Add per-chat settings UI in web app for additional system prompt and tool checkboxes

docs/api/rest.md

@@ -42,6 +42,23 @@ Chat upload limits:
 - `hermes-agent` is included only when `HERMES_AGENT_API_KEY` is configured. Set it to Hermes `API_SERVER_KEY`, or any non-empty value if that local server does not require auth. `HERMES_AGENT_API_BASE_URL` defaults to `http://127.0.0.1:8642/v1`; set `HERMES_AGENT_MODEL` only when you need an additional fallback/override model id.
 - The backend loads provider model lists at startup and refreshes them about once every 24 hours. If a later provider refresh fails, the response keeps the last loaded model list for that provider and sets `error` to the latest failure message.
 
+## Chat Tools
+
+### `GET /v1/chat-tools`
+- Response:
+```json
+{
+  "tools": [
+    { "name": "web_search", "description": "..." },
+    { "name": "fetch_url", "description": "..." }
+  ]
+}
+```
+
+Behavior notes:
+- Lists Sybil-managed chat tools that can be enabled for `openai` and `xai` chat completions.
+- Optional tools such as `codex_exec` and `shell_exec` appear only when enabled by server environment configuration.
+
 ## Active Runs
 
 ### `GET /v1/active-runs`
@@ -77,7 +94,9 @@ Behavior notes:
       "initiatedProvider": "openai",
       "initiatedModel": "gpt-4.1-mini",
       "lastUsedProvider": "openai",
-      "lastUsedModel": "gpt-4.1-mini"
+      "lastUsedModel": "gpt-4.1-mini",
+      "additionalSystemPrompt": null,
+      "enabledTools": ["web_search", "fetch_url"]
     },
     {
       "type": "search",
@@ -111,6 +130,8 @@ Behavior notes:
   "title": "optional title",
   "provider": "optional openai|anthropic|xai|hermes-agent",
   "model": "optional model id",
+  "additionalSystemPrompt": "optional stored system prompt",
+  "enabledTools": ["web_search", "fetch_url"],
   "messages": [
     {
       "role": "system|user|assistant|tool",
@@ -126,13 +147,17 @@ Behavior notes:
 Behavior notes:
 - `provider` and `model` must be supplied together when present.
 - When `provider`/`model` are supplied, the new chat initializes `initiatedProvider`/`initiatedModel` and `lastUsedProvider`/`lastUsedModel`.
+- `additionalSystemPrompt` is trimmed and stored on the chat; blank values are stored as `null`.
+- `enabledTools` stores the enabled Sybil-managed tool names for future chat completions. Unknown tool names are ignored; omitted values default to all currently available tools.
 - Optional `messages` are inserted as the initial transcript. Attachment metadata uses the same schema and limits as chat completion messages.
 
 ### `PATCH /v1/chats/:chatId`
-- Body: `{ "title": string }`
+- Body: any subset of `{ "title": string, "additionalSystemPrompt": string|null, "enabledTools": string[] }`
 - Response: `{ "chat": ChatSummary }`
 - Blank titles are rejected. The server trims surrounding whitespace before storing the title.
-- Renaming updates the returned chat's `updatedAt`.
+- `additionalSystemPrompt: null` clears the stored prompt. Blank string values are also stored as `null`.
+- `enabledTools: []` disables Sybil-managed tools for this chat. Omitted settings are left unchanged.
+- Updating chat fields changes the returned chat's `updatedAt`.
 - Not found: `404 { "message": "chat not found" }`
 
 ### `PATCH /v1/chats/:chatId/star`
@@ -237,6 +262,8 @@ Notes:
       ]
     }
   ],
+  "additionalSystemPrompt": "optional one-off system prompt",
+  "enabledTools": ["web_search", "fetch_url"],
   "temperature": 0.2,
   "maxTokens": 256
 }
@@ -256,6 +283,8 @@ Notes:
 Behavior notes:
 - If `chatId` is present, server validates chat existence.
 - For `chatId` calls, server stores only *new* non-assistant messages from provided history to avoid duplicates.
+- `additionalSystemPrompt`, when present directly or loaded from stored chat settings, is prepended to the provider request as a `system` message and is not inserted into the persisted chat transcript by this endpoint.
+- `enabledTools` limits Sybil-managed tools for this request. When omitted for a saved chat, the stored chat setting is used; otherwise all available tools are enabled by default. An empty array disables Sybil-managed tools.
 - Server persists final assistant output and call metadata (`LlmCall`) in DB.
 - Server updates chat-level model metadata on each call: `lastUsedProvider`/`lastUsedModel`; first successful/failed call also initializes `initiatedProvider`/`initiatedModel` if unset.
 - Attachments are optional and currently apply to `user` messages. Persisted chat history stores them under `message.metadata.attachments`.
@@ -390,7 +419,9 @@ Behavior notes:
   "initiatedProvider": "openai|anthropic|xai|hermes-agent|null",
   "initiatedModel": "string|null",
   "lastUsedProvider": "openai|anthropic|xai|hermes-agent|null",
-  "lastUsedModel": "string|null"
+  "lastUsedModel": "string|null",
+  "additionalSystemPrompt": null,
+  "enabledTools": ["web_search", "fetch_url"]
 }
 ```
 
@@ -441,6 +472,8 @@ Behavior notes:
   "initiatedModel": "string|null",
   "lastUsedProvider": "openai|anthropic|xai|hermes-agent|null",
   "lastUsedModel": "string|null",
+  "additionalSystemPrompt": null,
+  "enabledTools": ["web_search", "fetch_url"],
   "messages": [Message]
 }
 ```

