🟠 oxc — Mangle props (8)

• default/mangle_props_jsx_transform_namespace
• default/mangle_props_type_script_features
• ts/ts_experimental_decorators_mangle_props_assign_semantics
• ts/ts_experimental_decorators_mangle_props_define_semantics
• ts/ts_experimental_decorators_mangle_props_methods
• ts/ts_experimental_decorators_mangle_props_static_assign_semantics
• ts/ts_experimental_decorators_mangle_props_static_define_semantics
• ts/ts_experimental_decorators_mangle_props_static_methods

🟠 oxc — Label mangling (1)

• default/minify_nested_labels_no_bundle

🟠 oxc — verbatimModuleSyntax (1)

• ts/export_type_issue379 — verbatimModuleSyntax=false not supported in oxc_transformer

🔵 rolldown — Legal comments (14)

• default/legal_comments_avoid_slash_tag_end_of_file
• default/legal_comments_avoid_slash_tag_external
• default/legal_comments_avoid_slash_tag_inline
• default/legal_comments_end_of_file
• default/legal_comments_escape_slash_script_and_style_end_of_file
• default/legal_comments_escape_slash_script_and_style_external
• default/legal_comments_external
• default/legal_comments_linked
• default/legal_comments_many_end_of_file
• default/legal_comments_many_linked
• default/legal_comments_no_escape_slash_script_end_of_file
• default/legal_comments_no_escape_slash_style_end_of_file
• default/legal_comments_none

🔵 rolldown — Copy loader (14)

• default/metafile_various_cases
• default/metafile_very_long_external_paths
• loader/loader_bundle_with_unknown_import_attributes_and_copy_loader
• loader/loader_copy_entry_point_advanced
• loader/loader_copy_explicit_output_file
• loader/loader_copy_starts_with_dot_abs_path
• loader/loader_copy_starts_with_dot_rel_path
• loader/loader_copy_use_index
• loader/loader_copy_with_bundle_entry_point
• loader/loader_copy_with_bundle_from_css
• loader/loader_copy_with_bundle_from_js
• loader/loader_copy_with_format
• loader/loader_copy_with_injected_file_bundle
• loader/loader_copy_with_transform

🔵 rolldown — Empty/extensionless loader (2)

• loader/empty_loader_css
• loader/extensionless_loader_css

🔵 rolldown — Glob (10)

• glob/glob_basic_no_splitting
• glob/glob_basic_splitting
• glob/glob_entry_point_abs_path
• glob/glob_no_matches
• glob/glob_wildcard_no_slash
• glob/glob_wildcard_slash
• glob/ts_glob_basic_no_splitting
• glob/ts_glob_basic_splitting
• default/require_and_dynamic_import_invalid_template
• loader/with_type_bytes_override_loader_glob

🔵 rolldown — publicPath (4)

• loader/loader_file_public_path_js
• loader/loader_file_public_path_css
• loader/loader_file_public_path_asset_names_js
• loader/loader_file_public_path_asset_names_css

🔵 rolldown — File reference URL difference (4)

• loader/loader_file_relative_path_asset_names_css
• loader/loader_file_relative_path_asset_names_js
• loader/loader_file_relative_path_css
• loader/loader_file_relative_path_js

🔵 rolldown — Import attributes (9)

• default/comment_preservation_import_assertions
• default/metafile_import_with_type_json
• default/output_for_assert_type_json
• loader/loader_bundle_with_import_attributes
• loader/loader_bundle_with_unknown_import_attributes_and_js_loader
• loader/with_bad_attribute
• loader/with_bad_type
• loader/with_type_bytes_override_loader
• loader/with_type_json_override_loader

🔵 rolldown — Other (4)

• default/conditional_require_resolve — converting conditional require.resolve not supported
• default/require_shim_substitution — require second argument not supported
• dce/dead_code_inside_unused_cases — dce inside unused switch cases not supported
• default/import_with_hash_parameter / default/import_with_query_parameter / loader/loader_file_with_query_parameter / loader/loader_from_extension_with_query_parameter — stripping hash/query parameters not supported

🔵 rolldown — Test infra limitations (5)

• default/import_abs_path_as_dir
• default/import_abs_path_as_file
• default/entry_names_non_portable_character
• loader/loader_inline_source_map_absolute_path_issue4075_unix
• loader/loader_inline_source_map_absolute_path_issue4075_windows

