dsh-context-decay
简体中文
Model-driven, lossy context decay for DeepSeek Harness.
The model decides when and what to compress. Finished spans are replaced by
self-written summaries; the current turn is always kept. There is no recovery:
the summary is the only surviving record.
Install note: This is a manual-install plugin: it requires a DSH
checkout with the modelMessageDecoration seam and is not a drop-in
plugin-market bundle (see Requirements).
Sidebar panel: effective-window pressure, total-window occupancy, reminder state, and context-ordered position space
What it does
- Inline position anchors. Every model-addressable message with a visible
text block is prefixed with
⟦p<number>⟧; tool-call-only assistant turns are
unanchored by design. Compression ranges use those anchors directly:
⟦p<from>⟧ summary ⟦p<to>⟧. Anchors are presentation, never part of the content.
- Copied anchors removed. If the model starts a reply with one or more
anchors, the leading run is stripped at the request boundary and again before
the reply is committed, so the transcript and later requests stay clean.
- Model-selected spans. The model calls
compress with one or more
half-open ranges and writes each summary itself. No extra summarizer request.
Split around content that must stay live; pass all consumed spans in one call
so the prefix is not invalidated repeatedly.
- Lossy by design. Compressed content is gone. There is no
decompress, no
original-text search, and no external table. The summary must be self-contained.
- Tool results are compressible. All results of one assistant tool-call
message must stay in the same span. A boundary inside that group is rejected;
the plugin never silently widens a span.
- Current turn protection. The active turn and its tool results cannot be
compressed. If the turn starts with unanchored system/runtime messages, a
to
boundary at its first visible anchor keeps those messages and compresses only
the history before the turn; "end" remains the end-of-compressible-history
sentinel.
- Tiered re-compression. Compressing a live summary block again produces a
tier-2 summary; larger merges increase the tier.
drop removes a block
completely with no tombstone.
- Pressure without automation. The plugin reports context pressure and
injects reminders when context grows noticeably or crosses a warning level.
It never compresses automatically; the model decides.
- Live panel + audit. A sidebar panel shows pressure, blocks, positions,
request counts, and the reminder ledger. An optional JSONL audit records each
request and compression.
Requirements
- DeepSeek Harness 0.2.1-rc.2 with the local host patch in
patches/dsh-model-message-decoration.patch
applied. Stock DSH does not expose the decoration seam; there is no runtime
fallback. Installation alone is not enough: rebuild the host after patching.
- Node.js >= 22.19.
- A web profile. The client half needs the sidebar/session/locale UI packages
listed in
package.json.
- The bundle patch disables official automatic compaction
(
compaction-basic.auto: false), keeps the manual /compact command, and
disables the in-place surface rewriters (tool-result-pruner,
image-offload) when those rows exist. /compact remains an emergency
host fallback; its checkpoint is not a context-decay block.
Install
Manual patched install:
# 1. Apply the host patch to a DSH checkout and rebuild the host.
git -C /path/to/deepseek-harness apply /path/to/dsh-context-decay/patches/dsh-model-message-decoration.patch
pnpm -C /path/to/deepseek-harness install
pnpm -C /path/to/deepseek-harness build
# 2. Install this plugin into a profile (checkout or tarball).
dsh plugin --profile web add /path/to/dsh-context-decay
# or: dsh plugin --profile web add ./dsh-context-decay-0.1.0.tgz
# 3. Restart the web server and open the profile.
dsh web --profile web
See docs/INSTALL.md for the full patched-checkout workflow,
Windows commands, verification, updating, and rollback.
Tools
| Tool | Purpose |
|---|
compress({spans:[{from,to,summary,topic?}]}) | Replace one or more half-open ranges with self-written summaries. from/to are visible anchor texts such as "⟦p12⟧" (bare "p12" and integer 12 also work); to may also be "end". Several non-overlapping spans per call are allowed. Tool-group edges are rejected. |
drop({from,to}) | Remove exactly one live summary block. Use the block's printed anchor pair; "end" is allowed for a tail block. No tombstone, no recovery. |
A live summary block prints its pair inline as ⟦p<from>⟧ summary ⟦p<to>⟧; use that
pair for drop. The sidebar panel shows pressure and the block ledger, so no
extra status tool is needed.
