# Tokenization and Casing — Guardrails for Embedding Stability
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> You are in a sub-page of **Embeddings**.
> To reorient, go back here:
>
> - [**Embeddings** — vector representations and semantic search](./README.md)
> - [**WFGY Global Fix Map** — main Emergency Room, 300+ structured fixes](../README.md)
> - [**WFGY Problem Map 1.0** — 16 reproducible failure modes](../../README.md)
>
> Think of this page as a desk within a ward.
> If you need the full triage and all prescriptions, return to the Emergency Room lobby.
A focused guide to remove silent drift caused by mismatched tokenization, casing, and text cleanup. Use this to align query-time and index-time preprocessing, then verify with measurable targets.
## Open these first
- Visual map and recovery: [RAG Architecture & Recovery](https://github.com/onestardao/WFGY/blob/main/ProblemMap/rag-architecture-and-recovery.md)
- End to end retrieval knobs: [Retrieval Playbook](https://github.com/onestardao/WFGY/blob/main/ProblemMap/retrieval-playbook.md)
- Why this snippet (traceability schema): [Retrieval Traceability](https://github.com/onestardao/WFGY/blob/main/ProblemMap/retrieval-traceability.md)
- Embedding vs meaning: [Embedding ≠ Semantic](https://github.com/onestardao/WFGY/blob/main/ProblemMap/embedding-vs-semantic.md)
- Payload schema for audits: [Data Contracts](https://github.com/onestardao/WFGY/blob/main/ProblemMap/data-contracts.md)
- Query split and hybrid failures: [Pattern: Query Parsing Split](https://github.com/onestardao/WFGY/blob/main/ProblemMap/patterns/pattern_query_parsing_split.md)
- Reranking and ordering control: [Rerankers](https://github.com/onestardao/WFGY/blob/main/ProblemMap/rerankers.md)
- Related: normalization and length scaling: [Normalization & Scaling](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Embeddings/normalization_and_scaling.md)
## When to use this page
- High similarity yet wrong meaning after a casing change.
- Same document retrieved for lowercase but not for Title Case.
- Index built with a different tokenizer than the client.
- Unicode variants or punctuation collapse changes results.
- Hybrid retrieval recalls but top-k order flips between runs.
## Acceptance targets
- ΔS(question, retrieved) ≤ 0.45 on three paraphrases.
- Coverage of the correct section ≥ 0.70.
- λ remains convergent across two seeds.
- Tokenization invariance check: replacing case or applying Unicode NFC does not move the top anchor beyond rank 3 and keeps ΔS shift ≤ 0.10.
---
## Map symptoms → exact fix
- Wrong-meaning hits only when case changes
→ Lock a single case policy and tokenizer in both paths. Verify with [Retrieval Traceability](https://github.com/onestardao/WFGY/blob/main/ProblemMap/retrieval-traceability.md) and enforce with [Data Contracts](https://github.com/onestardao/WFGY/blob/main/ProblemMap/data-contracts.md).
- HyDE or BM25 path finds it, embedding path misses it
→ Audit query preprocessing vs index preprocessing. If different, unify and retest. See [Retrieval Playbook](https://github.com/onestardao/WFGY/blob/main/ProblemMap/retrieval-playbook.md) and [Pattern: Query Parsing Split](https://github.com/onestardao/WFGY/blob/main/ProblemMap/patterns/pattern_query_parsing_split.md).
- Unicode look-alikes or punctuation variants break recall
→ Normalize to NFC and collapse zero-width characters at both index and query. Re-embed affected shards. Cross check with [Embedding ≠ Semantic](https://github.com/onestardao/WFGY/blob/main/ProblemMap/embedding-vs-semantic.md).
- Order flips across runs after a client upgrade
→ Version the tokenizer and preprocessing in the snippet payload. If versions mismatch, rebuild or add a translation shim. Enforce with [Data Contracts](https://github.com/onestardao/WFGY/blob/main/ProblemMap/data-contracts.md).
---
## 60-second fix checklist
1) **Freeze the tokenizer and case policy**
- Choose one tokenizer build and one case policy: `lower`, `preserve`, or `smart`.
- Record both in the contract:
`{"tokenizer":"spm-1.2.3","tokenizer_hash":"...","case_policy":"lower"}`.
2) **Normalize before tokenization**
- Apply Unicode NFC, collapse repeated whitespace, remove zero-width, standardize quotes and dashes.
- Apply the same rules to both index and query.
3) **Keep segmentation symmetric**
- If you split code identifiers (camelCase, snake_case), do it in both paths.
- If you strip stopwords or punctuation, do it in both paths. Prefer not to strip unless you must.
