From 8220ec66b77296e982e3a58583561eddaa70c5f4 Mon Sep 17 00:00:00 2001
From: Fusion <noreply@runfusion.ai>
Date: Tue, 12 May 2026 20:35:00 -0700
Subject: [PATCH] feat(FN-4238): export merger errors from engine and polish
 workflow results

Exports merger error types from the engine package for use in the dashboard and CLI. Adds tests for the engine barrel exports and fixes workflow results tab styling to align the edit toggle with button styles.

Fusion-Task-Id: FN-4238
---
 .changeset/fn-4238-export-merger-errors.md    |  5 ++
 .../app/components/WorkflowResultsTab.css     | 28 ++++++---
 .../app/components/WorkflowResultsTab.tsx     |  2 +-
 .../__tests__/WorkflowResultsTab.test.tsx     | 11 ++++
 .../src/__tests__/engine-public-api.test.ts   | 60 +++++++++++++++++++
 packages/engine/src/index.ts                  |  3 +
 6 files changed, 99 insertions(+), 10 deletions(-)
 create mode 100644 .changeset/fn-4238-export-merger-errors.md
 create mode 100644 packages/engine/src/__tests__/engine-public-api.test.ts

diff --git a/.changeset/fn-4238-export-merger-errors.md b/.changeset/fn-4238-export-merger-errors.md
new file mode 100644
index 000000000..b189d81d3
--- /dev/null
+++ b/.changeset/fn-4238-export-merger-errors.md
@@ -0,0 +1,5 @@
+---
+"@runfusion/fusion": minor
+---
+
+Export `DiffVolumeRegressionError`, `MergeAbortedError`, and `SquashAuditError` from `@fusion/engine` so consumers can use `instanceof` checks without deep-importing.
diff --git a/packages/dashboard/app/components/WorkflowResultsTab.css b/packages/dashboard/app/components/WorkflowResultsTab.css
index cbebf2fc4..0b241f3d2 100644
--- a/packages/dashboard/app/components/WorkflowResultsTab.css
+++ b/packages/dashboard/app/components/WorkflowResultsTab.css
@@ -54,19 +54,13 @@
 
 .workflow-results-edit-toggle {
   width: auto;
-  height: calc(var(--space-lg) * 2 - var(--space-xs));
-  padding: 0 calc(var(--space-sm) + var(--space-xs) * 0.5);
-  border: 1px solid var(--border);
-  border-radius: var(--radius-sm);
-  background: var(--surface);
+  min-height: calc(var(--space-lg) * 2 - var(--space-xs));
+  padding-inline: calc(var(--space-sm) + var(--space-xs) * 0.5);
   color: var(--text-muted);
-  font-size: calc(var(--space-sm) + var(--space-xs));
-  font-weight: 500;
   gap: calc(var(--space-xs) + var(--space-xs) * 0.5);
 }
 
 .workflow-results-edit-toggle:hover {
-  background: var(--card-hover);
   color: var(--text);
 }
 
@@ -229,7 +223,7 @@
 /* Phase badge base and modifier classes */
 .phase-badge {
   margin-inline-start: var(--space-xs);
-  font-size: 11px;
+  font-size: calc(var(--space-sm) + var(--space-xs) * 0.75);
   padding: var(--space-xs) var(--space-sm);
   border-radius: var(--radius-sm);
 }
@@ -293,6 +287,7 @@
 
 .workflow-result-output-header {
   display: flex;
+  flex-wrap: wrap;
   align-items: center;
   gap: var(--space-sm);
   margin-bottom: var(--space-xs);
@@ -307,6 +302,8 @@
 }
 
 .workflow-result-output-preview {
+  flex: 1 1 calc(var(--space-2xl) * 6);
+  min-width: 0;
   font-size: calc(var(--space-sm) + var(--space-xs) * 0.75);
   color: var(--text-dim);
   font-style: italic;
@@ -504,6 +501,19 @@
     min-height: calc(var(--space-lg) * 2 + var(--space-xs));
   }
 
+  .workflow-result-output-header {
+    align-items: flex-start;
+  }
+
+  .workflow-result-output-preview {
+    flex-basis: 100%;
+    order: 3;
+  }
+
+  .workflow-result-mode-toggle {
+    margin-left: 0;
+  }
+
   .workflow-configured-header {
     align-items: flex-start;
   }
diff --git a/packages/dashboard/app/components/WorkflowResultsTab.tsx b/packages/dashboard/app/components/WorkflowResultsTab.tsx
index b19c1f07b..0771a2fb3 100644
--- a/packages/dashboard/app/components/WorkflowResultsTab.tsx
+++ b/packages/dashboard/app/components/WorkflowResultsTab.tsx
@@ -570,7 +570,7 @@ export function WorkflowResultsTab({
   const editButton = canEdit ? (
     <button
       type="button"
-      className="modal-edit-btn workflow-results-edit-toggle"
+      className="btn btn-sm workflow-results-edit-toggle"
       onClick={() => setIsEditing((prev) => !prev)}
       data-testid="workflow-steps-edit-toggle"
       aria-label={isEditing ? "Done editing workflow steps" : "Edit workflow steps"}
diff --git a/packages/dashboard/app/components/__tests__/WorkflowResultsTab.test.tsx b/packages/dashboard/app/components/__tests__/WorkflowResultsTab.test.tsx
index 79715b12f..b5a2b7d99 100644
--- a/packages/dashboard/app/components/__tests__/WorkflowResultsTab.test.tsx
+++ b/packages/dashboard/app/components/__tests__/WorkflowResultsTab.test.tsx
@@ -873,6 +873,17 @@ describe("WorkflowResultsTab", () => {
       expect(css).toMatch(/\.workflow-output-modal-name\s*\{[^}]*min-width:\s*0;[^}]*overflow-wrap:\s*anywhere;/);
     });
 
