---
title: "prag-opus-projection — Mova code model"
description: "Mova code model of prag/src/opus.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/prag/src/opus.rs.groupant/projection.groupant/"
---
Elamur: [Mova](https://md.mova.elamur.ai/free/en/) · [Dictionary](https://md.dictionary.elamur.ai/free/en/) · [Research](https://md.research.elamur.ai/free/en/) · **Groupants**

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# prag-opus-projection

The groupant beside prag/src/opus.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:** available partial
- **source:** [`prag/src/opus.rs`](https://github.com/ElamurAI/mova-free/blob/main/prag/src/opus.rs)
- **source SHA-256:** `0169f72bddab55f9…`
- **covers:** projection production operations (bytes 1901–2807)
- **part of:** [prag-opus](https://md.groupants.elamur.ai/free/en/mova/prag/src/opus.rs.groupant/)
- **repository folder:** [`prag/src/opus.rs.groupant/projection.groupant`](https://github.com/ElamurAI/mova-free/tree/main/prag/src/opus.rs.groupant/projection.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** | available partial | `model.md` |
| **ast** | partial | `../syntax.json` |
| **cost** | available partial | [Cost](#cost) |
| **descriptant** | available partial | `model.md` |
| **invariant** | available partial | `model.md` |
| **tests** | available partial | `../model.md#evidence` |

## 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 |
|---|---|---|---|
| `excluded` | behavior_complement | available partial | `model.md` |
| `fibers` | reverse_reconstruction | available partial | `model.md` |
| `reply-defaults` | default_field_fibers | available partial | [Reply default fibers](#reply-default-fibers) |

## Model text


Domain: supplied JSON Value, step string, batch/sentence usize and elapsed f64. Observation: returned answer and every Call field. Forward: copy metadata, string result or empty, numeric cost or zero, named unsigned token fields or zero. Invariant: no process/filesystem access; token slots retain key identity. Cost: O(answer bytes + step bytes + 1) for the fixed canonical schema; arbitrary extra keys add map lookup work as specified in the Cost section.

Behavior complement: altered metadata and different nondefault token slots are excluded. No lifecycle validation occurs here; decode_events owns that boundary. Reverse reconstruction: zero fields permit absent, mistyped or zero source values; extra JSON fields are unconstrained. Nondefault values constrain corresponding source fields. Supplied seconds are copied, including nonfinite values subsequently rejected by append.

Assumptions: production input is an already validated canonical teacher reply; arbitrary synthetic values only characterize compatibility defaults. Evidence: canonical_decode_accounting_join and supplied_projection_default_fibers; compiled cache-slot mutant fails canonical join. Source hash bound in manifest. Epoch 2026-10-30: extracted pure seam without changing defaults. No approximation error or process behavior claim.

### Cost

Let A and S be answer and step bytes, M outer object keys and U usage object keys. Copying strings allocates O(A+S) storage; token conversion and metadata copy cost O(1). The number of lookup operations is fixed, but default serde_json uses BTreeMap objects, giving O(log(M+1)+log(U+1)) key comparisons. Fixed literal lookup-key lengths bound each comparison cost. General supplied-Value time is therefore O(A+S+1+log(M+1)+log(U+1)); the fixed canonical schema reduces this to O(A+S+1). Enabling serde_json preserve_order changes the map implementation and requires separate lookup-cost assumptions. No JSON parsing, process execution, I/O or elapsed-time measurement is performed in this seam. This symbolic model excludes allocator costs and does not claim measured speed.

Scope/source revision: opus.rs SHA-256 0169f72bddab55f9e493b85a86918b5f0adbcf5153c7c12725bb249f2ed5c136; source and native evidence unchanged from d229375e0. These are symbolic inspection-based costs, not measured complexity guarantees for external services.

### Reply default fibers

Domain: arbitrary supplied JSON Value and fixed metadata. Observation: result string, cost and four token slots. Operator applies as_str/as_f64/as_u64 followed by empty/zero defaults. Complement: invalid types cannot become nonzero token counts; defaulted input does not produce a validation error here. Reverse fibers for zero include absent, null, wrong-type and numerical zero values; nonzero unsigned slots require their own corresponding key values. Extra keys remain free. Assumption: production calls pass decode_events output, while synthetic tests characterize wider compatibility behavior. Evidence: supplied_projection_default_fibers checks null, absent, negative/string fields and u64 maximum; canonical_decode_accounting_join checks named slots; cache-slot mutant fails that join.

Approximation semantics: scoped exact structural relation over the stated domain, supported by finite named evidence and source inspection; no probabilistic bound or general proof. Source revision: opus.rs SHA-256 0169f72bddab55f9e493b85a86918b5f0adbcf5153c7c12725bb249f2ed5c136, native code/evidence d229375e0. Tests refer to evidence.md at the file groupant root.