diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9ea3fea46..9be72e8d7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Changes
 - Models/Moonshot: add Kimi K2 0905 + turbo/thinking variants to the preset + docs. (#818 — thanks @mickahouan)
 - Memory: allow custom OpenAI-compatible embedding endpoints for memory search (remote baseUrl/apiKey/headers). (#819 — thanks @mukhtharcm)
+- Agents: make workspace bootstrap truncation configurable (default 20k) and warn when files are truncated.
 
 ### Fixes
 - Typing: keep typing indicators alive during tool execution. (#450, #447 — thanks @thewilloftheshadow)
diff --git a/docs/concepts/agent-workspace.md b/docs/concepts/agent-workspace.md
index d5f8e36ea..789097bc5 100644
--- a/docs/concepts/agent-workspace.md
+++ b/docs/concepts/agent-workspace.md
@@ -109,8 +109,10 @@ See [Memory](/concepts/memory) for the workflow and automatic memory flush.
   - Canvas UI files for node displays (for example `canvas/index.html`).
 
 If any bootstrap file is missing, Clawdbot injects a "missing file" marker into
-the session and continues. `clawdbot setup` can recreate missing defaults
-without overwriting existing files.
+the session and continues. Large bootstrap files are truncated when injected;
+adjust the limit with `agents.defaults.bootstrapMaxChars` (default: 20000).
+`clawdbot setup` can recreate missing defaults without overwriting existing
+files.
 
 ## What is NOT in the workspace
 
diff --git a/docs/concepts/system-prompt.md b/docs/concepts/system-prompt.md
index a81b1583b..75de873c1 100644
--- a/docs/concepts/system-prompt.md
+++ b/docs/concepts/system-prompt.md
@@ -38,7 +38,9 @@ Bootstrap files are trimmed and appended under **Project Context** so the model
 - `HEARTBEAT.md`
 - `BOOTSTRAP.md` (only on brand-new workspaces)
 
-Large files are truncated with a marker. Missing files inject a short missing-file marker.
+Large files are truncated with a marker. The max per-file size is controlled by
+`agents.defaults.bootstrapMaxChars` (default: 20000). Missing files inject a
+short missing-file marker.
 
 ## Time handling
 
diff --git a/docs/gateway/configuration.md b/docs/gateway/configuration.md
index 85a018c2b..2582a737d 100644
--- a/docs/gateway/configuration.md
+++ b/docs/gateway/configuration.md
@@ -1075,6 +1075,20 @@ Use this for pre-seeded deployments where your workspace files come from a repo.
 }
 ```
 
+### `agents.defaults.bootstrapMaxChars`
+
+Max characters of each workspace bootstrap file injected into the system prompt
+before truncation. Default: `20000`.
+
+When a file exceeds this limit, Clawdbot logs a warning and injects a truncated
+head/tail with a marker.
+
+```json5
+{
+  agents: { defaults: { bootstrapMaxChars: 20000 } }
+}
+```
+
 ### `agents.defaults.userTimezone`
 
 Sets the user’s timezone for **system prompt context** (not for timestamps in
diff --git a/docs/token-use.md b/docs/token-use.md
index d628b1fb6..c75108964 100644
--- a/docs/token-use.md
+++ b/docs/token-use.md
@@ -16,7 +16,7 @@ Clawdbot assembles its own system prompt on every run. It includes:
 - Tool list + short descriptions
 - Skills list (only metadata; instructions are loaded on demand with `read`)
 - Self-update instructions
-- Workspace + bootstrap files (`AGENTS.md`, `SOUL.md`, `TOOLS.md`, `IDENTITY.md`, `USER.md`, `HEARTBEAT.md`, `BOOTSTRAP.md` when new)
+- Workspace + bootstrap files (`AGENTS.md`, `SOUL.md`, `TOOLS.md`, `IDENTITY.md`, `USER.md`, `HEARTBEAT.md`, `BOOTSTRAP.md` when new). Large files are truncated by `agents.defaults.bootstrapMaxChars` (default: 20000).
 - Time (UTC + user timezone)
 - Reply tags + heartbeat behavior
 - Runtime metadata (host/OS/model/thinking)
diff --git a/src/agents/cli-runner.ts b/src/agents/cli-runner.ts
index 9bc7e2528..0706bbeb7 100644
--- a/src/agents/cli-runner.ts
+++ b/src/agents/cli-runner.ts
@@ -21,6 +21,7 @@ import {
   classifyFailoverReason,
   type EmbeddedContextFile,
   isFailoverErrorMessage,
+  resolveBootstrapMaxChars,
 } from "./pi-embedded-helpers.js";
 import type { EmbeddedPiRunResult } from "./pi-embedded-runner.js";
 import { buildAgentSystemPrompt } from "./system-prompt.js";
@@ -493,7 +494,11 @@ export async function runCliAgent(params: {
     await loadWorkspaceBootstrapFiles(workspaceDir),
     params.sessionKey ?? params.sessionId,
   );
-  const contextFiles = buildBootstrapContextFiles(bootstrapFiles);
+  const sessionLabel = params.sessionKey ?? params.sessionId;
+  const contextFiles = buildBootstrapContextFiles(bootstrapFiles, {
+    maxChars: resolveBootstrapMaxChars(params.config),
+    warn: (message) => log.warn(`${message} (sessionKey=${sessionLabel})`),
+  });
   const { defaultAgentId, sessionAgentId } = resolveSessionAgentIds({
     sessionKey: params.sessionKey,
     config: params.config,
diff --git a/src/agents/pi-embedded-helpers.test.ts b/src/agents/pi-embedded-helpers.test.ts
index dcb19ed83..74d898c98 100644
--- a/src/agents/pi-embedded-helpers.test.ts
+++ b/src/agents/pi-embedded-helpers.test.ts
@@ -1,9 +1,11 @@
 import type { AgentMessage } from "@mariozechner/pi-agent-core";
 import type { AssistantMessage } from "@mariozechner/pi-ai";
 import { describe, expect, it } from "vitest";
+import type { ClawdbotConfig } from "../config/config.js";
 import {
   buildBootstrapContextFiles,
   classifyFailoverReason,
+  DEFAULT_BOOTSTRAP_MAX_CHARS,
   formatAssistantErrorText,
   isAuthErrorMessage,
   isBillingErrorMessage,
@@ -13,6 +15,7 @@ import {
   isMessagingToolDuplicate,
   isFailoverErrorMessage,
   normalizeTextForComparison,
+  resolveBootstrapMaxChars,
   sanitizeGoogleTurnOrdering,
   sanitizeSessionMessagesImages,
   sanitizeToolCallId,
@@ -49,17 +52,58 @@ describe("buildBootstrapContextFiles", () => {
   });
 
   it("truncates large bootstrap content", () => {
-    const head = `HEAD-${"a".repeat(6000)}`;
-    const tail = `${"b".repeat(3000)}-TAIL`;
+    const head = `HEAD-${"a".repeat(600)}`;
+    const tail = `${"b".repeat(300)}-TAIL`;
     const long = `${head}${tail}`;
-    const files = [makeFile({ content: long })];
-    const [result] = buildBootstrapContextFiles(files);
+    const files = [makeFile({ name: "TOOLS.md", content: long })];
+    const warnings: string[] = [];
+    const maxChars = 200;
+    const expectedTailChars = Math.floor(maxChars * 0.2);
+    const [result] = buildBootstrapContextFiles(files, {
+      maxChars,
+      warn: (message) => warnings.push(message),
+    });
     expect(result?.content).toContain(
-      "[...truncated, read AGENTS.md for full content...]",
+      "[...truncated, read TOOLS.md for full content...]",
     );
     expect(result?.content.length).toBeLessThan(long.length);
     expect(result?.content.startsWith(long.slice(0, 120))).toBe(true);
-    expect(result?.content.endsWith(long.slice(-120))).toBe(true);
+    expect(result?.content.endsWith(long.slice(-expectedTailChars))).toBe(
+      true,
+    );
+    expect(warnings).toHaveLength(1);
+    expect(warnings[0]).toContain("TOOLS.md");
+    expect(warnings[0]).toContain("limit 200");
+  });
+
+  it("keeps content under the default limit", () => {
+    const long = "a".repeat(DEFAULT_BOOTSTRAP_MAX_CHARS - 10);
+    const files = [makeFile({ content: long })];
+    const [result] = buildBootstrapContextFiles(files);
+    expect(result?.content).toBe(long);
+    expect(result?.content).not.toContain(
+      "[...truncated, read AGENTS.md for full content...]",
+    );
+  });
+});
+
+describe("resolveBootstrapMaxChars", () => {
+  it("returns default when unset", () => {
+    expect(resolveBootstrapMaxChars()).toBe(DEFAULT_BOOTSTRAP_MAX_CHARS);
+  });
+
+  it("uses configured value when valid", () => {
+    const cfg = {
+      agents: { defaults: { bootstrapMaxChars: 12345 } },
+    } as ClawdbotConfig;
+    expect(resolveBootstrapMaxChars(cfg)).toBe(12345);
+  });
+
+  it("falls back when invalid", () => {
+    const cfg = {
+      agents: { defaults: { bootstrapMaxChars: -1 } },
+    } as ClawdbotConfig;
+    expect(resolveBootstrapMaxChars(cfg)).toBe(DEFAULT_BOOTSTRAP_MAX_CHARS);
   });
 });
 
diff --git a/src/agents/pi-embedded-helpers.ts b/src/agents/pi-embedded-helpers.ts
index 88e1b1447..02a05d4a5 100644
--- a/src/agents/pi-embedded-helpers.ts
+++ b/src/agents/pi-embedded-helpers.ts
@@ -53,23 +53,57 @@ export function stripThoughtSignatures<T>(content: T): T {
   }) as T;
 }
 
-const MAX_BOOTSTRAP_CHARS = 4000;
-const BOOTSTRAP_HEAD_CHARS = 2800;
-const BOOTSTRAP_TAIL_CHARS = 800;
+export const DEFAULT_BOOTSTRAP_MAX_CHARS = 20_000;
+const BOOTSTRAP_HEAD_RATIO = 0.7;
+const BOOTSTRAP_TAIL_RATIO = 0.2;
 
-function trimBootstrapContent(content: string, fileName: string): string {
+type TrimBootstrapResult = {
+  content: string;
+  truncated: boolean;
+  maxChars: number;
+  originalLength: number;
+};
+
+export function resolveBootstrapMaxChars(cfg?: ClawdbotConfig): number {
+  const raw = cfg?.agents?.defaults?.bootstrapMaxChars;
+  if (typeof raw === "number" && Number.isFinite(raw) && raw > 0) {
+    return Math.floor(raw);
+  }
+  return DEFAULT_BOOTSTRAP_MAX_CHARS;
+}
+
+function trimBootstrapContent(
+  content: string,
+  fileName: string,
+  maxChars: number,
+): TrimBootstrapResult {
   const trimmed = content.trimEnd();
-  if (trimmed.length <= MAX_BOOTSTRAP_CHARS) return trimmed;
+  if (trimmed.length <= maxChars) {
+    return {
+      content: trimmed,
+      truncated: false,
+      maxChars,
+      originalLength: trimmed.length,
+    };
+  }
 
-  const head = trimmed.slice(0, BOOTSTRAP_HEAD_CHARS);
-  const tail = trimmed.slice(-BOOTSTRAP_TAIL_CHARS);
-  return [
+  const headChars = Math.max(1, Math.floor(maxChars * BOOTSTRAP_HEAD_RATIO));
+  const tailChars = Math.max(1, Math.floor(maxChars * BOOTSTRAP_TAIL_RATIO));
+  const head = trimmed.slice(0, headChars);
+  const tail = trimmed.slice(-tailChars);
+  const contentWithMarker = [
     head,
     "",
     `[...truncated, read ${fileName} for full content...]`,
     "",
     tail,
   ].join("\n");
+  return {
+    content: contentWithMarker,
+    truncated: true,
+    maxChars,
+    originalLength: trimmed.length,
+  };
 }
 
 export async function ensureSessionHeader(params: {
@@ -254,7 +288,9 @@ export function sanitizeGoogleTurnOrdering(
 
 export function buildBootstrapContextFiles(
   files: WorkspaceBootstrapFile[],
+  opts?: { warn?: (message: string) => void; maxChars?: number },
 ): EmbeddedContextFile[] {
+  const maxChars = opts?.maxChars ?? DEFAULT_BOOTSTRAP_MAX_CHARS;
   const result: EmbeddedContextFile[] = [];
   for (const file of files) {
     if (file.missing) {
@@ -264,11 +300,20 @@ export function buildBootstrapContextFiles(
       });
       continue;
     }
-    const trimmed = trimBootstrapContent(file.content ?? "", file.name);
-    if (!trimmed) continue;
+    const trimmed = trimBootstrapContent(
+      file.content ?? "",
+      file.name,
+      maxChars,
+    );
+    if (!trimmed.content) continue;
+    if (trimmed.truncated) {
+      opts?.warn?.(
+        `workspace bootstrap file ${file.name} is ${trimmed.originalLength} chars (limit ${trimmed.maxChars}); truncating in injected context`,
+      );
+    }
     result.push({
       path: file.name,
-      content: trimmed,
+      content: trimmed.content,
     });
   }
   return result;
diff --git a/src/agents/pi-embedded-runner.ts b/src/agents/pi-embedded-runner.ts
index 51f711e74..521d22212 100644
--- a/src/agents/pi-embedded-runner.ts
+++ b/src/agents/pi-embedded-runner.ts
@@ -99,6 +99,7 @@ import {
   isRateLimitAssistantError,
   isTimeoutErrorMessage,
   pickFallbackThinkingLevel,
+  resolveBootstrapMaxChars,
   sanitizeGoogleTurnOrdering,
   sanitizeSessionMessagesImages,
   validateAnthropicTurns,
@@ -1152,7 +1153,12 @@ export async function compactEmbeddedPiSession(params: {
           await loadWorkspaceBootstrapFiles(effectiveWorkspace),
           params.sessionKey ?? params.sessionId,
         );
-        const contextFiles = buildBootstrapContextFiles(bootstrapFiles);
+        const sessionLabel = params.sessionKey ?? params.sessionId;
+        const contextFiles = buildBootstrapContextFiles(bootstrapFiles, {
+          maxChars: resolveBootstrapMaxChars(params.config),
+          warn: (message) =>
+            log.warn(`${message} (sessionKey=${sessionLabel})`),
+        });
         const runAbortController = new AbortController();
         const tools = createClawdbotCodingTools({
           exec: {
@@ -1584,7 +1590,12 @@ export async function runEmbeddedPiAgent(params: {
             await loadWorkspaceBootstrapFiles(effectiveWorkspace),
             params.sessionKey ?? params.sessionId,
           );
-          const contextFiles = buildBootstrapContextFiles(bootstrapFiles);
+          const sessionLabel = params.sessionKey ?? params.sessionId;
+          const contextFiles = buildBootstrapContextFiles(bootstrapFiles, {
+            maxChars: resolveBootstrapMaxChars(params.config),
+            warn: (message) =>
+              log.warn(`${message} (sessionKey=${sessionLabel})`),
+          });
           // Tool schemas must be provider-compatible (OpenAI requires top-level `type: "object"`).
           // `createClawdbotCodingTools()` normalizes schemas so the session can pass them through unchanged.
           const tools = createClawdbotCodingTools({
diff --git a/src/config/schema.ts b/src/config/schema.ts
index 738420b2d..b213b0ea2 100644
--- a/src/config/schema.ts
+++ b/src/config/schema.ts
@@ -115,6 +115,7 @@ const FIELD_LABELS: Record<string, string> = {
   "gateway.reload.mode": "Config Reload Mode",
   "gateway.reload.debounceMs": "Config Reload Debounce (ms)",
   "agents.defaults.workspace": "Workspace",
+  "agents.defaults.bootstrapMaxChars": "Bootstrap Max Chars",
   "agents.defaults.memorySearch": "Memory Search",
   "agents.defaults.memorySearch.enabled": "Enable Memory Search",
   "agents.defaults.memorySearch.provider": "Memory Search Provider",
@@ -233,6 +234,8 @@ const FIELD_HELP: Record<string, string> = {
     "Cap (hours) for billing backoff (default: 24).",
   "auth.cooldowns.failureWindowHours":
     "Failure window (hours) for backoff counters (default: 24).",
+  "agents.defaults.bootstrapMaxChars":
+    "Max characters of each workspace bootstrap file injected into the system prompt before truncation (default: 20000).",
   "agents.defaults.models":
     "Configured model catalog (keys are full provider/model IDs).",
   "agents.defaults.memorySearch":
diff --git a/src/config/types.ts b/src/config/types.ts
index ba008a610..16c43578b 100644
--- a/src/config/types.ts
+++ b/src/config/types.ts
@@ -1593,6 +1593,8 @@ export type AgentDefaultsConfig = {
   workspace?: string;
   /** Skip bootstrap (BOOTSTRAP.md creation, etc.) for pre-configured deployments. */
   skipBootstrap?: boolean;
+  /** Max chars for injected bootstrap files before truncation (default: 20000). */
+  bootstrapMaxChars?: number;
   /** Optional IANA timezone for the user (used in system prompt; defaults to host timezone). */
   userTimezone?: string;
   /** Optional display-only context window override (used for % in status UIs). */
diff --git a/src/config/zod-schema.ts b/src/config/zod-schema.ts
index 3f78fad7f..d6a020411 100644
--- a/src/config/zod-schema.ts
+++ b/src/config/zod-schema.ts
@@ -1169,6 +1169,7 @@ const AgentDefaultsSchema = z
       .optional(),
     workspace: z.string().optional(),
     skipBootstrap: z.boolean().optional(),
+    bootstrapMaxChars: z.number().int().positive().optional(),
     userTimezone: z.string().optional(),
     contextTokens: z.number().int().positive().optional(),
     cliBackends: z.record(z.string(), CliBackendSchema).optional(),