diff --git a/crates/cli/src/output/human.rs b/crates/cli/src/output/human.rs
index fb0e3fbc..1cf02742 100644
--- a/crates/cli/src/output/human.rs
+++ b/crates/cli/src/output/human.rs
@@ -1,8 +1,8 @@
-
-
 use prism_core::types::report::DiagnosticReport;
 
-use crate::output::renderers::{render_section_header, render_error_card, render_fix_list, BudgetBar};
+use crate::output::renderers::{
+    render_cause_list, render_error_card, render_fix_list, render_section_header, BudgetBar,
+};
 
 pub fn print_report(report: &DiagnosticReport) -> anyhow::Result<()> {
     println!("{}", render_error_card(report));
@@ -38,6 +38,11 @@ pub fn print_report(report: &DiagnosticReport) -> anyhow::Result<()> {
         );
     }
 
+    if !report.root_causes.is_empty() {
+        println!();
+        println!("{}", render_cause_list(&report.root_causes));
+    }
+
     if !report.suggested_fixes.is_empty() {
         println!();
         println!("{}", render_fix_list(&report.suggested_fixes));
diff --git a/crates/cli/src/output/renderers.rs b/crates/cli/src/output/renderers.rs
index 15f5830e..4c6bb764 100644
--- a/crates/cli/src/output/renderers.rs
+++ b/crates/cli/src/output/renderers.rs
@@ -1,12 +1,10 @@
-
-
 #![allow(dead_code)]
 
+use crate::output::theme::ColorPalette;
 use colored::Colorize;
-use prism_core::types::report::{DiagnosticReport, TransactionContext};
+use prism_core::types::report::{DiagnosticReport, RootCause, TransactionContext};
 use prism_core::types::trace::ResourceProfile;
 use tabled::{Table, Tabled};
-use crate::output::theme::ColorPalette;
 
 const BAR_WIDTH: usize = 10;
 const HEAT_BLOCKS: [&str; 4] = ["░", "▒", "▓", "█"];
@@ -23,6 +21,10 @@ pub fn render_fix_list(fixes: &[prism_core::types::report::SuggestedFix]) -> Str
     FixList::new(fixes).render()
 }
 
+pub fn render_cause_list(causes: &[RootCause]) -> String {
+    CauseList::new(causes).render()
+}
+
 pub fn render_state_diff_table(diff: &prism_core::types::trace::StateDiff) -> String {
     StateDiffTable::new(diff).render()
 }
@@ -64,12 +66,13 @@ impl<'a> ErrorCard<'a> {
         let mut output = String::new();
 
         let category_badge = format!("[{}]", self.report.error_category.to_uppercase());
-        let error_line = format!(
-            " {} ({})",
-            self.report.error_name, self.report.error_code
-        );
+        let error_line = format!(" {} ({})", self.report.error_name, self.report.error_code);
 
-        let max_width = error_line.len().max(self.report.summary.len()).max(category_badge.len()) + 4;
+        let max_width = error_line
+            .len()
+            .max(self.report.summary.len())
+            .max(category_badge.len())
+            + 4;
         let border = "█".repeat(max_width);
 
         let border_colored = border.red().bold().to_string();
@@ -83,7 +86,11 @@ impl<'a> ErrorCard<'a> {
 
         if let Some(contract_error) = &self.report.contract_error {
             let component_line = format!("Component: {}", contract_error.contract_id);
-            output.push_str(&format!("{} {}\n", "█".red().bold(), component_line.white()));
+            output.push_str(&format!(
+                "{} {}\n",
+                "█".red().bold(),
+                component_line.white()
+            ));
         }
 
         output.push_str(&format!("{} {}\n", "█".red().bold(), summary_colored));
@@ -128,6 +135,34 @@ impl<'a> FixList<'a> {
     }
 }
 
+pub struct CauseList<'a> {
+    causes: &'a [RootCause],
+}
+
+impl<'a> CauseList<'a> {
+    pub fn new(causes: &'a [RootCause]) -> Self {
+        Self { causes }
+    }
+
+    pub fn render(&self) -> String {
+        if self.causes.is_empty() {
+            return String::new();
+        }
+
+        let mut output = String::new();
+        let palette = ColorPalette::default();
+
+        output.push_str(&palette.accent_text("COMMON CAUSES\n"));
+
+        for cause in self.causes {
+            let likelihood = format!("[{}]", cause.likelihood).cyan();
+            output.push_str(&format!("  - {} {}\n", likelihood, cause.description));
+        }
+
+        output
+    }
+}
+
 /// Renders a colored budget utilization bar for Soroban resource usage.
 pub struct BudgetBar {
     label: &'static str,
@@ -414,7 +449,8 @@ mod tests {
             error_category: "Contract".to_string(),
             error_code: 1,
             error_name: "InsufficientBalance".to_string(),
-            summary: "The account does not have enough balance to complete this transaction.".to_string(),
+            summary: "The account does not have enough balance to complete this transaction."
+                .to_string(),
             detailed_explanation: String::new(),
             severity: Severity::Error,
             root_causes: Vec::new(),
@@ -448,15 +484,13 @@ mod tests {
 
     #[test]
     fn heatmap_renders_function_names() {
-        let profile = make_profile(vec![
-            ResourceHotspot {
-                location: "transfer::invoke".to_string(),
-                cpu_instructions: 800_000,
-                cpu_percentage: 80.0,
-                memory_bytes: 300_000,
-                memory_percentage: 30.0,
-            },
-        ]);
+        let profile = make_profile(vec![ResourceHotspot {
+            location: "transfer::invoke".to_string(),
+            cpu_instructions: 800_000,
+            cpu_percentage: 80.0,
+            memory_bytes: 300_000,
+            memory_percentage: 30.0,
+        }]);
         let output = render_heatmap(&profile);
         assert!(output.contains("transfer::invoke"));
     }
@@ -470,6 +504,21 @@ mod tests {
         assert!(rendered.contains("does not have enough balance"));
     }
 
+    #[test]
+    fn cause_list_renders_common_causes() {
+        let causes = vec![RootCause {
+            description: "The transaction was submitted with an undersized resource budget."
+                .to_string(),
+            likelihood: "high".to_string(),
+        }];
+
+        let rendered = render_cause_list(&causes);
+
+        assert!(rendered.contains("COMMON CAUSES"));
+        assert!(rendered.contains("undersized resource budget"));
+        assert!(rendered.contains("high"));
+    }
+
     #[test]
     fn render_context_table_with_arguments() {
         let context = TransactionContext {
diff --git a/crates/core/src/decode/report.rs b/crates/core/src/decode/report.rs
index b221c8ed..e4141c43 100644
--- a/crates/core/src/decode/report.rs
+++ b/crates/core/src/decode/report.rs
@@ -1,8 +1,6 @@
-
-
 use crate::decode::host_error::ClassifiedError;
-use crate::taxonomy::loader::TaxonomyDatabase;
 use crate::error::PrismResult;
+use crate::taxonomy::loader::TaxonomyDatabase;
 use crate::types::report::{DiagnosticReport, RootCause, Severity, SuggestedFix};
 
