docs(agents): trim restated rationale to restore AG002 chain headroom (#6759)

* docs(agents): trim restated rationale to restore AG002 chain headroom

The agents/middlewares AGENTS.md chain crossed the 96 KiB AG002 hard
limit at 3f7a0769 (98441 > 98304 bytes); that push produced no lint-check
run, and later pushes compare equal to their base, so main stayed green
while a full-worktree check_agent_guidance run reports an error. Trim
restated rationale:

- backend/AGENTS.md: the Feishu button-card sentence restated semantics
  app/channels/AGENTS.md already owns (originator-validated, one-time,
  fail-closed clicks); keep the flag visibility and point at the module
  guide.
- agents/middlewares/AGENTS.md: drop the membership-probe rationale
  duplicated by the model_response.py paragraph, the ToolOutputBudget
  ordering narration, and the lead-only append note restated by the
  lead-only middlewares heading.

Chain: 98441 -> 98198 bytes (106 under the hard limit).

* docs(channels): own the Feishu card fail-closed invariant in the module guide

Review follow-up on #6759: the backend/AGENTS.md trim dropped two things
app/channels/AGENTS.md item 7 does not own - the fail-closed-across-workers
guarantee and the owning file's name - so the invariant left every
instruction chain and the pointer dead-ended one level above the
implementation. State both in item 7, paid by dropping the therefore-clause
restated by the single-active-owner invariant above it (the partial unique
index and the losing-writer retry already imply deterministic resolution).

channels/AGENTS.md: 49134 -> 49129 bytes (AG001 headroom 18 -> 23).

---------

Co-authored-by: xiaodu55 <xiaodu55@users.noreply.github.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/AGENTS.md

@@ -175,7 +175,7 @@ More specific `AGENTS.md` files in backend code directories contain the subsyste
 The backend is split into two layers with a strict dependency direction:
 
 - **Harness** (`packages/harness/deerflow/`): Publishable agent framework package (`deerflow-harness`). Import prefix: `deerflow.*`. Contains agent orchestration, tools, sandbox, models, MCP, skills, config — everything needed to build and run agents.
-- **App** (`app/`): Unpublished application code. Import prefix: `app.*`. Contains the FastAPI Gateway API and IM channel integrations (Feishu, Slack, Telegram, DingTalk). Feishu option clarifications can render as interactive button cards behind `channels.feishu.card_interaction_enabled` (default off); clicks are originator-validated and one-time, and fail closed across workers — ownership lives in `app/channels/feishu_card_interaction.py`.
+- **App** (`app/`): Unpublished application code. Import prefix: `app.*`. Contains the FastAPI Gateway API and IM channel integrations (Feishu, Slack, Telegram, DingTalk). Feishu option clarifications can render as interactive button cards behind `channels.feishu.card_interaction_enabled` (default off); see `app/channels/AGENTS.md`.
 
 **Dependency rule**: App imports deerflow, but deerflow never imports app. This boundary is enforced by `tests/test_harness_boundary.py` which runs in CI.
 

