[dylan-conway]

What does this PR do?

The dev server's framework and bundler options now own their strings. Before, they were &'static views into UserOptions.arena or into JS strings. The second copy of every options type is deleted.

Before. There were two families of the same types:

• bake_body::{Framework, FileSystemRouterType, ServerComponents, ...} held &'static [u8]. Three safe helpers made those from borrowed data: arena_erase, arena_dupe_z and StringRefList::track. from_js, react, auto and bun build --app used it.
• bake::{Framework, ...} held Cow<'static, [u8]>. The dev server used it.

For Bun.serve HTML routes, ServerConfig copied the Cow family into the arena to build the 'static family. server/mod.rs then converted back with Cow::Borrowed, so the dev server's copy still pointed into the arena.

After. Only the bake family is left, and its string fields are Utf8Bytes<'static>.

• Borrowed is only ever a literal or a path the resolver interned. Owned is a computed or transcoded string. Shared holds a ref on an ASCII string from the JS options, which is what StringRefList held, now in the field that reads it. UserOptions.root is a ZBox and env_prefix a Box<[u8]>.
• None of the option structs is Clone, so a copy of one does not compile.
• bun_bundler::bake_types::BuiltInModule holds Cow<'static, [u8]> instead of Box<[u8]>. Borrowed is one of Bun's embedded sources (the react framework, the react-refresh fallback), in the options and in every as_bundler_view. One from JS is owned bytes and not a ref, because the bundler's threads read it.
• from_js, react and auto are impls on that family. auto is infallible, as react is.
• One init_transpiler, taking &self. There were two bodies, one per family. It takes the source map and minify settings from BuildConfigSubset in production, and ignores them in development, as before.
• One resolve, in place. The production one cloned the Framework.
• One resolve_path behind resolve_helper and resolve_or_null.

Behaviour changes

• A framework entry point or runtime import that resolves to a module with no usable path aborted the process (panic: just resolved in the dev server, an unwrap in bun build --app). It now prints Failed to resolve '...' for framework (...), and Bun.serve throws or the build exits 1. That is a module a "browser" map disables, and also "fs" and "node:fs".
• A dev server that fails to start drops framework and bundler_options: DevServer::init keeps them in options until its fallible steps are done. What else it has written by then still leaks, as on main.
• resolve_or_null maps instead of unwrapping. The None cannot be reached: auto uses the VM's resolver, which ignores "browser" maps.

Deleted:

• the bake_body copies of the types, and their duplicate resolve, resolve_helper, as_bundler_view, add_react_install_command_note and clone
• the From bridges and convert_file_system_router_type
• the three erasure helpers, and the unused arena parameters
• get_optional_string, which was get_optional_slice plus track
• init_transpiler_with_options's four extra parameters and the wrapper around it, whose ProductionStatic arm no caller reached
• BuildConfigSubset.{conditions, drop, ignore_dce_annotations}. Nothing wrote them, on main either, and two were keyed by &'static [u8]. bake.d.ts lists all three; they were and are ignored.

Unchanged:

• The arena stays: the transpilers, their bake_types::Framework views and DefineData live in it. The drop order from Bun.serve: drop the DevServer before the config that owns its arena when listen fails #39630 is still needed.
• The order of JS property reads in from_js.
• ignoreDirs still iterates the wrong array.
• serverEntryPoint is still resolved with the client's resolver.
• The dev server's plugin handle is still never destroyed: main also takes bundler_options out of UserOptions, the only owner that destroys it.
• production.rs still never drops its transpilers or their framework views.
• bun build --app still unwraps the resolved path of its config file. It cannot be None: the VM's resolver ignores "browser" maps, and the specifier always starts with ./ or /. On a build of main, a config file that a "browser" map names is loaded, and fs and node:fs report could not resolve application config file.
• sync_resolver_opts still copies every built-in module's source into the resolver's options, twice per transpiler, embedded ones included. The resolver never reads it.

