feat(llm-deepseek): configure max token defaults

.agents/notes/implemented/architecture/2026-07-30-adapter-owned-max-token-defaults.i18n.yaml

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+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# 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 .agents/notes/implemented/architecture/2026-07-30-adapter-owned-max-token-defaults.md
+2026-07-30-adapter-owned-max-token-defaults.md: c6fc9f014124607a3e2c3520f9f3b9023b77935f
+2026-07-30-adapter-owned-max-token-defaults.zh.md: e0670f43eb5f27c2307c734e01a5b6718c09a67e

.agents/notes/implemented/architecture/2026-07-30-adapter-owned-max-token-defaults.md

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+# Agent Note: Adapter-owned max-token defaults
+
+Status: implemented
+
+English | [中文](2026-07-30-adapter-owned-max-token-defaults.zh.md)
+
+## Problem
+
+An LLM adapter could serialize an explicit `GenerateOptions.maxTokens`, but its Cordis configuration could not establish a reconstructable conversation default. Applying a fallback only inside provider serialization would make the wire request differ from the durable `request/header`; putting every provider's default in Agent Loop would instead transfer deployment and model policy into the provider-neutral driver.
+
+## Decision
+
+`LlmResolvedModelInfo.defaultMaxTokens` carries an optional adapter-configured per-request output cap for one exact provider/model route. `LlmService` validates it as a positive safe integer and materializes it into `LlmCallConfig.maxTokens` only when the caller omitted a value. Explicit request or Agent options therefore win without clamping.
+
+The agent loop continues to prepare calls before logging `request/header`, so an adapter default becomes a durable request fact before dispatch. Direct `LlmService.stream()` calls resolve the same default at the final adapter boundary. The field is a request default rather than a hard model output limit; adapters that preserve provider-owned defaults omit it.
+
+The native DeepSeek adapter exposes `maxTokens` in Cordis config with a 256,000-token default and maps the effective value to `max_tokens`. Its default context capacity is 1,000,000 tokens: both built-in V4 entries publish that exact capacity, while configured entries without capacity and unlisted pass-through ids inherit the same adapter-wide fallback.
+
+## Alternatives considered
+
+**Apply the default only in DeepSeek serialization.** Rejected because the provider wire would contain a model-visible value absent from the durable request header.
+
+**Set `AgentOptions.maxTokens` in every shipped application.** Rejected because applications would duplicate adapter deployment policy, direct LLM calls would behave differently, and selecting another provider would retain a DeepSeek-specific cap.
+
+**Represent 256,000 as a hard per-model maximum.** Rejected because the configured value is the desired request budget, not evidence that every configured endpoint rejects larger outputs. Explicit callers remain authoritative.
+
+**Leave the provider default in control.** Rejected for the native DeepSeek deployment because the product requires a stable 256,000-token conversation budget across compatible endpoints.
+
+## Consequences
+
+DeepSeek conversations send `max_tokens: 256000` by default, and the same value appears in the session request header. Deployments can change the adapter default through `llm-deepseek.config.maxTokens`; per-agent and per-request values override it. Other adapters retain their existing behavior until they intentionally publish `defaultMaxTokens`.
+
+The 256,000-token output budget reserves a large part of the one-million-token context on endpoints that pre-allocate requested output. Deployments whose gateway or model supports a smaller budget must lower `maxTokens`; the explicit configuration is preferable to an undocumented provider fallback.

.agents/notes/implemented/architecture/2026-07-30-adapter-owned-max-token-defaults.zh.md

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+# Agent Note: 适配器持有的最大 token 默认值
+
+Status: implemented
+
+[English](2026-07-30-adapter-owned-max-token-defaults.md) | 中文
+
+## Problem
+
+LLM（大语言模型）适配器可以序列化显式的 `GenerateOptions.maxTokens`，但无法通过 Cordis 配置建立可重建的对话默认值。仅在提供方序列化中应用回退，会导致协议请求与持久 `request/header` 不一致；若将各提供方默认值都放进 agent loop（智能体循环），则会把部署与模型策略转移到提供方无关的驱动器中。
+
+## Decision
+
+`LlmResolvedModelInfo.defaultMaxTokens` 携带一条确切提供方／模型路由的可选单次请求输出上限，该值由适配器配置。`LlmService` 将其校验为正安全整数，并且仅在调用方省略值时才填入 `LlmCallConfig.maxTokens`。因此，显式请求值或 Agent 选项优先，且不会被自动调整。
+
+agent loop 仍在记录 `request/header` 前准备调用，因此适配器默认值会在分派前成为持久请求事实。直接调用 `LlmService.stream()` 时，也会在最终适配器边界解析同一默认值。该字段是请求默认值，而非模型输出硬上限；保留提供方持有默认值的适配器会省略它。
+
+原生 DeepSeek 适配器在 Cordis 配置中公开 `maxTokens`，默认值为 256,000 token，并将生效值映射为 `max_tokens`。其默认上下文容量为 1,000,000 token：两个内置 V4 配置项均公布这一精确容量；不含容量的已配置项和未列出的原样传递 id 则继承同一个适配器级回退值。
+
+## Alternatives considered
+
+**仅在 DeepSeek 序列化中应用默认值。** 不予采纳，因为提供方协议会包含持久请求 header 中缺失的模型可见值。
+
+**在每个已发布应用中设置 `AgentOptions.maxTokens`。** 不予采纳，因为应用会重复适配器部署策略，直接 LLM 调用的行为将不同，而且选择另一个提供方后仍会保留 DeepSeek 专用上限。
+
+**将 256,000 表示为每模型硬上限。** 不予采纳，因为配置值是所需请求预算，无法证明每个已配置端点都会拒绝更大的输出。显式调用方仍具有最终决定权。
+
+**由提供方默认值控制。** 对原生 DeepSeek 部署不予采纳，因为产品要求各兼容端点都采用稳定的 256,000 token 对话预算。
+
+## Consequences
+
+DeepSeek 对话默认发送 `max_tokens: 256000`，会话请求 header 中也会出现相同的值。部署可以通过 `llm-deepseek.config.maxTokens` 更改适配器默认值；每个 agent 和每次请求的值都会覆盖它。其他适配器会保留现有行为，直至主动公布 `defaultMaxTokens`。
+
+对于预分配请求输出的端点，256,000 token 的输出预算会占用 1,000,000 token 上下文中的很大部分。如果部署使用的 gateway 或模型仅支持较小预算，则必须调低 `maxTokens`；显式配置优于未记录的提供方回退值。