Handle reconnect and cancellation

Resume after the last accepted event, not the last partial byte.

Type: Build Languages: TypeScript, Go Stage: 3 of 4 Prerequisites: Basic functions, collections, JSON and the previous stages when applicable. Time: ~2 hours

What you build

Go serves an authored SSE stream in three-byte writes and deliberately closes the first request halfway through é. TypeScript connect sends Last-Event-ID on the next request, creates a fresh decoder, preserves accepted answer state and handles AbortSignal cancellation.

Worked example

First connection accepts event 1 then ends with a truncated UTF-8 error: text Caf, status interrupted, lastID 1. Reconnect sends Last-Event-ID:1. Go emits complete event 2 onward, producing Café once, one citation and completed state.

Implement the contract

TypeScript connect(url,state,onState,signal?):Promise<Answer> bounds each connection to one MiB and marks failures interrupted. Cancel and release the response reader after malformed data, cancellation or application completion so failed streams cannot remain open. Go Encode(StreamEvent)([]byte,error), After(events,last)([]StreamEvent,error), Handler(events)http.Handler. No automatic reconnect loop is hidden; the caller chooses each connection.

Reject malformed input before producing a partial artifact. The tests include held-out records separate from the demonstration fixture.

Run your work

python3 scripts/project_test.py streaming-answer-recovery --init /tmp/streaming-answer-recovery-work
python3 scripts/project_test.py streaming-answer-recovery --stage 3 --path /tmp/streaming-answer-recovery-work --strict

Initialization copies cumulative scaffolding without replacing your work. Implement the TODO functions in the first-stage starter; later-stage starter notes describe the new behavior. Tests import the learner workspace. Run the command in the README against your own input after passing the stage.

Inspect and extend

Abort between two events. A cancelled answer must keep its draft text and must not reconnect when the user clicks resume.

Go standard library and Node standard library. All fixtures and implementations are original.