diff --git a/.golangci.yml b/.golangci.yml
index ea9604e..e0e4d65 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -1,4 +1,3 @@
-version: "2"
 run:
   timeout: 5m
 linters:
diff --git a/AUDIT-ERROR-HANDLING.md b/AUDIT-ERROR-HANDLING.md
new file mode 100644
index 0000000..1e7af41
--- /dev/null
+++ b/AUDIT-ERROR-HANDLING.md
@@ -0,0 +1,69 @@
+# Audit: Error Handling & Logging
+
+This audit reviews the error handling and logging practices of the Poindexter Go library, focusing on the core `kdtree.go` implementation and the `wasm/main.go` wrapper.
+
+## Error Handling
+
+### Exception Handling
+- [x] **Are exceptions caught appropriately?**
+  - **Finding:** Yes. As a Go library, it doesn't use exceptions but instead returns `error` types. The code diligently checks for and propagates errors. For instance, `NewKDTree` returns an error for invalid input, and callers are expected to handle it.
+
+- [x] **Generic catches hiding bugs?**
+  - **Finding:** No. The library defines specific, exported error variables (e.g., `ErrEmptyPoints`, `ErrDimMismatch`) in `kdtree.go`. This allows consumers to programmatically check for specific error conditions using `errors.Is`, which is a best practice.
+
+- [x] **Error information leakage?**
+  - **Finding:** Previously, the WASM wrapper at `wasm/main.go` would return raw Go error strings to the JavaScript client. This has been **remediated** by introducing a structured `WasmError` type with a `code` and `message`, preventing the leakage of internal implementation details.
+
+### Error Recovery
+- [x] **Graceful degradation?**
+  - **Finding:** Yes. The `KDTree` constructor attempts to use the `gonum` backend if requested, but it gracefully falls back to the `linear` backend if the `gonum` build tag is not present or if the backend fails to initialize. This ensures the library remains functional even without the optimized backend.
+
+- [ ] **Retry logic with backoff?**
+  - **Finding:** Not applicable. This is a computational library, not a networked service, so retry logic is not relevant.
+
+- [ ] **Circuit breaker patterns?**
+  - **Finding:** Not applicable. This is not a networked service.
+
+### User-Facing Errors
+- [x] **Helpful without exposing internals?**
+  - **Finding:** Yes. The error messages are clear and actionable for developers (e.g., "inconsistent dimensionality in points") without revealing sensitive internal state.
+
+- [x] **Consistent error format?**
+  - **Finding:** Yes. The Go API uses the standard `error` interface. The WASM API has been updated to use a consistent JSON structure for all errors: `{ "ok": false, "error": { "code": "...", "message": "..." } }`.
+
+- [ ] **Localization support?**
+  - **Finding:** No. Error messages are in English. For a developer-facing library, this is generally acceptable and localization is not expected.
+
+### API Errors
+- [x] **Standard error response format?**
+  - **Finding:** Yes. As noted above, the WASM API now has a standardized JSON error format.
+
+- [ ] **Appropriate HTTP status codes?**
+  - **Finding:** Not applicable. This is a WASM module, not an HTTP service.
+
+- [x] **Error codes for clients?**
+  - **Finding:** Yes. The WASM API now includes standardized string-based error codes (e.g., `bad_request`, `not_found`), allowing clients to handle different error types programmatically.
+
+## Logging
+
+The library itself does not perform any logging, which is appropriate for its role. It returns errors to the calling application, which is then responsible for its own logging strategy. The library does include analytics and metrics collection (`kdtree_analytics.go`), but this is separate from logging and does not record any sensitive information.
+
+### What is Logged
+- [ ] Security events (auth, access)? - **N/A**
+- [ ] Errors with context? - **N/A**
+- [ ] Performance metrics? - **N/A** (collected, but not logged by the library)
+
+### What Should NOT be Logged
+- [ ] Passwords/tokens - **N/A**
+- [ ] PII without consent - **N/A**
+- [ ] Full credit card numbers - **N/A**
+
+### Log Quality
+- [ ] Structured logging (JSON)? - **N/A**
+- [ ] Correlation IDs? - **N/A**
+- [ ] Log levels used correctly? - **N/A**
+
+### Log Security
+- [ ] Injection-safe? - **N/A**
+- [ ] Tamper-evident? - **N/A**
+- [ ] Retention policy? - **N/A**
diff --git a/npm/poindexter-wasm/PROJECT_README.md b/npm/poindexter-wasm/PROJECT_README.md
index 634752c..396a316 100644
--- a/npm/poindexter-wasm/PROJECT_README.md
+++ b/npm/poindexter-wasm/PROJECT_README.md
@@ -71,7 +71,9 @@ Explore runnable examples in the repository:
 - examples/kdtree_2d_ping_hop
 - examples/kdtree_3d_ping_hop_geo
 - examples/kdtree_4d_ping_hop_geo_score
+- examples/dht_helpers (convenience wrappers for common DHT schemas)
 - examples/wasm-browser (browser demo using the ESM loader)
+- examples/wasm-browser-ts (TypeScript + Vite local demo)
 
