fix: read prompt subcommand input from stdin

ROADMAP.md

@@ -6345,7 +6345,7 @@ Original filing (2026-04-18): the session emitted `SessionStart hook (completed)
 422. **Unknown top-level subcommands fall through to chat prompt path instead of returning `unknown_subcommand` error — typos silently send the subcommand string as a chat message to the configured LLM** — dogfooded 2026-05-11 by Jobdori on `b98b9a71` in response to Clawhip pinpoint nudge at `1503215095088676956`. Reproduction: `unset ANTHROPIC_AUTH_TOKEN; export ANTHROPIC_API_KEY=fake-key-for-routing-test; claw completely-bogus-subcommand --output-format json` returns `{"error":"api returned 401 Unauthorized (authentication_error) [trace req_011...]: invalid x-api-key","kind":"api_http_error"}` — proving the unknown token reached the Anthropic API endpoint as a chat prompt. With valid credentials, the bogus subcommand string would be silently consumed as a chat message, billing the user for a typo and producing whatever continuation the LLM generates. **Pre-error path:** `claw <unknown> --output-format json` with no creds returns `kind:"missing_credentials"` (the auth gate fires first), masking the routing bug. Only with creds present does the fallthrough manifest as the actual prompt being sent. **Sibling exit-code bug:** when the chat-path 401 returns, the JSON envelope is `kind:"api_http_error"` but exit code is **0**, while `cli_parse` errors (e.g. `--no-such-flag`) and `missing_credentials` errors correctly exit **1**. Exit-code parity between error envelopes is broken — automation that gates on `$?` will treat the 401-as-chat as success. **Required fix shape:** (a) reserve unknown top-level tokens that match no registered subcommand and emit `kind:"unknown_subcommand"` with `unknown:<token>` field and exit code 1, BEFORE the chat fallback path; (b) when a token is intended as a chat prompt, require an explicit verb (`prompt`, `chat`, `ask`) or `--prompt` flag; (c) ensure exit codes are non-zero for all `kind:*_error` envelopes; (d) regression test: `claw <bogus> --output-format json` with valid auth returns `kind:"unknown_subcommand"` exit 1, never reaches the API. **Why this matters:** automation that calls `claw <subcommand>` with a programmatically constructed verb (typo, version drift, refactored command) silently bills tokens and produces hallucinated output instead of a typed error. Cross-cluster with #108 (CLI fallthrough discovered earlier) — #422 is the post-#108 audit confirming the routing bug still bites with valid credentials. Source: Jobdori live dogfood, `b98b9a71`, 2026-05-11.
 
 
-423. **`claw prompt` does not read prompt text from stdin when no positional prompt arg is provided — `echo "what is 2+2" | claw prompt --output-format json` returns `kind:"unknown" error:"prompt subcommand requires a prompt string"` instead of consuming stdin** — dogfooded 2026-05-11 by Jobdori on `3c563fa1` in response to Clawhip pinpoint nudge at `1503222644739276951`. Reproduction: `echo "what is 2+2" | claw prompt --output-format json` → `{"error":"prompt subcommand requires a prompt string","hint":null,"kind":"unknown","type":"error"}` exit 1. Same for `claw prompt --output-format json` with stdin redirected from a file. The most common Unix automation pattern (`cmd | claw prompt`) is broken because the prompt subcommand only reads the positional argument, never falls through to stdin. **Sibling envelope-kind bug:** the error `kind` is `"unknown"` instead of a typed `"missing_argument"` or `"validation_error"`. The `unknown` discriminator is the catch-all bucket — automation that switches on `kind` to differentiate input-validation errors from runtime errors gets no signal here. **Required fix shape:** (a) when `prompt` subcommand has no positional prompt arg AND stdin is not a TTY (i.e., piped or redirected), read stdin to EOF and use that as the prompt; (b) emit `kind:"missing_argument"` (not `"unknown"`) when both positional arg and stdin are absent; (c) add `--prompt-stdin` or `--stdin` opt-in flag for explicit control; (d) regression tests: `echo X | claw prompt --output-format json` reaches the runtime with prompt=X, AND `claw prompt < /dev/null` returns `kind:"missing_argument"` exit 1. **Why this matters:** Unix pipelines are the foundation of CLI automation. Every other major CLI (curl, jq, gh, kubectl) accepts stdin as the primary input when no positional arg is given. Breaking this convention forces automation to either inline the prompt as a shell-quoted string (escaping nightmare for multiline/code) or write to a temp file first. The `kind:"unknown"` error category compounds the problem by making the failure indistinguishable from a runtime crash. Source: Jobdori live dogfood, `3c563fa1`, 2026-05-11.
+423. **DONE — `claw prompt` reads prompt text from stdin when no positional prompt arg is provided** — fixed 2026-06-03 in `fix: read prompt subcommand input from stdin`. `parse_args()` now treats non-empty piped stdin as the prompt body for `claw prompt` when the positional prompt is empty, and supports `--stdin` / `--prompt-stdin` to append piped context to an explicit positional prompt. The existing `missing_prompt` JSON/stdout contract is preserved for closed or whitespace-only stdin. User docs now show `printf '...' | ./target/debug/claw prompt --output-format json`, and regression coverage verifies both a pure stdin prompt and explicit stdin context reach the mock Anthropic provider request and return structured JSON output.
 
