diff --git a/tests/runner-e2e/catalog.test.ts b/tests/runner-e2e/catalog.test.ts
index 56d3cdeb37..7c4e5620d7 100644
--- a/tests/runner-e2e/catalog.test.ts
+++ b/tests/runner-e2e/catalog.test.ts
@@ -196,6 +196,16 @@ describe("runner E2E catalog", () => {
       );
       expect(prompt).toContain("refer to it only as “the terminal marker.”");
     }
+
+    const breadthHello = openRouterBreadthTasks
+      .find((task) => task.id === "hello-complete")
+      ?.buildPrompt("nonce");
+    expect(breadthHello).toContain(
+      "Your first response action must be the paperclip_finish tool call",
+    );
+    expect(breadthHello).toContain(
+      "Do not emit any assistant text, acknowledgement, or preamble before calling it",
+    );
   });
 
   it("uses only declared secret references in generated payloads", () => {
diff --git a/tests/runner-e2e/catalog.ts b/tests/runner-e2e/catalog.ts
index 1045336f33..28c34e99c8 100644
--- a/tests/runner-e2e/catalog.ts
+++ b/tests/runner-e2e/catalog.ts
@@ -651,6 +651,7 @@ export const openRouterBreadthTasks: readonly RunnerTaskFixture[] = [
     buildPrompt: (nonce) =>
       [
         "Complete this deterministic hello task in one turn.",
+        "Your first response action must be the paperclip_finish tool call. Do not emit any assistant text, acknowledgement, or preamble before calling it.",
         `Call paperclip_finish exactly once with {reportedWorkDisposition:"done",summary:"${breadthMarker("H", nonce)}",completionClaim:{contractRevision:"1",objectiveSatisfied:true,criteria:[{criterionId:"objective",status:"satisfied",evidenceRefs:[]}],remainingWork:[]},evidence:[],verification:[]}. Wait for that tool call to succeed, then emit exactly ${breadthMarker("H", nonce)} as the complete user-facing final response. Do not write a user-facing final response before paperclip_finish succeeds, and do not call another tool.`,
         "Do not create files, plans, interactions, or additional work.",
       ].join("\n"),
diff --git a/tests/runner-e2e/run-observations.ts b/tests/runner-e2e/run-observations.ts
index 90d4312f19..74938a3ac7 100644
--- a/tests/runner-e2e/run-observations.ts
+++ b/tests/runner-e2e/run-observations.ts
@@ -15,6 +15,29 @@ export interface ObservableProviderSessionRun {
   contextSnapshot?: Record<string, unknown> | null;
 }
 
+export interface ObservableMatcherResult {
+  matcher: {
+    kind?: string;
+    expected?: unknown;
+    count?: unknown;
+  };
+  passed: boolean;
+}
+
+export interface OpenRouterHelloTerminalVarianceObservation {
+  suiteId: string;
+  profileId: string;
+  taskId: string;
+  expectedMarker: string;
+  finalRunMessage: string;
+  allAgentMessages: string;
+  semanticSummary: unknown;
+  issueStatus: string;
+  runStatuses: readonly string[];
+  matcherResults: readonly ObservableMatcherResult[];
+  invariantFailures: readonly string[];
+}
+
 export function acceptedPlanSessionResetFailures(
   provider: "codex" | "opencode" | "acpx",
   previousSessionId: string | null | undefined,
@@ -59,6 +82,66 @@ export function isNonExecutingReviewFenceRun(run: ObservableRunState) {
   );
 }
 
+function normalizeMessage(value: string) {
+  return value
+    .replace(/\r\n/g, "\n")
+    .replace(/\\_/g, "_")
+    .replace(/[ \t]+/g, " ")
+    .trim();
+}
+
+function countOccurrences(value: string, expected: string) {
+  if (!expected) return 0;
+  let count = 0;
+  let cursor = 0;
+  while (cursor <= value.length - expected.length) {
+    const index = value.indexOf(expected, cursor);
+    if (index < 0) break;
+    count += 1;
+    cursor = index + expected.length;
+  }
+  return count;
+}
+
+export function isOpenRouterDeepSeekHelloTerminalVariance(
+  observation: OpenRouterHelloTerminalVarianceObservation,
+) {
+  const marker = normalizeMessage(observation.expectedMarker);
+  const finalRunMessage = normalizeMessage(observation.finalRunMessage);
+  const allAgentMessages = normalizeMessage(observation.allAgentMessages);
+  const failedMatchers = observation.matcherResults.filter(
+    (result) => !result.passed,
+  );
+  const hasExpectedExactFailure = failedMatchers.some(
+    (result) =>
+      result.matcher.kind === "message_exact" &&
+      result.matcher.expected === observation.expectedMarker,
+  );
+  const hasExpectedOccurrenceFailure = failedMatchers.some(
+    (result) =>
+      result.matcher.kind === "message_occurrences" &&
+      result.matcher.expected === observation.expectedMarker &&
+      result.matcher.count === 1,
+  );
+
+  return (
+    observation.suiteId === "openrouter-model-breadth" &&
+    observation.profileId === "openrouter-deepseek-deepseek-v4-flash-0731" &&
+    observation.taskId === "hello-complete" &&
+    observation.issueStatus === "done" &&
+    observation.runStatuses.length === 1 &&
+    observation.runStatuses[0] === "succeeded" &&
+    observation.semanticSummary === observation.expectedMarker &&
+    finalRunMessage.length > 0 &&
+    countOccurrences(finalRunMessage, marker) === 0 &&
+    countOccurrences(allAgentMessages, marker) === 0 &&
+    observation.invariantFailures.length === 0 &&
+    failedMatchers.length === 2 &&
+    hasExpectedExactFailure &&
+    hasExpectedOccurrenceFailure
+  );
+}
+
 export function isControlPlaneGovernedResponseWait(
   events: readonly ObservableRunEvent[],
 ) {
diff --git a/tests/runner-e2e/runner.spec.ts b/tests/runner-e2e/runner.spec.ts
index 6386b864f7..d85ca19939 100644
--- a/tests/runner-e2e/runner.spec.ts
+++ b/tests/runner-e2e/runner.spec.ts
@@ -13,6 +13,7 @@ import {
   acceptedPlanSessionResetFailures,
   isControlPlaneGovernedResponseWait,
   isNonExecutingReviewFenceRun,
+  isOpenRouterDeepSeekHelloTerminalVariance,
   numberedPlanStepCount,
   providerSessionContinuityFailures,
 } from "./run-observations.js";
@@ -1646,6 +1647,29 @@ for (const execution of executions) {
         secrets,
       );
 