 ### KDTree performance and notes
 - Dual backend support: Linear (always available) and an optimized KD backend enabled when building with `-tags=gonum`. Linear is the default; with the `gonum` tag, the optimized backend becomes the default.
@@ -216,4 +218,21 @@ This project is licensed under the European Union Public Licence v1.2 (EUPL-1.2)
 
 ## Contributing
 
-Contributions are welcome! Please feel free to submit a Pull Request.
\ No newline at end of file
+Contributions are welcome! Please feel free to submit a Pull Request.
+
+
+## Coverage
+
+- CI produces coverage summaries as artifacts on every push/PR:
+  - Default job: `coverage-summary.md` (from `coverage.out`)
+  - Gonum-tag job: `coverage-summary-gonum.md` (from `coverage-gonum.out`)
+- Locally, you can generate and inspect coverage with the Makefile:
+
+```bash
+make cover         # runs tests with race + coverage and prints the total
+make coverfunc     # prints per-function coverage
+make cover-kdtree  # filters coverage to kdtree.go
+make coverhtml     # writes coverage.html for visual inspection
+```
+
+Note: CI also uploads raw coverage profiles as artifacts (`coverage.out`, `coverage-gonum.out`).
diff --git a/npm/poindexter-wasm/loader.js b/npm/poindexter-wasm/loader.js
index e8da38d..b78696d 100644
--- a/npm/poindexter-wasm/loader.js
+++ b/npm/poindexter-wasm/loader.js
@@ -6,6 +6,11 @@
 //   await tree.insert({ id: 'a', coords: [0,0], value: 'A' });
 //   const res = await tree.nearest([0.1, 0.2]);
 
+// --- Environment detection ---
+const isBrowser = typeof window !== 'undefined';
+const isNode = typeof process !== 'undefined' && process.versions != null && process.versions.node != null;
+
+// --- Browser-specific helpers ---
 async function loadScriptOnce(src) {
   return new Promise((resolve, reject) => {
     // If already present, resolve immediately
@@ -18,20 +23,44 @@ async function loadScriptOnce(src) {
   });
 }
 
+// --- Loader logic ---
 async function ensureWasmExec(url) {
-  if (typeof window !== 'undefined' && typeof window.Go === 'function') return;
-  await loadScriptOnce(url);
-  if (typeof window === 'undefined' || typeof window.Go !== 'function') {
-    throw new Error('wasm_exec.js did not define window.Go');
+  if (typeof globalThis.Go === 'function') return;
+
+  if (isBrowser) {
+    await loadScriptOnce(url);
+  } else if (isNode) {
+    const { fileURLToPath } = await import('url');
+    const wasmExecPath = fileURLToPath(url);
+    await import(wasmExecPath);
+  } else {
+    throw new Error(`Unsupported environment: cannot load ${url}`);
+  }
+
+  if (typeof globalThis.Go !== 'function') {
+    throw new Error('wasm_exec.js did not define globalThis.Go');
   }
 }
 
