Merge remote-tracking branch 'origin/master' into codex/invariant-service-seam

# Conflicts:
#	.agents/notes/implemented/architecture/2026-07-19-package-owned-invariant-service.i18n.yaml
#	.agents/notes/implemented/architecture/2026-07-19-package-owned-invariant-service.md
#	.agents/notes/implemented/architecture/2026-07-19-package-owned-invariant-service.zh.md
#	.agents/notes/implemented/feature/2026-06-18-compaction-capability-seam.md
#	.agents/notes/implemented/feature/2026-07-07-session-prefix.md
#	.agents/notes/implemented/process/2026-07-14-typescript-program-backed-semantic-gates.i18n.yaml
#	docs/architecture.md
#	docs/config-catalog.md
#	docs/core-data-structures/session.md
#	docs/rfc/INDEX.md
#	packages/examples/agent-spine-demo/README.md
#	packages/examples/agent-spine-demo/src/index.ts
#	packages/examples/agent-spine-demo/tests/agent-core.spec.ts
#	packages/support/invariants/README.md
#	packages/support/invariants/src/index.ts
#	packages/support/invariants/tests/invariants.spec.ts

packages/compact/README.md

@@ -1,6 +1,6 @@
 # compact/ — compaction capability family
 
-A three-package capability seam (see [capability seams](../../docs/rfc/implemented/architecture/2026-06-13-capability-seams.md)): an abstract compaction interface, a backend that summarizes, and the model-facing tool that consumes it. The interface and a first backend (`compact-basic/`) exist; the consumer tool is deferred. All **product** packages.
+A three-package capability seam (see [capability seams](../../.agents/notes/implemented/architecture/2026-06-13-capability-seams.md)): an abstract compaction interface, a backend that summarizes, and the model-facing tool that consumes it. The interface and a first backend (`compact-basic/`) exist; the consumer tool is deferred. All **product** packages.
 
 | Package | Role | ctx key |
 |---|---|---|
@@ -8,4 +8,4 @@ A three-package capability seam (see [capability seams](../../docs/rfc/implement
 | `compact-basic/` | A backend: `ctx.tokenMeter` pressure + token-budget retention + `llm.stream()` summarization | (registers `ctx.compact`) |
 | `tool-compact/` (deferred) | Model-facing `/compact` tool over `ctx.compact` | (registers on `ctx.tools`) |
 
-The interface lives at `compact/compact/`, the backend at `compact/compact-basic/`. Unlike the bash seam, it depends on `dsh-session` and `dsh-llm` — its verbs are defined over a `Session` and its output is the `ContentBlock` vocabulary, so the contract cannot be expressed without naming them. That deviation from the "interface depends only on cordis" guidance is intentional and recorded in the [compaction capability-seam RFC](../../docs/rfc/implemented/feature/2026-06-18-compaction-capability-seam.md). Token measurement is a reusable LLM-family service rather than a `CompactService` method; a template- or model-backed compactor can replace `compact-basic` without changing the meter or callers.
+The interface lives at `compact/compact/`, the backend at `compact/compact-basic/`. Unlike the bash seam, it depends on `dsh-session` and `dsh-llm` — its verbs are defined over a `Session` and its output is the `ContentBlock` vocabulary, so the contract cannot be expressed without naming them. That deviation from the "interface depends only on cordis" guidance is intentional and recorded in the [compaction capability-seam Agent Note](../../.agents/notes/implemented/feature/2026-06-18-compaction-capability-seam.md). Token measurement is a reusable LLM-family service rather than a `CompactService` method; a template- or model-backed compactor can replace `compact-basic` without changing the meter or callers.

packages/compact/compact-basic/README.md

@@ -2,7 +2,7 @@
 
 The **basic compaction backend**: a `BasicCompactService` implementing the `@deepseek-ai/dsh-compact` seam with reusable `ctx.tokenMeter` pressure, token-budget retention, and summarization as a direct one-shot `ctx.llm.stream()` call (interceptable at `llm/stream`).
 
-This is the implementation tier of the compaction capability — see the [interface package](../compact/README.md) for the seam and the [capability-seam RFC](../../../docs/rfc/implemented/feature/2026-06-18-compaction-capability-seam.md) for the design.
+This is the implementation tier of the compaction capability — see the [interface package](../compact/README.md) for the seam and the [capability-seam Agent Note](../../../.agents/notes/implemented/feature/2026-06-18-compaction-capability-seam.md) for the design.
 
 ## What it owns
 
@@ -56,29 +56,45 @@ Loading the plugin registers `ctx.compact`. With `auto: true` (the default) it c
 
 ### Conversation history
 
-**What the model sees**: After a successful step crosses the threshold, the next request receives the checkpoint preamble below, a blank line, `<compacted-summary>`, the data-dependent summary, and `</compacted-summary>`. Overflow recovery rebuilds the immediate retry from that replacement. This one checkpoint replaces the selected older range and is followed by the retained recent units.
+#### What the model sees
 
-**Token effect**: The replacement reduces future input history rather than appending a second copy. The summary remains until a later compaction replaces it; one oversized indivisible unit can still exceed the budget.
+After a successful step crosses the threshold, the next request receives the checkpoint preamble below, a blank line, `<compacted-summary>`, the data-dependent summary, and `</compacted-summary>`. Overflow recovery rebuilds the immediate retry from that replacement. This one checkpoint replaces the selected older range and is followed by the retained recent units.
 
