ambient context: give every project's model a clock

Models consuming projects have no idea what day it is. Three always-on
layers from mcplocal plus one from mcpd:

- initialize instructions and the begin_session briefing carry
  '[context] now: <date/time> — project: <name>' (frozen at session
  start by design);
- a get_current_time virtual tool (ungated catalogs only, same pattern
  as read_prompts);
- every tools/call result gets a trailing '[context] now: …' content
  item at the endpoint send site — the only chokepoint that also covers
  virtual tools, gate intercepts and failure results, and the layer
  that keeps a days-old chat session current;
- mcpd agent/project chat system blocks append the same line each turn.

Time renders as UTC plus an optional local timezone from
MCPLOCAL_AMBIENT_TZ (IANA name; both services read it; invalid or unset
means UTC only). ~15 tokens per stamp, minute precision.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/mcpd/src/services/chat.service.ts

@@ -22,6 +22,7 @@
  * adapter default. `extra` is forwarded as-is for provider-specific knobs.
  */
 import type { ChatMessage } from '@prisma/client';
+import { ambientContextLine } from '@mcpctl/shared';
 import type { AgentService } from './agent.service.js';
 import type { LlmService } from './llm.service.js';
 import { effectivePoolName } from './llm.service.js';
@@ -728,6 +729,9 @@ export class ChatService {
       ...sortedProjectPrompts.map((p) => p.content),
       ...personalityPromptContents,
       mergedParams.systemAppend ?? '',
+      // Rebuilt every turn, so the agent's clock stays current. Reads the
+      // same MCPLOCAL_AMBIENT_TZ env as mcplocal (see shared/ambient-time).
+      ambientContextLine(),
     ]
       .filter((s) => s.length > 0)
       .join('\n\n');
@@ -842,6 +846,8 @@ export class ChatService {
       baseSystem,
       ...projectPrompts.map((p) => p.content),
       mergedParams.systemAppend ?? '',
+      // Rebuilt every turn — the model's clock (same env as mcplocal).
+      ambientContextLine(),
     ]
       .filter((s) => s.length > 0)
       .join('\n\n');

src/mcpd/tests/chat-service-project.test.ts

@@ -155,10 +155,11 @@ describe('ChatService — project chat', () => {
     expect(t.projectId).toBe('proj-1');
     expect(t.agentId).toBeNull();
     expect(t.ownerId).toBe('owner-1');
-    // system message = project.prompt then HIGH then LOW
+    // system message = project.prompt then HIGH then LOW, then the ambient
+    // context line (the model's clock, appended every turn).
     const sys = (adapter.infer as ReturnType<typeof vi.fn>).mock.calls[0][0].body.messages[0];
     expect(sys.role).toBe('system');
-    expect(sys.content).toBe('Project system prompt.\n\nHIGH\n\nLOW');
+    expect(sys.content).toMatch(/^Project system prompt\.\n\nHIGH\n\nLOW\n\n\[context\] now: /);
   });
 
   it('routes tool calls to the project dispatcher with projectId', async () => {

src/mcpd/tests/chat-service.test.ts

@@ -388,6 +388,8 @@ describe('ChatService', () => {
     expect(text.indexOf('HIGH prompt')).toBeLessThan(text.indexOf('LOW prompt'));
     // Agent's own system prompt leads.
     expect(text.indexOf('You are a helpful agent.')).toBeLessThan(text.indexOf('HIGH prompt'));
+    // The ambient context line (the model's clock) closes the block.
+    expect(text).toMatch(/\n\n\[context\] now: .+$/);
   });
 
