.sh"
 
 echo ""
 echo "=== Python tests ==="
@@ -14,6 +15,7 @@ python -m pytest "$TESTS_DIR/python/test_install_python_stack.py" -v
 python -m pytest "$TESTS_DIR/python/test_cross_platform_parity.py" -v
 python -m pytest "$TESTS_DIR/python/test_no_torch_filtering.py" -v
 python -m pytest "$TESTS_DIR/python/test_studio_import_no_torch.py" -v
+python -m pytest "$TESTS_DIR/python/test_tokenizers_and_torch_constraint.py" -v -k "not e2e"
 
 echo ""
 echo "All tests passed."
diff --git a/tests/sh/test_torch_constraint.sh b/tests/sh/test_torch_constraint.sh
new file mode 100644
index 0000000000..8766635209
--- /dev/null
+++ b/tests/sh/test_torch_constraint.sh
@@ -0,0 +1,266 @@
+#!/bin/bash
+# Tests for TORCH_CONSTRAINT variable in install.sh and tokenizers in no-torch-runtime.txt.
+# Follows the same assertion pattern as test_mac_intel_compat.sh.
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+INSTALL_SH="$SCRIPT_DIR/../../install.sh"
+INSTALL_PS1="$SCRIPT_DIR/../../install.ps1"
+NO_TORCH_RT="$SCRIPT_DIR/../../studio/backend/requirements/no-torch-runtime.txt"
+PASS=0
+FAIL=0
+
+assert_eq() {
+    _label="$1"; _expected="$2"; _actual="$3"
+    if [ "$_actual" = "$_expected" ]; then
+        echo "  PASS: $_label"
+        PASS=$((PASS + 1))
+    else
+        echo "  FAIL: $_label (expected '$_expected', got '$_actual')"
+        FAIL=$((FAIL + 1))
+    fi
+}
+
+assert_contains() {
+    _label="$1"; _haystack="$2"; _needle="$3"
+    if echo "$_haystack" | grep -qF "$_needle"; then
+        echo "  PASS: $_label"
+        PASS=$((PASS + 1))
+    else
+        echo "  FAIL: $_label (expected to find '$_needle')"
+        FAIL=$((FAIL + 1))
+    fi
+}
+
+assert_not_contains() {
+    _label="$1"; _haystack="$2"; _needle="$3"
+    if echo "$_haystack" | grep -qF "$_needle"; then
+        echo "  FAIL: $_label (found '$_needle' but should not)"
+        FAIL=$((FAIL + 1))
+    else
+        echo "  PASS: $_label"
+        PASS=$((PASS + 1))
+    fi
+}
+
+# ── Helper: create a mock python that reports a given minor version ──
+make_mock_python() {
+    _minor="$1"
+    _venv_dir="$2"
+    mkdir -p "$_venv_dir/bin"
+    cat > "$_venv_dir/bin/python" <<MOCK_EOF
+#!/bin/bash
+if echo "\$@" | grep -q "sys.version_info.minor"; then
+    echo "$_minor"
+else
+    echo "0"
+fi
+MOCK_EOF
+    chmod +x "$_venv_dir/bin/python"
+}
+
+# ── Helper: run the TORCH_CONSTRAINT snippet with given params ──
+run_constraint_snippet() {
+    _skip_torch="$1"
+    _os="$2"
+    _arch="$3"
+    _py_minor="$4"
+    _venv_dir="$5"
+
+    make_mock_python "$_py_minor" "$_venv_dir"
+
+    bash -c "
+        SKIP_TORCH=\"$_skip_torch\"
+        OS=\"$_os\"
+        _ARCH=\"$_arch\"
+        VENV_DIR=\"$_venv_dir\"
+        TORCH_CONSTRAINT=\"torch>=2.4,<2.11.0\"
+        if [ \"\$SKIP_TORCH\" = false ] && [ \"\$OS\" = \"macos\" ] && [ \"\$_ARCH\" = \"arm64\" ]; then
+            _PY_MINOR=\$(\"\$VENV_DIR/bin/python\" -c \"import sys; print(sys.version_info.minor)\" 2>/dev/null || echo \"0\")
+            if [ \"\$_PY_MINOR\" -ge 13 ] 2>/dev/null; then
+                TORCH_CONSTRAINT=\"torch>=2.6,<2.11.0\"
+            fi
+        fi
+        echo \"\$TORCH_CONSTRAINT\"
+    " 2>/dev/null
+}
+
+# ======================================================================
+# Structural checks
+# ======================================================================
+echo "=== Structural: TORCH_CONSTRAINT in install.sh ==="
+
+_SH_CONTENT=$(cat "$INSTALL_SH")
+
+_count=$(grep -c 'TORCH_CONSTRAINT="torch>=2.4,<2.11.0"' "$INSTALL_SH" || true)
+assert_eq "default TORCH_CONSTRAINT assignment exists" "1" "$_count"
+
+_count=$(grep -c 'TORCH_CONSTRAINT="torch>=2.6,<2.11.0"' "$INSTALL_SH" || true)
