feat(acp): tool-owned tool-call UI presentation (title/command/output)

In Zed the tool-call card showed only "bash" — the bare tool name — instead
of what the command does. Fix it by letting each TOOL own how its calls render,
rather than the bridge special-casing names.

dsh-tools: add an optional two-state presentation seam to ToolDefinition /
defineTool — `presentCall(args)` (pending: title, kind, rawInput) and
`presentResult(args, result)` (completed: title?, content?). Provider-neutral
`ToolCallKind`/`ToolCallPresentation`/`ToolResultPresentation` vocabulary so
tools never depend on ACP. defineTool soft-validates args (display runs on log
replay, so a malformed/old shape returns undefined instead of throwing).

dsh-tool-bash: bash declares presentCall (model `description` → title, exact
`command` → rawInput, kind execute) and presentResult (wrap output in a fenced
```console block — a UI-only affordance kept out of the model-facing result);
bash_output/bash_kill present task-scoped titles.

dsh-acp: inject `tools`; a per-session `ToolPresenter` looks the tool up by name
and maps its neutral presentation to the ACP tool_call/tool_call_update wire
shape, with a generic fallback (title = name) for tools that declare nothing.
Because the `tool/result` event carries only {callId, content, isError}, the
presenter keeps a small bridge-local map of ONLY in-flight calls' (name, args),
keyed by callId and removed as each result is presented — no event-schema or
core change. Replay uses a throwaway presenter so loaded sessions render
identically to live ones.

Tests: dsh-tools defineTool presenters (typed args, soft-validate), tool-bash
bash/bash_output/bash_kill presenters, acp ToolPresenter (tool-owned mapping,
unknown-callId fallback, in-flight-only map), and an end-to-end turn through the
bridge. The key-gated e2e now asserts a real bash call's title is the model
description (not "bash") and rawInput is the command — verified against the real
DeepSeek model. The test harness derives its inject from the bridge's exported
`inject` so it can't drift again.

docs/module-graph.md

@@ -15,10 +15,6 @@ graph TD
   agent --> llm
   agent --> session
   session-persistence --> session
-  acp --> agent
-  acp --> llm
-  acp --> session
-  acp --> session-persistence
   invariants --> agent
   invariants --> llm
   invariants --> session
@@ -29,6 +25,11 @@ graph TD
   tools --> agent
   tools --> llm
   tools --> system-prompt
+  acp --> agent
+  acp --> llm
+  acp --> session
+  acp --> session-persistence
+  acp --> tools
   agent-loop --> agent
   agent-loop --> llm
   agent-loop --> session
@@ -52,10 +53,10 @@ graph TD
 | `system-prompt` | `llm` |
 | `agent` | `llm`, `session` |
 | `session-persistence` | `session` |
-| `acp` | `agent`, `llm`, `session`, `session-persistence` |
 | `invariants` | `agent`, `llm`, `session` |
 | `session-persistence-jsonl` | `session`, `session-persistence` |
 | `session-persistence-sqlite` | `session`, `session-persistence` |
 | `tools` | `agent`, `llm`, `system-prompt` |
+| `acp` | `agent`, `llm`, `session`, `session-persistence`, `tools` |
 | `agent-loop` | `agent`, `llm`, `session`, `session-persistence`, `system-prompt`, `tools` |
 | `tool-bash` | `agent`, `bash`, `llm`, `tools` |

examples/acp-agent/tests/acp.e2e.ts

@@ -174,6 +174,21 @@ describe.skipIf(!process.env.DEEPSEEK_API_KEY)('acp-agent e2e: real prompt over
     expect(proof).toContain('ACP_OK')
 
     // And the client saw tool-call activity stream through.
-    expect(updates.some(u => u.sessionUpdate === 'tool_call')).toBe(true)
+    const toolCalls = updates.filter(u => u.sessionUpdate === 'tool_call')
+    expect(toolCalls.length).toBeGreaterThan(0)
+
+    // Tool-call UI quality (the tool owns its presentation): the bash tool's
+    // `presentCall` sets the title to the model's human-readable `description`
+    // and the `rawInput` to the exact command — NOT the bare tool name "bash".
+    // A `bash` call must therefore carry an execute kind, a non-"bash" title,
+    // and a string rawInput (the command). `toolCalls` is already narrowed to
+    // the `tool_call` shape by the filter above, so these fields are reachable.
+    const bashCall = toolCalls.find(u => u.kind === 'execute')
+    expect(bashCall).toBeDefined()
+    if (bashCall === undefined) throw new Error('expected an execute tool_call')
+    expect(typeof bashCall.title).toBe('string')
+    expect(bashCall.title.length).toBeGreaterThan(0)
+    expect(bashCall.title).not.toBe('bash') // the old, unhelpful title
+    expect(typeof bashCall.rawInput).toBe('string') // the exact command
   }, 180_000)
 })

packages/acp/README.md

@@ -28,7 +28,7 @@ It is a **client-driver / UI plugin**, the structured analogue of the readline `
 | `session/load` | `ctx.agents.resume(...)` | replays the persisted event log to the client as `session/update` — the USER side (`user/message` → `user_message_chunk`), assistant text/reasoning (`assistant/chunk`), and tool calls/results (`tool/call` + `tool/result`). Re-loading an already-live id is rejected; the id's load slot is reserved (`loadingIds`) BEFORE the async resume so a pipelined load of the SAME id can't leak a second agent (distinct ids load concurrently). The resumed session keeps its PERSISTED header `cwd`, so its bash tools run in the original workspace; the requested `cwd` only needs to be absolute. After the async resume a `closed` re-check refuses to install a record if the bridge tore down mid-load |
 | `session/prompt` | `agent.send()` | text-only; rejects image/audio and empty prompts; one in-flight prompt PER session (independent); settles on the OWNING turn's end (a turn that ends in `error` rejects the RPC) |
 | `session/cancel` | `agent.abort()` | aborts a running step + settles the prompt `cancelled` for ONLY that session — a cancel never touches another session's stream or prompt (see limitation below) |
-| `session/update` | `session/event` | `agent_message_chunk` (text-delta), `agent_thought_chunk` (reasoning-delta), `user_message_chunk` (load replay), `tool_call`/`tool_call_update` |
+| `session/update` | `session/event` | `agent_message_chunk` (text-delta), `agent_thought_chunk` (reasoning-delta), `user_message_chunk` (load replay), `tool_call`/`tool_call_update` (title/kind/rawInput/content owned by the TOOL via `presentCall`/`presentResult` — see Tool-call presentation) |
 
 ## Multi-session (RFC 011)
 
@@ -40,6 +40,12 @@ Background-task isolation rides on `dsh-tool-bash`: bash task ids are global and
 
 Each session runs in its own workspace, recorded as the session's `SessionHeader.cwd`. On `session/new` the (absolute) request `cwd` becomes that header cwd; on `session/load` the resumed session keeps its PERSISTED header cwd (the request `cwd` is only shape-checked — it does not override the stored one), and a load whose persisted session has no absolute cwd is REJECTED up front via a metadata-only `list()` check, BEFORE resume constructs an agent (else bash would silently fall back to the server's launch dir, and a post-resume reject would leak the registered agent). `dsh-tool-bash` then defaults the bash workdir to the calling agent's `session.header.cwd` (an explicit model `workdir` still wins; a relative one resolves against the session cwd; with no session cwd the executor falls back to its own config / `process.cwd()`). So the server no longer has to be launched in the workspace — an editor can open any project folder, and N sessions over one connection can each target a different directory. (`additionalDirectories` is still rejected: widening the tool/filesystem scope beyond the single cwd is a separate sandbox concern.)
