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"""A typed analysis graph that replaces transcript replay.
Motivation is a measurement, not an aesthetic. On BioMysteryBench with a 25-step budget,
a step costs a median **9,267 tokens** while contributing only **~400 tokens** of genuinely
new content (921 chars of tool output plus 684 chars of command). Roughly 96% of the spend
is the loop re-sending its own history, so cost grows as O(T^2) and the step budget binds
long before the task is finished -- 75% of attempts exhaust it, and the median *correct*
answer uses every step it is given.
This module makes the conditioning context a bounded, structured summary instead. A node
stores an artifact **handle** (a path) rather than the artifact, so the graph stays small
regardless of how much data the analysis touches. Step cost becomes O(B) for a rendering
budget B, and the total becomes O(T*B): at the measured rate of new content, a 4k-token
state supports roughly 100 steps for the token cost that buys 25 today.
The graph is also what makes verification composable: each node carries the checks that
its own artifact must satisfy (see `vera.checks`), so a dense progress signal falls out of
the structure rather than being bolted on.
"""
from __future__ import annotations
from dataclasses import dataclass, field
from typing import Iterable, Sequence
from .checks import CheckResult, rho
# Node kinds, ordered by their position in a typical analysis pipeline. Used only for
# rendering and weighting; the graph itself imposes no ordering constraint.
KINDS = ("load", "qc", "transform", "test", "interpret", "answer")
# Rough chars-per-token for budget accounting. Deliberately conservative: overestimating
# tokens truncates a little early, which is safe, whereas underestimating overflows the
# context, which is not.
CHARS_PER_TOKEN = 3.5
@dataclass(frozen=True)
class Node:
"""One step of an analysis, with its artifact and the checks it must satisfy.
Attributes:
id: Short unique handle, e.g. ``n7``.
kind: One of `KINDS`.
summary: One line stating what this node established. This is what the model
reads on later steps, so it must carry the *finding*, not the activity
("14,203 of 34,460 cells pass QC", not "ran QC").
artifact: Path to the produced file, or "" if the node produced only a scalar.
Never the contents -- holding contents here would reintroduce the O(T^2)
cost this module exists to remove.
parents: Ids of nodes this one consumed.
command: The shell command that produced it, for provenance and replay.
checks: Consistency checks over this node's artifact.
"""
id: str
kind: str
summary: str
artifact: str = ""
parents: tuple[str, ...] = ()
command: str = ""
checks: tuple[CheckResult, ...] = ()
def __post_init__(self) -> None:
if self.kind not in KINDS:
raise ValueError(f"unknown node kind {self.kind!r}; expected one of {KINDS}")
@property
def rho(self) -> float:
"""Verification score of this node: the fraction of its checks that passed."""
return rho(self.checks)
def render(self) -> str:
"""One-line rendering for the model-facing state summary."""
n_ok = sum(c.passed for c in self.checks)
mark = f"{n_ok}/{len(self.checks)}" if self.checks else "unverified"
parents = f" <- {','.join(self.parents)}" if self.parents else ""
art = f" [{self.artifact}]" if self.artifact else ""
return f"({self.id}) {self.kind}: {self.summary}{art} checks={mark}{parents}"
class AnalysisState:
"""The agent's working memory: a DAG of nodes, rendered under a token budget.
Use `add` after each step and `render` to build the next prompt. `reward` gives the
dense per-step signal that test-time steering consumes.
"""
def __init__(self) -> None:
self._nodes: dict[str, Node] = {}
self._order: list[str] = []
def __len__(self) -> int:
return len(self._nodes)
def __contains__(self, node_id: object) -> bool:
return node_id in self._nodes
def __getitem__(self, node_id: str) -> Node:
return self._nodes[node_id]
@property
def nodes(self) -> tuple[Node, ...]:
"""All nodes, in insertion order."""
return tuple(self._nodes[i] for i in self._order)
def add(self, node: Node) -> Node:
"""Insert a node.