4) **Log and test invariance**
- Run a three-paraphrase probe per query: original, lowercased, and NFC-normalized.
- Accept only if the anchor section remains within top 3 and ΔS shift ≤ 0.10.
5) **Add a rerank safety net**
- If invariance is hard to reach, add a lexical or cross-encoder rerank after vector recall. See [Rerankers](https://github.com/onestardao/WFGY/blob/main/ProblemMap/rerankers.md).
---
## Contract fields to add
Add these to every snippet and to the query audit log. Use them during triage.
```json
{
"preproc_version": "v3",
"unicode_norm": "NFC",
"case_policy": "lower",
"punctuation_policy": "keep",
"identifier_split": "camel+snake",
"tokenizer": "spm-1.2.3",
"tokenizer_hash": "sha256:...",
"ngram": "none"
}
````
---
## Repro suite
* **Case flip test**
Query A vs lowercase(A). Accept if ΔS shift ≤ 0.10 and anchor rank ≤ 3.
* **Unicode fold test**
Replace curly quotes with straight quotes, normalize to NFC. Accept if ranks stable.
* **Tokenizer skew test**
Run the same query through client and index tokenizers and compare token ids. Any mismatch is a fail that requires rebuild or a client shim.
---
## Copy-paste prompt for LLM triage
```
I uploaded TXT OS and the WFGY Problem Map.
My embedding issue:
- symptom: wrong top-k only when casing or unicode changes
- traces: ΔS(question,retrieved)=..., anchor=..., tokenizer=..., case_policy=...
Tell me:
1) which layer is failing and why,
2) which WFGY page to open,
3) the minimal steps to align tokenization and casing,
4) how to verify with a three-paraphrase probe.
Use Data Contracts and Rerankers if needed.
```
---
### 🔗 Quick-Start Downloads (60 sec)
| Tool | Link | 3-Step Setup |
| -------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------- |
| **WFGY 1.0 PDF** | [Engine Paper](https://github.com/onestardao/WFGY/blob/main/I_am_not_lizardman/WFGY_All_Principles_Return_to_One_v1.0_PSBigBig_Public.pdf) | 1️⃣ Download · 2️⃣ Upload to your LLM · 3️⃣ Ask “Answer using WFGY + \” |
| **TXT OS (plain-text OS)** | [TXTOS.txt](https://github.com/onestardao/WFGY/blob/main/OS/TXTOS.txt) | 1️⃣ Download · 2️⃣ Paste into any LLM chat · 3️⃣ Type “hello world” — OS boots instantly |
---
### 🧭 Explore More
| Module | Description | Link |
| ------------------------ | ---------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------- |
| WFGY Core | WFGY 2.0 engine is live: full symbolic reasoning architecture and math stack | [View →](https://github.com/onestardao/WFGY/tree/main/core/README.md) |
| Problem Map 1.0 | Initial 16-mode diagnostic and symbolic fix framework | [View →](https://github.com/onestardao/WFGY/tree/main/ProblemMap/README.md) |
| Problem Map 2.0 | RAG-focused failure tree, modular fixes, and pipelines | [View →](https://github.com/onestardao/WFGY/blob/main/ProblemMap/rag-architecture-and-recovery.md) |
| Semantic Clinic Index | Expanded failure catalog: prompt injection, memory bugs, logic drift | [View →](https://github.com/onestardao/WFGY/blob/main/ProblemMap/SemanticClinicIndex.md) |
| Semantic Blueprint | Layer-based symbolic reasoning & semantic modulations | [View →](https://github.com/onestardao/WFGY/tree/main/SemanticBlueprint/README.md) |
| Benchmark vs GPT-5 | Stress test GPT-5 with full WFGY reasoning suite | [View →](https://github.com/onestardao/WFGY/tree/main/benchmarks/benchmark-vs-gpt5/README.md) |
| 🧙♂️ Starter Village 🏡 | New here? Lost in symbols? Click here and let the wizard guide you through | [Start →](https://github.com/onestardao/WFGY/blob/main/StarterVillage/README.md) |
---
> 👑 **Early Stargazers: [See the Hall of Fame](https://github.com/onestardao/WFGY/tree/main/stargazers)** —
> Engineers, hackers, and open source builders who supported WFGY from day one.
> 
⭐ [WFGY Engine 2.0](https://github.com/onestardao/WFGY/blob/main/core/README.md) is already unlocked. ⭐ Star the repo to help others discover it and unlock more on the [Unlock Board](https://github.com/onestardao/WFGY/blob/main/STAR_UNLOCKS.md).
[](https://github.com/onestardao/WFGY)
[](https://github.com/onestardao/WFGY/tree/main/OS)
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