 function unwrap(result) {
-  if (!result || typeof result !== 'object') throw new Error('bad result');
-  if (result.ok) return result.data;
-  throw new Error(result.error || 'unknown error');
+  if (!result || typeof result !== 'object') {
+    throw new Error(`bad/unexpected result type from WASM: ${typeof result}`);
+  }
+  if (result.ok) {
+    return result.data;
+  }
+  // Handle structured errors, which may be nested
+  const errorPayload = result.error || result;
+  if (errorPayload && typeof errorPayload === 'object') {
+    const err = new Error(errorPayload.message || 'unknown WASM error');
+    err.code = errorPayload.code;
+    throw err;
+  }
+  // Fallback for simple string errors
+  throw new Error(errorPayload || 'unknown WASM error');
 }
 
+
 function call(name, ...args) {
   const fn = globalThis[name];
   if (typeof fn !== 'function') throw new Error(`WASM function ${name} not found`);
@@ -65,18 +94,32 @@ export async function init(options = {}) {
   } = options;
 
   await ensureWasmExec(wasmExecURL);
-  const go = new window.Go();
+  const go = new globalThis.Go();
 
   let result;
   if (instantiateWasm) {
-    const source = await fetch(wasmURL).then(r => r.arrayBuffer());
+    let source;
+    if (isBrowser) {
+        source = await fetch(wasmURL).then(r => r.arrayBuffer());
+    } else {
+        const fs = await import('fs/promises');
+        const { fileURLToPath } = await import('url');
+        source = await fs.readFile(fileURLToPath(wasmURL));
+    }
     const inst = await instantiateWasm(source, go.importObject);
     result = { instance: inst };
-  } else if (WebAssembly.instantiateStreaming) {
+  } else if (isBrowser && WebAssembly.instantiateStreaming) {
     result = await WebAssembly.instantiateStreaming(fetch(wasmURL), go.importObject);
   } else {
-    const resp = await fetch(wasmURL);
-    const bytes = await resp.arrayBuffer();
+    let bytes;
+    if (isBrowser) {
+        const resp = await fetch(wasmURL);
+        bytes = await resp.arrayBuffer();
+    } else {
+        const fs = await import('fs/promises');
+        const { fileURLToPath } = await import('url');
+        bytes = await fs.readFile(fileURLToPath(wasmURL));
+    }
     result = await WebAssembly.instantiate(bytes, go.importObject);
   }
 
diff --git a/npm/poindexter-wasm/smoke.mjs b/npm/poindexter-wasm/smoke.mjs
index 925a246..c0a7b8a 100644
--- a/npm/poindexter-wasm/smoke.mjs
+++ b/npm/poindexter-wasm/smoke.mjs
@@ -4,11 +4,11 @@
 import { init } from './loader.js';
 
 (async function () {
+  let px;
   try {
-    const px = await init({
-      // In CI, dist/ is placed at repo root via make wasm-build && make npm-pack
-      wasmURL: new URL('./dist/poindexter.wasm', import.meta.url).pathname,
-      wasmExecURL: new URL('./dist/wasm_exec.js', import.meta.url).pathname,
+    px = await init({
+      wasmURL: new URL('./dist/poindexter.wasm', import.meta.url).toString(),
+      wasmExecURL: new URL('./dist/wasm_exec.js', import.meta.url).toString(),
     });
     const ver = await px.version();
     if (!ver || typeof ver !== 'string') throw new Error('version not string');
@@ -17,10 +17,24 @@ import { init } from './loader.js';
     await tree.insert({ id: 'a', coords: [0, 0], value: 'A' });
     await tree.insert({ id: 'b', coords: [1, 0], value: 'B' });
     const nn = await tree.nearest([0.9, 0.1]);
-    if (!nn || !nn.id) throw new Error('nearest failed');
-    console.log('WASM smoke ok:', ver, 'nearest.id=', nn.id);
+    if (!nn || !nn.point || !nn.point.id) throw new Error('nearest failed');
+    console.log('WASM smoke ok:', ver, 'nearest.id=', nn.point.id);
   } catch (err) {
     console.error('WASM smoke failed:', err);
     process.exit(1);
   }
+
+  // Test error handling
+  try {
+    await px.newTree(0);
+    console.error('Expected error from newTree(0) but got none');
+    process.exit(1);
+  } catch (err) {
+    if (err.code === 'bad_request' && err.message.includes('dimension')) {
+      console.log('WASM error handling ok:', err.code);
+    } else {
+      console.error('WASM smoke failed: unexpected error format:', err);
+      process.exit(1);
+    }
+  }
 })();
diff --git a/wasm/main.go b/wasm/main.go
index 373b827..509b49f 100644
--- a/wasm/main.go
+++ b/wasm/main.go
@@ -18,26 +18,62 @@ var (
 	nextTreeID   = 1
 )
 
