Task-specific query tools use wrong cache key, always get GRAPH_NOT_CACHED

[robotson]

Bug

find_definition, find_call_sites, trace_call_chain, and trace_data_flow all fail with GRAPH_NOT_CACHED even after explore_codebase has successfully generated and cached a graph.

Root Cause

Cache key mismatch between explore_codebase and the task-specific query tools.

explore_codebase stores the graph using generateIdempotencyKey() from api-helpers.ts:

{repoName}-{pathHash}:{graphType}:{gitHash}{statusHash}
# e.g. "workspace-8af22c4:supermodel:d16bfe05a7-6a95220"

find_definition et al. look it up using getCacheKey() in each tool file:

function getCacheKey(path: string): string {
  return `cache_${path}`;
}
// e.g. "cache_/workspace"

These keys never match. The graph is in memory but the query tools can't find it.

Reproduction

1. Start the MCP server
2. Call explore_codebase with query: "summary" on a repo — succeeds, returns graph with source: "api"
3. Call explore_codebase with query: "domain_map" — succeeds, source: "cache" (graph is cached)
4. Call find_definition with path and name — fails: GRAPH_NOT_CACHED

Observed in a local mcpbr trial run against swe-bench-verified (astropy__astropy-12907). Logs available.

Impact

All four task-specific query tools are effectively broken in the current release (v0.8.0). This affects the ongoing full SWE-bench Verified run — any agent that calls explore_codebase first and then tries to use query tools will hit this error. The agent in our trial run pivoted to Grep/Read after the failure, but the query tools provided zero value.

Fix

The query tools should use generateIdempotencyKey() from api-helpers.ts instead of their local getCacheKey() function. All tools should share a single cache key generation mechanism.

Affected Files

• src/tools/find-definition.ts (lines ~192-194)
• src/tools/find-call-sites.ts (same pattern)
• src/tools/trace-call-chain.ts (same pattern)
• src/tools/trace-data-flow.ts (same pattern)

Same issue exists in mcp-task-specific-tools repo.