[Bug] 新回合清空按需工具激活，历史 ToolSearch 成功记录仍在上下文 / New prompt drops on-demand activations while ToolSearch history remains

[xingleiwu]

Problem / 问题

On a new user prompt, the runtime clears on-demand tool activations (activeDeferredToolNames.clear()), but the transcript still contains successful ToolSearch results (addedToolNames, “Activated on-demand tools: …”).

The model therefore believes those tools are in the current schema. They are not. The next call fails or the model retries ToolSearch / invents a call.

新用户消息会清空按需激活集，但历史里成功的 ToolSearch 结果还在上下文。模型以为工具可用，实际拿不到。

Stock 0.14.6 (packages/agent-runtime/src/runtime.ts):

private resetDeferredToolsForPrompt(): void {
  this.activeDeferredToolNames.clear();
  this.agent.state.tools = this.activeTools();
}

Called from prompt() and executeApprovedPlan() at the start of every turn.

ToolSearch.execute already writes addedToolNames onto the tool result. Compaction / UI history keep those rows. Nothing reads them back into activeDeferredToolNames.

Repro

1. Agent mode, catalog with deferred tools (Skill, BrowserPreview, plugin tools, …).
2. ToolSearch { query: "Skill" } → “Activated on-demand tools: Skill.”
3. Use Skill successfully.
4. Send a new user message in the same session.
5. First provider request of the new turn: Skill is absent from tools. History still shows the activation. Model calls Skill anyway or ToolSearches again.

Proposed change / 期望改动

On each new prompt (and mode switch), rebuild the active deferred set from the effective context, do not start from empty:

• Walk buildSessionContext messages.
• Only successful toolResult rows (!isError).
• For ToolSearch, use addedToolNames; for a direct deferred-tool result, use toolName.
• Keep a name only if it is still in the current deferred catalog, still in toolCatalog, and allowed in the current mode.
• Ignore UI placeholders such as [no tool result recorded] / interrupted stubs — those are not evidence the tool ever succeeded.

Do not parse assistant/user prose. After restore, set agent.state.tools = activeTools().

Mode switch should restore after rebuild (clear then restore from context is fine; a bare clear is not).

Alternatives / 其他方案

• Make every on-demand tool core: blows request schemas (this is why ToolSearch exists). Related: [Feature] Agent 模式将 Skill 列为核心工具，避免先 ToolSearch / Keep Skill in the Agent core tool set #204 for Skill only.
• Strip ToolSearch rows from history on each prompt: loses the model’s memory of what was activated and still requires a restore path for tools that were used directly.

Additional context / 补充信息

PI-Desktop 0.14.6. packages/agent-runtime resetDeferredToolsForPrompt / buildToolSearchTool / activeTools().

Related: #204 (Skill as core) — even if Skill is core, BrowserPreview / Plugin* / MCP still hit this hole.