diff --git a/src/api/routes.ts b/src/api/routes.ts
index 651dcbda64..3ca414ce50 100644
--- a/src/api/routes.ts
+++ b/src/api/routes.ts
@@ -413,6 +413,7 @@ const slopRiskSchema = z.object({
   description: z.string().max(20000).optional(),
   tests: z.array(z.string().max(400)).max(2000).optional(),
   testFiles: z.array(z.string().max(400)).max(2000).optional(),
+  commitMessages: z.array(z.string().max(2000)).max(200).optional(),
 });
 const issueSlopSchema = z.object({
   title: z.string().max(500).optional(),
diff --git a/src/mcp/server.ts b/src/mcp/server.ts
index cf77d60f82..eee8d411d0 100644
--- a/src/mcp/server.ts
+++ b/src/mcp/server.ts
@@ -650,6 +650,7 @@ const checkSlopRiskShape = {
   description: z.string().max(20000).optional(),
   tests: z.array(z.string().max(400)).max(2000).optional(),
   testFiles: z.array(z.string().max(400)).max(2000).optional(),
+  commitMessages: z.array(z.string().max(2000)).max(200).optional(),
 };
 
 const checkSlopRiskOutputSchema = {
diff --git a/src/signals/engine.ts b/src/signals/engine.ts
index c2849785c0..80aed7f29a 100644
--- a/src/signals/engine.ts
+++ b/src/signals/engine.ts
@@ -4334,7 +4334,9 @@ export type PrTextLintReport = {
   summary: string;
 };
 
-const GENERIC_COMMIT_PATTERN = /^(?:wip|fix(?:es|ed|ing)?|updat(?:e|es|ed|ing)|change[sd]?|edit[sd]?|patch|minor|tweak[sd]?|misc|cleanup|chore|stuff|temp|tmp|test|final|done|commit|asdf+|\.+)\b[\s.!]*$/i;
+// Exported so the deterministic slop signal (#564) and the #549 lint tool share ONE definition of a
+// "generic" commit subject — a single low-effort word (wip / fix / update / "." …) that is the whole subject.
+export const GENERIC_COMMIT_PATTERN = /^(?:wip|fix(?:es|ed|ing)?|updat(?:e|es|ed|ing)|change[sd]?|edit[sd]?|patch|minor|tweak[sd]?|misc|cleanup|chore|stuff|temp|tmp|test|final|done|commit|asdf+|\.+)\b[\s.!]*$/i;
 // Conventional Commit subject: one of CONTRIBUTING's allowed types, optional `(scope)`, optional `!`,
 // then `: ` and a non-empty summary (e.g. `feat(api): add cursor pagination`). Single source of truth
 // with CONTRIBUTING.md "Commit And PR Titles".
diff --git a/src/signals/slop.ts b/src/signals/slop.ts
index d2ea5b9dd0..1fbc260458 100644
--- a/src/signals/slop.ts
+++ b/src/signals/slop.ts
@@ -1,4 +1,4 @@
-import type { SignalFinding } from "./engine";
+import { GENERIC_COMMIT_PATTERN, type SignalFinding } from "./engine";
 import { isCodeFile, isTestFile } from "./local-branch";
 import { hasLocalTestEvidence, isTestPath } from "./test-evidence";
 import { isFocusManifestPublicSafe } from "./focus-manifest";
@@ -18,6 +18,8 @@ export type SlopAssessmentInput = {
   testFiles?: string[] | undefined;
   /** PR/branch description. An empty/whitespace description on a code change is a weak-effort signal. */
   description?: string | null | undefined;
+  /** The PR's commit subject line(s). A generic/empty primary subject (wip / fix / update / ".") is a weak-effort signal. */
+  commitMessages?: string[] | undefined;
 };
 
 export type SlopAssessment = {
@@ -35,6 +37,7 @@ export const SLOP_WEIGHTS = {
   missingTestEvidence: 30,
   nonSubstantivePadding: 30,
   emptyDescription: 15,
+  lowQualityCommitMessage: 15,
 } as const;
 
 export const SLOP_RUBRIC_MARKDOWN = [
@@ -50,6 +53,7 @@ export const SLOP_RUBRIC_MARKDOWN = [
   "- missing test evidence",
   "- non-substantive padding (generated / vendored / minified output as source)",
   "- empty pull request description on a code change",
+  "- generic or empty commit message",
 ].join("\n");
 
 const MIN_CHURN_LINES = 40;
@@ -64,16 +68,19 @@ export function buildSlopAssessment(input: SlopAssessmentInput): SlopAssessment
   const missingTestEvidenceFinding = buildMissingTestEvidenceFinding(input);
   const nonSubstantivePaddingFinding = buildNonSubstantivePaddingFinding(input);
   const emptyDescriptionFinding = buildEmptyDescriptionFinding(input);
+  const lowQualityCommitMessageFinding = buildLowQualityCommitMessageFinding(input);
   if (trivialChurnFinding) findings.push(trivialChurnFinding);
   if (missingTestEvidenceFinding) findings.push(missingTestEvidenceFinding);
   if (nonSubstantivePaddingFinding) findings.push(nonSubstantivePaddingFinding);
   if (emptyDescriptionFinding) findings.push(emptyDescriptionFinding);
+  if (lowQualityCommitMessageFinding) findings.push(lowQualityCommitMessageFinding);
 
   const slopRisk = clamp(
     (trivialChurnFinding ? SLOP_WEIGHTS.trivialWhitespaceChurn : 0) +
       (missingTestEvidenceFinding ? SLOP_WEIGHTS.missingTestEvidence : 0) +
       (nonSubstantivePaddingFinding ? SLOP_WEIGHTS.nonSubstantivePadding : 0) +
-      (emptyDescriptionFinding ? SLOP_WEIGHTS.emptyDescription : 0),
+      (emptyDescriptionFinding ? SLOP_WEIGHTS.emptyDescription : 0) +
+      (lowQualityCommitMessageFinding ? SLOP_WEIGHTS.lowQualityCommitMessage : 0),
     0,
     100,
   );
@@ -155,6 +162,27 @@ export function buildEmptyDescriptionFinding(input: SlopAssessmentInput): Signal
   };
 }
 
