chore: remove accidentally committed .gjc session state and ignore .gjc/

refactor(cli): let the emitter report the output tail it leaves behind

Two places believed they owned terminal output: consume_stream streams
assistant deltas live while emit_output = true, and run_turn decided
whether to emit a separating newline before spinner.finish by guessing
from final_assistant_text(&summary).

That guess agrees with reality only because every *other* writer happens to
terminate its output with a newline — tool results go through
stream_markdown (which appends one), thinking summaries are written with a
trailing newline, and tool-call headers use writeln! — so the assistant
text path is the only one that can leave a partial line. That is a property
of the current renderers rather than of the streaming protocol, and it is
not enforced anywhere.

TerminalTail is state the emitter records into as it writes: both live
writers (AnthropicRuntimeClient::consume_stream and the tool-result blocks
in CliToolExecutor::execute) now push bytes through a TailTrackingWriter
that reports the last byte written, and the caller that ends a turn asks
where the emitter stopped instead of inferring it.

The heuristic also left the failure arm unguarded. A turn that streamed text
and then errored called spinner.fail on a partial line, which the line
clear then erased; that arm now carries the same guard.

Also gate the animated spinner.tick frame on is_terminal(). That frame is
pure cursor control (save, rewrite line, restore) and emits no newline, so
down a pipe it leaves an unterminated banner that the first streamed delta
then continues on the same physical line.

—
*[repo owner's gaebal-gajae (clawdbot) 🦞]*

.gitignore

@@ -13,3 +13,5 @@ archive/
 status-help.txt
 # Legacy Python port session scratch artifacts
 .port_sessions/
+# Local agent session state
+.gjc/

.gjc/_session-5e2dd1e8-ea4b-4af1-b56b-89ab7cca4299/runtime/runtime-state.json

@@ -1 +0,0 @@
-{"schema_version":1,"session_id":"5e2dd1e8-ea4b-4af1-b56b-89ab7cca4299","state":"running","ready_for_input":false,"updated_at":"2026-10-12T22:09:30.659Z","current_turn_id":null,"last_turn_id":null,"live":true,"reason":null,"source":"agent_session_event","event":"turn_start","cwd":"/home/bellman/Data/Workspace/gc-task-cc-issue-3257-lane","workdir":"/home/bellman/Data/Workspace/gc-task-cc-issue-3257-lane","branch":null,"session_file":"/home/bellman/.gajaeway/broker/agent/sessions/v2-6fji37qf7ld523ivvoiohlcpmz3nu45m2apxyrkusn5nxczjmouq/2026-10-12T22-04-33-362Z_5e2dd1e8-ea4b-4af1-b56b-89ab7cca4299.jsonl","activity":{"seq":115,"last_activity_at":"2026-10-12T22:09:34.144Z","tool":"bash","phase":"started","outcome":null,"elapsed_ms":null,"active_tool_count":1,"active_tools":[{"tool":"bash","started_at":"2026-10-12T22:09:34.144Z"}],"in_flight":[{"digest":"e603a70efb03b6b2b78c94b704197d26fc8a35113543291a21f68b3b08ca11a9","tool":"bash","started_at":"2026-10-12T22:09:34.144Z"}]}}

.gjc/_session-5e2dd1e8-ea4b-4af1-b56b-89ab7cca4299/runtime/runtime-state.json.lock

@@ -1 +0,0 @@
-{"pid":1,"start_time":"unknown","token":"1a2e8a33-76f2-4175-ac23-1521458f12a2","owner_host_id":"7af2fb0e8e37bd543e3d0bda6f205b56f30077b5a9b77e83208e94ae441315ac","released":true}

.gjc/_session-5e2dd1e8-ea4b-4af1-b56b-89ab7cca4299/runtime/runtime-state.json.lock.transition.owner

@@ -1 +0,0 @@
-{"pid":1,"start_time":"unknown","token":"a1342032-af80-4a49-a783-291bf73bf027","owner_host_id":"7af2fb0e8e37bd543e3d0bda6f205b56f30077b5a9b77e83208e94ae441315ac","released":true}

.gjc/state/sdk/5e2dd1e8-ea4b-4af1-b56b-89ab7cca4299.json

@@ -1,12 +0,0 @@
-{
-  "version": 1,
-  "sessionId": "5e2dd1e8-ea4b-4af1-b56b-89ab7cca4299",
-  "pid": 487360,
-  "host": "127.0.0.1",
-  "port": 37541,
-  "url": "ws://127.0.0.1:37541",
-  "token": "LlIfu_aHH57jfys2Ii0ORMrnu56NLAa1",
-  "startedAt": 1791842673967,
-  "updatedAt": 1791842673967,
-  "stale": false
-}

.gjc/state/sdk/5e2dd1e8-ea4b-4af1-b56b-89ab7cca4299.lifecycle.json

@@ -1 +0,0 @@
-{"effectMarker":"f441857a-f591-474b-b34a-6d89b2bf9feb","incarnation":"linux:159099652","pid":487360}

.gjc/state/sdk/5e2dd1e8-ea4b-4af1-b56b-89ab7cca4299.lifecycle.ready.json

@@ -1 +0,0 @@
-{"effectMarker":"f441857a-f591-474b-b34a-6d89b2bf9feb","incarnation":"linux:159099652","pid":487360}

rust/crates/mock-anthropic-service/src/lib.rs

@@ -13,6 +13,16 @@ use tokio::task::JoinHandle;
 pub const SCENARIO_PREFIX: &str = "PARITY_SCENARIO:";
 pub const DEFAULT_MODEL: &str = "claude-sonnet-4-6";
 
+/// The assistant text the `context_window_retry` scenario finally streams, after
+/// its first request was refused with a context-overflow error. Exposed so a
+/// test can assert on the exact body instead of restating the literal.
+pub const CONTEXT_WINDOW_RETRY_TEXT: &str = "auto compact retry parity complete.";
+
+/// The partial assistant text the `stream_then_error` scenario streams before it
+/// fails the response mid-stream. Exposed so a test can assert on the exact body
+/// instead of restating the literal.
+pub const STREAM_THEN_ERROR_TEXT: &str = "partial response before the stream failed";
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct CapturedRequest {
     pub method: String,
@@ -99,6 +109,8 @@ enum Scenario {
     BashPermissionPromptDenied,
     PluginToolRoundtrip,
     AutoCompactTriggered,
+    ContextWindowRetry,
+    StreamThenError,
     TokenCostReporting,
 }
 
@@ -116,6 +128,8 @@ impl Scenario {
             "bash_permission_prompt_denied" => Some(Self::BashPermissionPromptDenied),
             "plugin_tool_roundtrip" => Some(Self::PluginToolRoundtrip),
             "auto_compact_triggered" => Some(Self::AutoCompactTriggered),
+            "context_window_retry" => Some(Self::ContextWindowRetry),
+            "stream_then_error" => Some(Self::StreamThenError),
             "token_cost_reporting" => Some(Self::TokenCostReporting),
             _ => None,
         }
@@ -134,6 +148,8 @@ impl Scenario {
             Self::BashPermissionPromptDenied => "bash_permission_prompt_denied",
             Self::PluginToolRoundtrip => "plugin_tool_roundtrip",
             Self::AutoCompactTriggered => "auto_compact_triggered",
+            Self::ContextWindowRetry => "context_window_retry",
+            Self::StreamThenError => "stream_then_error",
             Self::TokenCostReporting => "token_cost_reporting",
         }
     }
@@ -149,6 +165,18 @@ async fn handle_connection(
     let scenario = detect_scenario(&request)
         .ok_or_else(|| io::Error::new(io::ErrorKind::InvalidInput, "missing parity scenario"))?;
 