 
+## Tool-call presentation
+
+How a tool call renders in the editor is owned by the TOOL, not the bridge — the bridge never special-cases tool names. Each tool may declare `presentCall(args)` (pending state: a human-readable `title`, a `kind` for the icon, and the salient `rawInput` to show in a detail view) and `presentResult(args, result)` (completed state: an optional replacement `title` and reformatted `content`) on its `dsh-tools` definition. The bridge looks the definition up by name in `ctx.tools` and maps the neutral `ToolCallPresentation`/`ToolResultPresentation` to the ACP `tool_call`/`tool_call_update` wire shapes. A tool that declares neither gets a generic fallback (title = tool name, raw parsed args as `rawInput`, kind inferred from the name). For example `dsh-tool-bash` makes the model-written one-line `description` the title ("List files in the current directory"), the exact `command` the `rawInput`, `kind: 'execute'`, and wraps the completed output in a fenced ` ```console ` block.
+
+The `tool/result` session event carries only `{ callId, content, isError }` — not the tool name or args — so to call a tool's `presentResult` the bridge keeps a small per-session map from `callId` to the in-flight call's `(name, args)`, populated on `tool/call` and removed as each result is presented (it holds only currently-in-flight calls, never finished ones). This is bridge-local state — NOT a change to the event schema or a core service. The map lives on the `SessionRecord`, so two concurrent sessions never cross their in-flight tool state; a `session/load` replay uses a throwaway presenter that pairs each `tool/call` with its `tool/result` as the log replays in order, so replayed tool cards render identically to live ones.
+
 ## Settle-exactly-once
 
 A `session/prompt` resolves (or rejects) exactly once, keyed off the canonical session log (the `session/event` stream), NOT the `agent/turn-start`/`agent/turn-end` events. One listener captures the prompt's owning turn from the log's `turn/start` and settles on the matching `turn/end` — the one signal that always fires (`closeTurn` appends it unconditionally, even when a boundary emit throws and the `agent/turn-end` EVENT is skipped). A prompt settles only on ITS OWN turn (`inflight.turn === turn/end.turn`), so a stale `turn/end` for a previously-cancelled turn whose end arrives late can never settle the wrong prompt. A turn that ends `error` REJECTS the RPC with an internal error carrying the failure message (ACP has no error stop reason); every other reason resolves via the codec. As a fallback, when the agent settles to `idle`/`disposed` with a prompt still pending — e.g. a `session/event` listener registered before the bridge threw and starved the bridge's listener — an `agent/status` handler reconciles the prompt from the log (the owning turn's `turn/end`, or `cancelled` if the turn was torn down without one). An empty/whitespace prompt is rejected up front — it would queue no work, so no turn would start and the RPC would hang.

packages/acp/package.json

@@ -29,6 +29,7 @@
     "@deepseek-ai/dsh-llm": "^0.0.1",
     "@deepseek-ai/dsh-session": "^0.0.1",
     "@deepseek-ai/dsh-session-persistence": "^0.0.1",
+    "@deepseek-ai/dsh-tools": "^0.0.1",
     "cordis": "^4.0.0-rc.6"
   },
   "devDependencies": {

packages/acp/src/index.ts

@@ -60,6 +60,7 @@ import {
 import type { ContentBlock } from '@deepseek-ai/dsh-llm'
 import type { Agent, AgentStatus } from '@deepseek-ai/dsh-agent'
 import type { SessionEvent } from '@deepseek-ai/dsh-session'
+import type { ToolCallKind, ToolRegistry } from '@deepseek-ai/dsh-tools'
 // Side-effect type import: declaration-merges `ctx.sessionPersistence` onto
 // Context (the bridge injects it and reads `list()` for load cwd validation).
 import type {} from '@deepseek-ai/dsh-session-persistence'
@@ -73,8 +74,10 @@ import {
 export const name = 'acp'
 // The bridge programs against the interface packages only (architecture rule:
 // plugins never depend on dsh-agent-loop). `sessionPersistence` is required
-// because `initialize` advertises `loadSession: true`.
-export const inject = ['agents', 'sessions', 'sessionPersistence']
+// because `initialize` advertises `loadSession: true`. `tools` lets a tool own
+// how its calls render (`presentCall`/`presentResult`); the bridge looks up the
+// definition by name and falls back to a generic presentation when absent.
+export const inject = ['agents', 'sessions', 'sessionPersistence', 'tools']
 
 /**
  * Build an ACP "invalid params" error whose human detail rides in the message.
@@ -131,6 +134,13 @@ export const Config: Schema<AcpConfig> = Schema.object({
 interface SessionRecord {
   sessionId: string
   agent: Agent
+  /**
+   * Resolves tool-owned presentation for THIS session's tool calls and remembers
+   * each in-flight call's `(name, args)` so the matching `tool/result` can find
+   * its tool. Per-session so two concurrent sessions never cross their in-flight
+   * tool state.
+   */
+  presenter: ToolPresenter
   /**
    * The in-flight `session/prompt`, or `undefined` when none is pending. A
    * prompt resolves with a {@link StopReason} or rejects with an Error (a
@@ -182,6 +192,7 @@ export function apply(ctx: Context, config: AcpConfig): void {
   const agents = ctx.agents
   const sessionPersistence = ctx.sessionPersistence
   const logger = ctx.logger
+  const tools = ctx.tools
 
   // Live sessions keyed by id (RFC 011 multi-session), plus an agent→sessionId
   // reverse map so `agent/*` events (which carry only the Agent) demux in O(1).
@@ -270,7 +281,7 @@ export function apply(ctx: Context, config: AcpConfig): void {
   ctx.on('session/event', (session, event: SessionEvent) => {
     const rec = sessions.get(session.header.id)
     if (rec === undefined) return
-    streamSessionEventUpdate(rec.sessionId, event, notify)
+    streamSessionEventUpdate(rec.sessionId, event, notify, rec.presenter)
     const inflight = rec.inflight
     if (inflight === undefined) return
     if (event.type === 'turn/start') {
@@ -395,7 +406,7 @@ export function apply(ctx: Context, config: AcpConfig): void {
           agentOptions: agentOptions(config),
         })
         bySession.set(agent, sessionId)
-        sessions.set(sessionId, { sessionId, agent, inflight: undefined })
+        sessions.set(sessionId, { sessionId, agent, presenter: new ToolPresenter(tools), inflight: undefined })
         return Promise.resolve({ sessionId })
       },
 
@@ -448,14 +459,18 @@ export function apply(ctx: Context, config: AcpConfig): void {
             throw invalidParams('connection closed during session/load')
           }
           bySession.set(agent, params.sessionId)
-          sessions.set(params.sessionId, { sessionId: params.sessionId, agent, inflight: undefined })
+          const record: SessionRecord = { sessionId: params.sessionId, agent, presenter: new ToolPresenter(tools), inflight: undefined }
+          sessions.set(params.sessionId, record)
           // Replay the persisted event log to the client as session/update. Use
           // the raw event log (NOT deriveMessages, which drops assistant/chunk
           // and trace events): RFC 010's load contract reconstructs the streamed
           // turns — user prompts (user/message → user_message_chunk), assistant
-          // text and reasoning (assistant/chunk), and tool calls/results.
