diff --git a/backend/apps/agents/manager/prompt/compose_turn_system_prompt.py b/backend/apps/agents/manager/prompt/compose_turn_system_prompt.py
index 78e88acc..b74dfb0f 100644
--- a/backend/apps/agents/manager/prompt/compose_turn_system_prompt.py
+++ b/backend/apps/agents/manager/prompt/compose_turn_system_prompt.py
@@ -13,6 +13,7 @@ from backend.apps.agents.core.models import AgentSession
 from backend.apps.agents.manager.prompt.tool_catalog import get_all_tool_names
 from backend.apps.agents.manager.prompt.repo_staleness_note import repo_staleness_note
 from backend.apps.agents.manager.prompt.prompt_context import (
+    apps_created_by_session,
     build_app_runtime_contract,
     build_browser_context,
     build_installed_skills_catalog,
@@ -142,7 +143,12 @@ def compose_turn_system_prompt(
         pass
 
     # App cards the user picked via the dashboard element picker: give the agent each app's on-disk path + meta + SKILL.md pointer so it can edit them in place (the dashboard card's runtime live-reloads). Additive and independent of view-builder mode above.
-    app_ctx = build_selected_app_context(selected_app_output_ids)
+    # An explicit pick wins; only when nothing is picked does the chat fall back to the apps it
+    # built itself, so the common path costs nothing and a selection is never overridden (ENG-416).
+    p_app_ids = list(selected_app_output_ids or [])
+    if not p_app_ids:
+        p_app_ids = apps_created_by_session(session.parent_session_id or session.id)
+    app_ctx = build_selected_app_context(p_app_ids)
     # Nothing picked: name the apps anyway so the agent can point the user at the selection step instead of acting like their app does not exist.
     if not app_ctx:
         app_ctx = build_unselected_app_context()
diff --git a/backend/apps/agents/manager/prompt/prompt_context.py b/backend/apps/agents/manager/prompt/prompt_context.py
index 9dadcde2..d99ea7be 100644
--- a/backend/apps/agents/manager/prompt/prompt_context.py
+++ b/backend/apps/agents/manager/prompt/prompt_context.py
@@ -165,6 +165,36 @@ def build_unselected_app_context() -> Optional[str]:
 P_UNSELECTED_APP_CAP = 12
 
 
+# A chat that built an app can edit it without the user re-selecting the card. Only consulted when
+# NOTHING is selected: an explicit pick always wins, and the common path pays nothing.
+APPS_OWNED_CAP = 3
+
+
+@typechecked
+def apps_created_by_session(owning_session_id: Optional[str]) -> List[str]:
+    """Output ids this CHAT created, newest first.
+
+    The agent had no link at all from "this session made that app" to "this session may edit it",
+    so it told the user to go select a card it had produced itself, and then to "save or reopen"
+    an app that was sitting on their canvas (ENG-416).
+
+    `output.session_id` is written from `parent_session_id` at creation, so it is already the chat
+    rather than the per-dispatch view-builder child; callers must pass the chat for the same reason
+    ENG-403 had to (a child id would match nothing and the feature would be silently dead).
+    """
+    if not owning_session_id:
+        return []
+    try:
+        from backend.apps.outputs.workspace_io import load_all
+        p_mine = [o for o in load_all()
+                  if getattr(o, "session_id", None) == owning_session_id
+                  and getattr(o, "workspace_id", None)]
+    except Exception:
+        return []
+    p_mine.sort(key=lambda o: getattr(o, "updated_at", "") or "", reverse=True)
+    return [o.id for o in p_mine[:APPS_OWNED_CAP]]
+
+
 @typechecked
 def build_selected_app_context(selected_app_output_ids: Optional[List[str]]) -> Optional[str]:
     """Build a context block for dashboard App cards the user selected to edit.
diff --git a/backend/tests/test_chat_owns_its_app.py b/backend/tests/test_chat_owns_its_app.py
new file mode 100644
index 00000000..39160c81
--- /dev/null
+++ b/backend/tests/test_chat_owns_its_app.py
@@ -0,0 +1,105 @@
+"""A chat can edit the app it built, without the user re-selecting the card.
+
+ENG-416, production 1.7.9. The agent built an app in a chat and then, in that same chat, said:
+"I don't have access to its files in this chat. Click that app's card on your dashboard to select
+it, then resend." He selected it; the next turn asked him to "save or reopen it from the dashboard".
+Two round trips of clerical work to reintroduce an agent to its own output.
