feat(code_runner): rename module, fix __del__ + kernel name, expand tests

- Rename `wrenn.code_interpreter` → `wrenn.code_runner` (canonical).
  Keep old path as deprecation alias that emits a FutureWarning on
  import, mirroring the existing `Sandbox` → `Capsule` pattern.
  Submodule shims `code_interpreter/{capsule,async_capsule,models}.py`
  keep direct-submodule imports working.

- Fix sync/async ctor-failure-safe `__del__`: initialise `_kernel_id`,
  `_kernel_name`, `_proxy_client` before calling `super().__init__` so
  a failed creation no longer crashes the destructor with
  AttributeError.

- Send the kernel name to Jupyter. Previously `POST /api/kernels` had
  no body, so the server picked an arbitrary default kernelspec. Now
  sends `{"name": "wrenn"}` (override via `Capsule(kernel=...)`) and
  reuses an existing kernel only when its `name` matches.

- Preserve Jupyter `text/plain` verbatim in `Result.from_bundle`.
  The previous outer-quote strip was lossy (the string `'2'` became
  indistinguishable from the int `2`, and strings containing escaped
  quotes were mangled). `text` is now the `repr()` Jupyter sends.
  Updated the stale `test_capsule_features` quote-strip test.

- Validate `run_code(language=...)`. Anything other than `"python"`
  now raises `ValueError` instead of being silently ignored.

- Async `__del__` no longer touches the event loop; users must call
  `await close()` or use `async with`.

- New unit suite `tests/test_code_runner_unit.py` (46 tests): MIME
  unpacking, deprecation alias + warning, default template + kernel,
  custom kernel override, ctor-failure-safe __del__, kernel
  create/reuse/cache, retry on 5xx, 4xx propagation, request shape,
  run_code stream/result/error/foreign-parent/idle/unsupported-language,
  async variants.

- New e2e suite `tests/test_code_runner_e2e.py` (44 tests, integration
  marker): template == `code-runner-beta`, kernel == `wrenn`, stdout
  /stderr capture, state/import/function/class persistence, exceptions
  (Value/Name/Syntax), callbacks, multi-line, `text` repr preservation,
  filesystem round-trip, isolation between capsules, deprecated import
  path. MIME-type class covers html, markdown, json, latex, svg,
  javascript, png (matplotlib + seaborn), jpeg, multi-format bundles,
  and text-round-trip via numpy + requests.

- `make test-code-runner` runs unit + e2e together. `make test`
  extended to include the unit file.

- README: "Code Interpreter" section renamed to "Code Runner", all
  imports updated, `kernel=` documented, removed the incorrect
  "quotes stripped automatically" claim, replaced with the actual
  `text/plain` semantics.

- CLAUDE.md: appended a "Code Runner Module" section covering module
  path, defaults, kernel-reuse semantics, lifecycle invariant, and
  the new test files + make target.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_capsule_features.py

@@ -4,7 +4,7 @@ import httpx
 import respx
 
 from wrenn.capsule import Capsule, _build_proxy_url
-from wrenn.code_interpreter.models import Execution, ExecutionError, Logs, Result
+from wrenn.code_runner.models import Execution, ExecutionError, Logs, Result
 
 BASE = "https://app.wrenn.dev/api"
 
@@ -152,10 +152,11 @@ class TestExecutionModels:
         assert r.png == "base64data"
         assert r.is_main_result is True
 
-    def test_result_from_bundle_strips_quotes(self):
+    def test_result_from_bundle_preserves_text_plain(self):
+        # ``text/plain`` is the Jupyter repr — preserved verbatim now.
         bundle = {"text/plain": "'hello'"}
         r = Result.from_bundle(bundle)
-        assert r.text == "hello"
+        assert r.text == "'hello'"
 
     def test_result_from_bundle_extra_mimes(self):
         bundle = {"text/plain": "x", "application/vnd.custom": "data"}