docs/api/streaming-chat.md

@@ -49,6 +49,8 @@ Authentication:
       ]
     }
   ],
+  "additionalSystemPrompt": "optional one-off system prompt",
+  "enabledTools": ["web_search", "fetch_url"],
   "temperature": 0.2,
   "maxTokens": 256
 }
@@ -60,6 +62,8 @@ Notes:
 - If `chatId` is provided, backend validates it exists.
 - If `persist` is `false`, `chatId` must be omitted. Backend does not create a chat and does not persist input messages, tool-call messages, assistant output, or `LlmCall` metadata.
 - For persisted streams, backend stores only new non-assistant input history rows to avoid duplicates.
+- `additionalSystemPrompt`, when present directly or loaded from stored chat settings, is prepended to the provider request as a `system` message and is not inserted into the persisted chat transcript by this endpoint.
+- `enabledTools` limits Sybil-managed tools for this request. When omitted for a saved chat, the stored chat setting is used; otherwise all available tools are enabled by default. An empty array disables Sybil-managed tools.
 - Attachments are optional and are persisted under `message.metadata.attachments` on stored user messages when `persist` is `true`.
 
 Persisted chat streams with a `chatId` are backend-owned active runs:

server/prisma/migrations/20260524000000_add_chat_settings/migration.sql

@@ -0,0 +1,3 @@
+-- AlterTable
+ALTER TABLE "Chat" ADD COLUMN "additionalSystemPrompt" TEXT;
+ALTER TABLE "Chat" ADD COLUMN "enabledTools" JSONB;

server/prisma/schema.prisma

@@ -57,6 +57,9 @@ model Chat {
   lastUsedProvider  Provider?
   lastUsedModel     String?
 
+  additionalSystemPrompt String?
+  enabledTools           Json?
+
   user   User?   @relation(fields: [userId], references: [id])
   userId String?
 

server/src/llm/chat-tools.ts

@@ -192,7 +192,43 @@ const CHAT_TOOLS: any[] = [
   ...(env.CHAT_SHELL_TOOL_ENABLED ? [SHELL_EXEC_TOOL] : []),
 ];
 
-const RESPONSES_CHAT_TOOLS: any[] = CHAT_TOOLS.map((tool) => {
+function getToolName(tool: any) {
+  return typeof tool?.function?.name === "string" ? tool.function.name : null;
+}
+
+export function getAvailableChatTools() {
+  return CHAT_TOOLS.map((tool) => {
+    const name = getToolName(tool);
+    if (!name) return null;
+    return {
+      name,
+      description: typeof tool?.function?.description === "string" ? tool.function.description : "",
+    };
+  }).filter((tool): tool is { name: string; description: string } => tool !== null);
+}
+
+export function normalizeEnabledChatTools(value: unknown) {
+  if (!Array.isArray(value)) return getAvailableChatTools().map((tool) => tool.name);
+  const available = new Set(getAvailableChatTools().map((tool) => tool.name));
+  return [...new Set(value.filter((item): item is string => typeof item === "string").map((item) => item.trim()).filter(Boolean))].filter((name) =>
+    available.has(name)
+  );
+}
+
+function getEnabledToolSet(params: Pick<ToolAwareCompletionParams, "enabledTools">) {
+  return new Set(normalizeEnabledChatTools(params.enabledTools));
+}
+
+function getEnabledChatTools(params: Pick<ToolAwareCompletionParams, "enabledTools">) {
+  const enabled = getEnabledToolSet(params);
+  return CHAT_TOOLS.filter((tool) => {
+    const name = getToolName(tool);
+    return name ? enabled.has(name) : false;
+  });
+}
+
+function toResponsesChatTools(tools: any[]) {
+  return tools.map((tool) => {
   if (tool?.type !== "function") return tool;
   return {
     type: "function",
@@ -201,7 +237,8 @@ const RESPONSES_CHAT_TOOLS: any[] = CHAT_TOOLS.map((tool) => {
     parameters: tool.function.parameters,
     strict: false,
   };
-});
+  });
+}
 
 export const CHAT_TOOL_SYSTEM_PROMPT =
   "You can use tools to gather up-to-date web information when needed. " +
@@ -243,6 +280,7 @@ type ToolAwareCompletionParams = {
   client: OpenAI;
   model: string;
   messages: ChatMessage[];
+  enabledTools?: string[];
   userLocation?: string;
   temperature?: number;
   maxTokens?: number;
@@ -384,20 +422,38 @@ function extractHtmlTitle(html: string) {
   );
 }
 
