diff --git a/docs/gateway/configuration-reference.md b/docs/gateway/configuration-reference.md
index 30559b5d55d..749b0d2b261 100644
--- a/docs/gateway/configuration-reference.md
+++ b/docs/gateway/configuration-reference.md
@@ -1003,6 +1003,7 @@ Periodic heartbeat runs.
         reserveTokensFloor: 24000,
         identifierPolicy: "strict", // strict | off | custom
         identifierInstructions: "Preserve deployment IDs, ticket IDs, and host:port pairs exactly.", // used when identifierPolicy=custom
+        postCompactionSections: ["Session Startup", "Red Lines"], // [] disables reinjection
         memoryFlush: {
           enabled: true,
           softThresholdTokens: 6000,
@@ -1018,6 +1019,7 @@ Periodic heartbeat runs.
 - `mode`: `default` or `safeguard` (chunked summarization for long histories). See [Compaction](/concepts/compaction).
 - `identifierPolicy`: `strict` (default), `off`, or `custom`. `strict` prepends built-in opaque identifier retention guidance during compaction summarization.
 - `identifierInstructions`: optional custom identifier-preservation text used when `identifierPolicy=custom`.
+- `postCompactionSections`: optional AGENTS.md H2/H3 section names to re-inject after compaction. Defaults to `["Session Startup", "Red Lines"]`; set `[]` to disable reinjection. When unset or explicitly set to that default pair, older `Every Session`/`Safety` headings are also accepted as a legacy fallback.
 - `memoryFlush`: silent agentic turn before auto-compaction to store durable memories. Skipped when workspace is read-only.
 
 ### `agents.defaults.contextPruning`
diff --git a/src/config/schema.help.quality.test.ts b/src/config/schema.help.quality.test.ts
index 146ffc17101..2ef7d8aae3a 100644
--- a/src/config/schema.help.quality.test.ts
+++ b/src/config/schema.help.quality.test.ts
@@ -375,6 +375,7 @@ const TARGET_KEYS = [
   "agents.defaults.compaction.qualityGuard",
   "agents.defaults.compaction.qualityGuard.enabled",
   "agents.defaults.compaction.qualityGuard.maxRetries",
+  "agents.defaults.compaction.postCompactionSections",
   "agents.defaults.compaction.memoryFlush",
   "agents.defaults.compaction.memoryFlush.enabled",
   "agents.defaults.compaction.memoryFlush.softThresholdTokens",
@@ -795,6 +796,11 @@ describe("config help copy quality", () => {
     expect(identifierPolicy.includes('"off"')).toBe(true);
     expect(identifierPolicy.includes('"custom"')).toBe(true);
 
+    const postCompactionSections = FIELD_HELP["agents.defaults.compaction.postCompactionSections"];
+    expect(/Session Startup|Red Lines/i.test(postCompactionSections)).toBe(true);
+    expect(/Every Session|Safety/i.test(postCompactionSections)).toBe(true);
+    expect(/\[\]|disable/i.test(postCompactionSections)).toBe(true);
+
     const flush = FIELD_HELP["agents.defaults.compaction.memoryFlush.enabled"];
     expect(/pre-compaction|memory flush|token/i.test(flush)).toBe(true);
   });
diff --git a/src/config/schema.help.ts b/src/config/schema.help.ts
index f2ef2ff4ab8..ee760f2d23f 100644
--- a/src/config/schema.help.ts
+++ b/src/config/schema.help.ts
@@ -1003,6 +1003,8 @@ export const FIELD_HELP: Record<string, string> = {
     "Enables summary quality audits and regeneration retries for safeguard compaction. Default: false, so safeguard mode alone does not turn on retry behavior.",
   "agents.defaults.compaction.qualityGuard.maxRetries":
     "Maximum number of regeneration retries after a failed safeguard summary quality audit. Use small values to bound extra latency and token cost.",
+  "agents.defaults.compaction.postCompactionSections":
+    'AGENTS.md H2/H3 section names re-injected after compaction so the agent reruns critical startup guidance. Leave unset to use "Session Startup"/"Red Lines" with legacy fallback to "Every Session"/"Safety"; set to [] to disable reinjection entirely.',
   "agents.defaults.compaction.memoryFlush":
     "Pre-compaction memory flush settings that run an agentic memory write before heavy compaction. Keep enabled for long sessions so salient context is persisted before aggressive trimming.",
   "agents.defaults.compaction.memoryFlush.enabled":