tests/test_code_runner_e2e.py

@@ -0,0 +1,538 @@
+from __future__ import annotations
+
+import asyncio
+import os
+import warnings
+from pathlib import Path
+
+import pytest
+
+from wrenn.code_runner import (
+    AsyncCapsule,
+    Capsule,
+    Execution,
+    Result,
+)
+
+pytestmark = pytest.mark.integration
+
+_env_loaded = False
+
+
+def _ensure_env() -> None:
+    global _env_loaded
+    if _env_loaded:
+        return
+    _env_loaded = True
+    env_file = Path(__file__).resolve().parent.parent / ".env"
+    if not env_file.exists():
+        return
+    for line in env_file.read_text().splitlines():
+        line = line.strip()
+        if not line or line.startswith("#") or "=" not in line:
+            continue
+        key, _, value = line.partition("=")
+        key, value = key.strip(), value.strip().strip("\"'")
+        if key and key not in os.environ:
+            os.environ[key] = value
+
+
+# ───────────────────────── Sync e2e ─────────────────────────
+
+
+class TestCodeRunnerSync:
+    """Shared capsule — kernel state persists across tests."""
+
+    capsule: Capsule
+
+    @classmethod
+    def setup_class(cls):
+        _ensure_env()
+        cls.capsule = Capsule(wait=True)
+
+    @classmethod
+    def teardown_class(cls):
+        try:
+            cls.capsule.destroy()
+        except Exception:
+            pass
+
+    def test_uses_code_runner_beta_template(self):
+        assert self.capsule.info is not None
+        assert self.capsule.info.template == "code-runner-beta"
+
+    def test_default_kernel_name_is_wrenn(self):
+        assert self.capsule._kernel_name == "wrenn"
+
+    def test_simple_expression(self):
+        ex = self.capsule.run_code("1 + 1")
+        assert isinstance(ex, Execution)
+        assert ex.error is None
+        assert ex.text == "2"
+        assert ex.execution_count is not None
+        assert ex.execution_count >= 1
+
+    def test_print_captures_stdout(self):
+        ex = self.capsule.run_code("print('hello world')")
+        assert ex.error is None
+        joined = "".join(ex.logs.stdout)
+        assert "hello world" in joined
+
+    def test_stderr_captured(self):
+        ex = self.capsule.run_code("import sys; sys.stderr.write('an error\\n')")
+        assert ex.error is None
+        joined = "".join(ex.logs.stderr)
+        assert "an error" in joined
+
+    def test_kernel_state_persists_across_calls(self):
+        self.capsule.run_code("persistent_value = 12345")
+        ex = self.capsule.run_code("persistent_value")
+        assert ex.text == "12345"
+
+    def test_import_persists(self):
+        self.capsule.run_code("import math")
+        ex = self.capsule.run_code("round(math.pi, 4)")
+        assert ex.text == "3.1416"
+
+    def test_function_definition_persists(self):
+        self.capsule.run_code(
+            "def fib(n):\n"
+            "    a, b = 0, 1\n"
+            "    for _ in range(n):\n"
+            "        a, b = b, a + b\n"
+            "    return a\n"
+        )
+        ex = self.capsule.run_code("fib(10)")
+        assert ex.text == "55"
+
+    def test_class_definition_persists(self):
+        self.capsule.run_code(
+            "class Counter:\n"
+            "    def __init__(self): self.n = 0\n"
+            "    def inc(self): self.n += 1; return self.n\n"
+            "c = Counter()\n"
+        )
+        ex = self.capsule.run_code("c.inc(); c.inc(); c.inc(); c.n")
+        assert ex.text == "3"
+
+    def test_exception_captured(self):
+        ex = self.capsule.run_code("raise ValueError('boom')")
+        assert ex.error is not None
+        assert ex.error.name == "ValueError"
+        assert "boom" in ex.error.value
+        assert "ValueError" in ex.error.traceback
+
+    def test_name_error(self):
+        ex = self.capsule.run_code("undefined_symbol_xyz")
+        assert ex.error is not None
+        assert ex.error.name == "NameError"
+
+    def test_syntax_error(self):
+        ex = self.capsule.run_code("def )(\n")
+        assert ex.error is not None
+        assert "SyntaxError" in ex.error.name
+
+    def test_callbacks_fire(self):
+        stdout_chunks: list[str] = []
+        stderr_chunks: list[str] = []
+        results: list[Result] = []
+        errors = []
+        self.capsule.run_code(
+            "import sys\nprint('on stdout')\nsys.stderr.write('on stderr\\n')\n42\n",
+            on_stdout=stdout_chunks.append,
+            on_stderr=stderr_chunks.append,
+            on_result=results.append,
+            on_error=errors.append,
+        )
+        assert any("on stdout" in c for c in stdout_chunks)
+        assert any("on stderr" in c for c in stderr_chunks)
+        assert any(r.text == "42" for r in results)
+        assert errors == []
+
+    def test_multi_line_output(self):
+        ex = self.capsule.run_code("for i in range(3):\n    print(i)\n")
+        joined = "".join(ex.logs.stdout)
+        assert "0" in joined and "1" in joined and "2" in joined
+
+    def test_no_main_result_when_statement_only(self):
+        ex = self.capsule.run_code("x = 5")
+        assert ex.text is None
+        assert ex.error is None
+
+    def test_html_repr_result(self):
+        ex = self.capsule.run_code(
+            "from IPython.display import HTML\nHTML('<b>bold</b>')"
+        )
+        assert ex.error is None
+        main = [r for r in ex.results if r.is_main_result]
+        assert main, "expected execute_result"
+        assert main[0].html is not None
+        assert "<b>bold</b>" in main[0].html
+
+    def test_display_data_separate_from_execute_result(self):
+        ex = self.capsule.run_code(
+            "from IPython.display import display, HTML\n"
+            "display(HTML('<i>shown</i>'))\n"
+            "'final'\n"
+        )
+        assert ex.error is None
+        mains = [r for r in ex.results if r.is_main_result]
+        displays = [r for r in ex.results if not r.is_main_result]
+        assert len(mains) == 1
+        assert mains[0].text == "'final'"
+        assert len(displays) >= 1
+        assert any(r.html and "shown" in r.html for r in displays)
+
+    def test_matplotlib_png(self):
+        ex = self.capsule.run_code(
+            "%matplotlib inline\n"
+            "import matplotlib.pyplot as plt\n"
+            "plt.figure()\n"
+            "plt.plot([1,2,3],[4,1,5])\n"
+            "plt.show()\n"
+        )
+        if ex.error is not None and ex.error.name == "ModuleNotFoundError":
+            pytest.skip("matplotlib not in template")
