js_parser: fix four crashes of exports.eliminate and exports.replace by robobun · Pull Request #44137 · oven-sh/bun

robobun · 2026-09-27T17:24:49Z

Problem

Four inputs of exports in Bun.Transpiler end the process. replace on a name of a re-export list: panic: index out of bounds: the len is 6 but the index is 10. eliminate on export let A: panic: called `Option::unwrap()` on a `None` value.
eliminate on export class A {} or on export default: panic: unreachable. A string value of replace after another parse in the process: Segmentation fault.

Fix

replace_reexport declares the exported name for both re-export forms. The name default goes through the visitor of export default.
visit_decls drops the declaration that the entry removes. _parse moves only a part that append_part appended. The string node lives in the arena of the instance.
A namespace member is not an export, so no entry applies to it.
Verified: test/bundler/transpiler/transpiler.test.js, 10 new tests, all fail without the src/ change. Self-reviewed: 12 concerns raised, 12 addressed (re-export part).

Background

exports.eliminate removes a named export. exports.replace gives it another value or, with [name, value], another name.
This PR has the changes of js_parser: fix panic when exports.eliminate removes a hoistable export #33376, Bun.Transpiler: allocate exports.replace string values in the instance arena #38541 and js_parser: fix exports.eliminate/replace on a declaration with no initializer and on namespace members #44179, which are closed.
Bun.Transpiler: exports.replace prints a module that does not parse when the module cannot declare the export name #44138 asks what a replaced export does when the module cannot declare its name.

Downsides

Outputs that change: a replaced re-export throws when the module binds or imports its name, replace on export let A prints the export, and a namespace member stays as it is.
A reserved word as the name prints export var class = 1 (Bun.Transpiler: exports.replace prints a module that does not parse when the module cannot declare the export name #44138).
Release .text +3584 B. No exports option: +1 instruction for each export default, +5 for each part.

Notes

Found by fuzzing. There is no issue and no user report. #12892 and #2084 are about the same option. This PR does not change what they describe.

The parts of this PR

Part	Was	Commits
A name of a re-export	this PR	`a3d8904`, `1de33bf`, `10f0370`, `e1527b3`
A string value after another parse	#38541	`59da676`, `e946a11`
A declaration with no initializer, a member of a namespace	#44179	`540701e`, `a219ce3`, `0c94fd8`, `aa89336`
A hoistable export	#33376	`c67695a`, `089fd53`
An entry that injects from `export default`	new	`36bb20b`, `603fb7f`

The crashes

Input	Option	1.4.2 and `main` `a4f1429`	this PR
`export { ReadStream, WriteStream } from "node:fs"`	`replace: { ReadStream: "x" }`	`panic: index out of bounds: the len is 6 but the index is 10`	`export var ReadStream = "x";` and the list with `WriteStream`
`export let A`	`eliminate: ["A"]`	panic: called `Option::unwrap()` on a `None` value	empty module
`export class A {}` and `export const keep = 1`	`eliminate: ["A"]`	`panic: unreachable`	`export const keep = 1;`
`export default 42` and `export const keep = 1`	`replace: { default: ["N", 1] }`	`panic: unreachable`	`export var N = 1;` and `export const keep = 1;`
`export const ReadStream = 5`, after `require()` of another file	`replace: { ReadStream: "hello-value" }`	`Segmentation fault`, or `panic: capacity overflow`	`export const ReadStream = "hello-value";`

Bun 1.3.13 prints the right module for the first row. Bun 1.3.14 prints it with bun -e and ends in Segmentation fault from a file. For the second row, 1.3.13 and 1.3.14 end in Segmentation fault at address 0x8. The Zig source had the same logic, so it was never correct, and the tests are not in test/regression/issue.

The causes (lines of main)

s_export_from (src/js_parser/visit/visit_stmt.rs:293) passes the parse-time ref of the list item to inject_replacement_export. The index of that ref is the length of the imported name, and visit_binding uses it as an index into the symbol table.
The arm of visit_decls for a declaration with no value (src/js_parser/visit/mod.rs:601) reads the result of replace_decl_and_possibly_remove the wrong way round. It visits the declaration that it must drop, and visit_decl unwraps the missing value.
_parse (src/js_parser/parse/parse_entry.rs:1164 and :1176) moves the part of a hoistable statement to the top with parts.pop().expect("unreachable"). append_part appends nothing when the visit removed each statement.
export_replacement_value (src/runtime/api/JSTranspiler.rs:919) makes the string node with Expr::init, in the store that the next parse of the thread resets.

What replace_reexport does

Entry	Exported name	Result
replaces, or injects	`default`	`export default <value>`, visited with no entries
replaces	other	`declare_symbol` for the name, then `export var name = <value>` through `inject_replacement_export`
injects	other	`inject_replacement_export`, which declares the injected name as before
eliminates		nothing

For export * as name, the second row is what main does. The first row is new for it, and so is the fact that the last two rows do not declare name. On main, const ns = 1; export * as ns from "x" with eliminate: ["ns"] throws "ns" has already been declared, and export * as default from "x" with replace: { default: 1 } prints export var default = 1.

Why the default export is visited, and with no entries

The lowering of a top-level using wraps the module body in try. s_export_default then prints var x = <value> and export { x as default }, and the wrap pass drops each export default statement (src/js_parser/p.rs:10078). A statement that does not go through the visitor has no such pair, and the module loses the export. #38287 moves that split and asserts that no export default statement reaches the wrap pass. The visited statement is correct before and after #38287.

The visitor looks default up in the entries. With replace: { a: ["default", 1], default: 2 } it changed the value to 2. So replace_reexport takes the entries away (core::mem::take) while the visitor runs, and puts them back. The first version was a flag on the parser that the visitor reads. With it, s_export_default for ts kept the parser in a stack slot, grew 412 B, and ran 12 more instructions for each export default with no exports option.

An injected export var still goes through s_local, which looks its name up, as on main. #44138 asks which rule all forms get.

The visit cannot fail for a value of exports.replace, which is a string, a number, a boolean, null or undefined. The expect is the one that inject_replacement_export has on its own visit. With ? in its place, s_export_from can return an error, and it runs 1 more instruction for each statement with no exports option (measured: 37,130 to 37,328 for 200 statements).

declare_symbol and new_symbol

The first version made the symbol with new_symbol, as s_export_from does for the items it keeps. That symbol is not a member of the module scope, so nothing sees a collision, and the module prints two declarations of the name. declare_symbol reports the collision.

With the ts loader, declare_symbol lets a declaration take the place of an import of its name (can_merge_symbol_kinds, src/ast/scope.rs:459). So import { a } from "x"; export { a, b } from "x"; export const t = a with replace: { a: 7 } printed a module with no import, and t was 7. replace_reexport looks for an import of the name first and reports "a" has already been declared, which is what the js loader does.

An entry that injects from export default

The visitor of export default marks the value as dead code when an entry takes the export away, and it returned before it injected the export of the entry. With dead code elimination off it injected it. On main this input ends in panic: unreachable, so the missing export was not visible. The three exits for a dead value now inject, and so does the exit for a default export that is a type.

A member of a namespace

s_local selects visit_decls::<true> for a member of a TypeScript namespace too, because its gate tests is_export and the size of the map only. s_function and s_class visited such a member as dead code and then kept the statement, so its body was empty. A member is a property of the namespace object. visit_decls does the test once, and only in the instantiation for true. A test in s_local cost 3 instructions for each statement with no exports option, so it moved.

Input	Option	`main`	this PR
`namespace NS { export let A = 1 }`	`eliminate: ["A"]`	the namespace with no member	`NS.A = 1`
`namespace NS { export let A = 1 }`	`replace: { A: 2 }`	`NS.A = 2`	`NS.A = 1`
`namespace NS { export function A() { return f() } }`	`eliminate: ["A"]`	`function A() {}`	the function with its body

The tests

4 child processes in place of 1 for each input: the rows of the re-exports, the rows with no initializer, the hoistable rows, and the test of the string values from Bun.Transpiler: allocate exports.replace string values in the instance arena #38541.
The key is the exported name: replace: { bb: 1 } matches export { a as bb } from "x", and replace: { a: 1 } does not. main looks the alias up too.
Each list keeps one name, so no row pins the text of an empty list. js_printer: print esbuild's pretty-mode spaces in bare import, for(;;), and empty export-from #40808 changes that text.
No row pins which of replace and eliminate wins for one name.
The rows with using import the printed module and compare its exports, because the lowering prints helper names.
The it.failing test expects a module that parses and exports the name, so it changes with the decision in Bun.Transpiler: exports.replace prints a module that does not parse when the module cannot declare the export name #44138. It is red when the child process did not print its line.

What stays wrong

Input	Option	Result
`export { a as class, b } from "x"`	`replace: { class: 1 }`	prints `export var class = 1`
`let bb = 2; export { a as bb } from "x"`	`replace: { bb: 1 }`	throws `"bb" has already been declared`
`export function g() {}`	`replace: { g: ["default", 1] }`	prints `export var default = 1`, as on `main`
`export const x = 5`	`replace: { x: ["default", 1] }`	prints `export const default = 1`, as on `main`
`export default 42`	`replace: { default: ["default", 1] }`	throws `"default" has already been declared`
`export default class A {}`	`replace: { default: 1 }`	prints the class, as on `main`
`import { a } from "y"; export function f() {} export const t = a`	`replace: { f: ["a", 7] }`, ts loader	prints a module with no import, as on `main`
`let a = 1; export { a as bb }`	`replace: { bb: 1 }`	the key does not match, as on `main`. `s_export_clause` looks the local name up
`export { a, b } from "x"`	`eliminate: ["a", "b"]`	prints `export { } from "x"`, as on `main`. `export * as` prints nothing
`using r = f(); export default 5`	`replace: { default: 1 }`	prints `var input_default = 5`, as on `main`. #38287 changes the order that causes it

For the first two rows, main aborts when the imported name is as long as the symbol table, which has 6 symbols in these modules. For a shorter name it binds an unrelated symbol, and prints export var a = 1 for the one-letter name a. The first 4 rows are the it.failing test. #44138 has the rows and the questions.

#33378 has the swap of the arm in visit_decls among other changes, and conflicts with main since August. That hunk becomes empty when it rebases over this PR.

Measurements (release builds, main a4f1429 against 603fb7f, linux x64)

What	Result
`.text`	58,143,477 B to 58,147,061 B, +3584 B (`llvm-size -A`). `size`: text 80,660,492 to 80,664,076
`replace_reexport` (new, `#[cold]`)	1410 B (ts), 603 B (js) (`nm -S`)
`s_export_default`	9107 to 10,209 B (ts), 8557 to 9554 B (js)
`s_export_from`, `s_export_star`	2521 to 2537 and 1106 to 905 B (ts), 2253 to 2307 and 1031 to 833 B (js)
`s_local`, `s_function`, `s_class`, `append_part`	+45, +28, +10 and +15 B, both instantiations
`_parse`	31,187 to 31,125 B (ts), 26,320 to 26,174 B (js)
`export_replacement_value`	527 to 563 B
Instructions with no `exports` option, in a module of 1300 statements	`s_export_from`: 37,130 to 36,736 (ts), 32,922 to 32,718 (js), for 200 statements. `s_export_default`: 121 on both (ts), 109 to 110 (js), for 1 statement. `append_part`: 28,132 to 28,202 for 14 parts (js). `s_export_star`, `s_export_clause`, `s_function`, `s_class`, `s_local`: 0 change (gdb step count, JIT off)
`visit_binding`, `visit_decl`, `record_declared_symbol`, `replace_decl_and_possibly_remove`, `inject_replacement_export`	0 of 10 function bodies differ (normalized `objdump`, sha256)

valgrind, strace and perf are not on the machine that ran this, so the instruction counts come from gdb.

