fix(server): use T3 sender for Claude userEmail (TEC-1031)

apps/server/src/provider/Layers/ClaudeAdapter.ts

@@ -102,6 +102,8 @@ import {
 import { makeObservableLifecycle } from "../observableLifecycle.ts";
 import { type ClaudeAdapterShape } from "../Services/ClaudeAdapter.ts";
 import { type EventNdjsonLogger, makeEventNdjsonLogger } from "./EventNdjsonLogger.ts";
+// T3-CUSTOM(expbkt3): Claude's shared account email is not the T3 message sender.
+import { claudeSessionIdentitySystemPrompt } from "../claudeSessionIdentity.expbkt3.ts";
 const encodeUnknownJsonStringExit = Schema.encodeUnknownExit(Schema.fromJsonString(Schema.Unknown));
 const decodeUnknownJsonStringExit = Schema.decodeUnknownExit(Schema.fromJsonString(Schema.Unknown));
 
@@ -4193,11 +4195,20 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
         ...(input.cwd ? [input.cwd] : []),
         serverConfig.attachmentsDir,
       ];
+      // T3-CUSTOM(expbkt3): BEGIN override Claude's shared-account userEmail context.
+      const sessionIdentitySystemPrompt = claudeSessionIdentitySystemPrompt(sessionEnvironment);
+      // T3-CUSTOM(expbkt3): END
       const queryOptions: ClaudeQueryOptions = {
         ...(input.cwd ? { cwd: input.cwd } : {}),
         ...(apiModelId ? { model: apiModelId } : {}),
         pathToClaudeCodeExecutable: claudeBinaryPath,
-        systemPrompt: { type: "preset", preset: "claude_code" },
+        // T3-CUSTOM(expbkt3): BEGIN preserve the native prompt with T3 sender identity appended.
+        systemPrompt: {
+          type: "preset",
+          preset: "claude_code",
+          ...(sessionIdentitySystemPrompt ? { append: sessionIdentitySystemPrompt } : {}),
+        },
+        // T3-CUSTOM(expbkt3): END
         settingSources: [...CLAUDE_SETTING_SOURCES],
         // `ultracode` is a Claude Code setting, not an API effort level. It is
         // normalized to `xhigh` above and paired with `settings.ultracode`.

apps/server/src/provider/claudeSessionIdentity.expbkt3.test.ts

@@ -0,0 +1,39 @@
+import { assert, describe, it } from "@effect/vitest";
+
+import { claudeSessionIdentitySystemPrompt } from "./claudeSessionIdentity.expbkt3.ts";
+
+describe("claudeSessionIdentitySystemPrompt", () => {
+  it("uses the current T3 message sender instead of the shared Claude account", () => {
+    assert.equal(
+      claudeSessionIdentitySystemPrompt({
+        BK_IDENTITY_RUNTIME: "t3-code",
+        BK_SESSION_OWNER_EMAIL: "owner@example.test",
+        BK_MESSAGE_SENDER_EMAIL: " sender@example.test ",
+      }),
+      [
+        "T3 Code session identity:",
+        '- userEmail is "sender@example.test".',
+        "- This session-scoped value identifies the user who sent the current message and overrides the Claude account email for user attribution.",
+      ].join("\n"),
+    );
+  });
+
+  it("keeps the user unknown when T3 cannot resolve the message sender", () => {
+    assert.include(
+      claudeSessionIdentitySystemPrompt({
+        BK_IDENTITY_RUNTIME: "t3-code",
+        BK_SESSION_OWNER_EMAIL: "owner@example.test",
+      }) ?? "",
+      "userEmail is unavailable",
+    );
+  });
+
+  it("does not change upstream Claude sessions", () => {
+    assert.equal(
+      claudeSessionIdentitySystemPrompt({
+        BK_MESSAGE_SENDER_EMAIL: "sender@example.test",
+      }),
+      undefined,
+    );
+  });
+});

apps/server/src/provider/claudeSessionIdentity.expbkt3.ts

@@ -0,0 +1,34 @@
+// T3-CUSTOM(expbkt3): Claude Code derives its native `userEmail` context from
+// the authenticated Claude account. Beknown runs that account on a shared
+// machine, so it identifies the subscription rather than the person sending
+// the current T3 message. Append the session-scoped identity to Claude's native
+// system prompt without changing the account used for authentication.
+
+import {
+  MESSAGE_SENDER_EMAIL_KEY,
+  SESSION_IDENTITY_RUNTIME,
+  SESSION_IDENTITY_RUNTIME_KEY,
+} from "../identity/SessionIdentityEnvironment.ts";
+
+export function claudeSessionIdentitySystemPrompt(
+  environment: NodeJS.ProcessEnv,
+): string | undefined {
+  if (environment[SESSION_IDENTITY_RUNTIME_KEY] !== SESSION_IDENTITY_RUNTIME) {
+    return undefined;
+  }
+
+  const senderEmail = environment[MESSAGE_SENDER_EMAIL_KEY]?.trim();
+  if (!senderEmail) {
+    return [
+      "T3 Code session identity:",
+      "- userEmail is unavailable for the user who sent the current message.",
+      "- Do not use the Claude account email, operating-system identity, or Git identity to infer the user.",
+    ].join("\n");
+  }
+
+  return [
+    "T3 Code session identity:",
+    `- userEmail is ${JSON.stringify(senderEmail)}.`,
+    "- This session-scoped value identifies the user who sent the current message and overrides the Claude account email for user attribution.",
+  ].join("\n");
+}

docs/operations/expbkt3-customizations.md

@@ -395,6 +395,14 @@ Four rules carry the behaviour:
   live session was started with and restarts on an owner transfer or a new
   sender, next to the existing credential-actor restart.
 
+Claude Code's native system prompt normally derives `userEmail` from the
+authenticated Claude account. That account is shared in the Beknown runtime, so
+the Claude adapter appends the resolved `BK_MESSAGE_SENDER_EMAIL` as the
+authoritative `userEmail`. When the sender is unresolved, the appended context
+explicitly leaves `userEmail` unknown and forbids inference from the shared
+Claude account, operating-system identity, or Git identity. Non-T3 Claude
+sessions keep the upstream system prompt unchanged.
+
 The markers compose with source-control profiles rather than replacing them:
 `mergeSourceControlEnvironment` scrubs the machine's inherited Git and GitHub
 credentials only when the overlay carries a source-control identity of its own,