fix(learning-harness): the three defects the group 2 review found

Task 2.3: two of the five unscorable reasons had no code path, so an unparsable
row was reported as a corpus labelling defect when the true cause was a tooling
gap. They have different owners and different fixes, and conflating them is the
dishonesty this spec exists to remove. The design's unscorable_reason is
reinstated with the parse result as an input, and a handler that arrived without
its registration is now named as missing context for the families whose bug
shape is a missing check.

Task 2.6: a verification stamped its own word for proof onto the shared evidence
level, which is not a value the project's ladder defines, and three existing
helpers raised on it. Nothing in production called it yet, so the suite stayed
green while the wiring in the next group would have broken a scan. A
verification now writes only its tag, and a caller that wants to move a claim up
the ladder goes through an explicit mapping that can only produce a level the
ladder has.

Task 2.7: the injection canary planted its row in a private in-memory database
the target could never reach, so it could not fire; the fake sandbox handed the
token back regardless of the snippet, which is why nothing noticed. It is now an
execution canary whose marker only an interpreter could write, and each template
is tested by running it for real against a vulnerable fixture and its fixed
twin. That test immediately caught a second flaw: a handler that merely echoes
its input printed the oracle token and satisfied the oracle without any
vulnerability, so an injected payload now carries a value unrelated to the token
the oracle looks for.

Also from the review: a configuration with no tools is refused instead of
producing a detector that silently reports nothing, the classifier abstains when
its fallback call fails too, and the archive docstring says which version wins.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG

tests/test_learning_canaries.py

@@ -5,6 +5,8 @@ from __future__ import annotations
 import json
 from pathlib import Path
 
+import pytest
+
 from openultrasast.config import SandboxConfig
 from openultrasast.findings import StaticFinding
 from openultrasast.learning.families import load_families
@@ -47,7 +49,7 @@ def test_every_canary_template_renders_and_passes_the_snippet_safety_check() ->
     assert render_canary("injection", language="rust", path="a.rs", function="f") is None
 
 
-def test_a_canary_token_is_unique_per_claim_so_one_family_never_answers_for_another() -> None:
+def test_a_canary_token_is_unique_to_the_experiment_it_names() -> None:
     from openultrasast.learning.canaries import render_canary
 
     first = render_canary("injection", language="python", path="app.py", function="lookup")
@@ -55,6 +57,8 @@ def test_a_canary_token_is_unique_per_claim_so_one_family_never_answers_for_anot
     third = render_canary("path", language="python", path="app.py", function="lookup")
     assert first and second and third
     assert first[1] != second[1] != third[1] and first[1] != third[1]
+    # the same family, file and function is the same experiment, so it is deliberately the same token
+    assert render_canary("injection", language="python", path="app.py", function="lookup")[1] == first[1]  # type: ignore[index]
 
 
 def test_the_canary_verifier_proves_only_when_the_oracle_fires(tmp_path: Path) -> None:
@@ -143,3 +147,51 @@ def _runner(reply: object) -> FakeSandboxRunner:
             return reply(marker)  # type: ignore[operator]
 
     return _Runner()
+
+
+VULNERABLE = {
+    "injection": "import os\n\n\ndef lookup(value):\n    os.system(value)\n    return 'done'\n",
+    "path": "def lookup(value):\n    with open(value, encoding='utf-8') as handle:\n        return handle.read()\n",
+    "deserialization": "import pickle\n\n\ndef lookup(value):\n    return pickle.loads(value)\n",
+}
+FIXED = {
+    "injection": (
+        "import shlex, subprocess\n\n\ndef lookup(value):\n"
+        "    subprocess.run(['echo', shlex.quote(value)], check=False)\n    return 'done'\n"
+    ),
+    "path": (
+        "from pathlib import Path\n\n\ndef lookup(value):\n"
+        "    name = Path(value).name\n    return (Path('/tmp') / name).read_text(encoding='utf-8') if False else ''\n"
+    ),
+    "deserialization": "import json\n\n\ndef lookup(value):\n    return json.loads(value.decode('utf-8', 'ignore') or '{}')\n",
+}
+
+
+@pytest.mark.parametrize("family", CANARY_FAMILIES)
+def test_each_canary_fires_on_a_real_bug_and_stays_quiet_on_its_fixed_twin(tmp_path: Path, family: str) -> None:
+    """The oracle must be a property of the code, not of the harness: run the snippet for real, both sides.
+
+    The injection fixture's fixed twin deliberately echoes its input, which is why the payload carries a
+    value unrelated to the oracle token: an echoing handler must not be able to satisfy the oracle.
+    """
+    import subprocess
+    import sys
+
+    from openultrasast.learning.canaries import render_canary
+
+    for side, sources in (("vuln", VULNERABLE), ("fixed", FIXED)):
+        workspace = tmp_path / side / "workspace"
+        scratch = tmp_path / side / "scratch"
+        workspace.mkdir(parents=True)
+        scratch.mkdir(parents=True)
+        (workspace / "app.py").write_text(sources[family])
+        rendered = render_canary(
+            family, language="python", path="app.py", function="lookup", workspace=str(workspace), scratch=str(scratch)
+        )
+        assert rendered is not None
+        snippet, token = rendered
+        script = scratch / "case.py"
+        script.write_text(snippet)
+        completed = subprocess.run([sys.executable, str(script)], capture_output=True, text=True, timeout=60, check=False)
+        fired = token in completed.stdout or token in completed.stderr
+        assert fired is (side == "vuln"), f"{family} {side}: {completed.stdout!r} {completed.stderr!r}"