docs: document 9 previously undocumented features

New documentation for features that existed in code but had no docs:

New page:
- context-references.md: Full docs for @-syntax inline context
  injection (@file:, @folder:, @diff, @staged, @git:, @url:) with
  line ranges, CLI autocomplete, size limits, sensitive path blocking,
  and error handling

configuration.md additions:
- Environment variable substitution: ${VAR_NAME} syntax in config.yaml
  with expansion, fallback, and multi-reference support
- Gateway streaming: Progressive token delivery on messaging platforms
  via message editing (StreamingConfig: enabled, transport, edit_interval,
  buffer_threshold, cursor) with platform support matrix
- Web search backends: Three providers (Firecrawl, Parallel, Tavily)
  with web.backend config key, capability matrix, auto-detection from
  API keys, self-hosted Firecrawl, and Parallel search modes

security.md additions:
- SSRF protection: Always-on URL validation blocking private networks,
  loopback, link-local, CGNAT, cloud metadata hostnames, with
  fail-closed DNS and redirect chain re-validation
- Tirith pre-exec security scanning: Content-level command scanning
  for homograph URLs, pipe-to-interpreter, terminal injection with
  auto-install, SHA-256/cosign verification, config options, and
  fail-open/fail-closed modes

sessions.md addition:
- Auto-generated session titles: Background LLM-powered title
  generation after first exchange

creating-skills.md additions:
- Conditional skill activation: requires_toolsets, requires_tools,
  fallback_for_toolsets, fallback_for_tools frontmatter fields with
  matching logic and use cases
- Environment variable requirements: required_environment_variables
  frontmatter for automatic env passthrough to sandboxed execution,
  plus terminal.env_passthrough user config

website/docs/user-guide/configuration.md

@@ -55,6 +55,22 @@ Settings are resolved in this order (highest priority first):
 Secrets (API keys, bot tokens, passwords) go in `.env`. Everything else (model, terminal backend, compression settings, memory limits, toolsets) goes in `config.yaml`. When both are set, `config.yaml` wins for non-secret settings.
 :::
 
+## Environment Variable Substitution
+
+You can reference environment variables in `config.yaml` using `${VAR_NAME}` syntax:
+
+```yaml
+auxiliary:
+  vision:
+    api_key: ${GOOGLE_API_KEY}
+    base_url: ${CUSTOM_VISION_URL}
+
+delegation:
+  api_key: ${DELEGATION_KEY}
+```
+
+Multiple references in a single value work: `url: "${HOST}:${PORT}"`. If a referenced variable is not set, the placeholder is kept verbatim (`${UNDEFINED_VAR}` stays as-is). Only the `${VAR}` syntax is supported — bare `$VAR` is not expanded.
+
 ## Inference Providers
 
 You need at least one way to connect to an LLM. Use `hermes model` to switch providers and models interactively, or configure directly:
@@ -1329,6 +1345,23 @@ Usage: type `/status`, `/disk`, `/update`, or `/gpu` in the CLI or any messaging
 - **Type** — only `exec` is supported (runs a shell command); other types show an error
 - **Works everywhere** — CLI, Telegram, Discord, Slack, WhatsApp, Signal, Email, Home Assistant
 
+## Gateway Streaming
+
+Enable progressive token delivery on messaging platforms. When streaming is enabled, responses appear character-by-character in Telegram, Discord, and Slack via message editing, rather than waiting for the full response.
+
+```yaml
+streaming:
+  enabled: false              # Enable streaming token delivery (default: off)
+  transport: edit             # "edit" (progressive message editing) or "off"
+  edit_interval: 0.3          # Min seconds between message edits
+  buffer_threshold: 40        # Characters accumulated before forcing an edit
+  cursor: " ▉"               # Cursor character shown during streaming
+```
+
+**Platform support:** Telegram, Discord, and Slack support edit-based streaming. Platforms that don't support message editing (Signal, Email, Home Assistant) are auto-detected on the first attempt — streaming is gracefully disabled for that session with no flood of messages.
+
+**Overflow handling:** If the streamed text exceeds the platform's message length limit (~4096 chars), the current message is finalized and a new one starts automatically.
+
 ## Human Delay
 