+    // How many times this scenario has already been served *on this endpoint*.
+    // Scenarios that need to behave differently on a retry (reject once, then
+    // succeed) key off this; counting per endpoint keeps the token-counting
+    // preflight on `/v1/messages/count_tokens` from consuming the first attempt.
+    let attempt = {
+        let served = requests.lock().await;
+        served
+            .iter()
+            .filter(|captured| captured.scenario == scenario.name() && captured.path == path)
+            .count()
+    };
+
     requests.lock().await.push(CapturedRequest {
         method,
         path,
@@ -158,7 +186,7 @@ async fn handle_connection(
         raw_body,
     });
 
-    let response = build_http_response(&request, scenario);
+    let response = build_http_response(&request, scenario, attempt);
     socket.write_all(response.as_bytes()).await?;
     Ok(())
 }
@@ -308,7 +336,11 @@ fn flatten_tool_result_content(content: &[api::ToolResultContentBlock]) -> Strin
 }
 
 #[allow(clippy::too_many_lines)]
-fn build_http_response(request: &MessageRequest, scenario: Scenario) -> String {
+fn build_http_response(request: &MessageRequest, scenario: Scenario, attempt: usize) -> String {
+    if let Some(rejection) = context_window_rejection(scenario, attempt) {
+        return rejection;
+    }
+
     let response = if request.stream {
         let body = build_stream_body(request, scenario);
         return http_response(
@@ -329,6 +361,37 @@ fn build_http_response(request: &MessageRequest, scenario: Scenario) -> String {
     )
 }
 
+/// The first request of [`Scenario::ContextWindowRetry`] is refused with a
+/// context-overflow error instead of a streamed answer, so the client's
+/// auto-compact recovery path runs and the *retry* is what produces the
+/// response text. Every later request against the same endpoint succeeds.
+///
+/// HTTP 400 is deliberately chosen: it is not in the client's retryable status
+/// set, so the client surfaces the error rather than silently re-sending it —
+/// which is exactly the situation a real context-overflow rejection creates.
+/// The body carries the `context_window` marker the client greps for.
+fn context_window_rejection(scenario: Scenario, attempt: usize) -> Option<String> {
+    if scenario != Scenario::ContextWindowRetry || attempt > 0 {
+        return None;
+    }
+
+    let body = json!({
+        "type": "error",
+        "error": {
+            "type": "invalid_request_error",
+            "message": "prompt is too long: context_window exceeded for this model",
+        },
+    })
+    .to_string();
+
+    Some(http_response(
+        "400 Bad Request",
+        "application/json",
+        &body,
+        &[("request-id", request_id_for(scenario))],
+    ))
+}
+
 #[allow(clippy::too_many_lines)]
 fn build_stream_body(request: &MessageRequest, scenario: Scenario) -> String {
     match scenario {
@@ -461,6 +524,8 @@ fn build_stream_body(request: &MessageRequest, scenario: Scenario) -> String {
         Scenario::AutoCompactTriggered => {
             final_text_sse_with_usage("auto compact parity complete.", 50_000, 200)
         }
+        Scenario::ContextWindowRetry => final_text_sse(CONTEXT_WINDOW_RETRY_TEXT),
+        Scenario::StreamThenError => stream_then_error_sse(STREAM_THEN_ERROR_TEXT),
         Scenario::TokenCostReporting => {
             final_text_sse_with_usage("token cost reporting parity complete.", 1_000, 500)
         }
@@ -628,6 +693,12 @@ fn build_message_response(request: &MessageRequest, scenario: Scenario) -> Messa
             50_000,
             200,
         ),
+        Scenario::ContextWindowRetry => {
+            text_message_response("msg_context_window_retry", CONTEXT_WINDOW_RETRY_TEXT)
+        }
+        Scenario::StreamThenError => {
+            text_message_response("msg_stream_then_error", STREAM_THEN_ERROR_TEXT)
+        }
         Scenario::TokenCostReporting => text_message_response_with_usage(
             "msg_token_cost_reporting",
             "token cost reporting parity complete.",
@@ -650,6 +721,8 @@ fn request_id_for(scenario: Scenario) -> &'static str {
         Scenario::BashPermissionPromptDenied => "req_bash_permission_prompt_denied",
         Scenario::PluginToolRoundtrip => "req_plugin_tool_roundtrip",
         Scenario::AutoCompactTriggered => "req_auto_compact_triggered",
+        Scenario::ContextWindowRetry => "req_context_window_retry",
+        Scenario::StreamThenError => "req_stream_then_error",
         Scenario::TokenCostReporting => "req_token_cost_reporting",
     }
 }
@@ -971,6 +1044,84 @@ fn final_text_sse(text: &str) -> String {
     body
 }
 
+/// Streams a text block to completion and then fails the response, which is
+/// what a provider does when it dies partway through an answer.
+///
+/// The block is closed before the failure on purpose: the client only flushes
+/// its buffered markdown to the terminal on `content_block_stop`, so without
+/// that frame the partial text would still be sitting in the renderer and the
+/// scenario would not reproduce a turn that streamed text and *then* errored.
+///
+/// The response is cut off in the middle of the failing frame rather than
+/// carrying a complete one. Two things fall out of that, both deliberate.
+///
+/// It is what a provider that dies on the socket actually looks like, and it
+/// keeps the failure in a *later* parser call than the answer text. The whole
+/// response is one `write_all` on the mock's side, so a complete trailing frame
+/// would land in the same read chunk as the deltas — and `SseParser::push`
+/// returns `Err` from inside its frame loop, which discards the events it had
+/// already parsed from that same chunk. The client would then never render the
+/// text at all, and the scenario would be exercising that parser behaviour
+/// instead of the terminal state it is meant to reproduce. A truncated tail
+/// stays in the parser's buffer, so `push` returns the deltas normally and the
+/// failure only surfaces from `finish()`, once the client has consumed every
+/// event ahead of it.
+///
+/// The failure is a frame that does not deserialize — `api::types::StreamEvent`
+/// is `#[serde(tag = "type")]` with no fallback arm, so an unknown frame type or
+/// a truncated payload is an `ApiError::Json`. That is non-retryable, and it is
+/// raised while reading the body rather than while acquiring the response, so the
+/// client reports it on the first attempt rather than retrying.
+fn stream_then_error_sse(text: &str) -> String {
+    let mut body = String::new();
+    append_sse(
+        &mut body,
+        "message_start",
+        json!({
+            "type": "message_start",
+            "message": {
+                "id": unique_message_id(),
+                "type": "message",
+                "role": "assistant",
+                "content": [],
+                "model": DEFAULT_MODEL,
+                "stop_reason": null,
+                "stop_sequence": null,
+                "usage": usage_json(14, 0)
+            }
+        }),
+    );
+    append_sse(
+        &mut body,
+        "content_block_start",
+        json!({
+            "type": "content_block_start",
+            "index": 0,
+            "content_block": {"type": "text", "text": ""}
+        }),
+    );
+    append_sse(
+        &mut body,
+        "content_block_delta",
+        json!({
+            "type": "content_block_delta",
+            "index": 0,
+            "delta": {"type": "text_delta", "text": text}
+        }),
+    );
+    append_sse(
+        &mut body,
+        "content_block_stop",
+        json!({"type": "content_block_stop", "index": 0}),
+    );
+    // No terminating blank line: the frame is still arriving when the provider
+    // drops the connection, so it stays in the client's parser buffer until the
+    // body ends. See the note above for why the failure has to trail the deltas
+    // by a parser call rather than sharing their chunk.
+    body.push_str("event: error\ndata: {\"type\":\"error\",\"error\":{\"type\":\"overloaded_");
+    body
+}
+
 fn final_text_sse_with_usage(text: &str, input_tokens: u32, output_tokens: u32) -> String {
     let mut body = String::new();
     append_sse(

rust/crates/runtime/src/json.rs

@@ -49,10 +49,10 @@ impl JsonValue {
                     .join(",");
                 format!("[{rendered}]")
             }
-            Self::Object(map) => {
-                let rendered = map
+            Self::Object(entries) => {
+                let rendered = entries
                     .iter()
-                    .map(|(k, v)| format!("{}:{}", render_string(k), v.render()))
+                    .map(|(key, value)| format!("{}:{}", render_string(key), value.render()))
                     .collect::<Vec<_>>()
                     .join(",");
                 format!("{{{rendered}}}")
@@ -60,26 +60,21 @@ impl JsonValue {
         }
     }
 
