feat(constrained-detector): candidates from the semantic IR, shaped by family

Task 1.1. The detector stops searching: something deterministic decides what
it looks at, ordered by (path, line, name) and bounded by a constant, so the
batches a later task forms are determined by the input alone.

A call candidate carries what the model used to grep for -- the arguments,
and the binding chain the IR resolved for them, nearest first. An access
control candidate is the operation with the guards in scope, because an
absence bug has no sink.

Two things the fixture taught while writing it. The IR emits a chained call
twice at one line, once bare and once carrying the keyword arguments, so
deduplication keeps the richest: a bare `filter_by` and
`filter_by(user_id=owner)` are the same site and only one of them says what
the constraint was. And `leaky` and `constrained` in the shared obligations
fixture both discharge through `filter_by` -- what separates them is that one
chain ends at `request.args.get('owner')` and the other at `request.user.id`.
That contrast is now the test, and it is exactly the judgement the model is
being narrowed down to make.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG
This commit is contained in:
Marius Ciepluch
2026-09-06 18:23:54 +02:00
co-authored by Claude Opus 5
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"""What a detector is asked to judge, enumerated deterministically (constrained-detector, Req 1).
The detector stops searching. Measured on 2026-09-06, 120 runs of the unconstrained loop over the same twelve pairs
produced 120 distinct tool-call trajectories, and outcome disagreement tracked trajectory divergence rather than
judgement: the model was spending its budget guessing grep patterns to find sinks the semantic IR already knows.
So something deterministic decides what the model looks at, and that enumerator becomes a hard ceiling on recall.
Which is why it was measured before any of this was built: the pattern ruleset finds a candidate inside the labeled
function for **12.1%** of the corpus — below the 64.9% the unconstrained loop already reaches — while the IR's call
sites and bindings reach **96.6%**, a median of ten sites per function. The ruleset is never the generator here.
Ordering is `(path, line, name)` and the bound is a constant, so the batches the judgment step forms, and therefore
the sequence of model calls, are determined by the input alone.
"""
from __future__ import annotations
from collections.abc import Sequence
from dataclasses import dataclass, field
from pathlib import Path
from typing import Literal
CandidateKind = Literal["call", "bind", "operation", "config"]
# What can carry each family's bug. An injection lives at a call; an access-control bug is the *absence* of a guard
# around an operation, so its candidate is the operation and what the model needs is the guards in scope.
FAMILY_SHAPE: dict[str, tuple[CandidateKind, ...]] = {
"injection": ("call",),
"path": ("call",),
"deserialization": ("call",),
"untrusted_destination": ("call",),
"output_encoding": ("call",),
"memory": ("call",),
"prototype": ("call", "bind"),
"access_control": ("operation",),
"config_secrets": ("bind", "config"),
"unknown": ("call", "bind"),
}
# The p90 of the measured distribution is 22 sites per labeled function, so two batches cover all but the tail.
MAX_CANDIDATES_PER_CALL = 12
_MAX_TEXT = 400
_LANGUAGE = {"python": "python", "javascript": "javascript", "typescript": "typescript", "c_cpp": "c", "java": "java"}
@dataclass(frozen=True)
class Candidate:
"""One site the model will be asked a single bounded question about."""
path: str
line: int
kind: CandidateKind
name: str
text: str
function: str
arg_texts: tuple[str, ...] = ()
arg_names: tuple[tuple[str, ...], ...] = ()
# What the IR resolved for the arguments, nearest binding first. This is the work the model used to do by
# grepping, and the reason it no longer has to.
binding_chain: tuple[str, ...] = ()
guards: tuple[str, ...] = ()
@property
def id(self) -> str:
return f"{self.path}:{self.line}:{self.name}"
def to_dict(self) -> dict[str, object]:
return {
"id": self.id,
"kind": self.kind,
"name": self.name,
"line": self.line,
"function": self.function,
"text": self.text,
"arguments": list(self.arg_texts),
"binding_chain": list(self.binding_chain),
"guards": list(self.guards),
}
@dataclass(frozen=True)
class CandidateSet:
"""The sites to judge, what was dropped past the bound, and why there is nothing when there is nothing."""
candidates: tuple[Candidate, ...] = ()
discarded: int = 0
reason: str = "" # "", unsupported_language, no_candidate
function_found: bool = True
def enumerate_candidates(
root: Path,
region: object,
family: str,
*,
taxonomy: object,
limit: int = MAX_CANDIDATES_PER_CALL,
) -> CandidateSet:
"""Every site in the region that could carry ``family``'s bug, ordered and bounded."""
del taxonomy # the family id is the key; the taxonomy validates it elsewhere
from ..semantic.ir import parse_file
path = str(getattr(region, "path", "") or "")
wanted = str(getattr(region, "function", "") or "")
target = root / path
if not target.is_file():
return CandidateSet(reason="unsupported_language", function_found=False)
text = target.read_text(errors="ignore")
ir = parse_file(path, text, _language_of(path))
if not ir.parse_ok:
return CandidateSet(reason="unsupported_language", function_found=False)
