Merge pull request #2532 from dgageot/board/file-path-resolution-issue-with-sub-agen-1bc0a174

Inherit user-attached files in sub-agent sessions

Author: dgageot

e2e/testdata/cassettes/TestA2AServer_MultiAgent.yaml

@@ -8,7 +8,7 @@ interactions:
         proto_minor: 1
         content_length: 0
         host: api.openai.com
-        body: '{"input":[{"content":[{"text":"You are a multi-agent system, make sure to answer the user query in the most helpful way possible. You have access to these sub-agents:\nName: web | Description: \n\nIMPORTANT: You can ONLY transfer tasks to the agents listed above using their ID. The valid agent names are: web. You MUST NOT attempt to transfer to any other agent IDs - doing so will cause system errors.\n\nIf you are the best to answer the question according to your description, you can answer it.\n\nIf another agent is better for answering the question according to its description, call `transfer_task` function to transfer the question to that agent using the agent''s ID. When transferring, do not generate any text other than the function call.\n\n","type":"input_text"}],"role":"system"},{"content":[{"text":"You are a knowledgeable assistant that helps users with various tasks.\nBe helpful, accurate, and concise in your responses.\n","type":"input_text"}],"role":"system"},{"content":"Say hello.","role":"user"}],"model":"gpt-5-mini","reasoning":{"summary":"detailed"},"tools":[{"strict":true,"parameters":{"additionalProperties":false,"properties":{"agent":{"description":"The name of the agent to transfer the task to.","type":"string"},"expected_output":{"description":"The expected output from the member (optional).","type":"string"},"task":{"description":"A clear and concise description of the task the member should achieve.","type":"string"}},"required":["agent","expected_output","task"],"type":"object"},"name":"transfer_task","description":"Use this function to transfer a task to the selected team member.\n            You must provide a clear and concise description of the task the member should achieve AND the expected output.","type":"function"}],"stream":true}'
+        body: '{"input":[{"content":[{"text":"You are a multi-agent system, make sure to answer the user query in the most helpful way possible. You have access to these sub-agents:\nName: web | Description: \n\nIMPORTANT: You can ONLY transfer tasks to the agents listed above using their ID. The valid agent names are: web. You MUST NOT attempt to transfer to any other agent IDs - doing so will cause system errors.\n\nIf you are the best to answer the question according to your description, you can answer it.\n\nIf another agent is better for answering the question according to its description, call `transfer_task` function to transfer the question to that agent using the agent''s ID. When transferring, do not generate any text other than the function call.\n\nWhen the task involves files, always include their absolute paths in the `task` description (never just bare filenames). Sub-agents start in a fresh session and do not see the conversation history or files attached by the user, so a non-absolute path may resolve to the wrong file or force the sub-agent to scan the filesystem.\n\n","type":"input_text"}],"role":"system"},{"content":[{"text":"You are a knowledgeable assistant that helps users with various tasks.\nBe helpful, accurate, and concise in your responses.\n","type":"input_text"}],"role":"system"},{"content":"Say hello.","role":"user"}],"model":"gpt-5-mini","reasoning":{"summary":"detailed"},"tools":[{"strict":true,"parameters":{"additionalProperties":false,"properties":{"agent":{"description":"The name of the agent to transfer the task to.","type":"string"},"expected_output":{"description":"The expected output from the member (optional).","type":"string"},"task":{"description":"A clear and concise description of the task the member should achieve.","type":"string"}},"required":["agent","expected_output","task"],"type":"object"},"name":"transfer_task","description":"Use this function to transfer a task to the selected team member.\n            You must provide a clear and concise description of the task the member should achieve AND the expected output.","type":"function"}],"stream":true}'
         url: https://api.openai.com/v1/responses
         method: POST
       response:

e2e/testdata/cassettes/TestRuntime_MultiAgent_SessionReload.yaml

@@ -139,7 +139,9 @@ func (a *App) SendFirstMessage() tea.Cmd {
 	cmds := []tea.Cmd{
 		func() tea.Msg {
 			// Use the shared PrepareUserMessage function for consistent attachment handling
-			userMsg := cli.PrepareUserMessage(context.Background(), a.runtime, *a.firstMessage, a.firstMessageAttach)
+			userMsg, attachedPath := cli.PrepareUserMessage(context.Background(), a.runtime, *a.firstMessage, a.firstMessageAttach)
+			// Inherit the attachment in any sub-session created by this turn.
+			a.session.AddAttachedFile(attachedPath)
 
