diff --git a/src/agents/pi-embedded-block-chunker.ts b/src/agents/pi-embedded-block-chunker.ts
new file mode 100644
index 000000000..798ea4e2d
--- /dev/null
+++ b/src/agents/pi-embedded-block-chunker.ts
@@ -0,0 +1,302 @@
+export type BlockReplyChunking = {
+  minChars: number;
+  maxChars: number;
+  breakPreference?: "paragraph" | "newline" | "sentence";
+};
+
+type FenceSpan = {
+  start: number;
+  end: number;
+  openLine: string;
+  marker: string;
+  indent: string;
+};
+
+type FenceSplit = {
+  closeFenceLine: string;
+  reopenFenceLine: string;
+};
+
+type BreakResult = {
+  index: number;
+  fenceSplit?: FenceSplit;
+};
+
+export class EmbeddedBlockChunker {
+  #buffer = "";
+  readonly #chunking: BlockReplyChunking;
+
+  constructor(chunking: BlockReplyChunking) {
+    this.#chunking = chunking;
+  }
+
+  append(text: string) {
+    if (!text) return;
+    this.#buffer += text;
+  }
+
+  reset() {
+    this.#buffer = "";
+  }
+
+  get bufferedText() {
+    return this.#buffer;
+  }
+
+  hasBuffered(): boolean {
+    return this.#buffer.length > 0;
+  }
+
+  drain(params: { force: boolean; emit: (chunk: string) => void }) {
+    const { force, emit } = params;
+    const minChars = Math.max(1, Math.floor(this.#chunking.minChars));
+    const maxChars = Math.max(minChars, Math.floor(this.#chunking.maxChars));
+    if (this.#buffer.length < minChars && !force) return;
+
+    while (
+      this.#buffer.length >= minChars ||
+      (force && this.#buffer.length > 0)
+    ) {
+      const breakResult =
+        force && this.#buffer.length <= maxChars
+          ? this.#pickSoftBreakIndex(this.#buffer, 1)
+          : this.#pickBreakIndex(this.#buffer);
+      if (breakResult.index <= 0) {
+        if (force) {
+          emit(this.#buffer);
+          this.#buffer = "";
+        }
+        return;
+      }
+
+      const breakIdx = breakResult.index;
+      let rawChunk = this.#buffer.slice(0, breakIdx);
+      if (rawChunk.trim().length === 0) {
+        this.#buffer = stripLeadingNewlines(
+          this.#buffer.slice(breakIdx),
+        ).trimStart();
+        continue;
+      }
+
+      let nextBuffer = this.#buffer.slice(breakIdx);
+      const fenceSplit = breakResult.fenceSplit;
+      if (fenceSplit) {
+        const closeFence = rawChunk.endsWith("\n")
+          ? `${fenceSplit.closeFenceLine}\n`
+          : `\n${fenceSplit.closeFenceLine}\n`;
+        rawChunk = `${rawChunk}${closeFence}`;
+
+        const reopenFence = fenceSplit.reopenFenceLine.endsWith("\n")
+          ? fenceSplit.reopenFenceLine
+          : `${fenceSplit.reopenFenceLine}\n`;
+        nextBuffer = `${reopenFence}${nextBuffer}`;
+      }
+
+      emit(rawChunk);
+
+      if (fenceSplit) {
+        this.#buffer = nextBuffer;
+      } else {
+        const nextStart =
+          breakIdx < this.#buffer.length && /\s/.test(this.#buffer[breakIdx])
+            ? breakIdx + 1
+            : breakIdx;
+        this.#buffer = stripLeadingNewlines(this.#buffer.slice(nextStart));
+      }
+
+      if (this.#buffer.length < minChars && !force) return;
+      if (this.#buffer.length < maxChars && !force) return;
+    }
+  }
+
+  #pickSoftBreakIndex(buffer: string, minCharsOverride?: number): BreakResult {
+    const minChars = Math.max(
+      1,
+      Math.floor(minCharsOverride ?? this.#chunking.minChars),
+    );
+    if (buffer.length < minChars) return { index: -1 };
+    const fenceSpans = parseFenceSpans(buffer);
+    const preference = this.#chunking.breakPreference ?? "paragraph";
+
+    if (preference === "paragraph") {
+      let paragraphIdx = buffer.indexOf("\n\n");
+      while (paragraphIdx !== -1) {
+        if (paragraphIdx >= minChars && isSafeBreak(fenceSpans, paragraphIdx)) {
+          return { index: paragraphIdx };
