diff --git a/docs/en/configuration/config-files.md b/docs/en/configuration/config-files.md
index b671922578e..23633b29396 100644
--- a/docs/en/configuration/config-files.md
+++ b/docs/en/configuration/config-files.md
@@ -190,7 +190,11 @@ You can also switch models temporarily without touching the config file — by s
 
 ## `secondary_model`
 
-The secondary model is a second model pointer next to the primary `default_model` — typically a cheaper model that features can bind to when they do not need the main model. Its consumer today is subagent spawning: when set, newly spawned subagents (`Agent` / `AgentSwarm`) bind to it by default instead of inheriting the main agent's model, and the main agent is told it can pick per spawn between `"secondary"` (this model) and `"primary"` (the main model). When unset, subagents inherit the main agent's model.
+The secondary model is a second model configuration alongside the main model — typically a cheaper one, for features that do not need the main model's capability. Its consumer today is subagent spawning: when set, newly spawned subagents (`Agent` / `AgentSwarm`) bind to it by default instead of inheriting the main agent's model; when unset, subagents inherit the main agent's model.
+
+This is a default binding, not a forced one. With the experiment enabled, the `Agent` / `AgentSwarm` tools gain a `model` parameter (accepting only the symbolic values `"secondary"` / `"primary"`), and the tool description lists the available models with the default marked. A spawn resolves the subagent's model in this order: an explicit tool-call `model` → the profile's [`model_preference`](../customization/agents.md#agent-file-format) → the configured secondary model (the default). Here `"primary"` means the model the main agent is currently running, not necessarily `default_model` — for example after a mid-session `/model` switch.
+
+Because overriding the default is the main agent's own decision (the tool description merely suggests `"secondary"` for routine tasks and `"primary"` for hard, quality-sensitive ones), there is no per-spawn switch on the user side. To steer a specific subagent to the main model, ask the main agent in your prompt to pass `model: "primary"`, or set `model_preference: "primary"` in the corresponding profile.
 
 This feature is experimental and disabled by default. Enable it with `KIMI_CODE_EXPERIMENTAL_SECONDARY_MODEL=1`, or the master `KIMI_CODE_EXPERIMENTAL_FLAG=1`. It takes effect in every launch mode, including the interactive TUI.
 
@@ -198,7 +202,7 @@ In the interactive TUI, the [`/secondary_model`](../reference/slash-commands.md)
 
 | Field | Type | Default | Description |
 | --- | --- | --- | --- |
-| `model` | `string` | — | A model id from your configured `[models]` (any provider, not limited to Kimi models) |
+| `model` | `string` | — | The alias of a configured [`[models]`](#models) entry, e.g. `kimi-code/kimi-k2.5` (any provider, not limited to Kimi models) |
 | `default_effort` | `string` | — | Thinking effort applied when subagents bind to the secondary model. Unset, the effort resolves naturally (global `[thinking]` config → the bound model's default effort) instead of inheriting the main agent's effort. Follows the main model's thinking-effort semantics: models with strict effort validation (e.g. Kimi models) fall back to their default effort for unsupported values; other providers receive the value as-is |
 | Other fields | — | — | Accepts every field of [`[models."<alias>".overrides]`](#models) (`max_context_size`, `max_output_size`, `support_efforts`, …) as a model patch applied only to subagents |
 
