feat: add session-owned uploaded file attachments

crates/protocol/src/lib.rs

@@ -251,6 +251,48 @@ pub struct PasteArtifactRef {
     pub source_entry_id: String,
 }
 
+/// Availability recorded for an uploaded client-local file.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+#[cfg_attr(feature = "json-schema", derive(schemars::JsonSchema))]
+#[serde(rename_all = "snake_case")]
+pub enum UploadedFileAvailability {
+    Available,
+    Unavailable,
+    IntegrityFailed,
+}
+
+impl UploadedFileAvailability {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            Self::Available => "available",
+            Self::Unavailable => "unavailable",
+            Self::IntegrityFailed => "integrity_failed",
+        }
+    }
+}
+
+/// Session-owned immutable reference to a client-local uploaded file.
+///
+/// Upload transports return an unbound reference. Worker fills
+/// `source_entry_id` immediately before the containing user input is committed;
+/// committed Session Log and public snapshot records therefore always retain
+/// the durable source-entry identity without storing the file body.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+#[cfg_attr(feature = "json-schema", derive(schemars::JsonSchema))]
+pub struct UploadedFileRef {
+    pub artifact_id: String,
+    pub file_name: String,
+    pub media_type: String,
+    pub created_at_ms: u64,
+    pub availability: UploadedFileAvailability,
+    pub byte_len: u64,
+    pub sha256: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub source_entry_id: Option<String>,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
 #[cfg_attr(feature = "json-schema", derive(schemars::JsonSchema))]
@@ -272,6 +314,10 @@ pub enum Segment {
     /// committing input. Clients may receive this in history/event projections;
     /// the body is intentionally absent.
     PasteArtifact { artifact: PasteArtifactRef },
+    /// Client-local file uploaded into the owning Worker session before submit.
+    /// The Session Log stores only this immutable reference, never file bytes or
+    /// the client's local path.
+    UploadedFile { file: UploadedFileRef },
     /// `@<path>` file-system reference. Worker resolves readable files to
     /// `[File: <path>]` attachments and readable normal directories to shallow
     /// `[Dir: <path>]` listings; the flattened user text keeps the literal
@@ -327,6 +373,20 @@ impl Segment {
                         artifact.sha256
                     );
                 }
+                Segment::UploadedFile { file } => {
+                    use std::fmt::Write as _;
+                    let _ = write!(
+                        out,
+                        "[Attached file {} stored as input artifact {}: {} bytes, {}, {}, created at {} ms, sha256 {}; use SearchInputArtifact and ReadInputArtifact for supported text content]",
+                        file.file_name,
+                        file.artifact_id,
+                        file.byte_len,
+                        file.media_type,
+                        file.availability.as_str(),
+                        file.created_at_ms,
+                        file.sha256
+                    );
+                }
                 Segment::FileRef { path } => {
                     out.push('@');
                     out.push_str(path);
@@ -1305,6 +1365,29 @@ mod tests {
         assert!(!projected.contains("pasted body"));
     }
 
+    #[test]
+    fn uploaded_file_segment_roundtrips_without_path_or_body() {
+        let file = UploadedFileRef {
+            artifact_id: "019ca7c8-57b6-7f05-8edf-524147aba7b3".to_string(),
+            file_name: "notes.md".to_string(),
+            media_type: "text/markdown".to_string(),
+            created_at_ms: 1_700_000_000_001,
+            availability: UploadedFileAvailability::Available,
+            byte_len: 128,
+            sha256: "b".repeat(64),
+            source_entry_id: Some("entry-2".to_string()),
+        };
+        let segment = Segment::UploadedFile { file: file.clone() };
+        let json = serde_json::to_string(&segment).unwrap();
+        assert!(!json.contains("/home/user/private"));
+        assert!(!json.contains("file body"));
+        assert_eq!(serde_json::from_str::<Segment>(&json).unwrap(), segment);
+        let projected = Segment::flatten_to_text(&[segment]);
+        assert!(projected.contains("notes.md"));
+        assert!(projected.contains(&file.artifact_id));
+        assert!(projected.contains("ReadInputArtifact"));
+    }
+
     #[test]
     fn method_run_flow_segment_roundtrip() {
         let method = Method::Run {

crates/protocol/src/typescript.rs

@@ -11,7 +11,8 @@ use crate::{
     PasteArtifactRef, Permission, RewindSummary, RewindTarget, RewindTargetId, RunResult,
     ScopeRule, Segment, SessionContentPart, SessionEntryProvenance, SessionMessageRole,
     SessionSnapshot, SessionSnapshotEntry, SessionSnapshotEntryData, SessionToolAttachment,
-    ToolResultDisposition, TurnResult, WorkerEvent, WorkerStatus,
+    ToolResultDisposition, TurnResult, UploadedFileAvailability, UploadedFileRef, WorkerEvent,
+    WorkerStatus,
     subscription::{
         EventSubscriptionSelector, SubscriptionEvent, SubscriptionEventPayload, SubscriptionFrame,
         SubscriptionFramePayload, SubscriptionId, SubscriptionRejectionCode, SubscriptionRequest,
@@ -59,6 +60,8 @@ pub fn generated_protocol_types() -> String {
     push_decl::<CommandEvent>(&cfg, &mut output);
     push_decl::<CompactionLifecycleState>(&cfg, &mut output);
     push_decl::<CompactionLifecycle>(&cfg, &mut output);
+    push_decl::<UploadedFileAvailability>(&cfg, &mut output);
+    push_decl::<UploadedFileRef>(&cfg, &mut output);
     push_decl::<ScopeRule>(&cfg, &mut output);
     push_decl::<CompletionEntry>(&cfg, &mut output);
     push_decl::<RewindTargetId>(&cfg, &mut output);

crates/session-store/src/fs_store.rs

@@ -19,8 +19,12 @@ use crate::event_trace::TraceEntry;
 use crate::paste_artifact::{read_from_dir, write_to_dir};
 use crate::segment_log::LogEntry;
 use crate::store::{Store, StoreError};
-use crate::{PasteArtifactLimits, SegmentId, SessionId};
+use crate::uploaded_file::{
-use protocol::PasteArtifactRef;
+    bind_uploaded_file, delete_uploaded_file, read_uploaded_file, read_uploaded_file_by_id,
+    write_uploaded_file,
+};
+use crate::{PasteArtifactLimits, SegmentId, SessionId, UploadedFileLimits};
+use protocol::{PasteArtifactRef, UploadedFileRef};
 use std::fs;
 use std::io::{Read, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
@@ -389,6 +393,72 @@ impl Store for FsStore {
         read_from_dir(&self.paste_artifact_dir(session_id), artifact_id)
     }
 
+    fn write_uploaded_file(
+        &self,
+        session_id: SessionId,
+        file_name: &str,
+        media_type: &str,
+        content: &[u8],
+        limits: UploadedFileLimits,
+    ) -> Result<UploadedFileRef, StoreError> {
+        let _guard = self
+            .append_lock
+            .lock()
+            .map_err(|_| std::io::Error::other("session store append lock was poisoned"))?;
+        write_uploaded_file(
+            &self.paste_artifact_dir(session_id),
+            file_name,
+            media_type,
+            content,
+            limits,
+        )
+    }
+
+    fn read_uploaded_file(
+        &self,
+        session_id: SessionId,
+        reference: &UploadedFileRef,
+    ) -> Result<Vec<u8>, StoreError> {
+        read_uploaded_file(&self.paste_artifact_dir(session_id), reference)
+    }
+
+    fn read_uploaded_file_by_id(
+        &self,
+        session_id: SessionId,
+        artifact_id: &str,
+    ) -> Result<(UploadedFileRef, Vec<u8>), StoreError> {
+        read_uploaded_file_by_id(&self.paste_artifact_dir(session_id), artifact_id)
+    }
+
+    fn bind_uploaded_file(
+        &self,
+        session_id: SessionId,
+        reference: &UploadedFileRef,
+        source_entry_id: &str,
+    ) -> Result<UploadedFileRef, StoreError> {
+        let _guard = self
+            .append_lock
+            .lock()
+            .map_err(|_| std::io::Error::other("session store append lock was poisoned"))?;
+        bind_uploaded_file(
+            &self.paste_artifact_dir(session_id),
+            reference,
+            source_entry_id,
+        )
+    }
+
+    fn delete_uploaded_file(
+        &self,
+        session_id: SessionId,
+        artifact_id: &str,
+    ) -> Result<bool, StoreError> {
+        let _guard = self
+            .append_lock
+            .lock()
+            .map_err(|_| std::io::Error::other("session store append lock was poisoned"))?;
+        delete_uploaded_file(&self.paste_artifact_dir(session_id), artifact_id)
+    }
+
     fn append_trace(
         &self,
         session_id: SessionId,
@@ -548,6 +618,84 @@ mod tests {
         );
     }
 