+
+`build_selected_app_context` opens with `if not selected_app_output_ids: return None`, and that list
+is populated ONLY by the dashboard element picker. Nothing linked "this session created that output"
+to "this session may edit it".
+"""
+
+import pytest
+
+from backend.apps.agents.manager.prompt import prompt_context as p_ctx
+
+COMPOSER = "backend/apps/agents/manager/prompt/compose_turn_system_prompt.py"
+
+
+class P_Out:
+    def __init__(self, oid, session_id, workspace_id="ws", updated_at="2026-01-01"):
+        self.id = oid
+        self.session_id = session_id
+        self.workspace_id = workspace_id
+        self.updated_at = updated_at
+
+
+def p_store(monkeypatch, outs):
+    import backend.apps.outputs.workspace_io as io
+    monkeypatch.setattr(io, "load_all", lambda: outs, raising=True)
+
+
+def test_a_chat_finds_the_app_it_created(monkeypatch):
+    p_store(monkeypatch, [P_Out("app-1", "chat-A")])
+    assert p_ctx.apps_created_by_session("chat-A") == ["app-1"]
+
+
+def test_another_chats_app_is_never_picked_up(monkeypatch):
+    """The control. Owning what you built must not become owning everything."""
+    p_store(monkeypatch, [P_Out("app-1", "chat-A")])
+    assert p_ctx.apps_created_by_session("chat-B") == []
+
+
+def test_an_app_with_no_workspace_is_skipped(monkeypatch):
+    """`build_selected_app_context` would drop it anyway; offering it would only produce the second
+    bad message he saw ("that app doesn't have a saved workspace yet")."""
+    p_store(monkeypatch, [P_Out("app-1", "chat-A", workspace_id=None)])
+    assert p_ctx.apps_created_by_session("chat-A") == []
+
+
+def test_newest_first_and_capped(monkeypatch):
+    """A chat that built a dozen apps must not dump a dozen workspace blocks into every turn."""
+    outs = [P_Out(f"app-{i}", "chat-A", updated_at=f"2026-01-{i:02d}") for i in range(1, 9)]
+    got = p_ctx.apps_created_by_session("chat-A")
+    p_store(monkeypatch, outs)
+    got = p_ctx.apps_created_by_session("chat-A")
+    assert got == ["app-8", "app-7", "app-6"], got
+    assert len(got) == p_ctx.APPS_OWNED_CAP
+
+
+def test_a_broken_store_is_silent_not_fatal(monkeypatch):
+    """Prompt composition must never die because the outputs dir is unreadable."""
+    import backend.apps.outputs.workspace_io as io
+
+    def p_boom():
+        raise OSError("disk gone")
+
+    monkeypatch.setattr(io, "load_all", p_boom, raising=True)
+    assert p_ctx.apps_created_by_session("chat-A") == []
+
+
+def test_no_session_id_asks_the_store_nothing(monkeypatch):
+    called = {"n": 0}
+    import backend.apps.outputs.workspace_io as io
+    monkeypatch.setattr(io, "load_all", lambda: called.__setitem__("n", called["n"] + 1) or [], raising=True)
+    assert p_ctx.apps_created_by_session(None) == []
+    assert called["n"] == 0, "a session with no id must not scan every output on disk"
+
+
+def test_an_explicit_selection_always_wins():
+    """A pick is the user speaking; falling back over it would be worse than the bug."""
+    src = open(COMPOSER).read()
+    i = src.index("p_app_ids = list(selected_app_output_ids or [])")
+    body = src[i:i + 400]
+    assert "if not p_app_ids:" in body, "the fallback must be conditional on nothing being selected"
+    assert body.index("if not p_app_ids:") > 0
+
+
+def test_ownership_is_the_CHAT_not_the_sub_agent():
+    """`output.session_id` is written from parent_session_id, so a per-dispatch child id matches
+    nothing and the feature would be silently dead -- the ENG-403 mistake."""
+    src = open(COMPOSER).read()
+    i = src.index("apps_created_by_session(")
+    assert "session.parent_session_id or session.id" in src[i:i + 120]
+
+
+def test_the_common_path_pays_nothing(monkeypatch):
+    """With a selection present the outputs dir must not be scanned at all."""
+    called = {"n": 0}
+    import backend.apps.outputs.workspace_io as io
+    monkeypatch.setattr(io, "load_all", lambda: called.__setitem__("n", called["n"] + 1) or [], raising=True)
+    src = open(COMPOSER).read()
+    assert "if not p_app_ids:" in src
+    # The guard is structural; assert it directly rather than booting a whole turn.
+    assert called["n"] == 0