fix(workflow): allow Coding (Ideas) cards to move back from Todo to Ideas

A legacy source column (todo/in-progress/...) validated moves only against the
closed VALID_TRANSITIONS map, which cannot know about a workflow-declared
column, so Todo -> Ideas was rejected even though the board drag pre-check and
context menu both offered it. Legacy sources now union VALID_TRANSITIONS with
the task's workflow-resolved adjacency, resolved lazily only when the legacy
table alone would reject. builtin:coding adjacency is unchanged.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.changeset/coding-ideas-todo-back-to-ideas.md

@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Coding (Ideas) boards can now move cards back from Todo to Ideas.
+category: fix
+dev: Legacy source columns in the flag-OFF `moveTaskInternal` path now union `VALID_TRANSITIONS` with the task's workflow-resolved adjacency (`resolveAllowedColumns`), resolved lazily only when the legacy table alone would reject. builtin:coding adjacency is unchanged.

packages/core/src/__tests__/coding-ideas-move.test.ts

@@ -68,6 +68,59 @@ pgDescribe("Coding (Ideas) custom-column moves (workflow-columns graduation)", (
     expect(moved.column).toBe("todo");
   });
 
+  /*
+  FNXC:CodingIdeasWorkflow 2026-07-25-10:05:
+  Regression for the one-way Ideas intake. The reverse move (Todo → Ideas) was rejected with
+  "Invalid transition: 'todo' → 'ideas'. Valid targets: in-progress, triage, archived" because `todo`
+  is a LEGACY column id, so validation used the closed VALID_TRANSITIONS map — which cannot know
+  about a workflow-declared "ideas" column — instead of the task's own workflow adjacency. Legacy
+  source columns now UNION both, so an operator can demote a card back to Ideas.
+
+  Surface enumeration (invariant: a legacy source column honors the task's workflow adjacency in
+  addition to the legacy table):
+   - Board drag / context menu / task detail / List view / CLI + tools all funnel through
+     store.moveTask, so the store-level assertions below cover every move surface.
+   - Both move sources (user and engine).
+   - Round-trip: the demoted card can be promoted again.
+   - Default (legacy-column) workflow parity: the union never widens builtin:coding, and a column
+     the workflow does not declare still rejects.
+  */
+  it("moves an ideas-workflow task back from todo to the ideas intake column", async () => {
+    const store = harness.store();
+    const task = await store.createTask({ description: "idea", workflowId: "builtin:coding-ideas" });
+    await store.moveTask(task.id, "todo", { moveSource: "user" });
+
+    const demoted = await store.moveTask(task.id, "ideas", { moveSource: "user" });
+    expect(demoted.column).toBe("ideas");
+
+    // Round-trip: still promotable after the demotion.
+    expect((await store.moveTask(task.id, "todo", { moveSource: "user" })).column).toBe("todo");
+  });
+
+  it("allows the todo → ideas move from an engine source too", async () => {
+    const store = harness.store();
+    const task = await store.createTask({ description: "idea", workflowId: "builtin:coding-ideas" });
+    await store.moveTask(task.id, "todo", { moveSource: "user" });
+
+    const demoted = await store.moveTask(task.id, "ideas", { moveSource: "engine" });
+    expect(demoted.column).toBe("ideas");
+  });
+
+  it("keeps the default workflow's legacy adjacency unchanged", async () => {
+    const store = harness.store();
+    const task = await store.createTask({ description: "legacy", workflowId: "builtin:coding" });
+
+    // A column the default workflow never declares is still rejected...
+    await expect(
+      store.moveTask(task.id, "ideas", { moveSource: "user" }),
+    ).rejects.toThrow(/Invalid transition: '.*' → 'ideas'/);
+    // ...and so is a legacy-but-non-adjacent target, with the verbatim legacy target list.
+    await store.moveTask(task.id, "todo", { moveSource: "user" });
+    await expect(
+      store.moveTask(task.id, "in-review", { moveSource: "user" }),
+    ).rejects.toThrow("Invalid transition: 'todo' → 'in-review'. Valid targets: in-progress, triage, archived");
+  });
+
   it("cancels an active task continuation when a user sends implementation back to todo", async () => {
     const store = harness.store();
     const task = await store.createTask({ description: "idea", workflowId: "builtin:coding-ideas" });

packages/core/src/task-store/moves.ts

@@ -655,15 +655,37 @@ export async function moveTaskInternalImpl(store: TaskStore, id: string, toColum
         column's targets from the task's own workflow adjacency instead, still throwing the same
         legacy-style bare Error (not TransitionRejectionError) so the flag-OFF characterization contract
         holds for legacy columns. Ported from main's FN-7591 fix into the extracted moves.ts.
+
+        FNXC:CodingIdeasWorkflow 2026-07-25-10:05:
+        A LEGACY source column must also honor the task's own workflow adjacency, not only
+        VALID_TRANSITIONS. Symptom: in Coding (Ideas) an operator could move Ideas → Todo but the
+        reverse drag/menu action ("Move to Ideas") failed with "Invalid transition: 'todo' → 'ideas'.
+        Valid targets: in-progress, triage, archived" — `todo` IS a legacy column, so the legacy branch
+        ran and VALID_TRANSITIONS (a closed six-id map that cannot know about "ideas") had the final
+        say. Both the Board drag pre-check and the context menu already offered the move, so the
+        rejection surfaced only after the optimistic move snapped back.
+        Fix: UNION the legacy targets with the workflow-resolved adjacency for legacy sources. This
+        only ever RELAXES (never narrows) the legacy set, so builtin:coding stays byte-identical — its
+        resolved adjacency reproduces VALID_TRANSITIONS verbatim — while any workflow that inserts its
+        own column beside a legacy one (Ideas ↔ Todo here) becomes freely movable in both directions.
+        The workflow IR is resolved lazily, only when VALID_TRANSITIONS alone would reject, so the
+        happy-path move cost is unchanged.
         */
-        const validTargets = sourceIsLegacy
+        const legacyTargets: readonly string[] = sourceIsLegacy
           ? (VALID_TRANSITIONS[task.column as Column] ?? [])
-          : resolveAllowedColumns(await resolveTaskWorkflowIrForMove(store, id), task.column);
-        if (!validTargets.includes(toColumn as Column)) {
-          throw new Error(
-            `Invalid transition: '${task.column}' → '${toColumn}'. ` +
-              `Valid targets: ${validTargets.join(", ") || "none"}`,
+          : [];
+        if (!legacyTargets.includes(toColumn)) {
+          const workflowTargets = resolveAllowedColumns(
+            await resolveTaskWorkflowIrForMove(store, id),
+            task.column,
           );
+          const validTargets = [...new Set([...legacyTargets, ...workflowTargets])];
+          if (!validTargets.includes(toColumn)) {
+            throw new Error(
+              `Invalid transition: '${task.column}' → '${toColumn}'. ` +
+                `Valid targets: ${validTargets.join(", ") || "none"}`,
+            );
+          }
         }
       }