Outputs that change (102 inputs, ts loader, one process for each input, node --check on each printed module)

	`main`	this PR
aborts	25	0
throws	5	10
prints a module that `node --check` rejects	15	8
prints a module that parses	57	84

73 inputs change. The 10 that throw: 9 bind or import the name of a replaced re-export, or have the name eval, and 1 is replace: { default: ["default", 1] }. The 8 rejected modules: 5 have a reserved word as the name, and 3 come from producers that this PR does not change (the export clause forms, and export const default = 1).

[human-review] gate passed · iteration 3 · 7 files touched

fails on main (without fix)

ASAN without fix: 10 failed, 22 skipped
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" test/bundler/transpiler/transpiler.test.js
bun test v1.4.3 (367d939d9)

test/bundler/transpiler/transpiler.test.js:
(pass) Bun.Transpiler > handles errors when parsing macros [6.89ms]
(pass) Bun.Transpiler > normalizes \r\n [8.55ms]
1
(pass) Bun.Transpiler > doesn't hang indefinitely #2746 [6.07ms]
(pass) Bun.Transpiler > property access inlining > bails out with spread [9.87ms]
(pass) Bun.Transpiler > property access inlining > bails out with multiple items [3.51ms]
(pass) Bun.Transpiler > property access inlining > works [3.88ms]
(pass) Bun.Transpiler > property access inlining > works nested [3.79ms]
(pass) Bun.Transpiler > property access inlining > bails out when the array item is an optional chain [92.23ms]
(pass) Bun.Transpiler > property access inlining > bails out or strips `this` when the index is a call/assignment target [35.03ms]
(pass) Bun.Transpiler > property access inlining > preserves runtime semantics when inlining from a literal index [742.10ms]
(pass) Bun.Transpiler > property access inlining > bails out on optional-
... (truncated)

release without fix: 8 failed, 22 skipped
bun test v1.4.3-canary.1 (e1527b332)

test/bundler/transpiler/transpiler.test.js:
(pass) Bun.Transpiler > handles errors when parsing macros [1.59ms]
(pass) Bun.Transpiler > normalizes \r\n [0.31ms]
1
(pass) Bun.Transpiler > doesn't hang indefinitely #2746 [0.13ms]
(pass) Bun.Transpiler > property access inlining > bails out with spread [0.17ms]
(pass) Bun.Transpiler > property access inlining > bails out with multiple items [0.03ms]
(pass) Bun.Transpiler > property access inlining > works [0.03ms]
(pass) Bun.Transpiler > property access inlining > works nested [0.03ms]
(pass) Bun.Transpiler > property access inlining > bails out when the array item is an optional chain [0.72ms]
(pass) Bun.Transpiler > property access inlining > bails out or strips `this` when the index is a call/assignment target [0.42ms]
(pass) Bun.Transpiler > property access inlining > preserves runtime semantics when inlining from a literal index [28.22ms]
(pass) Bun.Transpiler > property access inlining > bails out on optional-chain index into enum [0.84ms]
(pass) Bun.Transpiler > property access inlining > template literal around an inlined string enum member > member as the first part of the
... (truncated)

passes on PR (with fix)

ASAN with fix: 22 skipped
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" test/bundler/transpiler/transpiler.test.js
bun test v1.4.3 (367d939d9)

test/bundler/transpiler/transpiler.test.js:
(pass) Bun.Transpiler > handles errors when parsing macros [5.32ms]
(pass) Bun.Transpiler > normalizes \r\n [7.75ms]
1
(pass) Bun.Transpiler > doesn't hang indefinitely #2746 [4.62ms]
(pass) Bun.Transpiler > property access inlining > bails out with spread [8.03ms]
(pass) Bun.Transpiler > property access inlining > bails out with multiple items [2.80ms]
(pass) Bun.Transpiler > property access inlining > works [3.06ms]
(pass) Bun.Transpiler > property access inlining > works nested [2.96ms]
(pass) Bun.Transpiler > property access inlining > bails out when the array item is an optional chain [72.15ms]
(pass) Bun.Transpiler > property access inlining > bails out or strips `this` when the index is a call/assignment target [38.01ms]
(pass) Bun.Transpiler > property access inlining > preserves runtime semantics when inlining from a literal index [1428.82ms]
(pass) Bun.Transpiler > property access inlining > bails out on optional
... (truncated)

release with fix: 22 skipped
$ bun scripts/build.ts --profile=release
[configured] bun-profile → bun (stripped) in 2867ms (unchanged)
ninja: Entering directory `/workspace/bun/build/release'
[1/213] gen generated_host_exports.rs
generated_host_exports.rs: 121 exports (host=5, lazy=10, generic=106, rust=0); 248 extern-C blocks audited
[2/213] gen ErrorCode+*.h
[3/213] gen NodeModuleModule.lut.h
Generating /workspace/bun/build/release/codegen/NodeModuleModule.lut.h from /workspace/bun/src/jsc/modules/NodeModuleModule.cpp
[4/213] gen cpp.rs (cppbind)
[5/213] gen JS modules (bundle-modules)
Preprocess modules (14231ms)
Bundle modules (459ms)
Postprocesss modules (253ms)
Bundle Functions (1419ms)
Generate Code (93ms)

[16.48s] Bundled "src/js" for production
  2612 kb
  198 internal modules
  13 native modules
  50 internal functions across 16 files
[6/178] build.rs build_script_build
[7/178] cxx obj/unified/UnifiedSource-src_jsc_bindings-4.cpp.o
[8/178] cxx obj/unified/UnifiedSource-src_jsc_bindings-0.cpp.o
[9/178] cxx obj/unified/UnifiedSource-src_jsc_bindings_node-0.cpp.o
[10/178] cxx obj/unified/UnifiedSource-src_jsc_bindings-3.cpp.o
[11/178] cxx obj/src/jsc/bindings/webcore/streams/JSReadable
... (truncated)

diff hotspot

src/ast/expr.rs                            |   2 +-
 src/js_parser/p.rs                         |   8 +-
 src/js_parser/parse/parse_entry.rs         |  12 +-
 src/js_parser/visit/mod.rs                 |  28 +-
 src/js_parser/visit/visit_stmt.rs          | 101 ++++++-
 src/runtime/api/JSTranspiler.rs            |   6 +-
 test/bundler/transpiler/transpiler.test.js | 447 +++++++++++++++++++++++++++++
 7 files changed, 569 insertions(+), 35 deletions(-)

gate history · 1 passed · 0 rejected · iteration 3

evidence per changed file

file                                        reads  edits  tests
src/ast/expr.rs                                 0      0    152
src/js_parser/p.rs                              9      8    155
src/js_parser/parse/parse_entry.rs              1      2    153
src/js_parser/visit/mod.rs                      4      1    154
src/js_parser/visit/visit_stmt.rs               8      2    156
src/runtime/api/JSTranspiler.rs                 1      0    156
test/bundler/transpiler/transpiler.test.js      5      6    152

s_export_from passed the parse-time name ref of a list item to inject_replacement_export. That ref is not a symbol: its index is the length of the name. visit_binding indexed the symbol table with it, so a name longer than the table aborted the process and a shorter name read an unrelated symbol. The ref also named the imported binding, so `export { a as b } from` declared `a`. s_export_from and s_export_star now call one function. For an entry that replaces, it declares the exported name, as s_export_star did. For an entry that eliminates or injects, it declares nothing. An export with the name `default` goes to the visitor of `export default` as `export default <value>`, so the lowering of a top-level `using` applies to it.

robobun · 2026-09-27T17:26:47Z

Status: open at 603fb7f. CI is green (Buildkite #121525), and all review threads are resolved. Waits for a maintainer review. This is the one PR for the crashes of the exports option. #33376, #38541 and #44179 are closed, and their changes are here.

Reproduced on main (a4f1429) and on Bun 1.4.2:

const print = (exports, source) => new Bun.Transpiler({ loader: "ts", exports }).transformSync(source);
print({ replace: { ReadStream: "x" } }, 'export { ReadStream, WriteStream } from "node:fs"');
// panic: index out of bounds: the len is 6 but the index is 10
print({ eliminate: ["A"] }, "export let A");
// panic: called `Option::unwrap()` on a `None` value
print({ eliminate: ["A"] }, "export class A {}\nexport const keep = 1;\n");
// panic: unreachable

Verification with bun bd test test/bundler/transpiler/transpiler.test.js -t "exports.replace|exports.eliminate":

src/ from main:     2 pass, 10 fail   (the 10 new tests. The child processes abort with the panics above)
src/ from this PR:  12 pass, 0 fail   (full file: 247 pass, 0 fail)

What stays wrong, and the decision that it needs, is in #44138.

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📒 Files selected for processing (7)

src/ast/expr.rs
src/js_parser/p.rs
src/js_parser/parse/parse_entry.rs
src/js_parser/visit/mod.rs
src/js_parser/visit/visit_stmt.rs
src/runtime/api/JSTranspiler.rs
test/bundler/transpiler/transpiler.test.js

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Walkthrough

Export replacement handling now covers named and namespace re-exports, default exports, and declarations without initializers. Parser part creation reports whether it appended a part. String replacement expressions use the supplied arena. Regression tests cover transformed output, exports, and runtime results.

Changes

Export replacement behavior

Layer / File(s)	Summary
Handle re-export replacements `src/js_parser/visit/visit_stmt.rs`, `test/bundler/transpiler/transpiler.test.js`	A shared helper handles matched named and namespace-alias re-export entries. Tests check transformed output, scanned export names, runtime exports, duplicate-binding errors, and names that cannot be bound.
Handle declarations and dead default exports `src/js_parser/visit/mod.rs`, `src/js_parser/visit/visit_stmt.rs`, `test/bundler/transpiler/transpiler.test.js`	Module replacement lookup excludes namespace members. Declarations without initializers are retained when no replacement exists. Dead default-export paths can inject eligible replacement entries. Tests cover declaration and namespace cases.
Track whether parser parts are appended `src/js_parser/p.rs`, `src/js_parser/parse/parse_entry.rs`, `test/bundler/transpiler/transpiler.test.js`	`P::append_part` returns whether it appended a part. Class and default-export statements move to `before` only when a part was appended. Tests check hoistable exports and statement order.
Allocate replacement expressions in the supplied arena `src/ast/expr.rs`, `src/runtime/api/JSTranspiler.rs`, `test/bundler/transpiler/transpiler.test.js`	String replacement expressions use the supplied arena. Tests cover replacements across module loads and synchronous and asynchronous transforms.

