feat: /model display, /diff, cost estimation, multiline input

- /model without args now shows current model (inspired by PR #4)
- /diff lists files modified by edit_file/write_file this session
- /tokens shows estimated cost for known models (GPT-4o, DeepSeek, etc.)
- Multiline input via Esc+Enter, Enter still submits
- Fix __version__ 0.1.0 -> 0.2.0 mismatch with pyproject.toml

Author: he-yufeng

README.md

@@ -139,9 +139,11 @@ class HttpTool(Tool):
 ## Commands
 
 ```
+/model           Show current model
 /model <name>    Switch model mid-conversation
 /compact         Compress context (like Claude Code's /compact)
-/tokens          Token usage
+/tokens          Token usage + cost estimate
+/diff            Show files modified this session
 /save            Save session to disk
 /sessions        List saved sessions
 /reset           Clear history

README_CN.md

@@ -139,9 +139,11 @@ class HttpTool(Tool):
 ## 命令
 
 ```
+/model           查看当前模型
 /model <名称>    切换模型
 /compact         压缩上下文（对标 Claude Code 的 /compact）
-/tokens          查看 token 用量
+/tokens          查看 token 用量 + 费用估算
+/diff            查看本次会话修改的文件
 /save            保存会话
 /sessions        列出已保存的会话
 /reset           清空历史

corecoder/__init__.py

@@ -1,6 +1,6 @@
 """CoreCoder - Minimal AI coding agent inspired by Claude Code's architecture."""
 
-__version__ = "0.1.0"
+__version__ = "0.2.0"
 
 from corecoder.agent import Agent
 from corecoder.llm import LLM

corecoder/cli.py

@@ -9,6 +9,7 @@
 from rich.panel import Panel
 from prompt_toolkit import prompt as pt_prompt
 from prompt_toolkit.history import FileHistory
+from prompt_toolkit.key_binding import KeyBindings
 
 from .agent import Agent
 from .llm import LLM
@@ -118,9 +119,26 @@ def _repl(agent: Agent, config: Config):
     hist_path = os.path.expanduser("~/.corecoder_history")
     history = FileHistory(hist_path)
 
+    # Enter submits, Escape+Enter inserts a newline (for pasting code blocks etc.)
+    kb = KeyBindings()
+
+    @kb.add("enter")
+    def _submit(event):
+        event.current_buffer.validate_and_handle()
+
+    @kb.add("escape", "enter")
+    def _newline(event):
+        event.current_buffer.insert_text("\n")
+
     while True:
         try:
-            user_input = pt_prompt("You > ", history=history).strip()
+            user_input = pt_prompt(
+                "You > ",
+                history=history,
+                multiline=True,
+                key_bindings=kb,
+                prompt_continuation="...  ",
+            ).strip()
         except (EOFError, KeyboardInterrupt):
             console.print("\nBye!")
             break
@@ -141,14 +159,20 @@ def _repl(agent: Agent, config: Config):
         if user_input == "/tokens":
             p = agent.llm.total_prompt_tokens
             c = agent.llm.total_completion_tokens
-            console.print(f"Tokens used this session: [cyan]{p}[/cyan] prompt + [cyan]{c}[/cyan] completion = [bold]{p+c}[/bold] total")
+            line = f"Tokens: [cyan]{p}[/cyan] prompt + [cyan]{c}[/cyan] completion = [bold]{p+c}[/bold] total"
+            cost = agent.llm.estimated_cost
+            if cost is not None:
+                line += f"  (~${cost:.4f})"
+            console.print(line)
             continue
-        if user_input.startswith("/model "):
-            new_model = user_input[7:].strip()
+        if user_input == "/model" or user_input.startswith("/model "):
+            new_model = user_input[7:].strip() if user_input.startswith("/model ") else ""
             if new_model:
                 agent.llm.model = new_model
                 config.model = new_model
                 console.print(f"Switched to [cyan]{new_model}[/cyan]")
+            else:
+                console.print(f"Current model: [cyan]{config.model}[/cyan]")
             continue
         if user_input == "/compact":
             from .context import estimate_tokens
@@ -165,6 +189,15 @@ def _repl(agent: Agent, config: Config):
             console.print(f"[green]Session saved: {sid}[/green]")
             console.print(f"Resume with: corecoder -r {sid}")
             continue
+        if user_input == "/diff":
+            from .tools.edit import _changed_files
+            if not _changed_files:
+                console.print("[dim]No files modified this session.[/dim]")
+            else:
+                console.print(f"[bold]Files modified this session ({len(_changed_files)}):[/bold]")
+                for f in sorted(_changed_files):
+                    console.print(f"  [cyan]{f}[/cyan]")
+            continue
         if user_input == "/sessions":
             sessions = list_sessions()
             if not sessions:
@@ -202,12 +235,18 @@ def _show_help():
         "[bold]Commands:[/bold]\n"
         "  /help          Show this help\n"
         "  /reset         Clear conversation history\n"
+        "  /model         Show current model\n"
         "  /model <name>  Switch model mid-conversation\n"
         "  /tokens        Show token usage\n"
         "  /compact       Compress conversation context\n"
+        "  /diff          Show files modified this session\n"
         "  /save          Save session to disk\n"
         "  /sessions      List saved sessions\n"
-        "  quit           Exit CoreCoder",
+        "  quit           Exit CoreCoder\n"
+        "\n"
+        "[bold]Input:[/bold]\n"
+        "  Enter          Submit message\n"
+        "  Esc+Enter      Insert newline (for pasting code)",
         title="CoreCoder Help",
         border_style="dim",
     ))

