feat: refine subagents + add chat.inject

Co-authored-by: Tyler Yust <tyler6204@users.noreply.github.com>

src/gateway/server-methods/chat.ts

@@ -1,9 +1,11 @@
 import { randomUUID } from "node:crypto";
+import fs from "node:fs";
+import path from "node:path";
 
 import { resolveThinkingDefault } from "../../agents/model-selection.js";
 import { resolveAgentTimeoutMs } from "../../agents/timeout.js";
 import { agentCommand } from "../../commands/agent.js";
-import { mergeSessionEntry, saveSessionStore } from "../../config/sessions.js";
+import { mergeSessionEntry, updateSessionStore } from "../../config/sessions.js";
 import { registerAgentRunContext } from "../../infra/agent-events.js";
 import { defaultRuntime } from "../../runtime.js";
 import { resolveSendPolicy } from "../../sessions/send-policy.js";
@@ -21,6 +23,7 @@ import {
   formatValidationErrors,
   validateChatAbortParams,
   validateChatHistoryParams,
+  validateChatInjectParams,
   validateChatSendParams,
 } from "../protocol/index.js";
 import { MAX_CHAT_HISTORY_MESSAGES_BYTES } from "../server-constants.js";
@@ -205,7 +208,7 @@ export const chatHandlers: GatewayRequestHandlers = {
         return;
       }
     }
-    const { cfg, storePath, store, entry, canonicalKey } = loadSessionEntry(p.sessionKey);
+    const { cfg, storePath, entry, canonicalKey } = loadSessionEntry(p.sessionKey);
     const timeoutMs = resolveAgentTimeoutMs({
       cfg,
       overrideMs: p.timeoutMs,
@@ -284,11 +287,10 @@ export const chatHandlers: GatewayRequestHandlers = {
         clientRunId,
       });
 
-      if (store) {
-        store[canonicalKey] = sessionEntry;
-        if (storePath) {
-          await saveSessionStore(storePath, store);
-        }
+      if (storePath) {
+        await updateSessionStore(storePath, (store) => {
+          store[canonicalKey] = sessionEntry;
+        });
       }
 
       const ackPayload = {
@@ -355,4 +357,80 @@ export const chatHandlers: GatewayRequestHandlers = {
       });
     }
   },
+  "chat.inject": async ({ params, respond, context }) => {
+    if (!validateChatInjectParams(params)) {
+      respond(
+        false,
+        undefined,
+        errorShape(
+          ErrorCodes.INVALID_REQUEST,
+          `invalid chat.inject params: ${formatValidationErrors(validateChatInjectParams.errors)}`,
+        ),
+      );
+      return;
+    }
+    const p = params as {
+      sessionKey: string;
+      message: string;
+      label?: string;
+    };
+
+    // Load session to find transcript file
+    const { storePath, entry } = loadSessionEntry(p.sessionKey);
+    const sessionId = entry?.sessionId;
+    if (!sessionId || !storePath) {
+      respond(false, undefined, errorShape(ErrorCodes.INVALID_REQUEST, "session not found"));
+      return;
+    }
+
+    // Resolve transcript path
+    const transcriptPath = entry?.sessionFile
+      ? entry.sessionFile
+      : path.join(path.dirname(storePath), `${sessionId}.jsonl`);
+
+    if (!fs.existsSync(transcriptPath)) {
+      respond(false, undefined, errorShape(ErrorCodes.INVALID_REQUEST, "transcript file not found"));
+      return;
+    }
+
+    // Build transcript entry
+    const now = Date.now();
+    const messageId = randomUUID().slice(0, 8);
+    const labelPrefix = p.label ? `[${p.label}]\n\n` : "";
+    const messageBody: Record<string, unknown> = {
+      role: "assistant",
+      content: [{ type: "text", text: `${labelPrefix}${p.message}` }],
+      timestamp: now,
+      stopReason: "injected",
+      usage: { input: 0, output: 0, totalTokens: 0 },
+    };
+    const transcriptEntry = {
+      type: "message",
+      id: messageId,
+      timestamp: new Date(now).toISOString(),
+      message: messageBody,
+    };
+
+    // Append to transcript file
+    try {
+      fs.appendFileSync(transcriptPath, `${JSON.stringify(transcriptEntry)}\n`, "utf-8");
+    } catch (err) {
+      const errMessage = err instanceof Error ? err.message : String(err);
+      respond(false, undefined, errorShape(ErrorCodes.UNAVAILABLE, `failed to write transcript: ${errMessage}`));
+      return;
+    }
+
+    // Broadcast to webchat for immediate UI update
+    const chatPayload = {
+      runId: `inject-${messageId}`,
+      sessionKey: p.sessionKey,
+      seq: 0,
+      state: "final" as const,
+      message: transcriptEntry.message,
+    };
+    context.broadcast("chat", chatPayload);
+    context.bridgeSendToSession(p.sessionKey, "chat", chatPayload);
+
+    respond(true, { ok: true, messageId });
+  },
 };