+          // text and reasoning (assistant/chunk), and tool calls/results. The
+          // record's presenter pairs each tool/call with its tool/result as the
+          // log replays in order, so the replayed tool cards render identically
+          // to the live ones.
           for (const event of agent.session.events) {
-            streamSessionEventUpdate(params.sessionId, event, notify)
+            streamSessionEventUpdate(params.sessionId, event, notify, record.presenter)
           }
           return {}
         } finally {
@@ -659,6 +674,14 @@ function validateWorkspaceParams(params: { cwd: string; additionalDirectories?:
  * - `tool/call`   → `tool_call` (pending)
  * - `tool/result` → `tool_call_update` (completed/failed)
  *
+ * Tool-call presentation (title/kind/rawInput, and the completed-state content)
+ * is owned by each TOOL via `presentCall`/`presentResult` — the bridge never
+ * special-cases tool names. `presenter` resolves those from the tool registry
+ * and remembers each call's `(name, args)` so the completed `tool/result` (which
+ * carries neither) can find its tool. A {@link nullToolPresenter} gives the
+ * generic fallback (title = tool name, raw args as input) when no registry is
+ * available (e.g. pure translator tests).
+ *
  * Other event types (turn/step boundaries, context/message, usage, …) produce
  * no client update.
  */
@@ -666,6 +689,7 @@ export function streamSessionEventUpdate(
   sessionId: string,
   event: SessionEvent,
   notify: (notification: SessionNotification) => void,
+  presenter: Pick<ToolPresenter, 'call' | 'result'> = nullToolPresenter,
 ): void {
   switch (event.type) {
     case 'assistant/chunk': {
@@ -690,27 +714,30 @@ export function streamSessionEventUpdate(
       return
     }
     case 'tool/call': {
+      const present = presenter.call(event.data.callId, event.data.name, event.data.arguments)
       notify({
         sessionId,
         update: {
           sessionUpdate: 'tool_call',
           toolCallId: event.data.callId,
-          title: event.data.name,
-          kind: toolKindFor(event.data.name),
+          title: present.title,
+          kind: present.kind,
           status: 'in_progress',
-          rawInput: parseToolArguments(event.data.arguments),
+          ...present.rawInput !== undefined ? { rawInput: present.rawInput } : {},
         },
       })
       return
     }
     case 'tool/result': {
+      const present = presenter.result(event.data.callId, event.data.content, event.data.isError)
       notify({
         sessionId,
         update: {
           sessionUpdate: 'tool_call_update',
           toolCallId: event.data.callId,
           status: event.data.isError ? 'failed' : 'completed',
-          content: toolResultContent(event.data.content),
+          content: toolResultContent(present.content),
+          ...present.title !== undefined ? { title: present.title } : {},
         },
       })
       return
@@ -722,8 +749,84 @@ export function streamSessionEventUpdate(
   }
 }
 
+/**
+ * Resolved pending-state presentation the bridge feeds into a `tool_call`
+ * update: a title is always present (tool name when the tool gives none), `kind`
+ * and `rawInput` are optional.
+ */
+interface ResolvedCallPresentation {
+  title: string
+  kind: ToolCallKind
+  rawInput?: unknown
+}
+
+/** Resolved completed-state presentation fed into a `tool_call_update`. */
+interface ResolvedResultPresentation {
+  /** UI content for the result (harness blocks; the tool may reformat, else the raw result). */
+  content: ContentBlock[]
+  /** Optional replacement title for the completed call. */
+  title?: string
+}
+
+/**
+ * Resolves tool-owned presentation for a session's tool-call events. A tool
+ * declares `presentCall`/`presentResult` (see `dsh-tools`); this looks them up
+ * by name in the registry and applies the generic fallback when a tool defines
+ * neither.
+ *
+ * The `tool/result` session event carries only `{ callId, content, isError }` —
+ * NOT the tool name or args — so to call a tool's `presentResult` (which needs
+ * both), the presenter remembers each `tool/call`'s `{ name, args }` keyed by
+ * callId and looks it up on the matching result. The map is bridge-LOCAL (not a
+ * change to the event schema or a core service): one presenter per live session
+ * (and a throwaway per `session/load` replay), entries removed as each result
+ * arrives, so it holds only the currently-in-flight calls.
+ */
+export class ToolPresenter {
+  private readonly pending = new Map<string, { name: string; args: unknown }>()
+
+  constructor(private readonly tools: Pick<ToolRegistry, 'get'>) {}
+
+  /** Pending-state presentation for a `tool/call`; remembers `(name, args)` for the matching result. */
+  call(callId: string, name: string, argsJson: string): ResolvedCallPresentation {
+    const args = parseToolArguments(argsJson)
+    this.pending.set(callId, { name, args })
+    const present = this.tools.get(name)?.presentCall?.(args)
+    if (present === undefined) {
+      // No tool-owned presentation: fall back to the tool name as the title and
+      // the full parsed args as the raw input (the pre-seam behavior).
+      return { title: name, kind: toolKindFor(name), rawInput: args }
+    }
+    return { title: present.title, kind: present.kind ?? 'other', rawInput: present.rawInput }
+  }
+
+  /** Completed-state presentation for a `tool/result`; consumes the remembered `(name, args)`. */
+  result(callId: string, content: ContentBlock[], isError: boolean): ResolvedResultPresentation {
+    const call = this.pending.get(callId)
+    this.pending.delete(callId)
+    const present = call !== undefined
+      ? this.tools.get(call.name)?.presentResult?.(call.args, { content, isError })
+      : undefined
+    if (present === undefined) return { content }
+    return {
+      content: present.content ?? content,
+      ...present.title !== undefined ? { title: present.title } : {},
+    }
+  }
+}
+
+/**
+ * The no-op presenter used when no tool registry is available (e.g. the pure
+ * translator tests): every tool gets the generic fallback presentation, and
+ * results pass their raw content through unchanged.
+ */
+export const nullToolPresenter: Pick<ToolPresenter, 'call' | 'result'> = {
+  call: (_callId, name, argsJson) => ({ title: name, kind: toolKindFor(name), rawInput: parseToolArguments(argsJson) }),
+  result: (_callId, content) => ({ content }),
+}
+
 /** Map a harness tool name to an ACP ToolKind (best-effort; default `other`). */
-function toolKindFor(name: string): 'read' | 'edit' | 'delete' | 'move' | 'search' | 'execute' | 'fetch' | 'other' {
+function toolKindFor(name: string): ToolCallKind {
   if (name === 'bash' || name === 'bash_output' || name === 'bash_kill') return 'execute'
   if (name === 'read' || name.startsWith('read')) return 'read'
   if (name === 'write' || name === 'edit' || name.startsWith('edit')) return 'edit'

packages/acp/tests/harness.ts

@@ -234,7 +234,11 @@ export async function makeBridgeHarness(options: {
   // tears down JUST the bridge (its listeners + effect) for the HMR test.
   harness.acpFiber = await ctx.plugin({
     name: 'acp-test',
-    inject: ['agents', 'sessions', 'sessionPersistence'],
+    // Use the bridge's REAL exported `inject` so this never drifts from the
+    // plugin's actual dependency list (adding a service to the bridge must not
+    // require editing the harness — a hardcoded list silently broke when `tools`
+    // was added). The bridge programs against the interface packages only.
