diff --git a/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.i18n.yaml b/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.i18n.yaml
index 843feb7a4c..38fd140342 100644
--- a/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.i18n.yaml
+++ b/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.i18n.yaml
@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write
-2026-07-20-code-mode-typed-tool-returns.md: f902aa4ff8cdaa0979f09850ea15deede5fdf576
-2026-07-20-code-mode-typed-tool-returns.zh.md: 4bdec90960e270f5be03b0a4c30d7c829dd27f6a
+2026-07-20-code-mode-typed-tool-returns.md: bcaefb196d12660177ad2bbc9c20ad71f6537eae
+2026-07-20-code-mode-typed-tool-returns.zh.md: 72946f4cc1ab7569fc1e3f90785debf8314f1d35
diff --git a/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.md b/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.md
index f902aa4ff8..bcaefb196d 100644
--- a/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.md
+++ b/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.md
@@ -49,7 +49,7 @@ declare const tools: {
 
 ### Binding values and failures
 
-Before dispatch the bridge snapshots binding arguments as lossless JSON and makes independent clones for execution and the durable summary event. `undefined`, non-finite numbers, `-0`, sparse arrays, cycles, functions, and exotic objects reject that call before the tool runs. Successful dispatch returns `ToolExecutionResult.value`; Native `content`, metadata, and internal error information do not cross to the program.
+Before dispatch the bridge snapshots binding arguments as lossless JSON and snapshots the detached value again for an independent durable summary event. Host-side detachment, immutable execution, and output-schema projection all use iterative traversals rather than nested structured clone or recursive freezing. `undefined`, non-finite numbers, `-0`, sparse arrays, cycles, functions, and exotic objects reject that call before the tool runs. Successful dispatch returns `ToolExecutionResult.value`; Native `content`, metadata, and internal error information do not cross to the program.
 
 The worker exposes the actual `ToolCallError` constructor used for `tools` binding failures, so `error instanceof ToolCallError` works. The error has the standard `Error` message plus the exact `toolName`; it deliberately omits `ToolFailure.info`, error codes, and Native content. This is an exception contract for control flow, not a failure union for programmatic classification.
 
diff --git a/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.zh.md b/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.zh.md
index 4bdec90960..72946f4cc1 100644
--- a/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.zh.md
+++ b/.agents/notes/implemented/feature/2026-07-20-code-mode-typed-tool-returns.zh.md
@@ -49,7 +49,7 @@ declare const tools: {
 
 ### 绑定值与失败
 
-分发前，桥接层会把绑定参数快照为无损 JSON，并为执行和持久摘要事件分别创建独立副本。`undefined`、非有限数、`-0`、稀疏数组、循环引用、函数和非普通对象都会使该调用在工具运行前 reject。成功分发会返回 `ToolExecutionResult.value`；Native `content`、元数据和内部错误信息不会传入程序。
+分发前，桥接层会把绑定参数快照为无损 JSON，再对分离后的值生成一次快照，供独立的持久摘要事件使用。宿主侧的值分离、执行数据的不可变处理与输出 schema 投影均采用迭代遍历，而不使用嵌套结构化克隆或递归冻结。`undefined`、非有限数、`-0`、稀疏数组、循环引用、函数和非普通对象都会使该调用在工具运行前 reject。成功分发会返回 `ToolExecutionResult.value`；Native `content`、元数据和内部错误信息不会传入程序。
 
 worker 暴露的是真正用于 `tools` 绑定失败的 `ToolCallError` 构造函数，因此 `error instanceof ToolCallError` 能够成立。该错误包含标准的 `Error` 消息和确切的 `toolName`，并有意省略 `ToolFailure.info`、错误代码与 Native 内容。这是一项用于控制流的异常契约，而不是供程序分类的失败联合。
 
diff --git a/packages/core/tools/src/code-mode.ts b/packages/core/tools/src/code-mode.ts
index 44a9839b02..2c7f8faedd 100644
--- a/packages/core/tools/src/code-mode.ts
+++ b/packages/core/tools/src/code-mode.ts
@@ -85,9 +85,9 @@ function summarize(text: string, cwd: string | undefined): string {
 }
 
