cleanup: remove unused HashSet import from 96b46cd + tighten applier gates

96b46cd ("first auto-applied commit") added `use tracing;` and
`use std::collections::HashSet;` to queryd/service.rs under a commit
message claiming to add a destructive SQL filter. HashSet was unused —
cargo check passed (warnings aren't errors) but the workspace now
carries a permanent `unused_imports` warning. `use tracing;` is
redundant but not flagged by the compiler, leave it.

This is an honest postmortem of the rationale-diff divergence problem:
emitter claimed one thing, diffed another. The cargo-green gate alone
can't catch that.

Applier hardening in this commit addresses all three failure modes:
  - new-warning gate: reject patches that keep build green but add
    warnings (baseline → post-patch diff)
  - rationale-diff token alignment heuristic: reject patches whose
    rationale shares no vocabulary with the actual new_string
  - dry-run workspace revert: COMMIT=0 was silently leaving files
    modified between runs; now reverts after each cargo check
  - prompt additions: forbid unused-symbol imports; require rationale
    vocabulary to appear in the diff

Next-iter applier runs should produce cleaner commits or none at all.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/queryd/src/service.rs

@@ -12,8 +12,6 @@ use serde::{Deserialize, Serialize};
 use crate::context::QueryEngine;
 use crate::delta;
 use crate::paged::ResultStore;
-use tracing;
-use std::collections::HashSet;
 
 #[derive(Clone)]
 pub struct QueryState {

tests/real-world/scrum_applier.ts

@@ -184,9 +184,15 @@ HARD CONSTRAINTS (violations → patch rejected):
        • function signature changes
        • new modules, new traits, new dependencies
        • any change that requires editing another file to keep it compiling
+       • adding a 'use' import whose symbol is NOT referenced in the same patch
+         or already referenced in the surrounding file (no "import and hope")
+       • rationale that describes functionality not present in the diff
+         (if rationale says "destructive SQL filter", the diff must contain SQL/filter tokens)
   7. Each "new_string" MUST compile in isolation with the same surrounding code.
   8. Max 2 patches per file — quality over quantity.
-  9. If you cannot produce at least one high-confidence mechanical patch under these constraints, output {"patches": []}. Don't guess.
+  9. The "rationale" field MUST use vocabulary that appears in the new_string.
+     Generic rationales like "improve code" or "add missing feature" are rejected.
+  10. If you cannot produce at least one high-confidence mechanical patch under these constraints, output {"patches": []}. Don't guess.
 
 ─── SOURCE (${source.length} bytes) ───
 ${source.slice(0, 14000)}
@@ -254,9 +260,13 @@ async function applyPatches(file: string, patches: Patch[]): Promise<{ applied:
   return { applied, rejected };
 }
 
-async function cargoCheck(): Promise<boolean> {
+async function cargoCheck(): Promise<{ green: boolean; warnings: number }> {
   const r = await sh(["cargo", "check", "--workspace"]);
-  return r.code === 0;
+  // Count warnings: cargo emits "warning:" lines on stderr (and sometimes stdout).
+  // We count unique "warning: <msg>" opening lines, not continuation context.
+  const combined = r.stdout + r.stderr;
+  const warnings = (combined.match(/^warning: /gm) || []).length;
+  return { green: r.code === 0, warnings };
 }
 
 async function gitCommit(file: string, patches: Patch[]): Promise<boolean> {
@@ -274,6 +284,36 @@ async function revertFile(file: string): Promise<void> {
   await sh(["git", "checkout", "--", file]);
 }
 
+// Cheap, conservative check that the rationale actually describes the
+// diff. Tokenizes the new_string (what's actually being added), drops
+// Rust keywords + common filler, and requires the rationale to share
+// at least one meaningful token. Catches rationale-diff divergence like
+// "Add destructive SQL filter" for a diff that only adds `use tracing;`.
+const STOPWORDS = new Set([
+  "use", "let", "pub", "mut", "fn", "self", "the", "a", "and", "or", "in",
+  "to", "for", "of", "on", "at", "add", "added", "adds", "new", "is",
+  "as", "if", "else", "match", "return", "crate", "mod", "struct",
+  "trait", "impl", "this", "that", "with", "from", "into", "by", "be",
+  "it", "its", "not", "one", "two", "line", "lines",
+]);
+function tokenize(s: string): Set<string> {
+  const out = new Set<string>();
+  for (const raw of s.toLowerCase().split(/[^a-z0-9_]+/)) {
+    if (raw.length >= 4 && !STOPWORDS.has(raw)) out.add(raw);
+  }
+  return out;
+}
+function rationaleMatchesDiff(p: Patch): boolean {
+  // Only check tokens introduced by the patch (what's in new but not old).
+  const newToks = tokenize(p.new_string);
+  const oldToks = tokenize(p.old_string);
+  const added = new Set([...newToks].filter((t) => !oldToks.has(t)));
+  if (added.size === 0) return true;  // pure deletion — rationale unconstrained
+  const rationaleToks = tokenize(p.rationale);
+  for (const t of added) if (rationaleToks.has(t)) return true;
+  return false;
+}
+
 async function main() {
   log(`starting · min_conf=${MIN_CONF} max_files=${MAX_FILES} model=${MODEL} commit=${COMMIT}`);
 
