One read of Claude Code CLIclaude-code-20260929T190701Z
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### Failed to start OAuth callback server
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7272| `OAuth token revoked` / `OAuth token has expired` | [Authentication](#oauth-token-revoked-or-expired) |
7373| `API Error: 401 Invalid authentication credentials` | [Authentication](#api-error-401-invalid-authentication-credentials) |
7474| `Login expired · Please run /login` | [Authentication](#login-expired) |
75| `Failed to start OAuth callback server` | [Authentication](#failed-to-start-oauth-callback-server) |
7576| `Claude login not accepted · Run /login, then try again` | [Authentication](#claude-login-not-accepted) |
7677| `Artifacts need a claude.ai login` | [Authentication](#artifacts-need-a-claude-ai-login) |
7778| `Not signed in to the Cloud gateway — run /login.` | [Authentication](#administrator-policy-requires-a-cloud-gateway-sign-in) |
from line 139
138139| `Request too large for the API's 32MB request limit` | [Request errors](#request-too-large) |
139140| `Image was too large` | [Request errors](#image-was-too-large) |
140141| `Unable to resize image` | [Request errors](#unable-to-resize-image) |
141| `PDF too large` / `PDF is password protected` | [Request errors](#pdf-errors) |
142| `PDF too large` / `PDF is password protected` / `pdftoppm is not installed` | [Request errors](#pdf-errors) |
142143| `Extra inputs are not permitted` | [Request errors](#extra-inputs-are-not-permitted) |
143144| `API Error: 400 ... tools.N.custom.input_schema: JSON schema is invalid` / `Property keys should match pattern` | [Request errors](#tool-input-schema-is-invalid) |
144145| `tool_use.name: String should have at most 200 characters` | [Request errors](#tool-use-name-over-200-characters) |
from line 1223
12221223* On other platforms, run `/login` again
12231224* If the login still doesn't save, see [Not logged in or token expired](/docs/en/troubleshoot-install#not-logged-in-or-token-expired) for the keychain unlock command and other credential-storage recovery steps
12241225
1226### Failed to start OAuth callback server
1227
1228When `/login`, `claude auth login`, or `claude setup-token` signs you in through the browser, Claude Code opens a listening port on `127.0.0.1` so your browser can return the sign-in result to it. This message means Claude Code couldn't open that port, and the sign-in stops before a browser window or login URL appears:
1229
1230```text theme={null}
1231Failed to start OAuth callback server: Failed to start server. Is port 0 in use?
1232```
1233
1234If your message ends with `Is port 0 in use?`, the attempt to listen on the IPv4 loopback address `127.0.0.1` failed outright. Because the failure happens before a login URL exists, the `Paste code here if prompted` flow isn't available as a workaround.
1235
1236**What to do:**
1237
1238* To sign in right away without the local listener: if you use a claude.ai subscription, run [`claude setup-token`](/docs/en/authentication#generate-a-long-lived-token) on a machine where sign-in works and set the token it prints as `CLAUDE_CODE_OAUTH_TOKEN` on this machine. Otherwise set `ANTHROPIC_API_KEY` to a key from the [Claude Console](https://platform.claude.com/settings/keys). [Authentication precedence](/docs/en/authentication#authentication-precedence) explains how Claude Code chooses between credentials.
1239* To use browser sign-in on this machine instead, Claude Code must be able to listen on `127.0.0.1`. If it runs inside a sandbox, check that the sandbox's policy allows listening on local ports, then run `/login` again. If it should be able to and still fails, run `/feedback` so the report includes your environment details.
1240
12251241### Claude login not accepted
12261242
12271243You tried to start a [cloud session](/docs/en/claude-code-on-the-web), and the server refused to create it with a 401: it didn't accept the Claude login this machine sent, usually because the login expired or was revoked.
from line 2111
20952111* For oversized PDFs, ask Claude to read a page range with the Read tool instead of attaching the whole file, or extract text with a tool like `pdftotext` and reference the output file by path
20962112* For protected or invalid PDFs, remove the password or re-export the file from its source application, then try again
20972113
2114When Claude reads a page range from a PDF with the Read tool, the read can fail with a different message:
2115
2116```text theme={null}
2117pdftoppm is not installed. Install poppler-utils (e.g. `brew install poppler` or `apt-get install poppler-utils`) to enable PDF page rendering.
2118```
2119
2120Page-range reads render pages with `pdftoppm`. Install poppler-utils with the command the message gives, or on other platforms a poppler build that puts `pdftoppm` on your `PATH`. See [Read tool behavior](/docs/en/tools-reference#read-tool-behavior) for which PDFs are read by page range.
2121
20982122### Extra inputs are not permitted
20992123
21002124A proxy or LLM gateway between Claude Code and the API stripped the `anthropic-beta` request header, so the API rejected fields that depend on it.
from line 2841
28172841Could not import my server: Invalid name my server. Names can only contain letters, numbers, hyphens, and underscores.