 			// If the message has multi-content (attachments), we need to handle it specially
 			if len(userMsg.Message.MultiContent) > 0 {
@@ -301,7 +303,13 @@ func (a *App) Run(ctx context.Context, cancel context.CancelFunc, message string
 				switch {
 				case att.FilePath != "":
 					// File-reference attachment: read and classify from disk.
-					a.processFileAttachment(ctx, att, &textBuilder, &binaryParts)
+					// Only remember the path on the session when the file actually
+					// exists as a regular file — we don't want sub-agents to inherit
+					// dangling references to directories or missing paths. The editor
+					// resolves @-mentions to absolute paths before this point.
+					if a.processFileAttachment(ctx, att, &textBuilder, &binaryParts) {
+						a.session.AddAttachedFile(att.FilePath)
+					}
 				case att.Content != "":
 					// Inline content attachment (e.g. pasted text).
 					a.processInlineAttachment(att, &textBuilder)
@@ -342,7 +350,14 @@ func (a *App) Run(ctx context.Context, cancel context.CancelFunc, message string
 
 // processFileAttachment reads a file from disk, classifies it, and either
 // appends its text content to textBuilder or adds a binary part to binaryParts.
-func (a *App) processFileAttachment(ctx context.Context, att messages.Attachment, textBuilder *strings.Builder, binaryParts *[]chat.MessagePart) {
+// Returns true when the path resolved to a real, regular file that we attempted
+// to surface to the model — even if the content itself was rejected (too
+// large, unsupported MIME, transient read error, etc.). The boolean is meant
+// for callers that want to record the path on the session for later reuse by
+// sub-agents; we don't want those references to point at directories or
+// missing files, but we do want them to cover "the agent has bigger tools
+// than us" cases.
+func (a *App) processFileAttachment(ctx context.Context, att messages.Attachment, textBuilder *strings.Builder, binaryParts *[]chat.MessagePart) bool {
 	absPath := att.FilePath
 
 	fi, err := os.Stat(absPath)
@@ -358,20 +373,20 @@ func (a *App) processFileAttachment(ctx context.Context, att messages.Attachment
 		}
 		slog.Warn("skipping attachment", "path", absPath, "reason", reason)
 		a.sendEvent(ctx, runtime.Warning(fmt.Sprintf("Skipped attachment %s: %s", att.Name, reason), ""))
-		return
+		return false
 	}
 
 	if !fi.Mode().IsRegular() {
 		slog.Warn("skipping attachment: not a regular file", "path", absPath, "mode", fi.Mode().String())
 		a.sendEvent(ctx, runtime.Warning(fmt.Sprintf("Skipped attachment %s: not a regular file", att.Name), ""))
-		return
+		return false
 	}
 
 	const maxAttachmentSize = 100 * 1024 * 1024 // 100MB
 	if fi.Size() > maxAttachmentSize {
 		slog.Warn("skipping attachment: file too large", "path", absPath, "size", fi.Size(), "max", maxAttachmentSize)
 		a.sendEvent(ctx, runtime.Warning(fmt.Sprintf("Skipped attachment %s: file too large (max 100MB)", att.Name), ""))
-		return
+		return true
 	}
 
