diff --git a/src/api/routes.ts b/src/api/routes.ts
index 7ff51ed8d5..c9ed0e7c2f 100644
--- a/src/api/routes.ts
+++ b/src/api/routes.ts
@@ -159,6 +159,7 @@ import { loadOrComputeIssueQualityResponse } from "../services/issue-quality";
 import { loadOrComputeBurdenForecastResponse } from "../services/burden-forecast";
 import { buildUnavailableQueueTrendReport } from "../services/queue-trends";
 import { loadOrComputeRepoOutcomePatternsResponse } from "../services/repo-outcome-patterns";
+import { PREFLIGHT_LIMITS } from "../signals/preflight-limits";
 import {
   buildBountyAdvisory,
   buildBurdenForecast,
@@ -306,21 +307,21 @@ const PR_VISIBILITY_SKIP_REASONS = [
 ] as const satisfies readonly PublicSurfaceSkipReason[];
 
 const preflightSchema = z.object({
-  repoFullName: z.string().min(3),
-  contributorLogin: z.string().min(1).optional(),
-  title: z.string().min(1),
-  body: z.string().optional(),
-  labels: z.array(z.string()).optional(),
-  changedFiles: z.array(z.string()).optional(),
-  linkedIssues: z.array(z.number().int().positive()).optional(),
-  tests: z.array(z.string()).optional(),
-  authorAssociation: z.string().optional(),
+  repoFullName: z.string().min(3).max(PREFLIGHT_LIMITS.repoFullNameChars),
+  contributorLogin: z.string().min(1).max(PREFLIGHT_LIMITS.contributorLoginChars).optional(),
+  title: z.string().min(1).max(PREFLIGHT_LIMITS.titleChars),
+  body: z.string().max(PREFLIGHT_LIMITS.bodyChars).optional(),
+  labels: z.array(z.string().max(PREFLIGHT_LIMITS.labelChars)).max(PREFLIGHT_LIMITS.labels).optional(),
+  changedFiles: z.array(z.string().max(PREFLIGHT_LIMITS.changedFileChars)).max(PREFLIGHT_LIMITS.changedFiles).optional(),
+  linkedIssues: z.array(z.number().int().positive()).max(PREFLIGHT_LIMITS.linkedIssues).optional(),
+  tests: z.array(z.string().max(PREFLIGHT_LIMITS.testChars)).max(PREFLIGHT_LIMITS.tests).optional(),
+  authorAssociation: z.string().max(PREFLIGHT_LIMITS.authorAssociationChars).optional(),
 });
 
 const localDiffPreflightSchema = preflightSchema.extend({
   changedLineCount: z.number().int().min(0).optional(),
-  testFiles: z.array(z.string()).optional(),
-  commitMessage: z.string().optional(),
+  testFiles: z.array(z.string().max(PREFLIGHT_LIMITS.changedFileChars)).max(PREFLIGHT_LIMITS.changedFiles).optional(),
+  commitMessage: z.string().max(PREFLIGHT_LIMITS.bodyChars).optional(),
 });
 
 const skippedPrAuditQuerySchema = z
diff --git a/src/mcp/server.ts b/src/mcp/server.ts
index d019990199..7c8f1d47c2 100644
--- a/src/mcp/server.ts
+++ b/src/mcp/server.ts
@@ -76,6 +76,7 @@ import { buildContributorOpenPrMonitor } from "../signals/contributor-open-pr-mo
 import { buildLocalBranchAnalysis, findCurrentBranchPullRequest } from "../signals/local-branch";
 import { loadRepoFocusManifest } from "../signals/focus-manifest-loader";
 import { buildRepoDataQuality } from "../signals/data-quality";
+import { PREFLIGHT_LIMITS } from "../signals/preflight-limits";
 import { loadUpstreamStatus } from "../upstream/ruleset";
 
 type AppContext = Context<{ Bindings: Env }>;
@@ -111,22 +112,22 @@ const bountyShape = {
 };
 
 const preflightShape = {
-  repoFullName: z.string().min(3),
-  contributorLogin: z.string().min(1).optional(),
-  title: z.string().min(1),
-  body: z.string().optional(),
-  labels: z.array(z.string()).optional(),
-  changedFiles: z.array(z.string()).optional(),
-  linkedIssues: z.array(z.number().int().positive()).optional(),
-  tests: z.array(z.string()).optional(),
-  authorAssociation: z.string().optional(),
+  repoFullName: z.string().min(3).max(PREFLIGHT_LIMITS.repoFullNameChars),
+  contributorLogin: z.string().min(1).max(PREFLIGHT_LIMITS.contributorLoginChars).optional(),
+  title: z.string().min(1).max(PREFLIGHT_LIMITS.titleChars),
+  body: z.string().max(PREFLIGHT_LIMITS.bodyChars).optional(),
+  labels: z.array(z.string().max(PREFLIGHT_LIMITS.labelChars)).max(PREFLIGHT_LIMITS.labels).optional(),
+  changedFiles: z.array(z.string().max(PREFLIGHT_LIMITS.changedFileChars)).max(PREFLIGHT_LIMITS.changedFiles).optional(),
+  linkedIssues: z.array(z.number().int().positive()).max(PREFLIGHT_LIMITS.linkedIssues).optional(),
+  tests: z.array(z.string().max(PREFLIGHT_LIMITS.testChars)).max(PREFLIGHT_LIMITS.tests).optional(),
+  authorAssociation: z.string().max(PREFLIGHT_LIMITS.authorAssociationChars).optional(),
 };
 
