Bun.serve: remove unsafe from server/mod.rs and server_body.rs

[Jarred-Sumner]

What

Same programme as #40055 / #40135 / #40136 / #40139 / #40187 / #40190 / #40200 / #40202 / #40203 / #40204 / #40212 / #40213, applied to the Bun.serve core: src/runtime/server/mod.rs 99 → 1 and server_body.rs 83 → 1 (each residual is an unsafe extern "C" { block whose items are all safe fn and name runtime types, so it can't move to uws_sys). Incidental: NodeHTTPResponse.rs 31 → 25, DevServer.rs 203 → 197, Response.rs 29 → 25. Overlaps #40203 in RequestContext.rs (hunk list in the commit message); I'll rebase whichever lands second.

• NewServer<SSL, DEBUG> is #[derive(CellRefCounted)], all fields Cell/JsCell, all methods &self/ThisPtr<Self> (the sharedThis: false opt-out in server.classes.ts is gone). Two refs: the creator's (transferred to the JS wrapper by ptr_to_js, released by finalize_js_box) and self_ref held on behalf of the uWS app's registrations (taken when the app is created in listen(), released by teardown(), which destroys the apps first). schedule_deinit queues DeinitTask(RefPtr) whose RunOnce::cancelled also tears down, so a released-unrun deinit doesn't leak the server. AnyServer is an enum of BackRef<NewServer<..>>; UserRoute is OwnedThis carrying BackRef<NewServer, Root>; ServePlugins is CellRefCounted with a typed promise_ref and HOST_EXPORTed reactions (keeps main's behaviour of never destroying the shared plugin cell).
• uws registrations: bun_uws_sys::app::{OwnedApp<SSL>, filter_this, on_client_error_this, listen_with_config_this, listen_on_unix_socket_this, ws_this<S: WebSocketUpgradeServer, T>} and h3::{OwnedApp, listen_with_config_this} — ThisPtr<U> userdata trampolines with the same contract as server: take StaticRoute, FileRoute, HTMLBundle and DirectoryRoute to zero unsafe #40136's method_this/any_this; App::ws (raw userdata) becomes unsafe fn; dead h3::App::listen_with_config removed; WebSocketUpgradeServer::on_websocket_upgrade(this: ThisPtr<Self>, ..) is a safe trait fn.
• Request contexts: hive_array::Fallback::claim_init(&self, FnOnce(NonNull<T>) -> T) -> Pooled<'_, T, N> (owning slot handle) + new_boxed(); RequestContext::init(slot, server: BackRef<_, Root>, ..) -> Self and the context owns its pool_slot; PreparedRequestFor<Ctx> carries BackRef<Ctx> + the root NonNull<Request> for C++ and reaches the Request through ctx.request_weakref.peek() at point of use (request() -> Option<&Request>); WeakPtr gains init_leaked(Box<T>) -> (Self, NonNull<T>), peek, Clone, Drop (WeakPtrData is Cell<u32>).
• node:http: Rust creates the NodeHTTPResponse (NodeHTTPResponse::create) and passes its JS object + has_body into NodeHTTPServer__onRequest_* — no packed tagged pointer / out-slot round-trip through C++ (NodeHTTP.cpp updated). HeadersRef moves to bun_jsc (FetchHeaders::clone_this_ref); Server__set* / BunServe__on*Plugins are HOST_EXPORTs.

Pre-existing bugs fixed in passing: server.fetch(url, { headers }) adopted the JS Headers wrapper's ref without incrementing it (double deref) — now deep-copies; Bun.serve() throwing after init() leaked the half-built server — now freed.

Perf (release, perf stat -e instructions:u,cycles:u on the server process, taskset-pinned 8 cores per side, client in a separate pinned process, interleaved runs): keep-alive 100 k × fetch → new Response("hi"), 8 runs each — main 1591.2 M instr / branch 1591.9 M (+0.04 %, σ ≈ 0.4 %), cycles +0.3 % (σ ≈ 2 %); connection-close 30 k requests, 6 runs each — main 540.6 M / branch 541.7 M (+0.19 %, σ ≈ 0.2 %), cycles −0.7 %. PreparedRequestFor carries only js_request, the Request root pointer for C++ and BackRef<Ctx>; the Request is reached through ctx.request_weakref.peek() at each point of use — no per-request refcount traffic.