functions = [item for item in ir.functions if item.name != "<module>" and (not wanted or item.name == wanted)]
if wanted and not functions:
return CandidateSet(reason="no_candidate", function_found=False)
kinds = FAMILY_SHAPE.get(family, ("call", "bind"))
lines = text.splitlines()
found: list[Candidate] = []
for function in functions:
guards = _guards(ir, function, text, path) if "operation" in kinds else ()
found.extend(_from_function(path, function, kinds, lines, guards))
found.sort(key=lambda item: (item.path, item.line, item.name))
# One question per site: a chained expression reaches the IR as several calls at the same line and name — one
# bare, one carrying the arguments — and asking twice would spend budget and double-count the answer. Keep the
# richest, because `filter_by(user_id=owner)` and a bare `filter_by` are the same site and only one of them
# says what the constraint was.
best: dict[str, Candidate] = {}
for item in found:
current = best.get(item.id)
if current is None or (len(item.arg_texts), len(item.binding_chain)) > (len(current.arg_texts), len(current.binding_chain)):
best[item.id] = item
found = sorted(best.values(), key=lambda item: (item.path, item.line, item.name))
if not found:
return CandidateSet(reason="no_candidate")
return CandidateSet(candidates=tuple(found[:limit]), discarded=max(len(found) - limit, 0))
def _from_function(path: str, function: object, kinds: Sequence[str], lines: Sequence[str], guards: tuple[str, ...]): # type: ignore[no-untyped-def]
binds = tuple(getattr(function, "binds", ()) or ())
name = str(getattr(function, "name", ""))
out: list[Candidate] = []
if "call" in kinds or "operation" in kinds:
kind: CandidateKind = "operation" if "operation" in kinds else "call"
for site in getattr(function, "calls", ()) or ():
out.append(
Candidate(
path=path,
line=site.line,
kind=kind,
name=site.name,
text=_line_text(lines, site.line),
function=name,
arg_texts=tuple(site.arg_texts),
arg_names=tuple(tuple(names) for names in site.arg_names),
binding_chain=_chain(binds, [n for names in site.arg_names for n in names], site.line),
guards=guards,
)
)
if "bind" in kinds or "config" in kinds:
for bind in binds:
if "config" in kinds and "bind" not in kinds and not bind.is_constant:
continue
out.append(
Candidate(
path=path,
line=bind.line,
kind="config" if (bind.is_constant and "config" in kinds) else "bind",
name=bind.name,
text=_line_text(lines, bind.line),
function=name,
arg_texts=(bind.value_text[:_MAX_TEXT],),
arg_names=(tuple(bind.names),),
binding_chain=_chain(binds, list(bind.names), bind.line),
guards=guards,
)
)
return out
def _chain(binds: Sequence[object], names: Sequence[str], before: int, depth: int = 4) -> tuple[str, ...]:
"""Walk the bindings backwards from the names an argument mentions, nearest first.
This is exactly the work the unconstrained loop was doing with `grep_repo`, and it is deterministic."""
chain: list[str] = []
seen: set[str] = set()
wanted = [name for name in names if name]
for _ in range(depth):
step = None
for bind in sorted(binds, key=lambda item: -int(getattr(item, "line", 0))):
line = int(getattr(bind, "line", 0))
bound = str(getattr(bind, "name", ""))
if line >= before or bound not in wanted or bound in seen:
continue
step = bind
break
if step is None:
break
seen.add(str(step.name)) # type: ignore[attr-defined]
chain.append(f"{step.name} = {str(step.value_text)[:_MAX_TEXT]}") # type: ignore[attr-defined]
before = int(step.line) # type: ignore[attr-defined]
wanted = [name for name in getattr(step, "names", ()) or () if name]
if not wanted:
break
return tuple(chain)
def _guards(ir: object, function: object, text: str, path: str) -> tuple[str, ...]:
"""Decorators and in-body witnesses that discharge an obligation on this function, by identifier only."""
try:
from ..semantic.facts import load_facts
from ..semantic.obligations import load_obligation_facts
from ..semantic.obligations.operations import find_discharges
except ImportError: # pragma: no cover - the obligations facts are shipped, this is belt and braces
return ()
name = str(getattr(function, "name", ""))
try:
witnesses = find_discharges(ir, load_obligation_facts(), load_facts(), text=text) # type: ignore[arg-type]
except Exception: # noqa: BLE001 - a missing fact file must not stop enumeration
return ()
del path
return tuple(sorted({item.detail or item.fact_id for item in witnesses if item.function == name}))
def _line_text(lines: Sequence[str], line: int) -> str:
return lines[line - 1].strip()[:_MAX_TEXT] if 0 < line <= len(lines) else ""
def _language_of(path: str) -> str:
from ..preprocess import detect_language
return _LANGUAGE.get(detect_language(Path(path)), detect_language(Path(path)))
@dataclass(frozen=True)
class CandidateReport:
"""The ceiling: what a candidate-driven detector could find before any model is asked anything."""
per_family: dict[str, dict[str, object]] = field(default_factory=dict)
per_slice: dict[str, dict[str, object]] = field(default_factory=dict)
gaps: tuple[tuple[str, str, str], ...] = () # (slice, pair, reason)
def to_dict(self) -> dict[str, object]:
return {
"per_family": {name: dict(block) for name, block in sorted(self.per_family.items())},
"per_slice": {name: dict(block) for name, block in sorted(self.per_slice.items())},
"gaps": [list(row) for row in self.gaps],
}
__all__ = [
"FAMILY_SHAPE",
"MAX_CANDIDATES_PER_CALL",
"Candidate",
"CandidateKind",
"CandidateReport",
"CandidateSet",
"enumerate_candidates",
]