core/cli+config: attach files to a turn with @path mentions

Typing `@shot.png` in the line attaches that picture to the turn — no separate
command — and `@notes.txt` appends the file as text under a `--- @path ---`
header, capped like a tool result with a resumable `truncate_token`.
`@"my shot.png"` is the quoted form, and Tab completes the path after `@`
(directories end in `/`, a name with a space completes quoted).

An image is skipped, with a note naming the key to set, on a model without
`image_in`; a missing or denylisted path is a note too, and the turn still goes.
The default catalogs mark what can take a picture (`deepseek-flash` yes,
`deepseek-v4-pro` no, the OpenAI defaults yes).

`Agent.run` takes the parts, so the turn is stored with its images and shows up
as `[image]` wherever only prose is wanted.

src/plyngent/agent/chat.py

@@ -28,6 +28,7 @@ from .directive_checkpoint import (
     parse_checkpoint_bands,
 )
 from .events import UsageEvent
+from .images import user_content
 from .loop import DEFAULT_MAX_ROUNDS, DEFAULT_MAX_TRUNCATION_CONTINUES, run_chat_loop
 from .notices import TRUNCATED_NOTICE_KIND, notice_of_kind
 from .todo_nag import (
@@ -41,7 +42,7 @@ from .usage import TokenUsage
 if TYPE_CHECKING:
     from collections.abc import AsyncIterator, Awaitable, Callable, Sequence
 
-    from plyngent.lmproto.openai_compatible.model import AnyAssistantToolCall, AnyChatMessage
+    from plyngent.lmproto.openai_compatible.model import AnyAssistantToolCall, AnyChatMessage, ChatImagePart
     from plyngent.memory import MemoryStore
 
     from .events import AgentEvent
@@ -664,11 +665,20 @@ class ChatAgent:
             await self._persist_range(self._persist_from, len(self.messages))
         await self._persist_context_usage()
 
-    async def run(self, user_text: str) -> AsyncIterator[AgentEvent]:
-        """Append a user message (persist immediately), run the tool loop, yield events."""
+    async def run(
+        self,
+        user_text: str,
+        *,
+        images: Sequence[ChatImagePart] | None = None,
+    ) -> AsyncIterator[AgentEvent]:
+        """Append a user message (persist immediately), run the tool loop, yield events.
+
+        *images* ride along with the text as content parts, which is the shape
+        the model sees an attachment in (see ``agent.images``).
+        """
         _ = reset_lineno_tracker()
         self._ensure_system_prompt()
-        user_msg = UserChatMessage(content=user_text)
+        user_msg = UserChatMessage(content=user_content(user_text, images))
         self.messages.append(user_msg)
         await self._persist(user_msg)
         self._persist_from = len(self.messages)

src/plyngent/agent/images.py

@@ -14,8 +14,19 @@ and over. A larger image has to be resized first.
 from __future__ import annotations
 
 import base64
+from typing import TYPE_CHECKING
 
-from plyngent.lmproto.openai_compatible.model import ChatImagePart, ChatImageUrl, ImageDetail
+from plyngent.lmproto.openai_compatible.model import (
+    ChatImagePart,
+    ChatImageUrl,
+    ChatTextPart,
+    ImageDetail,
+)
+
+if TYPE_CHECKING:
+    from collections.abc import Sequence
+
+    from plyngent.lmproto.openai_compatible.model import ChatContentPart
 