-function normalizeIncomingMessages(messages: ChatMessage[], userLocation?: string) {
+function buildChatToolSystemPrompt(params: Pick<ToolAwareCompletionParams, "enabledTools">) {
+  const enabled = getEnabledToolSet(params);
+  return (
+    "You can use tools to gather up-to-date web information when needed. " +
+    (enabled.has("web_search") ? "Use web_search for discovery and recent facts. " : "") +
+    (enabled.has("fetch_url") ? "Use fetch_url to read the full content of a specific page. " : "") +
+    "Prefer tools when the user asks for current events, verification, sources, or details you do not already have. " +
+    "When you decide tool use is needed, call the tool immediately in the same response; do not say you are running a tool unless you actually call it. " +
+    (enabled.has("codex_exec")
+      ? "Use codex_exec when a request needs substantial coding work, repository inspection, shell commands, tests, debugging, or another complex task suited to a persistent Codex workspace. Provide codex_exec a complete prompt with the goal, constraints, assumptions, and expected report-back format. Never ask codex_exec to wait for user input or run interactive commands. "
+      : "") +
+    (enabled.has("shell_exec")
+      ? "Use shell_exec for direct non-interactive command-line work on the remote devbox, including quick Python programs, calculations, file inspection, running tests, and small scripts. "
+      : "") +
+    "Do not fabricate tool outputs; reason only from provided tool results."
+  );
+}
+
+function normalizeIncomingMessages(messages: ChatMessage[], userLocation?: string, params: Pick<ToolAwareCompletionParams, "enabledTools"> = {}) {
   const normalized = messages.map((message) => buildOpenAIConversationMessage(message));
 
-  return [{ role: "system", content: CHAT_TOOL_SYSTEM_PROMPT }, buildSystemPromptAugmentationMessage(userLocation), ...normalized];
+  return [{ role: "system", content: buildChatToolSystemPrompt(params) }, buildSystemPromptAugmentationMessage(userLocation), ...normalized];
 }
 
 function normalizePlainIncomingMessages(messages: ChatMessage[], userLocation?: string) {
   return [buildSystemPromptAugmentationMessage(userLocation), ...messages.map((message) => buildOpenAIConversationMessage(message))];
 }
 
-function normalizeIncomingResponsesInput(messages: ChatMessage[], userLocation?: string) {
+function normalizeIncomingResponsesInput(messages: ChatMessage[], userLocation?: string, params: Pick<ToolAwareCompletionParams, "enabledTools"> = {}) {
   const normalized = messages.map((message) => buildOpenAIResponsesInputMessage(message));
 
-  return [{ role: "system", content: CHAT_TOOL_SYSTEM_PROMPT }, buildSystemPromptAugmentationMessage(userLocation), ...normalized];
+  return [{ role: "system", content: buildChatToolSystemPrompt(params) }, buildSystemPromptAugmentationMessage(userLocation), ...normalized];
 }
 
 async function runExaWebSearchTool(args: WebSearchArgs): Promise<ToolRunOutcome> {
@@ -962,7 +1018,8 @@ async function executeToolCallAndBuildEvent(
 }
 
 export async function runToolAwareOpenAIChat(params: ToolAwareCompletionParams): Promise<ToolAwareCompletionResult> {
-  const input: any[] = normalizeIncomingResponsesInput(params.messages, params.userLocation);
+  const enabledTools = getEnabledChatTools(params);
+  const input: any[] = normalizeIncomingResponsesInput(params.messages, params.userLocation, params);
   const rawResponses: unknown[] = [];
   const toolEvents: ToolExecutionEvent[] = [];
   const usageAcc: Required<ToolAwareUsage> = { inputTokens: 0, outputTokens: 0, totalTokens: 0 };
@@ -976,7 +1033,7 @@ export async function runToolAwareOpenAIChat(params: ToolAwareCompletionParams):
       input,
       temperature: params.temperature,
       max_output_tokens: params.maxTokens,
-      tools: RESPONSES_CHAT_TOOLS,
+      tools: toResponsesChatTools(enabledTools),
       tool_choice: "auto",
       parallel_tool_calls: true,
       // Tool loops pass response output items back as input; reasoning items need persistence.
@@ -1031,7 +1088,8 @@ export async function runToolAwareOpenAIChat(params: ToolAwareCompletionParams):
 }
 