Testing

Debug+ASAN: serve.test.ts 296/297 (uid-0 port case), bun-serve-{args,body-json-async,cookies,date,fetch-invalid-args,file,headers,html-,propagate-errors,routes,ssl,static,static-stress-}, bun-server, serve-body-leak, serve-http3, websocket-server*.test.ts (the it.concurrent timeouts adjacent to the 300k-message benchmark case reproduce identically on a main debug build), 19 node-http*.test.ts files, node-https-checkServerIdentity, express 296/296, hono, bake dev html/plugins/react-spa/hot/request-cookies/response-to-bake-response/ssg-pages-router; fetch.test.ts unchanged vs main. Hand-driven: sync/promise/throw handlers, ws upgrade+close, graceful/abrupt stop() with in-flight requests, reload(), using, unix socket, TLS, routes, node:http, listen failures; native NewServer drop verified (20/20 servers freed after stop+GC, and on listen/TLS failure). clippy clean; rust-check-all windows-msvc + apple-darwin pass.

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📒 Files selected for processing (31)

• src/collections/hive_array.rs
• src/event_loop/ManagedTask.rs
• src/jsc/FetchHeaders.rs
• src/jsc/HTTPServerAgent.rs
• src/jsc/bindings/NodeHTTP.cpp
• src/jsc/lib.rs
• src/ptr/lib.rs
• src/ptr/weak_ptr.rs
• src/runtime/api/BunObject.rs
• src/runtime/api/bun/h2_frame_parser.rs
• src/runtime/bake/DevServer.rs
• src/runtime/dispatch.rs
• src/runtime/jsc_hooks.rs
• src/runtime/server/AnyRequestContext.rs
• src/runtime/server/DirectoryRoute.rs
• src/runtime/server/FileRoute.rs
• src/runtime/server/HTMLBundle.rs
• src/runtime/server/NodeHTTPResponse.rs
• src/runtime/server/RequestContext.rs
• src/runtime/server/ServerWebSocket.rs
• src/runtime/server/StaticRoute.rs
• src/runtime/server/mod.rs
• src/runtime/server/server.classes.ts
• src/runtime/server/server_body.rs
• src/runtime/webcore/Request.rs
• src/runtime/webcore/Response.rs
• src/uws_sys/App.rs
• src/uws_sys/Request.rs
• src/uws_sys/WebSocket.rs
• src/uws_sys/h2.rs
• src/uws_sys/h3.rs

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Walkthrough

This change replaces raw-pointer ownership and callback paths with owning wrappers, typed ThisPtr adapters, shared request-context access, and RAII-managed headers. It also moves Node HTTP response creation into a typed Rust constructor and updates server lifecycle wiring.

Changes

Server runtime migration

Layer / File(s)	Summary
Ownership and lifecycle primitives src/collections/hive_array.rs, src/event_loop/ManagedTask.rs, src/ptr/*, src/runtime/dispatch.rs, src/runtime/jsc_hooks.rs, src/uws_sys/h2.rs, src/uws_sys/h3.rs	Owning pooled handles, boxed tasks, weak-pointer metadata, and uWS app wrappers now manage allocation and cleanup through ownership and Drop.
Typed uWS callbacks and WebSocket upgrades src/uws_sys/App.rs, src/uws_sys/WebSocket.rs, src/uws_sys/h3.rs, src/runtime/bake/DevServer.rs, src/runtime/server/ServerWebSocket.rs	Callback APIs now use ThisPtr, typed responses, and typed listen-socket values. WebSocket registration and upgrade handling no longer forward raw receiver and response pointers.
RAII-managed FetchHeaders references src/jsc/FetchHeaders.rs, src/jsc/lib.rs, src/runtime/webcore/Response.rs	HeadersRef centralizes C++ reference ownership, construction, cloning, dereferencing, release, and module re-exports.
Pooled request contexts and shared request state src/runtime/server/AnyRequestContext.rs, src/runtime/server/RequestContext.rs, src/runtime/webcore/Request.rs, src/runtime/server/*Route.rs, src/runtime/server/HTMLBundle.rs, src/runtime/server/server.classes.ts	Request contexts now retain pooled slots and rooted server references. Request uses Cell<AnyRequestContext>, and server access paths use shared or immutable references.
Typed Node response construction and server wiring src/runtime/server/NodeHTTPResponse.rs, src/jsc/bindings/NodeHTTP.cpp, src/runtime/api/BunObject.rs, src/jsc/HTTPServerAgent.rs, src/uws_sys/Request.rs	Node response creation moves to NodeHTTPResponse::create. HTTP bindings pass the response object and body flag, and server lifecycle code uses typed server state.

Suggested reviewers: robobun

Merge Risk: ⚪ Minimal · up to 955d4

The ownership migration has no substantiated merge-blocking issue at the current head.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the primary change: removing most unsafe usage from the Bun.serve server core files.
Description check	✅ Passed	The description explains the implementation, related fixes, performance impact, and extensive verification results. It uses different headings from the repository template, but it provides the require…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[robobun]

^{Updated 6:05 AM PT - Sep 8th, 2026}

@Jarred-Sumner, your commit 955d4d7 is building: #112856

[claude]

I reviewed this PR and didn't find any bugs (the earlier dead-parameter nit was addressed in 1a1d590). Because it redesigns NewServer's ownership/refcount model, the request-context pool lifetime, and the NodeHTTP FFI boundary across 31 files in the Bun.serve hot path, a human look would still be worthwhile.

Checked: the two-ref (ptr_to_js wrapper + self_ref) accounting and teardown()/DeinitTask::cancelled release ordering; Pooled slot ownership via pool_slot in RequestContext::deinit; WeakPtr::{Drop,Clone,peek} against existing deref() call sites (idempotent, no double-decrement); the server.fetch(url, {headers}) fix now deep-copies via clone_this_ref instead of adopting the wrapper's ref.

Extended reasoning...

Overview

This PR completes the unsafe-removal programme for Bun.serve's core: src/runtime/server/mod.rs (99→1 unsafe) and server_body.rs (83→1). NewServer<SSL,DEBUG> becomes #[derive(CellRefCounted)] with all-Cell/JsCell fields and &self/ThisPtr methods; AnyServer becomes an enum of BackRefs; UserRoute is now OwnedThis; request contexts own their pool slot via a new hive_array::Pooled handle; WeakPtr gains Clone/Drop/peek; HeadersRef moves to bun_jsc; the node:http path creates NodeHTTPResponse in Rust and passes it to C++ (removing the packed-tagged-pointer round-trip). New primitives added: OwnedThis<T>, Pooled<'_, T, N>, ManagedTask::new_boxed/RunOnce, uws_sys::app::OwnedApp and the *_this registration helpers.

Security risks

None identified. This is an internal ownership/borrowing refactor with no change to input validation, auth, or trust boundaries. The two incidental bugfixes (headers double-deref in server.fetch, half-built server leak on Bun.serve() throw) are memory-safety improvements, not new attack surface.

Level of scrutiny

High. Bun.serve is the most-exercised production hot path in the runtime; the change redesigns the server's refcount model, request-context pool ownership, and the teardown/drain sequencing that prevents UAF under abrupt stop(). Refcount balance across every terminal path (listen failure, TLS failure, VM shutdown mid-schedule_deinit, graceful vs abrupt stop, reload) is exactly the bug class REVIEW.md flags as most-blocked. The author's testing (Debug+ASAN across the serve/node-http/websocket/bake suites, hand-driven stop/reload/listen-failure with drop verification, perf-stat noise-floor confirmation) is thorough, but the surface area and number of interacting invariants warrant a maintainer pass.

