slm-compress — Reversible Context Compression (Surface B)

Purpose

When a tool output, transcript, or accumulated context grows large enough to crowd out working space, slm_compress reduces it in-place. The compressed form is used for the remainder of the session; the exact original is recoverable on demand via slm_retrieve. This works without a proxy and without touching ANTHROPIC_BASE_URL, so the full 1M context window is never sacrificed.

Primary MCP Tool: slm_compress

slm_compress(
    content:      str,          # required — text to compress (max 1 MB)
    mode:         str = "auto",  # "normalize" | "auto" | "aggressive"
    reversible:   bool = True,  # store original in CCR for later retrieval
    ttl_seconds:  int = 86400,  # CCR lifetime in seconds (default 24 h)
) -> dict

Return dict (all keys always present)

Mode semantics (verified from source)

• `"normalize"` — lossless whitespace collapse; no daemon dependency; lossy: false, ccr_id: null.
• `"auto"` — delegates to CompressRouter; may be lossy depending on daemon config; default.
• `"aggressive"` — requests aggressive compression from the daemon; daemon must have compress_mode=aggressive set in config; note field will warn if daemon config does not match.

Recovery Tool: slm_retrieve

When slm_compress returns lossy: true, the original is stored under the ccr_id. Use slm_retrieve to get it back:

slm_retrieve(ccr_id: str) -> dict

ccr_id must be a valid UUID4. Non-UUID4 strings return ok: false immediately.

CCR security rule

ccr_id values are unguessable session tokens. Treat them like short-lived credentials:

• Never log them.
• Never share them across agents.
• Never pass them as tool arguments to any tool other than slm_retrieve.
• Never compress a ccr_id string itself.
• They expire after ttl_seconds (default 24 h); slm_retrieve returns ok: false after expiry.

Decision: When to Compress

Compress when:

• A single tool output or transcript exceeds approximately 2 000 characters.
• You are accumulating repeated context (e.g. full file reads across multiple steps).
• Context is nearing the point where recall quality or response quality degrades.

Do NOT compress:

• Code you are about to read, edit, or diff — you need every character.
• JSON you will parse programmatically — compression may alter structure.
• Secrets, credentials, or ccr_id strings.
• Anything under ~500 characters — overhead exceeds benefit.
• The compressed form of content already compressed this session.

Fail-Open Guarantee

slm_compress never raises an exception. On any internal error it returns:

{ "ok": false, "compressed": "<original input>", "ratio": 1.0, ... }

When `ok` is `false`, continue with the original content. Never block a task waiting for compression to succeed.

Worked Example

# Step 1: compress a large tool output
result = await slm_compress(
    content=long_log_text,
    mode="auto",
    reversible=True,
    ttl_seconds=3600,
)

if result["ok"]:
    working_text = result["compressed"]
    ccr_id = result["ccr_id"]   # None if lossless
else:
    working_text = long_log_text  # fail-open
    ccr_id = None

# ... work with working_text ...

# Step 2: restore original when needed (e.g. before final summary)
if ccr_id:
    restore = await slm_retrieve(ccr_id=ccr_id)
    if restore["ok"]:
        original_text = restore["content"]

Secondary CLI (fallback when MCP is unavailable)

The slm compress subcommand exists but has known pre-existing parse-test failures. Prefer the MCP tools above. If you must use CLI:

slm compress status [--json]
slm compress mode safe|aggressive [--json]
slm compress code on|off [--json]
slm compress prose on|off [--json]
slm compress ccr on|off [--json]
slm compress align on|off [--json]

These subcommands control daemon-level compression settings — they do not compress content inline. For inline compression, use slm_compress via MCP.

Size Cap

Content over 1 MB (1 000 000 bytes UTF-8) is processed but reversible is forced to False and ccr_id will be None. The note field will state "content over 1MB: ccr skipped".

SuperLocalMemory v3.6.18 · Qualixar · AGPL-3.0-or-later