feat: remove limit from git-base memory frontmatter and increase default to 100k (#9537)

- Remove `limit` from YAML frontmatter in `serialize_block()` and
  `merge_frontmatter_with_body()` (deprecated for git-base memory)
- Remove `limit` from `_render_memory_blocks_git()` in-context rendering
- Existing frontmatter with `limit` is automatically cleaned up on next write
- Parsing still accepts `limit` from frontmatter for backward compatibility
- Increase `CORE_MEMORY_BLOCK_CHAR_LIMIT` from 20,000 to 100,000
- Update integration tests to assert `limit` is not in frontmatter

Fixes #9536

Co-authored-by: letta-code <248085862+letta-code@users.noreply.github.com>
Co-authored-by: Sarah Wooders <sarahwooders@users.noreply.github.com>
Co-authored-by: Sarah Wooders <sarahwooders@gmail.com>

letta/constants.py

@@ -419,7 +419,7 @@ MAX_ERROR_MESSAGE_CHAR_LIMIT = 1000
 # Default memory limits
 CORE_MEMORY_PERSONA_CHAR_LIMIT: int = 20000
 CORE_MEMORY_HUMAN_CHAR_LIMIT: int = 20000
-CORE_MEMORY_BLOCK_CHAR_LIMIT: int = 20000
+CORE_MEMORY_BLOCK_CHAR_LIMIT: int = 100000
 
 # Function return limits
 FUNCTION_RETURN_CHAR_LIMIT = 50000  # ~300 words

letta/schemas/memory.py

@@ -226,8 +226,6 @@ class Memory(BaseModel, validate_assignment=True):
             front_lines = []
             if block.description:
                 front_lines.append(f"description: {block.description}")
-            if block.limit is not None:
-                front_lines.append(f"limit: {block.limit}")
             if getattr(block, "read_only", False):
                 front_lines.append("read_only: true")
 

letta/services/memory_repo/block_markdown.py

@@ -3,11 +3,11 @@
 File format:
     ---
     description: "Who I am and how I approach work"
-    limit: 20000
     ---
     My name is Memo. I'm a stateful coding assistant...
 
 - Frontmatter fields are only rendered when they differ from defaults.
+- ``limit`` is intentionally excluded from frontmatter (deprecated for git-base memory).
 - Files without frontmatter are treated as value-only (backward compat).
 """
 
@@ -37,12 +37,12 @@ def serialize_block(
     This is used for initial file creation. For updates to existing files,
     prefer `merge_frontmatter_with_body` to preserve user formatting.
     """
-    # description and limit are always included in frontmatter.
+    # description is always included in frontmatter.
     # read_only and metadata are only included when non-default.
+    # limit is intentionally excluded (deprecated for git-base memory).
     front: Dict[str, Any] = {}
 
     front["description"] = description
-    front["limit"] = limit if limit is not None else _get_field_default("limit")
 
     if read_only != _get_field_default("read_only"):
         front["read_only"] = read_only
@@ -111,7 +111,6 @@ def merge_frontmatter_with_body(
 
     # Desired values
     desired_description = description
-    desired_limit = limit if limit is not None else _get_field_default("limit")
     desired_read_only = read_only
     desired_metadata = metadata if metadata is not None else _get_field_default("metadata")
 
@@ -122,8 +121,9 @@ def merge_frontmatter_with_body(
         parsed["description"] = desired_description
         changed = True
 
-    if "limit" not in parsed or parsed.get("limit") != desired_limit:
-        parsed["limit"] = desired_limit
+    # Remove limit from frontmatter if it exists (deprecated for git-base memory)
+    if "limit" in parsed:
+        del parsed["limit"]
         changed = True
 
     if desired_read_only != _get_field_default("read_only"):