diff --git a/docs/en/configuration/env-vars.md b/docs/en/configuration/env-vars.md
index 9fb803d56c0..50e3c968984 100644
--- a/docs/en/configuration/env-vars.md
+++ b/docs/en/configuration/env-vars.md
@@ -129,7 +129,7 @@ Switches that control the behavior of subsystems such as telemetry, background t
 | `KIMI_CODE_AGENT_SWARM_MAX_CONCURRENCY` | Cap how many AgentSwarm subagents run concurrently during the initial ramp; leave unset for no cap | Positive integer; invalid values fail fast |
 | `KIMI_SUBAGENT_TIMEOUT_MS` | Maximum wall-clock time (ms) a single subagent (`Agent` / `AgentSwarm`) may run; takes higher priority than `[subagent] timeout_ms` in `config.toml` (default `7200000`, i.e. 2 hours) | Positive integer; invalid values fall back to the config or default |
 | `KIMI_CODE_EXPERIMENTAL_SECONDARY_MODEL` | Enable the experimental secondary-model feature in every launch mode, including the interactive TUI; the master `KIMI_CODE_EXPERIMENTAL_FLAG=1` also enables it | Truthy: `1`/`true`/`yes`/`on`; falsy: `0`/`false`/`no`/`off` |
-| `KIMI_SECONDARY_MODEL` | Secondary model; takes higher priority than `[secondary_model] model` in `config.toml`. When the secondary-model experiment is enabled, newly spawned subagents (`Agent` / `AgentSwarm`) bind to it by default instead of inheriting the main agent's model | A model id from your configured `[models]`, e.g. `kimi-code/kimi-k2.5`; blank values are ignored |
+| `KIMI_SECONDARY_MODEL` | Secondary model; takes higher priority than [`[secondary_model] model`](./config-files.md#secondary-model) in `config.toml`. When the secondary-model experiment is enabled, newly spawned subagents (`Agent` / `AgentSwarm`) bind to it by default instead of inheriting the main agent's model | The alias of a configured `[models]` entry, e.g. `kimi-code/kimi-k2.5`; blank values are ignored |
 | `KIMI_SECONDARY_EFFORT` | Thinking effort for the secondary model; takes higher priority than `[secondary_model] default_effort` in `config.toml` and applies only when both the model and its experiment are enabled | An effort value, e.g. `low`; blank values are ignored |
 | `KIMI_MCP_STARTUP_TIMEOUT_MS` | Global default connection timeout (ms) for all MCP servers; takes higher priority than `[mcp] startup_timeout_ms` in `config.toml`, but a per-server `startupTimeoutMs` in `mcp.json` still wins (default `30000`) | Integer from `1` to `2147483647`; invalid values are ignored |
 | `KIMI_MCP_TOOL_TIMEOUT_MS` | Global default single tool-call timeout (ms) for all MCP servers; takes higher priority than `[mcp] tool_timeout_ms` in `config.toml`, but a per-server `toolTimeoutMs` in `mcp.json` still wins (default `60000`) | Integer from `1` to `2147483647`; invalid values are ignored |
diff --git a/docs/en/customization/agents.md b/docs/en/customization/agents.md
index b9c67039dde..2b247a3a025 100644
--- a/docs/en/customization/agents.md
+++ b/docs/en/customization/agents.md
@@ -100,7 +100,7 @@ You are a strict code reviewer. Read the diff, then report findings grouped by s
 | `description` | yes | What the agent does. Shown to the main Agent when it picks a sub-agent, so write it to guide delegation decisions |
 | `whenToUse` | no | Extra hint describing when the agent should be used |
 | `override` | no | Whether this file may replace a same-name built-in Agent. Defaults to `false`; `--agent-file` is already explicit and does not require this field |
-| `model_preference` | no | Symbolic default used when `Agent` or `AgentSwarm` spawns this profile: `primary` selects the caller's main model, while `secondary` selects `[secondary_model] model`. An explicit tool-call `model` wins; without either setting, the configured secondary model remains the default. If no secondary model is configured, the subagent inherits the caller's model |
+| `model_preference` | no | Symbolic default used when `Agent` or `AgentSwarm` spawns this profile: `primary` selects the model the caller is currently running, while `secondary` selects [`[secondary_model] model`](../configuration/config-files.md#secondary-model). An explicit tool-call `model` (which likewise accepts only `"primary"` / `"secondary"`) wins over this field; without either setting, the configured secondary model remains the default. If no secondary model is configured, the subagent inherits the caller's model |
 | `tools` | no | Allowlist of tool names such as `Read` or `Bash`; MCP tools are matched with globs such as `mcp__github__*`. Accepts a YAML list or a comma-separated string (`tools: Read, Grep`). Omit to allow all tools; a lone `*` also allows all tools; an empty list (`tools: []`) disables all tools |
 | `disallowedTools` | no | Denylist with the same syntax and matching rules, applied after `tools` |
 | `subagents` | no | Allowlist of sub-agent names this agent may delegate to, with the same syntax as `tools` (YAML list or comma-separated string). Omit to allow every type; a lone `*` also allows all types |
diff --git a/docs/en/reference/slash-commands.md b/docs/en/reference/slash-commands.md
index 602853cfdca..20d5bc97e42 100644
--- a/docs/en/reference/slash-commands.md
+++ b/docs/en/reference/slash-commands.md
@@ -16,7 +16,7 @@ Some commands are only available in the idle state. Executing these commands whi
 | `/logout` | — | Clear credentials for the currently selected account | No |
 | `/provider` | — | Open the interactive provider manager to view, add, and remove configured providers. See [Platforms & Models — `/provider` and provider management](../configuration/providers.md#provider-—-interactive-provider-management) | Yes |
 | `/model` | — | Switch the LLM model used in the current session | Yes |
-| `/secondary_model` | — | Configure the secondary model used by subagents (writes the [`[secondary_model]`](../configuration/config-files.md#secondary-model) section and applies to the current session immediately). Requires the `secondary-model` experiment | Yes |
+| `/secondary_model` | — | Configure the secondary model that newly spawned subagents bind to by default (writes the [`[secondary_model]`](../configuration/config-files.md#secondary-model) section and applies to the current session immediately). Requires the `secondary-model` experiment | Yes |
 | `/settings` | `/config` | Open the settings panel inside the TUI | Yes |
 | `/experiments` | `/experimental` | Open the experimental feature panel | Yes |
 | `/permission` | — | Select a permission mode | Yes |
diff --git a/docs/zh/configuration/config-files.md b/docs/zh/configuration/config-files.md
index 478959acf69..aaeea89b255 100644
--- a/docs/zh/configuration/config-files.md
+++ b/docs/zh/configuration/config-files.md
@@ -190,19 +190,23 @@ display_name = "Kimi for Coding (custom)"
 