 /**
- * Snapshot one binding call's argument as lossless JSON, then clone it into
- * independent dispatch/log values so a tool mutation cannot desynchronize the
- * durable event from what was called.
+ * Snapshot one binding call's argument as lossless JSON, then snapshot that
+ * detached value again so dispatch and logging stay independent without
+ * reintroducing structured-clone's platform-specific nesting limit.
  */
 function jsonNormalizeArgs(value: unknown): { dispatched: unknown; logged: unknown } {
   let snapshot: JsonValue | undefined
@@ -99,7 +99,12 @@ function jsonNormalizeArgs(value: unknown): { dispatched: unknown; logged: unkno
   if (snapshot === undefined) {
     throw new Error('tool arguments must be lossless JSON (call the tool with an arguments object, e.g. `{}`)')
   }
-  return { dispatched: structuredClone(snapshot), logged: structuredClone(snapshot) }
+  const logged = snapshotJsonValue(snapshot)
+  /* v8 ignore next -- snapshot is already a detached lossless JSON value. */
+  if (logged === undefined) {
+    throw new Error('tool arguments could not be detached for durable logging')
+  }
+  return { dispatched: snapshot, logged }
 }
 
 /** Two-space JSON presentation, matching the existing shallow `run_code` text contract. */
diff --git a/packages/core/tools/src/index.ts b/packages/core/tools/src/index.ts
index 2f4e4cbd5f..4b712b1d07 100644
--- a/packages/core/tools/src/index.ts
+++ b/packages/core/tools/src/index.ts
@@ -864,10 +864,17 @@ export class ToolRegistry extends Service {
   private sdkSchemas(scope?: ScopeKey): ToolSdkSchema[] {
     return [...this.view(scope).visible.values()]
       .filter(definition => definition.name !== RUN_CODE_NAME)
-      .map((definition): ToolSdkSchema => ({
-        ...this.schemaOf(definition, true),
-        output: structuredClone(definition.output.schema),
-      }))
+      .map((definition): ToolSdkSchema => {
+        const output = snapshotJsonValue(definition.output.schema)
+        /* v8 ignore next -- registration already validated and retained this schema as lossless JSON. */
+        if (output === undefined) {
+          throw new Error(`tool "${definition.name}" output schema must be lossless JSON before SDK projection`)
+        }
+        return {
+          ...this.schemaOf(definition, true),
+          output,
+        }
+      })
   }
 
   /** Project one definition onto the model-facing schema fields. */
diff --git a/packages/core/tools/tests/code-mode.spec.ts b/packages/core/tools/tests/code-mode.spec.ts
index 20e9c7e223..188e89503e 100644
--- a/packages/core/tools/tests/code-mode.spec.ts
+++ b/packages/core/tools/tests/code-mode.spec.ts
@@ -7,7 +7,7 @@ import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
 import { CodeRuntime } from '@deepseek-ai/dsh-code-runtime'
 import type { CodeRunRequest, CodeRunResult } from '@deepseek-ai/dsh-code-runtime'
 import ToolRegistry, { CodeRunFailedError, RUN_CODE_NAME, TOOL_ABORTED_BEFORE_DISPATCH, defineContentToolFixture, defineTool } from '@deepseek-ai/dsh-tools'
-import type { Config, PostToolDecision, ToolExecutionResult } from '@deepseek-ai/dsh-tools'
+import type { Config, JsonSchemaNode, PostToolDecision, ToolExecutionResult } from '@deepseek-ai/dsh-tools'
 import type { Agent } from '@deepseek-ai/dsh-agent'
 import { Session, SessionId } from '@deepseek-ai/dsh-session'
 import type { JsonValue, SessionEventMap } from '@deepseek-ai/dsh-session'
@@ -130,6 +130,30 @@ describe('mode-aware wire contribution', () => {
     expect(sdk?.text).not.toContain('run_code:')
   })
 