+    #[test]
+    fn uploaded_files_are_session_scoped_integrity_checked_and_removable() {
+        let tmp = tempfile::TempDir::new().unwrap();
+        let store = FsStore::new(tmp.path()).unwrap();
+        let owner = new_session_id();
+        let other = new_session_id();
+        let limits = UploadedFileLimits {
+            max_file_bytes: 16,
+            max_session_bytes: 16,
+        };
+        let reference = store
+            .write_uploaded_file(owner, "notes.txt", "text/plain", b"hello", limits)
+            .unwrap();
+
+        assert_eq!(reference.file_name, "notes.txt");
+        assert_eq!(reference.media_type, "text/plain");
+        assert_eq!(reference.byte_len, 5);
+        assert_eq!(reference.source_entry_id, None);
+        assert_eq!(
+            store.read_uploaded_file(owner, &reference).unwrap(),
+            b"hello"
+        );
+        assert!(store.read_uploaded_file(other, &reference).is_err());
+
+        let mut forged = reference.clone();
+        forged.file_name = "other.txt".to_string();
+        assert!(matches!(
+            store.read_uploaded_file(owner, &forged),
+            Err(StoreError::ArtifactIntegrityMismatch)
+        ));
+        assert!(
+            store
+                .delete_uploaded_file(owner, &reference.artifact_id)
+                .unwrap()
+        );
+        assert!(
+            !store
+                .delete_uploaded_file(owner, &reference.artifact_id)
+                .unwrap()
+        );
+        assert!(store.read_uploaded_file(owner, &reference).is_err());
+    }
+
+    #[test]
+    fn uploaded_file_validation_and_shared_quota_fail_closed() {
+        let tmp = tempfile::TempDir::new().unwrap();
+        let store = FsStore::new(tmp.path()).unwrap();
+        let session_id = new_session_id();
+        let limits = UploadedFileLimits {
+            max_file_bytes: 8,
+            max_session_bytes: 8,
+        };
+        assert!(matches!(
+            store.write_uploaded_file(session_id, "../secret", "text/plain", b"x", limits),
+            Err(StoreError::InvalidUploadedFileName)
+        ));
+        assert!(matches!(
+            store.write_uploaded_file(session_id, "notes.txt", "not a type", b"x", limits),
+            Err(StoreError::InvalidUploadedFileMediaType)
+        ));
+        store
+            .write_paste_artifact(
+                session_id,
+                "entry-1",
+                "1234",
+                PasteArtifactLimits {
+                    max_artifact_bytes: 8,
+                    max_session_bytes: 8,
+                    max_session_artifacts: 4,
+                },
+            )
+            .unwrap();
+        assert!(matches!(
+            store.write_uploaded_file(session_id, "notes.txt", "text/plain", b"56789", limits),
+            Err(StoreError::ArtifactQuotaExceeded)
+        ));
+    }
+
     #[test]
     fn paste_artifact_limits_and_corruption_fail_closed() {
         let tmp = tempfile::TempDir::new().unwrap();

crates/session-store/src/lib.rs

@@ -41,6 +41,7 @@ pub mod segment;
 pub mod segment_log;
 pub mod store;
 pub mod system_item;
+pub mod uploaded_file;
 pub mod worker_metadata;
 pub mod worker_session_store;
 
@@ -66,6 +67,10 @@ pub use store::{Store, StoreError};
 pub use system_item::{
     PromptRenderProvenance, SystemItem, SystemReminder, SystemReminderSource, render_worker_event,
 };
+pub use uploaded_file::{
+    DEFAULT_MAX_FILES_PER_SUBMISSION, DEFAULT_MAX_SESSION_ARTIFACT_BYTES,
+    DEFAULT_MAX_UPLOADED_FILE_BYTES, UploadedFileLimits,
+};
 pub use worker_metadata::{
     CombinedStore, FsWorkerStore, WorkerActiveSegmentRef, WorkerAggregateStore, WorkerMetadata,
     WorkerMetadataStore, WorkerPeer, WorkerReclaimedChild, WorkerSpawnedChild,

crates/session-store/src/paste_artifact.rs

@@ -38,6 +38,34 @@ pub(crate) struct StoredPasteArtifact {
     pub content: String,
 }
 
+pub(crate) fn stored_paste_usage(artifact_dir: &Path) -> Result<(u64, u64), StoreError> {
+    if !artifact_dir.exists() {
+        return Ok((0, 0));
+    }
+    let mut aggregate = 0_u64;
+    let mut artifact_count = 0_u64;
+    for entry in fs::read_dir(artifact_dir)? {
+        let path = entry?.path();
+        let Some(name) = path.file_name().and_then(|value| value.to_str()) else {
+            continue;
+        };
+        if !name.ends_with(".json") || name.ends_with(".file.json") {
+            continue;
+        }
+        let stored: StoredPasteArtifact = serde_json::from_slice(&fs::read(&path)?)?;
+        verify(&stored, &stored.reference.artifact_id)?;
+        artifact_count = artifact_count.checked_add(1).ok_or_else(|| {
+            StoreError::PasteArtifactLimit("session artifact count overflow".to_string())
+        })?;
+        aggregate = aggregate
+            .checked_add(stored.reference.byte_len)
+            .ok_or_else(|| {
+                StoreError::PasteArtifactLimit("session aggregate size overflow".to_string())
+            })?;
+    }
+    Ok((aggregate, artifact_count))
+}
+
 pub(crate) fn write_to_dir(
     artifact_dir: &Path,
     source_entry_id: &str,
@@ -58,24 +86,15 @@ pub(crate) fn write_to_dir(
         .write(true)
         .open(artifact_dir.join(".aggregate.lock"))?;
     FileExt::lock_exclusive(&aggregate_lock)?;
-    let mut aggregate = 0_u64;
+    let (paste_bytes, artifact_count) = stored_paste_usage(artifact_dir)?;
-    let mut artifact_count = 0_u64;
+    let (uploaded_bytes, uploaded_count) =
-    for entry in fs::read_dir(artifact_dir)? {
+        crate::uploaded_file::stored_uploaded_file_usage(artifact_dir)?;
-        let path = entry?.path();
+    let aggregate = paste_bytes.checked_add(uploaded_bytes).ok_or_else(|| {
-        if path.extension().and_then(|value| value.to_str()) != Some("json") {
+        StoreError::PasteArtifactLimit("session aggregate size overflow".to_string())
-            continue;
+    })?;
-        }
+    let artifact_count = artifact_count.checked_add(uploaded_count).ok_or_else(|| {
-        let stored: StoredPasteArtifact = serde_json::from_slice(&fs::read(&path)?)?;
+        StoreError::PasteArtifactLimit("session artifact count overflow".to_string())
-        verify(&stored, &stored.reference.artifact_id)?;
+    })?;
-        artifact_count = artifact_count.checked_add(1).ok_or_else(|| {
-            StoreError::PasteArtifactLimit("session artifact count overflow".to_string())
-        })?;
-        aggregate = aggregate
-            .checked_add(stored.reference.byte_len)
-            .ok_or_else(|| {
-                StoreError::PasteArtifactLimit("session aggregate size overflow".to_string())
-            })?;
-    }
     let projected = aggregate.checked_add(byte_len).ok_or_else(|| {
         StoreError::PasteArtifactLimit("session aggregate size overflow".to_string())
     })?;

crates/session-store/src/store.rs

@@ -13,8 +13,8 @@
 
 use crate::event_trace::TraceEntry;
 use crate::segment_log::LogEntry;
-use crate::{PasteArtifactLimits, SegmentId, SessionId};
+use crate::{PasteArtifactLimits, SegmentId, SessionId, UploadedFileLimits};
-use protocol::PasteArtifactRef;
+use protocol::{PasteArtifactRef, UploadedFileRef};
 
 /// Errors from the persistence store.
 #[derive(Debug, thiserror::Error)]
@@ -42,6 +42,30 @@ pub enum StoreError {
 
     #[error("paste artifact size limit exceeded: {0}")]
     PasteArtifactLimit(String),
+
+    #[error("uploaded file is too large")]
+    ArtifactTooLarge,
+
+    #[error("session artifact aggregate quota exceeded")]
+    ArtifactQuotaExceeded,
+
+    #[error("uploaded file reference integrity check failed")]
+    ArtifactIntegrityMismatch,
+
+    #[error("uploaded file name is invalid")]
+    InvalidUploadedFileName,
+
+    #[error("uploaded file media type is invalid")]
+    InvalidUploadedFileMediaType,
+
+    #[error("uploaded file is already committed to session history")]
+    ArtifactAlreadyCommitted,
+
+    #[error("artifact id is invalid")]
+    InvalidArtifactId,
+
+    #[error("artifact timestamp is invalid")]
+    InvalidTimestamp,
 }
 
 /// Sync persistence backend for segment logs.
@@ -150,6 +174,53 @@ pub trait Store: Send + Sync {
         Err(StoreError::PasteArtifactUnsupported)
     }
 