 export async function runToolAwareChatCompletions(params: ToolAwareCompletionParams): Promise<ToolAwareCompletionResult> {
-  const conversation: any[] = normalizeIncomingMessages(params.messages, params.userLocation);
+  const enabledTools = getEnabledChatTools(params);
+  const conversation: any[] = normalizeIncomingMessages(params.messages, params.userLocation, params);
   const rawResponses: unknown[] = [];
   const toolEvents: ToolExecutionEvent[] = [];
   const usageAcc: Required<ToolAwareUsage> = { inputTokens: 0, outputTokens: 0, totalTokens: 0 };
@@ -1045,7 +1103,7 @@ export async function runToolAwareChatCompletions(params: ToolAwareCompletionPar
       messages: conversation,
       temperature: params.temperature,
       max_tokens: params.maxTokens,
-      tools: CHAT_TOOLS,
+      tools: enabledTools,
       tool_choice: "auto",
     } as any);
     rawResponses.push(completion);
@@ -1139,7 +1197,8 @@ export async function runPlainChatCompletions(params: ToolAwareCompletionParams)
 export async function* runToolAwareOpenAIChatStream(
   params: ToolAwareCompletionParams
 ): AsyncGenerator<ToolAwareStreamingEvent> {
-  const input: any[] = normalizeIncomingResponsesInput(params.messages, params.userLocation);
+  const enabledTools = getEnabledChatTools(params);
+  const input: any[] = normalizeIncomingResponsesInput(params.messages, params.userLocation, params);
   const rawResponses: unknown[] = [];
   const toolEvents: ToolExecutionEvent[] = [];
   const usageAcc: Required<ToolAwareUsage> = { inputTokens: 0, outputTokens: 0, totalTokens: 0 };
@@ -1153,7 +1212,7 @@ export async function* runToolAwareOpenAIChatStream(
       input,
       temperature: params.temperature,
       max_output_tokens: params.maxTokens,
-      tools: RESPONSES_CHAT_TOOLS,
+      tools: toResponsesChatTools(enabledTools),
       tool_choice: "auto",
       parallel_tool_calls: true,
       // Tool loops pass response output items back as input; reasoning items need persistence.
@@ -1265,7 +1324,8 @@ export async function* runToolAwareOpenAIChatStream(
 export async function* runToolAwareChatCompletionsStream(
   params: ToolAwareCompletionParams
 ): AsyncGenerator<ToolAwareStreamingEvent> {
-  const conversation: any[] = normalizeIncomingMessages(params.messages, params.userLocation);
+  const enabledTools = getEnabledChatTools(params);
+  const conversation: any[] = normalizeIncomingMessages(params.messages, params.userLocation, params);
   const rawResponses: unknown[] = [];
   const toolEvents: ToolExecutionEvent[] = [];
   const usageAcc: Required<ToolAwareUsage> = { inputTokens: 0, outputTokens: 0, totalTokens: 0 };
@@ -1279,7 +1339,7 @@ export async function* runToolAwareChatCompletionsStream(
       messages: conversation,
       temperature: params.temperature,
       max_tokens: params.maxTokens,
-      tools: CHAT_TOOLS,
+      tools: enabledTools,
       tool_choice: "auto",
       stream: true,
       stream_options: { include_usage: true },

server/src/llm/multiplexer.ts

@@ -1,7 +1,7 @@
 import { performance } from "node:perf_hooks";
 import { prisma } from "../db.js";
 import { anthropicClient, hermesAgentClient, openaiClient, xaiClient } from "./providers.js";
-import { buildToolLogMessageData, runPlainChatCompletions, runToolAwareChatCompletions, runToolAwareOpenAIChat } from "./chat-tools.js";
+import { buildToolLogMessageData, normalizeEnabledChatTools, runPlainChatCompletions, runToolAwareChatCompletions, runToolAwareOpenAIChat } from "./chat-tools.js";
 import { buildAnthropicConversationMessage, getAnthropicSystemPrompt } from "./message-content.js";
 import { toPrismaProvider } from "./provider-ids.js";
 import type { MultiplexRequest, MultiplexResponse, Provider } from "./types.js";
@@ -47,13 +47,15 @@ export async function runMultiplex(req: MultiplexRequest): Promise<MultiplexResp
     let usage: MultiplexResponse["usage"] | undefined;
     let raw: unknown;
     let toolMessages: ReturnType<typeof buildToolLogMessageData>[] = [];
+    const enabledTools = normalizeEnabledChatTools(req.enabledTools);
 
-    if (req.provider === "openai") {
+    if (req.provider === "openai" && enabledTools.length > 0) {
       const client = openaiClient();
       const r = await runToolAwareOpenAIChat({
         client,
         model: req.model,
         messages: req.messages,
+        enabledTools,
         userLocation: req.userLocation,
         temperature: req.temperature,
         maxTokens: req.maxTokens,
@@ -67,12 +69,13 @@ export async function runMultiplex(req: MultiplexRequest): Promise<MultiplexResp
       outText = r.text;
       usage = r.usage;
       toolMessages = r.toolEvents.map((event) => buildToolLogMessageData(call.chatId, event));
-    } else if (req.provider === "xai") {
+    } else if (req.provider === "xai" && enabledTools.length > 0) {
       const client = xaiClient();
       const r = await runToolAwareChatCompletions({
         client,
         model: req.model,
         messages: req.messages,
+        enabledTools,
         userLocation: req.userLocation,
         temperature: req.temperature,
         maxTokens: req.maxTokens,
@@ -86,8 +89,8 @@ export async function runMultiplex(req: MultiplexRequest): Promise<MultiplexResp
       outText = r.text;
       usage = r.usage;
       toolMessages = r.toolEvents.map((event) => buildToolLogMessageData(call.chatId, event));
-    } else if (req.provider === "hermes-agent") {
+    } else if (req.provider === "openai" || req.provider === "xai" || req.provider === "hermes-agent") {
-      const client = hermesAgentClient();
+      const client = req.provider === "openai" ? openaiClient() : req.provider === "xai" ? xaiClient() : hermesAgentClient();
       const r = await runPlainChatCompletions({
         client,
         model: req.model,