Other factors

• The one prior finding (dead is_ssl parameter) was addressed in 1a1d590.
• CI build #104198 is still running with one failure so far (h2-conformance.test.ts on macOS aarch64) — the PR only touches h2 via the Fallback::new_boxed signature change in h2_frame_parser.rs, so likely unrelated flake, but worth confirming.
• The PR overlaps #40203 in RequestContext.rs per the description; whichever lands second needs a rebase.
• New WeakPtr::Drop composes with pre-existing explicit .deref() calls because deref() nulls raw_ptr (idempotent) — verified this doesn't introduce double-decrements at the request_weakref.with_mut(|w| w.deref()) sites in RequestContext.rs.

[claude]

I reviewed this PR and the bug hunting system found no issues on the latest revision (both earlier nits are addressed). Given the scope — a full ownership/refcount rework of NewServer, new Pooled/OwnedThis/WeakPtr::Drop abstractions, and a changed NodeHTTP.cpp FFI contract — a human pass is still warranted.

Checked: the two-ref model (self_ref taken in listen(), released in teardown(); wrapper ref via ptr_to_js/finalize_js_box) balances on all listen-failure and schedule_deinit paths including DeinitTask::cancelled.
Checked: Pooled slot self-ownership in RequestContext — deinit() drops pool_slot before on_request_complete, matching the old release_request_context order.
Checked: WeakPtr gaining Drop — existing explicit .deref() sites remain sound because deref() nulls raw_ptr, so the new Drop is a no-op after manual release.
Checked: server.fetch(url, {headers}) fix — clone_this_ref deep-copies instead of adopting the wrapper's ref, resolving the double-deref the PR description names.

Extended reasoning...

Overview

This PR is the Bun.serve core instalment of a 12-PR unsafe-removal programme. It touches 31 files (~477K diff chars) across src/runtime/server/ (mod.rs, server_body.rs, RequestContext.rs, NodeHTTPResponse.rs, all route types), src/ptr/ (new OwnedThis, WeakPtr gains Drop/Clone/peek/init_leaked), src/collections/hive_array.rs (new Pooled handle, claim_init), src/event_loop/ManagedTask.rs (new RunOnce trait), src/jsc/ (HeadersRef moves in, AbortSignal::to_ref), src/uws_sys/ (OwnedApp, *_this trampoline registrations, ws_this, WebSocketUpgradeServer becomes safe), and src/jsc/bindings/NodeHTTP.cpp (Rust now creates NodeHTTPResponse and passes it in; the packed-tagged-pointer/out-slot round-trip is gone).

The core structural change: NewServer<SSL, DEBUG> becomes #[derive(CellRefCounted)] with all fields Cell/JsCell and all methods &self/ThisPtr<Self>. AnyServer becomes an enum of BackRef<NewServer<..>> instead of a hand-rolled (tag, *mut ()). UserRoute is OwnedThis-boxed so its address is stable uWS user-data. Request contexts own their pool slot via the new Pooled handle rather than being put() by the server. ServePlugins is CellRefCounted with a typed promise_ref and HOST_EXPORTed reactions.

Security risks

No new attack surface. The change is internal ownership plumbing; user-facing behaviour is intended to be identical (perf numbers show ±0.2%). The one FFI contract change (NodeHTTPServer__onRequest_* now receives a pre-built JSNodeHTTPResponse JSValue + has_body bool instead of building it in C++) narrows the C++ side's responsibility and removes a raw out-pointer write. TLS/crypto paths are untouched beyond mechanical &self conversion.