 	mimeType := chat.DetectMimeType(absPath)
@@ -381,13 +396,13 @@ func (a *App) processFileAttachment(ctx context.Context, att messages.Attachment
 		if fi.Size() > chat.MaxInlineFileSize {
 			slog.Warn("skipping attachment: text file too large to inline", "path", absPath, "size", fi.Size(), "max", chat.MaxInlineFileSize)
 			a.sendEvent(ctx, runtime.Warning(fmt.Sprintf("Skipped attachment %s: text file too large to inline (max 5MB)", att.Name), ""))
-			return
+			return true
 		}
 		content, err := chat.ReadFileForInline(absPath)
 		if err != nil {
 			slog.Warn("skipping attachment: failed to read file", "path", absPath, "error", err)
 			a.sendEvent(ctx, runtime.Warning(fmt.Sprintf("Skipped attachment %s: failed to read file", att.Name), ""))
-			return
+			return true
 		}
 		textBuilder.WriteString("\n\n")
 		textBuilder.WriteString(content)
@@ -400,14 +415,14 @@ func (a *App) processFileAttachment(ctx context.Context, att messages.Attachment
 			if readErr != nil {
 				slog.Warn("skipping attachment: failed to read image", "path", absPath, "error", readErr)
 				a.sendEvent(ctx, runtime.Warning(fmt.Sprintf("Skipped attachment %s: failed to read image", att.Name), ""))
-				return
+				return true
 			}
 			resized, resizeErr := chat.ResizeImage(imgData, mimeType)
 			if resizeErr != nil {
 				// Don't bypass security checks - reject the file if resize failed
 				slog.Warn("skipping attachment: image resize failed", "path", absPath, "error", resizeErr)
 				a.sendEvent(ctx, runtime.Warning(fmt.Sprintf("Skipped attachment %s: %s", att.Name, resizeErr), ""))
-				return
+				return true
 			}
 			dataURL := fmt.Sprintf("data:%s;base64,%s", resized.MimeType, base64.StdEncoding.EncodeToString(resized.Data))
 			*binaryParts = append(*binaryParts, chat.MessagePart{
@@ -435,6 +450,8 @@ func (a *App) processFileAttachment(ctx context.Context, att messages.Attachment
 		slog.Warn("skipping attachment: unsupported file type", "path", absPath, "mime_type", mimeType)
 		a.sendEvent(ctx, runtime.Warning(fmt.Sprintf("Skipped attachment %s: unsupported file type", att.Name), ""))
 	}
+
+	return true
 }
 
 // sendEvent sends an event to the TUI, respecting context cancellation to

pkg/app/app.go

@@ -104,7 +104,9 @@ func Run(ctx context.Context, out *Printer, cfg Config, rt runtime.Runtime, sess
 			return nil
 		}
 
-		sess.AddMessage(PrepareUserMessage(ctx, rt, userInput, cfg.AttachmentPath))
+		userMsg, attachedPath := PrepareUserMessage(ctx, rt, userInput, cfg.AttachmentPath)
+		sess.AddMessage(userMsg)
+		sess.AddAttachedFile(attachedPath)
 
 		if cfg.OutputJSON {
 			for event := range rt.RunStream(ctx, sess) {
@@ -320,8 +322,11 @@ func Run(ctx context.Context, out *Printer, cfg Config, rt runtime.Runtime, sess
 //   - userInput: the raw user input (may contain /commands and /attach directives)
 //   - globalAttachPath: attachment path from --attach flag (can be empty)
 //
-// Returns the prepared session.Message ready to be added to the session.
-func PrepareUserMessage(ctx context.Context, rt runtime.Runtime, userInput, globalAttachPath string) *session.Message {
+// Returns the prepared session.Message ready to be added to the session, plus
+// the absolute path of the file that was actually attached (empty when no
+// attachment was used). Callers should pass that path to
+// session.Session.AddAttachedFile so sub-agents inherit the file context.
+func PrepareUserMessage(ctx context.Context, rt runtime.Runtime, userInput, globalAttachPath string) (*session.Message, string) {
 	// Resolve any /command to its prompt text
 	resolvedContent := runtime.ResolveCommand(ctx, rt, userInput)
 