 ## `secondary_model`
 
-次主力模型是主模型 `default_model` 之外的第二个模型指针——通常是一个更便宜的模型，供不需要主模型的功能绑定使用。目前的消费者是子 Agent 派生：设置后，新派生的子 Agent（`Agent` / `AgentSwarm`）默认绑定该模型，而不再继承主 Agent 的模型；主 Agent 会被告知每次派生可在 `"secondary"`（该模型）与 `"primary"`（主模型）之间选择。未设置时，子 Agent 继承主 Agent 的模型。
+次主力模型是主模型之外的第二个模型配置——通常是一个更便宜的模型，供不需要主模型能力的功能绑定使用。它目前的消费者是子 Agent 派生：设置后，新派生的子 Agent（`Agent` / `AgentSwarm`）默认绑定该模型，而不再继承主 Agent 的模型；未设置时，子 Agent 继承主 Agent 的模型。
+
+这是默认绑定而非强制。实验功能启用后，`Agent` / `AgentSwarm` 工具会获得 `model` 参数（仅接受 `"secondary"` / `"primary"` 两个符号值），工具描述中也会列出可选模型并标注默认值。派生时按以下顺序解析子 Agent 的模型：工具调用显式传入的 `model` → 子 Agent profile 的 [`model_preference`](../customization/agents.md#agent-文件格式) → 已配置的次主力模型（默认）。其中 `"primary"` 指主 Agent 当前正在运行的模型，不一定是 `default_model`——例如会话中途用 `/model` 切换过模型。
+
+由于是否覆盖默认值由主 Agent 自行决定（工具描述仅建议常规任务用 `"secondary"`、困难或质量敏感的任务用 `"primary"`，不构成强制），用户没有单次派生级别的直接开关。想让某个子 Agent 使用主模型，可以在提示词中要求主 Agent 传入 `model: "primary"`，或在对应 profile 中设置 `model_preference: "primary"`。
 
 该功能目前是实验功能，默认关闭。通过 `KIMI_CODE_EXPERIMENTAL_SECONDARY_MODEL=1` 启用，或使用 master `KIMI_CODE_EXPERIMENTAL_FLAG=1`。它在包括交互式 TUI 在内的所有启动方式下生效。
 
-在交互式 TUI 中，可以使用 [`/secondary_model`](../reference/slash-commands.md) 命令打开模型选择器来设置该配置：选择后会写入本小节配置，并在当前会话立即生效——之后派生的子 Agent 会直接绑定新的第二模型。
+在交互式 TUI 中，可以使用 [`/secondary_model`](../reference/slash-commands.md) 命令打开模型选择器来设置该配置：选择后会写入本小节配置，并在当前会话立即生效——之后派生的子 Agent 会直接绑定新的次主力模型。
 