+    inject: [...AcpPlugin.inject],
     apply: (inner: Context) => { AcpPlugin.apply(inner, cfg) },
   })
   harness.client = new ClientSideConnection(makeClient, clientStream)

packages/acp/tests/stream-update.spec.ts

@@ -2,15 +2,22 @@ import { describe, expect, it } from 'vitest'
 import { CallId } from '@deepseek-ai/dsh-llm'
 import type { SessionEvent } from '@deepseek-ai/dsh-session'
 import type { SessionNotification } from '@agentclientprotocol/sdk'
-import { streamSessionEventUpdate, agentOptions } from '../src/index.ts'
+import type { ToolDefinition, ToolRegistry } from '@deepseek-ai/dsh-tools'
+import { streamSessionEventUpdate, agentOptions, ToolPresenter } from '../src/index.ts'
 
-/** Collect the updates a single event produces. */
+/** Collect the updates a single event produces (no presenter → generic fallback). */
 function updatesFor(event: SessionEvent): SessionNotification['update'][] {
   const out: SessionNotification['update'][] = []
   streamSessionEventUpdate('s1', event, n => out.push(n.update))
   return out
 }
 
+/** A tiny tool registry stub exposing just `get` for {@link ToolPresenter}. */
+function registryOf(...tools: ToolDefinition[]): Pick<ToolRegistry, 'get'> {
+  const map = new Map(tools.map(t => [t.name, t]))
+  return { get: name => map.get(name) }
+}
+
 function evt<T extends SessionEvent['type']>(type: T, data: Extract<SessionEvent, { type: T }>['data']): SessionEvent {
   return { type, seq: 0, time: 0, data } as SessionEvent
 }
@@ -31,7 +38,7 @@ describe('streamSessionEventUpdate', () => {
       .toEqual([])
   })
 
-  it('maps tool/call to an in_progress tool_call with inferred kind and parsed rawInput', () => {
+  it('maps tool/call to an in_progress tool_call with inferred kind and parsed rawInput (generic fallback, no presenter)', () => {
     const updates = updatesFor(evt('tool/call', { turn: 1, step: 1, callId: CallId('c1'), name: 'bash', arguments: '{"command":"ls"}' }))
     expect(updates).toEqual([{
       sessionUpdate: 'tool_call',
@@ -99,6 +106,129 @@ describe('streamSessionEventUpdate', () => {
   })
 })
 
+describe('ToolPresenter (tool-owned presentation via the tool registry)', () => {
+  /** A tool whose presentCall/presentResult mirror what tool-bash declares. */
+  const bashLike: ToolDefinition = {
+    name: 'bash',
+    description: 'run a command',
+    parameters: {},
+    execute: async () => [],
+    presentCall: (args: unknown) => {
+      const a = args as { command: string; description: string }
+      return { title: a.description, kind: 'execute', rawInput: a.command }
+    },
+    presentResult: (_args: unknown, result: { content: { type: string }[] }) => ({
+      content: [{ type: 'text', text: `wrapped:${result.content.length}` }],
+    }),
+  }
+
+  function updatesWith(presenter: ToolPresenter, ...events: SessionEvent[]): SessionNotification['update'][] {
+    const out: SessionNotification['update'][] = []
+    for (const event of events) streamSessionEventUpdate('s1', event, n => out.push(n.update), presenter)
+    return out
+  }
+
+  it('tool/call uses the tool: description→title, command→rawInput, tool kind', () => {
+    const presenter = new ToolPresenter(registryOf(bashLike))
+    const [update] = updatesWith(presenter, evt('tool/call', {
+      turn: 1, step: 1, callId: CallId('c1'), name: 'bash',
+      arguments: JSON.stringify({ command: 'ls -la', description: 'List files' }),
+    }))
+    expect(update).toEqual({
+      sessionUpdate: 'tool_call',
+      toolCallId: 'c1',
+      title: 'List files',
+      kind: 'execute',
+      status: 'in_progress',
+      rawInput: 'ls -la',
+    })
+  })
+
+  it('tool/result uses the tool to reformat content (resolved by the remembered tool/call)', () => {
+    const presenter = new ToolPresenter(registryOf(bashLike))
+    const updates = updatesWith(
+      presenter,
+      evt('tool/call', { turn: 1, step: 1, callId: CallId('c1'), name: 'bash', arguments: JSON.stringify({ command: 'x', description: 'd' }) }),
+      evt('tool/result', { turn: 1, step: 1, callId: CallId('c1'), content: [{ type: 'text', text: 'out' }], isError: false }),
+    )
+    expect(updates[1]).toEqual({
+      sessionUpdate: 'tool_call_update',
+      toolCallId: 'c1',
+      status: 'completed',
+      content: [{ type: 'content', content: { type: 'text', text: 'wrapped:1' } }],
+    })
+  })
+
+  it('a result with NO preceding call (unknown callId) falls back to the raw content', () => {
+    const presenter = new ToolPresenter(registryOf(bashLike))
+    // No tool/call for c9 → presenter has nothing remembered → generic fallback.
+    const [update] = updatesWith(presenter, evt('tool/result', {
+      turn: 1, step: 1, callId: CallId('c9'), content: [{ type: 'text', text: 'raw' }], isError: false,
+    }))
+    expect(update).toEqual({
+      sessionUpdate: 'tool_call_update',
+      toolCallId: 'c9',
+      status: 'completed',
+      content: [{ type: 'content', content: { type: 'text', text: 'raw' } }],
+    })
+  })
+
+  it('a tool with no presentCall/presentResult gets the generic fallback (title = name)', () => {
+    const plain: ToolDefinition = { name: 'plain', description: 'p', parameters: {}, execute: async () => [] }
+    const presenter = new ToolPresenter(registryOf(plain))
+    const [update] = updatesWith(presenter, evt('tool/call', {
+      turn: 1, step: 1, callId: CallId('c1'), name: 'plain', arguments: '{"a":1}',
+    }))
+    expect(update).toMatchObject({ title: 'plain', kind: 'other', rawInput: { a: 1 } })
+  })
+
+  it('a presentation that omits kind/content/rawInput uses the defaults (kind other, raw result content kept)', () => {
+    // A minimal tool-owned presentation: presentCall returns only a title (no
+    // kind → defaults to `other`, no rawInput → omitted); presentResult returns
+    // only a title (no content → the raw result content is kept).