 const localDiffPreflightShape = {
   ...preflightShape,
   changedLineCount: z.number().int().min(0).optional(),
-  testFiles: z.array(z.string()).optional(),
-  commitMessage: z.string().optional(),
+  testFiles: z.array(z.string().max(PREFLIGHT_LIMITS.changedFileChars)).max(PREFLIGHT_LIMITS.changedFiles).optional(),
+  commitMessage: z.string().max(PREFLIGHT_LIMITS.bodyChars).optional(),
 };
 
 const branchEligibilityShape = {
diff --git a/src/signals/engine.ts b/src/signals/engine.ts
index c4a63865bb..6ae6662baa 100644
--- a/src/signals/engine.ts
+++ b/src/signals/engine.ts
@@ -23,6 +23,7 @@ import type { PublicContributorProfile } from "../github/public";
 import type { GittensorContributorSnapshot } from "../gittensor/api";
 import { nowIso } from "../utils/json";
 import { hasLocalTestEvidence } from "./test-evidence";
+import { PREFLIGHT_LIMITS } from "./preflight-limits";
 
 export type ParticipationLane = "direct_pr" | "issue_discovery" | "split" | "inactive" | "unknown";
 export type SignalFinding = AdvisoryFinding;
@@ -823,7 +824,7 @@ export function buildCollisionReport(
   /* v8 ignore stop */
 
   const clusterList = [...clusters.values()].sort((left, right) => riskRank(right.risk) - riskRank(left.risk));
-  return {
+  const report = {
     repoFullName,
     generatedAt: nowIso(),
     summary: {
@@ -833,6 +834,8 @@ export function buildCollisionReport(
     },
     clusters: clusterList,
   };
+  collisionReportTermCache.set(report, itemTerms);
+  return report;
 }
 
 export function buildQueueHealth(
@@ -2343,7 +2346,9 @@ export function buildPreflightResult(
   issueQuality?: IssueQualityReport | null | undefined,
 ): PreflightResult {
   const lane = buildLaneAdvice(repo, input.repoFullName);
-  const linkedIssues = [...new Set([...(input.linkedIssues ?? []), ...extractLinkedIssueNumbers(input.body ?? "")])].sort((left, right) => left - right);
+  const linkedIssues = [...new Set([...(input.linkedIssues ?? []), ...extractLinkedIssueNumbers(truncateText(input.body ?? "", PREFLIGHT_LIMITS.bodyChars))])].sort(
+    (left, right) => left - right,
+  );
   // Flag an existing open-work cluster as a possible duplicate when it shares a
   // linked issue, OR when its title/body meaningfully overlaps the planned
   // contribution. The previous check used `item.title.includes(input.title)`,
@@ -2354,12 +2359,14 @@ export function buildPreflightResult(
   // symmetric term-overlap heuristic `buildCollisionReport` uses between items
   // (>=2 shared meaningful terms), which is direction-independent.
   const plannedTerms = plannedContributionTerms(input);
-  const collisions = buildCollisionReport(input.repoFullName, issues, pullRequests).clusters.filter((cluster) =>
+  const collisionReport = buildCollisionReport(input.repoFullName, issues, pullRequests);
+  const itemTerms = collisionReportTermCache.get(collisionReport) ?? new Map<string, CollisionTerms>();
+  const collisions = collisionReport.clusters.filter((cluster) =>
     cluster.items.some((item) => {
       if (linkedIssues.includes(item.number)) {
         return true;
       }
-      const overlap = termOverlap(plannedTerms, collisionTerms(item));
+      const overlap = termOverlap(plannedTerms, itemTerms.get(itemKey(item)) ?? collisionTerms(item));
       return overlap.shared >= 2 && overlap.score >= 0.5;
     }),
   );
@@ -4067,6 +4074,8 @@ type CollisionTerms = {
   size: number;
 };
 