 | 字段 | 类型 | 默认值 | 说明 |
 | --- | --- | --- | --- |
-| `model` | `string` | — | 已配置 `[models]` 中的模型 id（不限 kimi 模型，可用任意供应商） |
-| `default_effort` | `string` | — | 子代理绑定次主力模型时使用的 thinking effort。未设置时按"全局 `[thinking]` 配置 → 模型默认 effort"的链路解析，不再继承主 Agent 的 effort。与主模型的 thinking effort 语义一致：严格校验 effort 的模型（如 kimi 模型）在不支持该取值时回退到模型默认 effort，其他供应商的模型按原样发送给后端 |
-| 其他字段 | — | — | 接受 [`[models."<alias>".overrides]`](#models) 的全部字段（`max_context_size`、`max_output_size`、`support_efforts` 等），作为仅对子代理生效的模型补丁 |
+| `model` | `string` | — | [`[models]`](#models) 中已配置条目的别名，如 `kimi-code/kimi-k2.5`（不限 kimi 模型，可用任意供应商） |
+| `default_effort` | `string` | — | 子 Agent 绑定次主力模型时使用的 thinking effort。未设置时按"全局 `[thinking]` 配置 → 模型默认 effort"的链路解析，不再继承主 Agent 的 effort。与主模型的 thinking effort 语义一致：严格校验 effort 的模型（如 kimi 模型）在不支持该取值时回退到模型默认 effort，其他供应商的模型按原样发送给后端 |
+| 其他字段 | — | — | 接受 [`[models."<alias>".overrides]`](#models) 的全部字段（`max_context_size`、`max_output_size`、`support_efforts` 等），作为仅对子 Agent 生效的模型补丁 |
 