+    it("keeps workflow output header actions visible without hardcoded badge sizing", () => {
+      const baseCss = loadAllAppCssBaseOnly();
+      const allCss = loadAllAppCss();
+
+      expect(baseCss).toMatch(/\.phase-badge\s*\{[^}]*font-size:\s*calc\(var\(--space-sm\) \+ var\(--space-xs\) \* 0\.75\);/);
+      expect(baseCss).toMatch(/\.workflow-result-output-header\s*\{[^}]*flex-wrap:\s*wrap;/);
+      expect(baseCss).toMatch(/\.workflow-result-output-preview\s*\{[^}]*flex:\s*1 1 calc\(var\(--space-2xl\) \* 6\);[^}]*min-width:\s*0;/);
+      expect(allCss).toMatch(/@media \(max-width: 768px\)\s*\{[\s\S]*?\.workflow-result-output-preview\s*\{[^}]*flex-basis:\s*100%;[^}]*order:\s*3;/);
+      expect(allCss).toMatch(/@media \(max-width: 768px\)\s*\{[\s\S]*?\.workflow-result-mode-toggle\s*\{[^}]*margin-left:\s*0;/);
+    });
+
     it("allows workflow modal controls to wrap on mobile so the close button stays visible", () => {
       const css = loadAllAppCss();
 
diff --git a/packages/engine/src/__tests__/engine-public-api.test.ts b/packages/engine/src/__tests__/engine-public-api.test.ts
new file mode 100644
index 000000000..e2f16ab56
--- /dev/null
+++ b/packages/engine/src/__tests__/engine-public-api.test.ts
@@ -0,0 +1,60 @@
+import { describe, expect, it } from "vitest";
+import {
+  BranchConflictError,
+  DiffVolumeRegressionError,
+  MergeAbortedError,
+  SquashAuditError,
+  type SquashAuditFindings,
+} from "../index.js";
+
+const emptySquashAuditFindings: SquashAuditFindings = {
+  strategy: "squash",
+  squashSha: "abc12345",
+  parentSha: "def67890",
+  squashSubject: "squash subject",
+  auditTargetLabel: "abc12345",
+  lookback: 30,
+  branchSubjects: [],
+  recentMainSubjects: [],
+  duplicateSubjects: [],
+  touchedFiles: [],
+  touchedFileOverlaps: [],
+  findings: [],
+  issueCount: 0,
+  clean: true,
+};
+
+describe("engine public api barrel", () => {
+  it.each([
+    {
+      name: "BranchConflictError",
+      ctor: () => new BranchConflictError({
+        branchName: "task/fn-4238",
+        conflictingWorktreePath: "/tmp/worktree",
+        existingTipSha: "0123456789ab",
+        strandedCommits: [],
+        startPoint: "main",
+        recommendedAction: "Rebase the task branch.",
+      }),
+    },
+    {
+      name: "DiffVolumeRegressionError",
+      ctor: () => new DiffVolumeRegressionError([]),
+    },
+    {
+      name: "MergeAbortedError",
+      ctor: () => new MergeAbortedError("merge aborted"),
+    },
+    {
+      name: "SquashAuditError",
+      ctor: () => new SquashAuditError("FN-4238", "abc12345", emptySquashAuditFindings),
+    },
+  ])("exports $name from ../index.js", ({ name, ctor }) => {
+    expect(ctor).toBeTypeOf("function");
+
+    const error = ctor();
+
+    expect(error).toBeInstanceOf(Error);
+    expect(error.name).toBe(name);
+  });
+});
diff --git a/packages/engine/src/index.ts b/packages/engine/src/index.ts
index 9cde782b9..9035be0fa 100644
--- a/packages/engine/src/index.ts
+++ b/packages/engine/src/index.ts
@@ -28,6 +28,9 @@ export {
   dropAutostashBySha,
   getAutostashDiff,
   notifyAutostashOrphans,
+  DiffVolumeRegressionError,
+  MergeAbortedError,
+  SquashAuditError,
   type MergerOptions,
   type AutostashOrphanRecord,
 } from "./merger.js";