 pub fn build_report(error: &ClassifiedError) -> PrismResult<DiagnosticReport> {
@@ -59,3 +57,34 @@ pub fn build_report(error: &ClassifiedError) -> PrismResult<DiagnosticReport> {
         ))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::taxonomy::schema::ErrorCategory;
+
+    #[test]
+    fn tier1_common_causes_surface_in_decoded_report() {
+        let classified = ClassifiedError {
+            category: ErrorCategory::Budget,
+            error_code: 0,
+            is_contract_error: false,
+            contract_id: None,
+            raw_data: serde_json::Value::Null,
+        };
+
+        let report = build_report(&classified).expect("Report should build");
+
+        assert!(
+            !report.root_causes.is_empty(),
+            "Decoded report should include at least one common cause"
+        );
+        assert!(
+            report
+                .root_causes
+                .iter()
+                .any(|cause| cause.description.contains("loops")),
+            "Decoded report should include taxonomy common cause descriptions"
+        );
+    }
+}
diff --git a/crates/core/src/taxonomy/data/budget.toml b/crates/core/src/taxonomy/data/budget.toml
index bafeb07a..03f5672f 100644
--- a/crates/core/src/taxonomy/data/budget.toml
+++ b/crates/core/src/taxonomy/data/budget.toml
@@ -10,7 +10,7 @@ source_module = "soroban-env-host/src/budget.rs"
 id = "host.budget.limit_exceeded.cpu"
 category = "budget"
 code = 0
-name = "LimitExceeded"
+name = "CPUExceeded"
 severity = "Error"
 since_protocol = 20
 summary = "The transaction exceeded its CPU instruction budget."
@@ -54,3 +54,110 @@ requires_upgrade = true
 related_errors = ["host.budget.limit_exceeded.memory"]
 source_file = "soroban-env-host/src/budget.rs"
 documentation_url = "https://soroban.stellar.org/docs/fundamentals/fees-and-metering"
+
+[[errors]]
+id = "host.budget.insufficient_instructions"
+category = "budget"
+code = 1
+name = "InsufficientInstructions"
+severity = "Error"
+since_protocol = 20
+summary = "The transaction did not have enough CPU instructions allocated."
+detailed_explanation = """
+The transaction's resource declaration did not reserve enough CPU instructions for the contract
+invocation to complete. This usually happens when submitted limits are stale, manually edited, or
+lower than the values returned by simulation.
+"""
+related_errors = ["host.budget.limit_exceeded.cpu"]
+source_file = "soroban-env-host/src/budget.rs"
+documentation_url = "https://soroban.stellar.org/docs/fundamentals/fees-and-metering"
+
+[[errors.common_causes]]
+description = "The transaction was submitted with CPU limits lower than the simulated requirement"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "Contract logic became more expensive after the transaction was prepared"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Re-run simulation and submit the transaction with the updated CPU instruction limit"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Reduce the amount of work performed by the contract invocation"
+difficulty = "medium"
+requires_upgrade = true
+
+[[errors]]
+id = "host.budget.insufficient_memory"
+category = "budget"
+code = 2
+name = "InsufficientMemory"
+severity = "Error"
+since_protocol = 20
+summary = "The transaction did not have enough memory allocated."
+detailed_explanation = """
+The transaction's resource declaration did not reserve enough memory for the host objects, contract
+data, or intermediate values created during execution.
+"""
+related_errors = ["host.budget.limit_exceeded.cpu"]
+source_file = "soroban-env-host/src/budget.rs"
+documentation_url = "https://soroban.stellar.org/docs/fundamentals/fees-and-metering"
+
+[[errors.common_causes]]
+description = "The invocation builds large vectors, maps, bytes, or strings in memory"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "A cross-contract call returned more data than the caller budgeted for"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Re-run simulation and submit the transaction with the updated memory limit"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Split large inputs or outputs into smaller contract calls"
+difficulty = "medium"
+requires_upgrade = true
+
+[[errors]]
+id = "host.budget.exceeded_limit"
+category = "budget"
+code = 8
+name = "ExceededLimit"
+severity = "Error"
+since_protocol = 20
+summary = "The transaction exceeded an allocated resource limit."
+detailed_explanation = """
+The host stopped execution because one of the metered resource limits was exceeded. The exact
+resource may depend on the diagnostic events and the resource profile for the transaction.
+"""
+related_errors = [
+    "host.budget.limit_exceeded.cpu",
+    "host.budget.insufficient_instructions",
+    "host.budget.insufficient_memory",
+]
+source_file = "soroban-env-host/src/budget.rs"
+documentation_url = "https://soroban.stellar.org/docs/fundamentals/fees-and-metering"
+
+[[errors.common_causes]]
+description = "The transaction used more CPU, memory, or ledger I/O than its declared resource limits allowed"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "The resource footprint was estimated before inputs or contract state changed"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Simulate the transaction again and submit it with the returned resource limits"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Inspect the resource profile to identify the expensive contract call"
+difficulty = "medium"
+requires_upgrade = false
diff --git a/crates/core/src/taxonomy/data/context.toml b/crates/core/src/taxonomy/data/context.toml
index 5955e4a2..26c4ab90 100644
--- a/crates/core/src/taxonomy/data/context.toml
+++ b/crates/core/src/taxonomy/data/context.toml
@@ -6,6 +6,39 @@ name = "Context"
 description = "Errors triggered by invalid execution context, such as calling host functions outside of a valid invocation or re-entrancy violations."
 source_module = "soroban-env-host/src/host.rs"
 
+[[errors]]
+id = "host.context.unknown_error"
+category = "context"
+code = 0
+name = "UnknownError"
+severity = "Error"
+since_protocol = 20
+summary = "An unexpected Soroban runtime error occurred."
+detailed_explanation = """
+The host returned a context error that does not map to a more specific execution-context failure.
+This can indicate malformed transaction data, an unsupported host state, or a platform issue.
+"""
+related_errors = ["host.context.internal_error"]
+source_file = "soroban-env-host/src/host.rs"
+
+[[errors.common_causes]]
+description = "The transaction reached a host state that Prism cannot classify more specifically"
+likelihood = "medium"
+
+[[errors.common_causes]]
+description = "Malformed or unsupported transaction data triggered a generic context failure"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Check diagnostic events and transaction metadata for the host operation that failed"
+difficulty = "medium"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Reproduce the transaction on the same network and report it if the error persists"
+difficulty = "medium"
+requires_upgrade = false
+
 [[errors]]
 id = "host.context.invalid_action"
 category = "context"
diff --git a/crates/core/src/taxonomy/data/storage.toml b/crates/core/src/taxonomy/data/storage.toml
index e3aea1b3..c72986ea 100644
--- a/crates/core/src/taxonomy/data/storage.toml
+++ b/crates/core/src/taxonomy/data/storage.toml
@@ -40,3 +40,102 @@ requires_upgrade = false
 
 related_errors = ["host.storage.missing_key"]
 source_file = "soroban-env-host/src/storage.rs"
+
+[[errors]]
+id = "host.storage.entry_not_found"
+category = "storage"
+code = 1
+name = "EntryNotFound"
+severity = "Error"
+since_protocol = 20
+summary = "The contract attempted to read a ledger key that does not exist or has been archived."
+detailed_explanation = """
+The host could not load the requested ledger entry. The key may never have been written, may have
+expired from live state, or may need restoration before the contract can access it.
+"""
+related_errors = ["host.storage.access_denied"]
+source_file = "soroban-env-host/src/storage.rs"
+
+[[errors.common_causes]]
+description = "The contract read a key before any transaction created it"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "The ledger entry expired or was archived before this transaction ran"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Create or initialize the missing ledger entry before reading it"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Restore archived contract data before submitting the transaction"
+difficulty = "medium"
+requires_upgrade = false
+
+[[errors]]
+id = "host.storage.exceeded_limit"
+category = "storage"
+code = 2
+name = "ExceededLimit"
+severity = "Error"
+since_protocol = 20
+summary = "The operation attempted to exceed resource or size limits for ledger data."
+detailed_explanation = """
+The storage operation would exceed a protocol limit for ledger data, such as entry size, footprint
+size, or the amount of data read or written by the transaction.
+"""
+related_errors = ["host.budget.exceeded_limit"]
+source_file = "soroban-env-host/src/storage.rs"
+
+[[errors.common_causes]]
+description = "The contract attempted to write a ledger entry larger than the protocol allows"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "The transaction touched more ledger entries than its footprint or limits allowed"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Reduce the size of stored values or split the data across smaller entries"
+difficulty = "medium"
+requires_upgrade = true
+
+[[errors.suggested_fixes]]
+description = "Break the storage update into multiple smaller transactions"
+difficulty = "medium"
+requires_upgrade = true
+
+[[errors]]
+id = "host.storage.internal_error"
+category = "storage"
+code = 3
+name = "InternalError"
+severity = "Error"
+since_protocol = 20
+summary = "An internal storage failure occurred while accessing contract data."
+detailed_explanation = """
+The storage layer reported an unexpected internal failure. This code alone is not enough to identify
+the root issue; diagnostic events and transaction context usually provide the next clue.
+"""
+related_errors = []
+source_file = "soroban-env-host/src/storage.rs"
+
+[[errors.common_causes]]
+description = "The host encountered an unexpected storage state while loading or writing ledger data"
+likelihood = "medium"
+
+[[errors.common_causes]]
+description = "The transaction hit a storage edge case that needs diagnostic events to identify"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Inspect diagnostic events for the ledger key or storage operation that failed"
+difficulty = "medium"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Retry on a fresh ledger state or report the transaction if the failure is reproducible"
+difficulty = "medium"
+requires_upgrade = false
diff --git a/crates/core/src/taxonomy/data/value.toml b/crates/core/src/taxonomy/data/value.toml
index e1968ca6..7b0e0e89 100644
--- a/crates/core/src/taxonomy/data/value.toml
+++ b/crates/core/src/taxonomy/data/value.toml
@@ -1,5 +1,5 @@
 # Value Error Taxonomy
-# Category: Value — errors related to SCVal type conversions and validation.
+# Category: Value - errors related to SCVal type conversions and validation.
 
 [category]
 name = "Value"
@@ -7,25 +7,26 @@ description = "Errors triggered when converting, validating, or operating on Sor
 source_module = "soroban-env-host/src/host/conversion.rs"
 
 [[errors]]
-id = "host.value.invalid_input"
+id = "host.value.unknown_error"
 category = "value"
 code = 0
-name = "InvalidInput"
+name = "UnknownError"
 severity = "Error"
 since_protocol = 20
-summary = "An invalid value was passed to a host function."
+summary = "Invalid value: a host function received an argument of the wrong type or format."
 detailed_explanation = """
-Host functions expect values of specific types. When a value of the wrong type or an invalid \
-representation is passed, this error is raised. Common examples include passing a negative \
-number where an unsigned value is expected, or passing a malformed byte array.
+The host could not classify the value failure more specifically. This usually means a value passed
+to a host function could not be converted, decoded, or validated against the expected shape.
 """
+related_errors = ["host.value.unexpected_type", "host.value.invalid_input"]
+source_file = "soroban-env-host/src/host/conversion.rs"
 
 [[errors.common_causes]]
-description = "Type mismatch between contract code arguments and host function expectations"
+description = "Type mismatch between contract call arguments and host function expectations"
 likelihood = "high"
 
 [[errors.common_causes]]
-description = "Malformed or corrupted data passed from contract storage"
+description = "Malformed or corrupted data was read from contract storage"
 likelihood = "medium"
 
 [[errors.suggested_fixes]]
@@ -33,5 +34,233 @@ description = "Check the function signature in the contract spec and ensure argu
 difficulty = "easy"
 requires_upgrade = false
 