 # Inline payload ceiling for one image (the API allows 32 MiB; see the module docstring).
 MAX_INLINE_IMAGE_BYTES = 8 * 1024 * 1024
@@ -74,3 +85,17 @@ def image_part_from_bytes(data: bytes, *, detail: ImageDetail = "auto") -> ChatI
 def image_part_from_url(url: str, *, detail: ImageDetail = "auto") -> ChatImagePart:
     """An image part for a public ``http(s)`` URL or an inline ``data:`` URL."""
     return ChatImagePart(image_url=ChatImageUrl(url=url, detail=detail))
+
+
+def user_content(
+    text: str,
+    images: Sequence[ChatImagePart] | None = None,
+) -> str | list[ChatContentPart]:
+    """A user turn's content: the text alone, or a part array when images ride along."""
+    if not images:
+        return text
+    parts: list[ChatContentPart] = []
+    if text:
+        parts.append(ChatTextPart(text=text))
+    parts.extend(images)
+    return parts

src/plyngent/cli/mentions.py

@@ -0,0 +1,217 @@
+"""``@path`` mentions in a REPL line: attach the file the line refers to.
+
+A mention starts a whitespace-delimited token, so an e-mail address (`a@b`) is
+not one. Both spellings work::
+
+    look at @shot.png and @src/plyngent/cli/repl.py
+    look at @"screens/my shot.png"
+
+The path resolves against the working directory (``~`` expands) and is checked
+against the path denylist, like every tool path. What is attached depends on
+the file:
+
+- an image (JPEG, PNG, GIF, WebP, sniffed from the bytes) becomes an image part,
+  so the model sees the picture itself. A model without
+  ``[providers.*.models.*].image_in`` skips it with a note instead of letting
+  the provider answer 400.
+- any other file is read as text and appended to the message under a
+  ``--- @path ---`` header, capped like a tool result; the remainder stays
+  resumable through the ``truncate_token`` in the marker.
+
+Images and text both keep the typed ``@path`` in the message, so the model can
+tell which attachment is which.
+"""
+
+from __future__ import annotations
+
+import os
+from dataclasses import dataclass, field
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+from plyngent.agent.budget import DEFAULT_TOOL_RESULT_MAX_CHARS
+from plyngent.agent.images import image_part_from_bytes, sniff_image_media_type
+from plyngent.tools.truncate_token import truncate_to_memory
+
+if TYPE_CHECKING:
+    from plyngent.cli.state import ReplState
+    from plyngent.lmproto.openai_compatible.model import ChatImagePart
+
+MENTION = "@"
+# One attached text file is capped like a tool result, and a turn's attachments
+# together cannot outgrow this (the message is re-sent on every round).
+MAX_MENTION_FILE_CHARS = DEFAULT_TOOL_RESULT_MAX_CHARS
+MAX_MENTION_TOTAL_CHARS = 64_000
+MAX_PATH_COMPLETIONS = 100
+
+
+@dataclass(frozen=True, slots=True)
+class Mention:
+    """One ``@path`` reference as it was typed."""
+
+    token: str
+    path: str
+
+
+@dataclass(slots=True)
+class MentionPayload:
+    """One turn's text plus what its mentions attached."""
+
+    text: str
+    images: list[ChatImagePart] = field(default_factory=list)
+    notes: list[str] = field(default_factory=list)
+
+
+def parse_mentions(line: str) -> list[Mention]:
+    """Every ``@path`` mention in *line*, in the order typed."""
+    mentions: list[Mention] = []
+    index = 0
+    length = len(line)
+    while index < length:
+        char = line[index]
+        if char != MENTION or (index > 0 and not line[index - 1].isspace()):
+            index += 1
+            continue
+        start = index
+        index += 1
+        if index < length and line[index] == '"':
+            end = line.find('"', index + 1)
+            if end == -1:
+                # An unterminated quote is still being typed: leave it alone.
+                break
+            path = line[index + 1 : end]
+            index = end + 1
+        else:
+            while index < length and not line[index].isspace():
+                index += 1
+            path = line[start + 1 : index]
+        if path and not path.startswith(MENTION):
+            mentions.append(Mention(token=line[start:index], path=path))
+    return mentions
+
+
+def mention_token_for(path: str) -> str:
+    """The ``@path`` spelling for *path* (quoted when it holds a space)."""
+    if any(char.isspace() for char in path):
+        return f'{MENTION}"{path}"'
+    return f"{MENTION}{path}"
+
+
+def resolve_mentions(state: ReplState, line: str) -> MentionPayload:
+    """Attach what *line*'s mentions point at; notes say what was skipped."""
+    payload = MentionPayload(text=line)
+    mentions = parse_mentions(line)
+    seen: set[str] = set()
