host: preserve journals, full traps and embedded agent output

Write new journal entries under logs/core and merge read-only legacy
history without moving SQLite/WAL files. Atomically spool failed batches,
retaining unspoolable entries for event-driven retries. Journal full trap
diagnostics before UTF-8-safe status display. Port session overflow archives
and followable line/byte excerpts to the still-shipped embedded agent.
Document retention/recovery and cover the contracts with regressions.
Include one rustfmt-only normalization in the existing SDK WASI test.

Card: SAU-143

PROTOCOL.md

@@ -34,7 +34,8 @@ Rust plugins use the SDK `sausage-plugin`. Its source is at
     source/                   the source. `cargo.build` builds it from here.
       imports/<plugin>.json   descriptions of the imported plugins
   state/<plugin>/             persistent state of a plugin, by convention
-  state/core/journal.sqlite   the journal
+  logs/core/journal.sqlite    the journal
+  state/core/                console history (state, not logs)
   config/                     global configuration
     boot.yaml                 the services
     agent.yaml                the API, base URL, model, and key of the agent
@@ -279,9 +280,23 @@ for example the control interface of a web server.
 
 ## 7. The journal
 
-- An SQLite file at `/state/core/journal.sqlite`. Only the core writes it.
+- New entries go to `/logs/core/journal.sqlite`. Only the core writes it.
+  An existing `/state/core/journal.sqlite` stays in place and is opened
+  read-only; queries merge both databases by entry ID before applying the
+  limit. The host never renames a live SQLite/WAL trio. Console history stays
+  in `/state/core`. No journal or log files are automatically pruned.
+- If a journal transaction fails, the complete batch (including original
+  IDs and timestamps) is saved in an exclusive, synced JSON file under
+  `/logs/core/failed-batches/`; the host reports its path on stderr. These
+  files are recovery artifacts, not query results: recovery/import is
+  deliberate, using IDs to avoid duplicates, and never deletes the source.
+  If spooling also fails, entries stay in memory and retry on the next
+  command (no polling); at writer shutdown their full text is reported to
+  host stderr. Storage failure plus host loss can still lose unsaved data.
 - Each entry has a UUIDv7 (it sorts by time), the process ID, the plugin, the
   stream (`stderr` or `core`), and the line.
+- Traps retain their full diagnostic text in the journal; short exit-status
+  displays are UTF-8-boundary-safe.
 - The core writes its own events too: start (with method and params), exit
   status, stop, kill, upgrades, and the warning about discarded stdout.
 - `core.log {plugin?, pid?, since?, until?, grep?, limit?}` queries the
@@ -473,3 +488,19 @@ Tests:
   files through `env!("CARGO_MANIFEST_DIR")`.
 - The test runner answers `core.lock`, `core.unlock`, `core.notify`, and
   `core.log`. A call to a plugin fails: a test has no other plugins.
+
+## 12. Embedded agent tool output
+
+The agent shipped by `sausage init` uses a context-size guard of 50 KiB or
+2000 lines, not a data-retention limit. Oversized tool results, including
+errors, are saved in full under `/logs/agent/<date>/default/` before history
+and provider delivery receive an excerpt. Overflow JSON string values are
+rendered as physical text lines so the reference's one-based inclusive line
+ranges can be followed with `read_file {path, line_offset, line_limit}`
+(zero-based offset; default 200 lines). Huge single lines give exact byte
+ranges and continuation offsets. Command/log/build/test results show the
+tail; other tools show the head. Reading an existing `/logs` file excerpts
+that same file without making another archive. Archives are exclusive and
+never automatically deleted. If archival fails, the agent reports the error
+to stderr and keeps the complete result instead of discarding it. Existing
+history formats and paths are unchanged.

agent/src/main.rs

@@ -94,19 +94,38 @@ impl Agent {
                 return Ok(final_text);
             }
             for (id, name, arguments) in calls {
-                let output = match serde_json::from_str(&arguments) {
+                let args = serde_json::from_str::<serde_json::Value>(&arguments);
-                    Ok(args) => tools::run(&name, &args)
+                let output = match &args {
+                    Ok(args) => tools::run(&name, args)
                         .await
                         .unwrap_or_else(|error| json!({"error":error})),
                     Err(error) => json!({"error":format!("arguments are not valid JSON: {error}")}),
                 };
-                append(
+                let output = if name == "read_file"
-                    &mut entries,
+                    && args
-                    Entry::ToolResult {
+                        .as_ref()
-                        id,
+                        .ok()
-                        output: tools::limit_output(output.to_string()),
+                        .and_then(|a| a["path"].as_str())
-                    },
+                        .is_some_and(|p| p.starts_with("/logs/"))
-                )?;
+                {
+                    output["content"]
+                        .as_str()
+                        .map(str::to_owned)
+                        .unwrap_or_else(|| output.to_string())
+                } else {
+                    output.to_string()
+                };
+                let tail = args
+                    .as_ref()
+                    .ok()
+                    .and_then(|a| a["method"].as_str())
+                    .is_some_and(|m| {
+                        [".exec", ".log", ".build", ".test"]
+                            .iter()
+                            .any(|suffix| m.ends_with(suffix))
+                    });
+                let output = tools::overflow::guard(output, "default", &id, tail);
+                append(&mut entries, Entry::ToolResult { id, output })?;
             }
         }
     }