Suggested reviewers: jarred-sumner

Priority: ➖ Normal

Merge Risk: 🔵 Low · up to 36bb2

A valid re-export can fail to transform when its replaced alias matches a local binding. The affected case is narrow and has a naming workaround; merge with explicit acceptance of this limitation or fix it first.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
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.
Title check	✅ Passed	The title clearly identifies the parser area and the primary change: fixing crashes in exports.eliminate and exports.replace.
Description check	✅ Passed	The description explains the problem, fix, scope, known limitations, and verification results. It does not use the exact template headings, but it provides the required information, including detailed…

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Inline comments:
Review comments at @src/js_parser/visit/visit_stmt.rs:
- Line 293: Update the synthetic default-export visit at
`p.visit_and_append_stmt` so it does not apply `exports.replace` a second time.
Preserve the replacement used to create the synthetic export, but visit that
export without allowing the `default` entry to replace its value or inject an
invalid declaration.
- Around line 297-300: In the re-export handling path around `declare_symbol`
and `inject_replacement_export`, stop using the exported alias as the local
symbol name. Declare a unique valid local binding, then export that binding
under the requested alias so re-exports do not collide with existing bindings or
require the alias to be a valid identifier.

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Run ID: c3ce15c7-4cd2-4bff-b90a-0316fa25f393

📥 Commits

Reviewing files that changed from the base of the PR and between a4f1429 and a3d8904.

📒 Files selected for processing (2)

src/js_parser/visit/visit_stmt.rs
test/bundler/transpiler/transpiler.test.js

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 8 remain after this review.

…port that an entry makes The visitor of `export default` looks `default` up in the map. So an entry with the key `default` also applied to the `export default` that replace_reexport made for another entry. An entry that replaces changed the value again. An entry that eliminates or injects dropped the export when dead code elimination is on. The visitor now skips the lookup while replace_reexport visits its statement.

robobun · 2026-09-27T17:47:12Z

Both findings of the review are correct. One is fixed, and one is not part of this PR.

1. A second entry applied to the export default that an entry made. Fixed in 1de33bf. The visitor of export default skips the lookup in exports.replace while replace_reexport visits its statement. Before the fix, on export { a, b } from "x":

`replace`	`a3d8904`	`1de33bf`
`{ a: ["default", 1], default: 2 }`	`export default 2`	`export default 1`
`{ a: ["default", 1], default: ["N", 2] }`	no export for `a` (dead code elimination on)	`export default 1`
`{ a: ["default", 1], default: ["default", 2] }`	no export for `a`, or `"default" has already been declared`	`export default 1`

The first two rows are in the new test. An injected export var still goes through s_local, which looks its name up, as on main. #44138 asks which rule all forms get.

2. The exported alias as the local binding. Not changed here. A unique local binding with an export by name (var tmp = 1; export { tmp as bb }) is one of three possible behaviors, and #44138 asks a maintainer to choose. Until then a collision throws "bb" has already been declared, which is what export * as does on main, and a reserved word prints export var class = 1. The it.failing test records both. The thread of this finding is marked as addressed by 1de33bf, but that commit does not change it.

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 both .expect("unreachable") calls in replace_reexport (src/js_parser/visit/visit_stmt.rs:295-305) for a user-reachable panic: declare_symbol only returns Err through mark_strict_mode_feature, which logs the reserved-word error and returns Ok(()), and with Loc::EMPTY (start == -1) range_of_identifier returns Range::NONE without indexing the source; the synthesized export default visit only visits a literal from exports.replace, which cannot fail. I also checked the is_visiting_replaced_export flag: it is set and cleared around a single infallible call with no early return in between, so it cannot leak into a later statement.

Extended reasoning...

The change routes both re-export replacement sites (export { .. } from and export * as) through a new cold helper in src/js_parser/visit/visit_stmt.rs, adds a parser flag in src/js_parser/p.rs, and adds a transpiler test table; it touches no security-sensitive surface. Inline findings are being posted, so this note only records the panic paths and flag lifetime that were examined and found not to be an issue.

…test expects

claude

Code review completed

Nothing new to post: everything this review found is already covered by existing comments on this pull request or didn't merit a separate one.

Still open from earlier reviews (2):

Unresolved: 2 minor or pre-existing.

…the ts loader too The ts loader lets a declaration take the place of an import of its name. So `import { a } from "x"; export { a, b } from "x"` with `replace: { a: 1 }` printed a module with no import, and each use of `a` read the replaced export. replace_reexport now reports `"a" has already been declared`, as the js loader does. The flag on the parser is gone. replace_reexport takes the entries away while the visitor of `export default` runs, so that visitor is the code of main again.

claude

Code review completed

Nothing new to post: everything this review found is already covered by existing comments on this pull request or didn't merit a separate one.

robobun · 2026-09-27T19:11:03Z

^{Updated 1:27 AM PT - Sep 29th, 2026}

✅ @robobun, your commit 603fb7f33238a9a412b10012cb22841080401910 passed in Build #121525! 🎉

🧪 To try this PR locally:

bunx bun-pr 44137

That installs a local version of the PR into your bun-44137 executable, so you can run:

bun-44137 --bun

robobun · 2026-09-28T19:56:58Z

@robobun wake up!!

Jarred-Sumner · 2026-09-28T20:41:14Z

@robobun wake up!!

robobun · 2026-09-28T20:50:51Z

I am here. The state of this PR at e1527b3:

CI is green: Buildkite #121286 passed, and so did the lint checks.
All 5 review threads are resolved. No change is pending from my side.
The PR merges cleanly into main (a4f1429). It waits for a maintainer review.

Two things stay open after this PR, and neither blocks it:

Bun.Transpiler: exports.replace prints a module that does not parse when the module cannot declare the export name #44138 asks what a replaced export does when the module cannot declare its name. The by-name form is ready on a branch, and I open it as a PR when the choice is made.
A string value of exports.replace is a freed node after another parse in the process. Bun.Transpiler: allocate exports.replace string values in the instance arena #38541 has the fix, and it conflicts with main since August. I rebase it now. The fix for export let A with eliminate is stacked on it, so that PR follows.

…e arena export_replacement_value copied the string bytes into the JSTranspiler's arena but built the E::EString node with Expr::init, which appends the node to the thread-local AST store. The Expr is kept in config.runtime.replace_exports for the life of the transpiler, while the next synchronous parse on the thread (a require() of a CommonJS file, a JSON import, ...) resets that store, so later transforms printed the replacement from a freed slot. Allocate the node in the same arena as its bytes with Expr::allocate; the arena lives exactly as long as the config that holds the Expr. Disabler::scope() makes a debug build panic if anything in this function appends to the thread-local Expr store again. The required module in the test declares enough strings to reuse the slot the replacement node used to occupy, so the test also fails on a release build without the fix.

…ith no initializer The arm of visit_decls for a declaration with no initializer read the result of replace_decl_and_possibly_remove the wrong way round. An eliminated export went to visit_decl, which unwraps the missing value and aborts the process. A replaced export was dropped from the module. The arm now does what the arm for a declaration with an initializer does: drop the declaration when the helper returns false, visit it otherwise. A namespace member with no value is left alone, so that it prints what it prints today.

…namespace alone s_local selected the visit that applies the entries for each exported declaration, and a member of a TypeScript namespace is one. So `namespace NS { export let A = 1 }` lost `NS.A` with `eliminate: ["A"]`, and got `NS.A = 2` with `replace: { A: 2 }`. The visitors of a function and of a class skip a member of a namespace. s_local now selects that visit at module level only. The guard in the arm for a declaration with no initializer is not necessary any more.

…that is a member of a namespace s_function and s_class visited a member of a namespace as dead code when its name was in the entries, and then kept the statement. So `namespace NS { export function A() { return f() } }` with `eliminate: ["A"]` printed `function A() {}`. Both now look at the entries at module level only, as s_local does. The tests of the declaration with no initializer run in one child process.

The test in s_local, where the visit is selected, cost s_local 3 instructions for each statement with no exports option. visit_decls now does the test once, and only in the instantiation that applies the entries.

append_part() appends nothing when every statement in the part was eliminated while visiting, but the SClass and SExportDefault arms of _parse() popped the part unconditionally when hoisting it to the top of the file. With exports.eliminate, the hoistable export is gone by then, so the pop either aborted the process on an empty list or stole the previous statement's part and reordered the output. append_part() now reports whether it appended, and the two hoisting sites only move a part that exists.

…t default with dead code elimination on The visitor of `export default` marks the value of the statement as dead code when an entry eliminates it or puts another export in its place, and it returned before it injected that export. So `export default 42` with `replace: { default: ["N", 1] }` lost the export. With dead code elimination off, the visitor injected it. The three exits for a dead value now inject the export of the entry.

claude

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

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

🟣 src/js_parser/visit/visit_stmt.rs — pre-existing: users of the ts loader with deadCodeElimination: false lose the export an exports.replace [name, value] entry should inject when the default export is a type. The type-only early return at src/js_parser/visit/visit_stmt.rs:526-528 drops the statement without the injection the sibling returns now get via inject_for_dead_value!. Fix: every early return of s_export_default that discards the value must still inject an Inject entry's export, e.g. call the same macro before the return at :528, which covers this remaining site alongside the three at :503, :688, :858.

Why this was flagged

Input: new Bun.Transpiler({ loader: "ts", deadCodeElimination: false, exports: { replace: { default: ["N", 1] } } }).transformSync("interface T {}\nexport default T"). At src/js_parser/visit/visit_stmt.rs:437-443 the entry is found, mark_for_replace is set, and is_control_flow_dead stays false because dead_code_elimination is off. visit_expr leaves T Unbound; :501 is false; the TS branch at :516-528 sees local_type_names["T"] == true and returns at :528 with only restore_dead!() and record_on_exit!(), so no export var N = 1 is emitted. With the default deadCodeElimination the same input takes the :501 return and the new inject_for_dead_value! at :503 emits it, so the output differs only by that option. The base branch has the same omission at :526-528; this PR added the injection to the three other early returns but not this one.

Verification: pre-existing. Trigger: ts loader, deadCodeElimination: false, exports.replace: { default: [name, value] } (an Inject entry), and a default export whose value is a bare identifier naming a module-level type (interface T {}\nexport default T). Mechanism verified in /home/claude/bun/src/js_parser/visit/visit_stmt.rs: at :437-443 the default entry sets mark_for_replace = true and…
🟣 src/js_parser/visit/visit_stmt.rs — pre-existing: users who replace default in a module with a lowered top-level using still get the original default export, not the replacement. The using branch at src/js_parser/visit/visit_stmt.rs:587-623 builds var <name> = *expr and export { <name> as default } from the original value, and only afterwards does the mark_for_replace block at :625-646 assign the Replace value into *expr or inject the Inject export. Fix: apply the default entry (Replace, and Inject when DCE is off) before the using-lowering branch so both forms and the class/function arms emit the replaced value, while keeping the replace_reexport synthesized export default path working.