server/src/llm/streaming.ts

@@ -3,6 +3,7 @@ import { prisma } from "../db.js";
 import { anthropicClient, hermesAgentClient, openaiClient, xaiClient } from "./providers.js";
 import {
   buildToolLogMessageData,
+  normalizeEnabledChatTools,
   runPlainChatCompletionsStream,
   runToolAwareChatCompletionsStream,
   runToolAwareOpenAIChatStream,
@@ -76,12 +77,14 @@ export async function* runMultiplexStream(req: MultiplexRequest): AsyncGenerator
   try {
     if (req.provider === "openai" || req.provider === "xai" || req.provider === "hermes-agent") {
       const client = req.provider === "openai" ? openaiClient() : req.provider === "xai" ? xaiClient() : hermesAgentClient();
+      const enabledTools = normalizeEnabledChatTools(req.enabledTools);
       const streamEvents =
-        req.provider === "openai"
+        req.provider === "openai" && enabledTools.length > 0
           ? runToolAwareOpenAIChatStream({
               client,
               model: req.model,
               messages: req.messages,
+              enabledTools,
               userLocation: req.userLocation,
               temperature: req.temperature,
               maxTokens: req.maxTokens,
@@ -91,7 +94,7 @@ export async function* runMultiplexStream(req: MultiplexRequest): AsyncGenerator
                 chatId: chatId ?? undefined,
               },
             })
-          : req.provider === "hermes-agent"
+          : req.provider === "hermes-agent" || enabledTools.length === 0
             ? runPlainChatCompletionsStream({
                 client,
                 model: req.model,
@@ -109,6 +112,7 @@ export async function* runMultiplexStream(req: MultiplexRequest): AsyncGenerator
               client,
               model: req.model,
               messages: req.messages,
+              enabledTools,
               userLocation: req.userLocation,
               temperature: req.temperature,
               maxTokens: req.maxTokens,

server/src/llm/types.ts

@@ -36,6 +36,8 @@ export type MultiplexRequest = {
   provider: Provider;
   model: string;
   messages: ChatMessage[];
+  additionalSystemPrompt?: string;
+  enabledTools?: string[];
   userLocation?: string;
   temperature?: number;
   maxTokens?: number;

server/src/routes.ts

@@ -8,6 +8,7 @@ import { env } from "./env.js";
 import { buildComparableAttachments } from "./llm/message-content.js";
 import { runMultiplex } from "./llm/multiplexer.js";
 import { runMultiplexStream, type StreamEvent } from "./llm/streaming.js";
+import { getAvailableChatTools, normalizeEnabledChatTools } from "./llm/chat-tools.js";
 import { getModelCatalogSnapshot } from "./llm/model-catalog.js";
 import { openaiClient } from "./llm/providers.js";
 import { serializeProviderFields, toPrismaProvider } from "./llm/provider-ids.js";
@@ -16,6 +17,8 @@ import { isFreshSearchCacheHit, normalizeSearchQuery } from "./search-cache.js";
 import type { ChatAttachment } from "./llm/types.js";
 
 const ProviderSchema = z.enum(["openai", "anthropic", "xai", "hermes-agent"]);
+const MAX_ADDITIONAL_SYSTEM_PROMPT_CHARS = 12_000;
+const EnabledToolsSchema = z.array(z.string().trim().min(1).max(80)).max(20).transform((value) => normalizeEnabledChatTools(value));
 
 type IncomingChatMessage = {
   role: "system" | "user" | "assistant" | "tool";
@@ -169,6 +172,8 @@ const CompletionStreamBody = z
     provider: ProviderSchema,
     model: z.string().min(1),
     messages: z.array(CompletionMessageSchema),
+    additionalSystemPrompt: z.string().max(MAX_ADDITIONAL_SYSTEM_PROMPT_CHARS).optional(),
+    enabledTools: EnabledToolsSchema.optional(),
     userLocation: z.string().trim().min(1).max(200).optional(),
     temperature: z.number().min(0).max(2).optional(),
     maxTokens: z.number().int().positive().optional(),
@@ -194,6 +199,41 @@ function mergeAttachmentsIntoMetadata(metadata: unknown, attachments?: ChatAttac
   };
 }
 
+function normalizeAdditionalSystemPrompt(value: string | null | undefined) {
+  const trimmed = value?.trim();
+  return trimmed || null;
+}
+
+function prependAdditionalSystemPrompt<T extends { messages: IncomingChatMessage[]; additionalSystemPrompt?: string | null }>(body: T): T {
+  const additionalSystemPrompt = normalizeAdditionalSystemPrompt(body.additionalSystemPrompt);
+  if (!additionalSystemPrompt) return { ...body, additionalSystemPrompt: undefined };
+  return {
+    ...body,
+    additionalSystemPrompt,
+    messages: [{ role: "system", content: additionalSystemPrompt }, ...body.messages],
+  };
+}
+
+async function applyStoredChatSettings<T extends { chatId?: string; messages: IncomingChatMessage[]; additionalSystemPrompt?: string; enabledTools?: string[] }>(
+  body: T
+) {
+  if (!body.chatId || (body.additionalSystemPrompt !== undefined && body.enabledTools !== undefined)) {
+    return prependAdditionalSystemPrompt(body);
+  }
+
+  const chat = await prisma.chat.findUnique({
+    where: { id: body.chatId },
+    select: { additionalSystemPrompt: true, enabledTools: true },
+  });
+  if (!chat) return prependAdditionalSystemPrompt(body);
+
+  return prependAdditionalSystemPrompt({
+    ...body,
+    additionalSystemPrompt: body.additionalSystemPrompt ?? chat.additionalSystemPrompt ?? undefined,
+    enabledTools: body.enabledTools ?? normalizeEnabledChatTools(chat.enabledTools),
+  });
+}
+
 const SearchRunBody = z.object({
   query: z.string().trim().min(1).optional(),
   title: z.string().trim().min(1).optional(),
@@ -377,6 +417,8 @@ const chatSummarySelect = {
   initiatedModel: true,
   lastUsedProvider: true,
   lastUsedModel: true,
+  additionalSystemPrompt: true,
+  enabledTools: true,
   projectItems: starredProjectItemsSelect,
 } as const;
 
