thrift-cursor

/thrift (Cursor port)

Installs cost-conscious patterns in the current Cursor workspace by writing a .thrift.json config and a .cursor/rules/thrift.mdc rule that the planner respects on every turn.

Why an advisory rule instead of hooks

Cursor's automation surface is rule-based (.cursor/rules/*.mdc) — there is no PreToolUse / PostToolUse / SessionStart / SessionEnd equivalent. The Claude Code version's Phase 2 (instrument) patches .claude/settings.local.json with hook entries; on Cursor that machinery doesn't exist. The advisory rule encodes the same intent: "prefer context-mode for large outputs, suggest summarisation every N turns, recap before ending a long session." Enforcement falls to the planner reading the rule each turn.

Cursor also exposes no prompt-cache primitive, so the Claude Code Phase 4 (cache prime) is removed in this port — there is nothing to prime.

The Claude Code Phase 5 (audit) degrades from a quantified token-cost report to a textual recap, because Cursor does not surface token counts in its planner output.

Usage

node plugins/harness-thrift-cursor/bin/install.mjs /path/to/project [--force] [--dry-run]

After install, the rule is applied to every chat automatically. There is no /thrift slash command on Cursor — the workflow is chat-driven.

Flags (install)

• --force — overwrite existing .thrift.json and .cursor/rules/thrift.mdc.
• --dry-run — print what would be written; do not write.
• --ctx <path> — JSON file overriding template context defaults.

Pipeline

Phase	File	Purpose
0	phases/0-preflight.md	detect Cursor workspace + optional context-mode-cursor
1	phases/1-config.md	seed/load .thrift.json (cache section omitted)
2	phases/2-instrument-as-rule.md	write .cursor/rules/thrift.mdc (replaces hook patching)
3	phases/3-summariser.md	advisory: planner suggests a manual summarisation pass at threshold
—	(no Phase 4)	cache prime removed — Cursor exposes no cache surface
5	phases/5-audit.md	advisory: planner writes a textual recap before session end

Rules

1. Single-file rule write. Phase 2 writes (or overwrites with --force) one file: .cursor/rules/thrift.mdc. There is no append-only patcher because there is no settings file to share with other plugins.
2. No metrics collection. .thrift-state.json is not produced — Cursor's planner has no API to read tool-call counts or token usage.
3. Summariser is advisory always. Even more so than the Claude Code v1: no Notification, no auto-trigger. The rule asks the planner to suggest a summarisation pass when it detects the conversation has grown long.
4. Cache prime omitted. Phase 4 of the Claude Code skill is removed entirely. The .thrift.json schema omits the cache section to avoid implying an unimplemented feature.
5. Audit is a textual recap. Phase 5 writes docs/thrift/cursor-recap-<date>.md containing a free-form summary of what happened in the session — no token counts, no cost numbers.

Lib modules

• lib/config-loader.mjs — loadConfig(path) → {ok, config | errors, warning?}. Same contract as the Claude Code version but with the cache section removed from DEFAULTS and validation.
• lib/cost-estimator.mjs — estimate({tokensInUncached, tokensInCached, tokensOut, model}) → {actualUSD, baselineUSD, savedRatio, breakdown}. Independent copy (Option B from the decomposition spec). Documented as advisory rates — Cursor does not surface token counts at runtime so this estimator is useful only when the user pastes token counts themselves into the recap.

Templates

• templates/thrift.config.json.hbs — .thrift.json seed (no cache section).
• templates/rules/thrift.mdc.hbs — alwaysApply: true Cursor rule.
• templates/audit-report.md.hbs — recap shape (used if the user runs the planner to fill the recap from pasted numbers).

On error

• .thrift.json invalid → install reports the field errors and aborts.
• .cursor/ directory missing → install creates it.
• .cursor/rules/thrift.mdc already exists without --force → install refuses with the same message pattern as harness-floor-cursor's init.mjs.

When done

Install prints:

Thrift install summary (Cursor):
  target:       <path>
  config:       .thrift.json
  rule:         .cursor/rules/thrift.mdc
  cache prime:  omitted (Cursor has no cache surface)
  audit:        advisory recap only (no token metrics)

References

• references/porting-notes.md — Cursor-specific simplifications
• plugins/harness-thrift/skills/thrift/SKILL.md — source-of-truth Claude Code skill
• docs/superpowers/specs/2026-05-18-harness-thrift-per-platform-decomposition.md — Cursor section