diff --git a/coworker/agent.py b/coworker/agent.py
index 9ed546fa..0b30a1a3 100644
--- a/coworker/agent.py
+++ b/coworker/agent.py
@@ -25,7 +25,7 @@
 from .environment import environment_context
 from .memory import MemoryStore, Scope, format_memories, memory_tools
 from .permissions import Mode, PermissionEngine
-from .project import load_agents_md
+from .project import load_agents_md, load_wiki_index
 from .roots import RootDir, normalize_roots, render_context
 from .providers import ProviderClient, ProviderRouter
 from .overrides import RiskOverrideStore
@@ -280,6 +280,9 @@ def build_engine(
         conventions = load_agents_md(ws)
         if conventions:
             instructions = f"{instructions}\n\n{conventions}"
+        wiki = load_wiki_index(ws)
+        if wiki:
+            instructions = f"{instructions}\n\n{wiki}"
 
     if memory_store is not None:
         registry.register_all(
diff --git a/coworker/project.py b/coworker/project.py
index c4775819..02229af7 100644
--- a/coworker/project.py
+++ b/coworker/project.py
@@ -1,4 +1,4 @@
-"""Project context — AGENTS.md ingestion (root + global) into the system prompt."""
+"""Project context — AGENTS.md + knowledge-wiki ingestion into the system prompt."""
 
 from __future__ import annotations
 
@@ -38,3 +38,34 @@ def load_agents_md(
         for label, text in parts
     ]
     return "Project conventions:\n" + "\n\n".join(blocks)
+
+
+# Knowledge-wiki index injection. Convention: a workspace that maintains a
+# long-lived knowledge base keeps it as markdown pages under `wiki/` with an
+# `INDEX.md` map-of-content. Injecting ONLY the index (progressive disclosure,
+# same trick as the skills catalog) gives every session standing knowledge of
+# what is known — pages load on demand via the normal file tools — at a context
+# cost that stays flat as the wiki grows.
+_WIKI_INDEX_CAP = 6_000  # chars; an index past this is a wiki smell, not a need
+
+
+def load_wiki_index(workspace: str | Path) -> str:
+    """System-prompt block from `<workspace>/wiki/INDEX.md`, if present."""
+    index = Path(workspace).expanduser().resolve() / "wiki" / "INDEX.md"
+    if not index.is_file():
+        return ""
+    try:
+        text = index.read_text(encoding="utf-8").strip()
+    except OSError:
+        return ""
+    if not text:
+        return ""
+    if len(text) > _WIKI_INDEX_CAP:
+        text = text[:_WIKI_INDEX_CAP] + "\n… (index truncated — trim it; an index is a map, not a page)"
+    return (
+        "This workspace maintains a knowledge wiki (markdown pages under `wiki/`, "
+        "linked with [[wikilinks]]). Its index follows. Open pages on demand with "
+        "the file tools; when you learn something durable that changes a page's "
+        "claims, revise that page in place rather than appending duplicates.\n"
+        f"<wiki INDEX.md>\n{text}\n</wiki INDEX.md>"
+    )
diff --git a/tests/test_skills.py b/tests/test_skills.py
index 203d163f..4465c512 100644
--- a/tests/test_skills.py
+++ b/tests/test_skills.py
@@ -101,3 +101,35 @@ def test_build_engine_code_has_agents_md_and_skills(tmp_path):
         assert engine.agent_name == "code"
     finally:
         engine.executor.close()
+
+
+def test_build_engine_injects_wiki_index(tmp_path):
+    (tmp_path / "wiki").mkdir()
+    (tmp_path / "wiki" / "INDEX.md").write_text(
+        "# Home Wiki\n- [[adrian/heart-rate]] — baselines\n"
+    )
+    engine = build_engine(agent=code_agent(), workspace=tmp_path, provider=_Stub())
+    try:
+        sys_msg = engine.messages[0]["content"]
+        assert "knowledge wiki" in sys_msg
+        assert "[[adrian/heart-rate]]" in sys_msg
+        assert "revise that page in place" in sys_msg
+    finally:
+        engine.executor.close()
+
+
+def test_no_wiki_no_injection(tmp_path):
+    engine = build_engine(agent=code_agent(), workspace=tmp_path, provider=_Stub())
+    try:
+        assert "knowledge wiki" not in engine.messages[0]["content"]
+    finally:
+        engine.executor.close()
+
+
+def test_wiki_index_truncated_when_huge(tmp_path):
+    (tmp_path / "wiki").mkdir()
+    (tmp_path / "wiki" / "INDEX.md").write_text("x" * 10_000)
+    from coworker.project import load_wiki_index
+
+    block = load_wiki_index(tmp_path)
+    assert "index truncated" in block and len(block) < 7_000