---
title: "vfs-host-confinement — Mova code model"
description: "Mova code model of vfs/src/host.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/vfs/src/host.rs.groupant/confinement.groupant/"
---
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# vfs-host-confinement

The groupant beside vfs/src/host.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.

## Facts

- **kind:** groupant_fragment
- **status:** partial source bound model
- **source:** [`vfs/src/host.rs`](https://github.com/ElamurAI/mova-free/blob/main/vfs/src/host.rs)
- **source SHA-256:** `d7a0bb0efff6f8f4…`
- **covers:** DirFs path preflight and journal wrapper. (bytes 2987–4308)
- **part of:** [vfs-host](https://md.groupants.elamur.ai/free/en/mova/vfs/src/host.rs.groupant/)
- **repository folder:** [`vfs/src/host.rs.groupant/confinement.groupant`](https://github.com/ElamurAI/mova-free/tree/main/vfs/src/host.rs.groupant/confinement.groupant)
- **repository commit:** `855da7bd4a7b`

> **Implementation material.** A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.

## Components

| component | label | where |
|---|---|---|
| **approximant** | partial | [approximant](#approximant) |
| **ast** | partial | `../syntax.json` |
| **composition** | partial | [composition](#composition) |
| **cost** | partial | [Cost](#cost) |
| **descriptant** | present | [descriptant](#descriptant) |
| **invariant** | partial | [Invariant](#invariant) |
| **tests** | executed bounded checks | [tests](#tests) |

## Obernants

The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.

| id | type | label | where |
|---|---|---|---|
| `behavior_complement` | behavior_complement | partial source derived model | [behavior_complement](#behavior-complement) |
| `reverse_reconstruction` | reverse_reconstruction | partial source derived model | [reverse_reconstruction](#reverse-reconstruction) |
| `lexical_first` | lexical_first | partial source derived model | [lexical_first](#lexical-first) |
| `dangling_link` | dangling_link | partial source derived model | [dangling_link](#dangling-link) |
| `ancestor_probe` | ancestor_probe | partial source derived model | [ancestor_probe](#ancestor-probe) |
| `check_access_race` | check_access_race | partial source derived model | [check_access_race](#check-access-race) |

## Model text


### descriptant

#### vfs-host-confinement

DirFs path preflight and journal wrapper.

##### Prospective epoch

2026-10-31: source reviewed before edits; prospective review retained under $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31/prospective.md. Predicted order/cost: Path construction O(bytes); up to depth canonicalize probes with OS-dependent work.

##### Observation epoch

Bounded actual calls and compiled negative controls are recorded in tests.md. Production behavior bytes unchanged; only focused test blocks added. Snapshot constant-time wording is conditional on cwd and destruction; recursive operations may partially commit.

##### Unsupported approximants

No executable percentage surrogate is claimed for these categorical/state/effect observations. Future 1%,2%,5%,10% require a useful metric, explicit domain and exact reference.

### approximant

#### Forward relation

DirFs path preflight and journal wrapper.

normalize virtual path then append components under canonical root. Final symlink must canonicalize inside; otherwise probe ancestors until canonicalization succeeds. with calls operation only after successful real_path.

Domain: bounded inputs with available allocation and nonoverflowing counters unless checked explicitly. The relation is partial and source-derived.

### composition

#### Composition

DirFs path preflight and journal wrapper. Shared state and order: normalize virtual path then append components under canonical root. Final symlink must canonicalize inside; otherwise probe ancestors until canonicalization succeeds. with calls operation only after successful real_path.

Scoped children project this same source. Their domains and effects remain conditional; source execution connects these clauses rather than independently proving their wiring. Stable root required; failed preflight recorded by with and OS closure not called.

### models

## Typed source models

Source-bound partial relations; no universal finite-test proof.

### behavior_complement

Subject: vfs-host-confinement. Domain: DirFs path preflight and journal wrapper. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: Outside final or ancestor link does not reach OS closure when Fault=None.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### reverse_reconstruction

Subject: vfs-host-confinement. Domain: DirFs path preflight and journal wrapper. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: Accepted canonical path admits virtual aliases; denied result cannot uniquely identify malicious vs dangling target.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### lexical_first

Subject: vfs-host-confinement. Domain: DirFs path preflight and journal wrapper. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: Above-root dotdot rejects before host canonicalization.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### dangling_link

Subject: vfs-host-confinement. Domain: DirFs path preflight and journal wrapper. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: Final symlink canonicalization failure returns escape rather than following missing target.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### ancestor_probe

Subject: vfs-host-confinement. Domain: DirFs path preflight and journal wrapper. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: Nonexistent regular child uses canonical deepest existing ancestor.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### check_access_race

Subject: vfs-host-confinement. Domain: DirFs path preflight and journal wrapper. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.

Operator: No atomic descriptor confinement between canonicalize and std IO.

Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.

### tests

#### Checks and limitations

Exact named observations: dirfs_confines_to_root, gates_green_and_negative_controls_red.

Fresh receipts: $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31; run.sh retains four profile/repetition sets with raw logs and numeric statuses. native-commands.json and source-test-map.json disambiguate targets. Compiled mutations and exact restoration are separately retained in mutation-summary.json.

These finite observations are not semantic completeness. Source syntax generated twice and compared byte-for-byte. Host effects are limited to owned TMPDIR fixtures. Existing absolute_paths_never_reach_the_host and open_modes are skipped; snapbench main is skipped. Standalone helpers/reexports are only observed through named callers or representation checks; RealFs effect methods unexecuted.

### invariant-and-cost

## Invariant and cost

### Invariant

Stable root required; failed preflight recorded by with and OS closure not called.

### Cost

Path construction O(bytes); up to depth canonicalize probes with OS-dependent work.

No timing or numerical error guarantee is inferred from finite tests.