Why this was flagged

Input: new Bun.Transpiler({ loader: "ts", exports: { replace: { default: 1 } } }).transformSync('using r = null; export default 5') through Bun.Transpiler.transformSync or transform. Bun.Transpiler's default target is not bun, so src/bundler/transpiler.rs:1641 sets lower_using, and parse_entry.rs:1046 sets will_wrap_module_in_try_catch_for_using. In s_export_default the entry is Replace, so is_control_flow_dead stays false (visit_stmt.rs:439); the visit reaches :587, which pushes S::Local { var main_default = *expr } with *expr still 5 (:600) and an export { main_default as default } clause (:616). Only then does :633-635 set *expr = replace_expr, mutating the SExportDefault that :952 pushes; finalize at src/js_parser/p.rs:10080-10082 drops every SExportDefault and merges the export clause at :10083-10098, so the module exports 5. With replace: { default: ["N", 1] } and deadCodeElimination: false, the same order keeps default (as 5) next to the injected export var N = 1 (:637). Without using the replacement applies. The base branch has the same order, so…

Verification: pre-existing. Trigger: a Bun.Transpiler with a non-bun target (default is Browser, /home/claude/bun/src/runtime/api/JSTranspiler.rs:58, so /home/claude/bun/src/bundler/transpiler.rs:1641 sets lower_using) transforms a module whose top level has a using declaration and an export default <expr>, with exports.replace: { default: <value> }. Mechanism verified in… | pre-existing. Trigger: a…
🟣 src/js_parser/visit/visit_stmt.rs — pre-existing: users who set exports.replace { default: <value> } on a module whose default export is a class declaration still get the original class printed, not the replacement. In the SClass branch of s_export_default, src/js_parser/visit/visit_stmt.rs:875 stores the replacement in data.value, but visit_stmt.rs:924 unconditionally overwrites data.value with the lowered class statement before visit_stmt.rs:925 pushes it. Fix: when a Replace entry applies, emit export default <value> and return without lowering the class (as the SFunction branch does at visit_stmt.rs:729), so every export default form honors a Replace entry; add a test for export default class A {} with replace: { default: 1 }.

Why this was flagged

Input: new Bun.Transpiler({ loader: "ts", exports: { replace: { default: 1 } } }).transformSync("export default class A {}") through Bun.Transpiler.transformSync or transform. At src/js_parser/visit/visit_stmt.rs:437-443 mark_for_replace becomes true and is_control_flow_dead stays false because the entry is Replace, so visit_class runs and the branch reaches visit_stmt.rs:863-875, which sets data.value = js_ast::StmtOrExpr::Expr(replace_expr). Execution then continues to visit_stmt.rs:910 p.lower_class(js_ast::StmtOrExpr::Stmt(s2_copy)) and visit_stmt.rs:924 data.value = js_ast::StmtOrExpr::Stmt(class_stmts[class_stmt_idx]), which discards the replacement, and visit_stmt.rs:925 pushes the statement. The printed module is export default class A {} and the value 1 never appears. The Expr branch at visit_stmt.rs:635 and the SFunction branch at visit_stmt.rs:729 do apply the replacement, so only class declarations lose it. The base branch has the same overwrite; this diff edits the same branch (inject_for_dead_value! at visit_stmt.rs:858) but only for the dead-value path, and…

Verification: pre-existing. Trigger: any Bun.Transpiler user with exports.replace: { default: <value> } (a Replace entry, not [name, value]) transforming a module whose default export is a class declaration (export default class A {}), through transformSync/transform. Mechanism verified in /home/claude/bun/src/js_parser/visit/visit_stmt.rs: at :437-442 mark_for_replace = true and… | pre-existing.…

… a type The exit of the visitor for `export default T`, where `T` is a type, dropped the statement and did not inject the export of the entry.

robobun · 2026-09-29T07:58:12Z

The three findings are correct. One is fixed, and two stay as they are on main.

1. The exit for a default export that is a type. Fixed in the commit after 36bb20b. That exit now injects the export of the entry, as the three other exits do. interface T {} and export default T with replace: { default: ["N", 1] } prints export var N = 1; with dead code elimination on and off. On main it prints no export for both. The test of the hoistable exports has both rows.

2. replace: { default: 1 } with a lowered top-level using. Not changed. The PR text lists it under "What stays wrong". #38287 moves the split of export default behind the block that applies the entry, which gives the right order.

3. replace: { default: 1 } on export default class A {}. Not changed. The PR text lists it under "What stays wrong" too. This PR is for the inputs that end the process, and for the outputs that those fixes reach. #44138 now has rows 2 and 3.

claude

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

robobun · 2026-09-29T17:02:57Z

The string value part of this PR (59da676 and e946a11, from #38541) has a debug-only guard that stops a debug build on valid input. Two commits on top of 603fb7f remove the guard and add test cases. They cherry-pick onto 603fb7f with no conflict:

53dc63b removes the guard, restores src/ast/expr.rs to main, and replaces the one test of the string values with one child process for each case.
7c4c5c4 adds a scan() case and prints with console.log.

Branch: robobun/d01710db/replace-string-values-no-guard (compare). It has no PR of its own.

The guard

let _guard = bun_ast::expr::Disabler::scope(); is active while to_js_string_view runs. JSValue::is_string() is also true for a String object, and for that value the call runs user JS.

const value = new String("ignored");
value.toString = () => {
  require("./small.cjs");
  return "bar";
};
new Bun.Transpiler({ exports: { replace: { foo: value } } });

A debug build with the guard stops while it parses the required file: panic: [bun_ast::expr::Expr] called while disabled (did you forget to call enable?), exit 134. main and release builds accept this input. I reproduced this on a debug build of main a4f1429 with the hunk of #38541, which is the hunk that this PR has.

Expr::allocate never appends to the store, so the guard has nothing to catch. The test cases protect against a return of Expr::init.

What changes

File	Change
`src/runtime/api/JSTranspiler.rs`	-3 lines: the guard and its comment. Against main the file is then +2/-1.
`src/ast/expr.rs`	The same as main again.
`test/bundler/transpiler/transpiler.test.js`	`describe("string values")` with 7 cases in place of the one test.

The 7 cases

Each case is one child process. Only the first load of a module parses it and resets the store, and a build with the defect ends the process in the first case.

Case	Release build of main `a4f1429`	With the change
`transformSync()` after a `require()`	`Segmentation fault`, exit 139	right text
`transform()` after a `require()`	`Segmentation fault`, exit 139	right text
16 `transform()` and 16 `transformSync()` calls at the same time	`Segmentation fault`, exit 139	right text, 32 of 32
`scan()` with `inline: true`	`imports` is `["a","b"]`, exit 0	`["a"]`
A getter of a later value loads a module while the constructor runs	`Segmentation fault`, exit 139	right text
`toString()` of a `String` object loads a module	wrong text, exit 0	right text
A macro creates the transpiler, the outer `transformSync` runs 3 times	right text 1 time, wrong text 2 times, exit 0	right text 3 times

The last case needs no module load. Expr::init puts the node in the arena of the outer parse when a parse is active, and that parse frees its arena when it returns. Expr::allocate ignores the active parse, so the same statement covers it.

Verification

On the branch (603fb7f plus the two commits), linux x64:

bun bd test test/bundler/transpiler/transpiler.test.js: 253 pass, 1 skip, 21 todo, 0 fail. The 7 cases take 0.6 s to 1.0 s each on the debug build.
Debug build with src/ of main 9f70da0: 7 of 7 cases fail at the stdout assertion. 6 children end with an AddressSanitizer report, and the scan() case gets ["a","b"].
Release 1.4.3-canary.1+367d939d9 (USE_SYSTEM_BUN=1): 7 of 7 fail at the stdout assertion. Bun 1.4.2 fails the same inputs. Bun 1.3.13 prints the right text for all of them.

Numbers for the body of this PR

Release builds of main a4f1429 with and without the one statement (Expr::allocate, no guard):

What	main	with the change
mimalloc allocations for each `new Bun.Transpiler`, 8 string values	987.081	987.0775
mimalloc allocations for each `transformSync()`, 8 string values	51.0184	51.0183
mimalloc pages held by a live instance with a string value	1.663	2.663
committed bytes for each live instance, 8 string values	62254	70070
instructions of `export_replacement_value`, first string value of an instance	30705	32929
instructions of `export_replacement_value`, each later string value	338	338
`size`: text, data, bss	80661482, 110424, 1822992	the same
syscalls of construct plus `transformSync()`	249 calls, 41 rows	the same
writes to the shared node in 55135 trapped accesses, 47226 of them on work-pool threads		0

The allocation and page numbers come from heapStats() in bun:jsc over 2000 live instances and 10000 calls. The instruction, syscall and write numbers come from gdb. valgrind, perf, strace and bloaty are not on the machine that ran this. The instruction count of the whole constructor is not measured.

So the cost is at construction only: one more mimalloc page (about 8 KB committed) for each live instance that has a string value. An instance with no string value does not change.

Not in these commits

Expr::init where the Zig code used Expr.allocate or a clone into the allocator of the manager: src/runtime/cli/pack_command.rs:3413, :3437, :3480 and src/install/PackageManager/PackageJSONEditor.rs:212, :222, :280. I found these by a read of the code. I did not reproduce a failure.
The body of this PR says "4 child processes" and "10 new tests". With these commits the string values have 7 child processes, and the file has 16 new tests.

robobun · 2026-09-29T17:52:54Z

Merge order with #44193

This PR and #44193 merge with no textual conflict, but they disagree about one input: a pair on the default key.

This PR makes replace: { default: ["N", 1] } print export var N = 1;. On main the input ends the process with panic: unreachable (3 of 3 runs, release and debug builds).
bun-types: declare the values that exports.replace of Bun.Transpiler accepts #44193 declares the values of exports.replace in bun.d.ts. Its type rejects a pair on the default key, because of that crash. Its doc page and its type fixture say the same.

If both PRs merge as they are, the type rejects an input that the runtime accepts. The PR that merges second owes one edit:

packages/bun-types/bun.d.ts: remove the sentence "The default key takes a value, and not a pair." and the & { default?: ... } part of the type.
docs/runtime/transpiler.mdx: remove the same comment line and the same part of the type.
test/integration/bun-types/fixture/transpiler.ts: remove the expectType<ExportsReplace["default"]> row and the three @ts-expect-error comments. The three rows stay as accepted input.

If #44193 merges first, the edit goes into this PR. If this PR merges first, the edit goes into #44193. Nothing changes before one of the two merges.

Checked on the branch of #44193 at c92c229:

With only the type changed, tsc reports 4 diagnostics in transpiler.ts: TS2554 at line 13, and TS2578 (unused @ts-expect-error) at lines 117, 121 and 126.
With the whole edit, test/integration/bun-types/bun-types.test.ts passes (22 pass, 0 fail).