agent/src/overflow.rs

@@ -0,0 +1,258 @@
+//! Context-size guard; full output is in the referenced file. Never a data limit.
+use std::io::{self, Write};
+use std::sync::atomic::{AtomicU64, Ordering};
+
+// One policy point: Pi's 50 KiB / 2000 lines, including room for the reference.
+const CONTEXT_LIMIT: (usize, usize) = (50 * 1024, 2000);
+static NEXT: AtomicU64 = AtomicU64::new(0);
+
+fn component(s: &str) -> String {
+    s.bytes()
+        .take(80)
+        .map(|b| {
+            if b.is_ascii_alphanumeric() || b == b'-' || b == b'_' {
+                b as char
+            } else {
+                '_'
+            }
+        })
+        .collect()
+}
+
+pub fn exceeds_limit(output: &str) -> bool {
+    output.len() > CONTEXT_LIMIT.0 || output.lines().count() > CONTEXT_LIMIT.1
+}
+
+/// Save before excerpting. On storage failure return all data, not a false reference.
+pub fn guard(output: String, session: &str, id: &str, tail: bool) -> String {
+    if !exceeds_limit(&output) {
+        return output;
+    }
+    // Decode only results that crossed the context guard. Archive physical
+    // string lines, not JSON escapes, even if decoding makes the text smaller.
+    let output = serde_json::from_str::<serde_json::Value>(&output)
+        .map(|value| super::render(&value))
+        .unwrap_or(output);
+    let pid = std::env::var("SAUSAGE_PID").unwrap_or_else(|_| "test".into());
+    let dir = format!("/logs/agent/{}/{}", date(), component(session));
+    let saved = (|| -> io::Result<String> {
+        std::fs::create_dir_all(&dir)?;
+        // create_new prevents overwriting even if an ID is reused or a process restarts.
+        loop {
+            let path = format!(
+                "{dir}/{}-{}-{}.txt",
+                component(id),
+                component(&pid),
+                NEXT.fetch_add(1, Ordering::Relaxed)
+            );
+            match std::fs::OpenOptions::new()
+                .write(true)
+                .create_new(true)
+                .open(&path)
+            {
+                Ok(mut f) => {
+                    f.write_all(output.as_bytes())?;
+                    return Ok(path);
+                }
+                Err(e) if e.kind() == io::ErrorKind::AlreadyExists => continue,
+                Err(e) => return Err(e),
+            }
+        }
+    })();
+    match saved {
+        Ok(path) => excerpt(&output, &path, tail, 0, output.len()),
+        Err(e) => {
+            eprintln!("overflow archive failed: {e}; retaining complete tool result");
+            output
+        }
+    }
+}
+
+fn date() -> String {
+    let days = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs()
+        / 86400;
+    let z = days as i64 + 719468;
+    let era = z / 146097;
+    let doe = z - era * 146097;
+    let yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
+    let y = yoe + era * 400;
+    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
+    let mp = (5 * doy + 2) / 153;
+    let d = doy - (153 * mp + 2) / 5 + 1;
+    let m = mp + if mp < 10 { 3 } else { -9 };
+    format!("{:04}-{m:02}-{d:02}", y + i64::from(m <= 2))
+}
+
+/// Excerpt an existing archive in place. Byte/line ranges refer to that file,
+/// including when a caller requests an oversized line or the entire archive.
+pub fn existing(bytes: &[u8], path: &str, args: &serde_json::Value) -> String {
+    let text = String::from_utf8_lossy(bytes);
+    let (mut from, mut to) = if let Some(line) = args["line_offset"].as_u64() {
+        let from = text
+            .split_inclusive('\n')
+            .take(line as usize)
+            .map(str::len)
+            .sum::<usize>();
+        let len = text[from..]
+            .split_inclusive('\n')
+            .take(args["line_limit"].as_u64().unwrap_or(200) as usize)
+            .map(str::len)
+            .sum::<usize>();
+        (from, from + len)
+    } else {
+        let from = (args["offset"].as_u64().unwrap_or(0) as usize).min(text.len());
+        (
+            from,
+            args["max_bytes"].as_u64().map_or(text.len(), |n| {
+                from.saturating_add(n as usize).min(text.len())
+            }),
+        )
+    };
+    while !text.is_char_boundary(from) {
+        from += 1;
+    }
+    while to > from && !text.is_char_boundary(to) {
+        to -= 1;
+    }
+    to = to.max(from);
+    excerpt(&text, path, false, from, to)
+}
+
+fn excerpt(output: &str, path: &str, tail: bool, from: usize, to: usize) -> String {
+    let selected = &output[from..to];
+    let lines: Vec<&str> = selected.split_inclusive('\n').collect();
+    let budget = CONTEXT_LIMIT.0.saturating_sub(1024);
+    let mut start = 0;
+    let mut end = lines.len();
+    let mut bytes = 0;
+    if tail {
+        start = end;
+        while start > 0
+            && end - start < CONTEXT_LIMIT.1.saturating_sub(2)
+            && bytes + lines[start - 1].len() <= budget
+        {
+            start -= 1;
+            bytes += lines[start].len();
+        }
+    } else {
+        end = 0;
+        while end < lines.len()
+            && end < CONTEXT_LIMIT.1.saturating_sub(2)
+            && bytes + lines[end].len() <= budget
+        {
+            bytes += lines[end].len();
+            end += 1;
+        }
+    }
+    let mut shown = lines[start..end].concat();
+    // A single huge line: preserve valid UTF-8 and explicitly label a partial line.
+    let partial = start == end;
+    if partial && !lines.is_empty() {
+        if tail {
+            start = lines.len() - 1;
+            let line = lines[start];
+            let mut from = line.len().saturating_sub(budget);
+            while !line.is_char_boundary(from) {
+                from += 1;
+            }
+            shown.push_str(&line[from..]);
+        } else {
+            let mut to = budget.min(lines[0].len());
+            while !lines[0].is_char_boundary(to) {
+                to -= 1;
+            }
+            shown.push_str(&lines[0][..to]);
+        }
+    }
+    let mut byte_start = from + lines[..start].iter().map(|s| s.len()).sum::<usize>();
+    if partial && tail {
+        byte_start = to - shown.len();
+    }
+    let byte_end = byte_start + shown.len();
+    let line_start = output[..byte_start].bytes().filter(|b| *b == b'\n').count();
+    let line_end = line_start + shown.split_inclusive('\n').count();
+    let total_lines = output.split_inclusive('\n').count();
+    let partial = partial
+        || (from > 0 && !output[..from].ends_with('\n'))
+        || (to < output.len() && !output[..to].ends_with('\n'));
+    let read = if partial {
+        format!(
+            "Shown byte range [{byte_start},{byte_end}); continue with read_file path={path}, offset={byte_end}, max_bytes={budget} (or choose an earlier byte offset)"
+        )
+    } else {
+        format!(
+            "Read with read_file path={path}, line_offset={line_start}, line_limit={}; next line_offset={line_end}",
+            line_end - line_start
+        )
+    };
+    format!(
+        "{shown}\n[Showing lines {}-{} of {}{}; total {} bytes. Full output: {path}. {read}]",
+        line_start + 1,
+        line_end,
+        total_lines,
+        if partial { " (partial line)" } else { "" },
+        output.len()
+    )
+}
+
+/// Zero-based line offsets; byte-based reads remain unchanged when absent.
+pub fn read_lines(bytes: &[u8], offset: usize, limit: usize) -> String {
+    String::from_utf8_lossy(bytes)
+        .split_inclusive('\n')
+        .skip(offset)
+        .take(limit)
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn full_archive_and_context_guard() {
+        let original = "😀 line\n".repeat(5400);
+        for tail in [false, true] {
+            let shown = guard(original.clone(), "guard-test", "call", tail);
+            assert!(shown.len() <= CONTEXT_LIMIT.0);
+            assert!(shown.lines().count() <= CONTEXT_LIMIT.1);
+            assert!(shown.contains(if tail {
+                "Showing lines 3403-5400"
+            } else {
+                "Showing lines 1-1998"
+            }));
+            let path = shown
+                .split("Full output: ")
+                .nth(1)
+                .unwrap()
+                .split(". Read with")
+                .next()
+                .unwrap();
+            assert_eq!(std::fs::read_to_string(path).unwrap(), original);
+        }
+        assert_eq!(guard("small".into(), "test", "id", false), "small");
+    }
+    #[test]
+    fn archive_failure_does_not_discard_data() {
+        std::fs::create_dir_all(format!("/logs/agent/{}", date())).unwrap();
+        std::fs::write(format!("/logs/agent/{}/not-a-directory", date()), "block").unwrap();
+        let output = "no loss\n".repeat(6000);
+        assert_eq!(
+            guard(output.clone(), "not-a-directory", "test", false),
+            output
+        );
+    }
+    #[test]
+    fn huge_line_and_exact_boundaries() {
+        for tail in [false, true] {
+            let result = guard("😀".repeat(40000), "test", "utf8", tail);
+            assert!(result.len() <= CONTEXT_LIMIT.0);
+            assert!(result.contains("partial line"));
+        }
+        let exact = "a\n".repeat(CONTEXT_LIMIT.1);
+        assert_eq!(guard(exact.clone(), "test", "exact", false), exact);
+        assert_eq!(read_lines(b"one\ntwo\nthree", 1, 1), "two\n");
+        assert_eq!(read_lines(b"one", 3, 1), "");
+    }
+}

