# 13 — Harden failure, cancellation, and restart semantics

Status: ready-for-agent

## Mandatory fresh-session context

- Read [RALPH-CONTEXT.md](../RALPH-CONTEXT.md) completely before changing code.
- This issue is `DGR-013` in [prd.json](../prd.json).
- Read the evidence README for every dependency listed below.
- Inspect current code and `git status`; historical text and previous agent claims are not evidence.

## Description

As a client, I need failures to be bounded and explicit so that distributed speed does not come with hanging or corrupted generations.

## Expected durable outputs

- Failure/cancel/restart test matrix
- Resource cleanup and billing-state evidence
- evidence/DGR-013/README.md

## Acceptance criteria

- [ ] Deadlines and heartbeat/health loss terminate blocked stream operations.
- [ ] Cancellation propagates across every Shard and releases local KV and queued buffers.
- [ ] Duplicate steps are idempotent; uncertain mutations are never replayed silently.
- [ ] Alpha failover restarts from token zero on a newly compatible route rather than importing unverified KV.
- [ ] Worker death, stream reset, malformed bundle, stale epoch, and cache miss tests pass.
- [ ] Billing/work records distinguish completed, cancelled, failed, and unverified work.
- [ ] Targeted pytest tests pass
- [ ] python -m compileall packages tests passes for Python changes
- [ ] git diff --check passes
- [ ] Default tests remain deterministic, model-download-free, API-credit-free, and GPU-free
- [ ] Full deterministic pytest -q passes, or the exact pre-existing unrelated failure is recorded with a clean-tree reproduction
- [ ] Pinned native C++ target builds and focused CTest/protocol tests pass where native code is touched
- [ ] llama.cpp patch stack applies cleanly to the exact pinned commit where patch code is touched
- [ ] Read .scratch/distributed-gguf-runtime/RALPH-CONTEXT.md and this story issue completely before changing code
- [ ] Read and verify every dependency evidence README before relying on dependency behavior
- [ ] Preserve all pre-existing working-tree changes and stage only files belonging to this story
- [ ] Write .scratch/distributed-gguf-runtime/evidence/DGR-013/README.md with files changed, exact commands and real results, limitations, compatibility notes, and dependent-story handoff
- [ ] Update only this story issue to Status: done after every acceptance criterion and quality gate passes

## Dependency handoff

- `DGR-008` must have `passes: true`; read `../evidence/DGR-008/README.md` and verify its referenced files/commands.
- `DGR-009` must have `passes: true`; read `../evidence/DGR-009/README.md` and verify its referenced files/commands.
- DGR-012 continuous batching is post-alpha; this story must harden single-session failure/cancellation first and later extend the same invariants to batched sessions.

## Finish contract

- Create the task evidence directory and durable handoff required above.
- Preserve real failures and blockers; never fabricate benchmark, model, test or hardware output.
- Change this issue to `Status: done` only after all criteria pass.
- Emit `<promise>COMPLETE</promise>` only after the evidence handoff exists.

## References

- [Ralph execution context](../RALPH-CONTEXT.md)
- [PRD](../PRD.md)
- [Implementation strategy](../implementation-strategy.md)
- [Current architecture](../architecture.md)
- [Architecture decision](../ADR-0020-distributed-gguf-runtime.md)