-related_errors = ["host.value.unexpected_type"]
+[[errors]]
+id = "host.value.unexpected_type"
+category = "value"
+code = 1
+name = "UnexpectedType"
+severity = "Error"
+since_protocol = 20
+summary = "The provided value is not of the expected type for this operation."
+detailed_explanation = """
+A host function or contract ABI expected one Soroban value type but received another, such as a
+symbol where an address was expected or a map where a vector was expected.
+"""
+related_errors = ["host.value.unknown_error", "host.value.invalid_input"]
+source_file = "soroban-env-host/src/host/conversion.rs"
+
+[[errors.common_causes]]
+description = "A caller passed an argument type that does not match the contract function signature"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "Stored contract data was decoded using a newer or different expected type"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Compare the submitted ScVal arguments with the contract spec"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Migrate or rewrite stored data so it matches the current contract type"
+difficulty = "medium"
+requires_upgrade = true
+
+[[errors]]
+id = "host.value.unexpected_size"
+category = "value"
+code = 2
+name = "UnexpectedSize"
+severity = "Error"
+since_protocol = 20
+summary = "The provided value has an unexpected size or length."
+detailed_explanation = """
+The host received a value with a length, byte count, or collection size that does not match the
+operation's requirements.
+"""
+related_errors = ["host.value.invalid_input"]
+source_file = "soroban-env-host/src/host/conversion.rs"
+
+[[errors.common_causes]]
+description = "A byte array, signature, key, or hash has the wrong length"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "A collection argument contains too many or too few elements"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Validate byte lengths and collection sizes before building the transaction"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Update the caller to encode fixed-size values using the exact expected length"
+difficulty = "medium"
+requires_upgrade = false
+
+[[errors]]
+id = "host.value.missing_value"
+category = "value"
+code = 3
+name = "MissingValue"
+severity = "Error"
+since_protocol = 20
+summary = "A required value was missing from the input."
+detailed_explanation = """
+The host expected a value to be present but found no value, such as a missing map key, absent
+optional argument, or missing decoded field.
+"""
+related_errors = ["host.value.invalid_input"]
+source_file = "soroban-env-host/src/host/conversion.rs"
+
+[[errors.common_causes]]
+description = "A required contract argument or map entry was omitted"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "The caller encoded an optional value as missing when the contract required it"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Include the missing argument or field when constructing the contract call"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Add input validation before submitting the transaction"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors]]
+id = "host.value.internal_error"
+category = "value"
+code = 4
+name = "InternalError"
+severity = "Fatal"
+since_protocol = 20
+summary = "An internal host error occurred while processing a value."
+detailed_explanation = """
+The host encountered an unexpected internal state while converting, validating, or handling a
+Soroban value.
+"""
+related_errors = ["host.context.internal_error"]
+source_file = "soroban-env-host/src/host/conversion.rs"
+
+[[errors.common_causes]]
+description = "The host hit an unexpected value conversion or validation state"
+likelihood = "medium"
+
+[[errors.common_causes]]
+description = "Malformed input exposed a host-side edge case"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Inspect diagnostic events for the value conversion that failed"