agent/src/tools.rs

@@ -4,21 +4,47 @@ use crate::llm::Tool;
 use serde_json::{Value, json};
 use std::io;
 
-/// Maximum UTF-8 bytes in a serialized tool result, including its truncation marker.
+#[path = "overflow.rs"]
-pub const MAX_OUTPUT_BYTES: usize = 65_536;
+pub mod overflow;
 
-/// Bound every tool result before it enters history or a provider request.
+/// Human-readable, lossless text representation of tool JSON. String values
-pub fn limit_output(mut output: String) -> String {
+/// retain real newlines, with JSON-quoted field/index labels for structure.
-    const MARKER: &str = "\n[tool output truncated at 65536 bytes]";
+fn render(value: &Value) -> String {
-    if output.len() > MAX_OUTPUT_BYTES {
+    fn visit(value: &Value, label: &str, out: &mut String) {
-        let mut end = MAX_OUTPUT_BYTES - MARKER.len();
+        match value {
-        while !output.is_char_boundary(end) {
+            Value::Object(fields) => {
-            end -= 1;
+                if fields.is_empty() {
+                    out.push_str(&format!("{label}: {{}}\n"));
                 }
-        output.truncate(end);
+                for (key, value) in fields {
-        output.push_str(MARKER);
+                    visit(
+                        value,
+                        &format!("{label}[{}]", serde_json::to_string(key).unwrap()),
+                        out,
+                    );
                 }
-    output
+            }
+            Value::Array(items) => {
+                if items.is_empty() {
+                    out.push_str(&format!("{label}: []\n"));
+                }
+                for (i, value) in items.iter().enumerate() {
+                    visit(value, &format!("{label}[{i}]"), out);
+                }
+            }
+            Value::String(text) => {
+                out.push_str(&format!("{label} (string, {} bytes):\n", text.len()));
+                out.push_str(text);
+                out.push('\n');
+            }
+            _ => {
+                out.push_str(&format!("{label}: {value}\n"));
+            }
+        }
+    }
+    let mut out = String::new();
+    visit(value, "$", &mut out);
+    out
 }
 