+    const minimal: ToolDefinition = {
+      name: 'mini',
+      description: 'm',
+      parameters: {},
+      execute: async () => [],
+      presentCall: () => ({ title: 'Doing a thing' }),
+      presentResult: () => ({ title: 'Did the thing' }),
+    }
+    const presenter = new ToolPresenter(registryOf(minimal))
+    const updates = updatesWith(
+      presenter,
+      evt('tool/call', { turn: 1, step: 1, callId: CallId('c1'), name: 'mini', arguments: '{}' }),
+      evt('tool/result', { turn: 1, step: 1, callId: CallId('c1'), content: [{ type: 'text', text: 'kept' }], isError: false }),
+    )
+    // No kind → 'other'; no rawInput key at all.
+    expect(updates[0]).toEqual({ sessionUpdate: 'tool_call', toolCallId: 'c1', title: 'Doing a thing', kind: 'other', status: 'in_progress' })
+    // Title replaced; content falls back to the raw result content.
+    expect(updates[1]).toEqual({
+      sessionUpdate: 'tool_call_update',
+      toolCallId: 'c1',
+      status: 'completed',
+      content: [{ type: 'content', content: { type: 'text', text: 'kept' } }],
+      title: 'Did the thing',
+    })
+  })
+
+  it('holds ONLY in-flight calls: the callId entry is removed once its result is presented', () => {
+    const presenter = new ToolPresenter(registryOf(bashLike))
+    updatesWith(
+      presenter,
+      evt('tool/call', { turn: 1, step: 1, callId: CallId('c1'), name: 'bash', arguments: JSON.stringify({ command: 'x', description: 'd' }) }),
+      evt('tool/result', { turn: 1, step: 1, callId: CallId('c1'), content: [{ type: 'text', text: 'o' }], isError: false }),
+    )
+    // A SECOND result for the same callId now finds nothing remembered, so it
+    // falls back to raw content (proving the first result consumed the entry —
+    // the map does not retain finished calls).
+    const [late] = updatesWith(presenter, evt('tool/result', {
+      turn: 1, step: 1, callId: CallId('c1'), content: [{ type: 'text', text: 'late' }], isError: false,
+    }))
+    expect(late).toMatchObject({ content: [{ type: 'content', content: { type: 'text', text: 'late' } }] })
+  })
+})
+
 describe('agentOptions', () => {
   it('includes only the fields present in config', () => {
     expect(agentOptions({})).toEqual({})

packages/acp/tests/turns.spec.ts

@@ -75,6 +75,42 @@ describe('acp bridge — turn outcomes', () => {
     expect(callIdx).toBeLessThan(updIdx)
   })
 
+  it('a tool-owned presentation flows end-to-end: presentCall sets title/rawInput, presentResult reformats output', async () => {
+    harness = await makeBridgeHarness({
+      storageDir,
+      script: [toolCallResponse('c1', 'bash', { command: 'ls -la', description: 'List files' }), textResponse('done')],
+    })
+    // A tool that declares its OWN presentation (like the real tool-bash). The
+    // bridge must use it — NOT the generic title=name fallback — proving the
+    // tool-owns-its-rendering seam works through the real session-event path.
+    harness.ctx.tools.register(defineTool({
+      name: 'bash',
+      description: 'run a command',
+      parameters: {
+        command: { type: 'string', required: true },
+        description: { type: 'string', required: true },
+      },
+      async execute() { return [{ type: 'text', text: 'a.txt\nb.txt\n' }] },
+      presentCall: args => ({ title: args.description, kind: 'execute', rawInput: args.command }),
+      presentResult: (_args, result) => {
+        const block = result.content.length === 1 ? result.content[0] : undefined
+        if (block === undefined || block.type !== 'text') return undefined
+        return { content: [{ type: 'text', text: `\`\`\`console\n${block.text.trimEnd()}\n\`\`\`` }] }
+      },
+    }))
+    const sessionId = await newSession(harness)
+    await harness.client.prompt({ sessionId, prompt: [{ type: 'text', text: 'list' }] })
+
+    const call = harness.updates.find(u => u.sessionUpdate === 'tool_call')
+    expect(call).toMatchObject({ toolCallId: 'c1', title: 'List files', kind: 'execute', rawInput: 'ls -la', status: 'in_progress' })
+    const update = harness.updates.find(u => u.sessionUpdate === 'tool_call_update')
+    expect(update).toMatchObject({
+      toolCallId: 'c1',
+      status: 'completed',
+      content: [{ type: 'content', content: { type: 'text', text: '```console\na.txt\nb.txt\n```' } }],
+    })
+  })
+
   it('a failing tool yields a failed tool_call_update', async () => {
     harness = await makeBridgeHarness({
       storageDir,

packages/acp/tsconfig.json

@@ -12,6 +12,7 @@
     { "path": "../llm" },
     { "path": "../session" },
     { "path": "../agent" },
+    { "path": "../tools" },
     { "path": "../session-persistence" }
   ]
 }

packages/tool-bash/README.md

@@ -32,6 +32,10 @@ Result text: stdout, then a `[stderr]` section, then status markers — `[timed
 
 The owning agent is recorded per task id at spawn and kept for the lifetime of the loaded plugin instance (it is **not** cleared on completion). `bash_output`/`bash_kill` reject a task owned by a *different* agent with `task <id> belongs to another session` (a task started with no agent — a non-loop caller — has no owner and is open to anyone; a call with no `exec.agent` cannot access an owned task). Task ids are global and predictable, so under multi-session ACP this ownership check is the fence that stops one session's agent from reading or killing another session's background task. (`TODO(tool-bash-owner-hmr)`: an independent HMR reload of this plugin starts a fresh map, so a task spawned before the reload becomes un-owned — acceptable as HMR is dev-only and the session boundary is one user's cooperative editor; a durable fix attaches ownership to the executor/task lifetime.)
 
+## UI presentation
+
+These tools own how their calls render in a UI (an editor's tool-call card) via the `dsh-tools` `presentCall`/`presentResult` seam — a UI never special-cases tool names. For `bash`: the model-written `description` is the always-visible **title** (e.g. "List files in the current directory"), the exact `command` is the **rawInput** (the verbatim command stays visible in a detail view without crowding the title), `kind` is `execute` (terminal/run treatment), and the completed output is wrapped in a fenced ` ```console ` block — a UI-only affordance, so the model-facing result text stays unfenced. `bash_output`/`bash_kill` present a task-scoped title ("Read output from background task bash-3" / "Kill background task bash-3") with the task id as rawInput. These methods are pure/display-only (they also run on `session/load` replay), and a malformed/older logged arg shape falls back to a generic presentation rather than throwing. See `packages/tools` ("Tool-owned UI presentation") and `packages/acp` ("Tool-call presentation").
+
 ## Background completion notices
 
 When a background task finishes, a short notice is injected into the owning agent's session (`agent.inject()`, source `{kind: 'plugin', plugin: 'tool-bash'}`). Injection is **durable context for the next model request, not a wake-up** — an idle agent stays idle until something sends a message. That's why the tool descriptions tell the model to poll with `bash_output`.