   it('refuses tool calls when the agent has no project attached', async () => {

src/mcplocal/src/http/project-mcp-endpoint.ts

@@ -22,6 +22,8 @@ import type { TrafficCapture } from './traffic.js';
 import { LLMProviderAdapter } from '../proxymodel/llm-adapter.js';
 import { FileCache } from '../proxymodel/file-cache.js';
 import { createDefaultPlugin } from '../proxymodel/plugins/default.js';
+import { createAmbientContextPlugin } from '../proxymodel/plugins/ambient-context.js';
+import { ambientContextLine } from '@mcpctl/shared';
 import { createAgentsPlugin } from '../proxymodel/plugins/agents.js';
 import { createFavouriteIndexPlugin } from '../proxymodel/plugins/favourite-index.js';
 import { composePlugins } from '../proxymodel/plugins/compose.js';
@@ -190,6 +192,11 @@ export function registerProjectMcpEndpoint(app: FastifyInstance, mcpdClient: Mcp
     // project show up as virtual MCP servers in tools/list, regardless of
     // which proxymodel the project is using.
     chain.push(createAgentsPlugin());
+    // Ambient context LAST: its onToolsList must see the gate's finished
+    // catalog (append get_current_time only when ungated), and its
+    // date/project instruction line belongs at the end of the merged
+    // instructions. Always on for every project.
+    chain.push(createAmbientContextPlugin());
     router.setPlugin(composePlugins(chain));
 
     // Fetch project instructions and set on router. Must ride the CALLER's
@@ -247,6 +254,24 @@ export function registerProjectMcpEndpoint(app: FastifyInstance, mcpdClient: Mcp
     return response;
   }
 
+  /**
+   * Append the ambient "now" line to every tools/call result as a SEPARATE
+   * trailing content item — never mutate existing items, so clients that
+   * JSON.parse a single text item keep working. Endpoint-level on purpose:
+   * this is the only chokepoint that also covers virtual tools (which bypass
+   * plugin onToolCallAfter), gate intercepts, drill-down pages, and
+   * failureResponse results. Initialize instructions carry the same line but
+   * freeze at session start; this trailer is what keeps a days-old chat
+   * session's model on today's date.
+   */
+  function appendAmbientTrailer(response: unknown, method?: string): unknown {
+    if (method !== 'tools/call') return response;
+    const r = response as { result?: { content?: unknown } };
+    if (!r.result || !Array.isArray(r.result.content)) return response;
+    r.result.content.push({ type: 'text', text: ambientContextLine() });
+    return response;
+  }
+
   /**
    * Turn a deadline or an unexpected throw into something the client can read.
    *
@@ -523,7 +548,10 @@ export function registerProjectMcpEndpoint(app: FastifyInstance, mcpdClient: Mcp
 
         try {
           await transport.send(
-            maybeAnnotateRecreation(response, sid, method) as unknown as JSONRPCMessage,
+            appendAmbientTrailer(
+              maybeAnnotateRecreation(response, sid, method),
+              method,
+            ) as unknown as JSONRPCMessage,
           );
         } catch (sendErr) {
           console.error(

src/mcplocal/src/proxymodel/plugins/ambient-context.ts

@@ -0,0 +1,56 @@
+/**
+ * Ambient Context plugin — gives every project's model a clock.
+ *
+ * Always on, composed LAST in the project plugin chain so that:
+ *  - onToolsList sees the gate's (and favourite-index's) finished list and
+ *    only appends get_current_time to UNGATED catalogs;
+ *  - its onInitialize line lands at the end of the merged instructions.
+ *
+ * The per-result "[context] now: …" trailer deliberately does NOT live here:
+ * virtual tools bypass plugin onToolCallAfter entirely (router dispatches
+ * them first), so the only chokepoint covering every tools/call result is
+ * endpoint-level — see appendAmbientTrailer in http/project-mcp-endpoint.ts.
+ */
+import { ambientContextLine, formatCurrentTimeResult } from '@mcpctl/shared';
+import type { ProxyModelPlugin } from '../plugin.js';
+import type { ToolDefinition } from '../types.js';
+
+export const GET_CURRENT_TIME_TOOL_NAME = 'get_current_time';
+
+function getCurrentTimeTool(): ToolDefinition {
+  return {
+    name: GET_CURRENT_TIME_TOOL_NAME,
+    description:
+      'Current date and time, in UTC and the configured local timezone. '
+      + 'Call this whenever a task depends on today\'s date or the current time.',
+    inputSchema: { type: 'object', properties: {} },
+  };
+}
+
+export function createAmbientContextPlugin(): ProxyModelPlugin {
+  return {
+    name: 'ambient-context',
+
+    async onSessionCreate(ctx) {
+      // Registered unconditionally: virtual dispatch precedes the gate
+      // intercept, so the tool is callable even while gated (same as
+      // read_prompts today). Visibility is controlled in onToolsList.
+      ctx.registerTool(getCurrentTimeTool(), async () => ({
+        content: [{ type: 'text', text: formatCurrentTimeResult() }],
+      }));
+    },
+
+    async onInitialize(_request, ctx) {
+      return { instructions: `${ambientContextLine()} — project: ${ctx.projectName}` };
+    },
+
+    async onToolsList(tools) {
+      // A gated catalog is exactly [begin_session] (gate.ts onToolsList);
+      // begin_session never appears in an ungated list. If the gate's gated
+      // list ever changes shape, revisit this marker.
+      if (tools.some((t) => t.name === 'begin_session')) return tools;
+      if (tools.some((t) => t.name === GET_CURRENT_TIME_TOOL_NAME)) return tools;
+      return [...tools, getCurrentTimeTool()];
+    },
+  };
+}

