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