# Sprint 66 Plan: Runtime Semantics Packs (Framework and Platform Awareness)

## Context

Language semantics alone are insufficient; framework/runtime behavior often drives
real compatibility. Sprint 66 adds runtime semantics packs.

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## Goals

1. Model framework-level semantics (selected high-impact runtimes)
2. Attach runtime assumptions to IR and migration dossiers
3. Improve projection quality for ecosystem-specific code
4. Add runtime-specific verification hooks

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## Steps

### Step 889: Runtime semantics pack schema (12 tests)
### Step 890: Pack loader and version manager (10 tests)
### Step 891: Runtime assumption extraction from source projects (10 tests)
### Step 892: Runtime-aware lowering extension points (10 tests)
### Step 893: Runtime-aware raising policy selectors (10 tests)
### Step 894: Runtime-specific verification plugin interface (8 tests)
### Step 895: `whetstone_get_runtime_assumptions` MCP tool (8 tests)
### Step 896: `whetstone_set_runtime_profile` MCP tool (8 tests)
### Step 897: Runtime compatibility risk report generator (8 tests)
### Step 898: Sprint 66 integration summary + regression (8 tests)

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## Compatibility Rule

- Missing runtime pack data downgrades pair confidence and requires review.