+    /// Persist a client-local file before a submission references it.
+    fn write_uploaded_file(
+        &self,
+        _session_id: SessionId,
+        _file_name: &str,
+        _media_type: &str,
+        _content: &[u8],
+        _limits: UploadedFileLimits,
+    ) -> Result<UploadedFileRef, StoreError> {
+        Err(StoreError::PasteArtifactUnsupported)
+    }
+
+    /// Read and integrity-check an uploaded file owned by `session_id`.
+    fn read_uploaded_file(
+        &self,
+        _session_id: SessionId,
+        _reference: &UploadedFileRef,
+    ) -> Result<Vec<u8>, StoreError> {
+        Err(StoreError::PasteArtifactUnsupported)
+    }
+
+    fn read_uploaded_file_by_id(
+        &self,
+        _session_id: SessionId,
+        _artifact_id: &str,
+    ) -> Result<(UploadedFileRef, Vec<u8>), StoreError> {
+        Err(StoreError::PasteArtifactUnsupported)
+    }
+
+    fn bind_uploaded_file(
+        &self,
+        _session_id: SessionId,
+        _reference: &UploadedFileRef,
+        _source_entry_id: &str,
+    ) -> Result<UploadedFileRef, StoreError> {
+        Err(StoreError::PasteArtifactUnsupported)
+    }
+
+    /// Delete an uncommitted uploaded file owned by `session_id`.
+    fn delete_uploaded_file(
+        &self,
+        _session_id: SessionId,
+        _artifact_id: &str,
+    ) -> Result<bool, StoreError> {
+        Err(StoreError::PasteArtifactUnsupported)
+    }
+
     /// Append a trace entry to the debug event trace file.
     fn append_trace(
         &self,

crates/session-store/src/uploaded_file.rs

@@ -0,0 +1,299 @@
+use std::{
+    fs,
+    path::Path,
+    time::{SystemTime, UNIX_EPOCH},
+};
+
+use base64::{Engine as _, engine::general_purpose::STANDARD as BASE64};
+use fs4::fs_std::FileExt;
+use protocol::{UploadedFileAvailability, UploadedFileRef};
+use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
+use uuid::Uuid;
+
+use crate::StoreError;
+
+type Result<T> = std::result::Result<T, StoreError>;
+
+pub const DEFAULT_MAX_UPLOADED_FILE_BYTES: u64 = 10 * 1024 * 1024;
+pub const DEFAULT_MAX_SESSION_ARTIFACT_BYTES: u64 = 32 * 1024 * 1024;
+pub const DEFAULT_MAX_FILES_PER_SUBMISSION: usize = 8;
+const MAX_FILE_NAME_CHARS: usize = 255;
+const MAX_MEDIA_TYPE_BYTES: usize = 127;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct UploadedFileLimits {
+    pub max_file_bytes: u64,
+    pub max_session_bytes: u64,
+}
+
+impl Default for UploadedFileLimits {
+    fn default() -> Self {
+        Self {
+            max_file_bytes: DEFAULT_MAX_UPLOADED_FILE_BYTES,
+            max_session_bytes: DEFAULT_MAX_SESSION_ARTIFACT_BYTES,
+        }
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+struct StoredUploadedFile {
+    file_name: String,
+    media_type: String,
+    created_at_ms: u64,
+    byte_len: u64,
+    sha256: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    source_entry_id: Option<String>,
+    content_base64: String,
+}
+
+pub(crate) fn validate_file_name(file_name: &str) -> Result<()> {
+    if file_name.is_empty()
+        || file_name.chars().count() > MAX_FILE_NAME_CHARS
+        || file_name == "."
+        || file_name == ".."
+        || file_name
+            .chars()
+            .any(|ch| ch.is_control() || matches!(ch, '/' | '\\'))
+    {
+        return Err(StoreError::InvalidUploadedFileName);
+    }
+    Ok(())
+}
+
+pub(crate) fn validate_media_type(media_type: &str) -> Result<()> {
+    let valid = !media_type.is_empty()
+        && media_type.len() <= MAX_MEDIA_TYPE_BYTES
+        && media_type.is_ascii()
+        && !media_type
+            .bytes()
+            .any(|byte| byte.is_ascii_control() || byte == b' ')
+        && media_type.split_once('/').is_some_and(|(kind, subtype)| {
+            !kind.is_empty()
+                && !subtype.is_empty()
+                && kind.bytes().chain(subtype.bytes()).all(|byte| {
+                    byte.is_ascii_alphanumeric()
+                        || matches!(
+                            byte,
+                            b'!' | b'#' | b'$' | b'&' | b'^' | b'_' | b'.' | b'+' | b'-'
+                        )
+                })
+        });
+    let allowed = media_type.starts_with("text/")
+        || matches!(
+            media_type,
+            "application/json"
+                | "application/pdf"
+                | "image/png"
+                | "image/jpeg"
+                | "image/gif"
+                | "image/webp"
+        );
+    if !valid || !allowed {
+        return Err(StoreError::InvalidUploadedFileMediaType);
+    }
+    Ok(())
+}
+
+fn record_path(dir: &Path, artifact_id: &str) -> Result<std::path::PathBuf> {
+    let id = Uuid::parse_str(artifact_id).map_err(|_| StoreError::InvalidArtifactId)?;
+    Ok(dir.join(format!("{id}.file.json")))
+}
+
+fn now_ms() -> Result<u64> {
+    let value = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map_err(|_| StoreError::InvalidTimestamp)?
+        .as_millis();
+    u64::try_from(value).map_err(|_| StoreError::InvalidTimestamp)
+}
+
+fn digest(bytes: &[u8]) -> String {
+    Sha256::digest(bytes)
+        .iter()
+        .map(|byte| format!("{byte:02x}"))
+        .collect()
+}
+
+pub(crate) fn stored_uploaded_file_usage(dir: &Path) -> Result<(u64, u64)> {
+    if !dir.exists() {
+        return Ok((0, 0));
+    }
+    let mut bytes = 0_u64;
+    let mut count = 0_u64;
+    for entry in fs::read_dir(dir)? {
+        let entry = entry?;
+        let path = entry.path();
+        if !entry.file_type()?.is_file()
+            || !path
+                .file_name()
+                .and_then(|name| name.to_str())
+                .is_some_and(|name| name.ends_with(".file.json"))
+        {
+            continue;
+        }
+        let stored: StoredUploadedFile = serde_json::from_slice(&fs::read(path)?)?;
+        bytes = bytes
+            .checked_add(stored.byte_len)
+            .ok_or(StoreError::ArtifactQuotaExceeded)?;
+        count = count
+            .checked_add(1)
+            .ok_or(StoreError::ArtifactQuotaExceeded)?;
+    }
+    Ok((bytes, count))
+}
+
+pub(crate) fn write_uploaded_file(
+    dir: &Path,
+    file_name: &str,
+    media_type: &str,
+    content: &[u8],
+    limits: UploadedFileLimits,
+) -> Result<UploadedFileRef> {
+    validate_file_name(file_name)?;
+    validate_media_type(media_type)?;
+    let byte_len = u64::try_from(content.len()).map_err(|_| StoreError::ArtifactTooLarge)?;
+    if byte_len > limits.max_file_bytes {
+        return Err(StoreError::ArtifactTooLarge);
+    }
+
+    fs::create_dir_all(dir)?;
+    let aggregate_lock = fs::OpenOptions::new()
+        .create(true)
+        .read(true)
+        .write(true)
+        .open(dir.join(".aggregate.lock"))?;
+    FileExt::lock_exclusive(&aggregate_lock)?;
+    let (paste_bytes, _) = crate::paste_artifact::stored_paste_usage(dir)?;
+    let (file_bytes, _) = stored_uploaded_file_usage(dir)?;
+    if paste_bytes
+        .checked_add(file_bytes)
+        .and_then(|total| total.checked_add(byte_len))
+        .is_none_or(|total| total > limits.max_session_bytes)
+    {
+        return Err(StoreError::ArtifactQuotaExceeded);
+    }
+
+    let artifact_id = Uuid::now_v7().to_string();
+    let created_at_ms = now_ms()?;
+    let sha256 = digest(content);
+    let stored = StoredUploadedFile {
+        file_name: file_name.to_owned(),
+        media_type: media_type.to_owned(),
+        created_at_ms,
+        byte_len,
+        sha256: sha256.clone(),
+        source_entry_id: None,
+        content_base64: BASE64.encode(content),
+    };
+    let path = record_path(dir, &artifact_id)?;
+    let temp = dir.join(format!(".{artifact_id}.file.tmp"));
+    fs::write(&temp, serde_json::to_vec(&stored)?)?;
+    fs::rename(&temp, &path)?;
+
+    Ok(UploadedFileRef {
+        artifact_id,
+        file_name: file_name.to_owned(),
+        media_type: media_type.to_owned(),
+        created_at_ms,
+        availability: UploadedFileAvailability::Available,
+        byte_len,
+        sha256,
+        source_entry_id: None,
+    })
+}
+
+pub(crate) fn read_uploaded_file_by_id(
+    dir: &Path,
+    artifact_id: &str,
+) -> Result<(UploadedFileRef, Vec<u8>)> {
+    let stored: StoredUploadedFile =
+        serde_json::from_slice(&fs::read(record_path(dir, artifact_id)?)?)?;
+    let content = BASE64
+        .decode(&stored.content_base64)
+        .map_err(|_| StoreError::ArtifactIntegrityMismatch)?;
+    if u64::try_from(content.len()).ok() != Some(stored.byte_len)
+        || digest(&content) != stored.sha256
+    {
+        return Err(StoreError::ArtifactIntegrityMismatch);
+    }
+    let reference = UploadedFileRef {
+        artifact_id: artifact_id.to_owned(),
+        file_name: stored.file_name,
+        media_type: stored.media_type,
+        created_at_ms: stored.created_at_ms,
+        availability: UploadedFileAvailability::Available,
+        byte_len: stored.byte_len,
+        sha256: stored.sha256,
+        source_entry_id: stored.source_entry_id,
+    };
+    Ok((reference, content))
+}
+
+pub(crate) fn read_uploaded_file(dir: &Path, reference: &UploadedFileRef) -> Result<Vec<u8>> {
+    let (stored_reference, content) = read_uploaded_file_by_id(dir, &reference.artifact_id)?;
+    if stored_reference.file_name != reference.file_name
+        || stored_reference.media_type != reference.media_type
+        || stored_reference.created_at_ms != reference.created_at_ms
+        || stored_reference.byte_len != reference.byte_len
+        || stored_reference.sha256 != reference.sha256
+        || stored_reference.source_entry_id != reference.source_entry_id
+    {
+        return Err(StoreError::ArtifactIntegrityMismatch);
+    }
+    Ok(content)
+}
+
+pub(crate) fn bind_uploaded_file(
+    dir: &Path,
+    reference: &UploadedFileRef,
+    source_entry_id: &str,
+) -> Result<UploadedFileRef> {
+    if source_entry_id.is_empty() || reference.source_entry_id.is_some() {
+        return Err(StoreError::ArtifactIntegrityMismatch);
+    }
+    let aggregate_lock = fs::OpenOptions::new()
+        .create(true)
+        .read(true)
+        .write(true)
+        .open(dir.join(".aggregate.lock"))?;
+    FileExt::lock_exclusive(&aggregate_lock)?;
+    read_uploaded_file(dir, reference)?;
+    let path = record_path(dir, &reference.artifact_id)?;
+    let mut stored: StoredUploadedFile = serde_json::from_slice(&fs::read(&path)?)?;
+    if stored.source_entry_id.is_some() {
+        return Err(StoreError::ArtifactAlreadyCommitted);
+    }
+    stored.source_entry_id = Some(source_entry_id.to_owned());
+    let temp = dir.join(format!(".{}.file.bind.tmp", reference.artifact_id));
+    fs::write(&temp, serde_json::to_vec(&stored)?)?;
+    fs::rename(&temp, path)?;
+    let mut bound = reference.clone();
+    bound.source_entry_id = Some(source_entry_id.to_owned());
+    Ok(bound)
+}
+
+pub(crate) fn delete_uploaded_file(dir: &Path, artifact_id: &str) -> Result<bool> {
+    fs::create_dir_all(dir)?;
+    let aggregate_lock = fs::OpenOptions::new()
+        .create(true)
+        .read(true)
+        .write(true)
+        .open(dir.join(".aggregate.lock"))?;
+    FileExt::lock_exclusive(&aggregate_lock)?;
+    let path = record_path(dir, artifact_id)?;
+    let stored = match fs::read(&path) {
+        Ok(bytes) => serde_json::from_slice::<StoredUploadedFile>(&bytes)?,
+        Err(error) if error.kind() == std::io::ErrorKind::NotFound => return Ok(false),
+        Err(error) => return Err(error.into()),
+    };
+    if stored.source_entry_id.is_some() {
+        return Err(StoreError::ArtifactAlreadyCommitted);
+    }
+    match fs::remove_file(path) {
+        Ok(()) => Ok(true),
+        Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(false),
+        Err(error) => Err(error.into()),
+    }
+}