+    for mention in mentions:
+        if mention.path in seen:
+            continue
+        seen.add(mention.path)
+        budget = MAX_MENTION_TOTAL_CHARS - (len(payload.text) - len(line))
+        note = _attach_mention(state, payload, mention, budget)
+        if note is not None:
+            payload.notes.append(note)
+    return payload
+
+
+def _attach_mention(  # noqa: PLR0911 — one early return per rejected file
+    state: ReplState,
+    payload: MentionPayload,
+    mention: Mention,
+    budget: int,
+) -> str | None:
+    """Attach one mention; a returned string is a note for the user."""
+    target = _resolve(state, mention.path)
+    if isinstance(target, str):
+        return target
+    if not target.exists():
+        return f"{mention.token}: file not found"
+    if not target.is_file():
+        return f"{mention.token}: not a file"
+    data = target.read_bytes()
+    if sniff_image_media_type(data) is not None:
+        return _attach_image(state, payload, mention, data)
+    if b"\x00" in data[:512]:
+        return f"{mention.token}: binary file skipped (only images and text are attached)"
+    if budget <= 0:
+        return f"{mention.token}: skipped, this turn's attachments are at the size cap"
+    return _attach_text(payload, mention, data, budget)
+
+
+def _resolve(state: ReplState, path: str) -> Path | str:
+    """The absolute path for a mention, or a note when it is denylisted."""
+    from plyngent.tools.context import bind_instance
+    from plyngent.tools.workspace import denylist_match
+
+    target = Path(path).expanduser()
+    if not target.is_absolute():
+        target = Path.cwd() / target
+    with bind_instance(state.instance_state):
+        denied = denylist_match(target)
+    if denied is not None:
+        return f"@{path}: matches the path denylist pattern {denied!r}"
+    return target
+
+
+def _attach_image(
+    state: ReplState,
+    payload: MentionPayload,
+    mention: Mention,
+    data: bytes,
+) -> str | None:
+    """Attach an image part, or explain why this turn cannot carry it."""
+    from plyngent.config.routing import model_config_for
+
+    model_config = model_config_for(state.provider, state.model)
+    if model_config is None or not model_config.image_in:
+        return (
+            f"{mention.token}: skipped, model {state.model!r} does not accept image input "
+            f'(set image_in = true under [providers.{state.provider_name}.models."{state.model}"])'
+        )
+    part = image_part_from_bytes(data, detail="auto")
+    if isinstance(part, str):
+        return f"{mention.token}: {part.removeprefix('error: ')}"
+    payload.images.append(part)
+    return None
+
+
+def _attach_text(payload: MentionPayload, mention: Mention, data: bytes, budget: int) -> str | None:
+    """Append a text file to the message under its own header."""
+    text = data.decode("utf-8", errors="replace")
+    # ``truncate_to_memory`` embeds the resumable token and marker itself.
+    body, token = truncate_to_memory(text, min(MAX_MENTION_FILE_CHARS, budget))
+    header = f"--- {mention.token} ({len(text)} chars{', truncated' if token is not None else ''}) ---"
+    payload.text = f"{payload.text}\n\n{header}\n{body}"
+    return None
+
+
+def complete_mention_paths(incomplete: str, *, cwd: Path | None = None) -> list[str]:
+    """Path candidates for the path part of a mention (directories end in ``/``)."""
+    base = cwd if cwd is not None else Path.cwd()
+    prefix = incomplete.rpartition("/")[2]
+    raw_dir = incomplete[: len(incomplete) - len(prefix)]
+    directory = Path(raw_dir).expanduser() if raw_dir else Path()
+    if not directory.is_absolute():
+        directory = base / directory
+    try:
+        entries = sorted(os.scandir(directory), key=lambda entry: entry.name)
+    except OSError:
+        return []
+    completions: list[str] = []
+    for entry in entries:
+        if prefix and not entry.name.startswith(prefix):
+            continue
+        if not prefix and entry.name.startswith("."):
+            continue
+        suffix = "/" if entry.is_dir() else ""
+        completions.append(f"{raw_dir}{entry.name}{suffix}")
+        if len(completions) >= MAX_PATH_COMPLETIONS:
+            break
+    return completions
+
+
+def mention_completions(token: str, *, cwd: Path | None = None) -> list[str]:
+    """Complete an ``@path`` token (including its ``@``) for readline."""
+    if not token.startswith(MENTION):
+        return []
+    paths = complete_mention_paths(token[len(MENTION) :], cwd=cwd)
+    return [mention_token_for(path) for path in paths]

src/plyngent/cli/readline_setup.py

@@ -45,12 +45,16 @@ def build_completer(state: ReplState) -> Callable[[str, int], str | None]:
     def completer(text: str, state_index: int) -> str | None:
         import readline
 
+        from plyngent.cli.mentions import mention_completions
         from plyngent.cli.slash import complete_slash_args
 
         buffer = readline.get_line_buffer()
         begidx = readline.get_begidx()
+        # An ``@path`` mention completes files wherever it sits in the line.
+        if text.startswith("@"):
+            options = mention_completions(text)
         # Completing the first token (command).
-        if begidx == 0 or (begidx > 0 and buffer[:begidx].strip() == ""):
+        elif begidx == 0 or (begidx > 0 and buffer[:begidx].strip() == ""):
             options = filter_prefix(text, slash_commands())
         else:
             head = buffer[:begidx].strip()

src/plyngent/cli/repl.py

@@ -34,6 +34,19 @@ def _echo_interrupted() -> None:
         click.echo()
 
 
+async def _send_turn(state: ReplState, text: str) -> None:
+    """Send one user turn, attaching whatever its ``@path`` mentions point at."""
+    from plyngent.cli.mentions import resolve_mentions
+
+    payload = resolve_mentions(state, text)
+    for note in payload.notes:
+        click.secho(note, fg="yellow")
+    try:
+        _ = await run_user_text_with_retries(state.agent, payload.text, images=payload.images or None)
+    finally:
+        state.expire_yolo_once()
+
+
 async def run_repl(state: ReplState) -> None:
     """Interactive chat loop with readline editing, history, and Tab completion."""
     setup_readline(state)
@@ -79,16 +92,10 @@ async def run_repl(state: ReplState) -> None:
                     text = state.pending_user_text
                     state.pending_user_text = None
                     _echo_user(text)
-                    try:
-                        _ = await run_user_text_with_retries(state.agent, text)
-                    finally:
-                        state.expire_yolo_once()
+                    await _send_turn(state, text)
                 continue
 
             _echo_user(entry)
-            try:
-                _ = await run_user_text_with_retries(state.agent, entry)
-            finally:
-                state.expire_yolo_once()
+            await _send_turn(state, entry)
         except KeyboardInterrupt:
             _echo_interrupted()

src/plyngent/cli/retry.py

@@ -13,10 +13,11 @@ from plyngent.cli.interrupt import install_sigint_router, sigint_cancels
 from plyngent.cli.limits import reset_auto_continue_turn
 
 if TYPE_CHECKING:
-    from collections.abc import AsyncIterator, Callable, Coroutine
+    from collections.abc import AsyncIterator, Callable, Coroutine, Sequence
 
     from plyngent.agent import AgentEvent
     from plyngent.agent.chat import ChatAgent
+    from plyngent.lmproto.openai_compatible.model import ChatImagePart
 
