feat(agent-loop): run safe tool calls in parallel

packages/web/tool-web/README.md

@@ -11,6 +11,8 @@ Each tool is registered independently; a product that wants only one disables th
 | `web_search` | `query` (string) | Discovery. Returns an optional answer plus source URLs. `max_results` is **not** model-facing — the tool sets the bound (the `searchMaxResults` config, default 8) and passes it to the seam. |
 | `web_fetch` | `url` (string) | Retrieves a specific URL. HTML bodies are rendered to markdown-ish text; text bodies pass through. A non-2xx status is reported, not an error. The tool-call timeout is deployment policy (`dsh-timeout-policy`), not a model argument. |
 
+Both tools declare `isConcurrencySafe: () => true` — they are read-only (fetch a provider/URL, return content, mutate no parent-agent state), so the agent loop may run sibling web calls in parallel.
+
 ## Config
 
 | Key | Default | Meaning |

packages/web/tool-web/src/fetch.ts

@@ -99,6 +99,9 @@ export function applyWebFetchTool(ctx: Context, timeoutMs: number): void {
       url: { type: 'string', required: true, description: 'The HTTP(S) URL to fetch.' },
     },
     timeoutMs,
+    // Read-only: fetching a URL returns content and mutates no parent-agent
+    // state — safe to run concurrently with sibling calls.
+    isConcurrencySafe: () => true,
     async execute(args, exec): Promise<ContentBlock[]> {
       const input = parseFetchArgs(args)
       const result = await ctx.web.fetch(

packages/web/tool-web/src/search.ts

@@ -109,6 +109,9 @@ export function applyWebSearchTool(ctx: Context, maxResults: number, timeoutMs:
       query: { type: 'string', required: true, description: 'The search query.' },
     },
     timeoutMs,
+    // Read-only: a search hits the provider and returns content, mutating no
+    // parent-agent state — safe to run concurrently with sibling calls.
+    isConcurrencySafe: () => true,
     async execute(args, exec): Promise<ContentBlock[]> {
       const input = parseSearchArgs(args)
       const result = await ctx.web.search(

packages/web/tool-web/tests/tool-web.spec.ts

@@ -166,6 +166,10 @@ describe('tool-web registration', () => {
     const names = ctx.tools.schemas().map(s => s.name)
     expect(names).toContain('web_search')
     expect(names).toContain('web_fetch')
+    expect(ctx.tools.executionMode({ callId: CallId('search-safe'), name: 'web_search', arguments: { query: 'q' } }))
+      .toEqual({ kind: 'parallel' })
+    expect(ctx.tools.executionMode({ callId: CallId('fetch-safe'), name: 'web_fetch', arguments: { url: 'https://a.test' } }))
+      .toEqual({ kind: 'parallel' })
     await fiber.dispose()
     expect(ctx.tools.schemas().map(s => s.name)).not.toContain('web_search')
   })