The edit, as a diff against #44193 (3 files, +3 -15)

diff --git a/docs/runtime/transpiler.mdx b/docs/runtime/transpiler.mdx
index ad86e8d7e6..55ebffcdbc 100644
--- a/docs/runtime/transpiler.mdx
+++ b/docs/runtime/transpiler.mdx
@@ -214,7 +214,6 @@ interface TranspilerOptions {
       // For a pair or a map that you keep in a variable, write as const
       // Write each key as an identifier or default, and each name as an identifier
       // The constructor throws a TypeError for a key or a name such as a-b
-      // The default key takes a value, and not a pair
       replace?: Record<
         string,
         | string
@@ -223,9 +222,7 @@ interface TranspilerOptions {
         | null
         | undefined
         | readonly [name: string, value: string | number | boolean | null | undefined]
-      > & {
-        default?: string | number | boolean | null | undefined;
-      };
+      >;
   },
 
   // Whether to remove unused imports from transpiled file
diff --git a/packages/bun-types/bun.d.ts b/packages/bun-types/bun.d.ts
index 7b8b7d66e6..fee5c4a82b 100644
--- a/packages/bun-types/bun.d.ts
+++ b/packages/bun-types/bun.d.ts
@@ -3029,8 +3029,6 @@ declare module "bun" {
        * identifier. The constructor throws a `TypeError` for a key or a
        * `name` such as `a-b`.
        *
-       * The `default` key takes a value, and not a pair.
-       *
        * @example
        * ```ts
        * const transpiler = new Bun.Transpiler({
@@ -3059,9 +3057,7 @@ declare module "bun" {
         | null
         | undefined
         | readonly [name: string, value: string | number | boolean | null | undefined]
-      > & {
-        default?: string | number | boolean | null | undefined;
-      };
+      >;
     };
     treeShaking?: boolean;
     trimUnusedImports?: boolean;
diff --git a/test/integration/bun-types/fixture/transpiler.ts b/test/integration/bun-types/fixture/transpiler.ts
index 8d3c2704cd..ca3b9c5674 100644
--- a/test/integration/bun-types/fixture/transpiler.ts
+++ b/test/integration/bun-types/fixture/transpiler.ts
@@ -10,7 +10,6 @@ expectType<ExportsReplace[string]>().is<
   | undefined
   | readonly [name: string, value: string | number | boolean | null | undefined]
 >();
-expectType<ExportsReplace["default"]>().is<string | number | boolean | null | undefined>();
 
 // The example in the JSDoc of `exports.replace`.
 {
@@ -109,21 +108,17 @@ new Bun.Transpiler({
   new Bun.Transpiler({ exports: { replace: inferredMap } });
 }
 
-// The `default` key takes a value, and not a pair.
+// The `default` key takes a value or a pair.
 {
   new Bun.Transpiler({ exports: { replace: { default: 60 } } });
   new Bun.Transpiler({ exports: { replace: { default: "bar", revalidate: 60 } } });
-
-  // @ts-expect-error - the default key takes a value, and not a pair
   new Bun.Transpiler({ exports: { replace: { default: ["__N_SSG", true] } } });
 
   const entry = ["__N_SSG", true] as const;
-  // @ts-expect-error - the default key takes a value, and not a pair
   new Bun.Transpiler({ exports: { replace: { default: entry } } });
 
   const replace: ExportsReplace = {};
   replace.default = 60;
-  // @ts-expect-error - the default key takes a value, and not a pair
   replace.default = ["__N_SSG", true];
 }