+        }
+        paragraphIdx = buffer.indexOf("\n\n", paragraphIdx + 2);
+      }
+    }
+
+    if (preference === "paragraph" || preference === "newline") {
+      let newlineIdx = buffer.indexOf("\n");
+      while (newlineIdx !== -1) {
+        if (newlineIdx >= minChars && isSafeBreak(fenceSpans, newlineIdx)) {
+          return { index: newlineIdx };
+        }
+        newlineIdx = buffer.indexOf("\n", newlineIdx + 1);
+      }
+    }
+
+    if (preference !== "newline") {
+      const matches = buffer.matchAll(/[.!?](?=\s|$)/g);
+      let sentenceIdx = -1;
+      for (const match of matches) {
+        const at = match.index ?? -1;
+        if (at < minChars) continue;
+        const candidate = at + 1;
+        if (isSafeBreak(fenceSpans, candidate)) {
+          sentenceIdx = candidate;
+        }
+      }
+      if (sentenceIdx >= minChars) return { index: sentenceIdx };
+    }
+
+    return { index: -1 };
+  }
+
+  #pickBreakIndex(buffer: string): BreakResult {
+    const minChars = Math.max(1, Math.floor(this.#chunking.minChars));
+    const maxChars = Math.max(minChars, Math.floor(this.#chunking.maxChars));
+    if (buffer.length < minChars) return { index: -1 };
+    const window = buffer.slice(0, Math.min(maxChars, buffer.length));
+    const fenceSpans = parseFenceSpans(buffer);
+
+    const preference = this.#chunking.breakPreference ?? "paragraph";
+    if (preference === "paragraph") {
+      let paragraphIdx = window.lastIndexOf("\n\n");
+      while (paragraphIdx >= minChars) {
+        if (isSafeBreak(fenceSpans, paragraphIdx)) {
+          return { index: paragraphIdx };
+        }
+        paragraphIdx = window.lastIndexOf("\n\n", paragraphIdx - 1);
+      }
+    }
+
+    if (preference === "paragraph" || preference === "newline") {
+      let newlineIdx = window.lastIndexOf("\n");
+      while (newlineIdx >= minChars) {
+        if (isSafeBreak(fenceSpans, newlineIdx)) {
+          return { index: newlineIdx };
+        }
+        newlineIdx = window.lastIndexOf("\n", newlineIdx - 1);
+      }
+    }
+
+    if (preference !== "newline") {
+      const matches = window.matchAll(/[.!?](?=\s|$)/g);
+      let sentenceIdx = -1;
+      for (const match of matches) {
+        const at = match.index ?? -1;
+        if (at < minChars) continue;
+        const candidate = at + 1;
+        if (isSafeBreak(fenceSpans, candidate)) {
+          sentenceIdx = candidate;
+        }
+      }
+      if (sentenceIdx >= minChars) return { index: sentenceIdx };
+    }
+
+    for (let i = window.length - 1; i >= minChars; i--) {
+      if (/\s/.test(window[i]) && isSafeBreak(fenceSpans, i)) {
+        return { index: i };
+      }
+    }
+
+    if (buffer.length >= maxChars) {
+      if (isSafeBreak(fenceSpans, maxChars)) return { index: maxChars };
+      const fence = findFenceSpanAt(fenceSpans, maxChars);
+      if (fence) {
+        return {
+          index: maxChars,
+          fenceSplit: {
+            closeFenceLine: `${fence.indent}${fence.marker}`,
+            reopenFenceLine: fence.openLine,
+          },
+        };
+      }
+      return { index: maxChars };
+    }
+
+    return { index: -1 };
+  }
+}
+
+function stripLeadingNewlines(value: string): string {
+  let i = 0;
+  while (i < value.length && value[i] === "\n") i++;
+  return i > 0 ? value.slice(i) : value;
+}
+
+function parseFenceSpans(buffer: string): FenceSpan[] {
+  const spans: FenceSpan[] = [];
+  let open:
+    | {
+        start: number;
+        markerChar: string;
+        markerLen: number;
+        openLine: string;
+        marker: string;
+        indent: string;
+      }
+    | undefined;
+  let offset = 0;
+  while (offset <= buffer.length) {
+    const nextNewline = buffer.indexOf("\n", offset);