🔵 rolldown — Intentional: hacky esbuild behavior (3)

• dce/package_json_side_effects_array_keep_main_implicit_main
• dce/package_json_side_effects_array_keep_module_implicit_main
• dce/package_json_side_effects_array_keep_module_use_main

🔵 rolldown — Compiler hints spec (1)

• dce/remove_unused_no_side_effects_tagged_templates

🔵 rolldown — ES5 target not supported (2)

• default/define_import_meta_es5
• loader/loader_json_prototype_es5

🔵 rolldown — Resolve alias behavior difference (3)

• default/package_alias_match_longest
• default/package_alias
• default/warnings_inside_node_modules

🟠 oxc — Extension resolution difference (2) — oxc_resolver prefers .js over .ts in node_modules

• ts/ts_import_in_node_modules_name_collision_with_css
• ts/ts_prefer_js_over_ts_inside_node_modules

🔵 rolldown — Inject feature aligned with @rollup/plugin-inject (5)

• default/inject_duplicate
• default/inject_import_order
• default/inject_import_ts
• default/inject_with_string_export_name_bundle
• default/inject_with_string_export_name_no_bundle

🔵 rolldown — Multi-pass transformer architecture limitation (3)

• default/inject_jsx
• default/jsx_import_meta_property
• default/jsx_import_meta_value

🟠 oxc — Covered by minifier (1)

• default/quoted_property_mangle

🔵 rolldown — Irrelevant/will not support (4)

• default/entry_names_no_slash_after_dir — no [dir] placeholder
• default/error_message_crash_stdin_issue2913 — stdin not supported
• default/line_limit_minified — lineLimit will not be supported
• default/line_limit_not_minified — lineLimit will not be supported

🔵 rolldown — CSS bundling not supported (10) — #4271

• dce/tree_shaking_js_with_associated_css (+ 6 variants)
• default/entry_names_chunk_names_ext_placeholder
• default/legal_comments_modify_indent
• default/metafile_no_bundle
• loader/loader_data_url_text_css

Source: packages/rollup-tests/src/ignored-tests.js

🔵 rolldown — Build timing difference (3) — rolldown builds on bundle.generate/write vs rollup()

• rollup@hooks@supports buildStart and buildEnd hooks
• rollup@hooks@supports warnings in buildStart and buildEnd hooks
• rollup@hooks@passes errors to the buildEnd hook

🔵 rolldown — import.meta.url polyfill difference (5)

• rollup@function@import-meta-url-b
• rollup@form@import-meta-url
• rollup@form@resolve-import-meta-url-export
• rollup@form@resolve-import-meta-url
• rollup@function@import-meta-url-with-compact

🔵 rolldown — Module type guessing difference (3)

• rollup@function@non-js-extensions
• rollup@function@error-parse-unknown-extension
• rollup@function@error-parse-json

🔵 rolldown — Bundle assignment not supported (8)

• rollup@function@error-file-name-absolute-path
• rollup@function@error-file-name-deep-traversal
• rollup@function@error-file-name-dot-dot
• rollup@function@error-file-name-escaped-via-filename-property
• rollup@function@error-file-name-path-traversal-plugin
• rollup@function@error-file-name-windows-absolute-path
• rollup@function@file-name-double-dot-prefix-is-valid
• rollup@function@file-name-leading-dot-slash-is-valid

🔵 rolldown — Warning/error differences (22)

• rollup@function@plugin-hook-filters
• rollup@function@generate-bundle-mutation
• rollup@function@missing-entry-export
• rollup@hooks@Throws when using the "file" option for multiple chunks
• 8 logging-related tests
• rollup@function@cannot-call-external-namespace
• rollup@function@cannot-call-internal-namespace
• 3 reassign-import tests
• rollup@function@warning-const-reassign
• rollup@function@namespace-reassign-import-fails
• rollup@function@namespace-update-import-fails

🔵 rolldown — Plugin dependencies (5)

• rollup@function@no-treeshake-react
• rollup@function@strip-bom-1
• rollup@form@supports-core-js
• rollup@form@supports-es5-shim
• rollup@form@supports-es6-shim