 /// Describe the five tools sent to either inference API.
@@ -26,7 +52,7 @@ pub fn definitions() -> Vec<Tool> {
     vec![
         Tool {
             name: "call",
-            description: "Call a plugin method through the core. Await its result. Set detach to let its process survive this caller. Output is capped at 65536 bytes with a truncation marker.",
+            description: "Call a plugin method through the core. Await its result. Set detach to let its process survive this caller. Large results show an excerpt with a full-output /logs reference.",
             parameters: schema(
                 json!({
                     "method": {"type": "string", "description": "Qualified plugin method"},
@@ -38,19 +64,21 @@ pub fn definitions() -> Vec<Tool> {
         },
         Tool {
             name: "read_file",
-            description: "Read a text file in the world, including `/proc`. `offset` and `max_bytes` are optional. Output is capped at 65536 bytes with a truncation marker.",
+            description: "Read a text file in the world, including `/proc`. `offset`/`max_bytes` select bytes; `line_offset`/`line_limit` select zero-based lines (default 200). Large results show an excerpt with a full-output /logs reference.",
             parameters: schema(
                 json!({
                     "path": {"type": "string"},
                     "offset": {"type": "integer", "description": "Byte offset (default 0)"},
-                    "max_bytes": {"type": "integer", "description": "Optional maximum number of bytes to read"}
+                    "max_bytes": {"type": "integer", "description": "Optional maximum number of bytes to read"},
+                    "line_offset": {"type": "integer", "description": "Zero-based starting line; overrides bytes"},
+                    "line_limit": {"type": "integer", "description": "Number of lines; default 200"}
                 }),
                 &["path"],
             ),
         },
         Tool {
             name: "write_file",
-            description: "Write a text file in the world. Parent folders are created. Output is capped at 65536 bytes with a truncation marker.",
+            description: "Write a text file in the world. Parent folders are created. Large results show an excerpt with a full-output /logs reference.",
             parameters: schema(
                 json!({"path": {"type": "string"}, "content": {"type": "string"}}),
                 &["path", "content"],
@@ -58,12 +86,12 @@ pub fn definitions() -> Vec<Tool> {
         },
         Tool {
             name: "list_dir",
-            description: "List entries in a world directory. Returns each name, type, and size. Output is capped at 65536 bytes with a truncation marker.",
+            description: "List entries in a world directory. Returns each name, type, and size. Large results show an excerpt with a full-output /logs reference.",
             parameters: schema(json!({"path": {"type": "string"}}), &["path"]),
         },
         Tool {
             name: "copy_dir",
-            description: "Copy a directory tree, for example a plugin source to a draft folder. Skips `target/` folders. Output is capped at 65536 bytes with a truncation marker.",
+            description: "Copy a directory tree, for example a plugin source to a draft folder. Skips `target/` folders. Large results show an excerpt with a full-output /logs reference.",
             parameters: schema(
                 json!({"from": {"type": "string"}, "to": {"type": "string"}}),
                 &["from", "to"],
@@ -103,6 +131,16 @@ pub async fn run(name: &str, args: &Value) -> sausage_plugin::Result<Value> {
 fn read_file(args: &Value) -> io::Result<Value> {
     let path = args["path"].as_str().unwrap_or_default();
     let bytes = std::fs::read(path)?;
+    if path.starts_with("/logs/") {
+        return Ok(
+            json!({"path":path,"size":bytes.len(),"content":overflow::existing(&bytes, path, args)}),
+        );
+    }
+    if let Some(line) = args["line_offset"].as_u64() {
+        return Ok(
+            json!({"path":path,"size":bytes.len(),"line_offset":line,"content":overflow::read_lines(&bytes, line as usize, args["line_limit"].as_u64().unwrap_or(200) as usize)}),
+        );
+    }
     let offset = (args["offset"].as_u64().unwrap_or(0) as usize).min(bytes.len());
     let end = args["max_bytes"].as_u64().map_or(bytes.len(), |max| {
         offset.saturating_add(max as usize).min(bytes.len())
@@ -185,11 +223,35 @@ fn copy_tree(from: &str, to: &str) -> io::Result<u64> {
 #[cfg(test)]
 mod tests {
     #[test]
-    fn tool_output_limit_preserves_utf8_and_marks_truncation() {
+    fn overflow_json_can_be_followed_by_line_without_rearchiving() {
-        let limited = super::limit_output("😀".repeat(40_000));
+        let value = serde_json::json!({"stdout":"hello 😀\n".repeat(4000),"exit":1,"error":{"text":"failure\n".repeat(4000)}});
-        assert!(limited.len() <= super::MAX_OUTPUT_BYTES);
+        let expected = super::render(&value);
-        assert!(limited.ends_with("[tool output truncated at 65536 bytes]"));
+        let shown = super::overflow::guard(value.to_string(), "json-test", "call", true);
-        assert_eq!(super::limit_output("small".into()), "small");
+        assert!(shown.len() <= 50 * 1024 && shown.lines().count() <= 2000);
+        let path = shown
+            .split("Full output: ")
+            .nth(1)
+            .unwrap()
+            .split(". Read with")
+            .next()
+            .unwrap();
+        assert_eq!(std::fs::read_to_string(path).unwrap(), expected);
+        let parent = std::path::Path::new(path).parent().unwrap();
+        let count = std::fs::read_dir(parent).unwrap().count();
+        let args = serde_json::json!({"path":path,"line_offset":30,"line_limit":5});
+        let read = super::read_file(&args).unwrap();
+        let read = read["content"].as_str().unwrap();
+        assert!(read.contains("Showing lines 31-35"));
+        assert!(read.contains(path));
+        assert_eq!(std::fs::read_dir(parent).unwrap().count(), count);
+        assert!(
+            super::overflow::existing(
+                expected.as_bytes(),
+                path,
+                &serde_json::json!({"line_offset":u64::MAX})
+            )
+            .contains("Full output:")
+        );
     }
     #[test]
     fn copy_rejects_a_destination_inside_the_source() {

cli/src/host.rs

@@ -66,8 +66,11 @@ impl Host {
             Ok((World::open(&path)?, Runtime::new(&cache)?))
         })
         .await??;
-        let journal =
+        let journal = journal::Journal::open_with_legacy(
-            journal::Journal::open(world.state_dir("core").join("journal.sqlite")).await?;
+            world.root.join("logs/core/journal.sqlite"),
+            Some(world.state_dir("core").join("journal.sqlite")),
+        )
+        .await?;
         let host = Self::with_parts(world, runtime, journal);
         let cargo_world = host.0.world.clone();
         let cargo = tokio::task::spawn_blocking(move || {