-#### Conversation checkpoint preamble
+##### Conversation checkpoint preamble
 
 ```markdown
 This is an automatically generated checkpoint condensing an earlier span of the conversation to free up context. Treat the captured context as established background and build on it without restating it. Continue the task directly from the messages that follow, without acknowledging this checkpoint.
 ```
 
+#### Token effect
+
+The replacement reduces future input history rather than appending a second copy. The summary remains until a later compaction replaces it; one oversized indivisible unit can still exceed the budget.
+
+#### KV Cache effect
+
+Replacing rather than append-only. Each checkpoint invalidates reuse from the first replaced history token; the unchanged request prefix before that range remains reusable.
+
 ### Auxiliary summarizer user message
 
-**What the model sees**: The summarization model receives exactly `Summarize this conversation history:` followed by a blank line, the data-dependent [`renderTranscript()`](../compact/README.md) output, another blank line, and `Summary:`. The conversation model never sees this private request or its reasoning; only returned text is stored.
+#### What the model sees
 
-**Token effect**: This is a separate model call with data-dependent input and `maxTokens`-capped output. Convergence retries can pay this cost more than once.
+The summarization model receives exactly `Summarize this conversation history:` followed by a blank line, the data-dependent [`renderTranscript()`](../compact/README.md) output, another blank line, and `Summary:`. The conversation model never sees this private request or its reasoning; only returned text is stored.
+
+#### Token effect
+
+This is a separate model call with data-dependent input and `maxTokens`-capped output. Convergence retries can pay this cost more than once.
+
+#### KV Cache effect
+
+Independent of the conversation request cache. An auxiliary call can reuse an exact transcript prefix, while a different selected range or rendering invalidates reuse from its first changed token.
 
 ### Auxiliary summarizer system prompt
 
-**What the model sees**: The summarization model receives the checkpoint-writing instruction below.
+#### What the model sees
 
-**Token effect**: Fixed auxiliary input cost plus the data-dependent transcript on every summarization attempt.
+The summarization model receives the checkpoint-writing instruction below.
 
-#### Auxiliary summarizer system prompt
+##### Auxiliary summarizer system prompt
 
 ```markdown
 You are a compaction engine for an AI coding assistant. Condense the conversation transcript into a structured checkpoint that lets another model resume the work with no loss of essential context.
@@ -116,6 +132,14 @@ Rules:
 - If the transcript already contains a <compacted-summary> block, it is a PRIOR checkpoint. Do not copy it forward verbatim: preserve still-true facts, drop stale ones, and merge newer information into a single consolidated summary under the same structure.
 ```
 
+#### Token effect
+
+Fixed auxiliary input cost plus the data-dependent transcript on every summarization attempt.
+
+#### KV Cache effect
+
+Prefix-stable for auxiliary calls while this instruction and the summarizer route are unchanged. Changing either starts a different prefix; transcript changes occur after the instruction.
+
 ## Known Limitations and Deferred Work
 
 - **Meter accuracy follows the fixed heuristic** — missing reusable provider usage falls back to character count plus structural overhead rather than exact tokenization.
@@ -123,4 +147,4 @@ Rules:
 - **Single-unit and envelope-only overflow remain outside surface compaction** — recovery cannot split one indivisible message/tool unit or shrink system/tools/prefix.
 - **`compactRegion` requires an open turn** — a manual call on a fully-closed session throws ("no open turn") rather than compacting.
 - **Summarization failure fails closed with full, over-budget history** — including truncation at the summarization `maxTokens`, which hidden reasoning tokens can consume; the auto path logs a warning and proceeds.
-- **The summarization call has no transcript-snapshot coverage** — `dsh-llm-replay` derives calls from `assistant/chunk` events, so this chunk-less direct `ctx.llm.stream()` call cannot replay (named deferred replay infrastructure in [the seam RFC](../../../docs/rfc/implemented/feature/2026-06-18-compaction-capability-seam.md)).
+- **The summarization call has no transcript-snapshot coverage** — `dsh-llm-replay` derives calls from `assistant/chunk` events, so this chunk-less direct `ctx.llm.stream()` call cannot replay (named deferred replay infrastructure in [the seam Agent Note](../../../.agents/notes/implemented/feature/2026-06-18-compaction-capability-seam.md)).

packages/compact/compact/README.md

@@ -10,7 +10,7 @@ This package is the interface tier of the compaction capability, split so each c
 | `@deepseek-ai/dsh-compact-basic` | a backend: `ctx.tokenMeter` pressure + token-budget retention + `llm.stream()` summarization |
 | `@deepseek-ai/dsh-tool-compact` (deferred) | the model-facing `/compact` tool over `ctx.compact` |
 