+    const lineEnd = nextNewline === -1 ? buffer.length : nextNewline;
+    const line = buffer.slice(offset, lineEnd);
+    const match = line.match(/^( {0,3})(`{3,}|~{3,})(.*)$/);
+    if (match) {
+      const indent = match[1];
+      const marker = match[2];
+      const markerChar = marker[0];
+      const markerLen = marker.length;
+      if (!open) {
+        open = {
+          start: offset,
+          markerChar,
+          markerLen,
+          openLine: line,
+          marker,
+          indent,
+        };
+      } else if (
+        open.markerChar === markerChar &&
+        markerLen >= open.markerLen
+      ) {
+        const end = nextNewline === -1 ? buffer.length : nextNewline + 1;
+        spans.push({
+          start: open.start,
+          end,
+          openLine: open.openLine,
+          marker: open.marker,
+          indent: open.indent,
+        });
+        open = undefined;
+      }
+    }
+    if (nextNewline === -1) break;
+    offset = nextNewline + 1;
+  }
+  if (open) {
+    spans.push({
+      start: open.start,
+      end: buffer.length,
+      openLine: open.openLine,
+      marker: open.marker,
+      indent: open.indent,
+    });
+  }
+  return spans;
+}
+
+function findFenceSpanAt(
+  spans: FenceSpan[],
+  index: number,
+): FenceSpan | undefined {
+  return spans.find((span) => index > span.start && index < span.end);
+}
+
+function isSafeBreak(spans: FenceSpan[], index: number): boolean {
+  return !findFenceSpanAt(spans, index);
+}
diff --git a/src/agents/pi-embedded-runner.ts b/src/agents/pi-embedded-runner.ts
index db5659e24..18c29d6e7 100644
--- a/src/agents/pi-embedded-runner.ts
+++ b/src/agents/pi-embedded-runner.ts
@@ -1,12 +1,7 @@
 import fs from "node:fs/promises";
 import os from "node:os";
 
-import type {
-  AgentMessage,
-  AgentToolResult,
-  AgentToolUpdateCallback,
-  ThinkingLevel,
-} from "@mariozechner/pi-agent-core";
+import type { AgentMessage, ThinkingLevel } from "@mariozechner/pi-agent-core";
 import type { Api, AssistantMessage, Model } from "@mariozechner/pi-ai";
 import {
   buildSystemPrompt,
@@ -16,7 +11,6 @@ import {
   SessionManager,
   SettingsManager,
   type Skill,
-  type ToolDefinition,
 } from "@mariozechner/pi-coding-agent";
 import type { ThinkLevel, VerboseLevel } from "../auto-reply/thinking.js";
 import { formatToolAggregate } from "../auto-reply/tool-meta.js";
@@ -45,6 +39,7 @@ import {
   subscribeEmbeddedPiSession,
 } from "./pi-embedded-subscribe.js";
 import { extractAssistantText } from "./pi-embedded-utils.js";
+import { toToolDefinitions } from "./pi-tool-definition-adapter.js";
 import { createClawdbotCodingTools } from "./pi-tools.js";
 import { resolveSandboxContext } from "./sandbox.js";
 import {
@@ -58,35 +53,6 @@ import {
 import { buildAgentSystemPromptAppend } from "./system-prompt.js";
 import { loadWorkspaceBootstrapFiles } from "./workspace.js";
 
-function toToolDefinitions(tools: { execute: unknown }[]): ToolDefinition[] {
-  return tools.map((tool) => {
-    const record = tool as {
-      name?: unknown;
-      label?: unknown;
-      description?: unknown;
-      parameters?: unknown;
-      execute: (
-        toolCallId: string,
-        params: unknown,
-        signal?: AbortSignal,
-        onUpdate?: AgentToolUpdateCallback<unknown>,
-      ) => Promise<AgentToolResult<unknown>>;
-    };
-    const name = typeof record.name === "string" ? record.name : "tool";
-    return {
-      name,
-      label: typeof record.label === "string" ? record.label : name,
-      description:
-        typeof record.description === "string" ? record.description : "",
-      // biome-ignore lint/suspicious/noExplicitAny: TypeBox schema from pi-agent-core uses a different module instance.