+        assert ex.error is None
+        pngs = [r for r in ex.results if r.png is not None]
+        assert pngs, "expected at least one PNG result from plt.show()"
+
+    def test_pandas_repr(self):
+        ex = self.capsule.run_code(
+            "import pandas as pd\npd.DataFrame({'a':[1,2],'b':[3,4]})\n"
+        )
+        if ex.error is not None and ex.error.name == "ModuleNotFoundError":
+            pytest.skip("pandas not in template")
+        assert ex.error is None
+        main = [r for r in ex.results if r.is_main_result]
+        assert main
+        assert main[0].html is not None or main[0].text is not None
+
+    def test_filesystem_round_trip(self):
+        self.capsule.run_code(
+            "with open('/tmp/from_kernel.txt','w') as f: f.write('written-by-kernel')"
+        )
+        content = self.capsule.files.read("/tmp/from_kernel.txt")
+        assert content == "written-by-kernel"
+
+    def test_text_preserves_string_repr(self):
+        """Strings keep their surrounding quotes — the ``text/plain`` MIME
+        is the Jupyter repr, which is what disambiguates ``'2'`` from
+        ``2``."""
+        ex = self.capsule.run_code("'hello'")
+        assert ex.text == "'hello'"
+        ex = self.capsule.run_code('"with\\"inside"')
+        assert ex.text is not None
+        assert ex.text.startswith("'") or ex.text.startswith('"')
+        ex = self.capsule.run_code("42")
+        assert ex.text == "42"
+        ex = self.capsule.run_code("[1, 2, 3]")
+        assert ex.text == "[1, 2, 3]"
+        ex = self.capsule.run_code("{'k': 'v'}")
+        assert ex.text == "{'k': 'v'}"
+
+    def test_kernel_id_cached(self):
+        first = self.capsule._kernel_id
+        self.capsule.run_code("1")
+        assert self.capsule._kernel_id == first
+
+    def test_complex_workflow(self):
+        ex = self.capsule.run_code(
+            "import json\n"
+            "data = [{'n': i, 'sq': i*i} for i in range(5)]\n"
+            "print(json.dumps(data))\n"
+            "sum(d['sq'] for d in data)\n"
+        )
+        assert ex.error is None
+        assert ex.text == "30"
+        assert any('"sq": 16' in c for c in ex.logs.stdout)
+
+
+class TestCodeRunnerMimeTypes:
+    """Cover every non-text MIME field on ``Result`` using the libs
+    baked into the ``code-runner-beta`` template
+    (numpy, pandas, matplotlib, seaborn, requests)."""
+
+    capsule: Capsule
+
+    @classmethod
+    def setup_class(cls):
+        _ensure_env()
+        cls.capsule = Capsule(wait=True)
+
+    @classmethod
+    def teardown_class(cls):
+        try:
+            cls.capsule.destroy()
+        except Exception:
+            pass
+
+    def _run(self, code: str) -> Execution:
+        ex = self.capsule.run_code(code, timeout=60)
+        assert ex.error is None, f"unexpected error: {ex.error}"
+        return ex
+
+    # ── html ──────────────────────────────────────────────────────
+    def test_html_via_ipython_display(self):
+        ex = self._run(
+            "from IPython.display import HTML\nHTML('<table><tr><td>x</td></tr></table>')"
+        )
+        main = next(r for r in ex.results if r.is_main_result)
+        assert main.html is not None
+        assert "<table>" in main.html
+        assert "html" in main.formats()
+
+    def test_html_via_pandas_dataframe(self):
+        ex = self._run(
+            "import pandas as pd\n"
+            "pd.DataFrame({'a': [1, 2, 3], 'b': ['x', 'y', 'z']})\n"
+        )
+        main = next(r for r in ex.results if r.is_main_result)
+        assert main.html is not None
+        # pandas emits a styled <table>
+        assert "<table" in main.html
+        assert "dataframe" in main.html.lower() or "<tr" in main.html
+        # text/plain still present alongside html
+        assert main.text is not None
+
+    # ── markdown ──────────────────────────────────────────────────
+    def test_markdown(self):
+        ex = self._run(
+            "from IPython.display import Markdown\nMarkdown('# heading\\n* a\\n* b')"
+        )
+        main = next(r for r in ex.results if r.is_main_result)
+        assert main.markdown is not None
+        assert "# heading" in main.markdown
+        assert "markdown" in main.formats()
+
+    # ── json ──────────────────────────────────────────────────────
+    def test_json_bundle(self):
+        ex = self._run(
+            "from IPython.display import JSON\nJSON({'a': 1, 'nested': {'b': [1, 2]}})"
+        )
+        main = next(r for r in ex.results if r.is_main_result)
+        # IPython.display.JSON emits application/json
+        assert main.json is not None
+        assert main.json == {"a": 1, "nested": {"b": [1, 2]}}
+        assert "json" in main.formats()
+
+    # ── latex ─────────────────────────────────────────────────────
+    def test_latex(self):
+        ex = self._run("from IPython.display import Latex\nLatex(r'$E = mc^2$')")
+        main = next(r for r in ex.results if r.is_main_result)
+        assert main.latex is not None
+        assert "mc^2" in main.latex
+
+    # ── svg ───────────────────────────────────────────────────────
+    def test_svg(self):
+        svg_payload = (
+            '<svg xmlns=\\"http://www.w3.org/2000/svg\\" width=\\"10\\" height=\\"10\\">'
+            '<rect width=\\"10\\" height=\\"10\\" fill=\\"red\\"/></svg>'
+        )
+        ex = self._run(f"from IPython.display import SVG\nSVG(data='{svg_payload}')")
+        main = next(r for r in ex.results if r.is_main_result)
+        assert main.svg is not None
+        assert "<svg" in main.svg
+        assert "<rect" in main.svg
+
+    # ── javascript ────────────────────────────────────────────────
+    def test_javascript(self):
+        ex = self._run(
+            "from IPython.display import Javascript\nJavascript('console.log(\"hi\")')"
+        )
+        main = next(r for r in ex.results if r.is_main_result)
+        # Some IPython versions only emit text/plain for Javascript;
+        # accept either javascript or extra/application/javascript.
+        js = main.javascript or (main.extra or {}).get("application/javascript")
+        assert js is not None, f"no js payload, got formats: {main.formats()}"
+        assert "console.log" in js
+
+    # ── png (matplotlib) ──────────────────────────────────────────
+    def test_png_from_matplotlib(self):
+        ex = self._run(
+            "%matplotlib inline\n"
+            "import matplotlib.pyplot as plt\n"
+            "import numpy as np\n"