-Unlike the bash seam, this interface depends on `@deepseek-ai/dsh-session` and `@deepseek-ai/dsh-llm` — the contract's verbs are defined over a `Session` and its output is the `ContentBlock` vocabulary, so they cannot be expressed without naming those packages. That deviation from the "interface depends only on cordis" guidance is intentional and recorded in the [compaction capability-seam RFC](../../../docs/rfc/implemented/feature/2026-06-18-compaction-capability-seam.md).
+Unlike the bash seam, this interface depends on `@deepseek-ai/dsh-session` and `@deepseek-ai/dsh-llm` — the contract's verbs are defined over a `Session` and its output is the `ContentBlock` vocabulary, so they cannot be expressed without naming those packages. That deviation from the "interface depends only on cordis" guidance is intentional and recorded in the [compaction capability-seam Agent Note](../../../.agents/notes/implemented/feature/2026-06-18-compaction-capability-seam.md).
 
 ## Service API (`ctx.compact`)
 
@@ -61,15 +61,31 @@ Subclass `CompactService`, implement `compactIfNeeded` and `compactRegion`, and
 
 ### Conversation history, when a backend is invoked
 
-**What the model sees**: A successful implementation replaces an older surface range with one user-role summary checkpoint; the raw events stay logged but stop appearing in derived model messages. The seam itself performs no rewrite.
+#### What the model sees
 
-**Token effect**: Zero direct tokens from this interface. A backend trades many retained history tokens for one summary and leaves the recent tail unchanged.
+A successful implementation replaces an older surface range with one user-role summary checkpoint; the raw events stay logged but stop appearing in derived model messages. The seam itself performs no rewrite.
+
+#### Token effect
+
+Zero direct tokens from this interface. A backend trades many retained history tokens for one summary and leaves the recent tail unchanged.
+
+#### KV Cache effect
+
+A successful backend replacement invalidates reuse from the first shadowed history token; the seam itself does not alter a request.
 
 ### Transcript supplied to a compaction consumer
 
-**What the model sees**: `renderTranscript()` joins entries with one blank line and renders them exactly as `User: <content>`, `Assistant: <content>`, `Tool result (call <callId>): <content>`, `Tool error (call <callId>): <content>`, `[Context: <content>]`, or `[Steering: <content>]`. Non-text blocks render exactly as `[reasoning: <text>]`, `[tool-call: <name>(<arguments>)]`, `[tool-result: <content>]`, `[tool-result]`, or `[<block-type>]`.
+#### What the model sees
 
-**Token effect**: Data-dependent input tokens are paid only by the auxiliary model or consumer that requests this transcript; the conversation model does not receive a duplicate transcript.
+`renderTranscript()` joins entries with one blank line and renders them exactly as `User: <content>`, `Assistant: <content>`, `Tool result (call <callId>): <content>`, `Tool error (call <callId>): <content>`, `[Context: <content>]`, or `[Steering: <content>]`. Non-text blocks render exactly as `[reasoning: <text>]`, `[tool-call: <name>(<arguments>)]`, `[tool-result: <content>]`, `[tool-result]`, or `[<block-type>]`.
+
+#### Token effect
+
+Data-dependent input tokens are paid only by the auxiliary model or consumer that requests this transcript; the conversation model does not receive a duplicate transcript.
+
+#### KV Cache effect
+
+No conversation-cache invalidation. A consumer's auxiliary request can reuse only the exact prefix produced by this rendering; changed or compacted entries invalidate reuse from their first difference.
 
 ## Known Limitations and Deferred Work
 

packages/compact/compact/src/index.ts

@@ -3,7 +3,7 @@
  * compact and replace a history range with one summary node by subclassing
  * {@link CompactService}. This interface necessarily depends on session and LLM
  * vocabulary; the rationale is in the
- * [compaction RFC](../../../../docs/rfc/implemented/feature/2026-06-18-compaction-capability-seam.md).
+ * [compaction Agent Note](../../../../.agents/notes/implemented/feature/2026-06-18-compaction-capability-seam.md).
  * @module @deepseek-ai/dsh-compact
  */
 

packages/compact/compact/src/types.ts

@@ -3,7 +3,7 @@
  * Those declaration-merged events are log-only lock/provenance markers, not
  * surface events; a separate replacement `user/message` carries the summary.
  * Backend packages own configuration and retention policy; see
- * `docs/rfc/implemented/feature/2026-06-18-compaction-capability-seam.md`.
+ * `.agents/notes/implemented/feature/2026-06-18-compaction-capability-seam.md`.
  * @module @deepseek-ai/dsh-compact/types
  */
 
@@ -30,7 +30,7 @@ declare module '@deepseek-ai/dsh-session' {
        * The model that wrote the summary — the summarize call's envelope,
        * reported by the backend that made the call, logged so the one-shot
        * request is reconstructable from log + code and "which model wrote
-       * this summary" has a durable answer (the reconstructability RFC).
+       * this summary" has a durable answer (the reconstructability Agent Note).
        */
       model: string
       /** The generation cap the summarize call sent, when one applied. */