Fix stale deepseek-v4-flash pricing and build_merge docstring

[adrianengkh]

Two independent fixes, both verified against primary sources on 2026-08-29.

1. deepseek-v4-flash pricing is stale (graphify/llm.py)

The backend is priced at $0.14 / $0.28 per 1M tokens. That is DeepSeek V3 pricing. Per the published table, deepseek-v4-flash is:

	off-peak	peak
input (cache miss)	$0.22	$0.44
output	$0.66	$1.32

So estimate_cost under-reports a v4-flash run by roughly 3x on input and 4.7x on output. On a real corpus this is the difference between a run reading as free and reading as real money.

Changed to the peak/cache-miss rates, consistent with how the other backends here are priced (undiscounted list price). Added an inline note for the peak window (01:00-04:00 and 06:00-10:00 UTC Mon-Fri, all other hours half price) and the cache-hit rate, since neither is derivable from the two numbers alone.

2. build_merge docstring promises a write it never performs (graphify/build.py)

The docstring opens with "Load existing graph.json, merge new chunks into it, and save back." The function ends at return G. graph_path is only ever read.

Following the docstring leaves the on-disk graph silently unchanged — the call succeeds, the returned graph is correct, and nothing persists. I lost a merge to this before checking the source.

The runbooks already do the right thing (build_merge → cluster → to_json), so this is a docs-only fix documenting the actual contract rather than a behaviour change — callers who already persist are unaffected.

Notes

No test asserts either value, so nothing in the suite changes. I was not able to run the full suite locally (no pytest in the environment I patched from) — happy to iterate if CI flags anything.

[graphify-labs]

Graphify reviewed this change.

Looks safe to merge — no coupling regressions and no blocking issues, checked against the code graph (not a self-assessment).

Formal verification. No changes could be formally verified in this run.

---

Graphify review — findings

Updates the DeepSeek v4-flash pricing in BACKENDS to the peak cache-miss rates ($0.44/$1.32 per 1M input/output tokens, up from $0.14/$0.28), so cost estimates now reflect worst-case pricing rather than off-peak/cache-hit rates. Also clarifies that build_merge returns the merged graph in memory without writing to disk, leaving persistence to the caller.

No blocking issues surfaced.

Analysis details — impact, health, verification

Impact & health

Graphify review

Impact — 1487 functions depend on the 252 functions this change touches.

Health — this change adds coupling hotspots:

• new: _rebuild_code() — 98 callers, 50 callees
• new: build_from_json() — 190 callers, 18 callees
• new: deduplicate_entities() — 63 callers, 21 callees
• new: build_merge() — 53 callers, 13 callees
• new: to_obsidian() — 36 callers, 13 callees
• new: extract_files_direct() — 17 callers, 20 callees
• new: to_wiki() — 41 callers, 7 callees
• new: extract_corpus_parallel() — 26 callers, 11 callees
• …and 50 more — each is listed as a finding

Verification — 1487 functions in the blast radius were not formally verified this run (proofs are advisory here).

Gate & verification

graphify gate

PASS — objectively clean (no health regressions, tests not run — proofs not run this pass (advisory)). Grounded, not self-assessed.

Advisory (not blocking):

• verification_scope: 1247 function(s) in the blast radius were not formally verified this run

Formal verification

Could not verify: Could not verify build\_merge.

The verifier did not have enough to check build\_merge, so it is saying so rather than guessing. No false assurance is the whole point.

Guarantee: No guarantee either way, this is an honest abstention, not a pass.

Note: Reason: parameter `graph_path` is annotated `str | Path | None` — outside the synthesizable primitive/collection set

· 58 more finding(s) on lines outside this diff (see the check run).

[safishamsi]

Shipped in v0.9.52 via authorship-preserving cherry-pick so you keep contributor-graph credit. Thanks @adrianengkh! Release: https://github.com/Graphify-Labs/graphify/releases/tag/v0.9.52