Merge remote-tracking branch 'origin/develop' into work/T-661-memory-document

Cargo.lock

@@ -6383,6 +6383,7 @@ dependencies = [
 name = "yoi-workspace-server"
 version = "0.1.0"
 dependencies = [
+ "agen",
  "async-trait",
  "axum",
  "chrono",
@@ -6410,6 +6411,7 @@ dependencies = [
  "tokio",
  "tokio-tungstenite 0.29.0",
  "toml",
+ "tools",
  "tower",
  "tracing",
  "tracing-subscriber",
@@ -6421,6 +6423,7 @@ dependencies = [
  "workdir",
  "worker",
  "worker-runtime",
+ "yoi",
  "zeroize",
 ]
 

crates/fs-operation/src/lib.rs

@@ -15,7 +15,8 @@ use thiserror::Error;
 
 pub use glob::run_glob;
 pub use local::{
-    resolve_access_path, run_edit, run_list, run_read, run_read_bounded, run_stat, run_write,
+    resolve_access_path, run_edit, run_list, run_read, run_read_bounded, run_read_bytes,
+    run_read_bytes_bounded, run_stat, run_write,
 };
 pub use operation::*;
 pub use search::run_grep;
@@ -569,6 +570,103 @@ mod tests {
         }
     }
 
+    #[test]
+    fn bounded_byte_reads_preserve_binary_ranges_and_fence_versions() {
+        let directory = tempfile::tempdir().unwrap();
+        let root = directory.path().canonicalize().unwrap();
+        let original = b"\x89PNG\r\n\x1a\n\0line\n\xfftail";
+        std::fs::write(root.join("image.bin"), original).unwrap();
+        let access = RootAccess(root.clone());
+        let limits = BoundedReadLimits::new(1024, 8).unwrap();
+
+        let first = run_read_bytes_bounded(
+            &root,
+            ReadBytesRequest {
+                path: FsPath::new("image.bin").unwrap(),
+                offset: 0,
+                max_bytes: 8,
+                expected_hash: None,
+            },
+            &access,
+            limits,
+        )
+        .unwrap();
+        assert_eq!(first.bytes, original[..8]);
+        assert_eq!(first.total_bytes, original.len() as u64);
+        assert!(!first.eof);
+
+        let second = run_read_bytes_bounded(
+            &root,
+            ReadBytesRequest {
+                path: FsPath::new("image.bin").unwrap(),
+                offset: 8,
+                max_bytes: 8,
+                expected_hash: Some(first.content_hash),
+            },
+            &access,
+            limits,
+        )
+        .unwrap();
+        assert_eq!(second.bytes, original[8..16]);
+        assert_eq!(second.content_hash, first.content_hash);
+
+        std::fs::write(root.join("image.bin"), b"different bytes long!").unwrap();
+        let error = run_read_bytes_bounded(
+            &root,
+            ReadBytesRequest {
+                path: FsPath::new("image.bin").unwrap(),
+                offset: 16,
+                max_bytes: 8,
+                expected_hash: Some(first.content_hash),
+            },
+            &access,
+            limits,
+        )
+        .expect_err("a later chunk must not cross file versions");
+        assert!(matches!(error, FsError::Conflict(_)));
+    }
+
+    #[test]
+    fn bounded_byte_reads_reject_request_and_source_limit_overflow() {
+        let directory = tempfile::tempdir().unwrap();
+        let root = directory.path().canonicalize().unwrap();
+        std::fs::write(root.join("image.bin"), [0_u8; 17]).unwrap();
+        let access = RootAccess(root.clone());
+        let limits = BoundedReadLimits::new(16, 8).unwrap();
+
+        let response_error = run_read_bytes_bounded(
+            &root,
+            ReadBytesRequest {
+                path: FsPath::new("image.bin").unwrap(),
+                offset: 0,
+                max_bytes: 9,
+                expected_hash: None,
+            },
+            &access,
+            limits,
+        )
+        .expect_err("requests above the response ceiling must be rejected");
+        assert!(
+            matches!(response_error, FsError::InvalidArgument(message) if message.contains("8 bytes"))
+        );
+
+        let source_error = run_read_bytes_bounded(
+            &root,
+            ReadBytesRequest {
+                path: FsPath::new("image.bin").unwrap(),
+                offset: 0,
+                max_bytes: 8,
+                expected_hash: None,
+            },
+            &access,
+            limits,
+        )
+        .expect_err("sources above the provider ceiling must be rejected");
+        assert!(
+            matches!(source_error, FsError::InvalidArgument(message) if message.contains("provider limit 16"))
+        );
+    }
+
     #[test]
     fn cancellation_stops_a_read_already_in_progress() {
         use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};

crates/fs-operation/src/local.rs

@@ -7,8 +7,9 @@ use sha2::{Digest, Sha256};
 
 use crate::{
     AtomicWriteMode, BoundedReadLimits, ContentHash, EditRequest, EditResult, EntryKind,
-    FsAccessPolicy, FsError, FsPath, ListEntry, ListRequest, ListResult, ReadRequest, ReadResult,
-    StatRequest, StatResult, WriteRequest, WriteResult, direct_symlink,
+    FsAccessPolicy, FsError, FsPath, ListEntry, ListRequest, ListResult, ReadBytesRequest,
+    ReadBytesResult, ReadRequest, ReadResult, StatRequest, StatResult, WriteRequest, WriteResult,
+    direct_symlink,
 };
 
 const READ_BUFFER_BYTES: usize = 16 * 1024;
@@ -195,6 +196,137 @@ fn run_read_with_limits(
     })
 }
 
+pub fn run_read_bytes(
+    root: &Path,
+    request: ReadBytesRequest,
+    access: &dyn FsAccessPolicy,
+) -> Result<ReadBytesResult, FsError> {
+    run_read_bytes_with_limits(root, request, access, None)
+}
+
+pub fn run_read_bytes_bounded(
+    root: &Path,
+    request: ReadBytesRequest,
+    access: &dyn FsAccessPolicy,
+    limits: BoundedReadLimits,
+) -> Result<ReadBytesResult, FsError> {
+    run_read_bytes_with_limits(root, request, access, Some(limits))
+}
+
+fn run_read_bytes_with_limits(
+    root: &Path,
+    request: ReadBytesRequest,
+    access: &dyn FsAccessPolicy,
+    limits: Option<BoundedReadLimits>,
+) -> Result<ReadBytesResult, FsError> {
+    let logical = request.path;
+    if request.max_bytes == 0 {
+        return Err(FsError::InvalidArgument(
+            "byte read max_bytes must be greater than zero".to_string(),
+        ));
+    }
+    if let Some(limits) = limits
+        && request.max_bytes > limits.max_response_bytes
+    {
+        return Err(FsError::InvalidArgument(format!(
+            "byte read response limit is {} bytes",
+            limits.max_response_bytes
+        )));
+    }
+
+    access
+        .check_cancelled()
+        .map_err(|error| map_io(&logical, error))?;
+    let path = resolve(root, &logical)?;
+    let target = require_access(&path, &logical, access, false, false)?;
+    let file = access
+        .open_read_file(&path, &target)
+        .map_err(|error| map_io(&logical, error))?;
+    let metadata = file.metadata().map_err(|error| map_io(&logical, error))?;
+    if metadata.is_dir() {
+        return Err(FsError::IsDirectory(PathBuf::from(logical.as_str())));
+    }
+    if !metadata.is_file() {
+        return Err(FsError::InvalidArgument(
+            "byte read source must be a regular file".to_string(),
+        ));
+    }
+    if let Some(limits) = limits
+        && metadata.len() > limits.max_source_bytes
+    {
+        return Err(FsError::InvalidArgument(format!(
+            "byte read source exceeds provider limit {}",
+            limits.max_source_bytes
+        )));
+    }
+
+    let mut bytes = Vec::with_capacity(request.max_bytes.min(READ_BUFFER_BYTES));
+    let mut source_bytes = 0_u64;
+    let mut hasher = Sha256::new();
+    let mut reader = BufReader::with_capacity(READ_BUFFER_BYTES, file);
+    let mut buffer = [0_u8; READ_BUFFER_BYTES];
+    loop {
+        access
+            .check_cancelled()
+            .map_err(|error| map_io(&logical, error))?;
+        let read_limit = limits
+            .map(|limits| {
+                limits
+                    .max_source_bytes
+                    .saturating_sub(source_bytes)
+                    .saturating_add(1)
+                    .min(READ_BUFFER_BYTES as u64) as usize
+            })
+            .unwrap_or(READ_BUFFER_BYTES);
+        let read = reader
+            .read(&mut buffer[..read_limit])
+            .map_err(|error| map_io(&logical, error))?;
+        if read == 0 {
+            break;
+        }
+        let chunk_start = source_bytes;
+        source_bytes = source_bytes.saturating_add(read as u64);
+        if let Some(limits) = limits
+            && source_bytes > limits.max_source_bytes
+        {
+            return Err(FsError::InvalidArgument(format!(
+                "byte read source exceeds provider limit {}",
+                limits.max_source_bytes
+            )));
+        }
+        hasher.update(&buffer[..read]);
+
+        if bytes.len() < request.max_bytes && source_bytes > request.offset {
+            let start = request.offset.saturating_sub(chunk_start).min(read as u64) as usize;
+            let retained = (request.max_bytes - bytes.len()).min(read - start);
+            bytes.extend_from_slice(&buffer[start..start + retained]);
+        }
+    }
+
+    let content_hash: ContentHash = hasher.finalize().into();
+    if request
+        .expected_hash
+        .is_some_and(|expected| expected != content_hash)
+    {
+        return Err(FsError::Conflict(logical.as_str().to_string()));
+    }
+    if request.offset > source_bytes {
+        return Err(FsError::InvalidArgument(format!(
+            "byte offset {} exceeds file size {source_bytes}",
+            request.offset
+        )));
+    }
+    let eof = request.offset.saturating_add(bytes.len() as u64) == source_bytes;
+    Ok(ReadBytesResult {
+        path: logical,
+        bytes,
+        offset: request.offset,
+        total_bytes: source_bytes,
+        content_hash,
+        eof,
+    })
+}
+
 pub fn run_write(
     root: &Path,
     request: WriteRequest,

crates/fs-operation/src/operation.rs

@@ -207,6 +207,36 @@ pub struct ReadResult {
     pub truncated: bool,
 }
 
+/// Binary-safe byte range read with an optional whole-file version fence.
+///
+/// Unlike [`ReadRequest`], offsets and limits are bytes rather than lines. The
+/// provider still hashes the complete bounded source so callers can reject
+/// chunks from different file versions.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub struct ReadBytesRequest {
+    pub path: FsPath,
+    #[schemars(range(min = 0, max = 9_007_199_254_740_991_u64))]
+    pub offset: u64,
+    #[schemars(range(min = 1, max = 9_007_199_254_740_991_usize))]
+    pub max_bytes: usize,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub expected_hash: Option<ContentHash>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub struct ReadBytesResult {
+    pub path: FsPath,
+    pub bytes: Vec<u8>,
+    #[schemars(range(min = 0, max = 9_007_199_254_740_991_u64))]
+    pub offset: u64,
+    #[schemars(range(min = 0, max = 9_007_199_254_740_991_u64))]
+    pub total_bytes: u64,
+    pub content_hash: ContentHash,
+    pub eof: bool,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 #[serde(deny_unknown_fields)]
 pub struct WriteRequest {

crates/tools/src/view_image.rs

@@ -7,12 +7,14 @@ use agen::tool::{
 };
 use async_trait::async_trait;
 use serde::Deserialize;
-use workdir::{ReadRequest, WorkdirPath, WorkdirSessionHandle, WorkdirSessionRouter};
+use workdir::{ReadBytesRequest, WorkdirPath, WorkdirSessionHandle, WorkdirSessionRouter};
 
 use crate::error::ToolsError;
 