cli/src/journal.rs

@@ -1,13 +1,17 @@
 //! A dedicated SQLite writer batches entries and serves ordered queries without propagating disk failures into the host.
-use rusqlite::{Connection, params};
+use rusqlite::{Connection, OpenFlags, params};
+use serde::{Deserialize, Serialize};
 use serde_json::{Value, json};
+use std::io::Write;
 use std::{
     collections::HashSet,
     path::PathBuf,
     sync::{Mutex, mpsc},
 };
 use tokio::sync::oneshot;
+#[derive(Debug, Serialize, Deserialize)]
 struct Entry {
+    time: String,
     id: String,
     pid: String,
     plugin: String,
@@ -21,44 +25,83 @@ enum Command {
 pub(crate) struct Journal {
     sender: mpsc::Sender<Command>,
     warned: Mutex<HashSet<String>>,
+    spool: PathBuf,
 }
 impl Journal {
     pub(crate) async fn memory() -> anyhow::Result<Self> {
         Self::open(PathBuf::from(":memory:")).await
     }
     pub(crate) async fn open(path: PathBuf) -> anyhow::Result<Self> {
+        Self::open_with_legacy(path, None).await
+    }
+    pub(crate) async fn open_with_legacy(
+        path: PathBuf,
+        legacy: Option<PathBuf>,
+    ) -> anyhow::Result<Self> {
+        let spool = path
+            .parent()
+            .unwrap_or(std::path::Path::new("."))
+            .join("failed-batches");
+        let worker_spool = spool.clone();
         let (sender, receiver) = mpsc::channel();
         let (ready, initialized) = oneshot::channel();
-        std::thread::spawn(move || match open_database(path) {
+        std::thread::spawn(move || {
-            Ok(mut db) => {
+            match (|| -> anyhow::Result<_> {
+                let db = open_database(path)?;
+                // Never rename, checkpoint, or write the old SQLite/WAL files.
+                let old = legacy
+                    .filter(|p| p.exists())
+                    .map(|p| Connection::open_with_flags(p, OpenFlags::SQLITE_OPEN_READ_ONLY))
+                    .transpose()?;
+                Ok((db, old))
+            })() {
+                Ok((mut db, old)) => {
                     let _ = ready.send(Ok(()));
+                    let mut pending = Vec::new();
                     while let Ok(first) = receiver.recv() {
                         let mut batch = vec![first];
                         batch.extend(receiver.try_iter().take(255));
-                    write_batch(&mut db, batch);
+                        pending = write_batch(&mut db, old.as_ref(), &worker_spool, pending, batch);
+                    }
+                    if !pending.is_empty() {
+                        // Both storage locations failed. Last resort: retain full text in host stderr.
+                        eprintln!(
+                            "journal shutdown with unpersisted entries: {}",
+                            serde_json::to_string(&pending).unwrap()
+                        );
                     }
                 }
                 Err(error) => {
                     eprintln!("journal open failed: {error}");
                     let _ = ready.send(Err(error));
                 }
+            }
         });
         initialized.await??;
         Ok(Self {
             sender,
             warned: Mutex::new(HashSet::new()),
+            spool,
         })
     }
     pub(crate) fn write(&self, pid: &str, plugin: &str, stream: &str, line: &str) {
         let entry = Entry {
+            time: chrono::Utc::now().to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
             id: uuid::Uuid::now_v7().to_string(),
             pid: pid.into(),
             plugin: plugin.into(),
             stream: stream.into(),
             line: line.into(),
         };
-        if self.sender.send(Command::Write(entry)).is_err() {
+        if let Err(mpsc::SendError(Command::Write(entry))) = self.sender.send(Command::Write(entry))
-            eprintln!("journal writer stopped");
+        {
+            eprintln!("journal writer stopped; saving entry outside SQLite");
+            if let Err(error) = spool_batch(&self.spool, std::slice::from_ref(&entry)) {
+                eprintln!(
+                    "journal spool failed: {error}; unpersisted entry: {}",
+                    serde_json::to_string(&entry).unwrap()
+                );
+            }
         }
     }
     pub(crate) fn warning(&self, pid: &str, plugin: &str) {
@@ -94,28 +137,94 @@ fn open_database(path: PathBuf) -> anyhow::Result<Connection> {
         CREATE INDEX IF NOT EXISTS journal_plugin ON journal(plugin);")?;
     Ok(db)
 }
-fn write_batch(db: &mut Connection, batch: Vec<Command>) {
+/// Exclusive, synced JSON files preserve failed transactions without a busy retry loop.
+/// Recovery is deliberate: files are never automatically removed or replayed.
+fn spool_batch(dir: &std::path::Path, entries: &[Entry]) -> anyhow::Result<PathBuf> {
+    std::fs::create_dir_all(dir)?;
+    let path = dir.join(format!("{}.json", uuid::Uuid::now_v7()));
+    // A failed/partial write must not look like a complete recovery batch.
+    let mut file = tempfile::NamedTempFile::new_in(dir)?;
+    serde_json::to_writer(&mut file, entries)?;
+    file.write_all(b"\n")?;
+    file.as_file().sync_all()?;
+    file.persist_noclobber(&path)?;
+    std::fs::File::open(dir)?.sync_all()?;
+    eprintln!(
+        "journal failed batch preserved: {} ({} entries)",
+        path.display(),
+        entries.len()
+    );
+    Ok(path)
+}
+
+fn write_batch(
+    db: &mut Connection,
+    old: Option<&Connection>,
+    spool: &std::path::Path,
+    mut pending: Vec<Entry>,
+    batch: Vec<Command>,
+) -> Vec<Entry> {
+    let mut queries = Vec::new();
+    for command in batch {
+        match command {
+            Command::Write(entry) => pending.push(entry),
+            Command::Query(filters, response) => queries.push((filters, response)),
+        }
+    }
+    if !pending.is_empty() {
         let write = (|| -> rusqlite::Result<()> {
             let transaction = db.transaction()?;
-        for command in &batch {
+            for e in &pending {
-            if let Command::Write(e) = command {
+                transaction.execute("INSERT OR IGNORE INTO journal (id,time,pid,plugin,stream,line) VALUES (?1,?2,?3,?4,?5,?6)",params![e.id,e.time,e.pid,e.plugin,e.stream,e.line])?;
-                transaction.execute("INSERT INTO journal (id,time,pid,plugin,stream,line) VALUES (?1,strftime('%Y-%m-%dT%H:%M:%fZ','now'),?2,?3,?4,?5)",params![e.id,e.pid,e.plugin,e.stream,e.line])?;
-            }
             }
             transaction.commit()
         })();
-    if let Err(error) = write {
+        match write {
+            Ok(()) => pending.clear(),
+            Err(error) => {
                 eprintln!("journal write failed: {error}");
+                match spool_batch(spool, &pending) {
