Module goal 

Goal-presence sensor (PSP-8): the verifier that refuses false stability.

The SRBN gate accepts a state once its energy V drops below the declared floor. But an empty or placeholder file compiles, has no failing tests, and no diagnostics — so every code-quality sensor reports r_e = 0 and the gate would declare it stable even though the requested work was never done. That is false stability: convergence to a fixed point that does not satisfy the goal.

PSP-8 closes this with a goal-presence sensor: a node carries a GoalSpec naming the symbols its work must bring into existence, and the sensor emits a blocking ResidualClass::SymbolMismatch residual for every expected symbol that is absent from the observed workspace. A blocking residual is a hard-gate failure (hard(y) is false), so the node cannot be accepted while its goal artifact is missing, regardless of how low the other energy components are.

This module is domain-neutral: it compares names. Extracting the expected names from a task contract and the observed names from source is the domain package’s job (see perspt-coding), keeping the mechanism/domain split of PSP-8 intact.

Structs

GoalSpec

The set of symbols a node’s work is required to bring into existence.

Functions

goal_presence_residual

Emit a single blocking goal-presence residual when any expected symbol is absent from observed. Returns None when the spec is empty or the goal is already satisfied.

goal_presence_sensor

The goal-presence sensor identifier and its independence route. It is a deterministic AST/source query, not a model critique, so it is full-weight eligible.

missing_symbols

The expected symbols absent from observed, preserving declared order and de-duplicating. Comparison is exact on the name string; the domain is responsible for normalizing names (e.g. stripping a module:: prefix) before building the GoalSpec and the observed set.