diff --git a/packages/core/tools/README.i18n.yaml b/packages/core/tools/README.i18n.yaml
index c3e4554f70..9ff6974195 100644
--- a/packages/core/tools/README.i18n.yaml
+++ b/packages/core/tools/README.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 packages/core/tools/README.md
-README.md: ac08bc72c6f9c6de6a0aef5cb866cd0488b1dd5c
-README.zh.md: e040d85b3eb75cf23f7fb2fa8d16d0685ff2f4ac
+README.md: 1b19a080759fa8b21f0c1058d049b2c3f6cf64fe
+README.zh.md: 07fc85e2fc51c0b528eb37f6e7599d72144db8fb
diff --git a/packages/core/tools/README.md b/packages/core/tools/README.md
index ac08bc72c6..1b19a08075 100644
--- a/packages/core/tools/README.md
+++ b/packages/core/tools/README.md
@@ -190,6 +190,6 @@ Append-only; newly visible content follows the reusable request prefix and does
 - **`tools/pre-execute` deliberately cannot rewrite `exec.arguments`** — logged and rendered args would desync from what ran; the rewrite design is [a proposed Agent Note](../../../.agents/notes/proposed/feature/2026-06-30-pre-tool-input-rewrite.md).
 - **Caller-defined subagent and workflow structured outputs remain object-rooted** — this is a consumer-level guard; the shared schema vocabulary and tool outputs support every JSON root.
 - **`timeoutMs` on a definition is declarative only** — the registry never enforces deadlines; enforcement requires the `@deepseek-ai/dsh-timeout-policy` wrapper.
-- **Code Mode's SDK language follows the one loaded runtime and the presentation mode is service-wide** — `mode: code`/`both` rejects prompt assembly unless `ctx.codeRuntime.language` has a registered SDK renderer (`typescript` via the worker backend, `python` via the python backend); scoped restrictions/shadows still choose each agent's visible bindings, but one tool cannot be native-only while another is code-only, and a single runtime fixes the language service-wide.
+- **Code Mode's SDK language follows the one loaded runtime and the presentation mode is service-wide** — `mode: code`/`both` rejects prompt assembly unless `ctx.codeRuntime.language` has a registered SDK renderer (`typescript` via the worker backend, `python` via the python backend); scoped restrictions/shadows still choose each agent's visible bindings, but one tool cannot be native-only while another is code-only, and a single runtime fixes the language service-wide (the [language-dispatch Agent Note](../../../.agents/notes/implemented/feature/2026-07-31-code-mode-language-dispatch.md) owns why per-agent language switching is deferred).
 - **Code Mode intermediate values are execution-local and unbounded by bytes** — the canonical typed values cannot be reconstructed from session replay and may exhaust process or worker memory; only the outer `run_code` output has the worker's configurable hard cap. The durable log copy of each sub-call IS bounded: the `tools/code-dispatch-log` waterfall lets the spill policy replace an oversized `tool/code-dispatch` content with a preview + locator ([rationale](../../../.agents/notes/implemented/feature/2026-07-26-code-dispatch-log-spill.md)).
 - **`run_code` state is fresh per run** — a persistent REPL-style kernel is rejected for the MVP (cross-call state would be invisible to the log); see [the Code Mode Agent Note](../../../.agents/notes/implemented/feature/2026-06-15-code-mode.md).
