Response compaction

std/agent/response_compaction retains a response exactly before optionally projecting it to a smaller typed value. It is a generic mechanism. Callers own the threshold, summary instructions, critical facts, and fallback value.

import {
  response_compact,
  response_compaction_read_exact,
} from "std/agent/response_compaction"

type Exact = {rows: list<dict>, total: int}
type Summary = {overview: string, critical_facts: list<string>}

const compacted = response_compact(
  {fs: harness.fs, llm: harness.llm},
  exact_response,
  schema_of(Exact),
  schema_of(Summary),
  {
    summarize_above_bytes: 32000,
    instructions: "Preserve identifiers, errors, and incomplete work.",
    fallback: {overview: "Exact response retained.", critical_facts: []},
    ladder: "agent_cheap",
    timeout_ms: 20000,
    ttl_seconds: 86400,
    max_entries: 256,
  },
)

const exact = response_compaction_read_exact(
  {fs: harness.fs, llm: harness.llm},
  compacted.receipt.exact_ref,
  schema_of(Exact),
)

Contract#

• The exact typed value is written to an atomic filesystem cache below harness.fs.workspace_temp_dir(), then schema-validated and checked against its canonical JSON digest on readback before a model call can begin.
• output.kind is exactly exact, summarized, or fallback.
• Summaries use a named catalog ladder. The cache identity includes the exact digest, summary schema, instructions, ladder, and token bound.
• Summarization has a validated bounded timeout (20 seconds by default). A timeout returns the deterministic fallback without weakening exact retention.
• Only schema-valid summaries enter the cache. A malformed or failed summary returns the caller's typed fallback while exact_ref remains readable.
• exact_ref contains no caller-controlled path. Readback derives the owned workspace-temporary root. Malformed references and schema-valid content tampering both return broken.
• TTL and LRU limits bound both exact and summary storage. Expired or evicted exact values read as missing, never as a successful empty value.
• Receipts contain digests, byte counts, cache and route facts, and optional token usage, not response content. A measured token count of zero is kept; an unavailable measurement remains absent.

response_compaction_read_exact returns {state: "found", value}, {state: "missing"}, or {state: "broken", detail}. Hosts that expose exact responses should wrap this function in their existing tool or MCP surface; they should not read the filesystem-cache layout directly.