feat(workspace): fix auto-detection, derive prefix from name, default coding workflow

- Fix workspace detection: change workspaceMode default from false to
  undefined so isWorkspaceModeExplicitlyDisabled no longer blocks
  auto-detection on fresh projects (config.json was being written with
  workspaceMode:false during store.init(), causing the guard to skip
  detection before it ever ran)
- Derive task prefix from project name (first 2-4 chars) instead of
  hardcoded 'FN' as the suggested default
- Default workflow is now builtin:coding instead of undefined
- CLI registerProjectInteractive: onboarding prompt for task prefix
  confirmation after project name
- Dashboard POST /api/projects: auto-derive prefix and set default
  workflow for new registrations

packages/cli/src/project-resolver.ts

@@ -537,6 +537,19 @@ export function suggestProjectName(path: string): string {
   return parts[parts.length - 1] || "unnamed";
 }
 
+/**
+ * FNXC:TaskPrefix 2026-06-24-18:00:
+ * Derive a task prefix from a project name by taking the first 2-4 uppercase
+ * letters. Falls back to "FN" for short names. Used as the suggested default
+ * during project onboarding so each project gets a recognizable prefix.
+ */
+export function suggestTaskPrefix(projectName: string): string {
+  const cleaned = projectName.replace(/[^a-zA-Z]/g, "").toUpperCase();
+  if (cleaned.length >= 2 && cleaned.length <= 4) return cleaned;
+  if (cleaned.length > 4) return cleaned.slice(0, 4);
+  return "FN";
+}
+
 /**
  * Resolve absolute path and validate it exists.
  */
@@ -743,6 +756,32 @@ export async function registerProjectInteractive(
     // Best-effort stamp only.
   }
 
+  /*
+  FNXC:Onboarding 2026-06-24-18:00:
+  After registration, prompt the user to confirm a task prefix and default workflow.
+  The prefix defaults to the first 2-4 chars of the project name so each project gets
+  recognizable task IDs (e.g., "MYPR" for "my-project"). The workflow defaults to coding.
+  Both are persisted to config.json via the TaskStore.
+  */
+  if (interactive) {
+    const { TaskStore } = await import("@fusion/core");
+    const store = new TaskStore(absPath);
+    await store.init();
+
+    const suggestedPrefix = suggestTaskPrefix(name);
+    const rl = createInterface({ input: process.stdin, output: process.stdout });
+    const prefixInput = await rl.question(`\n  Task prefix [${suggestedPrefix}]: `);
+    rl.close();
+    const prefix = prefixInput.trim().toUpperCase() || suggestedPrefix;
+
+    await store.updateSettings({
+      taskPrefix: prefix,
+      defaultWorkflowId: "builtin:coding",
+    });
+    await store.close();
+    console.log(`  ✓ Task prefix set to "${prefix}", default workflow: coding`);
+  }
+
   return createResolvedProject(project);
 }
 

packages/core/src/settings-schema.ts

@@ -258,7 +258,7 @@ export const DEFAULT_GLOBAL_SETTINGS = {
 export const DEFAULT_PROJECT_SETTINGS = {
   globalPause: false,
   globalPauseReason: undefined,
-  defaultWorkflowId: undefined,
+  defaultWorkflowId: "builtin:coding",
   enabledBuiltinWorkflowIds: undefined,
   approvedWorkflowCliCommands: undefined,
   approvedCliAutonomyAdapters: undefined,
@@ -307,7 +307,7 @@ export const DEFAULT_PROJECT_SETTINGS = {
     onFailure: "fail",
   },
   worktreesDir: undefined,
-  taskPrefix: "FN",
+  taskPrefix: undefined,
   taskAttributionTrailerNames: ["Fusion-Task-Id"],
   commitMsgHookEnabled: true,
   includeTaskIdInCommit: true,
@@ -538,7 +538,7 @@ export const DEFAULT_PROJECT_SETTINGS = {
   researchDefaultTimeout: 300000,
   researchMaxSourcesPerRun: 20,
   researchMaxSynthesisRounds: 2,
-  workspaceMode: false,
+  workspaceMode: undefined,
 } satisfies CompleteSettings<ProjectSettingsSchema>;
 
 /**

packages/dashboard/src/routes/register-project-routes.ts

@@ -374,6 +374,28 @@ export const registerProjectRoutes: ApiRouteRegistrar = (ctx) => {
         // Memory bootstrap failure is non-fatal - project registration succeeded
       });
 
+      /*
+      FNXC:Onboarding 2026-06-24-18:00:
+      For new registrations (not reattachments), set a derived task prefix and default
+      workflow via the per-project TaskStore config.json so the project is immediately
+      usable without manual settings configuration.
+      */
+      if (activeProjectWithOutcome.outcome === "registered") {
+        try {
+          const { TaskStore } = await import("@fusion/core");
+          const store = new TaskStore(normalizedPath);
+          await store.init();
+          const prefix = normalizedName.replace(/[^a-zA-Z]/g, "").toUpperCase().slice(0, 4) || "FN";
+          await store.updateSettings({
+            taskPrefix: prefix,
+            defaultWorkflowId: "builtin:coding",
+          });
+          await store.close();
+        } catch {
+          // Non-fatal: project registration succeeded; settings can be configured later
+        }
+      }
+
       // Notify the host (serve.ts/daemon.ts) so it can run project-setup
       // side-effects like installing the fusion Claude-skill into
       // .claude/skills/fusion when pi-claude-cli is configured. The callback