+                    Ok(_) => pending.clear(),
+                    Err(error) => eprintln!(
+                        "journal spool failed: {error}; retaining {} entries in memory until next command",
+                        pending.len()
+                    ),
                 }
-    for command in batch {
+            }
-        if let Command::Query(filters, response) = command {
+        }
-            let value = query_database(db, &filters).unwrap_or_else(|error| {
+    }
+    for (filters, response) in queries {
+        let value = query_all(db, old, &filters).unwrap_or_else(|error| {
             eprintln!("journal query failed: {error}");
             json!([])
         });
         let _ = response.send(value);
     }
+    pending
+}
+
+fn query_all(
+    db: &Connection,
+    old: Option<&Connection>,
+    filters: &Value,
+) -> rusqlite::Result<Value> {
+    let mut entries = query_database(db, filters)?.as_array().unwrap().clone();
+    if let Some(old) = old {
+        entries.extend(
+            query_database(old, filters)?
+                .as_array()
+                .unwrap()
+                .iter()
+                .cloned(),
+        );
+        entries.sort_by(|a, b| a["id"].as_str().cmp(&b["id"].as_str()));
+        entries.dedup_by(|a, b| a["id"] == b["id"]);
+        let limit = filters["limit"].as_i64().unwrap_or(100);
+        if limit >= 0 {
+            entries.drain(..entries.len().saturating_sub(limit as usize));
         }
+    }
+    Ok(json!(entries))
 }
 fn query_database(db: &Connection, filters: &Value) -> rusqlite::Result<Value> {
     let mut statement = db.prepare(
@@ -135,6 +244,140 @@ fn query_database(db: &Connection, filters: &Value) -> rusqlite::Result<Value> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    fn entry(line: &str) -> Entry {
+        Entry {
+            id: uuid::Uuid::now_v7().to_string(),
+            time: "2026-10-26T12:00:00.000Z".into(),
+            pid: "pid".into(),
+            plugin: "test".into(),
+            stream: "core".into(),
+            line: line.into(),
+        }
+    }
+
+    #[test]
+    fn failed_transaction_is_spooled_in_full_and_queries_finish() {
+        let dir = tempfile::tempdir().unwrap();
+        let mut db = open_database(PathBuf::from(":memory:")).unwrap();
+        db.execute_batch("PRAGMA query_only=ON").unwrap();
+        let original = "😀 full failure\n".repeat(6000);
+        let (tx, mut rx) = oneshot::channel();
+        let pending = write_batch(
+            &mut db,
+            None,
+            dir.path(),
+            vec![],
+            vec![
+                Command::Write(entry(&original)),
+                Command::Query(json!({}), tx),
+            ],
+        );
+        assert!(pending.is_empty());
+        assert_eq!(rx.try_recv().unwrap(), json!([]));
+        let path = std::fs::read_dir(dir.path())
+            .unwrap()
+            .next()
+            .unwrap()
+            .unwrap()
+            .path();
+        let saved: Vec<Entry> = serde_json::from_slice(&std::fs::read(path).unwrap()).unwrap();
+        assert_eq!(saved.len(), 1);
+        assert_eq!(saved[0].line, original);
+        assert_eq!(saved[0].time, "2026-10-26T12:00:00.000Z");
+    }
+
+    #[test]
+    fn failed_spool_retries_on_next_command_without_duplicates() {
+        let dir = tempfile::tempdir().unwrap();
+        let blocked = dir.path().join("blocked");
+        std::fs::write(&blocked, "not a directory").unwrap();
+        let mut db = open_database(PathBuf::from(":memory:")).unwrap();
+        db.execute_batch("PRAGMA query_only=ON").unwrap();
+        let pending = write_batch(
+            &mut db,
+            None,
+            &blocked,
+            vec![],
+            vec![Command::Write(entry("retained"))],
+        );
+        assert_eq!(pending.len(), 1);
+        db.execute_batch("PRAGMA query_only=OFF").unwrap();
+        let (tx, mut rx) = oneshot::channel();
+        let pending = write_batch(
+            &mut db,
+            None,
+            &blocked,
+            pending,
+            vec![Command::Query(json!({}), tx)],
+        );
+        assert!(pending.is_empty());
+        assert_eq!(rx.try_recv().unwrap()[0]["line"], "retained");
+        assert_eq!(
+            query_all(&db, None, &json!({}))
+                .unwrap()
+                .as_array()
+                .unwrap()
+                .len(),
+            1
+        );
+    }
+
+    #[tokio::test]
+    async fn legacy_wal_and_new_journal_share_filters_order_and_limit() {
+        let dir = tempfile::tempdir().unwrap();
+        let legacy = dir.path().join("state/core/journal.sqlite");
+        let mut old = open_database(legacy.clone()).unwrap();
+        write_batch(
+            &mut old,
+            None,
+            dir.path(),
+            vec![],
+            vec![Command::Write(entry("old match"))],
+        );
+        // Leave the WAL connection open: opening the new journal must not move its files.
+        let wal = legacy.with_extension("sqlite-wal");
+        let before = std::fs::read(&wal).unwrap();
+        let new = dir.path().join("logs/core/journal.sqlite");
+        let journal = Journal::open_with_legacy(new.clone(), Some(legacy.clone()))
+            .await
+            .unwrap();
+        journal.write("pid", "test", "core", "new match");
+        let entries = tokio::time::timeout(
+            std::time::Duration::from_secs(5),
+            journal.query(json!({"pid":"pid","grep":"match","limit":-1})),
+        )
+        .await
+        .unwrap();
+        assert_eq!(entries.as_array().unwrap().len(), 2);
+        assert_eq!(entries[0]["line"], "old match");
+        assert_eq!(entries[1]["line"], "new match");
+        assert_eq!(
+            journal.query(json!({"limit":1})).await[0]["line"],
+            "new match"
+        );
+        assert_eq!(
+            journal.query(json!({"until":entries[0]["id"]})).await[0]["line"],
+            "old match"
+        );
+        assert_eq!(
+            journal
+                .query(json!({"since":entries[1]["id"],"plugin":"test"}))
+                .await[0]["line"],
+            "new match"
+        );
+        assert_eq!(journal.query(json!({"grep":"absent"})).await, json!([]));
+        assert_eq!(std::fs::read(wal).unwrap(), before);
+        assert!(legacy.exists() && new.exists());
+        assert_eq!(
+            query_database(&old, &json!({}))
+                .unwrap()
+                .as_array()
+                .unwrap()
+                .len(),
+            1
+        );
+    }
+
     /// PROTOCOL 7: completed processes do not leave warning identities in memory.
     #[tokio::test]
     async fn completion_forgets_warning_identity() {