🔵 rolldown — Parallelism ordering (2)

• rollup@hooks@assigns chunk IDs before creating outputBundle chunks
• rollup@function@external-resolved

🔵 rolldown — external: true not supported (3)

• rollup@function@external-namespace-and-default-reexport-compat2
• rollup@function@external-namespace-and-default-reexport-compat3
• rollup@function@external-namespace-and-default-reexport-compat

🔵 rolldown — Test infra (3)

• rollup@function@preserve-symlink
• rollup@function@symlink
• rollup@form@sourcemaps-inline

🔵 rolldown — Other behavior differences (9)

• rollup@hooks@Throws when not specifying "file" or "dir"
• rollup@function@bundle-facade-order
• rollup@function@argument-deoptimization@global-calls
• rollup@function@es5-class-called-without-new
• rollup@function@jsx@unknown-mode
• rollup@function@jsx@unnecessary-import-source
• rollup@function@catch-rust-panic
• rollup@function@exports-are-not-defined
• rollup@function@dynamic-import-call-method-with-this-await

Source: packages/rollup-tests/src/ignored-treeshaking-tests.js + ignored-treeshaking-tests.json

All 278 tests are rolldown — tree-shaking is implemented in rolldown's link stage.

49 manually listed tests in ignored-treeshaking-tests.js covering:

• Scope handling and variable shadowing
• Deoptimization of recursive functions
• Const folding across modules
• Parameter optimization
• Property access side-effects tracking
• Namespace mutation tracking
• Class static block tree-shaking
• Proxy tree-shaking

229 auto-generated tests in ignored-treeshaking-tests.json covering:

• Array element tracking, arrow/function call parameters
• Async function effects, binary/unary expressions
• Break control flow, builtin prototypes
• Class fields/constructors/static blocks
• Conditional/logical expressions, dead branch elimination
• Decorator tree-shaking, empty statement removal
• Function mutation tracking, getter/setter side-effects
• Object expression tree-shaking, optional chaining
• Pattern assignments, property setters/getters
• Pure comment handling, recursive calls/values
• Self-calling functions, sequence expressions
• Side-effect detection (a through t, plus variants)
• Switch/try statement deoptimization, template literals
• Tree-shake literal parameters, unused imports/vars/functions

Full list in packages/rollup-tests/src/ignored-treeshaking-tests.json.

Source: packages/rollup-tests/src/ignored-passed-snapshot-different-tests.js

🔵 rolldown — Deconflict logic differences (~30)

• rollup@form@catch-parameter-shadowing
• rollup@form@body-less-for-loops
• rollup@form@import-specifier-deshadowing
• rollup@form@base64-deshadow
• rollup@form@conflicting-imports
• rollup@form@deconflict-format-specific-exports
• rollup@form@deconflict-format-specific-globals
• rollup@form@internal-conflict-resolution
• rollup@form@large-var-cnt-deduping
• rollup@form@deconflict-module-priority
• (and ~20 more deconflict-related tests)

🔵 rolldown — Reexport handling (~20) — rolldown converts reexport to import+export

• rollup@form@reexport-external-default-and-name
• rollup@form@reexport-external-default-and-namespace
• rollup@form@reexport-external-default-as-name-and-name
• rollup@form@reexport-external-default
• rollup@form@reexport-external-name-as-default2
• rollup@form@reexport-external-name-as-default
• rollup@form@reexport-external-name
• rollup@form@reexport-external-namespace-as
• rollup@form@reexport-external-namespace
• rollup@form@reexport-used-external-namespace-as
• rollup@form@external-export-tracing
• (and more)

🔵 rolldown — Dynamic import inlining (~5)

• rollup@form@dynamic-import-inlining
• rollup@form@dynamic-import-inlining-array
• rollup@form@inline-with-reexport
• rollup@form@nested-inlined-dynamic-import
• rollup@form@inlined-treeshaken-dynamic-import (from treeshaking json)

🔵 rolldown — Class rendering differences (~15) — class A → var A = class

• rollup@form@use-class-name-in-static-block
• rollup@form@static-method-deoptimization
• rollup@form@reassigned-exported-functions-and-classes
• rollup@form@computed-properties
• rollup@form@empty-statament-class-member
• rollup@form@exported-class-declaration-conflict
• rollup@form@support-decorators-after-export
• rollup@form@support-decorators-before-export
• rollup@form@default-export-anonymous-class-extends
• rollup@form@default-export-class
• (and more)

