Error Taxonomy

Every failure in Palimpsest is classified into exactly one category. No silent retries. No swallowed errors. Failures are stored artifacts — they are part of the crawl record, not noise to discard.

PalimpsestError

The top-level error enum. Every error in the system ultimately maps to one of these seven variants.

Network

#![allow(unused)]
fn main() {
PalimpsestError::Network(String)
}

Connection failures, DNS resolution errors, TCP timeouts, TLS handshake failures. The fetch could not reach the server.

Examples: DNS NXDOMAIN, connection refused, connect timeout, TLS certificate expired.

Protocol

#![allow(unused)]
fn main() {
PalimpsestError::Protocol(String)
}

HTTP protocol violations. The server responded, but the response is malformed or violates HTTP semantics.

Examples: Invalid status line, malformed headers, truncated chunked encoding, invalid Content-Length.

Rendering

#![allow(unused)]
fn main() {
PalimpsestError::Rendering(String)
}

Browser/DOM errors. Chrome launched but could not render the page correctly.

Examples: JavaScript execution error, page load timeout, CDP connection lost, DOM snapshot failure.

Policy

#![allow(unused)]
fn main() {
PalimpsestError::Policy(String)
}

The system refused to process a URL based on configured policy.

Examples: robots.txt disallow, scope violation (URL outside configured domain), rate limit enforcement, max depth exceeded.

DeterminismViolation

#![allow(unused)]
fn main() {
PalimpsestError::DeterminismViolation {
    context: String,
    expected: String,
    actual: String,
}
}

The nuclear option. This means a Law was broken. Two runs with the same seed produced different results. This should never happen in production — if it does, it’s a bug in the kernel.

Examples: Frontier produced different ordering for same seed, content hash mismatch for identical input, replay diverged from original.

Storage

#![allow(unused)]
fn main() {
PalimpsestError::Storage(String)
}

Blob store failures: write errors, read errors, integrity check failures, backend unavailability.

Examples: Disk full, permission denied, blob corrupted (hash mismatch on read), S3 connection error.

Replay

#![allow(unused)]
fn main() {
PalimpsestError::Replay(String)
}

Missing artifacts, incomplete capture groups, reconstruction failures. The stored data is insufficient to replay.

Examples: Missing blob for content hash, no envelope record in WARC, incomplete resource graph.

Other Error Types