 /// Maximum image body accepted for one model request.
 pub const MAX_IMAGE_BYTES: usize = 10 * 1024 * 1024;
+/// One binary response remains within the External Workdir transport bound.
+const IMAGE_READ_CHUNK_BYTES: usize = 1024 * 1024;
 
 const DESCRIPTION: &str = "Attach an image from the selected Workdir attachment to the next model request. \
 The path must be logical and Workdir-relative. Supported formats: PNG, JPEG, GIF, and WebP. \
@@ -47,42 +49,111 @@ impl Tool for ViewImageTool {
             workdir::WorkdirSessionCapability::Read,
         )?;
         let path = WorkdirPath::new(&input.path).map_err(ToolsError::from)?;
-        let result = selected
-            .session
-            .read(ReadRequest {
-                path: path.clone(),
-                offset: 0,
-                limit: usize::MAX,
-                // The scoped provider enforces this cap while reading, rather
-                // than allocating an unbounded binary body first.
-                max_bytes: MAX_IMAGE_BYTES + 1,
-            })
+        let bytes = read_image_bytes(selected.session.as_ref(), path.clone())
             .await
             .map_err(ToolsError::from)?;
-
-        if result.truncated || result.bytes.len() > MAX_IMAGE_BYTES {
-            return Err(ToolError::InvalidArgument(format!(
-                "image exceeds the {MAX_IMAGE_BYTES}-byte limit"
-            )));
-        }
-        let mime_type = detect_image_mime(&result.bytes).ok_or_else(|| {
+        let mime_type = detect_image_mime(&bytes).ok_or_else(|| {
             ToolError::InvalidArgument(
                 "unsupported image; expected PNG, JPEG, GIF, or WebP bytes".to_string(),
             )
         })?;
-        let bytes = result.bytes.len();
+        let byte_count = bytes.len();
 
         Ok(ToolOutput {
-            summary: format!("Attached image {path} ({mime_type}, {bytes} bytes)"),
+            summary: format!("Attached image {path} ({mime_type}, {byte_count} bytes)"),
             content: None,
             attachments: vec![Attachment::Image(ImageAttachment::new(
                 mime_type,
-                Arc::<[u8]>::from(result.bytes),
+                Arc::<[u8]>::from(bytes),
             ))],
         })
     }
 }
 
+async fn read_image_bytes(
+    session: &dyn workdir::WorkdirSession,
+    path: WorkdirPath,
+) -> Result<Vec<u8>, workdir::WorkdirError> {
+    let mut bytes = Vec::new();
+    let mut offset = 0_u64;
+    let mut expected_hash = None;
+    let mut expected_total = None;
+
+    loop {
+        let remaining = expected_total
+            .map(|total: u64| total.saturating_sub(offset) as usize)
+            .unwrap_or(IMAGE_READ_CHUNK_BYTES);
+        let request_bytes = remaining.min(IMAGE_READ_CHUNK_BYTES).max(1);
+        let result = session
+            .read_bytes(ReadBytesRequest {
+                path: path.clone(),
+                offset,
+                max_bytes: request_bytes,
+                expected_hash,
+            })
+            .await?;
+
+        if result.path != path || result.offset != offset {
+            return Err(workdir::WorkdirError::Transport(
+                "bounded binary read returned a mismatched path or offset".to_string(),
+            ));
+        }
+        if result.bytes.len() > request_bytes {
+            return Err(workdir::WorkdirError::Transport(
+                "bounded binary read exceeded the requested response size".to_string(),
+            ));
+        }
+        let end = result
+            .offset
+            .checked_add(result.bytes.len() as u64)
+            .ok_or_else(|| {
+                workdir::WorkdirError::Transport(
+                    "bounded binary read returned an invalid byte range".to_string(),
+                )
+            })?;
+        if end > result.total_bytes || result.eof != (end == result.total_bytes) {
+            return Err(workdir::WorkdirError::Transport(
+                "bounded binary read returned a truncated or invalid byte range".to_string(),
+            ));
+        }
+        if result.total_bytes > MAX_IMAGE_BYTES as u64 {
+            return Err(workdir::WorkdirError::InvalidArgument(format!(
+                "image exceeds the {MAX_IMAGE_BYTES}-byte limit"
+            )));
+        }
+        if expected_total.is_some_and(|total| total != result.total_bytes)
+            || expected_hash.is_some_and(|hash| hash != result.content_hash)
+        {
+            return Err(workdir::WorkdirError::Conflict(
+                "image changed while it was being read; retry ViewImage".to_string(),
+            ));
+        }
+        if expected_total.is_none() {
+            bytes
+                .try_reserve_exact(result.total_bytes as usize)
+                .map_err(|_| workdir::WorkdirError::OperationFailed)?;
+            expected_total = Some(result.total_bytes);
+            expected_hash = Some(result.content_hash);
+        }
+
+        if result.bytes.is_empty() && !result.eof {
+            return Err(workdir::WorkdirError::Transport(
+                "bounded binary read made no progress".to_string(),
+            ));
+        }
+        bytes.extend_from_slice(&result.bytes);
+        offset = end;
+        if result.eof {
+            if bytes.len() as u64 != result.total_bytes {
+                return Err(workdir::WorkdirError::Transport(
+                    "bounded binary read returned a partial image".to_string(),
+                ));
+            }
+            return Ok(bytes);
+        }
+    }
+}
+
 pub fn view_image_tool(session: WorkdirSessionHandle) -> ToolDefinition {
     routed_view_image_tool(crate::routing::singleton_router(session))
 }

crates/tools/tests/integration.rs

@@ -18,7 +18,9 @@ use tools::{
     Tracker, core_builtin_tools, routed_builtin_tools, routed_view_image_tool, view_image_tool,
 };
 use workdir::{
-    LocalWorkdirSession, WorkdirAttachmentAlias, WorkdirSessionHandle, WorkdirSessionRouter,
+    LocalWorkdirSession, WorkdirAttachmentAlias, WorkdirPath, WorkdirSessionHandle,
+    WorkdirSessionRouter, WorkdirToolBroker, WorkdirToolScope, WorkdirToolScopePermission,
+    WorkdirToolScopeRule,
 };
 
 fn scope_with_spill(workspace: &Path, spill: &Path) -> Scope {
@@ -94,6 +96,33 @@ fn setup_routed() -> (
     (left, right, spill, router, Registry::new(definitions))
 }
 
+fn valid_gif_with_len(target_len: usize) -> Vec<u8> {
+    let fixture = include_bytes!("fixtures/view-image/valid.gif");
+    assert_eq!(
+        fixture.last(),
+        Some(&0x3b),
+        "GIF fixture must end in trailer"
+    );
+    let mut bytes = fixture[..fixture.len() - 1].to_vec();
+    bytes.extend_from_slice(&[0x21, 0xfe]);
+    let mut remaining = target_len
+        .checked_sub(bytes.len() + 2)
+        .expect("target must leave room for comment terminator and GIF trailer");
+    while remaining > 0 {
+        let mut block = remaining.min(256);
+        if remaining - block == 1 {
+            block -= 1;
+        }
+        assert!(block >= 2);
+        bytes.push((block - 1) as u8);
+        bytes.extend(std::iter::repeat_n(b'x', block - 1));
+        remaining -= block;
+    }
+    bytes.extend_from_slice(&[0, 0x3b]);
+    assert_eq!(bytes.len(), target_len);
+    bytes
+}
+
 async fn call(tool: &Arc<dyn Tool>, input: serde_json::Value) -> agen::tool::ToolOutput {
     tool.execute(&input.to_string(), Default::default())
         .await
@@ -399,6 +428,301 @@ async fn detach_and_reattach_same_alias_requires_a_fresh_read() {
     router.close_all().await.unwrap();
 }
 