Copies, counted from the code against main

Fewer

• HTML and {dir, style} routes: every router type string was copied into the arena and the lists were collected again twice. They are moved, dir included.
• A resolved path: the dev server copied each one. It is borrowed when the resolver interned it.
• An embedded source: the dev server copied it at the bridge between the families, and both modes copied it in every as_bundler_view (one per transpiler, one after resolve, and one at the start of each dev server bundle). None of those copies it now.
• bun build --app: resolve cloned the router types and the built-in module map.
• root from the working directory: two arena copies.

The same. A string from a JS framework object: a ref when it is ASCII, one transcode when it is not.

More

• bun build --app, for each of builtInModules: the key is boxed and an ASCII path or code is copied once, as the dev server already did on main. An entry point that names a path built-in copies that path, also as the dev server did.
• bun build --app: a resolved path the resolver did not intern (external, data:) is copied. Main kept a 'static view of the specifier.
• No bytes, only a Vec: the default extensions and ignoreDirs lists in bun build --app, and the two lists in the router type react builds and auto replaces for {dir, style} routes.

How did you verify your code works?

Two new tests with a clientEntryPoint that a "browser" map disables: Bun.serve({ app }) in test/bake/app-options.test.ts and bun build --app in test/bake/dev/production.test.ts. Both fail on a debug build of main and on 1.4.3.

On this head, a local debug + ASAN build:

• 19 files under test/bake pass, with no failure: app-options, framework-router, deinitialization, serve-plugins-dev-server, dev-and-prod, hmr-socket-protocol, and dev/{bundle,html,css,plugins,production,esm,react-response,react-spa,ssg-pages-router,response-to-bake-response,request-cookies,import-meta-inline,server-sourcemap}. That includes the real react framework in development and in bun build --app.
• app-options also passes with BUN_JSC_validateExceptionChecks=1, as the ASAN lane runs it.
• test/internal/source-lints: 182 pass.
• Against a debug build of main, no difference and no ASAN report:
  • every string option as an atom, a rope, a substring and a fresh string, plus Latin-1 and UTF-16 ones and one string in four fields; the options object dropped, two full GCs and heap churn before the first fetch; failing starts, 15 start/stop cycles, {dir, style} routes, and a server in a Worker that is terminated while it runs (65 lines of output)
  • 9 custom frameworks x 4 URLs: extensions with and without the dot, non-ASCII, "*" and the two rejected forms; builtInModules with code, with path and with a duplicate key
  • the client bundle of an HTML route with react installed (the embedded react-refresh) and with react-refresh installed, three server starts each, by hash
  • bun build --app with the built-in react framework over faked dependencies: the files it writes, by hash, and stderr. It ends in Runtime file not found on both.

Behaviour, release builds from CI, 272ff43 against 4e5926d, each with an A/A control. The only differences are the aborts that became errors. No report from the ASAN build of the head.

• option parsing: 39 property paths x 46 values (1,794 cases), printing the error or the response
• the order of every property read, with logging, throwing, GC-ing and array-mutating getters
• resolution: 4 roles x 45 specifiers
• what the options do: 48 configurations x 20 URLs, with freshly built strings and a GC before the first fetch, comparing bodies, client bundles and source maps
• export conditions and import.meta.env per graph, HTML routes with and without react and react-refresh, 9 [serve.static] bunfigs, 170 {dir, style} routes
• lifecycle: 50 start/stop cycles, failing starts, two servers, reload(), workers, exits

Performance, the same two release builds. User-space instructions. The control is a byte-identical copy of the base. Not measured again since.

workload	head	control
800 start/stop cycles, HTML routes, no react	-0.51%	+0.83%
the same, react installed	-0.85%	-0.48%
the same, react-refresh installed	-0.44%	+0.12%
the same, a custom framework object	-3.83%	-0.21%
one server.reload(), in those three HTML set-ups	-4.8%, -4.3%, -4.7%	within 0.0%

Not covered. console: true forwarding, macOS and Windows locally.

[robobun]

^{Updated 11:05 PM PT - Oct 15th, 2026}

@dylan-conway, your commit 5480296 is building: #126414

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Reviewing files that changed from the base of the PR and between 4e5926d and 7fbbbfc.