cli/src/runtime.rs

@@ -212,7 +212,11 @@ fn short_trap(full: &str) -> String {
         .find_map(|l| l.find("wasm trap:").map(|i| l[i..].to_string()))
         .unwrap_or_else(|| full.lines().next().unwrap_or("trap").to_string());
     let mut line = line.trim().to_string();
-    line.truncate(300);
+    let mut end = line.len().min(300);
+    while !line.is_char_boundary(end) {
+        end -= 1;
+    }
+    line.truncate(end);
     line
 }
 
@@ -361,6 +365,7 @@ impl Runtime {
         });
 
         let (err_tx, err_rx) = mpsc::channel(1024);
+        let trap_log = log.clone();
         let stderr_task = tokio::spawn(async move {
             let mut reader = BufReader::new(host_err);
             let mut bytes = Vec::new();
@@ -400,6 +405,9 @@ impl Runtime {
                     Some(I32Exit(c)) => Exit::Code(*c),
                     None => {
                         let full = format!("{e:?}");
+                        if let Some((journal, pid, plugin)) = &trap_log {
+                            journal.write(pid, plugin, "core", &full);
+                        }
                         Exit::Trap(short_trap(&full))
                     }
                 },
@@ -416,3 +424,17 @@ impl Runtime {
         })
     }
 }
+
+#[cfg(test)]
+mod trap_text_tests {
+    use super::*;
+    #[test]
+    fn short_trap_display_is_utf8_safe() {
+        let full = format!("backtrace\nwasm trap: {}\nmore detail", "😀".repeat(1000));
+        let status = short_trap(&full);
+        assert!(status.len() <= 300);
+        assert!(status.starts_with("wasm trap:"));
+        assert_eq!(short_trap(""), "trap");
+        assert_eq!(short_trap("first line\nsecond"), "first line");
+    }
+}

cli/tests/crates/cargo-valid/src/main.rs

@@ -92,6 +92,7 @@ mod tests {
             "/config",
             "/state",
             "/state/core/journal.sqlite",
+            "/logs/core/journal.sqlite",
         ] {
             assert!(!std::path::Path::new(path).exists(), "{path}");
         }

cli/tests/host/agent.rs

@@ -489,7 +489,28 @@ async fn oversized_current_turn_preserves_the_previous_cursor() {
             .unwrap();
         let (body, reply) = server.next().await;
         let serialized = input(&body, api).to_string();
-        assert!(serialized.contains("[tool output truncated"));
+        assert!(serialized.contains("Full output: /logs/agent/"));
+        let history = world.history();
+        let result: Value = history
+            .lines()
+            .map(|line| serde_json::from_str::<Value>(line).unwrap())
+            .find(|entry| {
+                entry["output"]
+                    .as_str()
+                    .is_some_and(|out| out.contains("Full output: "))
+            })
+            .unwrap();
+        let output = result["output"].as_str().unwrap();
+        let path = output
+            .split("Full output: ")
+            .nth(1)
+            .unwrap()
+            .split(". ")
+            .next()
+            .unwrap();
+        let archive = std::fs::read_to_string(world.0.join(path.trim_start_matches('/'))).unwrap();
+        assert!(archive.contains(&"x".repeat(200_000)));
+        assert!(output.len() <= 50 * 1024);
         assert!(serialized.len() < 70_000);
         reply
             .send((413, json!({"type":"request_too_large"})))

cli/tests/host/cli.rs

@@ -36,7 +36,7 @@ async fn status(child: &mut Child) -> std::process::ExitStatus {
 }
 async fn journal_exists(world: &Path) {
     tokio::time::timeout(Duration::from_secs(15), async {
-        while !world.join("state/core/journal.sqlite").exists() {
+        while !world.join("logs/core/journal.sqlite").exists() {
             tokio::task::yield_now().await;
         }
     })
@@ -251,7 +251,7 @@ async fn signals_work_during_boot() {
         tokio::time::timeout(Duration::from_secs(15), async {
             loop {
                 let db =
-                    rusqlite::Connection::open(world.join("state/core/journal.sqlite")).unwrap();
+                    rusqlite::Connection::open(world.join("logs/core/journal.sqlite")).unwrap();
                 if let Ok(2) = db.query_row(
                     "SELECT count(*) FROM journal WHERE line='service start core.lock'",
                     [],
@@ -336,7 +336,7 @@ async fn console_error_stops_host() {
         .await
         .unwrap();
     assert_eq!(status(&mut child).await.code(), Some(1));
-    let db = rusqlite::Connection::open(world.join("state/core/journal.sqlite")).unwrap();
+    let db = rusqlite::Connection::open(world.join("logs/core/journal.sqlite")).unwrap();
     let stopped: i64 = db
         .query_row(
             "SELECT count(*) FROM journal WHERE plugin='probe' AND line='stop'",
@@ -363,9 +363,9 @@ async fn interrupt_leaves_call_running() {
     input.write_all(b"probe.busy\n").await.unwrap();
     let pid = tokio::time::timeout(Duration::from_secs(20), async {
         loop {
-            if world.join("state/core/journal.sqlite").exists() {
+            if world.join("logs/core/journal.sqlite").exists() {
                 let db =
-                    rusqlite::Connection::open(world.join("state/core/journal.sqlite")).unwrap();
+                    rusqlite::Connection::open(world.join("logs/core/journal.sqlite")).unwrap();
                 if let Ok(pid) = db.query_row(
                     "SELECT pid FROM journal WHERE plugin='probe' AND line='start busy {}'",
                     [],

