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css: keep a url() in an at-rule prelude as written, and never print the resolved path of a url() - #45604

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robobun/eb1e0d26/css-prelude-url-no-import

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@robobun

@robobun robobun commented Oct 16, 2026 •

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Problem

  • bun build writes the absolute build directory into CSS: @media print { @import url(sub/g.css); } prints @import url(/home/me/app/sub/g.css). So does background: url(sub/g.css). Found by a fuzzer.
  • parse_custom_at_rule_prelude (src/css/css_parser.rs:365) makes an import record for each url() in an unknown at-rule prelude, so the bundler loads the target or fails: Could not resolve: "sub/g.css".
  • Printer::get_import_record_url (src/css/printer.rs:380) prints the resolved path.text when the target has no data: URL or asset key.

Fix

  • A url() in an unknown at-rule prelude or in a media-query env() fallback stays a raw token with no import record. This also removes panic: index out of bounds: the len is 0 but the index is 0 for @import "./b.css" (min-width: env(x, url(y.css)));.
  • The printer returns original_path for a resolved record with no URL form.
  • Verified: test/bundler/esbuild/css.test.ts (17 new tests, 16 fail on main) and test/bake/dev/css.test.ts (1). Also test/bundler/css/, test/js/bun/css/.
  • Self-reviewed: 16 concerns raised, 13 addressed. Separate changes: the plain-CSS composes gate, the linker pairing, hoist tests.

Background

  • An import record is one url() or @import. Resolution overwrites its path. original_path keeps the written text.
  • A prelude is the at-rule text before { or ;. An unknown or misplaced at-rule (a nested @import) keeps it as tokens.
  • Considered the printer change alone: the target is still loaded. A flag in parse_at_rule: 7 instructions per at-rule.

Downsides

  • @foo url(x.png); is no longer inlined or copied.
  • A declaration url(x.css) prints as written, not copied. esbuild fails this build.
  • Cost: release .text +0 bytes. 15 stylesheets run the new code 18 times.
Notes

Report. No GitHub issue. An automated fuzz ledger found it (ledger #503290, row 42055). Repro:

mkdir -p sub
echo '.c0 { color: red }' > sub/g.css
echo '@media print { .c2 { z-index: 1 } @import url(sub/g.css); }' > entry.css
echo '.c0 { color: blue }' >> entry.css
bun build ./entry.css --minify --outdir out

Before: @media print{.c2{z-index:1}@import url(/abs/build/dir/sub/g.css);}.c0{color:#00f} and Bundled 2 modules. After: @media print{.c2{z-index:1}@import url(sub/g.css);}.c0{color:#00f} and Bundled 1 module. esbuild 0.21.5 prints the same bytes, with a warning that @import is only valid at the top level.

Reach is small. A scan of 16,977 stylesheets in 556 npm packages found one file with a local url() in an unknown at-rule prelude (a PostCSS source in maplibre-gl that uses @svg-load). It found no url() in an env() in a prelude and no declaration url() to a .css, .toml or .sh file.

Questions for a maintainer.

  1. A declaration url() to a file with no URL form (.css, .toml, .sh). This PR keeps exit 0 and prints the specifier as written. The target is still resolved and parsed, and nothing is emitted for it. esbuild fails the build (Cannot use "x.css" as a URL). Bun already fails for .json, .js and other loaders (Cannot import a ".json" file into a CSS file), and css/InvalidImportURLInCSS has a TODO FIX for the stylesheet case. The error is about 10 lines in scan_css_imports (src/bundler/LinkerContext.rs). It is a new build failure, so it is not in this PR. Say so if it must be. The tests for this case pin the written specifier. They become bundleErrors tests if the answer is the error.
  2. esbuild keeps the url() in @container style(<declaration>) as written. Then the query no longer matches the rewritten custom property. This PR does not change style(). Say so if it must follow esbuild.

Measured (base 5866b5f13d):

  • parse_at_rule: 8 of 8 instantiations identical, +0 instructions (objdump, bun_css object, base vs PR)
  • TokenList url arms: +2 and +2 instructions. add_import_record: +0 (objdump, base vs PR)
  • 15-fixture corpus (2.9 MB): 4 set/restore pairs, 14 url-arm flag tests, 0 hits of the new sink return (gdb)
  • release .text: +0 bytes (size -A, main 5866b5f vs PR)
  • reported input: modules 2 -> 1, metafile inputs 2 -> 1, import records 1 -> 0
  • 15 inputs: distinct outputs per input 1 (was 2), outputs containing the directory marker 0 (was 1800)
  • pinned outputs: 80 of 80 byte-identical, 0 new log lines