+  it('projects deeply nested output schemas into the Code Mode SDK without structured-clone recursion', async () => {
+    const { ctx, systemPrompt } = await setup({ mode: 'code' })
+    let output: JsonSchemaNode = { type: 'string' }
+    for (let depth = 0; depth < 5_000; depth++) {
+      output = { oneOf: [output, { type: 'null' }] }
+    }
+    ctx.tools.register({
+      name: 'deep_output',
+      description: 'Return a deeply nested output union.',
+      parameters: { type: 'object', properties: {} },
+      output: {
+        schema: output,
+        render: (_args, value) => [{ type: 'text', text: typeof value === 'string' ? value : 'null' }],
+      },
+      execute() { return Promise.resolve('ok') },
+    })
+
+    const assembly = await systemPrompt.assemble()
+    const sdk = assembly.sections.find(section => section.name === 'tools:sdk')?.text
+
+    expect(sdk).toContain('deep_output: Record<string, JsonValue>;')
+    expect(sdk).toContain('deep_output: string | null')
+  })
+
   it.each(['code', 'both'] as const)('treats expert assembly output as authoritative in mode %s', async (mode) => {
     const { ctx, systemPrompt } = await setup({ mode })
     registerEcho(ctx)
@@ -811,6 +835,57 @@ describe('the run_code dispatch bridge', () => {
     expect(events.filter(event => event.type === 'tool/code-dispatch')).toEqual([])
   })
 
+  it('dispatches and durably logs binding arguments deeper than the structured-clone call stack', async () => {
+    const { ctx, runtime } = await setup({ mode: 'code' })
+    const depth = 5_000
+    let observedDepth = 0
+    let observedLeaf: JsonValue | undefined
+    ctx.tools.register(defineTool({
+      name: 'deep_args',
+      description: 'Measure a deeply nested JSON argument.',
+      parameters: { nested: { type: 'json', required: true } },
+      output: {
+        schema: { type: 'integer' },
+        render: (_args, value) => [{ type: 'text', text: String(value) }],
+      },
+      execute(args) {
+        let cursor = args.nested
+        while (Array.isArray(cursor)) {
+          if (cursor.length !== 1) throw new Error('expected one item per nesting layer')
+          observedDepth++
+          cursor = cursor[0]!
+        }
+        observedLeaf = cursor
+        return Promise.resolve(observedDepth)
+      },
+    }))
+    const session = new Session(SessionId('deep-code-arguments'))
+    const agent = { session } as Agent
+    runtime.behavior = async (request) => {
+      let nested: JsonValue = 'leaf'
+      for (let index = 0; index < depth; index++) nested = [nested]
+      const value = await request.bindings[0]!.functions.deep_args!({ nested })
+      return { logs: [], value }
+    }
+
+    const result = await runCode(ctx, 'return tools.deep_args(...)', { agent })
+
+    expect(result.isError).toBe(false)
+    expect(result.isError ? undefined : result.value).toEqual({ logs: [], result: depth })
+    expect({ observedDepth, observedLeaf }).toEqual({ observedDepth: depth, observedLeaf: 'leaf' })
+    const dispatch = session.events.find(event => event.type === 'tool/code-dispatch')
+    if (dispatch === undefined) throw new Error('expected a durable tool/code-dispatch event')
+    const logged = dispatch.data.arguments as { nested: JsonValue }
+    let loggedDepth = 0
+    let loggedCursor = logged.nested
+    while (Array.isArray(loggedCursor)) {
+      if (loggedCursor.length !== 1) throw new Error('expected one logged item per nesting layer')
+      loggedDepth++
+      loggedCursor = loggedCursor[0]!
+    }
+    expect({ loggedDepth, loggedCursor }).toEqual({ loggedDepth: depth, loggedCursor: 'leaf' })
+  })
+
   it('gives the tool and durable log the same immutable argument value', async () => {
     const { ctx, runtime } = await setup({ mode: 'code' })
     const { agent, events } = fakeAgent()
diff --git a/packages/llm/llm/src/call-config.ts b/packages/llm/llm/src/call-config.ts
index fe723ec162..fd6ecf9df4 100644
--- a/packages/llm/llm/src/call-config.ts
+++ b/packages/llm/llm/src/call-config.ts
@@ -58,7 +58,8 @@ export function isAgentLoopRequest(request: GenerateOptions): boolean {
 }
 