+const collisionReportTermCache = new WeakMap<CollisionReport, Map<string, CollisionTerms>>();
+
 function collisionTerms(item: CollisionItem): CollisionTerms {
   const terms = new Set(tokenize(collisionItemText(item)));
   return { terms, size: terms.size };
@@ -4079,7 +4088,15 @@ function collisionTerms(item: CollisionItem): CollisionTerms {
  * uses between items, rather than a one-direction substring test.
  */
 function plannedContributionTerms(input: PreflightInput): CollisionTerms {
-  const terms = new Set(tokenize([input.title, ...(input.labels ?? []), ...(input.changedFiles ?? [])].join(" ")));
+  const terms = new Set(
+    tokenize(
+      [
+        truncateText(input.title, PREFLIGHT_LIMITS.titleChars),
+        ...boundedTextItems(input.labels, PREFLIGHT_LIMITS.labels, PREFLIGHT_LIMITS.labelChars),
+        ...boundedTextItems(input.changedFiles, PREFLIGHT_LIMITS.changedFiles, PREFLIGHT_LIMITS.changedFileChars),
+      ].join(" "),
+    ),
+  );
   return { terms, size: terms.size };
 }
 
@@ -4094,7 +4111,21 @@ function termOverlap(left: CollisionTerms, right: CollisionTerms): { score: numb
 }
 
 function collisionItemText(item: CollisionItem): string {
-  return [item.title, ...(item.labels ?? []), ...(item.changedFiles ?? [])].filter(Boolean).join(" ");
+  return [
+    truncateText(item.title, PREFLIGHT_LIMITS.titleChars),
+    ...boundedTextItems(item.labels, PREFLIGHT_LIMITS.labels, PREFLIGHT_LIMITS.labelChars),
+    ...boundedTextItems(item.changedFiles, PREFLIGHT_LIMITS.changedFiles, PREFLIGHT_LIMITS.changedFileChars),
+  ]
+    .filter(Boolean)
+    .join(" ");
+}
+
+function boundedTextItems(values: string[] | undefined, maxItems: number, maxChars: number): string[] {
+  return (values ?? []).slice(0, maxItems).map((value) => truncateText(value, maxChars));
+}
+
+function truncateText(value: string, maxChars: number): string {
+  return value.length > maxChars ? value.slice(0, maxChars) : value;
 }
 
 function tokenize(value: string): string[] {
diff --git a/src/signals/preflight-limits.ts b/src/signals/preflight-limits.ts
new file mode 100644
index 0000000000..dfefd36faf
--- /dev/null
+++ b/src/signals/preflight-limits.ts
@@ -0,0 +1,14 @@
+export const PREFLIGHT_LIMITS = {
+  repoFullNameChars: 200,
+  contributorLoginChars: 100,
+  titleChars: 300,
+  bodyChars: 20_000,
+  labelChars: 100,
+  changedFileChars: 300,
+  testChars: 300,
+  authorAssociationChars: 100,
+  labels: 50,
+  changedFiles: 200,
+  linkedIssues: 100,
+  tests: 50,
+} as const;
diff --git a/test/unit/signals-coverage.test.ts b/test/unit/signals-coverage.test.ts
index d479d63f19..d6748e26ff 100644
--- a/test/unit/signals-coverage.test.ts
+++ b/test/unit/signals-coverage.test.ts
@@ -34,6 +34,7 @@ import {
   buildPullRequestReviewability,
   buildRepoRewardRisk,
 } from "../../src/signals/reward-risk";
+import { PREFLIGHT_LIMITS } from "../../src/signals/preflight-limits";
 import type { GittensorContributorSnapshot } from "../../src/gittensor/api";
 import type {
   ContributorRepoStatRecord,
@@ -604,6 +605,35 @@ describe("signal coverage edge cases", () => {
     expect(preflight.findings.map((finding) => finding.code)).not.toContain("possible_duplicate_work");
   });
 
+  it("bounds preflight body scanning for linked issue extraction", () => {
+    const directRepo = repo("owner/direct");
+    const linkedInsideLimit = buildPreflightResult(
+      {
+        repoFullName: directRepo.fullName,
+        title: "Bounded body scan",
+        body: `Fixes #99 ${"x".repeat(PREFLIGHT_LIMITS.bodyChars + 100)}`,
+        linkedIssues: [],
+      },
+      directRepo,
+      [],
+      [],
+    );
+    const linkedPastLimit = buildPreflightResult(
+      {
+        repoFullName: directRepo.fullName,
+        title: "Bounded body scan",
+        body: `${"x".repeat(PREFLIGHT_LIMITS.bodyChars)} Fixes #100`,
+        linkedIssues: [],
+      },
+      directRepo,
+      [],
+      [],
+    );
+
+    expect(linkedInsideLimit.linkedIssues).toContain(99);
+    expect(linkedPastLimit.linkedIssues).not.toContain(100);
+  });
+
   it("sanitizes public PR comments and supports minimal public signal level", () => {
     const directRepo = repo("owner/direct");
     const prRecord = pr(directRepo.fullName, 55, "Fix cache", { authorLogin: "miner", linkedIssues: [] });