+// WasmError provides a structured error for WASM responses.
+type WasmError struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+}
+
+func (e *WasmError) Error() string {
+	return fmt.Sprintf("%s: %s", e.Code, e.Message)
+}
+
+// Standard error codes.
+const (
+	ErrCodeBadRequest = "bad_request"
+	ErrCodeNotFound   = "not_found"
+	ErrCodeConflict   = "conflict"
+)
+
+func newErr(code, msg string) *WasmError {
+	return &WasmError{Code: code, Message: msg}
+}
+
+func newErrf(code, format string, args ...any) *WasmError {
+	return &WasmError{Code: code, Message: fmt.Sprintf(format, args...)}
+}
+
 func export(name string, fn func(this js.Value, args []js.Value) (any, error)) {
 	js.Global().Set(name, js.FuncOf(func(this js.Value, args []js.Value) any {
 		res, err := fn(this, args)
 		if err != nil {
-			return map[string]any{"ok": false, "error": err.Error()}
+			var wasmErr *WasmError
+			if errors.As(err, &wasmErr) {
+				return map[string]any{
+					"ok":    false,
+					"error": map[string]any{"code": wasmErr.Code, "message": wasmErr.Message},
+				}
+			}
+			// Fallback for generic errors
+			return map[string]any{
+				"ok":    false,
+				"error": map[string]any{"code": ErrCodeBadRequest, "message": err.Error()},
+			}
 		}
 		return map[string]any{"ok": true, "data": res}
 	}))
 }
 
-func getInt(v js.Value, idx int) (int, error) {
-	if len := v.Length(); len > idx {
-		return v.Index(idx).Int(), nil
+func getInt(args []js.Value, idx int, name string) (int, error) {
+	if len(args) > idx {
+		return args[idx].Int(), nil
 	}
-	return 0, errors.New("missing integer argument")
+	return 0, newErrf(ErrCodeBadRequest, "missing integer argument: %s", name)
 }
 
-func getFloatSlice(arg js.Value) ([]float64, error) {
+func getFloatSlice(arg js.Value, name string) ([]float64, error) {
 	if arg.IsUndefined() || arg.IsNull() {
-		return nil, errors.New("coords/query is undefined or null")
+		return nil, newErrf(ErrCodeBadRequest, "argument is undefined or null: %s", name)
 	}
 	ln := arg.Length()
 	res := make([]float64, ln)
@@ -47,6 +83,19 @@ func getFloatSlice(arg js.Value) ([]float64, error) {
 	return res, nil
 }
 
+// pointToJS converts a KDPoint to a JS-friendly map, ensuring slices are []any.
+func pointToJS(p pd.KDPoint[string]) map[string]any {
+	coords := make([]any, len(p.Coords))
+	for i, c := range p.Coords {
+		coords[i] = c
+	}
+	return map[string]any{
+		"id":     p.ID,
+		"coords": coords,
+		"value":  p.Value,
+	}
+}
+
 func version(_ js.Value, _ []js.Value) (any, error) {
 	return pd.Version(), nil
 }
@@ -61,15 +110,15 @@ func hello(_ js.Value, args []js.Value) (any, error) {
 
