feat(custom-model): DeepSeek configDir injection via a per-session patch

Replace the deepseek env redirect with a deepseek-patch-json recipe: a per-session DSH_HOME holding a generated cordis.patch.yml that declares a codeman-custom openai-completions provider over the installed profile. Ported from PR #752 commits 941df574 and 4bb1bfe9, minus the core context-limit changes.

src/config/cli-registry/schema.ts

@@ -580,7 +580,7 @@ const capabilitiesSchema = z
           kind: z.literal('configDir'),
           dirEnvVar: envName,
           fileName: z.string().min(1).max(80),
-          template: z.enum(['codex-toml', 'pi-models-json', 'omp-models-yml', 'grok-toml']),
+          template: z.enum(['codex-toml', 'pi-models-json', 'omp-models-yml', 'grok-toml', 'deepseek-patch-json']),
           launchModel: launchModelTemplate,
         })
         .strict(),

src/config/cli-registry/stock.ts

@@ -1547,28 +1547,12 @@ const DEEPSEEK: CliEntry = {
     // privilege rather than granting it, and clamping it here was a real regression
     // (test/deepseek-mode.test.ts) fixed before this shipped.
     privilegedEnvKeys: ['DSH_PERMISSION_MODE', 'DSH_HOME', 'DEEPSEEK_BASE_URL'],
-    // Reuses the already-existing DEEPSEEK_BASE_URL/DEEPSEEK_API_KEY keys above. No
-    // modelVars — dsh's model is a profile-composition entry (see `model: { source: 'none'
-    // }` above), not an env var, so forcing a specific model name may not fully work;
-    // verify against a real profile before shipping.
-    //
-    // ⚠️ appendV1Suffix is REQUIRED, not optional-nice-to-have: without it every request
-    // 404s. Confirmed live and by reading dsh's own bundled source
-    // (@deepseek-ai/dsh-llm-deepseek): it builds the request URL as
-    // `${DEEPSEEK_BASE_URL}/chat/completions` with no "/v1" of its own (its real public
-    // API, https://api.deepseek.com, expects the caller's base URL to already carry any
-    // needed prefix), while llama-swap/llama.cpp only serves the OpenAI-conventional
-    // "/v1/chat/completions" — a bare POST to ".../chat/completions" 404s live, and the
-    // 404 reported here originally ("dsh: HTTP_404: DeepSeek API error (HTTP 404)")
-    // matches dsh's own error-message template for exactly this failure. See the
-    // customModelInjection doc comment in cli-registry/types.ts for the full reasoning,
-    // including why claude/gemini must NOT get this.
+    // The installed profile supplies the transport; a per-session patch selects its exact model.
     customModelInjection: {
-      kind: 'env',
-      baseUrlVar: 'DEEPSEEK_BASE_URL',
-      apiKeyVar: 'DEEPSEEK_API_KEY',
-      modelVars: [],
-      appendV1Suffix: true,
+      kind: 'configDir',
+      dirEnvVar: 'DSH_HOME',
+      fileName: 'cordis.patch.yml',
+      template: 'deepseek-patch-json',
     },
   },
   overlays: {

src/config/cli-registry/types.ts

@@ -888,7 +888,7 @@ export interface CliCapabilities {
         kind: 'configDir';
         dirEnvVar: string;
         fileName: string;
-        template: 'codex-toml' | 'pi-models-json' | 'omp-models-yml' | 'grok-toml';
+        template: 'codex-toml' | 'pi-models-json' | 'omp-models-yml' | 'grok-toml' | 'deepseek-patch-json';
         launchModel?: string;
       }
     | { kind: 'unsupported' };

src/custom-model-injection-apply.ts

@@ -46,6 +46,14 @@ export function applyConfigDirInjection(baseDir: string, injection: ConfigDirInj
     writeFileSync(filePath, file.content, { encoding: 'utf8', mode: 0o600 });
     chmodSync(filePath, 0o600);
   }
+  if (injection.dirEnvVar === 'DSH_HOME') {
+    // Reuse installed profile bundles without changing the user's profile or credentials.
+    const profiles = join(baseDir, 'profiles');
+    if (!existsSync(profiles)) {
+      const realHome = process.env.DSH_HOME?.trim() || join(homedir(), '.dsh');
+      symlinkSync(join(realHome, 'profiles'), profiles, platform() === 'win32' ? 'junction' : 'dir');
+    }
+  }
   return { [injection.dirEnvVar]: baseDir, ...injection.extraEnv };
 }
 