Args:
node: The node to add.
Raises:
ValueError: If the id is already used, or a parent is unknown. Both are
programming errors that would silently corrupt provenance, so they raise
rather than being tolerated.
"""
if node.id in self._nodes:
raise ValueError(f"duplicate node id {node.id!r}")
missing = [p for p in node.parents if p not in self._nodes]
if missing:
raise ValueError(f"node {node.id!r} references unknown parents {missing}")
self._nodes[node.id] = node
self._order.append(node.id)
return node
def leaves(self) -> tuple[Node, ...]:
"""Nodes that no other node consumes -- the current analysis frontier."""
consumed = {p for n in self._nodes.values() for p in n.parents}
return tuple(self._nodes[i] for i in self._order if i not in consumed)
def ancestors(self, node_id: str) -> set[str]:
"""Ids of all transitive parents of `node_id` (excluding itself)."""
seen: set[str] = set()
stack = list(self._nodes[node_id].parents)
while stack:
cur = stack.pop()
if cur in seen:
continue
seen.add(cur)
stack.extend(self._nodes[cur].parents)
return seen
def reward(self, new_nodes: Iterable[Node], weights: dict[str, float] | None = None) -> float:
"""Dense progress signal contributed by this step.
Args:
new_nodes: Nodes added at this step.
weights: Optional per-kind weight. Missing kinds default to 1.0.
Returns:
Sum over new nodes of ``weight(kind) * rho(node)``. Zero for no new nodes,
and zero for nodes carrying no checks -- see `vera.checks.rho`.
"""
weights = weights or {}
return sum(weights.get(n.kind, 1.0) * n.rho for n in new_nodes)
def render(self, budget_tokens: int = 4000) -> str:
"""Render the state as model-facing text, never exceeding `budget_tokens`.
Priority when the budget binds, highest first: the current frontier (leaves),
then their ancestors, then everything else by recency. Frontier nodes are what
the next action builds on, and their ancestors are what makes them interpretable;
an unrelated early branch is the first thing that can be dropped.
Args:
budget_tokens: Cap on the rendering, in tokens (estimated at
`CHARS_PER_TOKEN` chars per token).
Returns:
The rendering. If nodes were dropped, a final line says how many, so the
model knows its view is partial rather than believing the analysis is smaller
than it is.
"""
if not self._nodes:
return "(no analysis steps yet)"
# Frontier first, most recent first: when every node is a leaf (parallel
# branches), the newest is the one the next action builds on. Then the
# ancestors that make those leaves interpretable, then the rest by recency.
leaf_ids = [n.id for n in reversed(self.leaves())]
ordered = list(leaf_ids)
for lid in leaf_ids:
ordered.extend(sorted(self.ancestors(lid)))
rank: dict[str, int] = {}
for i, nid in enumerate(ordered):
rank.setdefault(nid, i)
for i, nid in enumerate(nid for nid in reversed(self._order) if nid not in rank):
rank[nid] = len(ordered) + i
budget_chars = int(budget_tokens * CHARS_PER_TOKEN)
# Reserve room for the elision note up front, so adding it cannot overflow.
note_tmpl = "\n... %d earlier node(s) elided to fit the state budget"
reserve = len(note_tmpl % len(self._order))
fill = max(0, budget_chars - reserve)
chosen: set[str] = set()
used = 0
for nid in sorted(self._order, key=lambda x: rank[x]):
line = self._nodes[nid].render()
if used + len(line) + 1 > fill:
continue
chosen.add(nid)
used += len(line) + 1
# Render in pipeline order, not priority order, so the analysis reads forwards.
body = "\n".join(self._nodes[nid].render() for nid in self._order if nid in chosen)
dropped = len(self._order) - len(chosen)
if dropped:
body += note_tmpl % dropped
if not body:
body = "(state budget too small to render any node)"
# Belt and braces: the cap is a guarantee callers size their context against.
return body[:budget_chars]