How: the bun_css object is the crate compiled alone with the release rustc flags and no LTO (llvm-objdump, llvm-nm -S). Its text grows 191 bytes (1,713,150 to 1,713,341). The two flag tests are testb $0x4, 0x19(%r15) and a jump. parse_custom_at_rule_prelude grows 6 instructions and get_import_record_url grows 5. In the LTO release binary the .text section is 81,071,045 bytes before and after. Four functions change size there, +189 bytes net (nm -S on bun-profile). The corpus is test/js/bun/css/files/*.css in one bun build, counted with gdb breakpoints on the debug build. The determinism run builds 15 inputs 60 times in each of two directories with --entry-naming '[name]-[hash].[ext]'. Before, each input gave one output per directory, and two files with a url() to the same stylesheet gave 4. The pinned outputs are the fixtures of css/MissingImportURLInCSS, ExternalImportURLInCSS, TextImportURLInCSSText, Png, FileImportURLInCSS, URLQueryFragmentPreserved*, PackageURLsInCSS, and the 15 stylesheets with and without --minify. The release builds and the last three lines are from 9cfe41342e. The head differs from it in comments, tests and the value of the flag bit.

What changes for users.

  • A url() in an unknown at-rule prelude (@foo url(x.png);, a nested @import url(), a nested @namespace url()) prints as written. Its target is not resolved, loaded, inlined or copied. A missing target no longer fails the build. A plugin onResolve does not see it. It is not a metafile import (esbuild lists it there as an external import).
  • The same applies to a url() in an env() fallback in @media, @container, @custom-media and the media list of @import.
  • Only the url() token is kept as written. The other prelude tokens still go through the value token list.
  • @foo url(a.css); @import "./b.css"; now inlines b.css. Before, the url() record took the place of the @import record and a.css was inlined.
  • A url() in a declaration, a custom property, image-set(), @font-face src or an unknown at-rule block still resolves. When its target has no URL form, the specifier prints as written. This includes a file with the dataurl or base64 loader, which still gets no data URL (plugin onLoad with dataurl loader bundles empty content "" broken and incompatible with esbuild #20917), and composes: a from "./x.css" in a file that is not a CSS module, which still bundles its target.
  • Two files with a url() to the same stylesheet print the same bytes in every build.
  • bun build --no-bundle no longer rejects a url() in an unknown at-rule prelude. A declaration url() still fails there (bun build --no-bundle: keep css url() references instead of failing to parse #38528).
  • Where Bun moves an invalid nested @import url() to the top level (a style rule with nesting lowered, @media all under --minify), the output now has a relative @import url(sub/g.css) that a browser loads. Before, it had the absolute path, or the build failed on a missing target. The string form @import "sub/g.css" already does this on main.

Not in this PR. Each has its own cause.

Related open PRs.

Design. esbuild decides this in the CSS parser. convertTokens passes allowImports: false for an at-rule prelude, and the record is made with ast.IsUnused and never resolved. Declarations and unknown at-rule blocks pass true. Bun has the same flag (IS_UNUSED), but a record that exists is not safe here: the linker pairs @import rules with records by position, and an import condition is printed with a different record list (the panic above). So the prelude url() gets no record. The flag is set at the two places that parse a prelude as a token list (parse_custom_at_rule_prelude, and the env() attempt in MediaFeatureValue::parse_unknown). It is read only by the two url arms of TokenList::parse_into_impl. parse_at_rule and Parser::add_import_record are not changed. A debug_assert in the helper checks that no import record appears while the flag is set.

Suites run with the debug build: test/bundler/esbuild/css.test.ts (72 pass, 1 skip, 1 todo), test/bake/dev/css.test.ts (16 pass), and 36 more files (test/bundler/css/, bundler_html, bundler_plugin, bundler_loader, bundler_files, metafile, standalone, test/js/bun/http/bun-serve-html.test.ts, test/js/bun/css/): 2992 pass. Three css-fuzz tests hit their own 10 s limit on the debug build, with and without this change. They pass on a release build of 9cfe41342e.