src/custom-model-injection.ts

@@ -141,7 +141,7 @@ export function buildCustomModelInjection(
     }
 
     case 'configDir': {
-      const { content, extraEnv } = renderConfigFile(cap.template, endpoint, modelId, apiKey);
+      const { content, extraEnv } = renderConfigFile(cap.template, endpoint, modelId, apiKey, contextLength);
       return withLaunchModel(
         { kind: 'configDir', dirEnvVar: cap.dirEnvVar, files: [{ relPath: cap.fileName, content }], extraEnv },
         cap.launchModel,
@@ -192,13 +192,53 @@ const CODEX_API_KEY_ENV_VAR = 'CODEMAN_CUSTOM_MODEL_API_KEY';
 export const GROK_CUSTOM_MODEL_NAME = 'codeman-custom';
 
 function renderConfigFile(
-  template: 'codex-toml' | 'pi-models-json' | 'omp-models-yml' | 'grok-toml',
+  template: 'codex-toml' | 'pi-models-json' | 'omp-models-yml' | 'grok-toml' | 'deepseek-patch-json',
   endpoint: CustomModelEndpoint,
   modelId: string,
-  apiKey: string
+  apiKey: string,
+  contextLength?: number
 ): { content: string; extraEnv?: Record<string, string> } {
   const baseUrl = withV1Suffix(endpoint.baseUrl);
   switch (template) {
+    case 'deepseek-patch-json': {
+      const route = { provider: 'codeman-custom', model: modelId };
+      return {
+        content: JSON.stringify(
+          [
+            {
+              id: 'llm-pi-ai',
+              name: '@deepseek-ai/dsh-llm-pi-ai',
+              config: {
+                providers: {
+                  'codeman-custom': {
+                    apiKeyEnv: 'DEEPSEEK_API_KEY',
+                    api: 'openai-completions',
+                    baseURL: baseUrl,
+                    models: [
+                      {
+                        id: modelId,
+                        name: modelId,
+                        ...(contextLength !== undefined && Number.isFinite(contextLength) && contextLength > 0
+                          ? {
+                              contextWindow: Math.trunc(contextLength),
+                              maxTokens: Math.max(1, Math.min(8192, Math.floor(contextLength / 4))),
+                            }
+                          : {}),
+                      },
+                    ],
+                  },
+                },
+              },
+            },
+            { id: 'dsh-tui', name: '@deepseek-harness-tui/dsh-tui', config: route },
+            { id: 'agent-default-model', name: '@deepseek-ai/dsh-agent-default-model', config: route },
+          ],
+          null,
+          2
+        ),
+        extraEnv: { DEEPSEEK_API_KEY: apiKey },
+      };
+    }
     case 'codex-toml': {
       // Verified against real codex (>= Feb 2026): `model` is a top-level STRING, never
       // a `[model].default` table — codex rejects that with "invalid type: map, expected

test/custom-model-injection-apply.test.ts

@@ -53,9 +53,12 @@ describe('applyCustomModelInjection: context length', () => {
     expect(applied?.envOverrides.CLAUDE_CODE_MAX_CONTEXT_TOKENS).toBeUndefined();
   });
 
-  it('deepseek: has no contextLengthVar declared, so a passed-in length is a no-op', () => {
-    const applied = applyCustomModelInjection(entryOrThrow('deepseek'), endpoint, 'qwen3', 'sess-ctx-3', 16384);
-    expect(Object.keys(applied?.envOverrides ?? {}).sort()).toEqual(['DEEPSEEK_API_KEY', 'DEEPSEEK_BASE_URL']);
+  it('deepseek: passes the known context through its isolated model catalogue', () => {
+    const sessionId = 'sess-deepseek-context';
+    sessionsToClean.push(sessionId);
+    const applied = applyCustomModelInjection(entryOrThrow('deepseek'), endpoint, 'qwen3', sessionId, 32768);
+    expect(Object.keys(applied?.envOverrides ?? {}).sort()).toEqual(['DEEPSEEK_API_KEY', 'DSH_HOME']);
+    expect(readFileSync(join(applied!.configDir!, 'cordis.patch.yml'), 'utf8')).toContain('"contextWindow": 32768');
   });
 });
 
@@ -103,11 +106,12 @@ describe('applyCustomModelInjection: CLAUDE_CONFIG_DIR isolation', () => {
     expect(applied?.envOverrides.HOME).toBe(customModelConfigDir(sessionId));
   });
 