 
 424. **DONE — `--model` accepts bare canonical provider model names and Anthropic routing prefixes are stripped before provider calls** — fixed 2026-06-03 in `fix: normalize Anthropic model routing`. `validate_model_syntax()` now accepts unambiguous bare `claude-*` and `gpt-*` model IDs while preserving raw model provenance, and Anthropic `/v1/messages` plus `/v1/messages/count_tokens` request bodies strip the CLI-only `anthropic/` routing prefix so default/alias models do not reach Anthropic as `anthropic/claude-*`. Existing `qwen-*`/`grok-*` prefix-hint behavior remains intentionally unchanged for provider families whose bare names are ambiguous with DashScope/xAI routing. Regression coverage: `standard_messages_body_strips_anthropic_routing_prefix`, `send_message_strips_anthropic_routing_prefix_on_wire`, `default_model_alias_uses_anthropic_routing_prefix`, and the bare `--model=claude-opus-4-6 status` / `--model gpt-4 prompt` parser assertions in `parses_single_word_command_aliases_without_falling_back_to_prompt_mode`.

USAGE.md

@@ -86,6 +86,12 @@ cd rust
 ./target/debug/claw prompt "summarize this repository"
 ```
 
+Pipe prompt text through stdin when automation already produces the prompt body:
+
+```bash
+printf 'summarize this repository\n' | ./target/debug/claw prompt --output-format json
+```
+
 ### Shorthand prompt mode
 
 ```bash

rust/crates/rusty-claude-cli/src/main.rs

@@ -1399,10 +1399,37 @@ fn parse_args(args: &[String]) -> Result<CliAction, String> {
         }
         "export" => parse_export_args(&rest[1..], output_format),
         "prompt" => {
-            let prompt = rest[1..].join(" ");
+            let mut read_stdin = false;
+            let prompt_parts = rest[1..]
+                .iter()
+                .filter_map(|arg| {
+                    if matches!(arg.as_str(), "--stdin" | "--prompt-stdin") {
+                        read_stdin = true;
+                        None
+                    } else {
+                        Some(arg.as_str())
+                    }
+                })
+                .collect::<Vec<_>>();
+            let positional_prompt = prompt_parts.join(" ");
+            let stdin_prompt = if read_stdin || positional_prompt.trim().is_empty() {
+                read_piped_stdin()
+            } else {
+                None
+            };
+            let prompt = if read_stdin {
+                merge_prompt_with_stdin(&positional_prompt, stdin_prompt.as_deref())
+            } else {
+                stdin_prompt
+                    .as_deref()
+                    .map(str::trim)
+                    .unwrap_or(&positional_prompt)
+                    .to_string()
+            };
             if prompt.trim().is_empty() {
-                // #750: provide error_kind-compatible prefix + \n for hint extraction
-                return Err("missing_prompt: prompt subcommand requires a prompt string.\nUsage: claw prompt <text>  or  echo '<text>' | claw".to_string());
+                // #750/#823/#423: provide error_kind-compatible prefix + \n for hint extraction.
+                return Err("missing_prompt: prompt subcommand requires a prompt string.
+Usage: claw prompt <text>  or  echo '<text>' | claw prompt".to_string());
             }
             Ok(CliAction::Prompt {
                 prompt,
@@ -11608,9 +11635,12 @@ fn print_help_to(out: &mut impl Write) -> io::Result<()> {
     writeln!(out, "      Start the interactive REPL")?;
     writeln!(
         out,
-        "  claw [--model MODEL] [--output-format text|json] prompt TEXT"
+        "  claw [--model MODEL] [--output-format text|json] prompt [--stdin] [TEXT]"
+    )?;
+    writeln!(
+        out,
+        "      Send one prompt and exit; reads stdin when TEXT is omitted"
     )?;
-    writeln!(out, "      Send one prompt and exit")?;
     writeln!(
         out,
         "  claw [--model MODEL] [--output-format text|json] TEXT"

rust/crates/rusty-claude-cli/tests/compact_output.rs

@@ -1,6 +1,7 @@
 #![allow(clippy::while_let_on_iterator)]
 
 use std::fs;
+use std::io::Write;
 use std::path::PathBuf;
 use std::process::{Command, Output, Stdio};
 use std::sync::atomic::{AtomicU64, Ordering};
@@ -245,6 +246,119 @@ stderr:
     fs::remove_dir_all(&workspace).expect("workspace cleanup should succeed");
 }
 