 # Auto-retry budget after the first failure (10 attempts by default).
 DEFAULT_MAX_AUTO_RETRIES = 10
@@ -238,10 +239,11 @@ async def run_user_text_with_retries(
     agent: ChatAgent,
     text: str,
     *,
+    images: Sequence[ChatImagePart] | None = None,
     delays: tuple[float, ...] = DEFAULT_RETRY_DELAYS_SECONDS,
 ) -> bool:
     """Send a new user message with auto-retry (empty ``delays`` = no auto-retry)."""
-    return await run_turn_with_retries(agent, starter=lambda: agent.run(text), delays=delays)
+    return await run_turn_with_retries(agent, starter=lambda: agent.run(text, images=images), delays=delays)
 
 
 async def retry_pending_with_retries(agent: ChatAgent) -> bool:

src/plyngent/config/models.py

@@ -344,9 +344,9 @@ class ProviderConfig(Struct, tag_field="preset", omit_defaults=True):
 def _default_openai_models() -> dict[str, ModelConfig]:
     """Current OpenAI text catalog when TOML omits ``models``."""
     return {
-        "gpt-5.4": ModelConfig(text=True),
-        "gpt-5.4-mini": ModelConfig(text=True),
-        "gpt-5.4-nano": ModelConfig(text=True),
+        "gpt-5.4": ModelConfig(text=True, image_in=True),
+        "gpt-5.4-mini": ModelConfig(text=True, image_in=True),
+        "gpt-5.4-nano": ModelConfig(text=True, image_in=True),
     }
 
 
@@ -382,9 +382,14 @@ class AnthropicProvider(ProviderConfig, tag="anthropic"):
 
 
 def _default_deepseek_models() -> dict[str, ModelConfig]:
-    """Current DeepSeek text catalog when TOML omits ``models``."""
+    """Current DeepSeek text catalog when TOML omits ``models``.
+
+    Only ``deepseek-flash`` reads pictures (JPEG, PNG, GIF, WebP in a user
+    message); ``deepseek-v4-pro`` stays text-only, so ``image_in`` is the flag
+    that decides whether a turn may carry one.
+    """
     return {
-        "deepseek-flash": ModelConfig(text=True),
+        "deepseek-flash": ModelConfig(text=True, image_in=True),
         "deepseek-v4-pro": ModelConfig(text=True),
     }
 

tests/test_agent/test_images.py

@@ -0,0 +1,80 @@
+"""Image parts: format sniffing, data URLs, and the inline size policy."""
+
+from __future__ import annotations
+
+import base64
+
+from plyngent.agent.images import (
+    MAX_INLINE_IMAGE_BYTES,
+    image_part_from_bytes,
+    image_part_from_url,
+    sniff_image_media_type,
+    split_data_url,
+    to_data_url,
+    user_content,
+)
+from plyngent.lmproto.openai_compatible.model import ChatImageUrl, ChatTextPart
+
+PNG = base64.b64decode(
+    "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg=="
+)
+
+
+def test_the_format_is_sniffed_from_the_bytes() -> None:
+    assert sniff_image_media_type(PNG) == "image/png"
+    assert sniff_image_media_type(b"\xff\xd8\xff\xe0JFIF") == "image/jpeg"
+    assert sniff_image_media_type(b"GIF89a....") == "image/gif"
+    assert sniff_image_media_type(b"RIFF\x00\x00\x00\x00WEBPVP8 ") == "image/webp"
+    assert sniff_image_media_type(b"not an image") is None
+    assert sniff_image_media_type(b"") is None
+
+
+def test_a_data_url_round_trips() -> None:
+    url = to_data_url("image/png", PNG)
+
+    assert url.startswith("data:image/png;base64,")
+    assert split_data_url(url) == ("image/png", base64.b64encode(PNG).decode("ascii"))
+    assert split_data_url("https://example.com/a.png") is None
+
+
+def test_bytes_become_an_image_part_with_a_detail_level() -> None:
+    part = image_part_from_bytes(PNG, detail="low")
+
+    assert not isinstance(part, str)
+    assert part.image_url.detail == "low"
+    assert part.image_url.url.startswith("data:image/png;base64,")
+
+
+def test_non_image_bytes_are_an_error_text() -> None:
+    result = image_part_from_bytes(b"plain text")
+
+    assert isinstance(result, str)
+    assert "not a JPEG, PNG, GIF, or WebP image" in result
+
+
+def test_an_oversized_image_is_refused() -> None:
+    result = image_part_from_bytes(PNG + b"\x00" * (MAX_INLINE_IMAGE_BYTES + 1))
+
+    assert isinstance(result, str)
+    assert "inline limit" in result
+
+
+def test_a_url_becomes_an_image_part() -> None:
+    part = image_part_from_url("https://example.com/a.jpg", detail="original")
+
+    assert part.image_url == ChatImageUrl(url="https://example.com/a.jpg", detail="original")
+
+
+def test_user_content_stays_a_string_without_images() -> None:
+    assert user_content("hello") == "hello"
+    assert user_content("hello", []) == "hello"
+
+
+def test_user_content_becomes_a_part_array_with_images() -> None:
+    part = image_part_from_url("https://example.com/a.jpg")
+
+    content = user_content("look", [part])
+
+    assert content == [ChatTextPart(text="look"), part]
+    # An image-only turn sends no empty text part.
+    assert user_content("", [part]) == [part]

tests/test_cli/test_mentions.py

@@ -0,0 +1,88 @@
+"""``@path`` mentions: parsing, token spelling, and Tab completion."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from plyngent.cli.mentions import (
+    complete_mention_paths,
+    mention_completions,
+    mention_token_for,
+    parse_mentions,
+)
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
+def _paths(line: str) -> list[str]:
+    return [mention.path for mention in parse_mentions(line)]
+
+
+def test_a_mention_is_a_whitespace_delimited_token() -> None:
+    assert _paths("look at @shot.png please") == ["shot.png"]
+    assert _paths("@a.png and @b/c.txt") == ["a.png", "b/c.txt"]
+    assert _paths("@a.png\n@b.png") == ["a.png", "b.png"]
+
+
+def test_an_email_address_is_not_a_mention() -> None:
+    assert _paths("mail me at someone@example.com") == []
+
+
+def test_a_quoted_mention_may_hold_spaces() -> None:
+    assert _paths('look at @"screens/my shot.png"') == ["screens/my shot.png"]
+    assert _paths('@"a b.png" and @c.png') == ["a b.png", "c.png"]
+
+
+def test_an_unterminated_quote_is_left_alone() -> None:
+    assert _paths('still typing @"my sh') == []
+
+
+def test_a_bare_at_sign_is_not_a_mention() -> None:
+    assert _paths("@ and @@@") == []
+
+
+def test_a_token_quotes_a_path_with_spaces() -> None:
+    assert mention_token_for("shot.png") == "@shot.png"
+    assert mention_token_for("my shot.png") == '@"my shot.png"'
+
+
+def test_completion_lists_a_directory(tmp_path: Path) -> None:
+    (tmp_path / "shot.png").write_bytes(b"")
+    (tmp_path / "screens").mkdir()
+
+    completions = complete_mention_paths("sc", cwd=tmp_path)
+
+    assert completions == ["screens/"]
+
+
+def test_completion_continues_through_a_directory(tmp_path: Path) -> None:
+    (tmp_path / "screens").mkdir()
+    (tmp_path / "screens" / "shot.png").write_bytes(b"")
+
+    assert complete_mention_paths("screens/sh", cwd=tmp_path) == ["screens/shot.png"]
+    assert complete_mention_paths("screens/", cwd=tmp_path) == ["screens/shot.png"]
+
+
+def test_completion_hides_dot_files_unless_asked(tmp_path: Path) -> None:
+    (tmp_path / ".env").write_text("x", encoding="utf-8")
+
+    assert complete_mention_paths("", cwd=tmp_path) == []
+    assert complete_mention_paths(".", cwd=tmp_path) == [".env"]
+
+
+def test_completion_ignores_a_missing_directory(tmp_path: Path) -> None:
+    assert complete_mention_paths("nope/x", cwd=tmp_path) == []
+
+
+def test_completions_keep_the_at_sign_and_quote_spaces(tmp_path: Path) -> None:
+    (tmp_path / "my shot.png").write_bytes(b"")
+    (tmp_path / "shots").mkdir()
+
+    assert mention_completions("@my", cwd=tmp_path) == ['@"my shot.png"']
+    assert mention_completions("@shots", cwd=tmp_path) == ["@shots/"]
+    assert mention_completions("@", cwd=tmp_path) == ['@"my shot.png"', "@shots/"]
+
+
+def test_mention_completions_ignores_a_plain_word() -> None:
+    assert mention_completions("shot") == []