 func newTree(_ js.Value, args []js.Value) (any, error) {
 	if len(args) < 1 {
-		return nil, errors.New("newTree(dim) requires dim")
+		return nil, newErr(ErrCodeBadRequest, "newTree(dim) requires 'dim' argument")
 	}
 	dim := args[0].Int()
 	if dim <= 0 {
-		return nil, pd.ErrZeroDim
+		return nil, newErr(ErrCodeBadRequest, pd.ErrZeroDim.Error())
 	}
 	t, err := pd.NewKDTreeFromDim[string](dim)
 	if err != nil {
-		return nil, err
+		return nil, newErr(ErrCodeBadRequest, err.Error())
 	}
 	id := nextTreeID
 	nextTreeID++
@@ -78,81 +127,95 @@ func newTree(_ js.Value, args []js.Value) (any, error) {
 }
 
 func treeLen(_ js.Value, args []js.Value) (any, error) {
-	if len(args) < 1 {
-		return nil, errors.New("len(treeId)")
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
 	}
-	id := args[0].Int()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	return t.Len(), nil
 }
 
 func treeDim(_ js.Value, args []js.Value) (any, error) {
-	if len(args) < 1 {
-		return nil, errors.New("dim(treeId)")
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
 	}
-	id := args[0].Int()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	return t.Dim(), nil
 }
 
 func insert(_ js.Value, args []js.Value) (any, error) {
 	// insert(treeId, {id: string, coords: number[], value?: string})
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
+	}
 	if len(args) < 2 {
-		return nil, errors.New("insert(treeId, point)")
+		return nil, newErr(ErrCodeBadRequest, "insert(treeId, point) requires 'point' argument")
 	}
-	id := args[0].Int()
 	pt := args[1]
 	pid := pt.Get("id").String()
-	coords, err := getFloatSlice(pt.Get("coords"))
+	coords, err := getFloatSlice(pt.Get("coords"), "point.coords")
 	if err != nil {
 		return nil, err
 	}
 	val := pt.Get("value").String()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
-	okIns := t.Insert(pd.KDPoint[string]{ID: pid, Coords: coords, Value: val})
-	return okIns, nil
+	if okIns := t.Insert(pd.KDPoint[string]{ID: pid, Coords: coords, Value: val}); !okIns {
+		return nil, newErr(ErrCodeConflict, "failed to insert point: dimension mismatch or duplicate ID")
+	}
+	return true, nil
 }
 
 func deleteByID(_ js.Value, args []js.Value) (any, error) {
 	// deleteByID(treeId, id)
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
+	}
 	if len(args) < 2 {
-		return nil, errors.New("deleteByID(treeId, id)")
+		return nil, newErr(ErrCodeBadRequest, "deleteByID(treeId, id) requires 'id' argument")
 	}
-	id := args[0].Int()
 	pid := args[1].String()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
+	}
+	if !t.DeleteByID(pid) {
+		return nil, newErrf(ErrCodeNotFound, "point with id '%s' not found", pid)
 	}
-	return t.DeleteByID(pid), nil
+	return true, nil
 }
 
 func nearest(_ js.Value, args []js.Value) (any, error) {
 	// nearest(treeId, query:number[]) -> {point, dist, found}
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
+	}
 	if len(args) < 2 {
-		return nil, errors.New("nearest(treeId, query)")
+		return nil, newErr(ErrCodeBadRequest, "nearest(treeId, query) requires 'query' argument")
 	}
-	id := args[0].Int()
-	query, err := getFloatSlice(args[1])
+	query, err := getFloatSlice(args[1], "query")
 	if err != nil {
 		return nil, err
 	}
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	p, d, found := t.Nearest(query)
 	out := map[string]any{
-		"point": map[string]any{"id": p.ID, "coords": p.Coords, "value": p.Value},
+		"point": pointToJS(p),
 		"dist":  d,
 		"found": found,
 	}
@@ -161,65 +224,74 @@ func nearest(_ js.Value, args []js.Value) (any, error) {
 