+assert_eq "tightened TORCH_CONSTRAINT assignment exists" "1" "$_count"
+
+_count=$(grep -c '"\$TORCH_CONSTRAINT"' "$INSTALL_SH" || true)
+_has_var=$([ "$_count" -ge 1 ] && echo "yes" || echo "no")
+assert_eq "\$TORCH_CONSTRAINT used in pip install" "yes" "$_has_var"
+
+# Hardcoded torch>=2.4,<2.11.0 should only appear once (the default assignment)
+_hardcoded=$(grep -c '"torch>=2.4,<2.11.0"' "$INSTALL_SH" || true)
+assert_eq "hardcoded torch>=2.4 appears exactly once" "1" "$_hardcoded"
+
+echo ""
+echo "=== Structural: tokenizers in no-torch-runtime.txt ==="
+
+_has_tokenizers=$(grep -c '^tokenizers$' "$NO_TORCH_RT" || true)
+assert_eq "tokenizers present as standalone line" "1" "$_has_tokenizers"
+
+# tokenizers before transformers
+_tok_line=$(grep -n '^tokenizers$' "$NO_TORCH_RT" | head -1 | cut -d: -f1)
+_tf_line=$(grep -n '^transformers' "$NO_TORCH_RT" | head -1 | cut -d: -f1)
+_tok_first=$([ "$_tok_line" -lt "$_tf_line" ] && echo "yes" || echo "no")
+assert_eq "tokenizers before transformers" "yes" "$_tok_first"
+
+# torch itself NOT in no-torch file
+_has_torch=$(grep -c '^torch$' "$NO_TORCH_RT" || true)
+assert_eq "torch not in no-torch-runtime.txt" "0" "$_has_torch"
+
+echo ""
+echo "=== Structural: install.ps1 unchanged ==="
+
+_PS1_CONTENT=$(cat "$INSTALL_PS1")
+_ps1_has_var=$(echo "$_PS1_CONTENT" | grep -c 'TORCH_CONSTRAINT\|TorchConstraint' || true)
+assert_eq "install.ps1 has no TORCH_CONSTRAINT variable" "0" "$_ps1_has_var"
+
+_ps1_hardcoded=$(echo "$_PS1_CONTENT" | grep -c '"torch>=2.4,<2.11.0"' || true)
+_ps1_has_hc=$([ "$_ps1_hardcoded" -ge 1 ] && echo "yes" || echo "no")
+assert_eq "install.ps1 has hardcoded torch constraint" "yes" "$_ps1_has_hc"
+
+# ======================================================================
+# Runtime: mocked platform/version combos
+# ======================================================================
+echo ""
+echo "=== Runtime: TORCH_CONSTRAINT with mocked inputs ==="
+
+TMPDIR_BASE=$(mktemp -d)
+trap 'rm -rf "$TMPDIR_BASE"' EXIT
+
+# 1. arm64 macOS py3.13 -> tightened
+_result=$(run_constraint_snippet false macos arm64 13 "$TMPDIR_BASE/v1")
+assert_eq "arm64+macos+py313 -> tightened" "torch>=2.6,<2.11.0" "$_result"
+
+# 2. arm64 macOS py3.14 -> tightened (future-proofed)
+_result=$(run_constraint_snippet false macos arm64 14 "$TMPDIR_BASE/v2")
+assert_eq "arm64+macos+py314 -> tightened" "torch>=2.6,<2.11.0" "$_result"
+
+# 3. arm64 macOS py3.12 -> default
+_result=$(run_constraint_snippet false macos arm64 12 "$TMPDIR_BASE/v3")
+assert_eq "arm64+macos+py312 -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# 4. arm64 macOS py3.11 -> default
+_result=$(run_constraint_snippet false macos arm64 11 "$TMPDIR_BASE/v4")
+assert_eq "arm64+macos+py311 -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# 5. Linux x86_64 py3.13 -> default (Linux unaffected)
+_result=$(run_constraint_snippet false linux x86_64 13 "$TMPDIR_BASE/v5")
+assert_eq "linux+x86_64+py313 -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# 6. Linux aarch64 py3.13 -> default (guard checks OS=macos)
+_result=$(run_constraint_snippet false linux aarch64 13 "$TMPDIR_BASE/v6")
+assert_eq "linux+aarch64+py313 -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# 7. Intel Mac x86_64 py3.12 -> default (arch mismatch)
+_result=$(run_constraint_snippet false macos x86_64 12 "$TMPDIR_BASE/v7")
+assert_eq "macos+x86_64+py312 -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# 8. SKIP_TORCH=true arm64 macOS py3.13 -> block skipped, default
+_result=$(run_constraint_snippet true macos arm64 13 "$TMPDIR_BASE/v8")
+assert_eq "SKIP_TORCH=true -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# 9. WSL py3.13 -> default