+            "x = np.linspace(0, 6.28, 100)\n"
+            "plt.figure()\n"
+            "plt.plot(x, np.sin(x))\n"
+            "plt.title('sine')\n"
+            "plt.show()\n"
+        )
+        pngs = [r for r in ex.results if r.png is not None]
+        assert pngs, "expected PNG from plt.show()"
+        # Base64 PNG starts with iVBORw0KGgo (== PNG magic in base64)
+        assert pngs[0].png.startswith("iVBORw0KGgo")
+        assert "png" in pngs[0].formats()
+
+    def test_png_from_seaborn(self):
+        ex = self._run(
+            "%matplotlib inline\n"
+            "import matplotlib.pyplot as plt\n"
+            "import seaborn as sns\n"
+            "import pandas as pd\n"
+            "df = pd.DataFrame({'x': [1, 2, 3, 4], 'y': [10, 20, 15, 25]})\n"
+            "plt.figure()\n"
+            "sns.barplot(data=df, x='x', y='y')\n"
+            "plt.show()\n"
+        )
+        pngs = [r for r in ex.results if r.png is not None]
+        assert pngs, "expected PNG from seaborn plot"
+        assert pngs[0].png.startswith("iVBORw0KGgo")
+
+    # ── jpeg ──────────────────────────────────────────────────────
+    def test_jpeg_via_matplotlib(self):
+        ex = self._run(
+            "%matplotlib inline\n"
+            "import matplotlib.pyplot as plt\n"
+            "import matplotlib_inline.backend_inline as bi\n"
+            "bi.set_matplotlib_formats('jpeg')\n"
+            "plt.figure()\n"
+            "plt.plot([1, 2, 3])\n"
+            "plt.show()\n"
+            "bi.set_matplotlib_formats('png')\n"
+        )
+        jpegs = [r for r in ex.results if r.jpeg is not None]
+        if not jpegs:
+            pytest.skip("matplotlib_inline jpeg backend unavailable")
+        # JPEG magic in base64 starts with /9j/
+        assert jpegs[0].jpeg.startswith("/9j/")
+
+    # ── multi-format bundle ───────────────────────────────────────
+    def test_pandas_emits_text_and_html(self):
+        ex = self._run("import pandas as pd\npd.DataFrame({'n': range(3)})")
+        main = next(r for r in ex.results if r.is_main_result)
+        fmts = main.formats()
+        assert "text" in fmts
+        assert "html" in fmts
+        assert main.is_main_result is True
+
+    def test_matplotlib_figure_emits_png_and_text(self):
+        ex = self._run(
+            "%matplotlib inline\n"
+            "import matplotlib.pyplot as plt\n"
+            "fig, ax = plt.subplots()\n"
+            "ax.plot([1, 2, 3])\n"
+            "fig\n"  # return the figure as the last expression
+        )
+        main = next(r for r in ex.results if r.is_main_result)
+        fmts = main.formats()
+        # Figure repr bundles both text and png.
+        assert "png" in fmts
+        assert "text" in fmts
+
+    # ── numpy / requests round-trips through .text ────────────────
+    def test_numpy_array_text_repr(self):
+        ex = self._run("import numpy as np\nnp.arange(5)")
+        assert ex.text is not None
+        assert "array([0, 1, 2, 3, 4])" in ex.text
+
+    def test_requests_status_code(self):
+        ex = self._run(
+            "import requests\n"
+            "r = requests.get('https://httpbin.org/status/204', timeout=10)\n"
+            "r.status_code\n"
+        )
+        if ex.error is not None:
+            pytest.skip(f"network unavailable: {ex.error.name}")
+        assert ex.text == "204"
+
+
+class TestCodeRunnerIsolation:
+    """Each test gets its own capsule — verifies fresh-kernel boot."""
+
+    def setup_method(self):
+        _ensure_env()
+
+    def test_fresh_capsule_no_state_leak(self):
+        c1 = Capsule(wait=True)
+        try:
+            c1.run_code("leaked = 'c1'")
+            c2 = Capsule(wait=True)
+            try:
+                ex = c2.run_code("leaked")
+                assert ex.error is not None
+                assert ex.error.name == "NameError"
+            finally:
+                c2.destroy()
+        finally:
+            c1.destroy()
+
+    def test_context_manager(self):
+        with Capsule(wait=True) as c:
+            ex = c.run_code("'ctx'")
+            assert ex.text == "'ctx'"
+
+    def test_deprecated_code_interpreter_import_still_works(self):
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", FutureWarning)
+            from wrenn.code_interpreter import Capsule as LegacyCapsule
+        with LegacyCapsule(wait=True) as c:
+            ex = c.run_code("'legacy'")
+            assert ex.text == "'legacy'"
+
+
+# ───────────────────────── Async e2e ─────────────────────────
+
+
+class TestCodeRunnerAsync:
+    def setup_method(self):
+        _ensure_env()
+
+    @pytest.mark.asyncio
+    async def test_async_simple(self):
+        c = await AsyncCapsule.create(wait=True)
+        try:
+            ex = await c.run_code("21 * 2")
+            assert ex.error is None
+            assert ex.text == "42"
+        finally:
+            await c.close()
+            await c.destroy()
+
+    @pytest.mark.asyncio
+    async def test_async_persistence(self):
+        c = await AsyncCapsule.create(wait=True)
+        try:
+            await c.run_code("v = 'persisted'")
+            ex = await c.run_code("v")
+            assert ex.text == "'persisted'"
+        finally:
+            await c.close()
+            await c.destroy()
+
+    @pytest.mark.asyncio
+    async def test_async_callbacks(self):
+        c = await AsyncCapsule.create(wait=True)
+        try:
+            chunks: list[str] = []
+            await c.run_code(
+                "print('async out')",
+                on_stdout=chunks.append,
+            )
+            assert any("async out" in s for s in chunks)
+        finally:
+            await c.close()
+            await c.destroy()
+
+    @pytest.mark.asyncio
+    async def test_async_context_manager(self):
+        c = await AsyncCapsule.create(wait=True)
+        async with c:
+            ex = await c.run_code("'in-ctx'")
+            assert ex.text == "'in-ctx'"
+
+    @pytest.mark.asyncio
+    async def test_async_concurrent_capsules(self):
+        c1 = await AsyncCapsule.create(wait=True)
+        c2 = await AsyncCapsule.create(wait=True)
+        try:
+            r1, r2 = await asyncio.gather(
+                c1.run_code("1 + 1"),
+                c2.run_code("10 * 10"),
+            )
+            assert r1.text == "2"
+            assert r2.text == "100"
+        finally:
+            await asyncio.gather(c1.close(), c2.close(), return_exceptions=True)
+            await asyncio.gather(c1.destroy(), c2.destroy(), return_exceptions=True)