28182842```
28192843
2820The text after the server name is the reason. The most common one is the name check: Claude Desktop allows characters in server names, such as spaces and periods, that `claude mcp` restricts to letters, numbers, hyphens, and underscores. Other reasons include a server configuration that fails validation and a server blocked by your organization's [MCP policy](/docs/en/managed-mcp).
2821
2822**What to do:**
2823
2824* Rename the server in `claude_desktop_config.json` to use only letters, numbers, hyphens, and underscores, then run `claude mcp add-from-claude-desktop` again
2825* Add that server directly with `claude mcp add` or `claude mcp add-json` under a valid name. See [Import MCP servers from Claude Desktop](/docs/en/mcp#import-mcp-servers-from-claude-desktop).
2826
2827### Cannot add MCP server to the managed scope
2828
2829You ran `claude mcp add` or `claude mcp add-json` with `--scope managed`. That scope holds the servers your organization provides through the [`managedMcpServers`](/docs/en/settings-reference#managedmcpservers) managed setting. Claude Code reads them from managed settings only, so the command can't write a server to that scope.
2830
2831```text theme={null}
2832Cannot add MCP server to scope: managed
2833```
2834
2835**What to do:**
2836
2837* Add the server to a scope you can write: `local`, `user`, or `project`. Without `--scope`, the command uses `local`. See [MCP installation scopes](/docs/en/mcp#mcp-installation-scopes)
2838* To provide the server to every user in your organization, add it to [`managedMcpServers`](/docs/en/settings-reference#managedmcpservers) in the managed settings you deploy
2839
2840<h3 id="cant-read-mcp-json">
2841 Can't read .mcp.json
2842</h3>
2843
2844A command that reads the project's [`.mcp.json`](/docs/en/mcp#project-scope), such as `claude mcp add` or `claude mcp add-json` with `--scope project`, or `claude mcp remove`, found that the file in your current directory isn't a regular file or is larger than 2 MiB, so it exits with this error instead of reading the file.
2845
2846```text theme={null}
2847Can't read .mcp.json: it isn't a regular file or is larger than 2097152 bytes. Fix or remove it, then run the command again.
2848```
2849
2850Before v2.1.257, a FIFO at `.mcp.json` left the command waiting forever with no output, and a symlink to a device file such as `/dev/zero` grew memory until the process was killed.
2851
2852**What to do:**
2853
2854* Check what sits at `.mcp.json` in your current directory. Repla
2844The text after the server name is the reason. The most common one is the name check: Cla
tools-reference Changed · +1 / -1 lines
from line 454
454454Read handles several file types beyond plain text:
455455
456456* **Images**: PNG, JPG, and other image formats are returned as visual content that Claude can see, not as raw bytes. Claude Code resizes and recompresses large images to fit the model's image size limits before sending them, so Claude may see a downscaled version of a large screenshot. As of v2.1.196, an image that is still larger than 500KB after that resize is re-encoded as a JPEG at reduced quality with its pixel dimensions unchanged. If Claude misses fine pixel-level detail in a large image, ask it to crop the region of interest first, for example with ImageMagick via Bash.
457* **PDFs**: Claude reads short `.pdf` files whole. For PDFs longer than 10 pages, it reads in ranges with a `pages` parameter, such as `"1-5"`, up to 20 pages at a time.
457* **PDFs**: Claude reads short `.pdf` files whole. For PDFs longer than 10 pages, it reads in ranges with a `pages` parameter, such as `"1-5"`, up to 20 pages at a time. Page-range reads render pages with `pdftoppm` from poppler-utils, so install it with `brew install poppler` on macOS or `apt-get install poppler-utils` on Debian and Ubuntu. On Windows and other platforms, install a poppler build that puts `pdftoppm` on your `PATH`. Without it, a page-range read fails with `pdftoppm is not installed`.
458458* **Jupyter notebooks**: `.ipynb` files return all cells with their outputs, including code, markdown, and visualizations. Claude Code refuses to read a notebook file over 100 MB; the error tells Claude how to read a portion of the notebook instead, such as a slice of cells, with a shell command.
459459
460460Read only reads files, not directories. Claude lists directory contents with a shell command such as `ls`.
vs-code Changed · +1 / -1 lines
from line 171
171171What's in @src/components/ (include a trailing slash for folders)
172172```
173173
174For large PDFs, you can ask Claude to read specific pages instead of the whole file: a single page, a range like pages 1-10, or an open-ended range like page 3 onward.
174For large PDFs, you can ask Claude to read specific pages instead of the whole file: a single page, a range like pages 1-10, or an open-ended range like page 3 onward. Reading specific pages requires [poppler-utils](/docs/en/tools-reference#read-tool-behavior) on the machine where Claude Code runs.
175175
176176When you select text in the editor, Claude can see your highlighted code automatically. The prompt box footer shows how many lines are selected. Press `Option+K` (Mac) / `Alt+K` (Windows/Linux) to insert an @-mention with the file path and line numbers (e.g., `@app.ts#5-10`). Click the **X** on the selection indicator to remove it so Claude doesn't receive the selection. The indicator comes back when you select other text.
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