+#[derive(Debug)]
+struct ExternalValidatingSession {
+    inner: LocalWorkdirSession,
+    truncate_first_binary_response: bool,
+    mutate_after_first_binary_response: Option<std::path::PathBuf>,
+}
+
+#[async_trait::async_trait]
+impl workdir::WorkdirSession for ExternalValidatingSession {
+    fn workdir(&self) -> &workdir::Workdir {
+        self.inner.workdir()
+    }
+
+    fn capabilities(&self) -> workdir::WorkdirSessionCapabilities {
+        self.inner.capabilities()
+    }
+
+    async fn stat(
+        &self,
+        request: workdir::StatRequest,
+    ) -> Result<workdir::StatResult, workdir::WorkdirError> {
+        self.inner.stat(request).await
+    }
+
+    async fn read(
+        &self,
+        request: workdir::ReadRequest,
+    ) -> Result<workdir::ReadResult, workdir::WorkdirError> {
+        let operation = workdir::http::WorkdirSessionOperation::Read(request);
+        let operation = workdir::external::ExternalWorkdirOperation::try_from(operation)
+            .map_err(workdir::WorkdirError::UnsupportedOperation)?;
+        let workdir::http::WorkdirSessionOperation::Read(request) = operation.into_inner() else {
+            unreachable!("validated Read changed operation kind")
+        };
+        self.inner.read(request).await
+    }
+
+    async fn read_bytes(
+        &self,
+        request: workdir::ReadBytesRequest,
+    ) -> Result<workdir::ReadBytesResult, workdir::WorkdirError> {
+        let operation = workdir::http::WorkdirSessionOperation::ReadBytes(request);
+        let operation = workdir::external::ExternalWorkdirOperation::try_from(operation)
+            .map_err(workdir::WorkdirError::UnsupportedOperation)?;
+        let workdir::http::WorkdirSessionOperation::ReadBytes(request) = operation.into_inner()
+        else {
+            unreachable!("validated ReadBytes changed operation kind")
+        };
+        let result = self.inner.read_bytes(request).await?;
+        let result = workdir::external::ExternalWorkdirOperationResult::try_from(
+            workdir::http::WorkdirSessionOperationResult::ReadBytes(result),
+        )
+        .map_err(workdir::WorkdirError::UnsupportedOperation)?;
+        let workdir::http::WorkdirSessionOperationResult::ReadBytes(mut result) =
+            result.into_inner()
+        else {
+            unreachable!("validated ReadBytes result changed operation kind")
+        };
+        if result.offset == 0 {
+            if let Some(path) = &self.mutate_after_first_binary_response {
+                std::fs::write(path, vec![b'z'; result.total_bytes as usize]).unwrap();
+            }
+            if self.truncate_first_binary_response {
+                result.bytes.pop();
+            }
+        }
+        Ok(result)
+    }
+
+    async fn write(
+        &self,
+        request: workdir::WriteRequest,
+    ) -> Result<workdir::WriteResult, workdir::WorkdirError> {
+        self.inner.write(request).await
+    }
+
+    async fn edit(
+        &self,
+        request: workdir::EditRequest,
+    ) -> Result<workdir::EditResult, workdir::WorkdirError> {
+        self.inner.edit(request).await
+    }
+
+    async fn list(
+        &self,
+        request: workdir::ListRequest,
+    ) -> Result<workdir::ListResult, workdir::WorkdirError> {
+        self.inner.list(request).await
+    }
+
+    async fn glob(
+        &self,
+        request: workdir::GlobRequest,
+    ) -> Result<workdir::GlobResult, workdir::WorkdirError> {
+        self.inner.glob(request).await
+    }
+
+    async fn grep(
+        &self,
+        request: workdir::GrepRequest,
+    ) -> Result<workdir::GrepResult, workdir::WorkdirError> {
+        self.inner.grep(request).await
+    }
+
+    async fn start_command(
+        &self,
+        request: workdir::CommandRequest,
+    ) -> Result<workdir::CommandHandle, workdir::WorkdirError> {
+        self.inner.start_command(request).await
+    }
+
+    async fn command_status(
+        &self,
+        handle: workdir::CommandHandle,
+    ) -> Result<workdir::CommandStatus, workdir::WorkdirError> {
+        self.inner.command_status(handle).await
+    }
+
+    async fn command_output(
+        &self,
+        request: workdir::CommandOutputRequest,
+    ) -> Result<workdir::CommandOutput, workdir::WorkdirError> {
+        self.inner.command_output(request).await
+    }
+
+    async fn cancel_command(
+        &self,
+        handle: workdir::CommandHandle,
+    ) -> Result<(), workdir::WorkdirError> {
+        self.inner.cancel_command(handle).await
+    }
+
+    async fn close(&self) -> Result<(), workdir::WorkdirError> {
+        self.inner.close().await
+    }
+}
+
+#[tokio::test]
+async fn external_view_image_uses_a_protocol_bounded_request() {
+    let dir = TempDir::new().unwrap();
+    let spill = TempDir::new().unwrap();
+    let scope = scope_with_spill(dir.path(), spill.path());
+    let session: WorkdirSessionHandle = Arc::new(ExternalValidatingSession {
+        inner: LocalWorkdirSession::new(scope, dir.path().to_path_buf()),
+        truncate_first_binary_response: false,
+        mutate_after_first_binary_response: None,
+    });
+    let png = include_bytes!("fixtures/view-image/valid.png");
+    assert!(png.contains(&0));
+    assert!(png.iter().any(|byte| *byte >= 0x80));
+    std::fs::write(dir.path().join("image.png"), png).unwrap();
+    let (_meta, tool) = view_image_tool(session)();
+
+    let output = call(&tool, json!({ "path": "image.png" })).await;
+    let agen::tool::Attachment::Image(image) = &output.attachments[0];
+    assert_eq!(image.mime_type(), "image/png");
+    assert_eq!(image.data(), png);
+}
+
+#[tokio::test]
+async fn external_view_image_rejects_truncated_and_cross_version_chunks() {
+    let dir = TempDir::new().unwrap();
+    let spill = TempDir::new().unwrap();
+    let image_path = dir.path().join("image.png");
+    let scope = scope_with_spill(dir.path(), spill.path());
+    std::fs::write(&image_path, include_bytes!("fixtures/view-image/valid.png")).unwrap();
+    let truncated: WorkdirSessionHandle = Arc::new(ExternalValidatingSession {
+        inner: LocalWorkdirSession::new(scope.clone(), dir.path().to_path_buf()),
+        truncate_first_binary_response: true,
+        mutate_after_first_binary_response: None,
+    });
+    let (_meta, tool) = view_image_tool(truncated)();
+    let error = call_err(&tool, json!({ "path": "image.png" }))
+        .await
+        .to_string();
+    assert!(
+        error.contains("truncated") || error.contains("partial"),
+        "{error}"
+    );
+
+    let large = valid_gif_with_len(1024 * 1024 + 32);
+    std::fs::write(&image_path, large).unwrap();
+    let changing: WorkdirSessionHandle = Arc::new(ExternalValidatingSession {
+        inner: LocalWorkdirSession::new(scope, dir.path().to_path_buf()),
+        truncate_first_binary_response: false,
+        mutate_after_first_binary_response: Some(image_path),
+    });
+    let (_meta, tool) = view_image_tool(changing)();
+    let error = call_err(&tool, json!({ "path": "image.png" }))
+        .await
+        .to_string();
+    assert!(error.contains("changed"), "{error}");
+}
+
+#[tokio::test]
+async fn view_image_enforces_the_ten_mib_boundary_without_partial_attachments() {
+    const LIMIT: usize = 10 * 1024 * 1024;
+    let dir = TempDir::new().unwrap();
+    let spill = TempDir::new().unwrap();
+    let scope = scope_with_spill(dir.path(), spill.path());
+    let session: WorkdirSessionHandle =
+        Arc::new(LocalWorkdirSession::new(scope, dir.path().to_path_buf()));
+    let (_meta, tool) = view_image_tool(session)();
+    let mut image = valid_gif_with_len(LIMIT);
+    std::fs::write(dir.path().join("boundary.gif"), &image).unwrap();
+
+    let output = call(&tool, json!({ "path": "boundary.gif" })).await;
+    let agen::tool::Attachment::Image(attachment) = &output.attachments[0];
+    assert_eq!(attachment.mime_type(), "image/gif");
+    assert_eq!(attachment.data(), image);
+
+    image.push(0);
+    std::fs::write(dir.path().join("boundary.gif"), image).unwrap();
+    let error = call_err(&tool, json!({ "path": "boundary.gif" }))
+        .await
+        .to_string();
+    assert!(error.contains("10485760-byte limit"), "{error}");
+}
+
+#[tokio::test]
+async fn view_image_attaches_valid_supported_image_fixtures() {
+    let dir = TempDir::new().unwrap();
+    let spill = TempDir::new().unwrap();
+    let scope = scope_with_spill(dir.path(), spill.path());
+    let session: WorkdirSessionHandle =
+        Arc::new(LocalWorkdirSession::new(scope, dir.path().to_path_buf()));
+    let (_meta, tool) = view_image_tool(session)();
+    let fixtures: [(&str, &[u8], &str); 4] = [
+        (
+            "valid.png",
+            include_bytes!("fixtures/view-image/valid.png"),
+            "image/png",
+        ),
+        (
+            "valid.jpg",
+            include_bytes!("fixtures/view-image/valid.jpg"),
+            "image/jpeg",
+        ),
+        (
+            "valid.gif",
+            include_bytes!("fixtures/view-image/valid.gif"),
+            "image/gif",
+        ),
+        (
+            "valid.webp",
+            include_bytes!("fixtures/view-image/valid.webp"),
+            "image/webp",
+        ),
+    ];
+
+    for (name, fixture, mime) in fixtures {
+        std::fs::write(dir.path().join(name), fixture).unwrap();
+        let output = call(&tool, json!({ "path": name })).await;
+        let agen::tool::Attachment::Image(image) = &output.attachments[0];
+        assert_eq!(image.mime_type(), mime);
+        assert_eq!(image.data(), fixture);
+    }
+}
+
+#[tokio::test]
+async fn delegated_view_image_preserves_caller_relative_path_identity() {
+    let dir = TempDir::new().unwrap();
+    std::fs::create_dir(dir.path().join("docs")).unwrap();
+    let fixture = include_bytes!("fixtures/view-image/valid.png");
+    std::fs::write(dir.path().join("docs/image.png"), fixture).unwrap();
+    let source: WorkdirSessionHandle = Arc::new(LocalWorkdirSession::new(
+        Scope::writable(dir.path()).unwrap(),
+        dir.path().to_path_buf(),
+    ));
+    let broker = WorkdirToolBroker::new(source);
+    let lease = broker
+        .scope(WorkdirToolScope {
+            rules: vec![WorkdirToolScopeRule {
+                target: WorkdirPath::new("docs").unwrap(),
+                permission: WorkdirToolScopePermission::Read,
+                recursive: true,
+                symlink_policy: Default::default(),
+            }],
+            cwd: WorkdirPath::new("docs").unwrap(),
+            command: false,
+        })
+        .await
+        .unwrap();
+    let (_meta, tool) = view_image_tool(lease.tool_session())();
+
+    let output = call(&tool, json!({ "path": "image.png" })).await;
+    assert!(output.summary.contains("image.png"));
+    assert!(!output.summary.contains("docs/image.png"));
+    let agen::tool::Attachment::Image(image) = &output.attachments[0];
+    assert_eq!(image.data(), fixture);
+
+    lease.close().await.unwrap();
+    broker.close().await.unwrap();
+}
+
 #[tokio::test]
 async fn view_image_reads_scoped_bytes_into_durable_tool_detail() {
     let dir = TempDir::new().unwrap();
@@ -406,7 +730,7 @@ async fn view_image_reads_scoped_bytes_into_durable_tool_detail() {
     let scope = scope_with_spill(dir.path(), spill.path());
     let session: WorkdirSessionHandle =
         Arc::new(LocalWorkdirSession::new(scope, dir.path().to_path_buf()));
-    let png = b"\x89PNG\r\n\x1a\nprivate-image-body";
+    let png = include_bytes!("fixtures/view-image/valid.png");
     std::fs::write(dir.path().join("image.png"), png).unwrap();
     let definition = view_image_tool(session);
     let (_meta, tool) = definition();
@@ -417,7 +741,6 @@ async fn view_image_reads_scoped_bytes_into_durable_tool_detail() {
     assert_eq!(image.mime_type(), "image/png");
     assert_eq!(image.data(), png);
     let serialized = serde_json::to_string(&output).unwrap();
-    assert!(!serialized.contains("private-image-body"));
     assert!(serialized.contains("attachments"));
     let restored: agen::tool::ToolOutput = serde_json::from_str(&serialized).unwrap();
     let agen::tool::Attachment::Image(restored_image) = &restored.attachments[0];

crates/workdir/src/external.rs

@@ -12,7 +12,7 @@ use serde::{Deserialize, Serialize};
 use crate::http::{WorkdirSessionOperation, WorkdirSessionOperationResult, WorkdirTransportError};
 use crate::{BoundedReadLimits, WorkdirId, WorkdirPath, WorkdirSessionCapabilities};
 