-    #[must_use]
-    pub fn as_bool(&self) -> Option<bool> {
-        match self {
-            Self::Bool(b) => Some(*b),
-            _ => None,
+    pub fn parse(source: &str) -> Result<Self, JsonError> {
+        let mut parser = Parser::new(source);
+        let value = parser.parse_value()?;
+        parser.skip_whitespace();
+        if parser.is_eof() {
+            Ok(value)
+        } else {
+            Err(JsonError::new("unexpected trailing content"))
         }
     }
 
     #[must_use]
-    pub fn as_i64(&self) -> Option<i64> {
+    pub fn as_object(&self) -> Option<&BTreeMap<String, JsonValue>> {
         match self {
-            Self::Number(n) => Some(*n),
-            _ => None,
-        }
-    }
-
-    #[must_use]
-    pub fn as_str(&self) -> Option<&str> {
-        match self {
-            Self::String(s) => Some(s),
+            Self::Object(value) => Some(value),
             _ => None,
         }
     }
@@ -87,354 +82,273 @@ impl JsonValue {
     #[must_use]
     pub fn as_array(&self) -> Option<&[JsonValue]> {
         match self {
-            Self::Array(a) => Some(a),
+            Self::Array(value) => Some(value),
             _ => None,
         }
     }
 
     #[must_use]
-    pub fn as_object(&self) -> Option<&BTreeMap<String, JsonValue>> {
+    pub fn as_str(&self) -> Option<&str> {
         match self {
-            Self::Object(o) => Some(o),
+            Self::String(value) => Some(value),
             _ => None,
         }
     }
 
-    pub fn parse(input: &str) -> Result<Self, JsonError> {
-        let mut chars = input.trim().chars().peekable();
-        let value = parse_value(&mut chars)?;
-        if chars.peek().is_some() {
-            return Err(JsonError::new("trailing content"));
+    #[must_use]
+    pub fn as_bool(&self) -> Option<bool> {
+        match self {
+            Self::Bool(value) => Some(*value),
+            _ => None,
+        }
+    }
+
+    #[must_use]
+    pub fn as_i64(&self) -> Option<i64> {
+        match self {
+            Self::Number(value) => Some(*value),
+            _ => None,
+        }
+    }
+}
+
+fn render_string(value: &str) -> String {
+    let mut rendered = String::with_capacity(value.len() + 2);
+    rendered.push('"');
+    for ch in value.chars() {
+        match ch {
+            '"' => rendered.push_str("\\\""),
+            '\\' => rendered.push_str("\\\\"),
+            '\n' => rendered.push_str("\\n"),
+            '\r' => rendered.push_str("\\r"),
+            '\t' => rendered.push_str("\\t"),
+            '\u{08}' => rendered.push_str("\\b"),
+            '\u{0C}' => rendered.push_str("\\f"),
+            control if control.is_control() => push_unicode_escape(&mut rendered, control),
+            plain => rendered.push(plain),
+        }
+    }
+    rendered.push('"');
+    rendered
+}
+
+fn push_unicode_escape(rendered: &mut String, control: char) {
+    const HEX: &[u8; 16] = b"0123456789abcdef";
+
+    rendered.push_str("\\u");
+    let value = u32::from(control);
+    for shift in [12_u32, 8, 4, 0] {
+        let nibble = ((value >> shift) & 0xF) as usize;
+        rendered.push(char::from(HEX[nibble]));
+    }
+}
+
+struct Parser<'a> {
+    chars: Vec<char>,
+    index: usize,
+    _source: &'a str,
+}
+
+impl<'a> Parser<'a> {
+    fn new(source: &'a str) -> Self {
+        Self {
+            chars: source.chars().collect(),
+            index: 0,
+            _source: source,
+        }
+    }
+
+    fn parse_value(&mut self) -> Result<JsonValue, JsonError> {
+        self.skip_whitespace();
+        match self.peek() {
+            Some('n') => self.parse_literal("null", JsonValue::Null),
+            Some('t') => self.parse_literal("true", JsonValue::Bool(true)),
+            Some('f') => self.parse_literal("false", JsonValue::Bool(false)),
+            Some('"') => self.parse_string().map(JsonValue::String),
+            Some('[') => self.parse_array(),
+            Some('{') => self.parse_object(),
+            Some('-' | '0'..='9') => self.parse_number().map(JsonValue::Number),
+            Some(other) => Err(JsonError::new(format!("unexpected character: {other}"))),
+            None => Err(JsonError::new("unexpected end of input")),
+        }
+    }
+
+    fn parse_literal(&mut self, expected: &str, value: JsonValue) -> Result<JsonValue, JsonError> {
+        for expected_char in expected.chars() {
+            if self.next() != Some(expected_char) {
+                return Err(JsonError::new(format!(
+                    "invalid literal: expected {expected}"
+                )));
+            }
         }
         Ok(value)
     }
-}
 
-fn parse_value(chars: &mut std::iter::Peekable<std::str::Chars>) -> Result<JsonValue, JsonError> {
-    match chars.peek() {
-        Some('n') => parse_null(chars),
-        Some('t') | Some('f') => parse_bool(chars),
-        Some('"') => parse_string(chars).map(JsonValue::String),
-        Some('[') => parse_array(chars),
-        Some('{') => parse_object(chars),
-        Some('-') | Some('0'..='9') => parse_number(chars),
-        Some(c) => Err(JsonError::new(format!("unexpected char: {c}"))),
-        None => Err(JsonError::new("empty input")),
-    }
-}
-
-fn parse_null(chars: &mut std::iter::Peekable<std::str::Chars>) -> Result<JsonValue, JsonError> {
-    if consume_literal(chars, "null") {
-        Ok(JsonValue::Null)
-    } else {
-        Err(JsonError::new("invalid null"))
-    }
-}
-
-fn parse_bool(chars: &mut std::iter::Peekable<std::str::Chars>) -> Result<JsonValue, JsonError> {
-    if consume_literal(chars, "true") {
-        return Ok(JsonValue::Bool(true));
-    }
-    if consume_literal(chars, "false") {
-        return Ok(JsonValue::Bool(false));
-    }
-    Err(JsonError::new("invalid bool"))
-}
-
-fn parse_string(chars: &mut std::iter::Peekable<std::str::Chars>) -> Result<String, JsonError> {
-    if chars.next() != Some('"') {
-        return Err(JsonError::new("expected opening quote"));
+    fn parse_string(&mut self) -> Result<String, JsonError> {
+        self.expect('"')?;
+        let mut value = String::new();
+        while let Some(ch) = self.next() {
+            match ch {
+                '"' => return Ok(value),
+                '\\' => value.push(self.parse_escape()?),
+                plain => value.push(plain),
+            }
+        }
+        Err(JsonError::new("unterminated string"))
     }
 
