Files
kebab/tasks/p3/p3-1-embedder-trait.md
kb bc1b3147cd refactor(spec): cleanup pass over component specs
Address 8 issues found in spec audit (post PR #2):

1. §refs label: distinguish design vs report sections in p3-1 / p3-2 / p4-2 /
   p9-1 / p9-5 contract_sections (e.g., "report §11.2 Ollama" not "§11.2").
2. mock feature gate: gate MockEmbedder (p3-1) and MockLanguageModel (p4-1)
   behind `mock` cargo feature, default OFF; add CI symbol-scan as DoD item.
3. Warning type unification: p1-2 frontmatter now emits
   `kb_parse_types::Warning` (matches p1-3 / p1-4); drops crate-internal type.
4. p4-3 streaming thread: explicitly single-threaded inside RagPipeline::ask;
   collection + sink.send share the calling thread, no race. UI concurrency
   is callers responsibility (TUI worker thread pattern in p9-3).
5. p6-2 tesseract version: noted that `tesseract` 0.13 has no stable Rust
   `version()` accessor; use TessVersion FFI or shell-out + cache approach.
6. p9-* App struct extensions: introduce `kb_tui::{Library,Search,Ask,Inspect}State`
   slots in p9-1 forward-decl form; p9-2/3/4 fill bodies in their own crate
   without editing `App`. Parallel-safety contract added.
7. p3-3 cosine score: shift `(sim+1)/2` instead of clamp; preserve ranking
   signal between unrelated and opposite vectors. Clamp reserved for NaN.
8. fixtures/ root: p0-1 DoD now creates all fixture subdirs with .gitkeep so
   downstream tasks have a stable target path.
2026-04-27 23:38:13 +00:00

4.4 KiB

phase, component, task_id, title, status, depends_on, unblocks, contract_source, contract_sections
phase component task_id title status depends_on unblocks contract_source contract_sections
P3 kb-embed (trait crate) p3-1 Embedder trait + EmbeddingInput/Kind validation planned
p0-1
p3-2
p3-3
p3-4
../../docs/superpowers/specs/2026-04-27-kb-final-form-design.md
design §3.7 SearchHit.embedding_model
design §7.1 EmbeddingInput/Kind
design §7.2 Embedder
report §11 LLM/embedding split

p3-1 — Embedder trait crate

Goal

Provide the kb-embed crate that re-exports Embedder trait, EmbeddingInput/EmbeddingKind, and offers a mock implementation for downstream tests. This task is trait-only; concrete adapters live in p3-2.

Why now / why this size

Concrete adapters (fastembed, ollama-embed, candle) need a stable trait surface. Owning the trait + a mock implementation in a tiny crate keeps kb-store-vector and kb-search testable without touching real models.

Allowed dependencies

  • kb-core
  • kb-config
  • serde
  • thiserror
  • tracing
  • [features] mock = [] — opt-in feature flag exposing MockEmbedder. Default OFF. Release builds (omit --features mock) compile MockEmbedder out entirely.

Forbidden dependencies

  • fastembed, ort, tokenizers, kb-source-fs, kb-parse-md, kb-normalize, kb-chunk, kb-store-*, kb-search, kb-llm*, kb-rag, kb-tui, kb-desktop

Inputs

input type source
EmbeddingInput kb_core::EmbeddingInput<'_> callers (parser-side or query-side)
model identity (EmbeddingModelId, EmbeddingVersion, dimensions) adapter at construction

Outputs

output type downstream
Vec<Vec<f32>> row-aligned with input kb-store-vector, kb-search (vector mode)

Public surface (signatures only — no new types)

pub use kb_core::{EmbeddingInput, EmbeddingKind, EmbeddingModelId, EmbeddingVersion, Embedder};

/// Test-only mock that produces deterministic vectors. Compiled only when `mock` feature is on.
#[cfg(feature = "mock")]
pub struct MockEmbedder { /* internal: model_id, dims, seed */ }
#[cfg(feature = "mock")]
impl MockEmbedder {
    pub fn new(model_id: kb_core::EmbeddingModelId, version: kb_core::EmbeddingVersion, dimensions: usize) -> Self;
}
#[cfg(feature = "mock")]
impl kb_core::Embedder for MockEmbedder { /* per §7.2 */ }

Behavior contract

  • MockEmbedder::embed produces vectors deterministically from (text, kind): e.g., vector[i] = hash_to_unit_float(text, kind, i, seed) so two identical inputs produce identical vectors and different inputs produce nearly-orthogonal vectors. Used by downstream tests.
  • MockEmbedder must respect EmbeddingKind::Document vs Query — different prefix mixed into the hash so query embeddings differ from document embeddings of the same text (mirrors real e5 behavior).
  • dimensions() returns the value passed at construction; callers must trust it.
  • Real adapters (p3-2) MUST NOT implement Embedder here.
  • The crate may expose a tiny helper pub fn assert_vector_shape(vecs: &[Vec<f32>], expected_dims: usize) for downstream tests.

Storage / wire effects

  • None.

Test plan

kind description fixture / data
unit trait dyn dispatch via Box<dyn Embedder> works inline
unit MockEmbedder produces identical vector for identical input inline
unit EmbeddingKind::Document vs Query for same text yield different vectors inline
unit dimensions match construction-time value inline
contract property test: 100 random inputs, each vector has length == dimensions, all finite floats inline (proptest)

All tests under cargo test -p kb-embed.

Definition of Done

  • cargo check -p kb-embed passes
  • cargo test -p kb-embed passes
  • No external embedding dep present
  • PR links design §7.2 Embedder, §11

Out of scope

  • Real adapter (kb-embed-local is p3-2).
  • Reranker traits (P+).

Risks / notes

  • MockEmbedder is gated by mock feature (default OFF). Downstream tests opt in via [dev-dependencies] kb-embed = { path = "...", features = ["mock"] }. CI build of release binary (cargo build --release without --features mock) MUST NOT include MockEmbedder symbol — verifiable via cargo bloat or nm symbol scan.
  • Trait re-exports keep the call site stable even if kb-core reorganizes; downstream crates should use kb_embed::Embedder rather than use kb_core::Embedder.