📒 Files selected for processing (8)

• src/bundler/bundle_v2.rs
• src/bundler/transpiler.rs
• src/ptr/lib.rs
• src/runtime/bake/bake_body.rs
• src/runtime/bake/mod.rs
• src/runtime/bake/production.rs
• src/runtime/server/ServerConfig.rs
• test/bake/app-options.test.ts

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Walkthrough

Bake framework configuration now uses owned or borrowed values for roots, imports, modules, and router settings. Transpiler initialization returns a framework projection and applies source-map and minification settings. Server and production setup use the updated configuration and resolution paths.

Changes

Bake Framework Configuration

Layer / File(s)	Summary
Framework configuration and parsing src/runtime/bake/bake_body.rs, src/runtime/bake/mod.rs	User options and framework parsing use owned or borrowed values for roots, imports, modules, and router settings. Array extensions gain a leading . when missing; "*" still selects no extension filter.
Framework projection and transpiler configuration src/runtime/bake/bake_body.rs, src/runtime/bake/mod.rs, src/bundler/bundle_v2.rs, src/bundler/transpiler.rs, src/ptr/lib.rs	BuildConfigSubset stores owned environment-prefix bytes and includes source-map and optional minification settings. Transpiler initialization returns a pointer to the framework projection. Development disables minification and uses external source maps; production uses configured settings.
Server setup and framework resolution src/runtime/server/ServerConfig.rs, src/runtime/server/mod.rs, src/runtime/server/server_body.rs, src/runtime/bake/DevServer.rs, src/runtime/bake/production.rs, test/bake/app-options.test.ts	Server setup passes the root, framework, and bundler options directly. Framework resolution and filesystem-router setup use the updated configuration, and route parsing borrows directory bytes. A test checks the error for a client entry point disabled by a browser map.

Suggested reviewers: robobun

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to 7fbbb

No actionable regression remains identified; the PR is mergeable after normal checks.

Pre-merge checks: 4

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title clearly identifies the main change: consolidating option types so they own their strings.
Description check		The description includes both required sections. It explains the implementation, behavior changes, unchanged behavior, deleted code, and extensive verification results.

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Actionable comments posted: 1

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Inline comments:
Review comments at @src/runtime/bake/bake_body.rs:
- Line 872: Update resolve_or_null to handle a missing path from
res.path_const() without panicking: map a present path to its text bytes and
return None when no path is available.

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📒 Files selected for processing (7)

• src/runtime/bake/DevServer.rs
• src/runtime/bake/bake_body.rs
• src/runtime/bake/mod.rs
• src/runtime/bake/production.rs
• src/runtime/server/ServerConfig.rs
• src/runtime/server/mod.rs
• src/runtime/server/server_body.rs

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[claude]

Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

Beyond the inline findings, I also checked two spots where the refactor could have changed behavior: Framework::init_transpiler now passes None for the three minify overrides, but init_transpiler_with_options falls back to mode != Development for None (src/runtime/bake/bake_body.rs:782-784), so dev-server minify defaults are unchanged; and the StringRefList::track(dir) removal in src/runtime/server/server_body.rs:794 is safe because relative_root is copied into Cow::Owned before the JS slice goes out of scope.

Extended reasoning...

The change collapses the duplicated bake Framework/BuildConfigSubset type families into one owned-string set across src/runtime/bake and src/runtime/server, with no security-sensitive surface. Inline findings cover ownership leaks on the DevServer init error path, production.rs, and the moved-out plugin handle; the note above records the two additional behavior-preservation points I verified from the code.

Additional findings (outside the current diff — GitHub can't attach inline comments there):

• 🟡 src/runtime/bake/DevServer.rs — Users whose dev server fails during transpiler setup leak every owned framework string, the already-built transpiler and the JS plugin handle on each failed Bun.serve call. DevServer::init writes options.framework and options.bundler_options into the uninit box at DevServer.rs:509, then returns Err at DevServer.rs:659, :670, :682 before assume_init, so no field Drop runs. After this PR those fields own heap Cow::Owned strings, Vecs and StringArrayHashMap boxes copied from the user's config. Fix: on every early return before assume_init, drop_in_place the fields already written (framework, bundler_options, any initialized transpiler) or build those owned values after the fallible steps.