-    let mut result = String::new();
-    loop {
-        match chars.next() {
-            None => return Err(JsonError::new("unterminated string")),
-            Some('"') => return Ok(result),
-            Some('\\') => match chars.next() {
-                Some('"') => result.push('"'),
-                Some('\\') => result.push('\\'),
-                Some('/') => result.push('/'),
-                Some('b') => result.push('\u{08}'),
-                Some('f') => result.push('\u{0C}'),
-                Some('n') => result.push('\n'),
-                Some('r') => result.push('\r'),
-                Some('t') => result.push('\t'),
-                Some('u') => {
-                    let mut hex = String::new();
-                    for _ in 0..4 {
-                        match chars.next() {
-                            Some(c @ '0'..='9') | Some(c @ 'a'..='f') | Some(c @ 'A'..='F') => {
-                                hex.push(c)
-                            }
-                            _ => return Err(JsonError::new("invalid unicode escape")),
-                        }
-                    }
-                    let code = u32::from_str_radix(&hex, 16)
-                        .map_err(|_| JsonError::new("invalid hex code"))?;
-                    if (0xD800..=0xDFFF).contains(&code) {
-                        return Err(JsonError::new("surrogate not allowed"));
-                    }
-                    result.push(
-                        char::from_u32(code).ok_or_else(|| JsonError::new("invalid codepoint"))?,
-                    );
-                }
-                _ => return Err(JsonError::new("invalid escape")),
-            },
-            Some(c) => result.push(c),
+    fn parse_escape(&mut self) -> Result<char, JsonError> {
+        match self.next() {
+            Some('"') => Ok('"'),
+            Some('\\') => Ok('\\'),
+            Some('/') => Ok('/'),
+            Some('b') => Ok('\u{08}'),
+            Some('f') => Ok('\u{0C}'),
+            Some('n') => Ok('\n'),
+            Some('r') => Ok('\r'),
+            Some('t') => Ok('\t'),
+            Some('u') => self.parse_unicode_escape(),
+            Some(other) => Err(JsonError::new(format!("invalid escape sequence: {other}"))),
+            None => Err(JsonError::new("unexpected end of input in escape sequence")),
         }
     }
-}
 
-fn parse_number(chars: &mut std::iter::Peekable<std::str::Chars>) -> Result<JsonValue, JsonError> {
-    let mut num_str = String::new();
-
-    if chars.peek() == Some(&'-') {
-        num_str.push(chars.next().unwrap());
+    fn parse_unicode_escape(&mut self) -> Result<char, JsonError> {
+        let mut value = 0_u32;
+        for _ in 0..4 {
+            let Some(ch) = self.next() else {
+                return Err(JsonError::new("unexpected end of input in unicode escape"));
+            };
+            value = (value << 4)
+                | ch.to_digit(16)
+                    .ok_or_else(|| JsonError::new("invalid unicode escape"))?;
+        }
+        char::from_u32(value).ok_or_else(|| JsonError::new("invalid unicode scalar value"))
     }
 
-    while let Some(&c) = chars.peek() {
-        if c.is_ascii_digit() {
-            num_str.push(chars.next().unwrap());
+    fn parse_array(&mut self) -> Result<JsonValue, JsonError> {
+        self.expect('[')?;
+        let mut values = Vec::new();
+        loop {
+            self.skip_whitespace();
+            if self.try_consume(']') {
+                break;
+            }
+            values.push(self.parse_value()?);
+            self.skip_whitespace();
+            if self.try_consume(']') {
+                break;
+            }
+            self.expect(',')?;
+        }
+        Ok(JsonValue::Array(values))
+    }
+
+    fn parse_object(&mut self) -> Result<JsonValue, JsonError> {
+        self.expect('{')?;
+        let mut entries = BTreeMap::new();
+        loop {
+            self.skip_whitespace();
+            if self.try_consume('}') {
+                break;
+            }
+            let key = self.parse_string()?;
+            self.skip_whitespace();
+            self.expect(':')?;
+            let value = self.parse_value()?;
+            entries.insert(key, value);
+            self.skip_whitespace();
+            if self.try_consume('}') {
+                break;
+            }
+            self.expect(',')?;
+        }
+        Ok(JsonValue::Object(entries))
+    }
+
+    fn parse_number(&mut self) -> Result<i64, JsonError> {
+        let mut value = String::new();
+        if self.try_consume('-') {
+            value.push('-');
+        }
+
+        while let Some(ch @ '0'..='9') = self.peek() {
+            value.push(ch);
+            self.index += 1;
+        }
+
+        if value.is_empty() || value == "-" {
+            return Err(JsonError::new("invalid number"));
+        }
+
+        value
+            .parse::<i64>()
+            .map_err(|_| JsonError::new("number out of range"))
+    }
+
+    fn expect(&mut self, expected: char) -> Result<(), JsonError> {
+        match self.next() {
+            Some(actual) if actual == expected => Ok(()),
+            Some(actual) => Err(JsonError::new(format!(
+                "expected '{expected}', found '{actual}'"
+            ))),
+            None => Err(JsonError::new(format!(
+                "expected '{expected}', found end of input"
+            ))),
+        }
+    }
+
+    fn try_consume(&mut self, expected: char) -> bool {
+        if self.peek() == Some(expected) {
+            self.index += 1;
+            true
         } else {
-            break;
+            false
         }
     }
 
-    if num_str.is_empty() || num_str == "-" {
-        return Err(JsonError::new("invalid number"));
-    }
-
-    num_str
-        .parse::<i64>()
-        .map(JsonValue::Number)
-        .map_err(|_| JsonError::new("number out of range"))
-}
-
-fn parse_array(chars: &mut std::iter::Peekable<std::str::Chars>) -> Result<JsonValue, JsonError> {
-    if chars.next() != Some('[') {
-        return Err(JsonError::new("expected ["));
-    }
-
-    let mut values = Vec::new();
-
-    skip_whitespace(chars);
-    if chars.peek() == Some(&']') {
-        chars.next();
-        return Ok(JsonValue::Array(values));
-    }
-
-    loop {
-        skip_whitespace(chars);
-        values.push(parse_value(chars)?);
-        skip_whitespace(chars);
-
-        match chars.peek() {
-            Some(',') => {
-                chars.next();
-            }
-            Some(']') => {
-                chars.next();
-                return Ok(JsonValue::Array(values));
-            }
-            _ => return Err(JsonError::new("expected , or ]")),
+    fn skip_whitespace(&mut self) {
+        while matches!(self.peek(), Some(' ' | '\n' | '\r' | '\t')) {
+            self.index += 1;
         }
     }
-}
 
-fn parse_object(chars: &mut std::iter::Peekable<std::str::Chars>) -> Result<JsonValue, JsonError> {
-    if chars.next() != Some('{') {
-        return Err(JsonError::new("expected {"));
+    fn peek(&self) -> Option<char> {
+        self.chars.get(self.index).copied()
     }
 
-    let mut map = BTreeMap::new();
-
-    skip_whitespace(chars);
-    if chars.peek() == Some(&'}') {
-        chars.next();
-        return Ok(JsonValue::Object(map));
+    fn next(&mut self) -> Option<char> {
+        let ch = self.peek()?;
+        self.index += 1;
+        Some(ch)
     }
 
-    loop {
-        skip_whitespace(chars);
-
-        if chars.peek() != Some(&'"') {
-            return Err(JsonError::new("expected key string"));
-        }
-        let key = parse_string(chars)?;
-
-        skip_whitespace(chars);
-        if chars.next() != Some(':') {
-            return Err(JsonError::new("expected :"));
-        }
-
-        skip_whitespace(chars);
-        let value = parse_value(chars)?;
-        map.insert(key, value);
-
-        skip_whitespace(chars);
-        match chars.peek() {
-            Some(',') => {
-                chars.next();
-            }
-            Some('}') => {
-                chars.next();
-                return Ok(JsonValue::Object(map));
-            }
-            _ => return Err(JsonError::new("expected , or }")),
-        }
+    fn is_eof(&self) -> bool {
+        self.index >= self.chars.len()
     }
 }
 
-fn consume_literal(chars: &mut std::iter::Peekable<std::str::Chars>, literal: &str) -> bool {
-    let remaining: String = chars.clone().collect();
-    if remaining.starts_with(literal) {
-        for _ in literal.chars() {
-            chars.next();
-        }
-        true
-    } else {
-        false
-    }
-}
-
-fn skip_whitespace(chars: &mut std::iter::Peekable<std::str::Chars>) {
-    while let Some(&c) = chars.peek() {
-        if c.is_whitespace() {
-            chars.next();
-        } else {
-            break;
-        }
-    }
-}
-
-fn render_string(s: &str) -> String {
-    let mut result = String::from('"');
-    for c in s.chars() {
-        match c {
-            '"' => result.push_str("\\\""),
-            '\\' => result.push_str("\\\\"),
-            '\n' => result.push_str("\\n"),
-            '\r' => result.push_str("\\r"),
-            '\t' => result.push_str("\\t"),
-            '\u{08}' => result.push_str("\\b"),
-            '\u{0C}' => result.push_str("\\f"),
-            c if c.is_control() => {
-                let code = c as u32;
-                result.push_str(&format!("\\u{code:04x}"));
-            }
-            c => result.push(c),
-        }
-    }
-    result.push('"');
-    result
-}
-
 #[cfg(test)]
 mod tests {
-    use super::*;
+    use super::{render_string, JsonValue};
+    use std::collections::BTreeMap;
 
