Repository navigation
fix: keep surrogate pairs and emoji whole when truncating titles, names and bodies - #3215
Conversation
Address OrKoN review on ChromeDevTools#3215: count graphemes instead of UTF-16 code units so emoji sequences stay intact.
Address review on ChromeDevTools#3215: generalize the Intl.Segmenter truncation from truncateTitle into truncateText() in src/utils/text.ts and use it for page titles, heap snapshot names and network bodies/URLs. Drop sliceWithoutSplittingSurrogates.
OrKoN
left a comment
There was a problem hiding this comment.
Please check the following:
-
In
src/utils/text.ts, keepmaxLengthas a UTF-16 code-unit bound and move the cut back to the last grapheme boundary at or before it, instead of counting graphemes.truncateTextnow counts graphemes, soBODY_CONTEXT_SIZE_LIMIT = 10000no longer bounds output: a body of 20 000 family emoji (ZWJ sequences) returns 110 003 code units, and a page can inflate the response by 11x. -
Retitle the PR and the commit to match the final behavior, or revert to the code-unit semantics from item 1. The title and description say "keep surrogate pairs whole", but the shipped helper changes what
maxLengthmeans for every caller. -
In
tests/McpResponse.test.ts, replace the real-browser title test with a mock-based one (acreateMockMcpPage()whosetitle()returns the long title, thensetIncludePages(true)+handle()). The truncation is pure string logic;AGENTS.mdasks for mocks when no browser integration is under test.
Nit (non-blocking): hoist new Intl.Segmenter(undefined, {granularity: 'grapheme'}) to a module-level constant; it is created on every truncating call.
|
@OrKoN thanks, addressed in 35548d8:
Nit: the On |
|
@kevin9327 could you please rebase? |
Address OrKoN review on ChromeDevTools#3215: count graphemes instead of UTF-16 code units so emoji sequences stay intact.
Address review on ChromeDevTools#3215: generalize the Intl.Segmenter truncation from truncateTitle into truncateText() in src/utils/text.ts and use it for page titles, heap snapshot names and network bodies/URLs. Drop sliceWithoutSplittingSurrogates.
Move the cut back to the last grapheme boundary at or before maxLength instead of counting grapheme clusters, so the limit still bounds the output. Hoist the Intl.Segmenter to a module constant and test the page title truncation with a mock page instead of a real browser.
35548d8 to
1c9be67
Compare
🤖 I have created a release *beep* *boop* --- ## [1.12.0](chrome-devtools-mcp-v1.11.0...chrome-devtools-mcp-v1.12.0) (2026-10-22) ### 🎉 Features * add --maxNavigationSaved flag to configure retained navigation history ([#3018](#3018)) ([a580d13](a580d13)) * add Kimi Code plugin manifest ([#3029](#3029)) ([cd00b64](cd00b64)) * Analyze heap snapshots without a browser connection ([#3156](#3156)) ([78c8320](78c8320)) * **config:** add --watchConfig to reload config file changes ([#3248](#3248)) ([b48561f](b48561f)) * **config:** introduce layered ServerConfig for live reload ([#3203](#3203)) ([37f1fda](37f1fda)) * **config:** share ReadonlyServerConfig with McpContext and McpPage ([#3204](#3204)) ([0813bf3](0813bf3)) * **config:** support reloading blockedUrlPattern and allowedUrlPattern ([#3268](#3268)) ([cc850f5](cc850f5)) * **context:** release disabled feature state on config reload ([#3049](#3049)) ([c0140d1](c0140d1)) * Paginate by default in heap snapshot tools ([#3201](#3201)) ([fb8375b](fb8375b)) * Paginate detailed diff in compare_heapsnapshots ([#3195](#3195)) ([4a9dd53](4a9dd53)) * run independent tool calls in parallel with a TaskRunner ([#3243](#3243)) ([8a8d877](8a8d877)) * run page-scoped tools on different pages in parallel ([#3252](#3252)) ([f8f18ac](f8f18ac)) * **server:** add McpServer.applyConfig() to reload configuration ([#3051](#3051)) ([f874aeb](f874aeb)) * **slim:** support filepath in slim mode screenshot ([#3296](#3296)) ([d399c4a](d399c4a)) * Sort objects for class by self size in compare_heapsnapshots ([#3205](#3205)) ([f8a18c6](f8a18c6)) * **tools:** support updating ToolHandler definitions in place ([#3050](#3050)) ([8064138](8064138)) * **wait_for:** support opt-in visible text matching ([#3212](#3212)) ([eef92da](eef92da)) ### 🛠️ Fixes * allow paths below a filesystem-root workspace root ([#3277](#3277)) ([296ccef](296ccef)) * block evaluate_script while a dialog is open ([#3196](#3196)) ([545bcbb](545bcbb)) * bound take_snapshot wait and clear the geolocation override ([#3265](#3265)) ([6282f54](6282f54)) * **browser:** redact