packages/tool-bash/src/index.ts

@@ -39,6 +39,8 @@
 import type { Context } from 'cordis'
 import { isAbsolute, resolve as resolvePath } from 'node:path'
 import { defineTool } from '@deepseek-ai/dsh-tools'
+import type { ToolCallPresentation, ToolResult, ToolResultPresentation } from '@deepseek-ai/dsh-tools'
+import type { ContentBlock } from '@deepseek-ai/dsh-llm'
 import type { Agent } from '@deepseek-ai/dsh-agent'
 import type { BashRunResult, BashTask, CollectedOutput } from '@deepseek-ai/dsh-bash'
 
@@ -124,6 +126,44 @@ export function renderResult(result: BashRunResult): string {
   return body + markers.join('\n')
 }
 
+// ---------------------------------------------------------------------------
+// UI presentation (tool-owned). These shape how a UI (e.g. the ACP bridge)
+// renders a bash call's pending and completed states. They are display-only and
+// pure — a UI may call them during live streaming AND a session-log replay.
+// ---------------------------------------------------------------------------
+
+/**
+ * Pending-state presentation for a `bash` call: the model-written `description`
+ * is the always-visible title (the schema requires it precisely so a UI has a
+ * readable summary — "List files in the current directory"), `kind: 'execute'`
+ * (a terminal/run treatment), and the exact `command` is the `rawInput` so the
+ * verbatim command stays visible in a UI's detail view without crowding the
+ * title. Mirrors how Zed / the reference ACP adapters render execute tools.
+ */
+function presentBashCall(args: { command: string; description: string }): ToolCallPresentation {
+  return { title: args.description, kind: 'execute', rawInput: args.command }
+}
+
+/**
+ * Completed-state presentation for a `bash` call: wrap the model-facing result
+ * text in a fenced ```console block so a UI renders the output monospaced as a
+ * terminal transcript. The model-facing `content` (what `execute` returned) is
+ * intentionally NOT fenced — the fences are a UI-only affordance, so they live
+ * here, not in `renderResult`. A non-text result (unexpected for bash) is left
+ * untouched by falling back to `undefined`.
+ */
+function presentBashResult(_args: unknown, result: ToolResult): ToolResultPresentation | undefined {
+  const block = result.content.length === 1 ? result.content[0] : undefined
+  if (block === undefined || block.type !== 'text') return undefined
+  const fenced: ContentBlock = { type: 'text', text: `\`\`\`console\n${block.text.replace(/\n+$/, '')}\n\`\`\`` }
+  return { content: [fenced] }
+}
+
+/** Pending-state presentation for `bash_output`/`bash_kill` (background-task tools). */
+function presentTaskCall(verb: string, args: { task_id: string }): ToolCallPresentation {
+  return { title: `${verb} background task ${args.task_id}`, kind: 'execute', rawInput: args.task_id }
+}
+
 /**
  * Resolve the working directory for a bash call. Precedence: an explicit model
  * `workdir` wins; otherwise default to the calling agent's session cwd
@@ -242,6 +282,8 @@ export function apply(ctx: Context): void {
       if (result.aborted) throw new Error('command aborted')
       return [{ type: 'text', text: renderResult(result) }]
     },
+    presentCall: presentBashCall,
+    presentResult: presentBashResult,
   }))
 
   ctx.tools.register(defineTool({
@@ -266,6 +308,7 @@ export function apply(ctx: Context): void {
       text += `\n${statusLine(read.task)}`
       return Promise.resolve([{ type: 'text', text }])
     },
+    presentCall: args => presentTaskCall('Read output from', args),
   }))
 
   ctx.tools.register(defineTool({
@@ -283,5 +326,6 @@ export function apply(ctx: Context): void {
         text: killed ? `killed background task ${id}` : `task ${id} had already finished`,
       }])
     },
+    presentCall: args => presentTaskCall('Kill', args),
   }))
 }

packages/tool-bash/tests/tools.spec.ts

@@ -562,3 +562,58 @@ describe('status lines', () => {
     expect(text(read)).toContain('[status: completed, exit code: 0]')
   })
 })
+
+describe('tool-owned UI presentation (presentCall / presentResult)', () => {
+  it('bash presentCall: the model description is the title, the command is the rawInput, kind execute', async () => {
+    const ctx = await setup()
+    const present = ctx.tools.get('bash')!.presentCall!({ command: 'ls -la src', description: 'List files in src' })
+    expect(present).toEqual({ title: 'List files in src', kind: 'execute', rawInput: 'ls -la src' })
+  })
+
+  it('bash presentResult: wraps the model-facing text in a fenced console block', async () => {
+    const ctx = await setup()
+    const present = ctx.tools.get('bash')!.presentResult!(
+      { command: 'echo hi', description: 'echo' },
+      { content: [{ type: 'text', text: 'hi\n[exit code: 0]\n\n' }], isError: false },
+    )
+    // Trailing blank lines are trimmed; the body is fenced as ```console.
+    expect(present).toEqual({ content: [{ type: 'text', text: '```console\nhi\n[exit code: 0]\n```' }] })
+  })
+
+  it('bash presentResult: leaves a non-text (unexpected) result untouched → undefined (UI keeps raw content)', async () => {
+    const ctx = await setup()
+    const present = ctx.tools.get('bash')!.presentResult!(
+      { command: 'x', description: 'x' },
+      { content: [{ type: 'image', url: 'https://x/y.png' }], isError: false },
+    )
+    expect(present).toBeUndefined()
+  })
+
+  it('bash presentResult: a result that is not exactly one block → undefined (no single text to fence)', async () => {
+    const ctx = await setup()
+    const args = { command: 'x', description: 'x' }
+    // Empty content (no block) and multi-block content both fall through.
+    expect(ctx.tools.get('bash')!.presentResult!(args, { content: [], isError: false })).toBeUndefined()
+    expect(ctx.tools.get('bash')!.presentResult!(args, {
+      content: [{ type: 'text', text: 'a' }, { type: 'text', text: 'b' }],
+      isError: false,
+    })).toBeUndefined()
+  })
+
+  it('bash_output / bash_kill presentCall: a readable task-scoped title, task id as rawInput', async () => {
+    const ctx = await setup()
+    expect(ctx.tools.get('bash_output')!.presentCall!({ task_id: 'bash-3' }))
+      .toEqual({ title: 'Read output from background task bash-3', kind: 'execute', rawInput: 'bash-3' })
+    expect(ctx.tools.get('bash_kill')!.presentCall!({ task_id: 'bash-3' }))
+      .toEqual({ title: 'Kill background task bash-3', kind: 'execute', rawInput: 'bash-3' })
+  })
+
+  it('presentCall validates softly: malformed args (missing required description) return undefined, never throw', async () => {
+    const ctx = await setup()
+    // defineTool wraps presentCall to soft-validate against the schema and fall
+    // back to undefined (a generic UI presentation) rather than throwing on the
+    // display path — it may run on replay of arbitrary logged args. The
+    // ToolDefinition.presentCall takes `unknown`, so a malformed shape needs no cast.
+    expect(ctx.tools.get('bash')?.presentCall?.({ command: 'ls' })).toBeUndefined()
+  })
+})

packages/tools/README.md

@@ -24,9 +24,10 @@ Tool registry and execution waterfall. Tool plugins register their schemas and e
 
 ### Key types
 
-- `ToolDefinition` — `ToolSchema` + `execute(args, exec): Promise<ContentBlock[]>`.
