docs: map Bun in Rust blog post as advisory

Bun acquired by Anthropic Dec 2025. Rewritten Zig->Rust using
Claude Fable 5. Systematic memory safety (12+ use-after-free/leak
bugs). Validates LLM-as-compiler pattern, verify-gate architecture,
FlatLedger state isolation. 22M monthly downloads. No vendoring.

docs/receipts/README.md

@@ -43,6 +43,7 @@ Current authority order: **live receipt > committed receipt > memory**.
 - `cmux-herdr-multi-agent-orchestration-advisory-map-20260705.json` — maps cmux (macOS agent terminal), herdr (AGPL agent multiplexer), and disler/learning-cmux-with-agents (31 NL fleet prompts) as advisory-only. 12 pattern mappings. Validates: execution-pipeline orchestrates fleet lifecycle, FlatLedger = external state, worktree-isolation = agent isolation. No vendoring.
 - `kunchen-dotfiles-advisory-map-20260705.json` — maps Kun Chen's dotfiles video + repo (Nix-based Mac agentic setup) as advisory-only. Includes 10 Windows adaptation mappings (Nix→winget/WSL, Homebrew→Chocolatey, Zsh→PowerShell, Westerm→Windows Terminal, Herder→tmux, etc.). Validates: TRUTH.md reproducibility pattern, flat-ledger.ts global memory pattern, worktree-isolation.ts agent isolation pattern. No vendoring.
 - `claude-multi-agent-docs-advisory-map-20260709.json` — maps Claude Platform managed agents multi-agent docs as advisory-only. Auth-walled page (HTML extracted via curl, content in JSON hydration blob). Validates execution-pipeline primary/worker pattern. No code changes warranted.
+- `bun-in-rust-advisory-map-20260709.json` — maps Jarred Sumner's "Rewriting Bun in Rust" blog post as advisory-only. Key: Bun acquired by Anthropic (Dec 2025), rewritten from Zig to Rust using Claude Fable 5 for memory safety. Validates LLM-as-compiler pattern (Fable 5 wrote the Rust), verify-gate pattern (systematic prevention > one-off fixes), FlatLedger pattern (state must live outside unsafe context). 22M monthly downloads. 5 takeaways. No vendoring.
 
 ## Memory quarantine
 

docs/receipts/bun-in-rust-advisory-map-20260709.json

@@ -0,0 +1,44 @@
+{
+  "schema": "fable.external_project.review.v1",
+  "id": "bun-in-rust-advisory-map-20260709",
+  "title": "Rewriting Bun in Rust \u2014 Advisory Map",
+  "source": {
+    "type": "blog post",
+    "url": "https://bun.com/blog/bun-in-rust",
+    "md_url": "https://bun.com/blog/bun-in-rust.md",
+    "published": "2026-07-08T16:00:00.000Z",
+    "author": "Jarred Sumner (Bun/Oven)",
+    "fetchedAt": "2026-07-09T02:15:10.917437+00:00"
+  },
+  "keyFindings": {
+    "acquisition": "Bun was acquired by Anthropic in December 2025. Jarred and team now work at Anthropic.",
+    "rewrite": "Rewritten from Zig to Rust. Used pre-release Claude Fable 5 for much of the rewrite.",
+    "reason": "Systematic memory safety issues from mixing GC (JavaScriptCore) with manually-managed Zig memory. 12+ use-after-free, memory leak, and double-free bugs listed.",
+    "scope": "JavaScript/TypeScript/CSS transpiler, minifier, bundler, package manager, test runner, HTTP/1.1, WebSocket, Node.js API implementations.",
+    "downloads": "22 million monthly CLI downloads.",
+    "users": "Claude Code, OpenCode, Vercel, Railway, DigitalOcean \u2014 all use Bun as their runtime."
+  },
+  "relevanceToFableAgent": {
+    "pattern": "Language migration driven by memory safety guarantees. Same principle as fable-agent harness: when a component (LLM prompt context, memory-managed state) causes systemic bugs, isolate it behind a hard verification gate rather than fixing symptoms.",
+    "mapping": "Bun moved GC-managed Zig code to Rust for safety. fable-agent moves LLM state out of context (FlatLedger), gates agent actions (verify-gate, interrupt-gate), and isolates worktrees (worktree-isolation). Both solve the same problem: contain the blast radius of an unsafe runtime.",
+    "fable5": "Claude Fable 5 was used to write the Rust rewrite. This validates the LLM-as-compiler pattern: model generates safety-critical code, human+CI verifies."
+  },
+  "keyTakeaways": [
+    "Bun was acquired by Anthropic (Dec 2025). Fable 5 used for the rewrite \u2014 validates LLM-as-compiler pattern.",
+    "Language migration from Zig to Rust for memory safety. Same pattern as fable-agent's verify-gate + FlatLedger: systemic bugs need architectural fixes, not symptom patches.",
+    "Jarred lists 12+ use-after-free, memory leak, and double-free bugs that motivated the rewrite. Systematic prevention > one-off fixes.",
+    "Bun runs 22M monthly downloads. Claude Code + OpenCode depend on it. fable-agent already uses Bun-compatible toolchain (node, npm).",
+    "Advisory only. No vendoring. Pattern validation is the value."
+  ],
+  "contentVerified": true,
+  "liveVerification": "HTTP 200 from bun.com/blog/bun-in-rust.md \u2014 full markdown content fetched and verified.",
+  "advisoryOnly": true,
+  "noActionRequired": true,
+  "fableAgentStatus": {
+    "containers": 11,
+    "phase": 4,
+    "autoPatchProven": false,
+    "tests": "295 passing, 69 files",
+    "commit": "2233297"
+  }
+}