src/mcplocal/src/proxymodel/plugins/gate.ts

@@ -7,6 +7,7 @@
  *
  * This plugin replaces the hardcoded gate logic in router.ts.
  */
+import { ambientContextLine } from '@mcpctl/shared';
 import type { JsonRpcRequest, JsonRpcResponse } from '../../types.js';
 import type { ToolDefinition } from '../types.js';
 import type { ProxyModelPlugin, PluginSessionContext } from '../plugin.js';
@@ -413,6 +414,10 @@ async function handleBeginSession(
   // Build response
   const responseParts: string[] = [];
 
+  // The model starting this session has no clock; the briefing anchors it.
+  // (The endpoint's per-result trailer keeps later turns current.)
+  responseParts.push(`${ambientContextLine()}\n`);
+
   if (degradedReason !== null) {
     responseParts.push(
       `⚠ Smart prompt-selection unavailable (${degradedReason}). `

src/mcplocal/tests/ambient-time.test.ts

@@ -0,0 +1,75 @@
+import { describe, it, expect, afterEach } from 'vitest';
+import {
+  AMBIENT_TZ_ENV,
+  ambientTz,
+  formatAmbientNow,
+  ambientContextLine,
+  formatCurrentTimeResult,
+} from '@mcpctl/shared';
+
+const SUMMER = new Date('2026-07-01T09:30:00Z'); // London = BST, +01:00
+const WINTER = new Date('2026-01-15T09:30:00Z'); // London = GMT, +00:00
+
+afterEach(() => {
+  delete process.env[AMBIENT_TZ_ENV];
+});
+
+describe('ambientTz', () => {
+  it('returns undefined when unset', () => {
+    delete process.env[AMBIENT_TZ_ENV];
+    expect(ambientTz()).toBeUndefined();
+  });
+
+  it('returns a valid IANA name', () => {
+    process.env[AMBIENT_TZ_ENV] = 'Europe/London';
+    expect(ambientTz()).toBe('Europe/London');
+  });
+
+  it('falls back to undefined on an invalid name without throwing', () => {
+    process.env[AMBIENT_TZ_ENV] = 'Not/AZone';
+    expect(ambientTz()).toBeUndefined();
+  });
+});
+
+describe('formatAmbientNow', () => {
+  it('renders UTC-only when no tz', () => {
+    expect(formatAmbientNow(SUMMER, undefined)).toBe('Wed 2026-07-01 09:30 UTC');
+  });
+
+  it('renders local + UTC in summer (BST +01:00)', () => {
+    expect(formatAmbientNow(SUMMER, 'Europe/London'))
+      .toBe('Wed 2026-07-01 10:30 +01:00 Europe/London (09:30 UTC)');
+  });
+
+  it('renders local + UTC in winter (GMT +00:00)', () => {
+    expect(formatAmbientNow(WINTER, 'Europe/London'))
+      .toBe('Thu 2026-01-15 09:30 +00:00 Europe/London (09:30 UTC)');
+  });
+
+  it('stays short (~15 tokens)', () => {
+    expect(formatAmbientNow(SUMMER, 'Europe/London').length).toBeLessThan(70);
+  });
+});
+
+describe('ambientContextLine', () => {
+  it('prefixes with [context] now:', () => {
+    delete process.env[AMBIENT_TZ_ENV];
+    expect(ambientContextLine(SUMMER)).toBe('[context] now: Wed 2026-07-01 09:30 UTC');
+  });
+});
+
+describe('formatCurrentTimeResult', () => {
+  it('includes UTC ISO and epoch, no local line when tz unset', () => {
+    delete process.env[AMBIENT_TZ_ENV];
+    const text = formatCurrentTimeResult(SUMMER);
+    expect(text).toContain('UTC: 2026-07-01T09:30:00.000Z');
+    expect(text).toContain(`Unix epoch seconds: ${Math.floor(SUMMER.getTime() / 1000)}`);
+    expect(text).not.toContain('Europe/London');
+  });
+
+  it('includes the local rendering when tz set', () => {
+    process.env[AMBIENT_TZ_ENV] = 'Europe/London';
+    const text = formatCurrentTimeResult(SUMMER);
+    expect(text).toContain('Europe/London: Wed 2026-07-01 10:30 +01:00 Europe/London (09:30 UTC)');
+  });
+});