tests/test_code_runner_unit.py

@@ -0,0 +1,632 @@
+from __future__ import annotations
+
+import importlib
+import json
+import sys
+import warnings
+from unittest.mock import patch
+
+import httpx
+import pytest
+import respx
+
+from wrenn.code_runner import (
+    AsyncCapsule,
+    Capsule,
+    Execution,
+    Logs,
+    Result,
+)
+from wrenn.code_runner.capsule import DEFAULT_KERNEL, DEFAULT_TEMPLATE
+
+BASE = "https://app.wrenn.dev/api"
+API_KEY = "wrn_test1234567890abcdef12345678"
+
+
+# ───────────────────────── Result / Execution models ─────────────────────────
+
+
+class TestResultFromBundle:
+    def test_unpacks_known_mime_types(self):
+        r = Result.from_bundle(
+            {
+                "text/plain": "42",
+                "text/html": "<b>42</b>",
+                "image/png": "iVBORw0KGgo=",
+                "application/json": {"x": 1},
+            },
+            is_main_result=True,
+        )
+        assert r.text == "42"
+        assert r.html == "<b>42</b>"
+        assert r.png == "iVBORw0KGgo="
+        assert r.json == {"x": 1}
+        assert r.is_main_result is True
+        assert r.extra is None
+
+    def test_unknown_mime_lands_in_extra(self):
+        r = Result.from_bundle({"application/vnd.custom+json": "{}"})
+        assert r.extra == {"application/vnd.custom+json": "{}"}
+        assert r.is_main_result is False
+
+    @pytest.mark.parametrize(
+        "raw",
+        [
+            "'hello'",
+            '"hello"',
+            "hello",
+            "'x",
+            "''",
+            "'",
+            "'it\\'s'",
+            "{'a': 1}",
+            "[1, 2, 3]",
+        ],
+    )
+    def test_text_plain_preserved_verbatim(self, raw):
+        """``text/plain`` is the Jupyter repr — pass through unchanged.
+        Stripping outer quotes would lose string identity (a string
+        ``'2'`` would become indistinguishable from the int ``2``)."""
+        r = Result.from_bundle({"text/plain": raw})
+        assert r.text == raw
+
+    def test_formats_lists_present_fields(self):
+        r = Result.from_bundle({"text/plain": "x", "image/svg+xml": "<svg/>"})
+        fmts = r.formats()
+        assert "text" in fmts
+        assert "svg" in fmts
+        assert "html" not in fmts
+
+    def test_formats_includes_extra(self):
+        r = Result.from_bundle({"application/x-foo": "bar"})
+        assert "application/x-foo" in r.formats()
+
+    def test_all_mime_types_map(self):
+        r = Result.from_bundle(
+            {
+                "text/plain": "a",
+                "text/html": "b",
+                "text/markdown": "c",
+                "image/svg+xml": "d",
+                "image/png": "e",
+                "image/jpeg": "f",
+                "application/pdf": "g",
+                "text/latex": "h",
+                "application/json": {"k": 1},
+                "application/javascript": "j",
+            }
+        )
+        for attr in (
+            "text",
+            "html",
+            "markdown",
+            "svg",
+            "png",
+            "jpeg",
+            "pdf",
+            "latex",
+            "json",
+            "javascript",
+        ):
+            assert getattr(r, attr) is not None
+
+
+class TestExecution:
+    def test_text_returns_main_result(self):
+        ex = Execution(
+            results=[
+                Result(text="display", is_main_result=False),
+                Result(text="main", is_main_result=True),
+            ]
+        )
+        assert ex.text == "main"
+
+    def test_text_none_when_no_main(self):
+        ex = Execution(results=[Result(text="x", is_main_result=False)])
+        assert ex.text is None
+
+    def test_defaults(self):
+        ex = Execution()
+        assert ex.results == []
+        assert isinstance(ex.logs, Logs)
+        assert ex.error is None
+        assert ex.execution_count is None
+
+
+# ───────────────────────── deprecation alias ─────────────────────────
+
+
+class TestDeprecationAlias:
+    def test_code_interpreter_emits_warning_on_import(self):
+        # Force a fresh import to observe the warning.
+        sys.modules.pop("wrenn.code_interpreter", None)
+        # Reset the one-shot flag in case the module was previously imported.
+        with warnings.catch_warnings(record=True) as captured:
+            warnings.simplefilter("always")
+            ci = importlib.import_module("wrenn.code_interpreter")
+            ci.warnings_emitted = False  # type: ignore[attr-defined]
+            # Re-import to trigger again
+            sys.modules.pop("wrenn.code_interpreter", None)
+            importlib.import_module("wrenn.code_interpreter")
+            msgs = [
+                str(w.message)
+                for w in captured
+                if issubclass(w.category, FutureWarning)
+            ]
+        assert any("code_interpreter" in m and "code_runner" in m for m in msgs)
+
+    def test_alias_re_exports_same_classes(self):
+        from wrenn import code_interpreter as ci
+
+        assert ci.Capsule is Capsule
+        assert ci.AsyncCapsule is AsyncCapsule
+        assert ci.Execution is Execution
+        assert ci.Result is Result
+
+    def test_sandbox_attr_deprecated(self):
+        from wrenn import code_runner as cr
+
+        with warnings.catch_warnings(record=True) as captured:
