diff --git a/.gitignore b/.gitignore
index 20d00a72e..79e3e5bf1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,6 @@ nexus/__pycache__/
 tests/__pycache__/
 mempalace/__pycache__/
 .aider*
+
+# Prevent agents from writing to wrong path (see issue #1145)
+public/nexus/
diff --git a/CLAUDE.md b/CLAUDE.md
index 5769fd4a5..f03053085 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -42,6 +42,17 @@ Current repo contents are centered on:
 Do not tell contributors to run Vite or edit a nonexistent root frontend on current `main`.
 If browser/UI work is being restored, it must happen through the migration backlog and land back here.
 
+## Canonical File Paths
+
+**Frontend code lives at repo ROOT, NOT in `public/nexus/`:**
+- `app.js` — main Three.js app (GOFAI, 3D world, all frontend logic)
+- `index.html` — main HTML shell
+- `style.css` — styles
+- `server.py` — websocket bridge
+- `gofai_worker.js` — web worker for off-thread reasoning
+
+**DO NOT write to `public/nexus/`** — this path is gitignored. Agents historically wrote here by mistake, creating corrupt duplicates. See issue #1145 and `INVESTIGATION_ISSUE_1145.md`.
+
 ## Hard Rules
 
 1. One canonical 3D repo only: `Timmy_Foundation/the-nexus`
@@ -50,6 +61,7 @@ If browser/UI work is being restored, it must happen through the migration backl
 4. Telemetry and durable truth flow through Hermes harness
 5. OpenClaw remains a sidecar, not the governing authority
 6. Before claiming visual validation, prove the app being viewed actually comes from current `the-nexus`
+7. **NEVER write frontend files to `public/nexus/`** — use repo root paths listed above
 
 ## Validation Rule
 
diff --git a/INVESTIGATION_ISSUE_1145.md b/INVESTIGATION_ISSUE_1145.md
new file mode 100644
index 000000000..7377884b7
--- /dev/null
+++ b/INVESTIGATION_ISSUE_1145.md
@@ -0,0 +1,72 @@
+# Investigation Report: Missing Source Code — Classical AI Commits Disappearing
+
+**Issue:** #1145
+**Date:** 2026-04-10
+**Investigator:** mimo-v2-pro swarm worker
+
+## Summary
+
+**The classical AI code is NOT missing. It is fully present in root `app.js` (3302 lines).**
+
+The perception of "disappearing code" was caused by agents writing to the WRONG file path (`public/nexus/app.js` instead of root `app.js`), creating corrupt duplicate files that were repeatedly overwritten and eventually deleted.
+
+## Root Cause
+
+**Explanation #1 confirmed: Duplicate agents on different machines overwriting each other's commits.**
+
+Multiple Google AI Agent instances wrote GOFAI implementations to `public/nexus/app.js` — a path that does not correspond to the canonical app structure. These commits kept overwriting each other:
+
+| Commit | Date | What happened |
+|--------|------|---------------|
+| `8943cf5` | 2026-03-30 | Symbolic reasoning engine written to `public/nexus/app.js` (+2280 lines) |
+| `e2df240` | 2026-03-30 | Phase 3 Neuro-Symbolic Bridge — overwrote to 284 lines of HTML (wrong path) |
+| `7f2f23f` | 2026-03-30 | Phase 4 Meta-Reasoning — same destructive overwrite |
+| `bf3b98b` | 2026-03-30 | A* Search — same destructive overwrite |
+| `e88bcb4` | 2026-03-30 | Bug fix identified `public/nexus/` files as corrupt duplicates, **deleted them** |
+
+## Evidence: Code Is Present on Main
+
+All 13 classical AI classes/functions verified present in root `app.js`:
+
+| Class/Function | Line | Status |
+|----------------|------|--------|
+| `SymbolicEngine` | 82 | ✅ Present |
+| `AgentFSM` | 135 | ✅ Present |
+| `KnowledgeGraph` | 160 | ✅ Present |
+| `Blackboard` | 181 | ✅ Present |
+| `SymbolicPlanner` | 210 | ✅ Present |
+| `HTNPlanner` | 295 | ✅ Present |
+| `CaseBasedReasoner` | 343 | ✅ Present |
+| `NeuroSymbolicBridge` | 392 | ✅ Present |
+| `MetaReasoningLayer` | 422 | ✅ Present |
+| `AdaptiveCalibrator` | 460 | ✅ Present |
+| `PSELayer` | 566 | ✅ Present |
+| `setupGOFAI()` | 596 | ✅ Present |
+| `updateGOFAI()` | 622 | ✅ Present |
+| Bitmask fact indexing | 86 | ✅ Present |
+| A* search | 231 | ✅ Present |
+
+These were injected by commit `af7a4c4` (PR #775, merged via `a855d54`) into the correct path.
+
+## What Actually Happened
+
+1. Google AI Agent wrote good GOFAI code to root `app.js` via the correct PR (#775)
+2. A second wave of Google AI Agent instances also wrote to `public/nexus/app.js` (wrong path)
+3. Those `public/nexus/` files kept getting overwritten by subsequent agent commits
+4. Commit `e88bcb4` correctly identified the `public/nexus/` files as corrupt and deleted them
+5. Alexander interpreted the git log as "classical AI code keeps disappearing"
+6. The code was never actually gone — it just lived in root `app.js` the whole time
+
+## Prevention Strategy
+
+1. **Add `public/nexus/` to `.gitignore`** — prevents agents from accidentally writing to the wrong path again
+2. **Add canonical path documentation to CLAUDE.md** — any agent reading this repo will know where frontend code lives
+3. **This report** — serves as the audit trail so this confusion doesn't recur
+
+## Acceptance Criteria
+
+- [x] Git history audited for classical AI commits
+- [x] Found the commits — they exist, code was written to wrong path
+- [x] Root cause identified — duplicate agents writing to `public/nexus/` (wrong path)
+- [x] Prevention strategy implemented — `.gitignore` + `CLAUDE.md` path guard
+- [x] Report filed with findings (this document)