+#[test]
+fn prompt_subcommand_reads_prompt_from_stdin_when_no_positional_arg_423() {
+    let runtime = tokio::runtime::Runtime::new().expect("tokio runtime should build");
+    let server = runtime
+        .block_on(MockAnthropicService::spawn())
+        .expect("mock service should start");
+    let base_url = server.base_url();
+
+    let workspace = unique_temp_dir("prompt-stdin-423");
+    let config_home = workspace.join("config-home");
+    let home = workspace.join("home");
+    fs::create_dir_all(&workspace).expect("workspace should exist");
+    fs::create_dir_all(&config_home).expect("config home should exist");
+    fs::create_dir_all(&home).expect("home should exist");
+
+    let prompt = format!("{SCENARIO_PREFIX}streaming_text\n");
+    let output = run_claw_with_stdin(
+        &workspace,
+        &config_home,
+        &home,
+        &base_url,
+        &[
+            "prompt",
+            "--output-format",
+            "json",
+            "--compact",
+            "--permission-mode",
+            "read-only",
+            "--model",
+            "sonnet",
+        ],
+        &prompt,
+    );
+
+    assert!(
+        output.status.success(),
+        "prompt stdin run should succeed\nstdout:\n{}\n\nstderr:\n{}",
+        String::from_utf8_lossy(&output.stdout),
+        String::from_utf8_lossy(&output.stderr),
+    );
+    let parsed: Value = serde_json::from_slice(&output.stdout).expect("stdout should parse");
+    assert_eq!(
+        parsed["message"],
+        "Mock streaming says hello from the parity harness."
+    );
+    let captured = runtime.block_on(server.captured_requests());
+    assert!(
+        captured
+            .iter()
+            .any(|request| request.raw_body.contains("PARITY_SCENARIO:streaming_text")),
+        "stdin prompt should reach the provider request: {captured:?}"
+    );
+
+    fs::remove_dir_all(&workspace).expect("workspace cleanup should succeed");
+}
+
+#[test]
+fn prompt_subcommand_stdin_flag_appends_pipe_context_423() {
+    let runtime = tokio::runtime::Runtime::new().expect("tokio runtime should build");
+    let server = runtime
+        .block_on(MockAnthropicService::spawn())
+        .expect("mock service should start");
+    let base_url = server.base_url();
+
+    let workspace = unique_temp_dir("prompt-stdin-flag-423");
+    let config_home = workspace.join("config-home");
+    let home = workspace.join("home");
+    fs::create_dir_all(&workspace).expect("workspace should exist");
+    fs::create_dir_all(&config_home).expect("config home should exist");
+    fs::create_dir_all(&home).expect("home should exist");
+
+    let prompt_context = format!("{SCENARIO_PREFIX}streaming_text\n");
+    let output = run_claw_with_stdin(
+        &workspace,
+        &config_home,
+        &home,
+        &base_url,
+        &[
+            "prompt",
+            "Use stdin context",
+            "--stdin",
+            "--output-format",
+            "json",
+            "--compact",
+            "--permission-mode",
+            "read-only",
+            "--model",
+            "sonnet",
+        ],
+        &prompt_context,
+    );
+
+    assert!(
+        output.status.success(),
+        "prompt --stdin run should succeed\nstdout:\n{}\n\nstderr:\n{}",
+        String::from_utf8_lossy(&output.stdout),
+        String::from_utf8_lossy(&output.stderr),
+    );
+    let captured = runtime.block_on(server.captured_requests());
+    let provider_body = captured
+        .iter()
+        .find(|request| request.raw_body.contains("Use stdin context"))
+        .expect("merged prompt should reach provider");
+    assert!(
+        provider_body
+            .raw_body
+            .contains("PARITY_SCENARIO:streaming_text"),
+        "merged prompt should include stdin context: {provider_body:?}"
+    );
+
+    fs::remove_dir_all(&workspace).expect("workspace cleanup should succeed");
+}
+
 #[test]
 fn compact_subcommand_json_help_fails_fast_when_stdin_closed() {
     let workspace = unique_temp_dir("compact-nontty-json-help");
@@ -356,6 +470,39 @@ fn run_claw(
     command.output().expect("claw should launch")
 }
 
+fn run_claw_with_stdin(
+    cwd: &std::path::Path,
+    config_home: &std::path::Path,
+    home: &std::path::Path,
+    base_url: &str,
+    args: &[&str],
+    stdin: &str,
+) -> Output {
+    let mut child = Command::new(env!("CARGO_BIN_EXE_claw"))
+        .current_dir(cwd)
+        .env_clear()
+        .env("ANTHROPIC_API_KEY", "test-compact-key")
+        .env("ANTHROPIC_BASE_URL", base_url)
+        .env("CLAW_CONFIG_HOME", config_home)
+        .env("HOME", home)
+        .env("NO_COLOR", "1")
+        .env("PATH", "/usr/bin:/bin")
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .args(args)
+        .spawn()
+        .expect("claw should launch");
+    child
+        .stdin
+        .as_mut()
+        .expect("stdin should be piped")
+        .write_all(stdin.as_bytes())
+        .expect("stdin should write");
+    child.stdin.take();
+    child.wait_with_output().expect("output should collect")
+}
+
 fn run_claw_closed_stdin_with_timeout(
     cwd: &std::path::Path,
     config_home: &std::path::Path,