-pub const EXTERNAL_WORKDIR_PROVIDER_PROTOCOL_VERSION: u16 = 1;
+pub const EXTERNAL_WORKDIR_PROVIDER_PROTOCOL_VERSION: u16 = 2;
 /// Maximum serialized Backend-to-provider command frame size.
 pub const MAX_EXTERNAL_SERVER_FRAME_BYTES: usize = 1024 * 1024;
 /// Maximum serialized provider-to-Backend result frame size. Read bytes are
@@ -155,6 +155,12 @@ fn validate_external_operation(operation: &WorkdirSessionOperation) -> Result<()
                 && request.limit <= 1_000_000
                 && request.max_bytes <= BoundedReadLimits::EXTERNAL_DEFAULT.max_response_bytes
         }
+        WorkdirSessionOperation::ReadBytes(request) => {
+            is_root_relative(&request.path)
+                && request.offset <= BoundedReadLimits::EXTERNAL_DEFAULT.max_source_bytes
+                && (1..=BoundedReadLimits::EXTERNAL_DEFAULT.max_response_bytes)
+                    .contains(&request.max_bytes)
+        }
         WorkdirSessionOperation::List(request) => {
             is_root_relative(&request.path) && request.limit <= MAX_EXTERNAL_RESULT_ITEMS
         }
@@ -275,6 +281,15 @@ fn validate_external_result(result: &WorkdirSessionOperationResult) -> Result<()
             is_root_relative(&result.path)
                 && result.bytes.len() <= BoundedReadLimits::EXTERNAL_DEFAULT.max_response_bytes
         }
+        WorkdirSessionOperationResult::ReadBytes(result) => {
+            let returned_end = result.offset.checked_add(result.bytes.len() as u64);
+            is_root_relative(&result.path)
+                && result.bytes.len() <= BoundedReadLimits::EXTERNAL_DEFAULT.max_response_bytes
+                && result.total_bytes <= BoundedReadLimits::EXTERNAL_DEFAULT.max_source_bytes
+                && returned_end.is_some_and(|end| {
+                    end <= result.total_bytes && result.eof == (end == result.total_bytes)
+                })
+        }
         WorkdirSessionOperationResult::List(result) => {
             result.entries.len() <= MAX_EXTERNAL_RESULT_ITEMS
                 && result
@@ -482,8 +497,8 @@ mod tests {
 
     use super::*;
     use crate::{
-        CommandRequest, EditRequest, GrepResult, ListRequest, ReadRequest, Workdir, WorkdirPath,
-        WriteRequest,
+        CommandRequest, EditRequest, GrepResult, ListRequest, ReadBytesRequest, ReadBytesResult,
+        ReadRequest, Workdir, WorkdirPath, WriteRequest,
     };
 
     fn assert_no_provider_authority(value: &Value) {
@@ -614,7 +629,7 @@ mod tests {
     #[test]
     fn unsupported_protocol_versions_and_invalid_read_limits_fail_closed() {
         let future = r#"{
-            "version": 2,
+            "version": 3,
             "message": {"kind": "heartbeat", "generation": 1, "sequence": 1}
         }"#;
         assert!(serde_json::from_str::<ExternalWorkdirServerFrame>(future).is_err());
@@ -726,10 +741,51 @@ mod tests {
         );
     }
 
+    #[test]
+    fn protocol_bounds_binary_read_requests_and_rejects_partial_results() {
+        let path = WorkdirPath::new("image.png").unwrap();
+        let bounded = WorkdirSessionOperation::ReadBytes(ReadBytesRequest {
+            path: path.clone(),
+            offset: 0,
+            max_bytes: BoundedReadLimits::EXTERNAL_DEFAULT.max_response_bytes,
+            expected_hash: None,
+        });
+        assert!(ExternalWorkdirOperation::try_from(bounded).is_ok());
+
+        let oversized = WorkdirSessionOperation::ReadBytes(ReadBytesRequest {
+            path: path.clone(),
+            offset: 0,
+            max_bytes: BoundedReadLimits::EXTERNAL_DEFAULT.max_response_bytes + 1,
+            expected_hash: None,
+        });
+        assert!(ExternalWorkdirOperation::try_from(oversized).is_err());
+
+        let hash = [7; 32];
+        let complete = WorkdirSessionOperationResult::ReadBytes(ReadBytesResult {
+            path: path.clone(),
+            bytes: vec![1, 2, 3],
+            offset: 0,
+            total_bytes: 3,
+            content_hash: hash,
+            eof: true,
+        });
+        assert!(ExternalWorkdirOperationResult::try_from(complete).is_ok());
+
+        let partial_marked_complete = WorkdirSessionOperationResult::ReadBytes(ReadBytesResult {
+            path,
+            bytes: vec![1, 2],
+            offset: 0,
+            total_bytes: 3,
+            content_hash: hash,
+            eof: true,
+        });
+        assert!(ExternalWorkdirOperationResult::try_from(partial_marked_complete).is_err());
+    }
+
     #[test]
     fn protocol_rejects_unknown_nested_fields_and_unbounded_requests() {
         let unknown = r#"{
-            "version": 1,
+            "version": 2,
             "message": {
                 "kind": "heartbeat",
                 "generation": 1,

crates/workdir/src/http.rs

@@ -11,9 +11,9 @@ use serde::{Deserialize, Serialize};
 use crate::{
     CommandHandle, CommandOutput, CommandOutputRequest, CommandRequest, CommandStatus, EditRequest,
     EditResult, GlobRequest, GlobResult, GrepRequest, GrepResult, ListRequest, ListResult,
-    ReadRequest, ReadResult, StatRequest, StatResult, WorkdirError, WorkdirId,
-    WorkdirScopeAuthorizationRequest, WorkdirScopeOverlapRequest, WorkdirSession,
-    WorkdirSessionCapabilities, WriteRequest, WriteResult,
+    ReadBytesRequest, ReadBytesResult, ReadRequest, ReadResult, StatRequest, StatResult,
+    WorkdirError, WorkdirId, WorkdirScopeAuthorizationRequest, WorkdirScopeOverlapRequest,
+    WorkdirSession, WorkdirSessionCapabilities, WriteRequest, WriteResult,
 };
 
 /// Opaque Runtime-owned identifier for one ephemeral Workdir session.
@@ -66,6 +66,7 @@ pub enum WorkdirSessionOperation {
     ScopeRulesOverlap(WorkdirScopeOverlapRequest),
     Stat(StatRequest),
     Read(ReadRequest),
+    ReadBytes(ReadBytesRequest),
     Write(WriteRequest),
     Edit(EditRequest),
     List(ListRequest),
@@ -97,6 +98,7 @@ pub enum WorkdirSessionOperationResult {
     ScopeRulesOverlap { overlaps: bool },
     Stat(StatResult),
     Read(ReadResult),
+    ReadBytes(ReadBytesResult),
     Write(WriteResult),
     Edit(EditResult),
     List(ListResult),
@@ -135,6 +137,10 @@ pub async fn dispatch_workdir_session_operation(
             .read(request)
             .await
             .map(WorkdirSessionOperationResult::Read),
+        WorkdirSessionOperation::ReadBytes(request) => session
+            .read_bytes(request)
+            .await
+            .map(WorkdirSessionOperationResult::ReadBytes),
         WorkdirSessionOperation::Write(request) => session
             .write(request)
             .await
@@ -572,6 +578,19 @@ mod client {
             }
         }
 
+        async fn read_bytes(
+            &self,
+            request: ReadBytesRequest,
+        ) -> Result<ReadBytesResult, WorkdirError> {
+            match self
+                .operate(WorkdirSessionOperation::ReadBytes(request))
+                .await?
+            {
+                WorkdirSessionOperationResult::ReadBytes(result) => Ok(result),
+                _ => Err(Self::mismatch("read_bytes")),
+            }
+        }
+
         async fn write(&self, request: WriteRequest) -> Result<WriteResult, WorkdirError> {
             match self
                 .operate(WorkdirSessionOperation::Write(request))

crates/workdir/src/lib.rs

@@ -27,7 +27,8 @@ use tokio::sync::broadcast;
 pub use fs_operation::{
     BoundedReadLimits, ContentHash, EditRequest, EditResult, EntryKind, FsPath as WorkdirPath,
     GlobRequest, GlobResult, GrepOutputMode, GrepRequest, GrepResult, ListEntry, ListRequest,
-    ListResult, ReadRequest, ReadResult, StatRequest, StatResult, WriteRequest, WriteResult,
+    ListResult, ReadBytesRequest, ReadBytesResult, ReadRequest, ReadResult, StatRequest,
+    StatResult, WriteRequest, WriteResult,
 };
 pub use http::dispatch_workdir_session_operation;
 pub use local::{
@@ -220,6 +221,14 @@ pub trait WorkdirSession: std::fmt::Debug + Send + Sync {
 
     async fn stat(&self, request: StatRequest) -> Result<StatResult, WorkdirError>;
     async fn read(&self, request: ReadRequest) -> Result<ReadResult, WorkdirError>;
+    async fn read_bytes(
+        &self,
+        _request: ReadBytesRequest,
+    ) -> Result<ReadBytesResult, WorkdirError> {
+        Err(WorkdirError::UnsupportedOperation(
+            "bounded binary reads are not supported by this provider".to_string(),
+        ))
+    }
     async fn write(&self, request: WriteRequest) -> Result<WriteResult, WorkdirError>;
     async fn edit(&self, request: EditRequest) -> Result<EditResult, WorkdirError>;
     async fn list(&self, request: ListRequest) -> Result<ListResult, WorkdirError>;

crates/workdir/src/local.rs

@@ -30,10 +30,10 @@ use crate::{
     BoundedReadLimits, CommandEvent, CommandHandle, CommandOutput, CommandOutputRequest,
     CommandRequest, CommandSnapshot, CommandStatus, CommandStream, CommandStreamSlice, EditRequest,
     EditResult, GlobRequest, GlobResult, GrepRequest, GrepResult, ListRequest, ListResult,
-    ReadRequest, ReadResult, StatRequest, StatResult, Workdir, WorkdirError, WorkdirPath,
-    WorkdirScopeAuthorizationRequest, WorkdirScopeOverlapRequest, WorkdirSession,
-    WorkdirSessionCapabilities, WorkdirSessionCapability, WorkdirToolScopePermission, WriteRequest,
-    WriteResult,
+    ReadBytesRequest, ReadBytesResult, ReadRequest, ReadResult, StatRequest, StatResult, Workdir,
+    WorkdirError, WorkdirPath, WorkdirScopeAuthorizationRequest, WorkdirScopeOverlapRequest,
+    WorkdirSession, WorkdirSessionCapabilities, WorkdirSessionCapability,
+    WorkdirToolScopePermission, WriteRequest, WriteResult,
 };
 #[cfg(test)]
 use crate::{EntryKind, WriteOutcome};
@@ -1261,6 +1261,21 @@ impl WorkdirSession for LocalWorkdirSession {
         .map_err(|error| sanitize_error(error, &logical))
     }
 