 Simulate human-like response pacing in messaging platforms:
@@ -1350,6 +1383,27 @@ code_execution:
   max_tool_calls: 50           # Max tool calls within code execution
 ```
 
+## Web Search Backends
+
+The `web_search`, `web_extract`, and `web_crawl` tools support three backend providers. Configure the backend in `config.yaml` or via `hermes tools`:
+
+```yaml
+web:
+  backend: firecrawl    # firecrawl | parallel | tavily
+```
+
+| Backend | Env Var | Search | Extract | Crawl |
+|---------|---------|--------|---------|-------|
+| **Firecrawl** (default) | `FIRECRAWL_API_KEY` | ✔ | ✔ | ✔ |
+| **Parallel** | `PARALLEL_API_KEY` | ✔ | ✔ | — |
+| **Tavily** | `TAVILY_API_KEY` | ✔ | ✔ | ✔ |
+
+**Backend selection:** If `web.backend` is not set, the backend is auto-detected from available API keys. If only `TAVILY_API_KEY` is set, Tavily is used. If only `PARALLEL_API_KEY` is set, Parallel is used. Otherwise Firecrawl is the default.
+
+**Self-hosted Firecrawl:** Set `FIRECRAWL_API_URL` to point at your own instance. When a custom URL is set, the API key becomes optional (set `USE_DB_AUTHENTICATION=false` on the server to disable auth).
+
+**Parallel search modes:** Set `PARALLEL_SEARCH_MODE` to control search behavior — `fast`, `one-shot`, or `agentic` (default: `agentic`).
+
 ## Browser
 
 Configure browser automation behavior:

website/docs/user-guide/features/context-references.md

@@ -0,0 +1,109 @@
+---
+sidebar_position: 9
+title: "Context References"
+description: "Inline @-syntax for attaching files, folders, git diffs, and URLs directly into your messages"
+---
+
+# Context References
+
+Type `@` followed by a reference to inject content directly into your message. Hermes expands the reference inline and appends the content under an `--- Attached Context ---` section.
+
+## Supported References
+
+| Syntax | Description |
+|--------|-------------|
+| `@file:path/to/file.py` | Inject file contents |
+| `@file:path/to/file.py:10-25` | Inject specific line range (1-indexed, inclusive) |
+| `@folder:path/to/dir` | Inject directory tree listing with file metadata |
+| `@diff` | Inject `git diff` (unstaged working tree changes) |
+| `@staged` | Inject `git diff --staged` (staged changes) |
+| `@git:5` | Inject last N commits with patches (max 10) |
+| `@url:https://example.com` | Fetch and inject web page content |
+
+## Usage Examples
+
+```text
+Review @file:src/main.py and suggest improvements
+
+What changed? @diff
+
+Compare @file:old_config.yaml and @file:new_config.yaml
+
+What's in @folder:src/components?
+
+Summarize this article @url:https://arxiv.org/abs/2301.00001
+```
+
+Multiple references work in a single message:
+
+```text
+Check @file:main.py, and also @file:test.py.
+```
+
+Trailing punctuation (`,`, `.`, `;`, `!`, `?`) is automatically stripped from reference values.
+
+## CLI Tab Completion
+
+In the interactive CLI, typing `@` triggers autocomplete:
+
+- `@` shows all reference types (`@diff`, `@staged`, `@file:`, `@folder:`, `@git:`, `@url:`)
+- `@file:` and `@folder:` trigger filesystem path completion with file size metadata
+- Bare `@` followed by partial text shows matching files and folders from the current directory
+
+## Line Ranges
+
+The `@file:` reference supports line ranges for precise content injection:
+
+```text
+@file:src/main.py:42        # Single line 42
+@file:src/main.py:10-25     # Lines 10 through 25 (inclusive)
+```
+
+Lines are 1-indexed. Invalid ranges are silently ignored (full file is returned).
+
+## Size Limits
+
+Context references are bounded to prevent overwhelming the model's context window:
+
+| Threshold | Value | Behavior |
+|-----------|-------|----------|
+| Soft limit | 25% of context length | Warning appended, expansion proceeds |
+| Hard limit | 50% of context length | Expansion refused, original message returned unchanged |
+| Folder entries | 200 files max | Excess entries replaced with `- ...` |
+| Git commits | 10 max | `@git:N` clamped to range [1, 10] |
+
+## Security
+
+### Sensitive Path Blocking
+
+These paths are always blocked from `@file:` references to prevent credential exposure:
+
+- SSH keys and config: `~/.ssh/id_rsa`, `~/.ssh/id_ed25519`, `~/.ssh/authorized_keys`, `~/.ssh/config`
+- Shell profiles: `~/.bashrc`, `~/.zshrc`, `~/.profile`, `~/.bash_profile`, `~/.zprofile`
+- Credential files: `~/.netrc`, `~/.pgpass`, `~/.npmrc`, `~/.pypirc`
+- Hermes env: `$HERMES_HOME/.env`
+
