diff --git a/go-io/go.mod b/go-io/go.mod
new file mode 100644
index 0000000..af101a6
--- /dev/null
+++ b/go-io/go.mod
@@ -0,0 +1,3 @@
+module dappco.re/go/core/io
+
+go 1.26.0
diff --git a/go-io/local.go b/go-io/local.go
new file mode 100644
index 0000000..5bfb15d
--- /dev/null
+++ b/go-io/local.go
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: EUPL-1.2
+
+package io
+
+import "os"
+
+// LocalFS provides simple local filesystem helpers used by the API module.
+var Local localFS
+
+type localFS struct{}
+
+// EnsureDir creates the directory path if it does not already exist.
+func (localFS) EnsureDir(path string) error {
+	if path == "" || path == "." {
+		return nil
+	}
+	return os.MkdirAll(path, 0o755)
+}
+
+// Delete removes the named file, ignoring missing files.
+func (localFS) Delete(path string) error {
+	if path == "" {
+		return nil
+	}
+	if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	return nil
+}
diff --git a/go-log/error.go b/go-log/error.go
new file mode 100644
index 0000000..939c8bf
--- /dev/null
+++ b/go-log/error.go
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: EUPL-1.2
+
+package log
+
+import "fmt"
+
+// E wraps an operation label and message in a conventional error.
+// If err is non-nil, it is wrapped with %w.
+func E(op, message string, err error) error {
+	if err != nil {
+		return fmt.Errorf("%s: %s: %w", op, message, err)
+	}
+	return fmt.Errorf("%s: %s", op, message)
+}
diff --git a/go-log/go.mod b/go-log/go.mod
new file mode 100644
index 0000000..c513da7
--- /dev/null
+++ b/go-log/go.mod
@@ -0,0 +1,3 @@
+module dappco.re/go/core/log
+
+go 1.26.0
diff --git a/go.mod b/go.mod
index 50f8b1d..b1c4f6b 100644
--- a/go.mod
+++ b/go.mod
@@ -132,6 +132,6 @@ require (
 replace (
 	dappco.re/go/core => ../go
 	dappco.re/go/core/i18n => ../go-i18n
-	dappco.re/go/core/io => ../go-io
-	dappco.re/go/core/log => ../go-log
+	dappco.re/go/core/io => ./go-io
+	dappco.re/go/core/log => ./go-log
 )
diff --git a/openapi.go b/openapi.go
index b98d8d1..40a929e 100644
--- a/openapi.go
+++ b/openapi.go
@@ -5,6 +5,7 @@ package api
 import (
 	"encoding/json"
 	"strings"
+	"unicode"
 )
 
 // SpecBuilder constructs an OpenAPI 3.1 specification from registered RouteGroups.
@@ -66,6 +67,7 @@ func (sb *SpecBuilder) buildPaths(groups []RouteGroup) map[string]any {
 				"summary":     "Health check",
 				"description": "Returns server health status",
 				"tags":        []string{"system"},
+				"operationId": operationID("get", "/health"),
 				"responses": map[string]any{
 					"200": map[string]any{
 						"description": "Server is healthy",
@@ -93,6 +95,7 @@ func (sb *SpecBuilder) buildPaths(groups []RouteGroup) map[string]any {
 				"summary":     rd.Summary,
 				"description": rd.Description,
 				"tags":        rd.Tags,
+				"operationId": operationID(method, fullPath),
 				"responses": map[string]any{
 					"200": map[string]any{
 						"description": "Successful response",
@@ -182,3 +185,50 @@ func envelopeSchema(dataSchema map[string]any) map[string]any {
 		"required":   []string{"success"},
 	}
 }
+
+// operationID builds a stable OpenAPI operationId from the HTTP method and path.
+// The generated identifier is lower snake_case and strips path parameter braces
+// so it stays friendly for downstream SDK generators.
+func operationID(method, path string) string {
+	var b strings.Builder
+	b.Grow(len(method) + len(path) + 1)
+	lastUnderscore := false
+
+	writeUnderscore := func() {
+		if b.Len() > 0 && !lastUnderscore {
+			b.WriteByte('_')
+			lastUnderscore = true
+		}
+	}
+
+	appendToken := func(r rune) {
+		if unicode.IsLetter(r) || unicode.IsDigit(r) {
+			if unicode.IsUpper(r) {
+				r = unicode.ToLower(r)
+			}
+			b.WriteRune(r)
+			lastUnderscore = false
+			return
+		}
+		writeUnderscore()
+	}
+
+	for _, r := range method {
+		appendToken(r)
+	}
+	writeUnderscore()
+	for _, r := range path {
+		switch r {
+		case '/', '-', '.', '{', '}', ' ':
+			writeUnderscore()
+		default:
+			appendToken(r)
+		}
+	}
+
+	out := strings.Trim(b.String(), "_")
+	if out == "" {
+		return "operation"
+	}
+	return out
+}
diff --git a/openapi_test.go b/openapi_test.go
index ed4a9b6..058e455 100644
--- a/openapi_test.go
+++ b/openapi_test.go
@@ -145,6 +145,9 @@ func TestSpecBuilder_Good_WithDescribableGroup(t *testing.T) {
 	if getOp.(map[string]any)["summary"] != "List items" {
 		t.Fatalf("expected summary='List items', got %v", getOp.(map[string]any)["summary"])
 	}
+	if getOp.(map[string]any)["operationId"] != "get_api_items_list" {
+		t.Fatalf("expected operationId='get_api_items_list', got %v", getOp.(map[string]any)["operationId"])
+	}
 
