diff --git a/src/agents/pi-embedded-runner/replay-history.ts b/src/agents/pi-embedded-runner/replay-history.ts
index 29fe1692eef..45aaf25499c 100644
--- a/src/agents/pi-embedded-runner/replay-history.ts
+++ b/src/agents/pi-embedded-runner/replay-history.ts
@@ -418,7 +418,10 @@ export async function sanitizeSessionHistory(params: {
     : sanitizedImages;
   const sanitizedToolCalls = sanitizeToolCallInputs(droppedThinking, {
     allowedToolNames: params.allowedToolNames,
-    preserveImmutableThinkingTurns: policy.validateAnthropicTurns,
+    allowProviderOwnedThinkingReplay:
+      policy.validateAnthropicTurns &&
+      params.provider === "anthropic" &&
+      params.modelApi === "anthropic-messages",
   });
   const repairedTools = policy.repairToolUseResultPairing
     ? sanitizeToolUseResultPairing(sanitizedToolCalls, {
diff --git a/src/agents/pi-embedded-runner/run/attempt.tool-call-normalization.ts b/src/agents/pi-embedded-runner/run/attempt.tool-call-normalization.ts
index e7b5fad16a8..b73ad716534 100644
--- a/src/agents/pi-embedded-runner/run/attempt.tool-call-normalization.ts
+++ b/src/agents/pi-embedded-runner/run/attempt.tool-call-normalization.ts
@@ -2,7 +2,10 @@ import type { AgentMessage, StreamFn } from "@mariozechner/pi-agent-core";
 import { streamSimple } from "@mariozechner/pi-ai";
 import { normalizeLowercaseStringOrEmpty } from "../../../shared/string-coerce.js";
 import { validateAnthropicTurns, validateGeminiTurns } from "../../pi-embedded-helpers.js";
-import { sanitizeToolUseResultPairing } from "../../session-transcript-repair.js";
+import {
+  isRedactedSessionsSpawnAttachment,
+  sanitizeToolUseResultPairing,
+} from "../../session-transcript-repair.js";
 import { normalizeToolName } from "../../tool-policy.js";
 import type { TranscriptPolicy } from "../../transcript-policy.js";
 
@@ -251,14 +254,7 @@ function hasUnredactedSessionsSpawnAttachments(block: ReplayToolCallBlock): bool
       continue;
     }
     for (const attachment of attachments) {
-      if (!attachment || typeof attachment !== "object") {
-        continue;
-      }
-      if (!Object.hasOwn(attachment, "content")) {
-        continue;
-      }
-      const content = (attachment as { content?: unknown }).content;
-      if (content !== "__OPENCLAW_REDACTED__") {
+      if (!isRedactedSessionsSpawnAttachment(attachment)) {
         return true;
       }
     }
@@ -331,7 +327,7 @@ function resolveReplayToolCallName(
 function sanitizeReplayToolCallInputs(
   messages: AgentMessage[],
   allowedToolNames?: Set<string>,
-  preserveImmutableThinkingTurns?: boolean,
+  allowProviderOwnedThinkingReplay?: boolean,
 ): ReplayToolCallSanitizeReport {
   let changed = false;
   let droppedAssistantMessages = 0;
@@ -347,7 +343,7 @@ function sanitizeReplayToolCallInputs(
       continue;
     }
     if (
-      preserveImmutableThinkingTurns &&
+      allowProviderOwnedThinkingReplay &&
       message.content.some((block) => isThinkingLikeReplayBlock(block)) &&
       message.content.some((block) => isReplayToolCallBlock(block))
     ) {
@@ -641,7 +637,8 @@ export function wrapStreamFnSanitizeMalformedToolCalls(
     const sanitized = sanitizeReplayToolCallInputs(
       messages as AgentMessage[],
       allowedToolNames,
-      transcriptPolicy?.validateAnthropicTurns === true,
+      transcriptPolicy?.validateAnthropicTurns === true &&
+        (model as { api?: unknown })?.api === "anthropic-messages",
     );
     if (sanitized.messages === messages) {
       return baseFn(model, context, options);
diff --git a/src/agents/session-transcript-repair.ts b/src/agents/session-transcript-repair.ts
index b7196c0745d..81cd70ad378 100644
--- a/src/agents/session-transcript-repair.ts
+++ b/src/agents/session-transcript-repair.ts
@@ -8,6 +8,8 @@ import { extractToolCallsFromAssistant, extractToolResultId } from "./tool-call-
 
