fix(cli-runner): drop volatile systemPromptHash from claude-cli live fingerprint

benjamin1492 · benjamin1492 · commit 9daea4081cc3 · 2026-05-29T12:03:47.000-04:00
diff --git a/src/agents/cli-runner/claude-live-session.fingerprint.test.ts b/src/agents/cli-runner/claude-live-session.fingerprint.test.ts
@@ -0,0 +1,119 @@
+import { describe, expect, it } from "vitest";
+import { buildClaudeLiveFingerprint } from "./claude-live-session.js";
+import type { PreparedCliRunContext } from "./types.js";
+
+function buildContext(overrides?: {
+  systemPrompt?: string;
+  extraSystemPromptHash?: string;
+  normalizedModel?: string;
+  workspaceDir?: string;
+}): PreparedCliRunContext {
+  const backend = {
+    command: "claude",
+    args: [],
+    output: "jsonl" as const,
+    input: "stdin" as const,
+    serialize: true,
+    liveSession: "claude-stdio" as const,
+    sessionArg: "--session",
+    systemPromptArg: "--system-prompt",
+    systemPromptFileArg: "--system-prompt-file",
+  };
+  return {
+    params: {
+      sessionId: "session-1",
+      sessionFile: "/tmp/session.jsonl",
+      workspaceDir: overrides?.workspaceDir ?? "/tmp/workspace",
+      prompt: "hi",
+      provider: "claude-cli",
+      model: "model",
+      timeoutMs: 1_000,
+      runId: "run-1",
+    },
+    started: Date.now(),
+    workspaceDir: overrides?.workspaceDir ?? "/tmp/workspace",
+    backendResolved: {
+      id: "claude-cli",
+      config: backend,
+      bundleMcp: false,
+    },
+    preparedBackend: {
+      backend,
+      env: {},
+    },
+    reusableCliSession: {},
+    modelId: "model",
+    normalizedModel: overrides?.normalizedModel ?? "model",
+    systemPrompt: overrides?.systemPrompt ?? "you are an agent",
+    systemPromptReport: {} as PreparedCliRunContext["systemPromptReport"],
+    bootstrapPromptWarningLines: [],
+    authEpochVersion: 2,
+    extraSystemPromptHash: overrides?.extraSystemPromptHash ?? "static-hash-a",
+  };
+}
+
+describe("buildClaudeLiveFingerprint", () => {
+  it("ignores volatile changes to the per-turn system prompt", () => {
+    // Per-turn inbound metadata (timestamps, sender envelope, heartbeat, channel
+    // guidance) is folded into `context.systemPrompt`. The fingerprint must not
+    // diverge on these volatile chunks — otherwise the runtime rotates the live
+    // claude-cli subprocess on every turn and loses prior context.
+    const baselineArgv = ["claude", "--model", "model"];
+    const a = buildClaudeLiveFingerprint({
+      context: buildContext({ systemPrompt: "[turn 1 metadata]\nyou are an agent" }),
+      argv: baselineArgv,
+      env: {},
+    });
+    const b = buildClaudeLiveFingerprint({
+      context: buildContext({ systemPrompt: "[turn 2 different metadata]\nyou are an agent" }),
+      argv: baselineArgv,
+      env: {},
+    });
+    expect(a).toBe(b);
+  });
+
+  it("diverges when extraSystemPromptHash changes (static config still gates session reuse)", () => {
+    const argv = ["claude", "--model", "model"];
+    const a = buildClaudeLiveFingerprint({
+      context: buildContext({ extraSystemPromptHash: "static-hash-a" }),
+      argv,
+      env: {},
+    });
+    const b = buildClaudeLiveFingerprint({
+      context: buildContext({ extraSystemPromptHash: "static-hash-b" }),
+      argv,
+      env: {},
+    });
+    expect(a).not.toBe(b);
+  });
+
+  it("diverges when the normalized model changes", () => {
+    const argv = ["claude", "--model", "model"];
+    const a = buildClaudeLiveFingerprint({
+      context: buildContext({ normalizedModel: "sonnet-4.6" }),
+      argv,
+      env: {},
+    });
+    const b = buildClaudeLiveFingerprint({
+      context: buildContext({ normalizedModel: "opus-4.7" }),
+      argv,
+      env: {},
+    });
+    expect(a).not.toBe(b);
+  });
+
+  it("diverges when the workspace directory changes", () => {
+    const argv = ["claude", "--model", "model"];
+    const a = buildClaudeLiveFingerprint({
+      context: buildContext({ workspaceDir: "/tmp/one" }),
+      argv,
+      env: {},
+    });
+    const b = buildClaudeLiveFingerprint({
+      context: buildContext({ workspaceDir: "/tmp/two" }),
+      argv,
+      env: {},
+    });
+    expect(a).not.toBe(b);
+  });
+});
diff --git a/src/agents/cli-runner/claude-live-session.ts b/src/agents/cli-runner/claude-live-session.ts
@@ -259,7 +259,7 @@ function buildClaudeLiveKey(context: PreparedCliRunContext): string {
   )}`;
 }
 
-function buildClaudeLiveFingerprint(params: {
+export function buildClaudeLiveFingerprint(params: {
   context: PreparedCliRunContext;
   argv: string[];
   env: Record<string, string>;
@@ -326,7 +326,6 @@ function buildClaudeLiveFingerprint(params: {
     cwdHash: params.context.cwdHash ?? sha256(params.context.cwd ?? params.context.workspaceDir),
     provider: params.context.params.provider,
     model: params.context.normalizedModel,
-    systemPromptHash: sha256(params.context.systemPrompt),
     authProfileIdHash: params.context.effectiveAuthProfileId
       ? sha256(params.context.effectiveAuthProfileId)
       : undefined,