src/mcplocal/tests/plugin-ambient-context.test.ts

@@ -0,0 +1,117 @@
+/**
+ * ambient-context plugin tests — get_current_time visibility (gated vs
+ * ungated, no double-append), callable result, and the initialize
+ * instruction line. Driven through a real McpRouter with the gate composed
+ * first, mirroring project-mcp-endpoint wiring (ambient-context LAST).
+ */
+import { describe, it, expect, vi } from 'vitest';
+import { McpRouter } from '../src/router.js';
+import type { UpstreamConnection, JsonRpcRequest, JsonRpcResponse } from '../src/types.js';
+import type { McpdClient } from '../src/http/mcpd-client.js';
+import { createGatePlugin } from '../src/proxymodel/plugins/gate.js';
+import { composePlugins } from '../src/proxymodel/plugins/compose.js';
+import {
+  createAmbientContextPlugin,
+  GET_CURRENT_TIME_TOOL_NAME,
+} from '../src/proxymodel/plugins/ambient-context.js';
+import type { LLMProviderAdapter } from '../src/proxymodel/llm-adapter.js';
+import { MemoryCache } from '../src/proxymodel/cache.js';
+
+function mockUpstream(name: string, tools: Array<{ name: string }>): UpstreamConnection {
+  return {
+    name,
+    isAlive: vi.fn(() => true),
+    close: vi.fn(async () => {}),
+    onNotification: vi.fn(),
+    send: vi.fn(async (req: JsonRpcRequest): Promise<JsonRpcResponse> => {
+      if (req.method === 'tools/list') return { jsonrpc: '2.0', id: req.id, result: { tools } };
+      if (req.method === 'resources/list') return { jsonrpc: '2.0', id: req.id, result: { resources: [] } };
+      if (req.method === 'prompts/list') return { jsonrpc: '2.0', id: req.id, result: { prompts: [] } };
+      return { jsonrpc: '2.0', id: req.id, error: { code: -32601, message: 'Not found' } };
+    }),
+  } as UpstreamConnection;
+}
+
+function mockMcpdClient(): McpdClient {
+  return {
+    get: vi.fn(async () => []),
+    post: vi.fn(async () => ({})),
+    put: vi.fn(async () => ({})),
+    delete: vi.fn(async () => {}),
+    forward: vi.fn(async () => ({ status: 200, body: {} })),
+    withHeaders: vi.fn(function (this: McpdClient) { return this; }),
+  } as unknown as McpdClient;
+}
+
+function setup(opts: { gated?: boolean } = {}) {
+  const router = new McpRouter();
+  router.setPromptConfig(mockMcpdClient(), 'test-project');
+  router.setPlugin(composePlugins([
+    createGatePlugin({ gated: opts.gated ?? false, providerRegistry: null }),
+    createAmbientContextPlugin(),
+  ]));
+  router.setProxyModel('default', { complete: async () => '', available: () => false } as unknown as LLMProviderAdapter, new MemoryCache());
+  router.addUpstream(mockUpstream('k8s', [{ name: 'get_pods' }]));
+  return router;
+}
+
+async function listTools(router: McpRouter, sessionId = 's1'): Promise<string[]> {