tests/test_cli/test_readline_setup.py

@@ -170,6 +170,46 @@ def test_completer_stream_on_off(tmp_path: object, monkeypatch: object) -> None:
     assert completer("o", 1) == "off"
 
 
+def test_completer_path_mentions(tmp_path: object, monkeypatch: object) -> None:
+    """An ``@path`` token completes files, wherever it sits in the line."""
+    import readline
+    from pathlib import Path
+
+    import pytest
+
+    assert isinstance(tmp_path, Path)
+    assert isinstance(monkeypatch, pytest.MonkeyPatch)
+    (tmp_path / "shot.png").write_bytes(b"")
+    (tmp_path / "screens").mkdir()
+
+    state = _minimal_state(tmp_path)
+    completer = build_completer(state)
+    monkeypatch.setattr(readline, "get_line_buffer", lambda: "look at @sh")
+    monkeypatch.setattr(readline, "get_begidx", lambda: len("look at "))
+    monkeypatch.chdir(tmp_path)
+
+    found = [item for index in range(10) if (item := completer("@sh", index)) is not None]
+    assert found == ["@shot.png"]
+
+
+def test_a_plain_word_is_still_a_slash_argument(tmp_path: object, monkeypatch: object) -> None:
+    """The mention branch must not swallow ordinary argument completion."""
+    import readline
+    from pathlib import Path
+
+    import pytest
+
+    assert isinstance(tmp_path, Path)
+    assert isinstance(monkeypatch, pytest.MonkeyPatch)
+
+    state = _minimal_state(tmp_path)
+    completer = build_completer(state)
+    monkeypatch.setattr(readline, "get_line_buffer", lambda: "/provider r")
+    monkeypatch.setattr(readline, "get_begidx", lambda: len("/provider "))
+
+    assert completer("r", 0) == "remote"
+
+
 def test_complete_slash_args_from_registry(tmp_path: object) -> None:
     from pathlib import Path
 

tests/test_cli/test_repl_commands.py

@@ -1,14 +1,17 @@
 from __future__ import annotations
 
+import base64
 from typing import TYPE_CHECKING, Literal, overload
 
 import pytest
 import tomlkit
 
 from plyngent.agent import ChatAgent, Notice
+from plyngent.cli.mentions import resolve_mentions
+from plyngent.cli.repl import _send_turn
 from plyngent.cli.slash import handle_slash
 from plyngent.cli.state import ReplState
-from plyngent.config.models import DatabaseConfig, OpenAIProvider
+from plyngent.config.models import DatabaseConfig, ModelConfig, OpenAIProvider
 from plyngent.config.store import ConfigStore
 from plyngent.lmproto.openai_compatible.model import (
     AssistantChatMessage,
@@ -16,6 +19,9 @@ from plyngent.lmproto.openai_compatible.model import (
     ChatCompletionChunk,
     ChatCompletionResponse,
     ChatCompletionsParam,
+    ChatImagePart,
+    ChatTextPart,
+    UserChatMessage,
 )
 from plyngent.memory import MemoryStore
 