crates/worker-runtime/src/execution.rs

@@ -8,7 +8,7 @@ use crate::interaction::WorkerInput;
 #[cfg(feature = "ws-server")]
 use crate::observation::WorkerObservationEvent;
 use crate::working_directory::{WorkingDirectoryBinding, WorkingDirectoryDiagnostic};
-use protocol::Method;
+use protocol::{Method, UploadedFileRef};
 use serde::{Deserialize, Serialize};
 use std::fmt;
 use std::sync::Arc;
@@ -33,6 +33,8 @@ pub enum WorkerExecutionOperation {
     Spawn,
     Restore,
     Input,
+    UploadFile,
+    DeleteUploadedFile,
     ProtocolMethod,
     Stop,
     Cancel,
@@ -385,6 +387,30 @@ pub trait WorkerExecutionBackend: Send + Sync + 'static {
         input: WorkerInput,
     ) -> WorkerExecutionResult;
 
+    fn upload_file(
+        &self,
+        _handle: &WorkerExecutionHandle,
+        _file_name: &str,
+        _media_type: &str,
+        _content: &[u8],
+    ) -> Result<UploadedFileRef, WorkerExecutionResult> {
+        Err(WorkerExecutionResult::unsupported(
+            WorkerExecutionOperation::UploadFile,
+            "execution backend does not support file upload",
+        ))
+    }
+
+    fn delete_uploaded_file(
+        &self,
+        _handle: &WorkerExecutionHandle,
+        _artifact_id: &str,
+    ) -> WorkerExecutionResult {
+        WorkerExecutionResult::unsupported(
+            WorkerExecutionOperation::DeleteUploadedFile,
+            "execution backend does not support uploaded-file deletion",
+        )
+    }
+
     fn dispatch_method(
         &self,
         _handle: &WorkerExecutionHandle,
@@ -514,6 +540,25 @@ impl WorkerExecutionBackendRef {
         self.backend.dispatch_input(handle, input)
     }
 
+    pub(crate) fn upload_file(
+        &self,
+        handle: &WorkerExecutionHandle,
+        file_name: &str,
+        media_type: &str,
+        content: &[u8],
+    ) -> Result<UploadedFileRef, WorkerExecutionResult> {
+        self.backend
+            .upload_file(handle, file_name, media_type, content)
+    }
+
+    pub(crate) fn delete_uploaded_file(
+        &self,
+        handle: &WorkerExecutionHandle,
+        artifact_id: &str,
+    ) -> WorkerExecutionResult {
+        self.backend.delete_uploaded_file(handle, artifact_id)
+    }
+
     pub(crate) fn dispatch_method(
         &self,
         handle: &WorkerExecutionHandle,

crates/worker-runtime/src/http_server.rs

@@ -32,7 +32,7 @@ use axum::body::{Body, Bytes};
 use axum::extract::rejection::{JsonRejection, QueryRejection};
 #[cfg(feature = "ws-server")]
 use axum::extract::ws::{Message as WsMessage, WebSocket, WebSocketUpgrade};
-use axum::extract::{Extension, Path, Query, State};
+use axum::extract::{DefaultBodyLimit, Extension, Path, Query, State};
 use axum::http::{Method, Request, StatusCode, header};
 use axum::middleware::{self, Next};
 use axum::response::{IntoResponse, Response};
@@ -238,6 +238,14 @@ fn runtime_http_router_with_optional_auth(
             post(execute_worker_retention),
         )
         .route("/v1/workers/{worker_id}/input", post(send_worker_input))
+        .route(
+            "/v1/workers/{worker_id}/attachments",
+            post(upload_worker_file).layer(DefaultBodyLimit::max(MAX_WORKER_FILE_UPLOAD_BYTES)),
+        )
+        .route(
+            "/v1/workers/{worker_id}/attachments/{artifact_id}",
+            delete(delete_worker_uploaded_file),
+        )
         .route("/v1/workers/{worker_id}/restore", post(restore_worker))
         .route(
             "/v1/workers/{worker_id}/workspace-api",
@@ -263,6 +271,9 @@ fn runtime_http_router_with_optional_auth(
         .layer(middleware::from_fn_with_state(state, require_runtime_auth))
 }
 
+pub const MAX_WORKER_FILE_UPLOAD_BYTES: usize =
+    session_store::DEFAULT_MAX_UPLOADED_FILE_BYTES as usize;
+
 #[derive(Clone)]
 struct RuntimeHttpState {
     runtime: Runtime,
@@ -375,6 +386,22 @@ pub struct RuntimeHttpWorkerInputResponse {
     pub ack: WorkerInteractionAck,
 }
 
+#[derive(Clone, Debug, Deserialize)]
+pub struct RuntimeHttpUploadFileQuery {
+    pub file_name: String,
+    pub media_type: String,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct RuntimeHttpUploadedFileResponse {
+    pub file: protocol::UploadedFileRef,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct RuntimeHttpUploadedFileDeleteResponse {
+    pub deleted: bool,
+}
+
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub struct RuntimeHttpWorkerCompletionsRequest {
     pub kind: protocol::CompletionKind,
@@ -1420,6 +1447,55 @@ async fn worker_completions(
     }))
 }
 
+async fn upload_worker_file(
+    State(state): State<RuntimeHttpState>,
+    auth: Option<Extension<RuntimeAuthContext>>,
+    Path(worker_id): Path<String>,
+    Query(query): Query<RuntimeHttpUploadFileQuery>,
+    body: Bytes,
+) -> RestResult<RuntimeHttpUploadedFileResponse> {
+    let worker_ref = worker_ref_for(&state.runtime, worker_id)?;
+    let file = match auth_workspace_scope(&state, auth.as_ref())? {
+        Some(scope) => state.runtime.upload_worker_file_scoped(
+            &scope,
+            &worker_ref,
+            &query.file_name,
+            &query.media_type,
+            &body,
+        ),
+        None => state.runtime.upload_worker_file(
+            &worker_ref,
+            &query.file_name,
+            &query.media_type,
+            &body,
+        ),
+    }
+    .map_err(RuntimeHttpRestError::runtime)?;
+    Ok(Json(RuntimeHttpUploadedFileResponse { file }))
+}
+
+async fn delete_worker_uploaded_file(
+    State(state): State<RuntimeHttpState>,
+    auth: Option<Extension<RuntimeAuthContext>>,
+    Path((worker_id, artifact_id)): Path<(String, String)>,
+) -> RestResult<RuntimeHttpUploadedFileDeleteResponse> {
+    let worker_ref = worker_ref_for(&state.runtime, worker_id)?;
+    match auth_workspace_scope(&state, auth.as_ref())? {
+        Some(scope) => {
+            state
+                .runtime
+                .delete_worker_uploaded_file_scoped(&scope, &worker_ref, &artifact_id)
+        }
+        None => state
+            .runtime
+            .delete_worker_uploaded_file(&worker_ref, &artifact_id),
+    }
+    .map_err(RuntimeHttpRestError::runtime)?;
+    Ok(Json(RuntimeHttpUploadedFileDeleteResponse {
+        deleted: true,
+    }))
+}
+
 async fn stop_worker(
     State(state): State<RuntimeHttpState>,
     auth: Option<Extension<RuntimeAuthContext>>,
@@ -1621,7 +1697,7 @@ fn required_runtime_permission(method: &Method, path: &str) -> Option<&'static s
     if path.ends_with("/workspace-api") {
         return Some("workers:create");
     }
-    if path.ends_with("/input") || path.ends_with("/restore") {
+    if path.ends_with("/input") || path.ends_with("/restore") || path.contains("/attachments") {
         return Some("workers:input");
     }
     if path.ends_with("/stop") || path.ends_with("/cancel") {
@@ -1882,6 +1958,21 @@ mod tests {
         WorkdirPath, WorkdirSessionCapabilities,
     };
 
+    #[test]
+    fn attachment_routes_require_worker_input_permission() {
+        assert_eq!(
+            required_runtime_permission(&Method::POST, "/v1/workers/7/attachments"),
+            Some("workers:input")
+        );
+        assert_eq!(
+            required_runtime_permission(
+                &Method::DELETE,
+                "/v1/workers/7/attachments/019ca7c8-57b6-7f05-8edf-524147aba7b3"
+            ),
+            Some("workers:input")
+        );
+    }
+
     fn test_bundle(profile: ProfileSelector) -> ConfigBundle {
         ConfigBundle {
             metadata: ConfigBundleMetadata {

crates/worker-runtime/src/runtime.rs

@@ -1205,6 +1205,103 @@ impl Runtime {
         })
     }
 
+    /// Store a client-local file in the owning Worker session before input submit.
+    pub fn upload_worker_file_scoped(
+        &self,
+        scope: &RuntimeWorkspaceScope,
+        worker_ref: &WorkerRef,
+        file_name: &str,
+        media_type: &str,
+        content: &[u8],
+    ) -> Result<protocol::UploadedFileRef, RuntimeError> {
+        self.ensure_worker_in_workspace(scope, worker_ref)?;
+        self.upload_worker_file(worker_ref, file_name, media_type, content)
+    }
+
+    pub fn upload_worker_file(
+        &self,
+        worker_ref: &WorkerRef,
+        file_name: &str,
+        media_type: &str,
+        content: &[u8],
+    ) -> Result<protocol::UploadedFileRef, RuntimeError> {
+        let (backend, handle) = {
+            let state = self.lock()?;
+            state.ensure_running()?;
+            state.ensure_worker_ref(worker_ref)?;
+            let worker = state.worker(worker_ref)?;
+            match (
+                state.execution_backend.clone(),
+                worker.execution_handle.clone(),
+            ) {
+                (Some(backend), Some(handle)) => (backend, handle),
+                _ => {
+                    return Err(RuntimeError::WorkerExecutionUnavailable {
+                        worker_id: worker_ref.worker_id.clone(),
+                        message: "worker has no live execution handle".to_string(),
+                    });
+                }
+            }
+        };
+        backend
+            .upload_file(&handle, file_name, media_type, content)
+            .map_err(|result| RuntimeError::WorkerExecutionRejected {
+                worker_id: worker_ref.worker_id.clone(),
+                operation: result.operation,
+                outcome: result.outcome,
+                message: result.message_or_default(),
+                result,
+            })
+    }
+
+    /// Delete an unsubmitted uploaded file from the owning Worker session.
+    pub fn delete_worker_uploaded_file_scoped(
+        &self,
+        scope: &RuntimeWorkspaceScope,
+        worker_ref: &WorkerRef,
+        artifact_id: &str,
+    ) -> Result<(), RuntimeError> {
+        self.ensure_worker_in_workspace(scope, worker_ref)?;
+        self.delete_worker_uploaded_file(worker_ref, artifact_id)
+    }
+
+    pub fn delete_worker_uploaded_file(
+        &self,
+        worker_ref: &WorkerRef,
+        artifact_id: &str,
+    ) -> Result<(), RuntimeError> {
+        let (backend, handle) = {
+            let state = self.lock()?;
+            state.ensure_running()?;
+            state.ensure_worker_ref(worker_ref)?;
+            let worker = state.worker(worker_ref)?;
+            match (
+                state.execution_backend.clone(),
+                worker.execution_handle.clone(),
+            ) {
+                (Some(backend), Some(handle)) => (backend, handle),
+                _ => {
+                    return Err(RuntimeError::WorkerExecutionUnavailable {
+                        worker_id: worker_ref.worker_id.clone(),
+                        message: "worker has no live execution handle".to_string(),
+                    });
+                }
+            }
+        };
+        let result = backend.delete_uploaded_file(&handle, artifact_id);
+        if result.is_accepted() {
+            Ok(())
+        } else {
+            Err(RuntimeError::WorkerExecutionRejected {
+                worker_id: worker_ref.worker_id.clone(),
+                operation: result.operation,
+                outcome: result.outcome,
+                message: result.message_or_default(),
+                result,
+            })
+        }
+    }
+
     /// Return live completion entries through a workspace-scoped Runtime authorization context.
     pub fn worker_completions_scoped(
         &self,
@@ -1387,6 +1484,8 @@ impl Runtime {
             WorkerExecutionOperation::Spawn
             | WorkerExecutionOperation::Restore
             | WorkerExecutionOperation::Input
+            | WorkerExecutionOperation::UploadFile
+            | WorkerExecutionOperation::DeleteUploadedFile
             | WorkerExecutionOperation::ProtocolMethod => return Ok(()),
         };
         if result.is_accepted() {

crates/worker-runtime/src/worker_backend.rs

@@ -2025,6 +2025,51 @@ where
         result
     }
 
+    fn upload_file(
+        &self,
+        handle: &WorkerExecutionHandle,
+        file_name: &str,
+        media_type: &str,
+        content: &[u8],
+    ) -> Result<protocol::UploadedFileRef, WorkerExecutionResult> {
+        let (worker, _, _) = self.get_execution(handle).map_err(|mut result| {
+            result.operation = WorkerExecutionOperation::UploadFile;
+            result
+        })?;
+        worker
+            .upload_file(file_name, media_type, content)
+            .map_err(|error| {
+                WorkerExecutionResult::rejected(
+                    WorkerExecutionOperation::UploadFile,
+                    format!("uploaded_file_rejected: {error}"),
+                )
+            })
+    }
+
+    fn delete_uploaded_file(
+        &self,
+        handle: &WorkerExecutionHandle,
+        artifact_id: &str,
+    ) -> WorkerExecutionResult {
+        let (worker, _, _) = match self.get_execution(handle) {
+            Ok(execution) => execution,
+            Err(mut result) => {
+                result.operation = WorkerExecutionOperation::DeleteUploadedFile;
+                return result;
+            }
+        };
+        match worker.delete_uploaded_file(artifact_id) {
+            Ok(_) => WorkerExecutionResult::accepted(
+                WorkerExecutionOperation::DeleteUploadedFile,
+                WorkerExecutionRunState::Idle,
+            ),
+            Err(error) => WorkerExecutionResult::rejected(
+                WorkerExecutionOperation::DeleteUploadedFile,
+                format!("uploaded_file_delete_rejected: {error}"),
+            ),
+        }
+    }
+
     fn dispatch_method(
         &self,
         handle: &WorkerExecutionHandle,

crates/worker/src/controller.rs

@@ -31,7 +31,8 @@ use protocol::{
     AlertLevel, AlertSource, CommandEvent as ProtocolCommandEvent,
     CommandSnapshot as ProtocolCommandSnapshot, CommandStatus as ProtocolCommandStatus,
     CommandStream as ProtocolCommandStream, CommandStreamSlice as ProtocolCommandStreamSlice,
-    ErrorCode, Event, Method, RewindTargetId, RunResult, Segment, TurnResult, WorkerStatus,
+    ErrorCode, Event, Method, RewindTargetId, RunResult, Segment, TurnResult, UploadedFileRef,
+    WorkerStatus,
 };
 use workdir::{
     CommandEvent as WorkdirCommandEvent, CommandSnapshot as WorkdirCommandSnapshot,
@@ -55,6 +56,8 @@ pub struct WorkerHandle {
     /// subsequent commits (Event::Entry) on the receiver.
     pub sink: SegmentLogSink,
     spawned_registry: Arc<SpawnedWorkerRegistry>,
+    artifact_store: Arc<dyn Store>,
+    session_id: session_store::SessionId,
 }
 
 impl WorkerHandle {
@@ -62,6 +65,29 @@ impl WorkerHandle {
         self.method_tx.send(method).await
     }
 
