diff --git a/src/resources/extensions/gsd/auto-prompts.ts b/src/resources/extensions/gsd/auto-prompts.ts
index 97ce5cf3f..92ad153ec 100644
--- a/src/resources/extensions/gsd/auto-prompts.ts
+++ b/src/resources/extensions/gsd/auto-prompts.ts
@@ -994,10 +994,15 @@ export async function buildResearchSlicePrompt(
   const milestoneResearchPath = resolveMilestoneFile(base, mid, "RESEARCH");
   const milestoneResearchRel = relMilestoneFile(base, mid, "RESEARCH");
 
+  const sliceContextPath = resolveSliceFile(base, mid, sid, "CONTEXT");
+  const sliceContextRel = relSliceFile(base, mid, sid, "CONTEXT");
+
   const inlined: string[] = [];
   inlined.push(await inlineFile(roadmapPath, roadmapRel, "Milestone Roadmap"));
   const contextInline = await inlineFileOptional(contextPath, contextRel, "Milestone Context");
   if (contextInline) inlined.push(contextInline);
+  const sliceCtxInline = await inlineFileOptional(sliceContextPath, sliceContextRel, "Slice Context (from discussion)");
+  if (sliceCtxInline) inlined.push(sliceCtxInline);
   const researchInline = await inlineFileOptional(milestoneResearchPath, milestoneResearchRel, "Milestone Research");
   if (researchInline) inlined.push(researchInline);
   const decisionsInline = await inlineDecisionsFromDb(base, mid);
@@ -1045,6 +1050,8 @@ export async function buildPlanSlicePrompt(
   const roadmapRel = relMilestoneFile(base, mid, "ROADMAP");
   const researchPath = resolveSliceFile(base, mid, sid, "RESEARCH");
   const researchRel = relSliceFile(base, mid, sid, "RESEARCH");
+  const sliceContextPath = resolveSliceFile(base, mid, sid, "CONTEXT");
+  const sliceContextRel = relSliceFile(base, mid, sid, "CONTEXT");
 
   const inlined: string[] = [];
 
@@ -1053,6 +1060,8 @@ export async function buildPlanSlicePrompt(
   if (researchSliceAnchor) inlined.push(formatAnchorForPrompt(researchSliceAnchor));
 
   inlined.push(await inlineFile(roadmapPath, roadmapRel, "Milestone Roadmap"));
+  const sliceCtxInline = await inlineFileOptional(sliceContextPath, sliceContextRel, "Slice Context (from discussion)");
+  if (sliceCtxInline) inlined.push(sliceCtxInline);
   const researchInline = await inlineFileOptional(researchPath, researchRel, "Slice Research");
   if (researchInline) inlined.push(researchInline);
   if (inlineLevel !== "minimal") {
@@ -1253,9 +1262,13 @@ export async function buildCompleteSlicePrompt(
   const roadmapRel = relMilestoneFile(base, mid, "ROADMAP");
   const slicePlanPath = resolveSliceFile(base, mid, sid, "PLAN");
   const slicePlanRel = relSliceFile(base, mid, sid, "PLAN");
+  const sliceContextPath = resolveSliceFile(base, mid, sid, "CONTEXT");
+  const sliceContextRel = relSliceFile(base, mid, sid, "CONTEXT");
 
   const inlined: string[] = [];
   inlined.push(await inlineFile(roadmapPath, roadmapRel, "Milestone Roadmap"));
+  const sliceCtxInline = await inlineFileOptional(sliceContextPath, sliceContextRel, "Slice Context (from discussion)");
+  if (sliceCtxInline) inlined.push(sliceCtxInline);
   inlined.push(await inlineFile(slicePlanPath, slicePlanRel, "Slice Plan"));
   if (inlineLevel !== "minimal") {
     const requirementsInline = await inlineRequirementsFromDb(base, sid, inlineLevel);
@@ -1510,9 +1523,13 @@ export async function buildReplanSlicePrompt(
   const roadmapRel = relMilestoneFile(base, mid, "ROADMAP");
   const slicePlanPath = resolveSliceFile(base, mid, sid, "PLAN");
   const slicePlanRel = relSliceFile(base, mid, sid, "PLAN");
+  const sliceContextPath = resolveSliceFile(base, mid, sid, "CONTEXT");
+  const sliceContextRel = relSliceFile(base, mid, sid, "CONTEXT");
 