@@ -24,6 +30,17 @@ if TYPE_CHECKING:
     from pathlib import Path
 
 
+# A real 1x1 PNG: ``/image`` sniffs the format from these bytes.
+_PNG = base64.b64decode(
+    "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg=="
+)
+
+
+def _accept_images(state: ReplState) -> None:
+    """Mark the fixture's model as taking pictures (the config default is text-only)."""
+    state.provider.models[state.model] = ModelConfig(image_in=True)
+
+
 class DummyClient:
     @overload
     async def chat_completions(
@@ -543,7 +560,7 @@ async def test_repl_ctrl_c_from_turn_returns_to_prompt(
             raise EOFError
         return "hello"
 
-    async def interrupted_turn(_agent: object, _text: str) -> bool:
+    async def interrupted_turn(_agent: object, _text: str, **_kwargs: object) -> bool:
         raise KeyboardInterrupt
 
     monkeypatch.setattr(repl_mod, "setup_readline", lambda _state: None)
@@ -573,7 +590,7 @@ async def test_repl_second_ctrl_c_after_cancel_returns_to_prompt(
             raise EOFError
         return reads[calls["reads"] - 1]
 
-    async def cancel_turn(_agent: object, _text: str) -> bool:
+    async def cancel_turn(_agent: object, _text: str, **_kwargs: object) -> bool:
         raise KeyboardInterrupt  # first Ctrl+C: cancels every turn
 
     def echo_user(text: str) -> None:
@@ -780,3 +797,61 @@ async def test_todos_update_takes_a_listing_number(state: ReplState, capsys: pyt
 
     assert await handle_slash(state, "/todos pop") is True
     assert "popped TOP group (first, second)" in capsys.readouterr().out
+
+
+async def test_a_mention_attaches_the_picture_to_the_turn(state: ReplState, tmp_path: Path) -> None:
+    _accept_images(state)
+    shot = tmp_path / "shot.png"
+    _ = shot.write_bytes(_PNG)
+    state.agent.stream = False
+
+    payload = resolve_mentions(state, f"look at @{shot}")
+    assert payload.notes == []
+    assert len(payload.images) == 1
+    assert payload.text == f"look at @{shot}"
+
+    await _send_turn(state, payload.text)
+    user = next(m for m in state.agent.messages if isinstance(m, UserChatMessage))
+    assert isinstance(user.content, list)
+    text_part, image_part = user.content
+    assert isinstance(text_part, ChatTextPart)
+    assert text_part.text == f"look at @{shot}"
+    assert isinstance(image_part, ChatImagePart)
+    assert image_part.image_url.url.startswith("data:image/png;base64,")
+
+
+async def test_a_mention_inlines_a_text_file(state: ReplState, tmp_path: Path) -> None:
+    notes = tmp_path / "notes.txt"
+    _ = notes.write_text("the deploy needs acme", encoding="utf-8")
+
+    payload = resolve_mentions(state, f"read @{notes}")
+
+    assert payload.images == []
+    assert payload.notes == []
+    assert payload.text.startswith(f"read @{notes}")
+    assert f"--- @{notes} (21 chars) ---" in payload.text
+    assert payload.text.endswith("the deploy needs acme")
+
+
+async def test_a_mention_of_a_missing_file_is_a_note(state: ReplState, tmp_path: Path) -> None:
+    payload = resolve_mentions(state, "@nope.png is gone")
+
+    assert payload.images == []
+    assert payload.notes == ["@nope.png: file not found"]
+    assert payload.text == "@nope.png is gone"
+
+
+async def test_a_picture_mention_is_skipped_for_a_text_only_model(
+    state: ReplState,
+    tmp_path: Path,
+) -> None:
+    """``image_in`` is the gate: a text-only model never receives a picture."""
+    shot = tmp_path / "shot.png"
+    _ = shot.write_bytes(_PNG)
+
+    payload = resolve_mentions(state, f"@{shot}")
+
+    assert payload.images == []
+    note = payload.notes[0]
+    assert "does not accept image input" in note
+    assert "image_in = true" in note