… and CLI (#46021) ### What does this PR do? Hardening. This collects the open pull requests that fix a crash in Bun into one change, and fixes about 20 more crashes that had no pull request. "Crash" here means a segfault, a Rust panic, an abort, a failed assertion, memory corruption that a sanitizer reports, a native stack overflow, or an exception that ends the process and that the program can't catch. With this PR those cases throw a normal error, print a normal CLI error and exit 1, or just work. 306 pull requests are included: 227 whole, and 79 cut down to the crash fix where the rest was a refactor, a feature or a behavior change. Each one was checked against current `main` first. 45 more turned out to be fixed already, and 17 were duplicates. The full list is at the bottom. #### Crashes you could hit in normal use - **`bun build` with macros and a `.env` file crashed at random.** In a repro with many macro modules, more than a third of the builds crashed. Now 3,000 of 3,000 produce the right bundle. (#45960) - **`bun run` and `bunx` aborted if a signal arrived while the child was being spawned.** (#38926, #45965) - **`bun build --compile ./index.js ./public/*` panicked** if an embedded file's name wasn't valid UTF-8. - **A truncated or corrupted compiled executable** died with SIGBUS or a panic at startup. It now prints an error. (#31787, #38251, #41360) - **Dev server:** several `Option::unwrap()` panics after a failed or deleted import (#38046, #44744, #44746), a segfault when an `onLoad` plugin throws while another bundle is queued, a request that hung and then panicked with `bundle active`, and `server.stop()` that never resolved after a client aborted a waiting request. - **`Bun.serve`:** `server.fetch(url, { headers: new Headers() })` followed by a GC segfaulted (#40888). Routes were used after free after `server.reload()` with `tls.serverName` (#38636). - **`text()` and `json()` on a stream of string chunks** could abort the process, a regression in 1.4.0. (#44269) - **`Bun.Transpiler` with `exports.eliminate` or `exports.replace`** aborted on `export default 1` and on most re-export clauses. (#44137) - **A decorated `declare` field in a class expression** with `experimentalDecorators` panicked. (#38095) - **YAML and JSON5 files with a key that isn't a string** panicked with `--no-bundle` and in `Bun.Transpiler`. (#41827) - **`Bun.FileSystemRouter`:** reading `.params` segfaulted when a rejected route candidate left its parameters behind. (#39290, #39291) - **Native addons that call `uv_async_*`, `uv_timer_*`, `uv_idle_*`, `uv_prepare_*`, `uv_check_*`, `uv_queue_work` or `uv_cwd`** aborted with "unsupported uv function" on Linux and macOS. They're implemented now. (#36609, #39652, #39892) - **`--watch` and `--hot`** panicked when the system was out of inotify instances or file descriptors, or when the reload `exec` failed. They print an error now. (#39629, #39975, #44837) - **Paths longer than the path buffer** panicked in `bun install`, the resolver, the bundler, `--compile`, `tsconfig.json` `paths` and `baseUrl`, `package.json` `main` and `sideEffects`, `bun run --filter`, `bun pm diff`, source maps and snapshots. They're ordinary errors now, or they work. (#36340, #37529, #39104, #39650, #43067) - **A Worker that creates a `ShadowRealm` and imports `node:worker_threads` in it** segfaulted. - **`structuredClone` or `postMessage` of an X25519 key** gave an object that aborted the process when read. (#45624) - **`node:stream` web adapters and `node:http2`** could end the process with an exception that no handler could catch. (#45076, #45975) - **Windows:** a watcher panic in a burst of file changes (#44344), a segfault after the machine resumes from sleep (#33015), crashes in the shell's pipe reader (#39638, #43606), and addons that import from `node.exe` without the delay-load hook (#35618). Most of the rest needs unusual input: strings near the 2 GiB limit, buffers that another thread or a getter resizes or detaches in the middle of a call, `worker.terminate()` at a bad moment, running out of memory or file descriptors, very deep nesting, or hostile arguments to `bun:ffi`, `node:vm` and `bun:sqlite`. #### Behavior changes Things that didn't crash before and behave differently now: - `new` on native functions that aren't constructors throws a `TypeError`, as in Node: `util.types.*`, `buffer.isAscii`, `isUtf8`, `transcode`, `resolveObjectURL`, `bun:jsc` exports, `cc()` symbols. It used to return the call's result. They also stop printing as `[class hostname]`. (#34575) - `` $`cmd` `` throws `ERR_INVALID_ARG_VALUE` if an environment variable's name or value contains a NUL byte. It used to cut the value at the NUL. (#44981) - `cc()` functions throw a `TypeError` for arguments that used to reach C as garbage, and `read.*(ptr, NaN)` throws. (#37989, #38057, #40773) - As PID 1, `bun` exits with 128 + the signal number on Ctrl+C or `docker stop`. (#38877) - A `NODE_MODULE` addon that's already loaded by the main thread throws `ERR_DLOPEN_FAILED` when a live Worker loads it too, as in Node. (#39968) - An exception from a `node:vm` context reaches `uncaughtException` handlers. (#39992) `vm.constants.DONT_CONTEXTIFY` returns the real global proxy. (#34623) - `createPrivateKey` rejects an EC JWK whose private value doesn't match its public point. (#33752) - `@dec static {}` is a syntax error, as in TypeScript and esbuild. (#44883) - `clearTimeout` ignores 0 and negative ids, and timer ids no longer wrap. (#44771) - HEAD for a `Response` whose body is an S3-backed `Blob` reports the length that GET sends. (#44734) - `bun:sqlite` and `node:sqlite`: if `iterate()` left a write unfinished on a connection that has a hook, a user function or an authorizer, the write is finished on the connection's next call instead of during garbage collection. If the database is gone too, it's rolled back. - `bun test --bail` runs exit listeners and closes SQLite databases. (#39010) - Dev server: a request for a client script waits while a bundle is in flight (#42733), query strings reach framework routes (#33232), and a request gets a 500 instead of hanging when plugins fail (#36812). #### File formats - `.jsc` bytecode files get a 24-byte footer so they can be verified before decoding. Files from an older Bun are ignored and the source is parsed instead. (#39396) - `node:vm` `cachedData` gets an 8-byte checksum. A blob from an older Bun is rejected, which the API allows. (#32839) - The built-in modules section of a compiled executable changes from format 1 to 2 and carries an engine stamp. (#44907) #### Performance Measured in instructions per operation on release builds of this branch and its base, with an A/A run for the noise floor (0.0 to 0.2 %). No change: `Bun.serve`, `node:http`, WebSocket echo and publish, `bun build` of 3,807 modules, `bun run` with 2,000 imports, `readdir` / `Glob` / `fs.cp` over 23,689 entries, startup and RSS. The binary grows by 176 KB (0.17 %). | Faster | Instructions | | --- | --- | | WebSocket echo of a 1 MB non-ASCII text message | −72 % | | `Bun.inspect` of a large non-ASCII string | −39 % | | `Bun.markdown.html` on large non-ASCII input | −33 % | | `` $`cmd` `` with 300 environment variables | −6 % | | `fs.readSync` | −5 % | | `TextEncoder.encodeInto`, short ASCII strings | −4 % | | async `crypto.pbkdf2`, 16-byte inputs | −17 % | | Slower | Instructions | Why | | --- | --- | --- | | `cc()` calls | +5 to +51 per call | Argument count and type checks, and a check for `close()` (#37989, #38057, #43802, #44921). `dlopen()` calls don't change | | `process.env.X = v` | 38 → 593 per write | Writes aren't cached. Reads don't change (#38871) | | async `crypto.pbkdf2`, inputs of 1 KB or more | +4 to +9 % | Password and salt are copied (#40554) | | `bun build` with an object `--define` used thousands of times | +4.5 % | The object is copied per use (#45969) | #### Not included - Fixes that need a WebKit change: #39967, #42534, #42982, #43764, #43786, #44226. #42185 too: a typed array that has no `ArrayBuffer` yet can't be pinned, so `view.buffer.transfer()` during an async call can still free its bytes. Creating the `ArrayBuffer` up front costs 7 to 12 % on every async `fs` call, so the fix belongs in JSC: an `ArrayBuffer` created while the view is borrowed should start out pinned. - #45442 (`calc()` sums as a flat list): it changes minified output for real stylesheets to survive a `calc()` with 25,000 terms. It deserves its own review. - #40023 (Windows event loop redesign), #29928 (Windows exit path), #40534, #43963, #39571, #42904, #42834, #36355, #43266: refactors or features whose crash is already covered or isn't a crash. - The pull requests marked *(crash fix only)* below should stay open for their other half. ### How did you verify your code works? - **Tests.** Every fix has a test that fails on `main` (a release or an ASAN build) and passes on this branch, except where that isn't practical: code that only runs on Windows or macOS, inputs that need several GB of memory, and a few rare races. Those were checked by hand or by reading. - **Stored repro scripts.** 230 crash repros ran on release and ASAN builds of this branch and of `main`, side by side. Release: 88 no longer crash. ASAN: 106 no longer crash. None crashes that didn't before. What still crashes needs WebKit, is SQLite's own bug, or isn't a crash. The ASAN number is from a later commit than the release number. - **Dev server.** Because one fix makes requests wait, 2,171 generated programs ran random interleavings of edits, build errors, failing plugins, reloads, stops and disconnects with about 120,000 requests. No request hung, was answered twice or got a stale body. `main` hung in 82 of 1,161 programs. This also found the four dev server bugs listed above. - **Path helpers.** 336,000 boundary cases with buffers of exactly the computed size, and 12,003 random calls through 30 JS APIs on an ASAN build, compared with `main`. No sanitizer report, and the results match wherever `main` doesn't panic. - **What worked on 1.4.3 still works.** Reviewers compared behavior with 1.4.3 and took out what changed it: for example an output directory layout change for 9 or more entry points, a `server.reload()` change, and a changed error message for `import("file:///50%deposit.ts")`. - **Not run locally:** the Windows, macOS and FreeBSD code paths. CI compiles and tests them. ### Included pull requests **Bundler, transpiler, CSS, macros** (33) - #33881 bundler: allocate wrapper_ref for CommonJS modules with no non-hoistable statements - #35055 Bun.build plugins: handle filter RegExp flags beyond i/m/v - #37769 bundler: fail the build instead of panicking when the bundle thread cannot create its waker - #37784 bundler: copy inlined env values into the define arena, and give each Bun.build its own env copy *(crash fix only)* - #37858 bundler: fail the build instead of panicking when a plugin answer string cannot be converted - #38046 bun build --server-components: require the bun target and reject directives without a framework *(crash fix only)* - #38095 js_parser: fix panic on decorated declare/abstract fields in class expressions with experimentalDecorators - #38966 bundler: keep deep CSS, export star and composes graphs from overflowing the linker's stack - #38984 bundler: stop an export star ambiguity that loops back into a re-export chain from overflowing the stack - #39113 css: reject stylesheets of 2 GiB or more instead of aborting on an int cast - #39396 bundler: frame .jsc bytecode sidecars and verify them before decoding - #39855 bundler: join the work still on the pools before the bundle is torn down *(crash fix only)* - #41157 dev server: leave out an html link to a cached json module instead of panicking, and mark a new placeholder file stale - #41801 css: decode ill-formed UTF-8 to U+FFFD before tokenizing *(crash fix only)* - #41827 bundler: handle YAML and JSON5 keys that are not strings instead of panicking - #42242 js_parser: compress symbol link chains when following merged declarations - #42387 bundler: check receivers on the Bun.build plugin object and freeze its filters during a build - #42413 Bounds-check the InternalSourceMap window reader - #42657 macros: keep visited values alive so a reused address does not get another value's Expr - #43330 transpiler: do not print an empty `var` for a data file with no named export - #43355 bundler: fix "The memory limit has been exceeded." on large HTML entries - #43658 react-compiler: fix skipped functions and build aborts for dead code in a try body *(crash fix only)* - #44137 js_parser: fix four crashes of exports.eliminate and exports.replace - #44467 js_parser: replace skipped expressions with E::Missing and skip argument checks after a stack overflow - #44662 js_parser: walk binary chains on the heap and check the stack when rewriting decorated #private accesses - #44712 json5: reject sources of 2 GiB or more before parsing instead of aborting on an int cast - #44864 js_parser: walk conditional chains in import()/require() and define keys in a loop - #44883 js_parser: reject a decorator on a class static block, keep decorators out of the body of `declare global` *(crash fix only)* - #45045 Fix a segfault in new Bun.Transpiler(): re-point options.log after the constructor moves its Log - #45604 css: keep a url() in an at-rule prelude as written, and never print the resolved path of a url() *(crash fix only)* - #45748 bundler: put --banner/--footer in the bytecode ESM module record (flags from a parse, entries from JSC) *(crash fix only)* - #45960 macros: give each parse-worker macro VM its own env loader - #45969 js_parser: copy object and array defines per use, and copy the list of a lone JSX spread object *(crash fix only)* **`bun build --compile` and standalone executables** (3) - #31787 Don't crash at startup when a standalone executable's embedded graph is corrupted *(crash fix only)* - #38251 compile: exit with an error instead of SIGBUS when a standalone executable is truncated - #41360 standalone: check every offset in the embedded module graph before reading it **Resolver, module loading, plugins, paths** (25) - #32269 Bun.plugin: validate the namespace without a shared regex - #33183 bun:jsc: filter internal cells out of getProtectedObjects() - #34575 Don't register native functions as their own constructors - #36340 paths: size the thread-local join output buffers to MAX_PATH_BYTES on Windows - #37037 mock.module: reject async factory results that are not objects - #37065 bun:jsc: propagate JSONParse exceptions from samplingProfilerStackTraces - #37529 resolver: don't abort on a package.json sideEffects entry longer than the join buffer - #38179 node:module: throw instead of crashing when module._compile is set to a non-function - #38273 bun test: report a test file or preload the loader cannot resolve instead of exiting; keep the JUnit report valid U… *(crash fix only)* - #38732 paths: compute the common path of 9+ inputs with the same loop as fewer *(crash fix only)* - #39228 paths: strip C:\\ down to the drive root in without_trailing_slash_windows_path *(crash fix only)* - #39650 bun run --filter: stop panicking on workspace paths longer than the path buffer - #40186 resolver: stop deeply nested exports targets from overflowing the stack - #40258 resolver: publish Entry.abs_path through the per-entry mutex - #42183 node:module: reject a _resolveFilename override result that contains a null byte - #42401 node:module: accept any `this` in Module.prototype.require *(crash fix only)* - #42405 Bun.plugin: transpile a copy of typed array onLoad contents - #42414 node:module: end the Module._stat path at the first null byte - #42685 resolver: strip the trailing separator inside bust_dir_cache - #42735 Throw a RangeError instead of aborting when require.resolve paths or Worker preload outgrows its Vector - #43067 Report a path that does not fit a path buffer instead of aborting *(crash fix only)* - #44410 Fix a crash when code from a node:vm context reads require.cache or require.extensions - #44466 Trace the value an object or data module exports from its JSSourceCode - #45044 Bun.plugin: give onLoad's args.path its own bytes - #45117 cjs: do not call an `__esModule` getter during the annotation lookup **Dev server, `bun bake`, routers, `--watch` and `--hot`** (28) - #28793 Stop file watcher thread before Global.exit tears down memory *(crash fix only)* - #32143 bake: fix "Runtime file not found" panic in production builds of custom frameworks - #32443 watcher: don't free the Watcher in the spawn-to-start window *(crash fix only)* - #33232 bake: normalize the HTTP request-target before matching framework routes - #36812 bake: respond 500 and release both RequestContext refs when on_plugins_rejected / OOM drains a deferred framework r… - #37039 bake: report per-file print failures in the dev server instead of serving empty modules - #37276 hot_reloader: take entries_mutex for watcher-thread directory cache probes - #37444 bake: unregister Bake::SourceProvider from the source map table when it is destroyed - #39290 FileSystemRouter: match / against a root-level optional catch-all route *(crash fix only)* - #39291 FileSystemRouter: order dynamic routes by per-segment precedence like Next.js *(crash fix only)* - #39629 watch: report a failed watcher init as an error instead of a crash - #41185 bake: check for exceptions in the production build's module loader hooks and helpers - #41340 bake: skip the directory watch when the directory cannot be opened - #41617 Decide a directory watch event from the watchlist, not from the resolver's cached listing *(crash fix only)* - #42547 bake: re-arm the memory visualizer timer when it fires - #42733 dev server: make a client script request wait for the bundle in flight - #42828 bake: serve routes from a router root outside the project root instead of aborting or answering 404 - #42831 bake: resolve app.root and router roots through one checked join - #42836 bake: report route scan errors instead of aborting, and fail bun build --app on them *(crash fix only)* - #42840 dev server: map a router type's server entry point to the root route of that type - #42862 Bun.serve: return before a pending app.plugins setup() settles *(crash fix only)* - #42920 Do not create a mimalloc heap per FileSystemRouter, reload() or :nth-child(An-B) selector - #42934 dev server: register a client component without evaluating it - #43329 dev server: check the route bundle index of a client script URL before Index::init - #44249 fs.watch: read each directory and close it before descending - #44344 Windows: fix a watcher panic and lost events in a burst of file changes, and a --hot that stops watching a deleted… - #44744 dev server: answer a cached-file lookup only for a graph that bundled the file - #44746 dev server: keep an importer in its own graph when an import fails or is deleted **`Bun.serve`, sockets, HTTP, WebSocket, HTTP/2, QUIC, DNS** (28) - #42667 Reland "usockets(windows): keep a closed poll alive until the outer tick and libuv are done with it" (#39643) - #33015 fix(windows): segfault in uv__wake_all_loops after system resume *(crash fix only)* - #35761 node:quic: detach lsquic ctx pointers before the finalize-order sweep at worker VM teardown - #37082 Bun.serve: terminate FIFO/pipe file responses at EOF - #38024 dns: keep the c-ares uv_poll_t alive while its poll callback is on the stack (Windows) - #38636 serve: fix route use-after-free after reload() with tls.serverName *(crash fix only)* - #40888 server.fetch: copy a Headers argument instead of adopting the wrapper's pointer - #41337 Update lsquic to 4.9.4 and free unsent stateless resets on destroy *(crash fix only)* - #41384 usockets: hold a tick level for the whole of close_all - #41412 Windows: wait for close completions when closing a worker's uv loop - #41516 node:http2: handle an empty byte range in respondWithFile and respondWithFD - #41521 udp: report every binaryType from the getter, reject a dgram bind of the other family *(crash fix only)* - #42188 net: do not assert a two-character host in SocketAddress.parse - #42210 libuv(windows): keep a pipe's completed read counted until