🟠 oxc — undefined → void 0 replacement (2) — oxc_codegen behavior

• rollup@form@proper-this-context
• rollup@form@this-is-undefined

🔵 rolldown — Sourcemap mapping differences (~8)

• rollup@function@sourcemap-true-generatebundle
• rollup@function@sourcemap-inline-generatebundle
• rollup@form@sourcemaps-external
• rollup@form@sourcemaps-hidden
• rollup@sourcemaps@render-chunk-babili
• rollup@form@render-chunk-plugin-sourcemaps
• rollup@sourcemaps@transform-low-resolution
• rollup@sourcemaps@names
• rollup@sourcemaps@basic-support

🔵 rolldown — Inlining/optimization differences (~20)

• rollup@form@assignment-to-exports
• rollup@form@deep-properties-access
• rollup@form@deep-properties
• rollup@form@handles-async-await
• rollup@form@recursive-computed-members
• rollup@form@recursive-multi-expressions
• rollup@form@reexport-star-deshadow
• rollup@form@function-id-as-parameter
• rollup@form@remove-whitespace-of-logical-expression
• rollup@form@pure-comment-scenarios-complex
• rollup@form@non-empty-block-statement
• rollup@form@nested-pure-comments
• rollup@form@unary-expressions-preserve-constants
• (and more)

🔵 rolldown — Other output differences (~70)

• Format-specific rendering, namespace objects, hash values, export handling, emit-asset, etc.
• rollup@form@hoisted-vars-in-dead-branches — var hoisting happens in Rollup but not Rolldown
• rollup@form@export-__proto__ — Rolldown uses __export helper
• rollup@function@emit-chunk-hash — hash value difference
• rollup@function@cycles-export-star — cycle handling
• (and many more — full list in source file)

Source: packages/rollup-tests/src/ignored-by-unsupported-features.md

🔵 rolldown — Plugin-related (31)

• NormalizedOptions at hooks not compatible (2)
• load hook ast return not supported (2)
• resolveId hook resolvedBy not supported (1)
• shouldTransformCachedModule hook not supported (1)
• resolveDynamicImport hook specifier: AstNode not supported (2)
• Plugin sequential not supported (2)
• renderDynamicImport/resolveFileUrl/resolveImportMeta hooks not supported (3)
• PluginContext.parse allowReturnOutsideFunction not supported (1)
• PluginContext.cache not supported (7)
• PluginContext.load not fully supported (4)
• maxParallelFileOps not supported (5)
• PluginContext.emitFile emit chunk partially supported (13)
• PluginContext.emitFile prebuilt chunk not supported (3)
• PluginContext.setAssetSource not supported (9)
• originalFileName/originalFileNames not supported (3)

🔵 rolldown — Options-related (102)

• output.format systemjs not supported (15)
• input.perf and bundle.getTimings() not supported (2)
• input.moduleContext not supported (2)
• output.compact not supported (4)
• output.validate not supported (1)
• output.interop not supported (16)
• Bundle.cache not supported (2)
• output.generatedCode not supported (21)
• output.preserveModules not compatible (11)
• output.manualChunks not compatible (8)
• format: amd not supported (3)
• output.sourcemapExcludeSources not supported (1)
• output.sourcemapBaseUrl not compatible (3)
• output.treeshake.preset not supported (1)
• output.treeshake.moduleSideEffect not compatible (2)
• ModuleInfo not compatible (8)
• Chunk information not compatible (2)

🔵 rolldown — Features (86)

• syntheticNamedExports not supported (25)
• Import assertions/attributes not supported (28)
• Watch behavior not compatible (1)
• Escaping external id not supported (1)
• Remove use strict from function body (1)
• Namespace object not compatible (12)
• hasOwnProperty export handling (1)
• __proto__ export handling (2)
• Source map combine logic (1)
• strictDeprecations option not supported (7)
• Error/warning information not compatible (52) — includes missing error codes like VALIDATION_ERROR, EMPTY_BUNDLE, ASSET_SOURCE_MISSING, UNUSED_EXTERNAL_IMPORT, etc.