code-graph - ask the index, then verify

imp has a symbol and call graph in .codegraph/codegraph.db (CodeGraph v1.5.0, codegraph on PATH). It answers reverse and scope-resolving questions a text search cannot: which function calls a symbol, who reaches it transitively, what a header change touches.

Hard rules

Commands

codegraph sync                    # first
codegraph query   <name>          # where is it
codegraph callers <symbol>        # who calls it
codegraph callees <symbol>        # what it calls
codegraph node    <symbol>        # source + immediate callers/callees (on a FILE arg: prints the file, NOT dependents)
codegraph impact  <symbol>        # what a change reaches
codegraph explore "<topic>"       # symbols + call paths in one shot

ccg = ~/github.com/kekzl/cplusplus-cuda-graph/ccg: ccg enrich (CUDA launch edges + implicit destructor calls + macro-generated symbols; BROKEN, rule 4), ccg coverage (one-level: a kernel with a dead launcher still counts as covered), ccg kernels, ccg revert.

Header dependents (SQL only)

docker run --rm -v "$PWD/.codegraph:/db:ro" python:3.12-slim python -c "
import sqlite3; c = sqlite3.connect('file:/db/codegraph.db?immutable=1', uri=True)
for (p,) in c.execute(\"select n.file_path from edges e join nodes n on n.id=e.source \"
    \"where e.target='file:src/runtime/config.h' and e.kind='imports'\"): print(p)"

Re-derive the count every time (config.h importers: 48 -> 23 -> 32 -> 28 across four measurements as src/core/dispatch_policy.h and src/core/config/*.h split the surface).

Three traps, all confirmed on this repo

1. A symbol the graph lacks is answered as if it had it. gemv_q6k_q8_1 is token-pasted (IMP_DP4A_QUANT_TYPES(IMP_DEFINE_GEMV_DP4A), src/compute/gemm_dp4a.cu); the query returned dispatch_gemv_fp32 (caller of the DIFFERENT gemv_q6k_q8_1_fp32) with no nearest-match warning. Enrich materialised those 21 symbols once (gemv_q6k_q8_1 -> dispatch_dp4a_gemv, src/exec/executor_kernels.cu); any other macro level or generated header misleads the same way. Name mismatch = stop and rg.
2. "No callers found" != dead. With enrich, 99% of 423 kernels (468 by 2026-08-27) had a launcher; 74% without; the rest are reached through function-pointer struct fields. Real reachability = BFS over calls/references/instantiates from roots in tools/, tests/, src/api/. Never re-flag: src/exec/gemm_kernel_*.cu (registry table binding), src/core/logging.cpp (IMP_LOG_*), src/memory/alloc_interpose.cpp (default-OFF flag), src/quant/turboquant_fp4.cuh (device inline), destructors. Confirm with rg -n '\bname\b' src/ tools/ tests/ include/ (the residue after that grep found the two dead kernels removed in #1220).
3. codegraph node <file> prints the file, not its dependents. Use the SQL above.

Destructors

Implicit destructor calls exist only through ccg enrich (85% of ~65-71 destructors had a caller with it, 0% without). With enrich broken, codegraph callers "~PinnedBuffer" returns nothing; rg for holders instead. Destruction through a base pointer is never covered (~HostPinnedAllocator, ~HostRegistrar show no caller and are live).

What it cannot know

No preprocessor (macro-generated functions absent, template instantiations collapse to the primary), no runtime (which try_* dispatch candidate fires: src/compute/dispatch_paths.h lists candidates, src/compute/dispatch_record.h records what ran).

Pairs with codebase-audit (verify before acting) and sm120-cuda-expert (once you know the kernel).