 /**
- * Deep-freeze a value in place, guarding cycles, so later mutation throws.
+ * Deep-freeze a value in place with an iterative traversal, guarding cycles,
+ * so later mutation throws without imposing a JavaScript call-stack depth cap.
  * {@link AbortSignal} objects are deliberately skipped because they are the
  * request's live cancellation channel and freezing them breaks abort.
  * @param value - the value to freeze in place.
@@ -66,16 +67,31 @@ export function isAgentLoopRequest(request: GenerateOptions): boolean {
  */
 export function deepFreeze<T>(value: T): T {
   const seen = new WeakSet<object>()
-  const walk = (node: unknown): void => {
-    if (node === null || typeof node !== 'object') return
-    if (node instanceof AbortSignal) return
-    if (seen.has(node)) return
+  const pending: (
+    | { kind: 'visit'; node: unknown }
+    | { kind: 'property'; source: Record<string, unknown>; key: string }
+  )[] = [{ kind: 'visit', node: value }]
+  while (pending.length > 0) {
+    const task = pending.pop()
+    /* v8 ignore next -- the loop condition guarantees one pending task. */
+    if (task === undefined) continue
+    if (task.kind === 'property') {
+      pending.push({ kind: 'visit', node: task.source[task.key] })
+      continue
+    }
+    const node = task.node
+    if (node === null || typeof node !== 'object') continue
+    if (node instanceof AbortSignal) continue
+    if (seen.has(node)) continue
     seen.add(node)
     Object.freeze(node)
-    for (const key of Object.keys(node)) {
-      walk((node as Record<string, unknown>)[key])
+    const keys = Object.keys(node)
+    for (let index = keys.length - 1; index >= 0; index--) {
+      const key = keys[index]
+      /* v8 ignore next -- the loop is bounded by the captured key count. */
+      if (key === undefined) continue
+      pending.push({ kind: 'property', source: node as Record<string, unknown>, key })
     }
   }
-  walk(value)
   return value
 }
diff --git a/packages/llm/llm/tests/call-config.spec.ts b/packages/llm/llm/tests/call-config.spec.ts
index 6479ec8f85..a5426e815f 100644
--- a/packages/llm/llm/tests/call-config.spec.ts
+++ b/packages/llm/llm/tests/call-config.spec.ts
@@ -56,6 +56,26 @@ describe('deepFreeze', () => {
     deepFreeze(cyclic)
     expect(Object.isFrozen(cyclic)).toBe(true)
   })
+
+  it('freezes nesting deeper than the JavaScript call stack', () => {
+    const depth = 5_000
+    const root: unknown[] = []
+    let cursor = root
+    for (let index = 0; index < depth; index++) {
+      const child: unknown[] = []
+      cursor.push(child)
+      cursor = child
+    }
+
+    deepFreeze(root)
+
+    cursor = root
+    for (let index = 0; index < depth; index++) {
+      expect(Object.isFrozen(cursor)).toBe(true)
+      cursor = cursor[0] as unknown[]
+    }
+    expect(Object.isFrozen(cursor)).toBe(true)
+  })
 })
 
 describe('agent-loop request identity', () => {