thrift-gemini

/thrift (Gemini port)

Bootstraps cost-conscious patterns in the current project for the Gemini CLI. Reads .thrift.json (or seeds it), patches ~/.gemini/settings.json with BeforeTool / AfterTool / SessionStart hook arrays, and starts a Vertex cache-prime + AfterTool summariser-trigger loop.

Usage

/thrift-gemini                         # one-time setup; idempotent
/thrift-gemini summarise               # manual summariser trigger
/thrift-gemini audit                   # write audit report now
/thrift-gemini --force                 # re-seed .thrift.json

Flags

• --force — overwrite existing .thrift.json.
• --no-instrument — skip the settings.json patch (just seed config).
• --dry-run — print what would be patched; don't write.

Pipeline

Phase	File	Purpose
0	phases/0-preflight.md	detect context-mode-gemini + Gemini CLI + BeforeTool surface + Vertex tier
1	phases/1-config.md	seed/load .thrift.json + compute thresholds (incl. Vertex min-token)
2	phases/2-instrument.md	patch ~/.gemini/settings.json (append-only to hook arrays)
3	phases/3-summariser.md	summarise current window via gemini-flash (manual OR auto)
4	phases/4-cache-prime.md	Vertex context caching, ROI-gated by minTokenThreshold + tier
5	phases/5-audit.md	write end-of-session audit (Vertex rates + storage-time cost)

Rules

1. Append-only hook patches. Never modify or remove existing entries in ~/.gemini/settings.json hooks.{BeforeTool,AfterTool,SessionStart}. Use thrift- command-path sentinel for safe revert.
2. Cache prime is disabled by default. Vertex caching has a minimum token threshold — sub-threshold prime calls pay full cost and yield no cache. Enable explicitly via .thrift.json cache.enabled = true.
3. Free-tier guardrail. On cache.vertex.tier === "free" the ROI gate refuses to prime regardless of cache.enabled. Free-tier rate limits make priming counterproductive.
4. Summariser is advisory in v1. Writes summary to file + suggests /compress (Gemini's compact equivalent). v2 will be programmatic once Gemini exposes a compact API.
5. Audit always runs at SessionStart-detected new session start (Gemini has no native SessionEnd; we infer end via next SessionStart or via /thrift-gemini audit manual invocation).

Lib modules

• lib/config-loader.mjs — loadConfig(path) → {ok, config | errors, warning?}. Same shape as CC version + cache.vertex block.
• lib/cost-estimator.mjs — estimate({...}) with Vertex/Gemini rate table; cache-read + cache-write + storage-time terms.
• lib/settings-patcher.mjs — patches ~/.gemini/settings.json (nested JSON hooks.<event>[] arrays). Append-only, sentinel-revert.
• lib/vertex-cache-eval.mjs — Vertex-specific ROI gate (minTokenThreshold check + storageTime payback period + free-tier short-circuit).

On error

• .thrift.json invalid → abort with field-level errors.
• Existing hook entry conflict (same matcher + same non-thrift command) → warn + skip; continue registering the others.
• Cache prime sub-threshold → log "skipped: < "; continue.
• Cache prime fails (network, Vertex quota) → log + continue.
• Summariser model call fails → log to .thrift-state.json; user can retry.

When done (Phase 5)

Print:

Thrift audit: <duration> session, <turns> turns, $<actual> actual vs $<baseline> baseline (saved <%>).
Vertex storage spend: $<storage> ({{storageHours}}h)
Report: <output-path>

Gemini primitive map

Action	Gemini
Hook event names	BeforeTool / AfterTool / SessionStart (no SessionEnd)
Hook file	~/.gemini/settings.json (single JSON, not per-event TOML/YAML)
Compact equivalent	/compress slash command
Summariser model	gemini-flash (cheapest Gemini family)
Cache surface	Vertex context caching — min-token gated, storage-time billed
Tier check	gemini auth list (future) OR cache.vertex.tier config (v1)

References

• references/porting-notes.md — phase-by-phase deltas vs CC
• plugins/harness-thrift/skills/thrift/SKILL.md — source-of-truth
• docs/superpowers/specs/2026-05-18-harness-thrift-per-platform-decomposition.md — Gemini section