+// Fires when commit-message data is supplied and the primary subject is empty/whitespace, or is entirely a
+// generic low-effort word (wip / fix / update / "." …) per the #549 lint tool's shared GENERIC_COMMIT_PATTERN.
+// High-precision: a specific subject — even one that isn't a Conventional Commit — never trips this blocking
+// signal; only a bare generic word that IS the whole subject does. Nothing to assess (undefined / no commit
+// data) returns null. Static, public-safe detail text — no interpolation, like the issue-side findings.
+export function buildLowQualityCommitMessageFinding(input: SlopAssessmentInput): SignalFinding | null {
+  if (input.commitMessages === undefined || input.commitMessages.length === 0) return null;
+  const messages = input.commitMessages.map((message) => message.trim()).filter((message) => message.length > 0);
+  const primary = messages[0];
+  if (primary !== undefined && !GENERIC_COMMIT_PATTERN.test(primary)) return null;
+  const detail = primary === undefined ? "The commit message is empty." : "The commit message is generic (e.g. wip / fix / update) with no specific detail.";
+  return {
+    code: "low_quality_commit_message",
+    title: "Commit message is generic or empty",
+    severity: "warning",
+    detail,
+    action: "Write a specific commit subject that names what changed and why (a Conventional Commit like 'feat(api): add cursor pagination' works well).",
+    publicText: detail,
+  };
+}
+
 export function buildMissingTestEvidenceFinding(input: SlopAssessmentInput): SignalFinding | null {
   const changedFiles = input.changedFiles ?? [];
   const changedPaths = changedFiles.map((file) => file.path).filter(Boolean);
diff --git a/test/unit/slop.test.ts b/test/unit/slop.test.ts
index f595542c20..363ebe6946 100644
--- a/test/unit/slop.test.ts
+++ b/test/unit/slop.test.ts
@@ -2,6 +2,7 @@ import { describe, expect, it } from "vitest";
 import {
   buildEmptyIssueBodyFinding,
   buildIssueSlopAssessment,
+  buildLowQualityCommitMessageFinding,
   buildMissingTestEvidenceFinding,
   buildNonSubstantivePaddingFinding,
   buildSlopAssessment,
@@ -20,12 +21,35 @@ describe("buildSlopAssessment", () => {
     expect(SLOP_RUBRIC_MARKDOWN).toContain("clean");
     expect(SLOP_RUBRIC_MARKDOWN).toContain("missing test evidence");
     expect(SLOP_RUBRIC_MARKDOWN).toContain("trivial / whitespace-only churn");
+    expect(SLOP_RUBRIC_MARKDOWN).toContain("generic or empty commit message");
 
     const clean = buildSlopAssessment({});
     expect(clean).toEqual({ slopRisk: 0, band: "clean", findings: [] });
     expect(buildSlopAssessment({})).toEqual(clean);
   });
 
+  it("raises low-quality-commit-message slop for a generic primary commit subject (#564)", () => {
+    const result = buildSlopAssessment({ commitMessages: ["wip"] });
+    expect(result.slopRisk).toBe(SLOP_WEIGHTS.lowQualityCommitMessage);
+    expect(result.band).toBe("low");
+    expect(result.findings).toEqual([expect.objectContaining({ code: "low_quality_commit_message", severity: "warning" })]);
+    expect(JSON.stringify(result)).not.toMatch(FORBIDDEN_PUBLIC_TERMS);
+  });
+
+  it("does not raise commit-message slop for a specific subject or when no commit data is supplied (#564)", () => {
+    expect(buildSlopAssessment({ commitMessages: ["feat(api): add cursor pagination to labels endpoint"] }).findings).toEqual([]);
+    expect(buildSlopAssessment({ commitMessages: [] }).findings).toEqual([]);
+    expect(buildSlopAssessment({}).findings).toEqual([]);
+  });
+
+  it("flags supplied-but-all-blank commit messages as empty, and uses the first non-blank as the primary subject (#564)", () => {
+    const empty = buildLowQualityCommitMessageFinding({ commitMessages: ["   ", ""] });
+    expect(empty).toMatchObject({ code: "low_quality_commit_message" });
+    expect(empty?.detail).toMatch(/empty/i);
+    // leading blanks are skipped; the first real subject ("update") is what gets judged.
+    expect(buildLowQualityCommitMessageFinding({ commitMessages: ["", "update"] })?.detail).toMatch(/generic/i);
+  });
+
   it("raises missing-test-evidence slop for code-only diffs without tests", () => {
     const result = buildSlopAssessment({
       changedFiles: [{ path: "src/registry/sync.ts", additions: 24, deletions: 2 }],