The base of this branch is fd539ca7c0. Main 91e7e3b140 is 19 commits later and changes Parser::add_import_record and its four callers. On a local merge with it (debug build): test/bundler/esbuild/css.test.ts 72 pass, 1 skip, 1 todo. test/bake/dev/css.test.ts 16 pass. test/bundler/css/ 184 pass. Ten more files (four of test/js/bun/css/, bundler_html, bundler_loader, bundler_files, bundler_plugin, metafile, test/bake/dev/html.test.ts): 1636 pass.

css/URLInEnvFallbackOfAtImportMediaQuery is skipped under ASAN because of the leak above. On main this test fails with the panic. CI ran the file at the head 31a82d0395: 73 pass and 1 todo on the release lanes (read from the darwin aarch64 and Windows 2019 x64 logs), and 72 pass, 1 skip and 1 todo on the ASAN lane. Under ASAN, the --no-bundle test covers the same input: it builds only when the url() gets no import record.

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Review in Change Stack →

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info
⚙️ Run configuration
  • Configuration used: Repository: oven-sh/bun/.coderabbit.yaml
  • Review profile: ASSERTIVE
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  • Run ID: 68a95394-5b9f-4dc1-9ce6-35d0f6fc0452
📥 Commits

Reviewing files that changed from the base of the PR and between fd539ca and c152bf1.

📒 Files selected for processing: 7
  • src/css/css_parser.rs
  • src/css/media_query.rs
  • src/css/printer.rs
  • src/css/properties/custom.rs
  • src/css/rules/container.rs
  • test/bake/dev/css.test.ts
  • test/bundler/esbuild/css.test.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 0 remain after this review.

Walkthrough

The parser preserves URLs in at-rule preludes instead of treating them as imports. The printer uses original import paths when no inlined CSS URL or copied-asset key applies.

Changes

CSS URL handling

Layer / File(s) Summary
At-rule prelude URL parsing
src/css/css_parser.rs, src/css/media_query.rs, src/css/properties/custom.rs, src/css/rules/container.rs, test/bundler/esbuild/css.test.ts, test/bake/dev/css.test.ts
The parser scopes an at-rule-prelude flag to token parsing. Tests cover preserved prelude URLs, environment-variable fallbacks, and URL resolution in declarations.
Original import path output
src/css/printer.rs, test/bundler/esbuild/css.test.ts
The printer uses a nonempty original path when no inlined CSS URL or copied-asset key applies. Tests cover emitted paths across bundling modes and entry types.

Suggested reviewers: jarred-sumner

Priority: ➖ Normal

Merge Risk: ⚪ Minimal · up to 31a82

Merge Risk: ⚪ Minimal · up to 31a82

No actionable merge-blocking regression was established. The change is ready for normal checks.

Pre-merge checks: Passed 4
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 and concisely describes the main CSS URL handling changes in the pull request.
Description check Passed The description thoroughly explains the problem, implementation, verification, user impact, design, and out-of-scope issues. It does not use the template headings exactly, but it contains the required…
Full details: Description check

Explanation

The description thoroughly explains the problem, implementation, verification, user impact, design, and out-of-scope issues. It does not use the template headings exactly, but it contains the required information.

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@robobun

robobun commented Oct 16, 2026 •

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Updated 11:05 PM PT - Oct 17th, 2026

❌ @robobun, your commit 31a82d0 has 1 failures in Build #127916 (All Failures):


🧪   To try this PR locally:

bunx bun-pr 45604

That installs a local version of the PR into your bun-45604 executable, so you can run:

bun-45604 --bun

@robobun

robobun commented Oct 16, 2026 •

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Status: CI is green on every job that ran tests. The PR waits for a maintainer.

CI on the head 31a82d0395 (build 127916): 180 of 181 jobs passed. The red job is one test shard on darwin aarch64 (2 of 2), and it ran no test:

Error: buildkite-agent artifact download timed out after 120s for step 'darwin-aarch64-build-bun'.

That shard passed in build 126968 with the same diff on an older base. Only that job needs a retry.

The new tests in build 127916:

  • test/bundler/esbuild/css.test.ts: 73 pass, 1 todo on darwin aarch64 and on Windows 2019 x64. 72 pass, 1 skip, 1 todo on the ASAN lane.
  • test/bake/dev/css.test.ts: 16 pass on Windows 2019 x64.

Main 91e7e3b140 changed Parser::add_import_record after this branch was cut. A local merge with it passes both files.

