Served-inline proxy-dedup hit-rate (served_inline) — results

Issue: #1350 · Mechanism: serve duplicate read-only tool calls inline from the vDSO (36122bc9) + proxy cache-warming (f2d1bec5) · Metric: fak_gateway_served_inline_total.

Numbers are authoritative only in ../../BENCHMARK-AUTHORITY.md. This sheet keeps its own provenance labels. The committed artifact is internal/gateway/testdata/served_inline_dedup_report.json; re-run the witness with go test ./internal/gateway -run TestServedInlineDedupMeasurement -count=1.

Headline

WITNESSED: on a redundant read pattern with read-only-shaped tool names, served-inline deduplicates 5 / 14 read-only proposals (35.7%) — and every served hit is a cross-turn re-read (W3). On the dominant Claude Code path (native Read/Grep/Glob names) the same pattern serves 0 / 14, because the read-only NAME gate does not recognize those names.

served-inline saves the EXECUTION of a duplicate/repeat read (the client tool round-trip), not the surviving call’s tokens (the honesty fence from 36122bc9).

Provenance

• The serve is WITNESSED — fak’s real adjudicateProposedServed seam served these calls in-process (the exact per-turn order messages.go drives: admitInboundResults warms the vDSO from the client’s returned tool_results, then adjudicateProposedServed probes/serves the next turn’s proposals). Not a model of what it would do.
• The trace redundancy is MODELED — a named, reproducible representative coding transcript (representative-coding-session-v1, 6 turns) embedding the three win classes + non-repeated reads + one write + one force-fresh re-read. It is not a capture of one specific real session.

Measured decomposition (eligible-name regime)

Tool names read-only-shaped (get_/read_/search_/list_/lookup_/find_/calc).

Win class	Proposed	Served	Note
cross_turn_reread (W3)	5	5	A read whose result a PRIOR turn already returned — the win the mechanism is built for.
within_turn_parallel (W1/W2)	1	0	Two identical reads in ONE turn are cold (no prior fill), so this mechanism does not dedup them.
force_fresh_declined	1	0	_fak_fresh re-read: the model opted out of the serve (escape hatch).
first_occurrence	7	0	Nothing warm to serve (expected — this is the denominator).
Total	14	5	dedup rate = 35.7%

Claude-native-name regime (the dominant path today)

Same 6-turn read pattern, tools renamed to Claude Code natives (Read/Grep/Glob/…):

Read-only proposed	Served inline	Dedup rate
14	0	0%

readOnlyPrefix matches get_/read_/search_/list_/lookup_/find_/calc (case-sensitive, underscore). Read does not start with read_, Grep/Glob match nothing — so on real Claude Code traffic no native read is ever eligible for the serve, regardless of how redundant it is.

Recommendation — should --vdso-proxy-fill default on?

No, not yet — keep it opt-in. A miss is byte-identical to today (TestServedInline_Miss), so the lever is safe to leave ON where it pays, and it delivers a real ~36% execution saving on a redundant read pattern with read-only-shaped names. But it fires zero on the dominant Claude Code path because the read-only NAME gate does not recognize Read/Grep/Glob.

Gate for default-on: first extend the serve eligibility classifier to recognize the harness’s real read-tool names (widen readOnlyPrefix / add a shape classifier for Read/Grep/Glob), OR scope default-on to MCP / snake_case tool deployments whose reads are already get_/read_/search_ shaped.

Assumptions, promotion, demotion

• Assumption (most likely to flip the result): the tool-NAMING regime. On real Claude Code traffic the read tool is Read (not read_*), so served_inline is 0 regardless of redundancy until the name gate is widened.
• Promotion: feed the SAME harness a captured real /v1/messages session (fak guard -- claude, or a tau2/SWE run) as the trace. If the real read pattern is redundant AND uses eligible tool names, the WITNESSED rate promotes the lever toward default-on.
• Demotion / retirement: if a captured real session shows near-zero cross-turn re-read, or the dominant harness keeps native Read/Grep names unrecognized, the lever is demoted to opt-in and the value claim is retired for that path.