diff --git a/packages/cli-workflow/src/commands/init/template.ts b/packages/cli-workflow/src/commands/init/template.ts
index 81ec9a6..d788343 100644
--- a/packages/cli-workflow/src/commands/init/template.ts
+++ b/packages/cli-workflow/src/commands/init/template.ts
@@ -13,19 +13,7 @@ import {
   templateTsconfigJson,
 } from "./templates.js";
 import type { CmdInitTemplateSuccess } from "./types.js";
-
-function validateWorkspaceSegment(name: string): Result<void, string> {
-  if (name.length === 0) {
-    return err("workspace name must not be empty");
-  }
-  if (name === "." || name === "..") {
-    return err("invalid workspace name");
-  }
-  if (name.includes("/") || name.includes("\\")) {
-    return err("workspace name must not contain path separators");
-  }
-  return ok(undefined);
-}
+import { validateWorkspaceSegment } from "./validate.js";
 
 function hasTemplatesWorkspaceGlob(workspaces: unknown): boolean {
   return Array.isArray(workspaces) && workspaces.includes("templates/*");
diff --git a/packages/cli-workflow/src/commands/init/validate.ts b/packages/cli-workflow/src/commands/init/validate.ts
new file mode 100644
index 0000000..e39ad19
--- /dev/null
+++ b/packages/cli-workflow/src/commands/init/validate.ts
@@ -0,0 +1,15 @@
+import { err, ok, type Result } from "@uncaged/workflow";
+
+/** Validates a single path segment for workspace / template names (no separators, not `.` / `..`). */
+export function validateWorkspaceSegment(name: string): Result<void, string> {
+  if (name.length === 0) {
+    return err("workspace name must not be empty");
+  }
+  if (name === "." || name === "..") {
+    return err("invalid workspace name");
+  }
+  if (name.includes("/") || name.includes("\\")) {
+    return err("workspace name must not contain path separators");
+  }
+  return ok(undefined);
+}
diff --git a/packages/cli-workflow/src/commands/init/workspace.ts b/packages/cli-workflow/src/commands/init/workspace.ts
index 8b6d0e1..26dba34 100644
--- a/packages/cli-workflow/src/commands/init/workspace.ts
+++ b/packages/cli-workflow/src/commands/init/workspace.ts
@@ -5,19 +5,7 @@ import { err, ok, type Result } from "@uncaged/workflow";
 
 import { pathExists } from "../../fs-utils.js";
 import type { CmdInitWorkspaceSuccess } from "./types.js";
-
-function validateWorkspaceSegment(name: string): Result<void, string> {
-  if (name.length === 0) {
-    return err("workspace name must not be empty");
-  }
-  if (name === "." || name === "..") {
-    return err("invalid workspace name");
-  }
-  if (name.includes("/") || name.includes("\\")) {
-    return err("workspace name must not contain path separators");
-  }
-  return ok(undefined);
-}
+import { validateWorkspaceSegment } from "./validate.js";
 
 function rootPackageJson(workspaceName: string): string {
   return `${JSON.stringify(
diff --git a/packages/workflow/src/config/index.ts b/packages/workflow/src/config/index.ts
index ecd62e1..029a409 100644
--- a/packages/workflow/src/config/index.ts
+++ b/packages/workflow/src/config/index.ts
@@ -1,2 +1,3 @@
 export { resolveModel } from "./resolve-model.js";
+export { splitProviderModelRef } from "./split-provider-model-ref.js";
 export type { ProviderConfig, ResolvedModel } from "./types.js";
diff --git a/packages/workflow/src/config/resolve-model.ts b/packages/workflow/src/config/resolve-model.ts
index 0941352..e766b44 100644
--- a/packages/workflow/src/config/resolve-model.ts
+++ b/packages/workflow/src/config/resolve-model.ts
@@ -1,22 +1,8 @@
 import type { WorkflowConfig } from "../registry/index.js";
 import { err, ok, type Result } from "../util/index.js";
+import { splitProviderModelRef } from "./split-provider-model-ref.js";
 import type { ResolvedModel } from "./types.js";
 
