diff --git a/.pi/extensions/goal-driven-loop/state-injector.ts b/.pi/extensions/goal-driven-loop/state-injector.ts
new file mode 100644
index 0000000..d6b0794
--- /dev/null
+++ b/.pi/extensions/goal-driven-loop/state-injector.ts
@@ -0,0 +1,138 @@
+/**
+ * State injection for goal-driven-loop.
+ *
+ * Reads .agents/goal/GOAL.md and injects goal state into
+ * the agent's context via before_agent_start.
+ */
+
+import { readFileSync, existsSync } from "node:fs";
+import { join } from "node:path";
+
+export interface GoalState {
+  goal: string;
+  status: "in-progress" | "blocked" | "complete";
+  iteration: number;
+  totalCriteria: number;
+  passedCriteria: number;
+  created: string;
+  updated: string;
+  blocker?: string;
+  progressLog: string[];
+}
+
+/**
+ * Parse GOAL.md frontmatter and body to extract goal state.
+ */
+export function readGoalState(cwd: string): GoalState | null {
+  const goalPath = join(cwd, ".agents", "goal", "GOAL.md");
+  if (!existsSync(goalPath)) {
+    return null;
+  }
+
+  const content = readFileSync(goalPath, "utf-8");
+
+  const frontmatterMatch = content.match(/^---\n([\s\S]*?)\n---/);
+  if (!frontmatterMatch) {
+    return null;
+  }
+
+  const frontmatter = frontmatterMatch[1];
+  const goal = extractField(frontmatter, "goal") || "";
+  const status =
+    (extractField(frontmatter, "status") as GoalState["status"]) ||
+    "in-progress";
+  const iteration = parseInt(
+    extractField(frontmatter, "iteration") || "0",
+    10
+  );
+  const created = extractField(frontmatter, "created") || "";
+  const updated = extractField(frontmatter, "updated") || "";
+
+  const criteriaSection = extractSection(content, "Acceptance Criteria");
+  const totalCriteria = countCheckboxes(criteriaSection);
+  const passedCriteria = countCheckedBoxes(criteriaSection);
+
+  const blockerSection = extractSection(content, "Blocked");
+  const blocker = blockerSection.trim() || undefined;
+
+  const progressSection = extractSection(content, "Progress Log");
+  const progressLog = extractIterations(progressSection);
+
+  return {
+    goal,
+    status,
+    iteration,
+    totalCriteria,
+    passedCriteria,
+    created,
+    updated,
+    blocker,
+    progressLog,
+  };
+}
+
+/**
+ * Build the injection text for the system prompt or message.
+ */
+export function buildInjectionText(state: GoalState): string {
+  if (state.status === "complete") {
+    return `[goal-driven-loop] GOAL COMPLETE
+${state.goal}
+Final: ${state.passedCriteria}/${state.totalCriteria} criteria passed across ${state.iteration} iterations.
+GOAL.md is being cleaned up.`;
+  }
+
+  if (state.status === "blocked" && state.blocker) {
+    return `[goal-driven-loop] GOAL BLOCKED
+${state.goal}
+Blocker: ${state.blocker}
+Progress: ${state.passedCriteria}/${state.totalCriteria} criteria passed, iteration ${state.iteration}.
+Continue by trying a different strategy. If still blocked after 2 attempts, surface to the user.`;
+  }
+
+  return `[goal-driven-loop] ACTIVE GOAL
+${state.goal}
+Progress: ${state.passedCriteria}/${state.totalCriteria} criteria passed, iteration ${state.iteration}
+Next step: read .agents/goal/GOAL.md and continue the loop.`;
+}
+
+/**
+ * Build a continuation prompt for context tension situations.
+ */
+export function buildContinuationPrompt(state: GoalState): string {
+  return `🔄 目标状态已保存至 .agents/goal/GOAL.md
+当前进度：${state.passedCriteria}/${state.totalCriteria} criteria 通过，第 ${state.iteration} 轮迭代。`;
+}
+
+// ---- helpers ----
+
+function extractField(frontmatter: string, field: string): string | null {
+  const match = frontmatter.match(new RegExp(`^${field}:\\s*(.*)$`, "m"));
+  if (!match) return null;
+  let value = match[1].trim();
+  if (
+    (value.startsWith('"') && value.endsWith('"')) ||
+    (value.startsWith("'") && value.endsWith("'"))
+  ) {
+    value = value.slice(1, -1);
+  }
+  return value;
+}
+
+function extractSection(content: string, sectionName: string): string {
+  const regex = new RegExp(`## ${sectionName}\\n([\\s\\S]*?)(?=\\n## |$)`);
+  const match = content.match(regex);
+  return match ? match[1] : "";
+}
+
+function countCheckboxes(section: string): number {
+  return (section.match(/^- \[[ x]\]/gm) || []).length;
+}
+
+function countCheckedBoxes(section: string): number {
+  return (section.match(/^- \[x\]/gim) || []).length;
+}
+
+function extractIterations(section: string): string[] {
+  return section.match(/### Iteration \d+/g) || [];
+}