feat(llm-deepseek): configure max token defaults

packages/llm/llm-deepseek/tests/adapter.spec.ts

@@ -124,6 +124,7 @@ describe('DeepSeekAdapter against a mock server', () => {
     // The wire request carried the auth header contents we configured.
     expect(server.requests[0]).toMatchObject({
       model: 'deepseek-v4-flash',
+      max_tokens: 256_000,
       reasoning_effort: 'high',
       stream: true,
       stream_options: { include_usage: true },
@@ -232,6 +233,20 @@ describe('DeepSeekAdapter against a mock server', () => {
     })
   })
 
+  it('uses the configured maxTokens default and preserves an explicit request cap', async () => {
+    const server = await mockServer([
+      { kind: 'sse', events: textEvents },
+      { kind: 'sse', events: textEvents },
+    ])
+    const ctx = await harness(server.url, { maxTokens: 32_000 })
+
+    await assemble(ctx, { model: 'deepseek-v4-flash', messages: [] })
+    await assemble(ctx, { model: 'deepseek-v4-flash', messages: [], maxTokens: 8_192 })
+
+    expect(server.requests[0]).toMatchObject({ max_tokens: 32_000 })
+    expect(server.requests[1]).toMatchObject({ max_tokens: 8_192 })
+  })
+
   it('publishes only off and omits the wire effort when thinking is disabled', async () => {
     const server = await mockServer([{ kind: 'sse', events: textEvents }])
     const ctx = await harness(server.url, { thinking: 'disabled' })
@@ -666,7 +681,8 @@ describe('plugin registration and config', () => {
         provider: 'deepseek',
         id: 'deepseek-v4-flash',
         name: 'DeepSeek-V4-Flash',
-        context: { contextWindow: 256_000 },
+        context: { contextWindow: 1_000_000 },
+        defaultMaxTokens: 256_000,
         reasoning: {
           efforts: [
             { id: ReasoningEffortId('off'), name: 'Off' },
@@ -795,7 +811,10 @@ describe('plugin registration and config', () => {
         description: 'Higher reasoning budget',
       })
     await expect(ctx.llm.resolveModelInfo('deepseek', 'arbitrary-unlisted'))
-      .resolves.not.toHaveProperty('context')
+      .resolves.toMatchObject({
+        context: { contextWindow: 1_000_000 },
+        defaultMaxTokens: 256_000,
+      })
   })
 
   it('uses exact model capacity before the adapter-wide default', async () => {
@@ -880,6 +899,26 @@ describe('plugin registration and config', () => {
     },
   )
 
+  it.each([0, 1.5, Number.MAX_SAFE_INTEGER + 1])(
+    'rejects invalid adapter-wide maxTokens %s',
+    async (maxTokens) => {
+      expect(() => new DeepSeekAdapter({
+        apiKey: 'k',
+        baseURL: 'http://127.0.0.1:1',
+        maxTokens,
+      })).toThrow(/maxTokens must be a positive safe integer/)
+
+      const ctx = new Context()
+      await ctx.plugin(LlmService)
+      await expect(ctx.plugin(LlmDeepSeek, {
+        apiKey: 'k',
+        baseURL: 'http://127.0.0.1:1',
+        maxTokens,
+      })).rejects.toThrow(/maxTokens/)
+      expect(ctx.llm.listProviders()).toEqual([])
+    },
+  )
+
   it('falls back to DEEPSEEK_API_KEY and DEEPSEEK_BASE_URL env vars', async () => {
     vi.stubEnv('DEEPSEEK_API_KEY', 'env-key')
     vi.stubEnv('DEEPSEEK_BASE_URL', 'http://127.0.0.1:1')

packages/llm/llm-deepseek/tests/serialize.spec.ts

@@ -170,6 +170,13 @@ describe('serializeRequest', () => {
     expect(wire.stop).toEqual(['END'])
   })
 
+  it('uses the adapter maxTokens default only when the request omits a cap', () => {
+    expect(serializeRequest(request({ messages: history }), {}, 256_000).max_tokens)
+      .toBe(256_000)
+    expect(serializeRequest(request({ messages: history, maxTokens: 8_192 }), {}, 256_000).max_tokens)
+      .toBe(8_192)
+  })
+
   it('maps tools to the wire function shape', () => {
     const wire = serializeRequest(request({
       messages: history,