  Why this was flagged

  Trigger: Bun.serve with HMR routes where init_transpiler fails (resolver/define parse error, OOM) at DevServer.rs:650-684, or watcher init fails at DevServer.rs:609; entry via server/mod.rs:2266. The box is MaybeUninit<DevServer> and the early return Err paths skip field drops. w!(framework, options.framework) at DevServer.rs:509 has already moved the framework in; the diff made those strings Cow::Owned/Box<[u8]> (bake_body.rs:629, :745, :839, :876) instead of arena views, so the leaked heap per failure grows from a few containers to every user string plus the react sources. The plugin handle was taken out of UserOptions at server/mod.rs:2272, so UserOptions::drop (bake_body.rs:52) sees None and the protected JSC cell is never destroyed either. The base leaked the same containers, but the owned-string conversion is this PR's change and REVIEW.md asks that new owning fields be released on all lifecycle exits. A server that retries Bun.serve in a loop after a config error accumulates these. Remedy: drop_in_place the written fields on each pre-assume_init exit.

  Verification: nit (pre-existing leak route, slightly widened by this PR); triggers when Bun.serve with HMR routes fails inside DevServer::init after the framework has been moved into the uninit box. The return Err(...) at DevServer.rs:597, :609, :659, :670, :682 occur before assume_init() at :706, so dropping Box<MaybeUninit<_>> runs no field Drop. After the PR the same strings are Cow::Owned, so their heap bytes now leak on those early returns too.

• 🟣 src/runtime/bake/production.rs — Every bun build --app run leaks the owned strings inside each per-graph framework view, and the new API contract that would free them is ignored. init_transpiler_with_options now returns the arena slot of the bake_types::Framework projection and its doc says the caller must drop_in_place it; production.rs:440, :451 and :463 discard it with ?;. Bumpalo runs no Drop, so the Box<[u8]> copies of the react client/server/ssr sources and every built-in module in each of the two or three views are never released. Fix: collect the returned pointers in production.rs and drop_in_place them before options.arena is dropped, as DevServer.rs:1176 does.

  Why this was flagged

  Trigger: any production build (bun build --app) reaching build_with_vm at src/runtime/bake/production.rs:429. The function returns *mut bake_types::Framework (src/runtime/bake/bake_body.rs:719, :861) built from arena.alloc(self.as_bundler_view()) at bake_body.rs:787. That view holds Box<[u8]> per built-in module and per server-component string (mod.rs:154-193). production.rs:440, :451, :463 discard the pointer. The arena is bumpalo (bake_body.rs:35) so no Drop runs on the boxes; the DevServer path tracks the same pointers in bundler_framework_views and frees them at DevServer.rs:1176-1180, production does not. The dismissal said the base leaked the same way, but this PR is what changed the return type to make freeing possible and left one of the two callers unwired; the PR also replaced the base's &'static [u8] embedded react sources with per-call heap copies (bake_body.rs:354), so the leaked bytes now include three full source files per view. Remedy: hold the returned pointers and drop_in_place them before the arena goes away.

  Verification: pre-existing. Trigger: any bun build --app run. The arena is bumpalo, which never runs Drop on allocated values. production.rs:440, :452 and :465 call framework.init_transpiler_with_options(...)?; and discard the returned pointer; nothing in production.rs ever drop_in_places those slots. The base already leaks exactly the same way by the same route.

[claude]

🟣 pre-existing, not blocking: pre-existing: users who pass ignoreDirs in a fileSystemRouterTypes entry get their list silently replaced by the router-type objects themselves, as on the base branch. The block at src/runtime/bake/bake_body.rs:656-658 iterates array (the outer fileSystemRouterTypes array) and sizes with its len, instead of iterating exts_js. Fix: iterate exts_js.array_iterator(global)? with exts_js.get_length(global)?, and reject non-string elements, so the user's directories are the ones ignored. The PR description acknowledges this is left as on main. [also at: src/runtime/bake/bake_body.rs:657 - pre-existing: a framework author who passes fileSystemRouterTypes[i].ignoreDirs gets their list silently replaced by the stringified router-type objects, so none of their directories are skipped.]
A small fix can ride a push you are already making; otherwise a short reply is enough.