its read callback returns - #42334 fetch, Bun.serve: throw a RangeError for Headers that total 4 GiB or more *(crash fix only)* - #43738 usockets: close a socket whose resume the kernel refuses from the loop, not from the caller - #44338 node:http: response trailers travel with the end call of the response *(crash fix only)* - #44433 bake: make the parked-request list non-owning and look up the DevServer when a plugin load settles - #44533 node:quic: capture the handshake while the conn is alive, set the application at session creation - #44734 Bun.serve: answer HEAD for an S3-backed Blob body without an S3 stat - #44751 node:quic: close() waits only for opened streams, and lsquic sends no GOAWAY before HTTP/3 starts *(crash fix only)* - #44897 node:http2: throw instead of panic when the native setNextStreamID() misses its argument - #45076 node:http2: let close() and destroy() win over the refusal of a request - #45341 uws: AsyncSocket::write takes a size_t length, so res.end() sends a body of 2 GiB or more whole - #45522 node:http2: throw for an ALTSVC frame that is too long and for a pushPromise id that is not a stream id - #45676 node:quic: do not reset a stream lsquic has already finished - #45822 node:quic: name a stream in queued session events by a per-session key, not by its address - #45858 Bun.serve WebSocket: a message that does not fit in memory fails one connection, not the server *(crash fix only)* **Streams, Blob, S3, files, `node:fs`** (28) - #33845 io: propagate IoRequestLoop init failure instead of aborting *(crash fix only)* - #36365 prompt: drop debug_assert that rejects answers containing CR - #37090 Deliver FIFO bodies whose writer connects after the reader opens *(crash fix only)* - #38039 node:fs: stop fs.copyFile(src, "") from segfaulting on Windows - #38653 shell(cp): reject copying a directory into itself; walk cp trees without recursion - #39207 Convert scope-object receivers in the chaining functions and inspect.custom fallbacks - #39390 Blob deserialize: reject over-long paths, treat size >= MAX_SIZE as unknown, make slice() non-panicking - #39639 fetch: drop the upload and drain hop refs at VM teardown *(crash fix only)* - #40008 inspect hooks: copy user options with putDirectMayBeIndex *(crash fix only)* - #40462 Windows: FileSink.start({ path }) on a live writer: hand the writer a libuv fd and close the old source *(crash fix only)* - #41440 node:fs: pass the buffer to the read/readv/write/writev callback on error - #41584 Walk the timer pairing heap without recursion - #41608 native-readable: accept a stream with no native handle - #41710 JSSink write(): convert the chunk before resolving the native sink *(crash fix only)* - #42711 webstreams: bound the native recursion through a chain of tees or text streams - #43264 fetch: reject a file: URL whose path has an encoded NUL - #43709 s3: fix double free of a multipart part's bytes on worker terminate - #43950 streams: link readers and writers last, reject their promises as handled - #44036 PipeReader: label a chunk Eof only when the reader is at its end - #44181 streams: throw instead of aborting when a direct stream's text sink cannot take a string chunk - #44195 fs: validate POSIX directory records in one parser, report a malformed record as EIO *(crash fix only)* - #44269 streams: join the string chunks of a text consumer with one allocation - #44490 watch(windows): report a failed child spawn as an error instead of a panic *(crash fix only)* - #44954 process.stdout/stderr with no FileSink: write synchronously, reset after a failed write *(crash fix only)* - #45004 streams: leave a stream alone when a consumer fails to lock it - #45521 FileSink: throw ERR_ILLEGAL_CONSTRUCTOR from the constructor that script reaches by writer.constructor - #45738 s3: own the Blob store across the calls that run user JS - #45975 node:stream: do not touch the web controller after the web side is done **Node-API, V8 API, `bun:ffi`, `process.dlopen`** (15) - #36609 napi: implement uv_cwd on POSIX - #37989 bun:ffi: stop cc() from turning non-numeric pointer arguments into garbage pointers - #38057 bun:ffi: make cc() reject non-numeric i64/u64 arguments instead of passing garbage - #38425 bun:ffi: throw on an empty cc() source array instead of panicking - #39652 napi: implement uv_async_t, uv_queue_work and uv_default_loop on posix - #39805 Share one handle scope implementation between Node-API and the V8 API - #39892 napi: implement uv_idle_t, uv_prepare_t, uv_check_t and uv_timer_t on posix - #40144 bun:ffi: return undefined for a NULL napi_value from cc() and throw the scheduled napi exception - #40773 bun:ffi: add the full byteOffset in read.*, do not truncate it to int32 - #41704 napi: hand the thrown value to napi_get_and_clear_last_exception after napi_run_script - #42960 process.dlopen: run a V8 addon's init function after dlopen() returns - #43797 Fix debug assertion on an empty error message from a V8 addon or SQLite *(crash fix only)* - #43802 bun:ffi: throw a TypeError when a cc() symbol is called after its library's close() - #43940 napi: fail with ERR_BUFFER_TOO_LARGE instead of aborting above the ArrayBuffer limit *(crash fix only)* - #44921 bun:ffi: pad a short call to a cc() symbol with undefined **`node:vm`, workers, process, timers** (19) - #34623 node:vm: run DONT_CONTEXTIFY contexts directly against the real global - #32839 node:vm: reject invalid cachedData instead of crashing - #36921 error printer: clear the pending exception when formatting a non-Error uncaught value throws - #37270 error printer: one render per error, [Circular] under the key that closes the cycle - #38740 bun:test: give each VM its own fake clock *(crash fix only)* - #39864 Report a refused HTTP, bundle, IO or process waiter thread as an error instead of a crash *(crash fix only)* - #39992 process: deliver exceptions reported against a node:vm context to uncaughtException - #41654 node:vm: give each SourceTextModule request the import attributes of the declaration that created it *(crash fix only)* - #41739 Do not forward the inherited IPC channel to spawned scripts and tools - #41769 node:vm: stop compiling accepted cachedData, report each cachedData decode to the GC *(crash fix only)* - #42045 bun:test fake timers: never move the fake clock backwards - #42308 process.execve: throw instead of aborting for a string past the string limits - #42734 node:vm: report cachedData of 2 GiB or more as rejected instead of aborting - #42843 process.dlopen: reject a filename of PATH_MAX or more before dlopen() - #43500 process: accept SIGSTKFLT, SIGPOLL and SIGPWR, and emit every name of a signal number *(crash fix only)* - #44486 worker: stop the start sequence when a handler it calls stops the worker - #44771 timers: allocate ids from one 64-bit counter that never wraps - #44837 --hot: defer a reload during the preloads, and report a reload that cannot start - #44991 Fix a use-after-free in the VM ref-string intern for a string over the length limit **Shell, spawn, CLI, `bun test`, `bun install`** (31) - #30642 Fail fast at startup when simdutf has no usable implementation for this CPU - #34223 Fix four crashes: HTMLRewriter disturbed body, S3 locked-stream upload, ConnectionsList closed parser, shell brace… *(crash fix only)* - #34884 Guard the console and test-runner formatters against native stack overflow on deeply nested values *(crash fix only)* - #36584 process.chdir: publish an immutable cwd slice so no thread sees a torn cwd - #37135 bun test --parallel: hold the JSC API lock while draining the worker's final IPC backlog - #37527 shell(mv): report ENAMETOOLONG instead of panicking when a source name does not fit the path buffers - #37528 cli: stop aborting on absolute script paths longer than 1024 bytes on Windows - #38162 shell(cp): report ENAMETOOLONG instead of panicking on operands longer than the path buffers - #38205 shell(windows): report ENAMETOOLONG for operands that do not fit the path buffer - #39010 bun test: exit through the VM teardown path when --bail stops a run - #39104 bun test: report over-long coverage dir, JUnit outfile and bunfig root instead of panicking *(crash fix only)* - #39638 shell(cat): serve a second cat on the same stdin instead of hanging or panicking - #39641 usockets: report an out-of-descriptors event loop init as an error, not a crash *(crash fix only)* - #40181 shell: stop deeply nested if clauses from overflowing the parser stack - #40885 shell: throw instead of panicking when a ReadableStream is used as a redirect - #41155 ipc: send a queue item larger than 2 GiB in capped write requests - #42298 bun:test: print String objects with 16-bit storage correctly - #42577 bun:test: root the return values toHaveReturnedWith collects - #43606 shell(windows): report a failed pipe reader start through on_reader_error instead of leaking the subprocess *(crash fix only)* - #43838 node:cluster: read a worker's `ack` and `addressType` in the primary only when they are int32 - #44172 node:cluster: refuse a descriptor of the wrong kind in the primary *(crash fix only)* - #44185 node:cluster: one handle for each descriptor that workers name *(crash fix only)* - #44491 bun test: run every callback when native code leaves an exception pending *(crash fix only)* - #44694 shell mv: refuse to copy a directory into itself on the cross-device fallback - #44752 shell: take the command-substitution capture and drop its NUL bytes - #44981 shell: reject NUL bytes in .cwd() and .env() at the native setters - #45206 ini: reject a source of 2 GiB or more in Parser::parse instead of aborting on an int cast *(crash fix only)* - #45348 bun test: fix a segfault in .not.toThrow(Class) when Symbol.hasInstance accepts a thrown string, symbol or BigInt - #45649 shell: replace the output counters in mkdir, cp, ls and touch with the OutputTask queue - #45792 bun test: SIGKILL a spawnSync child that is still running 500 ms after the test's timeout *(crash fix only)* - #45910 create: own the remote-template response buffers instead of parking them in the CLI arena **Web APIs, Buffer, encoding, URL, crypto, zlib, SQLite, Redis and the rest** (96) - #29709 console: guard JSX/Proxy recursion in Bun.inspect (stack overflow SIGSEGV) - #30817 console.takeHeapSnapshot: clear prior snapshots before building - #30956 spawnSync: make signal-forwarding register/unregister safe for concurrent callers *(crash fix only)* - #31505 node:zlib: reject invalid brotli flush values at validation *(crash fix only)* - #31735 node:path: fix win32 drive-relative resolve on non-Windows hosts *(crash fix only)* - #32085 Fix crash when RedisClient onclose/onconnect is set to a non-callable - #32240 Fix BroadcastChannel custom inspect crash with numeric option keys - #33181 Reject interior null bytes in Bun.mmap, Glob.scan, and FileSystemRouter paths *(crash fix only)* - #33752 node:crypto: validate EC JWK private scalar matches public point in createPrivateKey - #34976 spyOn: install and restore through one writer that throws when the object refuses *(crash fix only)* - #35562 structuredClone: purify NaN in deserialized Date timestamp so getTime never returns a forged JSValue - #35618 napi(windows): load addons that import node.exe without win_delay_load_hook - #35757 Coerce later arguments before capturing input buffers in Bun.Transpiler and Bun.RedisClient - #37252 Report UTF-16 to UTF-8 encode counts through size_t so exactly 2^32 written bytes doesn't wrap to 0 - #37338 node:module: build require.cache without user-writable globals and propagate its exceptions *(crash fix only)* - #37340 redis: accept unsubscribe acks that arrive outside subscriber mode - #37370 Error.appendStackTrace: make appending an error's trace to itself a no-op - #37443 node:crypto: fix null deref when worker.terminate() lands during an EC JWK private key import - #37448 jsc: check for exceptions before using a stored constructEmptyArray result *(crash fix only)* - #38009 MessagePort: fix a heap-use-after-free in contextDestroyed(), release ref() when the last 'message' listener is rem… *(crash fix only)* - #38469 napi: settle or refuse async work queued during VM teardown instead of taking a ticket - #38708 Handle 16-bit module sources in the error preview, the new-position fix-up and the REPL *(crash fix only)* - #38821 process.env: make a failed env build throw instead of aborting (Windows 0xC0000409 on Bun.$ / Bun.sql / process.env… - #38871 process.env: coerce to string on every execution of an assignment, not just the first - #38877 cli: exit 128 + signo when bun cannot die from a re-raised signal (bun as container PID 1) - #38926 Clear the inherited signal mask at startup and exec children with an empty one *(crash fix only)* - #39382 Make a failed util.inspect load throw from custom inspect functions instead of aborting - #39481 Always create the error when a native error message exceeds the string length limit - #39651 performance: keep the user timing entry counts exact after clearMarks(name) and clearMeasures(name) - #39775 Turn seccomp SIGSYS traps into ENOSYS so the syscall fallbacks run on Android - #39968 process.dlopen: replay a non-context-aware V8 addon only while no other live VM owns it - #39975 watch: report a failed reload exec as an error instead of a panic *(crash fix only)* - #40346 Give Glob's native scan methods their own private names - #40554 node:crypto: copy password and salt for async pbkdf2 and scrypt - #40567 url: reject URL-encoded input over the WTF decode limit instead of aborting - #40577 url: throw a RangeError instead of aborting when URLSearchParams or FormData outgrows its Vector - #41073 Store array-index property names as indexed properties in native object builders - #41137 Write the sampling profiler report at exit from Bun, not JSC's atexit hook - #41365 webview: fail only the view when WebKit lacks initWithDirectory: - #41574 Decode a private copy of a JS buffer in the UTF-8 decoders *(crash fix only)* - #41652 console: read a BigInt depth option by value in console.dir - #41749 Startup: reopen fd 0-2 as /dev/null only when the fd is closed - #41819 Report an incoherent BUN_JSC_* option combination as a configuration error, not a crash *(crash fix only)* - #42158 webview: reject malformed Chrome replies instead of crashing - #42179 shell: clamp a `> ${buf}` redirect to the target buffer's live length - #42187 node:crypto: throw ERR_OUT_OF_RANGE for >2 GiB buffer arguments instead of aborting - #42191 URLPattern: throw instead of aborting when a pattern string passes the string limit - #42192 Copy WebAssembly.Memory bytes for native borrows that outlive the call *(crash fix only)* - #42198 Make Bun.$, Bun.sql, Bun.postgres and Bun.SQL custom value getters so reifying the Bun object passes exception chec… - #42203 node:fs: fs.read into a WebAssembly.Memory view writes into the block a grow freed - #42214 Headers: throw a RangeError instead of aborting when the set-cookie list cannot grow - #42218 Headers: throw instead of aborting when a value passes the string length limit - #42220 URLPattern: throw instead of aborting when the token list cannot grow - #42225 Throw ERR_STRING_TOO_LONG from Bun.wrapAnsi instead of aborting when the output passes the string length limit - #42226 Throw instead of aborting when a MIME string does not fit in a string *(crash fix only)* - #42237 Bun.Cookie: throw instead of aborting when the Set-Cookie string passes the string length limit - #42249 Copy a shared input before libdeflate compresses it in Bun.gzipSync and Bun.deflateSync - #42253 bun test: walk nested describe scopes without native recursion - #42259 Throw instead of aborting when a domainToASCII host passes the string length limit - #42310 Parse a private copy of a shared or resizable buffer in Bun.Transpiler, Bun.markdown, Bun.YAML and Bun.TOML *(crash fix only)* - #42312 YAML, JSON5, XML stringify: throw instead of aborting when the output passes the string length limit - #42318 Bound libdeflate's emit path so a racing input cannot overrun the output - #42338 inspector: check the type of process.argv in getModuleGraph - #42364 node:perf_hooks: do not truncate the monitorEventLoopDelay resolution to int32 - #42412 transpiler cache: reject an entry with no sourcemap section - #42479 worker_threads: do not abort when markAsUntransferable/markAsUncloneable gets a WebAssembly GC reference - #42517 EventTarget: skip a listener object that has no realm - #42518 fs.Stats: make the date accessors define the property like Object.defineProperty *(crash fix only)* - #42575 Stop natives from writing onto a foreign `this` with putDirect: process.ppid, require.cache, StringDecoder, the nat… *(crash fix only)* - #42631 JSStringView: pin the cell that owns the borrowed characters - #42660 bun_core: read /dev/urandom when getrandom(2) answers ENOSYS or EPERM - #42780 node:crypto: treat a name too long to convert to UTF-8 as unknown instead of aborting - #42782 node:crypto: throw ERR_OUT_OF_RANGE for a passphrase larger than INT_MAX bytes - #42856 url: do not abort when a host is too long for the IDNA conversion buffers - #42868 sqlite, console, process: do not abort on a string too long to convert to UTF-8 *(crash fix only)* - #42941 Bun.sliceAnsi: throw instead of aborting when the result passes the string length limit - #43058 Bun.serve: fix crash and cross-request 500 when inspecting a non-Response return value throws - #43904 JSC bindings: build property keys from a BunString through Bun::toIdentifier - #44124 Bun.Image: decode WebP into a Bun-owned canvas and read ICCP without the demuxer *(crash fix only)* - #44190 Convert scope-object receivers before Buffer read*/write* and vm.Script describe them - #44211 Stop getsockname(out), useFakeTimers() and the stream source pull() from writing onto a caller's object with putDirect - #44295 bun test --coverage: append a final newline to a text that lacks one *(crash fix only)* - #44360 rust-argon2: return OutOfMemory instead of aborting when the memory cost cannot be allocated - #44421 node:zlib: free zstd's workers before the dictionary they read - #44521 util.parseArgs: pick the default args start from a per-VM eval flag, as Node v26 does *(crash fix only)* - #44740 structured clone: tolerate a zero-sized shared WebAssembly.Memory in computeMemoryCost() - #44759 HTMLRewriter: park a suspended handler's token before the output flush - #44907 Builtins section format 2: an engine stamp says which buns compile its modules - #45188 Reject an oversized WebCrypto cipher output instead of aborting - #45354 Throw for a `file:` URL whose path is not UTF-8 on Linux and macOS, through one `fileSystemPath()` accessor *(crash fix only)* - #45608 ipc: refuse an over-long message before the receive buffer stores it - #45624 webcrypto: write the key type into the X25519 structured-clone record - #45625 node:sqlite: refuse session.close() and Symbol.dispose inside a SQLite callback - #45653 glob: a group with `?` or a class matches when an alternative takes 64 bytes or more - #45820 Bun.file, S3Client.file and Bun.write no longer keep a buffer path alive forever - #45832 `bun check`: fix a panic on `export *` without a module specifier, and a false error for one in parentheses ### Already fixed on `main`, or duplicates of a pull request above Already fixed: #27323 #30401 #31011 #31206 #31566 #31626 #31695 #31702 #31945 #32773 #34154 #34697 #34744 #34964 #35655 #35816 #36020 #36181 #36296 #36342 #36581 #36602 #36807 #36818 #36857 #37172 #37235 #37239 #37267 #37420 #37731 #37914 #38113 #38119 #38509 #38514 #38540 #38975 #39410 #40749 #41163 #41171 #42108 #43085 #43230 Duplicates: #45654 #29986 #33378 #36895 #37070 #37639 #38014 #39021 #41266 #42250 #42951 #43238 #44259 #45335 #45565 #45726 #45965 Fixes #5019 Fixes #6106 Fixes #10690 Fixes #10886 Fixes #13566 Fixes #14745 Fixes #15551 Fixes #20454 Fixes #21310 Fixes #29145 Fixes #30454 Fixes #30613 Fixes #30766 Fixes #32103 Fixes #32142 Fixes #32183 Fixes #32212 Fixes #39060 Fixes #42296 Fixes #42931 Fixes #43671 Fixes #44201 Fixes #44735 Fixes #44783 Fixes #45198 Fixes #45327 Fixes #45491 Fixes #45721 --------- Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Jarred-Sumner · 2026-10-20T21:39:39Z

