feat(core): add PDF vision bridge fallback (#6846)

* feat(core): add PDF vision bridge fallback

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

* codex: address PR review feedback (#6846)

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

* codex: address PR review feedback (#6846)

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

* codex: fix CI failure on PR #6846

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

* codex: address PR review feedback (#6846)

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

* codex: address PR review feedback (#6846)

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

* fix(cli): harden vision bridge output handling

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

* fix(cli): correct export sanitizer test typing

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

* fix(core): disclose selected vision endpoint before egress

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

---------

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

docs/developers/tools/file-system.md

@@ -24,18 +24,21 @@ Qwen Code provides a comprehensive suite of tools for interacting with the local
 
 ## 2. `read_file` (ReadFile)
 
-`read_file` reads and returns the content of a specified file. This tool handles text files and media files (images, PDFs, audio, video) whose modality is supported by the current model. For text files, it can read specific line ranges. Media files whose modality is not supported by the current model are rejected with a helpful error message. Other binary file types are generally skipped.
+`read_file` reads and returns the content of a specified file. This tool handles text files and media files (images, PDFs, audio, video) whose modality is supported by the current model. For text files, it can read specific line ranges. Unsupported PDFs attempt text extraction and the bounded vision fallback described below; other unsupported media files return a helpful error message. Other binary file types are generally skipped.
 
 - **Tool name:** `read_file`
 - **Display name:** ReadFile
 - **File:** `read-file.ts`
 - **Parameters:**
-  - `path` (string, required): The absolute path to the file to read.
+  - `file_path` (string, required): The absolute path to the file to read.
   - `offset` (number, optional): For text files, the 0-based line number to start reading from. Requires `limit` to be set.
   - `limit` (number, optional): For text files, the maximum number of lines to read. If omitted, reads a default maximum (e.g., 2000 lines) or the entire file if feasible.
+  - `pages` (string, optional): For PDFs, a 1-indexed page or closed page range such as `"3"` or `"20-25"`. A request may contain at most 20 pages.
 - **Behavior:**
   - For text files: Returns the content. If `offset` and `limit` are used, returns only that slice of lines. Indicates if content was truncated due to line limits or line length limits.
   - For media files (images, PDFs, audio, video): If the current model supports the file's modality, returns the file content as a base64-encoded `inlineData` object. If the model does not support the modality, returns an error message with guidance (e.g., suggesting skills or external tools).
+  - For PDFs with a text-only primary model: Text extraction is attempted first. If extraction fails, or an explicitly requested (or actual) single page still exceeds the 12K-token text budget, a configured vision bridge automatically renders and transcribes at most four pages beginning at the requested first page. The requested range is clipped to the actual document end when known. The result identifies the transcribed range and either the pages known to remain or, when the page count is unavailable, that additional pages may exist. Ordinary multi-page text overflow still asks for a narrower `pages` range instead of switching to vision.
+  - Vision bridge PDF transcription is lossy and marked as untrusted machine-generated content. The tool result contains text rather than rendered images, and its user-facing TUI, ACP, non-interactive structured output, and export displays identify the vision model and endpoint when known. If the bridge fails, the exact original PDF extraction error is returned to the model while the user display still discloses the bridge attempt.
   - For other binary files: Attempts to identify and skip them, returning a message indicating it's a generic binary file.
 - **Output:** (`llmContent`):
   - For text files: The file content, potentially prefixed with a truncation message (e.g., `[File content truncated: showing lines 1-100 of 500 total lines...]\nActual file content...`).