XDaLa Limits

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XDaLa Hard Limits Specification (XRC-137, XRC-729, CEL)

1. Scope and Rationale

This document specifies the deterministic hard limits (“caps”) enforced by the XDaLa Engine for:

  • XRC-137 (Rule / Validation Documents)
  • XRC-729 (Orchestration / Process Graphs)
  • CEL / Expression Evaluation (runtime evaluator safety)

These caps are hard protocol constraints. They are enforced before execution (parsing/preflight) or during evaluator preparation (checked AST), to ensure:

  • bounded CPU/memory usage
  • bounded fan-out and join cardinality
  • bounded log/receipt/database growth
  • deterministic worst-case behavior

Any cap violation results in a hard abort.

2. Abort Semantics

2.1 XRC-729 (Orchestration)

Caps are enforced before session start. Violations cause an early abort: - the JSON-RPC call fails immediately - no process is enqueued - no session state is created

2.2 XRC-137 (Rule Documents)

Caps are enforced when the rule document is read and parsed during session execution.
Violations result in a hard abort (ErrTx semantics), not a soft validation outcome.

2.3 CEL / Expression Evaluation

Evaluator caps are enforced: - on raw expression length (pre-check) - on checked AST size (node count) - on input list/array sizes (deep traversal)

Violations abort rule evaluation deterministically. :contentReference[oaicite:1]{index=1}

3. XRC-137 Limits (Rule Documents)

3.1 Document & Schema Caps

Key Description Limit
MaxXRC137Bytes Maximum size of the decrypted XRC-137 JSON blob 131072 bytes (128 KB)
MaxPayloadFields Maximum declared payload input fields 64
MaxFieldNameLen Maximum payload/output field name length (ASCII identifier) 64 chars
MaxRules Maximum number of rules in rules[] 64
MaxExprLen Maximum length of any rule expression string 2048 chars

Field names must be ASCII identifiers: [A-Za-z0-9_-].

3.2 API Caps

Key Description Limit
MaxAPICalls Maximum number of apiCalls[] 16
MaxURLTemplateLen Maximum urlTemplate length 2048 chars
MaxBodyTemplateLen Maximum bodyTemplate length 8192 chars (8 KB)
MaxExtractMapEntries Maximum extract entries per apiCalls[i].extractMap 64
MaxStringValueLen Maximum length of any string literal/default in API extract context 8192 chars (8 KB)

Notes: - Each extractMap key is subject to MaxFieldNameLen and ASCII identifier rules. - Expression-like strings inside extract specs are subject to MaxExprLen.

3.3 Contract Reads Caps

Key Description Limit
MaxContractReads Maximum number of contractReads[] 16
MaxContractReadSaveAs Maximum number of saveAs targets per contract read 64
MaxStringValueLen Maximum length of any string default in saveAs 8192 chars (8 KB)

3.4 Branch Outcome Caps (onValid / onInvalid)

Key Description Limit
MaxOutcomeKeys Maximum number of keys in onValid.payload / onInvalid.payload 64
MaxGrants Maximum number of grants per branch 16
MaxExecArgs Maximum number of execution.args[] per branch 16
MaxStringValueLen Maximum length of any string payload value in branches 8192 chars (8 KB)

4. XRC-729 Limits (Orchestration)

4.1 Document Caps

Key Description Limit
MaxOSTCBytes Maximum size of raw OSTC JSON returned by XRC-729 262144 bytes (256 KB)

4.2 Graph Caps

Key Description Limit
MaxSteps Maximum number of steps in structure 128
MaxStepIdLen Maximum step id length (ASCII identifier) 64 chars
MaxSpawnsPerBranch Maximum spawn edges per branch (onValid.spawns, onInvalid.spawns) 32
MaxJoinInputs Maximum join inputs per join (join.from[]) 32

Notes: - Step ids, spawn targets, join ids and join from.node MUST be ASCII identifiers. - Caps are applied during orchestration parsing; violations early-abort the RPC call.

5. CEL / Expression Limits (Evaluator Safety)

These limits are enforced in the CEL evaluation layer and are independent from XRC schema parsing. :contentReference[oaicite:2]{index=2}

Key Description Limit
MaxExprLen Maximum raw CEL source length (bytes) 1024
MaxAstNodes Maximum checked AST node count 4096
MaxListCap Maximum list/array size anywhere in input values (deep traversal) 64

6. Error Semantics

Limit violations return deterministic errors (hard abort):

  • ErrLimitsExceeded (parser/preflight caps)
  • CEL layer errors (e.g. ErrExprTooComplex, ErrListCapExceeded) for evaluator caps :contentReference[oaicite:3]{index=3}

Error messages include: - which cap was violated - observed value - maximum allowed value

Example: