diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9c802786..3d3388e0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -56,6 +56,9 @@ jobs:
       - name: Test history package
         run: pnpm --dir components/packages/foundation/history test
 
+      - name: Test artifact store package
+        run: pnpm --dir components/packages/foundation/artifact-store test
+
       - name: Test TokenPilot preset
         run: pnpm --dir components/presets/tokenpilot test
 
@@ -68,6 +71,9 @@ jobs:
       - name: Test eviction package
         run: pnpm --dir components/packages/features/eviction test
 
+      - name: Test reduction package
+        run: pnpm --dir components/packages/features/reduction test
+
       - name: Test DeepSeek Harness adapter
         run: pnpm --dir components/adapters/deepseek-harness test
 
diff --git a/components/packages/features/reduction/src/passes/pass-tool-payload-trim.ts b/components/packages/features/reduction/src/passes/pass-tool-payload-trim.ts
index f52b321e..15e2bcf5 100644
--- a/components/packages/features/reduction/src/passes/pass-tool-payload-trim.ts
+++ b/components/packages/features/reduction/src/passes/pass-tool-payload-trim.ts
@@ -324,6 +324,7 @@ export const toolPayloadTrimPass: ReductionPassHandler = {
         sessionId: turnCtx.sessionId,
         segmentId: segment.id,
         workspaceDir,
+        originalText: segment.text,
       });
 
       const replacementText = reduced.text + buildRecoveryHint({
diff --git a/components/packages/features/reduction/tests/archive-path-stability.test.ts b/components/packages/features/reduction/tests/archive-path-stability.test.ts
new file mode 100644
index 00000000..f1581fb1
--- /dev/null
+++ b/components/packages/features/reduction/tests/archive-path-stability.test.ts
@@ -0,0 +1,102 @@
+/**
+ * Regression matrix: recovery hints are byte-stable across requests
+ *
+ * Adapters re-run these passes over the whole history on every model request. The
+ * hint's `Archive:` path used to carry a timestamp, so the same tool output was sent
+ * with different text each time (prompt-cache miss from that point on), and
+ * tool_payload_trim could name a file other than the one it wrote.
+ *
+ * tool_payload_trim
+ *   T1 the same input reduced twice, later, gives byte-identical output
+ *   T2 the hint's Archive path is the file actually written, holding the original text
+ *   T3 different content under the same segment id gets a different Archive path
+ * exec_output_truncation
+ *   T4 the same input truncated twice, later, gives byte-identical output, and the
+ *      hint's Archive path is the file written
+ */
+import test from "node:test";
+import assert from "node:assert/strict";
+import { mkdtemp, readFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+import type { RuntimeTurnContext } from "@lightrsi/kernel";
+import { execOutputTruncationBeforeCall } from "../src/passes/pass-exec-output-truncation.js";
+import { toolPayloadTrimPass } from "../src/passes/pass-tool-payload-trim.js";
+
+const sleep = (ms: number) => new Promise((resolve) => setTimeout(resolve, ms));
+const archiveOf = (text: string) => /Archive: ([^\n]+)/.exec(text)?.[1];
+const LOG = Array.from({ length: 2000 }, (_, i) => `[build] step ${i} compiling src/module_${i}.ts ... ok`).join("\n");
+
+function turnCtx(workspaceDir: string, text: string, strategy: string, toolName = "bash"): RuntimeTurnContext {
+  return {
+    sessionId: "stability-session",
+    sessionMode: "single",
+    provider: "test",
+    model: "test",
+    prompt: "",
+    budget: { maxInputTokens: 100000, reserveOutputTokens: 1000 },
+    segments: [{
+      id: "tool-call_1",
+      kind: "volatile",
+      priority: 1,
+      text,
+      metadata: { toolName, fieldName: "output", toolPayload: { toolName }, isToolPayload: true },
+    }],
+    metadata: {
+      workspaceDir,
+      latestUserQuery: "did the build pass",
+      policy: { decisions: { reduction: { instructions: [{ strategy, segmentIds: ["tool-call_1"], parameters: { payloadKind: "stdout" } }] } } },
+    },
+  };
+}
+
+async function trim(workspaceDir: string, text: string): Promise<string> {
+  const result = await toolPayloadTrimPass.beforeCall?.({
+    turnCtx: turnCtx(workspaceDir, text, "tool_payload_trim"),
+    spec: { id: "tool_payload_trim", phase: "before_call", target: "tool_payload", options: { maxChars: 1200 } },
+  });
+  assert.equal(result?.changed, true, "precondition: the pass trims");
+  return result!.turnCtx!.segments[0]!.text;
+}
+
+async function truncate(workspaceDir: string, text: string): Promise<string> {
+  const result = await execOutputTruncationBeforeCall.beforeCall?.({
+    turnCtx: turnCtx(workspaceDir, text, "exec_output_truncation"),
+    spec: { id: "exec_output_truncation", phase: "before_call", target: "tool_payload", options: { toolThresholds: { bash: 5000 } } },
+  });
+  assert.equal(result?.changed, true, "precondition: the pass truncates");
+  return result!.turnCtx!.segments[0]!.text;
+}
+
+test("T1 tool_payload_trim output is byte-identical across requests", async () => {
+  const dir = await mkdtemp(join(tmpdir(), "stable-t1-"));
+  const first = await trim(dir, LOG);
+  await sleep(5);
+  assert.equal(await trim(dir, LOG), first);
+});
+
+test("T2 tool_payload_trim names the file it wrote", async () => {
+  const dir = await mkdtemp(join(tmpdir(), "stable-t2-"));
+  const path = archiveOf(await trim(dir, LOG));
+  assert.ok(path);
+  assert.equal(JSON.parse(await readFile(path, "utf8")).originalText, LOG);
+});
+
+test("T3 different content gets a different archive path", async () => {
+  const dir = await mkdtemp(join(tmpdir(), "stable-t3-"));
+  const a = archiveOf(await trim(dir, LOG));
+  const b = archiveOf(await trim(dir, `${LOG}\nBUILD OK`));
+  assert.ok(a && b);
+  assert.notEqual(a, b);
+});
+
+test("T4 exec_output_truncation output is byte-identical across requests", async () => {
+  const dir = await mkdtemp(join(tmpdir(), "stable-t4-"));
+  const first = await truncate(dir, LOG);
+  await sleep(5);
+  assert.equal(await truncate(dir, LOG), first);
+  const path = archiveOf(first);
+  assert.ok(path);
+  assert.equal(JSON.parse(await readFile(path, "utf8")).originalText, LOG);
+});
diff --git a/components/packages/foundation/artifact-store/src/archive-recovery/index.ts b/components/packages/foundation/artifact-store/src/archive-recovery/index.ts
index c36f895b..467a151b 100644
--- a/components/packages/foundation/artifact-store/src/archive-recovery/index.ts
+++ b/components/packages/foundation/artifact-store/src/archive-recovery/index.ts
@@ -54,6 +54,15 @@ export type ArchiveLocationParams = {
   segmentId: string;
   workspaceDir?: string;
   archiveDir?: string;
+  /**
+   * The content being archived. When given, the file name is derived from the
+   * segment id and a hash of the session id and this text instead of the current
+   * time, so the same content in the same session always gets the same path. Adapters re-reduce the whole history on
+   * every request; a timestamped name changed the recovery hint each time (breaking
+   * prompt caching), wrote a new file each time, and could differ from the file
+   * actually written when the clock ticked between the hint and the write.
+   */
+  originalText?: string;
 };
 
 export type ArchiveLocation = {
@@ -166,8 +175,9 @@ export async function archiveContent(params: ArchiveContentParams): Promise<Arch
 
 export function buildArchiveLocation(params: ArchiveLocationParams): ArchiveLocation {
   const archiveDir = params.archiveDir ?? defaultArchiveDir(params.sessionId, params.workspaceDir);
-  const timestamp = Date.now();
-  const fileName = `${timestamp}-${sanitizePathPart(params.segmentId)}.json`;
+  const fileName = typeof params.originalText === "string"
+    ? `${sanitizePathPart(params.segmentId)}-${hashText(`${params.sessionId}\u0000${params.originalText}`).slice(0, 16)}.json`
+    : `${Date.now()}-${sanitizePathPart(params.segmentId)}.json`;
   const archivePath = join(archiveDir, fileName);
   return { archiveDir, archivePath };
 }
diff --git a/components/packages/foundation/artifact-store/tests/archive-location-stability.test.ts b/components/packages/foundation/artifact-store/tests/archive-location-stability.test.ts
new file mode 100644
index 00000000..3a10c765
--- /dev/null
+++ b/components/packages/foundation/artifact-store/tests/archive-location-stability.test.ts
@@ -0,0 +1,73 @@
+/**
+ * Regression matrix: content-derived archive locations (src/archive-recovery/index.ts)
+ *
+ * Adapters re-reduce the full history on every request. A timestamped archive name
+ * changed the recovery hint every time (breaking prompt caching), wrote a new file
+ * every time, and could differ from the file actually written.
+ *
+ * buildArchiveLocation
+ *   A1 with originalText: the same (session, segment, text) → the same path, however
+ *      much time passes
+ *   A2 with originalText: different text, segment or session → a different path
+ *   A3 without originalText → the previous timestamped name (backward compatible)
+ *   A4 unsafe segment ids are sanitized in the file name (no path traversal)
+ * archiveContent
+ *   A5 returns the path it wrote, which equals buildArchiveLocation for the same inputs;
+ *      archiving the same content twice leaves one file and the dataKey still resolves
+ */
+import test from "node:test";
+import assert from "node:assert/strict";
+import { mkdtemp, readdir, readFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { basename, dirname, join } from "node:path";
+
+import { archiveContent, buildArchiveLocation } from "../src/index.js";
+
+const sleep = (ms: number) => new Promise((resolve) => setTimeout(resolve, ms));
+
+test("A1 the same content always maps to the same path", async () => {
+  const archiveDir = await mkdtemp(join(tmpdir(), "archive-a1-"));
+  const params = { sessionId: "s", segmentId: "tool-1", archiveDir, originalText: "body" };
+  const first = buildArchiveLocation(params);
+  await sleep(5);
+  assert.deepEqual(buildArchiveLocation(params), first);
+  assert.equal(dirname(first.archivePath), archiveDir);
+});
+
+test("A2 different text, segment or session gives a different path", () => {
+  const base = { sessionId: "s", segmentId: "tool-1", originalText: "body", workspaceDir: "/w" };
+  const path = buildArchiveLocation(base).archivePath;
+  assert.notEqual(buildArchiveLocation({ ...base, originalText: "body2" }).archivePath, path);
+  assert.notEqual(buildArchiveLocation({ ...base, segmentId: "tool-2" }).archivePath, path);
+  assert.notEqual(buildArchiveLocation({ ...base, sessionId: "s2" }).archivePath, path);
+});
+
+test("A3 without originalText the name stays timestamped", () => {
+  const before = Date.now();
+  const name = basename(buildArchiveLocation({ sessionId: "s", segmentId: "tool-1", archiveDir: "/a" }).archivePath);
+  const match = /^(\d+)-tool-1\.json$/.exec(name);
+  assert.ok(match, name);
+  assert.ok(Number(match[1]) >= before);
+});
+
+test("A4 unsafe segment ids are sanitized", async () => {
+  const nativeArchiveDir = await mkdtemp(join(tmpdir(), "archive-a4-"));
+  const { archivePath, archiveDir } = buildArchiveLocation({ sessionId: "s", segmentId: "../../etc/passwd", archiveDir: nativeArchiveDir, originalText: "x" });
+  assert.equal(dirname(archivePath), archiveDir);
+  assert.ok(!basename(archivePath).includes("/"));
+});
+
+test("A5 archiveContent writes where the location says, once per content", async () => {
+  const archiveDir = await mkdtemp(join(tmpdir(), "archive-a5-"));
+  const params = { sessionId: "s", segmentId: "tool-1", sourcePass: "tool_payload_trim", toolName: "read", dataKey: "/repo/a.ts", originalText: "full body", archiveDir };
+  const first = await archiveContent(params);
+  await sleep(5);
+  const second = await archiveContent(params);
+  assert.equal(second.archivePath, first.archivePath);
+  assert.equal(first.archivePath, buildArchiveLocation(params).archivePath);
+  const files = (await readdir(archiveDir)).filter((name) => name.endsWith(".json") && name !== "key-lookup.json");
+  assert.deepEqual(files, [basename(first.archivePath)]);
+  assert.equal(JSON.parse(await readFile(first.archivePath, "utf8")).originalText, "full body");
+  const lookup = JSON.parse(await readFile(join(archiveDir, "key-lookup.json"), "utf8")) as Record<string, string>;
+  assert.equal(lookup["/repo/a.ts"], first.archivePath);
+});