-function splitProviderModelRef(
-  ref: string,
-): Result<{ providerName: string; modelName: string }, string> {
-  const idx = ref.indexOf("/");
-  if (idx <= 0 || idx === ref.length - 1) {
-    return err(`invalid model reference "${ref}": expected providerName/modelName`);
-  }
-  const providerName = ref.slice(0, idx);
-  const modelName = ref.slice(idx + 1);
-  if (providerName === "" || modelName === "") {
-    return err(`invalid model reference "${ref}": expected providerName/modelName`);
-  }
-  return ok({ providerName, modelName });
-}
-
 /** Resolves scene → provider endpoint + model using {@link WorkflowConfig.providers} and {@link WorkflowConfig.models}. */
 export function resolveModel(config: WorkflowConfig, scene: string): Result<ResolvedModel, string> {
   const models = config.models;
diff --git a/packages/workflow/src/config/split-provider-model-ref.ts b/packages/workflow/src/config/split-provider-model-ref.ts
new file mode 100644
index 0000000..0002920
--- /dev/null
+++ b/packages/workflow/src/config/split-provider-model-ref.ts
@@ -0,0 +1,17 @@
+import { err, ok, type Result } from "../util/index.js";
+
+/** Parses `providerName/modelName` references used in {@link WorkflowConfig.models}. */
+export function splitProviderModelRef(
+  ref: string,
+): Result<{ providerName: string; modelName: string }, string> {
+  const idx = ref.indexOf("/");
+  if (idx <= 0 || idx === ref.length - 1) {
+    return err(`invalid model reference "${ref}": expected providerName/modelName`);
+  }
+  const providerName = ref.slice(0, idx);
+  const modelName = ref.slice(idx + 1);
+  if (providerName === "" || modelName === "") {
+    return err(`invalid model reference "${ref}": expected providerName/modelName`);
+  }
+  return ok({ providerName, modelName });
+}
diff --git a/packages/workflow/src/registry/registry-normalize.ts b/packages/workflow/src/registry/registry-normalize.ts
index 12b844a..3927941 100644
--- a/packages/workflow/src/registry/registry-normalize.ts
+++ b/packages/workflow/src/registry/registry-normalize.ts
@@ -1,5 +1,5 @@
-import type { ProviderConfig } from "../config/index.js";
-import { err, ok, type Result } from "../util/index.js";
+import { type ProviderConfig, splitProviderModelRef } from "../config/index.js";
+import { createLogger, err, ok, type Result } from "../util/index.js";
 import type {
   WorkflowConfig,
   WorkflowHistoryEntry,
@@ -7,6 +7,8 @@ import type {
   WorkflowRegistryFile,
 } from "./types.js";
 
+const registryNormalizeLog = createLogger({ sink: { kind: "stderr" } });
+
 function resolveRegistryApiKey(raw: string, ctx: string): Result<string, Error> {
   if (raw.startsWith("env:")) {
     const name = raw.slice("env:".length);
@@ -22,22 +24,6 @@ function resolveRegistryApiKey(raw: string, ctx: string): Result<string, Error>
   return ok(raw);
 }
 
-function parseModelProviderRef(
-  ref: string,
-  ctx: string,
-): Result<{ providerName: string; modelName: string }, Error> {
-  const idx = ref.indexOf("/");
-  if (idx <= 0 || idx === ref.length - 1) {
-    return err(new Error(`${ctx}: expected providerName/modelName, got "${ref}"`));
-  }
-  const providerName = ref.slice(0, idx);
-  const modelName = ref.slice(idx + 1);
-  if (providerName === "" || modelName === "") {
-    return err(new Error(`${ctx}: expected providerName/modelName, got "${ref}"`));
-  }
-  return ok({ providerName, modelName });
-}
-
 function normalizeProviderEntry(name: string, entryRaw: unknown): Result<ProviderConfig, Error> {
   if (name === "") {
     return err(new Error("config.providers must not contain an empty provider name"));
@@ -96,9 +82,9 @@ function normalizeModels(
       return err(new Error(`config.models.${scene} must be a non-empty string (provider/model)`));
     }
     const ctx = `config.models.${scene}`;
-    const parsed = parseModelProviderRef(refRaw, ctx);
+    const parsed = splitProviderModelRef(refRaw);
     if (!parsed.ok) {
-      return parsed;
+      return err(new Error(`${ctx}: ${parsed.error}`));
     }
     if (!providerKeys.has(parsed.value.providerName)) {
       return err(
@@ -109,6 +95,12 @@ function normalizeModels(
     }
     models[scene] = refRaw;
   }
+  if (!Object.hasOwn(models, "default")) {
+    registryNormalizeLog(
+      "Z2KP9NWQ",
+      'registry config: models mapping has no "default" key; scenes without explicit model mappings may fail at resolveModel',
+    );
+  }
   return ok(models);
 }