diff --git a/packages/core/tools/README.zh.md b/packages/core/tools/README.zh.md
index e040d85b3e..07fc85e2fc 100644
--- a/packages/core/tools/README.zh.md
+++ b/packages/core/tools/README.zh.md
@@ -190,6 +190,6 @@ The available tools:
 - **`tools/pre-execute` 有意不允许改写 `exec.arguments`**：否则日志记录和呈现的参数会与实际运行内容失去同步；改写设计记录在[拟议的 Agent Note](../../../.agents/notes/proposed/feature/2026-06-30-pre-tool-input-rewrite.md)中。
 - **调用方定义的 subagent 与工作流结构化输出仍要求对象根**：这是消费方层面的守卫；共享 schema 词汇和工具输出支持任意 JSON 根。
 - **定义上的 `timeoutMs` 仅为声明**：注册表绝不会强制执行截止时间；要强制执行，必须使用 `@deepseek-ai/dsh-timeout-policy` 包装层。
-- **Code Mode 只支持 TypeScript，且呈现模式在服务内统一**：`mode: code`/`both` 会拒绝组装提示词，除非 `ctx.codeRuntime.language === 'typescript'`；作用域限制／遮蔽仍会选择每个 agent 的可见绑定，但不能让一个工具仅使用 Native，而另一个仅使用 Code。
+- **Code Mode 的 SDK 语言跟随唯一加载的运行时，且呈现模式在服务内统一**：`mode: code`/`both` 会拒绝组装提示词，除非 `ctx.codeRuntime.language` 有已注册的 SDK 渲染器（`typescript` 经 worker 后端，`python` 经 python 后端）；作用域限制／遮蔽仍会选择每个 agent 的可见绑定，但不能让一个工具仅使用 Native、另一个仅使用 Code，且单个运行时把语言固定为服务级（[语言分发 Agent Note](../../../.agents/notes/implemented/feature/2026-07-31-code-mode-language-dispatch.md) 负责说明为何暂缓逐 agent 切换语言）。
 - **Code Mode 中间值只存在于执行局部，且没有字节上限**：这些规范的类型化值无法从会话回放重建，并可能耗尽进程或 worker 内存；只有外层 `run_code` 输出受 worker 可配置的硬上限约束。每个子调用的持久日志副本则确实有上限：`tools/code-dispatch-log` waterfall 允许 spill 策略把过大的 `tool/code-dispatch` 内容替换为预览加定位符（[原理](../../../.agents/notes/implemented/feature/2026-07-26-code-dispatch-log-spill.md)）。
 - **每次运行都会获得全新的 `run_code` 状态**：MVP 不采用持久 REPL 风格内核（跨调用状态不会出现在日志中）；参见 [Code Mode Agent Note](../../../.agents/notes/implemented/feature/2026-06-15-code-mode.md)。
diff --git a/packages/core/tools/src/code-mode.ts b/packages/core/tools/src/code-mode.ts
index 38a0654ced..22a660a8ef 100644
--- a/packages/core/tools/src/code-mode.ts
+++ b/packages/core/tools/src/code-mode.ts
@@ -120,18 +120,22 @@ const RUN_CODE_DESCRIPTION_PARAM_DESCRIPTION
 /**
  * Resolve the {@link RunCodeFlavor} for the loaded runtime's language, read at
  * schema-emission time so the model-visible `run_code` schema always matches
- * the SDK section's language. When no runtime is mounted the schema harvest
- * degrades to {@link TYPESCRIPT_FLAVOR} (a doc-only path — an assembly always
- * has one). A mounted runtime whose language has no flavor entry fails loud,
- * keeping this table coupled to `SDK_RENDERERS`.
+ * the SDK section's language. When no runtime is mounted, or one whose language
+ * has no renderer is, the schema harvest degrades to {@link TYPESCRIPT_FLAVOR}
+ * (a doc-only path — a real assembly always mounts a valid runtime, and
+ * `requireCodeRuntime` rejects an invalid language there first). A mounted
+ * runtime whose language passes that guard but is absent from this table fails
+ * loud, keeping this table coupled to `SDK_RENDERERS`.
  */
 function resolveFlavor(requireRuntime: () => CodeRuntime): RunCodeFlavor {
   let runtime: CodeRuntime
   try {
     runtime = requireRuntime()
   } catch {
-    // No runtime mounted: the only reader here is the static schema harvest
-    // (doc catalog), which never reaches a model — degrade to the TS default.
+    // Reached only by the static schema harvest (doc catalog), which never
+    // feeds a model: either no runtime is mounted, or requireRuntime rejected
+    // a language with no renderer. Both degrade to the TS default here; a real
+    // assembly hits requireCodeRuntime's loud rejection before this runs.
     return TYPESCRIPT_FLAVOR
   }
   // Own-property read: a language like `toString`/`constructor` would otherwise
diff --git a/packages/core/tools/src/index.ts b/packages/core/tools/src/index.ts
index 17d1935cf1..5f89fa23c6 100644
--- a/packages/core/tools/src/index.ts
+++ b/packages/core/tools/src/index.ts
@@ -806,6 +806,10 @@ export class ToolRegistry extends Service {
     if (this.mode === 'native') {
       return { schemas, knownNames: [...view.knownNames] }
     }
+    // Redundant with the per-getter resolveFlavor path (schemaOf's run_code
+    // description/parameters getters call requireCodeRuntime again): kept as a
+    // single explicit gate so a mode collapse rejects here regardless of
+    // whether any getter runs. The call is idempotent (ctx.get + Object.hasOwn).
     this.requireCodeRuntime()
     if (this.mode === 'code') {
       return {