+      if (
+        exactMessageMatcher?.kind === "message_exact" &&
+        isOpenRouterDeepSeekHelloTerminalVariance({
+          suiteId: execution.suite.id,
+          profileId: execution.profile.id,
+          taskId: execution.task.id,
+          expectedMarker: exactMessageMatcher.expected,
+          finalRunMessage,
+          allAgentMessages: message,
+          semanticSummary: record(finalRun.resultJson).summary,
+          issueStatus: issue.status,
+          runStatuses: selectedRuns.map((candidate) => candidate.status),
+          matcherResults,
+          invariantFailures,
+        })
+      ) {
+        // DeepSeek can occasionally complete the semantic finish correctly but
+        // expose its pre-tool acknowledgement as the visible final answer. Keep
+        // exact persisted-message, global occurrence, and DOM checks strict,
+        // while allowing one fresh-harness retry only for the zero-marker form.
+        failureClassOverride = "provider_variance";
+      }
+
       // The backend polling above can observe a terminal transition before a
       // websocket invalidation reaches the already-open task page. Reload the
       // canonical task route so the screenshot and UI assertions prove the
diff --git a/tests/runner-e2e/support.test.ts b/tests/runner-e2e/support.test.ts
index f1fe348abf..c40b6a605d 100644
--- a/tests/runner-e2e/support.test.ts
+++ b/tests/runner-e2e/support.test.ts
@@ -36,6 +36,7 @@ import {
   acceptedPlanSessionResetFailures,
   isControlPlaneGovernedResponseWait,
   isNonExecutingReviewFenceRun,
+  isOpenRouterDeepSeekHelloTerminalVariance,
   numberedPlanStepCount,
   providerSessionContinuityFailures,
 } from "./run-observations.js";
@@ -336,6 +337,71 @@ describe("runner E2E matchers", () => {
 });
 
 describe("runner E2E run observations", () => {
+  it("retries only the zero-marker DeepSeek hello terminal emission variance", () => {
+    const expectedMarker = "PC_H_nonce-1";
+    const observation = {
+      suiteId: "openrouter-model-breadth",
+      profileId: "openrouter-deepseek-deepseek-v4-flash-0731",
+      taskId: "hello-complete",
+      expectedMarker,
+      finalRunMessage:
+        "I'll complete this deterministic hello task by calling paperclip_finish once.",
+      allAgentMessages:
+        "I'll complete this deterministic hello task by calling paperclip_finish once.",
+      semanticSummary: expectedMarker,
+      issueStatus: "done",
+      runStatuses: ["succeeded"],
+      matcherResults: [
+        {
+          matcher: { kind: "message_exact", expected: expectedMarker },
+          passed: false,
+        },
+        {
+          matcher: {
+            kind: "message_occurrences",
+            expected: expectedMarker,
+            count: 1,
+          },
+          passed: false,
+        },
+        { matcher: { kind: "issue_status", expected: "done" }, passed: true },
+      ],
+      invariantFailures: [],
+    };
+
+    expect(isOpenRouterDeepSeekHelloTerminalVariance(observation)).toBe(true);
+    expect(
+      isOpenRouterDeepSeekHelloTerminalVariance({
+        ...observation,
+        allAgentMessages: `${expectedMarker}\n${expectedMarker}`,
+      }),
+    ).toBe(false);
+    expect(
+      isOpenRouterDeepSeekHelloTerminalVariance({
+        ...observation,
+        semanticSummary: "different-summary",
+      }),
+    ).toBe(false);
+    expect(
+      isOpenRouterDeepSeekHelloTerminalVariance({
+        ...observation,
+        invariantFailures: ["missing native terminal event"],
+      }),
+    ).toBe(false);
+    expect(
+      isOpenRouterDeepSeekHelloTerminalVariance({
+        ...observation,
+        matcherResults: [
+          ...observation.matcherResults,
+          {
+            matcher: { kind: "environment", expected: "local" },
+            passed: false,
+          },
+        ],
+      }),
+    ).toBe(false);
+  });
+
   it("counts provider-equivalent numbered Plan step formats", () => {
     expect(numberedPlanStepCount("1. First\n2) Second")).toBe(2);
     expect(