+    async fn read_bytes(&self, request: ReadBytesRequest) -> Result<ReadBytesResult, WorkdirError> {
+        self.ensure_capability(WorkdirSessionCapability::Read)?;
+        let logical = request.path.clone();
+        self.validate_operation_path(&request.path)?;
+        let access = self.scope_access();
+        match self.inner.read_limits {
+            Some(limits) => {
+                fs_operation::run_read_bytes_bounded(&self.inner.root, request, &access, limits)
+            }
+            None => fs_operation::run_read_bytes(&self.inner.root, request, &access),
+        }
+        .map_err(WorkdirError::from)
+        .map_err(|error| sanitize_error(error, &logical))
+    }
+
     async fn write(&self, request: WriteRequest) -> Result<WriteResult, WorkdirError> {
         self.ensure_capability(WorkdirSessionCapability::Write)?;
         let logical = request.path.clone();

crates/workdir/src/router.rs

@@ -16,9 +16,10 @@ use tokio::sync::broadcast;
 use crate::{
     CommandEvent, CommandHandle, CommandOutput, CommandOutputRequest, CommandRequest,
     CommandSnapshot, CommandStatus, EditRequest, EditResult, GlobRequest, GlobResult, GrepRequest,
-    GrepResult, ListRequest, ListResult, ReadRequest, ReadResult, StatRequest, StatResult, Workdir,
-    WorkdirError, WorkdirScopeAuthorizationRequest, WorkdirScopeOverlapRequest, WorkdirSession,
-    WorkdirSessionCapabilities, WorkdirSessionHandle, WriteRequest, WriteResult,
+    GrepResult, ListRequest, ListResult, ReadBytesRequest, ReadBytesResult, ReadRequest,
+    ReadResult, StatRequest, StatResult, Workdir, WorkdirError, WorkdirScopeAuthorizationRequest,
+    WorkdirScopeOverlapRequest, WorkdirSession, WorkdirSessionCapabilities, WorkdirSessionHandle,
+    WriteRequest, WriteResult,
 };
 
 /// Stable Worker-local routing key for one attached Workdir.
@@ -257,6 +258,11 @@ impl WorkdirSession for RoutedWorkdirSession {
         self.state.session.read(request).await
     }
 
+    async fn read_bytes(&self, request: ReadBytesRequest) -> Result<ReadBytesResult, WorkdirError> {
+        let _active = self.state.enter()?;
+        self.state.session.read_bytes(request).await
+    }
+
     async fn write(&self, request: WriteRequest) -> Result<WriteResult, WorkdirError> {
         let _active = self.state.enter()?;
         self.state.session.write(request).await

crates/workdir/src/scope.rs

@@ -6,7 +6,8 @@ use std::sync::{Arc, Mutex, Weak};
 use async_trait::async_trait;
 use fs_operation::{
     EditRequest, EditResult, FsPath, GlobRequest, GlobResult, GrepRequest, GrepResult, ListRequest,
-    ListResult, ReadRequest, ReadResult, StatRequest, StatResult, WriteRequest, WriteResult,
+    ListResult, ReadBytesRequest, ReadBytesResult, ReadRequest, ReadResult, StatRequest,
+    StatResult, WriteRequest, WriteResult,
 };
 use manifest::SymlinkPolicy;
 use schemars::JsonSchema;
@@ -1011,6 +1012,21 @@ impl WorkdirSession for ScopedWorkdirSession {
         self.source.read(request).await
     }
 
+    async fn read_bytes(
+        &self,
+        mut request: ReadBytesRequest,
+    ) -> Result<ReadBytesResult, WorkdirError> {
+        let caller_path = request.path.clone();
+        let path = self
+            .resolve_operation_path(&request.path, WorkdirToolScopePermission::Read)
+            .await?;
+        self.ensure_read(&path, WorkdirSessionCapability::Read)?;
+        request.path = path;
+        let mut result = self.source.read_bytes(request).await?;
+        result.path = caller_path;
+        Ok(result)
+    }
+
     async fn write(&self, mut request: WriteRequest) -> Result<WriteResult, WorkdirError> {
         let _scope_guard = self.scope_lock.lock().await;
         let path = self
@@ -1276,6 +1292,10 @@ impl WorkdirSession for ReadOnlyWorkdirSession {
         self.inner.read(request).await
     }
 
+    async fn read_bytes(&self, request: ReadBytesRequest) -> Result<ReadBytesResult, WorkdirError> {
+        self.inner.read_bytes(request).await
+    }
+
     async fn write(&self, _request: WriteRequest) -> Result<WriteResult, WorkdirError> {
         Err(WorkdirError::Denied("read-only workdir session".into()))
     }
@@ -1656,6 +1676,15 @@ mod tests {
         }
     }
 
+    fn read_bytes(path: &str) -> ReadBytesRequest {
+        ReadBytesRequest {
+            path: fs_path(path),
+            offset: 0,
+            max_bytes: 1024,
+            expected_hash: None,
+        }
+    }
+
     fn write(path: &str, content: &str) -> WriteRequest {
         WriteRequest {
             path: fs_path(path),
@@ -1887,6 +1916,9 @@ mod tests {
             child.read(read("readme.md")).await.unwrap().bytes,
             b"visible"
         );
+        let binary = child.read_bytes(read_bytes("readme.md")).await.unwrap();
+        assert_eq!(binary.path, fs_path("readme.md"));
+        assert_eq!(binary.bytes, b"visible");
         assert!(matches!(
             child.write(write("new.md", "no")).await,
             Err(WorkdirError::Denied(_))

crates/worker/src/feature/builtin/manage_workdir.rs

@@ -18,8 +18,8 @@ use workdir::workspace::WorkspaceWorkdirSessionOperationRequest;
 use workdir::{
     CommandHandle, CommandOutput, CommandOutputRequest, CommandRequest, CommandStatus, EditRequest,
     EditResult, GlobRequest, GlobResult, GrepRequest, GrepResult, ListRequest, ListResult,
-    ReadRequest, ReadResult, StatRequest, StatResult, Workdir, WorkdirError,
-    WorkdirScopeAuthorizationRequest, WorkdirScopeOverlapRequest, WorkdirSession,
+    ReadBytesRequest, ReadBytesResult, ReadRequest, ReadResult, StatRequest, StatResult, Workdir,
+    WorkdirError, WorkdirScopeAuthorizationRequest, WorkdirScopeOverlapRequest, WorkdirSession,
     WorkdirSessionCapabilities, WorkdirSessionHandle, WriteRequest, WriteResult,
 };
 
@@ -357,6 +357,13 @@ impl WorkdirSession for WorkspaceAttachedWorkdirSession {
         }
     }
 
+    async fn read_bytes(&self, request: ReadBytesRequest) -> Result<ReadBytesResult, WorkdirError> {
+        match self.operate(WorkdirSessionOperation::ReadBytes(request))? {
+            WorkdirSessionOperationResult::ReadBytes(result) => Ok(result),
+            _ => Err(Self::mismatch("read_bytes")),
+        }
+    }
+
     async fn write(&self, request: WriteRequest) -> Result<WriteResult, WorkdirError> {
         match self.operate(WorkdirSessionOperation::Write(request))? {
             WorkdirSessionOperationResult::Write(result) => Ok(result),

crates/workspace-server/Cargo.toml

@@ -50,7 +50,10 @@ zeroize.workspace = true
 webauthn-rs = { workspace = true }
 
 [dev-dependencies]
+agen.workspace = true
 tempfile.workspace = true
+tools.workspace = true
+yoi = { path = "../yoi" }
 tower = { workspace = true, features = ["util"] }
 tokio = { workspace = true, features = ["macros", "rt-multi-thread"] }
 webauthn-authenticator-rs = { version = "0.5.5", default-features = false, features = ["softpasskey"] }

crates/workspace-server/src/server.rs

@@ -5,7 +5,7 @@ use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::{Arc, Mutex, RwLock, Weak};
 
 use async_trait::async_trait;
-use axum::extract::ws::{Message as WsMessage, WebSocket, WebSocketUpgrade};
+use axum::extract::ws::{CloseFrame, Message as WsMessage, WebSocket, WebSocketUpgrade};
 use axum::extract::{DefaultBodyLimit, Extension, Path as AxumPath, Query, Request, State};
 #[cfg(test)]
 use axum::http::header::{CACHE_CONTROL, ETAG, IF_NONE_MATCH};
@@ -1074,6 +1074,7 @@ fn external_workdir_operation_kind(operation: &WorkdirSessionOperation) -> &'sta
         WorkdirSessionOperation::ScopeRulesOverlap(_) => "scope_rules_overlap",
         WorkdirSessionOperation::Stat(_) => "stat",
         WorkdirSessionOperation::Read(_) => "read",
+        WorkdirSessionOperation::ReadBytes(_) => "read_bytes",
         WorkdirSessionOperation::Write(_) => "write",
         WorkdirSessionOperation::Edit(_) => "edit",
         WorkdirSessionOperation::List(_) => "list",
@@ -1141,6 +1142,19 @@ impl workdir::WorkdirSession for ExternalProviderWorkdirSession {
             _ => Err(Self::mismatch("read")),
         }
     }
+    async fn read_bytes(
+        &self,
+        request: workdir::ReadBytesRequest,
+    ) -> std::result::Result<workdir::ReadBytesResult, workdir::WorkdirError> {
+        self.ensure_capability(workdir::WorkdirSessionCapability::Read)?;
+        match self
+            .operate(WorkdirSessionOperation::ReadBytes(request))
+            .await?
+        {
+            WorkdirSessionOperationResult::ReadBytes(value) => Ok(value),
+            _ => Err(Self::mismatch("read_bytes")),
+        }
+    }
     async fn write(
         &self,
         request: workdir::WriteRequest,
@@ -14824,6 +14838,7 @@ async fn scoped_execute_current_worker_workdir_operation(
         | WorkdirSessionOperation::ScopeRulesOverlap(_)
         | WorkdirSessionOperation::Stat(_)
         | WorkdirSessionOperation::Read(_)
+        | WorkdirSessionOperation::ReadBytes(_)
         | WorkdirSessionOperation::Write(_)
         | WorkdirSessionOperation::Edit(_)
         | WorkdirSessionOperation::List(_)
@@ -14890,6 +14905,10 @@ async fn execute_workdir_session_operation(
             .read(request)
             .await
             .map(WorkdirSessionOperationResult::Read),
+        WorkdirSessionOperation::ReadBytes(request) => session
+            .read_bytes(request)
+            .await
+            .map(WorkdirSessionOperationResult::ReadBytes),
         WorkdirSessionOperation::Write(request) => session
             .write(request)
             .await
@@ -17453,41 +17472,116 @@ async fn send_external_workdir_server_frame(
     )
 }
 