+  const res = await router.route({ jsonrpc: '2.0', id: 2, method: 'tools/list' }, { sessionId });
+  return (res.result as { tools: Array<{ name: string }> }).tools.map((t) => t.name);
+}
+
+describe('ambient-context plugin', () => {
+  it('appends get_current_time to an ungated catalog, once', async () => {
+    const router = setup();
+    await router.route({ jsonrpc: '2.0', id: 1, method: 'initialize' }, { sessionId: 's1' });
+
+    const names = await listTools(router);
+    expect(names).toContain('k8s/get_pods');
+    expect(names.filter((n) => n === GET_CURRENT_TIME_TOOL_NAME)).toHaveLength(1);
+
+    // Second list: still exactly one.
+    const again = await listTools(router);
+    expect(again.filter((n) => n === GET_CURRENT_TIME_TOOL_NAME)).toHaveLength(1);
+  });
+
+  it('does not leak get_current_time into a gated catalog', async () => {
+    const router = setup({ gated: true });
+    await router.route({ jsonrpc: '2.0', id: 1, method: 'initialize' }, { sessionId: 's1' });
+
+    const names = await listTools(router);
+    expect(names).toEqual(['begin_session']);
+  });
+
+  it('lists get_current_time after begin_session ungates the session', async () => {
+    const router = setup({ gated: true });
+    await router.route({ jsonrpc: '2.0', id: 1, method: 'initialize' }, { sessionId: 's1' });
+    await router.route(
+      { jsonrpc: '2.0', id: 2, method: 'tools/call', params: { name: 'begin_session', arguments: { description: 'testing ambient context' } } },
+      { sessionId: 's1' },
+    );
+
+    const names = await listTools(router);
+    expect(names).toContain(GET_CURRENT_TIME_TOOL_NAME);
+  });
+
+  it('get_current_time returns the UTC time', async () => {
+    const router = setup();
+    await router.route({ jsonrpc: '2.0', id: 1, method: 'initialize' }, { sessionId: 's1' });
+
+    const res = await router.route(
+      { jsonrpc: '2.0', id: 3, method: 'tools/call', params: { name: GET_CURRENT_TIME_TOOL_NAME, arguments: {} } },
+      { sessionId: 's1' },
+    );
+    const text = (res.result as { content: Array<{ text: string }> }).content[0]!.text;
+    expect(text).toMatch(/^UTC: \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}/m);
+    expect(text).toContain('Unix epoch seconds:');
+  });
+
+  it('adds the context line and project name to initialize instructions', async () => {
+    const router = setup();
+    const res = await router.route({ jsonrpc: '2.0', id: 1, method: 'initialize' }, { sessionId: 's1' });
+    const instructions = (res.result as { instructions?: string }).instructions ?? '';
+    expect(instructions).toContain('[context] now:');
+    expect(instructions).toContain('project: test-project');
+  });
+});

src/mcplocal/tests/plugin-gate.test.ts

@@ -199,6 +199,19 @@ describe('Gate Plugin via setPlugin()', () => {
   });
 
