# Sprint 122 Plan: Deterministic Patching and Replay for SLM Agents

## Context

Sprint 121 established deterministic failure capture and loop scaffolding.
Sprint 122 expands the debugging substrate so low-context agents can request
root-cause clusters, assemble minimal fix context, propose constrained patches,
and archive/replay repro packets through MCP tools.

---

## Goals

1. Add deterministic cluster/context/patch MCP tools
2. Add dry-run patch application and invariant enforcement
3. Persist and replay repro packets for training/eval loops
4. Emit machine-readable debugging metrics for SLM readiness

---

## Steps

### Step 1459: Failure fixture catalog for deterministic debug benchmarks (12 tests)
### Step 1460: Patch dry-run applier and validation result model (10 tests)
### Step 1461: Patch invariant checker (scope + safety rules) (10 tests)
### Step 1462: `whetstone_cluster_failures` MCP tool (8 tests)
### Step 1463: `whetstone_assemble_fix_context` MCP tool (8 tests)
### Step 1464: `whetstone_propose_patch_for_failure` MCP tool (8 tests)
### Step 1465: `whetstone_save_repro_packet` MCP tool (8 tests)
### Step 1466: `whetstone_replay_repro_packet` MCP tool (8 tests)
### Step 1467: Debugging metrics packet (`time_to_green`, `iterations`, etc.) (8 tests)
### Step 1468: Sprint 122 integration summary + regression (8 tests)

---

## Architecture Gate

- Patch generation must be validated before apply
- Repro packets must be deterministic and portable
- MCP outputs must be machine-readable and stable
- Max 600 lines per header