feat(embeddings): split camelCase identifiers by default and stamp vectors

README.md

@@ -94,12 +94,28 @@ one tool and exits without the MCP stdio handshake — ideal for scripting.
 | `--workspace <path>` | current dir | Directories to index (repeatable for multi-project) |
 | `--exclude <dir>` | — | Directories to skip (repeatable) |
 | `--embedding-model <model>` | `bge-small` | `bge-small` (384d, fast), `jina-code-v2` (768d, 6× slower), `granite-97m` (384d, 32K ctx, ~3× slower), or `static` (model2vec, 256d — ~100× faster indexing, no ONNX; needs a local model dir, see below) |
-| `--full-body-embedding` | `true` | Embed full function body (~50 lines) for better semantic search and duplicate detection |
+| `--full-body-embedding` | `true` | Embed full function body (~50 lines) for better semantic search and duplicate detection. Takes a value: `--full-body-embedding=false` turns it off |
+| `--split-identifiers` | `true` | Also embed the word-split form of identifiers whose words are run together, so `getUserById` embeds as "get user by id" too. Names already separated by `_` or `-` are left alone, since they tokenise into the same words; a leading or trailing delimiter separates nothing, so `_handleClick` is split like `handleClick`. Takes a value: `--split-identifiers=false` embeds raw names, as releases up to 0.20.1 did |
 | `--max-files <n>` | 5000 | Maximum files to index |
 | `--profile <name>` | `all` | Filter the exposed MCP tool surface to a named subset (see below) |
 | `--graph-only` | off | Skip embedding generation — build the graph and serve structural tools only. No ONNX model load, 10-50× faster indexing. Semantic search and memory tools unavailable. For CI / one-shot graph queries. |
 | `--run-tool <name>` | — | One-shot mode: index, run a single tool, print its result, exit. No MCP handshake. Pair with `--tool-args '<json>'`. |
 
+`--split-identifiers` and `--full-body-embedding` both change the text every
+symbol is embedded from, and vectors built from different text cannot be ranked
+against each other.
+A project's stored vectors are therefore stamped with the settings that built
+them - `--embedding-model` included, since models differ in dimension - and are
+ignored by any process configured differently.
+An index written by 0.20.1 or earlier carries no stamp, so it is re-embedded the
+first time this version opens it; changing any of the three re-embeds in the
+background rather than requiring a manual reindex.
+Run `--watch` with the same flags as the sessions that read the project, so both
+sides share one set instead of re-embedding over each other.
+A daemon left running across an upgrade keeps writing vectors the new build
+cannot match, and sessions attached to it serve without semantic search until it
+is restarted - so restart `--watch` after upgrading.
+
 #### `--embedding-model static` — model2vec fast indexing
 
 Static (model2vec) embeddings replace the ONNX transformer with a token→vector

crates/codegraph-memory/examples/embed_eval.rs

@@ -168,7 +168,15 @@ fn metrics(ranks: &[usize]) -> Scores {
 
 /// Returns (semantic-only, hybrid 0.4*BM25 + 0.6*cosine) scores.
 fn evaluate(engine: &VectorEngine, syms: &[Sym]) -> (Scores, Scores) {
-    let split = std::env::var("CODEGRAPH_SPLIT_IDS").is_ok();
+    // Presence is not the question - `CODEGRAPH_SPLIT_IDS=0` must mean off.
+    // `is_ok()` made setting it to 0 turn the feature ON, which silently turned
+    // an A/B run into two identical arms. `=1` is the one spelling this harness
+    // documents, so it is the one spelling it accepts.
+    //
+    // Note this forces splitting on every identifier, unlike the engine, which
+    // applies it only to delimiter-free names: the point of this harness is to
+    // measure the lever in isolation.
+    let split = std::env::var("CODEGRAPH_SPLIT_IDS").as_deref() == Ok("1");
     let sym_texts: Vec<String> = syms
         .iter()
         .map(|s| {