+These directories are fully blocked (any file inside):
+- `~/.ssh/`, `~/.aws/`, `~/.gnupg/`, `~/.kube/`, `$HERMES_HOME/skills/.hub/`
+
+### Path Traversal Protection
+
+All paths are resolved relative to the working directory. References that resolve outside the allowed workspace root are rejected.
+
+### Binary File Detection
+
+Binary files are detected via MIME type and null-byte scanning. Known text extensions (`.py`, `.md`, `.json`, `.yaml`, `.toml`, `.js`, `.ts`, etc.) bypass MIME-based detection. Binary files are rejected with a warning.
+
+## Error Handling
+
+Invalid references produce inline warnings rather than failures:
+
+| Condition | Behavior |
+|-----------|----------|
+| File not found | Warning: "file not found" |
+| Binary file | Warning: "binary files are not supported" |
+| Folder not found | Warning: "folder not found" |
+| Git command fails | Warning with git stderr |
+| URL returns no content | Warning: "no content extracted" |
+| Sensitive path | Warning: "path is a sensitive credential file" |
+| Path outside workspace | Warning: "path is outside the allowed workspace" |

website/docs/user-guide/security.md

@@ -358,6 +358,42 @@ When a blocked URL is requested, the tool returns an error explaining the domain
 
 See [Website Blocklist](/docs/user-guide/configuration#website-blocklist) in the configuration guide for full details.
 
+### SSRF Protection
+
+All URL-capable tools (web search, web extract, vision, browser) validate URLs before fetching them to prevent Server-Side Request Forgery (SSRF) attacks. Blocked addresses include:
+
+- **Private networks** (RFC 1918): `10.0.0.0/8`, `172.16.0.0/12`, `192.168.0.0/16`
+- **Loopback**: `127.0.0.0/8`, `::1`
+- **Link-local**: `169.254.0.0/16` (includes cloud metadata at `169.254.169.254`)
+- **CGNAT / shared address space** (RFC 6598): `100.64.0.0/10` (Tailscale, WireGuard VPNs)
+- **Cloud metadata hostnames**: `metadata.google.internal`, `metadata.goog`
+- **Reserved, multicast, and unspecified addresses**
+
+SSRF protection is always active and cannot be disabled. DNS failures are treated as blocked (fail-closed). Redirect chains are re-validated at each hop to prevent redirect-based bypasses.
+
+### Tirith Pre-Exec Security Scanning
+
+Hermes integrates [tirith](https://github.com/sheeki03/tirith) for content-level command scanning before execution. Tirith detects threats that pattern matching alone misses:
+
+- Homograph URL spoofing (internationalized domain attacks)
+- Pipe-to-interpreter patterns (`curl | bash`, `wget | sh`)
+- Terminal injection attacks
+
+Tirith auto-installs from GitHub releases on first use with SHA-256 checksum verification (and cosign provenance verification if cosign is available).
+
+```yaml
+# In ~/.hermes/config.yaml
+security:
+  tirith_enabled: true       # Enable/disable tirith scanning (default: true)
+  tirith_path: "tirith"      # Path to tirith binary (default: PATH lookup)
+  tirith_timeout: 5          # Subprocess timeout in seconds
+  tirith_fail_open: true     # Allow execution when tirith is unavailable (default: true)
+```
+
+When `tirith_fail_open` is `true` (default), commands proceed if tirith is not installed or times out. Set to `false` in high-security environments to block commands when tirith is unavailable.
+
+Tirith's verdict integrates with the approval flow: safe commands pass through, suspicious commands trigger user approval, and dangerous commands are blocked.
+
 ### Context File Injection Protection
 
 Context files (AGENTS.md, .cursorrules, SOUL.md) are scanned for prompt injection before being included in the system prompt. The scanner checks for:

website/docs/user-guide/sessions.md

@@ -114,7 +114,13 @@ Session IDs follow the format `YYYYMMDD_HHMMSS_<8-char-hex>`, e.g. `20250305_091
 
 Give sessions human-readable titles so you can find and resume them easily.
 
-### Setting a Title
+### Auto-Generated Titles
+
+Hermes automatically generates a short descriptive title (3–7 words) for each session after the first exchange. This runs in a background thread using a fast auxiliary model, so it adds no latency. You'll see auto-generated titles when browsing sessions with `hermes sessions list` or `hermes sessions browse`.
+
+Auto-titling only fires once per session and is skipped if you've already set a title manually.
+
+### Setting a Title Manually
 
 Use the `/title` slash command inside any chat session (CLI or gateway):