+    pub fn upload_file(
+        &self,
+        file_name: &str,
+        media_type: &str,
+        content: &[u8],
+    ) -> Result<UploadedFileRef, session_store::StoreError> {
+        self.artifact_store.write_uploaded_file(
+            self.session_id,
+            file_name,
+            media_type,
+            content,
+            session_store::UploadedFileLimits::default(),
+        )
+    }
+
+    pub fn delete_uploaded_file(
+        &self,
+        artifact_id: &str,
+    ) -> Result<bool, session_store::StoreError> {
+        self.artifact_store
+            .delete_uploaded_file(self.session_id, artifact_id)
+    }
+
     pub fn subscribe(&self) -> broadcast::Receiver<Event> {
         self.working_event_tx.subscribe()
     }
@@ -503,6 +529,8 @@ impl WorkerController {
         runtime_dir.write_manifest(&manifest_toml).await?;
         runtime_dir.write_status(&shared_state).await?;
 
+        let artifact_store: Arc<dyn Store> = Arc::new(worker.store().clone());
+        let session_id = worker.session_id();
         let handle = WorkerHandle {
             method_tx,
             working_event_tx: working_event_tx.clone(),
@@ -512,6 +540,8 @@ impl WorkerController {
             in_flight: in_flight.clone(),
             sink: worker.sink(),
             spawned_registry: spawned_registry.clone(),
+            artifact_store,
+            session_id,
         };
 
         let socket_server = match transport {

crates/worker/src/paste_artifact_tool.rs

@@ -4,6 +4,7 @@ use std::sync::Arc;
 
 use agen::tool::{Tool, ToolDefinition, ToolError, ToolExecutionContext, ToolMeta, ToolOutput};
 use async_trait::async_trait;
+use protocol::{PasteArtifactAvailability, PasteArtifactMediaType, PasteArtifactRef};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use session_store::{SessionId, Store, StoreError};
@@ -75,11 +76,8 @@ where
             .max_results
             .unwrap_or(DEFAULT_SEARCH_RESULTS)
             .clamp(1, MAX_SEARCH_RESULTS);
-        let (_, content) = self
+        let (_, content) =
-            .access
+            read_artifact_text(&self.access, &input.artifact_id).map_err(tool_store_error)?;
-            .store
-            .read_paste_artifact(self.access.session_id, &input.artifact_id)
-            .map_err(tool_store_error)?;
         let mut matches = Vec::new();
         let mut truncated = false;
         let mut byte_offset = 0_u64;
@@ -150,11 +148,8 @@ where
             .max_bytes
             .unwrap_or(DEFAULT_READ_BYTES)
             .clamp(4, MAX_READ_BYTES);
-        let (_, content) = self
+        let (_, content) =
-            .access
+            read_artifact_text(&self.access, &input.artifact_id).map_err(tool_store_error)?;
-            .store
-            .read_paste_artifact(self.access.session_id, &input.artifact_id)
-            .map_err(tool_store_error)?;
         let offset = usize::try_from(offset).map_err(|_| {
             ToolError::InvalidArgument("offset exceeds the artifact size".to_string())
         })?;
@@ -234,6 +229,47 @@ fn json_output(summary: String, value: &impl Serialize) -> Result<ToolOutput, To
     })
 }
 
+fn read_artifact_text<St: Store + Clone>(
+    access: &ArtifactAccess<St>,
+    artifact_id: &str,
+) -> Result<(PasteArtifactRef, String), StoreError> {
+    match access
+        .store
+        .read_paste_artifact(access.session_id, artifact_id)
+    {
+        Ok(result) => Ok(result),
+        Err(paste_error) => {
+            let (file, bytes) = match access
+                .store
+                .read_uploaded_file_by_id(access.session_id, artifact_id)
+            {
+                Ok(result) => result,
+                Err(_) => return Err(paste_error),
+            };
+            let content =
+                String::from_utf8(bytes).map_err(|_| StoreError::ArtifactIntegrityMismatch)?;
+            let char_count =
+                u64::try_from(content.chars().count()).map_err(|_| StoreError::ArtifactTooLarge)?;
+            let line_count =
+                u64::try_from(content.lines().count()).map_err(|_| StoreError::ArtifactTooLarge)?;
+            Ok((
+                PasteArtifactRef {
+                    artifact_id: file.artifact_id,
+                    created_at_ms: file.created_at_ms,
+                    media_type: PasteArtifactMediaType::TextPlainUtf8,
+                    availability: PasteArtifactAvailability::Available,
+                    byte_len: file.byte_len,
+                    char_count,
+                    line_count,
+                    sha256: file.sha256,
+                    source_entry_id: file.source_entry_id.unwrap_or_default(),
+                },
+                content,
+            ))
+        }
+    }
+}
+
 fn tool_store_error(error: StoreError) -> ToolError {
     let message = match error {
         StoreError::PasteArtifactNotFound(_) => "paste artifact not found",
@@ -263,6 +299,66 @@ mod tests {
 
     use super::*;
 
+    #[tokio::test]
+    async fn read_input_artifact_reads_uploaded_text_but_rejects_binary_content() {
+        let temp = tempfile::TempDir::new().unwrap();
+        let store = FsStore::new(temp.path()).unwrap();
+        let owner = new_session_id();
+        let text = store
+            .write_uploaded_file(
+                owner,
+                "notes.md",
+                "text/markdown",
+                b"alpha\nbeta",
+                session_store::UploadedFileLimits::default(),
+            )
+            .unwrap();
+        let read = ReadInputArtifactTool {
+            access: ArtifactAccess {
+                store: store.clone(),
+                session_id: owner,
+            },
+        };
+        let output = read
+            .execute(
+                &serde_json::json!({
+                    "artifact_id": text.artifact_id,
+                    "offset": 0,
+                    "max_bytes": 64
+                })
+                .to_string(),
+                ToolExecutionContext::default(),
+            )
+            .await
+            .unwrap();
+        let output: serde_json::Value =
+            serde_json::from_str(output.content.as_deref().unwrap()).unwrap();
+        assert_eq!(output["content"], "alpha\nbeta");
+
+        let binary = store
+            .write_uploaded_file(
+                owner,
+                "image.png",
+                "image/png",
+                &[0xff, 0xd8, 0x00],
+                session_store::UploadedFileLimits::default(),
+            )
+            .unwrap();
+        let error = read
+            .execute(
+                &serde_json::json!({
+                    "artifact_id": binary.artifact_id,
+                    "offset": 0,
+                    "max_bytes": 64
+                })
+                .to_string(),
+                ToolExecutionContext::default(),
+            )
+            .await
+            .unwrap_err();
+        assert!(error.to_string().contains("unavailable"));
+    }
+
     #[tokio::test]
     async fn search_and_read_are_bounded_and_owner_scoped() {
         let temp = tempfile::TempDir::new().unwrap();

crates/worker/src/worker.rs

@@ -3082,7 +3082,32 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
         projected_entry_ids: &[SessionHistoryEntryId],
         one_entry_per_segment: bool,
     ) -> Result<(), WorkerError> {
+        let uploaded_file_count = input
+            .iter()
+            .filter(|segment| matches!(segment, Segment::UploadedFile { .. }))
+            .count();
+        if uploaded_file_count > session_store::DEFAULT_MAX_FILES_PER_SUBMISSION {
+            return Err(WorkerError::Store(StoreError::ArtifactQuotaExceeded));
+        }
         for (index, segment) in input.iter_mut().enumerate() {
+            if let Segment::UploadedFile { file } = segment {
+                if file.source_entry_id.is_some()
+                    || file.availability != protocol::UploadedFileAvailability::Available
+                {
+                    return Err(WorkerError::Store(StoreError::ArtifactIntegrityMismatch));
+                }
+                let entry_index = if one_entry_per_segment { index } else { 0 };
+                let source_entry_id = projected_entry_ids
+                    .get(entry_index)
+                    .expect("projected input id exists for every uploaded file")
+                    .0
+                    .clone();
+                *file = self
+                    .store
+                    .bind_uploaded_file(self.session_id(), file, &source_entry_id)
+                    .map_err(WorkerError::Store)?;
+                continue;
+            }
             if let Segment::PasteArtifact { artifact } = segment {
                 let (stored, _) = self
                     .store
@@ -6471,6 +6496,11 @@ fn preview_segments(segments: &[Segment]) -> String {
                 preview.push_str(&artifact.artifact_id);
                 preview.push(']');
             }
+            Segment::UploadedFile { file } => {
+                preview.push_str("[Attached file: ");
+                preview.push_str(&file.file_name);
+                preview.push(']');
+            }
             Segment::FileRef { path } => {
                 preview.push('@');
                 preview.push_str(path);
@@ -8049,6 +8079,61 @@ mod build_summary_prompt_tests {
         );
     }
 