backend/app/channels/AGENTS.md

@@ -36,7 +36,7 @@ Cursor writes drain before cancellation; token expiry drains cursor/auth clearin
 5. Feishu/Telegram chat: `runs.stream()` → accumulate AI text → publish multiple outbound updates (`is_final=False`) → publish final outbound (`is_final=True`)
 6. Slack/Discord chat: `runs.wait()` → extract final response → publish outbound
 6b. GitHub chat (`ChannelRunPolicy.fire_and_forget=True`): `runs.create()` returns once the run is `pending`; the manager does not wait for the final state and does not publish an outbound; the agent posts its own reply via sandbox `gh`. `ConflictError` on a busy thread still trips the standard `THREAD_BUSY_MESSAGE` path (log-only on GitHub); with `buffer_followups_on_busy=True` (GitHub's default) the triggering message is captured into a per-thread buffer so a concurrent comment is not silently dropped (see "Follow-up buffering while busy").
-7. Feishu patches one card per source (`config.update_multi=true`), with topic previews and queued → running → final states. Opt-in cards show context/question; bounded tokens preserve request ID/source. Originator/option checks consume once. Card replies keep bound aliases in fields/metadata; ordinary replies preserve `/new`. Accepted intake retires only that card's buttons/text hint before terminal PATCH; rejected intake keeps text fallback.
+7. Feishu patches one card per source (`config.update_multi=true`), with topic previews and queued → running → final states. Opt-in cards show context/question; bounded tokens preserve request ID/source. Originator/option checks consume once; consumption fails closed across workers (`feishu_card_interaction.py`). Card replies keep bound aliases in fields/metadata; ordinary replies preserve `/new`. Accepted intake retires only that card's buttons/text hint before terminal PATCH; rejected intake keeps text fallback.
 8. Telegram streaming: the "Working on it..." placeholder message is registered as the stream target; non-final updates `editMessageText` it in place (channel-side throttle: 1s in private chats, 3s in groups due to Telegram's 20 msg/min group cap; 4096-char truncation; rate-limited updates dropped); the final update performs the last edit and splits >4096 texts into follow-up messages
 9. DingTalk AI Cards (`card_template_id`): `runs.stream()` → create card with initial text → `PUT /v1.0/card/streaming` → finalize (`is_final=True`). Creation/streaming failure uses `sampleMarkdown`; tables preserve escaped pipes and empty edge cells.
 10. For commands (`/new`, `/status`, `/models`, `/model`, `/memory`, `/goal`, `/agent`, `/help`): handle locally or query Gateway API. `/agent list` reads the effective owner's Custom Agents; `/agent use <name>` validates in the same owner bucket, creates a new thread, and persists `channel_agent_name` in its metadata. A Custom Agent writes canonical `metadata.agent_name` so thread-search routes Web continuation to `/workspace/agents/<name>/chats/<thread_id>`; `lead_agent` omits it and stays on the ordinary chat route. 
@@ -74,7 +74,7 @@ The cached value is reused for both the blocking (`runs.wait`) and streaming (`_
 - Slack replies use the configured operator bot token from `channels.slack` unless per-connection credentials are present; unreadable or corrupt stored credentials are treated as unavailable.
 - Telegram, Slack, Discord, Feishu/Lark, DingTalk, WeChat, and WeCom workers resolve incoming platform identities to connection records before reaching `ChannelManager`.
 - **Connect-code ordering**: `/connect <code>` (Telegram `/start <code>`) precedes `allowed_users`, so even non-allowlisted senders can bind with a valid code. The allowlist gates ordinary messages. Codes rely on secrecy: `secrets.token_urlsafe(16)`, 600 s TTL, one-time `consume_oauth_state`, shown only in the initiating browser, never echoed to chat.
-- **Single-active-owner transfer semantics**: an external identity is keyed by `(provider, external_account_id, workspace_id)`. The latest successful bind wins — `upsert_connection` revokes other owners' active rows for the same identity (ownership transfer). This invariant is enforced at the DB layer by the partial unique index `uq_channel_connection_active_identity` (`WHERE status != 'revoked'`), so concurrent connects from different owners cannot both end `connected`; the losing writer retries against the now-visible state. `find_connection_by_external_identity` therefore resolves deterministically.
+- **Single-active-owner transfer semantics**: an external identity is keyed by `(provider, external_account_id, workspace_id)`. The latest successful bind wins — `upsert_connection` revokes other owners' active rows for the same identity (ownership transfer). This invariant is enforced at the DB layer by the partial unique index `uq_channel_connection_active_identity` (`WHERE status != 'revoked'`), so concurrent connects from different owners cannot both end `connected`; the losing writer retries against the now-visible state.
 - See `backend/docs/IM_CHANNEL_CONNECTIONS.md` for provider setup, operational notes, and the architecture diagrams (connect-code flow, single-active-owner transfer, sync vs streaming dispatch, owner-scoped file storage pipeline).
 
 **GitHub event-driven agents** (webhook-driven IM channel):

backend/packages/harness/deerflow/agents/middlewares/AGENTS.md

@@ -26,7 +26,7 @@ It preserves resumes, same-run continuations, and entries without `run_id`.
 A pre-turn reply prevents cancellation; legacy replies without status metadata may
 stay `in_progress`. Never infer status from reply text.
 
-Assembly order: `tool_error_handling_middleware.py::_build_runtime_middlewares` (exposed as `build_lead_runtime_middlewares`), then `../lead_agent/agent.py::build_middlewares` appends lead-only entries. Optional entries require their config/runtime condition.
+Assembly order: `tool_error_handling_middleware.py::_build_runtime_middlewares` (exposed as `build_lead_runtime_middlewares`), then `../lead_agent/agent.py::build_middlewares`. Optional entries require their config/runtime condition.
 