@@ -391,22 +396,35 @@ func ParseAttachCommand(userInput string) (messageText, attachPath string) {
 // CreateUserMessageWithAttachment creates a user message with optional file attachment.
 // Text files are inlined directly as text content for cross-provider compatibility.
 // Binary files (images, PDFs) are stored as file references for provider-specific upload.
-func CreateUserMessageWithAttachment(userContent, attachmentPath string) *session.Message {
+//
+// Returns the prepared session.Message and the absolute path of the file that
+// was actually attached. The returned path is empty when no attachment was
+// produced (no path supplied, file unreadable, type unsupported, file too
+// large to inline, etc.). Callers should record successful attachments via
+// session.Session.AddAttachedFile so sub-agents inherit the file context.
+func CreateUserMessageWithAttachment(userContent, attachmentPath string) (*session.Message, string) {
+	// noAttachment returns the message without any attachment. It's used both
+	// when the caller didn't supply a path and as the fallback for every
+	// best-effort failure below (unreadable file, unsupported type, etc.) so
+	// the user always gets at least a plain text message.
+	noAttachment := func() (*session.Message, string) {
+		return session.UserMessage(userContent), ""
+	}
+
 	if attachmentPath == "" {
-		return session.UserMessage(userContent)
+		return noAttachment()
 	}
 
-	// Validate file exists
 	absPath, err := filepath.Abs(attachmentPath)
 	if err != nil {
 		slog.Warn("Failed to get absolute path for attachment", "path", attachmentPath, "error", err)
-		return session.UserMessage(userContent)
+		return noAttachment()
 	}
 
 	fi, err := os.Stat(absPath)
 	if err != nil {
 		slog.Warn("Attachment file not accessible", "path", absPath, "error", err)
-		return session.UserMessage(userContent)
+		return noAttachment()
 	}
 
 	// Ensure we have some text content when attaching a file
@@ -424,12 +442,12 @@ func CreateUserMessageWithAttachment(userContent, attachmentPath string) *sessio
 		// Text files are inlined directly as text content.
 		if fi.Size() > chat.MaxInlineFileSize {
 			slog.Warn("Attachment text file too large to inline", "path", absPath, "size", fi.Size())
-			return session.UserMessage(userContent)
+			return noAttachment()
 		}
 		content, err := chat.ReadFileForInline(absPath)
 		if err != nil {
 			slog.Warn("Failed to read attachment file", "path", absPath, "error", err)
-			return session.UserMessage(userContent)
+			return noAttachment()
 		}
 		multiContent = append(multiContent, chat.MessagePart{
 			Type: chat.MessagePartTypeText,
@@ -441,7 +459,7 @@ func CreateUserMessageWithAttachment(userContent, attachmentPath string) *sessio
 		mimeType := chat.DetectMimeType(absPath)
 		if !chat.IsSupportedMimeType(mimeType) {
 			slog.Warn("Unsupported attachment file type", "path", absPath, "mime_type", mimeType)
-			return session.UserMessage(userContent)
+			return noAttachment()
 		}
 		if chat.IsImageMimeType(mimeType) {
 			// Read, resize if needed, and inline as base64 data URL.
@@ -450,12 +468,12 @@ func CreateUserMessageWithAttachment(userContent, attachmentPath string) *sessio
 			imgData, readErr := os.ReadFile(absPath)
 			if readErr != nil {
 				slog.Warn("Failed to read image attachment", "path", absPath, "error", readErr)
-				return session.UserMessage(userContent)
+				return noAttachment()
 			}
 			resized, resizeErr := chat.ResizeImage(imgData, mimeType)
 			if resizeErr != nil {
 				slog.Warn("Image resize failed for attachment", "path", absPath, "error", resizeErr)
-				return session.UserMessage(userContent)
+				return noAttachment()
 			}
 			dataURL := fmt.Sprintf("data:%s;base64,%s", resized.MimeType, base64.StdEncoding.EncodeToString(resized.Data))
 			multiContent = append(multiContent, chat.MessagePart{
@@ -477,5 +495,5 @@ func CreateUserMessageWithAttachment(userContent, attachmentPath string) *sessio
 		}
 	}
 
