feat(FN-4333): emergency hot-fix for post-merge audit blocks

Stop the post-merge audit from parking tasks as `failed` when deterministic
merge verification already proved the merged tree. Adds `postMergeAuditMode`
project setting (`block` | `warn` | `off`, default `block`) and a
verified-tree short-circuit for rebase-strategy overlap-only findings.

- packages/engine/src/merger.ts: new `resolvePostMergeAuditAction` helper
  + audit call site gated on `postMergeAuditMode` and verification-cache
  lookup. Rebase + overlap-only + verified-tree → pass through with a
  short-circuit log entry instead of throwing SquashAuditError.
- packages/core/src/types.ts, settings-schema.ts, index.ts: new
  `PostMergeAuditMode` type, `postMergeAuditMode` field on Settings,
  default `block`, exports `normalizePostMergeAuditMode`.
- packages/engine/src/__tests__/post-merge-audit-action.test.ts: unit
  tests for the decision helper.
- packages/dashboard/app/components/SettingsModal.tsx: settings UI row.
- .changeset: minor bump for @runfusion/fusion.

The FN-3936 silent-drop guard is preserved: duplicate-subject findings
still block in `block` mode and squash-strategy audits still block
(no equivalent deterministic guarantee).

Fusion-Task-Id: FN-4333

.changeset/fn-4333-post-merge-audit-hotfix.md

@@ -0,0 +1,11 @@
+---
+"@runfusion/fusion": minor
+---
+
+Stop the post-merge audit from parking tasks as `failed` when deterministic merge verification already proved the resulting tree. Adds `postMergeAuditMode` project setting (`"block"` | `"warn"` | `"off"`, default `"block"`):
+
+- A `rebase`-strategy audit that flags only touched-file overlap risks now passes through when the merged tree has a verification cache hit — silent drops are impossible by construction in that case.
+- `warn` mode logs audit findings on the agent log but auto-completes the merge.
+- `off` skips the audit entirely.
+
+Duplicate-subject findings still block in `block` mode and squash-strategy audits still block (no equivalent deterministic guarantee). The FN-3936 silent-drop guard is preserved.