Reproduced with:

mkdir -p sub && echo '.c0 { color: red }' > sub/g.css
echo '@media print { .c2 { z-index: 1 } @import url(sub/g.css); }' > entry.css
bun build ./entry.css --minify --outdir out && cat out/entry.css
# bun 1.4.3-canary (367d939d9) and main (5866b5f13d): @import url(/abs/build/dir/sub/g.css), "Bundled 2 modules"
# this branch: @import url(sub/g.css), "Bundled 1 module"

USE_SYSTEM_BUN=1 bun test test/bundler/esbuild/css.test.ts   # 16 fail
bun bd test test/bundler/esbuild/css.test.ts                 # 72 pass, 1 skip, 1 todo
USE_SYSTEM_BUN=1 bun test test/bake/dev/css.test.ts          # 1 fail
bun bd test test/bake/dev/css.test.ts                        # 16 pass

PR: #45604

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

Beyond the inline note, I also checked that the AT_RULE_PRELUDE_TOKENS flag cannot leak: parse_nested_block and try_parse reuse the same Parser, and parse_at_rule_prelude_tokens restores self.flags on both the Ok and Err path before try_parse rewinds, so a declaration url() later in the stylesheet still gets an import record. I also checked the printer fallthrough: original_path is only returned for records with a valid source_index, so external and unresolved url()s still print path.text as before. The user-visible semantics change (prelude url() no longer resolved, not in the metafile, not seen by plugin onResolve) and the two questions the description poses are design calls for a maintainer.

Extended reasoning...

The change touches the Rust CSS parser and printer in src/css/ (a new ParserOpts flag, a scoped wrapper, two TokenList::parse guards, a printer fallthrough) plus ~540 lines of bundler and dev-server tests; it touches no auth, crypto or injection surface. The flag scoping and the printer fallthrough were traced and hold up, but the change alters bundler behavior for url() in at-rule preludes and for url() to non-asset files, and the description itself asks a maintainer to rule on whether to follow esbuild's build error, so a human decision is still needed.

Comment thread test/bundler/esbuild/css.test.ts Outdated

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

The exact url() assertions in b075ef3 address my earlier comment. Beyond the inline ASAN-skip finding, I also checked the new original_path fallback in src/css/printer.rs for ?query#fragment loss — the suffix is a slice of original_path itself, so it is preserved (the ./sub/g.css?x=1#y case in the test covers it) — and the flag save/restore in parse_at_rule_prelude_tokens: ParserOpts is not part of ParserState, nested blocks reuse the same Parser, so the flag reaches the env() fallback token list and is restored even when the enclosing try_parse fails.

Extended reasoning...

The PR adds a parser flag so url() tokens in unknown at-rule preludes and media-query env() fallbacks stay raw tokens without import records, and changes the CSS printer to emit the written specifier instead of the resolver's absolute path for records with no URL form. It touches no security-sensitive surface. A human look remains worthwhile because the change alters user-visible bundler behavior (at-rule prelude url() targets are no longer loaded or copied, and declaration url() to stylesheets now prints as written where esbuild errors), and the description itself poses two open questions for a maintainer.

Comment on lines +1430 to +1436
// Before: `panic: index out of bounds: the len is 0 but the index is 0`.
// The url() record index pointed into the importing file's records, and
// the condition was printed with the records of the import chain.
// Skipped under ASAN: the linker clones an import condition and never frees
// the token list of an env() fallback (`Direct leak of 72 byte(s)` in
// `TokenList::deep_clone`), also for `env(foo, 1px)` on main.
(isASAN ? itBundled.skip : itBundled)("css/URLInEnvFallbackOfAtImportMediaQuery", {

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🟡 nit (optional): maintainers get the only regression test for the @ import ... env(foo, url(...)) panic skipped on the ASAN lane, so that lane never exercises the fixed path. The skip at test/bundler/esbuild/css.test.ts:1436 routes around a leak instead of fixing it. The leak is pre-existing: MediaFeatureValue::deep_clone at src/css/media_query.rs:1379 clones the env fallback into a heap Vec inside an arena-allocated value that never runs Drop. Fix: free or arena-allocate the fallback TokenList in the linker's import-condition clone so the test runs under ASAN, then drop the isASAN ? itBundled.skip : itBundled gate.

Why this was flagged

The test css/URLInEnvFallbackOfAtImportMediaQuery at test/bundler/esbuild/css.test.ts:1436 is wrapped in (isASAN ? itBundled.skip : itBundled). On the ASAN CI lane it is skipped, so the input @ import "./b.css" (min-width: env(foo, url(sub/g.css))) that used to panic with index out of bounds: the len is 0 but the index is 0 is never built there. The comment at test/bundler/esbuild/css.test.ts:1433-1435 names the observed failure, Direct leak of 72 byte(s) in TokenList::deep_clone, which comes from MediaFeatureValue::deep_clone at src/css/media_query.rs:1379 cloning the env fallback; the token list is a heap Vec held by an arena value that never runs Drop. REVIEW.md says a test must not be edited to route around a runtime bug it exposed. On the base branch there is no test at all here; after this change the non-ASAN lanes cover the panic but the ASAN lane does not, and the leak stays.