-	return session.UserMessage(textContent, multiContent...)
+	return session.UserMessage(textContent, multiContent...), absPath
 }

pkg/cli/runner.go

@@ -49,13 +49,26 @@ func validateAgentInList(currentAgent, targetAgent, action, listDesc string, age
 }
 
 // buildTaskSystemMessage constructs the system message for a delegated task.
-func buildTaskSystemMessage(task, expectedOutput string) string {
-	msg := "You are a member of a team of agents. Your goal is to complete the following task:"
-	msg += fmt.Sprintf("\n\n<task>\n%s\n</task>", task)
+// attachedFiles, when non-empty, lists absolute paths of files the user
+// attached to the parent conversation; they are surfaced to the sub-agent so
+// it can use them directly without scanning the workspace or guessing from a
+// bare filename.
+func buildTaskSystemMessage(task, expectedOutput string, attachedFiles []string) string {
+	var b strings.Builder
+	b.WriteString("You are a member of a team of agents. Your goal is to complete the following task:")
+	fmt.Fprintf(&b, "\n\n<task>\n%s\n</task>", task)
 	if expectedOutput != "" {
-		msg += fmt.Sprintf("\n\n<expected_output>\n%s\n</expected_output>", expectedOutput)
+		fmt.Fprintf(&b, "\n\n<expected_output>\n%s\n</expected_output>", expectedOutput)
 	}
-	return msg
+	if len(attachedFiles) > 0 {
+		b.WriteString("\n\nThe user attached these files in the original conversation. They are available for you to read at these absolute paths; prefer them over any bare filenames mentioned in <task>:\n<attached_files>")
+		for _, p := range attachedFiles {
+			fmt.Fprintf(&b, "\n- %s", p)
+		}
+		b.WriteString("\n</attached_files>")
+	}
+	b.WriteString("\n\nIf the task references files, treat any absolute paths in <task> as authoritative and use them as-is. If a referenced file is given by name only (e.g. \"foo.go\"), do not guess: search the workspace or ask the calling agent for the absolute path before reading or modifying the file.")
+	return b.String()
 }
 
 // SubSessionConfig describes how to build and run a child session.
@@ -95,9 +108,16 @@ type SubSessionConfig struct {
 // session. It consolidates the session options that were previously duplicated
 // across handleTaskTransfer and RunAgent.
 func newSubSession(parent *session.Session, cfg SubSessionConfig, childAgent *agent.Agent) *session.Session {
+	// Sub-agents start in a fresh session, so they don't see the user's
+	// original messages or attached files. Snapshot the parent's attached
+	// files once and propagate them both to the system prompt (so the agent
+	// is told about them) and to the child session (so further nested
+	// transfers keep inheriting them).
+	attachedFiles := parent.AttachedFilesSnapshot()
+
 	sysMsg := cfg.SystemMessage
 	if sysMsg == "" {
-		sysMsg = buildTaskSystemMessage(cfg.Task, cfg.ExpectedOutput)
+		sysMsg = buildTaskSystemMessage(cfg.Task, cfg.ExpectedOutput, attachedFiles)
 	}
 
 	userMsg := cfg.ImplicitUserMessage
@@ -115,6 +135,7 @@ func newSubSession(parent *session.Session, cfg SubSessionConfig, childAgent *ag
 		session.WithToolsApproved(cfg.ToolsApproved),
 		session.WithSendUserMessage(false),
 		session.WithParentID(parent.ID),
+		session.WithAttachedFiles(attachedFiles),
 	}
 	if cfg.PinAgent {
 		opts = append(opts, session.WithAgentName(cfg.AgentName))