     #[test]
-    fn renders_primitive_values() {
-        assert_eq!(JsonValue::Null.render(), "null");
-        assert_eq!(JsonValue::Bool(true).render(), "true");
-        assert_eq!(JsonValue::Bool(false).render(), "false");
-        assert_eq!(JsonValue::Number(42).render(), "42");
-        assert_eq!(JsonValue::Number(-7).render(), "-7");
-        assert_eq!(JsonValue::String("hi".to_string()).render(), "\"hi\"");
-    }
-
-    #[test]
-    fn renders_arrays_and_objects_with_sorted_keys() {
-        assert_eq!(JsonValue::Array(Vec::new()).render(), "[]");
-        assert_eq!(
-            JsonValue::Array(vec![JsonValue::Number(1), JsonValue::Number(2)]).render(),
-            "[1,2]"
-        );
-        assert_eq!(JsonValue::Object(BTreeMap::new()).render(), "{}");
-
+    fn renders_and_parses_json_values() {
         let mut object = BTreeMap::new();
-        object.insert("b".to_string(), JsonValue::Bool(false));
-        object.insert("a".to_string(), JsonValue::Number(1));
-        // A BTreeMap iterates keys in sorted order, so object rendering is
-        // deterministic regardless of insertion order.
-        assert_eq!(JsonValue::Object(object).render(), "{\"a\":1,\"b\":false}");
-    }
-
-    #[test]
-    fn render_string_escapes_quotes_backslashes_and_other_controls() {
-        // Backslash and double-quote are backslash-escaped.
-        assert_eq!(render_string("\"\\"), "\"\\\"\\\\\"");
-        // Carriage return has a dedicated short escape.
-        assert_eq!(render_string("\r"), "\"\\r\"");
-        // Other control characters fall back to the \uXXXX form (U+0001 here).
-        assert_eq!(render_string("\u{1}"), "\"\\u0001\"");
-    }
-
-    #[test]
-    fn parses_primitive_values() {
-        assert_eq!(
-            JsonValue::parse("null").expect("null parses"),
-            JsonValue::Null
-        );
-        assert_eq!(
-            JsonValue::parse("true").expect("true parses"),
-            JsonValue::Bool(true)
-        );
-        assert_eq!(
-            JsonValue::parse("false").expect("false parses"),
-            JsonValue::Bool(false)
-        );
-        assert_eq!(
-            JsonValue::parse("\"hello\"").expect("string parses"),
-            JsonValue::String("hello".to_string())
-        );
-    }
-
-    #[test]
-    fn parses_signed_integers_and_ignores_surrounding_whitespace() {
-        assert_eq!(
-            JsonValue::parse("-42").expect("negative parses").as_i64(),
-            Some(-42)
-        );
-        assert_eq!(
-            JsonValue::parse("  123  ").expect("padded parses").as_i64(),
-            Some(123)
-        );
-    }
-
-    #[test]
-    fn parses_nested_arrays_and_objects() {
-        let value =
-            JsonValue::parse("{\"nums\": [1, 2], \"flag\": true}").expect("nested json parses");
-        let object = value.as_object().expect("top level is an object");
-
-        assert_eq!(object.len(), 2);
-
-        let nums = object
-            .get("nums")
-            .and_then(JsonValue::as_array)
-            .expect("nums is an array");
-        assert_eq!(nums.len(), 2);
-        assert_eq!(nums[0].as_i64(), Some(1));
-
-        assert_eq!(object.get("flag").and_then(JsonValue::as_bool), Some(true));
-    }
-
-    #[test]
-    fn round_trips_rendered_values_through_the_parser() {
-        let mut object = BTreeMap::new();
-        object.insert("name".to_string(), JsonValue::String("clawi".to_string()));
-        object.insert("count".to_string(), JsonValue::Number(-3));
+        object.insert("flag".to_string(), JsonValue::Bool(true));
         object.insert(
-            "tags".to_string(),
-            JsonValue::Array(vec![JsonValue::Bool(true), JsonValue::Null]),
+            "items".to_string(),
+            JsonValue::Array(vec![
+                JsonValue::Number(4),
+                JsonValue::String("ok".to_string()),
+            ]),
         );
-        let original = JsonValue::Object(object);
 
-        let reparsed = JsonValue::parse(&original.render()).expect("rendered json should re-parse");
+        let rendered = JsonValue::Object(object).render();
+        let parsed = JsonValue::parse(&rendered).expect("json should parse");
 
-        assert_eq!(reparsed, original);
+        assert_eq!(parsed.as_object().expect("object").len(), 2);
     }
 
     #[test]
@@ -519,7 +433,6 @@ mod tests {
         object.insert("a\nb".to_string(), JsonValue::String("c\td".to_string()));
         let original = JsonValue::Object(object);
         let reparsed = JsonValue::parse(&original.render()).expect("escaped key re-parses");
-
         assert_eq!(reparsed, original);
     }
 
@@ -558,37 +471,4 @@ mod tests {
             "i64::MIN - 1"
         );
     }
-
-    #[test]
-    fn parse_rejects_malformed_input() {
-        assert!(JsonValue::parse("").is_err(), "empty input");
-        assert!(JsonValue::parse("nul").is_err(), "truncated literal");
-        assert!(JsonValue::parse("true false").is_err(), "trailing content");
-        assert!(
-            JsonValue::parse("\"unterminated").is_err(),
-            "unterminated string"
-        );
-        assert!(JsonValue::parse("[1, 2").is_err(), "unterminated array");
-    }
-
-    #[test]
-    fn parse_rejects_integers_outside_the_i64_range() {
-        // Far beyond i64::MAX (~9.2e18): the parser must reject rather than
-        // silently truncate the value.
-        assert!(JsonValue::parse("9999999999999999999999999").is_err());
-    }
-
-    #[test]
-    fn accessors_return_none_for_mismatched_variants() {
-        assert_eq!(JsonValue::Null.as_bool(), None);
-        assert_eq!(JsonValue::Bool(true).as_i64(), None);
-        assert!(JsonValue::Number(1).as_str().is_none());
-        assert!(JsonValue::Number(1).as_array().is_none());
-        assert!(JsonValue::String("x".to_string()).as_object().is_none());
-    }
-
-    #[test]
-    fn json_error_displays_its_message() {
-        assert_eq!(JsonError::new("boom").to_string(), "boom");
-    }
 }