-  it('deepseek: no configDirVar declared, so no config dir is created at all', () => {
+  it('deepseek: creates an isolated profile patch', () => {
     const sessionId = 'sess-cfgdir-deepseek';
+    sessionsToClean.push(sessionId);
     const applied = applyCustomModelInjection(entryOrThrow('deepseek'), endpoint, 'qwen3', sessionId);
-    expect(applied?.configDir).toBeUndefined();
-    expect(existsSync(customModelConfigDir(sessionId))).toBe(false);
+    expect(applied?.configDir).toBe(customModelConfigDir(sessionId));
+    expect(existsSync(join(applied!.configDir!, 'cordis.patch.yml'))).toBe(true);
   });
 });
 

test/custom-model-injection-contract.test.ts

@@ -188,18 +188,18 @@ describe('custom-model-injection contract (mock server)', () => {
     expect(mock.requests[0].headers.authorization).toBe('Bearer contract-test-key');
   });
 
-  it('deepseek: DEEPSEEK_BASE_URL already carries the /v1 suffix dsh itself never adds, reaching the mock at the real path dsh requests', async () => {
-    // Confirmed by reading dsh's own bundled source: it fetches
-    // `${DEEPSEEK_BASE_URL}/chat/completions` verbatim, no /v1 insertion of its own — so
-    // this call (unlike gemini's above) passes DEEPSEEK_BASE_URL to callOpenAiCompat
-    // UNMODIFIED, exactly mirroring what the real harness does, rather than the test
-    // helping it along.
+  it('deepseek: the session patch carries the /v1 base URL and exact model, reaching the mock at the real path', async () => {
+    // dsh fetches `${baseURL}/chat/completions` verbatim, so the patch's baseURL already
+    // carries /v1 and is passed to callOpenAiCompat unmodified.
     const injection = buildCustomModelInjection(entryOrThrow('deepseek'), endpointFor(mock), 'qwen3');
-    if (injection.kind !== 'env') throw new Error('unreachable');
-    expect(Object.keys(injection.envOverrides).sort()).toEqual(['DEEPSEEK_API_KEY', 'DEEPSEEK_BASE_URL']);
-    expect(injection.envOverrides.DEEPSEEK_BASE_URL).toBe(`${mock.baseUrl}/v1`);
+    if (injection.kind !== 'configDir') throw new Error('unreachable');
+    expect(injection.dirEnvVar).toBe('DSH_HOME');
+    expect(Object.keys(injection.extraEnv ?? {})).toEqual(['DEEPSEEK_API_KEY']);
+    const provider = JSON.parse(injection.files[0].content)[0].config.providers['codeman-custom'];
+    expect(provider.baseURL).toBe(`${mock.baseUrl}/v1`);
+    expect(provider.models[0].id).toBe('qwen3');
 
-    await callOpenAiCompat(injection.envOverrides.DEEPSEEK_BASE_URL, injection.envOverrides.DEEPSEEK_API_KEY, 'qwen3');
+    await callOpenAiCompat(provider.baseURL, injection.extraEnv!.DEEPSEEK_API_KEY, 'qwen3');
 
     expect(mock.requests[0].path).toBe('/v1/chat/completions');
     expect(mock.requests[0].headers.authorization).toBe('Bearer contract-test-key');

test/custom-model-injection.test.ts

@@ -179,29 +179,25 @@ describe('buildCustomModelInjection', () => {
     expect(result.extraEnv).toEqual({ XAI_API_KEY: 'my-key' });
   });
 
-  it('deepseek: env kind sets base URL (with a /v1 suffix appended) and key, no model var', () => {
-    // appendV1Suffix is REQUIRED here, not cosmetic: confirmed by reading dsh's own
-    // bundled source (@deepseek-ai/dsh-llm-deepseek) that it builds the request URL as
-    // `${DEEPSEEK_BASE_URL}/chat/completions` with no "/v1" of its own, while
-    // llama-swap/llama.cpp only serves "/v1/chat/completions" — without this, every
-    // request 404s (confirmed live; this is the fix for the originally-reported
-    // "dsh: HTTP_404: DeepSeek API error (HTTP 404)").
+  it('deepseek: isolates the selected model route and passes its key by reference', () => {
     const result = buildCustomModelInjection(entryOrThrow('deepseek'), endpoint, 'qwen3');
-    if (result.kind !== 'env') throw new Error('unreachable');
-    expect(result.envOverrides).toEqual({
-      DEEPSEEK_BASE_URL: 'http://192.168.1.50:8080/v1',
-      DEEPSEEK_API_KEY: 'my-key',
-    });
+    if (result.kind !== 'configDir') throw new Error('Expected isolated DeepSeek config');
+    expect(result.dirEnvVar).toBe('DSH_HOME');
+    expect(result.extraEnv).toEqual({ DEEPSEEK_API_KEY: 'my-key' });
+    expect(result.files[0].content).not.toContain('my-key');
+    const patch = JSON.parse(result.files[0].content);
+    expect(patch.find((row: { id: string }) => row.id === 'dsh-tui').config.model).toBe('qwen3');
   });
 