packages/core/src/index.ts

@@ -1,5 +1,5 @@
-export { COLUMNS, DEFAULT_COLUMN, isColumn, normalizeColumn, COLUMN_LABELS, COLUMN_DESCRIPTIONS, VALID_TRANSITIONS, DEFAULT_SETTINGS, DEFAULT_GLOBAL_SETTINGS, DEFAULT_PROJECT_SETTINGS, GLOBAL_SETTINGS_KEYS, PROJECT_SETTINGS_KEYS, isGlobalSettingsKey, isProjectSettingsKey, resolvePersistAgentThinkingLog, THINKING_LEVELS, THEME_MODES, COLOR_THEMES, WORKFLOW_STEP_TEMPLATES, AGENT_PERMISSIONS, PERMANENT_AGENT_ACTION_CATEGORIES, AGENT_PERMISSION_POLICY_ACTION_CATEGORIES, AGENT_PROVISIONING_APPROVAL_MODES, AGENT_PERMISSION_POLICY_PRESET_IDS, LEGACY_AGENT_PERMISSION_POLICY_ACTION_CATEGORY_ALIASES, APPROVAL_REQUEST_STATUSES, APPROVAL_REQUEST_AUDIT_EVENT_TYPES, normalizeApprovalRequestActionCategory, isValidApprovalRequestTransition, agentToConfigSnapshot, diffConfigSnapshots, isEphemeralAgent, hasAgentIdentity, CheckoutConflictError, DEFAULT_HEARTBEAT_PROCEDURE_PATH, getDefaultHeartbeatProcedurePath, EXECUTION_MODES, DEFAULT_EXECUTION_MODE, TASK_PRIORITIES, DEFAULT_TASK_PRIORITY, HIGH_FANOUT_BLOCKER_TODO_THRESHOLD, STALE_HIGH_FANOUT_BLOCKER_AGE_THRESHOLD_MS, DASHBOARD_USER_ID, normalizeMessageParticipant, validateMessageMetadata, validateDockerNodeConfig, sanitizeDockerNodeConfigForResponse, normalizeMergeConflictStrategy, normalizeMergeStrategyOverlapBehavior, buildResearchDocumentKey, REPO_OVERRIDE_RE, SHARED_STATE_SNAPSHOT_VERSION } from "./types.js";
+export { COLUMNS, DEFAULT_COLUMN, isColumn, normalizeColumn, COLUMN_LABELS, COLUMN_DESCRIPTIONS, VALID_TRANSITIONS, DEFAULT_SETTINGS, DEFAULT_GLOBAL_SETTINGS, DEFAULT_PROJECT_SETTINGS, GLOBAL_SETTINGS_KEYS, PROJECT_SETTINGS_KEYS, isGlobalSettingsKey, isProjectSettingsKey, resolvePersistAgentThinkingLog, THINKING_LEVELS, THEME_MODES, COLOR_THEMES, WORKFLOW_STEP_TEMPLATES, AGENT_PERMISSIONS, PERMANENT_AGENT_ACTION_CATEGORIES, AGENT_PERMISSION_POLICY_ACTION_CATEGORIES, AGENT_PROVISIONING_APPROVAL_MODES, AGENT_PERMISSION_POLICY_PRESET_IDS, LEGACY_AGENT_PERMISSION_POLICY_ACTION_CATEGORY_ALIASES, APPROVAL_REQUEST_STATUSES, APPROVAL_REQUEST_AUDIT_EVENT_TYPES, normalizeApprovalRequestActionCategory, isValidApprovalRequestTransition, agentToConfigSnapshot, diffConfigSnapshots, isEphemeralAgent, hasAgentIdentity, CheckoutConflictError, DEFAULT_HEARTBEAT_PROCEDURE_PATH, getDefaultHeartbeatProcedurePath, EXECUTION_MODES, DEFAULT_EXECUTION_MODE, TASK_PRIORITIES, DEFAULT_TASK_PRIORITY, HIGH_FANOUT_BLOCKER_TODO_THRESHOLD, STALE_HIGH_FANOUT_BLOCKER_AGE_THRESHOLD_MS, DASHBOARD_USER_ID, normalizeMessageParticipant, validateMessageMetadata, validateDockerNodeConfig, sanitizeDockerNodeConfigForResponse, normalizeMergeConflictStrategy, normalizeMergeStrategyOverlapBehavior, normalizePostMergeAuditMode, POST_MERGE_AUDIT_MODES, buildResearchDocumentKey, REPO_OVERRIDE_RE, SHARED_STATE_SNAPSHOT_VERSION } from "./types.js";
-export type { Column, IssueInfo, IssueState, TaskSourceIssue, PrInfo, PrStatus, Task, TaskTokenUsage, TaskAttachment, TaskComment, TaskCommentInput, TaskDocument, TaskDocumentRevision, TaskDocumentCreateInput, TaskDocumentWithTask, TaskCreateInput, MeshReplicatedTaskCreatePayload, MeshReplicatedTaskApplyResult, TaskSource, SourceType, TaskDetail, InboxTask, TodoList, TodoItem, TodoListCreateInput, TodoListUpdateInput, TodoItemCreateInput, TodoItemUpdateInput, TodoListWithItems, AgentLogEntry, AgentLogType, AgentRole, BoardConfig, DistributedTaskIdReserveInput, DistributedTaskIdReserveResult, DistributedTaskIdCommitInput, DistributedTaskIdCommitResult, DistributedTaskIdAbortInput, DistributedTaskIdAbortResult, DistributedTaskIdStateInput, DistributedTaskIdStateResult, AutostashOrphanRecord, AutostashOutcome, MergeDetails, MergeResult, MergeConflictStrategy, CanonicalMergeConflictStrategy, MergeStrategyOverlapBehavior, DirectMergeCommitStrategy, Settings, GlobalSettings, ProjectSettings, WebSearchBackend, ResearchEnabledSources, ResearchGlobalDefaults, ResearchProjectLimits, ResearchProjectSettings, EvalFollowUpPolicy, EvalProjectSettings, ResolvedEvalSettings, SettingsScope, DaemonTokenSettings, TaskStep, StepStatus, TaskLogEntry, RunMutationContext, ActivityLogEntry, ActivityEventType, ThinkingLevel, ThemeMode, ColorTheme, ExecutionMode, TaskPriority, UnavailableNodePolicy, PlanningQuestion, PlanningSummary, PlanningResponse, PlanningQuestionType, ArchivedTaskEntry, BatchStatusRequest, BatchStatusResponse, BatchStatusEntry, BatchStatusResult, ModelPreset, WorkflowStep, WorkflowStepMode, WorkflowStepPhase, WorkflowStepInput, WorkflowStepResult, WorkflowStepTemplate, Agent, OrgTreeNode, AgentState, AgentDetail, AgentCreateInput, AgentUpdateInput, AgentApiKey, AgentApiKeyCreateResult, AgentCapability, AgentPromptTemplate, AgentPromptsConfig, AgentPermission, PermanentAgentActionCategory, PermanentAgentSensitiveActionCategory, PermanentAgentGatingContext, AgentPermissionPolicy, AgentPermissionPolicyRules, AgentPermissionPolicyActionCategory, AgentProvisioningApprovalMode, LegacyAgentPermissionPolicyActionCategory, ApprovalRequestActionCategoryInput, ApprovalRequestActionCategory, AgentPermissionPolicyDisposition, AgentPermissionPolicyPresetId, ApprovalRequestStatus, ApprovalRequestAuditEventType, ApprovalRequestActorSnapshot, ApprovalRequestTargetAction, ApprovalRequestAuditEvent, ApprovalRequest, ApprovalRequestCreateInput, ApprovalRequestDecisionInput, ApprovalRequestCompletionInput, ApprovalRequestListInput, TaskAssignSource, AgentAccessState, AgentHeartbeatConfig, AgentBudgetConfig, AgentBudgetStatus, InstructionsBundleConfig, MessageResponseMode, AgentHeartbeatEvent, AgentHeartbeatRun, BlockedStateSnapshot, HeartbeatInvocationSource, AgentTaskSession, AgentRating, AgentRatingSummary, AgentRatingInput, AgentConfigSnapshot, RevisionFieldDiff, AgentConfigRevision, AgentStats, ReflectionTrigger, ReflectionMetrics, AgentReflection, AgentPerformanceSummary, NtfyNotificationEvent, NotificationEvent, NotificationPayload, NotificationProviderConfig, CustomProvider, SteeringComment, ParticipantType, MessageType, Message, MessageCreateInput, MessageFilter, MessageMetadata, MessageReplyReference, Mailbox, CheckoutLease, RunAuditDomain, RunAuditEvent, RunAuditEventInput, RunAuditEventFilter } from "./types.js";
+export type { Column, IssueInfo, IssueState, TaskSourceIssue, PrInfo, PrStatus, Task, TaskTokenUsage, TaskAttachment, TaskComment, TaskCommentInput, TaskDocument, TaskDocumentRevision, TaskDocumentCreateInput, TaskDocumentWithTask, TaskCreateInput, MeshReplicatedTaskCreatePayload, MeshReplicatedTaskApplyResult, TaskSource, SourceType, TaskDetail, InboxTask, TodoList, TodoItem, TodoListCreateInput, TodoListUpdateInput, TodoItemCreateInput, TodoItemUpdateInput, TodoListWithItems, AgentLogEntry, AgentLogType, AgentRole, BoardConfig, DistributedTaskIdReserveInput, DistributedTaskIdReserveResult, DistributedTaskIdCommitInput, DistributedTaskIdCommitResult, DistributedTaskIdAbortInput, DistributedTaskIdAbortResult, DistributedTaskIdStateInput, DistributedTaskIdStateResult, AutostashOrphanRecord, AutostashOutcome, MergeDetails, MergeResult, MergeConflictStrategy, CanonicalMergeConflictStrategy, MergeStrategyOverlapBehavior, PostMergeAuditMode, DirectMergeCommitStrategy, Settings, GlobalSettings, ProjectSettings, WebSearchBackend, ResearchEnabledSources, ResearchGlobalDefaults, ResearchProjectLimits, ResearchProjectSettings, EvalFollowUpPolicy, EvalProjectSettings, ResolvedEvalSettings, SettingsScope, DaemonTokenSettings, TaskStep, StepStatus, TaskLogEntry, RunMutationContext, ActivityLogEntry, ActivityEventType, ThinkingLevel, ThemeMode, ColorTheme, ExecutionMode, TaskPriority, UnavailableNodePolicy, PlanningQuestion, PlanningSummary, PlanningResponse, PlanningQuestionType, ArchivedTaskEntry, BatchStatusRequest, BatchStatusResponse, BatchStatusEntry, BatchStatusResult, ModelPreset, WorkflowStep, WorkflowStepMode, WorkflowStepPhase, WorkflowStepInput, WorkflowStepResult, WorkflowStepTemplate, Agent, OrgTreeNode, AgentState, AgentDetail, AgentCreateInput, AgentUpdateInput, AgentApiKey, AgentApiKeyCreateResult, AgentCapability, AgentPromptTemplate, AgentPromptsConfig, AgentPermission, PermanentAgentActionCategory, PermanentAgentSensitiveActionCategory, PermanentAgentGatingContext, AgentPermissionPolicy, AgentPermissionPolicyRules, AgentPermissionPolicyActionCategory, AgentProvisioningApprovalMode, LegacyAgentPermissionPolicyActionCategory, ApprovalRequestActionCategoryInput, ApprovalRequestActionCategory, AgentPermissionPolicyDisposition, AgentPermissionPolicyPresetId, ApprovalRequestStatus, ApprovalRequestAuditEventType, ApprovalRequestActorSnapshot, ApprovalRequestTargetAction, ApprovalRequestAuditEvent, ApprovalRequest, ApprovalRequestCreateInput, ApprovalRequestDecisionInput, ApprovalRequestCompletionInput, ApprovalRequestListInput, TaskAssignSource, AgentAccessState, AgentHeartbeatConfig, AgentBudgetConfig, AgentBudgetStatus, InstructionsBundleConfig, MessageResponseMode, AgentHeartbeatEvent, AgentHeartbeatRun, BlockedStateSnapshot, HeartbeatInvocationSource, AgentTaskSession, AgentRating, AgentRatingSummary, AgentRatingInput, AgentConfigSnapshot, RevisionFieldDiff, AgentConfigRevision, AgentStats, ReflectionTrigger, ReflectionMetrics, AgentReflection, AgentPerformanceSummary, NtfyNotificationEvent, NotificationEvent, NotificationPayload, NotificationProviderConfig, CustomProvider, SteeringComment, ParticipantType, MessageType, Message, MessageCreateInput, MessageFilter, MessageMetadata, MessageReplyReference, Mailbox, CheckoutLease, RunAuditDomain, RunAuditEvent, RunAuditEventInput, RunAuditEventFilter } from "./types.js";
 export { AGENT_VALID_TRANSITIONS } from "./types.js";
 export type { TaskReviewData, TaskReviewSummary, TaskReviewItem } from "./types.js";
 export type {

packages/core/src/settings-schema.ts

@@ -217,6 +217,7 @@ export const DEFAULT_PROJECT_SETTINGS = {
   mergeDiffVolumeThreshold: undefined,
   mergeDiffVolumeAllowlist: undefined,
   mergeStrategyOverlapBehavior: "flip-to-prefer-branch",
+  postMergeAuditMode: "block",
   workflowStepTimeoutMs: 360_000,
   workflowRevisionForkOnScopeMismatch: true,
   strictScopeEnforcement: false,

packages/core/src/types.ts

@@ -197,6 +197,18 @@ export function normalizeMergeStrategyOverlapBehavior(
     ? value as MergeStrategyOverlapBehavior
     : "flip-to-prefer-branch";
 }
+
+export const POST_MERGE_AUDIT_MODES = ["block", "warn", "off"] as const;
+
+/** Controls how the merger reacts to a dirty post-merge audit (FN-4333). */
+export type PostMergeAuditMode = (typeof POST_MERGE_AUDIT_MODES)[number];
+
+export function normalizePostMergeAuditMode(value: unknown): PostMergeAuditMode {
+  return typeof value === "string"
+    && (POST_MERGE_AUDIT_MODES as readonly string[]).includes(value)
+    ? (value as PostMergeAuditMode)
+    : "block";
+}
 /** Policy for handling task execution when the selected node is unavailable/unhealthy. */
 export type UnavailableNodePolicy = "block" | "fallback-local";
 
@@ -2242,6 +2254,15 @@ export interface ProjectSettings {
   /** Controls overlap protection when `mergeConflictStrategy="smart-prefer-main"`
    *  reaches its Attempt 3 fallback. Default: "flip-to-prefer-branch". */
   mergeStrategyOverlapBehavior?: MergeStrategyOverlapBehavior;
+  /** Controls how the merger reacts to a dirty post-merge / post-rebase audit (FN-4333).
+   *  - "block" (default): throw `SquashAuditError`, park task as failed (today's behavior).
+   *  - "warn": log audit findings on the agent log but auto-complete the merge.
+   *  - "off": skip the post-merge audit entirely.
+   *
+   *  Regardless of mode, the merger short-circuits overlap-only findings on the
+   *  rebase-strategy path when deterministic merge verification has already proven
+   *  the resulting tree (silent drops are impossible by construction in that case). */
+  postMergeAuditMode?: PostMergeAuditMode;
   /** Wall-clock timeout (ms) for a single pre-merge workflow step's AI call.
    *  When a step exceeds this, the session is aborted and the executor is
    *  given one shot to retry with the configured fallback model before the

packages/dashboard/app/components/SettingsModal.tsx

@@ -4060,6 +4060,26 @@ export function SettingsModal({
                 When using smart-prefer-main, automatically prefer the branch side for files that main has recently modified to avoid silently discarding branch work.
               </small>
             </div>
+            <div className="form-group">
+              <label htmlFor="postMergeAuditMode">Post-Merge Audit Mode</label>
+              <select
+                id="postMergeAuditMode"
+                value={form.postMergeAuditMode ?? "block"}
+                onChange={(e) =>
+                  setForm((f) => ({
+                    ...f,
+                    postMergeAuditMode: e.target.value as "block" | "warn" | "off",
+                  }))
+                }
+              >
+                <option value="block">Block — refuse to auto-complete merges with duplicate-subject or touched-file overlap risks (default)</option>
+                <option value="warn">Warn — log audit findings but auto-complete the merge</option>
+                <option value="off">Off — skip the post-merge audit entirely</option>
+              </select>
+              <small>
+                Controls how the post-squash / post-rebase audit reacts to risk findings. Regardless of mode, the audit short-circuits overlap-only findings on rebase merges when deterministic verification has already proven the tree — those cannot have produced silent drops. Switch to Warn or Off only if you trust your branches don&apos;t silently drop edits.
+              </small>
+            </div>
             <div className="form-group">
               <label htmlFor="pushAfterMerge" className="checkbox-label">
                 <input

packages/engine/src/__tests__/post-merge-audit-action.test.ts

@@ -0,0 +1,149 @@
+import { describe, expect, it } from "vitest";
+import {
+  resolvePostMergeAuditAction,
+  type PostMergeAuditAction,
+} from "../merger.js";
+import type {
+  SquashAuditFindings,
+  SquashAuditTouchedFileOverlapFinding,
+  SquashAuditDuplicateSubjectFinding,
+} from "../merger-squash-audit.js";
+
+/**
+ * FN-4333 — unit tests for the post-merge audit decision helper.
+ *
+ * `resolvePostMergeAuditAction` decides whether a dirty audit should block
+ * the merge or be passed through. The merger uses this to apply the
+ * deterministic-verification short-circuit + the `postMergeAuditMode`
+ * setting without spinning up real git/store state.
+ */
+
+function overlap(file: string): SquashAuditTouchedFileOverlapFinding {
+  return {
+    type: "touched-file-overlap",
+    file,
+    recentMainCommits: [{ sha: "abcdef12", subject: "chore: recent main edit" }],
+  };
+}
+
+function duplicateSubject(subject: string): SquashAuditDuplicateSubjectFinding {
+  return { type: "duplicate-subject", subject };
+}
+
+function findings(opts: {
+  strategy: "squash" | "rebase";
+  duplicates?: SquashAuditDuplicateSubjectFinding[];
+  overlaps?: SquashAuditTouchedFileOverlapFinding[];
+}): SquashAuditFindings {
+  const duplicates = opts.duplicates ?? [];
+  const overlaps = opts.overlaps ?? [];
+  const list = [...duplicates, ...overlaps];
+  const base = {
+    parentSha: "0000000000000000000000000000000000000000",
+    lookback: 30,
+    branchSubjects: [],
+    recentMainSubjects: [],
+    duplicateSubjects: duplicates,
+    touchedFiles: overlaps.map((o) => o.file),
+    touchedFileOverlaps: overlaps,
+    findings: list,
+    issueCount: list.length,
+    clean: list.length === 0,
+  };
+  if (opts.strategy === "rebase") {
+    return {
+      ...base,
+      strategy: "rebase",
+      rangeBaseSha: "1".repeat(40),
+      rangeHeadSha: "2".repeat(40),
+      auditTargetLabel: "11111111..22222222",
+    };
+  }
+  return {
+    ...base,
+    strategy: "squash",
+    squashSha: "3".repeat(40),
+    squashSubject: "feat: squash",
+    auditTargetLabel: "33333333",
+  };
+}
+
+describe("resolvePostMergeAuditAction (FN-4333)", () => {
+  it("passes through when audit is clean (defensive default)", () => {
+    const result = resolvePostMergeAuditAction({
+      mode: "block",
+      strategy: "rebase",
+      findings: findings({ strategy: "rebase" }),
+      isTreeVerified: false,
+    });
+    expect(result.action).toBe("pass");
+  });
+
+  it("blocks duplicate-subject findings in block mode regardless of verification", () => {
+    const result = resolvePostMergeAuditAction({
+      mode: "block",
+      strategy: "rebase",
+      findings: findings({
+        strategy: "rebase",
+        duplicates: [duplicateSubject("feat: collide")],
+        overlaps: [overlap("docs/README.md")],
+      }),
+      isTreeVerified: true,
+    });
+    expect(result).toEqual<PostMergeAuditAction>({ action: "block", reason: "mode-block" });
+  });
+
+  it("short-circuits rebase-strategy overlap-only findings when the tree is verified", () => {
+    const result = resolvePostMergeAuditAction({
+      mode: "block",
+      strategy: "rebase",
+      findings: findings({ strategy: "rebase", overlaps: [overlap("docs/README.md")] }),
+      isTreeVerified: true,
+    });
+    expect(result).toEqual<PostMergeAuditAction>({ action: "pass", reason: "verified-short-circuit" });
+  });
+
+  it("does NOT short-circuit overlap-only findings when the tree was not verified", () => {
+    const result = resolvePostMergeAuditAction({
+      mode: "block",
+      strategy: "rebase",
+      findings: findings({ strategy: "rebase", overlaps: [overlap("docs/README.md")] }),
+      isTreeVerified: false,
+    });
+    expect(result).toEqual<PostMergeAuditAction>({ action: "block", reason: "mode-block" });
+  });
+
+  it("does NOT short-circuit squash-strategy overlap-only findings even when verified (no deterministic guarantee)", () => {
+    const result = resolvePostMergeAuditAction({
+      mode: "block",
+      strategy: "squash",
+      findings: findings({ strategy: "squash", overlaps: [overlap("docs/README.md")] }),
+      isTreeVerified: true,
+    });
+    expect(result).toEqual<PostMergeAuditAction>({ action: "block", reason: "mode-block" });
+  });
+
+  it("passes any dirty audit in warn mode", () => {
+    const result = resolvePostMergeAuditAction({
+      mode: "warn",
+      strategy: "squash",
+      findings: findings({
+        strategy: "squash",
+        duplicates: [duplicateSubject("feat: collide")],
+        overlaps: [overlap("packages/dashboard/app/x.tsx")],
+      }),
+      isTreeVerified: false,
+    });
+    expect(result).toEqual<PostMergeAuditAction>({ action: "pass", reason: "mode-warn" });
+  });
+
+  it("prefers verified-short-circuit reason over mode-warn when both would pass", () => {
+    const result = resolvePostMergeAuditAction({
+      mode: "warn",
+      strategy: "rebase",
+      findings: findings({ strategy: "rebase", overlaps: [overlap("a.txt")] }),
+      isTreeVerified: true,
+    });
+    expect(result).toEqual<PostMergeAuditAction>({ action: "pass", reason: "verified-short-circuit" });
+  });
+});