Verification: test/bundler/esbuild/css.test.ts:1436 reads (isASAN ? itBundled.skip : itBundled), so under ASAN the only bundled fixture for @ import "./b.css" (min-width: env(foo, url(sub/g.css))) is never built. The leak is pre-existing: MediaFeatureValue::deep_clone at src/css/media_query.rs:1377-1380 clones the env fallback TokenList heap Vec into a slab that is never dropped.

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Agreed: the skip goes around the leak, and the ASAN lane does not build the bundled path for this input.

The leak is on main without this PR. On a debug build of 5866b5f, @import "./b.css" (min-width: env(foo, 1px)); reports Direct leak of 144 byte(s) in 2 object(s) from the same TokenList::deep_clone frames. The fix must change who owns the cloned import conditions in the linker. There are three clone sites (conditions_with_import_records, deep_clone_conditions, wrap_rules_with_conditions), and none of the clones is dropped, because the Vec headers are shared bitwise. That is a separate change, and it is in progress outside this PR. It removes this skip.

Until then, the --no-bundle test builds the same input under ASAN. It passes only when the url() gets no import record, but it does not run the linker. I leave this thread open.

… a resolved path

A url() in the token-list prelude of an unknown at-rule, or in an env()
fallback of a media query, is not an import. The parser now keeps it as a
raw token, so it gets no import record: the bundler does not resolve it,
does not load its target, and it prints as written.

The CSS printer no longer falls back to the resolved path of a url() whose
target has no data: URL and no asset key. It prints the specifier as
written, so the output does not carry the absolute path of the build
directory.
The tests for a declaration url() with no asset URL now check only that
the build directory is not printed. A plain-CSS composes has its own
test. New tests: a url() in a CSS module token list is still an import,
and a prelude url() builds with --no-bundle.
#45487 adds a ParserOpts flag at 0b10. Two flags with the same value
compile, and the prelude flag would then be set for every CSS module.
The linker clones an import condition and never frees the token list of
an env() fallback. LeakSanitizer reports it for a spawned bun build, also
for env(foo, 1px) on main. The bundled test for that input is skipped
under ASAN. The --no-bundle test covers the same input there.
@robobun
robobun force-pushed the robobun/eb1e0d26/css-prelude-url-no-import branch from b075ef3 to c152bf1 Compare October 18, 2026 01:36
@robobun

robobun commented Oct 19, 2026 •

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#46040 has two questions for a maintainer. The first one also applies here, because css/URLInUnknownAtRuleBeforeAtImport in this PR pins the answer. (#46040 was stacked on this PR. It is on main now, because #46021 merged the part of this PR that it needs.)

1. An @import that follows an unknown at-rule statement (@foo x; @import "./b.css";)

  • Bun's parser accepts the import (css-cascade-5 keeps it valid), and the bundler inlines b.css.
  • esbuild 0.21.5 warns All "@import" rules must come first. It does not inline the file and it keeps the rule as written.
  • lightningcss-cli 1.33.0 --bundle also keeps the rule and does not inline the file.

Keep the inlining (this PR and #46040 do that), or leave the rule as written?

2. An @import of a file that is not a stylesheet (@import "./notes.txt";)

  • Bun drops the import with exit 0 and no message.
  • esbuild fails the build: Cannot import "notes.txt" into a CSS file.

This is the @import twin of question 1 in this PR. #46040 does not add the error. Is the error wanted?

@robobun

robobun commented Oct 20, 2026

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#46176 fixes the leak that css/URLInEnvFallbackOfAtImportMediaQuery is skipped for on ASAN builds. The linker no longer clones the import conditions, so the token list of an env() fallback has one owner.

After #46176 merges, remove the isASAN skip of that test and the three comment lines that explain it. I applied the head of this PR from 18 October together with the change of #46176 and removed the skip. The test then passed on a debug build with ASAN under the CI lane options.

If this PR merges first, I will remove the skip in #46176.

Jarred-Sumner added a commit that referenced this pull request Oct 20, 2026
… 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>
@robobun

robobun commented Oct 21, 2026

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Update to my comment above: #46021 fixed the leak on main and added css/URLInEnvFallbackOfAtImportMediaQuery there with no ASAN skip. #46176 is closed, so nothing in this PR depends on it.

When this PR is rebased on main, take the version of that test from main. The isASAN skip and the comment lines that explain it are no longer needed. I checked main at 963452075e with a debug build with ASAN: the test passes, and @import "./b.css" (min-width: env(foo, 1px)); builds with no LeakSanitizer report.

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