fix(gsd): stop stale forensics context hijacks

src/resources/extensions/gsd/bootstrap/system-context.ts

@@ -168,7 +168,7 @@ export async function buildBeforeAgentStartResult(
   const injection = await buildGuidedExecuteContextInjection(event.prompt, process.cwd());
 
   // Re-inject forensics context on follow-up turns (#2941)
-  const forensicsInjection = !injection ? buildForensicsContextInjection(process.cwd()) : null;
+  const forensicsInjection = !injection ? buildForensicsContextInjection(process.cwd(), event.prompt) : null;
 
   const worktreeBlock = buildWorktreeContextBlock();
   const fullSystem = `${event.systemPrompt}\n\n[SYSTEM CONTEXT — GSD]\n\n${systemContent}${preferenceBlock}${knowledgeBlock}${codebaseBlock}${memoryBlock}${newSkillsBlock}${worktreeBlock}`;
@@ -481,7 +481,7 @@ function oneLine(text: string): string {
  * Check for an active forensics session and return the prompt content
  * so it can be re-injected on follow-up turns.
  */
-function buildForensicsContextInjection(basePath: string): string | null {
+export function buildForensicsContextInjection(basePath: string, prompt: string): string | null {
   const marker = readForensicsMarker(basePath);
   if (!marker) return null;
 
@@ -492,6 +492,12 @@ function buildForensicsContextInjection(basePath: string): string | null {
     return null;
   }
 
+  const trimmed = prompt.trim().toLowerCase().replace(/[.!?,]+$/g, "");
+  if (trimmed && !RESUME_INTENT_PATTERNS.test(trimmed)) {
+    clearForensicsMarker(basePath);
+    return null;
+  }
+
   return marker.promptContent;
 }
 

src/resources/extensions/gsd/tests/forensics-context-persist.test.ts

@@ -126,4 +126,34 @@ describe("forensics context persistence (#2941)", () => {
     // Should not throw
     clearForensicsMarker(join(tmpBase, "nonexistent"));
   });
+
+  it("buildForensicsContextInjection keeps marker for low-entropy resume prompts", async () => {
+    const { buildForensicsContextInjection } = await import("../bootstrap/system-context.ts");
+
+    const markerPath = join(tmpBase, ".gsd", "runtime", "active-forensics.json");
+    writeFileSync(markerPath, JSON.stringify({
+      reportPath: "/some/report.md",
+      promptContent: "forensics prompt",
+      createdAt: new Date().toISOString(),
+    }), "utf-8");
+
+    const result = buildForensicsContextInjection(tmpBase, "continue");
+    assert.equal(result, "forensics prompt");
+    assert.ok(existsSync(markerPath), "resume-like follow-up should keep marker intact");
+  });
+
+  it("buildForensicsContextInjection clears marker on unrelated user prompts", async () => {
+    const { buildForensicsContextInjection } = await import("../bootstrap/system-context.ts");
+
+    const markerPath = join(tmpBase, ".gsd", "runtime", "active-forensics.json");
+    writeFileSync(markerPath, JSON.stringify({
+      reportPath: "/some/report.md",
+      promptContent: "forensics prompt",
+      createdAt: new Date().toISOString(),
+    }), "utf-8");
+
+    const result = buildForensicsContextInjection(tmpBase, "please summarize the README");
+    assert.equal(result, null);
+    assert.ok(!existsSync(markerPath), "unrelated follow-up should clear the stale marker");
+  });
 });