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

@@ -27,6 +27,7 @@ use std::net::TcpListener;
 use std::ops::{Deref, DerefMut};
 use std::path::{Path, PathBuf};
 use std::process::Command;
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::mpsc::{self, Receiver, RecvTimeoutError, Sender};
 use std::sync::{Arc, Mutex, OnceLock};
 use std::thread::{self, JoinHandle};
@@ -7702,6 +7703,7 @@ impl LiveCli {
             system_prompt.clone(),
             enable_tools,
             true,
+            TerminalTail::new(),
             allowed_tools.clone(),
             permission_mode,
             None,
@@ -7783,6 +7785,7 @@ impl LiveCli {
     fn prepare_turn_runtime(
         &self,
         emit_output: bool,
+        terminal_tail: TerminalTail,
     ) -> Result<(BuiltRuntime, HookAbortMonitor), Box<dyn std::error::Error>> {
         let hook_abort_signal = runtime::HookAbortSignal::new();
         let runtime = build_runtime(
@@ -7792,6 +7795,7 @@ impl LiveCli {
             self.system_prompt.clone(),
             true,
             emit_output,
+            terminal_tail,
             self.allowed_tools.clone(),
             self.permission_mode,
             None,
@@ -7809,27 +7813,39 @@ impl LiveCli {
     }
 
     fn run_turn(&mut self, input: &str) -> Result<(), Box<dyn std::error::Error>> {
-        let (mut runtime, hook_abort_monitor) = self.prepare_turn_runtime(true)?;
+        let terminal_tail = TerminalTail::new();
+        let (mut runtime, hook_abort_monitor) =
+            self.prepare_turn_runtime(true, terminal_tail.clone())?;
         let mut spinner = Spinner::new();
         let mut stdout = io::stdout();
-        spinner.tick(
-            "🦀 Thinking...",
-            TerminalRenderer::new().color_theme(),
-            &mut stdout,
-        )?;
+        // The animated frame is cursor control: it saves the cursor, rewrites the
+        // current line, and restores the cursor. None of that describes anything
+        // when stdout is a pipe — the escapes survive as literal bytes and the
+        // banner ends up glued to whatever the emitter writes next. Only animate
+        // on a terminal; the one-shot completion line below is plain text and is
+        // emitted either way.
+        if io::stdout().is_terminal() {
+            spinner.tick(
+                "🦀 Thinking...",
+                TerminalRenderer::new().color_theme(),
+                &mut stdout,
+            )?;
+        }
         let mut permission_prompter = CliPermissionPrompter::new(self.permission_mode);
         let result = runtime.run_turn(input, Some(&mut permission_prompter));
         hook_abort_monitor.stop();
         match result {
             Ok(summary) => {
                 self.replace_runtime(runtime)?;
-                // The assistant response was already streamed to the terminal live
-                // during the turn (emit_output = true), so reprinting the full text
-                // here would duplicate the entire message. When text was streamed,
-                // emit a newline first so `spinner.finish`'s line-clear lands on a
-                // fresh line instead of erasing the last streamed line.
-                let final_text = final_assistant_text(&summary);
-                if !final_text.is_empty() {
+                // The emitter owns the terminal during a turn: `emit_output = true`
+                // streams text deltas and echoes tool results live, so the response
+                // must not be printed again here — that was the duplicate output
+                // this PR's predecessor fixed.
+                //
+                // What the emitter may have left behind is a partial line, so ask it
+                // rather than guessing from `final_assistant_text(&summary)`: that
+                // guess is empty for tool-only turns, which still render.
+                if !terminal_tail.at_line_start() {
                     println!();
                 }
                 spinner.finish(
@@ -7849,6 +7865,13 @@ impl LiveCli {
             }
             Err(error) => {
                 runtime.shutdown_plugins()?;
+                // Same ownership rule as the success arm: `fail` clears the current
+                // line, so it may only do so when the emitter stopped on a line
+                // boundary. A turn that streamed text and then failed would
+                // otherwise lose its last partial line to the clear.
+                if !terminal_tail.at_line_start() {
+                    println!();
+                }
                 spinner.fail(
                     "❌ Request failed",
                     TerminalRenderer::new().color_theme(),
@@ -7961,14 +7984,14 @@ impl LiveCli {
 
                         // Build a new runtime with the compacted session and retry
                         let (mut new_runtime, hook_abort_monitor) =
-                            self.prepare_turn_runtime(true)?;
+                            self.prepare_turn_runtime(true, terminal_tail.clone())?;
                         drop(hook_abort_monitor);
 
                         let mut rp = CliPermissionPrompter::new(self.permission_mode);
                         match new_runtime.run_turn(input, Some(&mut rp)) {
                             Ok(summary) => {
                                 self.replace_runtime(new_runtime)?;
-                                if !final_assistant_text(&summary).is_empty() {
+                                if !terminal_tail.at_line_start() {
                                     println!();
                                 }
                                 spinner.finish(
@@ -8053,7 +8076,8 @@ impl LiveCli {
     }
 
     fn run_prompt_compact(&mut self, input: &str) -> Result<(), Box<dyn std::error::Error>> {
-        let (mut runtime, hook_abort_monitor) = self.prepare_turn_runtime(false)?;
+        let (mut runtime, hook_abort_monitor) =
+            self.prepare_turn_runtime(false, TerminalTail::new())?;
         let mut permission_prompter = CliPermissionPrompter::new(self.permission_mode);
         let result = runtime.run_turn(input, Some(&mut permission_prompter));
         hook_abort_monitor.stop();
@@ -8066,7 +8090,8 @@ impl LiveCli {
     }
 
     fn run_prompt_compact_json(&mut self, input: &str) -> Result<(), Box<dyn std::error::Error>> {
-        let (mut runtime, hook_abort_monitor) = self.prepare_turn_runtime(false)?;
+        let (mut runtime, hook_abort_monitor) =
+            self.prepare_turn_runtime(false, TerminalTail::new())?;
         let mut permission_prompter = CliPermissionPrompter::new(self.permission_mode);
         let result = runtime.run_turn(input, Some(&mut permission_prompter));
         hook_abort_monitor.stop();
@@ -8091,7 +8116,8 @@ impl LiveCli {
     }
 
     fn run_prompt_json(&mut self, input: &str) -> Result<(), Box<dyn std::error::Error>> {
-        let (mut runtime, hook_abort_monitor) = self.prepare_turn_runtime(false)?;
+        let (mut runtime, hook_abort_monitor) =
+            self.prepare_turn_runtime(false, TerminalTail::new())?;
         let mut permission_prompter = CliPermissionPrompter::new(self.permission_mode);
         let result = runtime.run_turn(input, Some(&mut permission_prompter));
         hook_abort_monitor.stop();
@@ -8447,6 +8473,7 @@ impl LiveCli {
             self.system_prompt.clone(),
             true,
             true,
+            TerminalTail::new(),
             self.allowed_tools.clone(),
             self.permission_mode,
             None,
@@ -8493,6 +8520,7 @@ impl LiveCli {
             self.system_prompt.clone(),
             true,
             true,
+            TerminalTail::new(),
             self.allowed_tools.clone(),
             self.permission_mode,
             None,
@@ -8523,6 +8551,7 @@ impl LiveCli {
             self.system_prompt.clone(),
             true,
             true,
+            TerminalTail::new(),
             self.allowed_tools.clone(),
             self.permission_mode,
             None,
@@ -8565,6 +8594,7 @@ impl LiveCli {
             self.system_prompt.clone(),
             true,
             true,
+            TerminalTail::new(),
             self.allowed_tools.clone(),
             self.permission_mode,
             None,
@@ -8918,6 +8948,7 @@ impl LiveCli {
                     self.system_prompt.clone(),
                     true,
                     true,
+                    TerminalTail::new(),
                     self.allowed_tools.clone(),
                     self.permission_mode,
                     None,
@@ -8953,6 +8984,7 @@ impl LiveCli {
                     self.system_prompt.clone(),
                     true,
                     true,
+                    TerminalTail::new(),
                     self.allowed_tools.clone(),
                     self.permission_mode,
                     None,
@@ -9047,6 +9079,7 @@ impl LiveCli {
             self.system_prompt.clone(),
             true,
             true,
+            TerminalTail::new(),
             self.allowed_tools.clone(),
             self.permission_mode,
             None,
@@ -9067,6 +9100,7 @@ impl LiveCli {
             self.system_prompt.clone(),
             true,
             true,
+            TerminalTail::new(),
             self.allowed_tools.clone(),
             self.permission_mode,
             None,
@@ -9091,6 +9125,7 @@ impl LiveCli {
             self.system_prompt.clone(),
             enable_tools,
             false,
+            TerminalTail::new(),
             self.allowed_tools.clone(),
             self.permission_mode,
             progress,
@@ -12500,6 +12535,7 @@ fn build_runtime(
     system_prompt: Vec<String>,
     enable_tools: bool,
     emit_output: bool,
+    terminal_tail: TerminalTail,
     allowed_tools: Option<AllowedToolSet>,
     permission_mode: PermissionMode,
     progress_reporter: Option<InternalPromptProgressReporter>,
@@ -12512,6 +12548,7 @@ fn build_runtime(
         system_prompt,
         enable_tools,
         emit_output,
+        terminal_tail,
         allowed_tools,
         permission_mode,
         progress_reporter,
@@ -12528,6 +12565,7 @@ fn build_runtime_with_plugin_state(
     system_prompt: Vec<String>,
     enable_tools: bool,
     emit_output: bool,
+    terminal_tail: TerminalTail,
     allowed_tools: Option<AllowedToolSet>,
     permission_mode: PermissionMode,
     progress_reporter: Option<InternalPromptProgressReporter>,
@@ -12553,6 +12591,7 @@ fn build_runtime_with_plugin_state(
             model,
             enable_tools,
             emit_output,
+            terminal_tail.clone(),
             allowed_tools.clone(),
             tool_registry.clone(),
             progress_reporter,
@@ -12560,6 +12599,7 @@ fn build_runtime_with_plugin_state(
         CliToolExecutor::new(
             allowed_tools.clone(),
             emit_output,
+            terminal_tail,
             tool_registry.clone(),
             mcp_state.clone(),
         ),
@@ -12655,6 +12695,76 @@ impl runtime::PermissionPrompter for CliPermissionPrompter {
     }
 }
 