+async fn reject_external_workdir_provider(socket: &mut WebSocket, code: u16, mut reason: String) {
+    const MAX_CLOSE_REASON_BYTES: usize = 123;
+    if reason.len() > MAX_CLOSE_REASON_BYTES {
+        reason.truncate(MAX_CLOSE_REASON_BYTES);
+    }
+    let _ = socket
+        .send(WsMessage::Close(Some(CloseFrame {
+            code,
+            reason: reason.into(),
+        })))
+        .await;
+}
+
+fn external_workdir_registration_parse_error(text: &str) -> String {
+    let actual_version = serde_json::from_str::<serde_json::Value>(text)
+        .ok()
+        .and_then(|value| value.get("version")?.as_u64());
+    match actual_version {
+        Some(actual)
+            if actual != workdir::external::EXTERNAL_WORKDIR_PROVIDER_PROTOCOL_VERSION as u64 =>
+        {
+            format!(
+                "unsupported External Workdir protocol version {actual}; Backend requires {}",
+                workdir::external::EXTERNAL_WORKDIR_PROVIDER_PROTOCOL_VERSION
+            )
+        }
+        _ => "invalid External Workdir provider registration".to_string(),
+    }
+}
+
 async fn serve_external_workdir_provider(
     api: WorkspaceApi,
     initial_grant: ExternalWorkdirGrantRecord,
     mut socket: WebSocket,
 ) {
-    let registration =
+    let registration_text =
         match tokio::time::timeout(std::time::Duration::from_secs(10), socket.next()).await {
-            Ok(Some(Ok(WsMessage::Text(text)))) if text.len() <= 64 * 1024 => {
-                serde_json::from_str::<ExternalWorkdirProviderFrame>(&text).ok()
+            Ok(Some(Ok(WsMessage::Text(text)))) if text.len() <= 64 * 1024 => text,
+            _ => {
+                reject_external_workdir_provider(
+                    &mut socket,
+                    1008,
+                    "External Workdir provider registration was missing or oversized".to_string(),
+                )
+                .await;
+                return;
             }
-            _ => None,
         };
-    let Some(ExternalWorkdirProviderFrame {
+    let registration_frame =
+        match serde_json::from_str::<ExternalWorkdirProviderFrame>(&registration_text) {
+            Ok(frame) => frame,
+            Err(_) => {
+                let reason = external_workdir_registration_parse_error(&registration_text);
+                reject_external_workdir_provider(&mut socket, 1002, reason).await;
+                return;
+            }
+        };
+    let ExternalWorkdirProviderFrame {
         message: ExternalWorkdirProviderMessage::Register { registration },
         ..
-    }) = registration
+    } = registration_frame
     else {
-        let _ = socket.close().await;
+        reject_external_workdir_provider(
+            &mut socket,
+            1008,
+            "expected External Workdir provider registration".to_string(),
+        )
+        .await;
         return;
     };
     let expected_capabilities = match external_workdir_capabilities(&initial_grant.permissions) {
         Ok(capabilities) => capabilities,
         Err(_) => {
-            let _ = socket.close().await;
+            reject_external_workdir_provider(
+                &mut socket,
+                1011,
+                "Backend could not validate External Workdir capabilities".to_string(),
+            )
+            .await;
             return;
         }
     };
+    if registration.read_limits != workdir::BoundedReadLimits::EXTERNAL_DEFAULT {
+        let required = workdir::BoundedReadLimits::EXTERNAL_DEFAULT;
+        reject_external_workdir_provider(
+            &mut socket,
+            1008,
+            format!(
+                "provider read limits source={} response={}; Backend requires source={} response={}",
+                registration.read_limits.max_source_bytes,
+                registration.read_limits.max_response_bytes,
+                required.max_source_bytes,
+                required.max_response_bytes,
+            ),
+        )
+        .await;
+        return;
+    }
     if registration.grant_id.as_str() != initial_grant.grant_id
         || registration.workdir_id.as_str() != initial_grant.workdir_id
         || registration.provider_instance_id.as_str() != initial_grant.provider_instance_id
         || registration.capabilities != expected_capabilities
-        || registration.read_limits != workdir::BoundedReadLimits::EXTERNAL_DEFAULT
         || registration.generation == 0
     {
-        let _ = socket.close().await;
+        reject_external_workdir_provider(
+            &mut socket,
+            1008,
+            "External Workdir provider registration does not match the grant".to_string(),
+        )
+        .await;
         return;
     }
     let now = Utc::now().to_rfc3339_opts(SecondsFormat::Nanos, true);
@@ -17642,7 +17736,7 @@ async fn serve_external_workdir_provider(
                         Ok(operation) => operation,
                         Err(message) => {
                             let _ = response.send(Err(WorkdirTransportError {
-                                code: workdir::http::WorkdirTransportErrorCode::Unsupported,
+                                code: workdir::http::WorkdirTransportErrorCode::InvalidRequest,
                                 message,
                             }));
                             continue;
@@ -26454,6 +26548,26 @@ mod tests {
         WorkspaceRuntimeBinding,
     };
 
+    fn valid_gif_with_len(target_len: usize) -> Vec<u8> {
+        let fixture = include_bytes!("../../tools/tests/fixtures/view-image/valid.gif");
+        assert_eq!(fixture.last(), Some(&0x3b));
+        let mut bytes = fixture[..fixture.len() - 1].to_vec();
+        bytes.extend_from_slice(&[0x21, 0xfe]);
+        let mut remaining = target_len.checked_sub(bytes.len() + 2).unwrap();
+        while remaining > 0 {
+            let mut block = remaining.min(256);
+            if remaining - block == 1 {
+                block -= 1;
+            }
+            bytes.push((block - 1) as u8);
+            bytes.extend(std::iter::repeat_n(b'x', block - 1));
+            remaining -= block;
+        }
+        bytes.extend_from_slice(&[0, 0x3b]);
+        assert_eq!(bytes.len(), target_len);
+        bytes
+    }
+
     #[test]
     fn external_permission_levels_map_to_existing_bits_and_reject_legacy_partial_grants() {
         let bits = |capabilities| {
@@ -27930,7 +28044,7 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn external_provider_websocket_routes_files_and_commands_then_reconnects_and_revokes() {
+    async fn external_provider_websocket_runs_production_cli_pump_for_images_and_revoke() {
         let dir = tempfile::tempdir().unwrap();
         init_clean_git_workspace(dir.path());
         let api = test_api(dir.path()).await;
@@ -27999,6 +28113,50 @@ mod tests {
             })
         };
 
+        let (mut old_provider, _) = connect_async(&url).await.unwrap();
+        let old_registration = serde_json::to_string(&register(1)).unwrap().replacen(
+            r#""version":2"#,
+            r#""version":1"#,
+            1,
+        );
+        old_provider
+            .send(Message::Text(old_registration.into()))
+            .await
+            .unwrap();
+        let rejected = old_provider.next().await.unwrap().unwrap();
+        let Message::Close(Some(frame)) = rejected else {
+            panic!("old provider must receive a bounded compatibility close reason");
+        };
+        assert!(
+            frame
+                .reason
+                .contains("unsupported External Workdir protocol version 1")
+        );
+        assert!(frame.reason.contains("requires 2"));
+
+        let (mut smaller_provider, _) = connect_async(&url).await.unwrap();
+        let mut smaller_registration = serde_json::to_value(register(1)).unwrap();
+        smaller_registration["message"]["registration"]["read_limits"] = serde_json::json!({
+            "max_source_bytes": 32 * 1024 * 1024,
+            "max_response_bytes": 512 * 1024,
+        });
+        smaller_provider
+            .send(Message::Text(
+                serde_json::to_string(&smaller_registration).unwrap().into(),
+            ))
+            .await
+            .unwrap();
+        let rejected = smaller_provider.next().await.unwrap().unwrap();
+        let Message::Close(Some(frame)) = rejected else {
+            panic!("smaller provider limits must receive the required effective limits");
+        };
+        assert!(frame.reason.contains("response=524288"), "{}", frame.reason);
+        assert!(
+            frame.reason.contains("response=1048576"),
+            "{}",
+            frame.reason
+        );
+
         let (mut first, _) = connect_async(&url).await.unwrap();
         first
             .send(Message::Text(
@@ -28026,20 +28184,49 @@ mod tests {
             tokio::time::sleep(std::time::Duration::from_millis(10)).await;
         }
 
-        let (mut second, _) = connect_async(&url).await.unwrap();
-        second
-            .send(Message::Text(
-                serde_json::to_string(&register(2)).unwrap().into(),
-            ))
-            .await
+        let provider_root = tempfile::tempdir().unwrap();
+        fs::write(provider_root.path().join("events.jsonl"), b"one\ntwo\n").unwrap();
+        let image_bytes = valid_gif_with_len(1024 * 1024 + 257);
+        fs::write(provider_root.path().join("image.gif"), &image_bytes).unwrap();
+        let pinned_provider_root = workdir::ExternalWorkdirRoot::pin(provider_root.path()).unwrap();
+        let local_session = workdir::LocalWorkdirSession::external_with_capabilities_pinned(
+            workdir::Workdir::new(&grant.working_directory_id),
+            pinned_provider_root,
+            workdir::BoundedReadLimits::EXTERNAL_DEFAULT,
+            workdir::WorkdirSessionCapabilities::ALL,
+        )
         .unwrap();
-        let registered = second.next().await.unwrap().unwrap().into_text().unwrap();
-        assert!(matches!(
-            serde_json::from_str::<ExternalWorkdirServerFrame>(&registered)
+        let (second, _) = connect_async(&url).await.unwrap();
+        let registration = register(2);
+        let provider = tokio::spawn(async move {
+            yoi::workdir_share::serve_external_workdir_provider_socket(
+                second,
+                registration,
+                &local_session,
+                2,
+                std::future::pending::<std::result::Result<(), String>>(),
+            )
+            .await
+        });
+        for _ in 0..50 {
+            if api
+                .store
+                .get_external_workdir_grant(TEST_WORKSPACE_ID, &grant.grant_id)
                 .unwrap()
-                .message,
-            ExternalWorkdirServerMessage::Registered { generation: 2, .. }
-        ));
+                .is_some_and(|stored| stored.status == "online")
+            {
+                break;
+            }
+            tokio::time::sleep(std::time::Duration::from_millis(10)).await;
+        }
+        assert_eq!(
+            api.store
+                .get_external_workdir_grant(TEST_WORKSPACE_ID, &grant.grant_id)
+                .unwrap()
+                .unwrap()
+                .status,
+            "online"
+        );
 
         api.store
             .upsert_workdir_registry(&WorkdirRegistryRecord {
@@ -28107,16 +28294,6 @@ mod tests {
             external_capabilities,
             workdir::WorkdirSessionCapabilities::ALL
         );
-        let provider_root = tempfile::tempdir().unwrap();
-        fs::write(provider_root.path().join("events.jsonl"), b"one\ntwo\n").unwrap();
-        let pinned_provider_root = workdir::ExternalWorkdirRoot::pin(provider_root.path()).unwrap();
-        let local_session = workdir::LocalWorkdirSession::external_with_capabilities_pinned(
-            workdir::Workdir::new(&grant.working_directory_id),
-            pinned_provider_root,
-            workdir::BoundedReadLimits::EXTERNAL_DEFAULT,
-            workdir::WorkdirSessionCapabilities::ALL,
-        )
-        .unwrap();
         let session_lock = current_worker_session_lock(&api, &worker);
         let session_guard = session_lock.lock().await;
         let broker_session =
@@ -28128,10 +28305,7 @@ mod tests {
             workdir::WorkdirSessionCapabilities::ALL
         );
         drop(session_guard);
-        let read = {
-            let broker_session = broker_session.clone();
-            tokio::spawn(async move {
-                broker_session
+        let read_result = broker_session
             .read(workdir::ReadRequest {
                 path: workdir::WorkdirPath::new("events.jsonl").unwrap(),
                 offset: 0,
@@ -28139,151 +28313,52 @@ mod tests {
                 max_bytes: 1024,
             })
             .await
-            })
-        };
-        let (operation_id, operation) = loop {
-            let text = second.next().await.unwrap().unwrap().into_text().unwrap();
-            let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&text).unwrap();
-            if let ExternalWorkdirServerMessage::Operation {
-                generation: 2,
-                operation_id,
-                operation,
-            } = frame.message
-            {
-                break (operation_id, operation);
-            }
-        };
-        let result = workdir::http::dispatch_workdir_session_operation(
-            &local_session,
-            operation.into_inner(),
-        )
-        .await
-        .unwrap()
-        .try_into()
             .unwrap();
-        second
-            .send(Message::Text(
-                serde_json::to_string(&ExternalWorkdirProviderFrame::current(
-                    ExternalWorkdirProviderMessage::OperationResult {
-                        generation: 2,
-                        operation_id,
-                        outcome: ExternalWorkdirOperationOutcome::Completed { result },
-                    },
-                ))
-                .unwrap()
-                .into(),
-            ))
-            .await
-            .unwrap();
-        let read_result = read.await.unwrap().unwrap();
         assert_eq!(read_result.bytes, b"one\ntwo\n");
 
