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Engineering & Technology - Engineering

Fullstack Engineer - Companions

IC / Practitioner

Independently audited

Builds and operates the software the business runs on. Owns a defined area of the function and the outcomes it produces.

Audited package

Built, independently audited role package. Everything on this page is written for this seat.

Your Stack (Swappable)

This role works against whatever tools you already run. We list the tool categories the role operates in, never a named vendor, so you are never asked to replace a system that works.

Client experience
Conversation service
AI / LLM Platform
API & Integration (iPaaS)
Observability & Monitoring
Source and delivery

Deliverables

Design documents
Review checklists
Technical standards
Delivery and sequencing plans

Responsibilities

Design multi-turn conversation, session, message, memory, and tool state across client, backend, model, and persistence.
Implement streaming response protocols with ordering, cancellation, backpressure, reconnect, duplicate suppression, and finalization semantics.
Integrate approved models, prompts, retrieval, and tools through shared platform contracts while preserving product-specific behavior and evidence.
Build explicit tool-call validation, authorization, confirmation, idempotency, timeout, result, and compensation paths for product actions.
Control context assembly, memory read and write, retrieval count, model retries, loop depth, token use, latency, and per-turn cost.
Implement safety checks and graceful fallback around user input, model output, tool use, and high-risk or uncertain conditions.
Instrument latency to first token, stream interruption, completion, tool success, session recovery, cost, user feedback, safety events, and quality evaluation.
Create offline and online evaluation sets for multi-turn coherence, task success, refusal, recovery, hallucination, and product-specific quality.

The essence of this seat

Signature move

Replay one complete turn from user input through context assembly, model request, stream chunks, tool calls, state updates, final response, and telemetry before changing the experience

What good looks like

separates provisional stream from committed conversation state and supports deterministic reconnect

Decision rights

- - The implementation and operation of approved companion product flows across client, conversation service, streaming, session state, memory interface, model call, tool result, and telemetry

Working vocabulary

turnsessionconversation statestreamlatency to first tokenchunkcancelreconnectcontext windowretrieval

What this role does

The Fullstack Engineer - Companions is an IC individual contributor and the full-stack engineer who builds conversational companion and assistant experiences across client, session backend, model integration, tool calls, and product telemetry. The role's working domain is multi-turn conversation state, streaming response delivery, latency to first token, model and tool-call integration, memory and context control, safety fallback, evaluation, and cost-aware product behavior. The seat is accountable for a responsive and coherent companion experience that survives failures, controls context and cost, and never turns uncertain model output into an unreviewed high-impact action. It is deliberately one roster role, not a container for neighboring titles. The boundary is behavioral and operational: this seat owns conversational and model-backed product behavior with streaming, memory, tool, safety, and cost constraints; the Fullstack Engineer - Product owns general product vertical slices without this AI-interaction domain; this seat owns the cross-platform vertical slice and session or inference integration; the iOS Engineer - Companions owns the native iOS client, lifecycle, streaming UI, battery, memory, offline, and App Store depth; this seat ships the companion product experience end to end; the AI Integrations Engineer owns the shared model, provider, prompt, tool, and evaluation integration platform used by many products. What separates a strong Fullstack Engineer - Companions from a generic engineer is domain judgment under failure. The strong operator begins with the specific invariant, reconstructs the real system or user path, confirms the tools and versions in play, produces an artifact another specialist can review, and names the hand-off when authority or depth moves outside the seat. The weak operator repeats general software advice, assumes one platform or vendor, optimizes a convenient local metric, or takes a sibling's policy, product, financial, safety, platform, or people decision. The core emphasis for this package is streaming conversational user experience, latency to first token, session and memory state, model and tool-call integration from a product seat, safety and fallback in the loop, context and cost control, and multi-turn quality.

Best-fit customer

engineering teams that want consistent judgement applied to design, review, and delivery

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