   describe('begin_session', () => {
+    it('opens the briefing with the ambient context line (the model has no clock)', async () => {
+      const { router } = setupPluginRouter();
+      await router.route({ jsonrpc: '2.0', id: 1, method: 'initialize' }, { sessionId: 's1' });
+
+      const res = await router.route(
+        { jsonrpc: '2.0', id: 2, method: 'tools/call', params: { name: 'begin_session', arguments: { tags: ['zigbee'] } } },
+        { sessionId: 's1' },
+      );
+
+      const text = ((res.result as { content: Array<{ text: string }> }).content[0]!.text);
+      expect(text).toMatch(/^\[context\] now: /);
+    });
+
     it('falls back with a visible warning when the LLM selector errors (no silent degrade)', async () => {
       const { router } = setupPluginRouter({ withLlm: true, llmError: true });
       await router.route({ jsonrpc: '2.0', id: 1, method: 'initialize' }, { sessionId: 's1' });

src/mcplocal/tests/project-mcp-endpoint-ambient.test.ts

@@ -0,0 +1,138 @@
+import { describe, it, expect, vi } from 'vitest';
+import Fastify from 'fastify';
+import { registerProjectMcpEndpoint } from '../src/http/project-mcp-endpoint.js';
+import type { McpRouter } from '../src/router.js';
+import type { JsonRpcRequest, JsonRpcResponse } from '../src/types.js';
+
+/**
+ * Ambient-context E2E on /projects/:name/mcp: every tools/call result —
+ * upstream AND virtual — carries a trailing `[context] now:` content item,
+ * initialize instructions carry the same line, tools/list stays clean, and
+ * get_current_time is served on an ungated project.
+ */
+
+vi.mock('../src/discovery.js', () => ({
+  refreshProjectUpstreams: vi.fn(async (router: McpRouter) => {
+    router.addUpstream({
+      name: 'websearch',
+      send: async (req: JsonRpcRequest): Promise<JsonRpcResponse> => {
+        if (req.method === 'tools/list') {
+          return {
+            jsonrpc: '2.0',
+            id: req.id,
+            result: { tools: [{ name: 'fetch_content', description: 'fetch a page', inputSchema: { type: 'object' } }] },
+          };
+        }
+        if (req.method === 'tools/call') {
+          return { jsonrpc: '2.0', id: req.id, result: { content: [{ type: 'text', text: 'page body' }] } };
+        }
+        return { jsonrpc: '2.0', id: req.id, result: {} };
+      },
+      close: async () => {},
+      isAlive: () => true,
+    });
+    return ['websearch'];
+  }),
+  // Ungated (content-pipeline style), like chat-web and personal-michal.
+  fetchProjectLlmConfig: vi.fn(async () => ({ gated: false, llmProvider: 'none' })),
+}));
+
+vi.mock('../src/http/config.js', async () => {
+  const actual = await vi.importActual<typeof import('../src/http/config.js')>('../src/http/config.js');
+  return { ...actual, loadProjectLlmOverride: vi.fn(() => undefined) };
+});
+
+function mockMcpdClient() {
+  const client: Record<string, unknown> = {
+    baseUrl: 'http://test:3100',
+    token: 'test-token',
+    get: vi.fn(async () => []),
+    post: vi.fn(async () => ({})),
+    put: vi.fn(),
+    delete: vi.fn(),
+    forward: vi.fn(async () => ({ status: 200, body: [] })),
+    withHeaders: vi.fn(),
+    withToken: vi.fn(),
+    withTimeout: vi.fn(),
+  };
+  (client.withHeaders as ReturnType<typeof vi.fn>).mockReturnValue(client);
+  (client.withToken as ReturnType<typeof vi.fn>).mockReturnValue(client);
+  (client.withTimeout as ReturnType<typeof vi.fn>).mockReturnValue(client);
+  return client;
+}
+
+function parseSse(body: string): JsonRpcResponse {
