Here’s a compact, plain‑English plan to make your scanner **faster, quieter, and auditor‑friendly** by (1) diff‑aware rescans and (2) unified binary+source reachability—both drop‑in for Stella Ops.

# Deterministic, diff‑aware rescans (clean SBOM/VEX diffs)
**Goal:** Only recompute what changed; emit stable, minimal diffs reviewers can trust.

**Core ideas**
- **Per‑layer SBOM artifacts (cacheable):** For each image layer `L#`, persist:
  - `sbom-L#.cdx.json` (CycloneDX), `hash(L#)`, `toolchain-hash`, `feeds-hash`.
  - **Symbol‑fingerprints** for each discovered file: `algo|path|size|mtime|xxh3|funcIDs[]`.
- **Slice recomputation:** On new image `I'`, match layers via hashes; for changed layers or files, recompute *only* their call‑graph slices and vuln joins.
- **Deterministic manifests:** Every scan writes a `scan.lock.json` (inputs, feed versions, rules, lattice policy hash, tool versions, clocks) so results are **replayable**.

**Minimal data model (Mongo)**
- `scan_runs(_id, imageDigest, inputsHash, policyHash, feedsHash, startedAt, finishedAt, parentRunId?)`
- `layer_sboms(scanRunId, layerDigest, sbomCid, symbolIndexCid, layerHash)`
- `file_symbols(scanRunId, path, fileHash, funcIDs[], lang, size, mtime)`
- `diffs(fromRunId, toRunId, kind: 'sbom'|'vex'|'reachability', stats, patch)` (store JSON Patch)

**Algorithm sketch**
1. Resolve base image ancestry → map `old layer digest ↔ new layer digest`.
2. For unchanged layers: reuse `layer_sboms` + `file_symbols`.
3. For changed/added files: re‑symbolize + re‑analyze; restrict call‑graph build to **impacted SCCs**.
4. Re‑join OSV/GHSA/vendor vulns → compute reachability deltas → emit **stable JSON Patch**.

**CLI impact**
- `stella scan --deterministic --cache-dir ~/.stella/cache --emit-diff previousRunId`
- `stella diff --from <runA> --to <runB> --format jsonpatch|md`

---

# Unified binary + source reachability (function‑level)
**Goal:** Decide “is the vulnerable function reachable/used here?” across native and managed code.

**Extraction**
- **Binary symbolizers:**  
  - ELF: parse `.symtab`/`.dynsym`, DWARF (if present).  
  - Mach‑O/PE: export tables + DWARF/PDB (if present).  
  - Build **Canonical Symbol ID (CSID)**: `lang:pkg@ver!binary#file:function(signature)`; normalize C++/Rust mangling.
- **Source symbolizers:**  
  - .NET (Roslyn+IL), JVM (bytecode), Go (SSA), Node/TS (TS AST), Python (AST), Rust (HIR/MIR if available).
- **Bindings join:** Map FFI edges (P/Invoke, cgo, JNI/JNA, N-API) → **cross‑ecosystem call edges**:
  - `.NET P/Invoke` → DLL export CSID.
  - Java JNI → `Java_com_pkg_Class_Method` ↔ native export.
  - Node N-API → addon exports ↔ JS require() site.

**Reachability pipeline**
1. Build per‑language call graphs (CG) with framework models (ASP.NET, Spring, Express, etc.).
2. Add FFI edges; merge into a **polyglot call graph**.
3. Mark **entrypoints** (container `CMD/ENTRYPOINT`, web handlers, cron, CLI verbs).
4. For each CVE → {pkg, version, affected symbols[]} map → **is any affected CSID on a path from an entrypoint?**
5. Output evidence:
   - `reachable: true|false|unknown`
   - shortest path (symbols list)
   - probes (optional): runtime samples (EventPipe/JFR/uprobes) hitting CSIDs

**Artifacts emitted**
- `symbols.csi.jsonl` (all CSIDs)
- `polyglot.cg.slices.json` (only impacted SCCs for diffs)
- `reach.vex.json` (OpenVEX/CSAF with function‑level notes + confidence)

---

# What to build next (low‑risk, high‑impact)
- **[Week 1–2]** Per‑layer caches + `scan.lock.json`; file symbol‑fingerprints (xxh3 + top‑K funcIDs).  
- **[Week 3–4]** ELF/PE/Mach‑O symbolizer lib with CSIDs; .NET IL + P/Invoke mapper.  
- **[Week 5–6]** Polyglot CG merge + entrypoint discovery from Docker metadata; JSON Patch diffs.  
- **[Week 7+]** Runtime probes (opt‑in) to boost confidence and suppress false positives.

---

# Tiny code seeds (C# hints)

**Symbol fingerprint (per file)**
```csharp
record SymbolFingerprint(
  string Algo, string Path, long Size, long MTimeUnix,
  string ContentHash, string[] FuncIds);
```

**Deterministic scan lock**
```csharp
record ScanLock(
  string FeedsHash, string RulesHash, string PolicyHash, string Toolchain,
  string ImageDigest, string[] LayerDigests, DateTimeOffset Clock,
  IDictionary<string,string> EnvPins);
```

**JSON Patch diff emit**
```csharp
var patch = JsonDiffPatch.Diff(oldVexJson, newVexJson); // stable sort keys beforehand
File.WriteAllText("vex.diff.json", patch);
```

---

If you want, I can turn this into:
- a **.proto** for the cache/index objects,
- a **Mongo schema + indexes** (including compound keys for fast layer reuse),
- and a **.NET 10** service skeleton (`StellaOps.Scanner.WebService`) with endpoints:
`/scan`, `/diff/{from}/{to}`, `/reach/{runId}`.