WebSocket headers from connection logs ([#2901](#2901)) ([3a2f91e](3a2f91e)) * capture thrown transform errors as Zod validation issues ([#3242](#3242)) ([0f95c21](0f95c21)) * clear handled dialog in McpPage.getDialog() ([#3241](#3241)) ([2ab93a3](2ab93a3)), closes [#2958](#2958) * **cli:** disallow --slim in CLI start options ([#2987](#2987)) ([#3113](#3113)) ([ae3f61c](ae3f61c)) * **cli:** do not forward tool args to start ([#3114](#3114)) ([fef1598](fef1598)) * **cli:** serialize object daemon arguments ([#2797](#2797)) ([f73a440](f73a440)) * close the tab opened by a failed new_page ([#2928](#2928)) ([c174677](c174677)) * **config:** accept native JSON objects for wsHeaders in config files ([#3262](#3262)) ([371e6c2](371e6c2)) * **console:** describe Map, Set, function, DOM node, symbol and cyclic arguments ([#3199](#3199)) ([968e4e5](968e4e5)) * **console:** include the reason of unhandled promise rejections ([#3148](#3148)) ([f7cdf73](f7cdf73)) * defer focus emulation until a page is explicitly targeted ([#3230](#3230)) ([35abe35](35abe35)) * disable Puppeteer signal handlers for launched browsers ([#3238](#3238)) ([3afec73](3afec73)), closes [#3154](#3154) * discover third-party developer tools before tool lookup ([#3208](#3208)) ([2777fa0](2777fa0)), closes [#2973](#2973) * discover third-party developer tools in page tools ([#3207](#3207)) ([cf33529](cf33529)), closes [#2980](#2980) * drop InlineTextBox nodes from text snapshots ([#3202](#3202)) ([f8c775a](f8c775a)) * **emulate:** keep previous viewport when setViewport fails ([#3150](#3150)) ([19d883c](19d883c)) * exclude source maps from the npm package ([#3295](#3295)) ([d575da4](d575da4)) * keep surrogate pairs and emoji whole when truncating titles, names and bodies ([#3215](#3215)) ([058adcf](058adcf)) * let resourceTypes match CORS preflights and prefetches ([#3217](#3217)) ([e342c6e](e342c6e)) * **lighthouse:** explain unsupported URL schemes in navigation mode ([#3144](#3144)) ([c6ad84a](c6ad84a)) * **lighthouse:** fail the audit when Lighthouse reports a runtime error ([#3188](#3188)) ([53ea78d](53ea78d)) * **lighthouse:** restore the emulated viewport after a navigation audit ([#3189](#3189)) ([c777ece](c777ece)) * **network:** list only earlier hops in a request's redirect chain ([#3198](#3198)) ([4675940](4675940)) * **network:** remove unsupported websocket from list_network_requests filter ([#2961](#2961)) ([#3282](#3282)) ([8b119d9](8b119d9)) * **network:** reset page network emulation before applying URL restrictions ([#3312](#3312)) ([f25f3df](f25f3df)) * **pages:** reject devtools:// URLs in navigate_page and new_page ([#2935](#2935)) ([#3128](#3128)) ([c94c03d](c94c03d)) * **pages:** report the actual page size after resize_page ([#2998](#2998)) ([#3132](#3132)) ([f003056](f003056)) * **pages:** revert reporting the page size after resize_page ([#3308](#3308)) ([186ea66](186ea66)), closes [#3306](#3306) * **pagination:** return all items when pageSize is omitted and pageIdx is 0 ([#2996](#2996)) ([#3134](#3134)) ([3ad9115](3ad9115)) * **performance:** populate structuredContent for traceInsight in performance_analyze_insight ([#2981](#2981)) ([#3115](#3115)) ([c2c6cc4](c2c6cc4)) * preserve unread page fallback across snapshots and deduplicate page disposal ([#3161](#3161)) ([8604365](8604365)) * print the no-roots temp-directory warning under default flags ([#2927](#2927)) ([0dd8ed9](0dd8ed9)) * reject empty, extra, and unknown parts in geolocation and viewport transforms ([#3097](#3097)) ([#3120](#3120)) ([3ea31fb](3ea31fb)) * resolve error causes on the session that reported the exception ([#3220](#3220)) ([b2d37e8](b2d37e8)) * resolve service worker IDs for console messages ([#2881](#2881)) ([3804a9a](3804a9a)) * return message when page exposes no 3p developer tools ([#3197](#3197)) ([663f3c3](663f3c3)), closes [#3004](#3004) * **script:** surface non-Error thrown and rejected values in evaluate_script ([#2951](#2951)) ([#3127](#3127)) ([b1e6e68](b1e6e68)) * **security:** validate filesystem paths that parse as http/ws URLs ([#3186](#3186)) ([91e112d](91e112d)) * **snapshot:** omit uid for accessibility nodes without backendNodeId ([#3187](#3187)) ([9054351](9054351)) * stop active screencast on McpPage.dispose() ([#3160](#3160)) ([558af81](558af81)) * stop get_network_request waiting forever for an unread no-store body ([#3216](#3216)) ([c556be1](c556be1)) * surface nested error causes and autoConnect hint on connection failure ([#3111](#3111)) ([d7f1e78](d7f1e78)) * treat 0.0.0.0 and [::] browser endpoints as local ([#3321](#3321)) ([7d5f7de](7d5f7de)) * treat IPv4-mapped IPv6 loopback as localhost ([#3255](#3255)) ([6cfb34c](6cfb34c)) * truncate data: URLs in accessibility snapshots ([#3292](#3292)) ([11e7d47](11e7d47)) * validate type_text submitKey before typing ([#3185](#3185)) ([c8615d7](c8615d7)) * **wait_for:** find text in dynamically attached iframes ([#3210](#3210)) ([5f84888](5f84888)) * warn when screenshot dimensions exceed 16384px limit ([#2952](#2952)) ([#3291](#3291)) ([10455b7](10455b7)) ### 📄 Documentation * add a pre-submit checklist to AGENTS.md ([#3236](#3236)) ([e96ee6c](e96ee6c)) * clarify URL pattern port and hostname matching ([#3287](#3287)) ([4723335](4723335)) * **config:** note that hot-reloaded URL restrictions keep open targets attached ([#3314](#3314)) ([47db2b8](47db2b8)) * correct CLI availability of extension tools ([#2852](#2852)) ([a7280ee](a7280ee)) * explain how to install skills, including the CLI skill ([#3274](#3274)) ([46eb546](46eb546)) * remove experimental status from CLI and promote it in README ([#3273](#3273)) ([0ced16b](0ced16b)) * require a rebase only when the branch has merge conflicts ([#3239](#3239)) ([d1143ac](d1143ac)) * **skills:** clarify Lighthouse score scale and contrast workflow ([#3006](#3006)) ([#3218](#3218)) ([bf8c6d9](bf8c6d9)) ### ⚡ Performance * **cli:** load a small third-party bundle in the chrome-devtools CLI ([#3200](#3200)) ([552e1f8](552e1f8)) * load the Lighthouse bundle on first use ([#3169](#3169)) ([798f03a](798f03a)) ### 🏗️ Refactor * **config:** isolate scripts and unit tests from home config discovery ([#3256](#3256)) ([65e6b97](65e6b97)) * **config:** lock slim and pageIdRouting options when viaCli is set ([#3257](#3257)) ([384d9aa](384d9aa)) * **config:** pass ReadonlyServerConfig to BrowserManager and add OptionGate ([#3267](#3267)) ([98302f2](98302f2)) * **config:** simplify watchConfig and start watcher inside connect ([#3259](#3259)) ([878c5f6](878c5f6)) * extract errorResult() and routedPageId() in ToolHandler ([#3251](#3251)) ([9a6b03a](9a6b03a)) * import types and values from a module in one statement ([#3303](#3303)) ([f4eaf1f](f4eaf1f)) * **lighthouse:** move Lighthouse runner methods to McpPage and add bundle types ([#3283](#3283)) ([e1823a2](e1823a2)) * list optional properties last in inline object types ([#3302](#3302)) ([dc929c0](dc929c0)) * register all tools upfront across modes ([#3163](#3163)) ([58f8d1f](58f8d1f)) * **response:** pass live ReadonlyServerConfig to McpResponse ([#3258](#3258)) ([6042490](6042490)) * **tools:** add explicit factory types to tool definitions ([#3284](#3284)) ([4d1d7b2](4d1d7b2)) * use #private names instead of the private modifier ([#3301](#3301)) ([2e13311](2e13311)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).
Fixes #3214.
Three places cut strings by UTF-16 code units:
truncateTitlefor page titles in the page list (text and structured output),truncateValuefor heap-snapshot names, andgetSizeLimitedStringfor request/response bodies and URLs. When an emoji or other astral character straddles the cut, the result keeps a lone high surrogate.JSON.stringifythen emits it as\ud83d, which strict JSON parsers reject, including the Pydantic-based one the Python MCP SDK uses. The whole tool response fails to parse on the client.This adds a shared
truncateText()helper insrc/utils/text.ts, and all three call sites use it.maxLengthstays a UTF-16 code-unit bound. The helper moves the cut back to the last grapheme boundary (Intl.Segmenter) at or before the limit, so surrogate pairs and emoji sequences stay whole and the output is never longer than the limit plus the ellipsis. Strings that do not split a grapheme truncate exactly as before.Tests:
tests/utils/text.test.ts(new): a pair straddling the limit, code-unit counting, a 20 000-family-emoji body that stays within 10 000 units, joined emoji sequences, and edge-case limitsHeapSnapshotFormatter:formatNamewith an emoji atMAX_NAME_LENGTHNetworkFormatter: a URL with an emoji straddling the 255-unit limitMcpResponse: a mock page whose title is the repro from the issue (46As plus an emoji). The listed title endsAAA...and the serialized response contains no\ud83d.The formatter and response tests fail on
mainand pass with this change.tscand eslint are clean.AI-assisted: I used an AI assistant to help write this change. I reviewed the code and tests and ran them locally.