 **Message provenance.** Stamp injected/rewritten messages with
 `provenance_kwargs()` from `deerflow_extension_api.provenance`: server-owned
@@ -62,7 +62,7 @@ No match: skip inspection, log ID. Tests: `test_read_mark_tool_call_correlation.
    **KnowledgeScopeMiddleware** follows input sanitization: it exposes only Gateway-admitted execution scope, removes scope/display data from model messages, and blocks `knowledge_search` when disabled without reading storage or RAGFlow.
 2. **ToolOutputBudgetMiddleware** - Budgets model-bound text/JSON with limits/exemptions; externalizes to thread outputs (`tool_output.storage_subdir`, default `.tool-results`, `TOOL_RESULTS_DIRNAME`) with synopsis/`read_file` refs. Preserve mixed-result media. Restore blob refs across hosts; hash/write failures fall back inline. Internal files bypass workspace/delivery scans. Publication/elision/bash exit marker: [contract](TOOL_OUTPUT_PERSISTENCE.md). Elision: `tool_call_args`; retain newest `keep_recent_writes` writes. Controls: `elide_superseded_writes`, `superseded_write_min_chars`.
    Tests: `tests/test_tool_output_synopsis_budget.py`.
-3. **ToolResultSanitizationMiddleware** - Neutralizes framework/injection tags (e.g. `<system-reminder>`) and boundary markers in *remote-content* tool results (`web_fetch`/`web_search`/`image_search`/`web_capture`) so attacker-controlled fetched pages cannot forge trusted framework context. Mirrors `InputSanitizationMiddleware`'s user-input guardrail for the other untrusted-content entry point; sits inner of `ToolOutputBudgetMiddleware` (neutralizes the raw output, then the budget truncates). Local tool output (bash/read_file) is left untouched. Scope is a name-based allowlist for the first-party web tools, plus every MCP-sourced tool via its `deerflow_mcp` metadata tag, so an MCP server naming its fetcher `fetch_url` is still covered
+3. **ToolResultSanitizationMiddleware** - Neutralizes framework/injection tags (e.g. `<system-reminder>`) and boundary markers in *remote-content* tool results (`web_fetch`/`web_search`/`image_search`/`web_capture`) so attacker-controlled fetched pages cannot forge trusted framework context. Mirrors `InputSanitizationMiddleware`'s user-input guardrail for the other untrusted-content entry point; sits inner of `ToolOutputBudgetMiddleware`. Local tool output (bash/read_file) is left untouched. Scope is a name-based allowlist for the first-party web tools, plus every MCP-sourced tool via its `deerflow_mcp` metadata tag, so an MCP server naming its fetcher `fetch_url` is still covered
 