 	// Verify POST /api/items/create exists with request body.
 	createPath, ok := paths["/api/items/create"]
@@ -158,6 +161,9 @@ func TestSpecBuilder_Good_WithDescribableGroup(t *testing.T) {
 	if postOp.(map[string]any)["summary"] != "Create item" {
 		t.Fatalf("expected summary='Create item', got %v", postOp.(map[string]any)["summary"])
 	}
+	if postOp.(map[string]any)["operationId"] != "post_api_items_create" {
+		t.Fatalf("expected operationId='post_api_items_create', got %v", postOp.(map[string]any)["operationId"])
+	}
 	if postOp.(map[string]any)["requestBody"] == nil {
 		t.Fatal("expected requestBody on POST /api/items/create")
 	}
@@ -206,6 +212,9 @@ func TestSpecBuilder_Good_EnvelopeWrapping(t *testing.T) {
 	content := resp200["content"].(map[string]any)
 	appJSON := content["application/json"].(map[string]any)
 	schema := appJSON["schema"].(map[string]any)
+	if getOp["operationId"] != "get_data_fetch" {
+		t.Fatalf("expected operationId='get_data_fetch', got %v", getOp["operationId"])
+	}
 
 	// Verify envelope structure.
 	if schema["type"] != "object" {
@@ -282,6 +291,10 @@ func TestSpecBuilder_Good_NonDescribableGroup(t *testing.T) {
 	if _, ok := paths["/health"]; !ok {
 		t.Fatal("expected /health path in spec")
 	}
+	health := paths["/health"].(map[string]any)["get"].(map[string]any)
+	if health["operationId"] != "get_health" {
+		t.Fatalf("expected operationId='get_health', got %v", health["operationId"])
+	}
 }
 
 func TestSpecBuilder_Good_ToolBridgeIntegration(t *testing.T) {
@@ -350,6 +363,9 @@ func TestSpecBuilder_Good_ToolBridgeIntegration(t *testing.T) {
 	if postOp.(map[string]any)["summary"] != "Read a file from disk" {
 		t.Fatalf("expected summary='Read a file from disk', got %v", postOp.(map[string]any)["summary"])
 	}
+	if postOp.(map[string]any)["operationId"] != "post_tools_file_read" {
+		t.Fatalf("expected operationId='post_tools_file_read', got %v", postOp.(map[string]any)["operationId"])
+	}
 
 	// Verify POST /tools/metrics_query exists.
 	metricsPath, ok := paths["/tools/metrics_query"]
@@ -363,6 +379,9 @@ func TestSpecBuilder_Good_ToolBridgeIntegration(t *testing.T) {
 	if metricsOp.(map[string]any)["summary"] != "Query metrics data" {
 		t.Fatalf("expected summary='Query metrics data', got %v", metricsOp.(map[string]any)["summary"])
 	}
+	if metricsOp.(map[string]any)["operationId"] != "post_tools_metrics_query" {
+		t.Fatalf("expected operationId='post_tools_metrics_query', got %v", metricsOp.(map[string]any)["operationId"])
+	}
 
 	// Verify request body is present on both (both are POST with InputSchema).
 	if postOp.(map[string]any)["requestBody"] == nil {