-      parameters: record.parameters as any,
-      execute: async (toolCallId, params, onUpdate, _ctx, signal) => {
-        return await record.execute(toolCallId, params, signal, onUpdate);
-      },
-    } satisfies ToolDefinition;
-  });
-}
-
 export type EmbeddedPiAgentMeta = {
   sessionId: string;
   provider: string;
diff --git a/src/agents/pi-embedded-subscribe.ts b/src/agents/pi-embedded-subscribe.ts
index d5204c92a..dd851e90d 100644
--- a/src/agents/pi-embedded-subscribe.ts
+++ b/src/agents/pi-embedded-subscribe.ts
@@ -6,6 +6,8 @@ import { formatToolAggregate } from "../auto-reply/tool-meta.js";
 import { emitAgentEvent } from "../infra/agent-events.js";
 import { createSubsystemLogger } from "../logging.js";
 import { splitMediaFromOutput } from "../media/parse.js";
+import type { BlockReplyChunking } from "./pi-embedded-block-chunker.js";
+import { EmbeddedBlockChunker } from "./pi-embedded-block-chunker.js";
 import {
   extractAssistantText,
   inferToolMetaFromArgs,
@@ -17,11 +19,7 @@ const THINKING_CLOSE_RE = /<\s*\/\s*think(?:ing)?\s*>/i;
 const TOOL_RESULT_MAX_CHARS = 8000;
 const log = createSubsystemLogger("agent/embedded");
 
-export type BlockReplyChunking = {
-  minChars: number;
-  maxChars: number;
-  breakPreference?: "paragraph" | "newline" | "sentence";
-};
+export type { BlockReplyChunking } from "./pi-embedded-block-chunker.js";
 
 function truncateToolText(text: string): string {
   if (text.length <= TOOL_RESULT_MAX_CHARS) return text;
@@ -176,6 +174,9 @@ export function subscribeEmbeddedPiSession(params: {
   };
 
   const blockChunking = params.blockReplyChunking;
+  const blockChunker = blockChunking
+    ? new EmbeddedBlockChunker(blockChunking)
+    : null;
   const shouldEmitToolResult = () =>
     typeof params.shouldEmitToolResult === "function"
       ? params.shouldEmitToolResult()
@@ -195,217 +196,6 @@ export function subscribeEmbeddedPiSession(params: {
     }
   };
 
-  type FenceSpan = {
-    start: number;
-    end: number;
-    openLine: string;
-    marker: string;
-    indent: string;
-  };
-
-  type FenceSplit = {
-    closeFenceLine: string;
-    reopenFenceLine: string;
-  };
-
-  type BreakResult = {
-    index: number;
-    fenceSplit?: FenceSplit;
-  };
-
-  const parseFenceSpans = (buffer: string): FenceSpan[] => {
-    const spans: FenceSpan[] = [];
-    let open:
-      | {
-          start: number;
-          markerChar: string;
-          markerLen: number;
-          openLine: string;
-          marker: string;
-          indent: string;
-        }
-      | undefined;
-    let offset = 0;
-    while (offset <= buffer.length) {
-      const nextNewline = buffer.indexOf("\n", offset);
-      const lineEnd = nextNewline === -1 ? buffer.length : nextNewline;
-      const line = buffer.slice(offset, lineEnd);
-      const match = line.match(/^( {0,3})(`{3,}|~{3,})(.*)$/);
-      if (match) {
-        const indent = match[1];
-        const marker = match[2];
-        const markerChar = marker[0];
-        const markerLen = marker.length;
-        if (!open) {
-          open = {
-            start: offset,
-            markerChar,
-            markerLen,
-            openLine: line,
-            marker,
-            indent,
-          };
-        } else if (
-          open.markerChar === markerChar &&
-          markerLen >= open.markerLen
-        ) {
-          const end = nextNewline === -1 ? buffer.length : nextNewline + 1;
-          spans.push({
-            start: open.start,
-            end,
-            openLine: open.openLine,
-            marker: open.marker,
-            indent: open.indent,
-          });
-          open = undefined;
-        }
-      }
-      if (nextNewline === -1) break;
-      offset = nextNewline + 1;