    Result-rewriting middlewares between the raw callable boundary and the
    model-visible result append a declared entry to
@@ -138,7 +138,7 @@ Before changing a later authorization phase, read the [authorization RFC](../../
 37. **TerminalResponseMiddleware** - When a provider returns an empty terminal `AIMessage` after tool execution, injects a hidden recovery prompt and retries the model once; a second empty response is replaced in checkpoint state by a visible error fallback marked for the run worker, so the run finishes as an error instead of a silent success
 38. **ModelLengthFinishReasonMiddleware** - Match stamps `stop_reason=model_length_capped` and ends tool loop. Suppresses calls, appends notice even with partial text, and stamps `model_length_termination` so downstream guards stand down. Preserves content blocks.
 39. **SafetyFinishReasonMiddleware** - *(optional, if `safety_finish_reason.enabled`)* Suppresses tool execution when the provider safety-terminated the response (e.g. `finish_reason=content_filter`); registered after terminal-response/custom/configured middlewares so LangChain's reverse-order `after_model` dispatch runs it first
-40. **ClarificationMiddleware** - Intercepts `ask_clarification`, writes a readable `ToolMessage.content` fallback plus a structured `ToolMessage.artifact.human_input` payload, and interrupts via `Command(goto=END)` (must be last). `after_model` drops same-turn sibling tool calls so they cannot run before the user answers; a malformed `ask_clarification` parked on `invalid_tool_calls` is the same stop signal. `disable_clarification` runs keep the siblings. Payloads are versioned — legacy `free_text`/`choice_with_other` stay `version: 1`; the v2 `form` mode (from `fields`) is `version: 2` so older frontends reject it and fall back to plain text. Field normalization is deterministic and lives in the middleware (it short-circuits before tool execution, so tool-arg typing gives no runtime validation), and it is atomic: any structurally broken entry — non-dict, bad/duplicate name, a name colliding with a JS `Object.prototype` member (`__proto__`/`constructor`), or exceeding the caps (16 fields / 24 options per field / 200 chars per text / `MAX_FORM_SERIALIZED_BYTES` = 16KB UTF-8, the per-item caps alone admitting forms whose IM text fallback overruns channel limits) — degrades the whole form to the legacy option/free-text modes, so a card never renders "complete" while missing a field. Benign issues degrade locally (unknown types — incl. unhashable JSON like `type: []`, which must not raise from the membership probe — and option-less selects become `text`); options are trimmed/deduped with blanks dropped (form- and top-level) since the frontend rejects blank labels. XML-to-dict option payloads are recursively flattened from dict/list containers in source order, scalar leaves kept, residual XML tags stripped before that trimming. Checkboxes are booleans defaulting to "no"; `required` on one means consent semantics. The response protocol is unchanged (v1 `text`/`option`): form cards submit a text summary as `response_kind: "text"`, so journal persistence needs no new allowlist entries. `RunJournal` reconciles visible, unpersisted `ToolMessage`s for current-run lead-agent calls at the next lead-agent `on_chat_model_start` after consumption, or at successful root `on_chain_end`. This preserves any middleware short-circuit, including blocked writes, across later model errors and checkpoint compaction (#4666). `_remember_current_run_tool_calls` excludes subagents; their results stay in `subagent.step`. Human Input Card replies are `hide_from_ui` `HumanMessage`s with `additional_kwargs.human_input_response`; `RunJournal` persists only allowlisted hidden sources (currently `ask_clarification`) as `llm.human.input`.
+40. **ClarificationMiddleware** - Intercepts `ask_clarification`, writes a readable `ToolMessage.content` fallback plus a structured `ToolMessage.artifact.human_input` payload, and interrupts via `Command(goto=END)` (must be last). `after_model` drops same-turn sibling tool calls so they cannot run before the user answers; a malformed `ask_clarification` parked on `invalid_tool_calls` is the same stop signal. `disable_clarification` runs keep the siblings. Payloads are versioned — legacy `free_text`/`choice_with_other` stay `version: 1`; the v2 `form` mode (from `fields`) is `version: 2` so older frontends reject it and fall back to plain text. Field normalization is deterministic and lives in the middleware (it short-circuits before tool execution, so tool-arg typing gives no runtime validation), and it is atomic: any structurally broken entry — non-dict, bad/duplicate name, a name colliding with a JS `Object.prototype` member (`__proto__`/`constructor`), or exceeding the caps (16 fields / 24 options per field / 200 chars per text / `MAX_FORM_SERIALIZED_BYTES` = 16KB UTF-8, the per-item caps alone admitting forms whose IM text fallback overruns channel limits) — degrades the whole form to the legacy option/free-text modes, so a card never renders "complete" while missing a field. Benign issues degrade locally (unknown types — incl. unhashable JSON like `type: []` — and option-less selects become `text`); options are trimmed/deduped with blanks dropped (form- and top-level) since the frontend rejects blank labels. XML-to-dict option payloads are recursively flattened from dict/list containers in source order, scalar leaves kept, residual XML tags stripped before that trimming. Checkboxes are booleans defaulting to "no"; `required` on one means consent semantics. The response protocol is unchanged (v1 `text`/`option`): form cards submit a text summary as `response_kind: "text"`, so journal persistence needs no new allowlist entries. `RunJournal` reconciles visible, unpersisted `ToolMessage`s for current-run lead-agent calls at the next lead-agent `on_chat_model_start` after consumption, or at successful root `on_chain_end`. This preserves any middleware short-circuit, including blocked writes, across later model errors and checkpoint compaction (#4666). `_remember_current_run_tool_calls` excludes subagents; their results stay in `subagent.step`. Human Input Card replies are `hide_from_ui` `HumanMessage`s with `additional_kwargs.human_input_response`; `RunJournal` persists only allowlisted hidden sources (currently `ask_clarification`) as `llm.human.input`.
 
 Inline `skill_references` accepts 1–16 names; empty lists retain slash/plain flow.
 Resolve the whole batch through user storage, enabled state and agent allowlist