cli/tests/host/core.rs

@@ -129,7 +129,7 @@ async fn stderr_flood_does_not_block_stdin() {
     let payload = json!({"large":"x".repeat(1024*1024)});
     assert_eq!(call(&h, "probe.echo", payload.clone()).await, payload);
     h.stop().await;
-    let db = rusqlite::Connection::open(w.0.join("state/core/journal.sqlite")).unwrap();
+    let db = rusqlite::Connection::open(w.0.join("logs/core/journal.sqlite")).unwrap();
     let count: i64 = db
         .query_row(
             "SELECT count(*) FROM journal WHERE line LIKE 'flood %'",
@@ -198,7 +198,7 @@ async fn null_error_is_success() {
 async fn journal_recovers_after_sqlite_write_failure() {
     let w = TestWorld::new();
     let h = w.start().await;
-    let db = rusqlite::Connection::open(w.0.join("state/core/journal.sqlite")).unwrap();
+    let db = rusqlite::Connection::open(w.0.join("logs/core/journal.sqlite")).unwrap();
     db.busy_timeout(std::time::Duration::from_secs(5)).unwrap();
     db.execute_batch("CREATE TRIGGER reject_writes BEFORE INSERT ON journal BEGIN SELECT RAISE(FAIL,'test failure'); END;").unwrap();
     assert_eq!(
@@ -206,6 +206,16 @@ async fn journal_recovers_after_sqlite_write_failure() {
         json!({"failed_log":true})
     );
     call(&h, "core.log", json!({})).await;
+    let batches: Vec<Value> = std::fs::read_dir(w.0.join("logs/core/failed-batches"))
+        .unwrap()
+        .map(|file| serde_json::from_slice(&std::fs::read(file.unwrap().path()).unwrap()).unwrap())
+        .collect();
+    assert!(
+        batches
+            .iter()
+            .flat_map(|batch| batch.as_array().unwrap())
+            .any(|entry| entry["line"].as_str().unwrap().contains("failed_log"))
+    );
     db.execute_batch("DROP TRIGGER reject_writes;").unwrap();
     assert_eq!(
         call(&h, "probe.echo", json!({"recovered":true})).await,
@@ -1068,7 +1078,7 @@ async fn journal_filters_and_entries_persist_in_sqlite() {
     );
     h.stop().await;
     assert!(
-        std::fs::read(w.0.join("state/core/journal.sqlite"))
+        std::fs::read(w.0.join("logs/core/journal.sqlite"))
             .unwrap()
             .starts_with(b"SQLite format 3")
     );
@@ -1254,8 +1264,9 @@ async fn journal_entries_have_uuid_time_identity_stream_and_line() {
 async fn journal_has_wal_and_identity_indexes() {
     let w = TestWorld::new();
     let h = w.start().await;
+    assert!(!w.0.join("state/core/journal.sqlite").exists());
     h.stop().await;
-    let db = rusqlite::Connection::open(w.0.join("state/core/journal.sqlite")).unwrap();
+    let db = rusqlite::Connection::open(w.0.join("logs/core/journal.sqlite")).unwrap();
     assert_eq!(
         db.query_row("PRAGMA journal_mode", [], |r| r.get::<_, String>(0))
             .unwrap(),
@@ -1941,7 +1952,7 @@ async fn core_restart_cleanly_stops_detached_caller() {
             std::fs::read_to_string(w.0.join("state/restart-stop")).unwrap(),
             "persisted after EOF"
         );
-        let db = rusqlite::Connection::open(w.0.join("state/core/journal.sqlite")).unwrap();
+        let db = rusqlite::Connection::open(w.0.join("logs/core/journal.sqlite")).unwrap();
         let count: i64 = db
             .query_row(
                 "SELECT count(*) FROM journal WHERE line = 'restart stop hook finished'",
@@ -1995,3 +2006,68 @@ async fn core_exit_alias_sets_executable_status_75() {
         String::from_utf8_lossy(&output.stderr)
     );
 }
+
+/// PROTOCOL 7: logs move, state and the old journal do not; core.log merges both.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn journal_location_preserves_legacy_history() {
+    let w = TestWorld::new();
+    let old = w.0.join("state/core/journal.sqlite");
+    let db = rusqlite::Connection::open(&old).unwrap();
+    db.execute_batch("CREATE TABLE journal (id TEXT PRIMARY KEY, time TEXT, pid TEXT, plugin TEXT, stream TEXT, line TEXT);
+        INSERT INTO journal VALUES ('0000','old time','old-pid','old-plugin','core','legacy history');").unwrap();
+    drop(db);
+    let before = std::fs::read(&old).unwrap();
+    let history = w.0.join("state/core/console-history");
+    std::fs::write(&history, "keep console history").unwrap();
+    let h = w.start().await;
+    call(&h, "probe.echo", json!({})).await;
+    assert!(w.0.join("logs/core/journal.sqlite").exists());
+    let entries = call(&h, "core.log", json!({"limit":-1})).await;
+    assert_eq!(entries[0]["line"], "legacy history");
+    assert!(entries.as_array().unwrap().len() > 1);
+    assert_eq!(
+        call(&h, "core.log", json!({"pid":"old-pid"})).await[0]["line"],
+        "legacy history"
+    );
+    h.stop().await;
+    assert_eq!(std::fs::read(&old).unwrap(), before);
+    assert_eq!(
+        std::fs::read_to_string(history).unwrap(),
+        "keep console history"
+    );
+}
+
+/// PROTOCOL 7: the journal retains the full trap, not just its short status reason.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn full_trap_diagnostic_is_journaled() {
+    let w = TestWorld::new();
+    let h = w.start().await;
+    let error = tokio::time::timeout(
+        std::time::Duration::from_secs(20),
+        h.call("probe.trap", json!({})),
+    )
+    .await
+    .unwrap()
+    .unwrap_err();
+    assert_eq!(error["code"], -32002);
+    assert!(
+        error["data"]["status"]
+            .as_str()
+            .unwrap()
+            .starts_with("trap: wasm trap:")
+    );
+    let entries = call(
+        &h,
+        "core.log",
+        json!({"plugin":"probe","grep":"wasm backtrace"}),
+    )
+    .await;
+    assert!(
+        entries.as_array().unwrap().iter().any(|e| {
+            let text = e["line"].as_str().unwrap();
+            text.contains("Caused by:") && text.contains("wasm trap:")
+        }),
+        "{entries}"
+    );
+    h.stop().await;
+}

cli/tests/plugins/probe/src/main.rs

@@ -376,6 +376,7 @@ fn dispatch(request: &Value, lines: &mut Lines) -> Option<Value> {
     let params = &request["params"];
     let result = match request["method"].as_str().unwrap() {
         "batch" => batch(lines),
+        "trap" => std::arch::wasm32::unreachable(),
         "nested_environment" => nested_environment(lines),
         "forget" => forget(lines),
         "forgotten" => {

sdk/tests/wasi.rs

@@ -34,10 +34,8 @@ impl Process {
             let mut s = String::new();
             if self.output.read_line(&mut s).unwrap() == 0 {
                 let mut stderr = String::new();
-                let _ = std::io::Read::read_to_string(
+                let _ =
-                    self.child.stderr.as_mut().unwrap(),
+                    std::io::Read::read_to_string(self.child.stderr.as_mut().unwrap(), &mut stderr);
-                    &mut stderr,
-                );
                 panic!("unexpected EOF from wasmtime. Its stderr:\n{stderr}");
             }
             if let Ok(v) = sausage_plugin::serde_json::from_str::<Value>(&s)