+- `ToolDefinition` — `ToolSchema` + `execute(args, exec): Promise<ContentBlock[]>`, plus optional `presentCall(args)` / `presentResult(args, result)` for tool-owned UI presentation (see below).
 - `ToolExecution` — one pending tool call: `{ callId, name, arguments, agent?, signal? }`.
 - `ToolExecutionResult` — outcome: `{ callId, content, isError, error? }`. On failure with a `HarnessError`, `error: { name, code }` carries the structured failure class alongside the model-facing text (the loop forwards it onto the `tool/result` session event for retry/sandbox plugins and replay).
+- `ToolCallPresentation` / `ToolResultPresentation` — provider-neutral shapes a tool returns from `presentCall` / `presentResult` to own how a UI renders ITS calls (see "Tool-owned UI presentation").
 
 ### Extension points
 
@@ -67,6 +68,39 @@ A `defineTool` tool also **validates the model-generated arguments against its `
 
 See `defineTool`, `validateArgs`, `ToolArgsError`, `SchemaSpec`, `InferArgs`, and `schemaSpecToJsonSchema` in the public API for details.
 
+### Tool-owned UI presentation
+
+A tool owns how ITS calls render in a UI (an editor's tool-call card, a CLI log line) — a UI plugin must NOT special-case tool names. A `ToolDefinition` may declare two optional, pure, display-only methods:
+
+- `presentCall(args): ToolCallPresentation | undefined` — the PENDING state: a human-readable `title` (always-visible label), an optional `kind` (`read`/`edit`/`execute`/… for icon/treatment, default `other`), and an optional `rawInput` (the salient input to show in a detail view — e.g. a shell command as a string, NOT the whole args object).
+- `presentResult(args, result): ToolResultPresentation | undefined` — the COMPLETED state, given the same `args` and the `{ content, isError }` result: an optional replacement `title` and reformatted `content` (e.g. wrap command output in a fenced ` ```console ` block — a UI-only affordance that must NOT appear in the model-facing `execute` result).
+
+Returning `undefined` (or omitting a method) tells a UI to fall back to a generic presentation (title = tool name, raw args as input, raw result content). Both methods must be **pure and side-effect-free**: a UI may call them during live streaming AND during a session-log replay, so they depend only on their arguments. With `defineTool`, `args` is the typed `InferArgs<S>` shape; the helper soft-validates before calling (a malformed/older logged arg shape yields `undefined` rather than throwing, since display must never crash a replay). The shapes are provider-neutral — the ACP bridge (`dsh-acp`) maps them to ACP `tool_call`/`tool_call_update` wire fields, and `dsh-tool-bash` is the reference implementation.
+
+```ts
+import { defineTool } from '@deepseek-ai/dsh-tools'
+
+const bash = defineTool({
+  name: 'bash',
+  description: 'Run a shell command.',
+  parameters: {
+    command: { type: 'string', required: true, description: 'The command to run.' },
+    description: { type: 'string', required: true, description: 'One-line summary shown in the UI.' },
+  },
+  async execute(args) {
+    return [{ type: 'text', text: `ran: ${args.command}` }]
+  },
+  // The model-written description is the readable title; the command is the detail.
+  presentCall: args => ({ title: args.description, kind: 'execute', rawInput: args.command }),
+  // Wrap the output as a console block for the UI (not in the model-facing result).
+  presentResult: (_args, result) => {
+    const block = result.content.length === 1 ? result.content[0] : undefined
+    if (block === undefined || block.type !== 'text') return undefined
+    return { content: [{ type: 'text', text: '```console\n' + block.text + '\n```' }] }
+  },
+})
+```
+
 ### What is NOT here (TODO)
 
 - **Tool shapes review** — when real tools land (e.g. a concurrency-safety hint for parallel execution); phase 1 executes tool calls sequentially.

packages/tools/src/index.ts

@@ -50,9 +50,87 @@ declare module 'cordis' {
 // parallel execution — Claude Code partitions read-only tools; phase 1
 // executes sequentially).
 
+/**
+ * Category of a tool call, used by a UI to pick an icon / treatment. A neutral
+ * vocabulary owned here (NOT an ACP type) so tools describe themselves without
+ * depending on any client protocol; a UI bridge maps it to its own enum. The
+ * member set mirrors the common ACP `ToolKind` values; `other` is the default.
+ */
+export type ToolCallKind = 'read' | 'edit' | 'delete' | 'move' | 'search' | 'execute' | 'fetch' | 'other'
+
+/**
+ * How a tool wants ONE of its calls shown in a UI (an editor's tool-call card,
+ * a CLI log line) BEFORE the result is known — the *pending* state. Provider-
+ * neutral: a tool returns this from {@link ToolDefinition.presentCall} and a UI
+ * plugin (e.g. the ACP bridge) maps it to its own wire shape. The tool owns its
+ * own presentation — the UI must not special-case tool names.
+ */
+export interface ToolCallPresentation {
+  /**
+   * Human-readable, always-visible label describing what THIS call does (e.g.
+   * the model-written one-line summary of a bash command). Keep it short — a UI
+   * shows it as a card header / log line. Required: a presentation must have a
+   * title (a UI falls back to the tool name only when `presentCall` is absent).
+   */
+  title: string
+  /** Category for icon/treatment; defaults to `other` when omitted. */
+  kind?: ToolCallKind
+  /**
+   * The salient input to surface in a detail/expanded view — e.g. the bash
+   * COMMAND itself (as a string), so the title can stay a readable summary
+   * while the exact command is still visible. Omit to show nothing; a string is
+   * rendered as-is, an object as pretty JSON. NOT the full raw args object
+   * unless that is genuinely what a reader wants.
+   */
+  rawInput?: unknown
+}
+
+/**
+ * How a tool wants the COMPLETED call shown — the *result* state, after
+ * `execute` returns. Lets the tool reformat its result for a UI distinctly from
+ * the model-facing text it returned from `execute` (e.g. wrap command output in
+ * a fenced ```console block for monospace rendering, which the model-facing
+ * result must NOT carry). All fields optional: a UI keeps the pending-state
+ * title and renders the raw result content for anything left unset.
+ */
+export interface ToolResultPresentation {
+  /** Replacement title for the completed call (e.g. append an exit status). Omit to keep the pending-state title. */
+  title?: string
+  /**
+   * UI-facing result content (harness {@link ContentBlock}s), reformatted from
+   * the model-facing result. Omit to let the UI render the raw result content.
+   * Stays in harness vocabulary; the UI maps these to its own content blocks.
+   */
+  content?: ContentBlock[]
+}
+
 /** A registered tool: its schema plus the execution function. */
 export interface ToolDefinition extends ToolSchema {
   execute(args: unknown, exec: ToolExecution): Promise<ContentBlock[]>
+  /**
+   * Optional: how to present the PENDING state of one call in a UI, derived
+   * from the call's `args` (parsed arguments, `unknown` — the tool validates/
+   * narrows its own input). Returning `undefined` (or omitting the method) tells
+   * a UI to fall back to a generic presentation (title = tool name, raw args as
+   * input). Pure and side-effect-free: a UI may call it during live streaming
+   * AND a session-log replay, so it must depend only on `args`.
