Add full shell, replaceable Omics adapter and bilingual interaction

Implement approved specification #32 and tickets #33-#37. Keep host authentication server-verified and pin session interaction language. Compile scoped base selectors for browser compatibility and retain full gutters during CSS pruning.

backend/src/pi/pi-process-manager.ts

@@ -25,6 +25,7 @@ export interface SessionRuntime {
 }
 
 export interface RuntimeOptions {
+  interactionLanguage?: string | null;
   provider?: string;
   model?: string;
   thinking?: string;
@@ -48,6 +49,7 @@ export class PiProcessManager {
   private spawnFn: (
     sessionId: string, author: string, provider: string | undefined, model: string | undefined,
     principal?: PrincipalContext, runtimeConfigPath?: string,
+    interactionLanguage?: string | null,
   ) => ChildProcessWithoutNullStreams;
   private loadAuthProviders: (agentDir: string) => ReadonlySet<string>;
   private modelCatalog: RuntimeModelCatalog;
@@ -67,11 +69,11 @@ export class PiProcessManager {
     this.loadAuthProviders = opts?.authProviders
       ?? ((agentDir) => loadPiAuthProviders({ agentDir }));
     if (opts?.spawnFn) {
-      this.spawnFn = (sessionId, author, provider, model, principal, runtimeConfigPath) =>
-        this.spawnPi(opts.spawnFn!, sessionId, author, provider, model, principal, runtimeConfigPath);
+      this.spawnFn = (sessionId, author, provider, model, principal, runtimeConfigPath, language) =>
+        this.spawnPi(opts.spawnFn!, sessionId, author, provider, model, principal, runtimeConfigPath, language);
     } else {
-      this.spawnFn = (sessionId, author, provider, model, principal, runtimeConfigPath) =>
-        this.spawnPi(nodeSpawn, sessionId, author, provider, model, principal, runtimeConfigPath);
+      this.spawnFn = (sessionId, author, provider, model, principal, runtimeConfigPath, language) =>
+        this.spawnPi(nodeSpawn, sessionId, author, provider, model, principal, runtimeConfigPath, language);
     }
   }
 
@@ -85,6 +87,7 @@ export class PiProcessManager {
   private spawnPi(
     spawnFn: SpawnFn, sessionId: string, author: string, provider: string | undefined,
     model: string | undefined, principal?: PrincipalContext, runtimeConfigPath?: string,
+    interactionLanguage?: string | null,
   ): ChildProcessWithoutNullStreams {
     // This is the final shared boundary for createFor(), spawnFor(), and resume(). Validate
     // before auth-provider inspection, then make Pi consume the exact copied bytes rather than
@@ -110,6 +113,9 @@ export class PiProcessManager {
         additions: { THT_SESSION: sessionId, THT_AUTHOR: author },
       });
       env.PI_CODING_AGENT_DIR = agent.agentDir;
+      // A launch hint only: the gate reads the authoritative manifest before each turn.
+      delete env.THT_INTERACTION_LANGUAGE;
+      if (interactionLanguage) env.THT_INTERACTION_LANGUAGE = interactionLanguage;
       env.PI_CODING_AGENT_SESSION_DIR = agent.sessionDir;
       clearPrincipalEnvironment(env);
       if (principal) Object.assign(env, principalEnvironment(principal));
@@ -187,7 +193,9 @@ export class PiProcessManager {
     const model = o.model ?? this.cfg.defaults.model;
     let child: ChildProcessWithoutNullStreams;
     try {
-      child = this.spawnFn(sessionId, author, provider, model, o.principal, o.runtimeConfig?.path);
+      child = this.spawnFn(
+        sessionId, author, provider, model, o.principal, o.runtimeConfig?.path, o.interactionLanguage,
+      );
     } catch (error) {
       o.runtimeConfig?.release();
       throw error;
@@ -296,8 +304,13 @@ export class PiProcessManager {
   }
 
   async resume(sessionId: string, tht: ThtRunner): Promise<SessionRuntime> {
-    const manifest = await tht.sessionShow(sessionId) as { provider?: string; model?: string; thinking?: string } | null;
+    const manifest = await tht.sessionShow(sessionId) as {
+      provider?: string; model?: string; thinking?: string; interaction_language?: string | null;
+    } | null;
+    const language = manifest?.interaction_language
+      ?? (await tht.ensureInteractionLanguage(sessionId)).interaction_language;
     return this.spawnFor(sessionId, {
+      interactionLanguage: language,
       provider: manifest?.provider,
       model: manifest?.model,
       thinking: manifest?.thinking,

backend/src/routes/sessions.ts

@@ -13,6 +13,7 @@ import type { MaintenanceBarrier } from "../runtime/maintenance-gate.js";
 import { hasPermission, isPrincipalContext, requirePermission } from "../auth/authorization.js";
 import { splitCanonicalModelId, type RuntimeModelCatalog } from "../models/runtime-model-catalog.js";
 import type { CatalogRepository } from "../catalog/types.js";
+import { interactionLanguage } from "../tht/interaction-language.js";
 