-    }
-    if (open) {
-      spans.push({
-        start: open.start,
-        end: buffer.length,
-        openLine: open.openLine,
-        marker: open.marker,
-        indent: open.indent,
-      });
-    }
-    return spans;
-  };
-
-  const findFenceSpanAt = (
-    spans: FenceSpan[],
-    index: number,
-  ): FenceSpan | undefined =>
-    spans.find((span) => index > span.start && index < span.end);
-
-  const isSafeBreak = (spans: FenceSpan[], index: number): boolean =>
-    !findFenceSpanAt(spans, index);
-
-  const stripLeadingNewlines = (value: string): string => {
-    let i = 0;
-    while (i < value.length && value[i] === "\n") i++;
-    return i > 0 ? value.slice(i) : value;
-  };
-
-  const pickSoftBreakIndex = (
-    buffer: string,
-    minCharsOverride?: number,
-  ): BreakResult => {
-    if (!blockChunking) return { index: -1 };
-    const minChars = Math.max(
-      1,
-      Math.floor(minCharsOverride ?? blockChunking.minChars),
-    );
-    if (buffer.length < minChars) return { index: -1 };
-    const fenceSpans = parseFenceSpans(buffer);
-    const preference = blockChunking.breakPreference ?? "paragraph";
-
-    if (preference === "paragraph") {
-      let paragraphIdx = buffer.indexOf("\n\n");
-      while (paragraphIdx !== -1) {
-        if (paragraphIdx >= minChars && isSafeBreak(fenceSpans, paragraphIdx)) {
-          return { index: paragraphIdx };
-        }
-        paragraphIdx = buffer.indexOf("\n\n", paragraphIdx + 2);
-      }
-    }
-
-    if (preference === "paragraph" || preference === "newline") {
-      let newlineIdx = buffer.indexOf("\n");
-      while (newlineIdx !== -1) {
-        if (newlineIdx >= minChars && isSafeBreak(fenceSpans, newlineIdx)) {
-          return { index: newlineIdx };
-        }
-        newlineIdx = buffer.indexOf("\n", newlineIdx + 1);
-      }
-    }
-
-    if (preference !== "newline") {
-      const matches = buffer.matchAll(/[.!?](?=\s|$)/g);
-      let sentenceIdx = -1;
-      for (const match of matches) {
-        const at = match.index ?? -1;
-        if (at < minChars) continue;
-        const candidate = at + 1;
-        if (isSafeBreak(fenceSpans, candidate)) {
-          sentenceIdx = candidate;
-        }
-      }
-      if (sentenceIdx >= minChars) return { index: sentenceIdx };
-    }
-
-    return { index: -1 };
-  };
-
-  const pickBreakIndex = (buffer: string): BreakResult => {
-    if (!blockChunking) return { index: -1 };
-    const minChars = Math.max(1, Math.floor(blockChunking.minChars));
-    const maxChars = Math.max(minChars, Math.floor(blockChunking.maxChars));
-    if (buffer.length < minChars) return { index: -1 };
-    const window = buffer.slice(0, Math.min(maxChars, buffer.length));
-    const fenceSpans = parseFenceSpans(buffer);
-
-    const preference = blockChunking.breakPreference ?? "paragraph";
-    if (preference === "paragraph") {
-      let paragraphIdx = window.lastIndexOf("\n\n");
-      while (paragraphIdx >= minChars) {
-        if (isSafeBreak(fenceSpans, paragraphIdx)) {
-          return { index: paragraphIdx };
-        }
-        paragraphIdx = window.lastIndexOf("\n\n", paragraphIdx - 1);
-      }
-    }
-
-    if (preference === "paragraph" || preference === "newline") {
-      let newlineIdx = window.lastIndexOf("\n");
-      while (newlineIdx >= minChars) {
-        if (isSafeBreak(fenceSpans, newlineIdx)) {
-          return { index: newlineIdx };
-        }
-        newlineIdx = window.lastIndexOf("\n", newlineIdx - 1);
-      }
-    }
-
-    if (preference !== "newline") {
-      const matches = window.matchAll(/[.!?](?=\s|$)/g);
-      let sentenceIdx = -1;
-      for (const match of matches) {
-        const at = match.index ?? -1;
-        if (at < minChars) continue;