@@ -300,8 +340,18 @@ async function main() {
   log(`${eligible.length} pass confidence gate + deny-list`);
   log(`taking top ${Math.min(MAX_FILES, eligible.length)} by confidence`);
 
+  // Establish pre-run warning baseline so post-patch cargo check can
+  // reject patches that keep the build green but add new warnings.
+  // This gate exists because 96b46cd landed unused imports through the
+  // green-only gate — compiled fine, left a permanent dead-code warning.
+  log(`baseline cargo check (warning count)...`);
+  let baselineWarnings = (await cargoCheck()).warnings;
+  log(`baseline warnings = ${baselineWarnings}`);
+
   let committedFiles = 0;
   let revertedFiles = 0;
+  let warningReverts = 0;
+  let rationaleReverts = 0;
 
   for (const r of eligible.slice(0, MAX_FILES)) {
     log(`${r.file} (conf_avg=${r.confidence_avg} tier=${r.gradient_tier})`);
@@ -328,7 +378,7 @@ async function main() {
     }
 
     log(`  running cargo check...`);
-    const green = await cargoCheck();
+    const { green, warnings } = await cargoCheck();
     if (!green) {
       log(`  ✗ build red — reverting ${r.file}`);
       await revertFile(r.file);
@@ -337,12 +387,54 @@ async function main() {
       continue;
     }
 
-    log(`  ✓ build green`);
-    const ok = await gitCommit(r.file, patches.slice(0, applied));
-    if (ok) {
-      committedFiles++;
+    // New-warning gate. If a patch keeps the build green but adds a
+    // warning (unused import, dead_code after removed allow, etc), treat
+    // it the same as build red: revert. The cargo-green gate alone let
+    // 96b46cd land unused imports; this closes that door.
+    if (warnings > baselineWarnings) {
+      log(`  ✗ warnings ${baselineWarnings} → ${warnings} (+${warnings - baselineWarnings}) — reverting ${r.file}`);
+      await revertFile(r.file);
+      warningReverts++;
       await auditLog({
-        action: COMMIT ? "committed" : "dry_run_committed",
+        action: "warnings_increased_reverted",
+        file: r.file,
+        patches_applied: applied,
+        warnings_before: baselineWarnings,
+        warnings_after: warnings,
+      });
+      continue;
+    }
+
+    // Rationale-diff alignment heuristic. At least one non-stopword
+    // token from the applied patches' combined new_string must appear
+    // in the rationale, OR the rationale must name the file's module.
+    // This catches cases like "Add destructive SQL filter" rationale
+    // with a diff that only adds `use tracing`.
+    const applied_patches = patches.slice(0, applied);
+    const rationale_ok = applied_patches.some((p) => rationaleMatchesDiff(p));
+    if (!rationale_ok) {
+      log(`  ✗ rationale doesn't name anything in diff — reverting ${r.file}`);
+      await revertFile(r.file);
+      rationaleReverts++;
+      await auditLog({
+        action: "rationale_mismatch_reverted",
+        file: r.file,
+        patches_applied: applied,
+        rationales: applied_patches.map((p) => p.rationale),
+      });
+      continue;
+    }
+
+    log(`  ✓ build green (warnings ${warnings}/${baselineWarnings})`);
+
+    // Dry-run MUST revert the file after a successful check so the
+    // workspace doesn't accumulate unpushed changes across dry-runs.
+    // Previously this left modified files, silently polluting state.
+    if (!COMMIT) {
+      log(`  (dry-run) would commit ${r.file} — reverting workspace change`);
+      await revertFile(r.file);
+      await auditLog({
+        action: "dry_run_would_commit",
         file: r.file,
         patches_applied: applied,
         patches_rejected: rejected.length,
@@ -350,10 +442,30 @@ async function main() {
         gradient_tier: r.gradient_tier,
         reviewer_model: r.accepted_model,
       });
+      continue;
+    }
+
+    const ok = await gitCommit(r.file, applied_patches);
+    if (ok) {
+      committedFiles++;
+      // Advance the warning baseline so a later patch on a different
+      // file is compared against the new (committed) state, not the
+      // pre-run state — otherwise every subsequent patch trips the gate.
+      baselineWarnings = warnings;
+      await auditLog({
+        action: "committed",
+        file: r.file,
+        patches_applied: applied,
+        patches_rejected: rejected.length,
+        confidence_avg: r.confidence_avg,
+        gradient_tier: r.gradient_tier,
+        reviewer_model: r.accepted_model,
+        warnings_after: warnings,
+      });
     }
   }
 
-  log(`DONE · committed=${committedFiles} reverted=${revertedFiles}`);
+  log(`DONE · committed=${committedFiles} build_red=${revertedFiles} warning_revert=${warningReverts} rationale_revert=${rationaleReverts}`);
 }
 
 await main();