 const TOOL_CALL_NAME_MAX_CHARS = 64;
 const TOOL_CALL_NAME_RE = /^[A-Za-z0-9_:.-]+$/;
+const REDACTED_SESSIONS_SPAWN_ATTACHMENT_CONTENT = "__OPENCLAW_REDACTED__";
+const SESSIONS_SPAWN_ATTACHMENT_METADATA_KEYS = ["name", "encoding", "mimeType"] as const;
 
 type RawToolCallBlock = {
   type?: unknown;
@@ -94,20 +96,59 @@ function redactSessionsSpawnAttachmentsArgs(value: unknown): unknown {
   if (!Array.isArray(raw)) {
     return value;
   }
+  let changed = false;
   const next = raw.map((item) => {
-    if (!item || typeof item !== "object") {
+    if (isRedactedSessionsSpawnAttachment(item)) {
       return item;
     }
-    const a = item as Record<string, unknown>;
-    if (!Object.hasOwn(a, "content")) {
-      return item;
-    }
-    const { content: _content, ...rest } = a;
-    return { ...rest, content: "__OPENCLAW_REDACTED__" };
+    changed = true;
+    return redactSessionsSpawnAttachment(item);
   });
+  if (!changed) {
+    return value;
+  }
   return { ...rec, attachments: next };
 }
 
+function redactSessionsSpawnAttachment(item: unknown): Record<string, unknown> {
+  const next: Record<string, unknown> = {
+    content: REDACTED_SESSIONS_SPAWN_ATTACHMENT_CONTENT,
+  };
+  if (!item || typeof item !== "object") {
+    return next;
+  }
+  const attachment = item as Record<string, unknown>;
+  for (const key of SESSIONS_SPAWN_ATTACHMENT_METADATA_KEYS) {
+    const value = attachment[key];
+    if (typeof value === "string" && value.trim().length > 0) {
+      next[key] = value;
+    }
+  }
+  return next;
+}
+
+export function isRedactedSessionsSpawnAttachment(item: unknown): boolean {
+  if (!item || typeof item !== "object") {
+    return false;
+  }
+  const attachment = item as Record<string, unknown>;
+  if (attachment.content !== REDACTED_SESSIONS_SPAWN_ATTACHMENT_CONTENT) {
+    return false;
+  }
+  for (const key of Object.keys(attachment)) {
+    if (key === "content") {
+      continue;
+    }
+    if (!(SESSIONS_SPAWN_ATTACHMENT_METADATA_KEYS as readonly string[]).includes(key)) {
+      return false;
+    }
+    if (typeof attachment[key] !== "string" || (attachment[key] as string).trim().length === 0) {
+      return false;
+    }
+  }
+  return true;
+}
+
 function sanitizeToolCallBlock(block: RawToolCallBlock): RawToolCallBlock {
   const rawName = readStringValue(block.name);
   const trimmedName = rawName?.trim();
@@ -232,7 +273,7 @@ export type ToolCallInputRepairReport = {
 
 export type ToolCallInputRepairOptions = {
   allowedToolNames?: Iterable<string>;
-  preserveImmutableThinkingTurns?: boolean;
+  allowProviderOwnedThinkingReplay?: boolean;
 };
 
 export type ErroredAssistantResultPolicy = "preserve" | "drop";
@@ -270,7 +311,7 @@ export function repairToolCallInputs(
   let changed = false;
   const out: AgentMessage[] = [];
   const allowedToolNames = normalizeAllowedToolNames(options?.allowedToolNames);
-  const preserveImmutableThinkingTurns = options?.preserveImmutableThinkingTurns === true;
+  const allowProviderOwnedThinkingReplay = options?.allowProviderOwnedThinkingReplay === true;
 
   for (const msg of messages) {
     if (!msg || typeof msg !== "object") {
@@ -284,7 +325,7 @@ export function repairToolCallInputs(
     }
 
     if (
-      preserveImmutableThinkingTurns &&
+      allowProviderOwnedThinkingReplay &&
       msg.content.some((block) => isThinkingLikeBlock(block)) &&
       countRawToolCallBlocks(msg.content) > 0
     ) {