@@ -754,6 +796,11 @@ export async function registerRoutes(app: FastifyInstance) {
     return { providers: getModelCatalogSnapshot() };
   });
 
+  app.get("/v1/chat-tools", async (req) => {
+    requireAdmin(req);
+    return { tools: getAvailableChatTools() };
+  });
+
   app.get("/v1/active-runs", async (req) => {
     requireAdmin(req);
     return {
@@ -784,6 +831,8 @@ export async function registerRoutes(app: FastifyInstance) {
         title: z.string().optional(),
         provider: ProviderSchema.optional(),
         model: z.string().trim().min(1).optional(),
+        additionalSystemPrompt: z.string().max(MAX_ADDITIONAL_SYSTEM_PROMPT_CHARS).optional(),
+        enabledTools: EnabledToolsSchema.optional(),
         messages: z.array(CompletionMessageSchema).optional(),
       })
       .superRefine((value, ctx) => {
@@ -812,6 +861,8 @@ export async function registerRoutes(app: FastifyInstance) {
         initiatedModel: body.model,
         lastUsedProvider: body.provider ? (toPrismaProvider(body.provider) as any) : undefined,
         lastUsedModel: body.model,
+        additionalSystemPrompt: normalizeAdditionalSystemPrompt(body.additionalSystemPrompt),
+        enabledTools: body.enabledTools as any,
         messages: body.messages?.length
           ? {
               create: body.messages.map((message) => ({
@@ -831,13 +882,22 @@ export async function registerRoutes(app: FastifyInstance) {
   app.patch("/v1/chats/:chatId", async (req) => {
     requireAdmin(req);
     const Params = z.object({ chatId: z.string() });
-    const Body = z.object({ title: z.string().trim().min(1) });
+    const Body = z.object({
+      title: z.string().trim().min(1).optional(),
+      additionalSystemPrompt: z.string().max(MAX_ADDITIONAL_SYSTEM_PROMPT_CHARS).nullable().optional(),
+      enabledTools: EnabledToolsSchema.optional(),
+    });
     const { chatId } = Params.parse(req.params);
     const body = Body.parse(req.body ?? {});
 
+    const data: Record<string, unknown> = {};
+    if (body.title !== undefined) data.title = body.title;
+    if (body.additionalSystemPrompt !== undefined) data.additionalSystemPrompt = normalizeAdditionalSystemPrompt(body.additionalSystemPrompt);
+    if (body.enabledTools !== undefined) data.enabledTools = body.enabledTools;
+
     const updated = await prisma.chat.updateMany({
       where: { id: chatId },
-      data: { title: body.title },
+      data: data as any,
     });
 
     if (updated.count === 0) return app.httpErrors.notFound("chat not found");
@@ -1249,6 +1309,8 @@ export async function registerRoutes(app: FastifyInstance) {
       provider: ProviderSchema,
       model: z.string().min(1),
       messages: z.array(CompletionMessageSchema),
+      additionalSystemPrompt: z.string().max(MAX_ADDITIONAL_SYSTEM_PROMPT_CHARS).optional(),
+      enabledTools: EnabledToolsSchema.optional(),
       userLocation: z.string().trim().min(1).max(200).optional(),
       temperature: z.number().min(0).max(2).optional(),
       maxTokens: z.number().int().positive().optional(),
@@ -1269,7 +1331,7 @@ export async function registerRoutes(app: FastifyInstance) {
       await storeNonAssistantMessages(body.chatId, body.messages);
     }
 
-    const result = await runMultiplex(body);
+    const result = await runMultiplex(await applyStoredChatSettings(body));
 
     return {
       chatId: body.chatId ?? null,
@@ -1300,14 +1362,14 @@ export async function registerRoutes(app: FastifyInstance) {
       if (activeChatStreams.has(body.chatId)) {
         return app.httpErrors.conflict("chat completion already running");
       }
-      const stream = startActiveChatStream(body.chatId, body);
+      const stream = startActiveChatStream(body.chatId, await applyStoredChatSettings(body));
       return streamActiveRun(req, reply, stream);
     }
 
     reply.raw.writeHead(200, buildSseHeaders(typeof req.headers.origin === "string" ? req.headers.origin : undefined));
     reply.raw.flushHeaders();
 
-    for await (const ev of runMultiplexStream(body)) {
+    for await (const ev of runMultiplexStream(await applyStoredChatSettings(body))) {
       writeSseEvent(reply, mapChatStreamEvent(ev));
     }
 

