BoundaryML/baml · error · JsonishError

No collection to consume token: {0:?}

Error message

No collection to consume token: {0:?}

What it means

`JsonishError::NoCollectionForToken(char)` is raised when the tokenizer/consumer encounters a collection-opening token (an object or array delimiter) while no collection is currently open on the parse stack — the input has a stray closing delimiter or an orphaned token with nothing to attach to. The `char` payload identifies the offending token.

Source

Thrown at baml_language/crates/bex_sap/src/jsonish/mod.rs:23

mod parser;
mod value;

pub use parser::{ParseOptions, parse};
pub use value::{CompletionState, Fixes, Value};

/// Error type for jsonish parsing failures.
#[derive(Debug, thiserror::Error)]
pub enum JsonishError {
    #[error("Depth limit reached. Likely a circular reference.")]
    DepthLimitReached,
    #[error("No JSON objects found")]
    NoJsonObjectsFound,
    #[error("No markdown blocks found")]
    NoMarkdownBlocksFound,
    #[error("Mismatched brackets")]
    MismatchedBrackets,
    #[error("No collection to consume token: {0:?}")]
    NoCollectionForToken(char),
    #[error("Failed to parse JSON")]
    ParseFailed,
}

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Examine the reported character's position in the input and remove the stray delimiter or restore the missing opening one.
2. Improve pre-extraction so it slices complete JSON objects, not fragments.
3. Ask the model for a single complete JSON value with no surrounding code samples.
4. Add a validation/sanitizing step before parsing to drop obviously incomplete fragments.

Example fix

// before
let v = jsonish::parse(frag, &opts)?; // frag: "...} ]"
// after
let frag = extract_first_complete_object(&raw).ok_or(MyErr::NoJson)?;
let v = jsonish::parse(&frag, &opts)?;

fn has_orphan_closers(s: &str) -> bool {
    let mut d = 0i32;
    for c in s.chars() {
        match c { '{' | '[' => d += 1, '}' | ']' => { d -= 1; if d < 0 { return true } }, _ => {} }
    }
    false
}
// if has_orphan_closers(raw), fix extraction boundaries first

match jsonish::parse(&frag, &opts) {
    Ok(v) => Ok(v),
    Err(JsonishError::NoCollectionForToken(c)) => Err(format!("stray '{c}' — fix extraction slice")),
    Err(e) => Err(e.into()),
}

When it happens

Trigger: Calling `bex_sap::jsonish::parse` on text with stray `}`, `]`, or similar delimiters outside any open `{`/`[` — e.g. fragments of JSON mixed into prose.

Common situations: The model emits partial JSON fragments or code samples containing braces; a regex-based pre-extraction step cut the JSON in the wrong place leaving orphaned delimiters.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

Related errors

• Mismatched brackets
• Mismatched brackets
• Depth limit reached. Likely a circular reference.
• No JSON objects found
• Failed to parse JSON

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/42626e11bfeb5ccb. Report an issue: GitHub.