diff --git a/src/lib/onboard/child-exit-tracker.test.ts b/src/lib/onboard/child-exit-tracker.test.ts
index 08ea8e961db..ba9fce48271 100644
--- a/src/lib/onboard/child-exit-tracker.test.ts
+++ b/src/lib/onboard/child-exit-tracker.test.ts
@@ -72,7 +72,6 @@ describe("trackChildExit (#3111)", () => {
           queueMicrotask(() => cb(null, null));
         }
       },
-      // biome-ignore lint/suspicious/noExplicitAny: narrowed mock shape
     } as any;
     const state = trackChildExit(fake);
     await waitFor(() => state.exited);
diff --git a/src/lib/shields/index.ts b/src/lib/shields/index.ts
index a5ad383ae1d..b34b1be45ef 100644
--- a/src/lib/shields/index.ts
+++ b/src/lib/shields/index.ts
@@ -4725,6 +4725,77 @@ function startFreshShieldsDownTimer(input: {
   }
 }
 
+function completeInterruptedShieldsDown(
+  sandboxName: string,
+  opts: ShieldsDownOpts,
+  state: LoadedShieldsState,
+  retainedProviderTarget: AgentConfigTarget | null,
+): boolean {
+  if (!state.shieldsDown) return false;
+
+  // Provider release deliberately precedes route convergence and the final
+  // timer-bound transition commit. A process can therefore die after the
+  // durable provider claim is gone while the host transition remains in
+  // preparing. Treat that marker as recovery authority too: verify (or
+  // repair) mutable posture, converge the route, then commit it active.
+  const completionTarget =
+    retainedProviderTarget ??
+    resolveReleasedProviderShieldsDownTarget(
+      sandboxName,
+      state,
+      opts.allowLegacyHermesProtocol === true,
+    );
+  if (!completionTarget) return false;
+
+  const completion = prepareRecoveredShieldsDownCompletion(sandboxName, completionTarget, state);
+  // The provisional DOWN record can outlive a process that lost its
+  // provider-unlock response. Recovery first restores the retained plan's
+  // restrictive rollback. Reconcile the recorded mutable posture and verify
+  // it before treating this retry as complete.
+  try {
+    applyRecoveredShieldsDownForwardPolicy(sandboxName, completion);
+    if (retainedProviderTarget) {
+      runHermesProviderProtectionTransition(
+        sandboxName,
+        retainedProviderTarget,
+        "locked",
+        "locked",
+      );
+    }
+    if (completion.authority) {
+      assertRecoveredShieldsDownAuthority(sandboxName, completion, completion.authority.phase);
+    }
+    unlockAgentConfigUnderMutationLock(
+      sandboxName,
+      completionTarget,
+      false,
+      "provider-state-mutation-v2",
+    );
+    if (completion.authority) {
+      assertRecoveredShieldsDownAuthority(sandboxName, completion, completion.authority.phase);
+    }
+    finishRecoveredHermesShieldsDown(sandboxName, completion);
+  } catch (error) {
+    return failRecoveredHermesShieldsDown(
+      sandboxName,
+      completionTarget,
+      state,
+      completion,
+      opts.allowLegacyHermesProtocol === true,
+      error,
+      opts.throwOnError,
+    );
+  }
+  if (!completion.alreadyCommitted) {
+    if (completion.authority) {
+      assertRecoveredShieldsDownAuthority(sandboxName, completion, "active");
+    }
+    appendAuditEntry(completion.audit);
+  }
+  console.log(`  Recovered interrupted config unlock for ${sandboxName}.`);
+  return true;
+}
+
 function persistIncompleteShieldsDownPosture(
   sandboxName: string,
   transition: ShieldsDownTransition,
@@ -4776,73 +4847,7 @@ function shieldsDownWithoutHostLock(sandboxName: string, opts: ShieldsDownOpts =
     recoveredProviderTarget = retainedProviderTarget;
   }
   const initialMode = deriveShieldsMode(state, state._hasStateFile);
-  if (state.shieldsDown) {
-    // Provider release deliberately precedes route convergence and the final
-    // timer-bound transition commit. A process can therefore die after the
-    // durable provider claim is gone while the exact host transition remains
-    // in preparing. Treat that marker as recovery authority too: verify (or
-    // repair) mutable posture, converge the route, then commit it active.
-    const completionTarget =
-      retainedProviderTarget ??
-      resolveReleasedProviderShieldsDownTarget(
-        sandboxName,
-        state,
-        opts.allowLegacyHermesProtocol === true,
-      );
-    if (completionTarget) {
-      const completion = prepareRecoveredShieldsDownCompletion(
-        sandboxName,
-        completionTarget,
-        state,
-      );
-      // The provisional DOWN record can outlive a process that lost its
-      // provider-unlock response. Recovery first restores the retained plan's
-      // restrictive rollback. Reconcile the recorded mutable posture and
-      // verify it before treating this retry as complete.