+difficulty = "medium"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Report a reproducible transaction with the full input values"
+difficulty = "medium"
+requires_upgrade = false
+
+[[errors]]
+id = "host.value.added_value"
+category = "value"
+code = 5
+name = "AddedValue"
+severity = "Error"
+since_protocol = 20
+summary = "An unexpected or disallowed value was provided."
+detailed_explanation = """
+The host received an extra value in a place where no additional value was allowed, such as an
+unexpected field, argument, or authorization payload component.
+"""
+related_errors = ["host.value.invalid_input"]
+source_file = "soroban-env-host/src/host/conversion.rs"
+
+[[errors.common_causes]]
+description = "The caller supplied extra arguments or fields that the contract does not accept"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "A generated transaction builder included stale data from an older contract interface"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Remove unexpected arguments or fields from the contract call"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Regenerate client bindings from the current contract spec"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors]]
+id = "host.value.invalid_input"
+category = "value"
+code = 6
+name = "InvalidInput"
+severity = "Error"
+since_protocol = 20
+summary = "Malformed ScVal conversion, out-of-range integer, or otherwise invalid input passed to a host function."
+detailed_explanation = """
+The input value had the right general shape but failed validation, conversion, or range checks
+required by the host function.
+"""
+related_errors = ["host.value.unexpected_type", "host.value.unexpected_size"]
 source_file = "soroban-env-host/src/host/conversion.rs"
+
+[[errors.common_causes]]
+description = "A ScVal was malformed or encoded with a value outside the allowed range"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "The caller passed contract input produced by an incompatible SDK or serializer"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Rebuild the transaction arguments with the current SDK and contract spec"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Validate numeric ranges, addresses, and encoded values before submission"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors]]
+id = "host.value.authentication_error"
+category = "value"
+code = 7
+name = "AuthenticationError"
+severity = "Error"
+since_protocol = 20
+summary = "An authentication-related value was invalid or malformed."
+detailed_explanation = """
+The host rejected a value used during authorization, such as an auth payload, signer value, nonce,
+or credential component.
+"""
+related_errors = ["host.auth.invalid_signature", "host.auth.missing_auth"]
+source_file = "soroban-env-host/src/host/conversion.rs"
+
+[[errors.common_causes]]
+description = "Authorization payload values do not match the invocation being authorized"
+likelihood = "high"
+
+[[errors.common_causes]]
+description = "Signer, nonce, or credential data was malformed before signature verification"
+likelihood = "medium"
+
+[[errors.suggested_fixes]]
+description = "Regenerate the auth entries from the exact invocation being submitted"
+difficulty = "easy"
+requires_upgrade = false
+
+[[errors.suggested_fixes]]
+description = "Check signer, nonce, and credential encoding before collecting signatures"
+difficulty = "medium"
+requires_upgrade = false
diff --git a/crates/core/src/taxonomy/loader.rs b/crates/core/src/taxonomy/loader.rs
index 7fa83fd6..99695dfd 100644
--- a/crates/core/src/taxonomy/loader.rs
+++ b/crates/core/src/taxonomy/loader.rs
@@ -1,29 +1,23 @@
-
-
-use crate::taxonomy::schema::{ErrorCategory, TaxonomyEntry, TaxonomySchema};
 use crate::error::{PrismError, PrismResult};
+use crate::taxonomy::schema::{ErrorCategory, TaxonomyEntry, TaxonomySchema};
 use std::collections::HashMap;
 