web/src/App.tsx

@@ -1,5 +1,22 @@
 import { useEffect, useMemo, useRef, useState } from "preact/hooks";
-import { Check, ChevronDown, Globe2, LoaderCircle, Menu, MessageSquare, Paperclip, Pencil, Plus, Rabbit, Search, SendHorizontal, Star, Trash2, X } from "lucide-preact";
+import {
+  Check,
+  ChevronDown,
+  Globe2,
+  LoaderCircle,
+  Menu,
+  MessageSquare,
+  Paperclip,
+  Pencil,
+  Plus,
+  Rabbit,
+  Search,
+  SendHorizontal,
+  Settings2,
+  Star,
+  Trash2,
+  X,
+} from "lucide-preact";
 import { Button } from "@/components/ui/button";
 import { Textarea } from "@/components/ui/textarea";
 import { Separator } from "@/components/ui/separator";
@@ -18,6 +35,7 @@ import {
   attachSearchStream,
   getActiveRuns,
   getChat,
+  listChatTools,
   listModels,
   getSearch,
   listWorkspaceItems,
@@ -27,6 +45,7 @@ import {
   updateChatTitle,
   updateChatStar,
   updateSearchStar,
+  updateChatSettings,
   getMessageAttachments,
   type ChatAttachment,
   type ActiveRunsResponse,
@@ -34,6 +53,7 @@ import {
   type Provider,
   type ChatDetail,
   type ChatSummary,
+  type ChatToolInfo,
   type CompletionRequestMessage,
   type Message,
   type SearchDetail,
@@ -379,6 +399,30 @@ function getProviderLabel(provider: Provider | null | undefined) {
   return "";
 }
 
+function getToolLabel(name: string) {
+  if (name === "web_search") return "Web search";
+  if (name === "fetch_url") return "Fetch URL";
+  if (name === "codex_exec") return "Codex";
+  if (name === "shell_exec") return "Shell";
+  return name
+    .split("_")
+    .filter(Boolean)
+    .map((part) => part.slice(0, 1).toUpperCase() + part.slice(1))
+    .join(" ");
+}
+
+function getDefaultEnabledTools(availableTools: ChatToolInfo[]) {
+  return availableTools.map((tool) => tool.name);
+}
+
+function normalizeEnabledTools(value: unknown, availableTools: ChatToolInfo[]) {
+  const available = new Set(availableTools.map((tool) => tool.name));
+  if (!Array.isArray(value)) return getDefaultEnabledTools(availableTools);
+  return [...new Set(value.filter((item): item is string => typeof item === "string").map((item) => item.trim()).filter(Boolean))].filter((name) =>
+    available.has(name)
+  );
+}
+
 function getChatModelSelection(chat: Pick<ChatSummary, "lastUsedProvider" | "lastUsedModel"> | Pick<ChatDetail, "lastUsedProvider" | "lastUsedModel"> | null) {
   if (!chat?.lastUsedProvider || !chat.lastUsedModel?.trim()) return null;
   return {
@@ -748,6 +792,7 @@ export default function App() {
   const [isComposerDropActive, setIsComposerDropActive] = useState(false);
   const [provider, setProvider] = useState<Provider>("openai");
   const [modelCatalog, setModelCatalog] = useState<ModelCatalogResponse["providers"]>(EMPTY_MODEL_CATALOG);
+  const [availableChatTools, setAvailableChatTools] = useState<ChatToolInfo[]>([]);
   const [providerModelPreferences, setProviderModelPreferences] = useState<ProviderModelPreferences>(() => loadStoredModelPreferences());
   const [model, setModel] = useState(() => {
     const stored = loadStoredModelPreferences();
@@ -774,6 +819,9 @@ export default function App() {
   const [renameChatDraft, setRenameChatDraft] = useState("");
   const [renameChatError, setRenameChatError] = useState<string | null>(null);
   const [isRenamingChat, setIsRenamingChat] = useState(false);
+  const [isChatSettingsOpen, setIsChatSettingsOpen] = useState(false);
+  const [additionalSystemPrompt, setAdditionalSystemPrompt] = useState("");
+  const [enabledTools, setEnabledTools] = useState<string[]>([]);
   const [transcriptTailSpacerHeight, setTranscriptTailSpacerHeight] = useState(TRANSCRIPT_BOTTOM_GAP);
   const transcriptContainerRef = useRef<HTMLDivElement>(null);
   const transcriptEndRef = useRef<HTMLDivElement>(null);
@@ -899,6 +947,9 @@ export default function App() {
     searchRunCountersRef.current.clear();
     setComposer("");
     setPendingAttachments([]);
+    setIsChatSettingsOpen(false);
+    setAdditionalSystemPrompt("");
+    setEnabledTools([]);
     setIsQuickQuestionOpen(false);
     setQuickPrompt("");
     setQuickSubmittedPrompt(null);
@@ -968,6 +1019,21 @@ export default function App() {
     }
   };
 
+  const refreshChatTools = async () => {
+    try {
+      const tools = await listChatTools();
+      setAvailableChatTools(tools);
+      setEnabledTools((current) => normalizeEnabledTools(current.length ? current : null, tools));
+    } catch (err) {
+      const message = err instanceof Error ? err.message : String(err);
+      if (message.includes("bearer token")) {
+        handleAuthFailure(message);
+      } else {
+        setError(message);
+      }
+    }
+  };
+
   const refreshActiveRuns = async () => {
     try {
       const data = await getActiveRuns();
@@ -1020,7 +1086,7 @@ export default function App() {
     if (!isAuthenticated) return;
     const preferredSelection = initialRouteSelectionRef.current;
     initialRouteSelectionRef.current = null;
-    void Promise.all([refreshCollections(preferredSelection ?? undefined), refreshModels(), refreshActiveRuns()]);
+    void Promise.all([refreshCollections(preferredSelection ?? undefined), refreshModels(), refreshChatTools(), refreshActiveRuns()]);
   }, [isAuthenticated]);
 
   useEffect(() => {
@@ -1287,6 +1353,19 @@ export default function App() {
     setModel(nextSelection.model);
   }, [draftKind, selectedChat, selectedChatSummary, selectedItem]);
 