-        let edit = {
-            let broker_session = broker_session.clone();
-            let expected_hash = read_result.content_hash;
-            tokio::spawn(async move {
-                broker_session
+        let (_meta, view_image) = tools::view_image_tool(broker_session.clone())();
+        let output = view_image
+            .execute(
+                r#"{"path":"image.gif"}"#,
+                agen::tool::ToolExecutionContext::default(),
+            )
+            .await
+            .unwrap();
+        let agen::tool::Attachment::Image(image) = &output.attachments[0];
+        assert_eq!(image.mime_type(), "image/gif");
+        assert_eq!(image.data(), image_bytes);
+
+        let error = view_image
+            .execute(
+                r#"{"path":"missing.gif"}"#,
+                agen::tool::ToolExecutionContext::default(),
+            )
+            .await
+            .unwrap_err()
+            .to_string();
+        assert!(error.contains("not found"), "{error}");
+
+        let edit = broker_session
             .edit(workdir::EditRequest {
                 path: workdir::WorkdirPath::new("events.jsonl").unwrap(),
                 old_string: "two".to_string(),
                 new_string: "changed".to_string(),
                 replace_all: false,
-                        expected_hash,
+                expected_hash: read_result.content_hash,
             })
             .await
-            })
-        };
-        let (operation_id, operation) = loop {
-            let text = second.next().await.unwrap().unwrap().into_text().unwrap();
-            let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&text).unwrap();
-            if let ExternalWorkdirServerMessage::Operation {
-                generation: 2,
-                operation_id,
-                operation,
-            } = frame.message
-            {
-                break (operation_id, operation);
-            }
-        };
-        assert!(matches!(
-            operation.as_inner(),
-            WorkdirSessionOperation::Edit(_)
-        ));
-        let result = workdir::http::dispatch_workdir_session_operation(
-            &local_session,
-            operation.into_inner(),
-        )
-        .await
-        .unwrap()
-        .try_into()
             .unwrap();
-        second
-            .send(Message::Text(
-                serde_json::to_string(&ExternalWorkdirProviderFrame::current(
-                    ExternalWorkdirProviderMessage::OperationResult {
-                        generation: 2,
-                        operation_id,
-                        outcome: ExternalWorkdirOperationOutcome::Completed { result },
-                    },
-                ))
-                .unwrap()
-                .into(),
-            ))
-            .await
-            .unwrap();
-        assert_eq!(edit.await.unwrap().unwrap().replacements, 1);
+        assert_eq!(edit.replacements, 1);
 
-        let write = {
-            let broker_session = broker_session.clone();
-            tokio::spawn(async move {
-                broker_session
+        let write = broker_session
             .write(workdir::WriteRequest {
                 path: workdir::WorkdirPath::new("created.txt").unwrap(),
                 content: b"created".to_vec(),
                 expected_hash: None,
             })
             .await
-            })
-        };
-        let (operation_id, operation) = loop {
-            let text = second.next().await.unwrap().unwrap().into_text().unwrap();
-            let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&text).unwrap();
-            if let ExternalWorkdirServerMessage::Operation {
-                generation: 2,
-                operation_id,
-                operation,
-            } = frame.message
-            {
-                break (operation_id, operation);
-            }
-        };
-        assert!(matches!(
-            operation.as_inner(),
-            WorkdirSessionOperation::Write(_)
-        ));
-        let result = workdir::http::dispatch_workdir_session_operation(
-            &local_session,
-            operation.into_inner(),
-        )
-        .await
-        .unwrap()
-        .try_into()
             .unwrap();
-        second
-            .send(Message::Text(
-                serde_json::to_string(&ExternalWorkdirProviderFrame::current(
-                    ExternalWorkdirProviderMessage::OperationResult {
-                        generation: 2,
-                        operation_id,
-                        outcome: ExternalWorkdirOperationOutcome::Completed { result },
-                    },
-                ))
-                .unwrap()
-                .into(),
-            ))
-            .await
-            .unwrap();
-        assert!(write.await.unwrap().unwrap().created);
+        assert!(write.created);
         assert_eq!(
             fs::read_to_string(provider_root.path().join("events.jsonl")).unwrap(),
             "one\nchanged\n"
@@ -28292,13 +28367,9 @@ mod tests {
             fs::read_to_string(provider_root.path().join("created.txt")).unwrap(),
             "created"
         );
-        let command_start = {
-            let broker_session = broker_session.clone();
-            tokio::spawn(async move {
-                broker_session
+        let command_handle = broker_session
             .start_command(workdir::CommandRequest {
-                        command: "sleep 30 & child=$!; echo $child > child.pid; wait $child"
-                            .to_string(),
+                command: "sleep 30 & child=$!; echo $child > child.pid; wait $child".to_string(),
                 timeout_secs: 30,
                 output_limit: 1024,
                 cwd: workdir::WorkdirPath::root(),
@@ -28306,50 +28377,7 @@ mod tests {
                 tool_call_id: Some("call-e2e".to_string()),
             })
             .await
-            })
-        };
-        let (operation_id, operation) = loop {
-            let text = second.next().await.unwrap().unwrap().into_text().unwrap();
-            let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&text).unwrap();
-            if let ExternalWorkdirServerMessage::Operation {
-                generation: 2,
-                operation_id,
-                operation,
-            } = frame.message
-            {
-                break (operation_id, operation);
-            }
-        };
-        assert!(matches!(
-            operation.as_inner(),
-            WorkdirSessionOperation::CommandStart(workdir::CommandRequest {
-                spill_dir: None,
-                ..
-            })
-        ));
-        let result = workdir::http::dispatch_workdir_session_operation(
-            &local_session,
-            operation.into_inner(),
-        )
-        .await
-        .unwrap()
-        .try_into()
             .unwrap();
-        second
-            .send(Message::Text(
-                serde_json::to_string(&ExternalWorkdirProviderFrame::current(
-                    ExternalWorkdirProviderMessage::OperationResult {
-                        generation: 2,
-                        operation_id,
-                        outcome: ExternalWorkdirOperationOutcome::Completed { result },
-                    },
-                ))
-                .unwrap()
-                .into(),
-            ))
-            .await
-            .unwrap();
-        let command_handle = command_start.await.unwrap().unwrap();
 
         for _ in 0..100 {
             if provider_root.path().join("child.pid").is_file() {
@@ -28359,162 +28387,25 @@ mod tests {
         }
         assert!(provider_root.path().join("child.pid").is_file());
 
-        let command_output = {
-            let broker_session = broker_session.clone();
-            let handle = command_handle.clone();
-            tokio::spawn(async move {
-                broker_session
+        let command_output = broker_session
             .command_output(workdir::CommandOutputRequest {
-                        handle,
+                handle: command_handle,
                 cursor: 0,
                 limit: 1024,
                 wait: false,
             })
             .await
-            })
-        };
-        let (operation_id, operation) = loop {
-            let text = second.next().await.unwrap().unwrap().into_text().unwrap();
-            let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&text).unwrap();
-            if let ExternalWorkdirServerMessage::Operation {
-                generation: 2,
-                operation_id,
-                operation,
-            } = frame.message
-            {
-                break (operation_id, operation);
-            }
-        };
-        assert!(matches!(
-            operation.as_inner(),
-            WorkdirSessionOperation::CommandOutput(workdir::CommandOutputRequest {
-                wait: false,
-                ..
-            })
-        ));
-        let result = workdir::http::dispatch_workdir_session_operation(
-            &local_session,
-            operation.into_inner(),
-        )
-        .await
-        .unwrap()
-        .try_into()
             .unwrap();
-        second
-            .send(Message::Text(
-                serde_json::to_string(&ExternalWorkdirProviderFrame::current(
-                    ExternalWorkdirProviderMessage::OperationResult {
-                        generation: 2,
-                        operation_id,
-                        outcome: ExternalWorkdirOperationOutcome::Completed { result },
-                    },
-                ))
-                .unwrap()
-                .into(),
-            ))
-            .await
-            .unwrap();
-        let command_output = command_output.await.unwrap().unwrap();
         assert_eq!(command_output.status, workdir::CommandStatus::Running);
         assert_eq!(command_output.output_path, None);
 
-        let revoker = {
-            let api = api.clone();
-            let grant_id = grant.grant_id.clone();
-            tokio::spawn(async move {
-                scoped_revoke_external_workdir_grant(
-                    State(api),
+        let Json(revoked) = scoped_revoke_external_workdir_grant(
+            State(api.clone()),
             Extension(test_browser_request_actor()),
-                    AxumPath((TEST_WORKSPACE_ID.to_string(), grant_id)),
-                )
-                .await
-            })
-        };
-        let (operation_id, operation) = loop {
-            let text = second.next().await.unwrap().unwrap().into_text().unwrap();
-            let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&text).unwrap();
-            if let ExternalWorkdirServerMessage::Operation {
-                generation: 2,
-                operation_id,
-                operation,
-            } = frame.message
-            {
-                break (operation_id, operation);
-            }
-        };
-        assert!(matches!(
-            operation.as_inner(),
-            WorkdirSessionOperation::CommandCancel(_)
-        ));
-        let result = workdir::http::dispatch_workdir_session_operation(
-            &local_session,
-            operation.into_inner(),
-        )
-        .await
-        .unwrap()
-        .try_into()
-        .unwrap();
-        second
-            .send(Message::Text(
-                serde_json::to_string(&ExternalWorkdirProviderFrame::current(
-                    ExternalWorkdirProviderMessage::OperationResult {
-                        generation: 2,
-                        operation_id,
-                        outcome: ExternalWorkdirOperationOutcome::Completed { result },
-                    },
-                ))
-                .unwrap()
-                .into(),
-            ))
-            .await
-            .unwrap();
-
-        let (operation_id, operation) = loop {
-            let text = second.next().await.unwrap().unwrap().into_text().unwrap();
-            let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&text).unwrap();
-            if let ExternalWorkdirServerMessage::Operation {
-                generation: 2,
-                operation_id,
-                operation,
-            } = frame.message
-            {
-                break (operation_id, operation);
-            }
-        };
-        assert!(matches!(
-            operation.as_inner(),
-            WorkdirSessionOperation::CommandOutput(workdir::CommandOutputRequest {
-                wait: true,
-                ..
-            })
-        ));
-        let provider_result = workdir::http::dispatch_workdir_session_operation(
-            &local_session,
-            operation.into_inner(),
+            AxumPath((TEST_WORKSPACE_ID.to_string(), grant.grant_id.clone())),
         )
         .await
         .unwrap();
-        assert!(matches!(
-            provider_result,
-            WorkdirSessionOperationResult::CommandOutput(ref output)
-                if output.status != workdir::CommandStatus::Running
-        ));
-        let result = provider_result.try_into().unwrap();
-        second
-            .send(Message::Text(
-                serde_json::to_string(&ExternalWorkdirProviderFrame::current(
-                    ExternalWorkdirProviderMessage::OperationResult {
-                        generation: 2,
-                        operation_id,
-                        outcome: ExternalWorkdirOperationOutcome::Completed { result },
-                    },
-                ))
-                .unwrap()
-                .into(),
-            ))
-            .await
-            .unwrap();
-        let Json(revoked) = revoker.await.unwrap().unwrap();
         assert_eq!(revoked.status, "revoked");
         let active_links = api
             .store
@@ -28526,27 +28417,12 @@ mod tests {
         assert_eq!(active_links.len(), 1);
         assert_eq!(active_links[0].alias, "repository");
         assert_eq!(active_links[0].workdir_id, "analysis-repository");
-        let revoke = loop {
-            let text = second.next().await.unwrap().unwrap().into_text().unwrap();
-            let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&text).unwrap();
-            if matches!(frame.message, ExternalWorkdirServerMessage::Revoke { .. }) {
-                break frame;
-            }
-        };
-        assert!(matches!(
-            revoke.message,
-            ExternalWorkdirServerMessage::Revoke { generation: 2, .. }
-        ));
-        second
-            .send(Message::Text(
-                serde_json::to_string(&ExternalWorkdirProviderFrame::current(
-                    ExternalWorkdirProviderMessage::RevokeAcknowledged { generation: 2 },
-                ))
-                .unwrap()
-                .into(),
-            ))
+        let provider_end = tokio::time::timeout(std::time::Duration::from_secs(2), provider)
             .await
+            .expect("production CLI provider pump did not acknowledge revocation")
+            .unwrap()
             .unwrap();
+        assert_eq!(provider_end, yoi::workdir_share::ProviderEnd::Revoked);
         server.abort();
     }
 

crates/yoi/src/lib.rs

@@ -0,0 +1 @@
+pub mod workdir_share;

crates/yoi/src/main.rs

@@ -4,10 +4,11 @@ mod objective_cli;
 mod plugin_cli;
 mod session_cli;
 mod ticket_cli;
-mod workdir_share;
 mod worker_cleanup_cli;
 mod workspace_bootstrap;
 
+use yoi::workdir_share;
+
 use std::collections::BTreeMap;
 use std::fmt;
 use std::fs;

crates/yoi/src/workdir_share.rs

@@ -25,7 +25,7 @@ use workdir::{
 };
 
 #[derive(Debug, Clone, PartialEq, Eq)]
-pub(crate) struct WorkdirShareOptions {
+pub struct WorkdirShareOptions {
     pub path: PathBuf,
     pub workspace_id: Option<String>,
     pub backend_url: String,
@@ -37,6 +37,39 @@ pub(crate) struct WorkdirShareOptions {
 
 const PROVIDER_OPERATION_TIMEOUT: Duration = Duration::from_secs(30);
 
+fn validate_provider_registration(message: Message, generation: u64) -> Result<(), String> {
+    let registered = match message {
+        Message::Text(text) => text,
+        Message::Close(Some(frame)) => {
+            let reason = frame.reason.trim();
+            return Err(if reason.is_empty() {
+                "Backend rejected the External Workdir provider registration".to_string()
+            } else {
+                format!("Backend rejected the External Workdir provider registration: {reason}")
+            });
+        }
+        Message::Close(None) => {
+            return Err("Backend rejected the External Workdir provider registration".to_string());
+        }
+        _ => {
+            return Err(
+                "Backend returned an invalid External Workdir registration frame".to_string(),
+            );
+        }
+    };
+    let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&registered)
+        .map_err(|error| format!("Backend returned an invalid External Workdir frame: {error}"))?;
+    if matches!(
+        frame.message,
+        ExternalWorkdirServerMessage::Registered { generation: registered_generation, .. }
+            if registered_generation == generation
+    ) {
+        Ok(())
+    } else {
+        Err("Backend rejected the External Workdir provider registration".to_string())
+    }
+}
+
 fn provider_operation_timeout(operation: &workdir::http::WorkdirSessionOperation) -> Duration {
     if matches!(
         operation,
@@ -49,7 +82,7 @@ fn provider_operation_timeout(operation: &workdir::http::WorkdirSessionOperation
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
-enum ProviderEnd {
+pub enum ProviderEnd {
     Disconnected,
     Revoked,
     Interrupted,
@@ -188,7 +221,7 @@ struct ResolvedWorkdirShareOptions {
     permissions: server_api::ExternalWorkdirPermissions,
 }
 
-pub(crate) fn parse_ttl(value: &str) -> Result<Duration, String> {
+pub fn parse_ttl(value: &str) -> Result<Duration, String> {
     let (number, multiplier) = if let Some(value) = value.strip_suffix('h') {
         (value, 60 * 60)
     } else if let Some(value) = value.strip_suffix('m') {
@@ -424,7 +457,7 @@ async fn resolve_share_options(
     configure_interactively(options, &workspaces, &mut input, &mut output)
 }
 
-pub(crate) async fn run(options: WorkdirShareOptions) -> Result<(), String> {
+pub async fn run(options: WorkdirShareOptions) -> Result<(), String> {
     let Some(options) = resolve_share_options(options).await? else {
         eprintln!("External Workdir share cancelled; no grant was created.");
         return Ok(());
@@ -636,7 +669,7 @@ async fn serve_provider_connection(
         .max_message_size(Some(workdir::external::MAX_EXTERNAL_SERVER_FRAME_BYTES))
         .max_frame_size(Some(workdir::external::MAX_EXTERNAL_SERVER_FRAME_BYTES));
     let connection = connect_async_with_config(request, Some(websocket_config), false);
-    let (mut socket, _) = tokio::select! {
+    let (socket, _) = tokio::select! {
         signal = tokio::signal::ctrl_c() => {
             signal.map_err(|error| format!("failed to wait for Ctrl-C: {error}"))?;
             revoke(server_api_client, &options.workspace_id, &grant.grant_id).await?;
@@ -658,11 +691,40 @@ async fn serve_provider_connection(
                 read_limits: BoundedReadLimits::EXTERNAL_DEFAULT,
             },
         });
+    let end =
+        serve_external_workdir_provider_socket(socket, registration, session, generation, async {
+            tokio::signal::ctrl_c()
+                .await
+                .map_err(|error| format!("failed to wait for Ctrl-C: {error}"))
+        })
+        .await?;
+    if end == ProviderEnd::Interrupted {
+        revoke(server_api_client, &options.workspace_id, &grant.grant_id).await?;
+    }
+    Ok(end)
+}
+
+/// Run the production External Workdir provider protocol over an established WebSocket.
+///
+/// The CLI uses this pump after opening its authenticated Backend connection. Keeping the
+/// protocol pump separate lets composed tests exercise the same registration, operation,
+/// cancellation, and result-forwarding implementation without spawning a second CLI process.
+pub async fn serve_external_workdir_provider_socket<S, I>(
+    mut socket: tokio_tungstenite::WebSocketStream<S>,
+    registration: ExternalWorkdirProviderFrame,
+    session: &LocalWorkdirSession,
+    generation: u64,
+    interrupt: I,
+) -> Result<ProviderEnd, String>
+where
+    S: tokio::io::AsyncRead + tokio::io::AsyncWrite + Unpin,
+    I: std::future::Future<Output = Result<(), String>>,
+{
+    tokio::pin!(interrupt);
     send_provider_frame(&mut socket, &registration).await?;
     let registered = tokio::select! {
-        signal = tokio::signal::ctrl_c() => {
-            signal.map_err(|error| format!("failed to wait for Ctrl-C: {error}"))?;
-            revoke(server_api_client, &options.workspace_id, &grant.grant_id).await?;
+        signal = &mut interrupt => {
+            signal?;
             return Ok(ProviderEnd::Interrupted);
         }
         registered = tokio::time::timeout(Duration::from_secs(10), socket.next()) => {
@@ -672,18 +734,7 @@ async fn serve_provider_connection(
                 .map_err(|error| format!("External Workdir provider registration failed: {error}"))?
         }
     };
-    let Message::Text(registered) = registered else {
-        return Err("Backend returned an invalid External Workdir registration frame".to_string());
-    };
-    let frame = serde_json::from_str::<ExternalWorkdirServerFrame>(&registered)
-        .map_err(|error| format!("Backend returned an invalid External Workdir frame: {error}"))?;
-    if !matches!(
-        frame.message,
-        ExternalWorkdirServerMessage::Registered { generation: registered_generation, .. }
-            if registered_generation == generation
-    ) {
-        return Err("Backend rejected the External Workdir provider registration".to_string());
-    }
+    validate_provider_registration(registered, generation)?;
     println!("Connection: online (generation {generation})");
 
     let (completion_sender, mut completions) =
@@ -691,10 +742,9 @@ async fn serve_provider_connection(
     let mut operations = HashMap::<String, OperationTask>::new();
     loop {
         tokio::select! {
-            signal = tokio::signal::ctrl_c() => {
-                signal.map_err(|error| format!("failed to wait for Ctrl-C: {error}"))?;
+            signal = &mut interrupt => {
+                signal?;
                 stop_provider_operations(session, &mut operations, &mut completions).await?;
-                revoke(server_api_client, &options.workspace_id, &grant.grant_id).await?;
                 return Ok(ProviderEnd::Interrupted);
             }
             completion = completions.recv() => {
@@ -903,7 +953,7 @@ async fn execute_operation(
             Ok(result) => ExternalWorkdirOperationOutcome::Completed { result },
             Err(message) => ExternalWorkdirOperationOutcome::Failed {
                 error: ExternalWorkdirOperationError::from_transport_error(WorkdirTransportError {
-                    code: workdir::http::WorkdirTransportErrorCode::Unsupported,
+                    code: workdir::http::WorkdirTransportErrorCode::InvalidRequest,
                     message,
                 }),
             },
@@ -1047,6 +1097,23 @@ mod tests {
         }
     }
 
+    #[test]
+    fn provider_registration_surfaces_backend_close_reason() {
+        use tokio_tungstenite::tungstenite::protocol::CloseFrame;
+        use tokio_tungstenite::tungstenite::protocol::frame::coding::CloseCode;
+
+        let error = validate_provider_registration(
+            Message::Close(Some(CloseFrame {
+                code: CloseCode::Policy,
+                reason: "provider read limits source=1024 response=512; Backend requires source=2048 response=1024".into(),
+            })),
+            1,
+        )
+        .unwrap_err();
+        assert!(error.contains("provider read limits"), "{error}");
+        assert!(error.contains("Backend requires"), "{error}");
+    }
+
     #[test]
     fn interactive_share_defaults_to_first_workspace_read_only_and_unlimited() {
         let workspaces = [workspace("workspace-a", "Alpha")];