+  const dataLine = body.split('\n').find((l) => l.startsWith('data: '));
+  if (!dataLine) throw new Error(`no SSE data line in: ${body}`);
+  return JSON.parse(dataLine.slice('data: '.length)) as JsonRpcResponse;
+}
+
+const CONTEXT_PREFIX = '[context] now:';
+
+describe('registerProjectMcpEndpoint ambient context', () => {
+  it('stamps instructions, tool results (upstream and virtual), but not tools/list', async () => {
+    const app = Fastify();
+    registerProjectMcpEndpoint(app, mockMcpdClient() as never);
+    await app.ready();
+    try {
+      const headers = {
+        'content-type': 'application/json',
+        accept: 'application/json, text/event-stream',
+      };
+
+      const init = await app.inject({
+        method: 'POST',
+        url: '/projects/chat-web/mcp',
+        headers,
+        payload: { jsonrpc: '2.0', id: 1, method: 'initialize', params: { protocolVersion: '2024-11-05', capabilities: {}, clientInfo: { name: 't', version: '0' } } },
+      });
+      expect(init.statusCode).toBe(200);
+      const initResponse = parseSse(init.body);
+      const instructions = (initResponse.result as { instructions?: string }).instructions ?? '';
+      expect(instructions).toContain(CONTEXT_PREFIX);
+      expect(instructions).toContain('project: chat-web');
+      // The initialize RESPONSE itself is not trailed (no result.content).
+      expect(JSON.stringify((initResponse.result as { content?: unknown }).content ?? null)).not.toContain(CONTEXT_PREFIX);
+
+      const sessionId = init.headers['mcp-session-id'] as string;
+      const sessionHeaders = { ...headers, 'mcp-session-id': sessionId };
+
+      const list = await app.inject({
+        method: 'POST',
+        url: '/projects/chat-web/mcp',
+        headers: sessionHeaders,
+        payload: { jsonrpc: '2.0', id: 2, method: 'tools/list' },
+      });
+      const listResponse = parseSse(list.body);
+      const names = (listResponse.result as { tools: Array<{ name: string }> }).tools.map((t) => t.name);
+      expect(names).toContain('get_current_time');
+      // tools/list is never trailed.
+      expect(JSON.stringify(listResponse.result)).not.toContain(CONTEXT_PREFIX);
+
+      // Upstream tool call: original content intact, trailer appended LAST.
+      const call = await app.inject({
+        method: 'POST',
+        url: '/projects/chat-web/mcp',
+        headers: sessionHeaders,
+        payload: { jsonrpc: '2.0', id: 3, method: 'tools/call', params: { name: 'websearch_fetch_content', arguments: { url: 'https://x' } } },
+      });
+      const callContent = (parseSse(call.body).result as { content: Array<{ type: string; text: string }> }).content;
+      expect(callContent.length).toBeGreaterThanOrEqual(2);
+      expect(callContent[0]?.text).toContain('page body');
+      expect(callContent[callContent.length - 1]?.text).toMatch(/^\[context\] now: /);
+
+      // Virtual tool call (bypasses plugin onToolCallAfter): still trailed.
+      const timeCall = await app.inject({
+        method: 'POST',
+        url: '/projects/chat-web/mcp',
+        headers: sessionHeaders,
+        payload: { jsonrpc: '2.0', id: 4, method: 'tools/call', params: { name: 'get_current_time', arguments: {} } },
+      });
+      const timeContent = (parseSse(timeCall.body).result as { content: Array<{ text: string }> }).content;
+      expect(timeContent[0]?.text).toContain('UTC:');
+      expect(timeContent[timeContent.length - 1]?.text).toMatch(/^\[context\] now: /);
+    } finally {
+      await app.close();
+    }
+  });
+});