Why this was flagged

A user configures Bun.serve/bake with framework: { fileSystemRouterTypes: [{ root, serverEntryPoint, ignoreDirs: ["dist"] }] }. Framework::from_js reaches the ignoreDirs branch at src/runtime/bake/bake_body.rs:656 and calls array.array_iterator(global)? where array is the fileSystemRouterTypes array obtained earlier, not exts_js. Each element is a router-type object, so array_item.to_utf8(global)? at bake_body.rs:660 yields "[object Object]" (or throws for an exotic object) and dirs ends up holding one such string per router type, while "dist" is never recorded. The router then scans dist and never ignores anything the user asked for. The base branch has the same bug with arena-backed slices; the diff rewrote these lines to owned Cows but kept the wrong iteration target, and the PR text says this is intentionally unchanged.

Verification: pre-existing: the PR description states "ignoreDirs still iterates the wrong array, as on main", and that claim is accurate. A user passes framework.fileSystemRouterTypes[i].ignoreDirs as an array. The branch at src/runtime/bake/bake_body.rs:656-661 checks exts_js.is_array() but then does let mut it_2 = array.array_iterator(global)?;, so the user's ignoreDirs list is silently replaced.

[dylan-conway]

Left as on main on purpose: this PR changes who owns the strings and nothing about what is parsed. It is listed under "Unchanged" in the description and belongs in its own PR with a test.

[claude]

🟣 pre-existing, not blocking: Servers that pass bundler plugins to a dev-mode Bun.serve never release the native JSBundler plugin after the server stops, holding its protected JS cells for the VM's lifetime. server/mod.rs:2272 moves bundler_options out of UserOptions with core::mem::take, so UserOptions::drop at bake_body.rs:52 finds plugin: None. The receiving SplitBundlerOptions (mod.rs:342) derives Default with no Drop, and DevServer::drop (DevServer.rs:989-1183) never calls PluginJscExt::destroy on self.bundler_options.plugin. Fix: give the plugin exactly one owner that destroys it, either by having DevServer::drop destroy bundler_options.plugin or by leaving the handle in UserOptions and lending it to DevServer.
A small fix can ride a push you are already making; otherwise a short reply is enough.

Why this was flagged

Trigger: Bun.serve with HMR and app.bundlerOptions.plugins (parse_plugin_array at bake_body.rs:184 calls Plugin::create), then server.stop(); entry at server/mod.rs:2266. The handle is moved out at server/mod.rs:2272, so the only destroy site in the codebase, UserOptions::drop at bake_body.rs:52-60, runs with None. SplitBundlerOptions in mod.rs:341-349 has no Drop and DevServer::drop (DevServer.rs:989 onward) only drops transpilers and framework views (DevServer.rs:1170-1180); grep for destroy in DevServer.rs finds no plugin destroy. The dismissal said the base did the same via .into(), which is true, but this PR rewrote the ownership of every field in UserOptions and stated the goal that options now own their strings; the one FFI-owned field was left with no owner on the dev path. Each stopped and restarted dev server leaks one plugin object and its protected JS values. Remedy: destroy the plugin in DevServer::drop or keep it owned by UserOptions.

Verification: pre-existing. Trigger: Bun.serve({ app: { bundlerOptions: { plugins: [...] } } }), then the server is stopped/dropped. server/mod.rs:2272 moves the plugin handle out of UserOptions, so UserOptions::drop (bake_body.rs:52-60) sees plugin: None; DevServer::drop (DevServer.rs:988) never destroys bundler_options.plugin. The base commit has the same path; the PR only removes the .into().

[dylan-conway]

Same on main: it also does mem::take(&mut bake_options.bundler_options) here, and UserOptions::drop is the only destroy site there too. Not changed by this PR.

[dylan-conway]

On the two findings outside the diff:

• DevServer::init failure path: fixed in 12c38cd. framework and bundler_options stay in options through the fallible steps and are written into the struct just before assume_init, so an early return drops them.
• production.rs discarding the returned view: same as main, not changed. bun build --app is one build per process, and the transpilers in those MaybeUninit slots are not dropped either.