packages/engine/src/merger.ts

@@ -36,6 +36,7 @@ import {
   getTaskMergeBlocker,
   normalizeMergeConflictStrategy,
   normalizeMergeStrategyOverlapBehavior,
+  normalizePostMergeAuditMode,
   resolveTaskMergeTarget,
   resolveTitleSummarizerSettingsModel,
   resolveAgentPrompt,
@@ -53,6 +54,7 @@ import {
   type AgentPromptsConfig,
   type CanonicalMergeConflictStrategy,
   type DirectMergeCommitStrategy,
+  type PostMergeAuditMode,
   type TaskSourceIssue,
   type Task,
   type AutostashOrphanRecord,
@@ -4599,6 +4601,58 @@ function shouldRunPostMergeAudit(
   return (result.autoResolvedCount ?? 0) > 0 || result.attemptsMade === 3;
 }
 
+/**
+ * Decide what to do with a dirty post-merge audit (FN-4333 hot-fix).
+ *
+ * Three modes (`postMergeAuditMode` setting):
+ *  - `"off"`   — caller should skip auditing entirely (handled before this fn).
+ *  - `"warn"`  — log findings on the agent log but proceed; never throws.
+ *  - `"block"` — today's behavior: throw `SquashAuditError` and park the task,
+ *                EXCEPT for the deterministic-verification short-circuit:
+ *                rebase-strategy + overlap-only findings + a verified merged tree
+ *                cannot have produced silent drops (the tree is provably the
+ *                rebase output by construction), so we pass through clean.
+ *
+ * Pure / side-effect-free so it is unit-testable without spinning up a real
+ * merger flow. The merger call site uses the returned action to decide whether
+ * to throw or fall through.
+ */
+export type PostMergeAuditAction =
+  | { action: "pass"; reason: "verified-short-circuit" | "mode-warn" }
+  | { action: "block"; reason: "mode-block" };
+
+export function resolvePostMergeAuditAction(opts: {
+  mode: PostMergeAuditMode;
+  strategy: PostMergeAuditStrategy;
+  findings: SquashAuditFindings;
+  isTreeVerified: boolean;
+}): PostMergeAuditAction {
+  if (opts.findings.clean) {
+    // Caller should never invoke this on a clean audit, but be defensive.
+    return { action: "pass", reason: "mode-warn" };
+  }
+
+  const overlapOnly =
+    opts.findings.duplicateSubjects.length === 0
+    && opts.findings.touchedFileOverlaps.length > 0;
+
+  // Stage 1 short-circuit: a verified rebase tree with overlap-only findings
+  // cannot have produced silent drops. Pass regardless of mode (warn/block).
+  if (
+    opts.strategy === "rebase"
+    && overlapOnly
+    && opts.isTreeVerified
+  ) {
+    return { action: "pass", reason: "verified-short-circuit" };
+  }
+
+  if (opts.mode === "warn") {
+    return { action: "pass", reason: "mode-warn" };
+  }
+
+  return { action: "block", reason: "mode-block" };
+}
+
 function buildPostMergeAuditBlockingMessage(taskId: string, findings: SquashAuditFindings): string {
   const riskParts: string[] = [];
   if (findings.duplicateSubjects.length > 0) {
@@ -6665,7 +6719,12 @@ export async function aiMergeTask(
     const recordedSha = (isEmptyCommit || mergeWasEmpty) ? undefined : commitSha;
 