 const BOOTSTRAP_FAILURE_MESSAGE =
   "Session startup failed. Check configuration and connectivity, then Resume the session.";
@@ -381,8 +382,13 @@ export function sessionRoutes(
   app.post("/sessions", async (req, reply) => {
     const b = req.body as {
       question: string; name?: string; workspace?: string; workspaceId?: string;
-      provider?: string; model?: string; thinking?: string;
+      provider?: string; model?: string; thinking?: string; interactionLanguage?: unknown;
     };
+    const language = interactionLanguage(b?.interactionLanguage);
+    if (!language) return reply.code(400).send({
+      code: "invalid_interaction_language",
+      error: "interactionLanguage must be a well-formed BCP-47 language tag",
+    });
     if ((b.provider === undefined) !== (b.model === undefined)
       || (b.provider !== undefined && (typeof b.provider !== "string" || typeof b.model !== "string" || !b.provider || !b.model))) {
       return reply.code(400).send({ error: "provider and model must be supplied together" });
@@ -507,6 +513,7 @@ export function sessionRoutes(
         ({ id } = await runner.sessionNew({
           question: b.question, name: b.name, workspaceConfigPath,
           workspaceId, workspaceRevision, provider, model, thinking,
+          interactionLanguage: language,
         }));
         manifestPersisted = true;
         if (revisionLease) {
@@ -520,6 +527,7 @@ export function sessionRoutes(
       } catch { return storageFailure(reply); }
       const options = {
         provider, model, thinking,
+        interactionLanguage: language,
         author: principal.displayName ?? principal.subject,
         principal,
         question: b.question,
@@ -664,6 +672,13 @@ export function sessionRoutes(
   app.post("/sessions/:id/resume", async (req, reply) => {
     const id = (req.params as any).id;
     const principal = getPrincipal(req);
+    if (Object.hasOwn(req.body ?? {}, "interactionLanguage")
+      || Object.hasOwn(req.body ?? {}, "interaction_language")) {
+      return reply.code(400).send({
+        code: "interaction_language_pinned",
+        error: "Resume uses the session's persisted interaction language; overrides are not accepted",
+      });
+    }
     return withSessionLifecycle(id, async () => {
       let settings: Settings;
       let located: LocatedSession | undefined;
@@ -681,6 +696,7 @@ export function sessionRoutes(
       const saved = manifest as {
         provider?: string; model?: string; thinking?: string;
         workspace_id?: string; workspace_revision?: string;
+        interaction_language?: string | null;
       };
 	  const requested = (req.body ?? {}) as { provider?: string; model?: string; thinking?: string };
 	  if ((requested.provider === undefined) !== (requested.model === undefined)
@@ -719,6 +735,12 @@ export function sessionRoutes(
         });
       }
       try { settings = await d.getSettings(principal); } catch { return storageFailure(reply); }
+      let language = saved.interaction_language;
+      if (language == null) {
+        try {
+          language = (await runner.ensureInteractionLanguage(id, workspaceConfigPath)).interaction_language;
+        } catch { return reply.code(503).send({ error: RESUME_FAILURE_MESSAGE }); }
+      }
       // This check belongs inside the per-session lock: a preceding cold Resume may have
       // installed a running runtime while this request was waiting.
       const existing = d.mgr.get(id);
@@ -737,6 +759,7 @@ export function sessionRoutes(
       });
       const options = {
         provider: selected.provider,
+        interactionLanguage: language,
         model: selected.model,
         thinking: saved?.thinking ?? settings.thinking,
         author: principal.displayName ?? principal.subject,

backend/src/tht/interaction-language.ts

@@ -0,0 +1,10 @@
+/** Validate/canonicalize the tag; available translation catalogs belong to the UI. */
+export function interactionLanguage(value: unknown): string | undefined {
+  if (typeof value !== "string") return undefined;
+  try {
+    const [canonical] = Intl.getCanonicalLocales(value);
+    return canonical;
+  } catch {
+    return undefined;
+  }
+}

backend/src/tht/tht-runner.ts

@@ -59,6 +59,7 @@ export interface SessionRow {
   author: string | null;
   workspace_id?: string | null;
   workspace_revision?: string | null;
+  interaction_language?: string | null;
   archived?: boolean;
 }
 
@@ -482,6 +483,7 @@ export class ThtRunner {
 
   async sessionNew(o: {
     question: string;
+    interactionLanguage?: string;
     provider?: string;
     model?: string;
     thinking?: string;
@@ -497,6 +499,7 @@ export class ThtRunner {
       ["--provider", o.provider],
       ["--model", o.model],
       ["--thinking", o.thinking],
+      ["--interaction-language", o.interactionLanguage],
       ["--name", o.name],
       ["--workspace-id", o.workspaceId],
       ["--workspace-revision", o.workspaceRevision],
@@ -533,6 +536,12 @@ export class ThtRunner {
     return this.json<unknown>(["session", "show", id, "--json"], workspace);
   }
 
+  ensureInteractionLanguage(id: string, workspace?: string) {
+    return this.json<{ interaction_language: string }>(
+      ["session", "ensure-interaction-language", id, "--json"], workspace,
+    );
+  }
+
   sqlPreview(id: string, p: { limit?: number; offset?: number }, workspace?: string) {
     // No positional FILE: the harness resolves sql_final.sql from the session
     // via _session_sql_file(cfg, session_id), which respects the workspace path.