# Sprint 134 Plan: End-to-End MCP Reachability and Routing Integrity

## Context

Tools can be registered but still unreachable due to routing or context issues.
Sprint 134 verifies deterministic end-to-end MCP tool reachability.

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## Goals

1. Model full request path from client call to handler execution
2. Validate reachability for all registered tools
3. Detect routing dead-ends and shadowed handlers
4. Export deterministic reachability diagnostics

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## Steps

### Step 1579: MCP request-route graph model (10 tests)
### Step 1580: Handler binding integrity checker (10 tests)
### Step 1581: Tool reachability runner with deterministic probes (10 tests)
### Step 1582: Shadowed/duplicate handler detector model (10 tests)
### Step 1583: `whetstone_probe_tool_reachability` MCP tool (8 tests)
### Step 1584: `whetstone_get_route_integrity` MCP tool (8 tests)
### Step 1585: Route integrity gate bindings (8 tests)
### Step 1586: Reachability exception ledger model (8 tests)
### Step 1587: Route integrity report artifact (8 tests)
### Step 1588: Sprint 134 integration summary + regression (8 tests)

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## Architecture Gate

- Reachability probes must be deterministic and replayable
- Duplicate/shadow detection must include explicit route evidence
- Route diagnostics must avoid ambiguous free text
- Max 600 lines per header