+/// Tracks whether the shared terminal stream currently sits at the start of a
+/// fresh line.
+///
+/// A turn's streamed assistant text has no trailing newline, and
+/// `Spinner::finish` moves to column 0 and clears the current line — so without
+/// a guard it erases the last thing the emitter rendered. Both writers that
+/// render live during a turn (the assistant/reasoning deltas in
+/// `AnthropicRuntimeClient::consume_stream` and the tool-result blocks in
+/// `CliToolExecutor::execute`) push their bytes
+/// through a `TailTrackingWriter` sharing one of these, which lets the caller
+/// that ends the turn ask the emitter what it actually left on the terminal.
+///
+/// The previous approach inferred this from `final_assistant_text(&summary)`,
+/// which agrees today only because every *other* writer terminates its output
+/// with a newline — tool results go through `stream_markdown` (which appends
+/// one), thinking summaries are written with a trailing newline, and tool-call
+/// headers use `writeln!`. That is a property of the current renderers rather
+/// than of the streaming protocol, and the text path already violates it, so
+/// recording the fact is cheaper than depending on it. The heuristic also left
+/// the failure arm unguarded: a turn that streamed text and then errored still
+/// had that line cleared.
+#[derive(Clone, Default)]
+struct TerminalTail {
+    at_line_start: Arc<AtomicBool>,
+}
+
+impl TerminalTail {
+    fn new() -> Self {
+        Self {
+            at_line_start: Arc::new(AtomicBool::new(true)),
+        }
+    }
+
+    /// True when nothing has been written since the last newline, so clearing
+    /// the current terminal line cannot destroy rendered output.
+    fn at_line_start(&self) -> bool {
+        self.at_line_start.load(Ordering::Relaxed)
+    }
+
+    fn record(&self, written: &[u8]) {
+        if let Some(last) = written.last() {
+            self.at_line_start.store(*last == b'\n', Ordering::Relaxed);
+        }
+    }
+}
+
+/// Forwards writes to `inner` while reporting the tail byte to a `TerminalTail`.
+struct TailTrackingWriter<'a, W: Write> {
+    inner: &'a mut W,
+    tail: TerminalTail,
+}
+
+impl<'a, W: Write> TailTrackingWriter<'a, W> {
+    fn new(inner: &'a mut W, tail: TerminalTail) -> Self {
+        Self { inner, tail }
+    }
+}
+
+impl<W: Write> Write for TailTrackingWriter<'_, W> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        let written = self.inner.write(buf)?;
+        self.tail.record(&buf[..written]);
+        Ok(written)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        self.inner.flush()
+    }
+}
+
 // NOTE: Despite the historical name `AnthropicRuntimeClient`, this struct
 // now holds an `ApiProviderClient` which dispatches to Anthropic, xAI,
 // OpenAI, or DashScope at construction time based on
@@ -12668,6 +12778,7 @@ struct AnthropicRuntimeClient {
     model: String,
     enable_tools: bool,
     emit_output: bool,
+    terminal_tail: TerminalTail,
     allowed_tools: Option<AllowedToolSet>,
     tool_registry: GlobalToolRegistry,
     progress_reporter: Option<InternalPromptProgressReporter>,
@@ -12680,6 +12791,7 @@ impl AnthropicRuntimeClient {
         model: String,
         enable_tools: bool,
         emit_output: bool,
+        terminal_tail: TerminalTail,
         allowed_tools: Option<AllowedToolSet>,
         tool_registry: GlobalToolRegistry,
         progress_reporter: Option<InternalPromptProgressReporter>,
@@ -12733,6 +12845,7 @@ impl AnthropicRuntimeClient {
             model,
             enable_tools,
             emit_output,
+            terminal_tail,
             allowed_tools,
             tool_registry,
             progress_reporter,
@@ -12832,8 +12945,9 @@ impl AnthropicRuntimeClient {
             })?;
         let mut stdout = io::stdout();
         let mut sink = io::sink();
+        let mut tracked = TailTrackingWriter::new(&mut stdout, self.terminal_tail.clone());
         let out: &mut dyn Write = if self.emit_output {
-            &mut stdout
+            &mut tracked
         } else {
             &mut sink
         };
@@ -13997,6 +14111,7 @@ fn prompt_cache_record_to_runtime_event(
 struct CliToolExecutor {
     renderer: TerminalRenderer,
     emit_output: bool,
+    terminal_tail: TerminalTail,
     allowed_tools: Option<AllowedToolSet>,
     tool_registry: GlobalToolRegistry,
     mcp_state: Option<Arc<Mutex<RuntimeMcpState>>>,
@@ -14006,12 +14121,14 @@ impl CliToolExecutor {
     fn new(
         allowed_tools: Option<AllowedToolSet>,
         emit_output: bool,
+        terminal_tail: TerminalTail,
         tool_registry: GlobalToolRegistry,
         mcp_state: Option<Arc<Mutex<RuntimeMcpState>>>,
     ) -> Self {
         Self {
             renderer: TerminalRenderer::new(),
             emit_output,
+            terminal_tail,
             allowed_tools,
             tool_registry,
             mcp_state,
@@ -14105,8 +14222,11 @@ impl ToolExecutor for CliToolExecutor {
             Ok(output) => {
                 if self.emit_output {
                     let markdown = format_tool_result(tool_name, &output, false);
+                    let mut stdout = io::stdout();
+                    let mut tracked =
+                        TailTrackingWriter::new(&mut stdout, self.terminal_tail.clone());
                     self.renderer
-                        .stream_markdown(&markdown, &mut io::stdout())
+                        .stream_markdown(&markdown, &mut tracked)
                         .map_err(|error| ToolError::new(error.to_string()))?;
                 }
                 Ok(output)
@@ -14114,8 +14234,11 @@ impl ToolExecutor for CliToolExecutor {
             Err(error) => {
                 if self.emit_output {
                     let markdown = format_tool_result(tool_name, &error.to_string(), true);
+                    let mut stdout = io::stdout();
+                    let mut tracked =
+                        TailTrackingWriter::new(&mut stdout, self.terminal_tail.clone());
                     self.renderer
-                        .stream_markdown(&markdown, &mut io::stdout())
+                        .stream_markdown(&markdown, &mut tracked)
                         .map_err(|stream_error| ToolError::new(stream_error.to_string()))?;
                 }
                 Err(error)
@@ -14430,8 +14553,8 @@ mod tests {
         CliOutputFormat, CliToolExecutor, GitOperation, GitWorkspaceSummary,
         InternalPromptProgressEvent, InternalPromptProgressState, LiveCli, LocalHelpTopic,
         PermissionModeProvenance, PromptHistoryEntry, SessionLifecycleKind,
-        SessionLifecycleSummary, SlashCommand, StatusUsage, TmuxPaneSnapshot, DEFAULT_MODEL,
-        LATEST_SESSION_REFERENCE, STUB_COMMANDS,
+        SessionLifecycleSummary, SlashCommand, StatusUsage, TerminalTail, TmuxPaneSnapshot,
+        DEFAULT_MODEL, LATEST_SESSION_REFERENCE, STUB_COMMANDS,
     };
     use api::{ApiError, MessageResponse, OutputContentBlock, Usage};
     use plugins::{
@@ -19354,6 +19477,7 @@ UU conflicted.rs",
         let mut executor = CliToolExecutor::new(
             None,
             false,
+            TerminalTail::new(),
             state.tool_registry.clone(),
             state.mcp_state.clone(),
         );
@@ -19452,6 +19576,7 @@ UU conflicted.rs",
         let mut executor = CliToolExecutor::new(
             None,
             false,
+            TerminalTail::new(),
             state.tool_registry.clone(),
             state.mcp_state.clone(),
         );
@@ -19512,6 +19637,7 @@ UU conflicted.rs",
             vec!["test system prompt".to_string()],
             true,
             false,
+            TerminalTail::new(),
             None,
             PermissionMode::DangerFullAccess,
             None,

