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 fix bugs upstream in packages the JavaScript ecosystem depends on. Most I found myself, by reading the source or by differential testing against a reference, and verified on generated inputs before opening. Where the diagnosis was someone else's, the entry says so.

magic-string (~733M downloads/month, the source-editing layer inside Vite and Rollup)

• #326: overlapping move() calls made the chunk list a cycle, so the next toString() hung forever. Shipped in 1.2.1.
• #331: a new hasChanged() reported changes on unchanged strings after a multi-chunk overwrite. 775 of 20,880 generated cases wrong before, 0 after. Fixed before the regression reached a release, 1.2.2.
• #335: replaceAll with a regexp that can match the empty string (/^/gm, /\b/g) looped until out of memory. Shipped in 1.2.3.
• #340, #342: $ patterns and replacer arguments now match String.prototype.replace. Before, $1 for an unmatched group wrote the text undefined into the output. 32,902 of 136,000 comparisons differed before, 0 after. Shipped in 1.3.1.
• #343: indent() ignored appended and prepended text, so code after an inserted newline lost its indent. 10,920 of 19,410 cases wrong before, 0 after. Shipped in 1.3.1.
• #361: update() over several chunks dropped inserts kept by contentOnly. Shipped in 1.4.3.
• #366, #367: replace matched inside removed and overwritten text at chunk boundaries. 17,070 of 19,761 exhaustive cases wrong before, 0 after. Shipped in 1.4.4.

postcss-selector-parser (~518M downloads/month)

• #330: unclosed [, ( and a trailing | threw a raw TypeError. Shipped in 7.1.5.
• #337: lossless mode dropped whitespace when a selector ended empty. Shipped in 7.1.7.
• #335: attribute selectors with no valid name threw, or wrote undefined into the CSS. Checked against 43,200 generated selectors. Shipped in 7.2.0.
• #336: $ was dropped from interpolated attribute names such as Sass [#{$attr}]. Shipped in 7.2.0.

Others

• recast#1438 (~144M/month): a comment before a closing parenthesis made the printer add a second pair, breaking print(parse(src)) === src. 2,540 of 5,076 generated inputs fixed, 0 regressions. Shipped in 0.23.20.
• knip#1960 (~50M/month): defineConfig on its own ./config entrypoint, so config files skip the index module's side effects. The entrypoint design came from a commenter on the issue. Shipped in 6.33.0.
• TanStack Query#11360: in solid-query v6, removeQueries() was undone by the hook's own removal event, which rebuilt the entry and refetched it. Matched the react adapter field by field as the reference. Reproduction and bisection were the reporter's. Shipped in 6.0.0-rc.4, a release candidate; the stable 5.x line was never affected.
• hast-util-from-parse5#16: crash on template inside SVG or MathML. The maintainer landed his own version of the fix, crediting me as a co-author, in 8.0.4.
• corsair#111: improved the Telegram integration.

• stacktrace-parser@dea87ba (~73M/month): quadratic regex backtracking on leading whitespace in err.stack, 3.3 s at 30,000 spaces down to 0.3 ms. Landed as a direct commit, so the PR reads as closed. npm latest is still 0.1.11.
• recast#1442: printing ?? with a || or && operand gave a SyntaxError. recast#1441: a hardcoded ecmaVersion: 6 made the README's own acorn setup reject modern syntax. Both on master after 0.24.0.
• eslint-plugin-import@7828a5f (~215M/month): no-cycle crashed the whole lint run on a file path that does not resolve, such as an unsaved buffer. Landed as a direct commit, after 2.32.0.

• magic-string #384, #385, #386: an empty-string replace, update() after move() deleting text, and Bundle#indent after an empty source. #384 fixes a regression from my own #366, found by my differential tester twincheck.
• TanStack Router (~82M/month): #8218 hydration mismatch in useCanGoBack, #8220 server-function form posts returning a 500, bisected to #5517, #8221 a static cache miss parsing the HTML shell as JSON, #8830 a reload that overrode navigation when the browser cancelled a lazy chunk during unload.
• Storybook (~83M/month): #36146 sidebar ids for punctuation-only folder names, fuzzed over 16,656 pairs to show no existing URL changes, #36145 the refs type missing sourceUrl.
• flash-list#2444: fix and deterministic test for a P1 diagnosed by the reporter. shadcn/ui#11463: the prefix transform stripped quotes inside class values; 1,435 registry components checked, 0 regressions. expo#48960: a lint rule for secrets in EXPO_PUBLIC_ variables. Also xml-js#224 and eslint-plugin-react-native#342.

• ReScience C, submission #113: reviewed a C++ replication of a sedimentation-driven suspension flow model for reproducibility and code clarity. Builds were warning-free and output byte-identical; the calibration recovered the article's six fitted values. Thirteen comments on packaging, since addressed by the author.

• llm-guard: validating and securing LLM prompts in TypeScript.
• bedrock-ui-stream: AWS Bedrock Agent Runtime streams to the Vercel AI SDK UI protocol, handling split multi-byte characters, partial tool calls and redaction on errors.
• react-native-virtual-list: keeps scroll position when item heights are only known after render, using Fenwick-tree offsets. Aimed at react-native-web.
• React Native lint rules: rn-security (WebView config, AsyncStorage credentials, cleartext endpoints, deep links), performance (nested lists, keyExtractor, inline props) and platform (unguarded platform APIs and styles).

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

TypeScript · JavaScript · React · Next.js · Node.js · AWS · PostgreSQL · Docker · Terraform

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