+   */
+  presentCall?(args: unknown): ToolCallPresentation | undefined
+  /**
+   * Optional: how to present the COMPLETED state, given the same `args` and the
+   * `result` (`execute`'s content + whether it errored). Returning `undefined`
+   * (or omitting the method) tells a UI to keep the pending title and render the
+   * raw result content. Pure and side-effect-free for the same replay reason.
+   */
+  presentResult?(args: unknown, result: ToolResult): ToolResultPresentation | undefined
+}
+
+/** The completed outcome handed to {@link ToolDefinition.presentResult}. */
+export interface ToolResult {
+  /** The model-facing content `execute` returned (or the error text on failure). */
+  content: ContentBlock[]
+  /** Whether the call failed. */
+  isError: boolean
 }
 
 /** One pending tool call, as it flows through the execution waterfall. */

packages/tools/src/schema.ts

@@ -21,7 +21,7 @@
 
 import type { ContentBlock } from '@deepseek-ai/dsh-llm'
 import { assertNever, HarnessError } from '@deepseek-ai/dsh-llm'
-import type { ToolDefinition, ToolExecution } from './index.ts'
+import type { ToolCallPresentation, ToolDefinition, ToolExecution, ToolResult, ToolResultPresentation } from './index.ts'
 
 // ---------------------------------------------------------------------------
 // SchemaSpec — the author-facing per-property type
@@ -287,6 +287,22 @@ export interface DefineToolOptions<S extends SchemaSpec> {
    * casts needed.
    */
   execute(args: InferArgs<S>, exec: ToolExecution): Promise<ContentBlock[]>
+  /**
+   * Optional: how to present the PENDING state of one call in a UI (an editor
+   * tool-call card, a CLI log line). `args` is the typed, schema-validated
+   * argument shape — zero casts. Pure and side-effect-free: a UI may call it
+   * during live streaming AND a session-log replay, so depend only on `args`.
+   * The tool owns its presentation so a UI never special-cases tool names. See
+   * {@link ToolCallPresentation}.
+   */
+  presentCall?(args: InferArgs<S>): ToolCallPresentation | undefined
+  /**
+   * Optional: how to present the COMPLETED state, given the typed `args` and the
+   * `result`. Use it to reformat result content for a UI distinctly from the
+   * model-facing text (e.g. a fenced ```console block). Pure and side-effect-
+   * free for the same replay reason. See {@link ToolResultPresentation}.
+   */
+  presentResult?(args: InferArgs<S>, result: ToolResult): ToolResultPresentation | undefined
   /** Whether the tool requires structured output (default false). */
   strict?: boolean
 }
@@ -322,7 +338,11 @@ export function defineTool<S extends SchemaSpec>(options: DefineToolOptions<S>):
   // Object-literal execute methods don't use `this`; the reference is safe.
   // eslint-disable-next-line @typescript-eslint/unbound-method
   const userExecute = options.execute
-  return {
+  // eslint-disable-next-line @typescript-eslint/unbound-method
+  const userPresentCall = options.presentCall
+  // eslint-disable-next-line @typescript-eslint/unbound-method
+  const userPresentResult = options.presentResult
+  const tool: ToolDefinition = {
     name: options.name,
     description: options.description,
     parameters: schemaSpecToJsonSchema(options.parameters) as unknown as Record<string, unknown>,
@@ -337,4 +357,21 @@ export function defineTool<S extends SchemaSpec>(options: DefineToolOptions<S>):
       return userExecute(args as InferArgs<S>, exec)
     },
   }
+  // Presentation is display-only and may run on REPLAY of arbitrary logged args
+  // (possibly from an older schema), so it must never throw: validate softly and
+  // fall back to `undefined` (a generic UI presentation) on any mismatch, rather
+  // than the hard `ToolArgsError` the execute path raises.
+  if (userPresentCall) {
+    tool.presentCall = (args: unknown): ToolCallPresentation | undefined => {
+      if (validateArgs(options.parameters, args).length > 0) return undefined
+      return userPresentCall(args as InferArgs<S>)
+    }
+  }
+  if (userPresentResult) {
+    tool.presentResult = (args: unknown, result: ToolResult): ToolResultPresentation | undefined => {
+      if (validateArgs(options.parameters, args).length > 0) return undefined
+      return userPresentResult(args as InferArgs<S>, result)
+    }
+  }
+  return tool
 }

packages/tools/tests/tools.spec.ts

@@ -814,3 +814,54 @@ describe('defineTool validation (the runtime-validation RFC, part 1)', () => {
     expect(result.isError).toBe(false)
   })
 })
+
+describe('defineTool presentation (presentCall / presentResult)', () => {
+  it('threads presentCall/presentResult onto the ToolDefinition with typed args', () => {
+    const tool = defineTool({
+      name: 'demo',
+      description: 'demo',
+      parameters: { path: { type: 'string', required: true }, n: { type: 'number' } },
+      async execute() { return [{ type: 'text', text: 'ok' }] },
+      presentCall(args) {
+        // args is typed { path: string; n?: number } — zero casts.
+        expectTypeOf(args).toEqualTypeOf<{ path: string; n?: number }>()
+        return { title: `Open ${args.path}`, kind: 'read', rawInput: args.path }
+      },
+      presentResult(args, result) {
+        return { title: `Opened ${args.path}`, content: result.content }
+      },
+    })
+    expect(tool.presentCall!({ path: '/a', n: 2 })).toEqual({ title: 'Open /a', kind: 'read', rawInput: '/a' })
+    expect(tool.presentResult!({ path: '/a' }, { content: [{ type: 'text', text: 'x' }], isError: false }))
+      .toEqual({ title: 'Opened /a', content: [{ type: 'text', text: 'x' }] })
+  })
+
+  it('a tool without presentCall/presentResult leaves them undefined (UI falls back generically)', () => {
+    const tool = defineTool({
+      name: 'plain',
+      description: 'plain',
+      parameters: { x: { type: 'string', required: true } },
+      async execute() { return [] },
+    })
+    expect(typeof tool.presentCall).toBe('undefined')
+    expect(typeof tool.presentResult).toBe('undefined')
+  })
+
+  it('presentCall/presentResult validate softly: malformed args return undefined, never throw (display runs on replay)', () => {
+    const tool = defineTool({
+      name: 'demo',
+      description: 'demo',
+      parameters: { path: { type: 'string', required: true } },
+      async execute() { return [] },
+      presentCall: args => ({ title: args.path }),
+      presentResult: (args, result) => ({ title: args.path, content: result.content }),
+    })
+    // Unlike execute (which throws ToolArgsError on a mismatch), the display
+    // methods soft-validate and fall back to undefined so a UI never crashes
+    // replaying an old/foreign log entry. The ToolDefinition methods take
+    // `unknown`, so malformed shapes pass without a cast.
+    expect(tool.presentCall?.({})).toBeUndefined()
+    expect(tool.presentResult?.({ wrong: 1 }, { content: [], isError: false })).toBeUndefined()
+  })
+})
+