+_result=$(run_constraint_snippet false wsl x86_64 13 "$TMPDIR_BASE/v9")
+assert_eq "wsl+py313 -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# 10. py_minor=0 (failed query fallback) -> default
+_result=$(run_constraint_snippet false macos arm64 0 "$TMPDIR_BASE/v10")
+assert_eq "py_minor=0 fallback -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# 11. Boundary: py_minor=12 -> NOT tightened
+_result=$(run_constraint_snippet false macos arm64 12 "$TMPDIR_BASE/v11")
+assert_eq "boundary py_minor=12 -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# 12. Boundary: py_minor=13 -> tightened
+_result=$(run_constraint_snippet false macos arm64 13 "$TMPDIR_BASE/v12")
+assert_eq "boundary py_minor=13 -> tightened" "torch>=2.6,<2.11.0" "$_result"
+
+# 13. Intel Mac py3.13 -> default (arch=x86_64, not arm64)
+_result=$(run_constraint_snippet false macos x86_64 13 "$TMPDIR_BASE/v13")
+assert_eq "macos+x86_64+py313 -> default" "torch>=2.4,<2.11.0" "$_result"
+
+# ======================================================================
+# Mock uv integration
+# ======================================================================
+echo ""
+echo "=== Mock uv: verify constraint passed to uv ==="
+
+# arm64 + py313 -> uv receives torch>=2.6
+_UV_LOG="$TMPDIR_BASE/uv_log_tight.txt"
+make_mock_python 13 "$TMPDIR_BASE/uv_venv1"
+cat > "$TMPDIR_BASE/mock_uv_tight" <<UVEOF
+#!/bin/bash
+echo "\$@" >> $_UV_LOG
+UVEOF
+chmod +x "$TMPDIR_BASE/mock_uv_tight"
+
+bash -c "
+    SKIP_TORCH=false
+    OS=\"macos\"
+    _ARCH=\"arm64\"
+    VENV_DIR=\"$TMPDIR_BASE/uv_venv1\"
+    TORCH_CONSTRAINT=\"torch>=2.4,<2.11.0\"
+    if [ \"\$SKIP_TORCH\" = false ] && [ \"\$OS\" = \"macos\" ] && [ \"\$_ARCH\" = \"arm64\" ]; then
+        _PY_MINOR=\$(\"\$VENV_DIR/bin/python\" -c \"import sys; print(sys.version_info.minor)\" 2>/dev/null || echo \"0\")
+        if [ \"\$_PY_MINOR\" -ge 13 ] 2>/dev/null; then
+            TORCH_CONSTRAINT=\"torch>=2.6,<2.11.0\"
+        fi
+    fi
+    \"$TMPDIR_BASE/mock_uv_tight\" pip install --python \"\$VENV_DIR/bin/python\" \"\$TORCH_CONSTRAINT\" torchvision torchaudio
+" 2>/dev/null
+_uv_got=$(cat "$_UV_LOG" 2>/dev/null || echo "")
+assert_contains "mock uv arm64+py313 receives torch>=2.6" "$_uv_got" "torch>=2.6,<2.11.0"
+
+# arm64 + py312 -> uv receives torch>=2.4
+_UV_LOG2="$TMPDIR_BASE/uv_log_default.txt"
+make_mock_python 12 "$TMPDIR_BASE/uv_venv2"
+cat > "$TMPDIR_BASE/mock_uv_default" <<UVEOF
+#!/bin/bash
+echo "\$@" >> $_UV_LOG2
+UVEOF
+chmod +x "$TMPDIR_BASE/mock_uv_default"
+
+bash -c "
+    SKIP_TORCH=false
+    OS=\"macos\"
+    _ARCH=\"arm64\"
+    VENV_DIR=\"$TMPDIR_BASE/uv_venv2\"
+    TORCH_CONSTRAINT=\"torch>=2.4,<2.11.0\"
+    if [ \"\$SKIP_TORCH\" = false ] && [ \"\$OS\" = \"macos\" ] && [ \"\$_ARCH\" = \"arm64\" ]; then
+        _PY_MINOR=\$(\"\$VENV_DIR/bin/python\" -c \"import sys; print(sys.version_info.minor)\" 2>/dev/null || echo \"0\")
+        if [ \"\$_PY_MINOR\" -ge 13 ] 2>/dev/null; then
+            TORCH_CONSTRAINT=\"torch>=2.6,<2.11.0\"
+        fi
+    fi
+    \"$TMPDIR_BASE/mock_uv_default\" pip install --python \"\$VENV_DIR/bin/python\" \"\$TORCH_CONSTRAINT\" torchvision torchaudio
+" 2>/dev/null
+_uv_got2=$(cat "$_UV_LOG2" 2>/dev/null || echo "")
+assert_contains "mock uv arm64+py312 receives torch>=2.4" "$_uv_got2" "torch>=2.4,<2.11.0"
+
+# ======================================================================
+# Summary
+# ======================================================================
+echo ""
+echo "=== Results ==="
+echo "  PASS: $PASS"
+echo "  FAIL: $FAIL"
+if [ "$FAIL" -gt 0 ]; then
+    echo "FAILED"
+    exit 1
+fi
+echo "ALL PASSED"