-  it('deepseek: appending the /v1 suffix is idempotent against a baseUrl that already ends in /v1', () => {
+  it('deepseek: preserves an existing version suffix', () => {
     const result = buildCustomModelInjection(
       entryOrThrow('deepseek'),
-      { ...endpoint, baseUrl: 'http://192.168.1.50:8080/v1' },
+      { ...endpoint, baseUrl: endpoint.baseUrl + '/v1' },
       'qwen3'
     );
-    if (result.kind !== 'env') throw new Error('unreachable');
-    expect(result.envOverrides.DEEPSEEK_BASE_URL).toBe('http://192.168.1.50:8080/v1');
+    if (result.kind !== 'configDir') throw new Error('Expected isolated DeepSeek config');
+    expect(result.files[0].content).toContain('http://192.168.1.50:8080/v1');
+    expect(result.files[0].content).not.toContain('/v1/v1');
   });
 
   it('antigravity: unsupported', () => {

test/deepseek-custom-endpoint.test.ts

@@ -0,0 +1,64 @@
+import { mkdirSync, readFileSync, realpathSync, writeFileSync } from 'node:fs';
+import { homedir } from 'node:os';
+import { join } from 'node:path';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { getCli } from '../src/config/cli-registry/index.js';
+import { buildCustomModelInjection } from '../src/custom-model-injection.js';
+import {
+  applyCustomModelInjection,
+  removeConfigDir,
+  customModelConfigDir,
+} from '../src/custom-model-injection-apply.js';
+
+afterEach(() => {
+  removeConfigDir(customModelConfigDir('deepseek-probe'));
+  vi.unstubAllEnvs();
+});
+
+describe('DeepSeek custom endpoint isolation', () => {
+  it('uses the chosen model and limits without changing installed profiles or embedding the key', () => {
+    const realHome = join(homedir(), '.dsh');
+    const profile = join(realHome, 'profiles', 'dsh-tui');
+    mkdirSync(profile, { recursive: true });
+    const original = join(profile, 'cordis.patch.yml');
+    writeFileSync(original, 'original profile');
+    vi.stubEnv('DSH_HOME', realHome);
+    const entry = getCli('deepseek');
+    if (!entry) throw new Error('Missing DeepSeek entry');
+    const endpoint = { id: 'local', label: 'Local', baseUrl: 'http://box:8080', apiKey: 'private-probe-key' };
+    const applied = applyCustomModelInjection(entry, endpoint, 'chosen-model', 'deepseek-probe', 131072);
+    if (!applied?.configDir) throw new Error('Missing isolated profile');
+    const content = readFileSync(join(applied.configDir, 'cordis.patch.yml'), 'utf8');
+    expect(content).not.toContain(endpoint.apiKey);
+    expect(applied.envOverrides.DEEPSEEK_API_KEY).toBe(endpoint.apiKey);
+    const patch = JSON.parse(content);
+    const provider = patch.find((row: { id: string }) => row.id === 'llm-pi-ai').config.providers['codeman-custom'];
+    expect(provider.api).toBe('openai-completions');
+    expect(provider.baseURL).toBe('http://box:8080/v1');
+    expect(provider.models).toEqual([
+      { id: 'chosen-model', name: 'chosen-model', contextWindow: 131072, maxTokens: 8192 },
+    ]);
+    expect(patch.find((row: { id: string }) => row.id === 'dsh-tui').config).toEqual({
+      provider: 'codeman-custom',
+      model: 'chosen-model',
+    });
+    expect(realpathSync(join(applied.configDir, 'profiles'))).toBe(join(realHome, 'profiles'));
+    removeConfigDir(applied.configDir);
+    expect(readFileSync(original, 'utf8')).toBe('original profile');
+  });
+
+  it('gives Codex its known context and compaction budget', () => {
+    const entry = getCli('codex');
+    if (!entry) throw new Error('Missing Codex entry');
+    const injection = buildCustomModelInjection(
+      entry,
+      { id: 'local', label: 'Local', baseUrl: 'http://box' },
+      'chosen-model',
+      131072
+    );
+    if (injection.kind !== 'configDir') throw new Error('Expected isolated Codex config');
+    expect(injection.files[0].content).toContain('model_context_window = 131072');
+    expect(injection.files[0].content).toContain('model_auto_compact_token_limit = 98304');
+    expect(injection.launchModel).toBe('chosen-model');
+  });
+});