-        const candidate = at + 1;
-        if (isSafeBreak(fenceSpans, candidate)) {
-          sentenceIdx = candidate;
-        }
-      }
-      if (sentenceIdx >= minChars) return { index: sentenceIdx };
-    }
-
-    for (let i = window.length - 1; i >= minChars; i--) {
-      if (/\s/.test(window[i]) && isSafeBreak(fenceSpans, i)) {
-        return { index: i };
-      }
-    }
-
-    if (buffer.length >= maxChars) {
-      if (isSafeBreak(fenceSpans, maxChars)) return { index: maxChars };
-      const fence = findFenceSpanAt(fenceSpans, maxChars);
-      if (fence) {
-        return {
-          index: maxChars,
-          fenceSplit: {
-            closeFenceLine: `${fence.indent}${fence.marker}`,
-            reopenFenceLine: fence.openLine,
-          },
-        };
-      }
-      return { index: maxChars };
-    }
-    return { index: -1 };
-  };
-
   const emitBlockChunk = (text: string) => {
     // Strip any <thinking> tags that may have leaked into the output (e.g., from Gemini mimicking history)
     const strippedText = stripThinkingSegments(stripUnpairedThinkingTags(text));
@@ -423,61 +213,6 @@ export function subscribeEmbeddedPiSession(params: {
     });
   };
 
-  const drainBlockBuffer = (force: boolean) => {
-    if (!blockChunking) return;
-    const minChars = Math.max(1, Math.floor(blockChunking.minChars));
-    const maxChars = Math.max(minChars, Math.floor(blockChunking.maxChars));
-    if (blockBuffer.length < minChars && !force) return;
-    while (
-      blockBuffer.length >= minChars ||
-      (force && blockBuffer.length > 0)
-    ) {
-      const breakResult =
-        force && blockBuffer.length <= maxChars
-          ? pickSoftBreakIndex(blockBuffer, 1)
-          : pickBreakIndex(blockBuffer);
-      if (breakResult.index <= 0) {
-        if (force) {
-          emitBlockChunk(blockBuffer);
-          blockBuffer = "";
-        }
-        return;
-      }
-      const breakIdx = breakResult.index;
-      let rawChunk = blockBuffer.slice(0, breakIdx);
-      if (rawChunk.trim().length === 0) {
-        blockBuffer = stripLeadingNewlines(
-          blockBuffer.slice(breakIdx),
-        ).trimStart();
-        continue;
-      }
-      let nextBuffer = blockBuffer.slice(breakIdx);
-      const fenceSplit = breakResult.fenceSplit;
-      if (fenceSplit) {
-        const closeFence = rawChunk.endsWith("\n")
-          ? `${fenceSplit.closeFenceLine}\n`
-          : `\n${fenceSplit.closeFenceLine}\n`;
-        rawChunk = `${rawChunk}${closeFence}`;
-        const reopenFence = fenceSplit.reopenFenceLine.endsWith("\n")
-          ? fenceSplit.reopenFenceLine
-          : `${fenceSplit.reopenFenceLine}\n`;
-        nextBuffer = `${reopenFence}${nextBuffer}`;
-      }
-      emitBlockChunk(rawChunk);
-      if (fenceSplit) {
-        blockBuffer = nextBuffer;
-      } else {
-        const nextStart =
-          breakIdx < blockBuffer.length && /\s/.test(blockBuffer[breakIdx])
-            ? breakIdx + 1
-            : breakIdx;
-        blockBuffer = stripLeadingNewlines(blockBuffer.slice(nextStart));
-      }
-      if (blockBuffer.length < minChars && !force) return;
-      if (blockBuffer.length < maxChars && !force) return;
-    }
-  };
-
   const resetForCompactionRetry = () => {
     assistantTexts.length = 0;
     toolMetas.length = 0;
@@ -485,6 +220,7 @@ export function subscribeEmbeddedPiSession(params: {
     toolSummaryById.clear();
     deltaBuffer = "";
     blockBuffer = "";
+    blockChunker?.reset();
     lastStreamedAssistant = undefined;
     lastBlockReplyText = undefined;
     assistantTextBaseline = 0;
@@ -500,6 +236,7 @@ export function subscribeEmbeddedPiSession(params: {
           // otherwise re-trigger block replies.