[claude]

Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

Still open from earlier reviews (3):

• Unresolved: 3 minor or pre-existing.

[claude]

Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

Still open from earlier reviews (2):

• Unresolved: 2 minor or pre-existing.

Additional findings (outside the current diff — GitHub can't attach inline comments there):

• 🟣 src/runtime/bake/mod.rs — pre-existing: a framework whose serverEntryPoint resolves differently for the browser gets the browser build bundled into the server graph, or fails to start. src/runtime/bake/mod.rs:282-288 resolves fsr.entry_server with the client resolver, whose target is Browser and whose conditions lack "node"/"react-server". Fix: resolve entry_server with the server resolver, as server_runtime_import already is at mod.rs:255-262, so exports conditions and browser maps apply per graph. The base passes client too; this PR only turned the disabled case from a panic into "Failed to resolve".

  Why this was flagged

  A user starts Bun.serve with app.framework.fileSystemRouterTypes[].serverEntryPoint set to a package specifier whose package.json exports has separate "browser" and "node"/"bun" targets, or to ./server.ts with a package.json browser map entry for it. Framework::resolve at src/runtime/bake/mod.rs:282-288 calls resolve_helper with client for fsr.entry_server, while server is used for server_runtime_import at mod.rs:255-262. The client transpiler is built with bun_ast::Target::Browser at bake_body.rs:735-737 and only Server/Ssr graphs get "node" and "react-server" conditions at bake_body.rs:765-776, so the server entry resolves to the browser-conditioned file. That path is then inserted into the server graph at DevServer.rs:931-935, so the server bundle runs the browser build; with a browser map of false the new branch at mod.rs:313-316 reports "Failed to resolve './server.ts' for framework (server side entrypoint)" and the server does not start. The base branch passes client at the same site, so this is pre-existing in a function this PR rewrites.

  Verification: pre-existing. A framework's serverEntryPoint resolves differently under browser conditions than under bun/node/react-server conditions. Framework::resolve at src/runtime/bake/mod.rs:282-288 calls Self::resolve_helper with the client resolver for fsr.entry_server, while server_runtime_import at mod.rs:255-262 correctly uses server. Base has the identical client choice, so this is pre-existing.

[claude]

I re-reviewed the latest push and found no new bugs; the earlier threads I opened (the expect("just resolved") on a disabled path, the stale root comment, and the loose test assertion) are addressed in the current code. Because this is a ~1400-line refactor of the dev server's unsafe init path and its arena/transpiler lifetimes, a human look is still worthwhile before merge.

What was reviewed:

• The merged init_transpiler against both old bodies: dev keeps External source maps and never minifies, production keeps from_api(source_map) and unwrap_or(true) minify, and env_prefix defaults to empty — no behavior change on either mode.
• The three deleted BuildConfigSubset fields (conditions, drop, ignore_dce_annotations): no writer on the base branch, only reads, so dropping them and the drop define loop is dead-code removal.
• Ownership of the strings that replaced &'static slices: StringArrayHashMap::put boxes keys, root copies into ZBox/Cow::Owned before the JSC slice drops, and resolve_path only borrows when as_interned_path proves the bytes live in the resolver's store.
• DevServer::init early returns now drop framework/bundler_options from options (no Drop on Options, so partial moves are sound); the pre-existing leak of already-written transpilers on those paths is unchanged.

Extended reasoning...

The change deletes the duplicate bake_body option types and the arena/StringRefList erasure helpers, making Framework/SplitBundlerOptions own their strings via Cow/Box/ZBox, and merges two init_transpiler bodies into one in bake_body.rs, touching DevServer::init's MaybeUninit field-write sequence, production.rs, ServerConfig.rs and server/mod.rs. It touches no auth, crypto or injection surface; the security-relevant parts are memory lifetimes in unsafe Rust. I verified the init_transpiler merge is behavior-preserving for both modes, the removed fields had no writers, and each new owned string is copied before its JSC source drops. The size, the unsafe partially-initialized DevServer construction, and the lack of a compile/test run in this environment are why this is a defer rather than an approve; no findings were reported this run and all prior threads of mine are addressed in code.

Still open from earlier reviews (2):

• Unresolved: 2 minor or pre-existing.