-      try {
-        applyRecoveredShieldsDownForwardPolicy(sandboxName, completion);
-        if (retainedProviderTarget) {
-          runHermesProviderProtectionTransition(
-            sandboxName,
-            retainedProviderTarget,
-            "locked",
-            "locked",
-          );
-        }
-        if (completion.authority) {
-          assertRecoveredShieldsDownAuthority(sandboxName, completion, completion.authority.phase);
-        }
-        unlockAgentConfigUnderMutationLock(
-          sandboxName,
-          completionTarget,
-          false,
-          "provider-state-mutation-v2",
-        );
-        if (completion.authority) {
-          assertRecoveredShieldsDownAuthority(sandboxName, completion, completion.authority.phase);
-        }
-        finishRecoveredHermesShieldsDown(sandboxName, completion);
-      } catch (error) {
-        return failRecoveredHermesShieldsDown(
-          sandboxName,
-          completionTarget,
-          state,
-          completion,
-          opts.allowLegacyHermesProtocol === true,
-          error,
-          opts.throwOnError,
-        );
-      }
-      if (!completion.alreadyCommitted) {
-        if (completion.authority) {
-          assertRecoveredShieldsDownAuthority(sandboxName, completion, "active");
-        }
-        appendAuditEntry(completion.audit);
-      }
-      console.log(`  Recovered interrupted config unlock for ${sandboxName}.`);
-      return;
-    }
-  }
+  if (completeInterruptedShieldsDown(sandboxName, opts, state, retainedProviderTarget)) return;
 
   const timeoutSeconds = parseDuration(opts.timeout || `${DEFAULT_TIMEOUT_SECONDS}`);
   const reason = opts.reason || null;
diff --git a/test/build-base-image-platform-action.test.ts b/test/build-base-image-platform-action.test.ts
new file mode 100644
index 00000000000..8201536a370
--- /dev/null
+++ b/test/build-base-image-platform-action.test.ts
@@ -0,0 +1,65 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import fs from "node:fs";
+import path from "node:path";
+
+import { describe, expect, it } from "vitest";
+import YAML from "yaml";
+
+type Step = {
+  env?: Record<string, unknown>;
+  if?: string;
+  name?: string;
+  run?: string;
+};
+
+const repoRoot = path.resolve(import.meta.dirname, "..");
+
+function required<T>(value: T | undefined, message: string): T {
+  return (
+    value ??
+    (() => {
+      throw new Error(message);
+    })()
+  );
+}
+
+describe("base-image platform action", () => {
+  it("executes dos2unix from each Deep Agents Code platform image before manifest publication (#8870)", () => {
+    const action = YAML.parse(
+      fs.readFileSync(
+        path.join(repoRoot, ".github", "actions", "build-base-image-platform", "action.yaml"),
+        "utf8",
+      ),
+    ) as { runs?: { steps?: Step[] } };
+    const steps = action.runs?.steps ?? [];
+    const validate = required(
+      steps.find((candidate) => candidate.name === "Validate Deep Agents Code dos2unix executable"),
+      "base-image platform action is missing the Deep Agents Code dos2unix validation",
+    );
+    const buildIndex = steps.findIndex(
+      (candidate) => candidate.name === "Build and push platform digest",
+    );
+    const validateIndex = steps.indexOf(validate);
+    const exportIndex = steps.findIndex((candidate) => candidate.name === "Export platform digest");
+
+    expect(validate.if).toBe("${{ inputs.agent == 'langchain-deepagents-code' }}");
+    expect(validate.env).toMatchObject({
+      DIGEST: "${{ steps.build.outputs.digest }}",
+      IMAGE: "${{ inputs.registry }}/${{ inputs.image }}",
+      PLATFORM: "${{ inputs.platform }}",
+    });
+    expect(validate.run).toContain('reference="${IMAGE}@${DIGEST}"');
+    expect(validate.run).toContain('docker run --rm --platform "$PLATFORM"');
+    expect(validate.run).toContain("--network none");
+    expect(validate.run).toContain("--cap-drop ALL");
+    expect(validate.run).toContain("--security-opt no-new-privileges");
+    expect(validate.run).toContain("--read-only");
+    expect(validate.run).toContain("--user 999:999");
+    expect(validate.run).toContain("test -x /usr/bin/dos2unix");
+    expect(validate.run).toContain("dos2unix --version");
+    expect(validateIndex).toBeGreaterThan(buildIndex);
+    expect(validateIndex).toBeLessThan(exportIndex);
+  });
+});