This is Claude (an AI assistant) commenting on Jarred's behalf.

This fix went in with #46021, which is merged. Closing.

robobun assigned Jarred-Sumner Sep 27, 2026

github-actions Bot added the claude label Sep 27, 2026

coderabbitai Bot reviewed Sep 27, 2026

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Comment thread src/js_parser/visit/visit_stmt.rs Resolved

Comment thread src/js_parser/visit/visit_stmt.rs Resolved

robobun mentioned this pull request Sep 27, 2026

Bun.Transpiler: exports.replace prints a module that does not parse when the module cannot declare the export name #44138

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claude Bot reviewed Sep 27, 2026

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Comment thread test/bundler/transpiler/transpiler.test.js Resolved

Comment thread src/js_parser/visit/visit_stmt.rs Resolved

Comment thread src/js_parser/visit/visit_stmt.rs Resolved

test: an unhealthy subprocess is not the failure that the it.failing …

10f0370

…test expects

claude Bot reviewed Sep 27, 2026

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robobun mentioned this pull request Sep 28, 2026

Bun.Transpiler: allocate exports.replace string values in the instance arena #38541

Closed

robobun added 6 commits September 29, 2026 05:34

test: shorten the comment in the exports.replace string test

e946a11

js_parser: test for a member of a namespace inside visit_decls::<true>

aa89336

The test in s_local, where the visit is selected, cost s_local 3 instructions for each statement with no exports option. visit_decls now does the test once, and only in the instantiation that applies the entries.

robobun mentioned this pull request Sep 29, 2026

bun-types: declare the values that exports.replace of Bun.Transpiler accepts #44193

Open

robobun added 3 commits September 29, 2026 05:40

test: run the hoistable exports.eliminate cases in one child process

089fd53

robobun mentioned this pull request Sep 29, 2026

js_parser: fix exports.eliminate/replace on a declaration with no initializer and on namespace members #44179

Closed

robobun mentioned this pull request Sep 29, 2026

js_parser: fix panic when exports.eliminate removes a hoistable export #33376

Closed

robobun changed the title ~~js_parser: declare a replaced re-export by its exported name~~ js_parser: fix four crashes of exports.eliminate and exports.replace Sep 29, 2026

claude Bot reviewed Sep 29, 2026

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js_parser: inject the export of an entry for a default export that is…

603fb7f

… a type The exit of the visitor for `export default T`, where `T` is a type, dropped the statement and did not inject the export of the entry.

claude Bot reviewed Sep 29, 2026

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Comment thread src/js_parser/visit/visit_stmt.rs Resolved

Comment thread src/js_parser/visit/visit_stmt.rs Resolved

This was referenced Sep 30, 2026

json: build define values in the arena of their owner and stop sharing one static {} #44222

Open

js_parser: replace skipped expressions with E::Missing and skip argument checks after a stack overflow #44467

Closed

robobun mentioned this pull request Oct 18, 2026

Remove dead code from Progress, Tag::infer and bun_jsc::Error #45974

Open

Jarred-Sumner mentioned this pull request Oct 19, 2026

Hardening: fix crashes across the runtime, bundler, dev server, shell and CLI #46021

Merged

This was referenced Oct 19, 2026

js_parser: keep a name of 2^28 bytes or more whole by storing it in allocated_names #46077

Open

js_parser: roll back a removed statement's tracked uses along with its use counts #45345

Open

Jarred-Sumner closed this Oct 20, 2026

Jarred-Sumner mentioned this pull request Oct 21, 2026

Hardening follow-up: fix regressions from #46021 and more crashes #46270

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robobun commented Sep 29, 2026

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