diff --git a/docs/concepts/system-prompt.md b/docs/concepts/system-prompt.md
index acb2bf8b5f..2a4adba532 100644
--- a/docs/concepts/system-prompt.md
+++ b/docs/concepts/system-prompt.md
@@ -59,11 +59,24 @@ Bootstrap files are trimmed and appended under **Project Context** so the model
 - `USER.md`
 - `HEARTBEAT.md`
 - `BOOTSTRAP.md` (only on brand-new workspaces)
+- `MEMORY.md` (when present in the workspace)
+
+All of these files are **injected into the context window** on every turn, which
+means they consume tokens. Keep them concise — especially `MEMORY.md`, which can
+grow over time and lead to unexpectedly high context usage and more frequent
+compaction.
+
+> **Note:** `memory/*.md` daily files are **not** injected automatically. They
+> are accessed on demand via the `memory_search` and `memory_get` tools, so they
+> do not count against the context window unless the model explicitly reads them.
 
 Large files are truncated with a marker. The max per-file size is controlled by
 `agents.defaults.bootstrapMaxChars` (default: 20000). Missing files inject a
 short missing-file marker.
 
+Sub-agent sessions only inject `AGENTS.md` and `TOOLS.md` (other bootstrap files
+are filtered out to keep the sub-agent context small).
+
 Internal hooks can intercept this step via `agent:bootstrap` to mutate or replace
 the injected bootstrap files (for example swapping `SOUL.md` for an alternate persona).