+            warnings.simplefilter("always")
+            S = cr.Sandbox
+        assert S is cr.Capsule
+        assert any(
+            issubclass(w.category, FutureWarning) and "Sandbox" in str(w.message)
+            for w in captured
+        )
+
+
+# ───────────────────────── Capsule (mock HTTP) ─────────────────────────
+
+
+@respx.mock
+def _make_capsule(capsule_id: str = "sb-1") -> Capsule:
+    respx.post(f"{BASE}/v1/capsules").respond(
+        202,
+        json={"id": capsule_id, "status": "starting", "template": DEFAULT_TEMPLATE},
+    )
+    return Capsule(api_key=API_KEY, base_url=BASE)
+
+
+class TestCapsuleDefaults:
+    @respx.mock
+    def test_default_template_sent(self):
+        route = respx.post(f"{BASE}/v1/capsules").respond(
+            202, json={"id": "sb-1", "status": "starting"}
+        )
+        Capsule(api_key=API_KEY, base_url=BASE)
+        body = json.loads(route.calls[0].request.content)
+        assert body["template"] == DEFAULT_TEMPLATE
+        assert DEFAULT_TEMPLATE == "code-runner-beta"
+
+    @respx.mock
+    def test_explicit_template_override(self):
+        route = respx.post(f"{BASE}/v1/capsules").respond(
+            202, json={"id": "sb-1", "status": "starting"}
+        )
+        Capsule(template="other-template", api_key=API_KEY, base_url=BASE)
+        body = json.loads(route.calls[0].request.content)
+        assert body["template"] == "other-template"
+
+    @respx.mock
+    def test_create_classmethod(self):
+        respx.post(f"{BASE}/v1/capsules").respond(
+            202, json={"id": "sb-2", "status": "starting"}
+        )
+        c = Capsule.create(api_key=API_KEY, base_url=BASE)
+        assert c.capsule_id == "sb-2"
+
+    @respx.mock
+    def test_default_kernel_name(self):
+        respx.post(f"{BASE}/v1/capsules").respond(
+            202, json={"id": "sb-1", "status": "starting"}
+        )
+        c = Capsule(api_key=API_KEY, base_url=BASE)
+        assert c._kernel_name == DEFAULT_KERNEL == "wrenn"
+
+    @respx.mock
+    def test_custom_kernel_name(self):
+        respx.post(f"{BASE}/v1/capsules").respond(
+            202, json={"id": "sb-1", "status": "starting"}
+        )
+        c = Capsule(kernel="python3", api_key=API_KEY, base_url=BASE)
+        assert c._kernel_name == "python3"
+
+
+class TestCtorFailureSafe:
+    """Bug regression: __del__ must not crash when ctor fails before
+    _proxy_client is initialised."""
+
+    @respx.mock
+    def test_del_safe_when_ctor_fails(self):
+        respx.post(f"{BASE}/v1/capsules").respond(
+            404,
+            json={"error": {"code": "not_found", "message": "no template"}},
+        )
+        from wrenn.exceptions import WrennNotFoundError
+
+        with pytest.raises(WrennNotFoundError):
+            Capsule(api_key=API_KEY, base_url=BASE)
+        # If we got here without an AttributeError on __del__, we're good.
+
+    @respx.mock
+    def test_close_idempotent(self):
+        c = _make_capsule()
+        c.close()
+        c.close()  # second call must not raise
+
+
+# ───────────────────────── _ensure_kernel ─────────────────────────
+
+
+class TestEnsureKernel:
+    @respx.mock
+    def test_creates_kernel_with_wrenn_name_when_none_exist(self):
+        c = _make_capsule()
+        proxy_base = "https://8888-sb-1.app.wrenn.dev"
+        list_route = respx.get(f"{proxy_base}/api/kernels").respond(200, json=[])
+        create_route = respx.post(f"{proxy_base}/api/kernels").respond(
+            201, json={"id": "k-new", "name": "wrenn"}
+        )
+
+        kid = c._ensure_kernel()
+        assert kid == "k-new"
+        # Body must request the wrenn kernelspec.
+        body = json.loads(create_route.calls[0].request.content)
+        assert body == {"name": "wrenn"}
+        assert list_route.called
+
+    @respx.mock
+    def test_reuses_existing_wrenn_kernel(self):
+        c = _make_capsule()
+        proxy_base = "https://8888-sb-1.app.wrenn.dev"
+        respx.get(f"{proxy_base}/api/kernels").respond(
+            200,
+            json=[
+                {"id": "k-other", "name": "python3"},
+                {"id": "k-wrenn", "name": "wrenn"},
+            ],
+        )
+        create = respx.post(f"{proxy_base}/api/kernels").respond(201, json={})
+        kid = c._ensure_kernel()
+        assert kid == "k-wrenn"
+        assert not create.called
+
+    @respx.mock
+    def test_creates_when_only_other_kernels_exist(self):
+        c = _make_capsule()
+        proxy_base = "https://8888-sb-1.app.wrenn.dev"
+        respx.get(f"{proxy_base}/api/kernels").respond(
+            200, json=[{"id": "k-other", "name": "python3"}]
+        )
+        respx.post(f"{proxy_base}/api/kernels").respond(
+            201, json={"id": "k-new", "name": "wrenn"}
+        )
+        kid = c._ensure_kernel()
+        assert kid == "k-new"
+
+    @respx.mock
+    def test_caches_kernel_id(self):
+        c = _make_capsule()
+        proxy_base = "https://8888-sb-1.app.wrenn.dev"
+        route = respx.get(f"{proxy_base}/api/kernels").respond(
+            200, json=[{"id": "k-1", "name": "wrenn"}]
+        )
+        c._ensure_kernel()
+        c._ensure_kernel()
+        assert route.call_count == 1
+
+    @respx.mock
+    def test_custom_kernel_name_sent(self):
+        respx.post(f"{BASE}/v1/capsules").respond(