           deltaBuffer = "";
           blockBuffer = "";
+          blockChunker?.reset();
           lastStreamedAssistant = undefined;
           lastBlockReplyText = undefined;
           assistantTextBaseline = assistantTexts.length;
@@ -662,7 +399,11 @@ export function subscribeEmbeddedPiSession(params: {
             }
             if (chunk) {
               deltaBuffer += chunk;
-              blockBuffer += chunk;
+              if (blockChunker) {
+                blockChunker.append(chunk);
+              } else {
+                blockBuffer += chunk;
+              }
             }
 
             const cleaned = params.enforceFinalTag
@@ -703,16 +444,17 @@ export function subscribeEmbeddedPiSession(params: {
               blockChunking &&
               blockReplyBreak === "text_end"
             ) {
-              drainBlockBuffer(false);
+              blockChunker?.drain({ force: false, emit: emitBlockChunk });
             }
 
             if (evtType === "text_end" && blockReplyBreak === "text_end") {
-              if (blockChunking && blockBuffer.length > 0) {
-                drainBlockBuffer(true);
+              if (blockChunker?.hasBuffered()) {
+                blockChunker.drain({ force: true, emit: emitBlockChunk });
+                blockChunker.reset();
               } else if (blockBuffer.length > 0) {
                 emitBlockChunk(blockBuffer);
+                blockBuffer = "";
               }
-              blockBuffer = "";
             }
           }
         }
@@ -745,12 +487,16 @@ export function subscribeEmbeddedPiSession(params: {
           assistantTextBaseline = assistantTexts.length;
 
           if (
-            (blockReplyBreak === "message_end" || blockBuffer.length > 0) &&
+            (blockReplyBreak === "message_end" ||
+              (blockChunker
+                ? blockChunker.hasBuffered()
+                : blockBuffer.length > 0)) &&
             text &&
             params.onBlockReply
           ) {
-            if (blockChunking && blockBuffer.length > 0) {
-              drainBlockBuffer(true);
+            if (blockChunker?.hasBuffered()) {
+              blockChunker.drain({ force: true, emit: emitBlockChunk });
+              blockChunker.reset();
             } else if (text !== lastBlockReplyText) {
               lastBlockReplyText = text;
               const { text: cleanedText, mediaUrls } =
@@ -765,6 +511,7 @@ export function subscribeEmbeddedPiSession(params: {
           }
           deltaBuffer = "";
           blockBuffer = "";
+          blockChunker?.reset();
           lastStreamedAssistant = undefined;
         }
       }
diff --git a/src/agents/pi-tool-definition-adapter.ts b/src/agents/pi-tool-definition-adapter.ts
new file mode 100644
index 000000000..48b33730a
--- /dev/null
+++ b/src/agents/pi-tool-definition-adapter.ts
@@ -0,0 +1,31 @@
+import type {
+  AgentTool,
+  AgentToolResult,
+  AgentToolUpdateCallback,
+} from "@mariozechner/pi-agent-core";
+import type { ToolDefinition } from "@mariozechner/pi-coding-agent";
+
+// biome-ignore lint/suspicious/noExplicitAny: TypeBox schema type from pi-agent-core uses a different module instance.
+type AnyAgentTool = AgentTool<any, unknown>;
+
+export function toToolDefinitions(tools: AnyAgentTool[]): ToolDefinition[] {
+  return tools.map((tool) => {
+    const name = tool.name || "tool";
+    return {
+      name,
+      label: tool.label ?? name,
+      description: tool.description ?? "",
+      // biome-ignore lint/suspicious/noExplicitAny: TypeBox schema from pi-agent-core uses a different module instance.
+      parameters: tool.parameters as any,
+      execute: async (
+        toolCallId,
+        params,
+        onUpdate: AgentToolUpdateCallback<unknown> | undefined,
+        _ctx,
+        signal,
+      ): Promise<AgentToolResult<unknown>> => {
+        return tool.execute(toolCallId, params, signal, onUpdate);
+      },
+    } satisfies ToolDefinition;
+  });
+}