+    #[tokio::test]
+    async fn uploaded_file_is_verified_and_bound_to_projected_entry_before_commit() {
+        let (_dir, worker) = rewind_test_worker().await;
+        let reference = worker
+            .store
+            .write_uploaded_file(
+                worker.session_id(),
+                "notes.md",
+                "text/markdown",
+                b"# private body",
+                session_store::UploadedFileLimits::default(),
+            )
+            .unwrap();
+        let entry_id = SessionHistoryEntryId::new();
+        let mut input = vec![Segment::UploadedFile { file: reference }];
+
+        worker
+            .materialize_large_pastes(&mut input, std::slice::from_ref(&entry_id), false)
+            .unwrap();
+        let file = match &input[0] {
+            Segment::UploadedFile { file } => file,
+            other => panic!("expected uploaded file, got {other:?}"),
+        };
+        assert_eq!(file.source_entry_id.as_deref(), Some(entry_id.0.as_str()));
+        assert_eq!(
+            worker
+                .store
+                .read_uploaded_file(worker.session_id(), file)
+                .unwrap(),
+            b"# private body"
+        );
+        assert!(matches!(
+            worker
+                .store
+                .delete_uploaded_file(worker.session_id(), &file.artifact_id),
+            Err(StoreError::ArtifactAlreadyCommitted)
+        ));
+        let projected = worker.projected_input_history(&input, None, &[entry_id]);
+        let text = projected[0].item.as_text().unwrap();
+        assert!(text.contains("notes.md"));
+        assert!(text.contains(&file.artifact_id));
+        assert!(!text.contains("private body"));
+
+        let mut forged = input.clone();
+        let Segment::UploadedFile { file } = &mut forged[0] else {
+            unreachable!();
+        };
+        file.source_entry_id = None;
+        file.sha256 = "0".repeat(64);
+        assert!(matches!(
+            worker.materialize_large_pastes(&mut forged, &[SessionHistoryEntryId::new()], false),
+            Err(WorkerError::Store(StoreError::ArtifactIntegrityMismatch))
+        ));
+    }
+
     #[tokio::test]
     async fn large_paste_is_stored_before_compact_history_is_committed() {
         let (_dir, worker) = rewind_test_worker().await;

crates/workspace-server/src/hosts.rs

@@ -40,6 +40,7 @@ use worker_runtime::fs_store::FsRuntimeStoreOptions;
 use worker_runtime::http_server::{
     RuntimeHttpConfigBundleAvailabilityResponse, RuntimeHttpConfigBundleSyncRequest,
     RuntimeHttpErrorResponse, RuntimeHttpRepositoryAccessResponse, RuntimeHttpSummaryResponse,
+    RuntimeHttpUploadedFileDeleteResponse, RuntimeHttpUploadedFileResponse,
     RuntimeHttpWorkerCompletionsRequest, RuntimeHttpWorkerCompletionsResponse,
     RuntimeHttpWorkerDeleteResponse, RuntimeHttpWorkerInputResponse,
     RuntimeHttpWorkerLifecycleRequest, RuntimeHttpWorkerLifecycleResponse,
@@ -1041,6 +1042,34 @@ pub trait WorkspaceWorkerRuntime: Send + Sync {
         }
     }
 
+    fn upload_worker_file(
+        &self,
+        worker_id: &str,
+        _file_name: &str,
+        _media_type: &str,
+        _content: &[u8],
+    ) -> Result<protocol::UploadedFileRef, RuntimeRegistryError> {
+        Err(RuntimeRegistryError::RuntimeOperationFailed {
+            runtime_id: self.runtime_id().to_string(),
+            code: "worker_file_upload_unsupported".to_string(),
+            message: format!("runtime does not support file upload for worker `{worker_id}`"),
+        })
+    }
+
+    fn delete_worker_uploaded_file(
+        &self,
+        worker_id: &str,
+        _artifact_id: &str,
+    ) -> Result<(), RuntimeRegistryError> {
+        Err(RuntimeRegistryError::RuntimeOperationFailed {
+            runtime_id: self.runtime_id().to_string(),
+            code: "worker_file_delete_unsupported".to_string(),
+            message: format!(
+                "runtime does not support uploaded-file deletion for worker `{worker_id}`"
+            ),
+        })
+    }
+
     fn worker_completions(
         &self,
         worker_id: &str,
@@ -1543,6 +1572,50 @@ impl RuntimeRegistry {
         Ok(runtime.send_input(worker_id, request))
     }
 
+    pub fn upload_worker_file(
+        &self,
+        worker: &RuntimeWorkerRef,
+        file_name: &str,
+        media_type: &str,
+        content: &[u8],
+    ) -> Result<protocol::UploadedFileRef, RuntimeRegistryError> {
+        let runtime_id = worker.runtime_id.as_str();
+        let worker_id = worker.worker_id.as_str();
+        validate_backend_identifier("runtime_id", runtime_id)?;
+        validate_backend_identifier("worker_id", worker_id)?;
+        let runtime = self.runtime(runtime_id)?;
+        let lookup = runtime.worker(worker_id);
+        if lookup.worker.is_none() {
+            return Err(operation_failed_or_unknown_worker(
+                runtime_id,
+                worker_id,
+                lookup.diagnostics,
+            ));
+        }
+        runtime.upload_worker_file(worker_id, file_name, media_type, content)
+    }
+
+    pub fn delete_worker_uploaded_file(
+        &self,
+        worker: &RuntimeWorkerRef,
+        artifact_id: &str,
+    ) -> Result<(), RuntimeRegistryError> {
+        let runtime_id = worker.runtime_id.as_str();
+        let worker_id = worker.worker_id.as_str();
+        validate_backend_identifier("runtime_id", runtime_id)?;
+        validate_backend_identifier("worker_id", worker_id)?;
+        let runtime = self.runtime(runtime_id)?;
+        let lookup = runtime.worker(worker_id);
+        if lookup.worker.is_none() {
+            return Err(operation_failed_or_unknown_worker(
+                runtime_id,
+                worker_id,
+                lookup.diagnostics,
+            ));
+        }
+        runtime.delete_worker_uploaded_file(worker_id, artifact_id)
+    }
+
     pub fn worker_completions(
         &self,
         worker: &RuntimeWorkerRef,
@@ -2509,6 +2582,46 @@ impl WorkspaceWorkerRuntime for EmbeddedWorkerRuntime {
         }
     }
 
+    fn upload_worker_file(
+        &self,
+        worker_id: &str,
+        file_name: &str,
+        media_type: &str,
+        content: &[u8],
+    ) -> Result<protocol::UploadedFileRef, RuntimeRegistryError> {
+        let worker_ref =
+            self.worker_ref(worker_id)
+                .ok_or_else(|| RuntimeRegistryError::UnknownWorker {
+                    worker: RuntimeWorkerRef::new(&self.runtime_id, worker_id),
+                })?;
+        self.runtime
+            .upload_worker_file(&worker_ref, file_name, media_type, content)
+            .map_err(|error| RuntimeRegistryError::RuntimeOperationFailed {
+                runtime_id: self.runtime_id.clone(),
+                code: "embedded_worker_file_upload_failed".to_string(),
+                message: error.to_string(),
+            })
+    }
+
+    fn delete_worker_uploaded_file(
+        &self,
+        worker_id: &str,
+        artifact_id: &str,
+    ) -> Result<(), RuntimeRegistryError> {
+        let worker_ref =
+            self.worker_ref(worker_id)
+                .ok_or_else(|| RuntimeRegistryError::UnknownWorker {
+                    worker: RuntimeWorkerRef::new(&self.runtime_id, worker_id),
+                })?;
+        self.runtime
+            .delete_worker_uploaded_file(&worker_ref, artifact_id)
+            .map_err(|error| RuntimeRegistryError::RuntimeOperationFailed {
+                runtime_id: self.runtime_id.clone(),
+                code: "embedded_worker_file_delete_failed".to_string(),
+                message: error.to_string(),
+            })
+    }
+
     fn worker_completions(
         &self,
         worker_id: &str,
@@ -2848,6 +2961,16 @@ impl RemoteWorkerRuntime {
         self.send_json(path, self.http.post(self.endpoint(path)).json(body))
     }
 
+    fn post_bytes<T>(&self, path: &str, body: &[u8]) -> Result<T, RuntimeDiagnostic>
+    where
+        T: DeserializeOwned + Send + 'static,
+    {
+        self.send_json(
+            path,
+            self.http.post(self.endpoint(path)).body(body.to_vec()),
+        )
+    }
+
     fn delete_json<T>(&self, path: &str) -> Result<T, RuntimeDiagnostic>
     where
         T: DeserializeOwned + Send + 'static,
@@ -3536,6 +3659,47 @@ impl WorkspaceWorkerRuntime for RemoteWorkerRuntime {
         }
     }
 