+            202, json={"id": "sb-1", "status": "starting"}
+        )
+        c = Capsule(kernel="python3", api_key=API_KEY, base_url=BASE)
+        proxy_base = "https://8888-sb-1.app.wrenn.dev"
+        respx.get(f"{proxy_base}/api/kernels").respond(200, json=[])
+        create = respx.post(f"{proxy_base}/api/kernels").respond(
+            201, json={"id": "k-py", "name": "python3"}
+        )
+        c._ensure_kernel()
+        body = json.loads(create.calls[0].request.content)
+        assert body == {"name": "python3"}
+
+    @respx.mock
+    def test_retries_on_5xx_then_succeeds(self):
+        c = _make_capsule()
+        proxy_base = "https://8888-sb-1.app.wrenn.dev"
+        responses = [
+            httpx.Response(503),
+            httpx.Response(200, json=[{"id": "k-1", "name": "wrenn"}]),
+        ]
+        respx.get(f"{proxy_base}/api/kernels").mock(side_effect=responses)
+        with patch("time.sleep"):
+            kid = c._ensure_kernel(jupyter_timeout=5)
+        assert kid == "k-1"
+
+    @respx.mock
+    def test_raises_on_4xx(self):
+        c = _make_capsule()
+        proxy_base = "https://8888-sb-1.app.wrenn.dev"
+        respx.get(f"{proxy_base}/api/kernels").respond(401)
+        with pytest.raises(httpx.HTTPStatusError):
+            c._ensure_kernel(jupyter_timeout=2)
+
+    @respx.mock
+    def test_timeout_raises(self):
+        c = _make_capsule()
+        proxy_base = "https://8888-sb-1.app.wrenn.dev"
+        respx.get(f"{proxy_base}/api/kernels").respond(503)
+        with patch("time.sleep"):
+            with pytest.raises(TimeoutError):
+                c._ensure_kernel(jupyter_timeout=0.01)
+
+
+# ───────────────────────── _jupyter_execute_request ─────────────────────────
+
+
+class TestJupyterRequest:
+    def test_structure(self):
+        msg = Capsule._jupyter_execute_request("print(1)")
+        assert msg["channel"] == "shell"
+        assert msg["header"]["msg_type"] == "execute_request"
+        assert msg["content"]["code"] == "print(1)"
+        assert msg["content"]["silent"] is False
+        assert msg["content"]["store_history"] is True
+        assert msg["content"]["allow_stdin"] is False
+        assert msg["content"]["stop_on_error"] is True
+        # msg_id must be a uuid-shaped string
+        assert len(msg["header"]["msg_id"]) == 36
+
+    def test_unique_msg_id_per_call(self):
+        a = Capsule._jupyter_execute_request("x")
+        b = Capsule._jupyter_execute_request("x")
+        assert a["header"]["msg_id"] != b["header"]["msg_id"]
+
+
+# ───────────────────────── run_code (WS-mocked) ─────────────────────────
+
+
+def _wrap(msg_type: str, parent_id: str, content: dict) -> dict:
+    return {
+        "msg_type": msg_type,
+        "header": {"msg_type": msg_type},
+        "parent_header": {"msg_id": parent_id},
+        "content": content,
+    }
+
+
+class _FakeWS:
+    """Minimal sync httpx_ws-shaped fake."""
+
+    def __init__(self, frames_factory):
+        self._frames_factory = frames_factory
+        self._sent: list[str] = []
+        self._iter = None
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *a):
+        return False
+
+    def send_text(self, s: str) -> None:
+        self._sent.append(s)
+        parent_id = json.loads(s)["header"]["msg_id"]
+        self._iter = iter(self._frames_factory(parent_id))
+
+    def receive_json(self, timeout: float = 0):
+        assert self._iter is not None
+        try:
+            return next(self._iter)
+        except StopIteration:
+            raise TimeoutError("no more frames")
+
+
+class _FakeAsyncWS:
+    def __init__(self, frames_factory):
+        self._frames_factory = frames_factory
+        self._iter = None
+
+    async def __aenter__(self):
+        return self
+
+    async def __aexit__(self, *a):
+        return False
+
+    async def send_text(self, s: str) -> None:
+        parent_id = json.loads(s)["header"]["msg_id"]
+        self._iter = iter(self._frames_factory(parent_id))
+
+    async def receive_json(self, timeout: float = 0):
+        assert self._iter is not None
+        try:
+            return next(self._iter)
+        except StopIteration:
+            raise TimeoutError("no more frames")
+
+
+class TestRunCode:
+    @respx.mock
+    def _make_ready(self):
+        c = _make_capsule()
+        # Pre-populate kernel so run_code skips ensure.
+        c._kernel_id = "k-1"
+        return c
+
+    def test_stream_stdout_and_stderr(self):
+        c = self._make_ready()
+
+        def frames(pid):
+            yield _wrap("stream", pid, {"name": "stdout", "text": "hello\n"})
+            yield _wrap("stream", pid, {"name": "stderr", "text": "warn\n"})
+            yield _wrap("status", pid, {"execution_state": "idle"})
+
+        stdout_chunks, stderr_chunks = [], []
+        with patch(
+            "wrenn.code_runner.capsule.httpx_ws.connect_ws",
+            return_value=_FakeWS(frames),
+        ):
+            ex = c.run_code(
+                "print('hello')",
+                on_stdout=stdout_chunks.append,
+                on_stderr=stderr_chunks.append,
+            )
+        assert ex.logs.stdout == ["hello\n"]
+        assert ex.logs.stderr == ["warn\n"]
+        assert stdout_chunks == ["hello\n"]
+        assert stderr_chunks == ["warn\n"]
+        assert ex.error is None