     const auditSha = recordedSha;
-    if (auditSha && shouldRunPostMergeAudit(selectedPostMergeAuditStrategy, result, mergeWasEmpty, isEmptyCommit, auditSha)) {
+    const postMergeAuditMode = normalizePostMergeAuditMode(settings.postMergeAuditMode);
+    if (
+      auditSha
+      && postMergeAuditMode !== "off"
+      && shouldRunPostMergeAudit(selectedPostMergeAuditStrategy, result, mergeWasEmpty, isEmptyCommit, auditSha)
+    ) {
       const auditFindings = selectedPostMergeAuditStrategy === "rebase" && rebaseMergeBaseSha
         ? await auditSquashMerge({
           rootDir,
@@ -6679,24 +6738,72 @@ export async function aiMergeTask(
           squashSha: auditSha,
         });
       if (!auditFindings.clean) {
-        const auditError = new SquashAuditError(taskId, auditSha, auditFindings);
+        // FN-4333: a verified rebase tree with overlap-only findings cannot have
+        // produced silent drops by construction. Check the verification cache to
+        // detect that case and pass through. `warn` mode passes any dirty audit.
+        let isTreeVerified = false;
+        try {
+          const { stdout: treeShaOut } = await execAsync(
+            `git rev-parse ${auditSha}^{tree}`,
+            { cwd: rootDir, encoding: "utf-8" },
+          );
+          const treeSha = treeShaOut.trim();
+          if (treeSha) {
+            const cacheHit = store.getVerificationCacheHit(
+              treeSha,
+              effectiveTestCommand ?? "",
+              effectiveBuildCommand ?? "",
+            );
+            isTreeVerified = Boolean(cacheHit);
+          }
+        } catch (err) {
+          mergerLog.warn(
+            `${taskId}: failed to resolve tree sha for audit verification short-circuit: ${err instanceof Error ? err.message : String(err)}`,
+          );
+        }
+
+        const decision = resolvePostMergeAuditAction({
+          mode: postMergeAuditMode,
+          strategy: selectedPostMergeAuditStrategy,
+          findings: auditFindings,
+          isTreeVerified,
+        });
+
+        if (decision.action === "block") {
+          const auditError = new SquashAuditError(taskId, auditSha, auditFindings);
+          await store.appendAgentLog(
+            taskId,
+            auditError.message,
+            "tool_error",
+            formatSquashAuditAgentLog(auditFindings),
+            "merger",
+          );
+          await store.updateTask(taskId, { status: null });
+          throw auditError;
+        }
+
+        const passLabel = decision.reason === "verified-short-circuit"
+          ? `${selectedPostMergeAuditStrategy === "rebase" ? "post-rebase" : "post-squash"} audit overlap cleared by deterministic verification`
+          : `${selectedPostMergeAuditStrategy === "rebase" ? "post-rebase" : "post-squash"} audit found ${auditFindings.issueCount} risk(s) — continuing (postMergeAuditMode=warn)`;
         await store.appendAgentLog(
           taskId,
-          auditError.message,
+          passLabel,
-          "tool_error",
+          "text",
           formatSquashAuditAgentLog(auditFindings),
           "merger",
         );
-        await store.updateTask(taskId, { status: null });
+        mergerLog.log(`${taskId}: ${passLabel}`);
-        throw auditError;
+      } else {
+        await store.appendAgentLog(
+          taskId,
+          selectedPostMergeAuditStrategy === "rebase" ? "post-rebase range audit clean" : "post-squash audit clean",
+          "text",
+          undefined,
+          "merger",
+        );
       }
-      await store.appendAgentLog(
+    } else if (auditSha && postMergeAuditMode === "off") {
-        taskId,
+      mergerLog.log(`${taskId}: post-merge audit skipped (postMergeAuditMode=off)`);
-        selectedPostMergeAuditStrategy === "rebase" ? "post-rebase range audit clean" : "post-squash audit clean",
-        "text",
-        undefined,
-        "merger",
-      );
     }
     if (isEmptyCommit) {
       mergerLog.warn(