-`model` 之外的字段构成补丁：存在补丁字段时，运行时会在内存中合成一个派生模型条目（被指向条目的拷贝，补丁并入其 overrides 且补丁优先），子代理实际绑定该派生条目；没有补丁字段时，子代理直接绑定 `model` 指向的条目。派生条目只存在于内存中（不写回 `config.toml`），也不会出现在模型选择列表里。
+`model` 之外的字段构成补丁：存在补丁字段时，运行时会在内存中合成一个派生模型条目（被指向条目的拷贝，补丁并入其 overrides 且补丁优先），子 Agent 实际绑定该派生条目；没有补丁字段时，子 Agent 直接绑定 `model` 指向的条目。派生条目只存在于内存中（不写回 `config.toml`），也不会出现在模型选择列表里。
 
 ```toml
 [secondary_model]
diff --git a/docs/zh/configuration/env-vars.md b/docs/zh/configuration/env-vars.md
index 2b5c461a4b7..40a31d6c31b 100644
--- a/docs/zh/configuration/env-vars.md
+++ b/docs/zh/configuration/env-vars.md
@@ -129,7 +129,7 @@ kimi
 | `KIMI_CODE_AGENT_SWARM_MAX_CONCURRENCY` | 限制 AgentSwarm 初始提升并发阶段可同时运行的子 Agent 数量；不设置表示不限制 | 正整数；非法值会立即失败 |
 | `KIMI_SUBAGENT_TIMEOUT_MS` | 单个子 Agent（`Agent` / `AgentSwarm`）可运行的最长时间（毫秒）；优先级高于 `config.toml` 的 `[subagent] timeout_ms`（默认 `7200000`，即 2 小时） | 正整数；非法值回退到配置或默认值 |
 | `KIMI_CODE_EXPERIMENTAL_SECONDARY_MODEL` | 在包括交互式 TUI 在内的所有启动方式下启用实验性的次主力模型功能；master `KIMI_CODE_EXPERIMENTAL_FLAG=1` 也会启用本功能 | 真值：`1`/`true`/`yes`/`on`；假值：`0`/`false`/`no`/`off` |
-| `KIMI_SECONDARY_MODEL` | 次主力模型；优先级高于 `config.toml` 的 `[secondary_model] model`。次主力模型实验功能启用后，新派生的子 Agent 默认绑定该模型，而不再继承主 Agent 的模型 | 已配置 `[models]` 中的模型 id，如 `kimi-code/kimi-k2.5`；空白值被忽略 |
+| `KIMI_SECONDARY_MODEL` | 次主力模型；优先级高于 `config.toml` 的 [`[secondary_model] model`](./config-files.md#secondary-model)。次主力模型实验功能启用后，新派生的子 Agent 默认绑定该模型，而不再继承主 Agent 的模型 | `[models]` 中已配置条目的别名，如 `kimi-code/kimi-k2.5`；空白值被忽略 |
 | `KIMI_SECONDARY_EFFORT` | 次主力模型的 thinking effort；优先级高于 `config.toml` 的 `[secondary_model] default_effort`，仅在次主力模型及其实验功能均启用时生效 | effort 取值，如 `low`；空白值被忽略 |
 | `KIMI_MCP_STARTUP_TIMEOUT_MS` | 所有 MCP server 的全局默认连接超时（毫秒）；优先级高于 `config.toml` 的 `[mcp] startup_timeout_ms`，但低于 `mcp.json` 中单个 server 的 `startupTimeoutMs`（默认 `30000`） | `1` 到 `2147483647` 的整数；非法值被忽略 |
 | `KIMI_MCP_TOOL_TIMEOUT_MS` | 所有 MCP server 的全局默认单次工具调用超时（毫秒）；优先级高于 `config.toml` 的 `[mcp] tool_timeout_ms`，但低于 `mcp.json` 中单个 server 的 `toolTimeoutMs`（默认 `60000`） | `1` 到 `2147483647` 的整数；非法值被忽略 |
diff --git a/docs/zh/customization/agents.md b/docs/zh/customization/agents.md
index 9a935e94fba..97d98de3e22 100644
--- a/docs/zh/customization/agents.md
+++ b/docs/zh/customization/agents.md
@@ -100,7 +100,7 @@ disallowedTools:
 | `description` | 是 | Agent 的用途。主 Agent 挑选子 Agent 时会看到，请围绕委派决策来写 |
 | `whenToUse` | 否 | 补充说明何时应使用该 Agent |
 | `override` | 否 | 是否允许覆盖同名内置 Agent，默认 `false`。`--agent-file` 属于显式启动意图，无需设置此字段 |
-| `model_preference` | 否 | `Agent` 或 `AgentSwarm` 启动该 profile 时的符号默认值：`primary` 选择调用方的主模型，`secondary` 选择 `[secondary_model] model`。工具调用显式传入的 `model` 优先；两者均未设置时，已配置的次主力模型仍为默认值。未配置次主力模型时，子 Agent 继承调用方模型 |
+| `model_preference` | 否 | `Agent` 或 `AgentSwarm` 启动该 profile 时的符号默认值：`primary` 选择调用方当前运行的模型，`secondary` 选择 [`[secondary_model] model`](../configuration/config-files.md#secondary-model)。工具调用显式传入的 `model`（同样只接受 `"primary"` / `"secondary"` 两个符号值）优先于该字段；两者均未设置时，已配置的次主力模型仍为默认值。未配置次主力模型时，子 Agent 继承调用方模型 |
 | `tools` | 否 | 工具名允许列表，如 `Read`、`Bash`；MCP 工具用 glob 匹配，如 `mcp__github__*`。支持 YAML 列表或逗号分隔字符串（`tools: Read, Grep`）两种写法。缺省表示允许全部工具；单独的 `*` 同样表示允许全部工具；空列表（`tools: []`）表示禁用全部工具 |
 | `disallowedTools` | 否 | 禁止列表，写法与匹配规则相同，在 `tools` 之后应用 |
 | `subagents` | 否 | 允许委派的子 Agent 名称列表，写法与 `tools` 相同（YAML 列表或逗号分隔字符串）。缺省表示可委派所有类型；单独的 `*` 同样表示全部 |
diff --git a/docs/zh/reference/slash-commands.md b/docs/zh/reference/slash-commands.md
index 199ca0a2248..34f37759b9b 100644
--- a/docs/zh/reference/slash-commands.md
+++ b/docs/zh/reference/slash-commands.md
@@ -16,7 +16,7 @@
 | `/logout` | — | 清除当前所选账号的凭据 | 否 |
 | `/provider` | — | 打开交互式供应商管理器，查看、添加和删除已配置的供应商。详见[平台与模型 — `/provider` 与供应商管理](../configuration/providers.md#provider-—-交互式供应商管理) | 是 |
 | `/model` | — | 切换当前会话使用的 LLM 模型 | 是 |
-| `/secondary_model` | — | 配置子 Agent 使用的第二模型（写入 [`[secondary_model]`](../configuration/config-files.md#secondary-model) 配置并在当前会话立即生效）。需开启 `secondary-model` 实验功能 | 是 |
+| `/secondary_model` | — | 配置子 Agent 默认绑定的次主力模型（写入 [`[secondary_model]`](../configuration/config-files.md#secondary-model) 配置并在当前会话立即生效）。需开启 `secondary-model` 实验功能 | 是 |
 | `/settings` | `/config` | 打开 TUI 内的设置面板 | 是 |
 | `/experiments` | `/experimental` | 打开实验功能面板 | 是 |
 | `/permission` | — | 选择权限模式 | 是 |