Senior Frontend Engineer at Horsefly Analytics, Manchester. I build production TypeScript and React for a labour-market analytics platform, and I work on the AWS and AI-agent infrastructure behind it.

Most of what I enjoy is the unglamorous half: parser edge cases, streaming protocols, the failure modes that only show up under real input.

I contribute fixes upstream to packages the JavaScript ecosystem depends on. Most of these I found and traced myself, reproduced, and verified against a differential build before opening; where the diagnosis was someone else's I say so and the contribution is the fix and the test.

Merged and released

• benjamn/recast#1438 — comment tokens sit in loc.tokens for the babel, TypeScript and flow parsers but not for esprima or acorn, so a comment between a node and its enclosing parenthesis hid the parenthesis from hasParens() and the printer emitted a second pair. This broke recast's own documented print(parse(source)) === source identity on unmodified source. Verified across 5,076 generated inputs: 2,540 identity violations fixed, zero regressions. Shipped in 0.23.20 — a package with ~148M downloads a month.
• Rich-Harris/magic-string#326 — two move() calls whose ranges overlapped spliced a chunk's next pointer to itself, so the list became a cycle and every later toString() or generateMap() spun forever on valid, in-bounds arguments. No error, just a hung build. Added the ordering check that throws instead, skipped behind a flag so a first move keeps costing nothing, and carried the flag through clone() since a clone inherits the reordering and hung the same way. Shipped in 1.2.1 — ~740M downloads a month, and the source-manipulation layer inside Vite and Rollup.
• Rich-Harris/magic-string#331 — a hasChanged() optimisation merged that morning compared each edited chunk against its own slice of the original, which assumes a chunk's content replaces its own range. An overwrite spanning several chunks stores the whole replacement on the first chunk and empties the rest, so hasChanged() reported a change on strings byte-identical to the input. Found by checking the new implementation differentially against the one it replaced over 20,880 generated operation sequences: 775 disagreed, every one a false positive, none after the fix. Shipped in 1.2.2, cut minutes after the merge, so the regression never reached a published version.
• postcss/postcss-selector-parser#330 — unclosed [, ( and a trailing | threw a raw TypeError instead of the parser's own error. Shipped in 7.1.5 — ~590M downloads a month.
• corsairdev/corsair#111 — improved the Telegram integration plugin.

Merged, not yet in a release

• import-js/eslint-plugin-import — no-cycle dereferenced a null strongly-connected-components graph when the linted file's own path does not resolve, which aborts the whole lint run with a TypeError. That happens for an unsaved editor buffer (eslint --stdin --stdin-filename=not-yet-written.js, ESLint#lintText) and for resolvers that cannot resolve absolute paths. Rather than fall back to the exhaustive traversal, the graph is built rooted at the imported module and cached, so the common case skips the work entirely. Landed on main as 7828a5f; the pull request it came from reads as closed because the maintainer landed the commit directly rather than merging the branch. ~246M downloads a month, unreleased as of the latest tag.

In review

• Shopify/flash-list#2444 — the fix and the regression test for a P1 open since June. The diagnosis is not mine: the reporter of #2307 traced it in full, down to the corrective pass recomputing positions only as far as initialScrollIndex and leaving the rows after it on stale estimates, which breaks the sort order the visible-range binary search relies on. What I added was the one-line fix and, the harder half, a test that pins the race down deterministically: mocked measurement forcing 300px rows above the 200px seed, a single-item draw batch and zero draw distance, asserting item 250 renders and item 333 does not. It fails on main. ~7M downloads a month.
• expo/expo#48960 — a rule for eslint-plugin-expo catching credentials held in EXPO_PUBLIC_ environment variables, which are inlined into the app bundle in plain text and readable by anyone with the app. Matches on _ separated name segments rather than substrings, so EXPO_PUBLIC_AUTHORITY and EXPO_PUBLIC_MONKEY stay quiet.
• shadcn-ui/ui#11463 — the Tailwind prefix transform rebuilt class literals as quoted source text by hand, so the step that stripped the delimiters also stripped every quote inside the class value. [stroke='#fff'] became [stroke=#fff], which is not valid CSS, so the browser silently discarded the rule. Found by reading the CLI source rather than from a bug report. Verified over all 1,435 registry components: 1,404 byte-identical, zero regressions.
• benjamn/recast#1442 — ?? cannot be combined with || or && without parentheses, because the CoalesceExpression production admits only BitwiseORExpression operands. recast decided parentheses by operator precedence, which covers a ?? nested inside || but never a || nested inside ??, so printing a ?? whose operand was a || or && emitted four shapes that are outright SyntaxErrors. The report is someone else's; the cause and the fix are mine. Every printed form now round-trips through new Function, and a second test locks in that ?? beside a non-logical operator is still left alone.
• benjamn/recast#1441 — lib/parser.ts passed a literal ecmaVersion: 6 into every parser while reading each neighbouring value from the caller's options, which silently overrode the acorn parser's own default. The acorn setup shown in recast's own README therefore rejected object spread, **, async/await and optional catch binding. Now read from the options like the values either side of it, and added to Options so it is typed and documented rather than reaching some parsers by accident.
• webpro-nl/knip#1960 — exposes defineConfig on a ./config entrypoint, so a config file can import it without the side effects of parsing the index module. The separate-entrypoint design is not mine: a commenter on the issue proposed it, with a reason neither of the two options I had offered covered. ~53M downloads a month.
• postcss/postcss-selector-parser#335 — attribute selectors with no valid attribute name threw a raw TypeError, or emitted the literal string undefined into CSS. Verified against 43,200 generated selectors.
• postcss/postcss-selector-parser#336 — $ dropped from attribute names, breaking Sass interpolation like [#{$attr}].
• postcss/postcss-selector-parser#337 — lossless mode dropped trailing whitespace when a selector ended before any node was created.
• Fixes also pending review in hast-util-from-parse5, stacktrace-parser, xml-js and eslint-plugin-react-native.

• llm-guard — validating and securing LLM prompts, in TypeScript.
• react-native-virtual-list — a virtualized list that holds its scroll position when item heights are only known after they render. Item offsets are prefix sums over a Fenwick tree rather than a position array that gets partially rebuilt, which makes them non-decreasing by construction and rules out the class of bug above. Aimed at react-native-web, which does not implement maintainVisibleContentPosition at all.
• bedrock-ui-stream — bridges AWS Bedrock Agent Runtime event streams to the Vercel AI SDK UI message stream protocol. Handles the parts that bite: chunk boundaries splitting multi-byte characters, partial tool-call state, and redaction on the error path.

Lint rules for React Native. General JavaScript linters do not know what a WebView is, that AsyncStorage writes to disk unencrypted, or that a FlatList inside a ScrollView renders every row. These cover only that gap, and each rule is statically detectable rather than heuristic where it can be.

• eslint-plugin-rn-security — unsafe WebView configuration, credentials in AsyncStorage, cleartext endpoints, unvalidated deep links, and credentials written to the device log.
• eslint-plugin-react-native-performance — nested virtualized lists, lists inside a ScrollView, missing and index-based keyExtractor, and props rebuilt inline on every render.
• eslint-plugin-react-native-platform — platform-specific APIs called without a guard, styles that only exist on one platform, and Platform.select with keys that will never match.

• MSc Computer Science, Manchester Metropolitan University
• AWS Certified Solutions Architect
• Cyber Runway Launch 2024 — the DSIT-funded national cyber accelerator delivered by Plexal
• Volunteer mentor, Manchester Metropolitan University

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