+  useEffect(() => {
+    if (draftKind === "chat") {
+      setAdditionalSystemPrompt("");
+      setEnabledTools(getDefaultEnabledTools(availableChatTools));
+      return;
+    }
+    if (selectedItem?.kind !== "chat") return;
+    const chat = selectedChat?.id === selectedItem.id ? selectedChat : selectedChatSummary;
+    if (!chat) return;
+    setAdditionalSystemPrompt(chat.additionalSystemPrompt ?? "");
+    setEnabledTools(normalizeEnabledTools(chat.enabledTools, availableChatTools));
+  }, [availableChatTools, draftKind, selectedChat, selectedChatSummary, selectedItem]);
+
   const selectedTitle = useMemo(() => {
     if (draftKind === "chat") return "New chat";
     if (draftKind === "search") return "New search";
@@ -1441,6 +1520,8 @@ export default function App() {
         initiatedModel: updatedChat.initiatedModel,
         lastUsedProvider: updatedChat.lastUsedProvider,
         lastUsedModel: updatedChat.lastUsedModel,
+        additionalSystemPrompt: updatedChat.additionalSystemPrompt,
+        enabledTools: updatedChat.enabledTools,
       };
     });
   };
@@ -1768,6 +1849,8 @@ export default function App() {
         initiatedModel: chat.initiatedModel,
         lastUsedProvider: chat.lastUsedProvider,
         lastUsedModel: chat.lastUsedModel,
+        additionalSystemPrompt: chat.additionalSystemPrompt,
+        enabledTools: chat.enabledTools,
         messages: [],
       });
       setSelectedSearch(null);
@@ -2349,6 +2432,8 @@ export default function App() {
         initiatedModel: chat.initiatedModel,
         lastUsedProvider: chat.lastUsedProvider,
         lastUsedModel: chat.lastUsedModel,
+        additionalSystemPrompt: chat.additionalSystemPrompt,
+        enabledTools: chat.enabledTools,
         messages: [],
       });
       setSelectedSearch(null);
@@ -2527,6 +2612,8 @@ export default function App() {
         initiatedModel: chat.initiatedModel,
         lastUsedProvider: chat.lastUsedProvider,
         lastUsedModel: chat.lastUsedModel,
+        additionalSystemPrompt: chat.additionalSystemPrompt,
+        enabledTools: chat.enabledTools,
         messages: [],
       });
       setSelectedSearch(null);

web/src/lib/api.ts

@@ -9,6 +9,8 @@ export type ChatSummary = {
   initiatedModel: string | null;
   lastUsedProvider: Provider | null;
   lastUsedModel: string | null;
+  additionalSystemPrompt: string | null;
+  enabledTools: string[] | null;
 };
 
 export type SearchSummary = {
@@ -64,6 +66,8 @@ export type ChatDetail = {
   initiatedModel: string | null;
   lastUsedProvider: Provider | null;
   lastUsedModel: string | null;
+  additionalSystemPrompt: string | null;
+  enabledTools: string[] | null;
   messages: Message[];
 };
 
@@ -157,6 +161,11 @@ export type ModelCatalogResponse = {
   providers: Partial<Record<Provider, ProviderModelInfo>>;
 };
 
+export type ChatToolInfo = {
+  name: string;
+  description: string;
+};
+
 export type ActiveRunsResponse = {
   chats: string[];
   searches: string[];
@@ -182,6 +191,8 @@ type CreateChatRequest = {
   title?: string;
   provider?: Provider;
   model?: string;
+  additionalSystemPrompt?: string;
+  enabledTools?: string[];
   messages?: CompletionRequestMessage[];
 };
 
@@ -257,6 +268,11 @@ export async function listModels() {
   return api<ModelCatalogResponse>("/v1/models");
 }
 
+export async function listChatTools() {
+  const data = await api<{ tools: ChatToolInfo[] }>("/v1/chat-tools");
+  return data.tools;
+}
+
 export async function getActiveRuns() {
   return api<ActiveRunsResponse>("/v1/active-runs");
 }
@@ -291,6 +307,14 @@ export async function updateChatStar(chatId: string, starred: boolean) {
   return data.chat;
 }
 
+export async function updateChatSettings(chatId: string, body: { additionalSystemPrompt?: string | null; enabledTools?: string[] }) {
+  const data = await api<{ chat: ChatSummary }>(`/v1/chats/${chatId}`, {
+    method: "PATCH",
+    body: JSON.stringify(body),
+  });
+  return data.chat;
+}
+
 export async function suggestChatTitle(body: { chatId: string; content: string }) {
   const data = await api<{ chat: ChatSummary }>("/v1/chats/title/suggest", {
     method: "POST",
@@ -613,6 +637,8 @@ export async function runCompletion(body: {
   provider: Provider;
   model: string;
   messages: CompletionRequestMessage[];
+  additionalSystemPrompt?: string;
+  enabledTools?: string[];
   userLocation?: string;
 }) {
   return api<CompletionResponse>("/v1/chat-completions", {
@@ -628,6 +654,8 @@ export async function runCompletionStream(
     provider: Provider;
     model: string;
     messages: CompletionRequestMessage[];
+    additionalSystemPrompt?: string;
+    enabledTools?: string[];
     userLocation?: string;
   },
   handlers: CompletionStreamHandlers,