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

@@ -7,7 +7,9 @@ use std::process::{Command, Output, Stdio};
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
 
-use mock_anthropic_service::{MockAnthropicService, SCENARIO_PREFIX};
+use mock_anthropic_service::{
+    MockAnthropicService, CONTEXT_WINDOW_RETRY_TEXT, SCENARIO_PREFIX, STREAM_THEN_ERROR_TEXT,
+};
 use serde_json::Value;
 
 static TEMP_COUNTER: AtomicU64 = AtomicU64::new(0);
@@ -189,6 +191,199 @@ fn text_prompt_mode_streams_assistant_text_once_before_spinner_completion() {
     fs::remove_dir_all(&workspace).expect("workspace cleanup should succeed");
 }
 
+#[test]
+fn text_prompt_mode_emits_the_response_body_exactly_once() {
+    // given a workspace pointed at the mock Anthropic service running the
+    // streaming_text scenario, which emits a single assistant text block
+    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("text-prompt-once");
+    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");
+
+    // when we invoke claw in normal text prompt mode
+    let prompt = format!("{SCENARIO_PREFIX}streaming_text");
+    let output = run_claw(
+        &workspace,
+        &config_home,
+        &home,
+        &base_url,
+        &[
+            "--model",
+            "sonnet",
+            "--permission-mode",
+            "read-only",
+            &prompt,
+        ],
+    );
+
+    // then the response body reaches stdout exactly once: the emitter owns the
+    // terminal while the turn runs, so the caller must not print the assistant
+    // text a second time
+    assert!(
+        output.status.success(),
+        "text prompt run should succeed\nstdout:\n{}\n\nstderr:\n{}",
+        String::from_utf8_lossy(&output.stdout),
+        String::from_utf8_lossy(&output.stderr),
+    );
+    let stdout = String::from_utf8(output.stdout).expect("stdout should be utf8");
+    let plain_stdout = strip_ansi_codes(&stdout);
+    assert_eq!(
+        plain_stdout
+            .matches("Mock streaming says hello from the parity harness.")
+            .count(),
+        1,
+        "text prompt stdout should carry the response body exactly once ({stdout:?})"
+    );
+
+    fs::remove_dir_all(&workspace).expect("workspace cleanup should succeed");
+}
+
+#[test]
+fn text_prompt_mode_emits_retried_body_once_after_auto_compact() {
+    // given a mock service whose first answer to this scenario is a context
+    // window rejection and whose answer to the retry is a streamed response
+    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("text-prompt-auto-compact-retry");
+    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");
+
+    // when claw is rejected for context window overflow and recovers by
+    // compacting the session and retrying the same prompt
+    let prompt = format!("{SCENARIO_PREFIX}context_window_retry");
+    let output = run_claw(
+        &workspace,
+        &config_home,
+        &home,
+        &base_url,
+        &[
+            "--model",
+            "sonnet",
+            "--permission-mode",
+            "read-only",
+            &prompt,
+        ],
+    );
+
+    // then the retry succeeds and its response body is on stdout exactly once.
+    // The recovery path builds a fresh runtime with its own terminal tail, so
+    // this is where a tail that only tracked the first attempt would leave the
+    // streamed line unterminated and let `spinner.finish` clear it.
+    assert!(
+        output.status.success(),
+        "auto-compact retry should succeed\nstdout:\n{}\n\nstderr:\n{}",
+        String::from_utf8_lossy(&output.stdout),
+        String::from_utf8_lossy(&output.stderr),
+    );
+    let stdout = String::from_utf8(output.stdout).expect("stdout should be utf8");
+    let plain_stdout = strip_ansi_codes(&stdout);
+    assert_eq!(
+        plain_stdout.matches(CONTEXT_WINDOW_RETRY_TEXT).count(),
+        1,
+        "auto-compact retry stdout should carry the response body exactly once ({stdout:?})"
+    );
+    assert!(
+        plain_stdout
+            .lines()
+            .any(|line| line == CONTEXT_WINDOW_RETRY_TEXT),
+        "the retried response body should land on its own line ({stdout:?})"
+    );
+    assert!(
+        plain_stdout.contains("✨ Done (after auto-compact)"),
+        "the retry should report the auto-compact completion ({stdout:?})"
+    );
+
+    // and the scenario really was requested twice, so the retry path ran
+    let captured = runtime.block_on(server.captured_requests());
+    let messages: Vec<_> = captured
+        .iter()
+        .filter(|request| request.path == "/v1/messages")
+        .collect();
+    assert!(
+        messages.len() >= 2,
+        "the scenario should be requested twice so the retry is exercised ({captured:?})"
+    );
+
+    fs::remove_dir_all(&workspace).expect("workspace cleanup should succeed");
+}
+
+#[test]
+fn text_prompt_mode_keeps_streamed_text_when_the_turn_fails() {
+    // given a mock service that streams part of an answer and then fails the
+    // response, so the turn ends with text already rendered on the terminal
+    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("text-prompt-stream-then-error");
+    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");
+
+    // when the turn fails after the emitter already streamed a partial line
+    let prompt = format!("{SCENARIO_PREFIX}stream_then_error");
+    let output = run_claw(
+        &workspace,
+        &config_home,
+        &home,
+        &base_url,
+        &[
+            "--model",
+            "sonnet",
+            "--permission-mode",
+            "read-only",
+            &prompt,
+        ],
+    );
+
+    // then the failed turn is reported...
+    assert!(
+        !output.status.success(),
+        "a mid-stream failure should fail the run\nstdout:\n{}\n\nstderr:\n{}",
+        String::from_utf8_lossy(&output.stdout),
+        String::from_utf8_lossy(&output.stderr),
+    );
+    let stdout = String::from_utf8(output.stdout).expect("stdout should be utf8");
+    let plain_stdout = strip_ansi_codes(&stdout);
+
+    // ...and the text the emitter already streamed survives the failure banner.
+    // `spinner.fail` moves to column 0 and clears the current line, so a caller
+    // that does not know a partial line is pending erases that text instead of
+    // printing the banner underneath it. This is the failure arm of the same
+    // ownership rule the success arm follows.
+    assert!(
+        plain_stdout
+            .lines()
+            .any(|line| line == STREAM_THEN_ERROR_TEXT),
+        "the streamed text should keep its own line despite the failure ({stdout:?})"
+    );
+    assert!(
+        plain_stdout.contains("Request failed"),
+        "the failure banner should still be reported ({stdout:?})"
+    );
+
+    fs::remove_dir_all(&workspace).expect("workspace cleanup should succeed");
+}
+
 #[test]
 fn compact_flag_with_json_output_emits_structured_json() {
     let runtime = tokio::runtime::Runtime::new().expect("tokio runtime should build");