# Achievable Status Fix Implementation Plan

> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.

**Goal:** Fix `determineStatuses` so specs that are infeasible alongside achieved specs show as "unreachable" instead of falsely "achievable."

**Architecture:** Add a feasibility check in `determineStatuses()` after the upper bound check passes. Uses the existing `checkWithS2` helper to LP-solve whether the spec can be achieved alongside the already-achieved set.

**Tech Stack:** TypeScript, Vitest, javascript-lp-solver

---

### Task 1: Write failing test for the bug scenario

**Files:**
- Modify: `app/src/solver/__tests__/optimizer.test.ts`

- [ ] **Step 1: Add test case for LCM being falsely marked achievable**

Add to the `determineStatuses` describe block:

```typescript
it('marks spec as unreachable when infeasible alongside achieved specs due to credit sharing', () => {
  // Bug scenario: CRF+STR achieved, LCM has 10 credit upper bound but
  // shared courses (spr3, fall3) are consumed by CRF/STR
  const selectedCourses = [
    'spr1-collaboration',              // LCM, MGT
    'spr2-financial-services',         // BNK, CRF, FIN, FIM
    'spr3-mergers-acquisitions',       // CRF, FIN, LCM, STR(S1)
    'spr4-foundations-entrepreneurship', // ENT, MGT, STR(S1)
    'spr5-corporate-finance',          // CRF, FIN
    'sum1-global-immersion',           // GLB
    'sum2-business-drivers',           // STR(S1)
    'sum3-valuation',                  // BNK, CRF, FIN, FIM
    'fall1-managing-change',           // LCM, MGT, STR(S2)
    'fall2-decision-models',           // MGT, MTO
    'fall3-corporate-governance',      // LCM, MGT, SBI, STR(S1)
    'fall4-game-theory',               // MGT, STR(S1)
  ];
  const achieved = ['CRF', 'STR', 'MGT'];
  const statuses = determineStatuses(selectedCourses, [], achieved);

  // LCM upper bound is 10 (>= 9) but infeasible alongside CRF+STR+MGT
  expect(statuses['LCM']).toBe('unreachable');
});
```

- [ ] **Step 2: Run the test to verify it fails**

Run: `cd /home/bill/dev/emba-course-solver/app && npx vitest run src/solver/__tests__/optimizer.test.ts -t "marks spec as unreachable when infeasible alongside achieved specs"`

Expected: FAIL — `statuses['LCM']` is `'achievable'` but expected `'unreachable'`

### Task 2: Implement the feasibility check in determineStatuses

**Files:**
- Modify: `app/src/solver/optimizer.ts:146-185`

- [ ] **Step 3: Add feasibility check after the upper bound gate**

In `app/src/solver/optimizer.ts`, in the `determineStatuses` function, replace:

```typescript
    statuses[spec.id] = 'achievable';
```

(line 181) with:

```typescript
    // Verify spec is actually feasible alongside already-achieved specs
    const testSet = [...achieved, spec.id];
    const feasResult = checkWithS2(selectedCourseIds, testSet);
    statuses[spec.id] = feasResult.feasible ? 'achievable' : 'unreachable';
```

- [ ] **Step 4: Run the failing test to verify it now passes**

Run: `cd /home/bill/dev/emba-course-solver/app && npx vitest run src/solver/__tests__/optimizer.test.ts -t "marks spec as unreachable when infeasible alongside achieved specs"`

Expected: PASS

- [ ] **Step 5: Run the full test suite to check for regressions**

Run: `cd /home/bill/dev/emba-course-solver/app && npx vitest run`

Expected: All tests pass

- [ ] **Step 6: Commit**

```bash
cd /home/bill/dev/emba-course-solver
git add app/src/solver/optimizer.ts app/src/solver/__tests__/optimizer.test.ts
git commit -m "fix: mark specs as unreachable when infeasible alongside achieved specs

determineStatuses() was marking specs as 'achievable' based solely on
per-specialization upper bounds, ignoring credit sharing with achieved
specs. Now performs an LP feasibility check to verify the spec can
actually be achieved alongside the current achieved set."
```