Level of scrutiny

High. This is the hottest production path in the runtime (every Bun.serve request), with intricate refcount/lifetime reasoning across the Rust↔C++↔uWS boundary. The PR rewires: server lifetime (two refs instead of one owning box), request-context pool slot ownership (self-owned Pooled instead of server-released), WeakPtr semantics (now has Drop — every pre-existing explicit .deref() must still be idempotent-safe), PreparedRequest shape (reaches Request through ctx.request_weakref.peek() instead of a stored raw pointer), and the node:http FFI handshake. Each of these is a place where a subtle ordering or refcount imbalance would manifest as a UAF or leak only under specific request patterns (abort mid-response, reload under load, VM shutdown with pending requests, etc.).

Other factors

• Two prior automated-review nits (dead is_ssl param; broken h3 doc link) were both addressed by the author.
• Extensive test coverage claimed in the description (debug+ASAN across serve/websocket/node-http/bake suites, hand-driven lifecycle scenarios, 20/20 servers freed after stop+GC).
• This is instalment 13 of an established series with the same reviewer patterns; the abstractions introduced here (ThisPtr trampolines, CellRefCounted, BackRef<_, Root>) match those from earlier PRs in the series.
• The diff is far too large and the ownership-model changes too architecturally significant for auto-approval; a maintainer should confirm the two-ref NewServer model, the DeinitTask::cancelled teardown path, and the WeakPtr::Drop addition against every existing explicit .deref() site.

[claude]

Code review found no issues

No high-confidence issues detected in this change.

[Jarred-Sumner]

93bac3d: RequestCtx::arm_on_data now takes &self and passes as_ctx_ptr() so the H1 and generic (H3) request-prep paths hand uws the same root-provenance context pointer (flagged on #40399, which carries this branch).

[claude]

Code review found no issues

No high-confidence issues detected in this change.

[claude]

Code review found no issues

No high-confidence issues detected in this change.

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Inline comments:
In `@src/ptr/lib.rs`:
- Around line 674-676: Update OwnedThis::this_ptr so the returned ThisPtr cannot
outlive its OwnedThis owner: either make this_ptr unsafe with the required
safety contract, or parameterize/tie the handle to the owner borrow lifetime and
propagate that lifetime through safe ThisPtr APIs. Preserve existing ownership
and drop behavior while preventing safe use-after-free through retained handles.

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📥 Commits

Reviewing files that changed from the base of the PR and between d393bf9 and 4f359b9.

📒 Files selected for processing (31)

• src/collections/hive_array.rs
• src/event_loop/ManagedTask.rs
• src/jsc/FetchHeaders.rs
• src/jsc/HTTPServerAgent.rs
• src/jsc/bindings/NodeHTTP.cpp
• src/jsc/lib.rs
• src/ptr/lib.rs
• src/ptr/weak_ptr.rs
• src/runtime/api/BunObject.rs
• src/runtime/api/bun/h2_frame_parser.rs
• src/runtime/bake/DevServer.rs
• src/runtime/dispatch.rs
• src/runtime/jsc_hooks.rs
• src/runtime/server/AnyRequestContext.rs
• src/runtime/server/DirectoryRoute.rs
• src/runtime/server/FileRoute.rs
• src/runtime/server/HTMLBundle.rs
• src/runtime/server/NodeHTTPResponse.rs
• src/runtime/server/RequestContext.rs
• src/runtime/server/ServerWebSocket.rs
• src/runtime/server/StaticRoute.rs
• src/runtime/server/mod.rs
• src/runtime/server/server.classes.ts
• src/runtime/server/server_body.rs
• src/runtime/webcore/Request.rs
• src/runtime/webcore/Response.rs
• src/uws_sys/App.rs
• src/uws_sys/Request.rs
• src/uws_sys/WebSocket.rs
• src/uws_sys/h2.rs
• src/uws_sys/h3.rs

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[claude]

Code review found no issues

No high-confidence issues detected in this change.

[claude]

Code review found no issues

No high-confidence issues detected in this change.

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Note

GitHub couldn't provide a complete incremental comparison for this pull request, so CodeRabbit is performing a full review instead. This review may take a little longer.

[claude]

Code review found no issues

No high-confidence issues detected in this change.