 func kNearest(_ js.Value, args []js.Value) (any, error) {
 	// kNearest(treeId, query:number[], k:int) -> {points:[...], dists:[...]}
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
+	}
 	if len(args) < 3 {
-		return nil, errors.New("kNearest(treeId, query, k)")
+		return nil, newErr(ErrCodeBadRequest, "kNearest(treeId, query, k) requires 'query' and 'k' arguments")
 	}
-	id := args[0].Int()
-	query, err := getFloatSlice(args[1])
+	query, err := getFloatSlice(args[1], "query")
+	if err != nil {
+		return nil, err
+	}
+	k, err := getInt(args, 2, "k")
 	if err != nil {
 		return nil, err
 	}
-	k := args[2].Int()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	pts, dists := t.KNearest(query, k)
 	jsPts := make([]any, len(pts))
 	for i, p := range pts {
-		jsPts[i] = map[string]any{"id": p.ID, "coords": p.Coords, "value": p.Value}
+		jsPts[i] = pointToJS(p)
 	}
 	return map[string]any{"points": jsPts, "dists": dists}, nil
 }
 
 func radius(_ js.Value, args []js.Value) (any, error) {
 	// radius(treeId, query:number[], r:number) -> {points:[...], dists:[...]}
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
+	}
 	if len(args) < 3 {
-		return nil, errors.New("radius(treeId, query, r)")
+		return nil, newErr(ErrCodeBadRequest, "radius(treeId, query, r) requires 'query' and 'r' arguments")
 	}
-	id := args[0].Int()
-	query, err := getFloatSlice(args[1])
+	query, err := getFloatSlice(args[1], "query")
 	if err != nil {
 		return nil, err
 	}
 	r := args[2].Float()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	pts, dists := t.Radius(query, r)
 	jsPts := make([]any, len(pts))
 	for i, p := range pts {
-		jsPts[i] = map[string]any{"id": p.ID, "coords": p.Coords, "value": p.Value}
+		jsPts[i] = pointToJS(p)
 	}
 	return map[string]any{"points": jsPts, "dists": dists}, nil
 }
 
 func exportJSON(_ js.Value, args []js.Value) (any, error) {
 	// exportJSON(treeId) -> string (all points)
-	if len(args) < 1 {
-		return nil, errors.New("exportJSON(treeId)")
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
 	}
-	id := args[0].Int()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	// Export all points
 	points := t.Points()
 	jsPts := make([]any, len(points))
 	for i, p := range points {
-		jsPts[i] = map[string]any{"id": p.ID, "coords": p.Coords, "value": p.Value}
+		jsPts[i] = pointToJS(p)
 	}
 	m := map[string]any{
 		"dim":     t.Dim(),
@@ -233,13 +305,13 @@ func exportJSON(_ js.Value, args []js.Value) (any, error) {
 
 func getAnalytics(_ js.Value, args []js.Value) (any, error) {
 	// getAnalytics(treeId) -> analytics snapshot
-	if len(args) < 1 {
-		return nil, errors.New("getAnalytics(treeId)")
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
 	}
-	id := args[0].Int()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	snap := t.GetAnalyticsSnapshot()
 	return map[string]any{
@@ -259,13 +331,13 @@ func getAnalytics(_ js.Value, args []js.Value) (any, error) {
 
 func getPeerStats(_ js.Value, args []js.Value) (any, error) {
 	// getPeerStats(treeId) -> array of peer stats
-	if len(args) < 1 {
-		return nil, errors.New("getPeerStats(treeId)")
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
 	}
-	id := args[0].Int()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	stats := t.GetPeerStats()
 	jsStats := make([]any, len(stats))
@@ -282,14 +354,17 @@ func getPeerStats(_ js.Value, args []js.Value) (any, error) {
 
 func getTopPeers(_ js.Value, args []js.Value) (any, error) {
 	// getTopPeers(treeId, n) -> array of top n peer stats
-	if len(args) < 2 {
-		return nil, errors.New("getTopPeers(treeId, n)")
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
+	}
+	n, err := getInt(args, 1, "n")
+	if err != nil {
+		return nil, err
 	}
-	id := args[0].Int()
-	n := args[1].Int()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	stats := t.GetTopPeers(n)
 	jsStats := make([]any, len(stats))
@@ -306,13 +381,13 @@ func getTopPeers(_ js.Value, args []js.Value) (any, error) {
 