corecoder/llm.py

@@ -45,6 +45,25 @@ def message(self) -> dict:
         return msg
 
 
+# pricing per million tokens: (input, output)
+_PRICING = {
+    "gpt-4o": (2.5, 10),
+    "gpt-4o-mini": (0.15, 0.6),
+    "gpt-4.1": (2, 8),
+    "gpt-4.1-mini": (0.4, 1.6),
+    "gpt-4.1-nano": (0.1, 0.4),
+    "o3": (2, 8),
+    "o4-mini": (1.1, 4.4),
+    "deepseek-chat": (0.27, 1.10),
+    "deepseek-reasoner": (0.55, 2.19),
+    "claude-sonnet-4-6": (3, 15),
+    "claude-opus-4-6": (15, 75),
+    "claude-haiku-4-5": (0.8, 4),
+    "qwen-max": (1.6, 6.4),
+    "kimi-k2.5": (0.7, 2.8),
+}
+
+
 class LLM:
     def __init__(
         self,
@@ -59,6 +78,18 @@ def __init__(
         self.total_prompt_tokens = 0
         self.total_completion_tokens = 0
 
+    @property
+    def estimated_cost(self) -> float | None:
+        """Rough cost estimate in USD. Returns None if model not in pricing table."""
+        pricing = _PRICING.get(self.model)
+        if not pricing:
+            return None
+        input_rate, output_rate = pricing
+        return (
+            self.total_prompt_tokens * input_rate / 1_000_000
+            + self.total_completion_tokens * output_rate / 1_000_000
+        )
+
     def chat(
         self,
         messages: list[dict],

corecoder/tools/edit.py

@@ -11,6 +11,9 @@
 
 from .base import Tool
 
+# track files changed this session for /diff
+_changed_files: set[str] = set()
+
 
 class EditFileTool(Tool):
     name = "edit_file"
@@ -61,6 +64,7 @@ def execute(self, file_path: str, old_string: str, new_string: str) -> str:
 
             new_content = content.replace(old_string, new_string, 1)
             p.write_text(new_content)
+            _changed_files.add(str(p))
 
             # generate a unified diff so the user/LLM can see exactly what changed
             diff = _unified_diff(content, new_content, str(p))

corecoder/tools/write.py

@@ -2,6 +2,7 @@
 
 from pathlib import Path
 from .base import Tool
+from .edit import _changed_files
 
 
 class WriteFileTool(Tool):
@@ -30,6 +31,7 @@ def execute(self, file_path: str, content: str) -> str:
             p = Path(file_path).expanduser().resolve()
             p.parent.mkdir(parents=True, exist_ok=True)
             p.write_text(content)
+            _changed_files.add(str(p))
             n_lines = content.count("\n") + (1 if content and not content.endswith("\n") else 0)
             return f"Wrote {n_lines} lines to {file_path}"
         except Exception as e:

tests/test_core.py

@@ -10,7 +10,7 @@
 
 
 def test_version():
-    assert __version__ == "0.1.0"
+    assert __version__ == "0.2.0"
 
 
 def test_public_api_exports():