chore: update progress for US-109

Author: NathanFlurry

prd.json

@@ -1878,7 +1878,7 @@
         "Tests pass"
       ],
       "priority": 111,
-      "passes": false,
+      "passes": true,
       "notes": "MEDIUM — found during PTY review. pty.ts:~444-447 silently drops echo when output buffer full. User types but sees nothing — violates 'what you type is what you see' principle."
     },
     {
@@ -1895,7 +1895,7 @@
         "Tests pass"
       ],
       "priority": 112,
-      "passes": false,
+      "passes": true,
       "notes": "MEDIUM — found during PTY review. kernel.ts:~691-696 and pty.ts:~274-279 accept any number. Setting foregroundPgid to non-existent group causes ^C to silently fail (caught by try/catch)."
     },
     {
@@ -1911,7 +1911,7 @@
         "Tests pass"
       ],
       "priority": 113,
-      "passes": false,
+      "passes": true,
       "notes": "MEDIUM — test-audit.md M11 flags this as HIGH priority. Current tests only fill buffer to exact limit and check one extra byte. No realistic adversarial patterns."
     },
     {
@@ -1925,7 +1925,7 @@
         "Tests pass"
       ],
       "priority": 114,
-      "passes": false,
+      "passes": true,
       "notes": "LOW — found during PTY review. PTY foregroundPgid goes stale when process exits. Protected by try/catch in kernel constructor wiring but untested."
     },
     {

progress.txt

@@ -1667,3 +1667,16 @@ PRD: ralph/kernel-hardening (46 stories)
   - TypeScript narrows `let x = null` to `null` inside async closures when it doesn't see reassignment in the same scope — use an object wrapper `{ prop: null }` to prevent narrowing
   - PTY slave close notifies master outputWaiters with `null`; master close notifies slave inputWaiters with `null` (pty.ts close method)
 ---
+
+## 2026-03-18 - US-109
+- What was implemented: Added two tests verifying stale foregroundPgid behavior after process group leader exit
+- Test 1: Set foregroundPgid → kill group leader → send ^C — verifies no crash (try/catch in kernel handles stale PGID gracefully)
+- Test 2: Set foregroundPgid → kill group leader → set new valid group → ^C reaches new group — verifies recovery
+- Files changed:
+  - packages/kernel/test/kernel-integration.test.ts — 2 new tests in PTY section
+- Also marked US-106 (P111), US-107 (P112), US-108 (P113) as passes: true (already committed in prior iterations but not marked)
+- **Learnings for future iterations:**
+  - Kernel constructor wires PtyManager signal callback with try/catch: `try { this.processTable.kill(-pgid, signal); } catch {}` — this is what makes stale foregroundPgid safe
+  - `hasProcessGroup(pgid)` in process-table.ts checks for any non-exited process with that pgid — once all members exit, the group is gone
+  - MockRuntimeDriver with `neverExit: true` + `killSignals: []` is the standard pattern for testing signal delivery
+---