fix(prompts): classify every sub-8B model (2b/4b/5b/6b) as SMALL

detect_model_size only matched 1b/3b/7b, so a genuinely small model such as
qwen*:4b fell through to LARGE and got the terse, less-guided prompt set it
can't follow — contributing to off-tone, rambling replies. Extend the small
patterns to cover all sub-8B sizes (1b-7b) across :/-/_ separators and sync the
spec table.

src/jarvis/reply/prompts/model_variants.py

@@ -22,11 +22,15 @@ class ModelSize(Enum):
     LARGE = "large"  # 8b+ - can infer tool usage from context
 
 
-# Model size patterns - models matching these are considered SMALL
+# Model size patterns - models matching these are considered SMALL.
+# Covers every sub-8B size (1b-7b): these models need the explicit, repeated
+# tool/greeting/instruction constraints and falter on the terse LARGE prompt.
+# Without 2b/4b/5b/6b here a genuinely small model (e.g. qwen*:4b) was
+# misclassified as LARGE and given the less-guided prompt set.
 _SMALL_MODEL_PATTERNS = (
-    ":1b", ":3b", ":7b",
+    ":1b", ":2b", ":3b", ":4b", ":5b", ":6b", ":7b",
-    "-1b", "-3b", "-7b",
+    "-1b", "-2b", "-3b", "-4b", "-5b", "-6b", "-7b",
-    "_1b", "_3b", "_7b",
+    "_1b", "_2b", "_3b", "_4b", "_5b", "_6b", "_7b",
     "gemma4",  # Gemma 4 - always small regardless of tag
 )
 

src/jarvis/reply/prompts/prompts.spec.md

@@ -4,7 +4,7 @@ This module provides model-size-aware prompt generation for the reply engine.
 
 ### Problem Statement
 
-Small models (1b, 3b, 7b parameters) lack the reasoning capacity to infer when NOT to use tools. When given prompts like "Proactively use available tools," they may incorrectly call tools for simple greetings like "hello" or "ni hao" because they cannot distinguish between:
+Small models (every sub-8B size, 1b-7b parameters) lack the reasoning capacity to infer when NOT to use tools. When given prompts like "Proactively use available tools," they may incorrectly call tools for simple greetings like "hello" or "ni hao" because they cannot distinguish between:
 - Requests that require tools (weather, search, data retrieval)
 - Simple conversation (greetings, small talk, general knowledge)
 
@@ -14,7 +14,7 @@ The module detects model size from the model name and selects appropriate prompt
 
 | Model Size | Detection Pattern | Tool Prompts |
 |------------|-------------------|--------------|
-| SMALL | `:1b`, `:3b`, `:7b`, `gemma4` | Conservative — explicit "DO NOT use tools for greetings" + worked negative examples + repetition |
+| SMALL | `:1b`-`:7b` (every size 1-7B, all separators), `gemma4` | Conservative — explicit "DO NOT use tools for greetings" + worked negative examples + repetition |
 | LARGE | All others (8b+) | Proactive — "use tools confidently" + short anti-confabulation + auto-derive clause |
 
 ### Architecture

tests/test_prompts.py

@@ -21,9 +21,15 @@ class TestModelSizeDetection:
         ("gemma:7b", True),
         ("phi3:3b", True),
         ("qwen2:7b", True),
+        # Sub-8B sizes that were previously misclassified as LARGE.
+        ("qwen3.5:4b", True),   # the deployed model that produced weak, off-tone replies
+        ("gemma2:2b", True),
+        ("model:5b", True),
+        ("model:6b", True),
         # Various separators
         ("model-3b-instruct", True),
         ("model_1b_chat", True),
+        ("model-4b-instruct", True),
         # Large models (should return LARGE)
         ("gpt-oss:20b", False),
         ("llama3.1:8b", False),