src/shared/src/utils/ambient-time.ts

@@ -0,0 +1,93 @@
+/**
+ * Ambient time rendering — gives models a clock.
+ *
+ * Models consuming projects have no idea what day it is, so mcplocal stamps a
+ * short context line into initialize instructions, the begin_session
+ * briefing, and every tools/call result, and mcpd appends it to agent system
+ * blocks. One env var, `MCPLOCAL_AMBIENT_TZ` (an IANA name like
+ * "Europe/London", read by BOTH services despite the mcplocal-flavoured
+ * name), adds a local rendering next to UTC; unset or invalid means UTC only.
+ *
+ * Minute precision on purpose: the line stays ~15 tokens and does not churn
+ * within a minute.
+ */
+
+export const AMBIENT_TZ_ENV = 'MCPLOCAL_AMBIENT_TZ';
+
+let warnedInvalidTz: string | undefined;
+
+/**
+ * The configured IANA timezone, or undefined for UTC-only rendering.
+ * Read at call time (not module load) so tests and config changes apply
+ * without a restart. An invalid name warns once and behaves as unset.
+ */
+export function ambientTz(env: NodeJS.ProcessEnv = process.env): string | undefined {
+  const tz = env[AMBIENT_TZ_ENV]?.trim();
+  if (!tz) return undefined;
+  try {
+    new Intl.DateTimeFormat('en-GB', { timeZone: tz });
+    return tz;
+  } catch {
+    if (warnedInvalidTz !== tz) {
+      warnedInvalidTz = tz;
+      console.warn(`[ambient-time] invalid ${AMBIENT_TZ_ENV} '${tz}', falling back to UTC`);
+    }
+    return undefined;
+  }
+}
+
+const pad = (n: number): string => String(n).padStart(2, '0');
+
+function utcParts(now: Date): { date: string; time: string; weekday: string } {
+  const weekday = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'][now.getUTCDay()] as string;
+  return {
+    weekday,
+    date: `${now.getUTCFullYear()}-${pad(now.getUTCMonth() + 1)}-${pad(now.getUTCDate())}`,
+    time: `${pad(now.getUTCHours())}:${pad(now.getUTCMinutes())}`,
+  };
+}
+
+/**
+ * One line of "now", ~15 tokens:
+ *   tz set:   `Thu 2026-10-02 10:30 +01:00 Europe/London (09:30 UTC)`
+ *   tz unset: `Thu 2026-10-02 09:30 UTC`
+ */
+export function formatAmbientNow(now: Date = new Date(), tz: string | undefined = ambientTz()): string {
+  const utc = utcParts(now);
+  if (!tz) return `${utc.weekday} ${utc.date} ${utc.time} UTC`;
+
+  const parts = new Intl.DateTimeFormat('en-GB', {
+    timeZone: tz,
+    weekday: 'short',
+    year: 'numeric',
+    month: '2-digit',
+    day: '2-digit',
+    hour: '2-digit',
+    minute: '2-digit',
+    hour12: false,
+    timeZoneName: 'longOffset',
+  }).formatToParts(now);
+  const get = (type: string) => parts.find((p) => p.type === type)?.value ?? '';
+  // "GMT+01:00" → "+01:00"; plain "GMT" (winter London) → "+00:00".
+  const rawOffset = get('timeZoneName');
+  const offset = rawOffset === 'GMT' ? '+00:00' : rawOffset.replace(/^(GMT|UTC)/, '');
+  // Intl can render "24:00" for midnight with hour12:false; normalize.
+  const hour = get('hour') === '24' ? '00' : get('hour');
+  return `${get('weekday')} ${get('year')}-${get('month')}-${get('day')} ${hour}:${get('minute')} ${offset} ${tz} (${utc.time} UTC)`;
+}
+
+/** The ambient context line stamped into instructions and tool results. */
+export function ambientContextLine(now: Date = new Date()): string {
+  return `[context] now: ${formatAmbientNow(now)}`;
+}
+
+/** Multi-line body for the get_current_time virtual tool. */
+export function formatCurrentTimeResult(now: Date = new Date()): string {
+  const tz = ambientTz();
+  const lines = [
+    `UTC: ${now.toISOString()}`,
+    ...(tz ? [`${tz}: ${formatAmbientNow(now, tz)}`] : []),
+    `Unix epoch seconds: ${Math.floor(now.getTime() / 1000)}`,
+  ];
+  return lines.join('\n');
+}

src/shared/src/utils/index.ts

@@ -1,2 +1,2 @@
 // Shared utility functions
-// Will be expanded as tasks are implemented
+export * from './ambient-time.js';