#8334: fix(webchat): Filter NO_REPLY messages from chat history

Fixes #8214 ## Problem The webchat interface was displaying "NO_REPLY" messages instead of filtering them out. The NO_REPLY token is used by the agent to signal silent responses (no visible output to the user), but the webchat was showing these messages as literal "NO_REPLY" text bubbles. ## Solution Added filtering logic to remove NO_REPLY messages from the chat history before sending to the webchat client: 1. **Created `filterNoReplyMessages()` function** in `chat-sanitize.ts` that: - Detects assistant messages containing only "NO_REPLY" (case-insensitive, with optional whitespace/punctuation) - Filters them out from the message array - Handles both string content and content blocks format 2. **Updated `chat.history` handler** in `server-methods/chat.ts` to apply the filter after envelope stripping and before byte capping ## Why this works - NO_REPLY messages are already filtered in other channels (Slack, Telegram) via `isSilentReplyText()` - Webchat receives messages via `chat.history` API which was missing this filtering - The fix applies the same filtering pattern used elsewhere in the codebase - Only filters assistant messages, preserving user messages intact ## Testing To verify the fix: 1. Trigger agent responses that result in NO_REPLY (e.g., after using the `message` tool) 2. Check webchat UI - NO_REPLY messages should not appear 3. Verify normal messages still display correctly 4. Verify other message types (user messages, system messages) are unaffected ## Changes - `src/gateway/chat-sanitize.ts`: Added `filterNoReplyMessages()`, `isNoReplyMessage()`, and `extractMessageText()` helper functions (69 lines) - `src/gateway/server-methods/chat.ts`: Import and apply filter in `chat.history` handler (3 lines changed) 🤖 Generated by agent-4bf217745721 via [AgentGit](https://github.com/agentgit) <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds `filterNoReplyMessages()` in `src/gateway/chat-sanitize.ts` to remove assistant messages whose content is effectively the `NO_REPLY` silent-token, and wires it into the `chat.history` handler in `src/gateway/server-methods/chat.ts` after envelope stripping and before JSON byte-capping. This fits the gateway’s existing sanitization pipeline by ensuring webchat history aligns with other channels that already suppress silent replies. <h3>Confidence Score: 4/5</h3> - This PR is likely safe to merge and addresses the reported UI issue, with minor edge-case risks in the NO_REPLY detection logic. - The change is small and localized (history sanitization only). Main risk is false negatives: NO_REPLY may not be detected for multi-block assistant messages, and the custom regex may drift from the shared silent-token helper over time. - src/gateway/chat-sanitize.ts (NO_REPLY detection and content-block handling) <!-- greptile_other_comments_section --> **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->