   const inlined: string[] = [];
   inlined.push(await inlineFile(roadmapPath, roadmapRel, "Milestone Roadmap"));
+  const sliceCtxInline = await inlineFileOptional(sliceContextPath, sliceContextRel, "Slice Context (from discussion)");
+  if (sliceCtxInline) inlined.push(sliceCtxInline);
   inlined.push(await inlineFile(slicePlanPath, slicePlanRel, "Current Slice Plan"));
 
   // Find the blocker task summary — the completed task with blocker_discovered: true
@@ -1627,9 +1644,13 @@ export async function buildReassessRoadmapPrompt(
   const roadmapRel = relMilestoneFile(base, mid, "ROADMAP");
   const summaryPath = resolveSliceFile(base, mid, completedSliceId, "SUMMARY");
   const summaryRel = relSliceFile(base, mid, completedSliceId, "SUMMARY");
+  const sliceContextPath = resolveSliceFile(base, mid, completedSliceId, "CONTEXT");
+  const sliceContextRel = relSliceFile(base, mid, completedSliceId, "CONTEXT");
 
   const inlined: string[] = [];
   inlined.push(await inlineFile(roadmapPath, roadmapRel, "Current Roadmap"));
+  const sliceCtxInline = await inlineFileOptional(sliceContextPath, sliceContextRel, "Slice Context (from discussion)");
+  if (sliceCtxInline) inlined.push(sliceCtxInline);
   inlined.push(await inlineFile(summaryPath, summaryRel, `${completedSliceId} Summary`));
   if (inlineLevel !== "minimal") {
     const projectInline = await inlineProjectFromDb(base);
diff --git a/src/resources/extensions/gsd/tests/slice-context-injection.test.ts b/src/resources/extensions/gsd/tests/slice-context-injection.test.ts
new file mode 100644
index 000000000..bb7cd2005
--- /dev/null
+++ b/src/resources/extensions/gsd/tests/slice-context-injection.test.ts
@@ -0,0 +1,50 @@
+/**
+ * Regression test: S##-CONTEXT.md from slice discussion must be
+ * injected into all 5 downstream prompt builders (#3452).
+ *
+ * Scans auto-prompts.ts for the 5 builder functions and verifies
+ * each one resolves and inlines the slice-level CONTEXT file.
+ */
+
+import { describe, test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const autoPromptsPath = join(__dirname, "..", "auto-prompts.ts");
+const source = readFileSync(autoPromptsPath, "utf-8");
+
+const BUILDERS = [
+  "buildResearchSlicePrompt",
+  "buildPlanSlicePrompt",
+  "buildCompleteSlicePrompt",
+  "buildReplanSlicePrompt",
+  "buildReassessRoadmapPrompt",
+];
+
+describe("slice CONTEXT.md injection into prompt builders (#3452)", () => {
+  for (const builder of BUILDERS) {
+    test(`${builder} resolves slice CONTEXT file`, () => {
+      // Find the function body
+      const fnStart = source.indexOf(`export async function ${builder}`);
+      assert.ok(fnStart !== -1, `${builder} should exist in auto-prompts.ts`);
+
+      // Get a reasonable chunk after the function start (enough to cover the inlining section)
+      const chunk = source.slice(fnStart, fnStart + 3000);
+
+      // Must resolve the slice CONTEXT path
+      assert.ok(
+        chunk.includes('resolveSliceFile(base, mid,') && chunk.includes('"CONTEXT"'),
+        `${builder} should call resolveSliceFile with "CONTEXT"`,
+      );
+
+      // Must inline it with inlineFileOptional
+      assert.ok(
+        chunk.includes('Slice Context'),
+        `${builder} should inline slice CONTEXT with a "Slice Context" label`,
+      );
+    });
+  }
+});