 pub struct TaxonomyParser;
 
 impl TaxonomyParser {
-
     pub fn parse(input: &str) -> PrismResult<TaxonomySchema> {
-        toml::from_str(input).map_err(|e| {
-            PrismError::TaxonomyError(format!("TOML parse error: {e}"))
-        })
+        toml::from_str(input)
+            .map_err(|e| PrismError::TaxonomyError(format!("TOML parse error: {e}")))
     }
 }
 
 pub struct TaxonomyDatabase {
-
     entries: HashMap<(ErrorCategory, u32), TaxonomyEntry>,
 
     all_entries: Vec<TaxonomyEntry>,
 }
 
 impl TaxonomyDatabase {
-
     pub fn load_embedded() -> PrismResult<Self> {
         let mut db = Self {
             entries: HashMap::new(),
@@ -105,6 +99,10 @@ impl TaxonomyDatabase {
             .collect()
     }
 
+    pub fn all_entries(&self) -> &[TaxonomyEntry] {
+        &self.all_entries
+    }
+
     pub fn len(&self) -> usize {
         self.entries.len()
     }
@@ -153,4 +151,99 @@ mod tests {
         let result = TaxonomyParser::parse(toml);
         assert!(result.is_err());
     }
+
+    #[test]
+    fn tier1_entries_with_fixes_have_common_causes() {
+        let db = TaxonomyDatabase::load_embedded().expect("Taxonomy should load");
+        assert!(!db.is_empty(), "Taxonomy should contain entries");
+
+        for entry in db.all_entries() {
+            if entry.suggested_fixes.is_empty() {
+                continue;
+            }
+
+            assert!(
+                !entry.common_causes.is_empty(),
+                "{} has suggested fixes but no common causes",
+                entry.id
+            );
+            assert!(
+                entry.common_causes.len() <= 3,
+                "{} has more than three common causes",
+                entry.id
+            );
+            assert!(
+                entry
+                    .common_causes
+                    .iter()
+                    .all(|cause| !cause.description.trim().is_empty()),
+                "{} has an empty common cause description",
+                entry.id
+            );
+        }
+    }
+
+    #[test]
+    fn taxonomy_covers_tier1_static_mapping_codes() {
+        let db = TaxonomyDatabase::load_embedded().expect("Taxonomy should load");
+
+        let expected_codes = [
+            (
+                ErrorCategory::Budget,
+                crate::decode::mappings::budget::BUDGET_ERROR_DETAILS
+                    .iter()
+                    .map(|detail| (detail.code, detail.name))
+                    .collect::<Vec<_>>(),
+            ),
+            (
+                ErrorCategory::Storage,
+                crate::decode::mappings::storage::STORAGE_ERROR_DETAILS
+                    .iter()
+                    .map(|detail| (detail.code, detail.name))
+                    .collect::<Vec<_>>(),
+            ),
+            (
+                ErrorCategory::Auth,
+                crate::decode::mappings::auth::AUTH_ERROR_DETAILS
+                    .iter()
+                    .map(|detail| (detail.code, detail.name))
+                    .collect::<Vec<_>>(),
+            ),
+            (
+                ErrorCategory::Context,
+                crate::decode::mappings::context::CONTEXT_ERROR_DETAILS
+                    .iter()
+                    .map(|detail| (detail.code, detail.name))
+                    .collect::<Vec<_>>(),
+            ),
+            (
+                ErrorCategory::Value,
+                crate::decode::mappings::value::VALUE_ERROR_DETAILS
+                    .iter()
+                    .map(|detail| (detail.code, detail.name))
+                    .collect::<Vec<_>>(),
+            ),
+        ];
+
+        for (category, details) in expected_codes {
+            for (code, name) in details {
+                let entry = db.lookup(&category, code).unwrap_or_else(|| {
+                    panic!("Missing taxonomy entry for {category} code {code} ({name})")
+                });
+
+                assert_eq!(
+                    entry.name, name,
+                    "Taxonomy entry name for {category} code {code} should match static mapping"
+                );
+                assert!(
+                    !entry.common_causes.is_empty(),
+                    "Taxonomy entry for {category} code {code} ({name}) has no common causes"
+                );
+                assert!(
+                    entry.common_causes.len() <= 3,
+                    "Taxonomy entry for {category} code {code} ({name}) has more than three common causes"
+                );
+            }
+        }
+    }
 }
diff --git a/crates/core/src/taxonomy/schema.rs b/crates/core/src/taxonomy/schema.rs
index d59cce2f..fb41fa04 100644
--- a/crates/core/src/taxonomy/schema.rs
+++ b/crates/core/src/taxonomy/schema.rs
@@ -1,10 +1,7 @@
-
-
 use serde::{Deserialize, Serialize};
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct TaxonomyEntry {
-
     pub id: String,
 
     pub category: ErrorCategory,
@@ -23,10 +20,13 @@ pub struct TaxonomyEntry {
 
     pub detailed_explanation: String,
 
+    #[serde(default)]
     pub common_causes: Vec<TaxonomyCause>,
 
+    #[serde(default)]
     pub suggested_fixes: Vec<TaxonomyFix>,
 
+    #[serde(default)]
     pub related_errors: Vec<String>,
 
     pub source_file: Option<String>,
@@ -38,7 +38,6 @@ pub struct TaxonomyEntry {
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct TaxonomyCause {
-
     pub description: String,
 
     pub likelihood: String,
@@ -46,7 +45,6 @@ pub struct TaxonomyCause {
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct TaxonomyFix {
-
     pub description: String,
 
     pub difficulty: String,