+
+    def test_execute_result_main_and_display_data(self):
+        c = self._make_ready()
+
+        def frames(pid):
+            yield _wrap(
+                "display_data",
+                pid,
+                {"data": {"image/png": "BASE64"}},
+            )
+            yield _wrap(
+                "execute_result",
+                pid,
+                {
+                    "execution_count": 7,
+                    "data": {"text/plain": "'42'"},
+                },
+            )
+            yield _wrap("status", pid, {"execution_state": "idle"})
+
+        results = []
+        with patch(
+            "wrenn.code_runner.capsule.httpx_ws.connect_ws",
+            return_value=_FakeWS(frames),
+        ):
+            ex = c.run_code("'42'", on_result=results.append)
+        assert ex.execution_count == 7
+        assert len(ex.results) == 2
+        main = [r for r in ex.results if r.is_main_result]
+        assert len(main) == 1
+        assert main[0].text == "'42'"  # text/plain preserved verbatim
+        display = [r for r in ex.results if not r.is_main_result]
+        assert display[0].png == "BASE64"
+        assert ex.text == "'42'"
+        assert len(results) == 2
+
+    def test_error_message(self):
+        c = self._make_ready()
+
+        def frames(pid):
+            yield _wrap(
+                "error",
+                pid,
+                {
+                    "ename": "NameError",
+                    "evalue": "name 'x' is not defined",
+                    "traceback": ["line1", "line2"],
+                },
+            )
+            yield _wrap("status", pid, {"execution_state": "idle"})
+
+        errors = []
+        with patch(
+            "wrenn.code_runner.capsule.httpx_ws.connect_ws",
+            return_value=_FakeWS(frames),
+        ):
+            ex = c.run_code("x", on_error=errors.append)
+        assert ex.error is not None
+        assert ex.error.name == "NameError"
+        assert ex.error.value == "name 'x' is not defined"
+        assert ex.error.traceback == "line1\nline2"
+        assert len(errors) == 1
+
+    def test_ignores_frames_with_other_parent(self):
+        c = self._make_ready()
+
+        def frames(pid):
+            yield _wrap("stream", "other-id", {"name": "stdout", "text": "drop\n"})
+            yield _wrap("stream", pid, {"name": "stdout", "text": "keep\n"})
+            yield _wrap("status", pid, {"execution_state": "idle"})
+
+        with patch(
+            "wrenn.code_runner.capsule.httpx_ws.connect_ws",
+            return_value=_FakeWS(frames),
+        ):
+            ex = c.run_code("print('keep')")
+        assert ex.logs.stdout == ["keep\n"]
+
+    def test_unsupported_language_raises(self):
+        c = self._make_ready()
+        with pytest.raises(ValueError, match="not supported"):
+            c.run_code("console.log('x')", language="javascript")
+
+    def test_idle_status_terminates_loop(self):
+        c = self._make_ready()
+        called = {"n": 0}
+
+        def frames(pid):
+            yield _wrap("status", pid, {"execution_state": "idle"})
+            # Following frame must never be consumed.
+            called["n"] += 1
+            yield _wrap("stream", pid, {"name": "stdout", "text": "post-idle\n"})
+
+        with patch(
+            "wrenn.code_runner.capsule.httpx_ws.connect_ws",
+            return_value=_FakeWS(frames),
+        ):
+            ex = c.run_code("pass")
+        assert ex.logs.stdout == []
+
+
+class TestAsyncRunCode:
+    @respx.mock
+    def _make_ready(self):
+        respx.post(f"{BASE}/v1/capsules").respond(
+            202, json={"id": "sb-1", "status": "starting"}
+        )
+        from wrenn.client import AsyncWrennClient
+        from wrenn.models import Capsule as CapsuleModel
+
+        client = AsyncWrennClient(api_key=API_KEY, base_url=BASE)
+        info = CapsuleModel(id="sb-1")
+        c = AsyncCapsule(_capsule_id="sb-1", _client=client, _info=info)
+        c._kernel_id = "k-1"
+        return c
+
+    @pytest.mark.asyncio
+    async def test_stream_and_result(self):
+        c = self._make_ready()
+
+        def frames(pid):
+            yield _wrap("stream", pid, {"name": "stdout", "text": "hi\n"})
+            yield _wrap(
+                "execute_result",
+                pid,
+                {"execution_count": 1, "data": {"text/plain": "7"}},
+            )
+            yield _wrap("status", pid, {"execution_state": "idle"})
+
+        with patch(
+            "wrenn.code_runner.async_capsule.httpx_ws.aconnect_ws",
+            return_value=_FakeAsyncWS(frames),
+        ):
+            ex = await c.run_code("7")
+        assert ex.logs.stdout == ["hi\n"]
+        assert ex.text == "7"
+        assert ex.execution_count == 1
+        await c.close()
+
+    @pytest.mark.asyncio
+    async def test_async_default_kernel(self):
+        c = self._make_ready()
+        assert c._kernel_name == "wrenn"
+        await c.close()
+
+
+class TestAsyncCtorFailureSafe:
+    def test_del_safe_when_not_constructed(self):
+        # Build without ever calling __init__'s parent path that needs network,
+        # by hand-poking attributes the way create() failure would leave them.
+        c = AsyncCapsule.__new__(AsyncCapsule)
+        # __del__ should be safe even with no attrs.
+        c.__del__()