SDE 1

Responsibilities:

• Build and ship the conversational surface of Sonic the chat interface, how the agent presents its work, how it renders generated artefacts (campaigns, copy variants, analysis), how it handles file uploads, how it surfaces deep-research outputs, and how the user shifts between different modes of working with the agent.
• Build the setup experience for new clients: the onboarding flow that walks a marketer through connecting their existing marketing tools, granting Sonic access to their organisation's data, and configuring their workspace.
• Build the system that lets Sonic feel native to each client's brand: the configurable theming layer and design-token system that turns one shared platform into something every marketer experiences as their own.
• Contribute to the system that brings external knowledge into the agent's working memory: brand guidelines, past campaigns, design references, and copy archives so that what Sonic produces reflects each client's voice and context.
• Author RFCs (Request for Comments) end-to-end written design documents that specify the problem, alternatives considered, trade-offs, the decision, and what is explicitly not being built. Sharp enough that another engineer or an AI agent can build the right thing without you in the room.
• Maintain strong PR, commit, and branch hygiene at a sustained cadence: squashed PRs, short-lived branches, descriptive commit messages, scoped PRs ( 500 lines on average), and substantive reviews on peers' PRs.
• Build verification rigour on the systems you own: integration tests, evaluation suites for the agent surfaces you ship, and catching AI-generated regressions before they reach production.
• Instrument latency and observability for at least one critical path you own, for example, time-to-first-token for an agent flow with a dashboard the team can use to monitor it.
• Ship through AI agents. Write specifications Claude (or equivalent) can execute against, review the output critically, and ship the result. Propel engineers do not measure their value in lines of code typed.
• Collaborate closely with the designer to translate UX specifications into shipped features, and route ambiguities back rather than resolving them on your own.
• Reach into core code without breaking its schema, routing, or orchestration.
• Past evidence of doing this responsibly in a complex codebase is required.

Requirements:

• 2-4 years of total engineering experience, with at least 1 year shipping product-shaped features that integrate with LLMs, agents, or AI APIs.
• Full-stack capability, comfortable in our stack: TypeScript, Node.js, PostgreSQL with Drizzle ORM, and React.
• Strong product instinct. You think in user flows, not just functions. You know what feels finished versus half-done and push for the former.
• AI-augmented engineering as a first-class part of your loop, not an afterthought. If working through Claude (or equivalent) feels uncomfortable to you, this role is not a fit.
• Written communication strong enough to author RFCs and durable specifications that survive contact with a fresh engineer or an AI agent.
• Past evidence of reaching into core code in a complex codebase without breaking its schema, routing, or orchestration.
• Smart and curious first-principles reasoning, comfortable in ambiguity, learns the next thing fast.
• Bonus: Experience with chat UI, artefact rendering, or streaming agent responses; has shipped an OAuth / connector integration end-to-end (e. g., Notion, Slack, Mixpanel); has worked closely with a designer on a complex product surface; startup-scale experience (Seed-Series B).