[claude]

I re-reviewed the latest push (8156c2f plus the merges) and found no bugs; since this collapses two option-type families across arena-backed, MaybeUninit-initialised code in the dev server, a human look is still worthwhile.

What was reviewed:

• bake_types::BuiltInModule as Cow<'static,[u8]>: the only raw-pointer consumer is ParseTask.rs:1483 (SharedBuffer into the arena-held framework view), whose lifetime is unchanged; StringArrayHashMap boxes its keys, so files.put_assume_capacity(path.slice(), ..) in from_js does not dangle.
• DevServer::init now writes framework/bundler_options after the three init_transpiler calls; the views those transpilers hold are separate arena copies, so an early return dropping options.framework leaves nothing dangling.
• Merged init_transpiler reproduces both old paths: dev always External source maps / no minify, production source_map from BuildConfigSubset and minify defaulting to true; conditions/drop/ignore_dce_annotations had no writers on the base branch.
• One description mismatch: "The config file of bun build --app gets the same check" no longer holds — 8156c2f reverted it, and production.rs:335 still does path_const().unwrap(). It looks unreachable (the VM resolver has care_about_browser_field off), but the description should say so rather than claim the check exists.

Extended reasoning...

The diff touches 11 files in src/runtime/bake, src/runtime/server and the bundler's bake_types, deleting the &'static [u8]-backed duplicate option types, the arena lifetime-erasure helpers, and the From bridges, and making the Cow-backed types canonical with owned root/env_prefix; it adds a test for a browser-map-disabled framework entry point. No security-sensitive surface (auth, crypto, injection) is involved. Not approved because the change is large, rewires unsafe arena/MaybeUninit initialisation in DevServer and production.rs, and a prior human review on this PR was dismissed rather than resolved; the bug hunt ran dry with no findings, and the only discrepancy found is a stale PR-description claim about the config-file check that the final commit reverted.

Still open from earlier reviews (2):

• Unresolved: 2 minor or pre-existing.

[claude]

I re-reviewed the latest push (JS option strings now held as Utf8Bytes::Shared WTF refs instead of copies) and found no new bugs; given the size of this refactor and the unsafe partial-init sequence in DevServer::init, a human look is still worthwhile.

What was reviewed on this push:

• Thread affinity of the new Shared refs: every reader of Framework/FileSystemRouterType strings runs on the JS thread (DevServer init, config hash, router setup, client bundle generation, build_with_vm); the bundler only ever sees owned copies made by as_bundler_view, and UserOptions/DevServer drop on the JS thread.
• DevServer::init write reordering: nothing reads (*p).framework or (*p).bundler_options before the moved w! writes (frontend_only now reads options.framework), so the early returns from init_transpiler drop the options rather than leaking them.
• init_transpiler merge: minify and source-map outcomes match both deleted bodies for dev and production; conditions/drop/ignore_dce_annotations had no writer on the base branch, so &[] and the removed drop loop are behavior-preserving.
• resolve_path: as_interned_path is a pointer-range check against the never-freed stores, so Borrowed only wraps store-backed bytes and everything else is copied.

Extended reasoning...

The range collapses the duplicated bake option types into one family in src/runtime/bake/mod.rs and bake_body.rs, switches string fields to bun_core::Utf8Bytes<'static> (Borrowed/Owned/Shared), makes UserOptions.root an owned ZBox, merges the two init_transpiler bodies, makes Framework::resolve in-place, and updates DevServer.rs, production.rs, ServerConfig.rs, server_body.rs and the bundler's bake_types accordingly, with two new tests for a browser-map-disabled entry point. It touches no auth, crypto or injection surface, but it does touch the MaybeUninit field-by-field construction in DevServer::init and arena-backed lifetimes that are erased to 'static. The bug hunt ran dry and the latest commit's new WTF-ref ownership checked out as JS-thread-only, but the diff is about 1,100 deleted and 370 added lines across unsafe init and lifetime code, which is too large and subtle to approve without a human reviewer; an earlier human review on the PR was dismissed rather than resolved.

Still open from earlier reviews (2):

• Unresolved: 2 minor or pre-existing.