Lock down CLI-to-mock behavioral parity for Anthropic flows

This adds a deterministic mock Anthropic-compatible /v1/messages service,
a clean-environment CLI harness, and repo docs so the first parity
milestone can be validated without live network dependencies.

Constraint: First milestone must prove Rust claw can connect from a clean environment and cover streaming, tool assembly, and permission/tool flow
Constraint: No new third-party dependencies; reuse the existing Rust workspace stack
Rejected: Record/replay live Anthropic traffic | nondeterministic and unsuitable for repeatable CI coverage
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Keep scenario markers and expected tool payload shapes synchronized between the mock service and the harness tests
Tested: cargo fmt --all
Tested: cargo clippy --workspace --all-targets -- -D warnings
Tested: cargo test --workspace
Tested: ./scripts/run_mock_parity_harness.sh
Not-tested: Live Anthropic responses beyond the five scripted harness scenarios

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

@@ -0,0 +1,257 @@
+use std::fs;
+use std::path::{Path, PathBuf};
+use std::process::{Command, Output};
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::time::{SystemTime, UNIX_EPOCH};
+
+use mock_anthropic_service::{MockAnthropicService, SCENARIO_PREFIX};
+use serde_json::Value;
+
+static TEMP_COUNTER: AtomicU64 = AtomicU64::new(0);
+
+#[test]
+fn clean_env_cli_reaches_mock_anthropic_service_across_scripted_parity_scenarios() {
+    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 cases = [
+        ScenarioCase {
+            name: "streaming_text",
+            permission_mode: "read-only",
+            allowed_tools: None,
+            seed: seed_noop,
+            assert: assert_streaming_text,
+        },
+        ScenarioCase {
+            name: "read_file_roundtrip",
+            permission_mode: "read-only",
+            allowed_tools: Some("read_file"),
+            seed: seed_read_fixture,
+            assert: assert_read_file_roundtrip,
+        },
+        ScenarioCase {
+            name: "grep_chunk_assembly",
+            permission_mode: "read-only",
+            allowed_tools: Some("grep_search"),
+            seed: seed_grep_fixture,
+            assert: assert_grep_chunk_assembly,
+        },
+        ScenarioCase {
+            name: "write_file_allowed",
+            permission_mode: "workspace-write",
+            allowed_tools: Some("write_file"),
+            seed: seed_noop,
+            assert: assert_write_file_allowed,
+        },
+        ScenarioCase {
+            name: "write_file_denied",
+            permission_mode: "read-only",
+            allowed_tools: Some("write_file"),
+            seed: seed_noop,
+            assert: assert_write_file_denied,
+        },
+    ];
+
+    for case in cases {
+        let workspace = unique_temp_dir(case.name);
+        fs::create_dir_all(&workspace).expect("workspace should exist");
+        (case.seed)(&workspace);
+        let response = run_case(case, &workspace, &base_url);
+        (case.assert)(&workspace, &response);
+        fs::remove_dir_all(&workspace).expect("workspace cleanup should succeed");
+    }
+
+    let captured = runtime.block_on(server.captured_requests());
+    assert_eq!(
+        captured.len(),
+        9,
+        "five scenarios should produce nine requests"
+    );
+    assert!(captured
+        .iter()
+        .all(|request| request.path == "/v1/messages"));
+    assert!(captured.iter().all(|request| request.stream));
+
+    let scenarios = captured
+        .iter()
+        .map(|request| request.scenario.as_str())
+        .collect::<Vec<_>>();
+    assert_eq!(
+        scenarios,
+        vec![
+            "streaming_text",
+            "read_file_roundtrip",
+            "read_file_roundtrip",
+            "grep_chunk_assembly",
+            "grep_chunk_assembly",
+            "write_file_allowed",
+            "write_file_allowed",
+            "write_file_denied",
+            "write_file_denied",
+        ]
+    );
+}
+
+#[derive(Clone, Copy)]
+struct ScenarioCase {
+    name: &'static str,
+    permission_mode: &'static str,
+    allowed_tools: Option<&'static str>,
+    seed: fn(&Path),
+    assert: fn(&Path, &Value),
+}
+
+fn run_case(case: ScenarioCase, workspace: &Path, base_url: &str) -> Value {
+    let config_home = workspace.join("config-home");
+    let home = workspace.join("home");
+    fs::create_dir_all(config_home.join(".claw")).expect("config home should exist");
+    fs::create_dir_all(&home).expect("home should exist");
+
+    let mut command = Command::new(env!("CARGO_BIN_EXE_claw"));
+    command
+        .current_dir(workspace)
+        .env_clear()
+        .env("ANTHROPIC_API_KEY", "test-parity-key")
+        .env("ANTHROPIC_BASE_URL", base_url)
+        .env("CLAW_CONFIG_HOME", &config_home)
+        .env("HOME", &home)
+        .env("NO_COLOR", "1")
+        .args([
+            "--model",
+            "sonnet",
+            "--permission-mode",
+            case.permission_mode,
+            "--output-format=json",
+        ]);
+
+    if let Some(allowed_tools) = case.allowed_tools {
+        command.args(["--allowedTools", allowed_tools]);
+    }
+
+    let prompt = format!("{SCENARIO_PREFIX}{}", case.name);
+    let output = command.arg(prompt).output().expect("claw should launch");
+    assert_success(&output);
+    serde_json::from_slice(&output.stdout).expect("prompt output should be valid json")
+}
+
+fn seed_noop(_: &Path) {}
+
+fn seed_read_fixture(workspace: &Path) {
+    fs::write(workspace.join("fixture.txt"), "alpha parity line\n").expect("fixture should write");
+}
+
+fn seed_grep_fixture(workspace: &Path) {
+    fs::write(
+        workspace.join("fixture.txt"),
+        "alpha parity line\nbeta line\ngamma parity line\n",
+    )
+    .expect("grep fixture should write");
+}
+
+fn assert_streaming_text(_: &Path, response: &Value) {
+    assert_eq!(
+        response["message"],
+        Value::String("Mock streaming says hello from the parity harness.".to_string())
+    );
+    assert_eq!(response["iterations"], Value::from(1));
+    assert_eq!(response["tool_uses"], Value::Array(Vec::new()));
+    assert_eq!(response["tool_results"], Value::Array(Vec::new()));
+}
+
+fn assert_read_file_roundtrip(workspace: &Path, response: &Value) {
+    assert_eq!(response["iterations"], Value::from(2));
+    assert_eq!(
+        response["tool_uses"][0]["name"],
+        Value::String("read_file".to_string())
+    );
+    assert_eq!(
+        response["tool_uses"][0]["input"],
+        Value::String(r#"{"path":"fixture.txt"}"#.to_string())
+    );
+    assert!(response["message"]
+        .as_str()
+        .expect("message text")
+        .contains("alpha parity line"));
+    let output = response["tool_results"][0]["output"]
+        .as_str()
+        .expect("tool output");
+    assert!(output.contains(&workspace.join("fixture.txt").display().to_string()));
+    assert!(output.contains("alpha parity line"));
+}
+
+fn assert_grep_chunk_assembly(_: &Path, response: &Value) {
+    assert_eq!(response["iterations"], Value::from(2));
+    assert_eq!(
+        response["tool_uses"][0]["name"],
+        Value::String("grep_search".to_string())
+    );
+    assert_eq!(
+        response["tool_uses"][0]["input"],
+        Value::String(
+            r#"{"pattern":"parity","path":"fixture.txt","output_mode":"count"}"#.to_string()
+        )
+    );
+    assert!(response["message"]
+        .as_str()
+        .expect("message text")
+        .contains("2 occurrences"));
+    assert_eq!(response["tool_results"][0]["is_error"], Value::Bool(false));
+}
+
+fn assert_write_file_allowed(workspace: &Path, response: &Value) {
+    assert_eq!(response["iterations"], Value::from(2));
+    assert_eq!(
+        response["tool_uses"][0]["name"],
+        Value::String("write_file".to_string())
+    );
+    assert!(response["message"]
+        .as_str()
+        .expect("message text")
+        .contains("generated/output.txt"));
+    let generated = workspace.join("generated").join("output.txt");
+    let contents = fs::read_to_string(&generated).expect("generated file should exist");
+    assert_eq!(contents, "created by mock service\n");
+    assert_eq!(response["tool_results"][0]["is_error"], Value::Bool(false));
+}
+
+fn assert_write_file_denied(workspace: &Path, response: &Value) {
+    assert_eq!(response["iterations"], Value::from(2));
+    assert_eq!(
+        response["tool_uses"][0]["name"],
+        Value::String("write_file".to_string())
+    );
+    let tool_output = response["tool_results"][0]["output"]
+        .as_str()
+        .expect("tool output");
+    assert!(tool_output.contains("requires workspace-write permission"));
+    assert_eq!(response["tool_results"][0]["is_error"], Value::Bool(true));
+    assert!(response["message"]
+        .as_str()
+        .expect("message text")
+        .contains("denied as expected"));
+    assert!(!workspace.join("generated").join("denied.txt").exists());
+}
+
+fn assert_success(output: &Output) {
+    assert!(
+        output.status.success(),
+        "stdout:\n{}\n\nstderr:\n{}",
+        String::from_utf8_lossy(&output.stdout),
+        String::from_utf8_lossy(&output.stderr)
+    );
+}
+
+fn unique_temp_dir(label: &str) -> PathBuf {
+    let millis = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .expect("clock should be after epoch")
+        .as_millis();
+    let counter = TEMP_COUNTER.fetch_add(1, Ordering::Relaxed);
+    std::env::temp_dir().join(format!(
+        "claw-mock-parity-{label}-{}-{millis}-{counter}",
+        std::process::id()
+    ))
+}