+    fn upload_worker_file(
+        &self,
+        worker_id: &str,
+        file_name: &str,
+        media_type: &str,
+        content: &[u8],
+    ) -> Result<protocol::UploadedFileRef, RuntimeRegistryError> {
+        let path = format!(
+            "/v1/workers/{}/attachments?file_name={}&media_type={}",
+            url_path_segment_encode(worker_id),
+            url_query_value_encode(file_name),
+            url_query_value_encode(media_type),
+        );
+        self.post_bytes::<RuntimeHttpUploadedFileResponse>(&path, content)
+            .map(|response| response.file)
+            .map_err(|diagnostic| RuntimeRegistryError::RuntimeOperationFailed {
+                runtime_id: self.runtime_id.clone(),
+                code: diagnostic.code,
+                message: diagnostic.message,
+            })
+    }
+
+    fn delete_worker_uploaded_file(
+        &self,
+        worker_id: &str,
+        artifact_id: &str,
+    ) -> Result<(), RuntimeRegistryError> {
+        let path = format!(
+            "/v1/workers/{}/attachments/{}",
+            url_path_segment_encode(worker_id),
+            url_path_segment_encode(artifact_id),
+        );
+        self.delete_json::<RuntimeHttpUploadedFileDeleteResponse>(&path)
+            .map(|_| ())
+            .map_err(|diagnostic| RuntimeRegistryError::RuntimeOperationFailed {
+                runtime_id: self.runtime_id.clone(),
+                code: diagnostic.code,
+                message: diagnostic.message,
+            })
+    }
+
     fn worker_completions(
         &self,
         worker_id: &str,

crates/workspace-server/src/server.rs

@@ -3,8 +3,9 @@ use std::path::{Component, Path, PathBuf};
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::{Arc, Mutex, Weak};
 
+use axum::body::Bytes;
 use axum::extract::ws::{Message as WsMessage, WebSocket, WebSocketUpgrade};
-use axum::extract::{Extension, Path as AxumPath, Query, Request, State};
+use axum::extract::{DefaultBodyLimit, Extension, Path as AxumPath, Query, Request, State};
 use axum::http::header::{CONTENT_TYPE, ETAG, IF_NONE_MATCH, LOCATION, ORIGIN, SET_COOKIE};
 use axum::http::{HeaderMap, Method, StatusCode, Uri};
 use axum::middleware::{self, Next};
@@ -156,8 +157,9 @@ use worker_runtime::catalog::{
 };
 use worker_runtime::config_bundle::ConfigBundle;
 use worker_runtime::http_server::{
-    RuntimeHttpConfigBundleAvailabilityResponse, RuntimeHttpConfigBundlesResponse,
+    MAX_WORKER_FILE_UPLOAD_BYTES, RuntimeHttpConfigBundleAvailabilityResponse,
-    RuntimeHttpSummaryResponse, RuntimeHttpWorkerResponse, RuntimeHttpWorkersResponse,
+    RuntimeHttpConfigBundlesResponse, RuntimeHttpSummaryResponse, RuntimeHttpWorkerResponse,
+    RuntimeHttpWorkersResponse,
 };
 use worker_runtime::identity::{RuntimeWorkerRef, WorkerId};
 
@@ -2679,10 +2681,26 @@ fn build_inner_router(api: WorkspaceApi) -> Router {
             "/api/runtimes/{runtime_id}/workers/{worker_id}/input",
             post(send_runtime_worker_input),
         )
+        .route(
+            "/api/runtimes/{runtime_id}/workers/{worker_id}/attachments",
+            post(upload_runtime_worker_file).layer(DefaultBodyLimit::max(MAX_WORKER_FILE_UPLOAD_BYTES)),
+        )
+        .route(
+            "/api/runtimes/{runtime_id}/workers/{worker_id}/attachments/{artifact_id}",
+            delete(delete_runtime_worker_uploaded_file),
+        )
         .route(
             "/api/w/{workspace_id}/runtimes/{runtime_id}/workers/{worker_id}/input",
             post(scoped_send_runtime_worker_input),
         )
+        .route(
+            "/api/w/{workspace_id}/runtimes/{runtime_id}/workers/{worker_id}/attachments",
+            post(scoped_upload_runtime_worker_file).layer(DefaultBodyLimit::max(MAX_WORKER_FILE_UPLOAD_BYTES)),
+        )
+        .route(
+            "/api/w/{workspace_id}/runtimes/{runtime_id}/workers/{worker_id}/attachments/{artifact_id}",
+            delete(scoped_delete_runtime_worker_uploaded_file),
+        )
         .route(
             "/api/runtimes/{runtime_id}/workers/{worker_id}/completions",
             post(runtime_worker_completions),
@@ -10733,6 +10751,51 @@ async fn scoped_execute_runtime_cleanup(
     Ok(Json(response))
 }
 
+#[derive(Debug, Deserialize)]
+#[serde(deny_unknown_fields)]
+struct WorkerFileUploadQuery {
+    file_name: String,
+    media_type: String,
+}
+
+#[derive(Debug, Serialize)]
+struct WorkerFileUploadResponse {
+    file: protocol::UploadedFileRef,
+}
+
+#[derive(Debug, Serialize)]
+struct WorkerFileDeleteResponse {
+    deleted: bool,
+}
+
+async fn scoped_upload_runtime_worker_file(
+    State(api): State<WorkspaceApi>,
+    AxumPath(path): AxumPath<ScopedRuntimeWorkerPath>,
+    Query(query): Query<WorkerFileUploadQuery>,
+    body: Bytes,
+) -> ApiResult<Json<WorkerFileUploadResponse>> {
+    validate_workspace_scope(&api, &path.workspace_id)?;
+    upload_runtime_worker_file(
+        State(api),
+        AxumPath((path.worker.runtime_id, path.worker.worker_id)),
+        Query(query),
+        body,
+    )
+    .await
+}
+
+async fn scoped_delete_runtime_worker_uploaded_file(
+    State(api): State<WorkspaceApi>,
+    AxumPath((path, artifact_id)): AxumPath<(ScopedRuntimeWorkerPath, String)>,
+) -> ApiResult<Json<WorkerFileDeleteResponse>> {
+    validate_workspace_scope(&api, &path.workspace_id)?;
+    delete_runtime_worker_uploaded_file(
+        State(api),
+        AxumPath((path.worker.runtime_id, path.worker.worker_id, artifact_id)),
+    )
+    .await
+}
+
 async fn scoped_send_runtime_worker_input(
     State(api): State<WorkspaceApi>,
     AxumPath(path): AxumPath<ScopedRuntimeWorkerPath>,
@@ -13260,6 +13323,31 @@ async fn send_runtime_worker_input(
     Ok(Json(result))
 }
 
+async fn upload_runtime_worker_file(
+    State(api): State<WorkspaceApi>,
+    AxumPath((runtime_id, worker_id)): AxumPath<(String, String)>,
+    Query(query): Query<WorkerFileUploadQuery>,
+    body: Bytes,
+) -> ApiResult<Json<WorkerFileUploadResponse>> {
+    let worker = resolve_workspace_worker_reference(&api, &runtime_id, &worker_id)?;
+    let file = api
+        .runtime
+        .upload_worker_file(&worker, &query.file_name, &query.media_type, &body)
+        .map_err(|err| err.into_error())?;
+    Ok(Json(WorkerFileUploadResponse { file }))
+}
+
+async fn delete_runtime_worker_uploaded_file(
+    State(api): State<WorkspaceApi>,
+    AxumPath((runtime_id, worker_id, artifact_id)): AxumPath<(String, String, String)>,
+) -> ApiResult<Json<WorkerFileDeleteResponse>> {
+    let worker = resolve_workspace_worker_reference(&api, &runtime_id, &worker_id)?;
+    api.runtime
+        .delete_worker_uploaded_file(&worker, &artifact_id)
+        .map_err(|err| err.into_error())?;
+    Ok(Json(WorkerFileDeleteResponse { deleted: true }))
+}
+
 async fn runtime_worker_completions(
     State(api): State<WorkspaceApi>,
     AxumPath((runtime_id, worker_id)): AxumPath<(String, String)>,

web/workspace/src/lib/generated/protocol.ts

@@ -42,6 +42,10 @@ export type CompactionLifecycle = { schema_version: number, compaction_id: strin
  */
 started_at_ms: number, ended_at_ms?: number | null, summary?: string | null, error?: string | null, new_segment_id?: string | null, };
 
+export type UploadedFileAvailability = "available" | "unavailable" | "integrity_failed";
+
+export type UploadedFileRef = { artifact_id: string, file_name: string, media_type: string, created_at_ms: number, availability: UploadedFileAvailability, byte_len: number, sha256: string, source_entry_id?: string | null, };
+
 export type ScopeRule = {
 /**
  * Target path. Must be absolute by the time a `Scope` is built from
@@ -144,7 +148,7 @@ export type PasteArtifactRef = { artifact_id: string, created_at_ms: number, med
  */
 availability: PasteArtifactAvailability, byte_len: number, char_count: number, line_count: number, sha256: string, source_entry_id: string, };
 
-export type Segment = { "kind": "text", content: string, } | { "kind": "paste", id: number, chars: number, lines: number, content: string, } | { "kind": "paste_artifact", artifact: PasteArtifactRef, } | { "kind": "file_ref", path: string, } | { "kind": "flow", selector: string, } | { "kind": "unknown" };
+export type Segment = { "kind": "text", content: string, } | { "kind": "paste", id: number, chars: number, lines: number, content: string, } | { "kind": "paste_artifact", artifact: PasteArtifactRef, } | { "kind": "uploaded_file", file: UploadedFileRef, } | { "kind": "file_ref", path: string, } | { "kind": "flow", selector: string, } | { "kind": "unknown" };
 
 export type WorkerEvent = { "kind": "turn_ended", worker_name: string, } | { "kind": "errored", worker_name: string, message: string, } | { "kind": "shut_down", worker_name: string, } | { "kind": "scope_sub_delegated",
 /**