Examples:
# one span
compress({spans:[{from:"⟦p4⟧", to:"⟦p9⟧", summary:"Read the three requirements files; constraints are ..."}]})
# two non-overlapping spans in one call
compress({spans:[
{from:"⟦p4⟧", to:"⟦p9⟧", summary:"Read the requirements; constraints are ..."},
{from:"⟦p9⟧", to:"end", summary:"Implemented the parser and tests; ..."}
]})
# drop one live summary block
drop({from:"⟦p4⟧", to:"⟦p9⟧"})
The anchor ids above are illustrative; use anchors visible in the current
session.
Configuration
| Key | Default | Meaning |
|---|
enabled | true | Enable the plugin. |
contextWindowTokens | route value | Override the total context window. |
reservedOutputTokens | route value | Override the reserved output budget. |
defaultContextWindowTokens | 128000 | Fallback when the route has no window. |
growthTokens | 20000 | Normal reminder after this much growth since the last reminder. |
warnRatios | [0.70, 0.81, 0.95] | Warning levels as fractions of the effective window. |
reminderCooldownTurns | 1 | Minimum turns between reminders. |
maxSpansPerCall | 8 | Maximum spans in one compress call. |
minSummaryChars | 20 | Minimum summary length. |
maxSummaryChars | 8000 | Maximum summary length. |
maxMissTokens | null | Optional one-time miss guard. |
maxPaybackRequests | null | Optional payback guard. |
audit | false | Write request/compression audit JSONL. |
debug | false | Verbose plugin logging. |
The effective window is total window - reserved output. The model sees
pressure as a fraction of the effective window. The panel labels that percentage
as effective pressure, shows the total and reservation, and adds a total-window
occupancy line for direct comparison with the built-in context meter. Pressure,
reminder, and request facts are kept per session, so switching sessions updates
the panel.
How it works
The host patch adds a modelMessageDecoration service. The plugin registers a
decoration provider that prefixes the messages selected by the replay state;
the agent loop, token meter, and request payload all apply the same decoration.
Positions come from the replayed surface, not from message text. Compressions
append compaction/start, compaction/summary, a replacement user message, and
compaction/end; replay rebuilds blocks, tiers, and the free list.
See docs/ARCHITECTURE.md for the state model,
invariants, and failure modes.
See docs/PROMPTS.zh-CN.md for a Chinese translation of
the model-facing prompts, tool descriptions, reminders, and error copy.
Limitations and non-goals
- No recovery. There is no decompress, search, or spill archive. This is
deliberate; it is also the main trade-off.
- Requires a patched host. The decoration seam is not upstream. Without it
the plugin cannot safely present anchors or replay positions.
- No automatic compression. Reminders are advisory. A model may ignore them;
the budget stays protected by the request guard, not by silent compaction.
The official automatic policy is off; manual
/compact remains available.
/compact is a manual fallback. It runs the official backend and writes an
official checkpoint, not a context-decay tier block. Use it only when a
session is already too large for a normal request.- Manual install, not a market bundle. A market index cannot express the
host-patch requirement, and
engines.dsh cannot distinguish a patched host
from a stock one. Distribute the checkout or tarball with the patch
instructions until the seam is upstream.
- One compression backend per profile. Do not run another compaction backend
or an in-place surface rewriter alongside it.
- Replay depends on the current event format. Compression replay uses the
current
surfaceOp and compaction event shape.
Development
npm install # if building outside a DSH checkout
npm run build # src/ -> lib/ (JS + declarations), client/ -> lib/client.js
npm run check # typecheck only
npm test # node:test suite against lib/
Local development can reuse a DSH checkout's TypeScript: set
DSH_HARNESS_ROOT or place the checkout next to this package.
License
MIT. See LICENSE.