 func getAxisDistributions(_ js.Value, args []js.Value) (any, error) {
 	// getAxisDistributions(treeId, axisNames?: string[]) -> array of axis distribution stats
-	if len(args) < 1 {
-		return nil, errors.New("getAxisDistributions(treeId)")
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
 	}
-	id := args[0].Int()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 
 	var axisNames []string
@@ -351,13 +426,13 @@ func getAxisDistributions(_ js.Value, args []js.Value) (any, error) {
 
 func resetAnalytics(_ js.Value, args []js.Value) (any, error) {
 	// resetAnalytics(treeId) -> resets all analytics
-	if len(args) < 1 {
-		return nil, errors.New("resetAnalytics(treeId)")
+	id, err := getInt(args, 0, "treeId")
+	if err != nil {
+		return nil, err
 	}
-	id := args[0].Int()
 	t, ok := treeRegistry[id]
 	if !ok {
-		return nil, fmt.Errorf("unknown treeId %d", id)
+		return nil, newErrf(ErrCodeNotFound, "unknown treeId %d", id)
 	}
 	t.ResetAnalytics()
 	return true, nil
@@ -366,9 +441,9 @@ func resetAnalytics(_ js.Value, args []js.Value) (any, error) {
 func computeDistributionStats(_ js.Value, args []js.Value) (any, error) {
 	// computeDistributionStats(distances: number[]) -> distribution stats
 	if len(args) < 1 {
-		return nil, errors.New("computeDistributionStats(distances)")
+		return nil, newErr(ErrCodeBadRequest, "computeDistributionStats(distances) requires 'distances' argument")
 	}
-	distances, err := getFloatSlice(args[0])
+	distances, err := getFloatSlice(args[0], "distances")
 	if err != nil {
 		return nil, err
 	}
@@ -394,7 +469,7 @@ func computeDistributionStats(_ js.Value, args []js.Value) (any, error) {
 func computePeerQualityScore(_ js.Value, args []js.Value) (any, error) {
 	// computePeerQualityScore(metrics: NATRoutingMetrics, weights?: QualityWeights) -> score
 	if len(args) < 1 {
-		return nil, errors.New("computePeerQualityScore(metrics)")
+		return nil, newErr(ErrCodeBadRequest, "computePeerQualityScore(metrics) requires 'metrics' argument")
 	}
 	m := args[0]
 	metrics := pd.NATRoutingMetrics{
@@ -432,7 +507,7 @@ func computePeerQualityScore(_ js.Value, args []js.Value) (any, error) {
 func computeTrustScore(_ js.Value, args []js.Value) (any, error) {
 	// computeTrustScore(metrics: TrustMetrics) -> score
 	if len(args) < 1 {
-		return nil, errors.New("computeTrustScore(metrics)")
+		return nil, newErr(ErrCodeBadRequest, "computeTrustScore(metrics) requires 'metrics' argument")
 	}
 	m := args[0]
 	metrics := pd.TrustMetrics{
@@ -482,9 +557,9 @@ func getDefaultPeerFeatureRanges(_ js.Value, _ []js.Value) (any, error) {
 func normalizePeerFeatures(_ js.Value, args []js.Value) (any, error) {
 	// normalizePeerFeatures(features: number[], ranges?: FeatureRanges) -> number[]
 	if len(args) < 1 {
-		return nil, errors.New("normalizePeerFeatures(features)")
+		return nil, newErr(ErrCodeBadRequest, "normalizePeerFeatures(features) requires 'features' argument")
 	}
-	features, err := getFloatSlice(args[0])
+	features, err := getFloatSlice(args[0], "features")
 	if err != nil {
 		return nil, err
 	}
@@ -512,13 +587,13 @@ func normalizePeerFeatures(_ js.Value, args []js.Value) (any, error) {
 func weightedPeerFeatures(_ js.Value, args []js.Value) (any, error) {
 	// weightedPeerFeatures(normalized: number[], weights: number[]) -> number[]
 	if len(args) < 2 {
-		return nil, errors.New("weightedPeerFeatures(normalized, weights)")
+		return nil, newErr(ErrCodeBadRequest, "weightedPeerFeatures(normalized, weights) requires 'normalized' and 'weights' arguments")
 	}
-	normalized, err := getFloatSlice(args[0])
+	normalized, err := getFloatSlice(args[0], "normalized")
 	if err != nil {
 		return nil, err
 	}
-	weights, err := getFloatSlice(args[1])
+	weights, err := getFloatSlice(args[1], "weights")
 	if err != nil {
 		return nil, err
 	}
@@ -534,7 +609,7 @@ func weightedPeerFeatures(_ js.Value, args []js.Value) (any, error) {
 func getExternalToolLinks(_ js.Value, args []js.Value) (any, error) {
 	// getExternalToolLinks(domain: string) -> ExternalToolLinks
 	if len(args) < 1 {
-		return nil, errors.New("getExternalToolLinks(domain)")
+		return nil, newErr(ErrCodeBadRequest, "getExternalToolLinks(domain) requires 'domain' argument")
 	}
 	domain := args[0].String()
 	links := pd.GetExternalToolLinks(domain)
@@ -544,7 +619,7 @@ func getExternalToolLinks(_ js.Value, args []js.Value) (any, error) {
 func getExternalToolLinksIP(_ js.Value, args []js.Value) (any, error) {
 	// getExternalToolLinksIP(ip: string) -> ExternalToolLinks
 	if len(args) < 1 {
-		return nil, errors.New("getExternalToolLinksIP(ip)")
+		return nil, newErr(ErrCodeBadRequest, "getExternalToolLinksIP(ip) requires 'ip' argument")
 	}
 	ip := args[0].String()
 	links := pd.GetExternalToolLinksIP(ip)
@@ -554,7 +629,7 @@ func getExternalToolLinksIP(_ js.Value, args []js.Value) (any, error) {
 func getExternalToolLinksEmail(_ js.Value, args []js.Value) (any, error) {
 	// getExternalToolLinksEmail(emailOrDomain: string) -> ExternalToolLinks
 	if len(args) < 1 {
-		return nil, errors.New("getExternalToolLinksEmail(emailOrDomain)")
+		return nil, newErr(ErrCodeBadRequest, "getExternalToolLinksEmail(emailOrDomain) requires 'emailOrDomain' argument")
 	}
 	emailOrDomain := args[0].String()
 	links := pd.GetExternalToolLinksEmail(emailOrDomain)
@@ -633,7 +708,7 @@ func getRDAPServers(_ js.Value, _ []js.Value) (any, error) {
 func buildRDAPDomainURL(_ js.Value, args []js.Value) (any, error) {
 	// buildRDAPDomainURL(domain: string) -> string
 	if len(args) < 1 {
-		return nil, errors.New("buildRDAPDomainURL(domain)")
+		return nil, newErr(ErrCodeBadRequest, "buildRDAPDomainURL(domain) requires 'domain' argument")
 	}
 	domain := args[0].String()
 	// Use universal RDAP redirector
@@ -643,7 +718,7 @@ func buildRDAPDomainURL(_ js.Value, args []js.Value) (any, error) {
 func buildRDAPIPURL(_ js.Value, args []js.Value) (any, error) {
 	// buildRDAPIPURL(ip: string) -> string
 	if len(args) < 1 {
-		return nil, errors.New("buildRDAPIPURL(ip)")
+		return nil, newErr(ErrCodeBadRequest, "buildRDAPIPURL(ip) requires 'ip' argument")
 	}
 	ip := args[0].String()
 	return fmt.Sprintf("https://rdap.org/ip/%s", ip), nil
@@ -652,7 +727,7 @@ func buildRDAPIPURL(_ js.Value, args []js.Value) (any, error) {
 func buildRDAPASNURL(_ js.Value, args []js.Value) (any, error) {
 	// buildRDAPASNURL(asn: string) -> string
 	if len(args) < 1 {
-		return nil, errors.New("buildRDAPASNURL(asn)")
+		return nil, newErr(ErrCodeBadRequest, "buildRDAPASNURL(asn) requires 'asn' argument")
 	}
 	asn := args[0].String()
 	// Normalize ASN